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[oweals/gnunet.git] / src / dht / gnunet-service-xdht_neighbours.c

/*
     This file is part of GNUnet.
     (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
     by the Free Software Foundation; either version 3, or (at your
     option) any later version.

     GNUnet is distributed in the hope that it will be useful, but
     WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     General Public License for more details.

     You should have received a copy of the GNU General Public License
     along with GNUnet; see the file COPYING.  If not, write to the
     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
     Boston, MA 02111-1307, USA.
*/

/**
 * @file dht/gnunet-service-xdht_neighbours.c
 * @brief GNUnet DHT service's finger and friend table management code
 * @author Supriti Singh
 */

#include "platform.h"
#include "gnunet_util_lib.h"
#include "gnunet_block_lib.h"
#include "gnunet_hello_lib.h"
#include "gnunet_constants.h"
#include "gnunet_protocols.h"
#include "gnunet_ats_service.h"
#include "gnunet_core_service.h"
#include "gnunet_datacache_lib.h"
#include "gnunet_transport_service.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_neighbours.h"
#include "gnunet-service-xdht_routing.h"
#include <fenv.h>
#include "dht.h"

/**
 * TODO:
 * 1. In X-Vine paper, there is no policy defined for replicating the data to
 * recover in case of peer failure. We can do it in Chord way. In R5N, the key
 * is hashed and then data is stored according to the key value generated after
 * hashing.
 */


/**
 * FIXME: URGENT
 * We should have a message type like notify successor result. only when 
 * this message is being recvied by the new successor. we should schedule
 * another round of verify successor. 
 */
#define DEBUG(...)                                           \
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, __VA_ARGS__)

/**
 * Maximum possible fingers (including predecessor) of a peer
 */
#define MAX_FINGERS 65

/**
 * Maximum allowed number of pending messages per friend peer.
 */
#define MAXIMUM_PENDING_PER_FRIEND 64

/**
 * How long to wait before sending another find finger trail request
 */
#define DHT_FIND_FINGER_TRAIL_INTERVAL GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MILLISECONDS, 500)

/**
 * How long to wait before sending another verify successor message.
 */
#define DHT_SEND_VERIFY_SUCCESSOR_INTERVAL GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MILLISECONDS, 60)

/**
 * How long at most to wait for transmission of a request to a friend ?
 */
#define PENDING_MESSAGE_TIMEOUT GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MINUTES, 2)

/**
 * Duration for which I may remain congested.
 * Note: Its a static value. In future, a peer may do some analysis and calculate
 * congestion_timeout based on 'some' parameters.
 */
#define CONGESTION_TIMEOUT GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MINUTES, 2)

/**
 * Maximum number of trails allowed to go through a friend.
 */
#define TRAILS_THROUGH_FRIEND_THRESHOLD 64

/**
 * Maximum number of trails stored per finger.
 */
#define MAXIMUM_TRAILS_PER_FINGER 1

/**
 * Finger map index for predecessor entry in finger table.
 */
#define PREDECESSOR_FINGER_ID 64

/**
 * Wrap around in peer identity circle.
 */
#define PEER_IDENTITES_WRAP_AROUND pow(2, 64) - 1

/**
 * FIXME: Its use only at 3 places check if you can remove it.
 * To check if a finger is predecessor or not.
 */
enum GDS_NEIGHBOURS_finger_type
{
  GDS_FINGER_TYPE_PREDECESSOR = 1,
  GDS_FINGER_TYPE_NON_PREDECESSOR = 0
};

GNUNET_NETWORK_STRUCT_BEGIN

/**
 * P2P PUT message
 */
struct PeerPutMessage
{
  /**
   * Type: #GNUNET_MESSAGE_TYPE_XDHT_P2P_PUT
   */
  struct GNUNET_MessageHeader header;

  /**
   * Processing options
   */
  uint32_t options GNUNET_PACKED;

  /**
   * Content type.
   */
  uint32_t block_type GNUNET_PACKED;

  /**
   * Hop count
   */
  uint32_t hop_count GNUNET_PACKED;

  /**
   * Replication level for this message
   * In the current implementation, this value is not used.
   */
  uint32_t desired_replication_level GNUNET_PACKED;

  /**
   * Length of the PUT path that follows (if tracked).
   */
  uint32_t put_path_length GNUNET_PACKED;

  /**
   * Best known destination (could be my friend or finger) which should
   * get this message next.
   */
  struct GNUNET_PeerIdentity best_known_destination;

  /**
   * In case best_known_destination is a finger, then trail to reach
   * to that finger. Else its default value is 0.
   */
  struct GNUNET_HashCode intermediate_trail_id;

  /**
   * When does the content expire?
   */
  struct GNUNET_TIME_AbsoluteNBO expiration_time;

  /**
   * The key to store the value under.
   */
  struct GNUNET_HashCode key GNUNET_PACKED;

  /* put path (if tracked) */

  /* Payload */

};

/**
 * P2P GET message
 */
struct PeerGetMessage
{
  /**
   * Type: #GNUNET_MESSAGE_TYPE_XDHT_P2P_GET
   */
  struct GNUNET_MessageHeader header;

  /**
   * Processing options
   */
  uint32_t options GNUNET_PACKED;

  /**
   * Desired content type.
   */
  uint32_t block_type GNUNET_PACKED;

  /**
   * Hop count
   */
  uint32_t hop_count GNUNET_PACKED;

  /**
   * Desired replication level for this request.
   * In the current implementation, this value is not used.
   */
  uint32_t desired_replication_level GNUNET_PACKED;

  /**
   * Total number of peers in get path.
   */
  unsigned int get_path_length;

  /**
   * Best known destination (could be my friend or finger) which should
   * get this message next.
   */
  struct GNUNET_PeerIdentity best_known_destination;

  /**
   * In case best_known_destination is a finger, then trail to reach
   * to that finger. Else its default value is 0.
   */
  struct GNUNET_HashCode intermediate_trail_id;

  /**
   * The key we are looking for.
   */
  struct GNUNET_HashCode key;

  /* Get path. */
  /* struct GNUNET_PeerIdentity[]*/
};

/**
 * P2P Result message
 */
struct PeerGetResultMessage
{
  /**
   * Type: #GNUNET_MESSAGE_TYPE_XDHT_P2P_GET_RESULT
   */
  struct GNUNET_MessageHeader header;

  /**
   * The type for the data.
   */
  uint32_t type GNUNET_PACKED;

  /**
   * Number of peers recorded in the outgoing path from source to the
   * stored location of this message.
   */
  uint32_t put_path_length GNUNET_PACKED;

  /**
   * Length of the GET path that follows (if tracked).
   */
  uint32_t get_path_length GNUNET_PACKED;

  /**
   * Peer which queried for get and should get the result.
   */
  struct GNUNET_PeerIdentity querying_peer;

  /**
   * When does the content expire?
   */
  struct GNUNET_TIME_Absolute expiration_time;

  /**
   * The key of the corresponding GET request.
   */
  struct GNUNET_HashCode key;

  /* put path (if tracked) */

  /* get path (if tracked) */

  /* Payload */

};

/**
 * P2P Trail setup message
 */
struct PeerTrailSetupMessage
{
  /**
   * Type: #GNUNET_MESSAGE_TYPE_XDHT_P2P_TRAIL_SETUP
   */
  struct GNUNET_MessageHeader header;

  /**
   * Is source_peer trying to setup the trail to a predecessor or any finger.
   */
  uint32_t is_predecessor;

  /**
   * Peer closest to this value will be our finger.
   */
  uint64_t final_destination_finger_value;

  /**
   * Source peer which wants to setup the trail to one of its finger.
   */
  struct GNUNET_PeerIdentity source_peer;

  /**
   * Best known destination (could be my friend or finger) which should
   * get this message next.
   *
   * FIXME: this could be removed if we include trail_source / trail_dest
   * in the routing table. This way we save 32 bytes of bandwidth by using
   * extra 8 bytes of memory (2 * sizeof (GNUNET_PEER_ID))
   */
  struct GNUNET_PeerIdentity best_known_destination;

  /**
   * In case best_known_destination is a finger, then trail id of trail to
   * reach to this finger.
   */
  struct GNUNET_HashCode intermediate_trail_id;

  /**
   * Trail id for trail which we are trying to setup.
   */
  struct GNUNET_HashCode trail_id;

  /* List of peers which are part of trail setup so far.
   * Trail does NOT include source_peer and peer which will be closest to
   * ultimate_destination_finger_value.
   * struct GNUNET_PeerIdentity trail[]
   */
};

/**
  * P2P Trail Setup Result message
 */
struct PeerTrailSetupResultMessage
{

  /**
   * Type: #GNUNET_MESSAGE_TYPE_XDHT_P2P_TRAIL_SETUP_RESULT
   */
  struct GNUNET_MessageHeader header;

  /**
   * Finger to which we have found the path.
   */
  struct GNUNET_PeerIdentity finger_identity;

  /**
   * Peer which started trail_setup to find trail to finger_identity
   */
  struct GNUNET_PeerIdentity querying_peer;

  /**
   * Is the trail setup to querying_peer's predecessor or finger?
   */
  uint32_t is_predecessor;

  /**
   * Value to which finger_identity is the closest peer.
   */
  uint64_t ulitmate_destination_finger_value;

  /**
   * Identifier of the trail from querying peer to finger_identity, NOT
   * including both endpoints.
   */
  struct GNUNET_HashCode trail_id;

  /* List of peers which are part of the trail from querying peer to
   * finger_identity, NOT including both endpoints.
   * struct GNUNET_PeerIdentity trail[]
   */
};

/**
 * P2P Verify Successor Message.
 */
struct PeerVerifySuccessorMessage
{
  /**
   * Type: #GNUNET_MESSAGE_TYPE_XDHT_P2P_VERIFY_SUCCESSOR
   */
  struct GNUNET_MessageHeader header;

  /**
   * Peer which wants to verify its successor.
   */
  struct GNUNET_PeerIdentity source_peer;

  /**
   * Source Peer's current successor.
   */
  struct GNUNET_PeerIdentity successor;

  /**
   * Identifier of trail to reach from source_peer to successor.
   */
  struct GNUNET_HashCode trail_id;

  /* List of the peers which are part of trail to reach  from source_peer
   * to successor, NOT including them
   * struct GNUNET_PeerIdentity trail[]
   */
};

/**
 * P2P Verify Successor Result Message
 */
struct PeerVerifySuccessorResultMessage
{
  /**
   * Type: #GNUNET_MESSAGE_TYPE_XDHT_P2P_VERIFY_SUCCESSOR_RESULT
   */
  struct GNUNET_MessageHeader header;

  /**
   * Peer which sent the request to verify its successor.
   */
  struct GNUNET_PeerIdentity querying_peer;

  /**
   * Successor to which PeerVerifySuccessorMessage was sent.
   */
  struct GNUNET_PeerIdentity current_successor;

  /**
   * Current Predecessor of source_successor. It can be same as querying peer
   * or different. In case it is different then it can be querying_peer's
   * probable successor.
   */
  struct GNUNET_PeerIdentity probable_successor;

  /**
   * Trail identifier of trail from querying_peer to current_successor.
   */
  struct GNUNET_HashCode trail_id;

  /**
   * Direction in which we are looking at the trail.
   */
  uint32_t trail_direction;

  /* In case probable_successor != querying_peer, then trail to reach from
   * querying_peer to probable_successor, NOT including end points.
   * struct GNUNET_PeerIdentity trail[]
   */
};

/**
 * P2P Notify New Successor Message.
 */
struct PeerNotifyNewSuccessorMessage
{
  /**
   * Type: #GNUNET_MESSAGE_TYPE_XDHT_P2P_NOTIFY_NEW_SUCCESSOR
   */
  struct GNUNET_MessageHeader header;

  /**
   * Peer which wants to notify its new successor.
   */
  struct GNUNET_PeerIdentity source_peer;

  /**
   * New successor of source_peer.
   */
  struct GNUNET_PeerIdentity new_successor;

  /**
   * Unique identifier of the trail from source_peer to new_successor,
   * NOT including the endpoints.
   */
  struct GNUNET_HashCode trail_id;

  /* List of peers in trail from source_peer to new_successor,
   * NOT including the endpoints.
   * struct GNUNET_PeerIdentity trail[]
   */
};


/**
 * P2P Trail Tear Down message.
 */
struct PeerTrailTearDownMessage
{
  /**
   * Type: #GNUNET_MESSAGE_TYPE_XDHT_P2P_TRAIL_TEARDOWN
   */
  struct GNUNET_MessageHeader header;

  /**
   * Unique identifier of the trail.
   */
  struct GNUNET_HashCode trail_id;

  /**
   * Direction of trail.
   */
  uint32_t trail_direction;
};


/**
 * P2P Trail Rejection Message.
 */
struct PeerTrailRejectionMessage
{
  /**
   * Type: #GNUNET_MESSAGE_TYPE_XDHT_P2P_TRAIL_SETUP_REJECTION
   */
  struct GNUNET_MessageHeader header;

  /**
   * Peer which wants to set up the trail.
   */
  struct GNUNET_PeerIdentity source_peer;

  /**
   * Peer which sent trail rejection message as it it congested.
   */
  struct GNUNET_PeerIdentity congested_peer;

  /**
   * Peer identity closest to this value will be finger of
   * source_peer.
   */
  uint64_t ultimate_destination_finger_value;

  /**
   * Is source_peer trying to setup the trail to its predecessor or finger.
   */
  uint32_t is_predecessor;

  /**
   * Identifier for the trail that source peer is trying to setup.
   */
  struct GNUNET_HashCode trail_id;

  /**
   * Relative time for which congested_peer will remain congested.
   */
  struct GNUNET_TIME_Relative congestion_time;

  /* Trail_list from source_peer to peer which sent the message for trail setup
   * to congested peer. This trail does NOT include source_peer.
   struct GNUNET_PeerIdnetity trail[]*/
};

/**
 * P2P Add Trail Message.
 */
struct PeerAddTrailMessage
{
  /**
   * Type: #GNUNET_MESSAGE_TYPE_XDHT_P2P_ADD_TRAIL
   */
  struct GNUNET_MessageHeader header;

  /**
   * Source of the routing trail.
   */
  struct GNUNET_PeerIdentity source_peer;

  /**
   * Destination of the routing trail.
   */
  struct GNUNET_PeerIdentity destination_peer;

  /**
   * Unique identifier of the trail from source_peer to destination_peer,
   * NOT including the endpoints.
   */
  struct GNUNET_HashCode trail_id;

  /* Trail from source peer to destination peer, NOT including them.
   * struct GNUNET_PeerIdentity trail[]
   */
};

GNUNET_NETWORK_STRUCT_END

/**
 * Linked list of messages to send to a particular other peer.
 */
struct P2PPendingMessage
{
  /**
   * Pointer to next item in the list
   */
  struct P2PPendingMessage *next;

  /**
   * Pointer to previous item in the list
   */
  struct P2PPendingMessage *prev;

  /**
   * Message importance level.  FIXME: used? useful?
   */
  unsigned int importance;

  /**
   * When does this message time out?
   */
  struct GNUNET_TIME_Absolute timeout;

  /**
   * Actual message to be sent, allocated at the end of the struct:
   * // msg = (cast) &pm[1];
   * // memcpy (&pm[1], data, len);
   */
  const struct GNUNET_MessageHeader *msg;

};

/**
 *  Entry in friend_peermap.
 */
struct FriendInfo
{
  /**
   * Friend Identity
   */
  struct GNUNET_PeerIdentity id;

  /**
   * Number of trails for which this friend is the first hop or if the friend
   * is finger.
   */
  unsigned int trails_count;

  /**
   * Count of outstanding messages for this friend.
   */
  unsigned int pending_count;

  /**
   * In case not 0, then amount of time for which this friend is congested.
   */
  struct GNUNET_TIME_Absolute congestion_timestamp;

  
  // TODO : Change name of head and tail to pending_messages_list_head and so.
  /**
   * Head of pending messages to be sent to this friend.
   */
  struct P2PPendingMessage *head;

  /**
   * Tail of pending messages to be sent to this friend.
   */
  struct P2PPendingMessage *tail;

  /**
   * Core handle for sending messages to this friend.
   */
  struct GNUNET_CORE_TransmitHandle *th;

};

/**
 * An individual element of the trail to reach to a finger.
 */
struct Trail_Element
{
  /**
    * Pointer to next item in the list
    */
  struct Trail_Element *next;

  /**
    * Pointer to prev item in the list
    */
  struct Trail_Element *prev;

  /**
   * An element in this trail.
   */
  struct GNUNET_PeerIdentity peer;
};

/**
 * Information about an individual trail.
 */
struct Trail
{
  /**
   * Head of trail.
   */
  struct Trail_Element *trail_head;

  /**
   * Tail of trail.
   */
  struct Trail_Element *trail_tail;

  /**
   * Unique identifier of this trail.
   */
  struct GNUNET_HashCode trail_id;

  /**
   * Length of trail pointed
   */
  unsigned int trail_length;

  /**
   * Is there a valid trail entry.
   */
  unsigned int is_present;
};

/**
 * An entry in finger_table
 */
struct FingerInfo
{
  /**
   * Finger identity.
   */
  struct GNUNET_PeerIdentity finger_identity;

  /**
   * Is any finger stored at this finger index.
   */
  unsigned int is_present;

  /**
   * Index in finger peer map
   */
  uint32_t finger_table_index;

  /**
   * Number of trails setup so far for this finger.
   * Should not cross MAXIMUM_TRAILS_PER_FINGER.
   */
  uint32_t trails_count;

  /**
   * Array of trails to reach to this finger.
   */
  struct Trail trail_list[MAXIMUM_TRAILS_PER_FINGER];
};


/**
 * Stores information about the peer which is closest to destination_finger_value.
 * 'closest' can be either successor or predecessor depending on is_predecessor
 * flag.
 */
struct Closest_Peer
{
  /**
   * Destination finger value.
   */
  uint64_t destination_finger_value;

  /**
   * Is finger_value a predecessor or any other finger.
   */
  unsigned int is_predecessor;

  /**
   * Trail id to reach to peer.
   * In case peer is my identity or friend, it is set to 0.
   */
  struct GNUNET_HashCode trail_id;

  /**
   * Next destination. In case of friend and my_identity , it is same as next_hop
   * In case of finger it is finger identity.
   */
  struct GNUNET_PeerIdentity best_known_destination;

  /**
   * In case best_known_destination is a finger, then first friend in the trail
   * to reach to it. In other case, same as best_known_destination.
   */
  struct GNUNET_PeerIdentity next_hop;
  
  /**
   * In case finger is the next hop, it contains a valid finger table index
   * at which the finger is stored. Else, It contains 65, which is out of range
   * of finger table index. 
   */
  unsigned int finger_table_index;
};


/**
 * 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;

/**
 * Task that sends verify successor message. This task is started when we get
 * our successor for the first time.
 */
static GNUNET_SCHEDULER_TaskIdentifier send_verify_successor_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;

/**
 * Array of all the fingers.
 */
static struct FingerInfo finger_table [MAX_FINGERS];

/**
 * Handle to CORE.
 */
static struct GNUNET_CORE_Handle *core_api;

/**
 * Handle for the statistics service.
 */
//extern struct GNUNET_STATISTICS_Handle *GDS_stats;

/**
 * The current finger index that we have want to find trail to. We start the
 * search with value = 0, i.e. successor  and then go to PREDCESSOR_FINGER_ID
 * and decrement it. For any index 63 <= index < 0, if finger is same as successor,
 * we reset this index to 0.
 */
static unsigned int current_search_finger_index;

/**
 * Should we store our topology predecessor and successor IDs into statistics?
 */
unsigned int track_topology;

/**
 * Should I be a malicious peer and drop the PUT/GET packets? 
 * if 0 then NOT malicious.
 */
unsigned int act_malicious;

/**
 * Time duration to schedule find finger trail task. 
 */
static struct GNUNET_TIME_Relative find_finger_trail_task_next_send_time;

/**
 * Time duration to schedule verify successor task.  
 */
static struct GNUNET_TIME_Relative verify_successor_next_send_time;

/**
 * Called when core is ready to send a message we asked for
 * out to the destination.
 *
 * @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
 */
static size_t
core_transmit_notify (void *cls, size_t size, void *buf)
{
  struct FriendInfo *peer = cls;
  char *cbuf = 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_free (pending);
  }
  if (NULL == pending)
  {
    /* no messages pending */
    return 0;
  }
  if (NULL == buf)
  {
    peer->th =
        GNUNET_CORE_notify_transmit_ready (core_api, GNUNET_NO,
                                           GNUNET_CORE_PRIO_BEST_EFFORT,
                                           GNUNET_TIME_absolute_get_remaining
                                           (pending->timeout), &peer->id,
                                           ntohs (pending->msg->size),
                                           &core_transmit_notify, peer);
    GNUNET_break (NULL != peer->th);
    return 0;
  }
  off = 0;
  while ((NULL != (pending = peer->head)) &&
         (size - off >= (msize = ntohs (pending->msg->size))))
  {
    GNUNET_STATISTICS_update (GDS_stats,
                              gettext_noop
                              ("# Bytes transmitted to other peers"), msize,
                              GNUNET_NO);
    memcpy (&cbuf[off], pending->msg, msize);
    off += msize;
    peer->pending_count--;
    GNUNET_CONTAINER_DLL_remove (peer->head, peer->tail, pending);
    GNUNET_free (pending);
  }
  if (peer->head != NULL)
  {
    peer->th =
        GNUNET_CORE_notify_transmit_ready (core_api, GNUNET_NO,
                                           GNUNET_CORE_PRIO_BEST_EFFORT,
                                           GNUNET_TIME_absolute_get_remaining
                                           (pending->timeout), &peer->id, msize,
                                           &core_transmit_notify, peer);
    GNUNET_break (NULL != peer->th);
  }
  return off;
}


/**
 * Transmit all messages in the friend's message queue.
 *
 * @param peer message queue to process
 */
static void
process_friend_queue (struct FriendInfo *peer)
{
  struct P2PPendingMessage *pending;

  if (NULL == (pending = peer->head))
  {
    return;
  }
  if (NULL != peer->th)
  {
    return;
  }
 
  peer->th =
      GNUNET_CORE_notify_transmit_ready (core_api, GNUNET_NO,
                                         pending->importance,
                                         GNUNET_TIME_absolute_get_remaining
                                         (pending->timeout), &peer->id,
                                         ntohs (pending->msg->size),
                                         &core_transmit_notify, peer);
  GNUNET_break (NULL != peer->th);
}


#if ENABLE_MALICIOUS
/**
 * Set the ENABLE_MALICIOUS value to malicious.
 * @param malicious
 */
void 
GDS_NEIGHBOURS_act_malicious (unsigned int malicious)
{
  act_malicious = malicious;
}
#endif

