-removing legacy dns/vpn/exit code and renaming -new versions to current
[oweals/gnunet.git] / src / vpn / gnunet-service-vpn.c
index 27490db502777c33ca58433156938e93d1ab8553..afa577f983e9efc2ec60cc2399228fe997d1fc30 100644 (file)
  * @author Christian Grothoff
  *
  * TODO:
- * - create tunnels
- * - implement service message handlers
- * - define mesh message formats between VPN and EXIT!
- * - build mesh messages
- * - parse mesh replies 
- * - build IP messages from mesh replies
- * - fully implement shutdown code
+ * Basics:
+ * - test!
+ * - better message queue management (bounded state, drop oldest/RED?)
+ * - actually destroy "stale" tunnels once we have too many!
+ *
+ * Features:
  * - add back ICMP support (especially needed for IPv6)
+ *
+ * Code cleanup:
+ * - consider moving IP-header building / checksumming code into shared library
+ *   with dns/exit/vpn (libgnunettun_tcpip?)
  */
 #include "platform.h"
 #include "gnunet_util_lib.h"
 #include "gnunet_protocols.h"
 #include "gnunet_applications.h"
 #include "gnunet_mesh_service.h"
+#include "gnunet_statistics_service.h"
 #include "gnunet_constants.h"
 #include "tcpip_tun.h"
 #include "vpn.h"
+#include "exit.h"
+
+
+/**
+ * State we keep for each of our tunnels.
+ */
+struct TunnelState;
 
 
 /**
  */
 struct DestinationEntry
 {
+
   /**
-   * Information about the tunnel to use, NULL if no tunnel
-   * is available right now.
+   * Key under which this entry is in the 'destination_map' (only valid
+   * if 'heap_node != NULL'.
    */
-  struct GNUNET_MESH_Tunnel *tunnel;
+  GNUNET_HashCode key;
+
+  /**
+   * Pre-allocated tunnel for this destination, or NULL for none.
+   */
+  struct TunnelState *ts;
 
   /**
    * Entry for this entry in the destination_heap.
@@ -69,37 +86,52 @@ struct DestinationEntry
    * GNUNET_YES if this tunnel is to a service.
    */
   int is_service;
-  
-  /**
-   * Address family used (AF_INET or AF_INET6).
-   */
-  int af;
 
   /**
    * Details about the connection (depending on is_service).
    */
   union
   {
-    /**
-     * The description of the service (only used for service tunnels).
-     */
-    GNUNET_HashCode desc;
 
-    /**
-     * IP address of the ultimate destination (only used for exit tunnels).
-     */
-    union
+    struct
     {
       /**
-       * Address if af is AF_INET.
+       * The description of the service (only used for service tunnels).
        */
-      struct in_addr v4;
+      GNUNET_HashCode service_descriptor;
 
       /**
-       * Address if af is AF_INET6.
+       * Peer offering the service.
+       */
+      struct GNUNET_PeerIdentity target;
+
+    } service_destination;
+
+    struct 
+    {
+  
+      /**
+       * Address family used (AF_INET or AF_INET6).
+       */
+      int af;
+      
+      /**
+       * IP address of the ultimate destination (only used for exit tunnels).
        */
-      struct in6_addr v6;
-    } ip;
+      union
+      {
+       /**
+        * Address if af is AF_INET.
+        */
+       struct in_addr v4;
+       
+       /**
+        * Address if af is AF_INET6.
+        */
+       struct in6_addr v6;
+      } ip;
+
+    } exit_destination;
 
   } details;
     
@@ -138,13 +170,20 @@ struct TunnelMessageQueueEntry
  */
 struct TunnelState
 {
+  /**
+   * Information about the tunnel to use, NULL if no tunnel
+   * is available right now.
+   */
+  struct GNUNET_MESH_Tunnel *tunnel;
+
   /**
    * Active transmission handle, NULL for none.
    */
   struct GNUNET_MESH_TransmitHandle *th;
 
   /**
-   * Entry for this entry in the tunnel_heap.
+   * Entry for this entry in the tunnel_heap, NULL as long as this
+   * tunnel state is not fully bound.
    */
   struct GNUNET_CONTAINER_HeapNode *heap_node;
 
@@ -158,6 +197,17 @@ struct TunnelState
    */
   struct TunnelMessageQueueEntry *tail;
 
+  /**
+   * Client that needs to be notified about the tunnel being
+   * up as soon as a peer is connected; NULL for none.
+   */
+  struct GNUNET_SERVER_Client *client;
+
+  /**
+   * ID of the client request that caused us to setup this entry.
+   */ 
+  uint64_t request_id;
+
   /**
    * Destination to which this tunnel leads.  Note that
    * this struct is NOT in the destination_map (but a
@@ -167,13 +217,23 @@ struct TunnelState
   struct DestinationEntry destination;
 
   /**
-   * GNUNET_NO if this is a tunnel to an Internet-exit,
-   * GNUNET_YES if this tunnel is to a service.
+   * Destination entry that has a pointer to this tunnel state;
+   * NULL if this tunnel state is in the tunnel map.
    */
-  int is_service;
+  struct DestinationEntry *destination_container;
+
+  /**
+   * Addess family used for this tunnel on the local TUN interface.
+   */
+  int af;
+
+  /**
+   * IPPROTO_TCP or IPPROTO_UDP once bound.
+   */
+  uint8_t protocol;
 
   /**
-   * IP address of the source on our end.
+   * IP address of the source on our end, initially uninitialized.
    */
   union
   {
@@ -190,7 +250,8 @@ struct TunnelState
   } source_ip;
 
   /**
-   * Destination IP address used by the source on our end.
+   * Destination IP address used by the source on our end (this is the IP
+   * that we pick freely within the VPN's tunnel IP range).
    */
   union
   {
@@ -207,12 +268,12 @@ struct TunnelState
   } destination_ip;
 
   /**
-   * Source port used by the sender on our end.
+   * Source port used by the sender on our end; 0 for uninitialized.
    */
   uint16_t source_port;
 
   /**
-   * Destination port used by the sender on our end.
+   * Destination port used by the sender on our end; 0 for uninitialized.
    */
   uint16_t destination_port;
 
@@ -247,10 +308,16 @@ static struct GNUNET_CONTAINER_Heap *destination_heap;
 static struct GNUNET_CONTAINER_MultiHashMap *tunnel_map;
 
 /**
- * Min-Heap sorted by activity time to expire old mappings.
+ * Min-Heap sorted by activity time to expire old mappings; values are
+ * of type 'struct TunnelState'.
  */
 static struct GNUNET_CONTAINER_Heap *tunnel_heap;
 
+/**
+ * Statistics.
+ */
+static struct GNUNET_STATISTICS_Handle *stats;
+
 /**
  * The handle to the VPN helper process "gnunet-helper-vpn".
  */
@@ -261,6 +328,16 @@ static struct GNUNET_HELPER_Handle *helper_handle;
  */
 static char *vpn_argv[7];
 
+/**
+ * Length of the prefix of the VPN's IPv6 network.
+ */
+static unsigned long long ipv6prefix;
+
+/**
+ * Notification context for sending replies to clients.
+ */
+static struct GNUNET_SERVER_NotificationContext *nc;
+
 /**
  * If there are more than this number of address-mappings, old ones
  * will be removed
@@ -360,6 +437,119 @@ get_tunnel_key_from_ips (int af,
 }
 
 
+/**
+ * Notify the client about the result of its request.
+ *
+ * @param client client to notify
+ * @param request_id original request ID to include in response
+ * @param result_af resulting address family
+ * @param addr resulting IP address
+ */
+static void
+send_client_reply (struct GNUNET_SERVER_Client *client,
+                  uint64_t request_id,
+                  int result_af,
+                  const void *addr)
+{
+  char buf[sizeof (struct RedirectToIpResponseMessage) + sizeof (struct in6_addr)];
+  struct RedirectToIpResponseMessage *res;
+  size_t rlen;
+
+  switch (result_af)
+  {
+  case AF_INET:
+    rlen = sizeof (struct in_addr);    
+    break;
+  case AF_INET6:
+    rlen = sizeof (struct in6_addr);
+    break;
+  case AF_UNSPEC:
+    rlen = 0;
+    break;
+  default:
+    GNUNET_assert (0);
+    return;
+  }
+  res = (struct RedirectToIpResponseMessage *) buf;
+  res->header.size = htons (sizeof (struct RedirectToIpResponseMessage) + rlen);
+  res->header.type = htons (GNUNET_MESSAGE_TYPE_VPN_CLIENT_USE_IP);
+  res->result_af = htonl (result_af);
+  res->request_id = request_id;
+  memcpy (&res[1], addr, rlen);
+  GNUNET_SERVER_notification_context_add (nc, client);
+  GNUNET_SERVER_notification_context_unicast (nc,
+                                             client,
+                                             &res->header,
+                                             GNUNET_NO);
+}
+
+
+/**
+ * Method called whenever a peer has disconnected from the tunnel.
+ *
+ * @param cls closure
+ * @param peer peer identity the tunnel stopped working with
+ */
+static void
+tunnel_peer_disconnect_handler (void *cls,
+                               const struct
+                               GNUNET_PeerIdentity * peer)
+{
+  struct TunnelState *ts = cls;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             "Peer %s disconnected from tunnel.\n",
+             GNUNET_i2s (peer));
+  GNUNET_STATISTICS_update (stats,
+                           gettext_noop ("# Peers connected to mesh tunnels"),
+                           -1, GNUNET_NO);
+  if (NULL != ts->th)
+  {
+    GNUNET_MESH_notify_transmit_ready_cancel (ts->th);
+    ts->th = NULL;
+  }
+  if (ts->destination.is_service)
+    return; /* hope for reconnect eventually */
+  /* as we are most likely going to change the exit node now,
+     we should just destroy the tunnel entirely... */
+  GNUNET_MESH_tunnel_destroy (ts->tunnel);
+}
+
+
+/**
+ * Method called whenever a peer has connected to the tunnel.  Notifies
+ * the waiting client that the tunnel is now up.
+ *
+ * @param cls closure
+ * @param peer peer identity the tunnel was created to, NULL on timeout
+ * @param atsi performance data for the connection
+ */
+static void
+tunnel_peer_connect_handler (void *cls,
+                            const struct GNUNET_PeerIdentity
+                            * peer,
+                            const struct
+                            GNUNET_ATS_Information * atsi)
+{
+  struct TunnelState *ts = cls;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             "Peer %s connected to tunnel.\n",
+             GNUNET_i2s (peer));
+  GNUNET_STATISTICS_update (stats,
+                           gettext_noop ("# Peers connected to mesh tunnels"),
+                           1, GNUNET_NO);
+  if (NULL == ts->client)
+    return; /* nothing to do */
+  send_client_reply (ts->client,
+                    ts->request_id,
+                    ts->af,
+                    &ts->destination_ip);
+  GNUNET_SERVER_client_drop (ts->client);
+  ts->client = NULL;
+}
+
+
 /**
  * Send a message from the message queue via mesh.
  *
@@ -381,6 +571,9 @@ send_to_peer_notify_callback (void *cls, size_t size, void *buf)
   tnq = ts->head;
   GNUNET_assert (NULL != tnq);
   GNUNET_assert (size >= tnq->len);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             "Sending %u bytes via mesh tunnel\n",
+             tnq->len);
   GNUNET_CONTAINER_DLL_remove (ts->head,
                               ts->tail,
                               tnq);
@@ -388,7 +581,7 @@ send_to_peer_notify_callback (void *cls, size_t size, void *buf)
   ret = tnq->len;
   GNUNET_free (tnq);
   if (NULL != (tnq = ts->head))
-    ts->th = GNUNET_MESH_notify_transmit_ready (ts->destination.tunnel, 
+    ts->th = GNUNET_MESH_notify_transmit_ready (ts->tunnel, 
                                                GNUNET_NO /* cork */, 
                                                42 /* priority */,
                                                GNUNET_TIME_UNIT_FOREVER_REL,
@@ -396,26 +589,34 @@ send_to_peer_notify_callback (void *cls, size_t size, void *buf)
                                                tnq->len,
                                                &send_to_peer_notify_callback,
                                                ts);
+  GNUNET_STATISTICS_update (stats,
+                           gettext_noop ("# Bytes given to mesh for transmission"),
+                           ret, GNUNET_NO);
   return ret;
 }
 
