remove protocol violation
[oweals/gnunet.git] / src / dht / gnunet-service-xdht_neighbours.c
index b0eb08fd199d66d28c89c915d0a8c23e94f2cb89..c2927f1002045e07e2c5b57372028e37506bca19 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"
 
+/**
+ * Maximum possible fingers of a peer.
+ */
+#define MAX_FINGERS 65
+
+/**
+ * Maximum allowed number of pending messages per friend peer.
+ */
+#define MAXIMUM_PENDING_PER_FRIEND 64
 
-/* FIXME:
- * 1. do we need some mechanism to check if we already have found trail to 
- * our finger at a particular index. also real finger identifier that we
- * were looking for and successor it that we got. and whats the benefit of sending
- * 64 bit finger for searching? can we just send gnuent_peeridentity finger id
- * and only in find_successor we give 64 bit.
- * 2. Think of better names for variable especially for variables of type
- * uint64_t
- * 3. Add content and route replication later. 
- * 4. Algorithm to shorten the trail length - one possible solution could be
- * when we are in trail seutp result part. each peer in the trail check if any of
- * the corresponding peers is its friend list. Then it can shortcut the path.
- * 4. As we start looking for finger from i = 0, using this parameter to 
- * generate random value does not look smart in send_find_finger_trail_message. 
- * 6. Need to add a new task, fix fingers. For node join/leave, we need to 
- * upgrade our finger table periodically. So, we should call fix_fingers 
- * and change our finger table. 
- * 7. Should we look for fingers one by one in send_find_finger_trail_setup
- * 8. Change the message is gnunet_protocols.h 
- * 9. Can we just send the whole peer list as array for verify successor
- * and verify successor result instead of the way in which we send in peertrailmessage.
- * 10. I have added a new field trail length in finger info. so in finger_table_add
- * find this value to be added.
+/**
+ * How long to wait before sending another find finger trail request
  */
+#define DHT_FIND_FINGER_TRAIL_INTERVAL GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, 30)
 
+/**
+ * How long at most to wait for transmission of a request to another peer?
+ */
+#define GET_TIMEOUT GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MINUTES, 2)
 
 /**
- * Maximum possible fingers of a peer.
- * FIXME: Should it be 64 as we are doing all the operation on 64 bit numbers now? 
+ * How long will I remain congested?
  */
-#define MAX_FINGERS 64
+#define CONGESTION_TIMEOUT GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MINUTES, 2)
 
 /**
- * Maximum allowed number of pending messages per friend peer.
+ * Maximum number of trails stored per finger.
  */
-#define MAXIMUM_PENDING_PER_FRIEND 64
+#define MAXIMUM_TRAILS_PER_FINGER 2
+
+/**
+ * Used to distinguish put/get request use of find_successor() from others
+ */
+#define PUT_GET_REQUEST 65
+
+/**
+ * Maximum number of trails that can go through a friend.
+ */
+#define TRAIL_THROUGH_FRIEND_THRESHOLD 64
 
 /**
- * How long at least to wait before sending another find finger trail request.
+ * Finger map index for predecessor entry in finger peermap.
  */
-#define DHT_MINIMUM_FIND_FINGER_TRAIL_INTERVAL GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, 30)
+#define PREDECESSOR_FINGER_ID 64
 
 /**
- * How long at most to wait before sending another find finger trail request.
+ * Maximum number of trails allowed to go through a friend.
  */
-#define DHT_MAXIMUM_FIND_FINGER_TRAIL_INTERVAL GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MINUTES, 10)
+#define TRAILS_THROUGH_FRIEND_THRESHOLD 64
 
 /**
- * FIXME: Currently used in GDS_NEIGHBOURS_handle_trail_setup.
- * I have just copied it from gnunet-service-dht_neighbours. Will it work here? 
- * How long at most to wait for transmission of a GET request to another peer?
+ * Wrap around in peer identity circle. 
  */
-#define GET_TIMEOUT GNUNET_TIME_relative_multiply(GNUNET_TIME_UNIT_MINUTES, 2)
+#define PEER_IDENTITES_WRAP_AROUND pow(2, 256) - 1
 
 GNUNET_NETWORK_STRUCT_BEGIN
 
-/* FIXME:
- * 1) Bloomfilter is not required for X-Vine.
- * Keep the field now but remove it when implementing PUT/GET.
- * 2) also, check the field of put/get/result if all are required for
- * x-vine or not. */
-  
 /**
- * P2P PUT message
+ * P2P Trail setup message
  */
-struct PeerPutMessage
+struct PeerTrailSetupMessage
 {
   /**
-   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_PUT
+   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_SETUP
    */
   struct GNUNET_MessageHeader header;
 
-  /**
-   * Processing options
-   */
-  uint32_t options GNUNET_PACKED;
+  /* Bitmask of options, 1 = IS_PREDECESSOR */
+  // int32_t options;
 
   /**
-   * Content type.
+   * Peer closest to this value will be our finger.
    */
-  uint32_t type GNUNET_PACKED;
+  uint64_t ultimate_destination_finger;
 
   /**
-   * Hop count
+   * Source peer which wants to setup the trail to one of its finger.
    */
-  uint32_t hop_count GNUNET_PACKED;
+  struct GNUNET_PeerIdentity source_peer;
 
   /**
-   * Replication level for this message
+   * Peer to which this packet is forwarded.
    */
-  uint32_t desired_replication_level GNUNET_PACKED;
+  struct GNUNET_PeerIdentity next_destination; // rename "best_known_dest"
 
   /**
-   * Length of the PUT path that follows (if tracked).
+   * Index into finger peer map, in Network Byte Order.
    */
-  uint32_t put_path_length GNUNET_PACKED;
+  uint32_t finger_map_index; // remove this, include ultimate_destination_finger in response, calculate index from it
 
   /**
-   * When does the content expire?
+   * Number of entries in trail_list, in Network Byte Order.
    */
-  struct GNUNET_TIME_AbsoluteNBO expiration_time;
+  uint32_t trail_length GNUNET_PACKED; // remove this, calculte length from message size
 
   /**
-   * Bloomfilter (for peer identities) to stop circular routes
+   * Trail id of any intermediate trail we may encounter while doing trail setup.
    */
-  char bloomfilter[DHT_BLOOM_SIZE];
+  struct GNUNET_HashCode intermediate_trail_id;
 
   /**
-   * The key we are storing under.
+   * Trail id for trail which we are trying to setup.
    */
-  struct GNUNET_HashCode key;
-
-  /* put path (if tracked) */
-
-  /* Payload */
+  struct GNUNET_HashCode new_trail_id; // rename to "trail_id"
 
+  /* Trail formed in the process. */
+  /* GNUNET_PeerIdentity trail_list[] */
 };
 
-
 /**
* P2P Result message
 * P2P Trail Setup Result message
  */
-struct PeerResultMessage
+struct PeerTrailSetupResultMessage
 {
+
   /**
-   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_RESULT
+   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_SETUP_RESULT
    */
   struct GNUNET_MessageHeader header;
 
   /**
-   * Content type.
+   * Finger to which we have found the path.
    */
-  uint32_t type GNUNET_PACKED;
+  struct GNUNET_PeerIdentity finger_identity;
 
   /**
-   * Length of the PUT path that follows (if tracked).
+   * Peer which was looking for the trail to finger.
    */
-  uint32_t put_path_length GNUNET_PACKED;
+  struct GNUNET_PeerIdentity destination_peer; // querying_peer
 
   /**
-   * Length of the GET path that follows (if tracked).
+   * Index into finger peer map in NBO.
    */
-  uint32_t get_path_length GNUNET_PACKED;
+  uint32_t finger_map_index; // flag/option with IS_PREDECESSOR
 
   /**
-   * When does the content expire?
+   * Number of entries in trail list in NBO.
    */
-  struct GNUNET_TIME_AbsoluteNBO expiration_time;
+  uint32_t trail_length GNUNET_PACKED; // remove, calculate
 
   /**
-   * The key of the corresponding GET request.
+   * Identifier of the trail.
    */
-  struct GNUNET_HashCode key;
-
-  /* put path (if tracked) */
-
-  /* get path (if tracked) */
-
-  /* Payload */
+  struct GNUNET_HashCode trail_id;
 
+  /* Trail from "destination_peer" to finger_identity, NOT including both */
+  /* struct GNUNET_PeerIdentity trail[] */
 };
 
-
 /**
- * P2P GET message
+ * P2P Verify Successor Message.
  */
-struct PeerGetMessage
+struct PeerVerifySuccessorMessage
 {
   /**
-   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_GET
+   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_VERIFY_SUCCESSOR
    */
   struct GNUNET_MessageHeader header;
 
   /**
-   * Processing options
+   * Source peer which wants to verify its successor.
    */
-  uint32_t options GNUNET_PACKED;
+  struct GNUNET_PeerIdentity source_peer;
 
   /**
-   * Desired content type.
+   * My current successor.
    */
-  uint32_t type GNUNET_PACKED;
+  struct GNUNET_PeerIdentity successor;
 
   /**
-   * Hop count
+   * Identifier of trail to reach from source_peer to successor.
    */
-  uint32_t hop_count GNUNET_PACKED;
+  struct GNUNET_HashCode trail_id;
 
   /**
-   * Desired replication level for this request.
+   * Total number of peers to reach from source to successor.
    */
-  uint32_t desired_replication_level GNUNET_PACKED;
+  unsigned int trail_length;
+
+  /* Trail. */
+};
 
+/**
+ * P2P Verify Successor Result Message
+ */
+struct PeerVerifySuccessorResultMessage
+{
   /**
-   * Size of the extended query.
+   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_VERIFY_SUCCESSOR_RESULT
    */
-  uint32_t xquery_size;
+  struct GNUNET_MessageHeader header;
 
   /**
-   * Bloomfilter mutator.
+   * Destination peer which sent the request to verify its successor.
    */
-  uint32_t bf_mutator;
+  struct GNUNET_PeerIdentity destination_peer;
 
   /**
-   * Bloomfilter (for peer identities) to stop circular routes
+   * Successor to which PeerVerifySuccessorMessage was sent.
    */
-  char bloomfilter[DHT_BLOOM_SIZE];
+  struct GNUNET_PeerIdentity source_successor;
 
   /**
-   * The key we are looking for.
+   * source_successor's predecessor
    */
-  struct GNUNET_HashCode key;
+  struct GNUNET_PeerIdentity my_predecessor;
 
-};
+  /**
+   * Trail identifier of trail from my_predecessor to source_successor.
+   */
+  struct GNUNET_HashCode trail_id;
 
+  /**
+   * Direction in which we are looking at the trail.
+   */
+  enum GDS_ROUTING_trail_direction trail_direction;
 
-/**
- * A destination can be either a friend or finger.
- */
-enum current_destination_type
-{
-  
-  /* Friend */
-  FRIEND ,
-  
-  /* Finger */
-  FINGER ,
+  /**
+   * Total number of peers in trail from source_successor to my_predecessor
+   * if my_predecessor is not same as destination_peer.
+   */
+  uint32_t trail_length;
 
-  /* My own identity */
-  MY_ID        
+  /* Trail from source_successor to my_predecessor where
+   * my_predecessor != destination_peer*/
 };
 
-
 /**
- * P2P Trail setup message
- * TODO: Take reference from put_path and get_path to understand how to use size of trail list.  
+ * P2P Notify New Successor Message.
  */
-struct PeerTrailSetupMessage
+struct PeerNotifyNewSuccessorMessage
 {
-  
   /**
-   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_SETUP
+   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_NOTIFY_NEW_SUCCESSOR
    */
   struct GNUNET_MessageHeader header;
 
   /**
-   * Source peer which wants to find trail to one of its finger. 
+   * Source peer which wants to notify its new successor.
    */
   struct GNUNET_PeerIdentity source_peer;
 
   /**
-   * FIXME: Do we need to store the real finger identifier we were searching
-   * for in our finger table. Whats the use of storing it if any?
-   * As we are not sending any hello messages to this destination
-   * finger, we are only searching for it, we can just send 64 bit. 
-   * Finger id to which we want to set up the trail to. 
-   *
-  struct GNUNET_PeerIdentity destination_finger; */
+   * New successor identity.
+   */
+  struct GNUNET_PeerIdentity destination_peer;
 
   /**
-   * Finger id to which we want to set up the trail to. 
+   * Total number of peers in trail from source_peer to destination_peer
    */
-  uint64_t destination_finger;
-  
+  unsigned int trail_length;
+
   /**
-   * If set to 1, then we are looking for trail to our immediate successor. 
+   * Unique identifier of the trail.
    */
-  unsigned int successor_flag;
-  
+  struct GNUNET_HashCode trail_id;
+
+  /* Trail. */
+};
+
+/**
+ * P2P Trail Compression Message.
+ */
+struct PeerTrailCompressionMessage
+{
   /**
-   * If set to 1, then we are looking for trail to our immediate predecessor. 
+   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_COMPRESSION
    */
-  unsigned int predecessor_flag;
-  
+  struct GNUNET_MessageHeader header;
+
   /**
-   * If the message is forwarded to finger or friend. 
+   * Source peer of this trail.
    */
-  enum current_destination_type current_destination_type;
-  
+  struct GNUNET_PeerIdentity source_peer;
+
   /**
-   * This field contains the peer to which this packet is forwarded.
+   * Destination of this trail.
    */
-  struct GNUNET_PeerIdentity current_destination;
+  struct GNUNET_PeerIdentity destination_peer;
+
   /**
-   * Number of entries in trail list.
-   * FIXME: Is this data type correct?
-   * FIMXE: Is usage of GNUNET_PACKED correct?
+   * Trail from source_peer to destination_peer compressed such that
+   * new_first_friend is the first hop in the trail from source to
+   * destination.
    */
-  uint32_t trail_length GNUNET_PACKED;
-  
+  struct GNUNET_PeerIdentity new_first_friend;
+
+  /**
+   * Unique identifier of trail.
+   */
+  struct GNUNET_HashCode trail_id;
 };
 
 
 /**
- * P2P verify successor message. 
+ * P2P Trail Tear Down message.
  */
-struct PeerVerifySuccessorMessage
+struct PeerTrailTearDownMessage
 {
-  
   /**
-   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_VERIFY_SUCCESSOR
+   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_TEARDOWN
    */
   struct GNUNET_MessageHeader header;
-  
+
   /**
-   * Source peer which wants to verify its successor. 
+   * Source peer of the trail.
    */
   struct GNUNET_PeerIdentity source_peer;
-  
+
   /**
-   * Identity of our current successor.
+   * Destination peer of the trail.
    */
-  struct GNUNET_PeerIdentity successor;
-  
+  struct GNUNET_PeerIdentity destination_peer;
+
   /**
-   * Total number of peers in trail. 
+   * Unique identifier of the trail.
    */
-  unsigned int trail_length;
-  
+  struct GNUNET_HashCode TRAIL_ID;
+
   /**
-   * The current index in trail for next destination to send this message to. 
+   * Direction of trail.
    */
-  unsigned int current_index;
-  
+  enum GDS_ROUTING_trail_direction trail_direction;
 };
 
 
 /**
- *
+ * P2P Trail Rejection Message.
  */
-struct PeerVerifySuccessorResultMessage
+struct PeerTrailRejectionMessage
 {
-  
   /**
-   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_VERIFY_SUCCESSOR_RESULT
+   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_REJECTION
    */
   struct GNUNET_MessageHeader header;
-  
+
   /**
-   * Destination peer which send the request to verify its successor. 
+   * Source peer which wants to set up the trail.
    */
-  struct GNUNET_PeerIdentity destination_peer;
-  
+  struct GNUNET_PeerIdentity source_peer;
+
   /**
-   * Identity of successor to which PeerVerifySuccessorMessage was sent.
+   * Peer which sent trail rejection message.
    */
-  struct GNUNET_PeerIdentity source_successor;
-  
+  struct GNUNET_PeerIdentity congested_peer;
+
   /**
-   * source_successor's predecessor
+   * Peer identity which will be successor to this value will be finger of
+   * source_peer.
    */
-  struct GNUNET_PeerIdentity my_predecessor;
-  
+  uint64_t ultimate_destination_finger_identity_value;
+
   /**
-   * Total number of peers in trail. 
+   * Index in finger peer map of source peer.
    */
-  unsigned int trail_length;
-  
+  uint32_t finger_map_index;
+
   /**
-   * The current index in trail for next destination to send this message to. 
+   * Total number of peers in the trail.
    */
-  unsigned int current_index;
-  
-};
+  uint32_t trail_length;
 
-/**
- *
- */
-struct PeerNotifyNewSuccessorMessage
-{
-  
-};
+  /**
+   * Identifier for the trail 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.*/
+};
 