/**
 * Construct a trail setup message and forward it to target_friend
 * @param source_peer Peer which wants to setup the trail
 * @param ultimate_destination_finger_value Peer identity closest to this value
 *                                          will be finger to @a source_peer
 * @param best_known_destination Best known destination (could be finger or friend)
 *                               which should get this message. In case it is
 *                               friend, then it is same as target_friend
 * @param target_friend Friend to which message is forwarded now.
 * @param trail_length Total number of peers in trail setup so far.
 * @param trail_peer_list Trail setup so far
 * @param is_predecessor Is @a source_peer looking for trail to a predecessor or not.
 * @param trail_id Unique identifier for the trail we are trying to setup.
 * @param intermediate_trail_id Trail id of intermediate trail to reach to
 *                              best_known_destination when its a finger. If not
 *                              used then set to 0.
 */
void
GDS_NEIGHBOURS_send_trail_setup (struct GNUNET_PeerIdentity source_peer,
                                 uint64_t ultimate_destination_finger_value,
                                 struct GNUNET_PeerIdentity best_known_destination,
                                 struct FriendInfo *target_friend,
                                 unsigned int trail_length,
                                 const struct GNUNET_PeerIdentity *trail_peer_list,
                                 unsigned int is_predecessor,
                                 struct GNUNET_HashCode trail_id,
                                 struct GNUNET_HashCode intermediate_trail_id)
{
  struct P2PPendingMessage *pending;
  struct PeerTrailSetupMessage *tsm;
  struct GNUNET_PeerIdentity *peer_list;
  size_t msize;

  msize = sizeof (struct PeerTrailSetupMessage) +
          (trail_length * sizeof (struct GNUNET_PeerIdentity));

  if (msize >= GNUNET_CONSTANTS_MAX_ENCRYPTED_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->timeout = GNUNET_TIME_relative_to_absolute (PENDING_MESSAGE_TIMEOUT);
  tsm = (struct PeerTrailSetupMessage *) &pending[1];
  pending->msg = &(tsm->header);
  tsm->header.size = htons (msize);
  tsm->header.type = htons (GNUNET_MESSAGE_TYPE_XDHT_P2P_TRAIL_SETUP);
  tsm->final_destination_finger_value = GNUNET_htonll (ultimate_destination_finger_value);
  tsm->source_peer = source_peer;
  tsm->best_known_destination = best_known_destination;
  tsm->is_predecessor = htonl (is_predecessor);
  tsm->trail_id = trail_id;
  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);
}


/**
 * Construct a trail setup result message and forward it to target friend.
 * @param querying_peer Peer which sent the trail setup request and should get
 *                      the result back.
 * @param Finger Peer to which the trail has been setup to.
 * @param target_friend Friend to which this message should be forwarded.
 * @param trail_length Numbers of peers in the trail.
 * @param trail_peer_list Peers which are part of the trail from
 *                        querying_peer to Finger, NOT including them.
 * @param is_predecessor Is @a Finger predecessor to @a querying_peer ?
 * @param ultimate_destination_finger_value Value to which @a finger is the closest
 *                                          peer.
 * @param trail_id Unique identifier of the trail.
 */
void
GDS_NEIGHBOURS_send_trail_setup_result (struct GNUNET_PeerIdentity querying_peer,
                                        struct GNUNET_PeerIdentity finger,
                                        struct FriendInfo *target_friend,
                                        unsigned int trail_length,
                                        const struct GNUNET_PeerIdentity *trail_peer_list,
                                        unsigned int is_predecessor,
                                        uint64_t ultimate_destination_finger_value,
                                        struct GNUNET_HashCode trail_id)
{
  struct P2PPendingMessage *pending;
  struct PeerTrailSetupResultMessage *tsrm;
  struct GNUNET_PeerIdentity *peer_list;
  size_t msize;

  msize = sizeof (struct PeerTrailSetupResultMessage) +
          (trail_length * sizeof (struct GNUNET_PeerIdentity));

  if (msize >= GNUNET_CONSTANTS_MAX_ENCRYPTED_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 (PENDING_MESSAGE_TIMEOUT); 
  tsrm = (struct PeerTrailSetupResultMessage *) &pending[1];
  pending->msg = &tsrm->header;
  tsrm->header.size = htons (msize);
  tsrm->header.type = htons (GNUNET_MESSAGE_TYPE_XDHT_P2P_TRAIL_SETUP_RESULT);
  tsrm->querying_peer = querying_peer;
  tsrm->finger_identity = finger;
  tsrm->is_predecessor = htonl (is_predecessor);
  tsrm->trail_id = trail_id;
  tsrm->ulitmate_destination_finger_value =
          GNUNET_htonll (ultimate_destination_finger_value);
  peer_list = (struct GNUNET_PeerIdentity *) &tsrm[1];
  memcpy (peer_list, trail_peer_list, trail_length * sizeof (struct GNUNET_PeerIdentity));
  
  /* 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 target friend
 * @param source_peer Peer which is trying to setup the trail.
 * @param ultimate_destination_finger_value Peer closest to this value will be
 *                                          @a source_peer's finger
 * @param congested_peer Peer which sent this message as it is congested.
 * @param is_predecessor Is source_peer looking for trail to a predecessor or not.
 * @param trail_peer_list Trails seen so far in trail setup before getting rejected
 *                        by congested_peer. This does NOT include @a source_peer
 *                        and congested_peer.
 * @param trail_length Total number of peers in trail_peer_list, NOT including
 *                     @a source_peer and @a congested_peer
 * @param trail_id Unique identifier of this trail.
 * @param congestion_timeout Duration given by congested peer as an estimate of
 *                           how long it may remain congested.
 */
void
GDS_NEIGHBOURS_send_trail_rejection (struct GNUNET_PeerIdentity source_peer,
                                     uint64_t ultimate_destination_finger_value,
                                     struct GNUNET_PeerIdentity congested_peer,
                                     unsigned int is_predecessor,
                                     const struct GNUNET_PeerIdentity *trail_peer_list,
                                     unsigned int trail_length,
                                     struct GNUNET_HashCode trail_id,
                                     struct FriendInfo *target_friend,
                                     const struct GNUNET_TIME_Relative congestion_timeout)
{
  struct 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_CONSTANTS_MAX_ENCRYPTED_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 (PENDING_MESSAGE_TIMEOUT);
  trm = (struct PeerTrailRejectionMessage *)&pending[1];
  pending->msg = &trm->header;
  trm->header.size = htons (msize);
  trm->header.type = htons (GNUNET_MESSAGE_TYPE_XDHT_P2P_TRAIL_SETUP_REJECTION);
  trm->source_peer = source_peer;
  trm->congested_peer = congested_peer;
  trm->congestion_time = congestion_timeout;
  trm->is_predecessor = htonl (is_predecessor);
  trm->trail_id = trail_id;
  trm->ultimate_destination_finger_value =
          GNUNET_htonll (ultimate_destination_finger_value);

  peer_list = (struct GNUNET_PeerIdentity *) &trm[1];
  if (trail_length > 0)
  {
    memcpy (peer_list, trail_peer_list, trail_length * sizeof (struct GNUNET_PeerIdentity));
  }

  /* Send the message to chosen friend. */
  GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
  target_friend->pending_count++;
  process_friend_queue (target_friend);
}


/**
 * Construct a verify successor message and forward it to target_friend.
 * @param source_peer Peer which wants to verify its successor.
 * @param successor Peer which is @a source_peer's current successor.
 * @param trail_id Unique Identifier of trail from @a source_peer to @a successor,
 *                 NOT including them.
 * @param trail List of peers which are part of trail to reach from @a source_peer
 *              to @a successor, NOT including them.
 * @param trail_length Total number of peers in @a trail.
 * @param target_friend Next friend to get this message.
 */
void
GDS_NEIGHBOURS_send_verify_successor_message (struct GNUNET_PeerIdentity source_peer,
                                              struct GNUNET_PeerIdentity successor,
                                              struct GNUNET_HashCode trail_id,
                                              struct GNUNET_PeerIdentity *trail,
                                              unsigned int trail_length,
                                              struct FriendInfo *target_friend)
{
  struct PeerVerifySuccessorMessage *vsm;
  struct P2PPendingMessage *pending;
  struct GNUNET_PeerIdentity *peer_list;
  size_t msize;

  msize = sizeof (struct PeerVerifySuccessorMessage) +
         (trail_length * sizeof (struct GNUNET_PeerIdentity));
  
  if (msize >= GNUNET_CONSTANTS_MAX_ENCRYPTED_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 (PENDING_MESSAGE_TIMEOUT);
  vsm = (struct PeerVerifySuccessorMessage *) &pending[1];
  pending->msg = &vsm->header;
  vsm->header.size = htons (msize);
  vsm->header.type = htons (GNUNET_MESSAGE_TYPE_XDHT_P2P_VERIFY_SUCCESSOR);
  vsm->source_peer = source_peer;
  vsm->successor = successor;
  vsm->trail_id = trail_id;
  peer_list = (struct GNUNET_PeerIdentity *) &vsm[1];
  memcpy (peer_list, trail, trail_length * sizeof (struct GNUNET_PeerIdentity));

  /* Send the message to chosen friend. */
  GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
  target_friend->pending_count++;
  process_friend_queue (target_friend);
}


/**
 * FIXME: In every function we pass target friend except for this one.
 * so, either change everything or this one. also, should se just store
 * the pointer to friend in routing table rather than gnunet_peeridentity.
 * if yes then we should keep friend info in.h  andmake lot of changes.
 * Construct a trail teardown message and forward it to target friend.
 * @param trail_id Unique identifier of the trail.
 * @param trail_direction Direction of trail.
 * @param target_friend Friend to get this message.
 */
void
GDS_NEIGHBOURS_send_trail_teardown (struct GNUNET_HashCode trail_id,
                                    unsigned int trail_direction,
                                    struct GNUNET_PeerIdentity peer)
{
  struct PeerTrailTearDownMessage *ttdm;
  struct P2PPendingMessage *pending;
  struct FriendInfo *target_friend;
  size_t msize;

  msize = sizeof (struct PeerTrailTearDownMessage);

  if (msize >= GNUNET_CONSTANTS_MAX_ENCRYPTED_MESSAGE_SIZE)
  {
    GNUNET_break (0);
    return;
  }

  /*FIXME:In what case friend can be null. ?*/
  if (NULL == (target_friend =
                 GNUNET_CONTAINER_multipeermap_get (friend_peermap, &peer)));
  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 (PENDING_MESSAGE_TIMEOUT);
  ttdm = (struct PeerTrailTearDownMessage *) &pending[1];
  pending->msg = &ttdm->header;
  ttdm->header.size = htons (msize);
  ttdm->header.type = htons (GNUNET_MESSAGE_TYPE_XDHT_P2P_TRAIL_TEARDOWN);
  ttdm->trail_id = trail_id;
  ttdm->trail_direction = htonl (trail_direction);

  /* Send the message to chosen friend. */
  GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
  target_friend->pending_count++;
  process_friend_queue (target_friend);
}


/**
 * Construct a verify successor result message and send it to target_friend
 * @param querying_peer Peer which sent the verify successor message.
 * @param source_successor Current_successor of @a querying_peer.
 * @param current_predecessor Current predecessor of @a successor. Could be same
 *                            or different from @a querying_peer.
 * @param trail_id Unique identifier of the trail from @a querying_peer to
 *                 @a successor, NOT including them.
 * @param trail List of peers which are part of trail from @a querying_peer to
 *                 @a successor, NOT including them.
 * @param trail_length Total number of peers in @a trail
 * @param trail_direction Direction in which we are sending the message. In this
 *                        case we are sending result from @a successor to @a querying_peer.
 * @param target_friend Next friend to get this message.
 */
void
GDS_NEIGHBOURS_send_verify_successor_result (struct GNUNET_PeerIdentity querying_peer,
                                             struct GNUNET_PeerIdentity current_successor,
                                             struct GNUNET_PeerIdentity probable_successor,
                                             struct GNUNET_HashCode trail_id,
                                             const struct GNUNET_PeerIdentity *trail,
                                             unsigned int trail_length,
                                             enum GDS_ROUTING_trail_direction trail_direction,
                                             struct FriendInfo *target_friend)
{
  struct PeerVerifySuccessorResultMessage *vsmr;
  struct P2PPendingMessage *pending;
  struct GNUNET_PeerIdentity *peer_list;
  size_t msize;

  msize = sizeof (struct PeerVerifySuccessorResultMessage) +
          (trail_length * sizeof(struct GNUNET_PeerIdentity));

  if (msize >= GNUNET_CONSTANTS_MAX_ENCRYPTED_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 (PENDING_MESSAGE_TIMEOUT);
  vsmr = (struct PeerVerifySuccessorResultMessage *) &pending[1];
  pending->msg = &vsmr->header;
  vsmr->header.size = htons (msize);
  vsmr->header.type = htons (GNUNET_MESSAGE_TYPE_XDHT_P2P_VERIFY_SUCCESSOR_RESULT);
  vsmr->querying_peer = querying_peer;
  vsmr->current_successor = current_successor;
  vsmr->probable_successor = probable_successor;
  vsmr->trail_direction = htonl (trail_direction);
  vsmr->trail_id = trail_id; 
  peer_list = (struct GNUNET_PeerIdentity *) &vsmr[1];
  memcpy (peer_list, trail, trail_length * sizeof (struct GNUNET_PeerIdentity));
  
   /* Send the message to chosen friend. */
  GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
  target_friend->pending_count++;
  process_friend_queue (target_friend);
}


/**
 * Construct a notify new successor message and send it to target_friend
 * @param source_peer Peer which wants to notify to its new successor that it
 *                    could be its predecessor.
 * @param successor New successor of @a source_peer
 * @param successor_trail List of peers in Trail to reach from
 *                            @a source_peer to @a new_successor, NOT including
 *                            the endpoints.
 * @param successor_trail_length Total number of peers in @a new_successor_trail.
 * @param successor_trail_id Unique identifier of @a new_successor_trail.
 * @param target_friend Next friend to get this message.
 */
void
GDS_NEIGHBOURS_send_notify_new_successor (struct GNUNET_PeerIdentity source_peer,
                                          struct GNUNET_PeerIdentity successor,
                                          const struct GNUNET_PeerIdentity *successor_trail,
                                          unsigned int successor_trail_length,
                                          struct GNUNET_HashCode succesor_trail_id,
                                          struct FriendInfo *target_friend)
{
  struct PeerNotifyNewSuccessorMessage *nsm;
  struct P2PPendingMessage *pending;
  struct GNUNET_PeerIdentity *peer_list;
  size_t msize;

  msize = sizeof (struct PeerNotifyNewSuccessorMessage) +
          (successor_trail_length * sizeof(struct GNUNET_PeerIdentity));

  if (msize >= GNUNET_CONSTANTS_MAX_ENCRYPTED_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 (PENDING_MESSAGE_TIMEOUT);
  nsm = (struct PeerNotifyNewSuccessorMessage *) &pending[1];
  pending->msg = &nsm->header;
  nsm->header.size = htons (msize);
  nsm->header.type = htons (GNUNET_MESSAGE_TYPE_XDHT_P2P_NOTIFY_NEW_SUCCESSOR);
  nsm->new_successor = successor;
  nsm->source_peer = source_peer;
  nsm->trail_id = succesor_trail_id;
  peer_list = (struct GNUNET_PeerIdentity *) &nsm[1];
  memcpy (peer_list, successor_trail,
          successor_trail_length * sizeof (struct GNUNET_PeerIdentity));
 
   /* Send the message to chosen friend. */
  GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
  target_friend->pending_count++;
  process_friend_queue (target_friend);
}


/**
 * Construct an add_trail message and send it to target_friend
 * @param source_peer Source of the trail.
 * @param destination_peer Destination of the trail.
 * @param trail_id Unique identifier of the trail from
 *                 @a source_peer to @a destination_peer, NOT including the endpoints.
 * @param trail List of peers in Trail from @a source_peer to @a destination_peer,
 *              NOT including the endpoints.
 * @param trail_length Total number of peers in @a trail.
 * @param target_friend Next friend to get this message.
 */
void
GDS_NEIGHBOURS_send_add_trail (struct GNUNET_PeerIdentity source_peer,
                               struct GNUNET_PeerIdentity destination_peer,
                               struct GNUNET_HashCode trail_id,
                               const struct GNUNET_PeerIdentity *trail,
                               unsigned int trail_length,
                               struct FriendInfo *target_friend)
{
  struct PeerAddTrailMessage *adm;
  struct GNUNET_PeerIdentity *peer_list;
  struct P2PPendingMessage *pending;
  size_t msize;

  msize = sizeof (struct PeerAddTrailMessage) +
          (trail_length * sizeof(struct GNUNET_PeerIdentity));

  if (msize >= GNUNET_CONSTANTS_MAX_ENCRYPTED_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 (PENDING_MESSAGE_TIMEOUT);
  adm = (struct PeerAddTrailMessage *) &pending[1];
  pending->msg = &adm->header;
  adm->header.size = htons (msize);
  adm->header.type = htons (GNUNET_MESSAGE_TYPE_XDHT_P2P_ADD_TRAIL);
  adm->source_peer = source_peer;
  adm->destination_peer = destination_peer;
  adm->trail_id = trail_id;
  peer_list = (struct GNUNET_PeerIdentity *)&adm[1];
  memcpy (peer_list, trail, sizeof (struct GNUNET_PeerIdentity) * trail_length);
  
  /* Send the message to chosen friend. */
  GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
  target_friend->pending_count++;
  process_friend_queue (target_friend);

}


/**
 * Search my location in trail. In case I am present more than once in the
 * trail (can happen during trail setup), then return my lowest index.
 * @param trail List of peers
 * @return my_index if found
 *         trail_length + 1 if an entry is present twice, It is an error.
 *         -1 if no entry found.
 */
static int
search_my_index (const struct GNUNET_PeerIdentity *trail,
                 int trail_length)
{
  int i;
  int index_seen = trail_length + 1;
  int flag = 0;
  
  for (i = 0; i < trail_length; i++)
  {
    if (0 == GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &trail[i]))
    {
      flag = 1;
      if(index_seen == (trail_length + 1))
        index_seen = i;
      else
      {
        DEBUG("Entry is present twice in trail. Its not allowed\n");
      }
      break;
    }
  }

  if (1 == flag)
    return index_seen;
  else
    return -1;
}


/**
 * Check if the friend is congested or have reached maximum number of trails
 * it can be part of of.
 * @param friend Friend to be checked.
 * @return #GNUNET_NO if friend is not congested or have not crossed threshold.
 *         #GNUNET_YES if friend is either congested or have crossed threshold
 */
static int
is_friend_congested (struct FriendInfo *friend)
{
  if (( friend->trails_count < TRAILS_THROUGH_FRIEND_THRESHOLD) &&
      ((0 == GNUNET_TIME_absolute_get_remaining
             (friend->congestion_timestamp).rel_value_us)))
    return GNUNET_NO;
  else
    return GNUNET_YES;
}


/**
 * Select closest finger 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_finger (const struct GNUNET_PeerIdentity *peer1,
                       const struct GNUNET_PeerIdentity *peer2,
                       uint64_t value)
{
  uint64_t peer1_value;
  uint64_t peer2_value;

  memcpy (&peer1_value, peer1, sizeof (uint64_t));
  memcpy (&peer2_value, peer2, sizeof (uint64_t));
  peer1_value = GNUNET_ntohll (peer1_value);
  peer2_value = GNUNET_ntohll (peer2_value);

  // TODO: Can use a simpler (to understand) idea here!
  if (peer1_value == value)
  {
    return *peer1;
  }

  if (peer2_value == value)
  {
    return *peer2;
  }

  if (peer2_value < peer1_value)
  {
    if ((peer2_value < value) && (value < peer1_value))
    {
      return *peer1;
    }
    else if (((peer1_value < value) && (value < PEER_IDENTITES_WRAP_AROUND)) ||
             ((0 < value) && (value < peer2_value)))
    {
      return *peer2;
    }
  }

  //if (peer1_value < peer2_value)
  //{
    if ((peer1_value < value) && (value < peer2_value))
    {
      return *peer2;
    }
    //else if (((peer2_value < value) && (value < PEER_IDENTITES_WRAP_AROUND)) ||
            // ((0 < value) && (value < peer1_value)))
    //{
      return *peer1;
    //}
 // }
}


/**
 * Select closest predecessor to value.
 * @param peer1 First peer
 * @param peer2 Second peer
 * @param value Value to be compare
 * @return Peer which precedes value in the network.
 */
static struct GNUNET_PeerIdentity 
select_closest_predecessor (const struct GNUNET_PeerIdentity *peer1,
                            const struct GNUNET_PeerIdentity *peer2,
                            uint64_t value)
{
  uint64_t peer1_value;
  uint64_t peer2_value;

  memcpy (&peer1_value, peer1, sizeof (uint64_t));
  memcpy (&peer2_value, peer2, sizeof (uint64_t));
  peer1_value = GNUNET_ntohll (peer1_value);
  peer2_value = GNUNET_ntohll (peer2_value);

  if (peer1_value == value)
    return *peer1;

  if (peer2_value == value)
    return *peer2;

  if (peer1_value < peer2_value)
  {
    if ((peer1_value < value) && (value < peer2_value))
    {
      return *peer1;
    }
    else if (((peer2_value < value) && (value < PEER_IDENTITES_WRAP_AROUND)) ||
             ((PEER_IDENTITES_WRAP_AROUND > value) && (value < peer1_value)))
    {
      return *peer2;
    }
  }

 // if (peer2_value < peer1_value)
  //{
    if ((peer2_value < value) && (value < peer1_value))
    {
      return *peer2;
    }
    //else if (((peer1_value < value) && (value < PEER_IDENTITES_WRAP_AROUND)) ||
    //         ((PEER_IDENTITES_WRAP_AROUND > value) && (value < peer2_value)))
    //{
      return *peer1;
    //}
 // }
}


/**
 * 
 *
 */
void
test_print_trail (struct GNUNET_PeerIdentity *trail,
                  unsigned int trail_length)
{
  struct GNUNET_PeerIdentity print_peer;
  int i;
  
  FPRINTF (stderr,_("\nSUPU %s, %s, %d,trail_length = %d"),
  __FILE__, __func__,__LINE__,trail_length);
  for (i =0 ; i< trail_length; i++)
  {
    print_peer = trail[i];
    FPRINTF (stderr,_("\nSUPU %s, %s, %d,trail[%d]=%s"),
            __FILE__, __func__,__LINE__,i,GNUNET_i2s(&print_peer));
  }
}


#if 0
/**
 * This is a test function to print all the entries of friend table.
 */
static void
test_friend_peermap_print ()
{
  struct FriendInfo *friend;
  struct GNUNET_CONTAINER_MultiPeerMapIterator *friend_iter;
  struct GNUNET_PeerIdentity print_peer;
  struct GNUNET_PeerIdentity key_ret;
  int i;

  print_peer = my_identity;
  FPRINTF (stderr,_("\nSUPU************  FRIEND_PEERMAP of %s"),GNUNET_i2s(&print_peer));
  friend_iter = GNUNET_CONTAINER_multipeermap_iterator_create (friend_peermap);

  for (i = 0; i < GNUNET_CONTAINER_multipeermap_size (friend_peermap); i++)
  {
    if(GNUNET_YES == GNUNET_CONTAINER_multipeermap_iterator_next (friend_iter,
                                                                  &key_ret,
                                                                  (const void **)&friend))
    {
      memcpy (&print_peer, &key_ret, sizeof (struct GNUNET_PeerIdentity));
      FPRINTF (stderr,_("\nSUPU %s, %s, %d, friend = %s, friend->trails_count = %d"),
              __FILE__, __func__,__LINE__, GNUNET_i2s(&print_peer), friend->trails_count);
    }
  }
}
#endif

