-fix time assertion introduce in last patch
[oweals/gnunet.git] / src / dht / gnunet-service-xdht_neighbours.c
index 8d99d54140a47e12c108f4a763f1cd5968bae777..a0b1c378fd2c539fcc6e9a8f1a163be2ae76dd2b 100644 (file)
@@ -1,6 +1,6 @@
 /*
      This file is part of GNUnet.
-     (C) 2009-2013 Christian Grothoff (and other contributing authors)
+     (C) 2009-2014 Christian Grothoff (and other contributing authors)
 
      GNUnet is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published
 #include "gnunet_hello_lib.h"
 #include "gnunet_constants.h"
 #include "gnunet_protocols.h"
-#include "gnunet_nse_service.h"
 #include "gnunet_ats_service.h"
 #include "gnunet_core_service.h"
 #include "gnunet_datacache_lib.h"
 #include "gnunet_transport_service.h"
-#include "gnunet_hello_lib.h"
 #include "gnunet_dht_service.h"
 #include "gnunet_statistics_service.h"
 #include "gnunet-service-xdht.h"
 #include "gnunet-service-xdht_clients.h"
 #include "gnunet-service-xdht_datacache.h"
-#include "gnunet-service-xdht_hello.h"
 #include "gnunet-service-xdht_neighbours.h"
-#include "gnunet-service-xdht_nse.h"
 #include "gnunet-service-xdht_routing.h"
 #include <fenv.h>
 #include "dht.h"
 
-/* TODO:
- * 1. when should we use const struct and replace wherever needed. 
- * 2. use assert for each function where you need to check the return value.
- 1. Use a global array of all known peers in find_successor, Only when 
- a new peer is added in finger or friend peer map, then re calculate
- the array. Or else use the old one.
- 2. Should we be using const in all the handle for the message we received 
- * and then copy the fields and make changes to the fields instead of sending
- * them as they come.
- * 3. Everywhere you are storing yourself as the first element in the trail.
- * It is obviously taking too much space. Try to remove it and think of something
- * better.
- 4. Choose the correct interval to send finger and verify message.
- 5. Do we need expiration time for trail setup and all other messages? TTL
- 6. In case of trail setup after TTL, we should again send the request but 
- * through a different route. How do we remeber each time which friend we
- * chose last time for the trail setup. We will need a data structure where we
- * add entry in finger table add and when setup is done remove it.
- * 7. I have not added any authentication on messages exachanged between peers.
- * Only when basic put/get is correct I will add it. */
-
-/**
- * Maximum possible fingers of a peer.
- */
-#define MAX_FINGERS 64
+/**
+ * FIXME: 
+ * 1. In X-Vine paper, there is no policy defined for replicating the data to
+ * recover in case of peer failure. We can do it in Chord way. In R5N, the key
+ * is hashed and then data is stored according to the key value generated after
+ * hashing.
+ * 2. We will keep an entry in routing table even if its a friend for the moment.
+ * Because I am not sure if there is a case where it will not work. 
+ * Trail id we can keep but actually there is no trail.
+ */
+
+/**
+ * Maximum possible fingers (including predecessor) of a peer 
+ */
+#define MAX_FINGERS 65
 
 /**
  * Maximum allowed number of pending messages per friend peer.
 #define MAXIMUM_PENDING_PER_FRIEND 64
 
 /**
- * How long at least to wait before sending another find finger trail request.
+ * How long to wait before sending another find finger trail request
  */
-#define DHT_MINIMUM_FIND_FINGER_TRAIL_INTERVAL GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, 30)
+#define DHT_FIND_FINGER_TRAIL_INTERVAL GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, 30)
 
 /**
- * How long at most to wait before sending another find finger trail request.
+ * How long at most to wait for transmission of a request to a friend ?
  */
-#define DHT_MAXIMUM_FIND_FINGER_TRAIL_INTERVAL GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MINUTES, 10)
+#define GET_TIMEOUT GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MINUTES, 2)
 
 /**
- * How long at most to wait for transmission of a GET request to another peer?
+ * Duration for which I may remain congested. 
+ * Note: Its a static value. In future, a peer may do some analysis and calculate 
+ * congestion_timeout based on 'some' parameters. 
  */
-#define GET_TIMEOUT GNUNET_TIME_relative_multiply(GNUNET_TIME_UNIT_MINUTES, 2)
+#define CONGESTION_TIMEOUT GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MINUTES, 2)
 
 /**
  * Maximum number of trails allowed to go through a friend.
  */
-#define LINK_THRESHOLD 64
+#define TRAILS_THROUGH_FRIEND_THRESHOLD 64
+
+/**
+ * Maximum number of trails stored per finger.
+ */
+#define MAXIMUM_TRAILS_PER_FINGER 1
+
+/**
+ * Finger map index for predecessor entry in finger table.
+ */
+#define PREDECESSOR_FINGER_ID 64
 
+/**
+ * Wrap around in peer identity circle. 
+ */
+#define PEER_IDENTITES_WRAP_AROUND pow(2, 64) - 1
+
+/**
+ * FIXME: Its use only at 3 places check if you can remove it.
+ * To check if a finger is predecessor or not. 
+ */
+enum GDS_NEIGHBOURS_finger_type
+{
+  GDS_FINGER_TYPE_PREDECESSOR = 0,
+  GDS_FINGER_TYPE_NON_PREDECESSOR = 1
+};
 
 GNUNET_NETWORK_STRUCT_BEGIN
-  
+
 /**
  * P2P PUT message
  */
@@ -129,6 +141,7 @@ struct PeerPutMessage
 
   /**
    * Replication level for this message
+   * In the current implementation, this value is not used. 
    */
   uint32_t desired_replication_level GNUNET_PACKED;
 
@@ -138,20 +151,17 @@ struct PeerPutMessage
   uint32_t put_path_length GNUNET_PACKED;
   
   /** 
-   * Current destination to which this message is forwarded.
+   * Best known destination (could be my friend or finger) which should
+   * get this message next. 
    */
-  struct GNUNET_PeerIdentity current_destination;
+  struct GNUNET_PeerIdentity best_known_destination;
   
   /**
-   * Peer whose finger is current_destination. 
+   * In case best_known_destination is a finger, then trail to reach
+   * to that finger. Else its default value is 0. 
    */
-  struct GNUNET_PeerIdentity current_source;
+  struct GNUNET_HashCode intermediate_trail_id;
   
-  /** 
-   * current_destination type.
-   */
-  enum current_destination_type current_destination_type;
-
   /**
    * When does the content expire?
    */
@@ -161,7 +171,6 @@ struct PeerPutMessage
    * The key to store the value under.
    */
   struct GNUNET_HashCode key GNUNET_PACKED;
 
   /* put path (if tracked) */
 
@@ -169,71 +178,6 @@ struct PeerPutMessage
  
 };
 
-
-/**
- * P2P Result message
- */
-struct PeerGetResultMessage
-{
-  /**
-   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_GET_RESULT
-   */
-  struct GNUNET_MessageHeader header;
-
-  /**
-   * The type for the data.
-   */
-  uint32_t type GNUNET_PACKED;
-  
-  /**
-   * Peer which is sending get result message.
-   */
-  struct GNUNET_PeerIdentity source_peer;
-  
-  /**
-   * Peer which will receive the get result message. 
-   */
-  struct GNUNET_PeerIdentity destination_peer;
-
-  /**
-   * Current index in get path. 
-   */
-  unsigned int current_path_index;
-  /**
-   * Number of peers recorded in the outgoing path from source to the
-   * storgage location of this message.
-   */
-  uint32_t put_path_length GNUNET_PACKED;
-  
-  /**
-   * When does this entry expire?
-   */
-  struct GNUNET_TIME_AbsoluteNBO expiration;
-  
-  /**
-   * Length of the GET path that follows (if tracked).
-   */
-  uint32_t get_path_length GNUNET_PACKED;
-
-  /**
-   * When does the content expire?
-   */
-  struct GNUNET_TIME_AbsoluteNBO expiration_time;
-
-  /**
-   * The key of the corresponding GET request.
-   */
-  struct GNUNET_HashCode key;
-  /* put path (if tracked) */
-
-  /* get path (if tracked) */
-
-  /* Payload */
-
-};
-
-
 /**
  * P2P GET message
  */
@@ -261,6 +205,7 @@ struct PeerGetMessage
  
   /**
    * Desired replication level for this request.
+   * In the current implementation, this value is not used. 
    */
   uint32_t desired_replication_level GNUNET_PACKED;
   
@@ -270,20 +215,17 @@ struct PeerGetMessage
   unsigned int get_path_length;
   
   /**
-   * Peer which is an intermediate destination. 
-   */
-  struct GNUNET_PeerIdentity current_destination;
-  
-  /**
-   * Source for which current_destination is the finger. 
+   * Best known destination (could be my friend or finger) which should
+   * get this message next. 
    */
-  struct GNUNET_PeerIdentity current_source;
+  struct GNUNET_PeerIdentity best_known_destination;
   
   /**
-   * Type of current destination
+   * In case best_known_destination is a finger, then trail to reach
+   * to that finger. Else its default value is 0. 
    */
-  enum current_destination_type current_dest_type;  
-  
+  struct GNUNET_HashCode intermediate_trail_id;
   /**
    * The key we are looking for.
    */
@@ -293,213 +235,223 @@ struct PeerGetMessage
 
 };
 
-
 /**
- * P2P Trail setup message
+ * P2P Result message
  */
-struct PeerTrailSetupMessage
+struct PeerGetResultMessage
 {
-  
   /**
-   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_SETUP
+   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_GET_RESULT
    */
   struct GNUNET_MessageHeader header;
 
   /**
-   * Source peer which wants to setup the trail to one of its finger. 
-   */
-  struct GNUNET_PeerIdentity source_peer;
-
-  /**
-   * Successor of this finger value will be our finger peer.
+   * The type for the data.
    */
-  uint64_t destination_finger;
+  uint32_t type GNUNET_PACKED;
   
   /**
-   * Peer which gets this message can be either an intermediate finger or friend. 
+   * Number of peers recorded in the outgoing path from source to the
+   * stored location of this message.
    */
-  enum current_destination_type current_destination_type;
+  uint32_t put_path_length GNUNET_PACKED;
   
   /**
-   * Peer to which this packet is forwarded.
+   * Length of the GET path that follows (if tracked).
    */
-  struct GNUNET_PeerIdentity current_destination;
+  uint32_t get_path_length GNUNET_PACKED;
   
   /**
-   * In case the packet is forwarded to an intermediate finger, then 
-   * current_source contains the peer id whose finger is the intermediate
-   * finger. In case the packet is forwarded to a friend, then it is NULL.
+   * Peer which queried for get and should get the result. 
    */
-  struct GNUNET_PeerIdentity current_source;
+  struct GNUNET_PeerIdentity querying_peer;
   
   /**
-   * Index into finger peer map. 
+   * When does the content expire?
    */
-  unsigned int finger_map_index;
-  
+  struct GNUNET_TIME_Absolute expiration_time;
+
   /**
-   * Number of entries in trail list.
+   * The key of the corresponding GET request.
    */
-  uint32_t trail_length GNUNET_PACKED;
-  
-};
+  struct GNUNET_HashCode key;
+  /* put path (if tracked) */
+
+  /* get path (if tracked) */
+
+  /* Payload */
 
+};
 
 /**
- * P2P Trail Setup Result message
+ * P2P Trail setup message
  */
-struct PeerTrailSetupResultMessage
+struct PeerTrailSetupMessage
 {
-  
   /**
-   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_SETUP_RESULT
+   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_SETUP
    */
   struct GNUNET_MessageHeader header;
   
   /**
-   * Finger to which we have found the path. 
+   * Is source_peer trying to setup the trail to a predecessor or any finger.
    */
-  struct GNUNET_PeerIdentity finger_identity;
+  uint32_t is_predecessor; 
+  
+  /**
+   * Peer closest to this value will be our finger.
+   */
+  uint64_t final_destination_finger_value;
 
   /**
-   * Peer which was looking for the trail to finger. 
+   * Source peer which wants to setup the trail to one of its finger.
    */
-  struct GNUNET_PeerIdentity destination_peer;
+  struct GNUNET_PeerIdentity source_peer;
 
   /**
-   * Trail index which points to next destination to send this message.
+   * Best known destination (could be my friend or finger) which should
+   * get this message next. 
    */
-  unsigned int current_index;
-  
+  struct GNUNET_PeerIdentity best_known_destination; 
+
   /**
-   * Index into finger peer map
+   * In case best_known_destination is a finger, then trail id of trail to
+   * reach to this finger.
    */
-  unsigned int finger_map_index;
+  struct GNUNET_HashCode intermediate_trail_id;
   
   /**
-   * Number of entries in trail list.
+   * Trail id for trail which we are trying to setup.
+   */
+  struct GNUNET_HashCode trail_id; 
+
+  /* List of peers which are part of trail setup so far.
+   * Trail does NOT include source_peer and peer which will be closest to
+   * ultimate_destination_finger_value.
+   * struct GNUNET_PeerIdentity trail[]
    */
-  uint32_t trail_length GNUNET_PACKED;
-  
 };
 
 /**
- *
+  * P2P Trail Setup Result message
  */
-struct PeerTrailRejectionMessage
+struct PeerTrailSetupResultMessage
 {
+
   /**
-   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_REJECTION
+   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_SETUP_RESULT
    */
   struct GNUNET_MessageHeader header;
-  
+
   /**
-   * Source peer which wants to set up the trail. 
+   * Finger to which we have found the path.
    */
-  struct GNUNET_PeerIdentity source_peer;
-  
+  struct GNUNET_PeerIdentity finger_identity;
+
   /**
-   * Finger identity value. 
+   * Peer which started trail_setup to find trail to finger_identity
    */
-  uint64_t finger_identity;
-  
+  struct GNUNET_PeerIdentity querying_peer; 
+
   /**
-   * Peer which sent trail rejection message. 
+   * Is the trail setup to querying_peer's predecessor or finger?
    */
-  struct GNUNET_PeerIdentity congested_peer;
-  
+  uint32_t is_predecessor; 
+
   /**
-   * Index in finger peer map of source peer.
+   * Value to which finger_identity is the closest peer. 
    */
-  unsigned int finger_map_index;
+  uint64_t ulitmate_destination_finger_value;
   
   /**
-   * Total number of peers in the trail.
+   * Identifier of the trail from querying peer to finger_identity, NOT
+   * including both endpoints. 
    */
-  unsigned int trail_length;
-  
-  /* trail_list */
-};
+  struct GNUNET_HashCode trail_id;
 
+  /* List of peers which are part of the trail from querying peer to 
+   * finger_identity, NOT including both endpoints.
+   * struct GNUNET_PeerIdentity trail[] 
+   */
+};
 
 /**
- * P2P Verify Successor message. 
+ * P2P Verify Successor Message.
  */
 struct PeerVerifySuccessorMessage
 {
-  
   /**
    * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_VERIFY_SUCCESSOR
    */
   struct GNUNET_MessageHeader header;
-  
+
   /**
-   * Source peer which wants to verify its successor. 
+   * Peer which wants to verify its successor.
    */
   struct GNUNET_PeerIdentity source_peer;
-  
+
   /**
-   * My current successor.
+   * Source Peer's current successor.
    */
   struct GNUNET_PeerIdentity successor;
-  
+
   /**
-   * Total number of peers in trail to current successor.
+   * Identifier of trail to reach from source_peer to successor.
    */
-  unsigned int trail_length;
-  
-  /**
-   * Trail index which points to next destination to send this message.
+  struct GNUNET_HashCode trail_id;
+
+  /* List of the peers which are part of trail to reach  from source_peer 
+   * to successor, NOT including them
+   * struct GNUNET_PeerIdentity trail[] 
    */
-  unsigned int current_trail_index;
-  
 };
 
-
 /**
- * P2P Verify Successor Result message. 
+ * P2P Verify Successor Result Message
  */
 struct PeerVerifySuccessorResultMessage
 {
-  
   /**
    * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_VERIFY_SUCCESSOR_RESULT
    */
   struct GNUNET_MessageHeader header;
-  
+
   /**
-   * Destination peer which sent the request to verify its successor. 
+   * Peer which sent the request to verify its successor.
    */
-  struct GNUNET_PeerIdentity destination_peer;
-  
+  struct GNUNET_PeerIdentity querying_peer;
+
   /**
    * Successor to which PeerVerifySuccessorMessage was sent.
    */
-  struct GNUNET_PeerIdentity source_successor;
-  
+  struct GNUNET_PeerIdentity current_successor;
+
   /**
-   * source_successor's predecessor
+   * Current Predecessor of source_successor. It can be same as querying peer
+   * or different. In case it is different then it can be querying_peer's
+   * probable successor. 
    */
-  struct GNUNET_PeerIdentity my_predecessor;
-  
+  struct GNUNET_PeerIdentity probable_successor;
+
   /**
-   * Total number of peers in trail.
-   * If source_successor is not destination peer, then trail is from destination_peer
-   * to my_predecessor.
-   * If source_successor is destination peer, then trail is from destination_peer
-   * to source_successor.
+   * Trail identifier of trail from querying_peer to current_successor.
    */
-  unsigned int trail_length;
-  
+  struct GNUNET_HashCode trail_id;
+
   /**
-   * Trail index which points to next destination to send this message.
+   * Direction in which we are looking at the trail.
+   */
+  uint32_t trail_direction;
+
+  /* In case probable_successor != querying_peer, then trail to reach from
+   * querying_peer to probable_successor, NOT including end points.
+   * struct GNUNET_PeerIdentity trail[]
    */
-  unsigned int current_index;
-  
 };
 
 /**
- * P2P Notify New Successor message.
+ * P2P Notify New Successor Message.
  */
 struct PeerNotifyNewSuccessorMessage
 {
@@ -507,121 +459,229 @@ struct PeerNotifyNewSuccessorMessage
    * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_NOTIFY_NEW_SUCCESSOR
    */
   struct GNUNET_MessageHeader header;
-  
+
   /**
-   * Source peer which wants to notify its new successor. 
+   * Peer which wants to notify its new successor.
    */
   struct GNUNET_PeerIdentity source_peer;
-  
+
   /**
-   * New successor identity.
+   * New successor of source_peer.
    */
-  struct GNUNET_PeerIdentity destination_peer;
-  
+  struct GNUNET_PeerIdentity new_successor;
+
   /**
-   * Number of peers in trail from source_peer to new successor.
+   * Unique identifier of the trail from source_peer to new_successor,
+   * NOT including the endpoints.
    */
-  unsigned int trail_length;
-  
-  /**
-   * Trail index which points to next destination to send this message.
+  struct GNUNET_HashCode trail_id;
+
+  /* List of peers in trail from source_peer to new_successor, 
+   * NOT including the endpoints. 
+   * struct GNUNET_PeerIdentity trail[]
    */
-  unsigned int current_index;
-  
 };
 
-
-GNUNET_NETWORK_STRUCT_END
-
-
 /**
- * Linked list of messages to send to a particular other peer.
+ * P2P Trail Compression Message.
  */
-struct P2PPendingMessage
+struct PeerTrailCompressionMessage
 {
   /**
-   * Pointer to next item in the list
+   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_COMPRESSION
    */
-  struct P2PPendingMessage *next;
+  struct GNUNET_MessageHeader header;
 
   /**
-   * Pointer to previous item in the list
+   * Source peer of this trail.
    */
-  struct P2PPendingMessage *prev;
+  struct GNUNET_PeerIdentity source_peer;
 
   /**
-   * When does this message time out?
-   */
-  struct GNUNET_TIME_Absolute timeout;
-
-   /**
-   * Message importance level.  FIXME: used? useful?
+   * Trail from source_peer to destination_peer compressed such that
+   * new_first_friend is the first hop in the trail from source to
+   * destination.
    */
-  unsigned int importance;
+  struct GNUNET_PeerIdentity new_first_friend;
 
   /**
-   * Actual message to be sent, allocated at the end of the struct:
-   * // msg = (cast) &pm[1];
-   * // memcpy (&pm[1], data, len);
+   * Unique identifier of trail.
    */
-  const struct GNUNET_MessageHeader *msg;
-
+  struct GNUNET_HashCode trail_id;
 };
 
 
 /**
- * Linked List of peers which are part of trail to reach a particular Finger.
+ * P2P Trail Tear Down message.
  */
-struct TrailPeerList
+struct PeerTrailTearDownMessage
 {
-   /**
-    * Pointer to next item in the list
-    */
-   struct TrailPeerList *next;
+  /**
+   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_TEARDOWN
+   */
+  struct GNUNET_MessageHeader header;
 
-   /**
-    * Pointer to previous item in the list
-    */
-   struct TrailPeerList *prev;
-   
-   /**
-    * An element in this trail list
-    */
-   struct GNUNET_PeerIdentity peer;
-  
+  /**
+   * Unique identifier of the trail.
+   */
+  struct GNUNET_HashCode trail_id;
+
+  /**
+   * Direction of trail.
+   */
+  uint32_t trail_direction;
 };
 
 
-/** 
- *  Entry in friend_peermap.
+/**
+ * P2P Trail Rejection Message.
  */
-struct FriendInfo
+struct PeerTrailRejectionMessage
 {
   /**
-   * Friend Identity 
+   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_SETUP_REJECTION
    */
-  struct GNUNET_PeerIdentity id;
+  struct GNUNET_MessageHeader header;
 
   /**
-   * Number of trail of which this friend is the first hop.
+   * Peer which wants to set up the trail.
    */
-  unsigned int trail_links;
-  
+  struct GNUNET_PeerIdentity source_peer;
+
   /**
-   * Count of outstanding messages for this friend.
+   * Peer which sent trail rejection message as it it congested. 
    */
-  unsigned int pending_count;
-  
+  struct GNUNET_PeerIdentity congested_peer;
+
   /**
-   * Head of pending messages to be sent to this friend.
+   * Peer identity closest to this value will be finger of
+   * source_peer.
    */
-  struct P2PPendingMessage *head;
+  uint64_t ultimate_destination_finger_value;
 
   /**
-   * Tail of pending messages to be sent to this friend.
+   * Is source_peer trying to setup the trail to its predecessor or finger.
    */
-  struct P2PPendingMessage *tail;
+  uint32_t is_predecessor;
+
+  /**
+   * Identifier for the trail that source peer is trying to setup.
+   */
+  struct GNUNET_HashCode trail_id;
+  
+  /**
+   * Relative time for which congested_peer will remain congested.
+   */
+  struct GNUNET_TIME_Relative congestion_time;
+
+  /* Trail_list from source_peer to peer which sent the message for trail setup
+   * to congested peer. This trail does NOT include source_peer.
+   struct GNUNET_PeerIdnetity trail[]*/
+};
+
+/**
+ * P2P Add Trail Message.
+ */
+struct PeerAddTrailMessage
+{
+  /**
+   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_ADD_TRAIL
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Source of the routing trail.
+   */
+  struct GNUNET_PeerIdentity source_peer;
+
+  /**
+   * Destination of the routing trail.
+   */
+  struct GNUNET_PeerIdentity destination_peer;
+
+  /**
+   * Unique identifier of the trail from source_peer to destination_peer,
+   * NOT including the endpoints.
+   */
+  struct GNUNET_HashCode trail_id;
+
+  /* Trail from source peer to destination peer, NOT including them.
+   * struct GNUNET_PeerIdentity trail[]
+   */
+};
+
+GNUNET_NETWORK_STRUCT_END
+
+/**
+ * Linked list of messages to send to a particular other peer.
+ */
+struct P2PPendingMessage
+{
+  /**
+   * Pointer to next item in the list
+   */
+  struct P2PPendingMessage *next;
+
+  /**
+   * Pointer to previous item in the list
+   */
+  struct P2PPendingMessage *prev;
+
+  /**
+   * Message importance level.  FIXME: used? useful?
+   */
+  unsigned int importance;
+
+  /**
+   * When does this message time out?
+   */
+  struct GNUNET_TIME_Absolute timeout;
+
+  /**
+   * Actual message to be sent, allocated at the end of the struct:
+   * // msg = (cast) &pm[1];
+   * // memcpy (&pm[1], data, len);
+   */
+  const struct GNUNET_MessageHeader *msg;
+
+};
+
+/**
+ *  Entry in friend_peermap.
+ */
+struct FriendInfo
+{
+  /**
+   * Friend Identity
+   */
+  struct GNUNET_PeerIdentity id;
+
+  /**
+   * Number of trails for which this friend is the first hop or if the friend
+   * is finger. 
+   */
+  unsigned int trails_count;
+
+  /**
+   * Count of outstanding messages for this friend.
+   */
+  unsigned int pending_count;
+
+  /**
+   * In case not 0, then amount of time for which this friend is congested.
+   */
+  struct GNUNET_TIME_Absolute congestion_timestamp;
+
+  /**
+   * Head of pending messages to be sent to this friend.
+   */
+  struct P2PPendingMessage *head;
+
+  /**
+   * Tail of pending messages to be sent to this friend.
+   */
+  struct P2PPendingMessage *tail;
+
   /**
    * Core handle for sending messages to this friend.
    */
@@ -629,97 +689,154 @@ struct FriendInfo
 
 };
 
+/**
+ * An individual element of the trail to reach to a finger.
+ */
+struct Trail_Element 
+{
+  /**
+    * Pointer to next item in the list
+    */
+  struct Trail_Element *next;
+
+  /**
+    * Pointer to prev item in the list
+    */
+  struct Trail_Element *prev;
+
+  /**
+   * An element in this trail.
+   */
+  struct GNUNET_PeerIdentity peer;
+};
 
 /**
- * Entry in finger_peermap.
+ * FIXME: removed first_friend_trails_count, need to write a function
+ * to calculate each time we need it. Else, keep a pointer to first
+ * friend of in the trail. 
+ * Information about an individual trail. 
  */
-struct FingerInfo
+struct Trail 
 {
   /**
-   * Finger identity.
+   * Head of trail.
    */
-  struct GNUNET_PeerIdentity finger_identity;
-  
+  struct Trail_Element *trail_head;
+
   /**
-   * Index in finger peer map
+   * Tail of trail.
    */
-  unsigned int finger_map_index;
-  
+  struct Trail_Element *trail_tail;
+
   /**
-   * Total number of entries in trail from (me,finger] 
+   * Unique identifier of this trail.
    */
-  unsigned int trail_length;
-  
+  struct GNUNET_HashCode trail_id;
+
   /**
-   * Head of trail to reach this finger.
+   * Length of trail pointed
    */
-  struct TrailPeerList *head;
+  unsigned int trail_length;
   
   /**
-   * Tail of trail to reach this finger.
+   * Is there a valid trail entry. 
    */
-  struct TrailPeerList *tail;
-  
+  unsigned int is_present;
 };
 
-
 /**
- * FIXME: Think of a better name. 
- * Data structure passed to sorting algorithm in find_successor.
+ * An entry in finger_table
  */
-struct Sorting_List
+struct FingerInfo
 {
   /**
-   * 64 bit value of peer identity
+   * Finger identity.
    */
-  uint64_t peer_id;
-  
+  struct GNUNET_PeerIdentity finger_identity;
+
   /**
-   * Type : MY_ID, FINGER, FINGER, Value 
+   * Is any finger stored at this finger index. 
    */
-  enum current_destination_type type;
+  unsigned int is_present;
   
   /**
-   * Pointer to original data structure linked to peer id.
+   * Index in finger peer map
+   */
+  uint32_t finger_table_index;
+
+  /**
+   * Number of trails setup so far for this finger.
+   * Should not cross MAXIMUM_TRAILS_PER_FINGER.
+   */
+  uint32_t trails_count;
+
+  /**
+   * Array of trails to reach to this finger.
    */
-  void *data;
+  struct Trail trail_list[MAXIMUM_TRAILS_PER_FINGER]; 
 };
 
 
 /**
- * FIXME: Think of better comments.
- * An entry in Failed_Trail_List
+ * Data structure to keep track of closest peer seen so far in find_successor()
  */
-struct FailedTrail
+struct Closest_Peer
 {
   /**
-   * Source peer which was trying to setup up the trail to @a destination_finger_value
+   * Destination finger vaule. 
    */
-  struct GNUNET_PeerIdentity source_peer;
+  uint64_t destination_finger_value;
   
   /**
-   * Value to which we were trying to find the closest successor.
+   * Is finger value predecessor or any other finge 
    */
-  uint64_t destination_finger_value;
+  unsigned int is_predecessor;
   
   /**
-   * Peer which has crossed the threshold limit on its routing table size.
+   * Trail id to reach to peer.
    */
-  struct GNUNET_PeerIdentity congested_peer;
-  
-};
+  struct GNUNET_HashCode trail_id;
 
+  /**
+   * FIXME: see the usage of this field and write comment. 
+   */
+  struct GNUNET_PeerIdentity next_hop;
+
+  /**
+   * Next destination. In case of friend and my_identity , it is same as next_hop
+   * In case of finger it is finger identity.
+   */
+  struct GNUNET_PeerIdentity best_known_destination;
+};
 
 /**
- * Task that sends FIND FINGER TRAIL requests.
+ * FIXME: now I have removed the first_friend_trail_count,
+ * Need to update the code to find the count.
+ * Data structure to store the trail chosen to reach to finger.
  */
-static GNUNET_SCHEDULER_TaskIdentifier find_finger_trail_task;
+struct Selected_Finger_Trail
+{
+  /**
+   * First friend in the trail to reach finger.
+   */
+  struct FriendInfo friend;
+
+  /**
+   * Identifier of this trail.
+   */
+  struct GNUNET_HashCode trail_id;
+
+  /**
+   * Total number of peers in this trail.
+   */
+  unsigned int trail_length;
+};
 
 /**
- * 
- * Task that periodically verifies my successor. 
+ * Task that sends FIND FINGER TRAIL requests. This task is started when we have
+ * get our first friend.
  */
-static GNUNET_SCHEDULER_TaskIdentifier verify_successor;
+static GNUNET_SCHEDULER_TaskIdentifier find_finger_trail_task;
 
 /**
  * Identity of this peer.
@@ -727,19 +844,14 @@ static GNUNET_SCHEDULER_TaskIdentifier verify_successor;
 static struct GNUNET_PeerIdentity my_identity;
 
 /**
- * Hash map of all the friends of a peer
+ * Peer map of all the friends of a peer
  */
 static struct GNUNET_CONTAINER_MultiPeerMap *friend_peermap;
 
 /**
- * Hash map of all the fingers of a peer
- */
-static struct GNUNET_CONTAINER_MultiPeerMap *finger_peermap;
-
-/**
- * Hash maps of all the trail which failed due to a congested peer. 
+ * Array of all the fingers. 
  */
-static struct GNUNET_CONTAINER_MultiPeerMap *failed_trail_list;
+static struct FingerInfo finger_table [MAX_FINGERS];
 
 /**
  * Handle to CORE.
@@ -747,10 +859,12 @@ static struct GNUNET_CONTAINER_MultiPeerMap *failed_trail_list;
 static struct GNUNET_CORE_Handle *core_api;
 
 /**
- * FIXME: Is it safe to assume its initialized to 0 by default.
- * The current finger index that we have found trail to.
+ * The current finger index that we have want to find trail to. We start the
+ * search with value = 0, i.e. successor  and then go to PREDCESSOR_FINGER_ID
+ * and decrement it. For any index 63 <= index < 0, if finger is same as successor,
+ * we reset this index to 0.
  */
-static unsigned int current_finger_index;
+static unsigned int current_search_finger_index;
 
 
 /**
@@ -770,13 +884,13 @@ core_transmit_notify (void *cls, size_t size, void *buf)
   struct P2PPendingMessage *pending;
   size_t off;
   size_t msize;
-  
+
   peer->th = NULL;
   while ((NULL != (pending = peer->head)) &&
          (0 == GNUNET_TIME_absolute_get_remaining (pending->timeout).rel_value_us))
   {
     peer->pending_count--;
-    GNUNET_CONTAINER_DLL_remove (peer->head, peer->tail, pending);  
+    GNUNET_CONTAINER_DLL_remove (peer->head, peer->tail, pending);
     GNUNET_free (pending);
   }
   if (NULL == pending)
@@ -820,6 +934,7 @@ core_transmit_notify (void *cls, size_t size, void *buf)
                                            &core_transmit_notify, peer);
     GNUNET_break (NULL != peer->th);
   }
+
   return off;
 }
 
@@ -833,18 +948,17 @@ static void
 process_friend_queue (struct FriendInfo *peer)
 {
   struct P2PPendingMessage *pending;
-  
+
   if (NULL == (pending = peer->head))
     return;
   if (NULL != peer->th)
     return;
-  
+
   GNUNET_STATISTICS_update (GDS_stats,
                             gettext_noop
                             ("# Bytes of bandwidth requested from core"),
                             ntohs (pending->msg->size), GNUNET_NO);
-  
-  /* FIXME: Are we correctly initializing importance and pending. */
+
   peer->th =
       GNUNET_CORE_notify_transmit_ready (core_api, GNUNET_NO,
                                          pending->importance,
@@ -856,68 +970,86 @@ process_friend_queue (struct FriendInfo *peer)
 }
 
