work in progress

- neighbour management based on a FSM
- 3-way connect handshake

1 files changed, 1588 insertions, 0 deletions

diff --git a/src/transport/gnunet-service-transport_neighbours_fsm.c b/src/transport/gnunet-service-transport_neighbours_fsm.c
new file mode 100644
index 000000000..f9794967a
--- /dev/null
+++ b/src/transport/gnunet-service-transport_neighbours_fsm.c
@@ -0,0 +1,1588 @@
+/*
+     This file is part of GNUnet.
+     (C) 2010,2011 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 transport/gnunet-service-transport_neighbours.c
+ * @brief neighbour management
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include "gnunet_ats_service.h"
+#include "gnunet-service-transport_neighbours.h"
+#include "gnunet-service-transport_plugins.h"
+#include "gnunet-service-transport_validation.h"
+#include "gnunet-service-transport_clients.h"
+#include "gnunet-service-transport.h"
+#include "gnunet_peerinfo_service.h"
+#include "gnunet_constants.h"
+#include "transport.h"
+
+
+/**
+ * Size of the neighbour hash map.
+ */
+#define NEIGHBOUR_TABLE_SIZE 256
+
+/**
+ * How often must a peer violate bandwidth quotas before we start
+ * to simply drop its messages?
+ */
+#define QUOTA_VIOLATION_DROP_THRESHOLD 10
+
+/**
+ * How often do we send KEEPALIVE messages to each of our neighbours?
+ * (idle timeout is 5 minutes or 300 seconds, so with 90s interval we
+ * send 3 keepalives in each interval, so 3 messages would need to be
+ * lost in a row for a disconnect).
+ */
+#define KEEPALIVE_FREQUENCY GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, 90)
+
+
+/**
+ * Entry in neighbours.
+ */
+struct NeighbourMapEntry;
+
+/**
+ * Message a peer sends to another to indicate its
+ * preference for communicating via a particular
+ * session (and the desire to establish a real
+ * connection).
+ */
+struct SessionConnectMessage
+{
+  /**
+   * Header of type 'GNUNET_MESSAGE_TYPE_TRANSPORT_SESSION_CONNECT'
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Always zero.
+   */
+  uint32_t reserved GNUNET_PACKED;
+
+  /**
+   * Absolute time at the sender.  Only the most recent connect
+   * message implies which session is preferred by the sender.
+   */
+  struct GNUNET_TIME_AbsoluteNBO timestamp;
+
+};
+
+
+struct SessionDisconnectMessage
+{
+  /**
+   * Header of type 'GNUNET_MESSAGE_TYPE_TRANSPORT_SESSION_DISCONNECT'
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Always zero.
+   */
+  uint32_t reserved GNUNET_PACKED;
+
+  /**
+   * Purpose of the signature.  Extends over the timestamp.
+   * Purpose should be GNUNET_SIGNATURE_PURPOSE_TRANSPORT_DISCONNECT.
+   */
+  struct GNUNET_CRYPTO_RsaSignaturePurpose purpose;
+
+  /**
+   * Absolute time at the sender.  Only the most recent connect
+   * message implies which session is preferred by the sender.
+   */
+  struct GNUNET_TIME_AbsoluteNBO timestamp;
+
+  /**
+   * Public key of the sender.
+   */
+  struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded public_key;
+  
+  /**
+   * Signature of the peer that sends us the disconnect.  Only
+   * valid if the timestamp is AFTER the timestamp from the
+   * corresponding 'CONNECT' message.
+   */
+  struct GNUNET_CRYPTO_RsaSignature signature;
+
+};
+
+
+/**
+ * For each neighbour we keep a list of messages
+ * that we still want to transmit to the neighbour.
+ */
+struct MessageQueue
+{
+
+  /**
+   * This is a doubly linked list.
+   */
+  struct MessageQueue *next;
+
+  /**
+   * This is a doubly linked list.
+   */
+  struct MessageQueue *prev;
+
+  /**
+   * Once this message is actively being transmitted, which
+   * neighbour is it associated with?
+   */
+  struct NeighbourMapEntry *n;
+
+  /**
+   * Function to call once we're done.
+   */
+  GST_NeighbourSendContinuation cont;
+
+  /**
+   * Closure for 'cont'
+   */
+  void *cont_cls;
+
+  /**
+   * The message(s) we want to transmit, GNUNET_MessageHeader(s)
+   * stuck together in memory.  Allocated at the end of this struct.
+   */
+  const char *message_buf;
+
+  /**
+   * Size of the message buf
+   */
+  size_t message_buf_size;
+
+  /**
+   * At what time should we fail?
+   */
+  struct GNUNET_TIME_Absolute timeout;
+
+};
+
+enum State
+{
+    /* fresh peer or completely disconnected */
+    S_NOT_CONNECTED = 0,
+    /* sent CONNECT message to other peer, waiting for CONNECT_ACK */
+    S_CONNECT_SENT = 1,
+    /* received CONNECT message to other peer, sending CONNECT_ACK */
+    S_CONNECT_RECV = 4,
+    /* sent CONNECT_ACK message to other peer, wait for ACK or payload */
+    S_CONNECT_RECV_ACK_SENT = 8,
+    /* received ACK or payload */
+    S_CONNECTED = 16,
+    S_DISCONNECTED = 32
+};
+
+/**
+ * Entry in neighbours.
+ */
+struct NeighbourMapEntry
+{
+
+  /**
+   * Head of list of messages we would like to send to this peer;
+   * must contain at most one message per client.
+   */
+  struct MessageQueue *messages_head;
+
+  /**
+   * Tail of list of messages we would like to send to this peer; must
+   * contain at most one message per client.
+   */
+  struct MessageQueue *messages_tail;
+
+  /**
+   * Performance data for the peer.
+   */
+  //struct GNUNET_ATS_Information *ats;
+
+  /**
+   * Are we currently trying to send a message? If so, which one?
+   */
+  struct MessageQueue *is_active;
+
+  /**
+   * Active session for communicating with the peer.
+   */
+  struct Session *session;
+
+  /**
+   * Name of the plugin we currently use.
+   */
+  char *plugin_name;
+
+  /**
+   * Address used for communicating with the peer, NULL for inbound connections.
+   */
+  void *addr;
+
+  /**
+   * Number of bytes in 'addr'.
+   */
+  size_t addrlen;
+
+  /**
+   * Identity of this neighbour.
+   */
+  struct GNUNET_PeerIdentity id;
+
+  /**
+   * ID of task scheduled to run when this peer is about to
+   * time out (will free resources associated with the peer).
+   */
+  GNUNET_SCHEDULER_TaskIdentifier timeout_task;
+
+  /**
+   * ID of task scheduled to send keepalives.
+   */
+  GNUNET_SCHEDULER_TaskIdentifier keepalive_task;
+
+  /**
+   * ID of task scheduled to run when we should try transmitting
+   * the head of the message queue.