 
 /**
- * Add the given message to the given tunnel and
- * trigger the transmission process.
+ * Add the given message to the given tunnel and trigger the
+ * transmission process.
+ *
+ * FIXME: bound queue length!
  *
  * @param tnq message to queue
  * @param ts tunnel to queue the message for
  */
 static void
 send_to_tunnel (struct TunnelMessageQueueEntry *tnq,
-                  struct TunnelState *ts)
+               struct TunnelState *ts)
 {
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             "Queueing %u bytes for transmission via mesh tunnel\n",
+             tnq->len);
   GNUNET_CONTAINER_DLL_insert_tail (ts->head,
                                    ts->tail,
                                    tnq);
   if (NULL == ts->th)
-    ts->th = GNUNET_MESH_notify_transmit_ready (ts->destination.tunnel, 
+    ts->th = GNUNET_MESH_notify_transmit_ready (ts->tunnel, 
                                                GNUNET_NO /* cork */,
                                                42 /* priority */,
                                                GNUNET_TIME_UNIT_FOREVER_REL,
@@ -426,6 +627,78 @@ send_to_tunnel (struct TunnelMessageQueueEntry *tnq,
 }
 
 
+/**
+ * Initialize the given destination entry's mesh tunnel.
+ *
+ * @param de destination entry for which we need to setup a tunnel
+ * @param client client to notify on successful tunnel setup, or NULL for none
+ * @param request_id request ID to send in client notification (unused if client is NULL)
+ * @return tunnel state of the tunnel that was created
+ */
+static struct TunnelState *
+create_tunnel_to_destination (struct DestinationEntry *de,
+                             struct GNUNET_SERVER_Client *client,
+                             uint64_t request_id)
+{
+  struct TunnelState *ts;
+
+  GNUNET_STATISTICS_update (stats,
+                           gettext_noop ("# Mesh tunnels created"),
+                           1, GNUNET_NO);
+  GNUNET_assert (NULL == de->ts);
+  ts = GNUNET_malloc (sizeof (struct TunnelState));
+  if (NULL != client)
+  {
+    ts->request_id = request_id;
+    ts->client = client;
+    GNUNET_SERVER_client_keep (client);
+  }
+  ts->destination = *de;
+  ts->destination.heap_node = NULL; /* copy is NOT in destination heap */
+  de->ts = ts;
+  ts->destination_container = de; /* we are referenced from de */
+  ts->af = AF_UNSPEC; /* so far, unknown */
+  ts->tunnel = GNUNET_MESH_tunnel_create (mesh_handle,
+                                         ts,
+                                         &tunnel_peer_connect_handler,
+                                         &tunnel_peer_disconnect_handler,
+                                         ts);
+  if (de->is_service)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+               "Creating tunnel to peer %s offering service %s\n",
+               GNUNET_i2s (&de->details.service_destination.target),
+               GNUNET_h2s (&de->details.service_destination.service_descriptor));
+    GNUNET_MESH_peer_request_connect_add (ts->tunnel,
+                                         &de->details.service_destination.target);  
+  }
+  else
+  {
+    switch (de->details.exit_destination.af)
+    {
+    case AF_INET:
+      GNUNET_MESH_peer_request_connect_by_type (ts->tunnel,
+                                               GNUNET_APPLICATION_TYPE_IPV4_GATEWAY);
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                 "Creating tunnel to exit peer for %s\n",
+                 "IPv4");
+     break;
+    case AF_INET6:
+      GNUNET_MESH_peer_request_connect_by_type (ts->tunnel,
+                                               GNUNET_APPLICATION_TYPE_IPV6_GATEWAY);
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                 "Creating tunnel to exit peer for %s\n",
+                 "IPv6");
+      break;
+    default:
+      GNUNET_assert (0);
+      break;
+    }
+  }  
+  return ts;
+}
+
+
 /**
  * Route a packet via mesh to the given destination.  
  *
@@ -449,13 +722,18 @@ route_packet (struct DestinationEntry *destination,
   GNUNET_HashCode key;
   struct TunnelState *ts;
   struct TunnelMessageQueueEntry *tnq;
-                  
+  size_t alen;
+  size_t mlen;
+  int is_new;
+  const struct udp_packet *udp;
+  const struct tcp_packet *tcp;
+  uint16_t spt;
+  uint16_t dpt;
+
   switch (protocol)
   {
   case IPPROTO_UDP:
     {
-      const struct udp_packet *udp;
-
       if (payload_length < sizeof (struct udp_packet))
       {
        /* blame kernel? */
@@ -463,19 +741,19 @@ route_packet (struct DestinationEntry *destination,
        return;
       }
       udp = payload;
+      spt = ntohs (udp->spt);
+      dpt = ntohs (udp->dpt);
       get_tunnel_key_from_ips (af,
                               IPPROTO_UDP,
                               source_ip,
-                              ntohs (udp->spt),
+                              spt,
                               destination_ip,
-                              ntohs (udp->dpt),
+                              dpt,
                               &key);
     }
     break;
   case IPPROTO_TCP:
     {
-      const struct tcp_packet *tcp;
-
       if (payload_length < sizeof (struct tcp_packet))
       {
        /* blame kernel? */
@@ -483,12 +761,14 @@ route_packet (struct DestinationEntry *destination,
        return;
       }
       tcp = payload;
+      spt = ntohs (tcp->spt);
+      dpt = ntohs (tcp->dpt);
       get_tunnel_key_from_ips (af,
                               IPPROTO_TCP,
                               source_ip,
-                              ntohs (tcp->spt),
+                              spt,
                               destination_ip,
-                              ntohs (tcp->dpt),
+                              dpt,
                               &key);
     }
     break;
@@ -498,25 +778,107 @@ route_packet (struct DestinationEntry *destination,
                (unsigned int) protocol);
     return;
   }
+  if (! destination->is_service)
+  {  
+    switch (destination->details.exit_destination.af)
+    {
+    case AF_INET:
+      alen = sizeof (struct in_addr);
+     break;
+    case AF_INET6:
+      alen = sizeof (struct in6_addr);
+      break;
+    default:
+      alen = 0;
+      GNUNET_assert (0);
+    }
+
+    {
+      char sbuf[INET6_ADDRSTRLEN];
+      char dbuf[INET6_ADDRSTRLEN];
+      char xbuf[INET6_ADDRSTRLEN];
+      
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                 "Routing %s packet from %s:%u -> %s:%u to destination %s:%u\n",
+                 (protocol == IPPROTO_TCP) ? "TCP" : "UDP",
+                 inet_ntop (af, source_ip, sbuf, sizeof (sbuf)),
+                 spt,
+                 inet_ntop (af, destination_ip, dbuf, sizeof (dbuf)),
+                 dpt,
+                 inet_ntop (destination->details.exit_destination.af,
+                            &destination->details.exit_destination.ip,
+                            xbuf, sizeof (xbuf)));
+    }
+  }
+  else
+  {
+    /* make compiler happy */
+    alen = 0;
+    {
+      char sbuf[INET6_ADDRSTRLEN];
+      char dbuf[INET6_ADDRSTRLEN];
+      
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                 "Routing %s packet from %s:%u -> %s:%u to service %s at peer %s\n",
+                 (protocol == IPPROTO_TCP) ? "TCP" : "UDP",
+                 inet_ntop (af, source_ip, sbuf, sizeof (sbuf)),
+                 spt,
+                 inet_ntop (af, destination_ip, dbuf, sizeof (dbuf)),
+                 dpt,
+                 GNUNET_h2s (&destination->details.service_destination.service_descriptor),
+                 GNUNET_i2s (&destination->details.service_destination.target));
+    }
+
+  }
 