#if 0
/**
 * This is a test function, to print all the entries of finger table.
 */
static void
test_finger_table_print()
{
  struct FingerInfo *finger;
  struct GNUNET_PeerIdentity print_peer;
  //struct Trail *trail;
  int i;
  //int j;
  //int k;
  print_peer = my_identity;
  FPRINTF (stderr,_("\nSUPU************  FINGER_TABLE of %s"),GNUNET_i2s(&print_peer));
  for (i = 0; i < MAX_FINGERS; i++)
  {
    finger = &finger_table[i];

    if (GNUNET_NO == finger->is_present)
      continue;

    print_peer = finger->finger_identity;
    FPRINTF (stderr,_("\nSUPU %s, %s, %d, finger_table[%d] = %s, trails_count = %d"),
            __FILE__, __func__,__LINE__,i,GNUNET_i2s (&print_peer), finger->trails_count);

#if 0
    for (j = 0; j < finger->trails_count; j++)
    {
      trail = &finger->trail_list[j];
      FPRINTF (stderr,_("\nSUPU %s, %s, %d, trail_id[%d]=%s"),__FILE__, __func__,__LINE__,j, GNUNET_h2s(&trail->trail_id));
      struct Trail_Element *element;
      element = trail->trail_head;
      for (k = 0; k < trail->trail_length; k++)
      {
        print_peer = element->peer;
        FPRINTF (stderr,_("\nSUPU %s, %s, %d,trail[%d] = %s "),__FILE__, __func__,__LINE__,k, GNUNET_i2s(&print_peer));
        element = element->next;
      }
    }
    #endif
  }
}
#endif

/**
 * Select the closest peer among two peers (which should not be same)
 * with respect to value and finger_table_index
 * NOTE: peer1 != peer2
 * @param peer1 First peer
 * @param peer2 Second peer
 * @param value Value relative to which we find the closest
 * @param is_predecessor Is value a predecessor or any other finger.
 * @return Closest peer among two peers.
 */
static struct GNUNET_PeerIdentity 
select_closest_peer (const struct GNUNET_PeerIdentity *peer1,
                     const struct GNUNET_PeerIdentity *peer2,
                     uint64_t value,
                     unsigned int is_predecessor)
{
  /* This check is here to ensure that calling function never sends
      same peer value in peer1 and peer2. Remove it later. */
  GNUNET_assert(0 != GNUNET_CRYPTO_cmp_peer_identity (peer1, peer2));
  if (1 == is_predecessor)
    return select_closest_predecessor (peer1, peer2, value);

  // TODO: Change name to something like select_closest_successor!!
  return select_closest_finger (peer1, peer2, value);
}


/**
 * Iterate over the list of all the trails of a finger. In case the first
 * friend to reach the finger has reached trail threshold or is congested,
 * then don't select it. In case there multiple available good trails to reach
 * to Finger, choose the one with shortest trail length.
 * Note: We use length as parameter. But we can use any other suitable parameter
 * also.
 * @param finger Finger
 * @return Trail
 */
static struct Trail *
select_finger_trail (struct FingerInfo *finger)
{
  struct FriendInfo *friend;
  struct Trail *current_finger_trail;
  struct Trail *best_trail = NULL;
  unsigned int i;

  GNUNET_assert (finger->trails_count > 0);

  for (i = 0; i < finger->trails_count; i++)
  {
    current_finger_trail = &finger->trail_list[i];

    /* No trail stored at this index. */
    if (GNUNET_NO == current_finger_trail->is_present)
      continue;

    /* SUPUS: I am not changing anything here. as i assume that in case we have
     a finger which is friend and we have trail length = 0, then it will
     be the first friend to which we send the request. As I have removed
     the condition in trail setup where we check for source is a friend. */
    GNUNET_assert (NULL !=
                  (friend =
                   GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                      &current_finger_trail->trail_head->peer)));

    /* First friend to reach trail is not free. */
    if (GNUNET_YES == is_friend_congested (friend))
      continue;

    if (NULL == best_trail || 
        best_trail->trail_length > current_finger_trail->trail_length)
    {
      best_trail = current_finger_trail;
    }
  }

  return best_trail;
}


/**
 * Compare FINGER entry with current successor. If finger's first friend of all
 * its trail is not congested and  has not crossed trail threshold, then check
 * if finger peer identity is closer to final_destination_finger_value than
 * current_successor. If yes then update current_successor.
 * @param current_successor[in/out]
 * @return
 */
static void
compare_finger_and_current_closest_peer (struct Closest_Peer *current_closest_peer)
{
  struct FingerInfo *finger;
  struct GNUNET_PeerIdentity closest_peer;
  struct Trail *finger_trail;
  int i;

  /* Iterate over finger table. */
  for (i = 0; i < MAX_FINGERS; i++)
  {
    finger = &finger_table[i];

    if (GNUNET_NO == finger->is_present)
      continue;

    /* SUPUS: As we have friend stored as finger also, it may happen that
     * friend corresponding to this finger has been chosen as the best
     * known destination, then just move to next element. */
    if (0 == GNUNET_CRYPTO_cmp_peer_identity (&finger->finger_identity,
                                              &current_closest_peer->best_known_destination))
      continue;

    /* If I am my own finger, then ignore this finger. */
    if (0 == GNUNET_CRYPTO_cmp_peer_identity (&finger->finger_identity,
                                              &my_identity))
      continue;
   
    /* If finger is a friend, then do nothing. As we have already checked
     * for each friend in compare_friend_and_current_successor().
     * SUPUS: Here we have all the friends in the friend table. So even if
     * that friend is a finger, we have checked it with trail length = 0.
     * So its okay. No need to change anything here. Note: finger may have
     * trail length > 0 but its okay.   */
    if (NULL != (GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                    &finger->finger_identity)))
    {
      continue;
    }

    closest_peer = select_closest_peer (&finger->finger_identity,
                                        &current_closest_peer->best_known_destination,
                                        current_closest_peer->destination_finger_value,
                                        current_closest_peer->is_predecessor);

    /* SUPUS: Ideally if finger is a friend, but with trail length > 0, then 
     also we have already handled the case in above condition. */
    if (0 == GNUNET_CRYPTO_cmp_peer_identity(&finger->finger_identity, &closest_peer))
    {
      /* Choose one of the trail to reach to finger. */
      finger_trail = select_finger_trail (finger);

      /* In case no trail found, ignore this finger. */
      if (NULL == finger_trail)
        continue;

      current_closest_peer->best_known_destination = closest_peer;
      current_closest_peer->next_hop = finger_trail->trail_head->peer;
      current_closest_peer->trail_id = finger_trail->trail_id;
      current_closest_peer->finger_table_index = i;
    }
    continue;
  }
}


/**
 * Compare friend entry with current successor.
 * If friend identity and current_successor is same, then do nothing.
 * If friend is not congested and has not crossed trail threshold, then check
 * if friend peer identity is closer to final_destination_finger_value than
 * current_successor. If yes then update current_successor.
 * @param cls closure
 * @param key current public key
 * @param value struct Closest_Peer
 * @return #GNUNET_YES if we should continue to iterate,
 *         #GNUNET_NO if not.
 */
static int
compare_friend_and_current_closest_peer (void *cls,
                                         const struct GNUNET_PeerIdentity *key,
                                         void *value)
{
  struct FriendInfo *friend = value;
  struct Closest_Peer *current_closest_peer = cls;
  struct GNUNET_PeerIdentity closest_peer;

  /* Friend is either congested or has crossed threshold. */
  if (GNUNET_YES == is_friend_congested (friend))
    return GNUNET_YES;

  /* If current_closest_peer and friend identity are same, then do nothing.*/
  if (0 == GNUNET_CRYPTO_cmp_peer_identity (&friend->id,
                                            &current_closest_peer->best_known_destination))
  {
    GNUNET_break (0);
    return GNUNET_YES;
  }

  closest_peer = select_closest_peer (&friend->id,
                                      &current_closest_peer->best_known_destination,
                                      current_closest_peer->destination_finger_value,
                                      current_closest_peer->is_predecessor);

  /* Is friend the closest successor? */
  if (0 == GNUNET_CRYPTO_cmp_peer_identity(&friend->id, &closest_peer))
  {
    current_closest_peer->best_known_destination = friend->id;
    current_closest_peer->next_hop = friend->id;
  }

  return GNUNET_YES;
}


/**
 * Initialize current_successor to my_identity.
 * @param my_identity My peer identity
 * @return Updated closest_peer
 */
static struct Closest_Peer
init_current_successor (struct GNUNET_PeerIdentity my_identity,
                        uint64_t destination_finger_value,
                        unsigned int is_predecessor)
{
  struct Closest_Peer current_closest_peer;

  memset (&current_closest_peer.trail_id, 0, sizeof(struct GNUNET_HashCode));
  current_closest_peer.destination_finger_value = destination_finger_value;
  current_closest_peer.is_predecessor = is_predecessor;
  current_closest_peer.next_hop = my_identity;
  current_closest_peer.best_known_destination = my_identity;
  current_closest_peer.finger_table_index = 65; //65 is a for non valid finger table index. 
  return current_closest_peer;
}


/**
 * FIXME: at the moment, there is not 100% get and put in case of non-malicious
 * peer. It could be because of the logic we wrote here. Verify if its correct.
 * If not then return immediate_successor.
 *
 * Find the successor for destination_finger_value among my_identity, my
 * friends and my fingers. Don't consider friends or fingers which are either
 * congested or have crossed the threshold.
 * NOTE: In case a friend is also a finger, then it is always chosen as friend
 * not a finger.
 * @param destination_finger_value Peer closest to this value will be the next successor.
 * @param is_predecessor Are we looking for predecessor or finger?
 * @return Successor It is never NULL, in case none of friend or finger is closest,
 *                   then we return my_identity.
 */
static struct Closest_Peer
find_successor (uint64_t destination_finger_value,
                unsigned int is_predecessor)
{
  struct Closest_Peer current_closest_peer;

   /* Initialize current_successor to my_identity. */
  current_closest_peer = init_current_successor (my_identity,
                                                 destination_finger_value,
                                                 is_predecessor);

  /* Compare each friend entry with current_successor and update current_successor
   * with friend if its closest. */
  GNUNET_assert
          (GNUNET_SYSERR !=
           GNUNET_CONTAINER_multipeermap_iterate (friend_peermap,
                                                  &compare_friend_and_current_closest_peer,
                                                  &current_closest_peer));

  /* Compare each finger entry with current_successor and update current_successor
   * with finger if its closest. */
  compare_finger_and_current_closest_peer (&current_closest_peer);
  return current_closest_peer;
}

/**
 * FIXME; Send put message across all the trail to reach to next hop to handle
 * malicious peers.
 * Construct a Put message and send it to target_peer.
 * @param key Key for the content
 * @param block_type Type of the block
 * @param options Routing options
 * @param desired_replication_level Desired replication count
 * @param best_known_dest Peer to which this message should reach eventually,
 *                        as it is best known destination to me.
 * @param intermediate_trail_id Trail id in case
 * @param target_peer Peer to which this message will be forwarded.
 * @param hop_count Number of hops traversed so far.
 * @param put_path_length Total number of peers in @a put_path
 * @param put_path Number of peers traversed so far
 * @param expiration_time When does the content expire
 * @param data Content to store
 * @param data_size Size of content @a data in bytes
 */
void
GDS_NEIGHBOURS_send_put (const struct GNUNET_HashCode *key,
                         enum GNUNET_BLOCK_Type block_type,
                                           enum GNUNET_DHT_RouteOption options,
                                           uint32_t desired_replication_level,
                                           struct GNUNET_PeerIdentity best_known_dest,
                                           struct GNUNET_HashCode intermediate_trail_id,
                                           struct GNUNET_PeerIdentity *target_peer,
                         uint32_t hop_count,
                         uint32_t put_path_length,
                         struct GNUNET_PeerIdentity *put_path,
                         struct GNUNET_TIME_Absolute expiration_time,
                         const void *data, size_t data_size)
{
  struct PeerPutMessage *ppm;
  struct P2PPendingMessage *pending;
  struct FriendInfo *target_friend;
  struct GNUNET_PeerIdentity *pp;
  size_t msize;
  
  msize = put_path_length * sizeof (struct GNUNET_PeerIdentity) + data_size +
          sizeof (struct PeerPutMessage);
  if (msize >= GNUNET_CONSTANTS_MAX_ENCRYPTED_MESSAGE_SIZE)
  {
    put_path_length = 0;
    msize = data_size + sizeof (struct PeerPutMessage);
  }

  /* Should it be GNUNET_SERVER_MAX_MESSAGE_SIZE? */
  if (msize >= GNUNET_CONSTANTS_MAX_ENCRYPTED_MESSAGE_SIZE)
  {
    DEBUG("msize = %lu\n",msize);
    GNUNET_break (0);
    return;
  }
 
  GNUNET_assert (NULL !=
                 (target_friend =
                  GNUNET_CONTAINER_multipeermap_get (friend_peermap, target_peer)));
  pending = GNUNET_malloc (sizeof (struct P2PPendingMessage) + msize);
  pending->timeout = expiration_time;
  ppm = (struct PeerPutMessage *) &pending[1];
  pending->msg = &ppm->header;
  ppm->header.size = htons (msize);
  ppm->header.type = htons (GNUNET_MESSAGE_TYPE_XDHT_P2P_PUT);
  ppm->options = htonl (options);
  ppm->block_type = htonl (block_type);
  ppm->hop_count = htonl (hop_count + 1);
  ppm->desired_replication_level = htonl (desired_replication_level);
  ppm->expiration_time = GNUNET_TIME_absolute_hton (expiration_time);
  ppm->best_known_destination = best_known_dest;
  ppm->intermediate_trail_id = intermediate_trail_id;
  ppm->key = *key;
  pp = (struct GNUNET_PeerIdentity *) &ppm[1];
  ppm->put_path_length = htonl (put_path_length);
  if(put_path_length > 0)
  {
    memcpy (pp, put_path,
            sizeof (struct GNUNET_PeerIdentity) * put_path_length);
  }
  memcpy (&pp[put_path_length], data, data_size);
  GNUNET_assert (NULL != target_friend);
  GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
  target_friend->pending_count++;
  process_friend_queue (target_friend);
}


/**
 * Handle the put request from the client. 
 * @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 expiration_time When does the content expire
 * @param data Content to store
 * @param data_size Size of content @a data in bytes
 */
void
GDS_NEIGHBOURS_handle_put (const struct GNUNET_HashCode *key,
                           enum GNUNET_BLOCK_Type block_type,
                           enum GNUNET_DHT_RouteOption options,
                           uint32_t desired_replication_level,
                           struct GNUNET_TIME_Absolute expiration_time,
                           const void *data, size_t data_size)
{
  struct GNUNET_PeerIdentity best_known_dest;
  struct GNUNET_HashCode intermediate_trail_id;
  struct GNUNET_PeerIdentity next_hop;
  uint64_t key_value;
  struct Closest_Peer successor;
  
  memcpy (&key_value, key, sizeof (uint64_t));
  key_value = GNUNET_ntohll (key_value);
  successor = find_successor (key_value, GDS_FINGER_TYPE_NON_PREDECESSOR);
  best_known_dest = successor.best_known_destination;
  next_hop = successor.next_hop;
  intermediate_trail_id = successor.trail_id;

  DEBUG("PUT_REQUEST_RECEVIED KEY = %s \n",GNUNET_h2s(key));
  if (0 == GNUNET_CRYPTO_cmp_peer_identity (&best_known_dest, &my_identity))
  {
    /* I am the destination. */
    GDS_DATACACHE_handle_put (expiration_time, key, 0, NULL,
                              block_type,data_size,data);
    GDS_CLIENTS_process_put (options, block_type, 0,
                             ntohl (desired_replication_level),
                             1, &my_identity, expiration_time, //FIXME: GNUNETnthoh something on expiration time. 
                             key, data, data_size);
    return;
  }
  
  /* In case we are sending the request to  a finger, then send across all of its
   trail.*/
#if 0
  if (0 != GNUNET_CRYPTO_cmp_peer_identity (&successor.best_known_destination,
                                            &successor.next_hop))
  {
    struct FingerInfo *next_hop_finger;
    unsigned int i;
    
    next_hop_finger = &finger_table[successor.finger_table_index];
    for (i = 0; i < next_hop_finger->trails_count; i++)
    {
      if (GNUNET_YES == next_hop_finger->trail_list[i].is_present)
      {
        GDS_NEIGHBOURS_send_put (key, block_type, options, desired_replication_level,
                                 best_known_dest, 
                                 next_hop_finger->trail_list[i].trail_id, 
                                 &next_hop, hop_count, put_path_length, put_path,
                                 expiration_time,
                                 data, data_size);
       }
    }
  }
  else
#endif
    GDS_NEIGHBOURS_send_put (key, block_type, options, desired_replication_level,
                             best_known_dest, intermediate_trail_id, &next_hop,
                             0, 1, &my_identity, expiration_time,
                             data, data_size);
}

/**
 * FIXME; Send get message across all the trail to reach to next hop to handle
 * malicious peers.
 * Construct a Get message and send it to target_peer.
 * @param key Key for the content
 * @param block_type Type of the block
 * @param options Routing options
 * @param desired_replication_level Desired replication count
 * @param best_known_dest Peer which should get this message. Same as target peer
 *                        if best_known_dest is a friend else its a finger.
 * @param intermediate_trail_id  Trail id to reach to @a best_known_dest
 *                              in case it is a finger else set to 0.
 * @param target_peer Peer to which this message will be forwarded.
 * @param hop_count Number of hops traversed so far.
 * @param data Content to store
 * @param data_size Size of content @a data in bytes
 * @param get_path_length Total number of peers in @a get_path
 * @param get_path Number of peers traversed so far
 */
void
GDS_NEIGHBOURS_send_get (const struct GNUNET_HashCode *key,
                         enum GNUNET_BLOCK_Type block_type,
                         enum GNUNET_DHT_RouteOption options,
                         uint32_t desired_replication_level,
                         struct GNUNET_PeerIdentity best_known_dest,
                         struct GNUNET_HashCode intermediate_trail_id,
                         struct GNUNET_PeerIdentity *target_peer,
                         uint32_t hop_count,
                         uint32_t get_path_length,
                         struct GNUNET_PeerIdentity *get_path)
{
  struct PeerGetMessage *pgm;
  struct P2PPendingMessage *pending;
  struct FriendInfo *target_friend;
  struct GNUNET_PeerIdentity *gp;
  size_t msize;

  msize = sizeof (struct PeerGetMessage) +
          (get_path_length * sizeof (struct GNUNET_PeerIdentity));

  if (msize >= GNUNET_CONSTANTS_MAX_ENCRYPTED_MESSAGE_SIZE)
  {
    GNUNET_break (0);
    return;
  }
  GNUNET_assert (NULL !=
                 (target_friend =
                  GNUNET_CONTAINER_multipeermap_get (friend_peermap, target_peer))); 

  pending = GNUNET_malloc (sizeof (struct P2PPendingMessage) + msize);
  pending->timeout = GNUNET_TIME_relative_to_absolute (PENDING_MESSAGE_TIMEOUT);
  pending->importance = 0;    /* FIXME */
  pgm = (struct PeerGetMessage *) &pending[1];
  pending->msg = &pgm->header;
  pgm->header.size = htons (msize);
  pgm->header.type = htons (GNUNET_MESSAGE_TYPE_XDHT_P2P_GET);
  pgm->get_path_length = htonl (get_path_length);
  pgm->best_known_destination = best_known_dest;
  pgm->key = *key;
  pgm->intermediate_trail_id = intermediate_trail_id;
  pgm->hop_count = htonl (hop_count + 1);
  pgm->get_path_length = htonl (get_path_length);
  gp = (struct GNUNET_PeerIdentity *) &pgm[1];
  memcpy (gp, get_path,
          sizeof (struct GNUNET_PeerIdentity) * get_path_length);
  GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
  target_friend->pending_count++;
  process_friend_queue (target_friend);
}


/**
 * Handle the get request from the client file. If I am destination do 
 * datacache put and return. Else find the target friend and forward message
 * to it. 
 * @param key Key for the content
 * @param block_type Type of the block
 * @param options Routing options
 * @param desired_replication_level Desired replication count
 */
void 
GDS_NEIGHBOURS_handle_get(const struct GNUNET_HashCode *key,
                          enum GNUNET_BLOCK_Type block_type,
                          enum GNUNET_DHT_RouteOption options,
                          uint32_t desired_replication_level)
{
  struct Closest_Peer successor;
  struct GNUNET_PeerIdentity best_known_dest;
  struct GNUNET_HashCode intermediate_trail_id;
  uint64_t key_value;
  
  memcpy (&key_value, key, sizeof (uint64_t));
  key_value = GNUNET_ntohll (key_value);

  successor = find_successor (key_value, GDS_FINGER_TYPE_NON_PREDECESSOR);
  
  best_known_dest = successor.best_known_destination;
  intermediate_trail_id = successor.trail_id;
  
  DEBUG("GET_REQUEST_RECEVIED KEY = %s \n",GNUNET_h2s(key));
  /* I am the destination. I have the data. */
  if (0 == GNUNET_CRYPTO_cmp_peer_identity (&my_identity,
                                            &best_known_dest))
  {
    GDS_DATACACHE_handle_get (key,block_type, NULL, 0,
                              NULL, 0, 1, &my_identity, NULL,&my_identity);
    return;
  }
    
  /* fixme; for multiple trails, we need to send back finger index and send trail
   across all the fingers. but in current implementation we don't have this case.
   compare finger and current_successor returns, */
  GDS_NEIGHBOURS_send_get (key, block_type, options, desired_replication_level,
                           best_known_dest,intermediate_trail_id, &successor.next_hop,
                           0, 1, &my_identity);
}