+   */
+  GNUNET_SCHEDULER_TaskIdentifier transmission_task;
+
+  /**
+   * Tracker for inbound bandwidth.
+   */
+  struct GNUNET_BANDWIDTH_Tracker in_tracker;
+
+  /**
+   * Timestamp of the 'SESSION_CONNECT' message we got from the other peer
+   */
+  struct GNUNET_TIME_Absolute connect_ts;
+
+  /**
+   * How often has the other peer (recently) violated the inbound
+   * traffic limit?  Incremented by 10 per violation, decremented by 1
+   * per non-violation (for each time interval).
+   */
+  unsigned int quota_violation_count;
+
+  /**
+   * Number of values in 'ats' array.
+   */
+  //unsigned int ats_count;
+
+  /**
+   * Are we already in the process of disconnecting this neighbour?
+   */
+  int in_disconnect;
+
+  /**
+   * Do we currently consider this neighbour connected? (as far as
+   * the connect/disconnect callbacks are concerned)?
+   */
+  int is_connected;
+
+  int state;
+
+};
+
+
+/**
+ * All known neighbours and their HELLOs.
+ */
+static struct GNUNET_CONTAINER_MultiHashMap *neighbours;
+
+/**
+ * Closure for connect_notify_cb and disconnect_notify_cb
+ */
+static void *callback_cls;
+
+/**
+ * Function to call when we connected to a neighbour.
+ */
+static GNUNET_TRANSPORT_NotifyConnect connect_notify_cb;
+
+/**
+ * Function to call when we disconnected from a neighbour.
+ */
+static GNUNET_TRANSPORT_NotifyDisconnect disconnect_notify_cb;
+
+/**
+ * counter for connected neighbours
+ */
+static int neighbours_connected;
+
+/**
+ * Lookup a neighbour entry in the neighbours hash map.
+ *
+ * @param pid identity of the peer to look up
+ * @return the entry, NULL if there is no existing record
+ */
+static struct NeighbourMapEntry *
+lookup_neighbour (const struct GNUNET_PeerIdentity *pid)
+{
+  return GNUNET_CONTAINER_multihashmap_get (neighbours, &pid->hashPubKey);
+}
+
+#define change_state(n, state, ...) change (n, state, __LINE__)
+
+static int
+change (struct NeighbourMapEntry * n, int state, int line)
+{
+  char * old;
+  char * new;
+
+  switch (n->state) {
+    case S_CONNECTED:
+        old = "S_CONNECTED";
+      break;
+    case S_CONNECT_RECV:
+      old = "S_CONNECT_RECV";
+      break;
+    case S_CONNECT_RECV_ACK_SENT:
+      old = "S_CONNECT_RECV_ACK_SENT";
+      break;
+    case S_CONNECT_SENT:
+      old = "S_CONNECT_SENT";
+      break;
+    case S_DISCONNECTED:
+      old = "S_DISCONNECTED";
+      break;
+    case S_NOT_CONNECTED:
+      old = "S_NOT_CONNECTED";
+      break;
+    default:
+      GNUNET_break (0);
+      break;
+  }
+
+  switch (state) {
+    case S_CONNECTED:
+      new = "S_CONNECTED";
+      break;
+    case S_CONNECT_RECV:
+      new = "S_CONNECT_RECV";
+      break;
+    case S_CONNECT_RECV_ACK_SENT:
+      new = "S_CONNECT_RECV_ACK_SENT";
+      break;
+    case S_CONNECT_SENT:
+      new = "S_CONNECT_SENT";
+      break;
+    case S_DISCONNECTED:
+      new = "S_DISCONNECTED";
+      break;
+    case S_NOT_CONNECTED:
+      new = "S_NOT_CONNECTED";
+      break;
+    default:
+      GNUNET_break (0);
+      break;
+  }
+
+  /* allowed transitions */
+  switch (n->state) {
+  case S_NOT_CONNECTED:
+    if (state == S_CONNECT_RECV)
+      break;
+    if (state == S_CONNECT_SENT)
+      break;
+  case S_CONNECT_RECV:
+    if (state == S_CONNECT_RECV_ACK_SENT)
+      break;
+  case S_CONNECT_SENT:
+    if (state == S_NOT_CONNECTED)
+      break;
+    if (state == S_CONNECTED)
+      break;
+  case S_CONNECTED:
+  case S_DISCONNECTED:
+  default:
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+        "Illegal state transition from `%s' to `%s' in line %u \n",
+        old, new, line);
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+
+  n->state = state;
+  GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "State for neighbour `%s' %X changed from `%s' to `%s' in line %u\n",
+      GNUNET_i2s (&n->id), n, old, new, line);
+  return GNUNET_OK;
+}
+
+/**
+ * Task invoked to start a transmission to another peer.
+ *
+ * @param cls the 'struct NeighbourMapEntry'
+ * @param tc scheduler context
+ */
+static void
+transmission_task (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc);
+
+
+/**
+ * We're done with our transmission attempt, continue processing.
+ *
+ * @param cls the 'struct MessageQueue' of the message
+ * @param receiver intended receiver
+ * @param success whether it worked or not
+ */
+static void
+transmit_send_continuation (void *cls,
+                            const struct GNUNET_PeerIdentity *receiver,
+                            int success)
+{
+  struct MessageQueue *mq;
+  struct NeighbourMapEntry *n;
+
+  mq = cls;
+  n = mq->n;
+  if (NULL != n)
+  {
+    GNUNET_assert (n->is_active == mq);
+    n->is_active = NULL;
+    if (success == GNUNET_YES)
+    {
+      GNUNET_assert (n->transmission_task == GNUNET_SCHEDULER_NO_TASK);
+      n->transmission_task = GNUNET_SCHEDULER_add_now (&transmission_task, n);
+    }
+  }
+
+  GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Sending message of type %u had result: %u\n",
+              ntohs (((struct GNUNET_MessageHeader *) mq->message_buf)->type), success);
+
+  if (NULL != mq->cont)
+    mq->cont (mq->cont_cls, success);
+  GNUNET_free (mq);
+}
+
+
+/**
+ * Check the ready list for the given neighbour and if a plugin is
+ * ready for transmission (and if we have a message), do so!