-/**FIXME: Here we can keep the whole list inside the message instead of attaching 
- * it all the time as the list remains constant all the time. 
- * P2P Trail setup Result message
+/**
+ * P2P Add Trail Message.
  */
-struct PeerTrailSetupResultMessage
+struct PeerAddTrailMessage
 {
-  
   /**
-   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_RESULT_SETUP
+   * Type: #GNUNET_MESSAGE_TYPE_DHT_P2P_ADD_TRAIL
    */
   struct GNUNET_MessageHeader header;
-  
+
   /**
-   * Finger to which we have found the path. 
+   * Source peer of the routing trail.
    */
-  struct GNUNET_PeerIdentity finger;
+  struct GNUNET_PeerIdentity source_peer;
 
   /**
-   * Peer which was looking for the trail to finger. 
+   * Destination peer of the routing trail.
    */
   struct GNUNET_PeerIdentity destination_peer;
 
   /**
-   * This field contains the peer to which this packet is forwarded.
-   */
-  struct GNUNET_PeerIdentity current_destination;
-  
-  /**
-   * FIXME: Temporary field used to remember at which index we should read
-   * to get our next peer. 
-   */
-  unsigned int current_index;
-  
-  /**
-   * If set to 1, then this trail is the trail to succcessor of our finger. 
+   * Total number of peers from source peer to destination peer.
    */
-  unsigned int successor_flag;
-  
-  /**
-   * If set to 1, then this trail is the trail to predecessor of our finger. 
-   */
-  unsigned int predecessor_flag;
-  
+  unsigned int trail_length;
+
   /**
-   * Number of entries in trail list.
-   * FIXME: Is this data type correct?
-   * FIXME: Is usage of GNUNET_PACKED correct?
+   * Unique identifier of the trail.
    */
-  uint32_t trail_length GNUNET_PACKED;
-  
+  struct GNUNET_HashCode trail_id;
+
+  /* Trail from source peer to destination peer. */
 };
 
 GNUNET_NETWORK_STRUCT_END
 
-
 /**
  * Linked list of messages to send to a particular other peer.
  */
@@ -495,15 +470,15 @@ struct P2PPendingMessage
   struct P2PPendingMessage *prev;
 
   /**
-   * When does this message time out?
-   */
-  struct GNUNET_TIME_Absolute timeout;
-
-   /**
    * 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];
@@ -514,135 +489,195 @@ struct P2PPendingMessage
 };
 
 
- /**
-  * Linked List of peers which are part of trail to reach a particular Finger.
-  */
-struct TrailPeerList
-{
-   /**
-   * Pointer to next item in the list
-   */
-   struct TrailPeerList *next;
-
-   /**
-   * Pointer to previous item in the list
-   */
-   struct TrailPeerList *prev;
-   
-   /**
-    * An element in this trail list
-    */
-   struct GNUNET_PeerIdentity peer;
-  
-};
-
-
-/** FIXME: 
- * 1.Previously I have added the field successor and predecessor of a friend.
- * But whats the use and is it even possible to have those values.
+/**
  *  Entry in friend_peermap.
  */
 struct FriendInfo
 {
   /**
-   * What is the identity of the peer?
+   * Friend Identity
    */
   struct GNUNET_PeerIdentity id;
 
   /**
-   * Count of outstanding messages for peer.
+   * Number of trails for which this friend is the first hop.
+   */
+  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;
+
   /**
-   * Head of pending messages to be sent to this peer.
+   * Tail of pending messages to be sent to this friend.
    */
struct P2PPendingMessage *head;
 struct P2PPendingMessage *tail;
 
- /**
-  * Tail of pending messages to be sent to this peer.
-  */
- struct P2PPendingMessage *tail;
- /**
-  * Core handle for sending messages to this peer.
-  */
- struct GNUNET_CORE_TransmitHandle *th;
+  /**
+   * Core handle for sending messages to this friend.
+   */
+  struct GNUNET_CORE_TransmitHandle *th;
 
 };
 
+/**
+ * An individual trail to reach to a finger.
+ */
+struct Trail // "node" "element" "relay"
+{
+  /**
+    * Pointer to next item in the list
+    */
+  struct Trail *next;
+
+  /**
+    * Pointer to prev item in the list
+    */
+  struct Trail *prev;
+
+  /**
+   * An element in this trail.
+   */
+  struct GNUNET_PeerIdentity peer;
+};
 
 /**
- * FIXME: We can also use an enum to say if its pred/suc/finger
- * FIXME: As in chord , where we store the actual finger identity we were looking
- * for and the real id which we got as successor. If we want to store like that 
- * then we will need to add a new field and search actual peer id. 
- * FIXME: Should we use another PeerIdentity which is smaller
- * than 256 bits while storing. 
- * Predcessor is needed in case of node join/fail. 
- * Entry in finger_peermap.
+ * List of all trails to reach a particular finger.
  */
-struct FingerInfo
+struct TrailList // "trail": list of "elements"
 {
   /**
-   * Finger identity.
+   * Head of trail.
    */
-  struct GNUNET_PeerIdentity finger_identity;
-  
+  struct Trail *trail_head;
+
   /**
-   * If 1, then this finger entry is first finger /successor of the peer.
+   * Tail of trail.
    */
-  unsigned int successor;
-  
+  struct Trail *trail_tail;
+
   /**
-   * If 1, then this finger entry is first predecessor of the peer.
+   * Unique identifier of this trail.
    */
-  unsigned int predecessor;
-  
+  struct GNUNET_HashCode trail_id;
+
   /**
-   * Total number of entries in trail. 
+   * Length of trail pointed
    */
   unsigned int trail_length;
-  
+
   /**
-   * List of peers in the trail to reach this finger.
+   * Number of trails that the first friend of this trail is a part of.
    */
-  struct GNUNET_PeerIdentity *trail_peer_list;
-  
+  unsigned int first_friend_trail_count; // remove this, duplicate variable!
+                                         // include a pointer to Friend or function that calculates it
 };
 
-
 /**
- * Task that sends FIND FINGER TRAIL requests.
+ * An entry in finger_hashmap.
  */
-static GNUNET_SCHEDULER_TaskIdentifier find_finger_trail_task;
+struct FingerInfo
+{
+  /**
+   * Finger identity.
+   */
+  struct GNUNET_PeerIdentity finger_identity;
 
-/**
- * 
- * Task that periodically checks for the immediate successor. 
- */
-static GNUNET_SCHEDULER_TaskIdentifier verify_successor;
+  /**
+   * Index in finger peer map
+   */
+  uint32_t finger_map_index;
 
-/**
* Identity of this peer.
- */
-static struct GNUNET_PeerIdentity my_identity;
+  /**
  * Number of trails setup so far for this finger.
  */
+  uint32_t trails_count;
 
-/**
- * Hash map of all the friends of a peer
- */
-static struct GNUNET_CONTAINER_MultiPeerMap *friend_peermap;
+  /**
+   * Array of trails.
+   */
+  struct TrailList trail_list[MAXIMUM_TRAILS_PER_FINGER]; // OK!
+};
 
 /**
- * Hash map of all the fingers of a peer
+ * Data structure to keep track of closest peer seen so far in find_successor()
  */
-static struct GNUNET_CONTAINER_MultiPeerMap *finger_peermap;
+struct Closest_Peer
+{
+  /**
+   * 64 bit value of the peer
+   */
+  uint64_t value;
+
+  /**
+   * Trail id to reach to peer.
+   */
+  struct GNUNET_HashCode trail_id;
+
+  /**
+   * First hop, NULL in case of friend and my_identity
+   */
+  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 next_destination;
+};
+
+/**
+ * Data structure to store the trail chosen to reach to finger.
+ */
+struct Correct_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 sends FIND FINGER TRAIL requests. This task is started when we have
+ * get our first friend.
+ */
+static GNUNET_SCHEDULER_TaskIdentifier find_finger_trail_task;
+
+/**
+ * Identity of this peer.
+ */
+static struct GNUNET_PeerIdentity my_identity;
+
+/**
+ * Peer map of all the friends of a peer
+ */
+static struct GNUNET_CONTAINER_MultiPeerMap *friend_peermap;
 
 /**
- * TODO: Ask whats the use of ATS.
- * Handle to ATS.
+ * Hash map of all the fingers of a peer
  */
-static struct GNUNET_ATS_PerformanceHandle *atsAPI;
+static struct GNUNET_CONTAINER_MultiHashMap32 *finger_hashmap;
 
 /**
  * Handle to CORE.
@@ -650,17 +685,19 @@ static struct GNUNET_ATS_PerformanceHandle *atsAPI;
 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 peer 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;
 
 
 /**
  * Called when core is ready to send a message we asked for
  * out to the destination.
  *
- * @param cls the 'struct PeerInfo' of the target peer
+ * @param cls the 'struct FriendInfo' of the target friend
  * @param size number of bytes available in buf
  * @param buf where the callee should write the message
  * @return number of bytes written to buf
@@ -673,13 +710,13 @@ 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)
@@ -723,11 +760,13 @@ core_transmit_notify (void *cls, size_t size, void *buf)
                                            &core_transmit_notify, peer);
     GNUNET_break (NULL != peer->th);
   }
+
   return off;
 }
 
 
 /**
+ * FIXME: assertion fails at the end of this function. also in core_api.c at 1299.
  * Transmit all messages in the friend's message queue.
  *
  * @param peer message queue to process
@@ -736,18 +775,17 @@ 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,
@@ -760,1399 +798,2894 @@ process_friend_queue (struct FriendInfo *peer)
 
 
 /**
- * SUPU:
- * We add the next destination i.e. friend to which we are sending the packet
- * to our peer list in the calling function and we also increment trail_length
- * in calling function i.e. send_find_finger_trail and handle_dht_p2p_trail_setup.
- * Here we only copy the whole trail into our peer_list. 
- * Setup the 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 Peer to which we want to set up the trail to.
- * @param current_destination Current peer 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 successor_flag If 1 then we are looking for trail to our successor. 
+ * Construct a trail setup message and forward it to target_friend
+ * @param source_peer Source peer which wants to setup the trail
+ * @param ultimate_destination_finger Peer identity closest to this value will
+ *                                    be finger to @a source_peer
+ * @param next_destination Peer which should get the packet. I can be same as
+ *                         target_friend or different.
+ * @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 finger_map_index Index in finger map for which we are looking for finger.
+ * @param trail_id Unique identifier for the trail we are trying to setup.
+ * @param intermediate_trail_id Trail id of any intermediate trail we may have to
+ *                              traverse during trail setup. If not used then set to
+ *                              0.
  */
 void
-GDS_NEIGHBOURS_handle_trail_setup(struct GNUNET_PeerIdentity *source_peer,
-                                  uint64_t *destination_finger,
-                                  struct FriendInfo *current_destination,
-                                  unsigned int trail_length,
-                                  struct GNUNET_PeerIdentity *trail_peer_list,
-                                  unsigned int successor_flag,
-                                  unsigned int predecessor_flag)
+GDS_NEIGHBOURS_send_trail_setup (const struct GNUNET_PeerIdentity source_peer,
+                                 uint64_t ultimate_destination_finger,
+                                 struct GNUNET_PeerIdentity next_destination,
+                                 struct FriendInfo *target_friend,
+                                 unsigned int trail_length,
+                                 const struct GNUNET_PeerIdentity *trail_peer_list,
+                                 unsigned int finger_map_index,
+                                 struct GNUNET_HashCode new_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 (current_destination->pending_count >= MAXIMUM_PENDING_PER_FRIEND)
-  {  
+
+  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->id), 
-          sizeof (struct GNUNET_PeerIdentity));
-  tsm->current_destination_type = htonl(FRIEND); 
-  tsm->trail_length = htonl(trail_length); 
-  if(successor_flag == 1)
-    tsm->successor_flag = 1;
-  if(predecessor_flag == 1)
-    tsm->predecessor_flag = 1;
-  
-  peer_list = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity) * trail_length); 
-  peer_list = (struct GNUNET_PeerIdentity *) &tsm[1];
-  memcpy (peer_list, trail_peer_list, trail_length * sizeof(struct GNUNET_PeerIdentity));
-  
-  GNUNET_CONTAINER_DLL_insert_tail (current_destination->head, current_destination->tail, pending);
-  current_destination->pending_count++;
-  process_friend_queue (current_destination);
-  
+  tsm->ultimate_destination_finger = GNUNET_htonll (ultimate_destination_finger);
+  tsm->source_peer = source_peer;
+  tsm->next_destination = next_destination;
+  tsm->trail_length = htonl (trail_length);
+  tsm->finger_map_index = htonl (finger_map_index);
+  tsm->new_trail_id = new_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));
+  }
+
+  GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
+  target_friend->pending_count++;
+  process_friend_queue (target_friend);
 }
 
-/**FIXME: As we are having a fixed list of trail peer list we can just 
- * store inside the message instead of attaching it all the time. 
- * Handle a tail setup result message. 
+
+/**
+ * Construct a trail setup result message and forward it to target 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.
- * @param current_destination Current peer to which this message should be forwarded.
+ * @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 this request has traversed so far 
- * @param current_trail_index Index in trail_peer_list. 
+ * @param trail_peer_list Peers which are part of the trail from source to destination.
+ * @param finger_map_index Index in finger peer map
+ * @param trail_id Unique identifier of the trail.
  */
 void
-GDS_NEIGHBOURS_handle_trail_setup_result (struct GNUNET_PeerIdentity *destination_peer,
-                                          struct GNUNET_PeerIdentity *source_finger,
-                                          struct FriendInfo *current_destination,
-                                          unsigned int trail_length,
-                                          const struct GNUNET_PeerIdentity *trail_peer_list,
-                                          unsigned int current_trail_index,
-                                          unsigned int successor_flag,
-                                          unsigned int predecessor_flag)
+GDS_NEIGHBOURS_send_trail_setup_result (struct GNUNET_PeerIdentity destination_peer,
+                                        struct GNUNET_PeerIdentity source_finger,
+                                        struct FriendInfo *target_friend,
+                                        unsigned int trail_length,
+                                        const struct GNUNET_PeerIdentity *trail_peer_list,
+                                        unsigned int finger_map_index,
+                                        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 (current_destination->pending_count >= MAXIMUM_PENDING_PER_FRIEND)
-  {  
+
+  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);
-  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->current_destination), &(current_destination->id), sizeof(struct GNUNET_PeerIdentity));
-  memcpy (&(tsrm->destination_peer), destination_peer, sizeof(struct GNUNET_PeerIdentity));
-  memcpy (&(tsrm->finger), source_finger, sizeof(struct GNUNET_PeerIdentity));
+  tsrm->destination_peer = destination_peer;
+  tsrm->finger_identity = source_finger;
   tsrm->trail_length = htonl (trail_length);
-  tsrm->current_index = htonl (current_trail_index);
-  tsrm->successor_flag = htonl (successor_flag);
-  tsrm->predecessor_flag = htonl (predecessor_flag);
+  tsrm->finger_map_index = htonl (finger_map_index);
+  tsrm->trail_id = trail_id;
+
   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++;
+  process_friend_queue (target_friend);
+}
+
+
+/**
+ * Send trail rejection message to next_hop
+ * @param source_peer Source peer which is trying to setup the trail.
+ * @param finger_identity 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 next_hop Peer to which we are forwarding this message.
+ * @param finger_map_index Index in finger peermap for which we are searching for finger.
+ * @param trail_peer_list Trails seen so far in trail setup before getting rejected
+ *                        by congested_peer
+ * @param trail_length Total number of peers in trail_peer_list
+ * @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 finger_identity,
+                                     struct GNUNET_PeerIdentity congested_peer,
+                                     unsigned int finger_map_index,
+                                     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 PeerTrailRejectionMessage *trm;
+  struct P2PPendingMessage *pending;
+  struct GNUNET_PeerIdentity *peer_list;
+  size_t msize;
+
+  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;
+  pending->timeout = GNUNET_TIME_relative_to_absolute (GET_TIMEOUT);
+  trm = (struct PeerTrailRejectionMessage *)&pending[1];
+  pending->msg = &trm->header;
+  trm->header.size = htons (msize);
+  trm->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_REJECTION);
+  trm->source_peer = source_peer;
+  trm->congested_peer = congested_peer;
+  trm->congestion_time = congestion_timeout;
+  trm->finger_map_index = htonl (finger_map_index);
+  trm->trail_id = trail_id;
+
+  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 (current_destination->head, current_destination->tail, pending);
-  current_destination->pending_count++;
-  process_friend_queue (current_destination);
+  GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
+  target_friend->pending_count++;
+  process_friend_queue (target_friend);
 }
 