 
-/**FIXME: add better comment for current_source which shows its relation
- * with current_destination. 
- * Construct a trail message and forward it to a friend. 
- * @param source_peer Peer which wants to set up the trail to one of its finger.
- * @param destination_finger Value whose successor we are searching the network.
- * @param current_destination Peer which gets this message. 
- * @param current_source Peer for which current_destination is its finger.
- * @param target_friend Current friend to which this message should be forwarded.
- * @param trail_length Numbers of peers in the trail.
- * @param trail_peer_list peers this request has traversed so far  
- * @param finger_map_index Index in finger peer map
- * @param type Type of current destination can be either FRIEND or FINGER
+/**
+ * Return friend corresponding to peer.
+ * @param peer
+ * @return  Friend
+ */
+struct FriendInfo *
+GDS_NEIGHBOURS_get_friend (struct GNUNET_PeerIdentity peer)
+{
+  struct FriendInfo *friend;
+  GNUNET_assert (NULL != (friend = 
+          GNUNET_CONTAINER_multipeermap_get (friend_peermap, &peer)));
+  return friend;
+}
+
+
+/**
+ * Construct a trail setup message and forward it to target_friend
+ * @param source_peer Peer which wants to setup the trail
+ * @param ultimate_destination_finger_value Peer identity closest to this value 
+ *                                          will be finger to @a source_peer
+ * @param best_known_destination Best known destination (could be finger or friend)
+ *                               which should get this message.
+ * @param target_friend Friend to which message is forwarded now.
+ * @param trail_length Total number of peers in trail setup so far.
+ * @param trail_peer_list Trail setup so far
+ * @param is_predecessor Is source_peer looking for trail to a predecessor or not.
+ * @param trail_id Unique identifier for the trail we are trying to setup.
+ * @param intermediate_trail_id Trail id of intermediate trail to reach to 
+ *                              best_known_destination when its a finger. If not 
+ *                              used then set to 0.
  */
 void
-GDS_NEIGHBOURS_send_trail_setup (struct GNUNET_PeerIdentity *source_peer,
-                                 uint64_t destination_finger,
-                                 struct GNUNET_PeerIdentity *current_destination,
-                                 struct GNUNET_PeerIdentity *current_source,
+GDS_NEIGHBOURS_send_trail_setup (struct GNUNET_PeerIdentity source_peer,
+                                 uint64_t ultimate_destination_finger_value,
+                                 struct GNUNET_PeerIdentity best_known_destination,
                                  struct FriendInfo *target_friend,
                                  unsigned int trail_length,
-                                 struct GNUNET_PeerIdentity *trail_peer_list,
-                                 unsigned int finger_map_index,
-                                 enum current_destination_type type)
+                                 const struct GNUNET_PeerIdentity *trail_peer_list,
+                                 unsigned int is_predecessor,
+                                 struct GNUNET_HashCode trail_id,
+                                 struct GNUNET_HashCode *intermediate_trail_id)
 {
   struct P2PPendingMessage *pending;
   struct PeerTrailSetupMessage *tsm;
   struct GNUNET_PeerIdentity *peer_list;
   size_t msize;
-  
-  msize = sizeof (struct PeerTrailSetupMessage) + 
+
+  msize = sizeof (struct PeerTrailSetupMessage) +
           (trail_length * sizeof (struct GNUNET_PeerIdentity));
-  
+
   if (msize >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
   {
     GNUNET_break (0);
     return;
   }
-  
+
   if (target_friend->pending_count >= MAXIMUM_PENDING_PER_FRIEND)
-  {  
+  {
     GNUNET_STATISTICS_update (GDS_stats, gettext_noop ("# P2P messages dropped due to full queue"),
                                1, GNUNET_NO);
   }
-  
-  pending = GNUNET_malloc (sizeof (struct P2PPendingMessage) + msize); 
-  pending->importance = 0;    /* FIXME */
+
+  pending = GNUNET_malloc (sizeof (struct P2PPendingMessage) + msize);
   pending->timeout = GNUNET_TIME_relative_to_absolute (GET_TIMEOUT);
-  tsm = (struct PeerTrailSetupMessage *) &pending[1]; 
+  tsm = (struct PeerTrailSetupMessage *) &pending[1];
   pending->msg = &tsm->header;
   tsm->header.size = htons (msize);
   tsm->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_SETUP);
-  memcpy (&(tsm->destination_finger), &destination_finger, sizeof (uint64_t));
-  memcpy (&(tsm->source_peer), source_peer, sizeof (struct GNUNET_PeerIdentity));
-  memcpy (&(tsm->current_destination), current_destination, sizeof (struct GNUNET_PeerIdentity));
-  /* FIXME: Is it correct to use NULL here for comparison? */
-  if (current_source != NULL)
-    memcpy (&(tsm->current_source), current_source, sizeof (struct GNUNET_PeerIdentity));
-  tsm->current_destination_type = htonl (type); 
-  tsm->trail_length = htonl (trail_length); 
-  tsm->finger_map_index = htonl (finger_map_index);
-  
-  if (trail_peer_list != NULL)
+  tsm->final_destination_finger_value = GNUNET_htonll (ultimate_destination_finger_value);
+  tsm->source_peer = source_peer;
+  tsm->best_known_destination = best_known_destination;
+  tsm->is_predecessor = htonl (is_predecessor);
+  tsm->trail_id = trail_id;
+  
+  if (NULL == intermediate_trail_id)
+    memset (&tsm->intermediate_trail_id, 0, sizeof (tsm->intermediate_trail_id));
+  else
+    tsm->intermediate_trail_id = *intermediate_trail_id;
+  
+  if (trail_length > 0)
   {
     peer_list = (struct GNUNET_PeerIdentity *) &tsm[1];
     memcpy (peer_list, trail_peer_list, trail_length * sizeof(struct GNUNET_PeerIdentity));
@@ -926,64 +1058,71 @@ GDS_NEIGHBOURS_send_trail_setup (struct GNUNET_PeerIdentity *source_peer,
   GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
   target_friend->pending_count++;
   process_friend_queue (target_friend);
-  
 }
 
 
 /**
- * Construct a trail setup result message and forward it to a friend. 
- * @param destination_peer Peer which will get the trail to one of its finger.
- * @param source_finger Peer to which the trail has been setup to.
+ * Construct a trail setup result message and forward it to target friend.
+ * @param querying_peer Peer which sent the trail setup request and should get
+ *                      the result back. 
+ * @param Finger Peer to which the trail has been setup to.
  * @param target_friend Friend to which this message should be forwarded.
  * @param trail_length Numbers of peers in the trail.
- * @param trail_peer_list Peers which are part of the trail from source to destination.
- * @param current_trail_index Index at which sender of this message is located.  
- * @param finger_map_index Index in finger peer map 
+ * @param trail_peer_list Peers which are part of the trail from q
+ *                        querying_peer to Finger, NOT including them. 
+ * @param is_predecessor Is @a Finger predecessor to @a querying_peer
+ * @param ultimate_destination_finger_value Value to which @a finger is the closest
+ *                                          peer. 
+ * @param trail_id Unique identifier of the trail.
  */
 void
-GDS_NEIGHBOURS_send_trail_setup_result (struct GNUNET_PeerIdentity *destination_peer,
-                                        struct GNUNET_PeerIdentity *source_finger,
+GDS_NEIGHBOURS_send_trail_setup_result (struct GNUNET_PeerIdentity querying_peer,
+                                        struct GNUNET_PeerIdentity finger,
                                         struct FriendInfo *target_friend,
                                         unsigned int trail_length,
-                                        struct GNUNET_PeerIdentity *trail_peer_list,
-                                        unsigned int current_trail_index,
-                                        unsigned int finger_map_index)
+                                        const struct GNUNET_PeerIdentity *trail_peer_list,
+                                        unsigned int is_predecessor,
+                                        uint64_t ultimate_destination_finger_value,
+                                        struct GNUNET_HashCode trail_id)
 {
   struct P2PPendingMessage *pending;
   struct PeerTrailSetupResultMessage *tsrm;
   struct GNUNET_PeerIdentity *peer_list;
   size_t msize;
-  
-  msize = sizeof (struct PeerTrailSetupResultMessage) + 
+
+  msize = sizeof (struct PeerTrailSetupResultMessage) +
           (trail_length * sizeof (struct GNUNET_PeerIdentity));
-  
+
   if (msize >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
   {
     GNUNET_break (0);
     return;
   }
-  
+
   if (target_friend->pending_count >= MAXIMUM_PENDING_PER_FRIEND)
-  {  
+  {
     GNUNET_STATISTICS_update (GDS_stats, gettext_noop ("# P2P messages dropped due to full queue"),
                                1, GNUNET_NO);
   }
 
-  pending = GNUNET_malloc (sizeof (struct P2PPendingMessage) + msize); 
-  pending->importance = 0;    
+  pending = GNUNET_malloc (sizeof (struct P2PPendingMessage) + msize);
+  pending->importance = 0;
   pending->timeout = GNUNET_TIME_relative_to_absolute (GET_TIMEOUT);
-  tsrm = (struct PeerTrailSetupResultMessage *) &pending[1]; 
+  tsrm = (struct PeerTrailSetupResultMessage *) &pending[1];
   pending->msg = &tsrm->header;
   tsrm->header.size = htons (msize);
   tsrm->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_SETUP_RESULT);
-  memcpy (&(tsrm->destination_peer), destination_peer, sizeof (struct GNUNET_PeerIdentity));
-  memcpy (&(tsrm->finger_identity), source_finger, sizeof (struct GNUNET_PeerIdentity));
-  tsrm->trail_length = htonl (trail_length);
-  tsrm->current_index = htonl (current_trail_index);
-  tsrm->finger_map_index = htonl (finger_map_index);
+  tsrm->querying_peer = querying_peer;
+  tsrm->finger_identity = finger;
+  tsrm->is_predecessor = htonl (is_predecessor);
+  tsrm->trail_id = trail_id;
+  tsrm->ulitmate_destination_finger_value = 
+          GNUNET_htonll (ultimate_destination_finger_value);
   peer_list = (struct GNUNET_PeerIdentity *) &tsrm[1];
-  memcpy (peer_list, trail_peer_list, trail_length * sizeof (struct GNUNET_PeerIdentity));
-  
+  if (trail_length > 0)
+  {
+    memcpy (peer_list, trail_peer_list, trail_length * sizeof (struct GNUNET_PeerIdentity));
+  }
   /* Send the message to chosen friend. */
   GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
   target_friend->pending_count++;
@@ -992,121 +1131,133 @@ GDS_NEIGHBOURS_send_trail_setup_result (struct GNUNET_PeerIdentity *destination_
 
 
 /**
- * Construct a PeerVerifySuccessor message and send it to friend.
- * @param source_peer Peer which wants to verify its successor
- * @param successor Peer which is our current successor
- * @param target_friend Friend to which this message should be forwarded.
- * @param trail_peer_list Peer which are part of trail from source to destination
- * @param trail_length Number of peers in the trail list.
- * @param current_trail_index Index in the trial list at which receiving peer should
- *                            read the next element.
- */
-void GDS_NEIGHBOURS_send_verify_successor(struct GNUNET_PeerIdentity *source_peer,
-                                          struct GNUNET_PeerIdentity *successor,
-                                          struct FriendInfo *target_friend,
-                                          struct GNUNET_PeerIdentity *trail_peer_list,
-                                          unsigned int trail_length,
-                                          unsigned int current_trail_index)
+ * Send trail rejection message to target friend
+ * @param source_peer Peer which is trying to setup the trail.
+ * @param ultimate_destination_finger_value Peer closest to this value will be 
+ *                                          @a source_peer's finger
+ * @param congested_peer Peer which sent this message as it is congested.
+ * @param is_predecessor Is source_peer looking for trail to a predecessor or not.
+ * @param trail_peer_list Trails seen so far in trail setup before getting rejected
+ *                        by congested_peer. This does not include @a source_peer
+ * @param trail_length Total number of peers in trail_peer_list, not including
+ *                     @a source_peer
+ * @param trail_id Unique identifier of this trail.
+ * @param congestion_timeout Duration given by congested peer as an estimate of
+ *                           how long it may remain congested.
+ */
+void
+GDS_NEIGHBOURS_send_trail_rejection (struct GNUNET_PeerIdentity source_peer,
+                                     uint64_t ultimate_destination_finger_value,
+                                     struct GNUNET_PeerIdentity congested_peer,
+                                     unsigned int is_predecessor,
+                                     const struct GNUNET_PeerIdentity *trail_peer_list,
+                                     unsigned int trail_length,
+                                     struct GNUNET_HashCode trail_id,
+                                     struct FriendInfo *target_friend,
+                                     const struct GNUNET_TIME_Relative congestion_timeout)
 {
-  struct PeerVerifySuccessorMessage *vsm;
+  struct PeerTrailRejectionMessage *trm;
   struct P2PPendingMessage *pending;
   struct GNUNET_PeerIdentity *peer_list;
   size_t msize;
-  
-  msize = sizeof (struct PeerVerifySuccessorMessage) + 
+
+  msize = sizeof (struct PeerTrailRejectionMessage) +
           (trail_length * sizeof (struct GNUNET_PeerIdentity));
-  
+
   if (msize >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
   {
     GNUNET_break (0);
     return;
   }
+
   if (target_friend->pending_count >= MAXIMUM_PENDING_PER_FRIEND)
-  {  
+  {
     GNUNET_STATISTICS_update (GDS_stats, gettext_noop ("# P2P messages dropped due to full queue"),
                                1, GNUNET_NO);
   }
-  
-  pending = GNUNET_malloc (sizeof (struct P2PPendingMessage) + msize); 
-  pending->importance = 0;    /* FIXME */
+
+  pending = GNUNET_malloc (sizeof (struct P2PPendingMessage) + msize);
+  pending->importance = 0;
   pending->timeout = GNUNET_TIME_relative_to_absolute (GET_TIMEOUT);
-  vsm = (struct PeerVerifySuccessorMessage *) &pending[1];
-  pending->msg = &vsm->header;
-  vsm->header.size = htons (msize);
-  vsm->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_P2P_VERIFY_SUCCESSOR);
-  memcpy (&(vsm->successor), successor, sizeof (struct GNUNET_PeerIdentity));
-  memcpy (&(vsm->source_peer), source_peer, sizeof (struct GNUNET_PeerIdentity));
-  vsm->trail_length = htonl (trail_length);
-  vsm->current_trail_index = htonl (current_trail_index);
-  peer_list = (struct GNUNET_PeerIdentity *) &vsm[1];
-  memcpy (peer_list, trail_peer_list, trail_length * sizeof (struct GNUNET_PeerIdentity));
+  trm = (struct PeerTrailRejectionMessage *)&pending[1];
+  pending->msg = &trm->header;
+  trm->header.size = htons (msize);
+  trm->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_SETUP_REJECTION);
+  trm->source_peer = source_peer;
+  trm->congested_peer = congested_peer;
+  trm->congestion_time = congestion_timeout;
+  trm->is_predecessor = htonl (is_predecessor);
+  trm->trail_id = trail_id;
+  trm->ultimate_destination_finger_value = GNUNET_htonll (ultimate_destination_finger_value);
+
+  peer_list = (struct GNUNET_PeerIdentity *) &trm[1];
+  if (trail_length > 0)
+  {
+    memcpy (peer_list, trail_peer_list, trail_length * sizeof (struct GNUNET_PeerIdentity));
+  }
   
   /* Send the message to chosen friend. */
   GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
   target_friend->pending_count++;
   process_friend_queue (target_friend);
-  
 }
 
 
 /**
- * Construct a PeerVerifySuccessorResult message and send it to friend.
- * @param destination_peer Peer which sent verify successor message
- * @param source_successor Peer to which verify successor message was sent.
- * @param my_predecessor source_successor's predecessor.
- * @param target_friend Friend to which this message should be forwarded.
- * @param trail_peer_list Peers which are part of trail from source to destination
- * @param trail_length Number of peers in the trail list.
- * @param current_trail_index Index in the trial list at which receiving peer should
- *                            get the next element.
- */
-void GDS_NEIGHBOURS_send_verify_successor_result (struct GNUNET_PeerIdentity *destination_peer,
-                                                  struct GNUNET_PeerIdentity *source_successor,
-                                                  struct GNUNET_PeerIdentity *my_predecessor,
-                                                  struct FriendInfo *target_friend,
-                                                  struct GNUNET_PeerIdentity *trail_peer_list,
-                                                  unsigned int trail_length,
-                                                  unsigned int current_trail_index)
+ * Construct a verify successor message and forward it to target_friend.
+ * @param source_peer Peer which wants to verify its successor.
+ * @param successor Peer which is @a source_peer's current successor.
+ * @param trail_id Unique Identifier of trail from @a source_peer to @a successor,
+ *                 NOT including them. 
+ * @param trail List of peers which are part of trail to reach from @a source_peer
+ *              to @a successor, NOT including them. 
+ * @param trail_length Total number of peers in @a trail.
+ * @param target_friend Next friend to get this message. 
+ */
+void
+GDS_NEIGHBOURS_send_verify_successor_message (struct GNUNET_PeerIdentity source_peer,
+                                              struct GNUNET_PeerIdentity successor,
+                                              struct GNUNET_HashCode trail_id,
+                                              struct GNUNET_PeerIdentity *trail,
+                                              unsigned int trail_length,
+                                              struct FriendInfo *target_friend)
 {
-  struct PeerVerifySuccessorResultMessage *vsmr;
+  struct PeerVerifySuccessorMessage *vsm;
   struct P2PPendingMessage *pending;
   struct GNUNET_PeerIdentity *peer_list;
   size_t msize;
-  
-  msize = sizeof (struct PeerVerifySuccessorResultMessage) + 
-          (trail_length * sizeof(struct GNUNET_PeerIdentity));
-  
+
+  msize = sizeof (struct PeerVerifySuccessorMessage);
   if (msize >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
   {
     GNUNET_break (0);
     return;
   }
-  
-  
+
   if (target_friend->pending_count >= MAXIMUM_PENDING_PER_FRIEND)
-  {  
+  {
     GNUNET_STATISTICS_update (GDS_stats, gettext_noop ("# P2P messages dropped due to full queue"),
                                1, GNUNET_NO);
   }
 
-  pending = GNUNET_malloc (sizeof (struct P2PPendingMessage) + msize); 
+  pending = GNUNET_malloc (sizeof (struct P2PPendingMessage) + msize);
   pending->importance = 0;    /* FIXME */
   pending->timeout = GNUNET_TIME_relative_to_absolute (GET_TIMEOUT);
-  vsmr = (struct PeerVerifySuccessorResultMessage *) &pending[1];
-  pending->msg = &vsmr->header;
-  vsmr->header.size = htons (msize);
-  vsmr->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_P2P_VERIFY_SUCCESSOR_RESULT);
-  memcpy (&(vsmr->destination_peer), destination_peer, sizeof (struct GNUNET_PeerIdentity));
-  memcpy (&(vsmr->source_successor), source_successor, sizeof (struct GNUNET_PeerIdentity));
-  memcpy (&(vsmr->my_predecessor), my_predecessor, sizeof (struct GNUNET_PeerIdentity));
-  vsmr->trail_length = htonl (trail_length);
-  vsmr->current_index = htonl (current_trail_index);
-  
-  peer_list = (struct GNUNET_PeerIdentity *) &vsmr[1];
-  memcpy (peer_list, trail_peer_list, trail_length * sizeof (struct GNUNET_PeerIdentity));
-  
-   /* Send the message to chosen friend. */
+  vsm = (struct PeerVerifySuccessorMessage *) &pending[1];
+  pending->msg = &vsm->header;
+  vsm->header.size = htons (msize);
+  vsm->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_P2P_VERIFY_SUCCESSOR);
+  vsm->source_peer = source_peer;
+  vsm->successor = successor;
+  vsm->trail_id = trail_id;
+  
+  if (trail_length > 0)
+  {
+    peer_list = (struct GNUNET_PeerIdentity *) &vsm[1];
+    memcpy (peer_list, trail, trail_length * sizeof (struct GNUNET_PeerIdentity));
+  }
+
+  /* Send the message to chosen friend. */
   GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
   target_friend->pending_count++;
   process_friend_queue (target_friend);
@@ -1114,57 +1265,189 @@ void GDS_NEIGHBOURS_send_verify_successor_result (struct GNUNET_PeerIdentity *de
 
 
 /**
- * Construct a PeerNotifyNewSuccessor message and send it to friend.
- * @param source_peer Peer which is sending notify message to its new successor.
- * @param destination_peer Peer which is the new destination.
- * @param target_friend Next friend to pass this message to. 
- * @param peer_list List of peers in the trail to reach to destination_peer.
- * @param current_trail_index Index of peer_list for next target friend position. 
- * @param trail_length Total number of peers in peer list 
+ * FIXME: In every function we pass target friend except for this one.
+ * so, either change everything or this one. also, should se just store
+ * the pointer to friend in routing table rather than gnunet_peeridentity.
+ * if yes then we should keep friend info in.h  andmake lot of changes. 
+ * Construct a trail teardown message and forward it to target friend. 
+ * @param trail_id Unique identifier of the trail.
+ * @param trail_direction Direction of trail.
+ * @param target_friend Friend to get this message.
  */
-void 
-GDS_NEIGHBOURS_send_notify_new_successor (struct GNUNET_PeerIdentity *source_peer,
-                                          struct GNUNET_PeerIdentity *destination_peer,
-                                          struct FriendInfo *target_friend,
-                                          struct GNUNET_PeerIdentity *trail_peer_list,
-                                          unsigned int trail_length,
-                                          unsigned int current_trail_index)
+void
+GDS_NEIGHBOURS_send_trail_teardown (struct GNUNET_HashCode trail_id,
+                                    unsigned int trail_direction,
+                                    struct GNUNET_PeerIdentity *peer)
 {
-  struct PeerNotifyNewSuccessorMessage *nsm;
+  struct PeerTrailTearDownMessage *ttdm;
   struct P2PPendingMessage *pending;
-  struct GNUNET_PeerIdentity *peer_list;
+  struct FriendInfo *target_friend;
   size_t msize;
+
+  msize = sizeof (struct PeerTrailTearDownMessage);
+
+  if (msize >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
+  {
+    GNUNET_break (0);
+    return;
+  }
   
-  msize = sizeof (struct PeerNotifyNewSuccessorMessage) + 
-          (trail_length * sizeof(struct GNUNET_PeerIdentity));
+  GNUNET_assert (NULL != (target_friend = 
+                GNUNET_CONTAINER_multipeermap_get (friend_peermap, peer)));
+  
+  if (target_friend->pending_count >= MAXIMUM_PENDING_PER_FRIEND)
+  {
+    GNUNET_STATISTICS_update (GDS_stats, gettext_noop ("# P2P messages dropped due to full queue"),
+                               1, GNUNET_NO);
+  }
+
+  pending = GNUNET_malloc (sizeof (struct P2PPendingMessage) + msize);
+  pending->importance = 0;    /* FIXME */
+  pending->timeout = GNUNET_TIME_relative_to_absolute (GET_TIMEOUT);
+  ttdm = (struct PeerTrailTearDownMessage *) &pending[1];
+  pending->msg = &ttdm->header;
+  ttdm->header.size = htons (msize);
+  ttdm->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_TEARDOWN);
+  ttdm->trail_id = trail_id;
+  ttdm->trail_direction = htonl (trail_direction);
+
+  /* Send the message to chosen friend. */
   
+  GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
+  target_friend->pending_count++;
+  process_friend_queue (target_friend);
+}
+
+
+/**
+ * Construct a verify successor result message and send it to target_friend
+ * @param querying_peer Peer which sent the verify successor message. 
+ * @param source_successor Current_successor of @a querying_peer. 
+ * @param current_predecessor Current predecessor of @a successor. Could be same
+ *                            or different from @a querying_peer.
+ * @param trail_id Unique identifier of the trail from @a querying_peer to 
+ *                 @a successor, NOT including them.
+ * @param trail List of peers which are part of trail from @a querying_peer to 
+ *                 @a successor, NOT including them.
+ * @param trail_length Total number of peers in @a trail
+ * @param trail_direction Direction in which we are sending the message. In this
+ *                        case we are sending result from @a successor to @a querying_peer.
+ * @param target_friend Next friend to get this message. 
+ */
+void
+GDS_NEIGHBOURS_send_verify_successor_result (struct GNUNET_PeerIdentity querying_peer,
+                                             struct GNUNET_PeerIdentity current_successor,
+                                             struct GNUNET_PeerIdentity probable_successor,
+                                             struct GNUNET_HashCode trail_id,
+                                             const struct GNUNET_PeerIdentity *trail,
+                                             unsigned int trail_length,
+                                             enum GDS_ROUTING_trail_direction trail_direction,
+                                             struct FriendInfo *target_friend)
+{
+  struct PeerVerifySuccessorResultMessage *vsmr;
+  struct P2PPendingMessage *pending;
+  struct GNUNET_PeerIdentity *peer_list;
+  size_t msize;
+
+  msize = sizeof (struct PeerVerifySuccessorResultMessage) +
+          (trail_length * sizeof(struct GNUNET_PeerIdentity));
+
   if (msize >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
   {
     GNUNET_break (0);
     return;
   }
-  
+
   if (target_friend->pending_count >= MAXIMUM_PENDING_PER_FRIEND)
-  {  
+  {
     GNUNET_STATISTICS_update (GDS_stats, gettext_noop ("# P2P messages dropped due to full queue"),
                                1, GNUNET_NO);
   }
+
+  pending = GNUNET_malloc (sizeof (struct P2PPendingMessage) + msize);
+  pending->importance = 0;    /* FIXME */
+  pending->timeout = GNUNET_TIME_relative_to_absolute (GET_TIMEOUT);
+  vsmr = (struct PeerVerifySuccessorResultMessage *) &pending[1];
+  pending->msg = &vsmr->header;
+  vsmr->header.size = htons (msize);
+  vsmr->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_P2P_VERIFY_SUCCESSOR_RESULT);
+  vsmr->querying_peer = querying_peer;
+  vsmr->current_successor = current_successor;
+  vsmr->probable_successor = probable_successor;
+  vsmr->trail_direction = htonl (trail_direction);
+  vsmr->trail_id = trail_id;
   
-  pending = GNUNET_malloc (sizeof (struct P2PPendingMessage) + msize); 
+  if (trail_length > 0)
+  {
+    peer_list = (struct GNUNET_PeerIdentity *) &vsmr[1];
+    memcpy (peer_list, trail, trail_length * sizeof (struct GNUNET_PeerIdentity));
+  }
+
+   /* Send the message to chosen friend. */
+  GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
+  target_friend->pending_count++;
+  process_friend_queue (target_friend);
+}
+
+
+/**
+ * Construct a notify new successor message and send it to target_friend
+ * @param source_peer Peer which wants to notify to its new successor that it
+ *                    could be its predecessor. 
+ * @param successor New successor of @a source_peer
+ * @param successor_trail List of peers in Trail to reach from 
+ *                            @a source_peer to @a new_successor, NOT including 
+ *                            the endpoints. 
+ * @param successor_trail_length Total number of peers in @a new_successor_trail.
+ * @param successor_trail_id Unique identifier of @a new_successor_trail. 
+ * @param target_friend Next friend to get this message. 
+ */
+void
+GDS_NEIGHBOURS_send_notify_new_successor (struct GNUNET_PeerIdentity source_peer,
+                                          struct GNUNET_PeerIdentity successor,
+                                          const struct GNUNET_PeerIdentity *successor_trail,
+                                          unsigned int successor_trail_length,
+                                          struct GNUNET_HashCode succesor_trail_id,
+                                          struct FriendInfo *target_friend)
+{
+  struct PeerNotifyNewSuccessorMessage *nsm;
+  struct P2PPendingMessage *pending;
+  struct GNUNET_PeerIdentity *peer_list;
+  size_t msize;
+
+  msize = sizeof (struct PeerNotifyNewSuccessorMessage) +
+          (successor_trail_length * sizeof(struct GNUNET_PeerIdentity));
+
+  if (msize >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
+  {
+    GNUNET_break (0);
+    return;
+  }
+
+  if (target_friend->pending_count >= MAXIMUM_PENDING_PER_FRIEND)
+  {
+    GNUNET_STATISTICS_update (GDS_stats, gettext_noop ("# P2P messages dropped due to full queue"),
+                               1, GNUNET_NO);
+  }
+
+  pending = GNUNET_malloc (sizeof (struct P2PPendingMessage) + msize);
   pending->importance = 0;    /* FIXME */
   pending->timeout = GNUNET_TIME_relative_to_absolute (GET_TIMEOUT);
   nsm = (struct PeerNotifyNewSuccessorMessage *) &pending[1];
   pending->msg = &nsm->header;
   nsm->header.size = htons (msize);
   nsm->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_P2P_NOTIFY_NEW_SUCCESSOR);
-  memcpy (&(nsm->source_peer), source_peer, sizeof (struct GNUNET_PeerIdentity));
-  memcpy (&(nsm->destination_peer), destination_peer, sizeof (struct GNUNET_PeerIdentity));
-  nsm->trail_length = htonl (trail_length);
-  nsm->current_index = htonl (current_trail_index);
-  
-  peer_list = (struct GNUNET_PeerIdentity *) &nsm[1];
-  memcpy (peer_list, trail_peer_list, trail_length * sizeof (struct GNUNET_PeerIdentity));
+  nsm->new_successor = successor;
+  nsm->source_peer = source_peer;
+  nsm->trail_id = succesor_trail_id;
   
+  if (successor_trail_length > 0)
+  {
+    peer_list = (struct GNUNET_PeerIdentity *) &nsm[1];
+    memcpy (peer_list, successor_trail,
+            successor_trail_length * sizeof (struct GNUNET_PeerIdentity));
+  }
+
    /* Send the message to chosen friend. */
   GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
   target_friend->pending_count++;
@@ -1172,965 +1455,611 @@ GDS_NEIGHBOURS_send_notify_new_successor (struct GNUNET_PeerIdentity *source_pee
 }
 
 
-/** 
- * FIXME: Optimizaiton Once the basic code is running. Add the optimization
- * where you check if the threshold on number of links that should go through
- * a particular friend has crossed. If yes then again choose a different
- * friend. Important that the new friend chosen should be different. How to 
- * ensure this? This is an important optimization as without this one x-vine
- * is actually not a sybil tolerant DHT.
- * Randomly choose one of your friends from the friends_peer map
- * @return Friend
+/**
+ * Construct an add_trail message and send it to target_friend
+ * @param source_peer Source of the trail.
+ * @param destination_peer Destination of the trail.
+ * @param trail_id Unique identifier of the trail from 
+ *                 @a source_peer to @a destination_peer, NOT including the endpoints.
+ * @param trail List of peers in Trail from @a source_peer to @a destination_peer,
+ *              NOT including the endpoints. 
+ * @param trail_length Total number of peers in @a trail.
+ * @param target_friend Next friend to get this message.
  */
-static struct FriendInfo *
-select_random_friend (struct GNUNET_PeerIdentity *congested_peer)
-{  
-  unsigned int current_size;
-  unsigned int *index; 
-  unsigned int j = 0;
-  struct GNUNET_CONTAINER_MultiPeerMapIterator *iter;
-  struct GNUNET_PeerIdentity key_ret;
-  struct FriendInfo *friend;
-  
-  current_size = GNUNET_CONTAINER_multipeermap_size (friend_peermap);
-  index = GNUNET_CRYPTO_random_permute (GNUNET_CRYPTO_QUALITY_WEAK, current_size);
-  iter = GNUNET_CONTAINER_multipeermap_iterator_create (friend_peermap);
-  while(j < (*index))
+void
+GDS_NEIGHBOURS_send_add_trail (struct GNUNET_PeerIdentity source_peer,
+                               struct GNUNET_PeerIdentity destination_peer,
+                               struct GNUNET_HashCode trail_id,
+                               const struct GNUNET_PeerIdentity *trail,
+                               unsigned int trail_length,
+                               struct FriendInfo *target_friend)
+{
+  struct PeerAddTrailMessage *adm;
+  struct GNUNET_PeerIdentity *peer_list;
+  struct P2PPendingMessage *pending;
+  size_t msize;
+
+  msize = sizeof (struct PeerAddTrailMessage) +
+          (trail_length * sizeof(struct GNUNET_PeerIdentity));
+
+  if (msize >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
   {
-    if(GNUNET_YES == GNUNET_CONTAINER_multipeermap_iterator_next (iter,NULL,NULL))
-    {
-      j++;
-    }
-    else 
-      return NULL;
-  }  
+    GNUNET_break (0);
+    return;
+  }
 
-  if(GNUNET_YES == GNUNET_CONTAINER_multipeermap_iterator_next (iter,&key_ret,(const void **)&friend))
+  if (target_friend->pending_count >= MAXIMUM_PENDING_PER_FRIEND)
   {
-    /* TODO: Here you have chosen a random friend. Now you should check the size
-     of its routing table size, and if its more than threshold, then check which
-     of the entries has trail length greater than trail length threshold. we
-     should without checking the routing table size also we should check the
-     trail with trail length greater than threshold. then 
-     you should try to find a new route through this new node that has joined in
-     only for those finger entries whose trail length is greater than threshold. 
-     But I don't want the new node to wait for this process to get over. so
-     should i declare a function which will be called after some interval.*/
-    return friend;
+    GNUNET_STATISTICS_update (GDS_stats, gettext_noop ("# P2P messages dropped due to full queue"),
+                               1, GNUNET_NO);
   }
-  else
-    return NULL;
+
+  pending = GNUNET_malloc (sizeof (struct P2PPendingMessage) + msize);
+  pending->importance = 0;    /* FIXME */
+  pending->timeout = GNUNET_TIME_relative_to_absolute (GET_TIMEOUT);
+  adm = (struct PeerAddTrailMessage *) &pending[1];
+  pending->msg = &adm->header;
+  adm->header.size = htons (msize);
+  adm->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_P2P_ADD_TRAIL);
+  adm->source_peer = source_peer;
+  adm->destination_peer = destination_peer;
+  adm->trail_id = trail_id;
+
+  peer_list = (struct GNUNET_PeerIdentity *)&adm[1];
+  memcpy (peer_list, trail, sizeof (struct GNUNET_PeerIdentity) * trail_length);
+
+  /* Send the message to chosen friend. */
+  GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
+  target_friend->pending_count++;
+  process_friend_queue (target_friend);
+
 }
 
 
 /**
- * Compute finger_identity to which we want to setup the trail
- * @return finger_identity 
+ * Construct a trail compression message and send it to target_friend.
+ * @param source_peer Source of the trail.
+ * @param trail_id Unique identifier of trail.
+ * @param first_friend First hop in compressed trail to reach from source to finger
+ * @param target_friend Next friend to get this message.
  */
-static uint64_t *
-compute_finger_identity()
+void
+GDS_NEIGHBOURS_send_trail_compression (struct GNUNET_PeerIdentity source_peer,
+                                       struct GNUNET_HashCode trail_id,
+                                       struct GNUNET_PeerIdentity first_friend,
+                                       struct FriendInfo *target_friend)
 {
-  uint64_t my_id64 ;
-  uint64_t *finger_identity64;
-  
-  finger_identity64 = GNUNET_malloc (sizeof (uint64_t));
-  memcpy (&my_id64, &my_identity, sizeof (uint64_t));
-  /*FIXME: Do we need a mod finger = ((my_id + pow(2, finger_index)) mod (pow (2, MAX_FINGERS))*/
-  *finger_identity64 = (my_id64 + (unsigned long) pow (2,current_finger_index));
-  
-  return finger_identity64;
+  struct P2PPendingMessage *pending;
+  struct PeerTrailCompressionMessage *tcm;
+  size_t msize;
+
+  msize = sizeof (struct PeerTrailCompressionMessage);
+
+  if (msize >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
+  {
+    GNUNET_break (0);
+    return;
+  }
+
+  if (target_friend->pending_count >= MAXIMUM_PENDING_PER_FRIEND)
+  {
+    GNUNET_STATISTICS_update (GDS_stats,
+                              gettext_noop ("# P2P messages dropped due to full queue"),
+                                                     1, GNUNET_NO);
+  }
+
+  pending = GNUNET_malloc (sizeof (struct P2PPendingMessage) + msize);
+  pending->importance = 0;    /* FIXME */
+  pending->timeout = GNUNET_TIME_relative_to_absolute (GET_TIMEOUT);
+  tcm = (struct PeerTrailCompressionMessage *) &pending[1];
+  pending->msg = &tcm->header;
+  tcm->header.size = htons (msize);
+  tcm->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_COMPRESSION);
+  tcm->source_peer = source_peer;
+  tcm->new_first_friend = first_friend;
+  tcm->trail_id = trail_id;
+
+  GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
+  target_friend->pending_count++;
+  process_friend_queue (target_friend);
+
 }
 
 
 /**
- * Compute immediate predecessor identity in the network.
- * @return peer identity of immediate predecessor.
+ * Search my location in trail.
+ * @param trail List of peers
+ * @return my_index if found
+ *         -1 if no entry found.
  */
-static uint64_t *
-compute_predecessor_identity()
+static int
+search_my_index (const struct GNUNET_PeerIdentity *trail,
+                 int trail_length)
 {
-  uint64_t my_id ;
-  uint64_t *predecessor;
+  int i;
+
+  for (i = 0; i < trail_length; i++)
+  {
+    if (0 == GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &trail[i]))
+      return i;
+  }
+
+  return -1;
+}
 
