Imported Upstream version 0.9.2upstream/0.9.2

1 files changed, 2115 insertions, 0 deletions

diff --git a/src/transport/plugin_transport_tcp.c b/src/transport/plugin_transport_tcp.c
new file mode 100644
index 0000000..2b2d728
--- /dev/null
+++ b/src/transport/plugin_transport_tcp.c
@@ -0,0 +1,2115 @@
+/*
+     This file is part of GNUnet
+     (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 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/plugin_transport_tcp.c
+ * @brief Implementation of the TCP transport service
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include "gnunet_hello_lib.h"
+#include "gnunet_constants.h"
+#include "gnunet_connection_lib.h"
+#include "gnunet_container_lib.h"
+#include "gnunet_nat_lib.h"
+#include "gnunet_os_lib.h"
+#include "gnunet_protocols.h"
+#include "gnunet_resolver_service.h"
+#include "gnunet_server_lib.h"
+#include "gnunet_service_lib.h"
+#include "gnunet_signatures.h"
+#include "gnunet_statistics_service.h"
+#include "gnunet_transport_service.h"
+#include "gnunet_transport_plugin.h"
+#include "transport.h"
+
+#define DEBUG_TCP GNUNET_EXTRA_LOGGING
+
+#define DEBUG_TCP_NAT GNUNET_EXTRA_LOGGING
+
+GNUNET_NETWORK_STRUCT_BEGIN
+
+/**
+ * Initial handshake message for a session.
+ */
+struct WelcomeMessage
+{
+  /**
+   * Type is GNUNET_MESSAGE_TYPE_TRANSPORT_TCP_WELCOME.
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Identity of the node connecting (TCP client)
+   */
+  struct GNUNET_PeerIdentity clientIdentity;
+
+};
+
+
+/**
+ * Basically a WELCOME message, but with the purpose
+ * of giving the waiting peer a client handle to use
+ */
+struct TCP_NAT_ProbeMessage
+{
+  /**
+   * Type is GNUNET_MESSAGE_TYPE_TRANSPORT_TCP_NAT_PROBE.
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Identity of the sender of the message.
+   */
+  struct GNUNET_PeerIdentity clientIdentity;
+
+};
+GNUNET_NETWORK_STRUCT_END
+
+/**
+ * Context for sending a NAT probe via TCP.
+ */
+struct TCPProbeContext
+{
+
+  /**
+   * Active probes are kept in a DLL.
+   */
+  struct TCPProbeContext *next;
+
+  /**
+   * Active probes are kept in a DLL.
+   */
+  struct TCPProbeContext *prev;
+
+  /**
+   * Probe connection.
+   */
+  struct GNUNET_CONNECTION_Handle *sock;
+
+  /**
+   * Message to be sent.
+   */
+  struct TCP_NAT_ProbeMessage message;
+
+  /**
+   * Handle to the transmission.
+   */
+  struct GNUNET_CONNECTION_TransmitHandle *transmit_handle;
+
+  /**
+   * Transport plugin handle.
+   */
+  struct Plugin *plugin;
+};
+
+
+GNUNET_NETWORK_STRUCT_BEGIN
+
+/**
+ * Network format for IPv4 addresses.
+ */
+struct IPv4TcpAddress
+{
+  /**
+   * IPv4 address, in network byte order.
+   */
+  uint32_t ipv4_addr GNUNET_PACKED;
+
+  /**
+   * Port number, in network byte order.
+   */
+  uint16_t t4_port GNUNET_PACKED;
+
+};
+
+
+/**
+ * Network format for IPv6 addresses.
+ */
+struct IPv6TcpAddress
+{
+  /**
+   * IPv6 address.
+   */
+  struct in6_addr ipv6_addr GNUNET_PACKED;
+
+  /**
+   * Port number, in network byte order.
+   */
+  uint16_t t6_port GNUNET_PACKED;
+
+};
+GNUNET_NETWORK_STRUCT_END
+
+/**
+ * Encapsulation of all of the state of the plugin.
+ */
+struct Plugin;
+
+
+/**
+ * Information kept for each message that is yet to
+ * be transmitted.
+ */
+struct PendingMessage
+{
+
+  /**
+   * This is a doubly-linked list.
+   */
+  struct PendingMessage *next;
+
+  /**
+   * This is a doubly-linked list.
+   */
+  struct PendingMessage *prev;
+
+  /**
+   * The pending message
+   */
+  const char *msg;
+
+  /**
+   * Continuation function to call once the message
+   * has been sent.  Can be NULL if there is no
+   * continuation to call.
+   */
+  GNUNET_TRANSPORT_TransmitContinuation transmit_cont;
+
+  /**
+   * Closure for transmit_cont.
+   */
+  void *transmit_cont_cls;
+
+  /**
+   * Timeout value for the pending message.
+   */
+  struct GNUNET_TIME_Absolute timeout;
+
+  /**
+   * So that the gnunet-service-transport can group messages together,
+   * these pending messages need to accept a message buffer and size
+   * instead of just a GNUNET_MessageHeader.
+   */
+  size_t message_size;
+
+};
+
+
+/**
+ * Session handle for TCP connections.
+ */
+struct Session
+{
+
+  /**
+   * API requirement.
+   */
+  struct SessionHeader header;
+
+  /**
+   * Stored in a linked list.
+   */
+  struct Session *next;
+
+  /**
+   * Pointer to the global plugin struct.
+   */
+  struct Plugin *plugin;
+
+  /**
+   * The client (used to identify this connection)
+   */
+  struct GNUNET_SERVER_Client *client;
+
+  /**
+   * Messages currently pending for transmission
+   * to this peer, if any.
+   */
+  struct PendingMessage *pending_messages_head;
+
+  /**
+   * Messages currently pending for transmission
+   * to this peer, if any.
+   */
+  struct PendingMessage *pending_messages_tail;
+
+  /**
+   * Handle for pending transmission request.
+   */
+  struct GNUNET_CONNECTION_TransmitHandle *transmit_handle;
+
+  /**
+   * To whom are we talking to (set to our identity
+   * if we are still waiting for the welcome message)
+   */
+  struct GNUNET_PeerIdentity target;
+
+  /**
+   * ID of task used to delay receiving more to throttle sender.
+   */
+  GNUNET_SCHEDULER_TaskIdentifier receive_delay_task;
+
+  /**
+   * Address of the other peer (either based on our 'connect'
+   * call or on our 'accept' call).
+   *
+   * struct IPv4TcpAddress or struct IPv6TcpAddress
+   *
+   */
+  void *addr;
+
+  /**
+   * Length of connect_addr.
+   */
+  size_t addrlen;
+
+  /**
+   * Last activity on this connection.  Used to select preferred
+   * connection.
+   */
+  struct GNUNET_TIME_Absolute last_activity;
+
+  /**
+   * Are we still expecting the welcome message? (GNUNET_YES/GNUNET_NO)
+   */
+  int expecting_welcome;
+
+  /**
+   * Was this a connection that was inbound (we accepted)? (GNUNET_YES/GNUNET_NO)
+   */
+  int inbound;
+
+  /**
+   * Was this session created using NAT traversal?
+   */
+  int is_nat;
+
+  /**
+   * ATS network type in NBO
+   */
+  uint32_t ats_address_network_type;
+};
+
+
+/**
+ * Encapsulation of all of the state of the plugin.
+ */
+struct Plugin
+{
+  /**
+   * Our environment.
+   */
+  struct GNUNET_TRANSPORT_PluginEnvironment *env;
+
+  /**
+   * The listen socket.
+   */
+  struct GNUNET_CONNECTION_Handle *lsock;
+
+  /**
+   * Our handle to the NAT module.
+   */
+  struct GNUNET_NAT_Handle *nat;
+
+  struct GNUNET_CONTAINER_MultiHashMap * sessionmap;
+
+  /**
+   * Handle to the network service.
+   */
+  struct GNUNET_SERVICE_Context *service;
+
+  /**
+   * Handle to the server for this service.
+   */
+  struct GNUNET_SERVER_Handle *server;
+
+  /**
+   * Copy of the handler array where the closures are
+   * set to this struct's instance.
+   */
+  struct GNUNET_SERVER_MessageHandler *handlers;
+
+  /**
+   * Map of peers we have tried to contact behind a NAT
+   */
+  struct GNUNET_CONTAINER_MultiHashMap *nat_wait_conns;
+
+  /**
+   * List of active TCP probes.
+   */
+  struct TCPProbeContext *probe_head;
+
+  /**
+   * List of active TCP probes.
+   */
+  struct TCPProbeContext *probe_tail;
+
+  /**
+   * Handle for (DYN)DNS lookup of our external IP.
+   */
+  struct GNUNET_RESOLVER_RequestHandle *ext_dns;
+
+  /**
+   * How many more TCP sessions are we allowed to open right now?
+   */
+  unsigned long long max_connections;
+
+  /**
+   * ID of task used to update our addresses when one expires.
+   */
+  GNUNET_SCHEDULER_TaskIdentifier address_update_task;
+
+  /**
+   * Port that we are actually listening on.
+   */
+  uint16_t open_port;
+
+  /**
+   * Port that the user said we would have visible to the
+   * rest of the world.
+   */
+  uint16_t adv_port;
+
+};
+
+
+/**
+ * Function to check if an inbound connection is acceptable.