 
-/**FIXME: Calling function should provide the current destination
- * and also should compute the new current_trail_index. Also you should add
- * yourself to the list of peers and increment the length correctly. its 
- * responsibility of send_verify_successor_message and handle_verify_succesor_message. 
- * This function is called from send_verify_successor_message funciton
- * and handle_dht_p2p_verify_successor. 
- * Construct a PeerVerifySuccessor message and send it to friend.
+/**
+ * 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 Identifier of trail to reach successor.
+ * @param trail Trail to reach from source_peer to successor
+ * @param trail_length Total number of peers in @a trail.
+ * @param target_friend Message send to this friend.
  */
-void GDS_NEIGUBOURS_handle_verify_successor(struct GNUNET_PeerIdentity *source_peer,
-                                            struct GNUNET_PeerIdentity *successor,
-                                            struct FriendInfo *current_destination,
-                                            struct GNUNET_PeerIdentity *trail_peer_list,
-                                            unsigned int trail_length,
-                                            unsigned int current_trail_index)
+void
+GDS_NEIGHBOURS_send_verify_successor_message (struct GNUNET_PeerIdentity source_peer,
+                                              struct GNUNET_PeerIdentity successor,
+                                              const struct GNUNET_HashCode trail_id,
+                                              struct GNUNET_PeerIdentity *trail,
+                                              unsigned int trail_length,
+                                              struct FriendInfo *target_friend)
 {
   struct PeerVerifySuccessorMessage *vsm;
   struct P2PPendingMessage *pending;
   struct GNUNET_PeerIdentity *peer_list;
   size_t msize;
-  
-  msize = sizeof (struct PeerVerifySuccessorMessage) + 
-          (trail_length * sizeof(struct GNUNET_PeerIdentity));
-  
+
+  msize = sizeof (struct PeerVerifySuccessorMessage);
   if (msize >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
   {
     GNUNET_break (0);
     return;
   }
-  
-  if (current_destination->pending_count >= MAXIMUM_PENDING_PER_FRIEND)
-  {  
+
+  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);
   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->source_peer = source_peer;
+  vsm->successor = successor;
+  vsm->trail_id = trail_id;
   vsm->trail_length = htonl (trail_length);
-  vsm->current_index = htonl (current_trail_index);
-  
-  peer_list = (struct GNUNET_PeerIdentity *) &vsm[1];
-  memcpy (peer_list, trail_peer_list, trail_length * sizeof (struct GNUNET_PeerIdentity));
-  
+
+  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 (current_destination->head, current_destination->tail, pending);
-  current_destination->pending_count++;
-  process_friend_queue (current_destination);
-  
+  GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
+  target_friend->pending_count++;
+  process_friend_queue (target_friend);
+}
+
+
+/**
+ * Construct a trail teardown 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.
+ * @param trail_direction Direction of trail.
+ * @param target_friend Friend to get this message.
+ */
+void
+GDS_NEIGHBOURS_send_trail_teardown (struct GNUNET_PeerIdentity source_peer,
+                                    struct GNUNET_PeerIdentity destination_peer,
+                                    struct GNUNET_HashCode trail_id,
+                                    enum GDS_ROUTING_trail_direction trail_direction,
+                                    struct FriendInfo *target_friend)
+{
+  struct PeerTrailTearDownMessage *ttdm;
+  struct P2PPendingMessage *pending;
+  size_t msize;
+
+  msize = sizeof (struct PeerTrailTearDownMessage);
+
+  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);
+  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->source_peer = source_peer;
+  ttdm->destination_peer = destination_peer;
+  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);
 }
 
 
-/**FIXME: 
- * 1. In this function we don't want the trail. so instead of maintaing the trail 
- * length and current_trail_index, we can just remove all the elements form trail list
- * and current_destination = last element of trail list. 
- * 1. Responsiblity of calling function to provide new current destination.
- * and correct current_trail_index. 
- * this function will be called by destination successor. and each peer 
- * which is in the trail to reach to the peer. as successor changed destination
- * peer may have replaced the entry in its finger table. so you have to use the
- * trial provided by source peer and so you should have source id in peerverifysuccessor 
- * Construct a PeerVerifySuccessorResult message and send it to friend.
- */
-void GDS_NEIGHBOURS_handle_verify_successor_result(struct GNUNET_PeerIdentity *destination_peer,
-                                                   struct GNUNET_PeerIdentity *source_successor,
-                                                   struct GNUNET_PeerIdentity *my_predecessor,
-                                                   struct FriendInfo *current_destination,
-                                                   struct GNUNET_PeerIdentity *trail_peer_list,
-                                                   unsigned int trail_length,
-                                                   unsigned int current_trail_index)
-{
-  /* In this funciton, you receive 
-   1. successor
-   2. trial to reach that successor
-   3. trail_length.
-   4. current trail index --> this gives the next_hop on whose pending queue you should
-   add the message. */
+/**
+ * Construct a verify successor message and send it to target_friend
+ * @param destination_peer
+ * @param source_successor
+ * @param succ_predecessor
+ * @param trail_id
+ * @param trail
+ * @param trail_length
+ * @param target_friend
+ */
+void
+GDS_NEIGHBOURS_send_verify_successor_result (struct GNUNET_PeerIdentity destination_peer,
+                                             struct GNUNET_PeerIdentity source_successor,
+                                             struct GNUNET_PeerIdentity succ_predecessor,
+                                             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) + 
+
+  msize = sizeof (struct PeerVerifySuccessorResultMessage) +
           (trail_length * sizeof(struct GNUNET_PeerIdentity));
-  
+
   if (msize >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
   {
     GNUNET_break (0);
     return;
   }
-  
-  if (current_destination->pending_count >= MAXIMUM_PENDING_PER_FRIEND)
-  {  
+
+  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));
-  
+  vsmr->destination_peer = destination_peer;
+  vsmr->my_predecessor = succ_predecessor;
+  vsmr->source_successor = source_successor;
+  vsmr->trail_direction = htonl (trail_direction);
+
+  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 (current_destination->head, current_destination->tail, pending);
-  current_destination->pending_count++;
-  process_friend_queue (current_destination);
+  GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
+  target_friend->pending_count++;
+  process_friend_queue (target_friend);
 }
 
 
 /**
- * Construct a PeerNotifyNewSuccessor message and send it to friend.
+ * Construct a notify new successor message and send it to target_friend
+ * @param source_peer
+ * @param new_successor
+ * @param new_successor_trail
+ * @param new_successor_trail_length
+ * @param new_succesor_trail_id
  */
-void GDS_NEIGHBOURS_handle_notify_new_successor()
+void
+GDS_NEIGHBOURS_send_notify_new_successor (struct GNUNET_PeerIdentity source_peer,
+                                          struct GNUNET_PeerIdentity new_successor,
+                                          struct GNUNET_PeerIdentity *new_successor_trail,
+                                          unsigned int new_successor_trail_length,
+                                          struct GNUNET_HashCode new_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) +
+          (new_successor_trail_length * sizeof(struct GNUNET_PeerIdentity));
 
-/**FIXME: Old implementation just to remove error
- * TODO: Modify this function to handle our get request. 
- * Perform a GET operation.  Forwards the given request to other
- * peers.  Does not lookup the key locally.  May do nothing if this is
- * the only peer in the network (or if we are the closest peer in the
- * network).
- *
- * @param 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 key key for the content
- * @param xquery extended query
- * @param xquery_size number of bytes in @a xquery
- * @param reply_bf bloomfilter to filter duplicates
- * @param reply_bf_mutator mutator for @a reply_bf
- * @param peer_bf filter for peers not to select (again)
- */
-void
-GDS_NEIGHBOURS_handle_get (enum GNUNET_BLOCK_Type type,
-                           enum GNUNET_DHT_RouteOption options,
-                           uint32_t desired_replication_level,
-                           uint32_t hop_count, const struct GNUNET_HashCode * key,
-                           const void *xquery, size_t xquery_size,
-                           const struct GNUNET_CONTAINER_BloomFilter *reply_bf,
-                           uint32_t reply_bf_mutator,
-                           struct GNUNET_CONTAINER_BloomFilter *peer_bf)
-{
-
-  /*
-   1. take the key, get the 64 bit value of the key.
-   2. call find_successor to get the successor of the key.
-   3. successor can be either a friend or finger.
-   4. update the field in get message to reflect if its a friend or finger table
-   5. add the put message to pending message and send it. 
-   */
-}
+  if (msize >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
+  {
+    GNUNET_break (0);
+    return;
+  }
 
-/**FIXME: Old implementation just to remove error.
- * TODO: Modify this function to handle our put request. 
- * Perform a PUT operation.   Forwards the given request to other
- * peers.   Does not store the data locally.  Does not give the
- * data to local clients.  May do nothing if this is the only
- * peer in the network (or if we are the closest peer in the
- * network).
- *
- * @param type type of the block
- * @param options routing options
- * @param desired_replication_level desired replication count
- * @param expiration_time when does the content expire
- * @param hop_count how many hops has this message traversed so far
- * @param bf Bloom filter of peers this PUT has already traversed
- * @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
- */
-void
-GDS_NEIGHBOURS_handle_put (enum GNUNET_BLOCK_Type type,
-                           enum GNUNET_DHT_RouteOption options,
-                           uint32_t desired_replication_level,
-                           struct GNUNET_TIME_Absolute expiration_time,
-                           uint32_t hop_count,
-                           struct GNUNET_CONTAINER_BloomFilter *bf,
-                           const struct GNUNET_HashCode *key,
-                           unsigned int put_path_length,
-                           struct GNUNET_PeerIdentity *put_path,
-                           const void *data, size_t data_size)
-{
-
-   /*
-   1. take the key, get the 64 bit value of the key.
-   2. call find_successor to get the successor of the key.
-   3. successor can be either a friend or finger.
-   4. update the field in put message to reflect if its a friend or finger table
-   5. add the put message to pending message and send it. 
-   */
+  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);
+  nsm->source_peer = source_peer;
+  nsm->destination_peer = new_successor;
+  nsm->trail_length = htonl (new_successor_trail_length);
+  nsm->trail_id = new_succesor_trail_id;
+  if (new_successor_trail_length > 0)
+  {
+    peer_list = (struct GNUNET_PeerIdentity *) &nsm[1];
+    memcpy (peer_list, new_successor_trail,
+            new_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++;
+  process_friend_queue (target_friend);
 }
 
 
 /**
- * FIXME: Check if this function actually iterates or not. 
- * 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 identifer of the trail
+ * @param trail Trail from @a source_peer to @a destination_peer
+ * @param trail_length Total number of peers in @a trail.
+ * @param target_friend Next peer to get this message.
  */
-static struct FriendInfo *
-select_random_friend()
-{  
-  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);
-  
-  /* Element stored at this index in friend_peermap should be selected friend. */
-  index = GNUNET_CRYPTO_random_permute (GNUNET_CRYPTO_QUALITY_WEAK, current_size);
-  
-  /* Create an iterator for friend_peermap. */
-  iter = GNUNET_CONTAINER_multipeermap_iterator_create (friend_peermap);
-  
-  /* Set the position of iterator to index. */
-  while(j < (*index))
+void
+GDS_NEIGHBOURS_send_add_trail (struct GNUNET_PeerIdentity source_peer,
+                               struct GNUNET_PeerIdentity destination_peer,
+                               struct GNUNET_HashCode trail_id,
+                               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))
-    {
-      /* FIXME: I don't think we are actually incrementing iter. iter is always
-       pointing to the same element. */
-      j++;
-    }
-    else 
-      return NULL;
-  }  
-  
-  if(GNUNET_YES == GNUNET_CONTAINER_multipeermap_iterator_next (iter,&key_ret,(const void **)&friend))
+    GNUNET_break (0);
+    return;
+  }
+
+  if (target_friend->pending_count >= MAXIMUM_PENDING_PER_FRIEND)
   {
-    return friend;
+    GNUNET_STATISTICS_update (GDS_stats, gettext_noop ("# P2P messages dropped due to full queue"),
+                               1, GNUNET_NO);
   }
 
-  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_length = htonl (trail_length);
+  adm->trail_id = trail_id;
+
+  if (trail_length > 0)
+  {
+    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
- * FIXME: If we maintain a index that is value of current_finger_index
- * to which a particular entry in finger map corresponds then should we first
- * check if there is already an entry for that index. If yes then don't
- * search for trail to that finger. 
- * @return finger_identity 
- */
-static uint64_t *
-compute_finger_identity()
-{
-  uint64_t *my_id64 ;
-  uint64_t *finger_identity64;
-  
-  my_id64 = GNUNET_malloc (sizeof (uint64_t));
-  finger_identity64 = GNUNET_malloc (sizeof (uint64_t));
-  
-  memcpy (my_id64, &(my_identity.public_key.q_y), sizeof (uint64_t));
-  *finger_identity64 = fmod ((*my_id64 + pow (2,current_finger_index)),( (pow (2,MAX_FINGERS))));
-  
-  return finger_identity64;
 }
 
 
 /**
- * Find immediate predecessor in the network.
- * @param me my own identity
- * @return peer identity of immediate predecessor.
+ * Merge into "teardown", add source and "last/new_first" in message struct.
+ * Construct a trail compression message and send it to target_friend.
+ * @param source_peer Source of the trail.
+ * @param destination_finger Destination of 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 *
-find_predecessor()
+void
+GDS_NEIGHBOURS_send_trail_compression (struct GNUNET_PeerIdentity source_peer,
+                                       struct GNUNET_PeerIdentity destination_peer,
+                                       struct GNUNET_HashCode trail_id,
+                                       struct GNUNET_PeerIdentity first_friend,
+                                       struct FriendInfo *target_friend)
 {
-  uint64_t *my_id ;
-  uint64_t *predecessor;
-  
-  my_id = GNUNET_malloc (sizeof (uint64_t));
-  predecessor = GNUNET_malloc (sizeof (uint64_t));
-  
-  memcpy (my_id, &(my_identity.public_key.q_y), sizeof (uint64_t));
-  *predecessor = fmod ((*my_id -1), (pow (2,MAX_FINGERS)));
-          
-  return predecessor;
-}
+  struct P2PPendingMessage *pending;
+  struct PeerTrailCompressionMessage *tcm;
+  size_t msize;
 
+  msize = sizeof (struct PeerTrailCompressionMessage);
 
-/**
- * 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
+  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;
+  tcm->destination_peer = destination_peer;
+
+  GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
+  target_friend->pending_count++;
+  process_friend_queue (target_friend);
+
+}
+
+
+/**
+ * Seach my location in trail.
+ * @param trail List of peers
+ * @return my_index if found
+ *         -1 if no entry found.
  */
-static void
-send_verify_successor_message(void *cls,
-          const struct GNUNET_SCHEDULER_TaskContext *tc )
+static int
+search_my_index (const struct GNUNET_PeerIdentity *trail,
+                 int trail_length)
 {
-  struct GNUNET_TIME_Relative next_send_time;
-  struct GNUNET_CONTAINER_MultiPeerMapIterator *finger_iter;
-  struct GNUNET_PeerIdentity key_ret;
-  struct FriendInfo *current_destination;
-  struct GNUNET_PeerIdentity *finger_trail;
-  unsigned int finger_trail_length;
-  unsigned int finger_trail_current_index;
-  struct FingerInfo *finger;
-  unsigned int finger_index;
-  
-  /* Iterate over your finger peermap to find the element with successor field set.
-     That field is your successor. */
-  /* FIXME: Again if the iteration is correct or not? */
-  finger_iter = GNUNET_CONTAINER_multipeermap_iterator_create (finger_peermap);  
-  for (finger_index = 0; finger_index < GNUNET_CONTAINER_multipeermap_size (finger_peermap); finger_index++)
-  {
-    /* FIXME: I don't think we are actually iterating.
-     Read about how to iterate over the multi peer map. */
-    if(GNUNET_YES == GNUNET_CONTAINER_multipeermap_iterator_next(finger_iter,&key_ret,(const void **)&finger)) 
-    {
-      if(1 == finger->successor)
-        break; /* FIXME: Do I come out of inner if or outer for */
-    }
+  int i;
+
+  for (i = 0; i < trail_length; i++)
+  {
+    if (0 == GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &trail[i]))
+      return i;
   }
-  
-  /* FIXME: Is this copy correct? */
-  finger_trail = GNUNET_malloc ((finger->trail_length * 
-                                 sizeof (struct GNUNET_PeerIdentity)));
-  current_destination = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-  
-  /* FIXME: Should we add ourself to peer list . When we get the result back
-   then we should have to be in the list so that message reaches to us. */
-  memcpy (finger_trail, finger->trail_peer_list, 
-         (finger->trail_length * sizeof (struct GNUNET_PeerIdentity)));
-  finger_trail_length = finger->trail_length; 
-  finger_trail_current_index = 1;
-  memcpy (current_destination, &finger_trail[1], 
-          sizeof (struct GNUNET_PeerIdentity));
-  
-  /* FIXME: current_destination should be friend not gnunet_peeridentity.
-   Search over your friend_peermap to find the friend corresponding to
-   current_destination. */
-  GDS_NEIGUBOURS_handle_verify_successor (&my_identity,
-                                         &(finger->finger_identity),
-                                         current_destination,
-                                         finger_trail,
-                                         finger_trail_length,
-                                         finger_trail_current_index);
-  
-  
-  /* FIXME: Use a random value so that this message is send not at the same
-   interval as send_find_finger_trail_message. */
-  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 + 1));
-  verify_successor =
-      GNUNET_SCHEDULER_add_delayed (next_send_time, &send_verify_successor_message,
-                                    NULL);
+
+  return -1;
 }
 