-  predecessor = GNUNET_malloc (sizeof (uint64_t));
-  memcpy (&my_id, &my_identity, sizeof (uint64_t));
-  /* FIXME: Do we need to use mod pow(2, MAX_FINGERS) here? */
-  *predecessor = (my_id -1);
-          
-  return predecessor;
+/**
+ * Check if the friend is congested or have reached maximum number of trails
+ * it can be part of of. 
+ * @param friend Friend to be chechked.
+ * @return #GNUNET_YES if friend is not congested or have not crossed threshold.
+ *         #GNUNET_NO if friend is either congested or have crossed threshold 
+ */
+static int
+is_friend_congested (struct FriendInfo *friend)
+{
+  if ((friend->trails_count == TRAILS_THROUGH_FRIEND_THRESHOLD)||
+      ((0 != GNUNET_TIME_absolute_get_remaining
+             (friend->congestion_timestamp).rel_value_us)))
+    return GNUNET_YES;
+  else
+    return GNUNET_NO;
 }
 
 
 /**
- * Periodically ping your successor to ask its current predecessor
- * 
- * @param cls closure for this task
- * @param tc the context under which the task is running
+ * FIXME: here we should also check if iterator is null or not. It can be NULL
+ * only if we insert randomly at locations. But as we are using trails_count
+ * as the parameter, it should not happen.
+ * Iterate over the list of all the trails of a finger. In case the first
+ * friend to reach the finger has reached trail threshold or is congested,
+ * then don't select it. In case there multiple available good trails to reach
+ * to Finger, choose the one with shortest trail length.
+ * Note: We use length as parameter. But we can use any other suitable parameter
+ * also. 
+ * @param finger Finger
+ * @return struct Selected_Finger_Trail which contains the first friend , trail id
+ * and trail length. NULL in case none of the trails are free.
  */
-static void
-send_verify_successor_message (void *cls,
-                               const struct GNUNET_SCHEDULER_TaskContext *tc )
+static struct Selected_Finger_Trail *
+select_finger_trail (struct FingerInfo *finger)
 {
-  struct GNUNET_TIME_Relative next_send_time;
-  struct GNUNET_CONTAINER_MultiPeerMapIterator *finger_iter;
-  struct GNUNET_PeerIdentity key_ret;
-  struct FriendInfo *target_friend;
-  struct GNUNET_PeerIdentity *next_hop;
-  struct GNUNET_PeerIdentity *peer_list;
-  unsigned int finger_trail_current_index;
-  struct FingerInfo *finger;
-  unsigned int finger_index;
+  struct FriendInfo *friend;
+  struct Trail *iterator;
+  struct Selected_Finger_Trail *finger_trail;
   unsigned int i;
-  int flag = 0;
+
+  finger_trail = GNUNET_new (struct Selected_Finger_Trail);
   
-  finger_iter = GNUNET_CONTAINER_multipeermap_iterator_create (finger_peermap);  
-  for (finger_index = 0; finger_index < GNUNET_CONTAINER_multipeermap_size (finger_peermap); finger_index++)
+  for (i = 0; i < finger->trails_count; i++)
   {
-    if(GNUNET_YES == GNUNET_CONTAINER_multipeermap_iterator_next (finger_iter, &key_ret,
-                                                                 (const void **)&finger)) 
+    iterator = &finger->trail_list[i];
+    friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                                &iterator->trail_head->peer);
+    if (GNUNET_YES == is_friend_congested (friend))
+      continue;
+   
+    /* Check if the trail length of this trail is least seen so far. If yes then
+     set finger_trail to this trail.*/
+    if (finger_trail->trail_length > iterator->trail_length)
     {
-      if (0 == finger->finger_map_index)
-      {
-        flag = 1;
-        break;
-      }
+      finger_trail->friend = *friend;
+      finger_trail->trail_id = iterator->trail_id;
+      finger_trail->trail_length = iterator->trail_length;
     }
   }
-  GNUNET_CONTAINER_multipeermap_iterator_destroy (finger_iter);
-  
-  if( flag == 0)
-    goto send_new_request;
-  
-  peer_list = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity) * finger->trail_length);
-  struct TrailPeerList *iterate;
-  iterate = finger->head;
-  i = 0;
-  while ( i < (finger->trail_length))
-  {
-    memcpy (&peer_list[i], &(iterate->peer), sizeof (struct GNUNET_PeerIdentity));
-    iterate = iterate->next;
-    i++;
-  }
-  next_hop = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-  memcpy (next_hop, &peer_list[0], sizeof (struct GNUNET_PeerIdentity));
-  target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop);
-  finger_trail_current_index = 0; 
-  
-  
-  GDS_NEIGHBOURS_send_verify_successor (&my_identity,
-                                        &(finger->finger_identity),
-                                        target_friend,
-                                        peer_list,
-                                        finger->trail_length,
-                                        finger_trail_current_index);
-  
+
+  /* No trail found. */  
+  if (i == finger->trails_count)
+    finger_trail = NULL;
   
-  /* FIXME: Use a random value so that this message is send not at the same
-   interval as send_find_finger_trail_message. */
-  send_new_request:
-  next_send_time.rel_value_us =
-      DHT_MINIMUM_FIND_FINGER_TRAIL_INTERVAL.rel_value_us +
-      GNUNET_CRYPTO_random_u64 (GNUNET_CRYPTO_QUALITY_WEAK,
-                                DHT_MAXIMUM_FIND_FINGER_TRAIL_INTERVAL.rel_value_us /
-                                (current_finger_index + 50));
-  verify_successor =
-      GNUNET_SCHEDULER_add_delayed (next_send_time, &send_verify_successor_message,
-                                    NULL);
+  return finger_trail;
 }
 
 
 /**
- * Task to send a find finger trail message. We attempt to find trail
- * to our fingers, successor and predecessor in the network.
- *
- * @param cls closure for this task
- * @param tc the context under which the task is running
+ * FIXME; not handling the wrap around logic correctly. 
+ * Select closest finger to value.
+ * @param peer1 First peer
+ * @param peer2 Second peer
+ * @param value Value to be compare
+ * @return Closest peer
  */
-static void
-send_find_finger_trail_message (void *cls,
-                                const struct GNUNET_SCHEDULER_TaskContext *tc)
+static struct GNUNET_PeerIdentity *
+select_closest_finger (struct GNUNET_PeerIdentity *peer1,
+                       struct GNUNET_PeerIdentity *peer2,
+                       uint64_t value)
 {
-  struct FriendInfo *target_friend;
-  struct GNUNET_TIME_Relative next_send_time;
-  uint64_t *finger_identity;
-  unsigned int finger_map_index;
+  uint64_t peer1_value;
+  uint64_t peer2_value;
   
-  if (1 == current_finger_index)
+  memcpy (&peer1_value, peer1, sizeof (uint64_t));
+  memcpy (&peer2_value, peer2, sizeof (uint64_t));
+  if (peer1_value == value)
   {
-    finger_identity = compute_predecessor_identity();  
-    goto select_friend;
+    return peer1;
   }
-  else
+  
+  if (peer2_value == value)
   {
-    finger_identity = compute_finger_identity();
+    return peer2;
   }
-  
-  select_friend:
-  target_friend = select_random_friend (NULL);
-  
-  finger_map_index = current_finger_index;
-  current_finger_index = ( current_finger_index + 1) % MAX_FINGERS;
-  
-  if(NULL != target_friend)
-  { 
-    /* FIXME: Here I am passing NULL for current source, is it correct? 
-     also, we set the current source only if current_destination_type
-     is finger. */
-    GDS_NEIGHBOURS_send_trail_setup (&my_identity, *finger_identity, &(target_friend->id),
-                                     NULL, target_friend, 0, NULL, finger_map_index, FRIEND);
+   
+  if (peer2_value < peer1_value)
+  {
+    if ((peer2_value < value) && (value < peer1_value))
+    {
+      return peer1;
+    }
+    else if (((peer1_value < value) && (value < PEER_IDENTITES_WRAP_AROUND)) ||
+             ((0 < value) && (value < peer2_value)))
+    {
+      return peer2;
+    }
+  }  
+   
+  if (peer1_value < peer2_value)
+  {
+    if ((peer1_value < value) && (value < peer2_value))
+    {
+      return peer2;
+    }
+    else if (((peer2_value < value) && (value < PEER_IDENTITES_WRAP_AROUND)) ||
+             ((0 < value) && (value < peer1_value)))
+    {
+      return peer1;
+    }
   }
-  
-  /* FIXME: How to decide the correct interval? */
-  next_send_time.rel_value_us =
-      DHT_MINIMUM_FIND_FINGER_TRAIL_INTERVAL.rel_value_us +
-      GNUNET_CRYPTO_random_u64 (GNUNET_CRYPTO_QUALITY_WEAK,
-                                DHT_MAXIMUM_FIND_FINGER_TRAIL_INTERVAL.rel_value_us /
-                                (current_finger_index + 10));
-  find_finger_trail_task =
-      GNUNET_SCHEDULER_add_delayed (next_send_time, &send_find_finger_trail_message,
-                                    NULL);
+  return NULL;
 }
 
 
 /**
- * Method called whenever a peer connects.
+ * FIMXE: COMPLETE THE LOGIC.
+ * my_id = 0
+ * finger = 5
+ * key = 3
+ * [0,5) â†’ my_id
+ * [5,0) â†’ finger
  *
- * @param cls closure
- * @param peer_identity peer identity this notification is about
+ * 0 <= key < 5, so my_id 0 is the predecessor. 
+ * peer1 != peer2 ever.
+ * Select closest predecessor to value.
+ * @param peer1 First peer
+ * @param peer2 Second peer
+ * @param value Value to be compare
+ * @return Closest peer
  */
-static void
-handle_core_connect (void *cls, const struct GNUNET_PeerIdentity *peer_identity)
+static struct GNUNET_PeerIdentity *
+select_closest_predecessor (struct GNUNET_PeerIdentity *peer1,
+                            struct GNUNET_PeerIdentity *peer2,
+                            uint64_t value)
 {
-  struct FriendInfo *friend;
-
-  /* Check for connect to self message */
-  if (0 == memcmp (&my_identity, peer_identity, sizeof (struct GNUNET_PeerIdentity)))
-    return;
-  
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Connected to %s\n", GNUNET_i2s (peer_identity));
-  
-  /* If peer already exists in our friend_peermap, then exit. */
-  if (GNUNET_YES == GNUNET_CONTAINER_multipeermap_contains (friend_peermap, peer_identity))
-  {
-    GNUNET_break (0);
-    return;
-  }
-
-  GNUNET_STATISTICS_update (GDS_stats, gettext_noop ("# peers connected"), 1,
-                            GNUNET_NO);
-
-  friend = GNUNET_new (struct FriendInfo);
-  friend->id = *peer_identity;
+  uint64_t peer1_value;
+  uint64_t peer2_value;
   
-  GNUNET_assert (GNUNET_OK ==
-                 GNUNET_CONTAINER_multipeermap_put (friend_peermap,
-                                                    peer_identity, friend,
-                                                    GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
-
-  /* got a first connection, good time to start with FIND FINGER TRAIL requests... */
-  if (1 == GNUNET_CONTAINER_multipeermap_size (friend_peermap))
-    find_finger_trail_task = GNUNET_SCHEDULER_add_now (&send_find_finger_trail_message, NULL);
-}
-
-
-/**
- * Method called whenever a peer disconnects.
- *
- * @param cls closure
- * @param peer peer identity this notification is about
- */
-static void
-handle_core_disconnect (void *cls,
-                       const struct GNUNET_PeerIdentity *peer)
-{
-  struct FriendInfo *remove_friend;
-  struct FingerInfo *remove_finger;
-  struct GNUNET_PeerIdentity key_ret;
-  struct GNUNET_CONTAINER_MultiPeerMapIterator *finger_iter;
-  struct TrailPeerList *iterator;
-  struct GNUNET_PeerIdentity *finger_identity;
-  int finger_index;
+  memcpy (&peer1_value, peer1, sizeof (uint64_t));
+  memcpy (&peer2_value, peer2, sizeof (uint64_t));
   
-  /* Check for self message. */
-  if (0 == memcmp (&my_identity, peer, sizeof (struct GNUNET_PeerIdentity)))
-    return;
+  if (peer1_value == value)
+    return peer1;
   
-   /* Search for peer to remove in your friend_peermap. */
-  remove_friend =
-      GNUNET_CONTAINER_multipeermap_get (friend_peermap, peer);
+  if (peer2_value == value)
+    return peer2;
   
-  if (NULL == remove_friend)
+  if (peer1_value < peer2_value)
   {
-    GNUNET_break (0);
-    return;
+    if ((peer1_value < value) && (value < peer2_value))
+      return peer1;
+    else if (((peer2_value < value) && (value < PEER_IDENTITES_WRAP_AROUND)) ||
+             ((PEER_IDENTITES_WRAP_AROUND > value) && (value < peer1_value)))
+      return peer2;
   }
   
-  iterator = GNUNET_malloc (sizeof (struct TrailPeerList));
-  finger_identity = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-  finger_iter = GNUNET_CONTAINER_multipeermap_iterator_create (finger_peermap);  
-  for (finger_index = 0; finger_index < GNUNET_CONTAINER_multipeermap_size (finger_peermap); finger_index++)
+  if (peer2_value < peer1_value)
   {
-    if(GNUNET_YES == GNUNET_CONTAINER_multipeermap_iterator_next (finger_iter, &key_ret,
-                                                                 (const void **)&remove_finger)) 
-    {
-      iterator = remove_finger->head->next;
-      if (0 == GNUNET_CRYPTO_cmp_peer_identity (&(iterator->peer), &(remove_friend->id)))
-      {
-        memcpy (finger_identity, &(remove_finger->finger_identity), sizeof (struct GNUNET_PeerIdentity));
-        GNUNET_assert (GNUNET_YES ==
-                       GNUNET_CONTAINER_multipeermap_remove (finger_peermap,
-                                                             finger_identity,
-                                                             remove_finger));
-      }
-    }
+    if ((peer2_value < value) && (value < peer1_value))
+      return peer2;
+    else if (((peer1_value < value) && (value < PEER_IDENTITES_WRAP_AROUND)) ||
+             ((PEER_IDENTITES_WRAP_AROUND > value) && (value < peer2_value)))
+      return peer1;
   }
-  
-  /* Remove the friend from friend_peermap. */
-  GNUNET_assert (GNUNET_YES ==
-                 GNUNET_CONTAINER_multipeermap_remove (friend_peermap,
-                                                       peer,
-                                                       remove_friend));
+  return NULL;
 }
 
 
+/* FIXME: select closest peer w.r.t. value. [finger->friend_id, current_successor->id)
+     and [current_successor->id, finger->friend_id). Check in which range value lies.
+     Also, check for wrap around. But this will give you the immediate predecessor
+     For example. if we have 0,1,6 and I am 0 and one of my finger is 6. Then
+     for 1, we will have ranges like [0,6) and [6,0) 1 lies in range from [0,6)
+     but successor is 6 not 0 as 6 is > than 1. If you are the closest one, 
+     then set the values
+     in current_successor. Want to write a generic code so that it is used in 
+     * finger_table_add also while choosing the closest one among new and existing
+     * one. */
 /**
- * To be called on core init/fail.
- *
- * @param cls service closure
- * @param identity the public identity of this peer
- */
-static void
-core_init (void *cls,
-           const struct GNUNET_PeerIdentity *identity)
-{
-  my_identity = *identity;
-  
-  /* SUPU TEST CODE */
-  struct GNUNET_PeerIdentity *print_peer;
-  print_peer = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-  memcpy (print_peer, &my_identity, sizeof (struct GNUNET_PeerIdentity));
-  FPRINTF (stderr,_("\nSUPU %s, %s, %d,my_identity = %s"),
-  __FILE__, __func__,__LINE__, GNUNET_i2s (print_peer));
-  /* SUPU TEST CODE ENDS */
-
-}
+ * my_id = 0
+ * finger = 5
+ * key = 3
+ * [0,5) â†’ my_id
+ * [5,0) â†’ finger
 
+ * 0 <= key < 5, so key should go to 5. 
 
+ */
 /**
- * 
- * @param destination_peer
- * @param existing_trail
- * @param trail_length
- * @return 
+ * Select the closest peer among two peers (which should not be same)
+ * with respect to value and finger_table_index
+ * @param peer1 First peer
+ * @param peer2 Second peer
+ * @param value Value relative to which we find the closest
+ * @param finger_table_index Index in finger map. If equal to PREDECESSOR_FINGER_ID,
+ *                         then we use different logic than other
+ *                         finger_table_index
+ * @return Closest peer among two peers.
  */
 static struct GNUNET_PeerIdentity *
-invert_trail_list (struct GNUNET_PeerIdentity *destination_peer,
-                   struct GNUNET_PeerIdentity *existing_trail, 
-                   unsigned int trail_length)
+select_closest_peer (struct GNUNET_PeerIdentity *peer1,
+                     struct GNUNET_PeerIdentity *peer2,
+                     uint64_t value,
+                     unsigned int finger_table_index)
 {
-  int i;
-  int j;
-  struct GNUNET_PeerIdentity *new_trail;
-  
-  j = 0;
-  new_trail = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity) * trail_length);
-  
-  if (trail_length > 1)
-  {
-    i = trail_length - 2;
-    while (i >= 0 )
-    {
-      memcpy( &new_trail[j], &existing_trail[i], sizeof (struct GNUNET_PeerIdentity));
-      i--;
-      j++;
-    }
-  }
-  memcpy (&new_trail[j], destination_peer, sizeof(struct GNUNET_PeerIdentity));
-  return new_trail;
-}
-
+  struct GNUNET_PeerIdentity *closest_peer;
+  /* FIXME: select closest peer w.r.t. value. [friend_id, current_successor->id)
+     and [current_successor->id, friend_id). Check in which range value lies.
+     Also, check for wrap around. Set the value of current_successor accordingly.*/
+  if (PREDECESSOR_FINGER_ID == finger_table_index)
+    closest_peer = select_closest_predecessor (peer1, peer2, value);
+  else
+    closest_peer = select_closest_finger (peer1, peer2, value);
 
-/**
- * 
- * @param existing_finger
- * @param new_finger
- * @return 
- */
-static int
-compare_finger_identity (struct GNUNET_PeerIdentity *existing_finger,
-                         struct GNUNET_PeerIdentity *new_finger)
-{
-  int ret;
-  ret = (existing_finger > new_finger) ? 1 : 
-          (existing_finger == new_finger) ? 0 : -1;
-  return ret;
+  return closest_peer;
 }
 
 
 /**
- * FIXME: Not sure of the logic to find the correct predecessor
- * I think logic of this code is wrong everything else seems to be correct. 
- * Given two finger identities, find the closest predecessor. 
- * @param existing_predecessor
- * @param new_predecessor
+ * FIXME: better names and more refactoring. 
+ * Compare FINGER entry with current successor. If finger's first friend of all
+ * its trail is not congested and  has not crossed trail threshold, then check 
+ * if finger peer identity is closer to final_destination_finger_value than
+ * current_successor. If yes then update current_successor. 
+ * @param current_successor[in/out]
  * @return 
  */
-static int
-compare_predecessor(struct GNUNET_PeerIdentity *existing_predecessor,
-                    struct GNUNET_PeerIdentity *new_predecessor)
+static struct Closest_Peer *
+compare_finger_and_current_successor (struct Closest_Peer *current_closest_peer)
 {
-  int ret;
-  ret = (existing_predecessor < new_predecessor) ? 1 : 
-          (existing_predecessor == new_predecessor) ? 0 : -1;
-  return ret;
-}
-
-
-
-/*
- * Add an entry in finger table. 
- * @param finger_identity Peer identity of finger
- * @param finger_trail Trail to reach the finger
- * @param trail_length Number of peers in the trail. 
- * @param finger_map_index Index in finger peer map.
- */
-static
-void finger_table_add (struct GNUNET_PeerIdentity *finger_identity,
-                       struct GNUNET_PeerIdentity *finger_trail,
-                       unsigned int trail_length,
-                       unsigned int finger_map_index)
-{
-  struct FingerInfo *new_finger_entry;
-  struct GNUNET_PeerIdentity key_ret;
+  struct FingerInfo *finger;
+  struct FriendInfo *friend;
+  struct GNUNET_PeerIdentity *closest_peer;
   int i;
-  struct GNUNET_CONTAINER_MultiPeerMapIterator *finger_iter;
-  struct FingerInfo *existing_finger;
-  int finger_index;
-
-  /* SUPU Here we trying to check if we already have an entry. If yes then we
-   can keep two trails for redundant routing. if they are different then we
-   need to choose the closest one. and remove the other one. */
-  finger_iter = GNUNET_CONTAINER_multipeermap_iterator_create (finger_peermap); 
-
-  for (finger_index = 0; finger_index < GNUNET_CONTAINER_multipeermap_size (finger_peermap); finger_index++)
-  {
-    if(GNUNET_YES == GNUNET_CONTAINER_multipeermap_iterator_next (finger_iter, &key_ret,
-                                                                 (const void **)&existing_finger)) 
-    {
-      if ((finger_map_index == existing_finger->finger_map_index))
-      {
-        if (0 == GNUNET_CRYPTO_cmp_peer_identity (&(existing_finger->finger_identity),finger_identity))
-        {
-          FPRINTF (stderr,_("\nSUPU Entries are same. %s, %s, %d"),    __FILE__, __func__,__LINE__);
-          /* FIXME: Here you should check if the trail is same. If yes then don't add the entry. it
-           seems to be very suboptimal. */
-          if ((existing_finger->trail_length) == trail_length)
-          {
-            struct TrailPeerList *iterate;
-            iterate = existing_finger->head;
-            int k;
-            k = 0;
-            while (k < trail_length)
-            {
-              if (0 == GNUNET_CRYPTO_cmp_peer_identity (&(iterate->peer), &finger_trail[k]))
-              {
-                k++;
-                iterate = iterate->next;
-              }
-            }
-            if (k == trail_length)
-              return;
-            else
-              goto add_new_entry;
-          }
-          goto add_new_entry;
-        }
-        else
-        {
-          int ret;
-          if (finger_map_index == 1)
-          {
-            FPRINTF (stderr,_("\nSUPUP Predecessor are different %s, %s, %d"),    __FILE__, __func__,__LINE__);
-            ret = compare_predecessor (&(existing_finger->finger_identity),
-                                       finger_identity);
-            goto add_new_entry;
-          }
-          else
-          {
-            FPRINTF (stderr,_("\nSUPU %s, %s, %d"),    __FILE__, __func__,__LINE__);
-            ret = compare_finger_identity (&(existing_finger->finger_identity),
-                                          finger_identity);
-          }
-          if (ret > 0)
-          {
-            FPRINTF (stderr,_("\nSUPU Adding the new one and removing the old one %s, %s, %d"),    __FILE__, __func__,__LINE__);
-            GNUNET_assert (GNUNET_YES ==
-                       GNUNET_CONTAINER_multipeermap_remove (finger_peermap,
-                                                             &(existing_finger->finger_identity),
-                                                             existing_finger));
-            goto add_new_entry;
-          }
-          else
-          {
-            FPRINTF (stderr,_("\nSUPU Nothing to do return %s, %s, %d"),    __FILE__, __func__,__LINE__);
-            return;
-          }
-        }
-      }
-    }
-  }
-
-  add_new_entry:
-  new_finger_entry = GNUNET_malloc (sizeof (struct FingerInfo));
-  memcpy (&(new_finger_entry->finger_identity), finger_identity, sizeof (struct GNUNET_PeerIdentity));
-  new_finger_entry->finger_map_index = finger_map_index;
   
-  if (0 == GNUNET_CRYPTO_cmp_peer_identity (&my_identity, finger_identity))
-  {
-    /* I am the finger */
-    new_finger_entry->trail_length = 0;
-  }
-  else
+  for (i = 0; i < MAX_FINGERS; i++)
   {
-    i = 0;
-    while (i < trail_length)
-    {
-      struct TrailPeerList *element;
-      element = GNUNET_malloc (sizeof (struct TrailPeerList));
-      element->next = NULL;
-      element->prev = NULL;
+    struct Selected_Finger_Trail *finger_trail;
+    finger = &finger_table[i];
     
-      memcpy (&(element->peer), &finger_trail[i], sizeof(struct GNUNET_PeerIdentity));
-      GNUNET_CONTAINER_DLL_insert_tail(new_finger_entry->head, new_finger_entry->tail, element);
-      i++;
-    }
-    new_finger_entry->trail_length = trail_length;
-  }
-  
-  /* FIXME: Here we are keeping multiple hashmap option so that there are
-   multiple routes to reach to same finger, redundant routing.
-   * Also same peers could be our fingers for different finger map index
-   * Should we handle the case where we have same fingers at the different
-   * finger index but with different trail to reach.  */
-  GNUNET_assert (GNUNET_OK ==
-                 GNUNET_CONTAINER_multipeermap_put (finger_peermap,
-                                                    &(new_finger_entry->finger_identity),
-                                                    new_finger_entry,
-                                                    GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE)); /* Fixme: change to multiple */
-  /* SUPU TEST CODE */
-  /* Here I want to iterate over finger peer map, print its id and the trail
-   to reach to the finger. */
-  int test_index;
-  struct GNUNET_CONTAINER_MultiPeerMapIterator *test_iter;
-  struct FingerInfo *test_finger;
-  test_iter = GNUNET_CONTAINER_multipeermap_iterator_create (finger_peermap); 
-  FPRINTF (stderr,_("\nSUPU #### %s, %s, %d, size = %d####"),__FILE__, __func__,__LINE__,GNUNET_CONTAINER_multipeermap_size (finger_peermap));
-  for (test_index = 0; test_index < GNUNET_CONTAINER_multipeermap_size (finger_peermap); test_index++)
-  {
-    FPRINTF (stderr,_("\nSUPU *********%s, %s, %d, %d entry*********"),__FILE__, __func__,__LINE__,test_index);
-    if(GNUNET_YES == GNUNET_CONTAINER_multipeermap_iterator_next (test_iter, &key_ret,
-                                                                 (const void **)&test_finger)) 
+    if (GNUNET_NO == finger->is_present)
+      continue;
+    
+    /* If my identity is same as current closest peer then don't consider me*/
+    if (0 == GNUNET_CRYPTO_cmp_peer_identity (&finger->finger_identity,
+                                              &current_closest_peer->best_known_destination))
+      continue;
+    
+    /* If I am my own finger, then ignore this finger. */
+    if (0 == GNUNET_CRYPTO_cmp_peer_identity (&finger->finger_identity,
+                                              &my_identity))
+      continue;
+    
+    /* If finger is friend. */
+    if (NULL != (friend = GNUNET_CONTAINER_multipeermap_get 
+                (friend_peermap, &finger->finger_identity)))
     {
-      FPRINTF (stderr,_("\nSUPU %s, %s, %d "),__FILE__, __func__,__LINE__);
-      struct GNUNET_PeerIdentity *print_peer;
-      struct TrailPeerList *iterator;
-      int z;
-      iterator = GNUNET_malloc (sizeof (struct TrailPeerList));
-      print_peer = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-      memcpy (print_peer, &(test_finger->finger_identity), sizeof (struct GNUNET_PeerIdentity));
-      FPRINTF (stderr,_("\nSUPU %s, %s, %d, finger_index = %d"),    __FILE__, __func__,__LINE__,test_finger->finger_map_index);
-      FPRINTF (stderr,_("\nSUPU %s, %s, %d, finger_identity = %s"),  
-              __FILE__, __func__,__LINE__, GNUNET_i2s (print_peer));
-      iterator = test_finger->head;
-      z = 0;
-      while (z < test_finger->trail_length)
+      if (GNUNET_YES == is_friend_congested (friend))
+        continue;
+      
+       /* If not congested then compare it with current_successor. */
+      if (0 == GNUNET_CRYPTO_cmp_peer_identity (&finger->finger_identity,
+                                                 &current_closest_peer->best_known_destination))
+        continue;
+      
+      closest_peer = select_closest_peer (&finger->finger_identity, 
+                                          &current_closest_peer->best_known_destination,
+                                          current_closest_peer->destination_finger_value,
+                                          current_closest_peer->is_predecessor);
+      if (0 == GNUNET_CRYPTO_cmp_peer_identity (&finger->finger_identity,
+                                                closest_peer))
       {
-        memcpy (print_peer, &(iterator->peer), sizeof (struct GNUNET_PeerIdentity));
-        FPRINTF (stderr,_("\nSUPU %s, %s, %d, trail[%d] = %s"),__FILE__, __func__,__LINE__,z,GNUNET_i2s (print_peer));
-        z++;
-        iterator = iterator->next;
+        current_closest_peer->best_known_destination = finger->finger_identity;
+        current_closest_peer->next_hop = finger->finger_identity;
       }
+      continue;
     }
+    
+    /* Choose one of the trail to reach to finger. */
+    finger_trail = select_finger_trail (finger);
+    
+    /* In case no trail found, ignore this finger. */
+    if (NULL == finger_trail)
+      continue;
+    
+     closest_peer = select_closest_peer (&finger->finger_identity, 
+                                         &current_closest_peer->best_known_destination,
+                                          current_closest_peer->destination_finger_value,
+                                          current_closest_peer->is_predecessor);
+     if (0 == GNUNET_CRYPTO_cmp_peer_identity (&finger->finger_identity,
+                                               closest_peer))
+     {
+       current_closest_peer->best_known_destination = finger->finger_identity;
+       current_closest_peer->next_hop = finger_trail->friend.id;
+       current_closest_peer->trail_id = finger_trail->trail_id;
+     }
+      continue;
   }
-  FPRINTF (stderr,_("\nSUPU End of loop%s, %s, %d"),__FILE__, __func__,__LINE__);
-  /* SUPU TEST CODE ENDS */
-
-  
-  if (1 == GNUNET_CONTAINER_multipeermap_size (finger_peermap)
-      && (new_finger_entry->finger_map_index!= 1))
-  {
-    verify_successor = GNUNET_SCHEDULER_add_now (&send_verify_successor_message, NULL);
-  }
+  return current_closest_peer;
 }
-  
 
-/**
- * Compare two peer identities.
- * @param p1 Peer identity
- * @param p2 Peer identity
- * @return 1 if p1 > p2, -1 if p1 < p2 and 0 if p1 == p2. 
- */
-  static int
-compare_peer_id (const void *p1, const void *p2)
-{
-  struct Sorting_List *p11;
-  struct Sorting_List *p22;
-  int ret;
-  p11 = GNUNET_malloc (sizeof (struct Sorting_List));
-  p22 = GNUNET_malloc (sizeof (struct Sorting_List));
-  p11 = (struct Sorting_List *)p1;
-  p22 = (struct Sorting_List *)p2;
-  ret = ( (p11->peer_id) > (p22->peer_id) ) ? 1 : 
-          ( (p11->peer_id) == (p22->peer_id) ) ? 0 : -1;
-  return ret;
-}
 
-  
 /**
- * Return the successor of value in all_known_peers.
- * @param all_known_peers list of all the peers
- * @param value value we have to search in the all_known_peers.
- * @return 
+ * Compare friend entry with current successor. If friend is not congested and
+ * has not crossed trail threshold, then check if friend peer identity is
+ * closer to final_destination_finger_value than current_successor. If yes
+ * then update current_successor. 
+ * @param cls closure
+ * @param key current public key
+ * @param value struct Closest_Peer
+ * @return #GNUNET_YES if we should continue to iterate,
+ *         #GNUNET_NO if not.
  */
-static struct Sorting_List *
-find_closest_successor(struct Sorting_List *all_known_peers, uint64_t value,
-                       unsigned int size)
+static int
+compare_friend_and_current_closest_peer (void *cls,
+                                         const struct GNUNET_PeerIdentity *key,
+                                         void *value)
 {
-  int first;
-  int last;
-  int middle;
+  struct FriendInfo *friend = value;
+  struct Closest_Peer *current_closest_peer = cls;
+  struct GNUNET_PeerIdentity *closest_peer;
   
-  first = 0;
-  last = size - 1;
-  middle = (first + last)/2;
+  if (GNUNET_YES == is_friend_congested (friend))
+    return GNUNET_YES;
   
-  while(first <= last)
-  {
-    if(all_known_peers[middle].peer_id < value)
-    {
-      first = middle + 1; 
-    }
-    else if(all_known_peers[middle].peer_id == value)
-    {
-      if(middle == (size -1))
-      {
-        return &all_known_peers[0];
-      }
-      else
-      {
-        return &all_known_peers[middle+1];
-      }
-    }
-    else
-    {
-       last = middle - 1;
-    }
+  if (0 == 
+          GNUNET_CRYPTO_cmp_peer_identity (&friend->id,
+                                           &current_closest_peer->best_known_destination))
+    return GNUNET_YES;
   
-    middle = (first + last)/2;  
+  closest_peer = select_closest_peer (&friend->id, 
+                                      &current_closest_peer->best_known_destination,
+                                      current_closest_peer->destination_finger_value,
+                                      current_closest_peer->is_predecessor);
+
+  /* If friend is the closest successor. */
+  if (0 == GNUNET_CRYPTO_cmp_peer_identity (&friend->id, closest_peer))
+  {
+    current_closest_peer->best_known_destination = friend->id;
+    current_closest_peer->next_hop = friend->id;
   }
-  return NULL;
+  
+  return GNUNET_YES;
 }
 
-
 /**
- * Find closest successor for the value.
- * @param value Value for which we are looking for successor
- * @param current_destination NULL if my_identity is successor else finger/friend 
- *                            identity 
- * @param type Next destination type
- * @return Peer identity of next destination i.e. successor of value. 
+ * Initialize current_successor to my_identity.
+ * @param my_identity My peer identity
+ * @return current_successor
  */
-static struct GNUNET_PeerIdentity *
-find_successor (uint64_t value, struct GNUNET_PeerIdentity *current_destination,
-               enum current_destination_type *type)
+static struct Closest_Peer *
+init_current_successor (struct GNUNET_PeerIdentity my_identity,
+                        uint64_t destination_finger_value,
+                        unsigned int is_predecessor)
 {
-  struct GNUNET_CONTAINER_MultiPeerMapIterator *friend_iter;
-  struct GNUNET_CONTAINER_MultiPeerMapIterator *finger_iter;
-  struct GNUNET_PeerIdentity key_ret;
-  struct FriendInfo *friend;
-  struct FingerInfo *finger;
-  unsigned int finger_index;
-  unsigned int friend_index;
-  struct Sorting_List *successor;
-  unsigned int size;
-  int j;
-  
-  /* 2 is added in size for my_identity and value which will part of all_known_peers. */
-  size = GNUNET_CONTAINER_multipeermap_size (friend_peermap)+
-         GNUNET_CONTAINER_multipeermap_size (finger_peermap)+
-         2;
-  
-  struct Sorting_List all_known_peers[size];
-  
-  int k;
-  for (k = 0; k < size; k++)
-    all_known_peers[k].peer_id = 0;
-  
-  /* Copy your identity at 0th index in all_known_peers. */
-  j = 0;
-  memcpy (&(all_known_peers[j].peer_id), &my_identity, sizeof (uint64_t));
-  all_known_peers[j].type = MY_ID;
-  all_known_peers[j].data = 0;
-  j++;
-  
-  /* Copy value */
-  all_known_peers[j].peer_id = value;
-  all_known_peers[j].type = VALUE;
-  all_known_peers[j].data = 0;
-  j++;
-  
-  /* Iterate over friend peer map and copy all the elements into array. */
-  friend_iter = GNUNET_CONTAINER_multipeermap_iterator_create (friend_peermap); 
-  for (friend_index = 0; friend_index < GNUNET_CONTAINER_multipeermap_size (friend_peermap); friend_index++)
-  {
-    if(GNUNET_YES == GNUNET_CONTAINER_multipeermap_iterator_next(friend_iter,&key_ret,(const void **)&friend)) 
-    {
-      memcpy (&(all_known_peers[j].peer_id), &(friend->id), sizeof (uint64_t));
-      all_known_peers[j].type = FRIEND;
-      all_known_peers[j].data = friend;
-      j++;
-    }
-  }
-  
-  /* Iterate over finger map and copy all the entries into all_known_peers array. */
-  finger_iter = GNUNET_CONTAINER_multipeermap_iterator_create (finger_peermap);  
-  for (finger_index = 0; finger_index < GNUNET_CONTAINER_multipeermap_size (finger_peermap); finger_index++)
-  {
-    if(GNUNET_YES == GNUNET_CONTAINER_multipeermap_iterator_next(finger_iter,&key_ret,(const void **)&finger)) 
-    {
-      memcpy (&(all_known_peers[j].peer_id), &(finger->finger_identity), sizeof (uint64_t));
-      all_known_peers[j].type = FINGER;
-      all_known_peers[j].data = finger;
-      j++;
-    }
-  }
-  
-  GNUNET_CONTAINER_multipeermap_iterator_destroy (finger_iter);
-  GNUNET_CONTAINER_multipeermap_iterator_destroy (friend_iter);   
+  struct Closest_Peer *current_closest_peer;
   