+ * Mostly used to limit the total number of open connections
+ * we can have.
+ *
+ * @param cls the 'struct Plugin'
+ * @param ucred credentials, if available, otherwise NULL
+ * @param addr address
+ * @param addrlen length of address
+ * @return GNUNET_YES to allow, GNUNET_NO to deny, GNUNET_SYSERR
+ *   for unknown address family (will be denied).
+ */
+static int
+plugin_tcp_access_check (void *cls,
+                         const struct GNUNET_CONNECTION_Credentials *ucred,
+                         const struct sockaddr *addr, socklen_t addrlen)
+{
+  struct Plugin *plugin = cls;
+
+  if (0 == plugin->max_connections)
+    return GNUNET_NO;
+  plugin->max_connections--;
+  return GNUNET_YES;
+}
+
+
+/**
+ * Our external IP address/port mapping has changed.
+ *
+ * @param cls closure, the 'struct LocalAddrList'
+ * @param add_remove GNUNET_YES to mean the new public IP address, GNUNET_NO to mean
+ *     the previous (now invalid) one
+ * @param addr either the previous or the new public IP address
+ * @param addrlen actual lenght of the address
+ */
+static void
+tcp_nat_port_map_callback (void *cls, int add_remove,
+                           const struct sockaddr *addr, socklen_t addrlen)
+{
+  struct Plugin *plugin = cls;
+  struct IPv4TcpAddress t4;
+  struct IPv6TcpAddress t6;
+  void *arg;
+  size_t args;
+
+  GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                   "NPMC called with %d for address `%s'\n", add_remove,
+                   GNUNET_a2s (addr, addrlen));
+  /* convert 'addr' to our internal format */
+  switch (addr->sa_family)
+  {
+  case AF_INET:
+    GNUNET_assert (addrlen == sizeof (struct sockaddr_in));
+    t4.ipv4_addr = ((struct sockaddr_in *) addr)->sin_addr.s_addr;
+    t4.t4_port = ((struct sockaddr_in *) addr)->sin_port;
+    arg = &t4;
+    args = sizeof (t4);
+    break;
+  case AF_INET6:
+    GNUNET_assert (addrlen == sizeof (struct sockaddr_in6));
+    memcpy (&t6.ipv6_addr, &((struct sockaddr_in6 *) addr)->sin6_addr,
+            sizeof (struct in6_addr));
+    t6.t6_port = ((struct sockaddr_in6 *) addr)->sin6_port;
+    arg = &t6;
+    args = sizeof (t6);
+    break;
+  default:
+    GNUNET_break (0);
+    return;
+  }
+  /* modify our published address list */
+  plugin->env->notify_address (plugin->env->cls, add_remove, arg, args);
+}
+
+
+/**
+ * Function called for a quick conversion of the binary address to
+ * a numeric address.  Note that the caller must not free the
+ * address and that the next call to this function is allowed
+ * to override the address again.
+ *
+ * @param cls closure ('struct Plugin*')
+ * @param addr binary address
+ * @param addrlen length of the address
+ * @return string representing the same address
+ */
+static const char *
+tcp_address_to_string (void *cls, const void *addr, size_t addrlen)
+{
+  static char rbuf[INET6_ADDRSTRLEN + 12];
+  char buf[INET6_ADDRSTRLEN];
+  const void *sb;
+  struct in_addr a4;
+  struct in6_addr a6;
+  const struct IPv4TcpAddress *t4;
+  const struct IPv6TcpAddress *t6;
+  int af;
+  uint16_t port;
+
+  if (addrlen == sizeof (struct IPv6TcpAddress))
+  {
+    t6 = addr;
+    af = AF_INET6;
+    port = ntohs (t6->t6_port);
+    memcpy (&a6, &t6->ipv6_addr, sizeof (a6));
+    sb = &a6;
+  }
+  else if (addrlen == sizeof (struct IPv4TcpAddress))
+  {
+    t4 = addr;
+    af = AF_INET;
+    port = ntohs (t4->t4_port);
+    memcpy (&a4, &t4->ipv4_addr, sizeof (a4));
+    sb = &a4;
+  }
+  else
+  {
+    GNUNET_log_from (GNUNET_ERROR_TYPE_ERROR, "tcp",
+                     _("Unexpected address length: %u bytes\n"),
+                     (unsigned int) addrlen);
+    GNUNET_break (0);
+    return NULL;
+  }
+  if (NULL == inet_ntop (af, sb, buf, INET6_ADDRSTRLEN))
+  {
+    GNUNET_log_strerror (GNUNET_ERROR_TYPE_WARNING, "inet_ntop");
+    return NULL;
+  }
+  GNUNET_snprintf (rbuf, sizeof (rbuf), (af == AF_INET6) ? "[%s]:%u" : "%s:%u",
+                   buf, port);
+  return rbuf;
+}
+
+
+struct SessionClientCtx
+{
+  const struct GNUNET_SERVER_Client *client;
+  struct Session *ret;
+};
+
+int session_lookup_by_client_it (void *cls,
+               const GNUNET_HashCode * key,
+               void *value)
+{
+  struct SessionClientCtx *sc_ctx = cls;
+  struct Session *s = value;
+
+  if (s->client == sc_ctx->client)
+  {
+    sc_ctx->ret = s;
+    return GNUNET_NO;
+  }
+  return GNUNET_YES;
+}
+
+/**
+ * Find the session handle for the given client.
+ *
+ * @param plugin the plugin
+ * @param client which client to find the session handle for
+ * @return NULL if no matching session exists
+ */
+static struct Session *
+lookup_session_by_client (struct Plugin *plugin,
+                        const struct GNUNET_SERVER_Client *client)
+{
+  struct SessionClientCtx sc_ctx;
+  sc_ctx.client = client;
+  sc_ctx.ret = NULL;
+
+  GNUNET_CONTAINER_multihashmap_iterate (plugin->sessionmap, &session_lookup_by_client_it, &sc_ctx);
+
+  return sc_ctx.ret;
+}
+
+
+/**
+ * Create a new session.  Also queues a welcome message.
+ *
+ * @param plugin the plugin
+ * @param target peer to connect to
+ * @param client client to use
+ * @param is_nat this a NAT session, we should wait for a client to
+ *               connect to us from an address, then assign that to
+ *               the session
+ * @return new session object
+ */
+static struct Session *
+create_session (struct Plugin *plugin, const struct GNUNET_PeerIdentity *target,
+                struct GNUNET_SERVER_Client *client, int is_nat)
+{
+  struct Session *ret;
+  struct PendingMessage *pm;
+  struct WelcomeMessage welcome;
+
+  if (is_nat != GNUNET_YES)
+    GNUNET_assert (client != NULL);
+  else
+    GNUNET_assert (client == NULL);
+
+  GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                   "Creating new session for peer `%4s'\n",
+                   GNUNET_i2s (target));
+
+  ret = GNUNET_malloc (sizeof (struct Session));
+  ret->last_activity = GNUNET_TIME_absolute_get ();
+  ret->plugin = plugin;
+  ret->is_nat = is_nat;
+  ret->client = client;
+  ret->target = *target;
+  ret->expecting_welcome = GNUNET_YES;
+  ret->ats_address_network_type = htonl (GNUNET_ATS_NET_UNSPECIFIED);
+  pm = GNUNET_malloc (sizeof (struct PendingMessage) +
+                      sizeof (struct WelcomeMessage));
+  pm->msg = (const char *) &pm[1];
+  pm->message_size = sizeof (struct WelcomeMessage);
+  welcome.header.size = htons (sizeof (struct WelcomeMessage));
+  welcome.header.type = htons (GNUNET_MESSAGE_TYPE_TRANSPORT_TCP_WELCOME);
+  welcome.clientIdentity = *plugin->env->my_identity;
+  memcpy (&pm[1], &welcome, sizeof (welcome));
+  pm->timeout = GNUNET_TIME_UNIT_FOREVER_ABS;
+  GNUNET_STATISTICS_update (plugin->env->stats,
+                            gettext_noop ("# bytes currently in TCP buffers"),
+                            pm->message_size, GNUNET_NO);
+  GNUNET_CONTAINER_DLL_insert (ret->pending_messages_head,
+                               ret->pending_messages_tail, pm);
+  if (is_nat != GNUNET_YES)
+    GNUNET_STATISTICS_update (plugin->env->stats,
+                              gettext_noop ("# TCP sessions active"), 1,
+                              GNUNET_NO);
+  return ret;
+}
+
+
+/**
+ * If we have pending messages, ask the server to
+ * transmit them (schedule the respective tasks, etc.)
+ *
+ * @param session for which session should we do this
+ */
+static void
+process_pending_messages (struct Session *session);
+
+
+/**
+ * Function called to notify a client about the socket
+ * being ready to queue more data.  "buf" will be
+ * NULL and "size" zero if the socket was closed for
+ * writing in the meantime.