 
 /**
- * Task to send a find finger trail message. We attempt to find trail
- * to our finger and successor in the network.
- *
- * @param cls closure for this task
- * @param tc the context under which the task is running
+ * Iterate over the list of all the trails to reach Finger. In case the first
+ * friend to reach the finger has crossed the 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.
+ * @param finger Finger
+ * @return struct Correct_Trail which contains the first friend , trail id
+ * and trail length. NULL in case none of the trails are free.
  */
-static void
-send_find_finger_trail_message (void *cls,
-                        const struct GNUNET_SCHEDULER_TaskContext *tc)
+static struct Correct_Trail *
+select_trail_to_finger (struct FingerInfo *finger)
 {
   struct FriendInfo *friend;
-  struct GNUNET_TIME_Relative next_send_time;
-  struct GNUNET_PeerIdentity *peer_list;
-  unsigned int successor_flag;
-  unsigned int predecessor_flag;
-  uint64_t *finger_identity;
-  
-  if (1 == current_finger_index)
-  {
-    /* We have started the process to find the successor. We should search 
-     for our predecessor. */
-    finger_identity = find_predecessor();  
-    
-    /* FIXME: There is no case in find_predecessor which returns NULL. It can
-     return NULL, only if we already have found a trial to predecessor. is it
-     required or not need to check.*/
-    if(NULL == finger_identity)
+  struct TrailList *iterator;
+  struct Correct_Trail *finger_trail;
+  int i;
+
+  if (0 == GNUNET_CRYPTO_cmp_peer_identity (&finger->finger_identity,
+                                            &my_identity))
+    return NULL;
+
+  finger_trail = GNUNET_new (struct Correct_Trail);
+
+  for (i = 0; i < finger->trails_count; i++)
+  {
+    iterator = &finger->trail_list[i];
+    if (iterator->trail_length > 0)
     {
-      /* We already have a trail to reach to immediate predecessor. */
-      goto new_find_finger_trail_request;
+      friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                                  &iterator->trail_head->peer);
     }
-    predecessor_flag = 1; 
-    goto choose_friend;
-  }
-  else
-  {
-    finger_identity = compute_finger_identity();
-    
-    if(finger_identity == NULL)
+    else
     {
-      goto new_find_finger_trail_request;
+      friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                                  &finger->finger_identity);
+    }
+
+    if ((friend->trails_count < TRAILS_THROUGH_FRIEND_THRESHOLD)||
+      ((0 == GNUNET_TIME_absolute_get_remaining (friend->congestion_timestamp).rel_value_us)))
+    {
+      if (iterator->trail_length == 0)
+      {
+        finger_trail->friend = *friend;
+        //finger_trail->trail_id = 0;
+        finger_trail->trail_length = 0;
+        return finger_trail;
+      }
+
+      if (finger_trail->trail_length > iterator->trail_length)
+      {
+        finger_trail->friend = *friend;
+        finger_trail->trail_id = iterator->trail_id;
+        finger_trail->trail_length = iterator->trail_length;
+      }
     }
   }
-  
-  if(0 == current_finger_index)
-  {
-    /* We are searching for our successor in the network. */
-    successor_flag = 1;
-  }
-  
-  choose_friend:
-  current_finger_index = current_finger_index + 1;
-  friend = GNUNET_malloc (sizeof (struct FriendInfo));
-  friend = select_random_friend();
-  /* We found a friend.*/
-  if(NULL != friend)
-  { 
-    /*SUPU: Here you are adding yourself to peer list so that trail result
-     reaches back to you. */
-    unsigned int trail_length = 2;
-    peer_list = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity) * trail_length);
-    memcpy (&peer_list[0], &(my_identity), sizeof (struct GNUNET_PeerIdentity)); 
-    memcpy (&peer_list[1], &(friend->id), sizeof (struct GNUNET_PeerIdentity)); 
-    
-    GDS_NEIGHBOURS_handle_trail_setup (&my_identity, finger_identity, 
-                                      friend, trail_length, peer_list,
-                                      successor_flag, predecessor_flag);
-  }
-  
-  /* FIXME: Should we be using current_finger_index to generate random interval.*/
-  new_find_finger_trail_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 + 1));
-  find_finger_trail_task =
-      GNUNET_SCHEDULER_add_delayed (next_send_time, &send_find_finger_trail_message,
-                                    NULL);
+
+  return finger_trail;
 }
 
 
 /**
- * Method called whenever a peer connects.
- *
- * @param cls closure
- * @param peer peer identity this notification is about
+ * Select closest finger 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)
+static struct GNUNET_PeerIdentity *
+select_closest_finger (struct GNUNET_PeerIdentity *peer1,
+                       struct GNUNET_PeerIdentity *peer2,
+                       uint64_t value)
 {
-  struct FriendInfo *ret;
-  
-  /* Check for connect to self message */
-  if (0 == memcmp (&my_identity, peer, sizeof (struct GNUNET_PeerIdentity)))
-    return;
-  
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-             "Connected to %s\n",
-              GNUNET_i2s (peer));
-  
-  /* If peer already exists in our friend_peermap, then exit. */
-  if (GNUNET_YES ==
-      GNUNET_CONTAINER_multipeermap_contains (friend_peermap,
-                                              peer))
-  {
-    GNUNET_break (0);
-    return;
-  }
+#if 0
+  uint64_t peer1_value;
+  uint64_t peer2_value;
+
+  memcpy (&peer1_value, peer1, sizeof (uint64_t));
+  memcpy (&peer2_value, peer2, sizeof (uint64_t));
+
+  if ((peer1_value <= value) && (value <= peer2_value))
+    return peer2;
+  else if ((peer2_value <= value) && (value <= peer1_value))
+    return peer1;
+  else if ((peer1_value <= peer2_value) && (peer2_value <= value))
+    return peer1;
+  else if ((peer2_value <= peer1_value) && (peer1_value <= value))
+    return peer2;
+  else if ((value <= peer1_value) && (peer1_value <= peer2_value))
+    return peer1;
+  else /*if ((value <= peer2_value) && (peer2_value <= peer1_value))*/
+    return peer2;
+#endif
+  return NULL;
+}
 
-  GNUNET_STATISTICS_update (GDS_stats, gettext_noop ("# peers connected"), 1,
-                            GNUNET_NO);
 
-  
-  ret = GNUNET_new (struct FriendInfo);
-  ret->id = *peer;
-  
-  GNUNET_assert (GNUNET_OK ==
-                 GNUNET_CONTAINER_multipeermap_put (friend_peermap,
-                                                    peer, ret,
-                                                    GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
+/**
+ * Select closest predecessor to value.
+ * @param peer1 First peer
+ * @param peer2 Second peer
+ * @param value Value to be compare
+ * @return Closest peer
+ */
+static struct GNUNET_PeerIdentity *
+select_closest_predecessor (struct GNUNET_PeerIdentity *peer1,
+                            struct GNUNET_PeerIdentity *peer2,
+                            uint64_t value)
+{
+  #if 0
+  uint64_t peer1_value;
+  uint64_t peer2_value;
 
-  
-  /* 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);
+  memcpy (&peer1_value, peer1, sizeof (uint64_t));
+  memcpy (&peer2_value, peer2, sizeof (uint64_t));
+
+#endif
+  return NULL;
 }
 
 
 /**
- * FIXME: Implement after testing finger/friend table setup.
- * Method called whenever a peer disconnects.
- *
- * @param cls closure
- * @param peer peer identity this notification is about
+ * Select the closest peer among two peers (which should not be same)
+ * with respect to value and finger_map_index
+ * @param peer1 First peer
+ * @param peer2 Second peer
+ * @param value Value relative to which we find the closest
+ * @param finger_map_index Index in finger map. If equal to PREDECESSOR_FINGER_ID,
+ *                         then we use different logic than other
+ *                         finger_map_index
+ * @return Closest peer among two peers.
  */
-static void
-handle_core_disconnect (void *cls,
-                       const struct GNUNET_PeerIdentity *peer)
+static struct GNUNET_PeerIdentity *
+select_closest_peer (struct GNUNET_PeerIdentity *peer1,
+                     struct GNUNET_PeerIdentity *peer2,
+                     uint64_t value,
+                     unsigned int finger_map_index)
 {
-  /**
-   * 1. remove the friend from the friend map.
-   * 2. remove the trail for the fingers for which this peer was the first hop.
-   * 3. start send_find_finger_trail for these fingers to find a new trail 
-   * in the network.
-   * 4. Also when a node gets disconnected, how should we update pointers of its
-   * immediate successor and predecessor in the network ?
-   * 5. Also how do we distribute the keys in the network?
-   * 6. Here is case where we started put operation but a peer got disconnected and 
-      we removed the entry from the table. How to handle such a case. 
-   */
+  struct GNUNET_PeerIdentity *closest_peer;
+
+  if (PREDECESSOR_FINGER_ID == finger_map_index)
+    closest_peer = select_closest_predecessor (peer1, peer2, value);
+  else
+    closest_peer = select_closest_finger (peer1, peer2, value);
+
+  return closest_peer;
 }
 
 
 /**
- * To be called on core init/fail.
- *
- * @param cls service closure
- * @param identity the public identity of this peer
+ * 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 next_destination [out] 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 we finger is the @a next_destination,
+ *                                then we updated the field with trail id to reach
+ *                                to that finger.
+ * @param finger_map_index Index in finger peermap for which we are
+ *                         looking for a finger, to discern between
+ *                         IS_PREDECESSOR or not.
+ * @return
  */
-static void
-core_init (void *cls,
-           const struct GNUNET_PeerIdentity *identity)
+static struct GNUNET_PeerIdentity *
+find_successor (uint64_t destination_finger_value,
+                struct GNUNET_PeerIdentity *next_destination,
+                struct GNUNET_HashCode *new_intermediate_trail_id,
+                unsigned int finger_map_index)
 {
-  my_identity = *identity;
-}
+  struct Closest_Peer *successor;
+  struct GNUNET_PeerIdentity *next_hop;
+  struct GNUNET_CONTAINER_MultiPeerMapIterator *friend_iter;
+  struct GNUNET_CONTAINER_MultiHashMap32Iterator *finger_iter;
+  struct GNUNET_PeerIdentity *closest_peer;
+  struct Correct_Trail *finger_trail;
+  struct FriendInfo *friend;
+  struct FingerInfo *finger;
+  int i;
+
+  successor = GNUNET_new (struct Closest_Peer);
+  memcpy (&successor->value, &my_identity, sizeof (uint64_t));
+  //successor->trail_id = 0; /* FIXME:Default value for trail id */
+  successor->next_hop = my_identity;
+  successor->next_destination = my_identity;
+
+  friend_iter = GNUNET_CONTAINER_multipeermap_iterator_create (friend_peermap);
+  for (i= 0; i < GNUNET_CONTAINER_multipeermap_size (friend_peermap); i++)
+  {
+    GNUNET_assert (GNUNET_YES ==
+      GNUNET_CONTAINER_multipeermap_iterator_next (friend_iter, NULL,
+                                                  (const void **)&friend));
+    if ((friend->trails_count > TRAILS_THROUGH_FRIEND_THRESHOLD)||
+        (0 != GNUNET_TIME_absolute_get_remaining (friend->congestion_timestamp).rel_value_us))
+      continue;
+
+    closest_peer = select_closest_peer (&my_identity, &friend->id,
+                                        destination_finger_value,
+                                        finger_map_index);
+    if (0 == GNUNET_CRYPTO_cmp_peer_identity (closest_peer, &friend->id))
+    {
+      memcpy (&successor->value, &friend->id, sizeof (uint64_t));
+      //successor->trail_id = 0;
+      successor->next_hop = friend->id;
+      successor->next_destination = friend->id;
+    }
+  }
+
+  finger_iter = GNUNET_CONTAINER_multihashmap32_iterator_create (finger_hashmap);
+  for (i = 0; i < GNUNET_CONTAINER_multihashmap32_size (finger_hashmap); i++)
+  {
+    GNUNET_assert (GNUNET_YES ==
+      GNUNET_CONTAINER_multihashmap32_iterator_next (finger_iter, NULL,
+                                                     (void *)&finger));
+   finger_trail = select_trail_to_finger (finger);
+   if (NULL == finger_trail)
+     continue;
+
+   closest_peer = select_closest_peer (&my_identity,
+                                       &finger->finger_identity,
+                                       destination_finger_value,
+                                       finger_map_index);
+   if (0 == GNUNET_CRYPTO_cmp_peer_identity (closest_peer,
+                                             &finger->finger_identity))
+   {
+      memcpy (&successor->value, &finger->finger_identity, sizeof (uint64_t));
+      successor->trail_id = finger_trail->trail_id;
+      successor->next_hop = finger_trail->friend.id;
+      successor->next_destination = finger->finger_identity;
+    }
+  }
 
+  next_destination = &successor->next_destination;
+  new_intermediate_trail_id = &successor->trail_id;
+  next_hop = &successor->next_hop;
+
+  return next_hop;
+}
 
 /**
- * Core handler for p2p put requests.
- *
- * @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)
+ * 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 current_destination Next current destination which will get this message.
+ * @param current_source Source for @a current_destination
+ * @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
  */
-static int
-handle_dht_p2p_put (void *cls,
-                   const struct GNUNET_PeerIdentity *peer,
-                    const struct GNUNET_MessageHeader *message)
+void
+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 current_destination,
+                         struct GNUNET_PeerIdentity current_source,
+                         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)
 {
-    /**
-    1. Check if destination is friend or finger.
-    2. If finger then get the next hop from routing table and 
-     * call GDS_NEGIHBOURS_handle_get.
-    3. If friend then call find_successor to get the next hop and again
-     * call GDS_NEIGHBOURS_handle_get to send to chosen hop.
-     4. If you are the destination then do datacache_store.
-     */
-  return 0;
-}
 
+}
 
 /**
- * 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)
+ * 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 current_destination Next current destination which will get this message.
+ * @param current_source Source for @a current_destination
+ * @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
  */
-static int
-handle_dht_p2p_get (void *cls, const struct GNUNET_PeerIdentity *peer,
-                    const struct GNUNET_MessageHeader *message)
+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 current_destination,
+                         struct GNUNET_PeerIdentity current_source,
+                         struct GNUNET_PeerIdentity *target_peer,
+                         uint32_t hop_count,
+                         uint32_t get_path_length,
+                         struct GNUNET_PeerIdentity *get_path)
 {
-  /**
-    1. Check if destination is friend or finger.
-    2. If finger then get the next hop from routing table and 
-     * call GDS_NEGIHBOURS_handle_get.
-    3. If friend then call find_successor to get the next hop and again
-     * call GDS_NEIGHBOURS_handle_get to send to chosen hop.
-     4. If you are the destination then send the data back to source peer
-   * Assuming we have trail setup we can
-   * either store the whole trail or again do the search process..
-     */
-  return 0;
+
 }
 
 
 /**
- * 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. 
+ * 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
  */
-static int
-compare_peer_id (const void *p1, const void *p2)
+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,
+                                unsigned int get_path_length,
+                                struct GNUNET_PeerIdentity *get_path,
+                                struct GNUNET_TIME_Absolute expiration,
+                                const void *data, size_t data_size)
 {
-  return memcmp (p1, p2, sizeof (uint64_t));
+
 }
 