+ *
+ * @param n target peer for which to transmit
+ */
+static void
+try_transmission_to_peer (struct NeighbourMapEntry *n)
+{
+  struct MessageQueue *mq;
+  struct GNUNET_TIME_Relative timeout;
+  ssize_t ret;
+  struct GNUNET_TRANSPORT_PluginFunctions *papi;
+
+  if (n->is_active != NULL)
+  {
+    GNUNET_break (0);
+    return;                     /* transmission already pending */
+  }
+  if (n->transmission_task != GNUNET_SCHEDULER_NO_TASK)
+  {
+    GNUNET_break (0);
+    return;                     /* currently waiting for bandwidth */
+  }
+  while (NULL != (mq = n->messages_head))
+  {
+    timeout = GNUNET_TIME_absolute_get_remaining (mq->timeout);
+    if (timeout.rel_value > 0)
+      break;
+    GNUNET_CONTAINER_DLL_remove (n->messages_head, n->messages_tail, mq);
+    n->is_active = mq;
+    mq->n = n;
+    transmit_send_continuation (mq, &n->id, GNUNET_SYSERR);     /* timeout */
+  }
+  if (NULL == mq)
+    return;                     /* no more messages */
+
+  papi = GST_plugins_find (n->plugin_name);
+  if (papi == NULL)
+  {
+    GNUNET_break (0);
+    return;
+  }
+  GNUNET_CONTAINER_DLL_remove (n->messages_head, n->messages_tail, mq);
+  n->is_active = mq;
+  mq->n = n;
+
+  if  ((n->session == NULL) && (n->addr == NULL) && (n->addrlen == 0))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "No address for peer `%s'\n",
+                GNUNET_i2s (&n->id));
+    transmit_send_continuation (mq, &n->id, GNUNET_SYSERR);
+    GNUNET_assert (n->transmission_task == GNUNET_SCHEDULER_NO_TASK);
+    n->transmission_task = GNUNET_SCHEDULER_add_now (&transmission_task, n);
+    return;
+  }
+  GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "try_transmission_to_peer\n");
+  papi = GST_plugins_find (n->plugin_name);
+  ret =
+      papi->send (papi->cls, &n->id, mq->message_buf, mq->message_buf_size,
+                  0 /* priority -- remove from plugin API? */ ,
+                  timeout, n->session, n->addr, n->addrlen, GNUNET_YES,
+                  &transmit_send_continuation, mq);
+  if (ret == -1)
+  {
+    /* failure, but 'send' would not call continuation in this case,
+     * so we need to do it here! */
+    transmit_send_continuation (mq, &n->id, GNUNET_SYSERR);
+  }
+
+}
+
+
+/**
+ * Task invoked to start a transmission to another peer.
+ *
+ * @param cls the 'struct NeighbourMapEntry'
+ * @param tc scheduler context
+ */
+static void
+transmission_task (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "transmission_task\n");
+  struct NeighbourMapEntry *n = cls;
+  GNUNET_assert (NULL != lookup_neighbour(&n->id));
+  n->transmission_task = GNUNET_SCHEDULER_NO_TASK;
+  try_transmission_to_peer (n);
+}
+
+
+/**
+ * Initialize the neighbours subsystem.
+ *
+ * @param cls closure for callbacks
+ * @param connect_cb function to call if we connect to a peer
+ * @param disconnect_cb function to call if we disconnect from a peer
+ */
+void
+GST_neighbours_start (void *cls, GNUNET_TRANSPORT_NotifyConnect connect_cb,
+                      GNUNET_TRANSPORT_NotifyDisconnect disconnect_cb)
+{
+  callback_cls = cls;
+  connect_notify_cb = connect_cb;
+  disconnect_notify_cb = disconnect_cb;
+  neighbours = GNUNET_CONTAINER_multihashmap_create (NEIGHBOUR_TABLE_SIZE);
+}
+
+
+/**
+ * Disconnect from the given neighbour, clean up the record.
+ *
+ * @param n neighbour to disconnect from
+ */
+static void
+disconnect_neighbour (struct NeighbourMapEntry *n)
+{
+  struct MessageQueue *mq;
+
+  if (GNUNET_YES == n->in_disconnect)
+    return;
+  n->in_disconnect = GNUNET_YES;
+  while (NULL != (mq = n->messages_head))
+  {
+    GNUNET_CONTAINER_DLL_remove (n->messages_head, n->messages_tail, mq);
+    if (NULL != mq->cont)
+      mq->cont (mq->cont_cls, GNUNET_SYSERR);
+    GNUNET_free (mq);
+  }
+  if (NULL != n->is_active)
+  {
+    n->is_active->n = NULL;
+    n->is_active = NULL;
+  }
+  if (GNUNET_YES == n->is_connected)
+  {
+    n->is_connected = GNUNET_NO;
+    GNUNET_assert (GNUNET_SCHEDULER_NO_TASK != n->keepalive_task);
+    GNUNET_SCHEDULER_cancel (n->keepalive_task);
+    n->keepalive_task = GNUNET_SCHEDULER_NO_TASK;  
+    GNUNET_assert (neighbours_connected > 0);
+    neighbours_connected--;
+    GNUNET_STATISTICS_update (GST_stats, gettext_noop ("# peers connected"), -1,
+                              GNUNET_NO);
+    disconnect_notify_cb (callback_cls, &n->id);
+  }
+  GNUNET_assert (GNUNET_YES ==
+                 GNUNET_CONTAINER_multihashmap_remove (neighbours,
+                                                       &n->id.hashPubKey, n));
+  if (GNUNET_SCHEDULER_NO_TASK != n->timeout_task)
+  {
+    GNUNET_SCHEDULER_cancel (n->timeout_task);
+    n->timeout_task = GNUNET_SCHEDULER_NO_TASK;
+  }
+  if (GNUNET_SCHEDULER_NO_TASK != n->transmission_task)
+  {
+    GNUNET_SCHEDULER_cancel (n->transmission_task);
+    n->transmission_task = GNUNET_SCHEDULER_NO_TASK;
+  }
+  if (NULL != n->plugin_name)
+  {
+    GNUNET_free (n->plugin_name);
+    n->plugin_name = NULL;
+  }
+  if (NULL != n->addr)
+  {
+    GNUNET_free (n->addr);
+    n->addr = NULL;
+    n->addrlen = 0;
+  }
+  n->session = NULL;
+  GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Deleting peer `%4s', %X\n",
+              GNUNET_i2s (&n->id), n);
+  GNUNET_free (n);
+}
+
+
+/**
+ * Peer has been idle for too long. Disconnect.
+ *
+ * @param cls the 'struct NeighbourMapEntry' of the neighbour that went idle
+ * @param tc scheduler context
+ */
+static void
+neighbour_timeout_task (void *cls,
+                        const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct NeighbourMapEntry *n = cls;
+
+  n->timeout_task = GNUNET_SCHEDULER_NO_TASK;
+  if (GNUNET_YES == n->is_connected)
+    GNUNET_STATISTICS_update (GST_stats,
+                            gettext_noop ("# peers disconnected due to timeout"), 1,
+                            GNUNET_NO);
+  disconnect_neighbour (n);
+}
+
+
+/**
+ * Send another keepalive message.