+ *
+ * @param cls closure
+ * @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
+do_transmit (void *cls, size_t size, void *buf)
+{
+  struct Session *session = cls;
+  struct GNUNET_PeerIdentity pid;
+  struct Plugin *plugin;
+  struct PendingMessage *pos;
+  struct PendingMessage *hd;
+  struct PendingMessage *tl;
+  struct GNUNET_TIME_Absolute now;
+  char *cbuf;
+  size_t ret;
+
+  GNUNET_assert (session != NULL);
+  session->transmit_handle = NULL;
+  plugin = session->plugin;
+  if (buf == NULL)
+  {
+#if DEBUG_TCP
+    GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                     "Timeout trying to transmit to peer `%4s', discarding message queue.\n",
+                     GNUNET_i2s (&session->target));
+#endif
+    /* timeout; cancel all messages that have already expired */
+    hd = NULL;
+    tl = NULL;
+    ret = 0;
+    now = GNUNET_TIME_absolute_get ();
+    while ((NULL != (pos = session->pending_messages_head)) &&
+           (pos->timeout.abs_value <= now.abs_value))
+    {
+      GNUNET_CONTAINER_DLL_remove (session->pending_messages_head,
+                                   session->pending_messages_tail, pos);
+#if DEBUG_TCP
+      GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                       "Failed to transmit %u byte message to `%4s'.\n",
+                       pos->message_size, GNUNET_i2s (&session->target));
+#endif
+      ret += pos->message_size;
+      GNUNET_CONTAINER_DLL_insert_after (hd, tl, tl, pos);
+    }
+    /* do this call before callbacks (so that if callbacks destroy
+     * session, they have a chance to cancel actions done by this
+     * call) */
+    process_pending_messages (session);
+    pid = session->target;
+    /* no do callbacks and do not use session again since
+     * the callbacks may abort the session */
+    while (NULL != (pos = hd))
+    {
+      GNUNET_CONTAINER_DLL_remove (hd, tl, pos);
+      if (pos->transmit_cont != NULL)
+        pos->transmit_cont (pos->transmit_cont_cls, &pid, GNUNET_SYSERR);
+      GNUNET_free (pos);
+    }
+    GNUNET_STATISTICS_update (plugin->env->stats,
+                              gettext_noop ("# bytes currently in TCP buffers"),
+                              -(int64_t) ret, GNUNET_NO);
+    GNUNET_STATISTICS_update (plugin->env->stats,
+                              gettext_noop
+                              ("# bytes discarded by TCP (timeout)"), ret,
+                              GNUNET_NO);
+    return 0;
+  }
+  /* copy all pending messages that would fit */
+  ret = 0;
+  cbuf = buf;
+  hd = NULL;
+  tl = NULL;
+  while (NULL != (pos = session->pending_messages_head))
+  {
+    if (ret + pos->message_size > size)
+      break;
+    GNUNET_CONTAINER_DLL_remove (session->pending_messages_head,
+                                 session->pending_messages_tail, pos);
+    GNUNET_assert (size >= pos->message_size);
+    GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                     "Transmitting message of type %u\n",
+                     ntohs (((struct GNUNET_MessageHeader *) pos->msg)->type));
+    /* FIXME: this memcpy can be up to 7% of our total runtime */
+    memcpy (cbuf, pos->msg, pos->message_size);
+    cbuf += pos->message_size;
+    ret += pos->message_size;
+    size -= pos->message_size;
+    GNUNET_CONTAINER_DLL_insert_tail (hd, tl, pos);
+  }
+  /* schedule 'continuation' before callbacks so that callbacks that
+   * cancel everything don't cause us to use a session that no longer
+   * exists... */
+  process_pending_messages (session);
+  session->last_activity = GNUNET_TIME_absolute_get ();
+  pid = session->target;
+  /* we'll now call callbacks that may cancel the session; hence
+   * we should not use 'session' after this point */
+  while (NULL != (pos = hd))
+  {
+    GNUNET_CONTAINER_DLL_remove (hd, tl, pos);
+    if (pos->transmit_cont != NULL)
+      pos->transmit_cont (pos->transmit_cont_cls, &pid, GNUNET_OK);
+    GNUNET_free (pos);
+  }
+  GNUNET_assert (hd == NULL);
+  GNUNET_assert (tl == NULL);
+#if DEBUG_TCP > 1
+  GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp", "Transmitting %u bytes\n",
+                   ret);
+#endif
+  GNUNET_STATISTICS_update (plugin->env->stats,
+                            gettext_noop ("# bytes currently in TCP buffers"),
+                            -(int64_t) ret, GNUNET_NO);
+  GNUNET_STATISTICS_update (plugin->env->stats,
+                            gettext_noop ("# bytes transmitted via TCP"), ret,
+                            GNUNET_NO);
+  return ret;
+}
+
+
+/**
+ * If we have pending messages, ask the server to
+ * transmit them (schedule the respective tasks, etc.)
+ *
+ * @param session for which session should we do this
+ */
+static void
+process_pending_messages (struct Session *session)
+{
+  struct PendingMessage *pm;
+
+  GNUNET_assert (session->client != NULL);
+  if (session->transmit_handle != NULL)
+    return;
+  if (NULL == (pm = session->pending_messages_head))
+    return;
+
+  session->transmit_handle =
+      GNUNET_SERVER_notify_transmit_ready (session->client, pm->message_size,
+                                           GNUNET_TIME_absolute_get_remaining
+                                           (pm->timeout), &do_transmit,
+                                           session);
+}
+
+
+/**
+ * Functions with this signature are called whenever we need
+ * to close a session due to a disconnect or failure to
+ * establish a connection.
+ *
+ * @param session session to close down
+ */
+static void
+disconnect_session (struct Session *session)
+{
+  struct PendingMessage *pm;
+  struct Plugin * plugin = session->plugin;
+
+  GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                   "Disconnecting session %p for peer `%s' address `%s'\n",
+                   session,
+                   GNUNET_i2s (&session->target),
+                   tcp_address_to_string(NULL, session->addr, session->addrlen));
+
+  GNUNET_assert (GNUNET_YES  == GNUNET_CONTAINER_multihashmap_remove(plugin->sessionmap, &session->target.hashPubKey, session));
+
+  /* clean up state */
+  if (session->transmit_handle != NULL)
+  {
+    GNUNET_CONNECTION_notify_transmit_ready_cancel (session->transmit_handle);
+    session->transmit_handle = NULL;
+  }
+  session->plugin->env->session_end (session->plugin->env->cls,
+                                     &session->target, session);
+  while (NULL != (pm = session->pending_messages_head))
+  {
+#if DEBUG_TCP
+    GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                     pm->transmit_cont !=
+                     NULL ? "Could not deliver message to `%4s'.\n" :
+                     "Could not deliver message to `%4s', notifying.\n",
+                     GNUNET_i2s (&session->target));
+#endif
+    GNUNET_STATISTICS_update (session->plugin->env->stats,
+                              gettext_noop ("# bytes currently in TCP buffers"),
+                              -(int64_t) pm->message_size, GNUNET_NO);
+    GNUNET_STATISTICS_update (session->plugin->env->stats,
+                              gettext_noop
+                              ("# bytes discarded by TCP (disconnect)"),
+                              pm->message_size, GNUNET_NO);
+    GNUNET_CONTAINER_DLL_remove (session->pending_messages_head,
+                                 session->pending_messages_tail, pm);
+    if (NULL != pm->transmit_cont)
+      pm->transmit_cont (pm->transmit_cont_cls, &session->target,
+                         GNUNET_SYSERR);
+    GNUNET_free (pm);
+  }
+  GNUNET_break (session->client != NULL);
+  if (session->receive_delay_task != GNUNET_SCHEDULER_NO_TASK)
+  {
+    GNUNET_SCHEDULER_cancel (session->receive_delay_task);
+    if (session->client != NULL)
+      GNUNET_SERVER_receive_done (session->client, GNUNET_SYSERR);
+  }
+  if (session->client != NULL)
+  {
+    GNUNET_SERVER_client_drop (session->client);
+    session->client = NULL;
+  }
+  GNUNET_STATISTICS_update (session->plugin->env->stats,
+                            gettext_noop ("# TCP sessions active"), -1,
+                            GNUNET_NO);
+  GNUNET_free_non_null (session->addr);
+  GNUNET_assert (NULL == session->transmit_handle);
+  GNUNET_free (session);
+}
+
+
+/**
+ * Function that can be used by the transport service to transmit
+ * a message using the plugin.   Note that in the case of a
+ * peer disconnecting, the continuation MUST be called
+ * prior to the disconnect notification itself.  This function
+ * will be called with this peer's HELLO message to initiate
+ * a fresh connection to another peer.