 
 /**
- * Returns the previous element 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 
+ * 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 GNUNET_PeerIdentity *
-binary_search(struct GNUNET_PeerIdentity *all_known_peers, uint64_t *value,
-              unsigned int size)
-{
-  unsigned int first;
-  unsigned int last;
-  unsigned int middle;
-  struct GNUNET_PeerIdentity *successor;
-  successor = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-  
-  first = 0;
-  last = size - 1;
-  middle = (first + last)/2;
-  
-  while(first <= last)
+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
   {
-    /* all_known_peers[middle] > value*/
-    if(0 > compare_peer_id(&all_known_peers[middle], &value))
-    {
-      first = middle + 1; 
-    }
-    else if(0 == compare_peer_id(&all_known_peers[middle], &value))
+    if (j == current_size)
     {
-      if(middle == 0)
-      {
-        successor = &(all_known_peers[size - 1]);
-      }
-      else
-        successor = &(all_known_peers[middle-1]);
+      j = 0;
+      GNUNET_CONTAINER_multipeermap_iterator_destroy (iter);
+      iter = GNUNET_CONTAINER_multipeermap_iterator_create (friend_peermap);
+
     }
-    else
+    GNUNET_assert (GNUNET_YES ==
+                GNUNET_CONTAINER_multipeermap_iterator_next (iter,
+                                                             &key_ret,
+                                                             (const void **)&friend));
+
+
+    if ((TRAILS_THROUGH_FRIEND_THRESHOLD > friend->trails_count) &&
+        (0 == GNUNET_TIME_absolute_get_remaining (friend->congestion_timestamp).rel_value_us))
     {
-       last = middle - 1;
+      break;
     }
-  
-    middle = (first + last)/2;  
-  }
-  return successor;
+    friend = NULL;
+    j++;
+  } while (j != index);
+
+  GNUNET_CONTAINER_multipeermap_iterator_destroy (iter);
+  return friend;
 }
 
