Merge branch 'getopt'
[oweals/gnunet.git] / src / vpn / gnunet-service-vpn.c
index 7b29cbbd46868331e758edcd48fa377cf9784209..4759f374661e0ba46c4969ee0383ba5e8eade6a6 100644 (file)
@@ -1,6 +1,6 @@
 /*
      This file is part of GNUnet.
-     (C) 2010, 2011, 2012 Christian Grothoff
+     Copyright (C) 2010, 2011, 2012, 2016, 2017 Christian Grothoff
 
      GNUnet is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published
 
      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.
+     Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+     Boston, MA 02110-1301, USA.
 */
 
 /**
  * @file vpn/gnunet-service-vpn.c
  * @brief service that opens a virtual interface and allows its clients
  *        to allocate IPs on the virtual interface and to then redirect
- *        IP traffic received on those IPs via the GNUnet mesh 
+ *        IP traffic received on those IPs via the GNUnet cadet
  * @author Philipp Toelke
  * @author Christian Grothoff
+ *
+ * TODO:
+ * - keep multiple peers/cadet channels ready as alternative exits /
+ *   detect & recover from channel-to-exit failure gracefully
  */
 #include "platform.h"
 #include "gnunet_util_lib.h"
 #include "gnunet_common.h"
 #include "gnunet_protocols.h"
 #include "gnunet_applications.h"
-#include "gnunet_mesh_service.h"
+#include "gnunet_cadet_service.h"
 #include "gnunet_statistics_service.h"
 #include "gnunet_constants.h"
 #include "gnunet_tun_lib.h"
+#include "gnunet_regex_service.h"
 #include "vpn.h"
 #include "exit.h"
 
 
 /**
- * Maximum number of messages we allow in the queue for mesh.
+ * Maximum number of messages we allow in the queue for cadet.
  */
 #define MAX_MESSAGE_QUEUE_SIZE 4
 
 
 /**
- * State we keep for each of our tunnels.
+ * State we keep for each of our channels.
+ */
+struct ChannelState;
+
+/**
+ * Information we track for each IP address to determine which channel
+ * to send the traffic over to the destination.
+ */
+struct DestinationEntry;
+
+/**
+ * List of channels we keep for each destination port for a given
+ * destination entry.
  */
-struct TunnelState;
+struct DestinationChannel
+{
+
+  /**
+   * Kept in a DLL.
+   */
+  struct DestinationChannel *next;
+
+  /**
+   * Kept in a DLL.
+   */
+  struct DestinationChannel *prev;
+
+  /**
+   * Destination entry list this `struct DestinationChannel` belongs with.
+   */
+  struct DestinationEntry *destination;
+
+  /**
+   * Destination port this channel state is used for.
+   */
+  uint16_t destination_port;
+
+};
 
 
 /**
- * Information we track for each IP address to determine which tunnel
+ * Information we track for each IP address to determine which channel
  * to send the traffic over to the destination.
  */
 struct DestinationEntry
@@ -62,12 +102,17 @@ struct DestinationEntry
    * Key under which this entry is in the 'destination_map' (only valid
    * if 'heap_node != NULL').
    */
-  GNUNET_HashCode key;
+  struct GNUNET_HashCode key;
 
   /**
-   * Pre-allocated tunnel for this destination, or NULL for none.
+   * Head of DLL of channels associated with this destination.
    */
-  struct TunnelState *ts;
+  struct DestinationChannel *dt_head;
+
+  /**
+   * Tail of DLL of channels associated with this destination.
+   */
+  struct DestinationChannel *dt_tail;
 
   /**
    * Entry for this entry in the destination_heap.
@@ -75,8 +120,8 @@ struct DestinationEntry
   struct GNUNET_CONTAINER_HeapNode *heap_node;
 
   /**
-   * GNUNET_NO if this is a tunnel to an Internet-exit,
-   * GNUNET_YES if this tunnel is to a service.
+   * #GNUNET_NO if this is a channel to an Internet-exit,
+   * #GNUNET_YES if this channel is to a service.
    */
   int is_service;
 