+ *
+ * @param cls closure
+ * @param session which session must be used
+ * @param msgbuf the message to transmit
+ * @param msgbuf_size number of bytes in 'msgbuf'
+ * @param priority how important is the message (most plugins will
+ *                 ignore message priority and just FIFO)
+ * @param to how long to wait at most for the transmission (does not
+ *                require plugins to discard the message after the timeout,
+ *                just advisory for the desired delay; most plugins will ignore
+ *                this as well)
+ * @param cont continuation to call once the message has
+ *        been transmitted (or if the transport is ready
+ *        for the next transmission call; or if the
+ *        peer disconnected...); can be NULL
+ * @param cont_cls closure for cont
+ * @return number of bytes used (on the physical network, with overheads);
+ *         -1 on hard errors (i.e. address invalid); 0 is a legal value
+ *         and does NOT mean that the message was not transmitted (DV)
+ */
+static ssize_t
+tcp_plugin_send (void *cls,
+    struct Session *session,
+    const char *msgbuf, size_t msgbuf_size,
+    unsigned int priority,
+    struct GNUNET_TIME_Relative to,
+    GNUNET_TRANSPORT_TransmitContinuation cont, void *cont_cls)
+{
+  struct Plugin * plugin = cls;
+  struct PendingMessage *pm;
+
+  GNUNET_assert (plugin != NULL);
+  GNUNET_assert (session != NULL);
+  GNUNET_assert (session->client != NULL);
+
+  GNUNET_SERVER_client_set_timeout (session->client,
+                                    GNUNET_CONSTANTS_IDLE_CONNECTION_TIMEOUT);
+  GNUNET_STATISTICS_update (plugin->env->stats,
+                            gettext_noop ("# bytes currently in TCP buffers"),
+                            msgbuf_size, GNUNET_NO);
+  /* create new message entry */
+  pm = GNUNET_malloc (sizeof (struct PendingMessage) + msgbuf_size);
+  pm->msg = (const char *) &pm[1];
+  memcpy (&pm[1], msgbuf, msgbuf_size);
+  pm->message_size = msgbuf_size;
+  pm->timeout = GNUNET_TIME_relative_to_absolute (to);
+  pm->transmit_cont = cont;
+  pm->transmit_cont_cls = cont_cls;
+
+  /* append pm to pending_messages list */
+  GNUNET_CONTAINER_DLL_insert_tail (session->pending_messages_head,
+                                    session->pending_messages_tail, pm);
+
+  GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                   "Asked to transmit %u bytes to `%s', added message to list.\n",
+                   msgbuf_size, GNUNET_i2s (&session->target));
+
+  process_pending_messages (session);
+  return msgbuf_size;
+}
+
+struct SessionItCtx
+{
+  void * addr;
+  size_t addrlen;
+  struct Session * result;
+};
+
+int session_lookup_it (void *cls,
+               const GNUNET_HashCode * key,
+               void *value)
+{
+  struct SessionItCtx * si_ctx = cls;
+  struct Session * session = value;
+#if 0
+  char * a1 = strdup (tcp_address_to_string(NULL, session->addr, session->addrlen));
+  char * a2 = strdup (tcp_address_to_string(NULL, si_ctx->addr, si_ctx->addrlen));
+  GNUNET_log_from (GNUNET_ERROR_TYPE_ERROR, "tcp",
+                   "Comparing: %s %u <-> %s %u\n",
+                   a1,
+                   session->addrlen,
+                   a2,
+                   si_ctx->addrlen);
+  GNUNET_free (a1);
+  GNUNET_free (a2);
+#endif
+  if (session->addrlen != si_ctx->addrlen)
+  {
+    return GNUNET_YES;
+  }
+  if (0 != memcmp (session->addr, si_ctx->addr, si_ctx->addrlen))
+  {
+    return GNUNET_YES;
+  }
+#if 0
+  a1 = strdup (tcp_address_to_string(NULL, session->addr, session->addrlen));
+  a2 = strdup (tcp_address_to_string(NULL, si_ctx->addr, si_ctx->addrlen));
+  GNUNET_log_from (GNUNET_ERROR_TYPE_ERROR, "tcp",
+                   "Comparing: %s %u <-> %s %u , OK!\n",
+                   a1,
+                   session->addrlen,
+                   a2,
+                   si_ctx->addrlen);
+  GNUNET_free (a1);
+  GNUNET_free (a2);
+#endif
+  /* Found existing session */
+  si_ctx->result = session;
+  return GNUNET_NO;
+}
+
+
+/**
+ * Create a new session to transmit data to the target
+ * This session will used to send data to this peer and the plugin will
+ * notify us by calling the env->session_end function
+ *
+ * @param cls closure
+ * @param address pointer to the GNUNET_HELLO_Address
+ * @return the session if the address is valid, NULL otherwise
+ */
+static struct Session *
+tcp_plugin_get_session (void *cls,
+                      const struct GNUNET_HELLO_Address *address)
+{
+  struct Plugin * plugin = cls;
+  struct Session * session = NULL;
+
+  int af;
+  const void *sb;
+  size_t sbs;
+  struct GNUNET_CONNECTION_Handle *sa;
+  struct sockaddr_in a4;
+  struct sockaddr_in6 a6;
+  const struct IPv4TcpAddress *t4;
+  const struct IPv6TcpAddress *t6;
+  struct GNUNET_ATS_Information ats;
+  unsigned int is_natd = GNUNET_NO;
+  size_t addrlen = 0;
+
+  GNUNET_assert (plugin != NULL);
+  GNUNET_assert (address != NULL);
+
+  addrlen = address->address_length;
+
+  GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                   "Trying to get session for `%s' address length %i\n",
+                   tcp_address_to_string(NULL, address->address, address->address_length),
+                   addrlen);
+
+  /* look for existing session */
+  if (GNUNET_CONTAINER_multihashmap_contains(plugin->sessionmap, &address->peer.hashPubKey))
+  {
+    struct SessionItCtx si_ctx;
+
+    si_ctx.addr = (void *) address->address;
+    si_ctx.addrlen = address->address_length;
+
+    si_ctx.result = NULL;
+
+    GNUNET_CONTAINER_multihashmap_get_multiple(plugin->sessionmap, &address->peer.hashPubKey, &session_lookup_it, &si_ctx);
+    if (si_ctx.result != NULL)
+    {
+      session = si_ctx.result;
+      GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                       "Found exisiting session for `%s' address `%s' session %p\n",
+                       GNUNET_i2s (&address->peer),
+                       tcp_address_to_string(NULL, address->address, address->address_length),
+                       session);
+      return session;
+    }
+  }
+
+  if (addrlen == sizeof (struct IPv6TcpAddress))
+  {
+    GNUNET_assert (NULL != address->address);     /* make static analysis happy */
+    t6 = address->address;
+    af = AF_INET6;
+    memset (&a6, 0, sizeof (a6));
+#if HAVE_SOCKADDR_IN_SIN_LEN
+    a6.sin6_len = sizeof (a6);
+#endif
+    a6.sin6_family = AF_INET6;
+    a6.sin6_port = t6->t6_port;
+    if (t6->t6_port == 0)
+      is_natd = GNUNET_YES;
+    memcpy (&a6.sin6_addr, &t6->ipv6_addr, sizeof (struct in6_addr));
+    sb = &a6;
+    sbs = sizeof (a6);
+  }
+  else if (addrlen == sizeof (struct IPv4TcpAddress))
+  {
+    GNUNET_assert (NULL != address->address);     /* make static analysis happy */
+    t4 = address->address;
+    af = AF_INET;
+    memset (&a4, 0, sizeof (a4));
+#if HAVE_SOCKADDR_IN_SIN_LEN
+    a4.sin_len = sizeof (a4);
+#endif
+    a4.sin_family = AF_INET;
+    a4.sin_port = t4->t4_port;
+    if (t4->t4_port == 0)
+      is_natd = GNUNET_YES;
+    a4.sin_addr.s_addr = t4->ipv4_addr;
+    sb = &a4;
+    sbs = sizeof (a4);
+  }
+  else
+  {
+    GNUNET_log_from (GNUNET_ERROR_TYPE_ERROR, "tcp",
+                     _("Address of unexpected length: %u\n"), addrlen);
+    GNUNET_break (0);
+    return NULL;
+  }
+
+  ats = plugin->env->get_address_type (plugin->env->cls, sb ,sbs);
+
+  if ((is_natd == GNUNET_YES) && (addrlen == sizeof (struct IPv6TcpAddress)))
+  {
+    /* NAT client only works with IPv4 addresses */
+    return NULL;
+  }
+
+  if (0 == plugin->max_connections)
+  {
+    /* saturated */
+    return NULL;
+  }
+
+  if ((is_natd == GNUNET_YES) &&
+      (GNUNET_YES ==
+       GNUNET_CONTAINER_multihashmap_contains (plugin->nat_wait_conns,
+                                               &address->peer.hashPubKey)))
+  {
+    /* Only do one NAT punch attempt per peer identity */
+     return NULL;
+  }
+
+  if ((is_natd == GNUNET_YES) && (NULL != plugin->nat) &&
+      (GNUNET_NO ==
+       GNUNET_CONTAINER_multihashmap_contains (plugin->nat_wait_conns,
+                                               &address->peer.hashPubKey)))
+  {
+#if DEBUG_TCP_NAT
+    GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                     _("Found valid IPv4 NAT address (creating session)!\n"));
+#endif
+    session = create_session (plugin, &address->peer, NULL, GNUNET_YES);
+    session->addrlen = 0;
+    session->addr = NULL;
+    session->ats_address_network_type = ats.value;
+    GNUNET_assert (session != NULL);
+
+    GNUNET_assert (GNUNET_CONTAINER_multihashmap_put
+                   (plugin->nat_wait_conns, &address->peer.hashPubKey, session,