 
 /**
- * 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. 
+ * FIXME: pass current_search_finger_index as parameter
+ * Compute finger_identity to which we want to setup the trail
+ * @return finger_identity
  */
-static struct GNUNET_PeerIdentity *
-find_successor(uint64_t *value, struct GNUNET_PeerIdentity *current_destination,
-               enum current_destination_type *type)
+static uint64_t
+compute_finger_identity()
 {
-  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 GNUNET_PeerIdentity *all_known_peers;
-  struct GNUNET_PeerIdentity *successor;
-  unsigned int size;
-  unsigned int j;
-  /* SUPU: 2 is added for my_identity and value. */
-  size = GNUNET_CONTAINER_multipeermap_size (friend_peermap)+
-         GNUNET_CONTAINER_multipeermap_size (finger_peermap)+
-         2;
-  
-  all_known_peers = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity) * size);
-  
-  j = 0;
-  memcpy (&all_known_peers[j], &(my_identity), sizeof (struct GNUNET_PeerIdentity));
-  j++;
-  memcpy (&all_known_peers[j], value, sizeof(struct GNUNET_PeerIdentity));
-  
-  /* Iterate over friend peermap 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++)
+  uint64_t my_id64;
+
+  memcpy (&my_id64, &my_identity, sizeof (uint64_t));
+  my_id64 = GNUNET_ntohll (my_id64);
+  return (my_id64 + (unsigned long) pow (2, current_search_finger_index));
+}
+
+
+/**
+ * Compute immediate predecessor identity in the network.
+ * @return peer identity of immediate predecessor.
+ */
+static uint64_t
+compute_predecessor_identity()
+{
+  uint64_t my_id64;
+
+  memcpy (&my_id64, &my_identity, sizeof (uint64_t));
+  my_id64 = GNUNET_ntohll (my_id64);
+  return (my_id64 -1);
+}
+
+
+/*
+ * Choose a random friend and start looking for the trail to reach to
+ * finger identity 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 finger_map_index;
+  uint64_t finger_identity;
+
+  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);
+
+  target_friend = select_random_friend ();
+  if (NULL == target_friend)
   {
-    /* FIXME: I don't think we are actually iterating.
-     Read about how to iterate over the multipeermap. */
-    if(GNUNET_YES == GNUNET_CONTAINER_multipeermap_iterator_next(friend_iter,&key_ret,(const void **)&friend)) 
-    {
-      memcpy (&all_known_peers[j], &(friend->id), sizeof (struct GNUNET_PeerIdentity));
-      j++;
-    }
+    return;
   }
-  
-  /* 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 (PREDECESSOR_FINGER_ID == current_search_finger_index)
   {
-    /* FIXME: I don't think we are actually iterating.
-     Read about how to iterate over the multi peer map. */
-    if(GNUNET_YES == GNUNET_CONTAINER_multipeermap_iterator_next(finger_iter,&key_ret,(const void **)&finger)) 
-    {
-      memcpy (&all_known_peers[j], &(finger->finger_identity), sizeof (struct GNUNET_PeerIdentity));
-      j++;
-    }
+    finger_identity = compute_predecessor_identity();
   }
-  
-  qsort (all_known_peers, size, sizeof (struct GNUNET_PeerIdentity), &compare_peer_id);
-  
-  /* search value in all_known_peers array. */
-  successor = binary_search (all_known_peers, value, size);
-  
-  /* compare successor with my_identity, finger and friend */
-  if(0 == GNUNET_CRYPTO_cmp_peer_identity(&(my_identity), successor))
+  else
   {
-    *type = MY_ID;
-    return NULL;
+    finger_identity = compute_finger_identity();
   }
-  else if (GNUNET_YES == GNUNET_CONTAINER_multipeermap_contains (friend_peermap,
-                                              successor))
-  {
-    *type = FRIEND;
-    memcpy (current_destination, successor, sizeof (struct GNUNET_PeerIdentity));
-    return successor;
+
+  finger_map_index = current_search_finger_index;
+
+  GNUNET_CRYPTO_random_block (GNUNET_CRYPTO_QUALITY_STRONG,
+                              &trail_id, sizeof (trail_id));
+  GDS_NEIGHBOURS_send_trail_setup (my_identity, finger_identity,
+                                   target_friend->id, target_friend, 0, NULL,
+                                   finger_map_index, 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,
+                          struct GNUNET_PeerIdentity *new_trail,
+                          unsigned int new_trail_length,
+                          struct GNUNET_HashCode new_trail_id)
+{
+  struct TrailList *trail_list_iterator;
+  unsigned int largest_trail_length;
+  unsigned int largest_trail_index;
+  struct Trail *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 TrailList *replace_trail = &existing_finger->trail_list[largest_trail_index];
+  struct FriendInfo *target_friend =
+      GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                         &replace_trail->trail_head->peer);
+
+  GDS_NEIGHBOURS_send_trail_teardown (my_identity,
+                                      existing_finger->finger_identity,
+                                      replace_trail->trail_id,
+                                      GDS_ROUTING_SRC_TO_DEST, target_friend);
+  /* 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 (trail_element);
+  }
+
+  /* Add new trial at that location. */
+  i = 0;
+  while (i < new_trail_length)
+  {
+    struct Trail *element = GNUNET_new (struct Trail);
+    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,
+                     struct GNUNET_PeerIdentity *new_trail,
+                     unsigned int trail_length)
+{
+  struct TrailList *trail_list_iterator;
+  struct Trail *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,
+               struct GNUNET_PeerIdentity *new_trail,
+               unsigned int new_trail_length,
+               struct GNUNET_HashCode new_trail_id)
+{
+  struct TrailList *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++;
+  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 = GNUNET_new (struct Trail);
+
+    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 on all trails associated with finger.
+ * @param finger_to_be_removed
+ */
+static void
+send_trail_teardown (struct FingerInfo *finger)
+{
+  struct TrailList *trail_list_iterator;
+  struct FriendInfo *target_friend;
+  int i;
+
+  if (0 == GNUNET_CRYPTO_cmp_peer_identity (&finger->finger_identity, &my_identity)
+     || (NULL != GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                                    &finger->finger_identity)))
+    return;
+
+  for (i = 0; i < finger->trails_count; i++)
+  {
+    trail_list_iterator = &finger->trail_list[i];
+    if (trail_list_iterator->trail_length > 0)
+    {
+      target_friend =
+              GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                                 &trail_list_iterator->trail_head->peer);
+      // check target_friend
+      GDS_NEIGHBOURS_send_trail_teardown (my_identity, finger->finger_identity,
+                                          trail_list_iterator->trail_id,
+                                          GDS_ROUTING_SRC_TO_DEST,
+                                          target_friend);
+    }
+  }
+}
+
+
+/**
+ * Decrement the trail count of the first friend to reach the finger
+ * In case finger is the friend, then decrement its trail count.
+ * @param finger
+ */
+static void
+decrement_friend_trail_count (struct FingerInfo *finger)
+{
+  struct TrailList *trail_list_iterator;
+  struct FriendInfo *target_friend;
+  int i = 0;
+
+  if (0 == GNUNET_CRYPTO_cmp_peer_identity (&finger->finger_identity,
+                                            &my_identity))
+    return;
+
+  for (i = 0; i < finger->trails_count; i++)
+  {
+    trail_list_iterator = &finger->trail_list[i];
+    if (trail_list_iterator->trail_length > 0)
+      target_friend =
+              GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                                 &trail_list_iterator->trail_head->peer);
+    else
+     target_friend =
+              GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                                 &finger->finger_identity);
+
+    // check target_friend for NULL
+    target_friend->trails_count--;
+    trail_list_iterator->first_friend_trail_count--;
+  }
+  return;
+}
+
+
+/**
+ * Free finger and its trail.
+ * @param finger Finger to be freed.
+ */
+static void
+free_finger (struct FingerInfo *finger)
+{
+  struct TrailList *trail_list_iterator;
+  struct Trail *trail_element;
+  unsigned int i;
+
+  for (i = 0; i < finger->trails_count; i++)
+  {
+    trail_list_iterator = &finger->trail_list[i];
+    while (NULL != (trail_element = trail_list_iterator->trail_head))
+    {
+      GNUNET_CONTAINER_DLL_remove (trail_list_iterator->trail_head,
+                                   trail_list_iterator->trail_tail,
+                                   trail_element);
+      GNUNET_free (trail_element);
+    }
+  }
+  GNUNET_free (finger);
+}
+
+
+/**
+ * FIXME: merge into finger_table_add
+ * FIXME: leave as simple a check
+ * Check if new finger is closer than existing_finger. If both new finger and
+ * existing finger are same then we may add a new trail (if there is space)
+ * or choose the best trail among existing trails and new trails.
+ * @param existing_finger Finger present in finger_peermap at @a finger_map_index
+ *                        or NULL if none
+ * @param new_finger_identity Peer identity of new finger.
+ * FIXME: all the following params *should* not be necessary
+ * @param new_finger_trail Trail to reach from source to new_finger.
+ * @param new_finger_trail_length Total number of peers in @a new_finger_trail.
+ * @param trail_id Unique identifier of trail.
+ * @param finger_map_index Index in finger map.
+ * @return #GNUNET_YES if the new finger is closest.
+ *         #GNUNET_NO either new_finger and existing_finger are same, or
+ *                    existing_finger is closest.
+ */
+static int
+is_new_finger_closest (struct FingerInfo *existing_finger,
+                       struct GNUNET_PeerIdentity new_finger_identity,
+                       struct GNUNET_PeerIdentity *new_finger_trail,
+                       unsigned int new_finger_trail_length,
+                       struct GNUNET_HashCode new_finger_trail_id,
+                       unsigned int finger_map_index)
+{
+  struct GNUNET_PeerIdentity *closest_peer;
+  uint64_t finger_identity_value;
+  uint64_t my_id64;
+
+  if (NULL == existing_finger)
+    return GNUNET_YES;
+
+  memcpy (&my_id64, &my_identity, sizeof (uint64_t));
+  if (0 != GNUNET_CRYPTO_cmp_peer_identity (&(existing_finger->finger_identity),
+                                            &new_finger_identity))
+  {
+    if (PREDECESSOR_FINGER_ID == finger_map_index)
+      finger_identity_value = my_id64 - 1;
+    else
+      finger_identity_value = my_id64 + (unsigned long) pow (2, finger_map_index);
+    closest_peer = select_closest_peer (&existing_finger->finger_identity,
+                                        &new_finger_identity,
+                                        finger_identity_value, finger_map_index);
+
+    if (0 == GNUNET_CRYPTO_cmp_peer_identity (&new_finger_identity, closest_peer))
+    {
+      GNUNET_assert (0 != GNUNET_CRYPTO_cmp_peer_identity (&my_identity,
+                                                           &new_finger_identity));
+
+      send_trail_teardown (existing_finger);
+      decrement_friend_trail_count (existing_finger);
+      free_finger (existing_finger);
+      return GNUNET_YES;
+    }
+  }
+  else
+  {
+    if (0 == GNUNET_CRYPTO_cmp_peer_identity (&(existing_finger->finger_identity),
+                                              &my_identity))
+    {
+      return GNUNET_NO;
+    }
+    if (NULL ==
+        GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                            &(existing_finger->finger_identity)))
+    {
+      if (existing_finger->trails_count < MAXIMUM_TRAILS_PER_FINGER)
+        add_new_trail (existing_finger, new_finger_trail,
+                        new_finger_trail_length, new_finger_trail_id);
+      else
+        select_and_replace_trail (existing_finger, new_finger_trail,
+                                  new_finger_trail_length, new_finger_trail_id);
+    }
+  }
+  return GNUNET_NO;
+}
+
+
+/**
+ * Add a new entry in finger hashmap at finger_map_index
+ * @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_map_index Index in finger hashmap.
+ * @return #GNUNET_OK if new entry is added
+ *         #GNUNET_NO -- FIXME: need to check what value does hahsmap put
+ *                       returns on failure.
+ */
+static int
+add_new_entry (struct GNUNET_PeerIdentity finger_identity,
+               struct GNUNET_PeerIdentity *finger_trail,
+               unsigned int finger_trail_length,
+               struct GNUNET_HashCode trail_id,
+               unsigned int finger_map_index)
+{
+  struct FingerInfo *new_entry;
+  struct FriendInfo *first_trail_hop;
+  struct TrailList *first_trail;
+  int i = 0;
+
+  new_entry = GNUNET_new (struct FingerInfo);
+  new_entry->finger_identity = finger_identity;
+  new_entry->finger_map_index = finger_map_index;
+  new_entry->trails_count = 1;
+
+  if (0 != GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &finger_identity))
+  {
+    if (finger_trail_length > 0)
+    {
+      first_trail_hop = GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                                           &finger_trail[0]);
+    }
+    else
+    {
+      first_trail_hop = GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                                           &finger_identity);
+    }
+
+    first_trail_hop->trails_count++;
+    first_trail = &new_entry->trail_list[0];
+    first_trail->first_friend_trail_count = first_trail_hop->trails_count;
+
+    while (i < finger_trail_length)
+    {
+      struct Trail *element = GNUNET_new (struct Trail);
+
+      element->next = NULL;
+      element->prev = NULL;
+      element->peer = finger_trail[i];
+      GNUNET_CONTAINER_DLL_insert_tail (first_trail->trail_head,
+                                        first_trail->trail_tail,
+                                        element);
+      i++;
+    }
+  }
+
+  return GNUNET_CONTAINER_multihashmap32_put (finger_hashmap,
+                                              new_entry->finger_map_index,
+                                              new_entry,
+                                              GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY);
+}
+
+
+/**
+ * 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 int
+scan_and_compress_trail (struct GNUNET_PeerIdentity finger_identity,
+                         struct GNUNET_PeerIdentity *trail,
+                         unsigned int trail_length,
+                         struct GNUNET_HashCode trail_id)
+{
+  struct FriendInfo *target_friend;
+  int i;
+
+  if (0 == GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &finger_identity))
+  {
+    return 0;
+  }
+
+  if (NULL != GNUNET_CONTAINER_multipeermap_get (friend_peermap, &finger_identity))
+  {
+    if (trail_length > 0)
+    {
+      target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                                       &trail[0]);
+      GDS_NEIGHBOURS_send_trail_compression (my_identity, finger_identity,
+                                           trail_id, finger_identity,
+                                           target_friend);
+      trail = NULL;
+    }
+    return 0;
+  }
+
+  for (i = trail_length - 1; i > 0; i--)
+  {
+    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, finger_identity,
+                                             trail_id, trail[i],
+                                             target_friend);
+
+      // FIXME WARNING WARNING WARNING rewrite!!! consider directly creating a
+      // struct TrailList (current) // struct Trial (after renaming).
+
+      /* Copy the trail from index i to index trail_length -1 and change
+       trail length and return */
+      while (i < trail_length)
+      {
+        memcpy (&trail[j], &trail[i], sizeof(struct GNUNET_PeerIdentity));
+        j++;
+        i++;
+      }
+      trail_length = j+1;
+      break;
+    }
+  }
+  return trail_length;
+}
+
+
+/**
+ * Send verify successor message to your successor on all trails to reach
+ * the successor.
+ * @param successor My current successor
+ */
+static void
+send_verify_successor_message (struct FingerInfo *successor)
+{
+  struct TrailList *trail_list_iterator;
+  struct GNUNET_HashCode trail_id;
+  struct GNUNET_PeerIdentity next_hop;
+  struct FriendInfo *target_friend;
+  struct GNUNET_PeerIdentity *trail;
+  unsigned int trail_length;
+  int i;
+  int j;
+
+  for (i = 0; i < MAXIMUM_TRAILS_PER_FINGER; i++)
+  {
+    trail_list_iterator = &successor->trail_list[i];
+
+//      FIXME check if this entry in the trail list is valid!
+//     if (NULL == trail_list_iterator->SOMETHING)
+//       continue;
+
+    if (trail_list_iterator->trail_length > 0)
+    {
+      struct Trail *element;
+
+      trail_length = trail_list_iterator->trail_length;
+      trail = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity)
+                             * trail_length);
+      element = trail_list_iterator->trail_head;
+      for (j = 0; j < trail_length; j++, element = element->next)
+        trail[j] = element->peer;
+      next_hop = trail_list_iterator->trail_head->peer;
+    }
+    else
+    {
+      trail = NULL;
+      trail_length = 0;
+      next_hop = successor->finger_identity;
+    }
+    trail_id = trail_list_iterator->trail_id;
+    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, &next_hop);
+    // check friend for NULL
+    GDS_NEIGHBOURS_send_verify_successor_message (my_identity,
+                                                  successor->finger_identity,
+                                                  trail_id, trail, trail_length,
+                                                  target_friend);
+    GNUNET_free_non_null (trail);
+  }
+}
+
+
+/**
+ * Check if there is already an entry in finger peermap for given finger map index.
+ * If yes, then select the closest finger. If new and existing finger are same,
+ * the 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, add it.
+ * Then, update current_search_finger_index.
+ * @param new_finger_identity Peer Identity of new finger
+ * @param new_finger_trail Trail to reach the new finger
+ * @param new_finger_length Total number of peers in @a new_finger_trail.
+ * @param finger_map_index Index in finger peermap.
+ * @param new_finger_trail_id Unique identifier of @new_finger_trail.
+ * @return #GNUNET_YES if the new entry is added
+ *         #GNUNET_NO if new entry is not added, either it was discarded or
+ *                    it was same as existing finger at finger map index.
+ */
+static int
+finger_table_add (struct GNUNET_PeerIdentity new_finger_identity, // "finger_id"
+                  struct GNUNET_PeerIdentity *new_finger_trail, // "trail"
+                  unsigned int new_finger_trail_length,
+                  unsigned int finger_map_index,
+                  struct GNUNET_HashCode new_finger_trail_id)
+{
+  struct FingerInfo *existing_finger;
+  struct FingerInfo *successor;
+  unsigned int new_entry_added = GNUNET_NO;
+  int new_finger_updated_trail_length; // new_finger_trail_length
+
+  new_finger_updated_trail_length =
+       scan_and_compress_trail (new_finger_identity, new_finger_trail,
+                                new_finger_trail_length, new_finger_trail_id);
+
+  existing_finger = GNUNET_CONTAINER_multihashmap32_get (finger_hashmap,
+                                                         finger_map_index);
+
+  if  (GNUNET_YES == is_new_finger_closest (existing_finger,
+                                            new_finger_identity,
+                                            new_finger_trail,
+                                            new_finger_updated_trail_length,
+                                            new_finger_trail_id, finger_map_index))
+  {
+    // send_destroy_existing_finger ...
+    // free_exisiting_finger ...
+    GNUNET_assert (GNUNET_YES == add_new_entry (new_finger_identity,
+                                                new_finger_trail,
+                                                new_finger_updated_trail_length,
+                                                new_finger_trail_id,
+                                                finger_map_index));
+    new_entry_added = GNUNET_YES;
+  }
+//   else if if_new_finger_equal () {
+//
+//   }
+//   else // existing finger is closest
+//   {
+//
+//   }
+
+  // FIXME move block to "update_succesor"
+  {
+    successor = GNUNET_CONTAINER_multihashmap32_get (finger_hashmap, 0);
+    // WARNING FIXME check that current_search_finger_index does not go out of bounds
+    if (0 == finger_map_index)
+    {
+      current_search_finger_index = PREDECESSOR_FINGER_ID;
+
+      if (0 != GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &new_finger_identity))
+      {
+        send_verify_successor_message (successor);
+      }
+    }
+    else if (0 == GNUNET_CRYPTO_cmp_peer_identity (&new_finger_identity,
+                                                  &(successor->finger_identity)))
+    {
+      current_search_finger_index = 0;
+    }
+    else
+      current_search_finger_index = current_search_finger_index - 1;
+  }
+
+  return new_entry_added;
+}
+
+
+/**
+ * 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)
+{
+  return GNUNET_OK;
+}
+
+
+/**
+ * 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)
+{
+  return GNUNET_OK;
+}
+
+
+/**
+ * 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)
+{
+  return GNUNET_OK;
+}
+
+
+/* Core handle for PeerTrailSetupMessage.
+ * @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_setup (void *cls, const struct GNUNET_PeerIdentity *peer,
+                            const struct GNUNET_MessageHeader *message)
+{
+  struct PeerTrailSetupMessage *trail_setup;
+  struct GNUNET_PeerIdentity *trail_peer_list;
+  struct GNUNET_PeerIdentity next_destination; // "local_best_known_destination"
+  struct GNUNET_PeerIdentity *current_destination;
+  struct GNUNET_PeerIdentity *next_hop;
+  struct GNUNET_PeerIdentity next_peer;
+  struct FriendInfo *target_friend;
+  struct GNUNET_PeerIdentity source;
+  uint64_t ultimate_destination_finger_value;
+  struct GNUNET_HashCode new_intermediate_trail_id;
+  //struct GNUNET_HashCode *intermediate_trail_id;
+  struct GNUNET_HashCode new_trail_id;
+  unsigned int finger_map_index;
+  uint32_t trail_length;
+  size_t msize;
+
+  msize = ntohs (message->size);
+  /* There are PeerId's appended to the end of the message! */
+  if (msize < sizeof (struct PeerTrailSetupMessage))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_YES;
+  }
+
+  trail_setup = (struct PeerTrailSetupMessage *) message;
+  trail_length = ntohl (trail_setup->trail_length); // (msize - sizeof (msg)) / sizeof(PI)
+  // if ((msize - sizeof (msg)) % sizeof(PI) != 0)
+  if ((msize != sizeof (struct PeerTrailSetupMessage) +
+       trail_length * sizeof (struct GNUNET_PeerIdentity)) ||
+       (trail_length >
+        GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity)))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_OK;
+  }
+
+  trail_peer_list = (struct GNUNET_PeerIdentity *)&trail_setup[1];
+  current_destination = &trail_setup->next_destination;
+  new_trail_id = trail_setup->new_trail_id;
+  ultimate_destination_finger_value = GNUNET_ntohll (trail_setup->ultimate_destination_finger);
+  source = trail_setup->source_peer;
+  finger_map_index = ntohl (trail_setup->finger_map_index);
+  //intermediate_trail_id = &trail_setup->intermediate_trail_id;
+  
+  if (GNUNET_YES == GDS_ROUTING_threshold_reached())
+  {
+    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, peer);
+    GDS_NEIGHBOURS_send_trail_rejection (source, ultimate_destination_finger_value,
+                                         my_identity, finger_map_index,
+                                         trail_peer_list, trail_length,
+                                         new_trail_id, target_friend,
+                                         CONGESTION_TIMEOUT);
+    return GNUNET_OK;
+  }
+
+  next_hop = find_successor (ultimate_destination_finger_value, &next_destination,
+                             &new_intermediate_trail_id, finger_map_index);
+
+  /* Are we just a part of a trail towards a finger? */
+  if (0 != (GNUNET_CRYPTO_cmp_peer_identity(&my_identity, current_destination)))
+  {
+//    struct GNUNET_PeerIdentity *closest_peer;
+//     struct GNUNET_PeerIdentity *peer1 =
+//         GDS_ROUTING_get_next_hop (intermediate_trail_id,
+//                                   GDS_ROUTING_SRC_TO_DEST);
+    /* Is next_destination better than the original best_known_dest? */
+    // BIG FIXME START
+//     if (0 != GNUNET_CRYPTO_cmp_peer_identity (next_destination,
+//                                               current_destination))
+//     {
+//        closest_peer = select_closest_peer (peer1, next_hop,
+//                                            ultimate_destination_finger_value,
+//                                            finger_map_index);
+//     }
+//     if (0 == GNUNET_CRYPTO_cmp_peer_identity (peer1, closest_peer) ||
+//         (0 == GNUNET_CRYPTO_cmp_peer_identity (peer1, next_hop)))
+//     {
+//       next_hop = peer1;
+//       next_destination = *current_destination;
+//       new_intermediate_trail_id = intermediate_trail_id;
+//     }
+    // BIG FIXME END
+  }
+
+  GNUNET_assert (NULL != next_hop);
+  /* Am I the final destination? */
+  if (0 == (GNUNET_CRYPTO_cmp_peer_identity (next_hop, &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,
+                                            finger_map_index, new_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;
+    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,
+                                     finger_map_index, new_trail_id,
+                                     &new_intermediate_trail_id);
+  }
+  return GNUNET_OK;
+}
+
+
+/**
+ * Core handle for p2p trail construction result messages.
+ * @param 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_setup_result(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 destination_peer;
+  struct GNUNET_PeerIdentity finger_identity;
+  uint32_t trail_length;
+  uint32_t finger_map_index;
+  struct GNUNET_HashCode trail_id;
+  size_t msize;
+
+  msize = ntohs (message->size);
+  if (msize < sizeof (struct PeerTrailSetupResultMessage))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_YES;
+  }
+
+  trail_result = (struct PeerTrailSetupResultMessage *) message;
+
+  // calculate trail_length with message size, check for % 0
+  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)))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_YES;
+  }
+
+  finger_map_index = htonl (trail_result->finger_map_index);
+  destination_peer = trail_result->destination_peer;
+  finger_identity = trail_result->finger_identity;
+  trail_id = trail_result->trail_id;
+  trail_peer_list = (struct GNUNET_PeerIdentity *) &trail_result[1];
+
+  // FIXME: check that trail_peer_list[my_index + 1] == peer or
+  // my_index == trail_length - 1 AND finger_identity == peer
+
+  /* Am I the one who initiated the query? */
+  if (0 == (GNUNET_CRYPTO_cmp_peer_identity (&destination_peer,
+                                             &my_identity)))
+  {
+    finger_table_add (finger_identity, trail_peer_list,
+                      trail_length,
+                      finger_map_index, trail_id);
+    return GNUNET_YES;
+  }
+
+  struct GNUNET_PeerIdentity next_hop;
+  struct FriendInfo *target_friend;
+  int my_index;
+
+  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->destination_peer;
+  else
+    next_hop = trail_peer_list[my_index - 1];
+
+  if (0 != (GNUNET_CRYPTO_cmp_peer_identity (&(trail_result->destination_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 (destination_peer, finger_identity,
+                                          target_friend, trail_length, trail_peer_list,
+                                          finger_map_index, 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 (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;
+}
+
+
+/**
+ * Check if the new finger can be our predecessor. If yes then update predecessor
+ *
+ * @param new_finger
+ * @param new_finger_trail
+ * @param new_finger_trail_length
+ * @return
+ */
+static int
+is_new_entry_correct_predecessor (struct FingerInfo *my_predecessor,
+                                struct GNUNET_PeerIdentity new_finger,
+                                struct GNUNET_PeerIdentity *new_finger_trail,
+                                unsigned int new_finger_trail_length)
+{
+  struct GNUNET_PeerIdentity *updated_trail;
+  struct GNUNET_HashCode new_trail_id;
+
+  updated_trail =  invert_trail (new_finger_trail, new_finger_trail_length);
+  if (GNUNET_YES == is_new_finger_closest (my_predecessor, new_finger,
+                                           new_finger_trail,
+                                           new_finger_trail_length,
+                                           new_trail_id, PREDECESSOR_FINGER_ID))
+  {
+    add_new_entry (new_finger, updated_trail, new_finger_trail_length,
+                   new_trail_id, PREDECESSOR_FINGER_ID);
+    /* FIXME: check where you send add trail message */
+    return GNUNET_YES;
+  }
+  return GNUNET_NO;
+}
+
+/**
+ * In case the source peer of verify successor message is not my successor,
+ * then construct a trail from source peer to my current 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 new_trail_length [out] Total number of peers in updated trail.
+ * @return Updated trail from source peer to my_predecessor.
+ */
+static struct GNUNET_PeerIdentity *
+trail_source_to_my_predecessor (struct FingerInfo *my_predecessor,
+                                struct GNUNET_PeerIdentity *current_trail,
+                                unsigned int current_trail_length,
+                                unsigned int *new_trail_length)
+{
+  struct GNUNET_PeerIdentity *new_trail;
+  struct TrailList *trail_list_iterator;
+  struct Trail *trail_iterator;
+  unsigned int i;
+  unsigned int j;
+  unsigned int shortest_trail_length = 0;
+  unsigned int trail_index = 0;
+
+  for (i = 0; i < my_predecessor->trails_count; i++)
+  {
+    trail_list_iterator = &my_predecessor->trail_list[i];
+    if (trail_list_iterator->trail_length > shortest_trail_length)
+      continue;
+    shortest_trail_length = trail_list_iterator->trail_length;
+    trail_index = i;
+  }
+
+  *new_trail_length = current_trail_length + shortest_trail_length + 1;
+  new_trail = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity) *
+                             *new_trail_length);
+  memcpy (new_trail, current_trail,
+         current_trail_length * sizeof (struct GNUNET_PeerIdentity));
+  new_trail[current_trail_length + 1] = my_identity;
+
+  i = 0;
+  j = current_trail_length + 1;
+  trail_list_iterator = &my_predecessor->trail_list[trail_index];
+  trail_iterator = trail_list_iterator->trail_head;
+  while ( i < shortest_trail_length)
+  {
+    new_trail[j] = trail_iterator->peer;
+    j++;
+    i++;
+    trail_iterator = trail_iterator->next;
+  }
+
+  *new_trail_length = j;
+  return new_trail;
+}
+
+
+/**
+ * Core handle for p2p verify 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_verify_successor(void *cls, const struct GNUNET_PeerIdentity *peer,
+                                const struct GNUNET_MessageHeader *message)
+{
+  struct PeerVerifySuccessorMessage *vsm;
+  struct GNUNET_PeerIdentity successor;
+  struct GNUNET_PeerIdentity source_peer;
+  struct GNUNET_PeerIdentity *next_hop;
+  struct FriendInfo *target_friend;
+  struct GNUNET_HashCode trail_id;
+  struct FingerInfo *my_predecessor;
+  struct GNUNET_PeerIdentity *trail;
+  struct GNUNET_PeerIdentity *new_trail;
+  unsigned int trail_length;
+  unsigned int new_trail_length;
+  size_t msize;
+
+  msize = ntohs (message->size);
+  if (msize != sizeof (struct PeerVerifySuccessorMessage))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_YES;
+  }
+
+  vsm = (struct PeerVerifySuccessorMessage *) message;
+  trail_length = ntohl (vsm->trail_length);
+  if ((msize != sizeof (struct PeerVerifySuccessorMessage) +
+               trail_length * sizeof (struct GNUNET_PeerIdentity)) ||
+      (trail_length > GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity)))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_YES;
+  }
+  trail = (struct GNUNET_PeerIdentity *)&vsm[1];
+  source_peer = vsm->source_peer;
+  successor = vsm->successor;
+  trail_id = vsm->trail_id;
+
+  if(0 != (GNUNET_CRYPTO_cmp_peer_identity (&successor, &my_identity)))
+  {
+    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;
+  }
+
+  my_predecessor = GNUNET_CONTAINER_multihashmap32_get (finger_hashmap,
+                                                        PREDECESSOR_FINGER_ID);
+  target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, peer);
+  if (GNUNET_NO == is_new_entry_correct_predecessor (my_predecessor, source_peer,
+                                                     trail, trail_length))
+  {
+    if (0 != GNUNET_CRYPTO_cmp_peer_identity (&source_peer,
+                                              &my_predecessor->finger_identity))
+    {
+      new_trail = trail_source_to_my_predecessor (my_predecessor, trail,
+                                                  trail_length, &new_trail_length);
+    }
+  }
+  else
+  {
+    my_predecessor = GNUNET_CONTAINER_multihashmap32_get (finger_hashmap,
+                                                          PREDECESSOR_FINGER_ID);
+    GDS_NEIGHBOURS_send_add_trail (my_predecessor->finger_identity,
+                                   source_peer, trail_id,
+                                   trail, trail_length,
+                                   target_friend);
+    new_trail_length = trail_length;
+    new_trail = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity) *
+                               new_trail_length);
+    memcpy (new_trail, trail, sizeof (struct GNUNET_PeerIdentity) *
+                              trail_length);
+  }
+
+  GDS_NEIGHBOURS_send_verify_successor_result (source_peer, my_identity,
+                                               my_predecessor->finger_identity,
+                                               trail_id, new_trail,
+                                               new_trail_length,
+                                               GDS_ROUTING_DEST_TO_SRC,
+                                               target_friend);
+  return GNUNET_OK;
+}
+
+
+/**
+ * FIXME: I will keep the logic to remove the old trail to reach from me to
+ * my old successor here and move adding a new trail from me to new successor to notify
+ * new successor. And in case if the new successor also take it as predecessor
+ * then call add_trail.
+ * 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
+ */
+static int
+handle_dht_p2p_verify_successor_result(void *cls, const struct GNUNET_PeerIdentity *peer,
+                                       const struct GNUNET_MessageHeader *message)
+{
+  struct PeerVerifySuccessorResultMessage *vsrm;
+  enum GDS_ROUTING_trail_direction trail_direction;
+  struct GNUNET_HashCode trail_id;
+  unsigned int new_trail_length;
+  struct GNUNET_PeerIdentity *new_trail;
+  struct GNUNET_PeerIdentity destination_peer;
+  struct GNUNET_PeerIdentity my_new_successor;
+  struct GNUNET_PeerIdentity old_successor;
+  struct GNUNET_PeerIdentity *next_hop;
+  struct FriendInfo *target_friend;
+  size_t msize;
+
+  msize = ntohs (message->size);
+  if (msize != sizeof (struct PeerVerifySuccessorResultMessage))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_YES;
+  }
+  vsrm = (struct PeerVerifySuccessorResultMessage *) message;
+  new_trail_length = ntohl (vsrm->trail_length);
+  trail_direction = ntohl (vsrm->trail_direction);
+  trail_id = vsrm->trail_id;
+
+  if ((msize !=
+       sizeof (struct PeerVerifySuccessorResultMessage) +
+       new_trail_length *
+       sizeof (struct GNUNET_PeerIdentity)) ||
+       (new_trail_length >
+       GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity)))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_YES;
+  }
+
+  new_trail = (struct GNUNET_PeerIdentity *) &vsrm[1];
+  destination_peer = vsrm->destination_peer;
+  my_new_successor = vsrm->my_predecessor;
+  old_successor = vsrm->source_successor;
+
+  if(0 == (GNUNET_CRYPTO_cmp_peer_identity (&destination_peer, &my_identity)))
+  {
+    struct GNUNET_HashCode new_finger_trail_id;
+    /* FIXME: generate a new trail id. */
+    if (GNUNET_YES == finger_table_add (my_new_successor,
+                                        new_trail,
+                                        new_trail_length,
+                                        PREDECESSOR_FINGER_ID, new_finger_trail_id))
+    {
+      if (new_trail_length > 0)
+        target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                                           &new_trail[0]);
+      else
+        target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                                           peer);
+      GDS_NEIGHBOURS_send_trail_teardown (my_identity, old_successor, trail_id,
+                                          GDS_ROUTING_SRC_TO_DEST, target_friend);
+      GDS_NEIGHBOURS_send_notify_new_successor (my_identity, my_new_successor,
+                                                new_trail,
+                                                new_trail_length,
+                                                new_finger_trail_id, target_friend);
+    }
+    return GNUNET_OK;
+  }
+
+  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 (destination_peer,
+                                               vsrm->source_successor,
+                                               my_new_successor, trail_id,
+                                               new_trail,
+                                               new_trail_length,
+                                               trail_direction, target_friend);
+  return GNUNET_OK;
+}
+
+
+/*
+ * 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)
+{
+  struct PeerNotifyNewSuccessorMessage *nsm;
+  struct GNUNET_PeerIdentity *trail;
+  struct GNUNET_PeerIdentity source;
+  struct GNUNET_PeerIdentity destination;
+  struct FriendInfo *target_friend;
+  struct GNUNET_HashCode trail_id;
+  unsigned int my_index;
+  struct GNUNET_PeerIdentity next_hop;
+  size_t msize;
+  uint32_t trail_length;
+
+  msize = ntohs (message->size);
+  if (msize != sizeof (struct PeerNotifyNewSuccessorMessage))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_YES;
+  }
+
+  nsm = (struct PeerNotifyNewSuccessorMessage *) message;
+  trail_length = ntohl (nsm->trail_length);
+
+  if ((msize < sizeof (struct PeerNotifyNewSuccessorMessage) +
+               trail_length * sizeof (struct GNUNET_PeerIdentity)) ||
+      (trail_length >
+       GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity)))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_YES;
+  }
+
+  trail = (struct GNUNET_PeerIdentity *) &nsm[1];
+  source  = nsm->source_peer;
+  destination = nsm->destination_peer;
+  trail_id = nsm->trail_id;
+
+  if ( 0 == GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &destination))
+  {
+    struct GNUNET_HashCode new_trail_id;
+    struct FingerInfo *my_predecessor;
+
+    my_predecessor =
+            GNUNET_CONTAINER_multihashmap32_get (finger_hashmap,
+                                                 PREDECESSOR_FINGER_ID);
+    /* FIXME: get new_trail_id*/
+
+    if (GNUNET_YES == is_new_entry_correct_predecessor (my_predecessor,
+                                                        source, trail,
+                                                        trail_length))
+    {
+
+      target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                                         peer);
+      GDS_NEIGHBOURS_send_add_trail (my_identity, source, new_trail_id,
+                                     trail, trail_length, target_friend);
+      return GNUNET_OK;
+    }
   }
-  else if (GNUNET_YES == GNUNET_CONTAINER_multipeermap_contains (finger_peermap,
-                                              successor))
+
+  my_index = search_my_index (trail, trail_length);
+  if (GNUNET_SYSERR == my_index)
   {
-    *type = FINGER;
-    memcpy (current_destination, successor, sizeof (struct GNUNET_PeerIdentity));
-    /* get the corresponding finger for succcesor and read the first element from
-     the trail list and return that element. */
-    struct FingerInfo *successor_finger;
-    struct GNUNET_PeerIdentity *next_hop;
-    next_hop = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-    successor_finger = GNUNET_malloc (sizeof (struct FingerInfo));
-    successor_finger = GNUNET_CONTAINER_multipeermap_get (finger_peermap, successor);
-    memcpy (next_hop, &(successor_finger->trail_peer_list[0]), sizeof (struct GNUNET_PeerIdentity));
-    return next_hop;
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
   }
-  return NULL;
+  if (trail_length == my_index)
+    next_hop = destination;
+  else
+    next_hop = trail[my_index + 1];
+  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, destination, trail,
+                                            trail_length,
+                                            trail_id, target_friend);
+  return GNUNET_OK;
 }
 