+ *
+ * @param cls the 'struct NeighbourMapEntry' of the neighbour that went idle
+ * @param tc scheduler context
+ */
+static void
+neighbour_keepalive_task (void *cls,
+                          const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct NeighbourMapEntry *n = cls;
+  struct GNUNET_MessageHeader m;
+  struct GNUNET_TRANSPORT_PluginFunctions *papi;
+
+  n->keepalive_task = GNUNET_SCHEDULER_add_delayed (KEEPALIVE_FREQUENCY,
+                                                    &neighbour_keepalive_task,
+                                                    n);
+  GNUNET_assert (GNUNET_YES == n->is_connected);
+  GNUNET_STATISTICS_update (GST_stats,
+                            gettext_noop ("# keepalives sent"), 1,
+                            GNUNET_NO);
+  m.size = htons (sizeof (struct GNUNET_MessageHeader));
+  m.type = htons (GNUNET_MESSAGE_TYPE_TRANSPORT_SESSION_KEEPALIVE);
+  papi = GST_plugins_find (n->plugin_name);
+  if (papi != NULL)
+    papi->send (papi->cls, 
+                &n->id, (const void *) &m,
+                sizeof (m),
+                UINT32_MAX /* priority */ ,
+                GNUNET_TIME_UNIT_FOREVER_REL, n->session, n->addr, n->addrlen,
+                GNUNET_YES, NULL, NULL);
+}
+
+
+/**
+ * Disconnect from the given neighbour.
+ *
+ * @param cls unused
+ * @param key hash of neighbour's public key (not used)
+ * @param value the 'struct NeighbourMapEntry' of the neighbour
+ */
+static int
+disconnect_all_neighbours (void *cls, const GNUNET_HashCode * key, void *value)
+{
+  struct NeighbourMapEntry *n = value;
+
+#if DEBUG_TRANSPORT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Disconnecting peer `%4s', %s\n",
+              GNUNET_i2s (&n->id), "SHUTDOWN_TASK");
+#endif
+  if (GNUNET_YES == n->is_connected)
+    GNUNET_STATISTICS_update (GST_stats,
+                              gettext_noop ("# peers disconnected due to global disconnect"), 1,
+                              GNUNET_NO);
+  disconnect_neighbour (n);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Cleanup the neighbours subsystem.
+ */
+void
+GST_neighbours_stop ()
+{
+  GNUNET_assert (neighbours != NULL);
+
+  GNUNET_CONTAINER_multihashmap_iterate (neighbours, &disconnect_all_neighbours,
+                                         NULL);
+  GNUNET_CONTAINER_multihashmap_destroy (neighbours);
+  GNUNET_assert (neighbours_connected == 0);
+  neighbours = NULL;
+  callback_cls = NULL;
+  connect_notify_cb = NULL;
+  disconnect_notify_cb = NULL;
+}
+
+
+/**
+ * We tried to send a SESSION_CONNECT message to another peer.  If this
+ * succeeded, we should mark the peer up.  If it failed, we should tell
+ * ATS to not use this address anymore (until it is re-validated).
+ *
+ * @param cls the 'struct NeighbourMapEntry'
+ * @param success GNUNET_OK on success
+ */
+static void
+send_connect_continuation (void *cls,
+                           int success)
+{
+  struct NeighbourMapEntry *n = cls;
+
+  GNUNET_assert (n != NULL);
+  if (GNUNET_YES == n->in_disconnect)
+    return; /* neighbour is going away */
+  if (GNUNET_YES != success)
+  {
+    change_state(n, S_NOT_CONNECTED);
+    GNUNET_ATS_address_destroyed (GST_ats,
+                                  &n->id,
+                                  n->plugin_name, 
+                                  n->addr,
+                                  n->addrlen,
+                                  NULL);
+    disconnect_neighbour (n);
+    return;
+  }
+}
+
+
+/**
+ * For an existing neighbour record, set the active connection to
+ * the given address.
+ *
+ * @param peer identity of the peer to switch the address for
+ * @param plugin_name name of transport that delivered the PONG
+ * @param address address of the other peer, NULL if other peer
+ *                       connected to us
+ * @param address_len number of bytes in address
+ * @param session session to use (or NULL)
+ * @param ats performance data
+ * @param ats_count number of entries in ats (excluding 0-termination)
+ * @return GNUNET_YES if we are currently connected, GNUNET_NO if the
+ *         connection is not up (yet)
+ */
+int
+GST_neighbours_switch_to_address (const struct GNUNET_PeerIdentity *peer,
+                                  const char *plugin_name, const void *address,
+                                  size_t address_len, struct Session *session,
+                                  const struct GNUNET_ATS_Information
+                                  *ats, uint32_t ats_count)
+{
+  struct NeighbourMapEntry *n;
+  struct SessionConnectMessage connect_msg;
+  //int was_connected;
+
+  GNUNET_assert (neighbours != NULL);
+  n = lookup_neighbour (peer);
+  if (NULL == n)
+  {
+    if (NULL == session)
+      GNUNET_ATS_address_destroyed (GST_ats,
+                                    peer,
+                                    plugin_name, address,
+                                    address_len, NULL);    
+    return GNUNET_NO;
+  }
+  /*
+  was_connected = n->is_connected;
+  n->is_connected = GNUNET_YES;
+  if (GNUNET_YES != was_connected)
+    n->keepalive_task = GNUNET_SCHEDULER_add_delayed (KEEPALIVE_FREQUENCY,
+                                                      &neighbour_keepalive_task,
+                                                      n);*/
+
+  change_state (n, S_CONNECT_SENT);
+
+#if DEBUG_TRANSPORT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "SWITCH! Peer `%4s' switches to plugin `%s' address '%s' session %X\n",
+              GNUNET_i2s (peer), plugin_name,
+              (address_len == 0) ? "<inbound>" : GST_plugins_a2s (plugin_name,
+                                                                  address,
+                                                                  address_len),
+              session);
+#endif
+  GNUNET_free_non_null (n->addr);
+  n->addr = GNUNET_malloc (address_len);
+  memcpy (n->addr, address, address_len);
+  n->addrlen = address_len;
+  n->session = session;
+  GNUNET_free_non_null (n->plugin_name);
+  n->plugin_name = GNUNET_strdup (plugin_name);
+  GNUNET_SCHEDULER_cancel (n->timeout_task);
+  n->timeout_task =
+      GNUNET_SCHEDULER_add_delayed (GNUNET_CONSTANTS_IDLE_CONNECTION_TIMEOUT,
+                                    &neighbour_timeout_task, n);
+  connect_msg.header.size = htons (sizeof (struct SessionConnectMessage));
+  connect_msg.header.type =
+      htons (GNUNET_MESSAGE_TYPE_TRANSPORT_SESSION_CONNECT);
+  connect_msg.reserved = htonl (0);
+  connect_msg.timestamp =
+      GNUNET_TIME_absolute_hton (GNUNET_TIME_absolute_get ());
+  GST_neighbours_send (peer, &connect_msg, sizeof (connect_msg),
+                       GNUNET_TIME_UNIT_FOREVER_REL, 
+                       &send_connect_continuation, 
+                       n);
+  /*
+  if (GNUNET_YES == was_connected)
+    return GNUNET_YES;
+  // First tell clients about connected neighbours...