/**
 * Send the get result to requesting client.
 * @param key Key of the requested data.
 * @param type Block type
 * @param target_peer Next peer to forward the message to.
 * @param source_peer Peer which has the data for the key.
 * @param put_path_length Number of peers in @a put_path
 * @param put_path Path taken to put the data at its stored location.
 * @param get_path_length Number of peers in @a get_path
 * @param get_path Path taken to reach to the location of the key.
 * @param expiration When will this result expire?
 * @param data Payload to store
 * @param data_size Size of the @a data
 */
void
GDS_NEIGHBOURS_send_get_result (const struct GNUNET_HashCode *key,
                                enum GNUNET_BLOCK_Type type,
                                const struct GNUNET_PeerIdentity *target_peer,
                                const struct GNUNET_PeerIdentity *source_peer,
                                unsigned int put_path_length,
                                const struct GNUNET_PeerIdentity *put_path,
                                unsigned int get_path_length,
                                const struct GNUNET_PeerIdentity *get_path,
                                struct GNUNET_TIME_Absolute expiration,
                                const void *data, size_t data_size)
{
  struct PeerGetResultMessage *get_result;
  struct GNUNET_PeerIdentity *paths;
  struct P2PPendingMessage *pending;
  struct FriendInfo *target_friend;
  int current_path_index;
  size_t msize;

  msize = (put_path_length + get_path_length )* sizeof (struct GNUNET_PeerIdentity) +
          data_size +
          sizeof (struct PeerGetResultMessage);

  if (msize >= GNUNET_CONSTANTS_MAX_ENCRYPTED_MESSAGE_SIZE)
  {
    put_path_length = 0;
    msize = msize - put_path_length;
    return;
  }

  if (msize >= GNUNET_CONSTANTS_MAX_ENCRYPTED_MESSAGE_SIZE)
  {
    GNUNET_break(0);
    return;
  }
  current_path_index = 0;
  if(get_path_length > 0)
  {
    current_path_index = search_my_index(get_path, get_path_length);
    if (-1 == current_path_index)
    {
      GNUNET_break (0);
      return;
    }
    if ((get_path_length + 1) == current_path_index)
    {
      DEBUG ("Peer found twice in get path. Not allowed \n");
      GNUNET_break (0);
      return;
    }
  }
  if (0 == current_path_index)
  {
    DEBUG ("GET_RESULT TO CLIENT KEY = %s, Peer = %s",GNUNET_h2s(key),GNUNET_i2s(&my_identity));
    GDS_CLIENTS_handle_reply (expiration, key, get_path_length,
                              get_path, put_path_length,
                              put_path, type, data_size, data);
    return;
  }

  pending = GNUNET_malloc (sizeof (struct P2PPendingMessage) + msize);
  pending->timeout = GNUNET_TIME_relative_to_absolute (PENDING_MESSAGE_TIMEOUT);
  pending->importance = 0;
  get_result = (struct PeerGetResultMessage *)&pending[1];
  pending->msg = &get_result->header;
  get_result->header.size = htons (msize);
  get_result->header.type = htons (GNUNET_MESSAGE_TYPE_XDHT_P2P_GET_RESULT);
  get_result->key = *key;
  get_result->querying_peer = *source_peer;
  get_result->expiration_time = expiration;
  get_result->get_path_length = htonl (get_path_length);
  get_result->put_path_length = htonl (put_path_length);
  paths = (struct GNUNET_PeerIdentity *)&get_result[1];
  memcpy (paths, put_path,
          put_path_length * sizeof (struct GNUNET_PeerIdentity));
  memcpy (&paths[put_path_length], get_path,
          get_path_length * sizeof (struct GNUNET_PeerIdentity));
  memcpy (&paths[put_path_length + get_path_length], data, data_size);

  GNUNET_assert (NULL !=
                (target_friend =
                 GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                    &get_path[current_path_index - 1])));
  GNUNET_CONTAINER_DLL_insert_tail (target_friend->head, target_friend->tail, pending);
  target_friend->pending_count++;
  process_friend_queue (target_friend);
}


/**
 * Randomly choose one of your friends (which is not congested and have not crossed
 * trail threshold) from the friend_peermap
 * @return Friend Randomly chosen friend.
 *         NULL in case friend peermap is empty, or all the friends are either
 *              congested or have crossed trail threshold.
 */
static struct FriendInfo *
select_random_friend ()
{
  unsigned int current_size;
  uint32_t index;
  unsigned int j = 0;
  struct GNUNET_CONTAINER_MultiPeerMapIterator *iter;
  struct GNUNET_PeerIdentity key_ret;
  struct FriendInfo *friend;

  current_size = GNUNET_CONTAINER_multipeermap_size (friend_peermap);

  /* No friends.*/
  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);

  /* Iterate till you don't reach to index. */
  for (j = 0; j < index ; j++)
    GNUNET_assert (GNUNET_YES ==
                   GNUNET_CONTAINER_multipeermap_iterator_next (iter, NULL, NULL));
  
  do
  {
    /* Reset the index in friend peermap to 0 as we reached to the end. */
    if (j == current_size)
    {
      j = 0;
      GNUNET_CONTAINER_multipeermap_iterator_destroy (iter);
      iter = GNUNET_CONTAINER_multipeermap_iterator_create (friend_peermap);

    }

    /* Get the friend stored at the index, j*/
    GNUNET_assert (GNUNET_YES ==
                   GNUNET_CONTAINER_multipeermap_iterator_next (iter,
                                                                &key_ret,
                                                                (const void **)&friend));

    /* This friend is not congested and has not crossed trail threshold. */
    if ((friend->trails_count < TRAILS_THROUGH_FRIEND_THRESHOLD) &&
        (0 == GNUNET_TIME_absolute_get_remaining (friend->congestion_timestamp).rel_value_us))
    {
      break;
    }
    friend = NULL;
    j++;
  } while (j != index);

  GNUNET_CONTAINER_multipeermap_iterator_destroy (iter);
  return friend;
}


/**
 * Compute 64 bit value of finger_identity corresponding to a finger index using
 * chord formula.
 * For all fingers, n.finger[i] = n + pow (2,i),
 * For predecessor, n.finger[PREDECESSOR_FINGER_ID] = n - 1, where
 * n = my_identity, i = finger_index, n.finger[i] = 64 bit finger value
 * @param finger_index Index corresponding to which we calculate 64 bit value.
 * @return 64 bit value.
 */
static uint64_t
compute_finger_identity_value (unsigned int finger_index)
{
  uint64_t my_id64;

  memcpy (&my_id64, &my_identity, sizeof (uint64_t));
  my_id64 = GNUNET_ntohll (my_id64);

  /* Are we looking for immediate predecessor? */
  if (PREDECESSOR_FINGER_ID == finger_index)
    return (my_id64 - 1);
  else
  {
    uint64_t add = (uint64_t)1 << finger_index;
    return (my_id64 + add);
  }
}


/*
 * Choose a random friend. Calculate the next finger identity to search,from
 * current_search_finger_index. 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_HashCode trail_id;
  struct GNUNET_HashCode intermediate_trail_id;
  unsigned int is_predecessor = 0;
  uint64_t finger_id_value;
  
  /* Schedule another send_find_finger_trail_message task. When we have seen
   * one round of fingers, then this time is exponentially backoff to reduce
   * traffic caused by this task. */
  find_finger_trail_task_next_send_time.rel_value_us =
      find_finger_trail_task_next_send_time.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 (find_finger_trail_task_next_send_time,
                                    &send_find_finger_trail_message,
                                    NULL);

   /* No space in my routing table. (Source and destination peers also store entries
   * in their routing table).  */
  if (GNUNET_YES == GDS_ROUTING_threshold_reached())
    return;

  target_friend = select_random_friend ();
  if (NULL == target_friend)
  {
    return;
  }

  finger_id_value = compute_finger_identity_value (current_search_finger_index);
  if (PREDECESSOR_FINGER_ID == current_search_finger_index)
    is_predecessor = 1;
  
  /* Generate a unique trail id for trail we are trying to setup. */
  GNUNET_CRYPTO_random_block (GNUNET_CRYPTO_QUALITY_STRONG,
                              &trail_id, sizeof (trail_id));
  memset(&intermediate_trail_id, 0, sizeof (struct GNUNET_HashCode));
  GDS_NEIGHBOURS_send_trail_setup (my_identity, finger_id_value,
                                   target_friend->id, target_friend, 0, NULL,
                                   is_predecessor, trail_id,
                                   intermediate_trail_id);
}


/**
 * 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 finger Finger 
 * @param new_finger_trail List of peers to reach from me to @a finger, NOT
 *                         including the endpoints. 
 * @param new_finger_trail_length Total number of peers in @a new_finger_trail
 * @param new_finger_trail_id Unique identifier of @a new_finger_trail.
 */
static void
select_and_replace_trail (struct FingerInfo *finger,
                          const struct GNUNET_PeerIdentity *new_trail,
                          unsigned int new_trail_length,
                          struct GNUNET_HashCode new_trail_id)
{
  struct Trail *trail;
  unsigned int largest_trail_length;
  unsigned int largest_trail_index;
  struct Trail_Element *trail_element;
  unsigned int i;

  largest_trail_length = new_trail_length;
  largest_trail_index = MAXIMUM_TRAILS_PER_FINGER + 1;

  GNUNET_assert (MAXIMUM_TRAILS_PER_FINGER == finger->trails_count);

  for (i = 0; i < finger->trails_count; i++)
  {
    trail = &finger->trail_list[i];
    if (trail->trail_length > largest_trail_length)
    {
      largest_trail_length = trail->trail_length;
      largest_trail_index = i;
    }
  }

  /* New trail is not better than existing ones. Send trail teardown. */
  if (largest_trail_index == (MAXIMUM_TRAILS_PER_FINGER + 1))
  {
    struct GNUNET_PeerIdentity next_hop;

    memcpy (&next_hop, &new_trail[0], sizeof(struct GNUNET_PeerIdentity));
    GDS_ROUTING_remove_trail (new_trail_id);
    GDS_NEIGHBOURS_send_trail_teardown (new_trail_id,
                                        GDS_ROUTING_SRC_TO_DEST,
                                        next_hop);
    return;
  }

  /* Send trail teardown message across the replaced trail. */
  struct Trail *replace_trail = &finger->trail_list[largest_trail_index];
  
  GNUNET_assert (GNUNET_YES == GDS_ROUTING_remove_trail (replace_trail->trail_id));
  GDS_NEIGHBOURS_send_trail_teardown (replace_trail->trail_id,
                                      GDS_ROUTING_SRC_TO_DEST,
                                      replace_trail->trail_head->peer);
  /* Free the trail. */
  while (NULL != (trail_element = replace_trail->trail_head))
  {
    GNUNET_CONTAINER_DLL_remove (replace_trail->trail_head,
                                 replace_trail->trail_tail, trail_element);
    GNUNET_free_non_null (trail_element);
  }

  /* Add new trial at that location. */
  replace_trail->is_present = GNUNET_YES;
  replace_trail->trail_length = new_trail_length;
  replace_trail->trail_id = new_trail_id;
  
  for (i = 0; i < new_trail_length; i++)
  {
    struct Trail_Element *element = GNUNET_new (struct Trail_Element);
    element->peer = new_trail[i];

    GNUNET_CONTAINER_DLL_insert_tail (replace_trail->trail_head,
                                      replace_trail->trail_tail,
                                      element);
  }
  /* FIXME: URGENT Are we adding the trail back to the list. */
}


/**
 * Check if the new trail to reach to finger is unique or do we already have
 * such a trail present for finger.
 * @param existing_finger Finger identity
 * @param new_trail New trail to reach @a existing_finger
 * @param trail_length Total number of peers in new_trail.
 * @return #GNUNET_YES if the new trail is unique
 *         #GNUNET_NO if same trail is already present.
 */
static int
is_new_trail_unique (struct FingerInfo *existing_finger,
                     const struct GNUNET_PeerIdentity *new_trail,
                     unsigned int trail_length)
{
  struct Trail *trail;
  struct Trail_Element *trail_element;
  int i;
  int j;
  
  GNUNET_assert (existing_finger->trails_count > 0);

  /* Iterate over list of trails. */
  for (i = 0; i < existing_finger->trails_count; i++)
  {
    trail = &(existing_finger->trail_list[i]);
    GNUNET_assert (GNUNET_YES == trail->is_present);

    /* New trail and existing trail length are not same. */
    if (trail->trail_length != trail_length)
    {
      return GNUNET_YES;
    }

    trail_element = trail->trail_head;
    GNUNET_assert (trail_element != NULL);
    for (j = 0; j < trail->trail_length; j++)
    {
      if (0 != GNUNET_CRYPTO_cmp_peer_identity (&new_trail[j],
                                                &trail_element->peer))
      {
        return GNUNET_YES;
      }
      trail_element = trail_element->next;
    }
  }
  return GNUNET_NO;
}


/** 
 * FIXME; In case of multiple trails, we may have a case where a trail from in
 * between has been removed, then we should try to find a free slot , not simply
 * add a trail at then end of the list. 
 * Add a new trail to existing finger. This function is called only when finger
 * is not my own identity or a friend.
 * @param existing_finger Finger
 * @param new_finger_trail New trail from me to finger, NOT including endpoints
 * @param new_finger_trail_length Total number of peers in @a new_finger_trail
 * @param new_finger_trail_id Unique identifier of the trail.
 */
static void
add_new_trail (struct FingerInfo *existing_finger,
               const struct GNUNET_PeerIdentity *new_trail,
               unsigned int new_trail_length,
               struct GNUNET_HashCode new_trail_id)
{
  struct Trail *trail;
  struct FriendInfo *first_friend;
  int i;
  int index;
  
  if (GNUNET_NO == is_new_trail_unique (existing_finger, new_trail,
                                        new_trail_length))
  {
    return;
  }
  
  index = existing_finger->trails_count;
  trail = &existing_finger->trail_list[index];
  GNUNET_assert (GNUNET_NO == trail->is_present);
  trail->trail_id = new_trail_id;
  trail->trail_length = new_trail_length;
  existing_finger->trails_count++;
  trail->is_present = GNUNET_YES;

  GNUNET_assert (NULL == (GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                             &existing_finger->finger_identity)));
  /* If finger is a friend then we never call this function. */
  GNUNET_assert (new_trail_length > 0);

  first_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                    &new_trail[0]);
  first_friend->trails_count++;

  for (i = 0; i < new_trail_length; i++)
  {
    struct Trail_Element *element;

    element = GNUNET_new (struct Trail_Element);
    element->peer = new_trail[i];
    GNUNET_CONTAINER_DLL_insert_tail (trail->trail_head,
                                      trail->trail_tail,
                                      element);
  }
  /* Do we need to add trail head and trail tail in the trail list itearator.*/
  existing_finger->trail_list[index].trail_head = trail->trail_head;
  existing_finger->trail_list[index].trail_tail = trail->trail_tail;
  existing_finger->trail_list[index].trail_length = new_trail_length;
  existing_finger->trail_list[index].trail_id = new_trail_id;
  existing_finger->trail_list[index].is_present = GNUNET_YES;
}


/**
 * FIXME Check if this function is called for opposite direction if yes then
 * take it as parameter.
 * Get the next hop to send trail teardown message from routing table and
 * then delete the entry from routing table. Send trail teardown message for a
 * specific trail of a finger.
 * @param finger Finger whose trail is to be removed.
 * @param trail List of peers in trail from me to a finger, NOT including
 *              endpoints.
 */
static void
send_trail_teardown (struct FingerInfo *finger,
                     struct Trail *trail)
{
  struct FriendInfo *friend;
  struct GNUNET_PeerIdentity *next_hop;

  next_hop = GDS_ROUTING_get_next_hop (trail->trail_id,
                                       GDS_ROUTING_SRC_TO_DEST);
  
  if (NULL == next_hop)
  {
    DEBUG(" NO ENTRY FOUND IN %s ROUTING TABLE for trail id %s, line",
            GNUNET_i2s(&my_identity), GNUNET_h2s(&trail->trail_id), __LINE__);
    GNUNET_break(0);
    return;
  }
  
  GNUNET_assert (0 != GNUNET_CRYPTO_cmp_peer_identity (&finger->finger_identity,
                                                       &my_identity));

  /*FIXME: here was an assertion that trail->is_present = GNUNET_YES. But it 
   used to fail. We have removed assertion with a condition, just for now.
   Find out the reason why assertion failed. */
  if (trail->is_present == GNUNET_NO)
  {
    DEBUG(" trail id %s of peer %s is not present to send a trail teardown message., line",
            GNUNET_i2s(&my_identity), GNUNET_h2s(&trail->trail_id), __LINE__);
    return;
  }

  /* Finger is not a friend. */
  if (trail->trail_length > 0)
  {
    friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                &trail->trail_head->peer);
  }
  else
  {
    friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                &finger->finger_identity);
  }

  if(NULL == friend)
  {
    DEBUG ("\n LINE NO: = %d, Friend not found for trail id  %s of peer %s trail length = %d",
           __LINE__,GNUNET_h2s(&trail->trail_id), GNUNET_i2s(&my_identity),trail->trail_length);
    return;
  }
  if (0 != GNUNET_CRYPTO_cmp_peer_identity (next_hop, &friend->id)
      && (0 == trail->trail_length))
  {
    //FIXME HERE WE GOT NEXT HOP FRM ROUTING TABLE, AND TRAIL ENGTH - 0, IT ITS
    // THE CASE WEHERE WE SET IT TO 0. 
     DEBUG ("\n LINE NO: = %d, Friend not found for trail id  %s of peer %s trail length = %d",
           __LINE__,GNUNET_h2s(&trail->trail_id), GNUNET_i2s(&my_identity),trail->trail_length);
    return;
  }
  GNUNET_assert (GNUNET_YES == GDS_ROUTING_remove_trail (trail->trail_id));
  friend->trails_count--;
  GDS_NEIGHBOURS_send_trail_teardown (trail->trail_id,
                                      GDS_ROUTING_SRC_TO_DEST,
                                      friend->id);
}


/**
 * Send trail teardown message across all the trails to reach to finger.
 * @param finger Finger whose all the trail should be freed.
 */
static void
send_all_finger_trails_teardown (struct FingerInfo *finger)
{
  unsigned int i;
  for (i = 0; i < finger->trails_count; i++)
  {
    struct Trail *trail;

    trail = &finger->trail_list[i];
    GNUNET_assert (trail->is_present == GNUNET_YES);
    send_trail_teardown (finger, trail);
    trail->is_present = GNUNET_NO;
   }
}


/**
 * Free a specific trail
 * @param trail List of peers to be freed.
 */
static void
free_trail (struct Trail *trail)
{
  struct Trail_Element *trail_element;

  while (NULL != (trail_element = trail->trail_head))
  {
    GNUNET_CONTAINER_DLL_remove (trail->trail_head,
                                 trail->trail_tail,
                                 trail_element);
    GNUNET_free_non_null (trail_element);
  }
  trail->trail_head = NULL;
  trail->trail_tail = NULL;
}


/**
 * Free finger and its trail.
 * @param finger Finger to be freed.
 * @param finger_table_index Index at which finger is stored.
 */
static void
free_finger (struct FingerInfo *finger, unsigned int finger_table_index)
{
  struct Trail *trail;
  unsigned int i;
  for (i = 0; i < finger->trails_count; i++)
  {
    trail = &finger->trail_list[i];
    if (GNUNET_NO == trail->is_present)
      continue;

    if (trail->trail_length > 0)
      free_trail (trail);
    trail->is_present = GNUNET_NO;
  }

  finger->is_present = GNUNET_NO;
  memset ((void *)&finger_table[finger_table_index], 0, sizeof (finger_table[finger_table_index]));
}


/**
 * Add a new entry in finger table at finger_table_index.
 * In case I am my own finger, then we don't have a trail. In case of a friend,
 * we have a trail with unique id and '0' trail length.
 * In case a finger is a friend, then increment the trails count of the friend.
 * @param finger_identity Peer Identity of new finger
 * @param finger_trail Trail to reach from me to finger (excluding both end points).
 * @param finger_trail_length Total number of peers in @a finger_trail.
 * @param trail_id Unique identifier of the trail.
 * @param finger_table_index Index in finger table.
 */
static void
add_new_finger (struct GNUNET_PeerIdentity finger_identity,
                const struct GNUNET_PeerIdentity *finger_trail,
                unsigned int finger_trail_length,
                struct GNUNET_HashCode trail_id,
                unsigned int finger_table_index)
{
  struct FingerInfo *new_entry;
  struct FriendInfo *first_trail_hop;
  struct Trail *trail;
  int i;
  
  new_entry = GNUNET_new (struct FingerInfo);
  new_entry->finger_identity = finger_identity;
  new_entry->finger_table_index = finger_table_index;
  new_entry->is_present = GNUNET_YES;
  
  /* If the new entry is my own identity. */
  if (0 == GNUNET_CRYPTO_cmp_peer_identity (&my_identity,
                                            &finger_identity))
  {
    new_entry->trails_count = 0;
    finger_table[finger_table_index] = *new_entry;
    GNUNET_free (new_entry);
    return;
  }
  
  /* If finger is a friend, then we don't actually have a trail.
   *  Just a trail id */
  if (NULL != GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                 &finger_identity))
  {
    //FIXME: HERE WE SET TRAIL LENGTH TO 0, EVEN THOUGH IT HAS ENTRIES. 
    new_entry->trail_list[0].trail_id = trail_id;
    new_entry->trails_count = 1;
    new_entry->trail_list[0].is_present = GNUNET_YES;
    new_entry->trail_list[0].trail_length = 0;
    new_entry->trail_list[0].trail_head = NULL;
    new_entry->trail_list[0].trail_tail = NULL;
    finger_table[finger_table_index] = *new_entry;
    GNUNET_assert (NULL !=
                  (first_trail_hop =
                       GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                          &finger_identity)));

    first_trail_hop->trails_count++;
    GNUNET_free (new_entry);
    return;
  }

  GNUNET_assert (NULL !=
                (first_trail_hop =
                       GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                          &finger_trail[0])));
  new_entry->trails_count = 1;
  first_trail_hop->trails_count++;
  GNUNET_assert (finger_trail_length != 0);
  /* Copy the finger trail into trail. */
  trail = GNUNET_new (struct Trail);
  for(i = 0; i < finger_trail_length; i++)
  {
    struct Trail_Element *element = GNUNET_new (struct Trail_Element);

    element->next = NULL;
    element->prev = NULL;
    element->peer = finger_trail[i];
    GNUNET_CONTAINER_DLL_insert_tail (trail->trail_head,
                                      trail->trail_tail,
                                      element);
  }
 

  /* Add trail to trail list. */
  new_entry->trail_list[0].trail_head = trail->trail_head;
  new_entry->trail_list[0].trail_tail = trail->trail_tail;
  new_entry->trail_list[0].trail_length = finger_trail_length;
  new_entry->trail_list[0].trail_id = trail_id;
  new_entry->trail_list[0].is_present = GNUNET_YES;
  finger_table[finger_table_index] = *new_entry;
  GNUNET_free (new_entry);
  return;
}


/**
 * Periodic task to verify current successor. There can be multiple trails to reach
 * to successor, choose the shortest one and send verify successor message
 * across that trail.
 * @param cls closure for this task
 * @param tc the context under which the task is running
 */
static void
send_verify_successor_message (void *cls,
                                const struct GNUNET_SCHEDULER_TaskContext *tc)
{
  struct FriendInfo *target_friend;
  struct GNUNET_HashCode trail_id;
  int i;
  struct Trail *trail;
  struct Trail_Element *element;
  unsigned int trail_length;
  unsigned int j = 0;
  struct FingerInfo *successor;

  /* Schedule another send_find_finger_trail_message task. 
  verify_successor_next_send_time.rel_value_us =
      verify_successor_next_send_time.rel_value_us +
      GNUNET_CRYPTO_random_u64 (GNUNET_CRYPTO_QUALITY_WEAK,
                                DHT_SEND_VERIFY_SUCCESSOR_INTERVAL.rel_value_us);*/
  send_verify_successor_task =
      GNUNET_SCHEDULER_add_delayed (verify_successor_next_send_time,
                                    &send_verify_successor_message,
                                    NULL);

  successor = &finger_table[0];
  for (i = 0; i < successor->trails_count; i++)
  {
    trail = &successor->trail_list[i];
    if(GNUNET_YES == trail->is_present)
      break;
  }
  