-  qsort (&all_known_peers, size, sizeof (struct Sorting_List), &compare_peer_id);
+  current_closest_peer = GNUNET_new (struct Closest_Peer);
+  memset (&current_closest_peer->trail_id, 0, sizeof (current_closest_peer->trail_id)); 
+  current_closest_peer->destination_finger_value = destination_finger_value;
+  current_closest_peer->is_predecessor = is_predecessor;
+  current_closest_peer->next_hop = my_identity;
+  current_closest_peer->best_known_destination = my_identity;
   
-  /* search value in all_known_peers array. */
-  successor = find_closest_successor (all_known_peers, value, size);
-  
-  if (successor->type == MY_ID)
-  {
-    *type = MY_ID;
-    return NULL;
-  }
-  else if (successor->type == FRIEND)
-  {
-    *type = FRIEND;
-    struct FriendInfo *target_friend;
-    target_friend = (struct FriendInfo *)successor->data;
-    memcpy (current_destination, &(target_friend->id), sizeof (struct GNUNET_PeerIdentity));
-    return current_destination;
-  }
-  else if (successor->type == FINGER)
-  {
-    *type = FINGER;
-    struct GNUNET_PeerIdentity *next_hop;
-    struct FingerInfo *finger;
-    struct TrailPeerList *iterator;
-    iterator = GNUNET_malloc (sizeof (struct TrailPeerList));
-    finger = successor->data;
-    iterator = finger->head;
-    next_hop = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-    memcpy (next_hop, &(iterator->peer), sizeof (struct GNUNET_PeerIdentity));
-    memcpy (current_destination, &(finger->finger_identity), sizeof (struct GNUNET_PeerIdentity));
-    return next_hop;
-  }
-  else
-  {
-   type = NULL;
-   return NULL;
-  }
+  return current_closest_peer;
 }
 
 
 /**
- * Send a get message to selected target friend. If target friend in NULL,
- * then search for a target friend. 
- * @param block_type type of the block
- * @param options routing options
- * @param desired_replication_level desired replication count
- * @param hop_count how many hops did this request traverse so far?
- * @param get_peer_path Peer list to reach to final destination which contains the data.
- * @param get_path_length Total numbers of peer in get_path
- * @param key Key key for the content
- * @param target_peer Next peer to forward the message to.
- * @param current_destination Peer which will get this message. 
- * @param current_dest_type Type of current destination can be either FRIEND or FINGER
+ * FIXME: first check if the finger == closest_peer then don't do anything. 
+ * Find the successor for destination_finger_value among my_identity, all my
+ * friend and all my fingers. Don't consider friends or fingers
+ * which are congested or have crossed the threshold.
+ * @param destination_finger_value Peer closest to this value will be the next successor.
+ * @param local_best_known_destination [out] Updated to my_identity if I am the 
+ *                                     final destination. Updated to friend 
+ *                                     identity in case a friend is successor,
+ *                                     updated to first friend to reach to finger
+ *                                     in case finger is the destination.
+ * @param new_intermediate_trail_id [out] In case a finger is the
+ *                                  @a local_best_known_destination,
+ *                                  then it is the trail to reach it. Else
+ *                                  default set to 0.
+ * @param is_predecessor Are we looking for predecessor or finger?
+ * @return Next hop to reach to local_best_known_destination. In case my_identity
+ *         or a friend is a local_best_known_destination, then 
+ *         next_hop = local_best_known_destination. Else
+ *         next_hop is the first friend to reach to finger (local_best_known_destination)
  */
-void
-GDS_NEIGHBOURS_handle_get (enum GNUNET_BLOCK_Type block_type,
-                           enum GNUNET_DHT_RouteOption options,
-                           uint32_t desired_replication_level,
-                           uint32_t hop_count,
-                           struct GNUNET_PeerIdentity *get_peer_path,
-                           unsigned int get_path_length,
-                           struct GNUNET_HashCode *key,
-                           struct GNUNET_PeerIdentity *target_peer,
-                           struct GNUNET_PeerIdentity *current_destination,
-                           struct GNUNET_PeerIdentity *current_source,
-                           enum current_destination_type *current_dest_type)
-{
-  struct PeerGetMessage *get_request;
-  struct P2PPendingMessage *pending;
-  struct GNUNET_PeerIdentity *get_path;
-  struct FriendInfo *target_friend;
-  uint64_t key_value;
-  size_t msize;
-  
-  msize = sizeof (struct PeerGetMessage) + 
-          (get_path_length * sizeof (struct GNUNET_PeerIdentity));
-  
-  if (msize >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
-  {
-    GNUNET_break (0);
-    return;
-  }
-  
-  memcpy (&key_value, key, sizeof (uint64_t));
+static struct GNUNET_PeerIdentity *
+find_successor (uint64_t destination_finger_value,
+                struct GNUNET_PeerIdentity *local_best_known_destination,
+                struct GNUNET_HashCode *new_intermediate_trail_id,
+                unsigned int is_predecessor)
+{
+  struct Closest_Peer *current_closest_peer;
+  struct GNUNET_PeerIdentity *next_hop;
+
+   /* Initialize current_successor to my_identity. */
+  current_closest_peer = init_current_successor (my_identity,
+                                                 destination_finger_value,
+                                                 is_predecessor);
+
+  /* Compare each friend entry with current_successor and update current_successor
+   * with friend if its closest. */
+  GNUNET_assert (GNUNET_SYSERR != 
+                 GNUNET_CONTAINER_multipeermap_iterate (friend_peermap, 
+                                                        &compare_friend_and_current_closest_peer,
+                                                        current_closest_peer));
   
-  /* FIXME: Is this correct comparison? */
-  if (NULL == target_peer)
-  {
-    /* We have received the request from the client file and we don't know
-     to which peer should we forward the message to. */
-    struct GNUNET_PeerIdentity *next_hop;  
-    next_hop = find_successor (key_value, current_destination, current_dest_type);
-    
-    if (*current_dest_type == MY_ID)
-    {
-      get_path = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-      memcpy (get_path, &my_identity, sizeof (struct GNUNET_PeerIdentity));
-      get_path_length = 1;
-      /* FIXME: At the moment I am just passing null,0 for values which I don't
-       have. Also, handle return type. Modify this function and pass get path
-       and get path length and then in datacache_handle. here in this case
-       you can diretly call gds_client_handle_reply. */
-#if 0
-      GDS_DATACACHE_handle_get (&(get_request->key),(get_request->block_type), 
-                                get_path, get_path_length,get_path_length - 1,NULL);
-#endif
-      return;
-    }
-    else 
-    {
-      if (*current_dest_type == FINGER)
-      {
-        memcpy (current_source, &my_identity, sizeof (struct GNUNET_PeerIdentity));
-      }
-      
-      target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop);
-    }
-  }
-  else
-    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, target_peer);
+  /* Compare each finger entry with current_successor and update current_successor
+   * with finger if its closest. */
+  compare_finger_and_current_successor (current_closest_peer);
   
-  pending = GNUNET_malloc (sizeof (struct P2PPendingMessage) + msize);
-  pending->importance = 0;    /* FIXME */
-  get_request = (struct PeerGetMessage *) &pending[1];
-  pending->msg = &get_request->header;
-  get_request->header.size = htons (msize);
-  get_request->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_P2P_GET);
-  get_request->get_path_length = htonl (get_path_length);
-  get_request->key = *key;
-  memcpy (&(get_request->current_destination), current_destination, sizeof (struct GNUNET_PeerIdentity));
-  /* FIXME: Is this comparison correct? */
-  if (current_source != NULL)
-    memcpy (&(get_request->current_source), current_source, sizeof (struct GNUNET_PeerIdentity));
-  get_request->current_dest_type = htonl (*current_dest_type);
-  get_path = (struct GNUNET_PeerIdentity *) &get_request[1];
-  memcpy (get_path, get_peer_path, get_path_length * sizeof (struct GNUNET_PeerIdentity));
-  GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
-  target_friend->pending_count++;
-  process_friend_queue (target_friend);
+  *local_best_known_destination = current_closest_peer->best_known_destination;
+  new_intermediate_trail_id = &current_closest_peer->trail_id;
+  next_hop = GNUNET_new (struct GNUNET_PeerIdentity);
+  *next_hop = current_closest_peer->next_hop;
   
+  return next_hop;
 }
 
 
 /**
- * FIXME: Here you should update the fields of struct PeerGetResultMessage.
- * At the end of this message you should add the data and get path and send 
- * to the original requesting client. and there you should call GDS_CLIENT_handle_reply
- * with correct parameter. 
- * @param expiration
- * @param key
- * @param get_path_length
- * @param get_path
- * @param put_path_length
- * @param put_path
- * @param type
- * @param data_size
- * @param data
- */
-void 
-GDS_NEIGHBOURS_datacache_get (struct GNUNET_TIME_Absolute expiration,
-                              const struct GNUNET_HashCode *key,
-                              unsigned int get_path_length,
-                              const struct GNUNET_PeerIdentity *get_path,
-                              unsigned int put_path_length,
-                              const struct GNUNET_PeerIdentity *put_path,
-                              enum GNUNET_BLOCK_Type type, size_t data_size,
-                              const void *data)
-{
-  /* Here you don't have the get path and get path length. you should call
-   some function get those values and update the message and send them. */
-}
-
-
-/** 
- * TODO: In case of put, you add the peer in the peer list in handle_dht_p2p_put.
- * Verify that the addition is correct and we are adding peers correctly and incrementing
- * the trail length correctly. 
- * Handle a put request from client file. If I am the final destination,
- * do a put else forward the message to next peer.
- * @param block_type type of the block
- * @param options routing options
- * @param desired_replication_level desired replication count, 0 for current
- *        implementation of X-Vine.
- * @param expiration_time when does the content expire
- * @param hop_count how many hops has this message traversed so far
- * @param key key for the content
- * @param put_path_length number of entries in @a put_path
- * @param put_path peers this request has traversed so far (if tracked)
- * @param data payload to store
- * @param data_size number of bytes in @a data
- * @param current_destination intermediate destination of the packet.
- * @param current_source source for which @a current_destination is destination.
- * @param dest_type type of @a current_destination.
- * @param target_peer_id Next peer to forward the message to.
+ * Construct a Put message and send it to target_peer.
+ * @param key Key for the content
+ * @param block_type Type of the block
+ * @param options Routing options
+ * @param desired_replication_level Desired replication count
+ * @param best_known_dest Peer to which this message should reach eventually,
+ *                        as it is best known destination to me. 
+ * @param intermediate_trail_id Trail id in case 
+ * @param target_peer Peer to which this message will be forwarded.
+ * @param hop_count Number of hops traversed so far.
+ * @param put_path_length Total number of peers in @a put_path
+ * @param put_path Number of peers traversed so far
+ * @param expiration_time When does the content expire
+ * @param data Content to store
+ * @param data_size Size of content @a data in bytes
  */
 void
-GDS_NEIGHBOURS_handle_put (enum GNUNET_BLOCK_Type block_type,
-                           enum GNUNET_DHT_RouteOption options,
-                           uint32_t desired_replication_level,
-                           struct GNUNET_TIME_Absolute expiration_time,
-                           uint32_t hop_count,
-                           const struct GNUNET_HashCode *key,
-                           unsigned int put_path_length,
-                           struct GNUNET_PeerIdentity *put_path,
-                           const void *data, size_t data_size,
-                           struct GNUNET_PeerIdentity *current_destination,
-                           struct GNUNET_PeerIdentity *current_source,
-                           enum current_destination_type dest_type,
-                           struct GNUNET_PeerIdentity *target_peer)
+GDS_NEIGHBOURS_send_put (const struct GNUNET_HashCode *key,
+                         enum GNUNET_BLOCK_Type block_type,
+                                          enum GNUNET_DHT_RouteOption options,
+                                          uint32_t desired_replication_level,
+                                          struct GNUNET_PeerIdentity *best_known_dest,
+                                          struct GNUNET_HashCode *intermediate_trail_id,
+                                          struct GNUNET_PeerIdentity *target_peer,
+                         uint32_t hop_count,
+                         uint32_t put_path_length,
+                         struct GNUNET_PeerIdentity *put_path,
+                         struct GNUNET_TIME_Absolute expiration_time,
+                         const void *data, size_t data_size)
 {
   struct PeerPutMessage *ppm;
   struct P2PPendingMessage *pending;
   struct FriendInfo *target_friend;
   struct GNUNET_PeerIdentity *pp;
+  struct GNUNET_PeerIdentity *local_best_known_dest;
   size_t msize;
-  uint64_t key_value;
-  
+
   msize = put_path_length * sizeof (struct GNUNET_PeerIdentity) + data_size +
           sizeof (struct PeerPutMessage);
   
@@ -2146,40 +2075,31 @@ GDS_NEIGHBOURS_handle_put (enum GNUNET_BLOCK_Type block_type,
     return;
   }
   
-  memcpy (&key_value, key, sizeof (uint64_t)); 
-  struct GNUNET_PeerIdentity *current_dest;
-  current_dest = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-  if (target_peer == NULL)
+   /* This is the first call made from clients file. So, we should search for the
+     target_friend. */
+  if (NULL == target_peer)
   {
-     /* This is the first time the call has been made from handle_dht_local_put.
-     So, you need to search for the next peer to send this message to. */
-    struct GNUNET_PeerIdentity *next_hop;  
+    uint64_t key_value;
+    struct GNUNET_PeerIdentity *next_hop;
    
-    next_hop = find_successor (key_value, current_dest, &dest_type);  
-    if (dest_type == MY_ID)
+    memcpy (&key_value, key, sizeof (uint64_t));
+    local_best_known_dest = GNUNET_new (struct GNUNET_PeerIdentity);
+    
+    next_hop = find_successor (key_value, local_best_known_dest, 
+                               intermediate_trail_id, GDS_FINGER_TYPE_NON_PREDECESSOR);
+    if (0 == GNUNET_CRYPTO_cmp_peer_identity (local_best_known_dest, &my_identity)) 
     {
-      /* FIXME: Choose one place to do datacache_put. I am doing put only if its
-         destination so I will do no put operation
-       in the client file.*/
-      GDS_DATACACHE_handle_put (expiration_time, key, put_path_length, put_path,
-                                block_type, data_size, data);
+      /* I am the destination but we have already done datacache_put in client file.  */
       return;
     }
     else
-    {
-      /* Find the friend corresponding to next_hop */
-      if (dest_type == FINGER)
-      {
-        memcpy (current_source, &my_identity, sizeof (struct GNUNET_PeerIdentity));
-      }
-      target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop);
-    }
+      target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop);   
   }
   else
-    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, target_peer);
-  
+  {
+    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, target_peer); 
+  }
   pending = GNUNET_malloc (sizeof (struct P2PPendingMessage) + msize);
-  pending->importance = 0;    /* FIXME */
   pending->timeout = expiration_time;
   ppm = (struct PeerPutMessage *) &pending[1];
   pending->msg = &ppm->header;
@@ -2191,25 +2111,16 @@ GDS_NEIGHBOURS_handle_put (enum GNUNET_BLOCK_Type block_type,
   ppm->desired_replication_level = htonl (desired_replication_level);
   ppm->put_path_length = htonl (put_path_length);
   ppm->expiration_time = GNUNET_TIME_absolute_hton (expiration_time);
-  /* FIXME: Here I am checking if we have a value in current_source then only copy.
-   I am not sure if this checking is correct or not. */
-  if (current_source != NULL)
-    memcpy (&(ppm->current_source), current_source, sizeof (struct GNUNET_PeerIdentity));
-  
-  /* FIXME: here current_destination is the parameter, current_dest is what you
-   get when you call find_successor. names don't do justice to the function.
-   Please change it*/
-  if (current_destination != NULL)
-    memcpy (&(ppm->current_destination), current_destination, sizeof (struct GNUNET_PeerIdentity));
+  if (NULL == best_known_dest)
+    ppm->best_known_destination = *local_best_known_dest;
   else
-    memcpy (&(ppm->current_destination), current_dest, sizeof (struct GNUNET_PeerIdentity));
-  ppm->current_destination_type = htonl (dest_type);
+    ppm->best_known_destination = *best_known_dest;
   ppm->key = *key;
-  
+  if (NULL == intermediate_trail_id)
+    memset (&ppm->intermediate_trail_id, 0, sizeof (ppm->intermediate_trail_id));
+  else
+    ppm->intermediate_trail_id = *intermediate_trail_id;
   pp = (struct GNUNET_PeerIdentity *) &ppm[1];
-  /* FIXME: Is this comparison correct? Do we need this comparison. What happens
-   in the case put_path_length is 0 and put_path is NULL, then at run time
-   memcpy will fail. And I am not sure if comparing NULL is correct or not. */
   if (put_path_length != 0)
   {
     memcpy (pp, put_path,
@@ -2222,43 +2133,141 @@ GDS_NEIGHBOURS_handle_put (enum GNUNET_BLOCK_Type block_type,
 }
 
 
+
 /**
- * FIXME: I am removing source peer as the first element in the trail
- * is source identity.
- * If I am adding myself when I am source then I don't need destination 
- * peer in get but if I am not adding then I need it. At the moment I am removing
- * it but will check later if its wrong. 
- * Send get result back to requesting client. 
- * @param expiration when will the reply expire
- * @param key the query this reply is for
- * @param get_path_length number of peers in @a get_path
- * @param get_path path the reply took on get
- * @param put_path_length number of peers in @a put_path
- * @param put_path path the reply took on put
- * @param type type of the reply
- * @param data_size number of bytes in @a data
- * @param data application payload data
- * @param get_path
- * @param get_path_length
- */
-void 
-GDS_NEIGHBOURS_send_get_result (struct GNUNET_TIME_Absolute expiration,
-                                const struct GNUNET_HashCode *key,
+ * Construct a Get message and send it to target_peer.
+ * @param key Key for the content
+ * @param block_type Type of the block
+ * @param options Routing options
+ * @param desired_replication_level Desired replication count
+ * @param best_known_dest 
+ * @param intermediate_trail_id 
+ * @param target_peer Peer to which this message will be forwarded.
+ * @param hop_count Number of hops traversed so far.
+ * @param data Content to store
+ * @param data_size Size of content @a data in bytes
+ * @param get_path_length Total number of peers in @a get_path
+ * @param get_path Number of peers traversed so far
+ */
+void
+GDS_NEIGHBOURS_send_get (const struct GNUNET_HashCode *key,
+                         enum GNUNET_BLOCK_Type block_type,
+                         enum GNUNET_DHT_RouteOption options,
+                         uint32_t desired_replication_level,
+                         struct GNUNET_PeerIdentity *best_known_dest,
+                         struct GNUNET_HashCode *intermediate_trail_id,
+                         struct GNUNET_PeerIdentity *target_peer,
+                         uint32_t hop_count,
+                         uint32_t get_path_length,
+                         struct GNUNET_PeerIdentity *get_path)
+{
+  struct PeerGetMessage *pgm;
+  struct P2PPendingMessage *pending;
+  struct FriendInfo *target_friend;
+  struct GNUNET_PeerIdentity *local_best_known_dest;
+  struct GNUNET_PeerIdentity *gp;
+  size_t msize;
+
+  msize = sizeof (struct PeerGetMessage) + 
+          (get_path_length * sizeof (struct GNUNET_PeerIdentity));
+  
+  if (msize >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
+  {
+    GNUNET_break (0);
+    return;
+  }
+  
+  if (NULL == target_peer)
+  {
+    struct GNUNET_PeerIdentity *next_hop;
+    uint64_t key_value;
+    
+    memcpy (&key_value, key, sizeof (uint64_t));
+       // FIXME: endianess of key_value!?
+    local_best_known_dest = GNUNET_new (struct GNUNET_PeerIdentity);
+    next_hop = find_successor (key_value, local_best_known_dest,
+                               intermediate_trail_id, GDS_FINGER_TYPE_NON_PREDECESSOR);
+    
+    if (0 == GNUNET_CRYPTO_cmp_peer_identity (&my_identity,next_hop)) 
+    {
+      GDS_DATACACHE_handle_get (key,block_type, NULL, 0, 
+                                NULL, 0, 1, &my_identity, NULL,&my_identity);
+      return;
+    }
+    else
+    {
+      target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop);
+    }
+  }
+  else
+  {
+    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, target_peer); 
+  }
+  
+  pending = GNUNET_malloc (sizeof (struct P2PPendingMessage) + msize);
+  pending->importance = 0;    /* FIXME */
+  pgm = (struct PeerGetMessage *) &pending[1];
+  pending->msg = &pgm->header;
+  pgm->header.size = htons (msize);
+  pgm->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_P2P_GET);
+  pgm->get_path_length = htonl (get_path_length);
+  pgm->key = *key;
+  if (NULL != best_known_dest)
+   pgm->best_known_destination = *best_known_dest;
+  else
+    pgm->best_known_destination = *local_best_known_dest;
+  
+  if (NULL == intermediate_trail_id)
+    memset (&pgm->intermediate_trail_id, 0, sizeof (pgm->intermediate_trail_id));
+  else
+    pgm->intermediate_trail_id = *intermediate_trail_id;
+  pgm->hop_count = htonl (hop_count + 1);
+  
+  if (get_path != 0)
+  {
+    gp = (struct GNUNET_PeerIdentity *) &pgm[1];
+    memcpy (gp, get_path, get_path_length * sizeof (struct GNUNET_PeerIdentity));
+  }
+  GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
+  target_friend->pending_count++;
+  process_friend_queue (target_friend);
+}
+
+
+/**
+ * Send the get result to requesting client.
+ * @param key Key of the requested data.
+ * @param type Block type
+ * @param target_peer Next peer to forward the message to.
+ * @param source_peer Peer which has the data for the key.
+ * @param put_path_length Number of peers in @a put_path
+ * @param put_path Path taken to put the data at its stored location.
+ * @param get_path_length Number of peers in @a get_path
+ * @param get_path Path taken to reach to the location of the key.
+ * @param expiration When will this result expire?
+ * @param data Payload to store
+ * @param data_size Size of the @a data
+ */
+void
+GDS_NEIGHBOURS_send_get_result (const struct GNUNET_HashCode *key,
+                                enum GNUNET_BLOCK_Type type,
+                                struct GNUNET_PeerIdentity *target_peer,
+                                struct GNUNET_PeerIdentity *source_peer,
                                 unsigned int put_path_length,
                                 const struct GNUNET_PeerIdentity *put_path,
-                                enum GNUNET_BLOCK_Type type, size_t data_size,
-                                const void *data,
-                                struct GNUNET_PeerIdentity *get_path,
                                 unsigned int get_path_length,
-                                unsigned int current_path_index,
-                                struct GNUNET_PeerIdentity *next_hop)
+                                struct GNUNET_PeerIdentity *get_path,
+                                struct GNUNET_TIME_Absolute expiration,
+                                const void *data, size_t data_size)
 {
   struct PeerGetResultMessage *get_result;
   struct GNUNET_PeerIdentity *get_result_path;
+  struct GNUNET_PeerIdentity *pp;
   struct P2PPendingMessage *pending;
   struct FriendInfo *target_friend;
+  int current_path_index;
   size_t msize;
-  
+
   msize = get_path_length * sizeof (struct GNUNET_PeerIdentity) + data_size +
           sizeof (struct PeerPutMessage);
  
@@ -2267,25 +2276,51 @@ GDS_NEIGHBOURS_send_get_result (struct GNUNET_TIME_Absolute expiration,
     GNUNET_break (0);
     return;
   }
-  /* GET_REULT should have all the things which we want to pass in client_handle_reply
-   put path put path length get path get length data data_size. and rest things
-   are required to reach to the correct peer. */
+  
+  if(get_path_length > 0)
+  {
+    current_path_index = search_my_index(get_path, get_path_length);
+    if (GNUNET_SYSERR == current_path_index)
+    {
+      GNUNET_break (0);
+      return;
+    }
+  }
+  if (0 == current_path_index)
+  {
+    GDS_CLIENTS_handle_reply (expiration, key, get_path_length, 
+                              get_path, put_path_length,
+                              put_path, type, data_size, data);
+    return;
+  }
+  
   pending = GNUNET_malloc (sizeof (struct P2PPendingMessage) + msize);
-  pending->importance = 0;    /* FIXME */
-  /* FIXME: Should we add an expiration time like in put message. */
+  pending->importance = 0;   
   get_result = (struct PeerGetResultMessage *)&pending[1];
   pending->msg = &get_result->header;
   get_result->header.size = htons (msize);
   get_result->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_P2P_GET_RESULT);
-  get_result->current_path_index = current_path_index;
   get_result->key = *key;
+  /* FIXME: check if you are passing the correct querying_peer as described in
+   the get_result documentation. */
+  memcpy (&(get_result->querying_peer), source_peer, sizeof (struct GNUNET_PeerIdentity));
+  get_result->expiration_time = expiration;
+  
   
   get_result_path = (struct GNUNET_PeerIdentity *)&get_result[1];
   memcpy (get_result_path, get_path,
-           sizeof (struct GNUNET_PeerIdentity) * get_path_length);
+            sizeof (struct GNUNET_PeerIdentity) * get_path_length);
   memcpy (&get_result_path[get_path_length], data, data_size);
   
-  target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop);
+  /* FIXME: Is this correct? */
+  if (put_path_length != 0)
+  {
+    pp = (struct GNUNET_PeerIdentity *)&get_result_path[1];
+    memcpy (pp, put_path,sizeof (struct GNUNET_PeerIdentity) * put_path_length);
+  }
+  
+  target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, 
+                                                     &get_result_path[current_path_index - 1]);
   GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
   target_friend->pending_count++;
   process_friend_queue (target_friend);
@@ -2293,24 +2328,1268 @@ GDS_NEIGHBOURS_send_get_result (struct GNUNET_TIME_Absolute expiration,
 