 
 /**
- * Handle a PeerTrailSetupMessage. 
+ * FIXME: Here you should keep the trail id with you.
+ * 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(void *cls, const struct GNUNET_PeerIdentity *peer,
-                    const struct GNUNET_MessageHeader *message)
+handle_dht_p2p_trail_rejection(void *cls, const struct GNUNET_PeerIdentity *peer,
+                               const struct GNUNET_MessageHeader *message)
 {
-  struct PeerTrailSetupMessage *trail_setup; 
-  struct GNUNET_PeerIdentity *next_hop; 
+  struct PeerTrailRejectionMessage *trail_rejection;
+  unsigned int trail_length;
+  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 finger_map_index;
   size_t msize;
-  uint32_t trail_length;
-  enum current_destination_type peer_type;
-  struct GNUNET_PeerIdentity *trail_peer_list; 
-  uint32_t current_trail_index;
-  struct GNUNET_PeerIdentity *next_peer;
 
-  
-  /* parse and validate message. */
   msize = ntohs (message->size);
-  if (msize < sizeof (struct PeerTrailSetupMessage))
+  if (msize != sizeof (struct PeerTrailRejectionMessage))
   {
     GNUNET_break_op (0);
     return GNUNET_YES;
   }
-  
-  trail_setup = (struct PeerTrailSetupMessage *) message; 
-  trail_length = ntohl (trail_setup->trail_length); 
-  peer_type = ntohl (trail_setup->current_destination_type);
-  trail_peer_list = (struct GNUNET_PeerIdentity *) &trail_setup[1];
-  
-  if ((msize <
-       sizeof (struct PeerTrailSetupMessage) +
-       trail_length * sizeof (struct GNUNET_PeerIdentity)) ||
+
+  trail_rejection = (struct PeerTrailRejectionMessage *) message;
+  trail_length = ntohl (trail_rejection->trail_length);
+
+  if ((msize != sizeof (struct PeerTrailRejectionMessage) +
+               trail_length * sizeof (struct GNUNET_PeerIdentity)) ||
       (trail_length >
        GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity)))
   {
     GNUNET_break_op (0);
-    return GNUNET_YES; /*TODO: Why do we send GNUNET_YES here? */
+    return GNUNET_YES;
   }
-  
-  GNUNET_STATISTICS_update (GDS_stats,
-                            gettext_noop ("# TRAIL SETUP requests received"), 1,
-                            GNUNET_NO);
-  GNUNET_STATISTICS_update (GDS_stats,
-                            gettext_noop ("# TRAIL SETUP bytes received"), msize,
-                            GNUNET_NO);
-  
-  if(peer_type == FRIEND)
+
+  trail_peer_list = (struct GNUNET_PeerIdentity *)&trail_rejection[1];
+  finger_map_index = ntohl (trail_rejection->finger_map_index);
+  congestion_timeout = trail_rejection->congestion_time;
+  source = trail_rejection->source_peer;
+  trail_id = trail_rejection->trail_id;
+  ultimate_destination_finger_value =
+  trail_rejection->ultimate_destination_finger_identity_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);
+
+  if(0 == (GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &source)))
   {
-    if(0 == (GNUNET_CRYPTO_cmp_peer_identity (&(trail_setup->current_destination),
-                                              &my_identity)))
-    {
-      next_hop = find_successor (&(trail_setup->destination_finger),
-                                 &(trail_setup->current_destination),
-                                 &(peer_type));
-    }
-    else
-      return GNUNET_SYSERR; /*TODO: Should we handle this case differently? */
+    return GNUNET_OK;
   }
-  else if(peer_type == FINGER)
+
+  /* If I am congested then pass this message to peer before me in trail. */
+  if(GNUNET_YES == GDS_ROUTING_threshold_reached())
   {
-    if(0 != (GNUNET_CRYPTO_cmp_peer_identity (&(trail_setup->current_destination),
-                                              &my_identity)))
+    struct GNUNET_PeerIdentity *new_trail;
+    unsigned int new_trail_length;
+
+    if (trail_length == 1)
     {
-      /* I am part of trail. 
-       SUPU: So, I should ask for next hop to reach the current_destination which is the finger
-       for which this packet has been sent. */
-      next_hop = GDS_ROUTING_search (&(trail_setup->source_peer),
-                                     &(trail_setup->current_destination));
-      
-      /*TODO: 
-       call find_successor and compare the two peer ids 
-       and choose whichever is closest to the destination finger. */
-    } 
+      new_trail = NULL;
+      new_trail_length = 0;
+      next_hop = &source;
+    }
     else
     {
-      /* I am the current_destination finger
-       FIXME: Why are we sending current_destination to find_successor. 
-       In this case, is it safe to assume current_Destination = my_identity.
-       I guess we are sending current_destination so that we update it with new
-       current_destination, if could either me, friend or finger.*/
-      next_hop = find_successor (&(trail_setup->destination_finger),
-                                 &(trail_setup->current_destination),&(peer_type));
+      next_hop = &trail_peer_list[trail_length - 2];
+      /* 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));
     }
-  }
-   
-  /* If you are the next hop */
-  if(peer_type == MY_ID)
-  {
-    /* FIXME: Verify if its allowed here to definer peer_list and define it
-       again in the next block below? */
-      struct GNUNET_PeerIdentity *peer_list;
-      peer_list = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity) * (trail_length));
-      memcpy (peer_list, trail_peer_list, trail_length * sizeof (struct GNUNET_PeerIdentity));
-      current_trail_index = trail_length - 2;
-      next_peer = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity)); //FIXME: Do we need to allocate the memory?
-      memcpy (next_peer, &peer_list[current_trail_index], sizeof (struct GNUNET_PeerIdentity));
-      
-      target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_peer);
-     
-      /* FIXME: It does not find a friend. Could be possible error in find_successor 
-       function. Change the logic in find_successor and change it again. */
-   
-      /* FIXME: Here as destination_finger is 64 bit instead of struct
-       GNUNET_PeerIdentity, but you need destination_peer id. If you calling the 
-       function handle_Trail_setup_result from here, it means you are the
-       destination. So, you can send your own identity. */
-      GDS_NEIGHBOURS_handle_trail_setup_result (&(trail_setup->source_peer),
-                                                &(my_identity),
-                                                target_friend, trail_length,
-                                                peer_list,current_trail_index,
-                                                trail_setup->successor_flag, 
-                                                trail_setup->predecessor_flag);
-  
+
+    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop);
+    GDS_NEIGHBOURS_send_trail_rejection (source,
+                                         ultimate_destination_finger_value,
+                                         my_identity, finger_map_index,
+                                         new_trail,new_trail_length,trail_id,
+                                         target_friend, CONGESTION_TIMEOUT);
     return GNUNET_YES;
   }
-  
-  /* Add next_hop to list of peers that trail setup message have traversed so far
-   and increment trail length. */
-  struct GNUNET_PeerIdentity *peer_list;
-  peer_list = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity) * (trail_length + 1));
-  memcpy (peer_list, trail_peer_list, trail_length * sizeof (struct GNUNET_PeerIdentity));
-  memcpy (&peer_list[trail_length], next_hop, sizeof (struct GNUNET_PeerIdentity));
-  trail_length++;
-  
-  target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop);
-  
-  if(peer_type == FINGER)
+
+  /* Look for next_hop to pass the trail setup message */
+  next_hop = find_successor (ultimate_destination_finger_value,
+                             &next_destination,
+                             &new_intermediate_trail_id,
+                             finger_map_index);
+
+  if (0 == (GNUNET_CRYPTO_cmp_peer_identity (next_hop, &my_identity)))/* This means I am the final destination */
   {
-    GDS_ROUTING_add (&(trail_setup->source_peer), 
-                     &(trail_setup->current_destination),
-                     next_hop);
+    if (0 == trail_length)
+      next_peer = source;
+    else
+      next_peer = trail_peer_list[trail_length-1];
+
+    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,
+                                            finger_map_index, trail_id);
   }
-  
-  GDS_NEIGHBOURS_handle_trail_setup (&(trail_setup->source_peer),
-                                     &(trail_setup->destination_finger),
-                                     target_friend,
-                                     trail_setup->trail_length,
-                                     peer_list,trail_setup->successor_flag,
-                                     trail_setup->predecessor_flag);
-return GNUNET_YES;
+  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;
+
+    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,
+                                     finger_map_index, trail_id,
+                                     &new_intermediate_trail_id);
+  }
+  return GNUNET_OK;
+}
+
+
+/*
+ * Core handle for p2p trail tear down 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_trail_compression (void *cls, const struct GNUNET_PeerIdentity *peer,
+                               const struct GNUNET_MessageHeader *message)
+{
+  struct PeerTrailCompressionMessage *trail_compression;
+  struct GNUNET_PeerIdentity *next_hop;
+  struct GNUNET_HashCode trail_id;
+  struct FriendInfo *target_friend;
+  size_t msize;
+
+  msize = ntohs (message->size);
+  if (msize != sizeof (struct PeerTrailCompressionMessage))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_OK;
+  }
+
+  trail_compression = (struct PeerTrailCompressionMessage *) message;
+  trail_id = trail_compression->trail_id;
+
+  if (0 == (GNUNET_CRYPTO_cmp_peer_identity (&(trail_compression->new_first_friend),
+                                             &my_identity)))
+  {
+     if(0 != (GNUNET_CRYPTO_cmp_peer_identity (&(trail_compression->destination_peer),
+                                               &my_identity)))
+     {
+       GDS_ROUTING_update_trail_prev_hop (trail_id,
+                                          trail_compression->source_peer);
+     }
+     return GNUNET_OK;
+  }
+
+  next_hop = GDS_ROUTING_get_next_hop (trail_id, GDS_ROUTING_SRC_TO_DEST);
+  if (NULL == next_hop)
+  {
+    GNUNET_break (0); /*FIXME: How to handle this case.  */
+    return GNUNET_OK;
+  }
+  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_compression->destination_peer,
+                                         trail_id,
+                                         trail_compression->new_first_friend,
+                                         target_friend);
+  return GNUNET_OK;
 }
 