-  /* find tunnel */
+  /* see if we have an existing tunnel for this destination */
   ts = GNUNET_CONTAINER_multihashmap_get (tunnel_map,
                                          &key);
   if (NULL == ts)
   {
-    /* create new tunnel */
-    // FIXME: create tunnel!
-#if 0
-            *cls =
-                GNUNET_MESH_tunnel_create (mesh_handle,
-                                           initialize_tunnel_state (16, NULL),
-                                           &send_pkt_to_peer, NULL, cls);
-
-            GNUNET_MESH_peer_request_connect_add (*cls,
-                                                  (struct GNUNET_PeerIdentity *)
-                                                  &me->desc);
-            me->tunnel = *cls;
-#endif
+    /* need to either use the existing tunnel from the destination (if still
+       available) or create a fresh one */
+    is_new = GNUNET_YES;
+    if (NULL == destination->ts)
+      ts = create_tunnel_to_destination (destination, NULL, 0);
+    else
+      ts = destination->ts;
+    destination->ts = NULL;
+    ts->destination_container = NULL; /* no longer 'contained' */
+    /* now bind existing "unbound" tunnel to our IP/port tuple */
+    ts->protocol = protocol;
+    ts->af = af; 
+    if (af == AF_INET)
+    {
+      ts->source_ip.v4 = * (const struct in_addr *) source_ip;
+      ts->destination_ip.v4 = * (const struct in_addr *) destination_ip;
+    }
+    else
+    {
+      ts->source_ip.v6 = * (const struct in6_addr *) source_ip;
+      ts->destination_ip.v6 = * (const struct in6_addr *) destination_ip;
+    }
+    ts->source_port = spt;
+    ts->destination_port = dpt;
+    ts->heap_node = GNUNET_CONTAINER_heap_insert (tunnel_heap,
+                                                 ts,
+                                                 GNUNET_TIME_absolute_get ().abs_value);
+    GNUNET_assert (GNUNET_YES ==
+                  GNUNET_CONTAINER_multihashmap_put (tunnel_map,
+                                                     &key,
+                                                     ts,
+                                                     GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY)); 
+    GNUNET_STATISTICS_update (stats,
+                             gettext_noop ("# Active tunnels"),
+                             1, GNUNET_NO);
+    /* FIXME: expire OLD tunnels if we have too many! */
+  }
+  else
+  {
+    is_new = GNUNET_NO;
+    GNUNET_CONTAINER_heap_update_cost (tunnel_heap, 
+                                      ts->heap_node,
+                                      GNUNET_TIME_absolute_get ().abs_value);
   }
   
   /* send via tunnel */
@@ -525,26 +887,166 @@ route_packet (struct DestinationEntry *destination,
   case IPPROTO_UDP:
     if (destination->is_service)
     {
-      tnq = GNUNET_malloc (sizeof (struct TunnelMessageQueueEntry) + 42);
-      // FIXME: build message!
+      struct GNUNET_EXIT_UdpServiceMessage *usm;
+
+      mlen = sizeof (struct GNUNET_EXIT_UdpServiceMessage) + 
+       payload_length - sizeof (struct udp_packet);
+      if (mlen >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
+      {
+       GNUNET_break (0);
+       return;
+      }
+      tnq = GNUNET_malloc (sizeof (struct TunnelMessageQueueEntry) + mlen);
+      tnq->len = mlen;
+      tnq->msg = &tnq[1];
+      usm = (struct GNUNET_EXIT_UdpServiceMessage *) &tnq[1];
+      usm->header.size = htons ((uint16_t) mlen);
+      usm->header.type = htons (GNUNET_MESSAGE_TYPE_VPN_UDP_TO_SERVICE);
+      /* if the source port is below 32000, we assume it has a special
+        meaning; if not, we pick a random port (this is a heuristic) */
+      usm->source_port = (ntohs (udp->spt) < 32000) ? udp->spt : 0;
+      usm->destination_port = udp->dpt;
+      usm->service_descriptor = destination->details.service_destination.service_descriptor;
+      memcpy (&usm[1],
+             &udp[1],
+             payload_length - sizeof (struct udp_packet));
     }
     else
     {
-      tnq = GNUNET_malloc (sizeof (struct TunnelMessageQueueEntry) + 42);
-      // FIXME: build message!
+      struct GNUNET_EXIT_UdpInternetMessage *uim;
+      struct in_addr *ip4dst;
+      struct in6_addr *ip6dst;
+      void *payload;
+
+      mlen = sizeof (struct GNUNET_EXIT_UdpInternetMessage) + 
+       alen + payload_length - sizeof (struct udp_packet);
+      if (mlen >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
+      {
+       GNUNET_break (0);
+       return;
+      }
+      tnq = GNUNET_malloc (sizeof (struct TunnelMessageQueueEntry) + 
+                          mlen);
+      tnq->len = mlen;
+      tnq->msg = &tnq[1];
+      uim = (struct GNUNET_EXIT_UdpInternetMessage *) &tnq[1];
+      uim->header.size = htons ((uint16_t) mlen);
+      uim->header.type = htons (GNUNET_MESSAGE_TYPE_VPN_UDP_TO_INTERNET); 
+      uim->af = htonl (destination->details.exit_destination.af);
+      uim->source_port = (ntohs (udp->spt) < 32000) ? udp->spt : 0;
+      uim->destination_port = udp->dpt;
+      switch (destination->details.exit_destination.af)
+      {
+      case AF_INET:
+       ip4dst = (struct in_addr *) &uim[1];
+       *ip4dst = destination->details.exit_destination.ip.v4;
+       payload = &ip4dst[1];
+       break;
+      case AF_INET6:
+       ip6dst = (struct in6_addr *) &uim[1];
+       *ip6dst = destination->details.exit_destination.ip.v6;
+       payload = &ip6dst[1];
+       break;
+      default:
+       GNUNET_assert (0);
+      }
+      memcpy (payload,
+             &udp[1],
+             payload_length - sizeof (struct udp_packet));
     }
     break;
   case IPPROTO_TCP:
-    if (destination->is_service)
+    if (is_new)
     {
-      tnq = GNUNET_malloc (sizeof (struct TunnelMessageQueueEntry) + 42);
-      // FIXME: build message!
+      if (destination->is_service)
+      {
+       struct GNUNET_EXIT_TcpServiceStartMessage *tsm;
+
+       mlen = sizeof (struct GNUNET_EXIT_TcpServiceStartMessage) + 
+         payload_length - sizeof (struct tcp_packet);
+       if (mlen >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
+       {
+         GNUNET_break (0);
+         return;
+       }
+       tnq = GNUNET_malloc (sizeof (struct TunnelMessageQueueEntry) + mlen);
+       tnq->len = mlen;
+       tnq->msg = &tnq[1];
+       tsm = (struct  GNUNET_EXIT_TcpServiceStartMessage *) &tnq[1];
+       tsm->header.size = htons ((uint16_t) mlen);
+       tsm->header.type = htons (GNUNET_MESSAGE_TYPE_VPN_TCP_TO_SERVICE_START);
+       tsm->reserved = htonl (0);
+       tsm->service_descriptor = destination->details.service_destination.service_descriptor;
+       tsm->tcp_header = *tcp;
+       memcpy (&tsm[1],
+               &tcp[1],
+               payload_length - sizeof (struct tcp_packet));
+      }
+      else
+      {
+       struct GNUNET_EXIT_TcpInternetStartMessage *tim;
+       struct in_addr *ip4dst;
+       struct in6_addr *ip6dst;
+       void *payload;
+
+       mlen = sizeof (struct GNUNET_EXIT_TcpInternetStartMessage) + 
+         alen + payload_length - sizeof (struct tcp_packet);
+       if (mlen >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
+       {
+         GNUNET_break (0);
+         return;
+       }
+       tnq = GNUNET_malloc (sizeof (struct TunnelMessageQueueEntry) + mlen);
+       tnq->len = mlen;
+       tnq->msg = &tnq[1];
+       tim = (struct  GNUNET_EXIT_TcpInternetStartMessage *) &tnq[1];
+       tim->header.size = htons ((uint16_t) mlen);
+       tim->header.type = htons (GNUNET_MESSAGE_TYPE_VPN_TCP_TO_INTERNET_START);
+       tim->af = htonl (destination->details.exit_destination.af);     
+       tim->tcp_header = *tcp;
+       switch (destination->details.exit_destination.af)
+       {
+       case AF_INET:
+         ip4dst = (struct in_addr *) &tim[1];
+         *ip4dst = destination->details.exit_destination.ip.v4;
+         payload = &ip4dst[1];
+         break;
+       case AF_INET6:
+         ip6dst = (struct in6_addr *) &tim[1];
+         *ip6dst = destination->details.exit_destination.ip.v6;
+         payload = &ip6dst[1];
+         break;
+       default:
+         GNUNET_assert (0);
+       }
+       memcpy (payload,
+               &tcp[1],
+               payload_length - sizeof (struct tcp_packet));
+      }
     }
     else
     {
-      tnq = GNUNET_malloc (sizeof (struct TunnelMessageQueueEntry) + 42);
-      // FIXME: build message!
-    }
+      struct GNUNET_EXIT_TcpDataMessage *tdm;
+
+      mlen = sizeof (struct GNUNET_EXIT_TcpDataMessage) + 
+       alen + payload_length - sizeof (struct tcp_packet);
+      if (mlen >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
+      {
+       GNUNET_break (0);
+       return;
+      }
+      tnq = GNUNET_malloc (sizeof (struct TunnelMessageQueueEntry) + mlen);
+      tnq->len = mlen;
+      tnq->msg = &tnq[1];
+      tdm = (struct  GNUNET_EXIT_TcpDataMessage *) &tnq[1];
+      tdm->header.size = htons ((uint16_t) mlen);
+      tdm->header.type = htons (GNUNET_MESSAGE_TYPE_VPN_TCP_DATA);
+      tdm->reserved = htonl (0);
+      tdm->tcp_header = *tcp;
+      memcpy (&tdm[1],
+             &tcp[1],
+             payload_length - sizeof (struct tcp_packet));
+     }
     break;
   default:
     /* not supported above, how can we get here !? */
@@ -555,7 +1057,6 @@ route_packet (struct DestinationEntry *destination,
 }
 
 
-
 /**
  * Receive packets from the helper-process (someone send to the local
  * virtual tunnel interface).  Find the destination mapping, and if it
@@ -575,6 +1076,9 @@ message_token (void *cls GNUNET_UNUSED, void *client GNUNET_UNUSED,
   GNUNET_HashCode key;
   struct DestinationEntry *de;
 