 
 /**
- * 
- * @param cls
- * @param peer
- * @param message
- * @return 
+ * Randomly choose one of your friends (which is not congested and have not crossed
+ * trail threshold) from the friends_peer map
+ * @return Friend Randomly chosen friend.
+ *         NULL in case friend peermap is empty, or all the friends are either
+ *              congested or have crossed trail threshold.
+ */
+static struct FriendInfo *
+select_random_friend ()
+{
+  unsigned int current_size;
+  uint32_t index;
+  unsigned int j = 0;
+  struct GNUNET_CONTAINER_MultiPeerMapIterator *iter;
+  struct GNUNET_PeerIdentity key_ret;
+  struct FriendInfo *friend;
+
+  current_size = GNUNET_CONTAINER_multipeermap_size (friend_peermap);
+  if (0 == current_size)
+    return NULL;
+
+  index = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK, current_size);
+  iter = GNUNET_CONTAINER_multipeermap_iterator_create (friend_peermap);
+
+  for (j = 0; j < index ; j++)
+    GNUNET_assert (GNUNET_YES ==
+                   GNUNET_CONTAINER_multipeermap_iterator_next (iter, NULL, NULL));
+  do
+  {
+    if (j == current_size)
+    {
+      j = 0;
+      GNUNET_CONTAINER_multipeermap_iterator_destroy (iter);
+      iter = GNUNET_CONTAINER_multipeermap_iterator_create (friend_peermap);
+
+    }
+    GNUNET_assert (GNUNET_YES ==
+                GNUNET_CONTAINER_multipeermap_iterator_next (iter,
+                                                             &key_ret,
+                                                             (const void **)&friend));
+
+    /* This friend is not congested and has not crossed trail threshold. */
+    if ((TRAILS_THROUGH_FRIEND_THRESHOLD > friend->trails_count) &&
+        (0 == GNUNET_TIME_absolute_get_remaining (friend->congestion_timestamp).rel_value_us))
+    {
+      break;
+    }
+    friend = NULL;
+    j++;
+  } while (j != index);
+
+  GNUNET_CONTAINER_multipeermap_iterator_destroy (iter);
+  return friend;
+}
+
+
+/**
+ * Compute 64 bit value of finger_identity corresponding to a finger index using 
+ * chord formula. 
+ * For all fingers:
+ * n.finger[i] = n + pow (2,i),
+ * For predecessor
+ * n.finger[i] = n - 1, where
+ * n = my_identity
+ * i = finger_index.
+ * n.finger[i] = 64 bit finger value
+ * @param finger_index Index corresponding to which we calculate 64 bit value.
+ * @return 64 bit value.
+ */
+static uint64_t
+compute_finger_identity_value (unsigned int finger_index)
+{
+  uint64_t my_id64;
+
+  memcpy (&my_id64, &my_identity, sizeof (uint64_t));
+  my_id64 = GNUNET_ntohll (my_id64);
+  
+  /* Are we looking for immediate predecessor? */
+  if (PREDECESSOR_FINGER_ID == finger_index)
+    return (my_id64 -1);
+  else
+    return (my_id64 + (unsigned long) pow (2, finger_index));
+}
+
+
+/*
+ * Choose a random friend. Start looking for the trail to reach to
+ * finger identity corresponding to current_search_finger_index through 
+ * this random friend.
+ *
+ * @param cls closure for this task
+ * @param tc the context under which the task is running
+ */
+static void
+send_find_finger_trail_message (void *cls,
+                                const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct FriendInfo *target_friend;
+  struct GNUNET_TIME_Relative next_send_time;
+  struct GNUNET_HashCode trail_id;
+  unsigned int is_predecessor;
+  uint64_t finger_id_value;
+
+  /* Schedule another send_find_finger_trail_message task. */
+  next_send_time.rel_value_us =
+      DHT_FIND_FINGER_TRAIL_INTERVAL.rel_value_us +
+      GNUNET_CRYPTO_random_u64 (GNUNET_CRYPTO_QUALITY_WEAK,
+                                DHT_FIND_FINGER_TRAIL_INTERVAL.rel_value_us);
+  find_finger_trail_task =
+      GNUNET_SCHEDULER_add_delayed (next_send_time, &send_find_finger_trail_message,
+                                    NULL);
+
+  /* My own routing table is all full. I can not store any more trails for which 
+     I am source. */
+  if (GNUNET_YES == GDS_ROUTING_threshold_reached())
+    return;
+  
+  target_friend = select_random_friend ();
+  if (NULL == target_friend)
+  {
+    return;
+  }
+  
+  finger_id_value = compute_finger_identity_value (current_search_finger_index);
+  if (PREDECESSOR_FINGER_ID == current_search_finger_index)
+    is_predecessor = 1;
+  else
+    is_predecessor = 0;
+
+  /* Generate a unique trail id for trail we are trying to setup. */
+  GNUNET_CRYPTO_random_block (GNUNET_CRYPTO_QUALITY_STRONG,
+                              &trail_id, sizeof (trail_id));
+  GDS_NEIGHBOURS_send_trail_setup (my_identity, finger_id_value,
+                                   target_friend->id, target_friend, 0, NULL,
+                                   is_predecessor, trail_id, NULL);
+}
+
+
+/**
+ * In case there are already maximum number of possible trails to reach to a
+ * finger, then check if the new trail's length is lesser than any of the
+ * existing trails.
+ * If yes then replace that old trail by new trail.
+ *
+ * Note: Here we are taking length as a parameter to choose the best possible
+ * trail, but there could be other parameters also like:
+ * 1. duration of existence of a trail - older the better.
+ * 2. if the new trail is completely disjoint than the
+ *    other trails, then may be choosing it is better.
+ *
+ * @param existing_finger
+ * @param new_finger_trail
+ * @param new_finger_trail_length
+ * @param new_finger_trail_id
+ */
+static void
+select_and_replace_trail (struct FingerInfo *existing_finger,
+                          const struct GNUNET_PeerIdentity *new_trail,
+                          unsigned int new_trail_length,
+                          struct GNUNET_HashCode new_trail_id)
+{
+  struct Trail *trail_list_iterator;
+  unsigned int largest_trail_length;
+  unsigned int largest_trail_index;
+  struct Trail_Element *trail_element;
+  unsigned int i;
+
+  largest_trail_length = new_trail_length;
+  largest_trail_index = MAXIMUM_TRAILS_PER_FINGER + 1;
+
+  GNUNET_assert (MAXIMUM_TRAILS_PER_FINGER == existing_finger->trails_count);
+
+  for (i = 0; i < existing_finger->trails_count; i++)
+  {
+    trail_list_iterator = &existing_finger->trail_list[i];
+    if (trail_list_iterator->trail_length > largest_trail_length)
+    {
+      largest_trail_length = trail_list_iterator->trail_length;
+      largest_trail_index = i;
+    }
+  }
+
+  if (largest_trail_index == (MAXIMUM_TRAILS_PER_FINGER + 1))
+  {
+    // tear down new trail: it's not better than the existing ones
+    return;
+  }
+
+  /* Send trail teardown message across the replaced trail. */
+  struct Trail *replace_trail = &existing_finger->trail_list[largest_trail_index];
+
+  GDS_NEIGHBOURS_send_trail_teardown (replace_trail->trail_id,
+                                      GDS_ROUTING_SRC_TO_DEST,
+                                      &replace_trail->trail_head->peer);
+  /* Free the trail. */
+  while (NULL != (trail_element = replace_trail->trail_head))
+  {
+    GNUNET_CONTAINER_DLL_remove (replace_trail->trail_head,
+                                 replace_trail->trail_tail, trail_element);
+    GNUNET_free_non_null (trail_element);
+  }
+
+  /* Add new trial at that location. */
+  i = 0;
+  while (i < new_trail_length)
+  {
+    struct Trail_Element *element = GNUNET_new (struct Trail_Element);
+    element->peer = new_trail[i];
+
+    GNUNET_CONTAINER_DLL_insert_tail (replace_trail->trail_head,
+                                      replace_trail->trail_tail,
+                                      element);
+  }
+}
+
+
+/**
+ * Check if the new trail to reach to finger is unique or do we already have
+ * such a trail present for finger.
+ * @param existing_finger Finger identity
+ * @param new_trail New trail to reach @a existing_finger
+ * @param trail_length Total number of peers in new_trail.
+ * @return #GNUNET_YES if the new trail is unique
+ *         #GNUNET_NO if same trail is already present.
+ */
+static int
+is_new_trail_unique (struct FingerInfo *existing_finger,
+                     const struct GNUNET_PeerIdentity *new_trail,
+                     unsigned int trail_length)
+{
+  struct Trail *trail_list_iterator;
+  struct Trail_Element *trail_element;
+  int i;
+  int j;
+  int trail_unique = GNUNET_NO;
+
+  for (i = 0; i < existing_finger->trails_count; i++)
+  {
+    trail_list_iterator = &existing_finger->trail_list[i];
+    if (trail_list_iterator->trail_length != trail_length)
+      continue;
+    trail_element = trail_list_iterator->trail_head;
+    for (j = 0; j < trail_list_iterator->trail_length; j++)
+    {
+      if (0 != GNUNET_CRYPTO_cmp_peer_identity (&new_trail[j],
+                                                &trail_element->peer))
+      {
+        trail_unique = GNUNET_YES;
+        break;
+      }
+    }
+  }
+  return trail_unique;
+}
+
+
+/**
+ * Add a new trail to existing finger.
+ * @param existing_finger
+ * @param new_finger_trail
+ * @param new_finger_trail_length
+ * @param new_finger_trail_id
+ */
+static void
+add_new_trail (struct FingerInfo *existing_finger,
+               const struct GNUNET_PeerIdentity *new_trail,
+               unsigned int new_trail_length,
+               struct GNUNET_HashCode new_trail_id)
+{
+  struct Trail *trail_list_iterator;
+  struct FriendInfo *first_friend;
+  int i;
+
+  if (GNUNET_NO == is_new_trail_unique (existing_finger, new_trail,
+                                        new_trail_length))
+  {
+    return;
+  }
+
+  // FIXME checking trail_head is NOT a valid way to verify an open slot
+  for (i = 0; existing_finger->trail_list[i].trail_head != NULL; i++)
+    GNUNET_assert (i < MAXIMUM_TRAILS_PER_FINGER);
+
+  trail_list_iterator = &existing_finger->trail_list[i];
+
+  if (new_trail_length > 0)
+    first_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                                      &new_trail[0]);
+  else
+    first_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                                      &(existing_finger->finger_identity));
+  first_friend->trails_count++;
+  /* FIXME; we removed this field but read fixme. */
+  //trail_list_iterator->first_friend_trail_count = first_friend->trails_count;
+  trail_list_iterator->trail_length = new_trail_length;
+
+  for (i = 0; i < new_trail_length; i++)
+  {
+    struct Trail_Element *element;
+    element = GNUNET_new (struct Trail_Element);
+
+    element->peer = new_trail[i];
+    GNUNET_CONTAINER_DLL_insert_tail (trail_list_iterator->trail_head,
+                                      trail_list_iterator->trail_tail,
+                                      element);
+  }
+  existing_finger->trails_count++;
+}
+
+
+/**
+ * Send trail teardown message for a specific trail of a finger.
+ * @param finger Finger whose trail is to be removed. 
+ * @param trail List of peers in trail from me to a finger, NOT including 
+ *              endpoints. 
+ */
+static void
+send_trail_teardown (struct FingerInfo *finger,
+                     struct Trail *trail)
+{
+  /* FIXME: Now source also stores a trail entry in its routing table. before
+   sending the trail teardown, you should get next_hop from routing table.
+   If it is NULL, it means that path is broken, then remove the trail. 
+   return a value to calling function so that if all trails are removed,
+   then remove finger. */
+  /* We should decerement the friend trail count here. */
+  struct FriendInfo *friend;
+  
+  GNUNET_assert (NULL != (friend = 
+          GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                             &trail->trail_head->peer)));
+  
+  friend->trails_count--;
+  GDS_NEIGHBOURS_send_trail_teardown (trail->trail_id,
+                                      GDS_ROUTING_SRC_TO_DEST,
+                                      &trail->trail_head->peer);
+}
+
+
+/**
+ * Send trail teardown message across all the trails to reach to finger. 
+ * @param finger Finger whose all the trail should be freed. 
+ */
+static void
+send_all_finger_trails_teardown (struct FingerInfo *finger)
+{
+  struct Trail *trail;
+  int i;
+
+  for (i = 0; i < finger->trails_count; i++)
+  {
+    trail = &finger->trail_list[i];
+    if (trail->trail_length > 0)
+    {
+     /* decerement the friend trails count. */
+     send_trail_teardown (finger, trail);
+    }
+  }
+}
+
+
+/**
+ * Free a specific trail
+ * @param trail List of peers to be freed. 
+ */
+static void
+free_trail (struct Trail *trail)
+{
+  struct Trail_Element *trail_element;
+
+  while (NULL != (trail_element = trail->trail_head))
+  {
+    GNUNET_CONTAINER_DLL_remove (trail->trail_head, 
+                                 trail->trail_tail,
+                                 trail_element);
+    GNUNET_free_non_null (trail_element);
+  }  
+  trail->trail_head = NULL;
+  trail->trail_tail = NULL;
+}
+
+
+/**
+ * Free finger and its trail.
+ * @param finger Finger to be freed.
+ */
+static void
+free_finger (struct FingerInfo *finger, unsigned int finger_table_index)
+{
+  struct Trail *trail;
+  unsigned int i;
+
+  for (i = 0; i < finger->trails_count; i++)
+  {
+    trail = &finger->trail_list[i];
+    if (GNUNET_NO == trail->is_present)
+      continue;
+    
+    if (trail->trail_length > 0)
+      free_trail (trail);
+  }
+  
+  finger->is_present = GNUNET_NO;
+  memset ((void *)&finger_table[finger_table_index], 0, sizeof (finger_table[finger_table_index]));
+}
+
+
+/**
+ * FIXME: ensure that you are not adding any trail to reach to a friend which
+ * is a finger. Also decide on should you increment trails count of a friend
+ * which is also a finger. 
+ * Add a new entry in finger table at finger_table_index. 
+ * In case finger identity is me or a friend, then don't add a trail. NOTE
+ * trail length to reach to a finger can be 0 only if the finger is a friend
+ * or my identity.
+ * In case a finger is a friend, then increment the trails count of the friend.
+ * @param finger_identity Peer Identity of new finger
+ * @param finger_trail Trail to reach from me to finger (excluding both end points).
+ * @param finger_trail_length Total number of peers in @a finger_trail.
+ * @param trail_id Unique identifier of the trail.
+ * @param finger_table_index Index in finger table.
+ */
+static void
+add_new_finger (struct GNUNET_PeerIdentity finger_identity,
+                const struct GNUNET_PeerIdentity *finger_trail,
+                unsigned int finger_trail_length,
+                struct GNUNET_HashCode trail_id,
+                unsigned int finger_table_index)
+{
+  struct FingerInfo *new_entry;
+  struct FriendInfo *first_trail_hop;
+  struct Trail *trail;
+  int i = 0;
+  
+  new_entry = GNUNET_new (struct FingerInfo);
+  new_entry->finger_identity = finger_identity;
+  new_entry->finger_table_index = finger_table_index;
+  new_entry->is_present = GNUNET_YES;
+  
+  /* If the new entry is my own identity or a friend. */
+  if ((0 == GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &finger_identity)) ||
+     (NULL != GNUNET_CONTAINER_multipeermap_get (friend_peermap, &finger_identity)))
+  {
+    new_entry->trails_count = 0;
+    finger_table[finger_table_index] = *new_entry;
+    return;
+  }
+  
+  /* finger trail length can be 0 only in case if finger is my identity or
+   finger is friend. We should never reach here. */
+  GNUNET_assert (finger_trail_length > 0);
+  
+  GNUNET_assert (NULL != 
+                (first_trail_hop = 
+                       GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                                          &finger_trail[0])));
+  new_entry->trails_count = 1;
+  first_trail_hop->trails_count++;
+   
+  /* Copy the finger trail into trail. */
+  trail = GNUNET_new (struct Trail);
+  while (i < finger_trail_length)
+  {
+    struct Trail_Element *element = GNUNET_new (struct Trail_Element);
+
+    element->next = NULL;
+    element->prev = NULL;
+    element->peer = finger_trail[i];
+    GNUNET_CONTAINER_DLL_insert_tail (trail->trail_head,
+                                      trail->trail_tail,
+                                      element);
+    i++;
+  }
+  
+  /* Add trail to trail list. */
+  new_entry->trail_list[0].trail_head = trail->trail_head;
+  new_entry->trail_list[0].trail_tail = trail->trail_tail;
+  new_entry->trail_list[0].trail_length = finger_trail_length;
+  new_entry->trail_list[0].trail_id = trail_id;
+  new_entry->trail_list[0].is_present = GNUNET_YES;
+  finger_table[finger_table_index] = *new_entry;
+  return;
+}
+
+
+/**
+ * Scan the trail to check if there is any other friend in the trail other than
+ * first hop. If yes then shortcut the trail, send trail compression message to
+ * peers which are no longer part of trail and send back the updated trail
+ * and trail_length to calling function.
+ * @param finger_identity Finger whose trail we will scan.
+ * @param finger_trail [in, out] Trail to reach from source to finger,
+ * @param finger_trail_length  Total number of peers in original finger_trail.
+ * @param finger_trail_id Unique identifier of the finger trail.
+ * @return updated trail length in case we shortcut the trail, else original
+ *         trail length.
+ */
+static struct GNUNET_PeerIdentity *
+scan_and_compress_trail (struct GNUNET_PeerIdentity finger_identity,
+                         const struct GNUNET_PeerIdentity *trail,
+                         unsigned int trail_length,
+                         struct GNUNET_HashCode trail_id,
+                         int *new_trail_length)
+{
+  struct FriendInfo *target_friend;
+  struct GNUNET_PeerIdentity *new_trail;
+  int i;
+  
+  /* If I am my own finger identity, then we set trail_length = 0.
+   Note: Here we don't send trail compression message, as no peer in its
+   trail added an entry in its routing table.*/
+  if (0 == GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &finger_identity))
+  {
+    *new_trail_length = 0;
+    return NULL;
+  }
+
+  /* If finger identity is a friend. */
+  if (NULL != GNUNET_CONTAINER_multipeermap_get (friend_peermap, &finger_identity))
+  {
+    *new_trail_length = 0;
+    
+    /* If there is trail to reach this finger/friend */
+    if (trail_length > 0)
+    {
+      target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                                         &trail[0]);
+      /* FIXME: In case its finger == friend, then may be we send a trail 
+       teardown message as it does not make any sense to have any routing e
+       entry in your own routing table.*/
+      GDS_NEIGHBOURS_send_trail_compression (my_identity, 
+                                             trail_id, finger_identity,
+                                             target_friend);
+    }
+    return NULL;
+  }
+
+  /*  For other cases, when its neither a friend nor my own identity.*/
+  for (i = trail_length - 1; i > 0; i--)
+  {
+    /* If the element at this index in trail is a friend. */
+    if (NULL != GNUNET_CONTAINER_multipeermap_get (friend_peermap, &trail[i]))
+    {
+      struct FriendInfo *target_friend;
+      int j = 0;
+
+      target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                                         &trail[0]);
+      GDS_NEIGHBOURS_send_trail_compression (my_identity, 
+                                             trail_id, trail[i],
+                                             target_friend);
+
+    
+      /* Copy the trail from index i to index (trail_length -1) into a new trail
+       *  and update new trail length */
+      new_trail = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity) * i);
+      while (i < trail_length)
+      {
+        memcpy (&new_trail[j], &trail[i], sizeof(struct GNUNET_PeerIdentity));
+        j++;
+        i++;
+      }
+      *new_trail_length = j+1;
+      return new_trail;
+    }
+  }
+  
+  /* If we found no other friend except the first hop, return the original
+     trail back.*/
+  new_trail = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity) * trail_length); 
+  *new_trail_length = trail_length;
+  memcpy (new_trail, trail, trail_length * sizeof (struct GNUNET_PeerIdentity));
+  return new_trail;
+}
+
+
+/**
+ * Send verify successor message to your current successor over the shortest
+ * trail. 
+ * @param successor Current successor.
+ */
+static void
+send_verify_successor_message (struct FingerInfo *successor)
+{
+  /*
+   * FIXME: should we send a verify successor message across all the trails
+   * in case we send through all friends. It complicates the logic, don't
+   * do it at the moment. Write it as optimization and do it later. 
+   * 1. Here we can have 3 types of fingers
+   * --> my own identity
+   *     Assumption that the calling function will not send request for
+   *     such successor. Move the logic here. 
+   * --> friend is a finger
+   *     Need to verify if we keep the trails count for a friend. In case of
+   *     friend there is no trail to reach to that friend, so
+   *     1. no entry in routing table
+   *     2. no trail id
+   *     3. no trails count
+   *     4. but do we increment the count of trails through the friend? 
+   *        Trails count is used only to keep a limit on number of trails
+   *        that a friend should be part of. No need to increment the trails
+   *        count for a friend which is a finegr also. so, if finger = friend
+   *        then don't increment the trails count. But if the same friend 
+   *        is the first friend to reach to some other finger then increment
+   *        the trails count. Not sure if this design is correct need to verify
+   *        again. 
+   * --> real finger
+   */
+  struct FriendInfo *target_friend;
+  struct GNUNET_HashCode trail_id;
+  int i;
+  
+  /* If successor is a friend. */
+  if (successor->trails_count == 0)
+  {
+    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                                       &successor->finger_identity);
+    memset ((void *)&trail_id, 0 , sizeof (trail_id));
+    GDS_NEIGHBOURS_send_verify_successor_message (my_identity,
+                                                  successor->finger_identity,
+                                                  trail_id, NULL, 0,
+                                                  target_friend);
+    return;
+  }
+  
+  for (i = 0; i < successor->trails_count; i++)
+  {
+    struct Trail *trail;
+    struct Trail_Element *element;
+    unsigned int trail_length;
+    int j;
+    
+    trail = &successor->trail_list[i];
+    
+    /* No trail stored at this index. */
+    if (GNUNET_YES == trail->is_present)
+      continue;
+    
+    /* Only in case of a friend we can have no trail. We have already handled
+     * that case. So, now we should never have any such trail. */
+    GNUNET_assert (trail->trail_length > 0);
+    trail_id = trail->trail_id;
+    trail_length = trail->trail_length;
+    
+    /* Copy the trail into peer list. */
+    element = trail->trail_head;
+    struct GNUNET_PeerIdentity peer_list[trail_length];
+    while (j < trail_length)
+    {
+      peer_list[j] = element->peer;
+      element = element->next;
+      j++;
+    }
+   
+    GNUNET_assert (NULL != (target_friend = 
+                           GNUNET_CONTAINER_multipeermap_get (friend_peermap, 
+                                                              &peer_list[0])));
+    GDS_NEIGHBOURS_send_verify_successor_message (my_identity,
+                                                  successor->finger_identity,
+                                                  trail_id, peer_list, trail_length,
+                                                  target_friend);
+    
+  }
+}
+
+
+/**
+ * FIXME" clear abstraction of current search finger index and finger map index.
+ * it never goes to 63. I don't know why
+ * Update the current search finger index. 
+ */
+static void
+update_current_search_finger_index (struct GNUNET_PeerIdentity finger_identity,
+                                    unsigned int finger_table_index)
+{
+  struct FingerInfo *successor;
+
+  if (finger_table_index != current_search_finger_index)
+    return;
+  
+  successor = &finger_table[0];
+  if (GNUNET_NO == successor->is_present)
+    GNUNET_break(0);
+  /* We were looking for immediate successor.  */
+  if (0 == current_search_finger_index)
+  {
+    /* Start looking for immediate predecessor. */
+    current_search_finger_index = PREDECESSOR_FINGER_ID;
+
+    /* If I am not my own successor, then send a verify successor message. */
+    if (0 != GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &finger_identity))
+    {
+      send_verify_successor_message (successor);
+    }
+    return;
+  }
+  
+  current_search_finger_index = current_search_finger_index - 1;
+  return;
+}
+
+
+/**
+ * Calculate finger_table_index from initial 64 bit finger identity value that 
+ * we send in trail setup message. 
+ * @param ultimate_destination_finger_value Value that we calculated from our
+ *                                          identity and finger_table_index.
+ * @param is_predecessor Is the entry for predecessor or not?
+ * @return finger_table_index Value between 0 <= finger_table_index <= 64
+ *                            -1, if no valid finger_table_index is found. 
+ */
+static unsigned int
+get_finger_table_index (uint64_t ultimate_destination_finger_value,
+                        unsigned int is_predecessor)
+{
+  uint64_t my_id64;
+  int diff;
+  unsigned int finger_table_index;
+
+  memcpy (&my_id64, &my_identity, sizeof (uint64_t));
+  my_id64 = GNUNET_ntohll (my_id64);
+  
+  /* Is this a predecessor finger? */
+  if (1 == is_predecessor)
+  {
+    diff =  my_id64 - ultimate_destination_finger_value;
+    if (1 == diff)
+      finger_table_index = PREDECESSOR_FINGER_ID;
+    else
+      finger_table_index = PREDECESSOR_FINGER_ID + 1; //error value
+    
+  }
+  else 
+  {
+    diff = ultimate_destination_finger_value - my_id64;
+    finger_table_index = (log10 (diff))/(log10 (2));
+  }
+  
+  return finger_table_index;
+}
+
+
+/**
+ * Remove finger and its associated data structures from finger table. 
+ * @param finger Finger to be removed.
+ */
+static void
+remove_existing_finger (struct FingerInfo *existing_finger, unsigned int finger_table_index)
+{
+  struct FriendInfo *friend;
+  struct FingerInfo *finger;
+  
+  finger = &finger_table[finger_table_index];
+  GNUNET_assert (GNUNET_YES == finger->is_present);
+  
+  /* If I am my own finger, then we have no trails. */
+  if (0 == GNUNET_CRYPTO_cmp_peer_identity (&finger->finger_identity,
+                                            &my_identity))
+  {
+    finger->is_present = GNUNET_NO;
+    memset ((void *)&finger_table[finger_table_index], 0, sizeof (finger_table[finger_table_index]));
+    return;
+  }
+  
+  /* If finger is a friend, then decrement the trail count and free the finger. */
+  friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                              &finger->finger_identity);
+  if (NULL != friend)
+  {
+    friend->trails_count--;
+    finger->is_present = GNUNET_NO;
+    memset ((void *)&finger_table[finger_table_index], 0, sizeof (finger_table[finger_table_index]));
+    return;
+  }
+  
+  /* For all other fingers, send trail teardown across all the trails to reach
+   finger, and free the finger. */
+  send_all_finger_trails_teardown (finger);
+  free_finger (finger, finger_table_index);
+  return;
+}
+
+#if 0
+/**
+ * This is a test function to print all the entries of friend table.
+ */
+static void
+test_friend_peermap_print ()
+{
+  struct FriendInfo *friend;
+  struct GNUNET_CONTAINER_MultiPeerMapIterator *friend_iter;
+  struct GNUNET_PeerIdentity print_peer;
+  struct GNUNET_PeerIdentity key_ret;
+  int i;
+  
+  friend_iter = GNUNET_CONTAINER_multipeermap_iterator_create (friend_peermap);
+  
+  for (i = 0; i < GNUNET_CONTAINER_multipeermap_size (friend_peermap); i++)
+  {
+    if(GNUNET_YES == GNUNET_CONTAINER_multipeermap_iterator_next (friend_iter,
+                                                                  &key_ret,
+                                                                  (const void **)&friend))
+    {
+      memcpy (&print_peer, &key_ret, sizeof (struct GNUNET_PeerIdentity));
+      FPRINTF (stderr,_("\nSUPU %s, %s, %d, friend = %s, friend->trails_count = %d"),
+              __FILE__, __func__,__LINE__, GNUNET_i2s(&print_peer), friend->trails_count);
+    }
+  }
+}
+
+
+/**
+ * This is a test function, to print all the entries of finger table.
+ */
+static void
+test_finger_table_print()
+{
+  struct FingerInfo *finger;
+  struct GNUNET_PeerIdentity print_peer;
+  struct Trail *trail;
+  int i;
+  int j;
+  int k;
+  
+  FPRINTF (stderr,_("\nSUPU************  FINGER_TABLE"));
+  for (i = 0; i < MAX_FINGERS; i++)
+  {
+    finger = &finger_table[i];
+    
+    if (GNUNET_NO == finger->is_present)
+      continue;
+    
+    print_peer = finger->finger_identity;
+    FPRINTF (stderr,_("\nSUPU %s, %s, %d, finger_table[%d] = %s, trails_count = %d"),
+            __FILE__, __func__,__LINE__,i,GNUNET_i2s (&print_peer), finger->trails_count);
+    
+    
+    for (j = 0; j < finger->trails_count; j++)
+    {
+      trail = &finger->trail_list[j];
+      FPRINTF (stderr,_("\nSUPU %s, %s, %d, trail_id[%d]=%s"),__FILE__, __func__,__LINE__,j, GNUNET_h2s(&trail->trail_id));
+      struct Trail_Element *element;
+      element = trail->trail_head;
+      for (k = 0; k < trail->trail_length; k++)
+      {  
+        print_peer = element->peer;
+        FPRINTF (stderr,_("\nSUPU %s, %s, %d,trail[%d] = %s "),__FILE__, __func__,__LINE__,k, GNUNET_i2s(&print_peer));
+        element = element->next;
+      }
+    }
+  }
+}
+#endif
+
+/**
+ * Check if there is already an entry in finger_table at finger_table_index.
+ * We get the finger_table_index from 64bit finger value we got from the network.
+ * -- If yes, then select the closest finger.
+ *   -- If new and existing finger are same, then check if you can store more 
+ *      trails. 
+ *      -- If yes then add trail, else keep the best trails to reach to the 
+ *         finger. 
+ *   -- If the new finger is closest, remove the existing entry, send trail
+ *      teardown message across all the trails to reach the existing entry.
+ *      Add the new finger.
+ *  -- If new and existing finger are different, and existing finger is closest
+ *     then do nothing.  
+ * -- Update current_search_finger_index.
+ * @param finger_identity Peer Identity of new finger
+ * @param finger_trail Trail to reach the new finger
+ * @param finger_length Total number of peers in @a new_finger_trail.
+ * @param is_predecessor Is this entry for predecessor in finger_table?
+ * @param finger_value 64 bit value of finger identity that we got from network.
+ * @param finger_trail_id Unique identifier of @finger_trail.
+ */
+static void
+finger_table_add (struct GNUNET_PeerIdentity finger_identity, 
+                  const struct GNUNET_PeerIdentity *finger_trail, 
+                  unsigned int finger_trail_length,
+                  unsigned int is_predecessor,
+                  uint64_t finger_value,
+                  struct GNUNET_HashCode finger_trail_id)
+{
+  struct FingerInfo *existing_finger;
+  struct GNUNET_PeerIdentity *closest_peer;
+  struct GNUNET_PeerIdentity *updated_trail;
+  struct FingerInfo *successor;
+  int updated_finger_trail_length; 
+  unsigned int finger_table_index;
+  
+  //test_friend_peermap_print();
+  //test_finger_table_print();
+  
+  /* Get the finger_table_index corresponding to finger_value we got from network.*/
+  finger_table_index = get_finger_table_index (finger_value, is_predecessor);
+
+  /* Invalid finger_table_index. */
+  if ((finger_table_index > PREDECESSOR_FINGER_ID))
+  {
+    GNUNET_break_op (0);
+    return;
+  }
+  
+  updated_finger_trail_length = finger_trail_length;
+  updated_trail =
+       scan_and_compress_trail (finger_identity, finger_trail,
+                                finger_trail_length, finger_trail_id, 
+                                &updated_finger_trail_length);
+   
+  /* If the new entry is same as successor then don't add it in finger table,
+   reset the current search finger index and exit. */
+  if ((0 != finger_table_index) && 
+      (PREDECESSOR_FINGER_ID != finger_table_index) &&
+      (finger_table_index == current_search_finger_index))
+  {
+    successor = &finger_table[0];
+    GNUNET_assert (GNUNET_YES == successor->is_present);
+    if (0 == GNUNET_CRYPTO_cmp_peer_identity (&finger_identity,
+                                              &successor->finger_identity))
+    {
+      current_search_finger_index = 0;
+      return;
+    }
+  }
+  
+  existing_finger = &finger_table[finger_table_index];
+  
+  /* No entry present in finger_table for given finger map index. */
+  if (GNUNET_NO == existing_finger->is_present)
+  {
+    add_new_finger (finger_identity, updated_trail, updated_finger_trail_length,
+                    finger_trail_id, finger_table_index);
+    update_current_search_finger_index (finger_identity, finger_table_index);
+    return;
+  }
+  
+  /* If existing entry and finger identity are not same. */
+  if (0 != GNUNET_CRYPTO_cmp_peer_identity (&(existing_finger->finger_identity),
+                                            &finger_identity))
+  {
+    closest_peer = select_closest_peer (&existing_finger->finger_identity,
+                                        &finger_identity,
+                                        finger_value, finger_table_index);
+    
+    /* If the new finger is the closest peer. */
+    if (0 == GNUNET_CRYPTO_cmp_peer_identity (&finger_identity, closest_peer))
+    {
+      remove_existing_finger (existing_finger, finger_table_index);
+      add_new_finger (finger_identity, updated_trail, updated_finger_trail_length,
+                      finger_trail_id, finger_table_index);
+    }
+  }
+  else
+  {
+    /* If both new and existing entry are same as my_identity, then do nothing. */
+    if (0 == GNUNET_CRYPTO_cmp_peer_identity (&(existing_finger->finger_identity),
+                                              &my_identity))
+      return;
+    
+    /* If the existing finger is not a friend. */
+    if (NULL ==
+        GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                           &existing_finger->finger_identity))
+    {
+      /* If there is space to store more trails. */
+      if (existing_finger->trails_count < MAXIMUM_TRAILS_PER_FINGER)
+        add_new_trail (existing_finger, updated_trail,
+                       finger_trail_length, finger_trail_id);
+      else
+        select_and_replace_trail (existing_finger, updated_trail,
+                                  finger_trail_length, finger_trail_id);
+    }
+  }
+  update_current_search_finger_index (finger_identity, finger_table_index);
+  return;
+}
+
+
+/**
+ * Core handler for P2P put messages.
+ * @param cls closure
+ * @param peer sender of the request
+ * @param message message
+ * @return #GNUNET_OK to keep the connection open,
+ *         #GNUNET_SYSERR to close it (signal serious error)
+ */
+static int
+handle_dht_p2p_put (void *cls, const struct GNUNET_PeerIdentity *peer,
+                    const struct GNUNET_MessageHeader *message)
+{
+   struct PeerPutMessage *put;
+  struct GNUNET_PeerIdentity *put_path;
+  struct GNUNET_HashCode test_key;
+  enum GNUNET_DHT_RouteOption options;
+  struct GNUNET_PeerIdentity best_known_dest;
+  struct GNUNET_HashCode intermediate_trail_id;
+  struct GNUNET_PeerIdentity *next_hop;
+  void *payload;
+  size_t msize;
+  uint32_t putlen;
+  size_t payload_size;
+  uint64_t key_value;
+  
+  msize = ntohs (message->size);
+  if (msize < sizeof (struct PeerPutMessage))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_YES;
+  }
+  
+  put = (struct PeerPutMessage *) message;
+  putlen = ntohl (put->put_path_length);
+   
+  if ((msize <
+       sizeof (struct PeerPutMessage) +
+       putlen * sizeof (struct GNUNET_PeerIdentity)) ||
+      (putlen >
+       GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity)))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_YES;
+  }
+
+  best_known_dest = put->best_known_destination;
+  put_path = (struct GNUNET_PeerIdentity *) &put[1];
+  payload = &put_path[putlen];
+  options = ntohl (put->options);
+  intermediate_trail_id = put->intermediate_trail_id;
+  
+  payload_size = msize - (sizeof (struct PeerPutMessage) + 
+                          putlen * sizeof (struct GNUNET_PeerIdentity));
+  
+  switch (GNUNET_BLOCK_get_key (GDS_block_context, ntohl (put->block_type),
+                                payload, payload_size, &test_key))
+  {
+    case GNUNET_YES:
+      if (0 != memcmp (&test_key, &put->key, sizeof (struct GNUNET_HashCode)))
+      {
+        char *put_s = GNUNET_strdup (GNUNET_h2s_full (&put->key));
+        GNUNET_break_op (0);
+        GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                    "PUT with key `%s' for block with key %s\n",
+                     put_s, GNUNET_h2s_full (&test_key));
+        GNUNET_free (put_s);
+        return GNUNET_YES;
+      }
+    break;
+    case GNUNET_NO:
+      GNUNET_break_op (0);
+      return GNUNET_YES;
+    case GNUNET_SYSERR:
+      /* cannot verify, good luck */
+      break;
+  }
+  
+   if (ntohl (put->block_type) == GNUNET_BLOCK_TYPE_REGEX) /* FIXME: do for all tpyes */
+  {
+    switch (GNUNET_BLOCK_evaluate (GDS_block_context,
+                                   ntohl (put->block_type),
+                                   NULL,    /* query */
+                                   NULL, 0, /* bloom filer */
+                                   NULL, 0, /* xquery */
+                                   payload, payload_size))
+    {
+    case GNUNET_BLOCK_EVALUATION_OK_MORE:
+    case GNUNET_BLOCK_EVALUATION_OK_LAST:
+      break;
+
+    case GNUNET_BLOCK_EVALUATION_OK_DUPLICATE:
+    case GNUNET_BLOCK_EVALUATION_RESULT_INVALID:
+    case GNUNET_BLOCK_EVALUATION_RESULT_IRRELEVANT:
+    case GNUNET_BLOCK_EVALUATION_REQUEST_VALID:
+    case GNUNET_BLOCK_EVALUATION_REQUEST_INVALID:
+    case GNUNET_BLOCK_EVALUATION_TYPE_NOT_SUPPORTED:
+    default:
+      GNUNET_break_op (0);
+      return GNUNET_OK;
+    }
+  }
+  
+  /* extend 'put path' by sender */
+  struct GNUNET_PeerIdentity pp[putlen + 1];
+  if (0 != (options & GNUNET_DHT_RO_RECORD_ROUTE))
+  {
+    memcpy (pp, put_path, putlen * sizeof (struct GNUNET_PeerIdentity));
+    pp[putlen] = *peer;
+    putlen++;
+  }
+  else
+    putlen = 0;
+  
+  memcpy (&key_value, &(put->key), sizeof (uint64_t));
+  if (0 != (GNUNET_CRYPTO_cmp_peer_identity (&best_known_dest, &my_identity)))
+  {
+    next_hop = GDS_ROUTING_get_next_hop (intermediate_trail_id, 
+                                         GDS_ROUTING_SRC_TO_DEST);
+  }
+  else
+  {
+    next_hop = find_successor (key_value, &best_known_dest, 
+                               &intermediate_trail_id, GDS_FINGER_TYPE_NON_PREDECESSOR); 
+  }
+  
+  if (NULL == next_hop)
+  {
+    GNUNET_STATISTICS_update (GDS_stats,
+                              gettext_noop ("# Next hop to forward the packet not found "
+                              "trail setup request, packet dropped."),
+                              1, GNUNET_NO);
+    return GNUNET_SYSERR;
+  }
+  
+  GDS_CLIENTS_process_put (options,
+                           ntohl (put->block_type),
+                           ntohl (put->hop_count),
+                           ntohl (put->desired_replication_level),
+                           putlen, pp,
+                           GNUNET_TIME_absolute_ntoh (put->expiration_time),
+                           &put->key,
+                           payload,
+                           payload_size);
+  
+  if (0 == GNUNET_CRYPTO_cmp_peer_identity(&my_identity, next_hop)) /* I am the final destination */
+  {
+    GDS_DATACACHE_handle_put (GNUNET_TIME_absolute_ntoh (put->expiration_time),
+                              &(put->key),putlen, pp, ntohl (put->block_type), 
+                              payload_size, payload);
+    return GNUNET_YES;
+  }
+  else
+  {
+    GDS_NEIGHBOURS_send_put (&put->key,  
+                             ntohl (put->block_type),ntohl (put->options),
+                             ntohl (put->desired_replication_level),
+                             &best_known_dest, &intermediate_trail_id, next_hop,
+                             ntohl (put->hop_count), putlen, pp,
+                             GNUNET_TIME_absolute_ntoh (put->expiration_time),
+                             payload, payload_size);
+     return GNUNET_YES;
+  }
+  return GNUNET_SYSERR;
+}
+
+
+/**
+ * Core handler for p2p get requests.
+ *
+ * @param cls closure
+ * @param peer sender of the request
+ * @param message message
+ * @return #GNUNET_OK to keep the connection open,
+ *         #GNUNET_SYSERR to close it (signal serious error)
+ */
+static int
+handle_dht_p2p_get (void *cls, const struct GNUNET_PeerIdentity *peer,
+                    const struct GNUNET_MessageHeader *message)
+{
+  struct PeerGetMessage *get;
+  struct GNUNET_PeerIdentity *get_path;
+  struct GNUNET_PeerIdentity best_known_dest;
+  struct GNUNET_HashCode intermediate_trail_id;
+  struct GNUNET_PeerIdentity *next_hop;
+  uint32_t get_length;
+  uint64_t key_value;
+  size_t msize;
+  
+  msize = ntohs (message->size);
+  if (msize < sizeof (struct PeerGetMessage))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_YES;
+  }
+  
+  get = (struct PeerGetMessage *)message;
+  get_length = ntohl (get->get_path_length);
+  best_known_dest = get->best_known_destination;
+  intermediate_trail_id = get->intermediate_trail_id;
+  get_path = (struct GNUNET_PeerIdentity *)&get[1];
+  
+  if ((msize <
+       sizeof (struct PeerGetMessage) +
+       get_length * sizeof (struct GNUNET_PeerIdentity)) ||
+       (get_length >
+        GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity)))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_YES; 
+  }
+  
+  /* Add sender to get path */
+  struct GNUNET_PeerIdentity gp[get_length + 1];
+  memcpy (gp, get_path, get_length * sizeof (struct GNUNET_PeerIdentity));
+  gp[get_length + 1] = *peer;
+  get_length = get_length + 1;
+  
+  memcpy (&key_value, &(get->key), sizeof (uint64_t));
+  if (0 != (GNUNET_CRYPTO_cmp_peer_identity (&best_known_dest, &my_identity)))
+  {
+    next_hop = GDS_ROUTING_get_next_hop (intermediate_trail_id, 
+                                         GDS_ROUTING_SRC_TO_DEST);
+  }
+  else
+  {
+    next_hop = find_successor (key_value, &best_known_dest, 
+                               &intermediate_trail_id, GDS_FINGER_TYPE_NON_PREDECESSOR);  
+  }
+  
+  if (NULL == next_hop)
+  {
+    GNUNET_STATISTICS_update (GDS_stats,
+                              gettext_noop ("# Next hop to forward the packet not found "
+                              "trail setup request, packet dropped."),
+                              1, GNUNET_NO);
+    return GNUNET_SYSERR;
+  }
+  if (0 == GNUNET_CRYPTO_cmp_peer_identity(&my_identity, next_hop))
+  {
+    /* I am the destination.*/
+    struct GNUNET_PeerIdentity final_get_path[get_length+1];
+    struct GNUNET_PeerIdentity next_hop;
+
+    memcpy (final_get_path, gp, get_length * sizeof (struct GNUNET_PeerIdentity));
+    memcpy (&final_get_path[get_length+1], &my_identity, sizeof (struct GNUNET_PeerIdentity));
+    get_length = get_length + 1;
+    memcpy (&next_hop, &final_get_path[get_length-2], sizeof (struct GNUNET_PeerIdentity));
+    GDS_DATACACHE_handle_get (&(get->key),(get->block_type), NULL, 0, NULL, 0,
+                              get_length, final_get_path,&next_hop, &my_identity);
+    
+    return GNUNET_YES;
+  }
+  else
+  {
+    GDS_NEIGHBOURS_send_get (&(get->key), get->block_type, get->options, 
+                             get->desired_replication_level, &best_known_dest,
+                             &intermediate_trail_id, next_hop, 0,
+                             get_length, gp);  
+  }
+  return GNUNET_SYSERR;
+}
+
+
+/**
+ * Core handler for get result
+ * @param cls closure
+ * @param peer sender of the request
+ * @param message message
+ * @return #GNUNET_OK to keep the connection open,
+ *         #GNUNET_SYSERR to close it (signal serious error)
  */
 static int
 handle_dht_p2p_get_result (void *cls, const struct GNUNET_PeerIdentity *peer,
                            const struct GNUNET_MessageHeader *message)
 {
-  /* If you are the source, go back to the client file and there search for
-   the requesting client and send back the result. */
   struct PeerGetResultMessage *get_result;
   struct GNUNET_PeerIdentity *get_path;
-  //void *payload;
-  //size_t payload_size;
+  struct GNUNET_PeerIdentity *put_path;
+  void *payload;
+  size_t payload_size;
   size_t msize;
   unsigned int getlen;
+  unsigned int putlen;
   int current_path_index;
   
   msize = ntohs (message->size);
@@ -2322,53 +3601,52 @@ handle_dht_p2p_get_result (void *cls, const struct GNUNET_PeerIdentity *peer,
   
   get_result = (struct PeerGetResultMessage *)message;
   getlen = ntohl (get_result->get_path_length);
+  putlen = ntohl (get_result->put_path_length);
   
   if ((msize <
        sizeof (struct PeerGetResultMessage) +
-       getlen * sizeof (struct GNUNET_PeerIdentity)) ||
+       getlen * sizeof (struct GNUNET_PeerIdentity) + 
+       putlen * sizeof (struct GNUNET_PeerIdentity)) ||
       (getlen >
-       GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity)))
+       GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity) ||
+      (putlen >
+         GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity))))
   {
     GNUNET_break_op (0);
     return GNUNET_YES;
   }
   