+  neighbours_connected++;
+  GNUNET_STATISTICS_update (GST_stats, gettext_noop ("# peers connected"), 1,
+                            GNUNET_NO);
+  connect_notify_cb (callback_cls, peer, ats, ats_count);
+  return GNUNET_YES;*/
+  /* connection not yet up */
+  return GNUNET_NO;
+}
+
+
+/**
+ * Create an entry in the neighbour map for the given peer
+ * 
+ * @param peer peer to create an entry for
+ * @return new neighbour map entry
+ */
+static struct NeighbourMapEntry *
+setup_neighbour (const struct GNUNET_PeerIdentity *peer)
+{
+  struct NeighbourMapEntry *n;
+
+#if DEBUG_TRANSPORT
+#endif
+  GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+              "Unknown peer `%s', creating new neighbour\n",
+              GNUNET_i2s (peer));
+
+  n = GNUNET_malloc (sizeof (struct NeighbourMapEntry));
+  n->id = *peer;
+  n->state = S_NOT_CONNECTED;
+  GNUNET_BANDWIDTH_tracker_init (&n->in_tracker,
+                                 GNUNET_CONSTANTS_DEFAULT_BW_IN_OUT,
+                                 MAX_BANDWIDTH_CARRY_S);
+  n->timeout_task =
+    GNUNET_SCHEDULER_add_delayed (GNUNET_CONSTANTS_IDLE_CONNECTION_TIMEOUT,
+                                  &neighbour_timeout_task, n);
+  GNUNET_assert (GNUNET_OK ==
+                 GNUNET_CONTAINER_multihashmap_put (neighbours,
+                                                    &n->id.hashPubKey, n,
+                                                    GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
+  return n;
+}
+
+
+/**
+ * Try to create a connection to the given target (eventually).
+ *
+ * @param target peer to try to connect to
+ */
+void
+GST_neighbours_try_connect (const struct GNUNET_PeerIdentity *target)
+{
+  struct NeighbourMapEntry *n;
+
+  GNUNET_assert (neighbours != NULL);
+#if DEBUG_TRANSPORT
+#endif
+  GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Trying to connect to peer `%s'\n",
+              GNUNET_i2s (target));
+
+  GNUNET_assert (0 !=
+                 memcmp (target, &GST_my_identity,
+                         sizeof (struct GNUNET_PeerIdentity)));
+  n = lookup_neighbour (target);
+  if ((NULL != n) && (GNUNET_YES == n->is_connected))
+    return;                     /* already connected */
+
+  if ((NULL != n) && (n->state > S_NOT_CONNECTED))
+    return;                     /* already connecting */
+
+  if (n == NULL)
+    n = setup_neighbour (target);
+#if DEBUG_TRANSPORT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Asking ATS for suggested address to connect to peer `%s'\n",
+              GNUNET_i2s (&n->id));
+#endif
+   GNUNET_ATS_suggest_address (GST_ats, &n->id);
+}
+
+
+/**
+ * Test if we're connected to the given peer.
+ *
+ * @param target peer to test
+ * @return GNUNET_YES if we are connected, GNUNET_NO if not
+ */
+int
+GST_neighbours_test_connected (const struct GNUNET_PeerIdentity *target)
+{
+  struct NeighbourMapEntry *n;
+
+  GNUNET_assert (neighbours != NULL);
+
+  n = lookup_neighbour (target);
+  if ((NULL == n) || (n->is_connected != GNUNET_YES))
+    return GNUNET_NO;           /* not connected */
+  return GNUNET_YES;
+}
+
+
+/**
+ * A session was terminated. Take note.
+ *
+ * @param peer identity of the peer where the session died
+ * @param session session that is gone
+ */
+void
+GST_neighbours_session_terminated (const struct GNUNET_PeerIdentity *peer,
+                                   struct Session *session)
+{
+  struct NeighbourMapEntry *n;
+
+  GNUNET_assert (neighbours != NULL);
+
+#if DEBUG_TRANSPORT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Session %X to peer `%s' ended \n",
+              session, GNUNET_i2s (peer));
+#endif
+  n = lookup_neighbour (peer);
+  if (NULL == n)
+    return;
+  if (session != n->session)
+    return;                     /* doesn't affect us */
+
+  n->session = NULL;
+  GNUNET_free (n->addr);
+  n->addr = NULL;
+  n->addrlen = 0;
+
+
+  if (GNUNET_YES != n->is_connected)
+    return;                     /* not connected anymore anyway, shouldn't matter */
+  /* fast disconnect unless ATS suggests a new address */
+  GNUNET_SCHEDULER_cancel (n->timeout_task);
+  n->timeout_task =
+      GNUNET_SCHEDULER_add_delayed (GNUNET_CONSTANTS_DISCONNECT_SESSION_TIMEOUT,
+                                    &neighbour_timeout_task, n);
+  /* try QUICKLY to re-establish a connection, reduce timeout! */
+  GNUNET_ATS_suggest_address (GST_ats, peer);
+}
+
+
+/**
+ * Transmit a message to the given target using the active connection.