  /* No valid trail found to reach to successor. */
  if (i == successor->trails_count)
    return;
  
  GNUNET_assert(0 != GNUNET_CRYPTO_cmp_peer_identity (&my_identity,
                                                      &successor->finger_identity));

  /* Trail stored at this index. */
  GNUNET_assert (GNUNET_YES == trail->is_present);
  
  trail_id = trail->trail_id;
  if (NULL == GDS_ROUTING_get_next_hop(trail_id,GDS_ROUTING_SRC_TO_DEST))
  {
    DEBUG(" NO ENTRY FOUND IN %s ROUTING TABLE for trail id %s, line",
            GNUNET_i2s(&my_identity), GNUNET_h2s(&trail->trail_id), __LINE__);
    GNUNET_break(0);
    return;
  }
  trail_length = trail->trail_length;
  
  if (trail_length > 0)
  {
     /* Copy the trail into peer list. */
    struct GNUNET_PeerIdentity peer_list[trail_length];

    element = trail->trail_head;
    for(j = 0; j < trail_length; j++)
    {
      peer_list[j] = element->peer;
      element = element->next;
    }

    GNUNET_assert (NULL != (target_friend =
                            GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                               &peer_list[0])));
    GDS_NEIGHBOURS_send_verify_successor_message (my_identity,
                                                  successor->finger_identity,
                                                  trail_id, peer_list, trail_length,
                                                  target_friend);
    return;
  }
  else
  {
    GNUNET_assert (NULL != (target_friend =
                            GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                               &successor->finger_identity)));
    GDS_NEIGHBOURS_send_verify_successor_message (my_identity,
                                                  successor->finger_identity,
                                                  trail_id, NULL, 0,
                                                  target_friend);
    return;
  }
}


/**
 * FIXME: should this be a periodic task, incrementing the search finger index?
 * Update the current search finger index.
 *
 * FIXME document parameters!
 */
static void
update_current_search_finger_index (struct GNUNET_PeerIdentity finger_identity,
                                    unsigned int finger_table_index)
{
  struct FingerInfo *successor;

  /* FIXME correct this: only move current index periodically */
  if (finger_table_index != current_search_finger_index)
    return;

  successor = &finger_table[0];
  GNUNET_assert (GNUNET_YES == successor->is_present);

  /* We were looking for immediate successor.  */
  if (0 == current_search_finger_index)
  {
    /* Start looking for immediate predecessor. */
    current_search_finger_index = PREDECESSOR_FINGER_ID;

    if (0 != GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &finger_identity))
    {
      if (GNUNET_SCHEDULER_NO_TASK == send_verify_successor_task)
      {
        send_verify_successor_task = 
                GNUNET_SCHEDULER_add_now (&send_verify_successor_message, NULL);
      }
    }
    return;
  }

  current_search_finger_index = current_search_finger_index - 1;
  return;
}


/**
 * Get the least significant bit set in val.
 *
 * @param val Value
 * @return Position of first bit set, 65 in case of error.
 */
static unsigned int
find_set_bit (uint64_t val)
{
  uint64_t i;
  unsigned int pos;

  i = 1;
  pos = 0;

  while (!(i & val))
  {
    i = i << 1;
    pos++;
    if (pos > 63)
    {
      GNUNET_break (0);
      return 65;
    }
  }

  if (val/i != 1)
    return 65; /* Some other bit was set to 1 as well. */

  return pos;
}


/**
 * Calculate finger_table_index from initial 64 bit finger identity value that
 * we send in trail setup message.
 * @param ultimate_destination_finger_value Value that we calculated from our
 *                                          identity and finger_table_index.
 * @param is_predecessor Is the entry for predecessor or not?
 * @return finger_table_index Value between 0 <= finger_table_index <= 64
 *         finger_table_index > PREDECESSOR_FINGER_ID, if error occurs.
 */
static unsigned int
get_finger_table_index (uint64_t ultimate_destination_finger_value,
                        unsigned int is_predecessor)
{
  uint64_t my_id64;
  uint64_t diff;
  unsigned int finger_table_index;

  memcpy (&my_id64, &my_identity, sizeof (uint64_t));
  my_id64 = GNUNET_ntohll (my_id64);

  /* Is this a predecessor finger? */
  if (1 == is_predecessor)
  {
    diff =  my_id64 - ultimate_destination_finger_value;
    if (1 == diff)
      finger_table_index = PREDECESSOR_FINGER_ID;
    else
      finger_table_index = PREDECESSOR_FINGER_ID + 1; //error value

  }
  else
  {
    diff = ultimate_destination_finger_value - my_id64;
    finger_table_index = find_set_bit (diff);
  }
  return finger_table_index;
}


/**
 * Remove finger and its associated data structures from finger table.
 * @param existing_finger Finger to be removed which is in finger table. 
 * @param finger_table_index Index in finger table where @a existing_finger
 *                           is stored.
 */
static void
remove_existing_finger (struct FingerInfo *existing_finger,
                        unsigned int finger_table_index)
{
  GNUNET_assert (GNUNET_YES == existing_finger->is_present);

  /* If I am my own finger, then we have no trails. */
  if (0 == GNUNET_CRYPTO_cmp_peer_identity (&existing_finger->finger_identity,
                                            &my_identity))
  {
    existing_finger->is_present = GNUNET_NO;
    memset ((void *)&finger_table[finger_table_index], 0,
            sizeof (finger_table[finger_table_index]));
    return;
  }

  /* For all other fingers, send trail teardown across all the trails to reach
   finger, and free the finger. */
  send_all_finger_trails_teardown (existing_finger);
  free_finger (existing_finger, finger_table_index);
  return;
}


/**
 * Check if there is already an entry in finger_table at finger_table_index.
 * We get the finger_table_index from 64bit finger value we got from the network.
 * -- If yes, then select the closest finger.
 *   -- If new and existing finger are same, then check if you can store more
 *      trails.
 *      -- If yes then add trail, else keep the best trails to reach to the
 *         finger.
 *   -- If the new finger is closest, remove the existing entry, send trail
 *      teardown message across all the trails to reach the existing entry.
 *      Add the new finger.
 *  -- If new and existing finger are different, and existing finger is closest
 *     then do nothing.
 * -- Update current_search_finger_index.
 * @param finger_identity Peer Identity of new finger
 * @param finger_trail Trail to reach the new finger
 * @param finger_trail_length Total number of peers in @a new_finger_trail.
 * @param is_predecessor Is this entry for predecessor in finger_table?
 * @param finger_value 64 bit value of finger identity that we got from network.
 * @param finger_trail_id Unique identifier of @finger_trail.
 */
static void
finger_table_add (struct GNUNET_PeerIdentity finger_identity,
                  const struct GNUNET_PeerIdentity *finger_trail,
                  unsigned int finger_trail_length,
                  unsigned int is_predecessor,
                  uint64_t finger_value,
                  struct GNUNET_HashCode finger_trail_id)
{
  struct FingerInfo *existing_finger;
  struct GNUNET_PeerIdentity closest_peer;
  struct FingerInfo *successor;
  unsigned int finger_table_index;

  /* Get the finger_table_index corresponding to finger_value we got from network.*/
  finger_table_index = get_finger_table_index (finger_value, is_predecessor);

  /* Invalid finger_table_index. */
  if ((finger_table_index > PREDECESSOR_FINGER_ID))
  {
    GNUNET_break_op (0);
    return;
  }

  /* New entry same as successor. */
  if ((0 != finger_table_index) &&
      (PREDECESSOR_FINGER_ID != finger_table_index))
  {
    successor = &finger_table[0];
    if (GNUNET_NO == successor->is_present)
    {
      GNUNET_break (0);
      return;
    }
    if (0 == GNUNET_CRYPTO_cmp_peer_identity (&finger_identity,
                                              &successor->finger_identity))
    {
      find_finger_trail_task_next_send_time = 
              GNUNET_TIME_STD_BACKOFF(find_finger_trail_task_next_send_time);
      current_search_finger_index = 0;
      return;
    }
    
    struct FingerInfo prev_finger;
    prev_finger = finger_table[finger_table_index - 1];
    if (0 == GNUNET_CRYPTO_cmp_peer_identity (&finger_identity,
                                              &prev_finger.finger_identity))
    {
       current_search_finger_index--;
       return;
    }
  }

  existing_finger = &finger_table[finger_table_index];

  /* No entry present in finger_table for given finger map index. */
  if (GNUNET_NO == existing_finger->is_present)
  {
    add_new_finger (finger_identity, finger_trail,
                    finger_trail_length,
                    finger_trail_id, finger_table_index);
    update_current_search_finger_index (finger_identity,
                                        finger_table_index);
    return;
  }


  /* If existing entry and finger identity are not same. */
  if (0 != GNUNET_CRYPTO_cmp_peer_identity (&(existing_finger->finger_identity),
                                            &finger_identity))
  {
    closest_peer = select_closest_peer (&existing_finger->finger_identity,
                                        &finger_identity,
                                        finger_value,
                                        is_predecessor);

    /* If the new finger is the closest peer. */
    if (0 == GNUNET_CRYPTO_cmp_peer_identity (&finger_identity, &closest_peer))
    {
      remove_existing_finger (existing_finger, finger_table_index);
      add_new_finger (finger_identity, finger_trail, finger_trail_length,
                      finger_trail_id, finger_table_index);
    }
    else
    {
      /* Existing finger is the closest one. We need to send trail teardown
         across the trail setup in routing table of all the peers. */
      if (0 != GNUNET_CRYPTO_cmp_peer_identity (&finger_identity, &my_identity))
      {
        if (finger_trail_length > 0)
          GDS_NEIGHBOURS_send_trail_teardown (finger_trail_id,
                                              GDS_ROUTING_SRC_TO_DEST,
                                              finger_trail[0]);
        else
          GDS_NEIGHBOURS_send_trail_teardown (finger_trail_id,
                                              GDS_ROUTING_SRC_TO_DEST,
                                              finger_identity);
      }
    }
  }
  else
  {
    /* If both new and existing entry are same as my_identity, then do nothing. */
    if (0 == GNUNET_CRYPTO_cmp_peer_identity (&(existing_finger->finger_identity),
                                              &my_identity))
    {
      return;
    }
    /* If the existing finger is not a friend. */
    if (NULL ==
        GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                           &existing_finger->finger_identity))
    {
      /* If there is space to store more trails. */
      if (existing_finger->trails_count < MAXIMUM_TRAILS_PER_FINGER)
        add_new_trail (existing_finger, finger_trail,
                       finger_trail_length, finger_trail_id);
      else
        select_and_replace_trail (existing_finger, finger_trail,
                                  finger_trail_length, finger_trail_id);

    }
  }
  update_current_search_finger_index (finger_identity, finger_table_index);
  return;
}


/**
 * FIXME: Check for loop in the request. If you already are part of put path,
 * then you need to reset the put path length.
 * Core handler for P2P put messages.
 * @param cls closure
 * @param peer sender of the request
 * @param message message
 * @return #GNUNET_OK to keep the connection open,
 *         #GNUNET_SYSERR to close it (signal serious error)
 */
static int
handle_dht_p2p_put (void *cls, const struct GNUNET_PeerIdentity *peer,
                    const struct GNUNET_MessageHeader *message)
{
  struct PeerPutMessage *put;
  struct GNUNET_PeerIdentity *put_path;
  struct GNUNET_PeerIdentity best_known_dest;
  struct GNUNET_HashCode intermediate_trail_id;
  struct GNUNET_PeerIdentity *next_hop;
  enum GNUNET_DHT_RouteOption options;
  struct GNUNET_HashCode test_key;
  void *payload;
  size_t msize;
  uint32_t putlen;
  uint32_t hop_count;
  size_t payload_size;
  uint64_t key_value;

#if ENABLE_MALICIOUS
  if(1 == act_malicious)
  {
    DEBUG("I am malicious,dropping put request. \n");
    return GNUNET_OK;
  }
#endif
  
  msize = ntohs (message->size);
  if (msize < sizeof (struct PeerPutMessage))
  {
    GNUNET_break_op (0);
    return GNUNET_OK;
  }

  put = (struct PeerPutMessage *) message;
  putlen = ntohl (put->put_path_length);
  if ((msize <
       sizeof (struct PeerPutMessage) +
       putlen * sizeof (struct GNUNET_PeerIdentity)) ||
      (putlen >
       GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity)))
  {
    GNUNET_break_op (0);
    return GNUNET_OK;
  }
  DEBUG("GET FOR DATA_SIZE = %lu\n",msize);
  GNUNET_STATISTICS_update (GDS_stats,
                            gettext_noop
                            ("# Bytes received from other peers"), (int64_t) msize,
                            GNUNET_NO);
  
  best_known_dest = put->best_known_destination;
  put_path = (struct GNUNET_PeerIdentity *) &put[1];
  payload = &put_path[putlen];
  options = ntohl (put->options);
  intermediate_trail_id = put->intermediate_trail_id;
  hop_count = ntohl(put->hop_count);
  payload_size = msize - (sizeof (struct PeerPutMessage) +
                          putlen * sizeof (struct GNUNET_PeerIdentity));
  hop_count++;
  switch (GNUNET_BLOCK_get_key (GDS_block_context, ntohl (put->block_type),
                                payload, payload_size, &test_key))
  {
    case GNUNET_YES:
      if (0 != memcmp (&test_key, &put->key, sizeof (struct GNUNET_HashCode)))
      {
        char *put_s = GNUNET_strdup (GNUNET_h2s_full (&put->key));
        GNUNET_break_op (0);
        GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                    "PUT with key `%s' for block with key %s\n",
                     put_s, GNUNET_h2s_full (&test_key));
        GNUNET_free (put_s);
        return GNUNET_OK;
      }
    break;
    case GNUNET_NO:
      GNUNET_break_op (0);
      return GNUNET_OK;
    case GNUNET_SYSERR:
      /* cannot verify, good luck */
      break;
  }

   if (ntohl (put->block_type) == GNUNET_BLOCK_TYPE_REGEX) /* FIXME: do for all tpyes */
  {
    switch (GNUNET_BLOCK_evaluate (GDS_block_context,
                                   ntohl (put->block_type),
                                   NULL,    /* query */
                                   NULL, 0, /* bloom filer */
                                   NULL, 0, /* xquery */
                                   payload, payload_size))
    {
    case GNUNET_BLOCK_EVALUATION_OK_MORE:
    case GNUNET_BLOCK_EVALUATION_OK_LAST:
      break;

    case GNUNET_BLOCK_EVALUATION_OK_DUPLICATE:
    case GNUNET_BLOCK_EVALUATION_RESULT_INVALID:
    case GNUNET_BLOCK_EVALUATION_RESULT_IRRELEVANT:
    case GNUNET_BLOCK_EVALUATION_REQUEST_VALID:
    case GNUNET_BLOCK_EVALUATION_REQUEST_INVALID:
    case GNUNET_BLOCK_EVALUATION_TYPE_NOT_SUPPORTED:
    default:
      GNUNET_break_op (0);
      return GNUNET_OK;
    }
  }
  
  /* Check if you are already a part of put path. */
  unsigned int i;
  for (i = 0; i < putlen; i++)
  {
    if(0 == GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &put_path[i]))
    {
      putlen = i;
      break;
    }
  }
    
  /* Add yourself to the list. */
  struct GNUNET_PeerIdentity pp[putlen + 1];
  if (0 != (options & GNUNET_DHT_RO_RECORD_ROUTE))
  {
    memcpy (pp, put_path, putlen * sizeof (struct GNUNET_PeerIdentity));
    pp[putlen] = my_identity;
    putlen++;
  }
  else
    putlen = 0;
  
  memcpy (&key_value, &(put->key), sizeof (uint64_t));
  if (0 != (GNUNET_CRYPTO_cmp_peer_identity (&best_known_dest, &my_identity)))
  {
    next_hop = GDS_ROUTING_get_next_hop (intermediate_trail_id,
                                         GDS_ROUTING_SRC_TO_DEST);
    if (NULL == next_hop)
    {
      DEBUG(" NO ENTRY FOUND IN %s ROUTING TABLE for trail id %s, line",
            GNUNET_i2s(&my_identity), GNUNET_h2s(&intermediate_trail_id), __LINE__);
      GNUNET_STATISTICS_update (GDS_stats,
                                gettext_noop ("# Next hop to forward the packet not found "
                                "trail setup request, packet dropped."),
                                1, GNUNET_NO);
      
      GNUNET_break_op (0);
      //FIXME: Adding put here,only to ensure that process does not hang. but
      // should not be here. fix the logic. 
      GDS_DATACACHE_handle_put (GNUNET_TIME_absolute_ntoh (put->expiration_time),
                                &(put->key),putlen, pp, ntohl (put->block_type),
                                 payload_size, payload);
      return GNUNET_OK;
    }
    else
    {
      GNUNET_assert (0 != GNUNET_CRYPTO_cmp_peer_identity (&my_identity, 
                                                            next_hop));
    }
  }
  else
  {
    struct Closest_Peer successor;
    key_value = GNUNET_ntohll (key_value);
    successor = find_successor (key_value, GDS_FINGER_TYPE_NON_PREDECESSOR);
    next_hop = GNUNET_new (struct GNUNET_PeerIdentity);
    *next_hop = successor.next_hop;
    intermediate_trail_id = successor.trail_id;
    best_known_dest = successor.best_known_destination;
  }
  

  
  GDS_CLIENTS_process_put (options,
                           ntohl (put->block_type),
                           hop_count,
                           ntohl (put->desired_replication_level),
                           putlen, pp,
                           GNUNET_TIME_absolute_ntoh (put->expiration_time),
                           &put->key,
                           payload,
                           payload_size);

  /* I am the final destination */
  if (0 == GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &best_known_dest))
  {
    GDS_DATACACHE_handle_put (GNUNET_TIME_absolute_ntoh (put->expiration_time),
                              &(put->key),putlen, pp, ntohl (put->block_type),
                              payload_size, payload);
  }
  else
  {
    GDS_NEIGHBOURS_send_put (&put->key,
                             ntohl (put->block_type),ntohl (put->options),
                             ntohl (put->desired_replication_level),
                             best_known_dest, intermediate_trail_id, next_hop,
                             hop_count, putlen, pp,
                             GNUNET_TIME_absolute_ntoh (put->expiration_time),
                             payload, payload_size);
   }
  return GNUNET_OK;
}


/**
 * FIXME: Check for loop in the request. If you already are part of get path,
 * then you need to reset the get path length.
 * 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)
{
  const struct PeerGetMessage *get;
  const struct GNUNET_PeerIdentity *get_path;
  struct GNUNET_PeerIdentity best_known_dest;
  struct GNUNET_HashCode intermediate_trail_id;
  struct GNUNET_PeerIdentity *next_hop;
  uint32_t get_length;
  uint64_t key_value;
  uint32_t hop_count;
  size_t msize;

#if ENABLE_MALICIOUS
  if(1 == act_malicious)
  {
    DEBUG("I am malicious,dropping get request. \n");
    return GNUNET_OK;
  }
#endif
  
  msize = ntohs (message->size);
  if (msize < sizeof (struct PeerGetMessage))
  {
    GNUNET_break_op (0);
    return GNUNET_YES;
  }

  get = (const struct PeerGetMessage *)message;
  get_length = ntohl (get->get_path_length);
  best_known_dest = get->best_known_destination;
  intermediate_trail_id = get->intermediate_trail_id;
  get_path = (const struct GNUNET_PeerIdentity *)&get[1];
  hop_count = get->hop_count;
  hop_count++;
  
  if ((msize <
       sizeof (struct PeerGetMessage) +
       get_length * sizeof (struct GNUNET_PeerIdentity)) ||
       (get_length >
        GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity)))
  {
    GNUNET_break_op (0);
    return GNUNET_YES;
  }
  
  GNUNET_STATISTICS_update (GDS_stats,
                            gettext_noop
                            ("# Bytes received from other peers"), msize,
                            GNUNET_NO);
  
  memcpy (&key_value, &(get->key), sizeof (uint64_t));
  key_value = GNUNET_ntohll (key_value);
  
  /* Check if you are already a part of get path. */
  unsigned int i;
  for (i = 0; i < get_length; i++)
  {
    if (0 == GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &get_path[i]))
    {
      get_length = i;
      break;
    }
  }
  
  /* Add yourself in the get path. */
  struct GNUNET_PeerIdentity gp[get_length + 1];
  memcpy (gp, get_path, get_length * sizeof (struct GNUNET_PeerIdentity));
  gp[get_length] = my_identity;
  get_length = get_length + 1;
  GDS_CLIENTS_process_get (get->options, get->block_type, hop_count,
                           get->desired_replication_level, get->get_path_length,
                           gp, &get->key);
  
  /* I am not the final destination. I am part of trail to reach final dest. */
  if (0 != (GNUNET_CRYPTO_cmp_peer_identity (&best_known_dest, &my_identity)))
  {
    next_hop = GDS_ROUTING_get_next_hop (intermediate_trail_id,
                                         GDS_ROUTING_SRC_TO_DEST);
    if (NULL == next_hop)
    {
      DEBUG(" NO ENTRY FOUND IN %s ROUTING TABLE for trail id %s, line",
            GNUNET_i2s(&my_identity), GNUNET_h2s(&intermediate_trail_id), __LINE__);
      GNUNET_STATISTICS_update (GDS_stats,
                                gettext_noop ("# Next hop to forward the packet not found "
                                "GET request, packet dropped."),
                                1, GNUNET_NO);
      GNUNET_break (0);
      /* We are not able to proceed further*/
      GDS_DATACACHE_handle_get (&(get->key),(get->block_type), NULL, 0, NULL, 0,
                                get_length, gp, &gp[get_length - 2], 
                                &my_identity);
      return GNUNET_OK;
    }
  }
  else
  {
    struct Closest_Peer successor;

    successor = find_successor (key_value, GDS_FINGER_TYPE_NON_PREDECESSOR);
    next_hop = GNUNET_new (struct GNUNET_PeerIdentity);
    *next_hop = successor.next_hop;
    best_known_dest = successor.best_known_destination;
    intermediate_trail_id = successor.trail_id;
  }
   
  /* I am the final destination. */
  if (0 == GNUNET_CRYPTO_cmp_peer_identity(&my_identity, &best_known_dest))
  {
    if (1 == get_length)
    {
      GDS_DATACACHE_handle_get (&(get->key),(get->block_type), NULL, 0,
                                NULL, 0, 1, &my_identity, NULL,&my_identity);
    }
    else
    {
      GDS_DATACACHE_handle_get (&(get->key),(get->block_type), NULL, 0, NULL, 0,
                                get_length, gp, &gp[get_length - 2], 
                                &my_identity);
    }
  }
  else
  {
    GDS_NEIGHBOURS_send_get (&(get->key), get->block_type, get->options,
                             get->desired_replication_level, best_known_dest,
                             intermediate_trail_id, next_hop, hop_count,
                             get_length, gp);
  }
  return GNUNET_YES;
}