+  GNUNET_STATISTICS_update (stats,
+                           gettext_noop ("# Packets received from TUN interface"),
+                           1, GNUNET_NO);
   mlen = ntohs (message->size);
   if ( (ntohs (message->type) != GNUNET_MESSAGE_TYPE_VPN_HELPER) ||
        (mlen < sizeof (struct GNUNET_MessageHeader) + sizeof (struct tun_header)) )
@@ -601,7 +1105,11 @@ message_token (void *cls GNUNET_UNUSED, void *client GNUNET_UNUSED,
                                   &pkt6->destination_address,
                                   &key);
       de = GNUNET_CONTAINER_multihashmap_get (destination_map, &key);
-      /* FIXME: do we need to guard against hash collision? */
+      /* FIXME: do we need to guard against hash collision? 
+        (if so, we need to also store the local destination IP in the
+        destination entry and then compare here; however, the risk
+        of collision seems minimal AND the impact is unlikely to be
+        super-problematic as well... */
       if (NULL == de)
       {
        char buf[INET6_ADDRSTRLEN];
@@ -638,7 +1146,11 @@ message_token (void *cls GNUNET_UNUSED, void *client GNUNET_UNUSED,
                                   &pkt4->destination_address,
                                   &key);
       de = GNUNET_CONTAINER_multihashmap_get (destination_map, &key);
-      /* FIXME: do we need to guard against hash collision? */
+      /* FIXME: do we need to guard against hash collision? 
+        (if so, we need to also store the local destination IP in the
+        destination entry and then compare here; however, the risk
+        of collision seems minimal AND the impact is unlikely to be
+        super-problematic as well... */
       if (NULL == de)
       {
        char buf[INET_ADDRSTRLEN];
@@ -694,170 +1206,165 @@ receive_udp_back (void *cls GNUNET_UNUSED, struct GNUNET_MESH_Tunnel *tunnel,
                   const struct GNUNET_MessageHeader *message,
                   const struct GNUNET_ATS_Information *atsi GNUNET_UNUSED)
 {
-  // FIXME: parse message, build IP packet, give to TUN!
-#if 0
-  GNUNET_HashCode *desc = (GNUNET_HashCode *) (message + 1);
-  struct remote_addr *s = (struct remote_addr *) desc;
-  struct udp_pkt *pkt = (struct udp_pkt *) (desc + 1);
-  const struct GNUNET_PeerIdentity *other = sender;
   struct TunnelState *ts = *tunnel_ctx;
+  const struct GNUNET_EXIT_UdpReplyMessage *reply;
+  size_t mlen;
 
-  if (16 == ts->addrlen)
+  GNUNET_STATISTICS_update (stats,
+                           gettext_noop ("# UDP packets received from mesh"),
+                           1, GNUNET_NO);
+  mlen = ntohs (message->size);
+  if (mlen < sizeof (struct GNUNET_EXIT_UdpReplyMessage))
   {
-    size_t size =
-        sizeof (struct ip6_udp) + ntohs (pkt->len) - 1 -
-        sizeof (struct udp_pkt);
-
-    struct ip6_udp *pkt6 = alloca (size);
-
-    GNUNET_assert (pkt6 != NULL);
-
-    if (ntohs (message->type) == GNUNET_MESSAGE_TYPE_VPN_SERVICE_UDP_BACK)
-      new_ip6addr (&pkt6->ip6_hdr.sadr, &other->hashPubKey, desc);
-    else
-      new_ip6addr_remote (&pkt6->ip6_hdr.sadr, s->addr, s->addrlen);
-
-    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                "Relaying calc:%d gnu:%d udp:%d bytes!\n", size,
-                ntohs (message->size), ntohs (pkt->len));
-
-    pkt6->shdr.type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
-    pkt6->shdr.size = htons (size);
-
-    pkt6->tun.flags = 0;
-    pkt6->tun.type = htons (0x86dd);
-
-    pkt6->ip6_hdr.version = 6;
-    pkt6->ip6_hdr.tclass_h = 0;
-    pkt6->ip6_hdr.tclass_l = 0;
-    pkt6->ip6_hdr.flowlbl = 0;
-    pkt6->ip6_hdr.paylgth = pkt->len;
-    pkt6->ip6_hdr.nxthdr = IPPROTO_UDP;
-    pkt6->ip6_hdr.hoplmt = 0xff;
-
-    {
-      char *ipv6addr;
-
-      GNUNET_assert (GNUNET_OK ==
-                     GNUNET_CONFIGURATION_get_value_string (cfg, "vpn",
-                                                            "IPV6ADDR",
-                                                            &ipv6addr));
-      inet_pton (AF_INET6, ipv6addr, &pkt6->ip6_hdr.dadr);
-      GNUNET_free (ipv6addr);
-    }
-    memcpy (&pkt6->udp_hdr, pkt, ntohs (pkt->len));
-
-    GNUNET_HashCode *key = address6_mapping_exists (&pkt6->ip6_hdr.sadr);
-
-    GNUNET_assert (key != NULL);
-
-    struct map_entry *me = GNUNET_CONTAINER_multihashmap_get (hashmap, key);
-
-    GNUNET_CONTAINER_heap_update_cost (heap, me->heap_node,
-                                       GNUNET_TIME_absolute_get ().abs_value);
-
-    GNUNET_free (key);
-
-    GNUNET_assert (me != NULL);
-
-    pkt6->udp_hdr.crc = 0;
-    uint32_t sum = 0;
-
-    sum =
-        GNUNET_CRYPTO_crc16_step (sum, (uint16_t *) & pkt6->ip6_hdr.sadr, 16);
-    sum =
-        GNUNET_CRYPTO_crc16_step (sum, (uint16_t *) & pkt6->ip6_hdr.dadr, 16);
-    uint32_t tmp = (pkt6->udp_hdr.len & 0xffff);
-
-    sum = GNUNET_CRYPTO_crc16_step (sum, (uint16_t *) & tmp, 4);
-    tmp = htons (((pkt6->ip6_hdr.nxthdr & 0x00ff)));
-    sum = GNUNET_CRYPTO_crc16_step (sum, (uint16_t *) & tmp, 4);
-
-    sum =
-        GNUNET_CRYPTO_crc16_step (sum, (uint16_t *) & pkt6->udp_hdr,
-                                   ntohs (pkt->len));
-    pkt6->udp_hdr.crc = GNUNET_CRYPTO_crc16_finish (sum);
-    
-    (void) GNUNET_HELPER_send (helper_handle,
-                              &pkt6->shdr,
-                              GNUNET_YES,
-                              NULL, NULL);
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
   }
-  else
+  if (NULL == ts->heap_node)
   {
-    size_t size =
-        sizeof (struct ip_udp) + ntohs (pkt->len) - 1 - sizeof (struct udp_pkt);
-
-    struct ip_udp *pkt4 = alloca (size);
-
-    GNUNET_assert (pkt4 != NULL);
-
-    GNUNET_assert (ntohs (message->type) ==
-                   GNUNET_MESSAGE_TYPE_VPN_REMOTE_UDP_BACK);
-    uint32_t sadr;
-
-    new_ip4addr_remote ((unsigned char *) &sadr, s->addr, s->addrlen);
-    pkt4->ip_hdr.sadr.s_addr = sadr;
-
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
+  }
+  if (AF_UNSPEC == ts->af)
+  {
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
+  }
+  reply = (const struct GNUNET_EXIT_UdpReplyMessage *) message;
+  mlen -= sizeof (struct GNUNET_EXIT_UdpReplyMessage);
+  {
+    char sbuf[INET6_ADDRSTRLEN];
+    char dbuf[INET6_ADDRSTRLEN];
+    
     GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                "Relaying calc:%d gnu:%d udp:%d bytes!\n", size,
-                ntohs (message->size), ntohs (pkt->len));
-
-    pkt4->shdr.type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
-    pkt4->shdr.size = htons (size);
-
-    pkt4->tun.flags = 0;
-    pkt4->tun.type = htons (0x0800);
-
-    pkt4->ip_hdr.version = 4;
-    pkt4->ip_hdr.hdr_lngth = 5;
-    pkt4->ip_hdr.diff_serv = 0;
-    pkt4->ip_hdr.tot_lngth = htons (20 + ntohs (pkt->len));
-    pkt4->ip_hdr.ident = 0;
-    pkt4->ip_hdr.flags = 0;
-    pkt4->ip_hdr.frag_off = 0;
-    pkt4->ip_hdr.ttl = 255;
-    pkt4->ip_hdr.proto = IPPROTO_UDP;
-    pkt4->ip_hdr.chks = 0;      /* Will be calculated later */
-
+               "Received UDP reply from mesh, sending %u bytes from %s:%u -> %s:%u via TUN\n",
+               (unsigned int) mlen,
+               inet_ntop (ts->af, &ts->destination_ip, sbuf, sizeof (sbuf)),
+               ts->destination_port,
+               inet_ntop (ts->af, &ts->source_ip, dbuf, sizeof (dbuf)),
+               ts->source_port);
+  }
+  switch (ts->af)
+  {
+  case AF_INET:
     {
-      char *ipv4addr;
-      uint32_t dadr;
-
-      GNUNET_assert (GNUNET_OK ==
-                     GNUNET_CONFIGURATION_get_value_string (cfg, "vpn",
-                                                            "IPV4ADDR",
-                                                            &ipv4addr));
-      inet_pton (AF_INET, ipv4addr, &dadr);
-      GNUNET_free (ipv4addr);
-      pkt4->ip_hdr.dadr.s_addr = dadr;
+      size_t size = sizeof (struct ip4_header) 
+       + sizeof (struct udp_packet) 
+       + sizeof (struct GNUNET_MessageHeader) +
+       sizeof (struct tun_header) +
+       mlen;
+      {
+       char buf[size];
+       struct GNUNET_MessageHeader *msg = (struct GNUNET_MessageHeader *) buf;
+       struct tun_header *tun = (struct tun_header*) &msg[1];
+       struct ip4_header *ipv4 = (struct ip4_header *) &tun[1];
+       struct udp_packet *udp = (struct udp_packet *) &ipv4[1];
+       msg->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
+       msg->size = htons (size);
+       tun->flags = htons (0);
+       tun->proto = htons (ETH_P_IPV4);
+       ipv4->version = 4;
+       ipv4->header_length = sizeof (struct ip4_header) / 4;
+       ipv4->diff_serv = 0;
+       ipv4->total_length = htons (sizeof (struct ip4_header) +
+                                   sizeof (struct udp_packet) +
+                                   mlen);
+       ipv4->identification = (uint16_t) GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK, 
+                                                                   UINT16_MAX + 1);
+       ipv4->flags = 0;
+       ipv4->fragmentation_offset = 0;
+       ipv4->ttl = 255;
+       ipv4->protocol = IPPROTO_UDP;
+       ipv4->checksum = 0; 
+       ipv4->source_address = ts->destination_ip.v4;
+       ipv4->destination_address = ts->source_ip.v4;
+       ipv4->checksum =
+         GNUNET_CRYPTO_crc16_n (ipv4, sizeof (struct ip4_header));
+       if (0 == ntohs (reply->source_port))
+         udp->spt = htons (ts->destination_port);
+       else
+         udp->spt = reply->source_port;
+       if (0 == ntohs (reply->destination_port))
+         udp->dpt = htons (ts->source_port);
+       else
+         udp->dpt = reply->destination_port;
+       udp->len = htons (mlen + sizeof (struct udp_packet));
+       udp->crc = 0; // FIXME: optional, but we might want to calculate this one anyway
+       memcpy (&udp[1],
+               &reply[1],
+               mlen);
+       (void) GNUNET_HELPER_send (helper_handle,
+                                  msg,
+                                  GNUNET_YES,
+                                  NULL, NULL);
+      }
     }
-    memcpy (&pkt4->udp_hdr, pkt, ntohs (pkt->len));
-
-    GNUNET_HashCode *key = address4_mapping_exists (pkt4->ip_hdr.sadr.s_addr);
-
-    GNUNET_assert (key != NULL);
-
-    struct map_entry *me = GNUNET_CONTAINER_multihashmap_get (hashmap, key);
-
-    GNUNET_CONTAINER_heap_update_cost (heap, me->heap_node,
-                                       GNUNET_TIME_absolute_get ().abs_value);
-
-    GNUNET_free (key);
-
-    GNUNET_assert (me != NULL);
-
-    pkt4->udp_hdr.crc = 0;      /* Optional for IPv4 */
-
-    pkt4->ip_hdr.chks =
-        GNUNET_CRYPTO_crc16_n ((uint16_t *) & pkt4->ip_hdr, 5 * 4);
-
-    (void) GNUNET_HELPER_send (helper_handle,
-                              &pkt4->shdr,
-                              GNUNET_YES,
-                              NULL, NULL);
+    break;
+  case AF_INET6:
+    {
+      size_t size = sizeof (struct ip6_header) 
+       + sizeof (struct udp_packet) 
+       + sizeof (struct GNUNET_MessageHeader) +
+       sizeof (struct tun_header) +
+       mlen;
+      {
+       char buf[size];
+       struct GNUNET_MessageHeader *msg = (struct GNUNET_MessageHeader *) buf;
+       struct tun_header *tun = (struct tun_header*) &msg[1];
+       struct ip6_header *ipv6 = (struct ip6_header *) &tun[1];
+       struct udp_packet *udp = (struct udp_packet *) &ipv6[1];
+       msg->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
+       msg->size = htons (size);
+       tun->flags = htons (0);
+       tun->proto = htons (ETH_P_IPV6);
+       ipv6->traffic_class_h = 0;
+       ipv6->version = 6;
+       ipv6->traffic_class_l = 0;
+       ipv6->flow_label = 0;
+       ipv6->payload_length = htons (sizeof (struct udp_packet) + sizeof (struct ip6_header) + mlen);
+       ipv6->next_header = IPPROTO_UDP;
+       ipv6->hop_limit = 255;
+       ipv6->source_address = ts->destination_ip.v6;
+       ipv6->destination_address = ts->source_ip.v6;
+       if (0 == ntohs (reply->source_port))
+         udp->spt = htons (ts->destination_port);
+       else
+         udp->spt = reply->source_port;
+       if (0 == ntohs (reply->destination_port))
+         udp->dpt = htons (ts->source_port);
+       else
+         udp->dpt = reply->destination_port;
+       udp->len = htons (mlen + sizeof (struct udp_packet));
+       udp->crc = 0;
+       memcpy (&udp[1],
+               &reply[1],
+               mlen);
+       {
+         uint32_t sum = 0;
+         sum =
+           GNUNET_CRYPTO_crc16_step (sum, &ipv6->source_address, 
+                                     sizeof (struct in6_addr) * 2);
+         uint32_t tmp = udp->len;
+         sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t));
+         tmp = htons (IPPROTO_UDP);
+         sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t));
+         sum = GNUNET_CRYPTO_crc16_step (sum, 
+                                         udp,
+                                         ntohs (udp->len));
+         udp->crc = GNUNET_CRYPTO_crc16_finish (sum);
+       }
+       (void) GNUNET_HELPER_send (helper_handle,
+                                  msg,
+                                  GNUNET_YES,
+                                  NULL, NULL);
+      }
+    }
+    break;
+  default:
+    GNUNET_assert (0);
   }
-#endif
+  GNUNET_CONTAINER_heap_update_cost (tunnel_heap, 
+                                    ts->heap_node,
+                                    GNUNET_TIME_absolute_get ().abs_value);
   return GNUNET_OK;
 }
 