-  /* FIXME: Get the put_path */
-  get_path = (struct GNUNET_PeerIdentity *) &get_result[1];
-  //payload = &get_path[getlen];
-  /* payload_size = msize - (sizeof (struct PeerGetResultMessage) + 
-                          getlen * sizeof (struct GNUNET_PeerIdentity));*/
-  current_path_index = ntohl (get_result->current_path_index);
+  if (getlen > 0)
+   get_path = (struct GNUNET_PeerIdentity *) &get_result[1];
+  payload = &get_path[getlen];
+  payload_size = msize - (sizeof (struct PeerGetResultMessage) + 
+                          getlen * sizeof (struct GNUNET_PeerIdentity));
   
-  /* Here you just have to check if you are the destination or not if not 
-   then read the next peer and send the message. */
-  if (0 == (GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &(get_result->destination_peer))))
+  if (putlen > 0)
+    put_path = &get_path[1];
+  else
+    put_path = NULL;
+  
+  if (0 == (GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &(get_path[0]))))
   {
-    /* I am the destination. Call the function in client file.
-     * FIXME: Here I don't know how I communicate the result back to client
-       file.  */
-    //GDS_CLIENTS_process_get_result();
+    GDS_CLIENTS_handle_reply (get_result->expiration_time, &(get_result->key), 
+                              getlen, get_path, putlen,
+                              put_path, get_result->type, payload_size, payload);
     return GNUNET_YES;
   }
   else
   {
-    /* Read the element from the get path at trail index. set the trail index 
-     and call gds_neighbours_send_get_result.*/
-    struct GNUNET_PeerIdentity *next_hop;
-    
-    next_hop = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-    memcpy (next_hop, &get_path[current_path_index], sizeof (struct GNUNET_PeerIdentity));
-    
-    if (current_path_index != 0)
-      current_path_index--;
-#if 0
-    GDS_NEIGHBOURS_send_get_result ((get_result->expiration), get_result->key,
-                                     get_result->put_path_length, put_path,
-                                     get_result->type, payload, payload_size
-                                     get_path, getlen,current_path_index,
-                                     next_hop);
-#endif
+    current_path_index = search_my_index (get_path, getlen);
+    if (GNUNET_SYSERR == current_path_index )
+    {
+      GNUNET_break (0);
+      return GNUNET_SYSERR;
+    }
+    GDS_NEIGHBOURS_send_get_result (&(get_result->key), get_result->type,
+                                    &get_path[current_path_index - 1],
+                                    &(get_result->querying_peer), putlen, put_path,
+                                    getlen, get_path, get_result->expiration_time,
+                                    payload, payload_size);
     return GNUNET_YES;
   }  
   return GNUNET_SYSERR;
@@ -2376,969 +3654,1670 @@ handle_dht_p2p_get_result (void *cls, const struct GNUNET_PeerIdentity *peer,
 
 
 /**
- * Core handler for p2p put requests.
- *
+ * Get the best known next destination (local_dest) among your fingers, friends 
+ * and my identity. If @a current_dest is some other peer and not me, then 
+ * compare curent_dest and local_dest. 
+ * @param final_dest_finger_value Peer closest to this value will be
+ *                                @a local_best_known_dest
+ * @param local_best_known_dest[out] Updated to peer identity which is closest to
+ *                                   @a final_dest_finger_value.
+ * @param new_intermediate_trail_id In case @a local_best_known_dest is a finger,
+ *                                  then the trail id to reach to the finger
+ * @param is_predecessor Is source peer trying to setup trail to its predecessor
+ *                       or not.
+ * @param current_dest Peer which should get this message ultimately according
+ *                     to the peer which sent me this message. It could be me
+ *                     or some other peer. In case it is not me, then I am a part
+ *                     of trail to reach to that peer.
+ * @return 
+ */
+static struct GNUNET_PeerIdentity *
+get_local_best_known_next_hop (uint64_t final_dest_finger_value,
+                               struct GNUNET_PeerIdentity *local_best_known_dest,
+                               struct GNUNET_HashCode *new_intermediate_trail_id,
+                               struct GNUNET_HashCode intermediate_trail_id,
+                               unsigned int is_predecessor,
+                               struct GNUNET_PeerIdentity *current_dest)
+{
+  struct GNUNET_PeerIdentity *next_hop_to_local_best_known_dest;
+  
+ /* Choose a local best known hop among your fingers, friends and you.  */
+  next_hop_to_local_best_known_dest = find_successor (final_dest_finger_value,
+                                                      local_best_known_dest,
+                                                      new_intermediate_trail_id,
+                                                      is_predecessor);
+
+  /* Are we just a part of a trail towards a finger (current_destination)? */
+  if (0 != (GNUNET_CRYPTO_cmp_peer_identity (&my_identity, current_dest)))
+  {
+    struct GNUNET_PeerIdentity *closest_peer;
+    
+    /* Select best successor among one found locally and current_destination 
+     * that we got from network.*/
+    closest_peer = select_closest_peer (local_best_known_dest,
+                                        current_dest,
+                                        final_dest_finger_value,
+                                        is_predecessor);
+    
+    /* Is current dest (end point of the trail of which I am a part) closest_peer? */
+    if (0 == GNUNET_CRYPTO_cmp_peer_identity (current_dest, closest_peer))
+    {
+      next_hop_to_local_best_known_dest = 
+              GDS_ROUTING_get_next_hop (intermediate_trail_id,
+                                        GDS_ROUTING_SRC_TO_DEST);
+      /* FIXME: Here we found next_hop NULL from routing table, but we still 
+       * have a next_hop from find_successor should we not break and choose that
+       * next_hop. */
+      if (NULL == next_hop_to_local_best_known_dest) 
+      {
+        GNUNET_break_op (0);
+        return NULL;
+      }
+      
+      local_best_known_dest =  current_dest;
+      *new_intermediate_trail_id = intermediate_trail_id;
+    }
+  }
+  
+  GNUNET_assert (NULL != next_hop_to_local_best_known_dest);
+  return next_hop_to_local_best_known_dest;
+}
+
+
+/* Core handle for PeerTrailSetupMessage.
  * @param cls closure
- * @param peer sender of the request
  * @param message message
  * @param peer peer identity this notification is about
- * @return #GNUNET_OK to keep the connection open,
- *         #GNUNET_SYSERR to close it (signal serious error)
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
  */
 static int
-handle_dht_p2p_put (void *cls, const struct GNUNET_PeerIdentity *peer,
-                    const struct GNUNET_MessageHeader *message)
+handle_dht_p2p_trail_setup (void *cls, const struct GNUNET_PeerIdentity *peer,
+                            const struct GNUNET_MessageHeader *message)
 {
-  struct PeerPutMessage *put;
-  struct GNUNET_PeerIdentity *put_path;
-  enum GNUNET_DHT_RouteOption options;
-  enum current_destination_type current_dst_type;
-  struct GNUNET_PeerIdentity *current_destination;
-  struct GNUNET_PeerIdentity *next_hop;
-  struct GNUNET_HashCode test_key;
-  uint64_t key_value;
-  void *payload;
-  size_t payload_size;
+  const struct PeerTrailSetupMessage *trail_setup;
+  const struct GNUNET_PeerIdentity *trail_peer_list;
+  struct GNUNET_PeerIdentity *local_best_known_dest; 
+  struct GNUNET_PeerIdentity current_dest;
+  struct GNUNET_PeerIdentity *next_hop_towards_local_best_known_dest;
+  struct GNUNET_PeerIdentity next_peer;
+  struct FriendInfo *target_friend;
+  struct GNUNET_PeerIdentity source;
+  uint64_t final_dest_finger_val;
+  struct GNUNET_HashCode new_intermediate_trail_id;
+  struct GNUNET_HashCode intermediate_trail_id;
+  struct GNUNET_HashCode trail_id;
+  unsigned int is_predecessor;
+  uint32_t trail_length;
   size_t msize;
-  uint32_t putlen;
-  
-  put = (struct PeerPutMessage *) message;
-  putlen = ntohl (put->put_path_length);
+
   msize = ntohs (message->size);
-   
-  if ((msize <
-       sizeof (struct PeerPutMessage) +
-       putlen * sizeof (struct GNUNET_PeerIdentity)) ||
-      (putlen >
-       GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity)))
+  if (msize < sizeof (struct PeerTrailSetupMessage))
   {
     GNUNET_break_op (0);
     return GNUNET_YES;
   }
+
+  trail_setup = (const struct PeerTrailSetupMessage *) message;
+  trail_length = (msize - sizeof (struct PeerTrailSetupMessage))/
+                  sizeof (struct GNUNET_PeerIdentity);
+  if ((msize - sizeof (struct PeerTrailSetupMessage)) % 
+      sizeof (struct GNUNET_PeerIdentity) != 0)
+  {
+    GNUNET_break_op (0);
+    return GNUNET_OK;      
+  }           
+  
+  trail_peer_list = (const struct GNUNET_PeerIdentity *)&trail_setup[1];
+  current_dest = trail_setup->best_known_destination;
+  trail_id = trail_setup->trail_id;
+  final_dest_finger_val = 
+          GNUNET_ntohll (trail_setup->final_destination_finger_value);
+  source = trail_setup->source_peer;
+  is_predecessor = ntohl (trail_setup->is_predecessor);
+  intermediate_trail_id = trail_setup->intermediate_trail_id;
+  
+  /* Is my routing table full?  */
+  if (GNUNET_YES == GDS_ROUTING_threshold_reached())
+  {
+    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, peer);
+    GDS_NEIGHBOURS_send_trail_rejection (source, final_dest_finger_val,
+                                         my_identity, is_predecessor,
+                                         trail_peer_list, trail_length,
+                                         trail_id, target_friend,
+                                         CONGESTION_TIMEOUT);
+    return GNUNET_OK;
+  }
+
+  local_best_known_dest = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
   
-  put_path = (struct GNUNET_PeerIdentity *) &put[1];
-  payload = &put_path[putlen];
-  options = ntohl (put->options);
-  payload_size = msize - (sizeof (struct PeerPutMessage) + 
-                          putlen * sizeof (struct GNUNET_PeerIdentity));
-  
-  switch (GNUNET_BLOCK_get_key (GDS_block_context, ntohl (put->block_type),
-                                payload, payload_size, &test_key))
+  /* Get the next hop to forward the trail setup request. */
+  next_hop_towards_local_best_known_dest = 
+          get_local_best_known_next_hop (final_dest_finger_val, 
+                                         local_best_known_dest,
+                                         &new_intermediate_trail_id,
+                                         intermediate_trail_id,
+                                         is_predecessor,
+                                         &current_dest);
+  /* Am I the final destination? */
+  if (0 == (GNUNET_CRYPTO_cmp_peer_identity (local_best_known_dest,
+                                             &my_identity)))
   {
-    case GNUNET_YES:
-      if (0 != memcmp (&test_key, &put->key, sizeof (struct GNUNET_HashCode)))
-      {
-        char *put_s = GNUNET_strdup (GNUNET_h2s_full (&put->key));
-        GNUNET_break_op (0);
-        GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
-                    "PUT with key `%s' for block with key %s\n",
-                     put_s, GNUNET_h2s_full (&test_key));
-        GNUNET_free (put_s);
-        return GNUNET_YES;
-      }
-    break;
-    case GNUNET_NO:
-      GNUNET_break_op (0);
-      return GNUNET_YES;
-    case GNUNET_SYSERR:
-      /* cannot verify, good luck */
-      break;
+    /* If I was not the source of this message for which now I am destination */
+    if ((0 != GNUNET_CRYPTO_cmp_peer_identity (&source, &my_identity)) ||
+        (trail_length > 0))
+    {
+      GDS_ROUTING_add (trail_id, *peer, my_identity);
+    }
+    if (0 == trail_length)
+      memcpy (&next_peer, &source, sizeof (struct GNUNET_PeerIdentity));
+    else
+      memcpy (&next_peer, &trail_peer_list[trail_length-1], sizeof (struct GNUNET_PeerIdentity));
+
+    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, &next_peer);
+    GDS_NEIGHBOURS_send_trail_setup_result (source,
+                                            my_identity,
+                                            target_friend, trail_length,
+                                            trail_peer_list,
+                                            final_dest_finger_val,
+                                            is_predecessor, trail_id);
+  }
+  else
+  {
+    /* Add yourself to list of peers. */
+    struct GNUNET_PeerIdentity peer_list[trail_length + 1];
+
+    memcpy (peer_list, trail_peer_list, trail_length * sizeof (struct GNUNET_PeerIdentity));
+    peer_list[trail_length] = my_identity;
+    target_friend = 
+            GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                               next_hop_towards_local_best_known_dest);
+    GDS_NEIGHBOURS_send_trail_setup (source,
+                                     final_dest_finger_val,
+                                     *local_best_known_dest,
+                                     target_friend, trail_length + 1, peer_list,
+                                     is_predecessor, trail_id,
+                                     &new_intermediate_trail_id);
   }
+  GNUNET_free (local_best_known_dest);
+  GNUNET_free (next_hop_towards_local_best_known_dest);
+  return GNUNET_OK;
+}
+
+
+/* FIXME: here we are calculating my_index and comparing also in this function.
+   And we are doing it again here in this function. Re factor the code. */
+/**
+ * FIXME: Should we call this function everywhere in all the handle functions
+ * where we have a trail to verify from or a trail id. something like
+ * if prev hop is not same then drop the message. 
+ * Check if sender_peer and peer from which we should receive the message are
+ * same or different.
+ * @param trail_peer_list List of peers in trail
+ * @param trail_length Total number of peers in @a trail_peer_list
+ * @param sender_peer Peer from which we got the message. 
+ * @param finger_identity Finger to which trail is setup. It is not part of trail.
+ * @return #GNUNET_YES if sender_peer and peer from which we should receive the
+ *                    message are different.
+ *         #GNUNET_NO if sender_peer and peer from which we should receive the
+ *                    message are different. 
+ */
+static int
+is_sender_peer_correct (const struct GNUNET_PeerIdentity *trail_peer_list,
+                        unsigned int trail_length,
+                        const struct GNUNET_PeerIdentity *sender_peer,
+                        struct GNUNET_PeerIdentity finger_identity,
+                        struct GNUNET_PeerIdentity source_peer)
+{
+  int my_index;
   
-  if (ntohl (put->block_type) == GNUNET_BLOCK_TYPE_REGEX) /* FIXME: do for all tpyes */
+  /* I am the source peer. */
+  if (0 == (GNUNET_CRYPTO_cmp_peer_identity (&source_peer,
+                                             &my_identity)))
   {
-    switch (GNUNET_BLOCK_evaluate (GDS_block_context,
-                                   ntohl (put->block_type),
-                                   NULL,    /* query */
-                                   NULL, 0, /* bloom filer */
-                                   NULL, 0, /* xquery */
-                                   payload, payload_size))
+    /* Is the first element of the trail is sender_peer.*/
+    if (trail_length > 0)
     {
-    case GNUNET_BLOCK_EVALUATION_OK_MORE:
-    case GNUNET_BLOCK_EVALUATION_OK_LAST:
-      break;
+      if (0 != GNUNET_CRYPTO_cmp_peer_identity (&trail_peer_list[0],
+                                                sender_peer))
+        return GNUNET_NO;
+    }
+    else
+    {
+      /* Is finger the sender peer? */
+      if (0 != GNUNET_CRYPTO_cmp_peer_identity (sender_peer,
+                                                &finger_identity))
+        return GNUNET_NO;
+    }
+  }
+  else
+  {
+    /* Get my current location in the trail. */
+    my_index = search_my_index (trail_peer_list, trail_length);
+    if (-1 == my_index)
+      return GNUNET_NO;
+    
+    /* I am the last element in the trail. */
+    if ((trail_length - 1) == my_index)
+    {
+      /* Is finger the sender_peer? */
+      if (0 != GNUNET_CRYPTO_cmp_peer_identity (sender_peer,
+                                                &finger_identity))
+        return GNUNET_NO;
+    }
+    else
+    {
+      /* Is peer after me in trail the sender peer? */
+      if (0 != GNUNET_CRYPTO_cmp_peer_identity (sender_peer,
+                                                &trail_peer_list[my_index + 1]))
+        return GNUNET_NO;
+    }
+  }
+  return GNUNET_YES;
+}
 
-    case GNUNET_BLOCK_EVALUATION_OK_DUPLICATE:
-    case GNUNET_BLOCK_EVALUATION_RESULT_INVALID:
-    case GNUNET_BLOCK_EVALUATION_RESULT_IRRELEVANT:
-    case GNUNET_BLOCK_EVALUATION_REQUEST_VALID:
-    case GNUNET_BLOCK_EVALUATION_REQUEST_INVALID:
-    case GNUNET_BLOCK_EVALUATION_TYPE_NOT_SUPPORTED:
-    default:
-      GNUNET_break_op (0);
-      return GNUNET_OK;
+
+/**
+ * FIXME: we should also add a case where we search if we are present in the trail
+ * twice.
+ * Core handle for p2p trail setup result messages.
+ * @param closure
+ * @param message message
+ * @param peer sender of this message. 
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
+ */
+static int
+handle_dht_p2p_trail_setup_result(void *cls, const struct GNUNET_PeerIdentity *peer,
+                                  const struct GNUNET_MessageHeader *message)
+{
+  const struct PeerTrailSetupResultMessage *trail_result;
+  const struct GNUNET_PeerIdentity *trail_peer_list;
+  struct GNUNET_PeerIdentity next_hop;
+  struct FriendInfo *target_friend;
+  struct GNUNET_PeerIdentity querying_peer;
+  struct GNUNET_PeerIdentity finger_identity;
+  uint32_t trail_length;
+  uint64_t ulitmate_destination_finger_value;
+  uint32_t is_predecessor;
+  struct GNUNET_HashCode trail_id;
+  int my_index;
+  size_t msize;
+
+  msize = ntohs (message->size);
+  if (msize < sizeof (struct PeerTrailSetupResultMessage))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_YES;
+  }
+
+  trail_result = (const struct PeerTrailSetupResultMessage *) message;
+  trail_length = (msize - sizeof (struct PeerTrailSetupResultMessage))/
+                  sizeof (struct GNUNET_PeerIdentity);
+  if ((msize - sizeof (struct PeerTrailSetupResultMessage)) % 
+      sizeof (struct GNUNET_PeerIdentity) != 0)
+  {
+    GNUNET_break_op (0);
+    return GNUNET_OK;      
+  }       
+  
+  is_predecessor = htonl (trail_result->is_predecessor);
+  querying_peer = trail_result->querying_peer;
+  finger_identity = trail_result->finger_identity;
+  trail_id = trail_result->trail_id;
+  trail_peer_list = (const struct GNUNET_PeerIdentity *) &trail_result[1];
+  ulitmate_destination_finger_value = 
+          GNUNET_ntohll (trail_result->ulitmate_destination_finger_value);
+
+  /* FIXME: here we are calculating my_index and comparing also in this function.
+   And we are doing it again here in this function. Re factor the code. */
+  /* Ensure that sender peer is the peer from which we were expecting the message. */
+  if (GNUNET_NO == is_sender_peer_correct (trail_peer_list,
+                                           trail_length,
+                                           peer, finger_identity, querying_peer))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
+  }
+  
+  /* Am I the one who initiated the query? */
+  if (0 == (GNUNET_CRYPTO_cmp_peer_identity (&querying_peer,
+                                             &my_identity)))
+  {
+    /* If I am not my own finger identity, then add routing table entry. */
+    if (0 != GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &finger_identity))
+    {
+      GDS_ROUTING_add (trail_id, my_identity, *peer);
     }
+    
+    finger_table_add (finger_identity, trail_peer_list,
+                      trail_length, ulitmate_destination_finger_value,
+                      is_predecessor, trail_id);
+    return GNUNET_YES;
+  }
+  
+  /* Get my location in the trail. */
+  my_index = search_my_index(trail_peer_list, trail_length);
+  if (-1 == my_index)
+  {
+    GNUNET_break_op(0);
+    return GNUNET_SYSERR;
+  }
+  
+  if (my_index == 0)
+    next_hop = trail_result->querying_peer;
+  else
+    next_hop = trail_peer_list[my_index - 1];
+
+  /* If the querying_peer is its own finger, then don't add an entry in routing
+   * table as querying peer will discard the trail. */
+  if (0 != (GNUNET_CRYPTO_cmp_peer_identity (&(trail_result->querying_peer),
+                                             &(trail_result->finger_identity))))
+  {
+    GDS_ROUTING_add (trail_id, next_hop, *peer);
   }
+
+  target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, &next_hop);
+  GDS_NEIGHBOURS_send_trail_setup_result (querying_peer, finger_identity,
+                                          target_friend, trail_length, trail_peer_list,
+                                          is_predecessor, 
+                                          ulitmate_destination_finger_value,
+                                          trail_id);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Invert the trail.
+ * @param trail Trail to be inverted
+ * @param trail_length Total number of peers in the trail.
+ * @return Updated trail
+ */
+static struct GNUNET_PeerIdentity *
+invert_trail (const struct GNUNET_PeerIdentity *trail,
+              unsigned int trail_length)
+{
+  int i;
+  int j;
+  struct GNUNET_PeerIdentity *inverted_trail;
+  inverted_trail = GNUNET_malloc (sizeof(struct GNUNET_PeerIdentity) *
+                                  trail_length);
+  i = 0;
+  j = trail_length - 1;
+  while (i < trail_length)
+  {
+    inverted_trail[i] = trail[j];
+    i++;
+    j--;
+  }
+  return inverted_trail;
+}
+
+
+/**
+ * Return the shortest trail to reach from me to my_predecessor. 
+ * @param my_predecessor my current predecessor.
+ * @param current_trail Trail from source to me.
+ * @param current_trail_length Total number of peers in @a current_trail
+ * @param trail_length [out] Total number of peers in selected trail.
+ * @return Updated trail from source peer to my_predecessor.
+ */
+static struct GNUNET_PeerIdentity *
+trail_source_to_my_predecessor (const struct GNUNET_PeerIdentity *current_trail,
+                                unsigned int current_trail_length,
+                                unsigned int *trail_length)
+{
+  struct GNUNET_PeerIdentity *trail_me_to_predecessor;
+  struct Trail *trail;
+  struct Trail_Element *trail_element;
+  struct FingerInfo *my_predecessor;
+  unsigned int i;
+  unsigned int shortest_trail_length = 0;
+  unsigned int trail_index = 0;
+  my_predecessor = &finger_table[PREDECESSOR_FINGER_ID];
+  
+  GNUNET_assert (GNUNET_YES == my_predecessor->is_present);
+  
+  //if my_predecessor is a friend then don't send back any trail. as
+  // there is no trail. 
+  *trail_length = 0;
+  
+  /* Choose the shortest path from me to my predecessor. */
+  for (i = 0; i < my_predecessor->trails_count; i++)
+  {
+    trail = &my_predecessor->trail_list[i];
+    if (trail->trail_length > shortest_trail_length)
+      continue;
+    shortest_trail_length = trail->trail_length;
+    trail_index = i;
+  }
+
+  *trail_length = shortest_trail_length;
+  trail_me_to_predecessor = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity)
+                                          * *trail_length);
+  
+  /* Copy the selected trail and send this trail to calling function. */
+  i = 0;
+  trail = &my_predecessor->trail_list[trail_index];
+  trail_element = trail->trail_head;
+  while ( i < shortest_trail_length)
+  {
+    trail_me_to_predecessor[i] = trail_element->peer;
+    i++;
+    trail_element = trail_element->next;
+  }
+
+  return trail_me_to_predecessor;
+}
+
+
+/**
+ * FIXME In case predecessor is a friend then do we add it in routing table.
+ * if not then check the logic of trail teardown in case we compress the trail
+ * such that friend is finger. then do we remove the entry from end points or
+ * not. Ideally we should remove the entries from end point. 
+ * Add finger as your predecessor. To add, first generate a new trail id, invert
+ * the trail to get the trail from me to finger, add an entry in your routing 
+ * table, send add trail message to peers which are part of trail from me to 
+ * finger and add finger in finger table.
+ * @param finger
+ * @param trail
+ * @param trail_length
+ */
+static void
+update_predecessor (struct GNUNET_PeerIdentity finger, 
+                    struct GNUNET_PeerIdentity *trail, 
+                    unsigned int trail_length)
+{
+  struct GNUNET_HashCode trail_to_new_predecessor_id;
+  struct GNUNET_PeerIdentity *trail_to_new_predecessor;
+  struct FriendInfo *target_friend;
+  
+  /* Generate trail id for trail from me to new predecessor = finger. */
+  GNUNET_CRYPTO_random_block (GNUNET_CRYPTO_QUALITY_STRONG,
+                              &trail_to_new_predecessor_id, 
+                              sizeof (trail_to_new_predecessor_id));
+    
+  /* Invert the trail from finger to me to get the trail from me to finger. */
+  if (trail_length == 0)
+    trail_to_new_predecessor = NULL;
+
+  if (trail_length > 0)
+  {
+    trail_to_new_predecessor = invert_trail (trail, trail_length);
+    /* Add an entry in your routing table. */
+    GDS_ROUTING_add (trail_to_new_predecessor_id, 
+                     trail_to_new_predecessor[trail_length - 1],
+                     my_identity);
+   
+    target_friend = 
+            GNUNET_CONTAINER_multipeermap_get (friend_peermap, 
+                                               &trail_to_new_predecessor[trail_length - 1]);
+      
+    // Before sending the trail may be you need to compress it. And in case
+    // it was a friend how did we got the trail. ?? 
+    
+    /* Add entry in routing table of all peers that are part of trail from me
+       to finger. */
+
+    GDS_NEIGHBOURS_send_add_trail (my_identity, 
+                                   finger,
+                                   trail_to_new_predecessor_id,
+                                   trail_to_new_predecessor,
+                                   trail_length,
+                                   target_friend);
+    }
+  
+    add_new_finger (finger, trail_to_new_predecessor, trail_length,
+                    trail_to_new_predecessor_id, PREDECESSOR_FINGER_ID);
+}
+
+
+/* 3. In case you are successor, then 
+   *   3.1 check if you have a predecessor
+   *   3.2 if no predecessor, then add the source of this message as your
+   *       predecessor. To add, first you should generate a new trail id,
+   *       invert the trail, send add trail message across new trail, add
+   *       an entry in finger table. Now, destination also have routing
+   *       table entry so add in your routing table also.
+   *   3.3 If its closer than existing one, then do everything in step 1 and
+   *       free existing finger. 
+   *   3.3 If its same as the old one, then do nothing.
+   *   3.4 if its not same as old one, and between source and old one, old one
+   *       is the correct predecessor, then construct a trail from source 
+   *       to your old successor. scan the trail to remove duplicate entries.
+   * 4. send verify successor result, with trail id of trail from source to
+   * me. And also send the new trail from source to reach to its probable
+   * predecessor. */
+ /*
+   * 1. this function is called from both verify and notify.
+   * 2. so write in a way that it is used in both.
+   */
+/**
+ * Check if you have a predecessor.
+ * 1. if no predecessor, then add finger as your predecessor. To add, first 
+ *    generate a new trail id, invert the trail to get the trail from me to finger,
+ *    add an entry in your routing table, send add trail message to peers which 
+ *    are part of trail from me to finger and add finger in finger table.
+ * 2. If there is a predecessor, then compare existing one and finger.
+ *    2.1 If finger is correct predecessor, then remove current_predecessor. And 
+ *        do everything in step 1 to add finger into finger table.
+ *    2.2 If current_predecessor is correct predecessor, the construct a trail from
+ *        finger to current_predecessor. 
+ * @param finger
+ * @param trail
+ * @param trail_length
+ * @return 
+ */
+static void
+compare_and_update_predecessor (struct GNUNET_PeerIdentity finger, 
+                                struct GNUNET_PeerIdentity *trail, 
+                                unsigned int trail_length)
+{
+  struct FingerInfo *current_predecessor;
+  struct GNUNET_PeerIdentity *closest_peer;
+  uint64_t predecessor_value;
   
-  struct GNUNET_PeerIdentity pp[putlen + 1];
+  current_predecessor = &finger_table[PREDECESSOR_FINGER_ID];
 
-  /* extend 'put path' by sender */
-  if (0 != (options & GNUNET_DHT_RO_RECORD_ROUTE))
+  /* No predecessor. Add finger as your predecessor. */
+  if (GNUNET_NO == current_predecessor->is_present) 
   {
-    memcpy (pp, put_path, putlen * sizeof (struct GNUNET_PeerIdentity));
-    pp[putlen] = *peer;
-    putlen++;
+    update_predecessor (finger, trail, trail_length);
+    return;
   }
-  else
-    putlen = 0;
   
-   current_destination = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-   memcpy (current_destination, &(put->current_destination), sizeof (struct GNUNET_PeerIdentity));
-   current_dst_type = ntohl (put->current_destination_type);
-   memcpy (&key_value, &(put->key), sizeof (uint64_t));
-   
-   if (current_dst_type == FRIEND)
-   {
-     next_hop = find_successor (key_value, current_destination, &current_dst_type);
-   }
-   else if (current_dst_type == FINGER)
-   {
-     if (0 == GNUNET_CRYPTO_cmp_peer_identity (&my_identity, current_destination))
-     {
-       next_hop = find_successor (key_value, current_destination, &current_dst_type);
-     } 
-     else
-     {
-       next_hop = GDS_ROUTING_search (&(put->current_source), current_destination, peer);
-       current_dst_type = FRIEND;
-     }
-   }
+  predecessor_value = compute_finger_identity_value (PREDECESSOR_FINGER_ID);
+  closest_peer = select_closest_peer (&finger, 
+                                      &current_predecessor->finger_identity,
+                                      predecessor_value, PREDECESSOR_FINGER_ID);
   
-   if (current_dst_type == MY_ID) 
-   {
-     GDS_DATACACHE_handle_put (GNUNET_TIME_absolute_ntoh (put->expiration_time),
-                              &(put->key),putlen, pp, ntohl (put->block_type), 
-                              payload_size, payload);
-     return GNUNET_YES;
-   }
-   else
-   {
-     struct GNUNET_PeerIdentity *current_source;
-     if (current_dst_type == FINGER)
-     {
-       current_source = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-       memcpy (current_source, &my_identity, sizeof (struct GNUNET_PeerIdentity));
-     }
-     else
-       current_source = NULL;
-     
-     GDS_CLIENTS_process_put (options,
-                              ntohl (put->block_type),
-                              ntohl (put->hop_count),
-                              ntohl (put->desired_replication_level),
-                              putlen, pp,
-                              GNUNET_TIME_absolute_ntoh (put->expiration_time),
-                              &put->key,
-                              payload,
-                              payload_size);
-    
-     GDS_NEIGHBOURS_handle_put (ntohl (put->block_type),ntohl (put->options),
-                                ntohl (put->desired_replication_level),
-                                GNUNET_TIME_absolute_ntoh (put->expiration_time),
-                                ntohl (put->hop_count),&put->key, putlen,
-                                pp, payload, payload_size,
-                                current_destination, current_source,current_dst_type, next_hop);
-     return GNUNET_YES;
-   }
-  return GNUNET_SYSERR;
+  /* Finger is the closest predecessor. Remove the existing one and add the new
+     one. */
+  if (0 == GNUNET_CRYPTO_cmp_peer_identity (closest_peer, &finger))
+  {
+    remove_existing_finger (current_predecessor, PREDECESSOR_FINGER_ID);
+    update_predecessor (finger, trail, trail_length);
+    return;
+  }
+  return;
 }
 