+                    GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY) == GNUNET_OK);
+#if DEBUG_TCP_NAT
+    GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                     "Created NAT WAIT connection to `%4s' at `%s'\n",
+                     GNUNET_i2s (&session->target), GNUNET_a2s (sb, sbs));
+#endif
+    GNUNET_NAT_run_client (plugin->nat, &a4);
+    return session;
+  }
+
+  /* create new outbound session */
+  GNUNET_assert (0 != plugin->max_connections);
+  sa = GNUNET_CONNECTION_create_from_sockaddr (af, sb, sbs);
+  if (sa == NULL)
+  {
+#if DEBUG_TCP
+    GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                     "Failed to create connection to `%4s' at `%s'\n",
+                     GNUNET_i2s (&session->target), GNUNET_a2s (sb, sbs));
+#endif
+    return NULL;
+  }
+  plugin->max_connections--;
+
+  GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                   "Asked to transmit to `%4s', creating fresh session using address `%s'.\n",
+                   GNUNET_i2s (&address->peer), GNUNET_a2s (sb, sbs));
+
+  session = create_session (plugin,
+                            &address->peer,
+                            GNUNET_SERVER_connect_socket (plugin->server, sa),
+                            GNUNET_NO);
+  session->addr = GNUNET_malloc (addrlen);
+  memcpy (session->addr, address->address, addrlen);
+  session->addrlen = addrlen;
+  session->ats_address_network_type = ats.value;
+
+  GNUNET_CONTAINER_multihashmap_put(plugin->sessionmap, &address->peer.hashPubKey, session, GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE);
+
+  GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                   "Creating new session for `%s' address `%s' session %p\n",
+                   GNUNET_i2s (&address->peer),
+                   tcp_address_to_string(NULL, address->address, address->address_length),
+                   session);
+
+  /* Send TCP Welcome */
+  process_pending_messages (session);
+
+  return session;
+}
+
+
+int session_disconnect_it (void *cls,
+               const GNUNET_HashCode * key,
+               void *value)
+{
+  struct Session *session = value;
+
+  GNUNET_STATISTICS_update (session->plugin->env->stats,
+                            gettext_noop
+                            ("# transport-service disconnect requests for TCP"),
+                            1, GNUNET_NO);
+  disconnect_session (session);
+  return GNUNET_YES;
+}
+
+int session_nat_disconnect_it (void *cls,
+               const GNUNET_HashCode * key,
+               void *value)
+{
+  struct Session *session = value;
+
+  if (session != NULL)
+  {
+    GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                     "Cleaning up pending NAT session for peer `%4s'\n", GNUNET_i2s (&session->target));
+    GNUNET_assert (GNUNET_YES == GNUNET_CONTAINER_multihashmap_remove (session->plugin->nat_wait_conns, &session->target.hashPubKey, session));
+    GNUNET_SERVER_client_drop (session->client);
+    GNUNET_SERVER_receive_done (session->client, GNUNET_SYSERR);
+    GNUNET_free (session);
+  }
+
+  return GNUNET_YES;
+}
+
+
+/**
+ * Function that can be called to force a disconnect from the
+ * specified neighbour.  This should also cancel all previously
+ * scheduled transmissions.  Obviously the transmission may have been
+ * partially completed already, which is OK.  The plugin is supposed
+ * to close the connection (if applicable) and no longer call the
+ * transmit continuation(s).
+ *
+ * Finally, plugin MUST NOT call the services's receive function to
+ * notify the service that the connection to the specified target was
+ * closed after a getting this call.
+ *
+ * @param cls closure
+ * @param target peer for which the last transmission is
+ *        to be cancelled
+ */
+static void
+tcp_plugin_disconnect (void *cls, const struct GNUNET_PeerIdentity *target)
+{
+  struct Plugin *plugin = cls;
+  struct Session *nat_session = NULL;
+
+  GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                   "Disconnecting peer `%4s'\n", GNUNET_i2s (target));
+
+  GNUNET_CONTAINER_multihashmap_get_multiple (plugin->sessionmap, &target->hashPubKey, session_disconnect_it, plugin);
+
+  nat_session = GNUNET_CONTAINER_multihashmap_get(plugin->nat_wait_conns, &target->hashPubKey);
+  if (nat_session != NULL)
+  {
+    GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                     "Cleaning up pending NAT session for peer `%4s'\n", GNUNET_i2s (target));
+    GNUNET_assert (GNUNET_YES == GNUNET_CONTAINER_multihashmap_remove (plugin->nat_wait_conns, &target->hashPubKey, nat_session));
+    GNUNET_SERVER_client_drop (nat_session->client);
+    GNUNET_SERVER_receive_done (nat_session->client, GNUNET_SYSERR);
+    GNUNET_free (nat_session);
+  }
+}
+
+
+/**
+ * Context for address to string conversion.
+ */
+struct PrettyPrinterContext
+{
+  /**
+   * Function to call with the result.
+   */
+  GNUNET_TRANSPORT_AddressStringCallback asc;
+
+  /**
+   * Clsoure for 'asc'.
+   */
+  void *asc_cls;
+
+  /**
+   * Port to add after the IP address.
+   */
+  uint16_t port;
+};
+
+
+/**
+ * Append our port and forward the result.
+ *
+ * @param cls the 'struct PrettyPrinterContext*'
+ * @param hostname hostname part of the address
+ */
+static void
+append_port (void *cls, const char *hostname)
+{
+  struct PrettyPrinterContext *ppc = cls;
+  char *ret;
+
+  if (hostname == NULL)
+  {
+    ppc->asc (ppc->asc_cls, NULL);
+    GNUNET_free (ppc);
+    return;
+  }
+  GNUNET_asprintf (&ret, "%s:%d", hostname, ppc->port);
+  ppc->asc (ppc->asc_cls, ret);
+  GNUNET_free (ret);
+}
+
+
+/**
+ * Convert the transports address to a nice, human-readable
+ * format.
+ *
+ * @param cls closure
+ * @param type name of the transport that generated the address
+ * @param addr one of the addresses of the host, NULL for the last address
+ *        the specific address format depends on the transport
+ * @param addrlen length of the address
+ * @param numeric should (IP) addresses be displayed in numeric form?
+ * @param timeout after how long should we give up?
+ * @param asc function to call on each string
+ * @param asc_cls closure for asc
+ */
+static void
+tcp_plugin_address_pretty_printer (void *cls, const char *type,
+                                   const void *addr, size_t addrlen,
+                                   int numeric,
+                                   struct GNUNET_TIME_Relative timeout,
+                                   GNUNET_TRANSPORT_AddressStringCallback asc,
+                                   void *asc_cls)
+{
+  struct PrettyPrinterContext *ppc;
+  const void *sb;
+  size_t sbs;
+  struct sockaddr_in a4;
+  struct sockaddr_in6 a6;
+  const struct IPv4TcpAddress *t4;
+  const struct IPv6TcpAddress *t6;
+  uint16_t port;
+
+  if (addrlen == sizeof (struct IPv6TcpAddress))
+  {
+    t6 = addr;
+    memset (&a6, 0, sizeof (a6));
+    a6.sin6_family = AF_INET6;
+    a6.sin6_port = t6->t6_port;
+    memcpy (&a6.sin6_addr, &t6->ipv6_addr, sizeof (struct in6_addr));
+    port = ntohs (t6->t6_port);
+    sb = &a6;
+    sbs = sizeof (a6);
+  }
+  else if (addrlen == sizeof (struct IPv4TcpAddress))
+  {
+    t4 = addr;
+    memset (&a4, 0, sizeof (a4));
+    a4.sin_family = AF_INET;
+    a4.sin_port = t4->t4_port;
+    a4.sin_addr.s_addr = t4->ipv4_addr;
+    port = ntohs (t4->t4_port);
+    sb = &a4;
+    sbs = sizeof (a4);
+  }
+  else
+  {
+    /* invalid address */
+    GNUNET_break_op (0);
+    asc (asc_cls, NULL);
+    return;
+  }
+  ppc = GNUNET_malloc (sizeof (struct PrettyPrinterContext));
+  ppc->asc = asc;
+  ppc->asc_cls = asc_cls;
+  ppc->port = port;
+  GNUNET_RESOLVER_hostname_get (sb, sbs, !numeric, timeout, &append_port, ppc);
+}
+
+
+/**
+ * Check if the given port is plausible (must be either our listen
+ * port or our advertised port), or any port if we are behind NAT
+ * and do not have a port open.  If it is neither, we return
+ * GNUNET_SYSERR.
+ *
+ * @param plugin global variables
+ * @param in_port port number to check
+ * @return GNUNET_OK if port is either open_port or adv_port
+ */
+static int
+check_port (struct Plugin *plugin, uint16_t in_port)
+{
+  if ((in_port == plugin->adv_port) || (in_port == plugin->open_port))
+    return GNUNET_OK;
+  return GNUNET_SYSERR;
+}
+
+
+/**
+ * Function that will be called to check if a binary address for this
+ * plugin is well-formed and corresponds to an address for THIS peer
+ * (as per our configuration).  Naturally, if absolutely necessary,
+ * plugins can be a bit conservative in their answer, but in general
+ * plugins should make sure that the address does not redirect
+ * traffic to a 3rd party that might try to man-in-the-middle our
+ * traffic.