@@ -882,185 +1389,267 @@ receive_tcp_back (void *cls GNUNET_UNUSED, struct GNUNET_MESH_Tunnel *tunnel,
                   const struct GNUNET_MessageHeader *message,
                   const struct GNUNET_ATS_Information *atsi GNUNET_UNUSED)
 {
-  // FIXME: parse message, build IP packet, give to TUN!
-#if 0
-  GNUNET_HashCode *desc = (GNUNET_HashCode *) (message + 1);
-  struct remote_addr *s = (struct remote_addr *) desc;
-  struct tcp_pkt *pkt = (struct tcp_pkt *) (desc + 1);
-  const struct GNUNET_PeerIdentity *other = sender;
   struct TunnelState *ts = *tunnel_ctx;
+  const struct GNUNET_EXIT_TcpDataMessage *data;
+  size_t mlen;
 
-  size_t pktlen =
-      ntohs (message->size) - sizeof (struct GNUNET_MessageHeader) -
-      sizeof (GNUNET_HashCode);
-
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "Received TCP-Packet back, addrlen = %d\n", s->addrlen);
-
-  if (ntohs (message->type) == GNUNET_MESSAGE_TYPE_VPN_SERVICE_TCP_BACK ||
-      ts->addrlen == 16)
+  GNUNET_STATISTICS_update (stats,
+                           gettext_noop ("# TCP packets received from mesh"),
+                           1, GNUNET_NO);
+  mlen = ntohs (message->size);
+  if (mlen < sizeof (struct GNUNET_EXIT_TcpDataMessage))
   {
-    size_t size = pktlen + sizeof (struct ip6_tcp) - 1;
-
-    struct ip6_tcp *pkt6 = alloca (size);
-
-    memset (pkt6, 0, size);
-
-    GNUNET_assert (pkt6 != NULL);
-
-    if (ntohs (message->type) == GNUNET_MESSAGE_TYPE_VPN_SERVICE_TCP_BACK)
-      new_ip6addr (&pkt6->ip6_hdr.sadr, &other->hashPubKey, desc);
-    else
-      new_ip6addr_remote (&pkt6->ip6_hdr.sadr, s->addr, s->addrlen);
-
-    pkt6->shdr.type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
-    pkt6->shdr.size = htons (size);
-
-    pkt6->tun.flags = 0;
-    pkt6->tun.type = htons (0x86dd);
-
-    pkt6->ip6_hdr.version = 6;
-    pkt6->ip6_hdr.tclass_h = 0;
-    pkt6->ip6_hdr.tclass_l = 0;
-    pkt6->ip6_hdr.flowlbl = 0;
-    pkt6->ip6_hdr.paylgth = htons (pktlen);
-    pkt6->ip6_hdr.nxthdr = IPPROTO_TCP;
-    pkt6->ip6_hdr.hoplmt = 0xff;
-
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
+  }
+  if (NULL == ts->heap_node)
+  {
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
+  }
+  data = (const struct GNUNET_EXIT_TcpDataMessage *) message;
+  mlen -= sizeof (struct GNUNET_EXIT_TcpDataMessage);
+  {
+    char sbuf[INET6_ADDRSTRLEN];
+    char dbuf[INET6_ADDRSTRLEN];
+    
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+               "Received TCP reply from mesh, sending %u bytes from %s:%u -> %s:%u via TUN\n",
+               (unsigned int) mlen,
+               inet_ntop (ts->af, &ts->destination_ip, sbuf, sizeof (sbuf)),
+               ts->destination_port,
+               inet_ntop (ts->af, &ts->source_ip, dbuf, sizeof (dbuf)),
+               ts->source_port);
+  }
+  switch (ts->af)
+  {
+  case AF_INET:
     {
-      char *ipv6addr;
-
-      GNUNET_assert (GNUNET_OK ==
-                     GNUNET_CONFIGURATION_get_value_string (cfg, "vpn",
-                                                            "IPV6ADDR",
-                                                            &ipv6addr));
-      inet_pton (AF_INET6, ipv6addr, &pkt6->ip6_hdr.dadr);
-      GNUNET_free (ipv6addr);
+      size_t size = sizeof (struct ip4_header) 
+       + sizeof (struct tcp_packet) 
+       + sizeof (struct GNUNET_MessageHeader) +
+       sizeof (struct tun_header) +
+       mlen;
+      {
+       char buf[size];
+       struct GNUNET_MessageHeader *msg = (struct GNUNET_MessageHeader *) buf;
+       struct tun_header *tun = (struct tun_header*) &msg[1];
+       struct ip4_header *ipv4 = (struct ip4_header *) &tun[1];
+       struct tcp_packet *tcp = (struct tcp_packet *) &ipv4[1];
+       msg->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
+       msg->size = htons (size);
+       tun->flags = htons (0);
+       tun->proto = htons (ETH_P_IPV4);
+       ipv4->version = 4;
+       ipv4->header_length = sizeof (struct ip4_header) / 4;
+       ipv4->diff_serv = 0;
+       ipv4->total_length = htons (sizeof (struct ip4_header) +
+                                   sizeof (struct tcp_packet) +
+                                   mlen);
+       ipv4->identification = (uint16_t) GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK, 
+                                                                   UINT16_MAX + 1);
+       ipv4->flags = 0;
+       ipv4->fragmentation_offset = 0;
+       ipv4->ttl = 255;
+       ipv4->protocol = IPPROTO_TCP;
+       ipv4->checksum = 0; 
+       ipv4->source_address = ts->destination_ip.v4;
+       ipv4->destination_address = ts->source_ip.v4;
+       ipv4->checksum =
+         GNUNET_CRYPTO_crc16_n (ipv4, sizeof (struct ip4_header));
+       *tcp = data->tcp_header;
+       tcp->spt = htons (ts->destination_port);
+       tcp->dpt = htons (ts->source_port);
+       tcp->crc = 0;
+       memcpy (&tcp[1],
+               &data[1],
+               mlen);
+       {
+         uint32_t sum = 0;
+         uint32_t tmp;
+         
+         sum = GNUNET_CRYPTO_crc16_step (sum, 
+                                         &ipv4->source_address,
+                                         2 * sizeof (struct in_addr));   
+         tmp = htonl ((IPPROTO_TCP << 16) | (mlen + sizeof (struct tcp_packet)));
+         sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t));
+         sum = GNUNET_CRYPTO_crc16_step (sum, tcp, mlen + sizeof (struct tcp_packet));
+         tcp->crc = GNUNET_CRYPTO_crc16_finish (sum);
+       }
+       (void) GNUNET_HELPER_send (helper_handle,
+                                  msg,
+                                  GNUNET_YES,
+                                  NULL, NULL);
+      }
     }
-    memcpy (&pkt6->tcp_hdr, pkt, pktlen);
-
-    GNUNET_HashCode *key = address6_mapping_exists (&pkt6->ip6_hdr.sadr);
-
-    GNUNET_assert (key != NULL);
-
-    struct map_entry *me = GNUNET_CONTAINER_multihashmap_get (hashmap, key);
-
-    GNUNET_CONTAINER_heap_update_cost (heap, me->heap_node,
-                                       GNUNET_TIME_absolute_get ().abs_value);
-
-    GNUNET_free (key);
-
-    GNUNET_assert (me != NULL);
-
-    pkt6->tcp_hdr.crc = 0;
-    uint32_t sum = 0;
-    uint32_t tmp;
-
-    sum =
-        GNUNET_CRYPTO_crc16_step (sum, (uint16_t *) & pkt6->ip6_hdr.sadr, 16);
-    sum =
-        GNUNET_CRYPTO_crc16_step (sum, (uint16_t *) & pkt6->ip6_hdr.dadr, 16);
-    tmp = htonl (pktlen);
-    sum = GNUNET_CRYPTO_crc16_step (sum, (uint16_t *) & tmp, 4);
-    tmp = htonl (((pkt6->ip6_hdr.nxthdr & 0x000000ff)));
-    sum = GNUNET_CRYPTO_crc16_step (sum, (uint16_t *) & tmp, 4);
-
-    sum =
-        GNUNET_CRYPTO_crc16_step (sum, (uint16_t *) & pkt6->tcp_hdr,
-                                   ntohs (pkt6->ip6_hdr.paylgth));
-    pkt6->tcp_hdr.crc = GNUNET_CRYPTO_crc16_finish (sum);
-
-    (void) GNUNET_HELPER_send (helper_handle,
-                              &pkt6->shdr,
-                              GNUNET_YES,
-                              NULL, NULL);
+    break;
+  case AF_INET6:
+    {
+      size_t size = sizeof (struct ip6_header) 
+       + sizeof (struct tcp_packet) 
+       + sizeof (struct GNUNET_MessageHeader) +
+       sizeof (struct tun_header) +
+       mlen;
+      {
+       char buf[size];
+       struct GNUNET_MessageHeader *msg = (struct GNUNET_MessageHeader *) buf;
+       struct tun_header *tun = (struct tun_header*) &msg[1];
+       struct ip6_header *ipv6 = (struct ip6_header *) &tun[1];
+       struct tcp_packet *tcp = (struct tcp_packet *) &ipv6[1];
+       msg->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
+       msg->size = htons (size);
+       tun->flags = htons (0);
+       tun->proto = htons (ETH_P_IPV6);
+       ipv6->traffic_class_h = 0;
+       ipv6->version = 6;
+       ipv6->traffic_class_l = 0;
+       ipv6->flow_label = 0;
+       ipv6->payload_length = htons (sizeof (struct tcp_packet) + sizeof (struct ip6_header) + mlen);
+       ipv6->next_header = IPPROTO_TCP;
+       ipv6->hop_limit = 255;
+       ipv6->source_address = ts->destination_ip.v6;
+       ipv6->destination_address = ts->source_ip.v6;
+       tcp->spt = htons (ts->destination_port);
+       tcp->dpt = htons (ts->source_port);
+       tcp->crc = 0;
+       {
+         uint32_t sum = 0;
+         uint32_t tmp;
+
+         sum = GNUNET_CRYPTO_crc16_step (sum, &ipv6->source_address, 2 * sizeof (struct in6_addr));
+         tmp = htonl (sizeof (struct tcp_packet) + mlen);
+         sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t));
+         tmp = htonl (IPPROTO_TCP);
+         sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t));
+         sum = GNUNET_CRYPTO_crc16_step (sum, tcp,
+                                         sizeof (struct tcp_packet) + mlen);
+         tcp->crc = GNUNET_CRYPTO_crc16_finish (sum);
+       }
+       (void) GNUNET_HELPER_send (helper_handle,
+                                  msg,
+                                  GNUNET_YES,
+                                  NULL, NULL);
+      }
+    }
+    break;
   }
-  else
-  {
-    size_t size = pktlen + sizeof (struct ip_tcp) - 1;
-
-    struct ip_tcp *pkt4 = alloca (size);
-
-    GNUNET_assert (pkt4 != NULL);
-    memset (pkt4, 0, size);
-
-    GNUNET_assert (ntohs (message->type) ==
-                   GNUNET_MESSAGE_TYPE_VPN_REMOTE_TCP_BACK);
-    uint32_t sadr;
-
-    new_ip4addr_remote ((unsigned char *) &sadr, s->addr, s->addrlen);
-    pkt4->ip_hdr.sadr.s_addr = sadr;
-
-    pkt4->shdr.type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
-    pkt4->shdr.size = htons (size);
-
-    pkt4->tun.flags = 0;
-    pkt4->tun.type = htons (0x0800);
+  GNUNET_CONTAINER_heap_update_cost (tunnel_heap, 
+                                    ts->heap_node,
+                                    GNUNET_TIME_absolute_get ().abs_value);
+  return GNUNET_OK;
+}
 