 
-/**
- * FIXME
- * 1. I don't do block evalute as it uses xquery and bf for evaluation.Is
- * it okay if I just pass NULL. I am anyways going to pass NULL in case of 
- * datacache_get? 
- * Core handler for p2p get requests.
+/* 
+ * FIXME: if i have no predecessor and I get a new predecessor but the first
+ * friend to reach to that hop is congested then?  
+ * 1. check if you are the successor or not.
+ * 2. if not then get the next hop from routing table, and pass the message,
+ * 3. In case you are successor, then 
+ *   3.1 check if you have a predecessor
+ *   3.2 if no predecessor, then add the source of this message as your
+ *       predecessor. To add, first you should generate a new trail id,
+ *       invert the trail, send add trail message across new trail, add
+ *       an entry in finger table. Now, destination also have routing
+ *       table entry so add in your routing table also.
+ *   3.3 If its closer than existing one, then do everything in step 1 and
+ *       free existing finger. 
+ *   3.3 If its same as the old one, then do nothing.
+ *   3.4 if its not same as old one, and between source and old one, old one
+ *       is the correct predecessor, then choose the shortest path to reach
+ *       from you to your predecessor. Pass this trail to source of this message.
+ *       It is the responsibility of source peer to scan the trail to reach to
+ *       its new probable successor. 
+ * 4. send verify successor result, with trail id of trail from source to
+ * me. And also send the  trail from me to reach to my predecessor, if
+ * my_predecessor != source. 
  *
+ * Core handle for p2p verify successor messages.
  * @param cls closure
- * @param peer sender of the request
  * @param message message
- * @return #GNUNET_OK to keep the connection open,
- *         #GNUNET_SYSERR to close it (signal serious error)
+ * @param peer peer identity this notification is about
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
  */
 static int
-handle_dht_p2p_get (void *cls, const struct GNUNET_PeerIdentity *peer,
-                    const struct GNUNET_MessageHeader *message)
+handle_dht_p2p_verify_successor(void *cls, 
+                                const struct GNUNET_PeerIdentity *peer,
+                                const struct GNUNET_MessageHeader *message)
 {
-  struct PeerGetMessage *get;
-  struct GNUNET_PeerIdentity *current_destination;
-  uint64_t key_value;
-  enum current_destination_type current_dest_type;
+  const struct PeerVerifySuccessorMessage *vsm;
+  struct GNUNET_HashCode trail_id;
+  struct GNUNET_PeerIdentity successor;
+  struct GNUNET_PeerIdentity source_peer;
+  struct GNUNET_PeerIdentity *trail;
   struct GNUNET_PeerIdentity *next_hop;
-  struct GNUNET_PeerIdentity *get_path;
-  enum GNUNET_BLOCK_Type block_type;
-  enum GNUNET_DHT_RouteOption options;
+  struct GNUNET_PeerIdentity *trail_to_predecessor;
+  struct FingerInfo *current_predecessor;
+  struct FriendInfo *target_friend;
+  unsigned int trail_to_predecessor_length;
   size_t msize;
-  unsigned int get_length;
+  unsigned int trail_length;
   
   msize = ntohs (message->size);
-  if (msize < sizeof (struct PeerGetMessage))
+  
+  /* Here we pass trail to reach from source to successor, and in case successor
+   * does not have any predecessor, then we will add source as my predecessor.
+   * So we pass the trail along with trail id. */
+  if (msize < sizeof (struct PeerVerifySuccessorMessage)) 
   {
     GNUNET_break_op (0);
     return GNUNET_YES;
   }
   
-  get = (struct PeerGetMessage *)message;
-  get_length = ntohl (get->get_path_length);
-  get_path = (struct GNUNET_PeerIdentity *)&get[1];
-  
-  if ((msize <
-       sizeof (struct PeerGetMessage) +
-       get_length * sizeof (struct GNUNET_PeerIdentity)) ||
-       (get_length >
-        GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity)))
+  vsm = (const struct PeerVerifySuccessorMessage *) message;
+  trail_length = (msize - sizeof (struct PeerVerifySuccessorMessage))/
+                  sizeof (struct GNUNET_PeerIdentity);
+  if ((msize - sizeof (struct PeerVerifySuccessorMessage)) % 
+      sizeof (struct GNUNET_PeerIdentity) != 0)
   {
     GNUNET_break_op (0);
-    return GNUNET_YES; 
-  }
-  
-  current_destination = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-  memcpy (current_destination, &(get->current_destination), sizeof (struct GNUNET_PeerIdentity));
-  memcpy (&key_value, &(get->key), sizeof (uint64_t));
-  current_dest_type = ntohl (get->current_dest_type);
-  block_type = ntohl (get->block_type);
-  options = ntohl (get->options);
-  if (current_dest_type == FRIEND)
+    return GNUNET_OK;      
+  } 
+  
+  trail_id = vsm->trail_id;
+  source_peer = vsm->source_peer;
+  successor = vsm->successor;
+  trail = (struct GNUNET_PeerIdentity *)&vsm[1];
+  
+  //GDS_ROUTING_test_print(); //FIXME REMOVE AFTERWARDS. 
+  //FIXME: we can have a check if peer is correct peer which should have
+  // sent this message. use same function is_sender_peer_correct
+  // but specify direction so that the function can be used in other functions
+  //also. 
+  
+  /* I am not the successor of source_peer. Pass the message to next_hop on
+   * the trail. */
+  if(0 != (GNUNET_CRYPTO_cmp_peer_identity (&successor, &my_identity)))
   {
-    next_hop = find_successor (key_value, current_destination, &current_dest_type);
-  }
-  else if (current_dest_type == FINGER)
-  {
-     if (0 == GNUNET_CRYPTO_cmp_peer_identity (&my_identity, current_destination))
-     {
-       next_hop = find_successor (key_value, current_destination, &current_dest_type);
-     } 
-     else
-     {
-       next_hop = GDS_ROUTING_search (&(get->current_source), current_destination, peer);
-       current_dest_type = FRIEND;
-     }
+    next_hop = GDS_ROUTING_get_next_hop (trail_id, GDS_ROUTING_SRC_TO_DEST);
+    if (NULL == next_hop)
+    {
+      GNUNET_break (0);
+      return GNUNET_SYSERR;
+    }
+    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop);
+
+    GDS_NEIGHBOURS_send_verify_successor_message (source_peer, successor,
+                                                  trail_id, trail, trail_length,
+                                                  target_friend);
+    return GNUNET_OK;
   }
   
-  /* Add sender to get path */
-  struct GNUNET_PeerIdentity gp[get_length + 1];
-  memcpy (gp, get_path, get_length * sizeof (struct GNUNET_PeerIdentity));
-  gp[get_length + 1] = *peer;
-  get_length = get_length + 1;
+  /* I am the destination of this message. */
   
-  if (current_dest_type == MY_ID)
+  /* Check if there is a predecessor or not. */
+  compare_and_update_predecessor (source_peer, trail, trail_length);
+  
+  current_predecessor = &finger_table[PREDECESSOR_FINGER_ID];
+  /* Is source of this message my predecessor. */
+  if (0 == (GNUNET_CRYPTO_cmp_peer_identity (&current_predecessor->finger_identity,
+                                             &source_peer)))
   {
-    struct GNUNET_PeerIdentity final_get_path[get_length+1];
-    memcpy (final_get_path, get_path, get_length * sizeof (struct GNUNET_PeerIdentity));
-    memcpy (final_get_path, &my_identity, sizeof (struct GNUNET_PeerIdentity));
-    get_length = get_length + 1;
-    struct GNUNET_PeerIdentity *next_hop;
-    next_hop = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-    /* FIXME: Check if we need to have a check on get length. */
-    memcpy (next_hop, &final_get_path[get_length-2], sizeof (struct GNUNET_PeerIdentity));
-#if 0
-    GDS_DATACACHE_handle_get (&(get->key),(get->block_type),
-                             final_get_path, get_length,get_length - 1,next_hop);
-#endif
-    return GNUNET_YES;
+    trail_to_predecessor = NULL;
+    trail_to_predecessor_length = 0;
   }
   else
   {
-    struct GNUNET_PeerIdentity *current_source;
-    current_source = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-    if (current_dest_type == FINGER)
+    if (NULL == (GNUNET_CONTAINER_multipeermap_get (friend_peermap, 
+                                                    &current_predecessor->finger_identity)))
     {
-      memcpy (current_source, &my_identity, sizeof (struct GNUNET_PeerIdentity));
+      /* Only if current predecessor is not a friend, we have a trail to reach
+       to it. Only in that case we pass the trail. */
+      trail_to_predecessor = 
+            trail_source_to_my_predecessor (trail, trail_length, 
+                                            &trail_to_predecessor_length);
     }
     else
-      /* FIXME: Is this correct? */
     {
-      /* how to handle the case when we don't have any value for current source.*/
+      trail_to_predecessor = NULL;
+      trail_to_predecessor_length = 0;
     }
-    
-    GDS_NEIGHBOURS_handle_get (block_type, options, get->desired_replication_level,
-                               get->hop_count, gp,
-                               get_length, &(get->key),next_hop,
-                               current_destination, &(get->current_source),&current_dest_type);
-    
-    return GNUNET_YES;
   }
-  return GNUNET_SYSERR;
+  
+  target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, peer);
+  GDS_NEIGHBOURS_send_verify_successor_result (source_peer, my_identity,
+                                               current_predecessor->finger_identity,
+                                               trail_id, trail_to_predecessor,
+                                               trail_to_predecessor_length,
+                                               GDS_ROUTING_DEST_TO_SRC,
+                                               target_friend);
+  return GNUNET_OK;
 }
 
 
+/**
+ * Construct the trail from me to probable successor that goes through current 
+ * successor. Scan this trail to check if you can shortcut the trail somehow. 
+ * In case we can shortcut the trail, don't send trail compression as we don't 
+ * have any entry in routing table.
+ * @param current_successor
+ * @param probable_successor
+ * @param trail_from_curr_to_probable_successor
+ * @param trail_from_curr_to_probable_successor_length
+ * @param trail_to_new_successor_length
+ * @return 
+ */
+static struct GNUNET_PeerIdentity *
+get_trail_to_new_successor (struct FingerInfo *current_successor,
+                            struct GNUNET_PeerIdentity probable_successor,
+                            const struct GNUNET_PeerIdentity *trail,
+                            unsigned int trail_length,
+                            unsigned int *trail_to_new_successor_length)
+{
+  struct GNUNET_PeerIdentity *trail_to_new_successor;
+  
+   /* If the probable successor is a friend, then we don't need to have a trail
+    * to reach to it.*/
+  if (NULL != GNUNET_CONTAINER_multipeermap_get (friend_peermap, 
+                                                 &probable_successor))
+  {
+    trail_to_new_successor = NULL;
+    *trail_to_new_successor_length = 0;
+    return trail_to_new_successor;
+  }
+  
+  /*
+   * FIXME: can we some how use the select_finger_trail here?? 
+   * complete this logic. 
+   * 1. Choose the shortest trail to reach to current successor.
+   * 2. append the trail with the current trail
+   * 3. scan the trail for duplicate elements
+   * 4. scan the trail for friend
+   * 5. get the shortest trail. 
+   * 6. send back the trail.
+   */
+  return NULL;
+}
+
 
 /**
- * Send tral rejection message
- * @param source_peer Source peer which wants to set up the trail.
- * @param finger_identity Finger identity to which it want to setup the trail.
- * @param congested_peer Peer which has send trail rejection message
- * @param next_hop Peer to which this message should be forwarded.
- * @param finger_map_index
- * @param trail_peer_list
- * @param trail_length
+ * Compare probable successor and current successor.
+ * If the probable successor is the correct successor, then construct the trail
+ * from me to probable successor that goes through current successor. Scan this
+ * trail to check if you can shortcut the trail somehow. In case we can short
+ * cut the trail, don't send trail compression as we don't have any entry in 
+ * routing table.
+ * Once you have scanned trail, then add an entry in finger table.
+ * Add an entry in routing table (Only if new successor is NOT a friend).
+ * @param probable_successor Peer which could be our successor
+ * @param trail_from_curr_to_probable_successor Trail from current successor 
+ *                                               to probable successor, NOT 
+ *                                               including them.
+ * @param trail_from_curr_to_probable_successor_length Total number of peers
+ *                                               in @a trail_from_curr_to_probable_successor
  */
-void
-GDS_NEIGHBOURS_send_trail_rejection_message(struct GNUNET_PeerIdentity *source_peer,
-                                            uint64_t finger_identity,
-                                            struct GNUNET_PeerIdentity *congested_peer,
-                                            const struct GNUNET_PeerIdentity *next_hop,
-                                            unsigned int finger_map_index,
-                                            struct GNUNET_PeerIdentity *trail_peer_list,
-                                            unsigned int trail_length)
-{
-  struct PeerTrailRejectionMessage *trail_rejection;
-  struct GNUNET_PeerIdentity *trail_list;
-  struct P2PPendingMessage *pending;
+static void
+compare_and_update_successor (struct GNUNET_PeerIdentity probable_successor,
+                              const struct GNUNET_PeerIdentity *trail_from_curr_to_probable_successor,
+                              unsigned int trail_from_curr_to_probable_successor_length)
+{
+  struct GNUNET_PeerIdentity *closest_peer;
+  struct GNUNET_PeerIdentity *trail_to_new_successor;
+  struct GNUNET_HashCode trail_id;
+  unsigned int trail_to_new_successor_length;
+  uint64_t successor_value;
+  struct FingerInfo *current_successor;
   struct FriendInfo *target_friend;
-  size_t msize;
   
-  msize =  sizeof (struct PeerTrailRejectionMessage);
+  current_successor = &finger_table[0];
+  GNUNET_assert (GNUNET_YES == current_successor->is_present);
   
-  pending = GNUNET_malloc (sizeof (struct P2PPendingMessage) + msize); 
-  pending->importance = 0;    /* FIXME */
-  pending->timeout = GNUNET_TIME_relative_to_absolute (GET_TIMEOUT);
-  trail_rejection = (struct PeerTrailRejectionMessage *) &pending[1]; 
-  pending->msg = &trail_rejection->header;
-  trail_rejection->header.size = htons (msize);
-  trail_rejection->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_SETUP);
-  memcpy (&(trail_rejection->source_peer), source_peer, sizeof (struct GNUNET_PeerIdentity));
-  memcpy (&(trail_rejection->congested_peer), congested_peer, sizeof (struct GNUNET_PeerIdentity));
-  memcpy (&(trail_rejection->finger_identity), &finger_identity, sizeof (uint64_t));
-  trail_rejection->finger_map_index = htonl(finger_map_index);
-  trail_rejection->trail_length = htonl (trail_length);
-  
-  trail_list = (struct GNUNET_PeerIdentity *)&trail_rejection[1];
-  memcpy (trail_list, trail_peer_list, trail_length * sizeof (struct GNUNET_PeerIdentity));
+  /* Compute the 64 bit value of successor identity. We need this as we need to
+   * find the closest peer w.r.t this value.*/
+  successor_value = compute_finger_identity_value (0);
+  closest_peer = select_closest_peer (&current_successor->finger_identity,
+                                      &probable_successor,
+                                      successor_value, GNUNET_NO);
   
-  target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop);
-  GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
-  target_friend->pending_count++;
-  process_friend_queue (target_friend);
+  /* If the current_successor is the closest one, then exit. */
+  if (0 == GNUNET_CRYPTO_cmp_peer_identity (closest_peer,
+                                            &current_successor->finger_identity))
+    return;
+  
+  /* probable successor  is the closest_peer. */
+  
+  /* Get the trail to reach to your new successor. */
+  trail_to_new_successor = get_trail_to_new_successor (current_successor,
+                                                       probable_successor,
+                                                       trail_from_curr_to_probable_successor,
+                                                       trail_from_curr_to_probable_successor_length,
+                                                       &trail_to_new_successor_length);
+  /* Remove the existing successor. */
+  remove_existing_finger (current_successor, 0);
+  
+  /* Generate a new trail id to reach to your new successor. */
+  GNUNET_CRYPTO_random_block (GNUNET_CRYPTO_QUALITY_STRONG,
+                              &trail_id, sizeof (trail_id));
+  add_new_finger (probable_successor, trail_to_new_successor, 
+                  trail_to_new_successor_length, trail_id, 0);
+  
+  /* If probable successor is not a friend, then add an entry in your own
+   routing table. */
+  if (trail_to_new_successor_length > 0)
+  {
+    GDS_ROUTING_add (trail_id, my_identity, trail_to_new_successor[0]);
+    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, 
+                                                       &trail_to_new_successor[0]);
+  }
+  else
+  {
+    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, 
+                                                       &probable_successor);
+  }
+  
+  GDS_NEIGHBOURS_send_notify_new_successor (my_identity, probable_successor,
+                                            trail_from_curr_to_probable_successor,
+                                            trail_from_curr_to_probable_successor_length,
+                                            trail_id,
+                                            target_friend);
+  return;
 }
 
 
-/** 
- * Handle a PeerTrailSetupMessage. 
+/*
+ * 1. If you are not the querying peer then pass on the message,
+ * 2. If you are querying peer, then
+ *   2.1 is new successor same as old one
+ *     2.1.1 if yes then do noting
+ *     2.1.2 if no then you need to notify the new one about your existence,
+ *     2.1.2,1 also you need to remove the older successor, remove entry
+ *             from finger table, send trail teardown message across all the trail
+ *             of older successor. Call notify new successor with new trail id 
+ *             and new trail to reach it. 
+ * Core handle for p2p verify successor result messages.
  * @param cls closure
  * @param message message
  * @param peer peer identity this notification is about
- * @return GNUNET_OK on success, GNUNET_SYSERR on error
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
  */
 static int
-handle_dht_p2p_trail_setup(void *cls, const struct GNUNET_PeerIdentity *peer,
-                           const struct GNUNET_MessageHeader *message)
+handle_dht_p2p_verify_successor_result(void *cls, 
+                                       const struct GNUNET_PeerIdentity *peer,
+                                       const struct GNUNET_MessageHeader *message)
 {
-  struct PeerTrailSetupMessage *trail_setup; 
-  struct GNUNET_PeerIdentity *next_hop; 
+  const struct PeerVerifySuccessorResultMessage *vsrm;
+  enum GDS_ROUTING_trail_direction trail_direction;
+  struct GNUNET_PeerIdentity querying_peer;
+  struct GNUNET_HashCode trail_id;
+  struct GNUNET_PeerIdentity *next_hop;
   struct FriendInfo *target_friend;
-  struct GNUNET_PeerIdentity *current_destination;
-  struct GNUNET_PeerIdentity *trail_peer_list;
-  enum current_destination_type current_dest_type;
-  struct GNUNET_PeerIdentity *next_peer;
+  struct GNUNET_PeerIdentity probable_successor;
+  const struct GNUNET_PeerIdentity *trail;
   unsigned int trail_length;
-  uint32_t current_trail_index;
-  unsigned int finger_map_index;
-  uint64_t destination_finger_value;
   size_t msize;
-  
+
   msize = ntohs (message->size);
-  if (msize < sizeof (struct PeerTrailSetupMessage))
+  /* We send a trail to reach from old successor to new successor, if
+   * old_successor != new_successor.*/
+  if (msize < sizeof (struct PeerVerifySuccessorResultMessage))
   {
     GNUNET_break_op (0);
     return GNUNET_YES;
   }
   
-  trail_setup = (struct PeerTrailSetupMessage *) message; 
-  trail_length = ntohl (trail_setup->trail_length); 
+  vsrm = (const struct PeerVerifySuccessorResultMessage *) message;
+  trail_length = (msize - sizeof (struct PeerVerifySuccessorResultMessage))/
+                      sizeof (struct GNUNET_PeerIdentity);
   
-  if ((msize < sizeof (struct PeerTrailSetupMessage) +
-       trail_length * sizeof (struct GNUNET_PeerIdentity)) ||
-       (trail_length >
-        GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity)))
+  if ((msize - sizeof (struct PeerVerifySuccessorResultMessage)) % 
+      sizeof (struct GNUNET_PeerIdentity) != 0)
   {
     GNUNET_break_op (0);
-    return GNUNET_YES; 
-  }
+    return GNUNET_OK;      
+  }  
   
-  current_dest_type = ntohl (trail_setup->current_destination_type);
-  finger_map_index = ntohl (trail_setup->finger_map_index);
-  trail_peer_list = (struct GNUNET_PeerIdentity *)&trail_setup[1];
-  destination_finger_value = trail_setup->destination_finger;
-  current_destination = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-  memcpy (current_destination, &(trail_setup->current_destination), sizeof (struct GNUNET_PeerIdentity));
-  
-  /* TODO:
-   each peer maintains a list of trail fail list. there it stores an entry with
-   source, finger identity it was trying, hop which rejected. it again call
-   select_random_friend but does not consider me. and starts trail setup 
-   again. */
-  if (GDS_ROUTING_size() > 1)
-  {
-    /* Setup the trail rejection message and send the message to peer. */
-    /* FIXME: you need to pass the trail, trail length and finger map index. */
-    GDS_NEIGHBOURS_send_trail_rejection_message (&(trail_setup->source_peer),
-                                                 trail_setup->destination_finger,
-                                                 &my_identity, peer, finger_map_index,
-                                                 trail_peer_list, trail_length);
-  }
-  /* Find the next hop to send the packet to. */
-  if (current_dest_type == FRIEND)
-  {
-    if (0 == (GNUNET_CRYPTO_cmp_peer_identity (&(trail_setup->current_destination),
-                                               &my_identity)))
-    {
-      next_hop = find_successor (destination_finger_value, current_destination, &(current_dest_type));
-    }
-    else
-      return GNUNET_SYSERR; 
+  trail = (const struct GNUNET_PeerIdentity *) &vsrm[1];
+  querying_peer = vsrm->querying_peer;
+  trail_direction = ntohl (vsrm->trail_direction);
+  trail_id = vsrm->trail_id;
+  probable_successor = vsrm->probable_successor;
+  
+  //FIXME: add a check to ensure that peer from which you got the message is
+  //the correct peer.
+  /* I am the querying_peer. */
+  if(0 == (GNUNET_CRYPTO_cmp_peer_identity (&querying_peer, &my_identity)))
+  {
+    compare_and_update_successor (probable_successor, trail, trail_length);
+    return GNUNET_OK;
   }
-  else if (current_dest_type == FINGER)
+  
+  /*If you are not the querying peer then pass on the message */
+  GNUNET_assert (NULL != (next_hop =
+                         GDS_ROUTING_get_next_hop (trail_id, trail_direction)));
+  target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop);
+  GDS_NEIGHBOURS_send_verify_successor_result (querying_peer,
+                                               vsrm->current_successor,
+                                               probable_successor, trail_id,
+                                               trail,
+                                               trail_length,
+                                               trail_direction, target_friend);
+  return GNUNET_OK;
+}
+
+
+/* 
+ * Add entry in your routing table if source of the message is not a friend.
+ * Irrespective if destination peer accepts source peer as predecessor or not, 
+ * we need to add an entry. So, that in next round to verify successor, source 
+ * is able to reach to its successor.
+ * Check if you are the new successor of this message
+ * 1. If yes the call function compare_and_update_successor(). This function
+ *    checks if source is real predecessor or not and take action accordingly.
+ * 2. If not then find the next hop to find the message from the trail that 
+ *    you got from the message and pass on the message.
+ * Core handle for p2p notify new successor messages.
+ * @param cls closure
+ * @param message message
+ * @param peer peer identity this notification is about
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
+ */
+static int
+handle_dht_p2p_notify_new_successor(void *cls, 
+                                    const struct GNUNET_PeerIdentity *peer,
+                                    const struct GNUNET_MessageHeader *message)
+{
+  const struct PeerNotifyNewSuccessorMessage *nsm;
+  struct GNUNET_PeerIdentity *trail;
+  struct GNUNET_PeerIdentity source;
+  struct GNUNET_PeerIdentity new_successor;
+  struct GNUNET_HashCode trail_id;
+  struct GNUNET_PeerIdentity next_hop;
+  struct FriendInfo *target_friend;
+  int my_index;
+  size_t msize;
+  uint32_t trail_length;
+
+  msize = ntohs (message->size);
+  /* We have the trail to reach from source to new successor. */
+  if (msize < sizeof (struct PeerNotifyNewSuccessorMessage))
   {
-    if (0 != (GNUNET_CRYPTO_cmp_peer_identity (&(trail_setup->current_destination),
-                                               &my_identity)))
-    {
-      next_hop = GDS_ROUTING_search (&(trail_setup->current_source),
-                                     &(trail_setup->current_destination), peer);
-      /* As an optimization, find the successor from the find successor and
-       compare both the ids to find the closest peer. */
-    } 
-    else
-    {
-      next_hop = find_successor (destination_finger_value, current_destination, &(current_dest_type)); 
-    }
+    GNUNET_break_op (0);
+    return GNUNET_YES;
   }
-  /* Add yourself to the trail list and increment the trail length. */
-  struct GNUNET_PeerIdentity *peer_list;
-  peer_list = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity) * (trail_length + 1));
-  if ( trail_length > 0)
+
+  nsm = (const struct PeerNotifyNewSuccessorMessage *) message;
+  trail_length = (msize - sizeof (struct PeerNotifyNewSuccessorMessage))/
+                  sizeof (struct GNUNET_PeerIdentity);
+  if ((msize - sizeof (struct PeerTrailRejectionMessage)) % 
+      sizeof (struct GNUNET_PeerIdentity) != 0)
   {
-    memcpy (peer_list, trail_peer_list, trail_length * sizeof (struct GNUNET_PeerIdentity));
+    GNUNET_break_op (0);
+    return GNUNET_OK;      
   }
-  memcpy (&peer_list[trail_length], &my_identity, sizeof (struct GNUNET_PeerIdentity));
-  trail_length++;
   
-  if (current_dest_type == MY_ID || 
-     (0 == GNUNET_CRYPTO_cmp_peer_identity(next_hop, &(trail_setup->source_peer))))
+  trail = (struct GNUNET_PeerIdentity *) &nsm[1];
+  source  = nsm->source_peer;
+  new_successor = nsm->new_successor;
+  trail_id = nsm->trail_id;  
+  
+  //FIXME: add a check to make sure peer is correct. 
+  
+  /* I am the new_successor to source_peer. */
+  if ( 0 == GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &new_successor))
   {
-    struct GNUNET_PeerIdentity *source_peer;
-    source_peer = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-    memcpy (source_peer, &(trail_setup->source_peer), sizeof (struct GNUNET_PeerIdentity));
-    
-    current_trail_index = trail_length - 1; 
-    next_peer=  GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-    if (current_trail_index == 0)
-    {
-      memcpy (next_peer, &(trail_setup->source_peer), sizeof (struct GNUNET_PeerIdentity));
-    }
-    else
-    {
-      memcpy (next_peer, &trail_peer_list[current_trail_index-1], sizeof (struct GNUNET_PeerIdentity));
-    }
-     
-    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_peer);
-    GNUNET_free (next_peer);
-    
-    if (0 == trail_setup->finger_map_index)
+    /* Add an entry in routing table only if new predecessor is not a friend. */
+    if (NULL == GNUNET_CONTAINER_multipeermap_get(friend_peermap, &source))
     {
-      struct GNUNET_PeerIdentity *new_trail_list;
-      new_trail_list = invert_trail_list (source_peer, peer_list, trail_length);
-      finger_table_add (source_peer, new_trail_list, trail_length, 1);
+      GDS_ROUTING_add (trail_id, *peer, my_identity);
     }
-    
-    GDS_NEIGHBOURS_send_trail_setup_result (&(trail_setup->source_peer),
-                                            &(my_identity),
-                                            target_friend, trail_length,
-                                            peer_list, current_trail_index,
-                                            finger_map_index);
-  
-    return GNUNET_YES;
+    compare_and_update_predecessor (source, trail, trail_length);
+    return GNUNET_OK;
   }
-  else 
+  
+  /* I am part of trail to reach to successor. */
+  my_index = search_my_index (trail, trail_length);
+  if (-1 == my_index)
   {
-    struct GNUNET_PeerIdentity *current_source;
-    current_source = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-    if (current_dest_type == FINGER)
-    {
-      memcpy (current_source, &my_identity, sizeof (struct GNUNET_PeerIdentity));
-    }
-    else
-      current_source = NULL;
-    
-    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop);
-   /* FiXME: Is it correct to use null value for current source. */
-    GDS_NEIGHBOURS_send_trail_setup (&(trail_setup->source_peer),
-                                     trail_setup->destination_finger,
-                                     current_destination,current_source,
-                                     target_friend, trail_length, peer_list, 
-                                     finger_map_index, current_dest_type);
-
-  return GNUNET_YES;
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
   }
-  return GNUNET_SYSERR;
+  if (trail_length == my_index)
+    next_hop = new_successor;
+  else
+    next_hop = trail[my_index + 1];
+  
+  /* Add an entry in routing table for trail from source to its new successor. */
+  GNUNET_assert (GNUNET_OK == GDS_ROUTING_add (trail_id, *peer, next_hop));
+  target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, &next_hop);
+  GDS_NEIGHBOURS_send_notify_new_successor (source, new_successor, trail,
+                                            trail_length,
+                                            trail_id, target_friend);
+  return GNUNET_OK;
+  
 }
 
 
 /**
- * Core handle for p2p trail construction result messages.
+ * 1. Set the congestion timeout for the friend which is congested and sent
+ * you this message.
+ * 2. Check if you were the source of this message
+ *   2.1 If yes then exit. find_finger_trail_task is scheduled periodically.
+ *       So, we will eventually send a new request to setup trail to finger.
+ * 2. Check if you can handle more trails through you. (Routing table space)
+ *   2.1 If not then you are congested. Set your congestion time and pass this
+ *       message to peer before you in the trail setup so far. 
+ *   2.2 If yes, the call find_successor(). It will give you the next hop to 
+ *       pass this message.
+ *      2.2.1 If you are the final destination, then send back the trail setup 
+ *            result.
+ *      2.2.2 If you are not the final dest, then send trail setup message to
+ *            next_hop.
+ * Core handler for P2P trail rejection message
  * @param cls closure
  * @param message message
  * @param peer peer identity this notification is about
- * @return GNUNET_OK on success, GNUNET_SYSERR on error
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
  */
 static int
-handle_dht_p2p_trail_setup_result(void *cls, const struct GNUNET_PeerIdentity *peer,
-                                  const struct GNUNET_MessageHeader *message)
+handle_dht_p2p_trail_setup_rejection (void *cls,
+                                      const struct GNUNET_PeerIdentity *peer,
+                                      const struct GNUNET_MessageHeader *message)
 {
-  struct PeerTrailSetupResultMessage *trail_result;
-  struct GNUNET_PeerIdentity *trail_peer_list;
-  struct GNUNET_PeerIdentity *next_hop;
-  struct FriendInfo *target_friend;
-  unsigned int current_trail_index;
-  unsigned int finger_map_index;
+  const struct PeerTrailRejectionMessage *trail_rejection;
   unsigned int trail_length;
+  const struct GNUNET_PeerIdentity *trail_peer_list;
+  struct FriendInfo *target_friend;
+  struct GNUNET_TIME_Relative congestion_timeout;
+  struct GNUNET_HashCode trail_id;
+  struct GNUNET_PeerIdentity next_destination;
+  struct GNUNET_HashCode new_intermediate_trail_id;
+  struct GNUNET_PeerIdentity next_peer;
+  struct GNUNET_PeerIdentity source;
+  struct GNUNET_PeerIdentity *next_hop;
+  uint64_t ultimate_destination_finger_value;
+  unsigned int is_predecessor;
   size_t msize;
-  
+
   msize = ntohs (message->size);
-  if (msize < sizeof (struct PeerTrailSetupResultMessage))
-  {
-    GNUNET_break_op (0);
-    return GNUNET_YES;
-  }
-  
-  trail_result = (struct PeerTrailSetupResultMessage *) message; 
-  trail_length = ntohl (trail_result->trail_length); 
-  
-  if ((msize <
-       sizeof (struct PeerTrailSetupResultMessage) +
-       trail_length * sizeof (struct GNUNET_PeerIdentity)) ||
-       (trail_length >
-        GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity)))
+  /* We are passing the trail setup so far. */
+  if (msize < sizeof (struct PeerTrailRejectionMessage))
   {
     GNUNET_break_op (0);
     return GNUNET_YES;
   }
-  
-  current_trail_index = ntohl (trail_result->current_index);
-  finger_map_index = ntohl (trail_result->finger_map_index);
 
-  trail_peer_list = (struct GNUNET_PeerIdentity *) &trail_result[1];
-  
-  if ( 0 == (GNUNET_CRYPTO_cmp_peer_identity (&(trail_result->destination_peer),
-                                              &my_identity)))
+  trail_rejection = (const struct PeerTrailRejectionMessage *) message;
+  trail_length = (msize - sizeof (struct PeerTrailRejectionMessage))/
+                  sizeof (struct GNUNET_PeerIdentity);
+  if ((msize - sizeof (struct PeerTrailRejectionMessage)) % 
+      sizeof (struct GNUNET_PeerIdentity) != 0)
   {
-      finger_table_add (&(trail_result->finger_identity), trail_peer_list, trail_length, 
-                       finger_map_index);
-     
-      return GNUNET_YES;
-
-  }
-  else
+    GNUNET_break_op (0);
+    return GNUNET_OK;      
+  }           
+
+  trail_peer_list = (const struct GNUNET_PeerIdentity *)&trail_rejection[1];
+  is_predecessor = ntohl (trail_rejection->is_predecessor);
+  congestion_timeout = trail_rejection->congestion_time;
+  source = trail_rejection->source_peer;
+  trail_id = trail_rejection->trail_id;
+  ultimate_destination_finger_value = 
+          GNUNET_ntohll (trail_rejection->ultimate_destination_finger_value);
+
+  /* First set the congestion time of the friend that sent you this message. */
+  target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, peer);
+  target_friend->congestion_timestamp = 
+          GNUNET_TIME_absolute_add (GNUNET_TIME_absolute_get(),
+                                    congestion_timeout);
+
+  /* I am the source peer which wants to setup the trail. Do nothing. 
+   * send_find_finger_trail_task is scheduled periodically.*/
+  if(0 == (GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &source)))
+    return GNUNET_OK;
+
+  /* If I am congested then pass this message to peer before me in trail. */
+  if(GNUNET_YES == GDS_ROUTING_threshold_reached())
   {
-    next_hop = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
+    struct GNUNET_PeerIdentity *new_trail;
+    unsigned int new_trail_length;
     
-    current_trail_index = current_trail_index - 1; 
-    if (current_trail_index == 0)
+    /* Remove yourself from the trail setup so far. */
+    if (trail_length == 1)
     {
-      memcpy (next_hop, &(trail_result->destination_peer),sizeof (struct GNUNET_PeerIdentity));
+      new_trail = NULL;
+      new_trail_length = 0;
+      next_hop = &source;
     }
     else
-    {   
-      memcpy (next_hop, &(trail_peer_list[current_trail_index-1]),sizeof (struct GNUNET_PeerIdentity));
+    {
+      memcpy (&next_hop , &trail_peer_list[trail_length - 2], 
+              sizeof (struct GNUNET_PeerIdentity));
+      
+      /* Remove myself from the trail. */
+      new_trail_length = trail_length -1;
+      new_trail = GNUNET_malloc (new_trail_length * sizeof (struct GNUNET_PeerIdentity));
+      memcpy (new_trail, trail_peer_list, new_trail_length * sizeof (struct GNUNET_PeerIdentity));
     }
+
+    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop);
+    GDS_NEIGHBOURS_send_trail_rejection (source,
+                                         ultimate_destination_finger_value,
+                                         my_identity, is_predecessor,
+                                         new_trail,new_trail_length,trail_id,
+                                         target_friend, CONGESTION_TIMEOUT);
+    GNUNET_free (new_trail);
+    return GNUNET_OK;
+  }
+
+  /* Look for next_hop to pass the trail setup message */
+  next_hop = find_successor (ultimate_destination_finger_value,
+                             &next_destination,
+                             &new_intermediate_trail_id,
+                             is_predecessor);
+  
+  /* Am I the final destination? */
+  if (0 == (GNUNET_CRYPTO_cmp_peer_identity (next_hop, &my_identity)))
+  {
+    /* Add an entry in routing table only 
+     * 1. If I am not the original source which sent the request for trail setup 
+     * 2. If trail length > 0. 
+     * NOTE: In case trail length > 0 and source is my friend, then also I add
+     *       an entry in routing table,as we will send a trail compression message
+     *       later.
+     */
+    if ((0 != GNUNET_CRYPTO_cmp_peer_identity (&source, &my_identity)) ||
+        (trail_length > 0))
+      GNUNET_assert (GNUNET_YES == GDS_ROUTING_add (trail_id, *peer, my_identity));
     