+ *
+ * @param cls closure, our 'struct Plugin*'
+ * @param addr pointer to the address
+ * @param addrlen length of addr
+ * @return GNUNET_OK if this is a plausible address for this peer
+ *         and transport, GNUNET_SYSERR if not
+ */
+static int
+tcp_plugin_check_address (void *cls, const void *addr, size_t addrlen)
+{
+  struct Plugin *plugin = cls;
+  struct IPv4TcpAddress *v4;
+  struct IPv6TcpAddress *v6;
+
+  if ((addrlen != sizeof (struct IPv4TcpAddress)) &&
+      (addrlen != sizeof (struct IPv6TcpAddress)))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
+  }
+  if (addrlen == sizeof (struct IPv4TcpAddress))
+  {
+    v4 = (struct IPv4TcpAddress *) addr;
+    if (GNUNET_OK != check_port (plugin, ntohs (v4->t4_port)))
+      return GNUNET_SYSERR;
+    if (GNUNET_OK !=
+        GNUNET_NAT_test_address (plugin->nat, &v4->ipv4_addr,
+                                 sizeof (struct in_addr)))
+      return GNUNET_SYSERR;
+  }
+  else
+  {
+    v6 = (struct IPv6TcpAddress *) addr;
+    if (IN6_IS_ADDR_LINKLOCAL (&v6->ipv6_addr))
+    {
+      GNUNET_break_op (0);
+      return GNUNET_SYSERR;
+    }
+    if (GNUNET_OK != check_port (plugin, ntohs (v6->t6_port)))
+      return GNUNET_SYSERR;
+    if (GNUNET_OK !=
+        GNUNET_NAT_test_address (plugin->nat, &v6->ipv6_addr,
+                                 sizeof (struct in6_addr)))
+      return GNUNET_SYSERR;
+  }
+  return GNUNET_OK;
+}
+
+
+/**
+ * We've received a nat probe from this peer via TCP.  Finish
+ * creating the client session and resume sending of queued
+ * messages.
+ *
+ * @param cls closure
+ * @param client identification of the client
+ * @param message the actual message
+ */
+static void
+handle_tcp_nat_probe (void *cls, struct GNUNET_SERVER_Client *client,
+                      const struct GNUNET_MessageHeader *message)
+{
+  struct Plugin *plugin = cls;
+  struct Session *session;
+  const struct TCP_NAT_ProbeMessage *tcp_nat_probe;
+  size_t alen;
+  void *vaddr;
+  struct IPv4TcpAddress *t4;
+  struct IPv6TcpAddress *t6;
+  const struct sockaddr_in *s4;
+  const struct sockaddr_in6 *s6;
+
+  GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp", "received NAT probe\n");
+
+  /* We have received a TCP NAT probe, meaning we (hopefully) initiated
+   * a connection to this peer by running gnunet-nat-client.  This peer
+   * received the punch message and now wants us to use the new connection
+   * as the default for that peer.  Do so and then send a WELCOME message
+   * so we can really be connected!
+   */
+  if (ntohs (message->size) != sizeof (struct TCP_NAT_ProbeMessage))
+  {
+    GNUNET_break_op (0);
+    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+    return;
+  }
+
+  tcp_nat_probe = (const struct TCP_NAT_ProbeMessage *) message;
+  if (0 ==
+      memcmp (&tcp_nat_probe->clientIdentity, plugin->env->my_identity,
+              sizeof (struct GNUNET_PeerIdentity)))
+  {
+    /* refuse connections from ourselves */
+    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+    return;
+  }
+
+  session =
+      GNUNET_CONTAINER_multihashmap_get (plugin->nat_wait_conns,
+                                         &tcp_nat_probe->
+                                         clientIdentity.hashPubKey);
+  if (session == NULL)
+  {
+    GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                     "Did NOT find session for NAT probe!\n");
+    GNUNET_SERVER_receive_done (client, GNUNET_OK);
+    return;
+  }
+  GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                   "Found session for NAT probe!\n");
+
+  GNUNET_assert (GNUNET_CONTAINER_multihashmap_remove
+                 (plugin->nat_wait_conns,
+                  &tcp_nat_probe->clientIdentity.hashPubKey,
+                  session) == GNUNET_YES);
+  if (GNUNET_OK != GNUNET_SERVER_client_get_address (client, &vaddr, &alen))
+  {
+    GNUNET_break (0);
+    GNUNET_free (session);
+    GNUNET_SERVER_receive_done (client, GNUNET_OK);
+    return;
+  }
+
+  GNUNET_SERVER_client_keep (client);
+  session->client = client;
+  session->last_activity = GNUNET_TIME_absolute_get ();
+  session->inbound = GNUNET_NO;
+
+#if DEBUG_TCP_NAT
+  GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                   "Found address `%s' for incoming connection\n",
+                   GNUNET_a2s (vaddr, alen));
+#endif
+  switch (((const struct sockaddr *) vaddr)->sa_family)
+  {
+  case AF_INET:
+    s4 = vaddr;
+    t4 = GNUNET_malloc (sizeof (struct IPv4TcpAddress));
+    t4->t4_port = s4->sin_port;
+    t4->ipv4_addr = s4->sin_addr.s_addr;
+    session->addr = t4;
+    session->addrlen = sizeof (struct IPv4TcpAddress);
+    break;
+  case AF_INET6:
+    s6 = vaddr;
+    t6 = GNUNET_malloc (sizeof (struct IPv6TcpAddress));
+    t6->t6_port = s6->sin6_port;
+    memcpy (&t6->ipv6_addr, &s6->sin6_addr, sizeof (struct in6_addr));
+    session->addr = t6;
+    session->addrlen = sizeof (struct IPv6TcpAddress);
+    break;
+  default:
+    GNUNET_break_op (0);
+
+    GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                     "Bad address for incoming connection!\n");
+    GNUNET_free (vaddr);
+
+    GNUNET_SERVER_client_drop (client);
+    GNUNET_free (session);
+    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+    return;
+  }
+  GNUNET_free (vaddr);
+
+  GNUNET_CONTAINER_multihashmap_put(plugin->sessionmap, &session->target.hashPubKey, session, GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE);
+
+  GNUNET_STATISTICS_update (plugin->env->stats,
+                            gettext_noop ("# TCP sessions active"), 1,
+                            GNUNET_NO);
+  process_pending_messages (session);
+  GNUNET_SERVER_receive_done (client, GNUNET_OK);
+}
+
+
+/**
+ * We've received a welcome from this peer via TCP.  Possibly create a
+ * fresh client record and send back our welcome.
+ *
+ * @param cls closure
+ * @param client identification of the client
+ * @param message the actual message
+ */
+static void
+handle_tcp_welcome (void *cls, struct GNUNET_SERVER_Client *client,
+                    const struct GNUNET_MessageHeader *message)
+{
+  struct Plugin *plugin = cls;
+  const struct WelcomeMessage *wm = (const struct WelcomeMessage *) message;
+  struct Session *session;
+  size_t alen;
+  void *vaddr;
+  struct IPv4TcpAddress *t4;
+  struct IPv6TcpAddress *t6;
+  const struct sockaddr_in *s4;
+  const struct sockaddr_in6 *s6;
+
+  if (0 ==
+      memcmp (&wm->clientIdentity, plugin->env->my_identity,
+              sizeof (struct GNUNET_PeerIdentity)))
+  {
+    /* refuse connections from ourselves */
+    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+    return;
+  }
+
+  GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                   "Received %s message from `%4s'\n", "WELCOME",
+                   GNUNET_i2s (&wm->clientIdentity));
+  GNUNET_STATISTICS_update (plugin->env->stats,
+                            gettext_noop ("# TCP WELCOME messages received"), 1,
+                            GNUNET_NO);
+
+  session = lookup_session_by_client (plugin, client);
+  if (session != NULL)
+  {
+    if (GNUNET_OK == GNUNET_SERVER_client_get_address (client, &vaddr, &alen))
+    {
+      GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                       "Found existing session %p for peer `%s'\n",
+                       session,
+                       GNUNET_a2s (vaddr, alen));
+      GNUNET_free (vaddr);
+    }
+  }
+  else
+  {
+    GNUNET_SERVER_client_keep (client);
+    session = create_session (plugin, &wm->clientIdentity, client, GNUNET_NO);
+    session->inbound = GNUNET_YES;
+
+    if (GNUNET_OK == GNUNET_SERVER_client_get_address (client, &vaddr, &alen))
+    {
+      if (alen == sizeof (struct sockaddr_in))
+      {
+        s4 = vaddr;
+        t4 = GNUNET_malloc (sizeof (struct IPv4TcpAddress));
+        t4->t4_port = s4->sin_port;
+        t4->ipv4_addr = s4->sin_addr.s_addr;
+        session->addr = t4;
+        session->addrlen = sizeof (struct IPv4TcpAddress);
+      }
+      else if (alen == sizeof (struct sockaddr_in6))
+      {
+        s6 = vaddr;
+        t6 = GNUNET_malloc (sizeof (struct IPv6TcpAddress));
+        t6->t6_port = s6->sin6_port;
+        memcpy (&t6->ipv6_addr, &s6->sin6_addr, sizeof (struct in6_addr));
+        session->addr = t6;
+        session->addrlen = sizeof (struct IPv6TcpAddress);
+      }
+
+      struct GNUNET_ATS_Information ats;
+      ats = plugin->env->get_address_type (plugin->env->cls, vaddr ,alen);
+      session->ats_address_network_type = ats.value;
+
+      GNUNET_free (vaddr);
+    }
+    else
+    {
+#if DEBUG_TCP
+      GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                       "Did not obtain TCP socket address for incoming connection\n");
+#endif
+    }
+    GNUNET_CONTAINER_multihashmap_put(plugin->sessionmap, &wm->clientIdentity.hashPubKey, session, GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE);
+  }
+
+  if (session->expecting_welcome != GNUNET_YES)
+  {
+    GNUNET_break_op (0);
+    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+    return;
+  }
+  session->last_activity = GNUNET_TIME_absolute_get ();
+  session->expecting_welcome = GNUNET_NO;
+
+
+  process_pending_messages (session);
+
+  GNUNET_SERVER_client_set_timeout (client,
+                                    GNUNET_CONSTANTS_IDLE_CONNECTION_TIMEOUT);
+  GNUNET_SERVER_receive_done (client, GNUNET_OK);
+}
+
+
+/**
+ * Task to signal the server that we can continue
+ * receiving from the TCP client now.