-    pkt4->ip_hdr.version = 4;
-    pkt4->ip_hdr.hdr_lngth = 5;
-    pkt4->ip_hdr.diff_serv = 0;
-    pkt4->ip_hdr.tot_lngth = htons (20 + pktlen);
-    pkt4->ip_hdr.ident = 0;
-    pkt4->ip_hdr.flags = 0;
-    pkt4->ip_hdr.frag_off = 0;
-    pkt4->ip_hdr.ttl = 255;
-    pkt4->ip_hdr.proto = IPPROTO_TCP;
-    pkt4->ip_hdr.chks = 0;      /* Will be calculated later */
 
+/**
+ * Allocate an IPv4 address from the range of the tunnel
+ * for a new redirection.
+ *
+ * @param v4 where to store the address
+ * @return GNUNET_OK on success,
+ *         GNUNET_SYSERR on error
+ */
+static int
+allocate_v4_address (struct in_addr *v4)
+{
+  const char *ipv4addr = vpn_argv[4];
+  const char *ipv4mask = vpn_argv[5];
+  struct in_addr addr;
+  struct in_addr mask;
+  struct in_addr rnd;
+  GNUNET_HashCode key;
+  unsigned int tries;
+
+  GNUNET_assert (1 == inet_pton (AF_INET, ipv4addr, &addr));
+  GNUNET_assert (1 == inet_pton (AF_INET, ipv4mask, &mask));           
+  /* Given 192.168.0.1/255.255.0.0, we want a mask 
+     of '192.168.255.255', thus:  */
+  mask.s_addr = addr.s_addr | ~mask.s_addr;  
+  tries = 0;
+  do
     {
-      char *ipv4addr;
-      uint32_t dadr;
-
-      GNUNET_assert (GNUNET_OK ==
-                     GNUNET_CONFIGURATION_get_value_string (cfg, "vpn",
-                                                            "IPV4ADDR",
-                                                            &ipv4addr));
-      inet_pton (AF_INET, ipv4addr, &dadr);
-      GNUNET_free (ipv4addr);
-      pkt4->ip_hdr.dadr.s_addr = dadr;
+      tries++;
+      if (tries > 16)
+      {
+       GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                   _("Failed to find unallocated IPv4 address in VPN's range\n"));
+       return GNUNET_SYSERR;
+      }
+      /* Pick random IPv4 address within the subnet, except 'addr' or 'mask' itself */
+      rnd.s_addr = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK, 
+                                            UINT32_MAX);       
+      v4->s_addr = (addr.s_addr | rnd.s_addr) & mask.s_addr;          
+      get_destination_key_from_ip (AF_INET,
+                                  v4,
+                                  &key);
     }
+  while ( (GNUNET_YES ==
+          GNUNET_CONTAINER_multihashmap_contains (destination_map,
+                                                  &key)) ||
+         (v4->s_addr == addr.s_addr) ||
+         (v4->s_addr == mask.s_addr) );
+  return GNUNET_OK;
+}
 
-    memcpy (&pkt4->tcp_hdr, pkt, pktlen);
-
-    GNUNET_HashCode *key = address4_mapping_exists (pkt4->ip_hdr.sadr.s_addr);
-
-    GNUNET_assert (key != NULL);
-
-    struct map_entry *me = GNUNET_CONTAINER_multihashmap_get (hashmap, key);
-
-    GNUNET_CONTAINER_heap_update_cost (heap, me->heap_node,
-                                       GNUNET_TIME_absolute_get ().abs_value);
-
-    GNUNET_free (key);
-
-    GNUNET_assert (me != NULL);
-    pkt4->tcp_hdr.crc = 0;
-    uint32_t sum = 0;
-    uint32_t tmp;
-
-    sum = GNUNET_CRYPTO_crc16_step (sum, (uint16_t *) &pkt4->ip_hdr.sadr, 4);
-    sum = GNUNET_CRYPTO_crc16_step (sum, (uint16_t *) &pkt4->ip_hdr.dadr, 4);
-
-    tmp = (0x06 << 16) | (0xffff & pktlen);     // 0x06 for TCP?
-
-    tmp = htonl (tmp);
-
-    sum = GNUNET_CRYPTO_crc16_step (sum, (uint16_t *) & tmp, 4);
-
-    sum = GNUNET_CRYPTO_crc16_step (sum, (uint16_t *) & pkt4->tcp_hdr, pktlen);
-    pkt4->tcp_hdr.crc = GNUNET_CRYPTO_crc16_finish (sum);
-
-    pkt4->ip_hdr.chks =
-        GNUNET_CRYPTO_crc16_n ((uint16_t *) & pkt4->ip_hdr, 5 * 4);
-
-    (void) GNUNET_HELPER_send (helper_handle,
-                              &pkt4->shdr,
-                              GNUNET_YES,
-                              NULL, NULL);
 