/**
 * 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)
{
  const struct PeerGetResultMessage *get_result;
  const struct GNUNET_PeerIdentity *get_path;
  const struct GNUNET_PeerIdentity *put_path;
  const void *payload;
  size_t payload_size;
  size_t msize;
  unsigned int getlen;
  unsigned int putlen;
  int current_path_index;

  msize = ntohs (message->size);
  if (msize < sizeof (struct PeerGetResultMessage))
  {
    GNUNET_break_op (0);
    return GNUNET_YES;
  }

  get_result = (const struct PeerGetResultMessage *)message;
  getlen = ntohl (get_result->get_path_length);
  putlen = ntohl (get_result->put_path_length);

  if ((msize <
       sizeof (struct PeerGetResultMessage) +
       getlen * sizeof (struct GNUNET_PeerIdentity) +
       putlen * sizeof (struct GNUNET_PeerIdentity)) ||
      (getlen >
       GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity) ||
      (putlen >
         GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity))))
  {
    GNUNET_break_op (0);
    return GNUNET_YES;
  }
  DEBUG("GET_RESULT  FOR DATA_SIZE = %lu\n",msize);
  GNUNET_STATISTICS_update (GDS_stats,
                            gettext_noop
                            ("# Bytes received from other peers"), msize,
                            GNUNET_NO);
  
  put_path = (const struct GNUNET_PeerIdentity *) &get_result[1];
  get_path = &put_path[putlen];
  payload = (const void *) &get_path[getlen];
  payload_size = msize - (sizeof (struct PeerGetResultMessage) +
                         (getlen + putlen) * sizeof (struct GNUNET_PeerIdentity));

  if (0 == (GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &(get_path[0]))))
  {
    GDS_CLIENTS_handle_reply (get_result->expiration_time, &(get_result->key),
                              getlen, get_path, putlen,
                              put_path, get_result->type, payload_size, payload);
    return GNUNET_YES;
  }
  else
  {
    current_path_index = search_my_index (get_path, getlen);
    if (-1 == current_path_index )
    {
      DEBUG ("No entry found in get path.\n");
      GNUNET_break (0);
      return GNUNET_SYSERR;
    }
    if((getlen + 1) == current_path_index)
    {
      DEBUG("Present twice in get path. Not allowed. \n");
      GNUNET_break (0);
      return GNUNET_SYSERR;
    }
    GDS_NEIGHBOURS_send_get_result (&(get_result->key), get_result->type,
                                    &get_path[current_path_index - 1],
                                    &(get_result->querying_peer), putlen, put_path,
                                    getlen, get_path, get_result->expiration_time,
                                    payload, payload_size);
    return GNUNET_YES;
  }
  return GNUNET_SYSERR;
}


/**
 * Find the next hop to pass trail setup message. First find the local best known
 * hop from your own identity, friends and finger. If you were part of trail,
 * then get the next hop from routing table. Compare next_hop from routing table
 * and local best known hop, and return the closest one to final_dest_finger_val
 * @param final_dest_finger_val 64 bit value of finger identity
 * @param intermediate_trail_id If you are part of trail to reach to some other
 *                              finger, then it is the trail id to reach to
 *                              that finger, else set to 0.
 * @param is_predecessor Are we looking for closest successor or predecessor.
 * @param current_dest In case you are part of trail, then finger to which
 *                     we should forward the message. Else my own identity
 * @return Closest Peer for @a final_dest_finger_val
 */
static struct Closest_Peer
get_local_best_known_next_hop (uint64_t final_dest_finger_val,
                               struct GNUNET_HashCode intermediate_trail_id,
                               unsigned int is_predecessor,
                                struct GNUNET_PeerIdentity prev_hop,
                               struct GNUNET_PeerIdentity source,
                               struct GNUNET_PeerIdentity *current_dest)
{
  struct Closest_Peer peer;

  /* Find a local best known peer. */
  peer = find_successor (final_dest_finger_val, is_predecessor);//FIXME: chnage to better name

  /* Am I just a part of a trail towards a finger (current_destination)? */
  /* Select best successor among one found locally and current_destination
   * that we got from network.*/
  if (0 != GNUNET_CRYPTO_cmp_peer_identity (&my_identity, current_dest) &&
      0 != GNUNET_CRYPTO_cmp_peer_identity (&peer.best_known_destination,
                                            current_dest))
  {
    struct GNUNET_PeerIdentity closest_peer;

    closest_peer = select_closest_peer (&peer.best_known_destination,
                                        current_dest,
                                        final_dest_finger_val,
                                        is_predecessor);

    /* Is current dest (end point of the trail of which I am a part) closest_peer? */
    if (0 == GNUNET_CRYPTO_cmp_peer_identity (current_dest, &closest_peer))
    {
      struct GNUNET_PeerIdentity *next_hop;
      
      next_hop = GDS_ROUTING_get_next_hop (intermediate_trail_id,
                                           GDS_ROUTING_SRC_TO_DEST);
      /* next_hop NULL is a valid case. This intermediate trail id is set by
       some other finger, and while this trail setup is in progress, that other
       peer might have found a better trail ,and send trail teardown message
       across the network. In case we got the trail teardown message first,
       then next_hop will be NULL. A possible solution could be to keep track
       * of all removed trail id, and be sure that there is no other reason . */
      if(NULL != next_hop)
      {
         peer.next_hop = *next_hop;
         peer.best_known_destination =  *current_dest;
         peer.trail_id = intermediate_trail_id;
      }
    }
  }
  return peer;
}


/*
 * 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)
{
  const struct PeerTrailSetupMessage *trail_setup;
  const struct GNUNET_PeerIdentity *trail_peer_list;
  struct GNUNET_PeerIdentity current_dest;
  struct FriendInfo *target_friend;
  struct GNUNET_PeerIdentity source;
  uint64_t final_dest_finger_val;
  struct GNUNET_HashCode intermediate_trail_id;
  struct GNUNET_HashCode trail_id;
  unsigned int is_predecessor;
  uint32_t trail_length;
  int i;
  size_t msize;

  msize = ntohs (message->size);
  if (msize < sizeof (struct PeerTrailSetupMessage))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }

  trail_setup = (const struct PeerTrailSetupMessage *) message;
  if ((msize - sizeof (struct PeerTrailSetupMessage)) %
      sizeof (struct GNUNET_PeerIdentity) != 0)
  {
    GNUNET_break_op (0);
    return GNUNET_OK;
  }
  trail_length = (msize - sizeof (struct PeerTrailSetupMessage))/
                  sizeof (struct GNUNET_PeerIdentity);
 
  GNUNET_STATISTICS_update (GDS_stats,
                            gettext_noop
                            ("# Bytes received from other peers"), msize,
                            GNUNET_NO);
  
  trail_peer_list = (const struct GNUNET_PeerIdentity *)&trail_setup[1];
  current_dest = trail_setup->best_known_destination;
  trail_id = trail_setup->trail_id;
  final_dest_finger_val =
          GNUNET_ntohll (trail_setup->final_destination_finger_value);
  source = trail_setup->source_peer;
  is_predecessor = ntohl (trail_setup->is_predecessor);
  intermediate_trail_id = trail_setup->intermediate_trail_id;

  /* Did the friend insert its ID in the trail list? */
  if (trail_length > 0 &&
      0 != memcmp (&trail_peer_list[trail_length-1], peer, sizeof (struct GNUNET_PeerIdentity)))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  
   /* If I was the source and got the message back, then set trail length to 0.*/
  if (0 == GNUNET_CRYPTO_cmp_peer_identity(&my_identity, &source))
  {   
    trail_length = 0;
  }
  
  /* SUPUS: remove the check that source is a friend, because again source
   may become aware about it later. and by that time lookup may fail. */
  
  /* Check if you are present in the trail seen so far? */
  for (i = 0; i < trail_length ; i++)
  {
    if(0 == GNUNET_CRYPTO_cmp_peer_identity(&trail_peer_list[i],&my_identity))
    {
      trail_length = i; /* Check that you add yourself again */
      break;
    }
  }

  /* Is my routing table full?  */
  if (GNUNET_YES == GDS_ROUTING_threshold_reached())
  {
    if (trail_length > 0)
      target_friend =
                   GNUNET_CONTAINER_multipeermap_get (friend_peermap, 
                                                      &trail_peer_list[trail_length - 1]);
    else
      target_friend =
                   GNUNET_CONTAINER_multipeermap_get (friend_peermap, 
                                                      &source);
    
    if(NULL == target_friend)
    {
      DEBUG ("\n friend not found");
      GNUNET_break(0);
      return GNUNET_OK;
    }
    
    GDS_NEIGHBOURS_send_trail_rejection (source, final_dest_finger_val,
                                         my_identity, is_predecessor,
                                         trail_peer_list, trail_length,
                                         trail_id, target_friend,
                                         CONGESTION_TIMEOUT);
    return GNUNET_OK;
  }

  /* Get the next hop to forward the trail setup request. */
  struct Closest_Peer next_peer =
          get_local_best_known_next_hop (final_dest_finger_val,
                                         intermediate_trail_id,
                                         is_predecessor,
                                         *peer,
                                         source,
                                         &current_dest);

  /* Am I the final destination? */
  if (0 == (GNUNET_CRYPTO_cmp_peer_identity (&next_peer.best_known_destination,
                                             &my_identity)))
  {
    if(0 == GNUNET_CRYPTO_cmp_peer_identity (&source, &my_identity))
    {
      finger_table_add (my_identity, NULL, 0, is_predecessor,
                        final_dest_finger_val, trail_id);
      return GNUNET_OK;
    }
    
    if (trail_length > 0)
      target_friend = 
              GNUNET_CONTAINER_multipeermap_get (friend_peermap, 
                                                 &trail_peer_list[trail_length-1]);
    else
      target_friend = 
              GNUNET_CONTAINER_multipeermap_get (friend_peermap, &source);
    
    if (NULL == target_friend)
    {
      GNUNET_break_op (0);
      return GNUNET_SYSERR;
    }
    GDS_ROUTING_add (trail_id, target_friend->id, my_identity);
    GDS_NEIGHBOURS_send_trail_setup_result (source,
                                            my_identity,
                                            target_friend, trail_length,
                                            trail_peer_list,
                                            is_predecessor,
                                            final_dest_finger_val,trail_id);
  }
  else /* I'm not the final destination. */
  {
    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                       &next_peer.next_hop);
    if(NULL == target_friend)
    {
      DEBUG ("\n target friend not found for peer = %s", GNUNET_i2s(&next_peer.next_hop));
      GNUNET_break (0);
      return GNUNET_OK;
    }

    if (0 != GNUNET_CRYPTO_cmp_peer_identity(&my_identity, &source))
    {
      /* Add yourself to list of peers. */
      struct GNUNET_PeerIdentity peer_list[trail_length + 1];

      memcpy (peer_list, trail_peer_list,
              trail_length * sizeof (struct GNUNET_PeerIdentity));
      peer_list[trail_length] = my_identity;
      GDS_NEIGHBOURS_send_trail_setup (source,
                                       final_dest_finger_val,
                                       next_peer.best_known_destination,
                                       target_friend, trail_length + 1, peer_list,
                                       is_predecessor, trail_id,
                                       next_peer.trail_id);
    }
    else
        GDS_NEIGHBOURS_send_trail_setup (source,
                                         final_dest_finger_val,
                                         next_peer.best_known_destination,
                                         target_friend, 0, NULL,
                                         is_predecessor, trail_id,
                                         next_peer.trail_id);
  }
  return GNUNET_OK;
}


/**
 * Core handle for p2p trail setup result messages.
 * @param closure
 * @param message message
 * @param peer sender of this message.
 * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
 */
static int
handle_dht_p2p_trail_setup_result(void *cls, const struct GNUNET_PeerIdentity *peer,
                                  const struct GNUNET_MessageHeader *message)
{
  const struct PeerTrailSetupResultMessage *trail_result;
  const struct GNUNET_PeerIdentity *trail_peer_list;
  struct GNUNET_PeerIdentity next_hop;
  struct FriendInfo *target_friend;
  struct GNUNET_PeerIdentity querying_peer;
  struct GNUNET_PeerIdentity finger_identity;
  uint32_t trail_length;
  uint64_t ulitmate_destination_finger_value;
  uint32_t is_predecessor;
  struct GNUNET_HashCode trail_id;
  int my_index;
  size_t msize;

  msize = ntohs (message->size);
  if (msize < sizeof (struct PeerTrailSetupResultMessage))
  {
    GNUNET_break_op (0);
    return GNUNET_YES;
  }

  trail_result = (const struct PeerTrailSetupResultMessage *) message;
  if ((msize - sizeof (struct PeerTrailSetupResultMessage)) %
      sizeof (struct GNUNET_PeerIdentity) != 0)
  {
    GNUNET_break_op (0);
    return GNUNET_OK;
  }
  trail_length = (msize - sizeof (struct PeerTrailSetupResultMessage))/
                  sizeof (struct GNUNET_PeerIdentity);
  
  GNUNET_STATISTICS_update (GDS_stats,
                            gettext_noop
                            ("# Bytes received from other peers"), msize,
                            GNUNET_NO);
  
  is_predecessor = ntohl (trail_result->is_predecessor);
  querying_peer = trail_result->querying_peer;
  finger_identity = trail_result->finger_identity;
  trail_id = trail_result->trail_id;
  trail_peer_list = (const struct GNUNET_PeerIdentity *) &trail_result[1];
  ulitmate_destination_finger_value =
          GNUNET_ntohll (trail_result->ulitmate_destination_finger_value);

  /* Am I the one who initiated the query? */
  if (0 == (GNUNET_CRYPTO_cmp_peer_identity (&querying_peer, &my_identity)))
  {
    /* Check that you got the message from the correct peer. */
    if (trail_length > 0)
    {
      GNUNET_assert(0 == GNUNET_CRYPTO_cmp_peer_identity (&trail_peer_list[0],
                                                          peer));
    }
    else
    {
      GNUNET_assert(0 == GNUNET_CRYPTO_cmp_peer_identity (&finger_identity,
                                                          peer));
    }
    GDS_ROUTING_add (trail_id, my_identity, *peer);
    finger_table_add (finger_identity, trail_peer_list, trail_length,
                      is_predecessor, ulitmate_destination_finger_value, trail_id);
    return GNUNET_YES;
  }

  /* Get my location in the trail. */
  my_index = search_my_index (trail_peer_list, trail_length);
  if (-1 == my_index)
  {
    DEBUG ("Not found in trail\n");
    GNUNET_break_op(0);
    return GNUNET_SYSERR;
  }
  //TODO; return -2.
  if ((trail_length + 1) == my_index)
  {
    DEBUG ("Found twice in trail.\n");
    GNUNET_break_op(0);
    return GNUNET_SYSERR;
  }
  
  //TODO; Refactor code here and above to check if sender peer is correct
  if (my_index == 0)
  {
    if(trail_length > 1)
      GNUNET_assert(0 == GNUNET_CRYPTO_cmp_peer_identity (&trail_peer_list[1],
                                                          peer));
    else
      GNUNET_assert(0 == GNUNET_CRYPTO_cmp_peer_identity (&finger_identity,
                                                          peer));
    next_hop = trail_result->querying_peer;
  }
  else
  {
    if(my_index == trail_length - 1)
    {
      GNUNET_assert(0 == 
                    GNUNET_CRYPTO_cmp_peer_identity (&finger_identity,
                                                     peer));  
    }
    else
      GNUNET_assert(0 == 
                    GNUNET_CRYPTO_cmp_peer_identity (&trail_peer_list[my_index + 1],
                                                      peer));
    next_hop = trail_peer_list[my_index - 1];
  }
  
  target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, &next_hop);
  if (NULL == target_friend)
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  GDS_ROUTING_add (trail_id, next_hop, *peer);
  GDS_NEIGHBOURS_send_trail_setup_result (querying_peer, finger_identity,
                                          target_friend, trail_length, trail_peer_list,
                                          is_predecessor,
                                          ulitmate_destination_finger_value,
                                          trail_id);
  return GNUNET_OK;
}


/**
 * Invert the trail.
 * @param trail Trail to be inverted
 * @param trail_length Total number of peers in the trail.
 * @return Updated trail
 */
static struct GNUNET_PeerIdentity *
invert_trail (const struct GNUNET_PeerIdentity *trail,
              unsigned int trail_length)
{
  int i;
  int j;
  struct GNUNET_PeerIdentity *inverted_trail;

  inverted_trail = GNUNET_malloc (sizeof(struct GNUNET_PeerIdentity) *
                                  trail_length);
  i = 0;
  j = trail_length - 1;
  while (i < trail_length)
  {
    inverted_trail[i] = trail[j];
    i++;
    j--;
  }

  GNUNET_assert(NULL != GNUNET_CONTAINER_multipeermap_get(friend_peermap,
                                                          &inverted_trail[0]));
  return inverted_trail;
}


/**
 * Return the shortest trail among all the trails to reach to finger from me.
 * @param finger Finger
 * @param shortest_trail_length[out] Trail length of shortest trail from me
 *                                   to @a finger
 * @return Shortest trail.
 */
static struct GNUNET_PeerIdentity *
get_shortest_trail (struct FingerInfo *finger,
                    unsigned int *trail_length)
{
  struct Trail *trail;
  unsigned int flag = 0;
  unsigned int shortest_trail_index = 0;
  int shortest_trail_length = -1;
  struct Trail_Element *trail_element;
  struct GNUNET_PeerIdentity *trail_list;
  unsigned int i;

  trail = GNUNET_new (struct Trail);

  /* Get the shortest trail to reach to current successor. */
  for (i = 0; i < finger->trails_count; i++)
  {
    trail = &finger->trail_list[i];

    if (0 == flag)
    {
      shortest_trail_index = i;
      shortest_trail_length = trail->trail_length;
      flag = 1;
      continue;
    }

    if (shortest_trail_length > trail->trail_length)
    {
      shortest_trail_index = i;
      shortest_trail_length = trail->trail_length;
    }
    continue;
  }

  /* Copy the shortest trail and return. */
  trail = &finger->trail_list[shortest_trail_index];
  trail_element = trail->trail_head;

  trail_list = GNUNET_malloc (sizeof(struct GNUNET_PeerIdentity)*
                              shortest_trail_length);

  for(i = 0; i < shortest_trail_length; i++,trail_element = trail_element->next)
  {
    trail_list[i] = trail_element->peer;
  }

  GNUNET_assert(shortest_trail_length != -1);

  *trail_length = shortest_trail_length;
  return trail_list;
}


/**
 * Check if trail_1 and trail_2 have any common element. If yes then join 
 * them at common element. trail_1 always preceeds trail_2 in joined trail. 
 * @param trail_1 Trail from source to me, NOT including endpoints.
 * @param trail_1_len Total number of peers @a trail_1
 * @param trail_2 Trail from me to current predecessor, NOT including endpoints.
 * @param trail_2_len Total number of peers @a trail_2
 * @param joined_trail_len Total number of peers in combined trail of trail_1
 *                          trail_2.
 * @return Joined trail.
 */
static struct GNUNET_PeerIdentity *
check_for_duplicate_entries (const struct GNUNET_PeerIdentity *trail_1,
                             unsigned int trail_1_len,
                             struct GNUNET_PeerIdentity *trail_2,
                             unsigned int trail_2_len,
                             unsigned int *joined_trail_len)
{
  struct GNUNET_PeerIdentity *joined_trail;
  unsigned int i;
  unsigned int j;
  unsigned int k;
  
  for (i = 0; i < trail_1_len; i++)
  {
    for (j = 0; j < trail_2_len; j++)
    {
      if(0 != GNUNET_CRYPTO_cmp_peer_identity (&trail_1[i],&trail_2[j]))
        continue;
      
      *joined_trail_len = i + (trail_2_len - j);
      joined_trail = GNUNET_malloc (*joined_trail_len * 
                                    sizeof(struct GNUNET_PeerIdentity));
      
      
      /* Copy all the elements from 0 to i into joined_trail. */
      for(k = 0; k < ( i+1); k++)
      {
        joined_trail[k] = trail_1[k];
      }
      
      /* Increment j as entry stored is same as entry stored at i*/
      j = j+1;
      
      /* Copy all the elements from j to trail_2_len-1 to joined trail.*/
      while(k <= (*joined_trail_len - 1))
      {
        joined_trail[k] = trail_2[j];
        j++;
        k++;
      }
      
      return joined_trail;
    }
  }
 
  /* Here you should join the  trails. */
  *joined_trail_len = trail_1_len + trail_2_len + 1;
  joined_trail = GNUNET_malloc (*joined_trail_len * 
                                sizeof(struct GNUNET_PeerIdentity));
  
  
  for(i = 0; i < trail_1_len;i++)
  {
    joined_trail[i] = trail_1[i];
  }
  
  joined_trail[i] = my_identity;
  i++;
  
  for (j = 0; i < *joined_trail_len; i++,j++)
  {
    joined_trail[i] = trail_2[j];
  }
  
  return joined_trail;
}


/**
 * Return the trail from source to my current predecessor. Check if source
 * is already part of the this trail, if yes then return the shorten trail.
 * @param current_trail Trail from source to me, NOT including the endpoints.
 * @param current_trail_length Number of peers in @a current_trail.
 * @param trail_src_to_curr_pred_length[out] Number of peers in trail from
 *                                           source to my predecessor, NOT including
 *                                           the endpoints.
 * @return Trail from source to my predecessor.
 */
static struct GNUNET_PeerIdentity *
get_trail_src_to_curr_pred (struct GNUNET_PeerIdentity source_peer,
                            const struct GNUNET_PeerIdentity *trail_src_to_me,
                            unsigned int trail_src_to_me_len,
                            unsigned int *trail_src_to_curr_pred_length)
{
  struct GNUNET_PeerIdentity *trail_me_to_curr_pred;
  struct GNUNET_PeerIdentity *trail_src_to_curr_pred;
  unsigned int trail_me_to_curr_pred_length;
  struct FingerInfo *current_predecessor;
  int i;
  unsigned int j;

  current_predecessor = &finger_table[PREDECESSOR_FINGER_ID];
  
  /* Check if trail_src_to_me contains current_predecessor. */
  for (i = 0; i < trail_src_to_me_len; i++)
  {
    if(0 != GNUNET_CRYPTO_cmp_peer_identity(&trail_src_to_me[i],
                                            &current_predecessor->finger_identity))
        continue;
      
      
    *trail_src_to_curr_pred_length = i;
    
    if(0 == i)
      return NULL;
    
     trail_src_to_curr_pred = GNUNET_malloc (*trail_src_to_curr_pred_length *
                                              sizeof(struct GNUNET_PeerIdentity));
     for(j = 0; j < i;j++)
       trail_src_to_curr_pred[j] = trail_src_to_me[j];
     return trail_src_to_curr_pred;
  }

 
  trail_me_to_curr_pred = get_shortest_trail (current_predecessor,
                                              &trail_me_to_curr_pred_length);
  