+ *
+ * @param cls the 'struct Session*'
+ * @param tc task context (unused)
+ */
+static void
+delayed_done (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct Session *session = cls;
+  struct GNUNET_TIME_Relative delay;
+  struct GNUNET_ATS_Information ats;
+
+  session->receive_delay_task = GNUNET_SCHEDULER_NO_TASK;
+  delay =
+      session->plugin->env->receive (session->plugin->env->cls,
+                                     &session->target, NULL, &ats, 0, session,
+                                     NULL, 0);
+  if (delay.rel_value == 0)
+    GNUNET_SERVER_receive_done (session->client, GNUNET_OK);
+  else
+    session->receive_delay_task =
+        GNUNET_SCHEDULER_add_delayed (delay, &delayed_done, session);
+}
+
+
+/**
+ * We've received data for this peer via TCP.  Unbox,
+ * compute latency and forward.
+ *
+ * @param cls closure
+ * @param client identification of the client
+ * @param message the actual message
+ */
+static void
+handle_tcp_data (void *cls, struct GNUNET_SERVER_Client *client,
+                 const struct GNUNET_MessageHeader *message)
+{
+  struct Plugin *plugin = cls;
+  struct Session *session;
+  struct GNUNET_TIME_Relative delay;
+  uint16_t type;
+
+  type = ntohs (message->type);
+  if ((GNUNET_MESSAGE_TYPE_TRANSPORT_TCP_WELCOME == type) ||
+      (GNUNET_MESSAGE_TYPE_TRANSPORT_TCP_NAT_PROBE == type))
+  {
+    /* We don't want to propagate WELCOME and NAT Probe messages up! */
+    GNUNET_SERVER_receive_done (client, GNUNET_OK);
+    return;
+  }
+  session = lookup_session_by_client (plugin, client);
+  if (NULL == session)
+  {
+    /* No inbound session found */
+    GNUNET_break_op (0);
+    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+    return;
+  }
+  else if (GNUNET_YES == session->expecting_welcome)
+  {
+    /* Session is expecting WELCOME message */
+    GNUNET_break_op (0);
+    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+    return;
+  }
+
+  session->last_activity = GNUNET_TIME_absolute_get ();
+
+  GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                   "Passing %u bytes of type %u from `%4s' to transport service.\n",
+                   (unsigned int) ntohs (message->size),
+                   (unsigned int) ntohs (message->type),
+                   GNUNET_i2s (&session->target));
+
+  GNUNET_STATISTICS_update (plugin->env->stats,
+                            gettext_noop ("# bytes received via TCP"),
+                            ntohs (message->size), GNUNET_NO);
+  struct GNUNET_ATS_Information distance[2];
+
+  distance[0].type = htonl (GNUNET_ATS_QUALITY_NET_DISTANCE);
+  distance[0].value = htonl (1);
+  distance[1].type = htonl (GNUNET_ATS_NETWORK_TYPE);
+  distance[1].value = session->ats_address_network_type;
+  GNUNET_break (ntohl(session->ats_address_network_type) != GNUNET_ATS_NET_UNSPECIFIED);
+
+  delay = plugin->env->receive (plugin->env->cls,
+                                &session->target,
+                                message,
+                                (const struct GNUNET_ATS_Information *) &distance,
+                                1, session,
+                                (GNUNET_YES == session->inbound) ? NULL : session->addr,
+                                (GNUNET_YES == session->inbound) ? 0 : session->addrlen);
+  if (delay.rel_value == 0)
+  {
+    GNUNET_SERVER_receive_done (client, GNUNET_OK);
+  }
+  else
+  {
+#if DEBUG_TCP
+    GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                     "Throttling receiving from `%s' for %llu ms\n",
+                     GNUNET_i2s (&session->target),
+                     (unsigned long long) delay.rel_value);
+#endif
+    GNUNET_SERVER_disable_receive_done_warning (client);
+    session->receive_delay_task =
+        GNUNET_SCHEDULER_add_delayed (delay, &delayed_done, session);
+  }
+}
+
+
+/**
+ * Functions with this signature are called whenever a peer
+ * is disconnected on the network level.
+ *
+ * @param cls closure
+ * @param client identification of the client
+ */
+static void
+disconnect_notify (void *cls, struct GNUNET_SERVER_Client *client)
+{
+  struct Plugin *plugin = cls;
+  struct Session *session;
+
+  if (client == NULL)
+    return;
+  plugin->max_connections++;
+  session = lookup_session_by_client (plugin, client);
+  if (session == NULL)
+    return;                     /* unknown, nothing to do */
+#if DEBUG_TCP
+  GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp",
+                   "Destroying session of `%4s' with %s due to network-level disconnect.\n",
+                   GNUNET_i2s (&session->target),
+                   (session->addr !=
+                    NULL) ? tcp_address_to_string (session->plugin,
+                                                   session->addr,
+                                                   session->addrlen) :
+                   "*");
+#endif
+  GNUNET_STATISTICS_update (session->plugin->env->stats,
+                            gettext_noop
+                            ("# network-level TCP disconnect events"), 1,
+                            GNUNET_NO);
+  disconnect_session (session);
+}
+
+
+/**
+ * We can now send a probe message, copy into buffer to really send.
+ *
+ * @param cls closure, a struct TCPProbeContext
+ * @param size max size to copy
+ * @param buf buffer to copy message to
+ * @return number of bytes copied into buf
+ */
+static size_t
+notify_send_probe (void *cls, size_t size, void *buf)
+{
+  struct TCPProbeContext *tcp_probe_ctx = cls;
+  struct Plugin *plugin = tcp_probe_ctx->plugin;
+  size_t ret;
+
+  tcp_probe_ctx->transmit_handle = NULL;
+  GNUNET_CONTAINER_DLL_remove (plugin->probe_head, plugin->probe_tail,
+                               tcp_probe_ctx);
+  if (buf == NULL)
+  {
+    GNUNET_CONNECTION_destroy (tcp_probe_ctx->sock, GNUNET_NO);
+    GNUNET_free (tcp_probe_ctx);
+    return 0;
+  }
+  GNUNET_assert (size >= sizeof (tcp_probe_ctx->message));
+  memcpy (buf, &tcp_probe_ctx->message, sizeof (tcp_probe_ctx->message));
+  GNUNET_SERVER_connect_socket (tcp_probe_ctx->plugin->server,
+                                tcp_probe_ctx->sock);
+  ret = sizeof (tcp_probe_ctx->message);
+  GNUNET_free (tcp_probe_ctx);
+  return ret;
+}
+
+
+/**
+ * Function called by the NAT subsystem suggesting another peer wants
+ * to connect to us via connection reversal.  Try to connect back to the
+ * given IP.
+ *
+ * @param cls closure
+ * @param addr address to try
+ * @param addrlen number of bytes in addr
+ */
+static void
+try_connection_reversal (void *cls, const struct sockaddr *addr,
+                         socklen_t addrlen)
+{
+  struct Plugin *plugin = cls;
+  struct GNUNET_CONNECTION_Handle *sock;
+  struct TCPProbeContext *tcp_probe_ctx;
+
+  /**
+   * We have received an ICMP response, ostensibly from a peer
+   * that wants to connect to us! Send a message to establish a connection.
+   */
+  sock = GNUNET_CONNECTION_create_from_sockaddr (AF_INET, addr, addrlen);
+  if (sock == NULL)
+  {
+    /* failed for some odd reason (out of sockets?); ignore attempt */
+    return;
+  }
+
+  /* FIXME: do we need to track these probe context objects so that
+   * we can clean them up on plugin unload? */
+  tcp_probe_ctx = GNUNET_malloc (sizeof (struct TCPProbeContext));
+  tcp_probe_ctx->message.header.size =
+      htons (sizeof (struct TCP_NAT_ProbeMessage));
+  tcp_probe_ctx->message.header.type =
+      htons (GNUNET_MESSAGE_TYPE_TRANSPORT_TCP_NAT_PROBE);
+  memcpy (&tcp_probe_ctx->message.clientIdentity, plugin->env->my_identity,
+          sizeof (struct GNUNET_PeerIdentity));
+  tcp_probe_ctx->plugin = plugin;
+  tcp_probe_ctx->sock = sock;
+  GNUNET_CONTAINER_DLL_insert (plugin->probe_head, plugin->probe_tail,
+                               tcp_probe_ctx);
+  tcp_probe_ctx->transmit_handle =
+      GNUNET_CONNECTION_notify_transmit_ready (sock,
+                                               ntohs (tcp_probe_ctx->
+                                                      message.header.size),
+                                               GNUNET_TIME_UNIT_FOREVER_REL,
+                                               &notify_send_probe,
+                                               tcp_probe_ctx);
+
+}
+
+
+/**
+ * Entry point for the plugin.