 
 /**
- * Add an entry in finger table. 
- * @param finger Finger to be added to finger table
- * @param peer_list peers this request has traversed so far
- * @param trail_length Numbers of peers 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
  */
-static 
-void finger_table_add(struct GNUNET_PeerIdentity *finger,
-                      const struct GNUNET_PeerIdentity *peer_list,
-                      unsigned int trail_length,
-                      unsigned int successor_flag,
-                      unsigned int predecessor_flag)
-{
-  /*FIXME: okay so there are two fields. one we should remember what finger 
-   identity we were looking for and what successor id we got. */
-  struct FingerInfo *finger_entry;
-  finger_entry = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-  memcpy (&(finger_entry->finger_identity), finger, sizeof (struct GNUNET_PeerIdentity));
-  memcpy (&(finger_entry->trail_peer_list), peer_list, 
-          sizeof (struct GNUNET_PeerIdentity)* trail_length);
-  finger_entry->successor = successor_flag;
-  finger_entry->predecessor = predecessor_flag;
-  
-  /*FIXME: Is it really a good time to call verify successor message. */
-  if (1 == GNUNET_CONTAINER_multipeermap_size (finger_peermap))
-    verify_successor = GNUNET_SCHEDULER_add_now (&send_verify_successor_message, NULL);
+static int
+handle_dht_p2p_trail_teardown (void *cls, const struct GNUNET_PeerIdentity *peer,
+                               const struct GNUNET_MessageHeader *message)
+{
+  struct PeerTrailTearDownMessage *trail_teardown;
+  struct GNUNET_HashCode trail_id;
+  enum GDS_ROUTING_trail_direction trail_direction;
+  size_t msize;
+
+  msize = ntohs (message->size);
+  if (msize != sizeof (struct PeerTrailTearDownMessage))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_OK;
+  }
+
+  trail_teardown = (struct PeerTrailTearDownMessage *) message;
+  trail_direction = ntohl (trail_teardown->trail_direction);
+  trail_id = trail_teardown->TRAIL_ID;
+
+  if (0 != GNUNET_CRYPTO_cmp_peer_identity (&my_identity,
+                                            &trail_teardown->destination_peer))
+  {
+    struct GNUNET_PeerIdentity *next_hop;
+    struct FriendInfo *target_friend;
+
+    next_hop = GDS_ROUTING_get_next_hop (trail_id, trail_direction);
+    if (NULL == next_hop)
+    {
+      GNUNET_break (0);
+      return GNUNET_SYSERR;
+    }
+
+    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap,
+                                                       next_hop);
+    GNUNET_assert (GNUNET_YES == GDS_ROUTING_remove_trail (trail_id));
+    GDS_NEIGHBOURS_send_trail_teardown (trail_teardown->source_peer,
+                                        trail_teardown->destination_peer,
+                                        trail_id, trail_direction,
+                                        target_friend);
+  }
+  return GNUNET_OK;
 }
 
 
 /**
- * Core handle for p2p trail construction result messages.
+ * Fixme: this function is called only in case in notify new successor, the new
+ * successor wants to add the source of the peer as its predecessor. Identify
+ * if there is any other use case where it is required and if yes then adapt the
+ * code for 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_trail_setup_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 PeerTrailSetupResultMessage *trail_result;
+  struct PeerAddTrailMessage *add_trail;
+  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 my_index;
   size_t msize;
-  uint32_t trail_length;
-  const struct GNUNET_PeerIdentity *trail_peer_list;
-  uint32_t current_trail_index;
-  struct GNUNET_PeerIdentity *next_peer;
-  struct FriendInfo *target_friend;
-  
+
   msize = ntohs (message->size);
-  if (msize < sizeof (struct PeerTrailSetupMessage))
+  if (msize != sizeof (struct PeerAddTrailMessage))
   {
     GNUNET_break_op (0);
-    return GNUNET_YES;
+    return GNUNET_OK;
   }
-  
-  trail_result = (struct PeerTrailSetupResultMessage *) message; 
-  trail_length = ntohl (trail_result->trail_length); 
-  current_trail_index = ntohl (trail_result->current_index);
-  trail_peer_list = (struct GNUNET_PeerIdentity *) &trail_result[1];
-  
-  if ((msize <
-       sizeof (struct PeerTrailSetupResultMessage) +
-       trail_length * sizeof (struct GNUNET_PeerIdentity)) ||
+
+  add_trail = (struct PeerAddTrailMessage *) message;
+  trail_length = ntohl (add_trail->trail_length);
+
+  if ((msize < sizeof (struct PeerAddTrailMessage) +
+               trail_length * sizeof (struct GNUNET_PeerIdentity)) ||
       (trail_length >
        GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity)))
   {
     GNUNET_break_op (0);
-    return GNUNET_YES;
+    return GNUNET_OK;
   }
-  if(0 == (GNUNET_CRYPTO_cmp_peer_identity (&(trail_result->current_destination),
-                                            &my_identity)))
+
+  trail = (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 (&my_identity,
+                                            &destination_peer))
   {
-    /* Am I the destination? */
-    if( 0 == (GNUNET_CRYPTO_cmp_peer_identity (&(trail_result->destination_peer),
-                                               &my_identity)))
+    struct FriendInfo *target_friend;
+
+    my_index = search_my_index (trail, trail_length);
+    if (GNUNET_SYSERR == my_index)
     {
-      finger_table_add (&(trail_result->finger), trail_peer_list,trail_length, 
-                       trail_result->successor_flag, trail_result->predecessor_flag);
-      
-      return GNUNET_YES;
+      GNUNET_break_op (0);
+      return GNUNET_SYSERR;
     }
+
+    if (0 == my_index)
+      next_hop = source_peer;
     else
-    {
-      next_peer = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-      current_trail_index = current_trail_index - 1;
-      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_handle_trail_setup_result(&(trail_result->destination_peer),
-                                               &(trail_result->finger),
-                                               target_friend, trail_length,
-                                               trail_peer_list,current_trail_index,
-                                               trail_result->successor_flag,
-                                               trail_result->predecessor_flag);
-      return GNUNET_YES;
-    }
+      next_hop = trail[trail_length - 1];
+
+    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);
   }
-  else
-    return GNUNET_SYSERR;
+  return GNUNET_OK;
 }
 
 
 /**
- * Core handle for p2p trail construction result messages.
+ *FIXME; call send_trail_teardown_message on all the trails of the finger that
+ * you remove. Also you don't need to decerement friend trail count as that
+ * friend is removed. But you can not send trail teardown message as the friend
+ * is disconnected. then you don't have any next_hop. and in case there are
+ * multiple trails. and friend is the first trail then you remove only the trail.
+ * Iterate over finger_hashmap, and remove entries if finger is the disconnected
+ * peer or if disconnected peer is the first friend in the trail to reach the
+ * finger.
  * @param cls closure
- * @param message message
- * @param peer peer identity this notification is about
- * @return GNUNET_OK on success, GNUNET_SYSERR on error
+ * @param key current public key
+ * @param value value in the hash map
+ * @return #GNUNET_YES if we should continue to
+ *         iterate,
+ *         #GNUNET_NO if not.
  */
 static int
-handle_dht_p2p_verify_successor(void *cls, const struct GNUNET_PeerIdentity *peer,
-                                const struct GNUNET_MessageHeader *message)
+remove_matching_finger (void *cls,
+                        uint32_t key,
+                        void *value)
 {
-  /*
-   * In this function you have received the message verify successor,
-   * Now, either you are the destination or just part of the trail.
-   * As we already know the whole path find out the next destination
-   * and pass the packet forward.
-   * If you are the final destination, check who is your predecessor.  
-   * and send your predecessor back to calling function. call GDS_NEIGHBOURS_handle_verify_successor
-   * FIXME: Should we have a different handler function for it. 
-   */
-  struct PeerVerifySuccessorMessage *vsm;
-  size_t msize;
-  unsigned int trail_length;
-  
-  /* Uncomment after initialization
-  struct GNUNET_PeerIdentity *trail_peer_list;
-  unsigned int current_trail_index;
-  struct GNUNET_PeerIdentity *next_peer;
-  struct FriendInfo *target_friend;
-  */  
-   msize = ntohs (message->size);
-  if (msize < sizeof (struct PeerVerifySuccessorMessage))
+  struct FingerInfo *remove_finger = value;
+  const struct GNUNET_PeerIdentity *disconnected_peer = cls;
+  struct TrailList *trail_list;
+  int i;
+
+  if (0 == GNUNET_CRYPTO_cmp_peer_identity (&remove_finger->finger_identity,
+                                            disconnected_peer))
   {
-    GNUNET_break_op (0);
+    GNUNET_assert (GNUNET_YES ==
+                   GNUNET_CONTAINER_multihashmap32_remove (finger_hashmap,
+                                                         key,
+                                                         remove_finger));
+    free_finger (remove_finger);
     return GNUNET_YES;
   }
-  
-  vsm = (struct PeerVerifySuccessorMessage *) message;
-  trail_length = ntohl (vsm->trail_length);
-  //current_trail_index = ntohl (vsm->current_index);
-          
-  //trail_peer_list = (struct GNUNET_PeerIdentity *) &vsm[1];
-  if ((msize <
-       sizeof (struct PeerVerifySuccessorMessage) +
-       trail_length * sizeof (struct GNUNET_PeerIdentity)) ||
-       (trail_length >
-       GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity)))
-       {
-         GNUNET_break_op (0);
-         return GNUNET_YES;
-       }
-  
-  if(0 == (GNUNET_CRYPTO_cmp_peer_identity (&(vsm->successor),
-                                            &my_identity)))
-  {
-    /* You are the successor for which this message has been sent. */
-    /* Search over your finger peer map to find the predecessor and then call
-     GDS_NEIGHBOURS_handle_verify_successor_result with correct parameters. */
-    struct GNUNET_CONTAINER_MultiPeerMapIterator *finger_iter;
-    struct GNUNET_PeerIdentity key_ret;
-    unsigned int finger_index;
-    struct FingerInfo *finger;
-    struct GNUNET_PeerIdentity *destination_peer;
-    
-    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< remove_finger->trails_count; i++)
+  {
+    trail_list = &remove_finger->trail_list[i];
+    if (0 == GNUNET_CRYPTO_cmp_peer_identity (&trail_list->trail_head->peer,
+                                                disconnected_peer))
     {
-      /* FIXME: I don't think we are actually iterating.
-      Read about how to iterate over the multi peer map. */
-      if(GNUNET_YES == GNUNET_CONTAINER_multipeermap_iterator_next(finger_iter,&key_ret,(const void **)&finger)) 
-      {
-       if(1 == finger->predecessor)
-        break; /* FIXME: Do I come out of inner if or outer for */
-      }
+      GNUNET_assert (GNUNET_YES ==
+                     GNUNET_CONTAINER_multihashmap32_remove (finger_hashmap,
+                                                           key,
+                                                           remove_finger));
+       free_finger (remove_finger);
     }
-    
-    destination_peer = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
-    memcpy (destination_peer, &(vsm->source_peer), sizeof (struct GNUNET_PeerIdentity));
-    
-    /*SUPU: Initialize all the fields. */
-    /* FIXME: Initialize all the parameters of this function.
-     Also, target_friend in this case is the peer id which is last in the trail.
-     check if destination peer is in peer list or not. To check you will have to
-     check the trail_setup and how we are adding the peer in there. */
-    /* FIXME: Uncomment after initializing the fields
-     * GDS_NEIGHBOURS_handle_verify_successor_result (destination_peer,
-                                                   &(my_identity),
-                                                   &(finger->finger_identity),
-                                                   target_friend,
-                                                   trail_peer_list,
-                                                   trail_length,
-                                                   current_trail_index); */
-  }
-  else
-  {
-    /* FIXME: Initialize all the parameters to 
-     * this function. Read the element at current_trail_index + 1
-     and call GDS_NEIGHBOURS_handle_verify_successor with correct parameters. */
-    /* FIXME: Uncomment after initializing the fields. 
-     * GDS_NEIGUBOURS_handle_verify_successor(&(vsm->source_peer),
-                                           &(vsm->successor),
-                                           target_friend,
-                                           trail_peer_list,
-                                           trail_length,
-                                           current_trail_index); */
   }
+
   return GNUNET_YES;
 }
 
 
 /**
- * Core handle for p2p trail construction result 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_notify_new_successor(void *cls, const struct GNUNET_PeerIdentity *peer,
-                                    const struct GNUNET_MessageHeader *message)
+static void
+handle_core_disconnect (void *cls,
+                                         const struct GNUNET_PeerIdentity *peer)
 {
-  /*
-   * So, if you are the destination you should update your
-   * predecessor field with peer id of source peer of this message.
-   * If you are not the destination peer, then just check your routing
-   * table and pass on the message. 
-   */
-  return GNUNET_YES;
+  struct FriendInfo *remove_friend;
+
+  if (0 == memcmp (&my_identity, peer, sizeof (struct GNUNET_PeerIdentity)))
+    return;
+
+  remove_friend =
+      GNUNET_CONTAINER_multipeermap_get (friend_peermap, peer);
+
+  if (NULL == remove_friend)
+  {
+    GNUNET_break (0);
+    return;
+  }
+
+  GNUNET_assert (GNUNET_SYSERR !=
+                 GNUNET_CONTAINER_multihashmap32_iterate (finger_hashmap,
+                                                          &remove_matching_finger,
+                                                          (void *)peer));
+  GDS_ROUTING_remove_trail_by_peer (peer);
+  GNUNET_assert (GNUNET_YES ==
+                 GNUNET_CONTAINER_multipeermap_remove (friend_peermap,
+                                                       peer,
+                                                       remove_friend));
+
+  if (0 != GNUNET_CONTAINER_multipeermap_size (friend_peermap))
+    return;
+
+  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);
 }
 
 
 /**
- * Core handle for p2p trail construction result messages.
+ * Method called whenever a peer connects.
+ *
  * @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_identity peer identity this notification is about
  */
-static int
-handle_dht_p2p_verify_successor_result(void *cls, const struct GNUNET_PeerIdentity *peer,
-                                       const struct GNUNET_MessageHeader *message)
+static void
+handle_core_connect (void *cls, const struct GNUNET_PeerIdentity *peer_identity)
 {
-  /*
-   * In this function you have received the message verify successor result,
-   If you are not the destination, just pass this message forward
-   * if you are destination,
-   * then check if immediate predecessor of this peer is you or someone else.
-   * If its you, then don't do anything.
-   * If its some one else, then call notify method to let your new successor
-   * know that you are its predecessor. 
-   */
-  return GNUNET_YES;
+  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 (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;
 }
 
 
 /**
  * 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_get, GNUNET_MESSAGE_TYPE_DHT_P2P_GET, 0},
     {&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_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_notify_new_successor, GNUNET_MESSAGE_TYPE_DHT_P2P_NOTIFY_NEW_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_compression, GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_COMPRESSION, 0},
+    {&handle_dht_p2p_trail_teardown, GNUNET_MESSAGE_TYPE_DHT_P2P_TRAIL_TEARDOWN, 0},
+    {&handle_dht_p2p_add_trail, GNUNET_MESSAGE_TYPE_DHT_P2P_ADD_TRAIL, 0},
     {NULL, 0, 0}
   };
 
-  /*TODO: What is ATS? Why do we need it? */
-  atsAPI = GNUNET_ATS_performance_init (GDS_cfg, NULL, NULL);
   core_api =
     GNUNET_CORE_connect (GDS_cfg, NULL, &core_init, &handle_core_connect,
-                           &handle_core_disconnect, NULL, GNUNET_NO, NULL,
-                           GNUNET_NO, core_handlers);
-  if (core_api == NULL)
+                         &handle_core_disconnect, NULL, GNUNET_NO, NULL,
+                         GNUNET_NO, core_handlers);
+  if (NULL == core_api)
     return GNUNET_SYSERR;
 
   friend_peermap = GNUNET_CONTAINER_multipeermap_create (256, GNUNET_NO);
-  finger_peermap = GNUNET_CONTAINER_multipeermap_create (MAX_FINGERS, GNUNET_NO); 
+  finger_hashmap = GNUNET_CONTAINER_multihashmap32_create (MAX_FINGERS * 4/3);
+
   return GNUNET_OK;
 }
 
-
 /**
  * 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_ATS_performance_done (atsAPI);
-  atsAPI = NULL;
 
-  /* FIXME: Once handle_core_disconnect is implemented, both below assertion should not
-   fail. */
   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;
+  GNUNET_assert (0 == GNUNET_CONTAINER_multihashmap32_size (finger_hashmap));
+  GNUNET_CONTAINER_multihashmap32_destroy (finger_hashmap);
+  finger_hashmap = 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;
   }
-  
-  /* FIXME: fix_fingers will also be a task like this.
-     Add it later. */
-  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 */
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