  /* Check if trail contains the source_peer. */
  for(i = trail_me_to_curr_pred_length - 1; i >= 0; i--)
  {
    if(0 != GNUNET_CRYPTO_cmp_peer_identity (&source_peer,
                                             &trail_me_to_curr_pred[i]))
      continue; 
    
     /* Source is NOT part of trail. */
     i = i+1;

     /* Source is the last element in the trail to reach to my pred.
         Source is direct friend of the pred. */
     if (trail_me_to_curr_pred_length == i)
     {
        *trail_src_to_curr_pred_length = 0;
        return NULL;
     }
     
     *trail_src_to_curr_pred_length = trail_me_to_curr_pred_length - i;
     trail_src_to_curr_pred = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity)*
                                              *trail_src_to_curr_pred_length);
     
     for(j = 0; j < *trail_src_to_curr_pred_length; i++,j++)
     {
       trail_src_to_curr_pred[j] = trail_me_to_curr_pred[i];
     }
     GNUNET_free_non_null(trail_me_to_curr_pred);
     return trail_src_to_curr_pred;
  }
  
  unsigned int len;
  trail_src_to_curr_pred = check_for_duplicate_entries (trail_src_to_me, 
                                                        trail_src_to_me_len,
                                                        trail_me_to_curr_pred,
                                                        trail_me_to_curr_pred_length,
                                                        &len); 
  *trail_src_to_curr_pred_length = len;
  GNUNET_free_non_null(trail_me_to_curr_pred);
  return trail_src_to_curr_pred;
}


/**
 * Add finger as your predecessor. To add, first generate a new trail id, invert
 * the trail to get the trail from me to finger, add an entry in your routing
 * table, send add trail message to peers which are part of trail from me to
 * finger and add finger in finger table.
 * @param finger
 * @param trail
 * @param trail_length
 */
static void
update_predecessor (struct GNUNET_PeerIdentity finger,
                    struct GNUNET_PeerIdentity *trail,
                    unsigned int trail_length)
{
  struct GNUNET_HashCode trail_to_new_predecessor_id;
  struct GNUNET_PeerIdentity *trail_to_new_predecessor;
  struct FriendInfo *target_friend;

  /* Generate trail id for trail from me to new predecessor = finger. */
  GNUNET_CRYPTO_random_block (GNUNET_CRYPTO_QUALITY_STRONG,
                              &trail_to_new_predecessor_id,
                              sizeof (trail_to_new_predecessor_id));

  /* Finger is a friend. */
  if (trail_length == 0)
  {
    trail_to_new_predecessor = NULL;
    GDS_ROUTING_add (trail_to_new_predecessor_id, my_identity, finger);
    GNUNET_assert (NULL != (target_friend =
                            GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                               &finger)));
  }
  else
  {
    /* Invert the trail to get the trail from me to finger, NOT including the
       endpoints.*/
    GNUNET_assert(NULL != GNUNET_CONTAINER_multipeermap_get(friend_peermap,
                                                            &trail[trail_length-1]));
  
    trail_to_new_predecessor = invert_trail (trail, trail_length);
    
    /* Add an entry in your routing table. */
    GDS_ROUTING_add (trail_to_new_predecessor_id,
                     my_identity,
                     trail_to_new_predecessor[0]);

    GNUNET_assert (NULL != (target_friend =
                   GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                      &trail_to_new_predecessor[0])));
    GNUNET_assert (NULL != (
                   GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                      &trail[trail_length - 1])));
  }

  /* Add entry in routing table of all peers that are part of trail from me
     to finger, including finger. */
  GDS_NEIGHBOURS_send_add_trail (my_identity,
                                 finger,
                                 trail_to_new_predecessor_id,
                                 trail_to_new_predecessor,
                                 trail_length,
                                 target_friend);

  add_new_finger (finger, trail_to_new_predecessor, trail_length,
                  trail_to_new_predecessor_id, PREDECESSOR_FINGER_ID);
  GNUNET_free_non_null(trail_to_new_predecessor);
}


/*
 * Check if you already have a predecessor. If not then add finger as your
 * predecessor. If you have predecessor, then compare two peer identites.
 * If finger is correct predecessor, then remove the old entry, add finger in
 * finger table and send add_trail message to add the trail in the routing
 * table of all peers which are part of trail to reach from me to finger.
 * @param finger New peer which may be our predecessor.
 * @param trail List of peers to reach from @finger to me.
 * @param trail_length Total number of peer in @a trail.
 */
static void
compare_and_update_predecessor (struct GNUNET_PeerIdentity finger,
                                struct GNUNET_PeerIdentity *trail,
                                unsigned int trail_length)
{
  struct FingerInfo *current_predecessor;
  struct GNUNET_PeerIdentity closest_peer;
  uint64_t predecessor_value;
  unsigned int is_predecessor = 1;

  current_predecessor = &finger_table[PREDECESSOR_FINGER_ID];
  GNUNET_assert (0 != GNUNET_CRYPTO_cmp_peer_identity (&finger, &my_identity));

  /* No predecessor. Add finger as your predecessor. */
  if (GNUNET_NO == current_predecessor->is_present)
  {
    update_predecessor (finger, trail, trail_length);
    return;
  }
  
  if (0 == GNUNET_CRYPTO_cmp_peer_identity (&current_predecessor->finger_identity,
                                            &finger))
  {
    return;
  }

  predecessor_value = compute_finger_identity_value (PREDECESSOR_FINGER_ID);
  closest_peer = select_closest_peer (&finger,
                                      &current_predecessor->finger_identity,
                                      predecessor_value, is_predecessor);

  /* Finger is the closest predecessor. Remove the existing one and add the new
     one. */
  if (0 == GNUNET_CRYPTO_cmp_peer_identity(&closest_peer, &finger))
  {
    remove_existing_finger (current_predecessor, PREDECESSOR_FINGER_ID);
    update_predecessor (finger, trail, trail_length);
    return;
  }
  return;
}


/*
 * 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)
{
  const struct PeerVerifySuccessorMessage *vsm;
  struct GNUNET_HashCode trail_id;
  struct GNUNET_PeerIdentity successor;
  struct GNUNET_PeerIdentity source_peer;
  struct GNUNET_PeerIdentity *trail;
  struct GNUNET_PeerIdentity *next_hop;
  struct FingerInfo current_predecessor;
  struct FriendInfo *target_friend;
  unsigned int trail_src_to_curr_pred_len = 0;
  struct GNUNET_PeerIdentity *trail_src_to_curr_pred;
  unsigned int trail_length;
  size_t msize;
  
  msize = ntohs (message->size);

  if (msize < sizeof (struct PeerVerifySuccessorMessage))
  {
    GNUNET_break_op (0);
    return GNUNET_YES;
  }

  vsm = (const struct PeerVerifySuccessorMessage *) message;
  trail_length = (msize - sizeof (struct PeerVerifySuccessorMessage))/
                  sizeof (struct GNUNET_PeerIdentity);
  if ((msize - sizeof (struct PeerVerifySuccessorMessage)) %
      sizeof (struct GNUNET_PeerIdentity) != 0)
  {
    GNUNET_break_op (0);
    return GNUNET_OK;
  }
  
  GNUNET_STATISTICS_update (GDS_stats,
                            gettext_noop
                            ("# Bytes received from other peers"), msize,
                            GNUNET_NO);
  
  trail_id = vsm->trail_id;
  source_peer = vsm->source_peer;
  successor = vsm->successor;
  trail = (struct GNUNET_PeerIdentity *)&vsm[1];
 
  /* I am NOT the successor of source_peer. Pass the message to next_hop on
   * the trail. */
  if(0 != (GNUNET_CRYPTO_cmp_peer_identity (&successor, &my_identity)))
  {
    next_hop = GDS_ROUTING_get_next_hop (trail_id, GDS_ROUTING_SRC_TO_DEST);    
    if (NULL == next_hop)
    {
      DEBUG(" NO ENTRY FOUND IN %s ROUTING TABLE for trail id %s, line",
            GNUNET_i2s(&my_identity), GNUNET_h2s(&trail_id), __LINE__);
      GNUNET_break_op (0);
      return GNUNET_OK;
    }
 
    target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop);
    
    if(NULL == target_friend)
    {
      GNUNET_break_op(0);
      return GNUNET_OK;
    }
    GDS_NEIGHBOURS_send_verify_successor_message (source_peer, successor,
                                                  trail_id, trail, trail_length,
                                                  target_friend);
    return GNUNET_OK;
  }

  /* I am the destination of this message. */

  /* Check if the source_peer could be our predecessor and if yes then update
   * it.  */
  compare_and_update_predecessor (source_peer, trail, trail_length);
  current_predecessor = finger_table[PREDECESSOR_FINGER_ID];
  
  /* Is source of this message NOT my predecessor. */
  if (0 != (GNUNET_CRYPTO_cmp_peer_identity (&current_predecessor.finger_identity,
                                             &source_peer)))
  {
    trail_src_to_curr_pred = 
              get_trail_src_to_curr_pred (source_peer,
                                          trail,
                                          trail_length,
                                          &trail_src_to_curr_pred_len);
  }
  else
  {
    trail_src_to_curr_pred_len = trail_length;
    unsigned int i;

    trail_src_to_curr_pred = 
            GNUNET_malloc (sizeof(struct GNUNET_PeerIdentity)
                           *trail_src_to_curr_pred_len);
    for(i = 0; i < trail_src_to_curr_pred_len; i++)
    {
      trail_src_to_curr_pred[i] = trail[i];
    }
  }
 
  GNUNET_assert (NULL !=
                (target_friend =
                 GNUNET_CONTAINER_multipeermap_get (friend_peermap, peer)));
  GDS_NEIGHBOURS_send_verify_successor_result (source_peer, my_identity,
                                               current_predecessor.finger_identity,
                                               trail_id, trail_src_to_curr_pred,
                                               trail_src_to_curr_pred_len,
                                               GDS_ROUTING_DEST_TO_SRC,
                                               target_friend);
  GNUNET_free_non_null(trail_src_to_curr_pred);
  return GNUNET_OK;
}


/**
 * If the trail from me to my probable successor contains a friend not
 * at index 0, then we can shorten the trail.
 * @param probable_successor Peer which is our probable successor
 * @param trail_me_to_probable_successor Peers in path from me to my probable
 *                                       successor, NOT including the endpoints.
 * @param trail_me_to_probable_successor_len Total number of peers in
 *                                           @a trail_me_to_probable_succesor.
 * @return Updated trail, if any friend found.
 *         Else the trail_me_to_probable_successor.
 */
struct GNUNET_PeerIdentity *
check_trail_me_to_probable_succ (struct GNUNET_PeerIdentity probable_successor,
                                 const struct GNUNET_PeerIdentity *trail_me_to_probable_successor,
                                 unsigned int trail_me_to_probable_successor_len,
                                 unsigned int *trail_to_new_successor_length)
{
  unsigned int i;
  unsigned int j;
  struct GNUNET_PeerIdentity *trail_to_new_successor;

  /* Probable successor is  a friend */
  if (NULL != GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                 &probable_successor))
  {
    trail_to_new_successor = NULL;
    *trail_to_new_successor_length = 0;
    return trail_to_new_successor;
  }
  
  /* Is there any friend of yours in this trail. */
  if(trail_me_to_probable_successor_len > 1)
  {
    for (i = trail_me_to_probable_successor_len - 1; i > 0; i--)
    {
      if (NULL == GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                     &trail_me_to_probable_successor[i]))
        continue;

      *trail_to_new_successor_length = (trail_me_to_probable_successor_len - i);
      trail_to_new_successor = GNUNET_malloc (sizeof(struct GNUNET_PeerIdentity)*
                                                *trail_to_new_successor_length);

     
      for(j = 0;j < *trail_to_new_successor_length;i++,j++)
      {
        trail_to_new_successor[j] = trail_me_to_probable_successor[i];
      }
      
      return trail_to_new_successor;
    }
  }

  *trail_to_new_successor_length = trail_me_to_probable_successor_len;
  return (struct GNUNET_PeerIdentity*)trail_me_to_probable_successor;
}


/**
 * Check if the peer which sent us verify successor result message is still ours
 * successor or not. If not, then compare existing successor and probable successor.
 * In case probable successor is the correct successor, remove the existing
 * successor. Add probable successor as new successor. Send notify new successor
 * message to new successor.
 * @param curr_succ Peer to which we sent the verify successor message. It may
 * or may not be our real current successor, as we may have few iterations of
 * find finger trail task.
 * @param probable_successor Peer which should be our successor accroding to @a 
 *                           curr_succ
 * @param trail List of peers to reach from me to @a probable successor, NOT including
 *              endpoints.
 * @param trail_length Total number of peers in @a trail.
 */
static void
compare_and_update_successor (struct GNUNET_PeerIdentity curr_succ,
                              struct GNUNET_PeerIdentity probable_successor,
                              const struct GNUNET_PeerIdentity *trail,
                              unsigned int trail_length)
{
  struct FingerInfo *current_successor;
  struct GNUNET_PeerIdentity closest_peer;
  struct GNUNET_HashCode trail_id;
  struct GNUNET_PeerIdentity *trail_me_to_probable_succ;
  struct FriendInfo *target_friend;
  unsigned int trail_me_to_probable_succ_len;
  unsigned int is_predecessor = 0;
  uint64_t successor_value;

  current_successor = &finger_table[0];
  successor_value = compute_finger_identity_value(0);

  /* If probable successor is same as current_successor, do nothing. */
  if(0 == GNUNET_CRYPTO_cmp_peer_identity (&probable_successor,
                                           &current_successor->finger_identity))
    return;
  
  closest_peer = select_closest_peer (&probable_successor,
                                      &current_successor->finger_identity,
                                      successor_value, is_predecessor);

  /* If the current_successor in the finger table is closest, then do nothing. */
  if (0 == GNUNET_CRYPTO_cmp_peer_identity (&closest_peer ,
                                            &current_successor->finger_identity))
  {
    if ((NULL != GDS_stats))
    {
      char *my_id_str;
      uint64_t succ;
      char *key;
    
      my_id_str = GNUNET_strdup (GNUNET_i2s_full (&my_identity));
      memcpy(&succ, &current_successor->finger_identity, sizeof(uint64_t));
      GNUNET_asprintf (&key, "XDHT:%s:", my_id_str);
      GNUNET_free (my_id_str);
      GNUNET_STATISTICS_set (GDS_stats, key, succ, 0);
      GNUNET_free (key);
    }
    return;
  }
  
  /* Probable successor is the closest peer.*/
  if(trail_length > 0)
  {
    GNUNET_assert(NULL != GNUNET_CONTAINER_multipeermap_get(friend_peermap,
                                                            &trail[0]));
  }
  else
  {
    GNUNET_assert(NULL != GNUNET_CONTAINER_multipeermap_get(friend_peermap,
                                                            &probable_successor));
  }
  
  trail_me_to_probable_succ_len = 0;
  trail_me_to_probable_succ =
          check_trail_me_to_probable_succ (probable_successor,
                                           trail, trail_length,
                                           &trail_me_to_probable_succ_len);

  /* Remove the existing successor. */
  remove_existing_finger (current_successor, 0);
   /* Generate a new trail id to reach to your new successor. */
  GNUNET_CRYPTO_random_block (GNUNET_CRYPTO_QUALITY_STRONG,
                              &trail_id, sizeof (trail_id));

  if (trail_me_to_probable_succ_len > 0)
  {
    GDS_ROUTING_add (trail_id, my_identity, trail_me_to_probable_succ[0]);
    GNUNET_assert (NULL !=
                  (target_friend =
                      GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                        &trail_me_to_probable_succ[0])));
  }
  else
  {
    GDS_ROUTING_add (trail_id, my_identity, probable_successor);
    GNUNET_assert (NULL !=
                  (target_friend =
                   GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                      &probable_successor)));
  }

  add_new_finger (probable_successor, trail_me_to_probable_succ,
                  trail_me_to_probable_succ_len, trail_id, 0);
 
  GDS_NEIGHBOURS_send_notify_new_successor (my_identity, probable_successor,
                                            trail_me_to_probable_succ,
                                            trail_me_to_probable_succ_len,
                                            trail_id,
                                            target_friend);
  return;
}


/*
 * FIXME: Check for duplicate elements everywhere when you are making
 * trails. 
 * 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)
{
  const struct PeerVerifySuccessorResultMessage *vsrm;
  enum GDS_ROUTING_trail_direction trail_direction;
  struct GNUNET_PeerIdentity querying_peer;
  struct GNUNET_HashCode trail_id;
  struct GNUNET_PeerIdentity *next_hop;
  struct FriendInfo *target_friend;
  struct GNUNET_PeerIdentity probable_successor;
  struct GNUNET_PeerIdentity current_successor;
  const struct GNUNET_PeerIdentity *trail;
  unsigned int trail_length;
  size_t msize;

  msize = ntohs (message->size);
  /* We send a trail to reach from old successor to new successor, if
   * old_successor != new_successor.*/
  if (msize < sizeof (struct PeerVerifySuccessorResultMessage))
  {
    GNUNET_break_op (0);
    return GNUNET_YES;
  }

  vsrm = (const struct PeerVerifySuccessorResultMessage *) message;
  trail_length = (msize - sizeof (struct PeerVerifySuccessorResultMessage))/
                      sizeof (struct GNUNET_PeerIdentity);

  if ((msize - sizeof (struct PeerVerifySuccessorResultMessage)) %
      sizeof (struct GNUNET_PeerIdentity) != 0)
  {
    GNUNET_break_op (0);
    return GNUNET_OK;
  }

  GNUNET_STATISTICS_update (GDS_stats,
                            gettext_noop
                            ("# Bytes received from other peers"), msize,
                            GNUNET_NO);
  
  trail = (const struct GNUNET_PeerIdentity *) &vsrm[1];
  querying_peer = vsrm->querying_peer;
  trail_direction = ntohl (vsrm->trail_direction);
  trail_id = vsrm->trail_id;
  probable_successor = vsrm->probable_successor;
  current_successor = vsrm->current_successor;
 
   verify_successor_next_send_time =
                GNUNET_TIME_STD_BACKOFF(verify_successor_next_send_time);
  /* I am the querying_peer. */
  if(0 == (GNUNET_CRYPTO_cmp_peer_identity (&querying_peer, &my_identity)))
  {
    compare_and_update_successor (current_successor,
                                  probable_successor, trail, trail_length);
    return GNUNET_OK;
  }
  
  /*If you are not the querying peer then pass on the message */
  if(NULL == (next_hop =
              GDS_ROUTING_get_next_hop (trail_id, trail_direction)))
  {
    DEBUG(" NO ENTRY FOUND IN %s ROUTING TABLE for trail id %s, line",
            GNUNET_i2s(&my_identity), GNUNET_h2s(&trail_id), __LINE__);
    GNUNET_break_op(0);
    return GNUNET_OK;
  }
  if (NULL == (target_friend =
                 GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop)))
  {
    GNUNET_break_op(0);
    return GNUNET_OK;
  }
  GDS_NEIGHBOURS_send_verify_successor_result (querying_peer,
                                               vsrm->current_successor,
                                               probable_successor, trail_id,
                                               trail,
                                               trail_length,
                                               trail_direction, target_friend);
  return GNUNET_OK;
}


/*
 * Core handle for p2p notify new successor messages.
 * @param cls closure
 * @param message message
 * @param peer peer identity this notification is about
 * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
 */
static int
handle_dht_p2p_notify_new_successor(void *cls,
                                    const struct GNUNET_PeerIdentity *peer,
                                    const struct GNUNET_MessageHeader *message)
{
  const struct PeerNotifyNewSuccessorMessage *nsm;
  struct GNUNET_PeerIdentity *trail;
  struct GNUNET_PeerIdentity source;
  struct GNUNET_PeerIdentity new_successor;
  struct GNUNET_HashCode trail_id;
  struct GNUNET_PeerIdentity next_hop;
  struct FriendInfo *target_friend;
  int my_index;
  size_t msize;
  uint32_t trail_length;

  msize = ntohs (message->size);

  /* We have the trail to reach from source to new successor. */
  if (msize < sizeof (struct PeerNotifyNewSuccessorMessage))
  {
    GNUNET_break_op (0);
    return GNUNET_YES;
  }

  nsm = (const struct PeerNotifyNewSuccessorMessage *) message;
  trail_length = (msize - sizeof (struct PeerNotifyNewSuccessorMessage))/
                  sizeof (struct GNUNET_PeerIdentity);
  if ((msize - sizeof (struct PeerNotifyNewSuccessorMessage)) %
      sizeof (struct GNUNET_PeerIdentity) != 0)
  {
    GNUNET_break_op (0);
    return GNUNET_OK;
  }

  GNUNET_STATISTICS_update (GDS_stats,
                            gettext_noop
                            ("# Bytes received from other peers"), msize,
                            GNUNET_NO);
  
  trail = (struct GNUNET_PeerIdentity *) &nsm[1];
  source  = nsm->source_peer;
  new_successor = nsm->new_successor;
  trail_id = nsm->trail_id;
 
  /* I am the new_successor to source_peer. */
  if ( 0 == GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &new_successor))
  {
    if(trail_length > 0)
      GNUNET_assert(0 == GNUNET_CRYPTO_cmp_peer_identity(&trail[trail_length - 1],
                                                          peer));
    else 
      GNUNET_assert(0 == GNUNET_CRYPTO_cmp_peer_identity(&source, peer));
  
    compare_and_update_predecessor (source, trail, trail_length);
    return GNUNET_OK;
  }

  GNUNET_assert(trail_length > 0);
  /* I am part of trail to reach to successor. */
  my_index = search_my_index (trail, trail_length);
  if (-1 == my_index)
  {
    DEBUG ("No entry found in trail\n");
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  if((trail_length + 1) == my_index)
  {
    DEBUG ("Found twice in trail.\n");
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  if ((trail_length-1) == my_index)
    next_hop = new_successor;
  else
    next_hop = trail[my_index + 1];
  /* Add an entry in routing table for trail from source to its new successor. */
  GNUNET_assert (GNUNET_OK == GDS_ROUTING_add (trail_id, *peer, next_hop));
  GNUNET_assert (NULL !=
                (target_friend =
                 GNUNET_CONTAINER_multipeermap_get (friend_peermap, &next_hop)));
  GDS_NEIGHBOURS_send_notify_new_successor (source, new_successor, trail,
                                            trail_length,
                                            trail_id, target_friend);
  return GNUNET_OK;