-  }
-#endif
+/**
+ * Allocate an IPv6 address from the range of the tunnel
+ * for a new redirection.
+ *
+ * @param v6 where to store the address
+ * @return GNUNET_OK on success,
+ *         GNUNET_SYSERR on error
+ */
+static int
+allocate_v6_address (struct in6_addr *v6)
+{
+  const char *ipv6addr = vpn_argv[2];
+  struct in6_addr addr;
+  struct in6_addr mask;
+  struct in6_addr rnd;
+  int i;
+  GNUNET_HashCode key;
+  unsigned int tries;
+
+  GNUNET_assert (1 == inet_pton (AF_INET6, ipv6addr, &addr));
+  GNUNET_assert (ipv6prefix < 128);
+  /* Given ABCD::/96, we want a mask of 'ABCD::FFFF:FFFF,
+     thus: */
+  mask = addr;
+  for (i=127;i>=128-ipv6prefix;i--)
+    mask.s6_addr[i / 8] |= (1 << (i % 8));
+  
+  /* Pick random IPv6 address within the subnet, except 'addr' or 'mask' itself */
+  tries = 0;
+  do
+    {
+      tries++;
+      if (tries > 16)
+       {
+         GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                     _("Failed to find unallocated IPv6 address in VPN's range\n"));
+         return GNUNET_SYSERR;
+
+       }
+      for (i=0;i<16;i++)
+       {
+         rnd.s6_addr[i] = (unsigned char) GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK, 
+                                                                    256);
+         v6->s6_addr[i]
+           = (addr.s6_addr[i] | rnd.s6_addr[i]) & mask.s6_addr[i];
+       }
+      get_destination_key_from_ip (AF_INET6,
+                                  v6,
+                                  &key);
+    }
+  while ( (GNUNET_YES ==
+          GNUNET_CONTAINER_multihashmap_contains (destination_map,
+                                                  &key)) ||
+         (0 == memcmp (v6,
+                       &addr,
+                       sizeof (struct in6_addr))) ||
+         (0 == memcmp (v6,
+                       &mask,
+                       sizeof (struct in6_addr))) );
   return GNUNET_OK;
 }
 
@@ -1078,7 +1667,148 @@ static void
 service_redirect_to_ip (void *cls GNUNET_UNUSED, struct GNUNET_SERVER_Client *client,
                        const struct GNUNET_MessageHeader *message)
 {
-  GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+  size_t mlen;
+  size_t alen;
+  const struct RedirectToIpRequestMessage *msg;
+  int addr_af;
+  int result_af;
+  struct in_addr v4;
+  struct in6_addr v6;
+  void *addr;
+  struct DestinationEntry *de;
+  GNUNET_HashCode key;
+  
+  /* validate and parse request */
+  mlen = ntohs (message->size);
+  if (mlen < sizeof (struct RedirectToIpRequestMessage))
+  {
+    GNUNET_break (0);
+    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+    return;
+  }
+  alen = mlen - sizeof (struct RedirectToIpRequestMessage);
+  msg = (const struct RedirectToIpRequestMessage *) message;
+  addr_af = (int) htonl (msg->addr_af);
+  switch (addr_af)
+  {
+  case AF_INET:
+    if (alen != sizeof (struct in_addr))
+    {
+      GNUNET_break (0);
+      GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+      return;      
+    }
+    break;
+  case AF_INET6:
+    if (alen != sizeof (struct in6_addr))
+    {
+      GNUNET_break (0);
+      GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+      return;      
+    }
+    break;
+  default:
+    GNUNET_break (0);
+    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+    return;      
+  }
+
+  /* allocate response IP */
+  addr = NULL;
+  result_af = (int) htonl (msg->result_af);
+  switch (result_af)
+  {
+  case AF_INET:
+    if (GNUNET_OK !=
+       allocate_v4_address (&v4))
+      result_af = AF_UNSPEC;
+    else
+      addr = &v4;
+    break;
+  case AF_INET6:
+    if (GNUNET_OK !=
+       allocate_v6_address (&v6))
+      result_af = AF_UNSPEC;
+    else
+      addr = &v6;
+    break;
+  case AF_UNSPEC:
+    if (GNUNET_OK ==
+       allocate_v4_address (&v4))
+    {
+      addr = &v4;
+      result_af = AF_INET;
+    }
+    else if (GNUNET_OK ==
+       allocate_v6_address (&v6))
+    {
+      addr = &v6;
+      result_af = AF_INET6;
+    }
+    break;
+  default:
+    GNUNET_break (0);
+    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+    return;      
+  }
+  if ( (result_af == AF_UNSPEC) ||
+       (GNUNET_NO == ntohl (msg->nac)) )
+  {
+    /* send reply "instantly" */
+    send_client_reply (client,
+                      msg->request_id,
+                      result_af,
+                      addr);
+  }
+  if (result_af == AF_UNSPEC)
+  {
+    /* failure, we're done */
+    GNUNET_SERVER_receive_done (client, GNUNET_OK);
+    return;
+  }
+
+  {
+    char sbuf[INET6_ADDRSTRLEN];
+    char dbuf[INET6_ADDRSTRLEN];
+    
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+               "Allocated address %s for redirection via exit to %s\n",
+               inet_ntop (result_af, addr, sbuf, sizeof (sbuf)),
+               inet_ntop (addr_af,
+                          &msg[1], dbuf, sizeof (dbuf)));
+  }
+  
+  /* setup destination record */
+  de = GNUNET_malloc (sizeof (struct DestinationEntry));
+  de->is_service = GNUNET_NO;
+  de->details.exit_destination.af = addr_af;
+  memcpy (&de->details.exit_destination.ip,
+         &msg[1],
+         alen);
+  get_destination_key_from_ip (result_af,
+                              addr,
+                              &key);
+  de->key = key;
+  GNUNET_assert (GNUNET_OK ==
+                GNUNET_CONTAINER_multihashmap_put (destination_map,
+                                                   &key,
+                                                   de,
+                                                   GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE));
+  de->heap_node = GNUNET_CONTAINER_heap_insert (destination_heap,
+                                               de,
+                                               GNUNET_TIME_absolute_ntoh (msg->expiration_time).abs_value);
+  GNUNET_STATISTICS_update (stats,
+                           gettext_noop ("# Active destinations"),
+                           1, GNUNET_NO);
+
+  /* FIXME: expire OLD destinations if we have too many! */
+  /* setup tunnel to destination */
+  (void) create_tunnel_to_destination (de, 
+                                      (GNUNET_NO == ntohl (msg->nac)) ? NULL : client,
+                                      msg->request_id);
+  GNUNET_assert (NULL != de->ts);
+  /* we're done */
+  GNUNET_SERVER_receive_done (client, GNUNET_OK);
 }
 
 
@@ -1095,62 +1825,411 @@ static void
 service_redirect_to_service (void *cls GNUNET_UNUSED, struct GNUNET_SERVER_Client *client,
                             const struct GNUNET_MessageHeader *message)
 {
-  GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+  const struct RedirectToServiceRequestMessage *msg;
+  int result_af;
+  struct in_addr v4;
+  struct in6_addr v6;
+  void *addr;
+  struct DestinationEntry *de;
+  GNUNET_HashCode key;
+  
+  /*  parse request */
+  msg = (const struct RedirectToServiceRequestMessage *) message;
+
+  /* allocate response IP */
+  addr = NULL;
+  result_af = (int) htonl (msg->result_af);
+  switch (result_af)
+  {
+  case AF_INET:
+    if (GNUNET_OK !=
+       allocate_v4_address (&v4))
+      result_af = AF_UNSPEC;
+    else
+      addr = &v4;
+    break;
+  case AF_INET6:
+    if (GNUNET_OK !=
+       allocate_v6_address (&v6))
+      result_af = AF_UNSPEC;
+    else
+      addr = &v6;
+    break;
+  case AF_UNSPEC:
+    if (GNUNET_OK ==
+       allocate_v4_address (&v4))
+    {
+      addr = &v4;
+      result_af = AF_INET;
+    }
+    else if (GNUNET_OK ==
+       allocate_v6_address (&v6))
+    {
+      addr = &v6;
+      result_af = AF_INET6;
+    }
+    break;
+  default:
+    GNUNET_break (0);
+    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+    return;      
+  }
+  if ( (result_af == AF_UNSPEC) ||
+       (GNUNET_NO == ntohl (msg->nac)) )
+  {
+    /* send reply "instantly" */
+    send_client_reply (client,
+                      msg->request_id,
+                      result_af,
+                      addr);
+  }
+  if (result_af == AF_UNSPEC)
+  {
+    /* failure, we're done */
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+               _("Failed to allocate IP address for new destination\n"));
+    GNUNET_SERVER_receive_done (client, GNUNET_OK);
+    return;
+  }
+
+  {
+    char sbuf[INET6_ADDRSTRLEN];
+    
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+               "Allocated address %s for redirection to service %s on peer %s\n",
+               inet_ntop (result_af, addr, sbuf, sizeof (sbuf)),
+               GNUNET_h2s (&msg->service_descriptor),
+               GNUNET_i2s (&msg->target));
+  }
+  
+  /* setup destination record */
+  de = GNUNET_malloc (sizeof (struct DestinationEntry));
+  de->is_service = GNUNET_YES;
+  de->details.service_destination.service_descriptor = msg->service_descriptor;
+  de->details.service_destination.target = msg->target;
+  get_destination_key_from_ip (result_af,
+                              addr,
+                              &key);
+  de->key = key;
+  GNUNET_assert (GNUNET_OK ==
+                GNUNET_CONTAINER_multihashmap_put (destination_map,
+                                                   &key,
+                                                   de,
+                                                   GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE));
+  de->heap_node = GNUNET_CONTAINER_heap_insert (destination_heap,
+                                               de,
+                                               GNUNET_TIME_absolute_ntoh (msg->expiration_time).abs_value);
+  /* FIXME: expire OLD destinations if we have too many! */
+  (void) create_tunnel_to_destination (de,
+                                      (GNUNET_NO == ntohl (msg->nac)) ? NULL : client,
+                                      msg->request_id);
+  /* we're done */
+  GNUNET_SERVER_receive_done (client, GNUNET_OK);
 }
 
 
 
 /**
- * FIXME: document.
+ * Function called for inbound tunnels.  As we don't offer
+ * any mesh services, this function should never be called.
+ *
+ * @param cls closure
+ * @param tunnel new handle to the tunnel
+ * @param initiator peer that started the tunnel
+ * @param atsi performance information for the tunnel
+ * @return initial tunnel context for the tunnel
+ *         (can be NULL -- that's not an error)
  */ 
 static void *
-new_tunnel (void *cls, struct GNUNET_MESH_Tunnel *tunnel,
-            const struct GNUNET_PeerIdentity *initiator,
-            const struct GNUNET_ATS_Information *atsi)
+inbound_tunnel_cb (void *cls, struct GNUNET_MESH_Tunnel *tunnel,
+                  const struct GNUNET_PeerIdentity *initiator,
+                  const struct GNUNET_ATS_Information *atsi)
 {
-  /* Why should anyone open an inbound tunnel to vpn? */
+  /* How can and why should anyone open an inbound tunnel to vpn? */
   GNUNET_break (0);
   return NULL;
 }
 