+ *
+ * @param target destination
+ * @param msg message to send
+ * @param msg_size number of bytes in msg
+ * @param timeout when to fail with timeout
+ * @param cont function to call when done
+ * @param cont_cls closure for 'cont'
+ */
+void
+GST_neighbours_send (const struct GNUNET_PeerIdentity *target, const void *msg,
+                     size_t msg_size, struct GNUNET_TIME_Relative timeout,
+                     GST_NeighbourSendContinuation cont, void *cont_cls)
+{
+  struct NeighbourMapEntry *n;
+  struct MessageQueue *mq;
+
+  GNUNET_assert (neighbours != NULL);
+
+  n = lookup_neighbour (target);
+  /* FIXME */
+  if ((n == NULL) /* || (GNUNET_YES != n->is_connected)*/)
+  {
+    GNUNET_STATISTICS_update (GST_stats,
+                              gettext_noop
+                              ("# messages not sent (no such peer or not connected)"),
+                              1, GNUNET_NO);
+#if DEBUG_TRANSPORT
+    if (n == NULL)
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Could not send message to peer `%s': unknown neighbor",
+                  GNUNET_i2s (target));
+    else if (GNUNET_YES != n->is_connected)
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Could not send message to peer `%s': not connected\n",
+                  GNUNET_i2s (target));
+#endif
+    if (NULL != cont)
+      cont (cont_cls, GNUNET_SYSERR);
+    return;
+  }
+  GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "GST_neighbours_send %u\n", __LINE__);
+  if ((n->session == NULL) && (n->addr == NULL) && (n->addrlen ==0))
+  {
+    GNUNET_STATISTICS_update (GST_stats,
+                              gettext_noop
+                              ("# messages not sent (no such peer or not connected)"),
+                              1, GNUNET_NO);
+#if DEBUG_TRANSPORT
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Could not send message to peer `%s': no address available\n",
+                  GNUNET_i2s (target));
+#endif
+
+    if (NULL != cont)
+      cont (cont_cls, GNUNET_SYSERR);
+    return;
+  }
+  GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "GST_neighbours_send %u\n", __LINE__);
+  GNUNET_assert (msg_size >= sizeof (struct GNUNET_MessageHeader));
+  GNUNET_STATISTICS_update (GST_stats,
+                            gettext_noop
+                            ("# bytes in message queue for other peers"),
+                            msg_size, GNUNET_NO);
+  mq = GNUNET_malloc (sizeof (struct MessageQueue) + msg_size);
+  mq->cont = cont;
+  mq->cont_cls = cont_cls;
+  /* FIXME: this memcpy can be up to 7% of our total runtime! */
+  memcpy (&mq[1], msg, msg_size);
+  mq->message_buf = (const char *) &mq[1];
+  mq->message_buf_size = msg_size;
+  mq->timeout = GNUNET_TIME_relative_to_absolute (timeout);
+  GNUNET_CONTAINER_DLL_insert_tail (n->messages_head, n->messages_tail, mq);
+
+  GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "GST_neighbours_send %u\n", __LINE__);
+
+  if ((GNUNET_SCHEDULER_NO_TASK == n->transmission_task) &&
+      (NULL == n->is_active))
+    n->transmission_task = GNUNET_SCHEDULER_add_now (&transmission_task, n);
+}
+
+
+/**
+ * We have received a message from the given sender.  How long should
+ * we delay before receiving more?  (Also used to keep the peer marked
+ * as live).
+ *
+ * @param sender sender of the message
+ * @param size size of the message
+ * @param do_forward set to GNUNET_YES if the message should be forwarded to clients
+ *                   GNUNET_NO if the neighbour is not connected or violates the quota,
+ *                   GNUNET_SYSERR if the connection is not fully up yet
+ * @return how long to wait before reading more from this sender
+ */
+struct GNUNET_TIME_Relative
+GST_neighbours_calculate_receive_delay (const struct GNUNET_PeerIdentity
+                                        *sender, ssize_t size, int *do_forward)
+{
+  struct NeighbourMapEntry *n;
+  struct GNUNET_TIME_Relative ret;
+
+  GNUNET_assert (neighbours != NULL);
+
+  n = lookup_neighbour (sender);
+  if (n == NULL)
+  {
+    GST_neighbours_try_connect (sender);
+    n = lookup_neighbour (sender);
+    if (NULL == n)
+    {
+      GNUNET_STATISTICS_update (GST_stats,
+                                gettext_noop
+                                ("# messages discarded due to lack of neighbour record"),
+                                1, GNUNET_NO);
+      *do_forward = GNUNET_NO;
+      return GNUNET_TIME_UNIT_ZERO;
+    }
+  }
+  if (GNUNET_YES != n->is_connected)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                _("Plugin gave us %d bytes of data but somehow the session is not marked as UP yet!\n"),
+                (int) size);
+    *do_forward = GNUNET_SYSERR;
+    return GNUNET_TIME_UNIT_ZERO;
+  }
+  if (GNUNET_YES == GNUNET_BANDWIDTH_tracker_consume (&n->in_tracker, size))
+  {
+    n->quota_violation_count++;
+#if DEBUG_TRANSPORT
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Bandwidth quota (%u b/s) violation detected (total of %u).\n",
+                n->in_tracker.available_bytes_per_s__,
+                n->quota_violation_count);
+#endif
+    /* Discount 32k per violation */
+    GNUNET_BANDWIDTH_tracker_consume (&n->in_tracker, -32 * 1024);
+  }
+  else
+  {
+    if (n->quota_violation_count > 0)
+    {
+      /* try to add 32k back */
+      GNUNET_BANDWIDTH_tracker_consume (&n->in_tracker, 32 * 1024);
+      n->quota_violation_count--;
+    }
+  }
+  if (n->quota_violation_count > QUOTA_VIOLATION_DROP_THRESHOLD)
+  {
+    GNUNET_STATISTICS_update (GST_stats,
+                              gettext_noop
+                              ("# bandwidth quota violations by other peers"),
+                              1, GNUNET_NO);
+    *do_forward = GNUNET_NO;
+    return GNUNET_CONSTANTS_QUOTA_VIOLATION_TIMEOUT;
+  }
+  *do_forward = GNUNET_YES;
+  ret = GNUNET_BANDWIDTH_tracker_get_delay (&n->in_tracker, 32 * 1024);
+  if (ret.rel_value > 0)
+  {
+#if DEBUG_TRANSPORT
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Throttling read (%llu bytes excess at %u b/s), waiting %llu ms before reading more.\n",
+                (unsigned long long) n->in_tracker.
+                consumption_since_last_update__,
+                (unsigned int) n->in_tracker.available_bytes_per_s__,
+                (unsigned long long) ret.rel_value);
+#endif
+    GNUNET_STATISTICS_update (GST_stats,
+                              gettext_noop ("# ms throttling suggested"),
+                              (int64_t) ret.rel_value, GNUNET_NO);
+  }
+  return ret;
+}
+
+
+/**
+ * Keep the connection to the given neighbour alive longer,
+ * we received a KEEPALIVE (or equivalent).
+ *
+ * @param neighbour neighbour to keep alive
+ */
+void
+GST_neighbours_keepalive (const struct GNUNET_PeerIdentity *neighbour)
+{
+  struct NeighbourMapEntry *n;
+
+  GNUNET_assert (neighbours != NULL);
+
+  n = lookup_neighbour (neighbour);
+  if (NULL == n)
+  {
+    GNUNET_STATISTICS_update (GST_stats,
+                              gettext_noop
+                              ("# KEEPALIVE messages discarded (not connected)"),
+                              1, GNUNET_NO);
+    return;
+  }
+  GNUNET_SCHEDULER_cancel (n->timeout_task);
+  n->timeout_task =
+      GNUNET_SCHEDULER_add_delayed (GNUNET_CONSTANTS_IDLE_CONNECTION_TIMEOUT,
+                                    &neighbour_timeout_task, n);
+}
+
+
+/**
+ * Change the incoming quota for the given peer.