+    if (0 == trail_length)
+      next_peer = source;
+    else
+      next_peer = trail_peer_list[trail_length-1];
     
-    /* If trail length  = 2, it means that destination and source peer are friends
-     Then don't add an entry. */
-    if (trail_length != 2)
-      GDS_ROUTING_add (&(trail_result->destination_peer), &(trail_result->finger_identity),
-                     peer, next_hop);   
-    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop);
-    GNUNET_free (next_hop);
-      
-    GDS_NEIGHBOURS_send_trail_setup_result (&(trail_result->destination_peer),
-                                            &(trail_result->finger_identity),
+    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, &next_peer);
+    GDS_NEIGHBOURS_send_trail_setup_result (source,
+                                            my_identity,
                                             target_friend, trail_length,
-                                            trail_peer_list,current_trail_index,
-                                            finger_map_index);
-      return GNUNET_YES;
-    }
-  
-  return GNUNET_SYSERR;
-}
+                                            trail_peer_list,
+                                            is_predecessor, 
+                                            ultimate_destination_finger_value,
+                                            trail_id);
+  }
+  else
+  {
+    struct GNUNET_PeerIdentity peer_list[trail_length + 1];
 
+    memcpy (peer_list, trail_peer_list, trail_length * sizeof (struct GNUNET_PeerIdentity));
+    peer_list[trail_length] = my_identity;
 
-/**
- * FIXME: Use flag in the case finger peer map does not contain predcessor
- * then its NULL. Ideally it should never happen. 
- * Get my current predecessor from the finger peer map
- * @return Current predecessor.
- */
-static struct FingerInfo *
-get_predecessor()
-{
-  struct GNUNET_CONTAINER_MultiPeerMapIterator *finger_iter;
-  struct GNUNET_PeerIdentity key_ret;
-  unsigned int finger_index;
-  struct FingerInfo *my_predecessor;
-  /* Iterate over finger peer map and extract your predecessor. */
-  finger_iter = GNUNET_CONTAINER_multipeermap_iterator_create (finger_peermap);  
-  for (finger_index = 0; finger_index < GNUNET_CONTAINER_multipeermap_size (finger_peermap); finger_index++)
-  {
-    if(GNUNET_YES == GNUNET_CONTAINER_multipeermap_iterator_next 
-                       (finger_iter,&key_ret,(const void **)&my_predecessor)) 
-    {
-      if(1 == my_predecessor->finger_map_index)
-      {
-        break;
-      }
-    }
+    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop);
+    GDS_NEIGHBOURS_send_trail_setup (source,
+                                     ultimate_destination_finger_value,
+                                     next_destination,
+                                     target_friend, trail_length + 1, peer_list,
+                                     is_predecessor, trail_id,
+                                     &new_intermediate_trail_id);
   }
-  GNUNET_CONTAINER_multipeermap_iterator_destroy (finger_iter);
-  return my_predecessor;
+  GNUNET_free (next_hop);
+  return GNUNET_OK;
 }
 
 
-/**
- * Core handle for p2p verify successor messages.
+/*
+ * If you are the new first friend, then update prev hop to source of this message
+ * else get the next hop and pass this message forward to ultimately reach
+ * new first_friend.
+ * Core handle for p2p trail tear compression messages.
  * @param cls closure
  * @param message message
  * @param peer peer identity this notification is about
- * @return GNUNET_OK on success, GNUNET_SYSERR on error
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
  */
 static int
-handle_dht_p2p_verify_successor(void *cls, const struct GNUNET_PeerIdentity *peer,
-                                const struct GNUNET_MessageHeader *message)
+handle_dht_p2p_trail_compression (void *cls, const struct GNUNET_PeerIdentity *peer,
+                                  const struct GNUNET_MessageHeader *message)
 {
-  struct PeerVerifySuccessorMessage *vsm;
-  struct GNUNET_PeerIdentity *trail_peer_list;
-  struct FriendInfo *target_friend;
+  const struct PeerTrailCompressionMessage *trail_compression;
   struct GNUNET_PeerIdentity *next_hop;
-  struct GNUNET_PeerIdentity *source_peer;
-  unsigned int trail_length;
-  unsigned int current_trail_index;
+  struct FriendInfo *target_friend;
+  struct GNUNET_HashCode trail_id;
   size_t msize;
-  
+
   msize = ntohs (message->size);
-  if (msize < sizeof (struct PeerVerifySuccessorMessage))
+  /* Here we pass only the trail id. */
+  if (msize != sizeof (struct PeerTrailCompressionMessage))
   {
     GNUNET_break_op (0);
-    return GNUNET_YES;
+    return GNUNET_OK;
   }
   
-  vsm = (struct PeerVerifySuccessorMessage *) message;
-  trail_length = ntohl (vsm->trail_length);
+  trail_compression = (const struct PeerTrailCompressionMessage *) message;
+  trail_id = trail_compression->trail_id;
+  //FIXME: again check if peer is the correct peer. same logic as 
+  //trail teardown make a generic function. 
   
-  if ((msize < sizeof (struct PeerVerifySuccessorMessage) +
-               trail_length * sizeof (struct GNUNET_PeerIdentity)) ||
-     (trail_length > GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity)))
+  /* Am I the new first friend to reach to finger of this trail. */
+  if (0 == (GNUNET_CRYPTO_cmp_peer_identity (&(trail_compression->new_first_friend),
+                                             &my_identity)))
   {
-    GNUNET_break_op (0);
-    return GNUNET_YES;
+    /* Update your prev hop to source of this message. */
+    GDS_ROUTING_update_trail_prev_hop (trail_id,
+                                       trail_compression->source_peer);
+    return GNUNET_OK;
   }
   
-  current_trail_index = ntohl (vsm->current_trail_index);       
-  trail_peer_list = (struct GNUNET_PeerIdentity *) &vsm[1];
-  source_peer = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-  memcpy (source_peer, &(vsm->source_peer), sizeof (struct GNUNET_PeerIdentity));
-  
-  next_hop = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-  
-  if(0 == (GNUNET_CRYPTO_cmp_peer_identity (&(vsm->successor),&my_identity)))
-  {
-    struct FingerInfo *my_predecessor;
-    current_trail_index = trail_length - 1; 
-    if (current_trail_index == 0)
-      memcpy (next_hop, source_peer, sizeof (struct GNUNET_PeerIdentity));
-    else
-      memcpy (next_hop, &trail_peer_list[current_trail_index-1], sizeof (struct GNUNET_PeerIdentity));
-    
-    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop);
-    GNUNET_free (next_hop);
-    
-    my_predecessor = get_predecessor();
-    if (0 == (GNUNET_CRYPTO_cmp_peer_identity (source_peer,
-                                               &(my_predecessor->finger_identity))))
-    {
-      GDS_NEIGHBOURS_send_verify_successor_result (source_peer,
-                                                   &(my_identity),
-                                                   &(my_predecessor->finger_identity),
-                                                   target_friend,
-                                                   trail_peer_list,
-                                                   trail_length,
-                                                   current_trail_index);
-    }
-    else
-    {
-      struct GNUNET_PeerIdentity *new_successor_trail;
-      int new_trail_length;
-      int i;
-      
-      new_trail_length = trail_length + my_predecessor->trail_length;
-      new_successor_trail = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity) * new_trail_length);
-      memcpy (new_successor_trail, trail_peer_list, (trail_length) * sizeof (struct GNUNET_PeerIdentity));
-      struct TrailPeerList *iterator;
-      iterator = GNUNET_malloc (sizeof (struct TrailPeerList));
-      iterator = my_predecessor->head; 
-      i = trail_length;
-      while (i < new_trail_length)
-      {
-        memcpy (&new_successor_trail[i], &(iterator->peer), sizeof (struct GNUNET_PeerIdentity));
-        iterator = iterator->next;
-        i++;
-      }
-      GDS_NEIGHBOURS_send_verify_successor_result (source_peer,
-                                                   &(my_identity),
-                                                   &(my_predecessor->finger_identity),
-                                                   target_friend,
-                                                   new_successor_trail,
-                                                   new_trail_length,
-                                                   current_trail_index); 
-    }      
-   
-  }
-  else
+  /* Pass the message to next hop to finally reach to new_first_friend. */
+  next_hop = GDS_ROUTING_get_next_hop (trail_id, GDS_ROUTING_SRC_TO_DEST);
+  if (NULL == next_hop)
   {
-    current_trail_index = current_trail_index + 1;
-    memcpy (next_hop, &trail_peer_list[current_trail_index], sizeof (struct GNUNET_PeerIdentity));
-    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop);
-    GNUNET_free (next_hop);
-        
-    GDS_NEIGHBOURS_send_verify_successor (source_peer, &(vsm->successor),target_friend,
-                                          trail_peer_list, trail_length, current_trail_index); 
+    GNUNET_break (0); 
+    return GNUNET_OK;
   }
-  return GNUNET_YES;
+  
+  GNUNET_assert (GNUNET_YES == GDS_ROUTING_remove_trail (trail_id));
+  target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop);
+  GDS_NEIGHBOURS_send_trail_compression (trail_compression->source_peer,
+                                         trail_id,
+                                         trail_compression->new_first_friend,
+                                         target_friend);
+  return GNUNET_OK;
 }
 
 
 /**
- * Core handle for p2p notify new successor messages.
+ * Remove entry from your own routing table and pass the message to next
+ * peer in the trail. 
+ * Core handler for trail teardown message.
  * @param cls closure
  * @param message message
- * @param peer peer identity this notification is about
- * @return GNUNET_OK on success, GNUNET_SYSERR on error
+ * @param peer sender of this messsage. 
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
  */
 static int
-handle_dht_p2p_notify_new_successor(void *cls, const struct GNUNET_PeerIdentity *peer,
-                                    const struct GNUNET_MessageHeader *message)
+handle_dht_p2p_trail_teardown (void *cls, const struct GNUNET_PeerIdentity *peer,
+                               const struct GNUNET_MessageHeader *message)
 {
-  struct PeerNotifyNewSuccessorMessage *nsm;
-  struct GNUNET_PeerIdentity *trail_peer_list;
-  unsigned int current_trail_index;
+  const struct PeerTrailTearDownMessage *trail_teardown;
+  enum GDS_ROUTING_trail_direction trail_direction;
+  struct GNUNET_HashCode trail_id;
+  struct GNUNET_PeerIdentity *prev_hop;
+  struct GNUNET_PeerIdentity *next_hop;
   size_t msize;
-  unsigned int trail_length;
-  
   msize = ntohs (message->size);
-  if (msize < sizeof (struct PeerNotifyNewSuccessorMessage))
+  /* Here we pass only the trail id. */
+  if (msize != sizeof (struct PeerTrailTearDownMessage))
   {
     GNUNET_break_op (0);
-    return GNUNET_YES;
+    return GNUNET_OK;
   }
   
-  nsm = (struct PeerNotifyNewSuccessorMessage *) message;
-  trail_length = ntohl (nsm->trail_length);
+  trail_teardown = (const struct PeerTrailTearDownMessage *) message;
+  trail_direction = ntohl (trail_teardown->trail_direction);
+  trail_id = trail_teardown->trail_id;
   
-  if ((msize < sizeof (struct PeerNotifyNewSuccessorMessage) +
-               trail_length * sizeof (struct GNUNET_PeerIdentity)) ||
-      (trail_length >
-       GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity)))
+  /* Check if peer is the real peer from which we should get this message.*/
+  /* Get the prev_hop for this trail by getting the next hop in opposite direction. */
+  /* FIXME: is using negation of trail direction correct. */
+  prev_hop = GDS_ROUTING_get_next_hop (trail_id, !trail_direction);
+  if (0 != GNUNET_CRYPTO_cmp_peer_identity (prev_hop, peer))
   {
-    GNUNET_break_op (0);
-    return GNUNET_YES;
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
   }
+  GNUNET_free_non_null (prev_hop);
   
-  current_trail_index = ntohl (nsm->current_index);
-  trail_peer_list = (struct GNUNET_PeerIdentity *) &nsm[1];
-  
-  if(0 == (GNUNET_CRYPTO_cmp_peer_identity (&(nsm->destination_peer), &my_identity)))
-  {
-    struct GNUNET_PeerIdentity *new_trail;
-    new_trail = invert_trail_list (&(nsm->source_peer), trail_peer_list, trail_length);
-    finger_table_add (&(nsm->source_peer), new_trail, trail_length, 1); 
-    return GNUNET_YES;
-  }
-  else
+  next_hop = GDS_ROUTING_get_next_hop (trail_id, trail_direction);
+  if (NULL == next_hop)
   {
-    struct FriendInfo *target_friend;
-    struct GNUNET_PeerIdentity *next_hop;
-    
-    target_friend = GNUNET_malloc (sizeof (struct FriendInfo));
-    next_hop = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-    
-    current_trail_index = current_trail_index + 1;
-    memcpy (next_hop, &trail_peer_list[current_trail_index], sizeof (struct GNUNET_PeerIdentity));
-    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop);
-    GNUNET_free (next_hop);
-    
-    GDS_NEIGHBOURS_send_notify_new_successor (&(nsm->source_peer), 
-                                              &(nsm->destination_peer),
-                                              target_friend, trail_peer_list,
-                                              trail_length, current_trail_index);
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
   }
-  return GNUNET_YES;
+  
+  GNUNET_assert (GNUNET_YES == GDS_ROUTING_remove_trail (trail_id));
+  
+  /* If next_hop is my_identity, it means I am the final destination. */
+  if (0 == GNUNET_CRYPTO_cmp_peer_identity (next_hop, &my_identity))
+    return GNUNET_OK;
+  
+  /* If not final destination, then send a trail teardown message to next hop.*/
+  GDS_NEIGHBOURS_send_trail_teardown (trail_id, trail_direction, next_hop);
+  GNUNET_free (next_hop);
+  return GNUNET_OK;
 }
 
 
 /**
- * Core handle for p2p verify successor result messages.
+ * Add an entry in your routing table. If you are destination of this message
+ * then next_hop in routing table should be your own identity. If you are NOT
+ * destination, then get the next hop and forward message to it.
+ * Core handle for p2p add trail message. 
  * @param cls closure
  * @param message message
  * @param peer peer identity this notification is about
- * @return GNUNET_OK on success, GNUNET_SYSERR on error
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
  */
 static int
-handle_dht_p2p_verify_successor_result(void *cls, const struct GNUNET_PeerIdentity *peer,
-                                       const struct GNUNET_MessageHeader *message)
+handle_dht_p2p_add_trail (void *cls, const struct GNUNET_PeerIdentity *peer,
+                          const struct GNUNET_MessageHeader *message)
 {
-  struct PeerVerifySuccessorResultMessage *vsrm;
-  struct FriendInfo *target_friend;
-  struct GNUNET_PeerIdentity *trail_peer_list;
-  struct GNUNET_PeerIdentity *next_hop;
+  const struct PeerAddTrailMessage *add_trail;
+  const struct GNUNET_PeerIdentity *trail;
+  struct GNUNET_HashCode trail_id;
+  struct GNUNET_PeerIdentity destination_peer;
+  struct GNUNET_PeerIdentity source_peer;
+  struct GNUNET_PeerIdentity next_hop;
   unsigned int trail_length;
-  unsigned int current_trail_index;
+  unsigned int my_index;
   size_t msize;
-  
+
   msize = ntohs (message->size);
-  if (msize < sizeof (struct PeerVerifySuccessorResultMessage))
+  /* In this message we pass the whole trail from source to destination as we
+   * are adding that trail.*/
+  if (msize < sizeof (struct PeerAddTrailMessage))
   {
     GNUNET_break_op (0);
-    return GNUNET_YES;
+    return GNUNET_OK;
   }
-  
-  vsrm = (struct PeerVerifySuccessorResultMessage *) message;
-  trail_length = ntohl (vsrm->trail_length); 
-  
-  if ((msize <
-       sizeof (struct PeerVerifySuccessorResultMessage) +
-       trail_length * sizeof (struct GNUNET_PeerIdentity)) ||
-       (trail_length >
-       GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity)))
+
+  add_trail = (const struct PeerAddTrailMessage *) message;
+  trail_length = (msize - sizeof (struct PeerAddTrailMessage))/
+                  sizeof (struct GNUNET_PeerIdentity);
+  if ((msize - sizeof (struct PeerAddTrailMessage)) % 
+      sizeof (struct GNUNET_PeerIdentity) != 0)
   {
     GNUNET_break_op (0);
-    return GNUNET_YES;
-  }
-  
-  current_trail_index = ntohl (vsrm->current_index);
-  trail_peer_list = (struct GNUNET_PeerIdentity *) &vsrm[1];
+    return GNUNET_OK;      
+  }           
+
+  trail = (const struct GNUNET_PeerIdentity *)&add_trail[1];
+  destination_peer = add_trail->destination_peer;
+  source_peer = add_trail->source_peer;
+  trail_id = add_trail->trail_id;
 
-  if(0 == (GNUNET_CRYPTO_cmp_peer_identity (&(vsrm->destination_peer), &(my_identity))))
+  //FIXME: add a check that sender peer is not malicious. Make it a generic
+  // function so that it can be used in all other functions where we need the
+  // same functionality.
+  
+  /* I am not the destination of the trail. */
+  if (0 != GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &destination_peer))
   {
-    if(0 != (GNUNET_CRYPTO_cmp_peer_identity (&(vsrm->my_predecessor), &(my_identity))))
+    struct FriendInfo *target_friend;
+
+    /* Get my location in the trail. */
+    my_index = search_my_index (trail, trail_length);
+    if (GNUNET_SYSERR == my_index)
     {
-      finger_table_add (&(vsrm->my_predecessor), trail_peer_list, trail_length, 0);
-      next_hop = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-      memcpy (next_hop, &trail_peer_list[0], sizeof (struct GNUNET_PeerIdentity));
-      target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop);
-      current_trail_index = 0;
-      GNUNET_free (next_hop);
-      
-      GDS_NEIGHBOURS_send_notify_new_successor (&my_identity, &(vsrm->my_predecessor),
-                                                target_friend, trail_peer_list,
-                                                trail_length, current_trail_index);
+      GNUNET_break_op (0);
+      return GNUNET_SYSERR;
     }
+
+    if (0 == my_index)
+      next_hop = source_peer;
+    else
+      next_hop = trail[trail_length - 1];
+    
+    /* Add in your routing table. */
+    GNUNET_assert (GNUNET_OK == GDS_ROUTING_add (trail_id, next_hop, *peer));
+    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, &next_hop);
+    GDS_NEIGHBOURS_send_add_trail (source_peer, destination_peer, trail_id,
+                                   trail, trail_length, target_friend);
+    return GNUNET_OK;
   }
-  else
+  
+  /* I am the destination. Add an entry in routing table. */
+  GNUNET_assert (GNUNET_OK == GDS_ROUTING_add (trail_id, *peer, my_identity));
+  return GNUNET_OK;
+}
+
+
+/**
+ * Send trail teardown and free the finger trail in which the first
+ * friend to reach to a finger is disconnected_friend 
+ * @param disconnected_friend PeerIdentity of friend which got disconnected
+ * @param remove_finger Finger whose trail we need to check if it has 
+ *                      disconnected_friend as the first hop.
+ * @return Total number of trails in which disconnected_friend was the first
+ *         hop.
+ */
+static int
+remove_matching_trails (const struct GNUNET_PeerIdentity *disconnected_friend,
+                        struct FingerInfo *remove_finger)
+{
+  unsigned int matching_trails_count;
+  int i;
+  
+  /* Number of trails with disconnected_friend as the first hop in the trail
+   * to reach from me to remove_finger, NOT including endpoints. */
+  matching_trails_count = 0;
+
+  /* Iterate over all the trails of finger. */
+  for (i = 0; i < remove_finger->trails_count; i++)
   {
-    next_hop = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-    current_trail_index = current_trail_index - 1;
-    if (current_trail_index == 0)
-      memcpy (next_hop, &(vsrm->destination_peer), sizeof (struct GNUNET_PeerIdentity));
-    else
-      memcpy (next_hop, &trail_peer_list[current_trail_index-1], sizeof (struct GNUNET_PeerIdentity));
-    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop);
-    GNUNET_free (next_hop);
+    struct Trail *trail;
+    trail = &remove_finger->trail_list[i];
+    
+    if (GNUNET_NO == trail->is_present)
+      continue;
+    
+    /* First friend to reach to finger is disconnected_peer. */
+    if (0 == GNUNET_CRYPTO_cmp_peer_identity (&trail->trail_head->peer,
+                                              disconnected_friend))
+    {
+      matching_trails_count++;
+      send_trail_teardown (remove_finger, trail);
+      if (trail->trail_length > 0)
+      free_trail (trail);
+    }
+  }  
+  return matching_trails_count;
+}
+
+
+/**
+ * Iterate over finger_table entries. 
+ * 0. Ignore finger which is my_identity or if no valid entry present at 
+ *    that finger index. 
+ * 1. If disconnected_friend is a finger, then free that entry. Don't send trail
+ *    teardown message, as there is no trail to reach to a finger which is a friend. 
+ * 2. Check if disconnected_friend is the first friend in the trail to reach to a finger.
+ *   2.1 Send trail teardown message across all the trails in which disconnected
+ *       friend is the first friend in the trail. If disconnected_friend is the 
+ *       first friend in all the trails to reach finger, then remove the finger. 
+ * @param disconnected_friend Peer identity of friend which got disconnected.
+ */
+static void
+remove_matching_fingers (const struct GNUNET_PeerIdentity *disconnected_friend)
+{
+  struct FingerInfo *remove_finger;
+  int removed_trails_count;
+  int i;
+  
+  /* Iterate over finger table entries. */
+  for (i = 0; i < MAX_FINGERS; i++)
+  {  
+    remove_finger = &finger_table[i];
+
+    /* No finger stored at this trail index. */
+    if (GNUNET_NO == remove_finger->is_present)
+      continue;
+    
+    /* I am my own finger, then ignore this finger. */
+    if (0 == GNUNET_CRYPTO_cmp_peer_identity (&remove_finger->finger_identity,
+                                              &my_identity))
+      continue;
+    
+    /* Is disconnected friend a finger? */
+    if (0 == GNUNET_CRYPTO_cmp_peer_identity (disconnected_friend,
+                                              &remove_finger->finger_identity))
+    {
+      /* No trail to reach this finger as it is a friend, don't send 
+       * trail_teardown message. */
+      remove_finger->is_present = GNUNET_NO;
+      memset ((void *)&finger_table[i], 0, sizeof (finger_table[i]));
+      continue;
+    }
+    
+    /* Iterate over the list of trails to reach remove_finger. Check if 
+     * disconnected_friend is the first friend in any of the trail. */
+    removed_trails_count = remove_matching_trails (disconnected_friend, 
+                                                   remove_finger);
     
-    GDS_NEIGHBOURS_send_verify_successor_result (&(vsrm->destination_peer),
-                                                 &(vsrm->source_successor),
-                                                 &(vsrm->my_predecessor),
-                                                 target_friend,
-                                                 trail_peer_list,
-                                                 trail_length,
-                                                 current_trail_index); 
+    /* All the finger trails had disconnected_friend as the first friend,
+     * so free the finger. */
+    if (removed_trails_count == remove_finger->trails_count)
+    {
+      remove_finger->is_present = GNUNET_NO;
+      memset ((void *)&finger_table[i], 0, sizeof (finger_table[i]));
+    }
   }
-  return GNUNET_YES;
 }
 
 
 /**
- * FIXME: Does it matter if the packet was going to a finger or friend?
- * Core handle for p2p trail rejection messages.
+ * Method called whenever a peer disconnects.
+ *
  * @param cls closure
- * @param message message
  * @param peer peer identity this notification is about
- * @return GNUNET_OK on success, GNUNET_SYSERR on error
  */
-static
-int handle_dht_p2p_trail_rejection(void *cls, const struct GNUNET_PeerIdentity *peer,
-                                   const struct GNUNET_MessageHeader *message)
+static void
+handle_core_disconnect (void *cls,
+                                         const struct GNUNET_PeerIdentity *peer)
 {
-  struct PeerTrailRejectionMessage *trail_rejection;
-  struct FailedTrail *trail_fail;
-  struct FriendInfo *target_friend;
-  struct GNUNET_PeerIdentity *trail_peer_list;
-  unsigned int finger_map_index;
-  size_t msize;
+  struct FriendInfo *remove_friend;
+
+  /* If disconnected to own identity, then return. */
+  if (0 == memcmp (&my_identity, peer, sizeof (struct GNUNET_PeerIdentity)))
+    return;
+
+  GNUNET_assert (NULL != (remove_friend =
+                          GNUNET_CONTAINER_multipeermap_get (friend_peermap, peer)));
   
-  msize = ntohs (message->size);
-  if (msize < sizeof (struct PeerTrailRejectionMessage))
-  {
-    GNUNET_break_op (0);
-    return GNUNET_YES;
-  }
+  /* Remove fingers with peer as first friend or if peer is a finger. */
+  remove_matching_fingers (peer);
+  
+  /* Remove any trail from routing table of which peer is a part of. This function
+   * internally sends a trail teardown message in the direction of which
+   * disconnected peer is not part of. */
+  GDS_ROUTING_remove_trail_by_peer (peer);
   
-  trail_rejection = (struct PeerTrailRejectionMessage *) message;
-  trail_peer_list = (struct GNUNET_PeerIdentity *)&trail_rejection[1];
-  finger_map_index = ntohl (trail_rejection->finger_map_index);
-  trail_fail = GNUNET_malloc (sizeof (struct FailedTrail));
-  memcpy (&(trail_fail->source_peer), &(trail_rejection->source_peer), sizeof (struct GNUNET_PeerIdentity));
-  memcpy (&(trail_fail->congested_peer), &(trail_rejection->congested_peer), sizeof (struct GNUNET_PeerIdentity));
-  memcpy (&(trail_fail->destination_finger_value), &(trail_rejection->finger_identity), sizeof (uint64_t));
+  /* Remove peer from friend_peermap. */
+  GNUNET_assert (GNUNET_YES ==
+                 GNUNET_CONTAINER_multipeermap_remove (friend_peermap,
+                                                       peer,
+                                                       remove_friend));
   
+  if (0 != GNUNET_CONTAINER_multipeermap_size (friend_peermap))
+    return;
+
+  /* If there are no more friends in friend_peermap, then don't schedule
+   * find_finger_trail_task. */
+  if (GNUNET_SCHEDULER_NO_TASK != find_finger_trail_task)
+  {
+      GNUNET_SCHEDULER_cancel (find_finger_trail_task);
+      find_finger_trail_task = GNUNET_SCHEDULER_NO_TASK;
+  }
+  else
+    GNUNET_break (0);
+
+}
+
+
+/**
+ * Method called whenever a peer connects.
+ *
+ * @param cls closure
+ * @param peer_identity peer identity this notification is about
+ */
+static void
+handle_core_connect (void *cls, const struct GNUNET_PeerIdentity *peer_identity)
+{
+  struct FriendInfo *friend;
+
+  /* Check for connect to self message */
+  if (0 == memcmp (&my_identity, peer_identity, sizeof (struct GNUNET_PeerIdentity)))
+    return;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Connected to %s\n", GNUNET_i2s (peer_identity));
+
+  /* If peer already exists in our friend_peermap, then exit. */
+  if (GNUNET_YES == GNUNET_CONTAINER_multipeermap_contains (friend_peermap, 
+                                                            peer_identity))
+  {
+    GNUNET_break (0);
+    return;
+  }
+
+  GNUNET_STATISTICS_update (GDS_stats, gettext_noop ("# peers connected"), 1,
+                            GNUNET_NO);
+
+  friend = GNUNET_new (struct FriendInfo);
+  friend->id = *peer_identity;
+
   GNUNET_assert (GNUNET_OK ==
-  GNUNET_CONTAINER_multipeermap_put (failed_trail_list, &(trail_fail->source_peer),
-                                     trail_fail, GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE));
-   
-  /* FIXME: Is it okay if I pass the struct as parameter. */
-  target_friend = select_random_friend (&(trail_fail->congested_peer));
-  
-  if(NULL != target_friend)
-  { 
-    /* FIXME: Here I am passing NULL for current source, is it correct? 
-     also, we set the current source only if current_destination_type
-     is finger. */
-    GDS_NEIGHBOURS_send_trail_setup (&(trail_fail->source_peer), 
-                                     trail_fail->destination_finger_value,
-                                     &(target_friend->id),
-                                     NULL, target_friend, ntohl (trail_rejection->trail_length),
-                                     trail_peer_list, 
-                                     finger_map_index, FRIEND);
-    return GNUNET_YES;
+                 GNUNET_CONTAINER_multipeermap_put (friend_peermap,
+                                                    peer_identity, friend,
+                                                    GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
+
+
+  /* got a first connection, good time to start with FIND FINGER TRAIL requests...*/ 
+  if (GNUNET_SCHEDULER_NO_TASK == find_finger_trail_task)
+    find_finger_trail_task = GNUNET_SCHEDULER_add_now (&send_find_finger_trail_message, NULL);
+}
+
+
+/**
+ * To be called on core init/fail.
+ *
+ * @param cls service closure
+ * @param identity the public identity of this peer
+ */
+static void
+core_init (void *cls,
+           const struct GNUNET_PeerIdentity *identity)
+{
+  my_identity = *identity;
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "my_indentity = %s\n",GNUNET_i2s(&my_identity));
+   FPRINTF (stderr,_("\nSUPU %s, %s, %d, my_identity = %s"),
+   __FILE__, __func__,__LINE__, GNUNET_i2s (&my_identity));
+}
+
+
+/**
+ * Initialize finger table entries.
+ */
+static void
+finger_table_init ()
+{
+  int i;
+  int j;
+  
+  for(i = 0; i < MAX_FINGERS; i++)
+  {
+    finger_table[i].is_present = GNUNET_NO;
+    for (j = 0; j < MAXIMUM_TRAILS_PER_FINGER; j++)
+      finger_table[i].trail_list[j].is_present = GNUNET_NO;
+    memset ((void *)&finger_table[i], 0, sizeof (finger_table[i]));
+    
   }
-  return GNUNET_SYSERR;
 }
 
 
 /**
  * Initialize neighbours subsystem.
- * @return GNUNET_OK on success, GNUNET_SYSERR on error
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
  */
 int
-GDS_NEIGHBOURS_init()
+GDS_NEIGHBOURS_init (void)
 {
   static struct GNUNET_CORE_MessageHandler core_handlers[] = {
+    {&handle_dht_p2p_put, GNUNET_MESSAGE_TYPE_DHT_P2P_PUT, 0},
     {&handle_dht_p2p_get, GNUNET_MESSAGE_TYPE_DHT_P2P_GET, 0},
     {&handle_dht_p2p_get_result, GNUNET_MESSAGE_TYPE_DHT_P2P_GET_RESULT, 0},
-    {&handle_dht_p2p_put, GNUNET_MESSAGE_TYPE_DHT_P2P_PUT, 0},
     {&handle_dht_p2p_trail_setup, GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_SETUP, 0},
     {&handle_dht_p2p_trail_setup_result, GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_SETUP_RESULT, 0},
     {&handle_dht_p2p_verify_successor, GNUNET_MESSAGE_TYPE_DHT_P2P_VERIFY_SUCCESSOR, 0},
     {&handle_dht_p2p_verify_successor_result, GNUNET_MESSAGE_TYPE_DHT_P2P_VERIFY_SUCCESSOR_RESULT, 0},
     {&handle_dht_p2p_notify_new_successor, GNUNET_MESSAGE_TYPE_DHT_P2P_NOTIFY_NEW_SUCCESSOR, 0},
-    {&handle_dht_p2p_trail_rejection, GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_REJECTION, 0},
+    {&handle_dht_p2p_trail_setup_rejection, GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_SETUP_REJECTION, 0},
+    {&handle_dht_p2p_trail_compression, GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_COMPRESSION, 
+                                        sizeof (struct PeerTrailCompressionMessage)},
+    {&handle_dht_p2p_trail_teardown, GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_TEARDOWN, 
+                                     sizeof (struct PeerTrailTearDownMessage)},
+    {&handle_dht_p2p_add_trail, GNUNET_MESSAGE_TYPE_DHT_P2P_ADD_TRAIL, 0},
     {NULL, 0, 0}
   };
-  
+
   core_api =
     GNUNET_CORE_connect (GDS_cfg, NULL, &core_init, &handle_core_connect,
                          &handle_core_disconnect, NULL, GNUNET_NO, NULL,
@@ -3347,9 +5326,8 @@ GDS_NEIGHBOURS_init()
     return GNUNET_SYSERR;
 
   friend_peermap = GNUNET_CONTAINER_multipeermap_create (256, GNUNET_NO);
-  finger_peermap = GNUNET_CONTAINER_multipeermap_create (MAX_FINGERS, GNUNET_NO);
-  /* FIXME: Not sure if this value is correct for this data structure. */
-  failed_trail_list = GNUNET_CONTAINER_multipeermap_create (LINK_THRESHOLD, GNUNET_NO);
+  finger_table_init ();
+  
   return GNUNET_OK;
 }
 
@@ -3358,47 +5336,34 @@ GDS_NEIGHBOURS_init()
  * Shutdown neighbours subsystem.
  */
 void
-GDS_NEIGHBOURS_done ()
+GDS_NEIGHBOURS_done (void)
 {
   if (NULL == core_api)
     return;
-  
+
   GNUNET_CORE_disconnect (core_api);
   core_api = NULL;
-  
+
   GNUNET_assert (0 == GNUNET_CONTAINER_multipeermap_size (friend_peermap));
   GNUNET_CONTAINER_multipeermap_destroy (friend_peermap);
   friend_peermap = NULL;
-  
-  GNUNET_assert (0 == GNUNET_CONTAINER_multipeermap_size (finger_peermap));
-  GNUNET_CONTAINER_multipeermap_destroy (finger_peermap);
-  finger_peermap = NULL;
 
   if (GNUNET_SCHEDULER_NO_TASK != find_finger_trail_task)
   {
+    GNUNET_break (0);
     GNUNET_SCHEDULER_cancel (find_finger_trail_task);
     find_finger_trail_task = GNUNET_SCHEDULER_NO_TASK;
   }
-  
-  if (GNUNET_SCHEDULER_NO_TASK != verify_successor)
-  {
-    GNUNET_SCHEDULER_cancel (verify_successor);
-    verify_successor = GNUNET_SCHEDULER_NO_TASK;
-  }
-  
 }
 
 
 /**
- * Get the ID of the local node.
+ * Get my identity
  *
- * @return identity of the local node
+ * @return my identity
  */
-struct GNUNET_PeerIdentity *
-GDS_NEIGHBOURS_get_id ()
+struct GNUNET_PeerIdentity
+GDS_NEIGHBOURS_get_my_id (void)
 {
-  return &my_identity;
+  return my_identity;
 }
-
-
-/* end of gnunet-service-xdht_neighbours.c */