+ *
+ * @param cls closure, the 'struct GNUNET_TRANSPORT_PluginEnvironment*'
+ * @return the 'struct GNUNET_TRANSPORT_PluginFunctions*' or NULL on error
+ */
+void *
+libgnunet_plugin_transport_tcp_init (void *cls)
+{
+  static const struct GNUNET_SERVER_MessageHandler my_handlers[] = {
+    {&handle_tcp_welcome, NULL, GNUNET_MESSAGE_TYPE_TRANSPORT_TCP_WELCOME,
+     sizeof (struct WelcomeMessage)},
+    {&handle_tcp_nat_probe, NULL, GNUNET_MESSAGE_TYPE_TRANSPORT_TCP_NAT_PROBE,
+     sizeof (struct TCP_NAT_ProbeMessage)},
+    {&handle_tcp_data, NULL, GNUNET_MESSAGE_TYPE_ALL, 0},
+    {NULL, NULL, 0, 0}
+  };
+  struct GNUNET_TRANSPORT_PluginEnvironment *env = cls;
+  struct GNUNET_TRANSPORT_PluginFunctions *api;
+  struct Plugin *plugin;
+  struct GNUNET_SERVICE_Context *service;
+  unsigned long long aport;
+  unsigned long long bport;
+  unsigned long long max_connections;
+  unsigned int i;
+  struct GNUNET_TIME_Relative idle_timeout;
+  int ret;
+  struct sockaddr **addrs;
+  socklen_t *addrlens;
+
+  if (GNUNET_OK !=
+      GNUNET_CONFIGURATION_get_value_number (env->cfg, "transport-tcp",
+                                             "MAX_CONNECTIONS",
+                                             &max_connections))
+    max_connections = 128;
+
+  aport = 0;
+  if ((GNUNET_OK !=
+       GNUNET_CONFIGURATION_get_value_number (env->cfg, "transport-tcp", "PORT",
+                                              &bport)) || (bport > 65535) ||
+      ((GNUNET_OK ==
+        GNUNET_CONFIGURATION_get_value_number (env->cfg, "transport-tcp",
+                                               "ADVERTISED-PORT", &aport)) &&
+       (aport > 65535)))
+  {
+    GNUNET_log_from (GNUNET_ERROR_TYPE_ERROR, "tcp",
+                     _
+                     ("Require valid port number for service `%s' in configuration!\n"),
+                     "transport-tcp");
+    return NULL;
+  }
+  if (aport == 0)
+    aport = bport;
+  if (bport == 0)
+    aport = 0;
+  if (bport != 0)
+  {
+    service = GNUNET_SERVICE_start ("transport-tcp", env->cfg);
+    if (service == NULL)
+    {
+      GNUNET_log_from (GNUNET_ERROR_TYPE_WARNING, "tcp",
+                       _("Failed to start service.\n"));
+      return NULL;
+    }
+  }
+  else
+    service = NULL;
+
+
+
+  plugin = GNUNET_malloc (sizeof (struct Plugin));
+  plugin->sessionmap = GNUNET_CONTAINER_multihashmap_create(max_connections);
+  plugin->max_connections = max_connections;
+  plugin->open_port = bport;
+  plugin->adv_port = aport;
+  plugin->env = env;
+  plugin->lsock = NULL;
+  if ((service != NULL) &&
+      (GNUNET_SYSERR !=
+       (ret =
+        GNUNET_SERVICE_get_server_addresses ("transport-tcp", env->cfg, &addrs,
+                                             &addrlens))))
+  {
+    plugin->nat =
+        GNUNET_NAT_register (env->cfg, GNUNET_YES, aport, (unsigned int) ret,
+                             (const struct sockaddr **) addrs, addrlens,
+                             &tcp_nat_port_map_callback,
+                             &try_connection_reversal, plugin);
+    while (ret > 0)
+    {
+      ret--;
+      GNUNET_assert (addrs[ret] != NULL);
+      GNUNET_free (addrs[ret]);
+    }
+    GNUNET_free_non_null (addrs);
+    GNUNET_free_non_null (addrlens);
+  }
+  else
+  {
+    plugin->nat =
+        GNUNET_NAT_register (env->cfg, GNUNET_YES, 0, 0, NULL, NULL, NULL,
+                             &try_connection_reversal, plugin);
+  }
+  api = GNUNET_malloc (sizeof (struct GNUNET_TRANSPORT_PluginFunctions));
+  api->cls = plugin;
+  api->send = &tcp_plugin_send;
+  api->get_session = &tcp_plugin_get_session;
+
+  api->disconnect = &tcp_plugin_disconnect;
+  api->address_pretty_printer = &tcp_plugin_address_pretty_printer;
+  api->check_address = &tcp_plugin_check_address;
+  api->address_to_string = &tcp_address_to_string;
+  plugin->service = service;
+  if (service != NULL)
+  {
+    plugin->server = GNUNET_SERVICE_get_server (service);
+  }
+  else
+  {
+    if (GNUNET_OK !=
+        GNUNET_CONFIGURATION_get_value_time (env->cfg, "transport-tcp",
+                                             "TIMEOUT", &idle_timeout))
+    {
+      GNUNET_log_from (GNUNET_ERROR_TYPE_ERROR, "tcp",
+                       _("Failed to find option %s in section %s!\n"),
+                       "TIMEOUT", "transport-tcp");
+      if (plugin->nat != NULL)
+        GNUNET_NAT_unregister (plugin->nat);
+      GNUNET_free (plugin);
+      GNUNET_free (api);
+      return NULL;
+    }
+    plugin->server =
+        GNUNET_SERVER_create_with_sockets (&plugin_tcp_access_check, plugin,
+                                           NULL, idle_timeout, GNUNET_YES);
+  }
+  plugin->handlers = GNUNET_malloc (sizeof (my_handlers));
+  memcpy (plugin->handlers, my_handlers, sizeof (my_handlers));
+  for (i = 0;
+       i < sizeof (my_handlers) / sizeof (struct GNUNET_SERVER_MessageHandler);
+       i++)
+    plugin->handlers[i].callback_cls = plugin;
+  GNUNET_SERVER_add_handlers (plugin->server, plugin->handlers);
+  GNUNET_SERVER_disconnect_notify (plugin->server, &disconnect_notify, plugin);
+  plugin->nat_wait_conns = GNUNET_CONTAINER_multihashmap_create (16);
+  if (bport != 0)
+    GNUNET_log_from (GNUNET_ERROR_TYPE_INFO, "tcp",
+                     _("TCP transport listening on port %llu\n"), bport);
+  else
+    GNUNET_log_from (GNUNET_ERROR_TYPE_INFO, "tcp",
+                     _
+                     ("TCP transport not listening on any port (client only)\n"));
+  if (aport != bport)
+    GNUNET_log_from (GNUNET_ERROR_TYPE_INFO, "tcp",
+                     _
+                     ("TCP transport advertises itself as being on port %llu\n"),
+                     aport);
+  return api;
+}
+
+
+/**
+ * Exit point from the plugin.
+ */
+void *
+libgnunet_plugin_transport_tcp_done (void *cls)
+{
+  struct GNUNET_TRANSPORT_PluginFunctions *api = cls;
+  struct Plugin *plugin = api->cls;
+  struct TCPProbeContext *tcp_probe;
+
+  GNUNET_log_from (GNUNET_ERROR_TYPE_DEBUG, "tcp", "Shutting down TCP plugin\n");
+
+
+  /* Removing leftover sessions */
+  GNUNET_CONTAINER_multihashmap_iterate(plugin->sessionmap, &session_disconnect_it, NULL);
+  /* Removing leftover NAT sessions */
+  GNUNET_CONTAINER_multihashmap_iterate(plugin->nat_wait_conns, &session_nat_disconnect_it, NULL);
+
+  if (plugin->service != NULL)
+    GNUNET_SERVICE_stop (plugin->service);
+  else
+    GNUNET_SERVER_destroy (plugin->server);
+  GNUNET_free (plugin->handlers);
+  if (plugin->nat != NULL)
+    GNUNET_NAT_unregister (plugin->nat);
+  while (NULL != (tcp_probe = plugin->probe_head))
+  {
+    GNUNET_CONTAINER_DLL_remove (plugin->probe_head, plugin->probe_tail,
+                                 tcp_probe);
+    GNUNET_CONNECTION_destroy (tcp_probe->sock, GNUNET_NO);
+    GNUNET_free (tcp_probe);
+  }
+  GNUNET_CONTAINER_multihashmap_destroy (plugin->nat_wait_conns);
+  GNUNET_CONTAINER_multihashmap_destroy (plugin->sessionmap);
+  GNUNET_free (plugin);
+  GNUNET_free (api);
+  return NULL;
+}
+
+/* end of plugin_transport_tcp.c */