+ *
+ * @param neighbour identity of peer to change qutoa for
+ * @param quota new quota
+ */
+void
+GST_neighbours_set_incoming_quota (const struct GNUNET_PeerIdentity *neighbour,
+                                   struct GNUNET_BANDWIDTH_Value32NBO quota)
+{
+  struct NeighbourMapEntry *n;
+
+  GNUNET_assert (neighbours != NULL);
+
+  n = lookup_neighbour (neighbour);
+  if (n == NULL)
+  {
+    GNUNET_STATISTICS_update (GST_stats,
+                              gettext_noop
+                              ("# SET QUOTA messages ignored (no such peer)"),
+                              1, GNUNET_NO);
+    return;
+  }
+  GNUNET_BANDWIDTH_tracker_update_quota (&n->in_tracker, quota);
+  if (0 != ntohl (quota.value__))
+    return;
+#if DEBUG_TRANSPORT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Disconnecting peer `%4s' due to `%s'\n",
+              GNUNET_i2s (&n->id), "SET_QUOTA");
+#endif
+  if (GNUNET_YES == n->is_connected)
+    GNUNET_STATISTICS_update (GST_stats,
+                              gettext_noop ("# disconnects due to quota of 0"), 1,
+                              GNUNET_NO);
+  disconnect_neighbour (n);
+}
+
+
+/**
+ * Closure for the neighbours_iterate function.
+ */
+struct IteratorContext
+{
+  /**
+   * Function to call on each connected neighbour.
+   */
+  GST_NeighbourIterator cb;
+
+  /**
+   * Closure for 'cb'.
+   */
+  void *cb_cls;
+};
+
+
+/**
+ * Call the callback from the closure for each connected neighbour.
+ *
+ * @param cls the 'struct IteratorContext'
+ * @param key the hash of the public key of the neighbour
+ * @param value the 'struct NeighbourMapEntry'
+ * @return GNUNET_OK (continue to iterate)
+ */
+static int
+neighbours_iterate (void *cls, const GNUNET_HashCode * key, void *value)
+{
+  struct IteratorContext *ic = cls;
+  struct NeighbourMapEntry *n = value;
+
+  if (GNUNET_YES != n->is_connected)
+    return GNUNET_OK;
+
+  ic->cb (ic->cb_cls, &n->id, NULL, 0, n->plugin_name, n->addr, n->addrlen);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Iterate over all connected neighbours.
+ *
+ * @param cb function to call
+ * @param cb_cls closure for cb
+ */
+void
+GST_neighbours_iterate (GST_NeighbourIterator cb, void *cb_cls)
+{
+  struct IteratorContext ic;
+
+  GNUNET_assert (neighbours != NULL);
+
+  ic.cb = cb;
+  ic.cb_cls = cb_cls;
+  GNUNET_CONTAINER_multihashmap_iterate (neighbours, &neighbours_iterate, &ic);
+}
+
+
+/**
+ * If we have an active connection to the given target, it must be shutdown.
+ *
+ * @param target peer to disconnect from
+ */
+void
+GST_neighbours_force_disconnect (const struct GNUNET_PeerIdentity *target)
+{
+  struct NeighbourMapEntry *n;
+  struct GNUNET_TRANSPORT_PluginFunctions *papi;
+  struct SessionDisconnectMessage disconnect_msg;
+
+  GNUNET_assert (neighbours != NULL);
+
+  n = lookup_neighbour (target);
+  if (NULL == n)
+    return;                     /* not active */
+  if (GNUNET_YES == n->is_connected)
+  {
+    /* we're actually connected, send DISCONNECT message */
+    disconnect_msg.header.size = htons (sizeof (struct SessionDisconnectMessage));
+    disconnect_msg.header.type = htons (GNUNET_MESSAGE_TYPE_TRANSPORT_DISCONNECT);
+    disconnect_msg.reserved = htonl (0);
+    disconnect_msg.purpose.size = htonl (sizeof (struct GNUNET_CRYPTO_RsaSignaturePurpose) +
+                                         sizeof (struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded) +
+                                         sizeof (struct GNUNET_TIME_AbsoluteNBO) );
+    disconnect_msg.purpose.purpose = htonl (GNUNET_MESSAGE_TYPE_TRANSPORT_SESSION_DISCONNECT);
+    disconnect_msg.timestamp = GNUNET_TIME_absolute_hton (GNUNET_TIME_absolute_get ());
+    disconnect_msg.public_key = GST_my_public_key;
+    GNUNET_assert (GNUNET_OK ==
+                   GNUNET_CRYPTO_rsa_sign (GST_my_private_key,
+                                           &disconnect_msg.purpose,
+                                           &disconnect_msg.signature));
+
+    papi = GST_plugins_find (n->plugin_name);
+    if (papi != NULL)
+      papi->send (papi->cls, target, (const void *) &disconnect_msg,
+                  sizeof (disconnect_msg),
+                  UINT32_MAX /* priority */ ,
+                  GNUNET_TIME_UNIT_FOREVER_REL, n->session, n->addr, n->addrlen,
+                  GNUNET_YES, NULL, NULL);
+    GNUNET_STATISTICS_update (GST_stats,
+                              gettext_noop ("# peers disconnected due to external request"), 1,
+                              GNUNET_NO);
+    n = lookup_neighbour (target);
+    if (NULL == n)
+      return;                     /* gone already */
+  }
+  disconnect_neighbour (n);
+}
+
+
+/**
+ * We received a disconnect message from the given peer,
+ * validate and process.
+ * 
+ * @param peer sender of the message
+ * @param msg the disconnect message
+ */
+void
+GST_neighbours_handle_disconnect_message (const struct GNUNET_PeerIdentity *peer,
+                                          const struct GNUNET_MessageHeader *msg)
+{
+  struct NeighbourMapEntry *n;
+  const struct SessionDisconnectMessage *sdm;
+  GNUNET_HashCode hc;
+
+  if (ntohs (msg->size) != sizeof (struct SessionDisconnectMessage))
+  {
+    // GNUNET_break_op (0);
+    GNUNET_STATISTICS_update (GST_stats,
+                              gettext_noop ("# disconnect messages ignored (old format)"), 1,
+                              GNUNET_NO);
+    return;
+  }
+  sdm = (const struct SessionDisconnectMessage* ) msg;
+  n = lookup_neighbour (peer);
+  if (NULL == n)
+    return;                     /* gone already */
+  if (GNUNET_TIME_absolute_ntoh (sdm->timestamp).abs_value <=
+      n->connect_ts.abs_value)
+  {
+    GNUNET_STATISTICS_update (GST_stats,
+                              gettext_noop ("# disconnect messages ignored (timestamp)"), 1,
+                              GNUNET_NO);
+    return;
+  }
+  GNUNET_CRYPTO_hash (&sdm->public_key,
+                      sizeof (struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded),
+                      &hc);
+  if (0 != memcmp (peer,
+                   &hc,
+                   sizeof (struct GNUNET_PeerIdentity)))
+  {
+    GNUNET_break_op (0);
+    return;
+  }
+  if (ntohl (sdm->purpose.size) != 
+      sizeof (struct GNUNET_CRYPTO_RsaSignaturePurpose) +
+      sizeof (struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded) +
+      sizeof (struct GNUNET_TIME_AbsoluteNBO))
+  {
+    GNUNET_break_op (0);
+    return;
+  }
+  if (GNUNET_OK !=
+      GNUNET_CRYPTO_rsa_verify (GNUNET_MESSAGE_TYPE_TRANSPORT_SESSION_DISCONNECT,
+                                &sdm->purpose,
+                                &sdm->signature,
+                                &sdm->public_key))
+  {
+    GNUNET_break_op (0);
+    return;
+  }
+  GST_neighbours_force_disconnect (peer);
+}
+
+static void neighbour_connected (struct NeighbourMapEntry *n,
+              const struct GNUNET_ATS_Information *ats,
+              uint32_t ats_count)
+{
+  /* LEGACY */
+  int was_connected;
+  was_connected = n->is_connected;
+  n->is_connected = GNUNET_YES;
+  /* END LEGACY */
+
+  if (GNUNET_YES != was_connected)
+    n->keepalive_task = GNUNET_SCHEDULER_add_delayed (KEEPALIVE_FREQUENCY,
+                                                      &neighbour_keepalive_task,
+                                                      n);
+  if (n->state == S_CONNECTED)
+    return;
+  // First tell clients about connected neighbours...