 
 /**
- * FIXME: document.
+ * Free resources associated with a tunnel state.
+ *
+ * @param ts state to free
+ */
+static void
+free_tunnel_state (struct TunnelState *ts)
+{
+  GNUNET_HashCode key;
+  struct TunnelMessageQueueEntry *tnq;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             "Cleaning up tunnel state\n");
+  GNUNET_STATISTICS_update (stats,
+                           gettext_noop ("# Active tunnels"),
+                           -1, GNUNET_NO);
+  while (NULL != (tnq = ts->head))
+  {
+    GNUNET_CONTAINER_DLL_remove (ts->head,
+                                ts->tail,
+                                tnq);
+    GNUNET_free (tnq);
+  }
+  if (NULL != ts->client)
+  {
+    GNUNET_SERVER_client_drop (ts->client);
+    ts->client = NULL;
+  }
+  if (NULL != ts->th)
+  {
+    GNUNET_MESH_notify_transmit_ready_cancel (ts->th);
+    ts->th = NULL;
+  }
+  GNUNET_assert (NULL == ts->destination.heap_node);
+  if (NULL != ts->tunnel)
+  {
+    GNUNET_MESH_tunnel_destroy (ts->tunnel);
+    ts->tunnel = NULL;
+  }
+  if (NULL != ts->heap_node)
+  {
+    GNUNET_CONTAINER_heap_remove_node (ts->heap_node);
+    ts->heap_node = NULL;
+    get_tunnel_key_from_ips (ts->af,
+                            ts->protocol,
+                            &ts->source_ip,
+                            ts->source_port,
+                            &ts->destination_ip,
+                            ts->destination_port,
+                            &key);
+    GNUNET_assert (GNUNET_YES ==
+                  GNUNET_CONTAINER_multihashmap_remove (tunnel_map,
+                                                        &key,
+                                                        ts));
+  }
+  if (NULL != ts->destination_container)
+  {
+    GNUNET_assert (ts == ts->destination_container->ts);
+    ts->destination_container->ts = NULL;
+    ts->destination_container = NULL;
+  }
+  GNUNET_free (ts);
+}
+
+
+/**
+ * Free resources occupied by a destination entry.
+ *
+ * @param de entry to free
+ */
+static void
+free_destination_entry (struct DestinationEntry *de)
+{
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             "Cleaning up destination entry\n");
+  GNUNET_STATISTICS_update (stats,
+                           gettext_noop ("# Active destinations"),
+                           -1, GNUNET_NO);
+  if (NULL != de->ts)
+  {
+    free_tunnel_state (de->ts);
+    GNUNET_assert (NULL == de->ts);
+  }
+  if (NULL != de->heap_node)
+  {
+    GNUNET_CONTAINER_heap_remove_node (de->heap_node);
+    de->heap_node = NULL;  
+    GNUNET_assert (GNUNET_YES ==
+                  GNUNET_CONTAINER_multihashmap_remove (destination_map,
+                                                        &de->key,
+                                                        de));
+  }
+  GNUNET_free (de);
+}
+
+
+/**
+ * Function called whenever an inbound tunnel is destroyed.  Should clean up
+ * any associated state.
+ *
+ * @param cls closure (set from GNUNET_MESH_connect)
+ * @param tunnel connection to the other end (henceforth invalid)
+ * @param tunnel_ctx place where local state associated
+ *                   with the tunnel is stored (our 'struct TunnelState')
  */ 
 static void
 tunnel_cleaner (void *cls, const struct GNUNET_MESH_Tunnel *tunnel, void *tunnel_ctx)
 {
-  /* Why should anyone open an inbound tunnel to vpn? */
-  /* FIXME: is this not also called for outbound tunnels that go down!? */
-  GNUNET_break (0);
+  struct TunnelState *ts = tunnel_ctx;
+
+  if (NULL == ts)
+  {
+    GNUNET_break (0);
+    return;     
+  }
+  GNUNET_assert (ts->tunnel == tunnel);
+  ts->tunnel = NULL;
+  free_tunnel_state (ts);
+}
+
+
+/**
+ * Free memory occupied by an entry in the destination map.
+ *
+ * @param cls unused
+ * @param key unused
+ * @param value a 'struct DestinationEntry *'
+ * @return GNUNET_OK (continue to iterate)
+ */
+static int
+cleanup_destination (void *cls,
+                    const GNUNET_HashCode *key,
+                    void *value)
+{
+  struct DestinationEntry *de = value;
+
+  free_destination_entry (de);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Free memory occupied by an entry in the tunnel map.
+ *
+ * @param cls unused
+ * @param key unused
+ * @param value a 'struct TunnelState *'
+ * @return GNUNET_OK (continue to iterate)
+ */
+static int
+cleanup_tunnel (void *cls,
+               const GNUNET_HashCode *key,
+               void *value)
+{
+  struct TunnelState *ts = value;
+
+  free_tunnel_state (ts);
+  return GNUNET_OK;
 }
 
 
 /**
  * Function scheduled as very last function, cleans up after us
+ *
+ * @param cls unused
+ * @param tc unused
  */
 static void
 cleanup (void *cls GNUNET_UNUSED,
-         const struct GNUNET_SCHEDULER_TaskContext *tskctx)
+         const struct GNUNET_SCHEDULER_TaskContext *tc)
 {
   unsigned int i;
 
-  // FIXME: clean up heaps and maps!
-  if (mesh_handle != NULL)
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             "VPN is shutting down\n");
+  if (NULL != destination_map)
+  {  
+    GNUNET_CONTAINER_multihashmap_iterate (destination_map,
+                                          &cleanup_destination,
+                                          NULL);
+    GNUNET_CONTAINER_multihashmap_destroy (destination_map);
+    destination_map = NULL;
+  }
+  if (NULL != destination_heap)
+  {
+    GNUNET_CONTAINER_heap_destroy (destination_heap);
+    destination_heap = NULL;
+  }
+  if (NULL != tunnel_map)
+  {  
+    GNUNET_CONTAINER_multihashmap_iterate (tunnel_map,
+                                          &cleanup_tunnel,
+                                          NULL);
+    GNUNET_CONTAINER_multihashmap_destroy (tunnel_map);
+    tunnel_map = NULL;
+  }
+  if (NULL != tunnel_heap)
+  {
+    GNUNET_CONTAINER_heap_destroy (tunnel_heap);
+    tunnel_heap = NULL;
+  }
+  if (NULL != mesh_handle)
   {
     GNUNET_MESH_disconnect (mesh_handle);
     mesh_handle = NULL;
   }
-  if (helper_handle != NULL)
-  {
+  if (NULL != helper_handle)
+    {
     GNUNET_HELPER_stop (helper_handle);
     helper_handle = NULL;
   }
+  if (NULL != nc)
+  {
+    GNUNET_SERVER_notification_context_destroy (nc);
+    nc = NULL;
+  }
+  if (stats != NULL)
+  {
+    GNUNET_STATISTICS_destroy (stats, GNUNET_YES);
+    stats = NULL;
+  }
   for (i=0;i<5;i++)
     GNUNET_free_non_null (vpn_argv[i]);
 }
 
 
+/**
+ * A client disconnected, clean up all references to it.
+ *
+ * @param cls the client that disconnected
+ * @param key unused
+ * @param value a 'struct TunnelState *'
+ * @return GNUNET_OK (continue to iterate)
+ */
+static int
+cleanup_tunnel_client (void *cls,
+                      const GNUNET_HashCode *key,
+                      void *value)
+{
+  struct GNUNET_SERVER_Client *client = cls;
+  struct TunnelState *ts = value;
+
+  if (client == ts->client)
+  {
+    GNUNET_SERVER_client_drop (ts->client);
+    ts->client = NULL;
+  }
+  return GNUNET_OK;
+}
+
+
+/**
+ * A client disconnected, clean up all references to it.
+ *
+ * @param cls the client that disconnected
+ * @param key unused
+ * @param value a 'struct DestinationEntry *'
+ * @return GNUNET_OK (continue to iterate)
+ */
+static int
+cleanup_destination_client (void *cls,
+                           const GNUNET_HashCode *key,
+                           void *value)
+{
+  struct GNUNET_SERVER_Client *client = cls;
+  struct DestinationEntry *de = value;
+  struct TunnelState *ts;
+
+  if (NULL == (ts = de->ts))
+    return GNUNET_OK;
+  if (client == ts->client)
+  {
+    GNUNET_SERVER_client_drop (ts->client);
+    ts->client = NULL;
+  }
+  return GNUNET_OK;
+}
+
+  
 /**
  * A client has disconnected from us.  If we are currently building
  * a tunnel for it, cancel the operation.
@@ -1161,7 +2240,14 @@ cleanup (void *cls GNUNET_UNUSED,
 static void
 client_disconnect (void *cls, struct GNUNET_SERVER_Client *client)
 {
-  // FIXME
+  if (NULL != tunnel_map)
+    GNUNET_CONTAINER_multihashmap_iterate (tunnel_map,
+                                          &cleanup_tunnel_client,
+                                          client);
+  if (NULL != destination_map)
+    GNUNET_CONTAINER_multihashmap_iterate (destination_map,
+                                          &cleanup_destination_client,
+                                          client);
 }
 
 
@@ -1202,9 +2288,9 @@ run (void *cls,
   char *ipv4mask;
   struct in_addr v4;
   struct in6_addr v6;
-  unsigned long long ipv6prefix;
 
   cfg = cfg_;
+  stats = GNUNET_STATISTICS_create ("vpn", cfg);
   if (GNUNET_OK !=
       GNUNET_CONFIGURATION_get_value_number (cfg, "vpn", "MAX_MAPPING",
                                             &max_destination_mappings))
@@ -1287,12 +2373,13 @@ run (void *cls,
 
   mesh_handle =
     GNUNET_MESH_connect (cfg_, 42 /* queue length */, NULL, 
-                        &new_tunnel
+                        &inbound_tunnel_cb
                         &tunnel_cleaner, 
                         mesh_handlers,
                         types);
   helper_handle = GNUNET_HELPER_start ("gnunet-helper-vpn", vpn_argv,
                                       &message_token, NULL);
+  nc = GNUNET_SERVER_notification_context_create (server, 1);
   GNUNET_SERVER_add_handlers (server, service_handlers);
   GNUNET_SERVER_disconnect_notify (server, &client_disconnect, NULL);
   GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_FOREVER_REL, &cleanup, cls);