}


/**
 * Core 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
 */
static int
handle_dht_p2p_trail_setup_rejection (void *cls,
                                      const struct GNUNET_PeerIdentity *peer,
                                      const struct GNUNET_MessageHeader *message)
{
  const struct PeerTrailRejectionMessage *trail_rejection;
  unsigned int trail_length;
  const struct GNUNET_PeerIdentity *trail_peer_list;
  struct FriendInfo *target_friend;
  struct GNUNET_TIME_Relative congestion_timeout;
  struct GNUNET_HashCode trail_id;
  struct GNUNET_PeerIdentity next_peer;
  struct GNUNET_PeerIdentity source;
  uint64_t ultimate_destination_finger_value;
  unsigned int is_predecessor;
  size_t msize;

  msize = ntohs (message->size);
  if (msize < sizeof (struct PeerTrailRejectionMessage))
  {
    GNUNET_break_op (0);
    return GNUNET_YES;
  }
  trail_rejection = (const struct PeerTrailRejectionMessage *) message;
  if ((msize - sizeof (struct PeerTrailRejectionMessage)) %
      sizeof (struct GNUNET_PeerIdentity) != 0)
  {
    GNUNET_break_op (0);
    return GNUNET_OK;
  }
  trail_length = (msize - sizeof (struct PeerTrailRejectionMessage))/
                  sizeof (struct GNUNET_PeerIdentity);
  GNUNET_STATISTICS_update (GDS_stats,
                            gettext_noop
                            ("# Bytes received from other peers"), msize,
                            GNUNET_NO);
  
  trail_peer_list = (const struct GNUNET_PeerIdentity *)&trail_rejection[1];
  is_predecessor = ntohl (trail_rejection->is_predecessor);
  congestion_timeout = trail_rejection->congestion_time;
  source = trail_rejection->source_peer;
  trail_id = trail_rejection->trail_id;
  ultimate_destination_finger_value =
          GNUNET_ntohll (trail_rejection->ultimate_destination_finger_value);
  /* First set the congestion time of the friend that sent you this message. */
  target_friend = GNUNET_CONTAINER_multipeermap_get (friend_peermap, peer);
  if (NULL == target_friend)
  {
    DEBUG ("\nLINE = %d ,No friend found.",__LINE__);
    GNUNET_break(0);
    return GNUNET_OK;
  }
  target_friend->congestion_timestamp =
          GNUNET_TIME_absolute_add (GNUNET_TIME_absolute_get(),
                                    congestion_timeout);

  /* I am the source peer which wants to setup the trail. Do nothing.
   * send_find_finger_trail_task is scheduled periodically.*/
  if(0 == (GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &source)))
    return GNUNET_OK;

  /* If I am congested then pass this message to peer before me in trail. */
  if(GNUNET_YES == GDS_ROUTING_threshold_reached())
  {
    /* First remove yourself from the trail. */
    unsigned int new_trail_length = trail_length - 1;
    struct GNUNET_PeerIdentity trail[new_trail_length];
    
    memcpy (trail, trail_peer_list, new_trail_length * sizeof(struct GNUNET_PeerIdentity));
    if (0 == trail_length)
      next_peer = source;
    else
      next_peer = trail[new_trail_length-1];

    target_friend =
                   GNUNET_CONTAINER_multipeermap_get (friend_peermap, &next_peer);
    if (NULL == target_friend)
    {
      DEBUG ("\nLINE = %d ,No friend found.",__LINE__);
      GNUNET_break(0);
      return GNUNET_OK;
    }
    GDS_NEIGHBOURS_send_trail_rejection (source,
                                         ultimate_destination_finger_value,
                                         my_identity, is_predecessor,
                                         trail, new_trail_length, trail_id,
                                         target_friend, CONGESTION_TIMEOUT);
    return GNUNET_OK;
  }

  struct Closest_Peer successor;
  successor = find_successor (ultimate_destination_finger_value, is_predecessor);

  /* Am I the final destination? */
  if (0 == (GNUNET_CRYPTO_cmp_peer_identity (&successor.best_known_destination,
                                             &my_identity)))
  {
     /*Here you are already part of trail. Copy the trail removing yourself. */
    unsigned int new_trail_length = trail_length - 1;
    struct GNUNET_PeerIdentity trail[new_trail_length];
    
    memcpy (trail, trail_peer_list, new_trail_length * sizeof(struct GNUNET_PeerIdentity));
    
    if (0 == new_trail_length)
      next_peer = source;
    else
    {
      next_peer = trail[new_trail_length-1];
    }
    target_friend =
                   GNUNET_CONTAINER_multipeermap_get (friend_peermap, &next_peer);
    
    if (NULL == target_friend)
    {
      DEBUG ("\nLINE = %d ,No friend found.",__LINE__);
      GNUNET_break(0);
      return GNUNET_OK;
    }
    GDS_NEIGHBOURS_send_trail_setup_result (source,
                                            my_identity,
                                            target_friend, new_trail_length,
                                            trail,
                                            is_predecessor,
                                            ultimate_destination_finger_value,
                                            trail_id);
  }
  else
  {
    /* Here I was already part of trail. So no need to add. */
    target_friend =
                   GNUNET_CONTAINER_multipeermap_get (friend_peermap, 
                                                      &successor.next_hop);
    if (NULL == target_friend)
    {
      DEBUG ("\nLINE = %d ,No friend found.",__LINE__);
      GNUNET_break(0);
      return GNUNET_OK;
    }
   
    GDS_NEIGHBOURS_send_trail_setup (source,
                                     ultimate_destination_finger_value,
                                     successor.best_known_destination,
                                     target_friend, trail_length, trail_peer_list,
                                     is_predecessor, trail_id,
                                     successor.trail_id);
  }
  return GNUNET_OK;
}


/**
 * Core handler for trail teardown message.
 * @param cls closure
 * @param message message
 * @param peer sender of this messsage.
 * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
 */
static int
handle_dht_p2p_trail_teardown (void *cls, const struct GNUNET_PeerIdentity *peer,
                               const struct GNUNET_MessageHeader *message)
{
  const struct PeerTrailTearDownMessage *trail_teardown;
  enum GDS_ROUTING_trail_direction trail_direction;
  struct GNUNET_HashCode trail_id;
  struct GNUNET_PeerIdentity *next_hop;
  size_t msize;

  msize = ntohs (message->size);

  /* Here we pass only the trail id. */
  if (msize != sizeof (struct PeerTrailTearDownMessage))
  {
    GNUNET_break_op (0);
    return GNUNET_OK;
  }

  GNUNET_STATISTICS_update (GDS_stats,
                            gettext_noop
                            ("# Bytes received from other peers"), msize,
                            GNUNET_NO);
  
  trail_teardown = (const struct PeerTrailTearDownMessage *) message;
  trail_direction = ntohl (trail_teardown->trail_direction);
  trail_id = trail_teardown->trail_id;

  /* Check if peer is the real peer from which we should get this message.*/
  /* Get the prev_hop for this trail by getting the next hop in opposite direction. */
#if 0
  GNUNET_assert (NULL != (prev_hop =
                 GDS_ROUTING_get_next_hop (trail_id, !trail_direction)));
  if (0 != GNUNET_CRYPTO_cmp_peer_identity (prev_hop, peer))
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
#endif

  next_hop = GDS_ROUTING_get_next_hop (trail_id, trail_direction);
  if (NULL == next_hop)
  {
    DEBUG(" NO ENTRY FOUND IN %s ROUTING TABLE for trail id %s, line",
            GNUNET_i2s(&my_identity), GNUNET_h2s(&trail_id), __LINE__);
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }

  /* I am the next hop, which means I am the final destination. */
  if (0 == GNUNET_CRYPTO_cmp_peer_identity (next_hop, &my_identity))
  {
    GNUNET_assert (GNUNET_YES == GDS_ROUTING_remove_trail (trail_id));
    return GNUNET_OK;
  }
  else
  {
    /* If not final destination, then send a trail teardown message to next hop.*/
    GNUNET_assert (NULL != GNUNET_CONTAINER_multipeermap_get (friend_peermap, next_hop));
    GNUNET_assert (GNUNET_YES == GDS_ROUTING_remove_trail (trail_id));
    GDS_NEIGHBOURS_send_trail_teardown (trail_id, trail_direction, *next_hop);
  }

  return GNUNET_OK;
}


/**
 * 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
 */
static int
handle_dht_p2p_add_trail (void *cls, const struct GNUNET_PeerIdentity *peer,
                          const struct GNUNET_MessageHeader *message)
{
  const struct PeerAddTrailMessage *add_trail;
  const struct GNUNET_PeerIdentity *trail;
  struct GNUNET_HashCode trail_id;
  struct GNUNET_PeerIdentity destination_peer;
  struct GNUNET_PeerIdentity source_peer;
  struct GNUNET_PeerIdentity next_hop;
  unsigned int trail_length;
  unsigned int my_index;
  size_t msize;

  msize = ntohs (message->size);
  /* In this message we pass the whole trail from source to destination as we
   * are adding that trail.*/
  //FIXME: failed when run with 1000 pears. check why.
  if (msize < sizeof (struct PeerAddTrailMessage))
  {
    GNUNET_break_op (0);
    return GNUNET_OK;
  }

  add_trail = (const struct PeerAddTrailMessage *) message;
  trail_length = (msize - sizeof (struct PeerAddTrailMessage))/
                  sizeof (struct GNUNET_PeerIdentity);
  if ((msize - sizeof (struct PeerAddTrailMessage)) %
      sizeof (struct GNUNET_PeerIdentity) != 0)
  {
    GNUNET_break_op (0);
    return GNUNET_OK;
  }

  GNUNET_STATISTICS_update (GDS_stats,
                            gettext_noop
                            ("# Bytes received from other peers"), msize,
                            GNUNET_NO);
  
  trail = (const struct GNUNET_PeerIdentity *)&add_trail[1];
  destination_peer = add_trail->destination_peer;
  source_peer = add_trail->source_peer;
  trail_id = add_trail->trail_id;

  //FIXME: add a check that sender peer is not malicious. Make it a generic
  // function so that it can be used in all other functions where we need the
  // same functionality.

  /* I am not the destination of the trail. */
  if (0 != GNUNET_CRYPTO_cmp_peer_identity (&my_identity, &destination_peer))
  {
    struct FriendInfo *target_friend;

    /* Get my location in the trail. */
    my_index = search_my_index (trail, trail_length);
    if (-1 == my_index)
    {
      GNUNET_break_op (0);
      return GNUNET_SYSERR;
    }
    if((trail_length + 1) == my_index)
    {
      DEBUG ("Found twice in trail.\n");
      GNUNET_break_op (0);
      return GNUNET_SYSERR;
    }
    if ((trail_length - 1) == my_index)
    {
      next_hop = destination_peer;
    }
    else
    {
      next_hop = trail[my_index + 1];
    }
    /* Add in your routing table. */
    GNUNET_assert (GNUNET_OK == GDS_ROUTING_add (trail_id, next_hop, *peer));
    GNUNET_assert (NULL !=
                  (target_friend =
                   GNUNET_CONTAINER_multipeermap_get (friend_peermap, &next_hop)));
    GDS_NEIGHBOURS_send_add_trail (source_peer, destination_peer, trail_id,
                                   trail, trail_length, target_friend);
    return GNUNET_OK;
  }
  /* I am the destination. Add an entry in routing table. */
  GNUNET_assert (GNUNET_OK == GDS_ROUTING_add (trail_id, *peer, my_identity));
  return GNUNET_OK;
}


/**
 * Free the finger trail in which the first friend to reach to a finger is
 * disconnected_friend. Also remove entry from routing table for that particular
 * trail id.
 * @param disconnected_friend PeerIdentity of friend which got disconnected
 * @param remove_finger Finger whose trail we need to check if it has
 *                      disconnected_friend as the first hop.
 * @return Total number of trails in which disconnected_friend was the first
 *         hop.
 */
static int
remove_matching_trails (const struct GNUNET_PeerIdentity *disconnected_friend,
                        struct FingerInfo *finger)
{
  unsigned int matching_trails_count = 0;
  int i;

  /* Iterate over all the trails of finger. */
  for (i = 0; i < finger->trails_count; i++)
  {
    struct Trail *current_trail;
    current_trail = &finger->trail_list[i];
    //FIXME: This assertion fails if we have gap in trail list from o to trails count.
    GNUNET_assert (GNUNET_YES == current_trail->is_present);
    /* First friend to reach to finger is disconnected_peer. */
    if (0 == GNUNET_CRYPTO_cmp_peer_identity (&current_trail->trail_head->peer,
                                              disconnected_friend))
    {
      struct GNUNET_PeerIdentity *next_hop;
      struct FriendInfo *remove_friend;

      GNUNET_assert (NULL !=
                    (remove_friend =
                     GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                        disconnected_friend)));
      next_hop = GDS_ROUTING_get_next_hop (current_trail->trail_id,
                                           GDS_ROUTING_SRC_TO_DEST);

      /* Here it may happen that as all the peers got disconnected, the entry in
       routing table for that particular trail has been removed, because the
       previously disconnected peer was either a next hop or prev hop of that
       peer. */
      if (NULL != next_hop)
      {
        GNUNET_assert (0 == (GNUNET_CRYPTO_cmp_peer_identity (disconnected_friend,
                                                            next_hop)));
        GNUNET_assert (GNUNET_YES == GDS_ROUTING_remove_trail (current_trail->trail_id));
      }
      matching_trails_count++;
      free_trail (current_trail);
      current_trail->is_present = GNUNET_NO;
    }
  }
  return matching_trails_count;
}


/**
 * Iterate over finger_table entries.
 * 0. Ignore finger which is my_identity or if no valid entry present at
 *    that finger index.
 * 1. If disconnected_friend is a finger, then remove the routing entry from
      your own table. Free the trail.
 * 2. Check if disconnected_friend is the first friend in the trail to reach to a finger.
 *   2.1 Remove all the trails and entry from routing table in which disconnected
 *       friend is the first friend in the trail. If disconnected_friend is the
 *       first friend in all the trails to reach finger, then remove the finger.
 * @param disconnected_friend Peer identity of friend which got disconnected.
 */
static void
remove_matching_fingers (const struct GNUNET_PeerIdentity *disconnected_peer)
{
  struct FingerInfo *current_finger;
  struct FriendInfo *remove_friend;
  int removed_trails_count;
  int i;

  /* Iterate over finger table entries. */
  for (i = 0; i < MAX_FINGERS; i++)
  {
    current_finger = &finger_table[i];
    
    /* No finger stored at this trail index. */
    if ((GNUNET_NO == current_finger->is_present) ||
        (0 == GNUNET_CRYPTO_cmp_peer_identity (&current_finger->finger_identity,
                                              &my_identity)))
      continue;
    
    /* Is disconnected_peer a finger? */
    if (0 == GNUNET_CRYPTO_cmp_peer_identity (disconnected_peer,
                                              &current_finger->finger_identity))
    {
      struct GNUNET_PeerIdentity *next_hop;
      struct GNUNET_HashCode trail_id;
      
      GNUNET_assert (0 == current_finger->trail_list[0].trail_length);
      GNUNET_assert (GNUNET_YES == (current_finger->trail_list[0].is_present));
      trail_id = current_finger->trail_list[0].trail_id;
 
      if(NULL !=
              (next_hop =
               GDS_ROUTING_get_next_hop (trail_id, GDS_ROUTING_SRC_TO_DEST)))
      {
        GNUNET_assert (GNUNET_YES == GDS_ROUTING_remove_trail (trail_id));
        GNUNET_assert (NULL !=
                       (remove_friend =
                        GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                           disconnected_peer)));
      }
      current_finger->trail_list[0].is_present = GNUNET_NO;
      current_finger->is_present = GNUNET_NO;
      memset ((void *)&finger_table[i], 0, sizeof (finger_table[i]));
      continue;
    }

    /* If finger is a friend but not disconnected_friend, then continue. */
    if (NULL != GNUNET_CONTAINER_multipeermap_get (friend_peermap,
                                                   &current_finger->finger_identity))
      continue;

    /* Iterate over the list of trails to reach remove_finger. Check if
     * disconnected_friend is the first friend in any of the trail. */
    removed_trails_count = remove_matching_trails (disconnected_peer,
                                                   current_finger);
    current_finger->trails_count =
            current_finger->trails_count - removed_trails_count;
    if (0 == current_finger->trails_count)
    {
      current_finger->is_present = GNUNET_NO;
      memset ((void *)&finger_table[i], 0, sizeof (finger_table[i]));
    }
  }
}


/**
 * Method called whenever a peer disconnects.
 *
 * @param cls closure
 * @param peer peer identity this notification is about
 */
static void
handle_core_disconnect (void *cls,
                                          const struct GNUNET_PeerIdentity *peer)
{
  struct FriendInfo *remove_friend;
  struct P2PPendingMessage *pos;
  unsigned int discarded;
  
  /* If disconnected to own identity, then return. */
  if (0 == memcmp (&my_identity, peer, sizeof (struct GNUNET_PeerIdentity)))
    return;

  if(NULL == (remove_friend =
                 GNUNET_CONTAINER_multipeermap_get (friend_peermap, peer)))
  {
    DEBUG("\n friend already disconnected.");
    return;
  }
  
  remove_matching_fingers (peer);
  GNUNET_assert (GNUNET_SYSERR != GDS_ROUTING_remove_trail_by_peer (peer));
  GNUNET_assert (GNUNET_YES ==
                 GNUNET_CONTAINER_multipeermap_remove (friend_peermap,
                                                       peer,
                                                       remove_friend));
  
  /* Remove all the messages queued in pending list of this peer is discarded.*/
  if (remove_friend->th != NULL)
  {
    GNUNET_CORE_notify_transmit_ready_cancel(remove_friend->th);
    remove_friend->th = NULL;
  }
  
  discarded = 0;
  while (NULL != (pos = remove_friend->head))
  {
    GNUNET_CONTAINER_DLL_remove (remove_friend->head, remove_friend->tail, pos);
    discarded++;
    GNUNET_free (pos);
  }
  
  GNUNET_STATISTICS_update (GDS_stats,
                            gettext_noop
                            ("# Queued messages discarded (peer disconnected)"),
                            discarded, GNUNET_NO);
  //GNUNET_free (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);
}


/**
 * Method called whenever a peer connects.
 *
 * @param cls closure
 * @param peer_identity peer identity this notification is about
 */
static void
handle_core_connect (void *cls, const struct GNUNET_PeerIdentity *peer_identity)
{
  struct FriendInfo *friend;

  /* Check for connect to self message */
  if (0 == memcmp (&my_identity, peer_identity, sizeof (struct GNUNET_PeerIdentity)))
    return;

  /* 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;
  }

  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));

  /* SUPUS: We should add a congestion timestamp on the friend, so that it is
   selected after some time out. This is to ensure that both peers have added 
   each other as their friend. */
  /* 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 finger table entries.
 */
static void
finger_table_init ()
{
  memset (&finger_table, 0, sizeof (finger_table));
}


/**
 * Initialize neighbours subsystem.
 * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
 */
int
GDS_NEIGHBOURS_init (void)
{
  static struct GNUNET_CORE_MessageHandler core_handlers[] = {
    {&handle_dht_p2p_put, GNUNET_MESSAGE_TYPE_XDHT_P2P_PUT, 0},
    {&handle_dht_p2p_get, GNUNET_MESSAGE_TYPE_XDHT_P2P_GET, 0},
    {&handle_dht_p2p_get_result, GNUNET_MESSAGE_TYPE_XDHT_P2P_GET_RESULT, 0},
    {&handle_dht_p2p_trail_setup, GNUNET_MESSAGE_TYPE_XDHT_P2P_TRAIL_SETUP, 0},
    {&handle_dht_p2p_trail_setup_result, GNUNET_MESSAGE_TYPE_XDHT_P2P_TRAIL_SETUP_RESULT, 0},
    {&handle_dht_p2p_verify_successor, GNUNET_MESSAGE_TYPE_XDHT_P2P_VERIFY_SUCCESSOR, 0},
    {&handle_dht_p2p_verify_successor_result, GNUNET_MESSAGE_TYPE_XDHT_P2P_VERIFY_SUCCESSOR_RESULT, 0},
    {&handle_dht_p2p_notify_new_successor, GNUNET_MESSAGE_TYPE_XDHT_P2P_NOTIFY_NEW_SUCCESSOR, 0},
    {&handle_dht_p2p_trail_setup_rejection, GNUNET_MESSAGE_TYPE_XDHT_P2P_TRAIL_SETUP_REJECTION, 0},
    {&handle_dht_p2p_trail_teardown, GNUNET_MESSAGE_TYPE_XDHT_P2P_TRAIL_TEARDOWN,
                                     sizeof (struct PeerTrailTearDownMessage)},
    {&handle_dht_p2p_add_trail, GNUNET_MESSAGE_TYPE_XDHT_P2P_ADD_TRAIL, 0},
    {NULL, 0, 0}
  };
  
#if ENABLE_MALICIOUS
  act_malicious = 0;
#endif
  
  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 (NULL == core_api)
    return GNUNET_SYSERR;

  //TODO: check size of this peer map? 
  friend_peermap = GNUNET_CONTAINER_multipeermap_create (256, GNUNET_NO);
  finger_table_init ();
  
  find_finger_trail_task_next_send_time.rel_value_us =
      DHT_FIND_FINGER_TRAIL_INTERVAL.rel_value_us +
      GNUNET_CRYPTO_random_u64 (GNUNET_CRYPTO_QUALITY_WEAK,
                                DHT_FIND_FINGER_TRAIL_INTERVAL.rel_value_us);
  
  verify_successor_next_send_time.rel_value_us = 
      DHT_SEND_VERIFY_SUCCESSOR_INTERVAL.rel_value_us +
      GNUNET_CRYPTO_random_u64 (GNUNET_CRYPTO_QUALITY_WEAK,
                                DHT_FIND_FINGER_TRAIL_INTERVAL.rel_value_us);
  
  return GNUNET_OK;
}

/**
 * Free the memory held up by trails of a finger. 
 */
static void
delete_finger_table_entries()
{
  unsigned int i;
  unsigned int j;
  
  for(i = 0; i < MAX_FINGERS; i++)
  {
    if(GNUNET_NO == finger_table[i].is_present)
      continue;
    
    /* FREE ALL THE TRAILS. */
    /* SUPUS: Here in free trail, it will delete the entry
     if there is a trail with trail length != 0.OKAY */
    for(j = 0; j < finger_table[i].trails_count; j++)
    {
      free_trail(&finger_table[i].trail_list[i]);
    }
  }
}


/**
 * Shutdown neighbours subsystem.
 */
void
GDS_NEIGHBOURS_done (void)
{
  if (NULL == core_api)
    return;

  GNUNET_CORE_disconnect (core_api);
  core_api = NULL;

  delete_finger_table_entries();
  
  GNUNET_assert (0 == GNUNET_CONTAINER_multipeermap_size (friend_peermap));
  GNUNET_CONTAINER_multipeermap_destroy (friend_peermap);
  friend_peermap = NULL;

  if (GNUNET_SCHEDULER_NO_TASK != find_finger_trail_task)
  {
    GNUNET_break (0);
    GNUNET_SCHEDULER_cancel (find_finger_trail_task);
    find_finger_trail_task = GNUNET_SCHEDULER_NO_TASK;
  }

  if (GNUNET_SCHEDULER_NO_TASK != send_verify_successor_task)
  {
    GNUNET_SCHEDULER_cancel (send_verify_successor_task);
    send_verify_successor_task = GNUNET_SCHEDULER_NO_TASK;
  }
}


/**
 * Get my identity
 *
 * @return my identity
 */
struct GNUNET_PeerIdentity
GDS_NEIGHBOURS_get_my_id (void)
{
  return my_identity;
}

/* end of gnunet-service-xdht_neighbours.c */