+  //change_state (n, S_CONNECTED);
+
+  neighbours_connected++;
+  GNUNET_STATISTICS_update (GST_stats, gettext_noop ("# peers connected"), 1,
+                            GNUNET_NO);
+  connect_notify_cb (callback_cls, &n->id, ats, ats_count);
+}
+
+
+/**
+ * We received a 'SESSION_CONNECT_ACK' message from the other peer.
+ * Consider switching to it.
+ *
+ * @param message possibly a 'struct SessionConnectMessage' (check format)
+ * @param peer identity of the peer to switch the address for
+ * @param plugin_name name of transport that delivered the PONG
+ * @param address address of the other peer, NULL if other peer
+ *                       connected to us
+ * @param address_len number of bytes in address
+ * @param session session to use (or NULL)
+ * @param ats performance data
+ * @param ats_count number of entries in ats
+  */
+void
+GST_neighbours_handle_connect_ack (const struct GNUNET_MessageHeader *message,
+                               const struct GNUNET_PeerIdentity *peer,
+                               const char *plugin_name,
+                               const char *sender_address, uint16_t sender_address_len,
+                               struct Session *session,
+                               const struct GNUNET_ATS_Information *ats,
+                               uint32_t ats_count)
+{
+  const struct SessionConnectMessage *scm;
+  struct GNUNET_TIME_Absolute ts;
+  struct NeighbourMapEntry *n;
+  GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+      "GST_neighbours_handle_connect_ack\n");
+  if (ntohs (message->size) != sizeof (struct SessionConnectMessage))
+  {
+    GNUNET_break_op (0);
+    return;
+  }
+
+  scm = (const struct SessionConnectMessage *) message;
+  GNUNET_break_op (ntohl (scm->reserved) == 0);
+  ts = GNUNET_TIME_absolute_ntoh (scm->timestamp);
+  n = lookup_neighbour (peer);
+  if (NULL == n)
+    n = setup_neighbour (peer);
+
+  if (n->state != S_CONNECT_SENT)
+  {
+    GNUNET_break (0);
+    return;
+  }
+
+  change_state (n, S_CONNECTED);
+  neighbour_connected (n, ats, ats_count);
+}
+
+
+/**
+ * We received a 'SESSION_CONNECT' message from the other peer.
+ * Consider switching to it.
+ *
+ * @param message possibly a 'struct SessionConnectMessage' (check format)
+ * @param peer identity of the peer to switch the address for
+ * @param plugin_name name of transport that delivered the PONG
+ * @param address address of the other peer, NULL if other peer
+ *                       connected to us
+ * @param address_len number of bytes in address
+ * @param session session to use (or NULL)
+ * @param ats performance data
+ * @param ats_count number of entries in ats (excluding 0-termination)
+  */
+void
+GST_neighbours_handle_connect (const struct GNUNET_MessageHeader *message,
+                               const struct GNUNET_PeerIdentity *peer,
+                               const char *plugin_name,
+                               const char *sender_address, uint16_t sender_address_len,
+                               struct Session *session,
+                               const struct GNUNET_ATS_Information *ats,
+                               uint32_t ats_count)
+{
+  const struct SessionConnectMessage *scm;
+  struct GNUNET_TIME_Absolute ts;
+  struct NeighbourMapEntry *n;
+  struct SessionConnectMessage connect_msg;
+  struct GNUNET_TRANSPORT_PluginFunctions *papi;
+  int ret;
+
+  if (ntohs (message->size) != sizeof (struct SessionConnectMessage))
+  {
+    GNUNET_break_op (0);
+    return;
+  }
+  scm = (const struct SessionConnectMessage *) message;
+  GNUNET_break_op (ntohl (scm->reserved) == 0);
+  ts = GNUNET_TIME_absolute_ntoh (scm->timestamp);
+  n = lookup_neighbour (peer);
+  if (NULL == n) 
+    n = setup_neighbour (peer);
+
+  if (n->state > S_NOT_CONNECTED)
+    return;
+
+  change_state (n, S_CONNECT_RECV);
+  /* send CONNECT_ACK */
+  connect_msg.header.size = htons (sizeof (struct SessionConnectMessage));
+  connect_msg.header.type =
+      htons (GNUNET_MESSAGE_TYPE_TRANSPORT_SESSION_CONNECT_ACK);
+  connect_msg.reserved = htonl (0);
+  connect_msg.timestamp =
+      GNUNET_TIME_absolute_hton (GNUNET_TIME_absolute_get ());
+
+  papi = GST_plugins_find (plugin_name);
+  ret = papi->send (papi->cls, &n->id, (const char *) &connect_msg, sizeof (struct SessionConnectMessage),
+                  0,
+                  GNUNET_TIME_UNIT_FOREVER_REL, NULL, sender_address, sender_address_len, GNUNET_YES,
+                  NULL, NULL);
+
+  if (ret == GNUNET_SYSERR)
+  {
+    change_state (n, S_NOT_CONNECTED);
+    GNUNET_break (0);
+    return;
+  }
+
+  if (ts.abs_value > n->connect_ts.abs_value)
+  {
+    if (NULL != session)
+      GNUNET_log_from (GNUNET_ERROR_TYPE_INFO | GNUNET_ERROR_TYPE_BULK,
+                       "transport-ats",
+                       "Giving ATS session %p of plugin %s for peer %s\n",
+                       session,
+                       plugin_name,
+                       GNUNET_i2s (peer));
+    GNUNET_ATS_address_update (GST_ats,
+                               peer,
+                               plugin_name, sender_address, sender_address_len,
+                               session, ats, ats_count);
+    n->connect_ts = ts;
+  }
+}
+
+
+/* end of file gnunet-service-transport_neighbours.c */