@@ -89,9 +134,9 @@ struct DestinationEntry
     struct
     {
       /**
-       * The description of the service (only used for service tunnels).
+       * The description of the service (only used for service channels).
        */
-      GNUNET_HashCode service_descriptor;
+      struct GNUNET_HashCode service_descriptor;
 
       /**
        * Peer offering the service.
@@ -100,16 +145,16 @@ struct DestinationEntry
 
     } service_destination;
 
-    struct 
+    struct
     {
-  
+
       /**
        * Address family used (AF_INET or AF_INET6).
        */
       int af;
-      
+
       /**
-       * IP address of the ultimate destination (only used for exit tunnels).
+       * IP address of the ultimate destination (only used for exit channels).
        */
       union
       {
@@ -117,7 +162,7 @@ struct DestinationEntry
         * Address if af is AF_INET.
         */
        struct in_addr v4;
-       
+
        /**
         * Address if af is AF_INET6.
         */
@@ -127,27 +172,27 @@ struct DestinationEntry
     } exit_destination;
 
   } details;
-    
+
 };
 
 
 /**
- * A messages we have in queue for a particular tunnel.
+ * A messages we have in queue for a particular channel.
  */
-struct TunnelMessageQueueEntry
+struct ChannelMessageQueueEntry
 {
   /**
    * This is a doubly-linked list.
    */
-  struct TunnelMessageQueueEntry *next;
+  struct ChannelMessageQueueEntry *next;
 
   /**
    * This is a doubly-linked list.
    */
-  struct TunnelMessageQueueEntry *prev;
-  
+  struct ChannelMessageQueueEntry *prev;
+
   /**
-   * Number of bytes in 'msg'.
+   * Number of bytes in @e msg.
    */
   size_t len;
 
@@ -159,57 +204,40 @@ struct TunnelMessageQueueEntry
 
 
 /**
- * State we keep for each of our tunnels.
+ * State we keep for each of our channels.
  */
-struct TunnelState
+struct ChannelState
 {
 
   /**
-   * Information about the tunnel to use, NULL if no tunnel
+   * Information about the channel to use, NULL if no channel
    * is available right now.
    */
-  struct GNUNET_MESH_Tunnel *tunnel;
+  struct GNUNET_CADET_Channel *channel;
 
   /**
-   * Active transmission handle, NULL for none.
+   * Active query with REGEX to locate exit.
    */
-  struct GNUNET_MESH_TransmitHandle *th;
+  struct GNUNET_REGEX_Search *search;
 
   /**
-   * Entry for this entry in the tunnel_heap, NULL as long as this
-   * tunnel state is not fully bound.
+   * Entry for this entry in the channel_heap, NULL as long as this
+   * channel state is not fully bound.
    */
   struct GNUNET_CONTAINER_HeapNode *heap_node;
 
   /**
    * Head of list of messages scheduled for transmission.
    */
-  struct TunnelMessageQueueEntry *tmq_head;
+  struct ChannelMessageQueueEntry *tmq_head;
 
   /**
    * Tail of list of messages scheduled for transmission.
    */
-  struct TunnelMessageQueueEntry *tmq_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;
-
-  /**
-   * Destination entry that has a pointer to this tunnel state;
-   * NULL if this tunnel state is in the tunnel map.
-   */
-  struct DestinationEntry *destination_container;
-
-  /**
-   * ID of the client request that caused us to setup this entry.
-   */ 
-  uint64_t request_id;
+  struct ChannelMessageQueueEntry *tmq_tail;
 
   /**
-   * Destination to which this tunnel leads.  Note that
+   * Destination to which this channel leads.  Note that
    * this struct is NOT in the destination_map (but a
    * local copy) and that the 'heap_node' should always
    * be NULL.
@@ -217,14 +245,15 @@ struct TunnelState
   struct DestinationEntry destination;
 
   /**
-   * Task scheduled to destroy the tunnel (or NO_TASK).
+   * Addess family used for this channel on the local TUN interface.
    */
-  GNUNET_SCHEDULER_TaskIdentifier destroy_task;
+  int af;
 
   /**
-   * Addess family used for this tunnel on the local TUN interface.
+   * Is this channel new (#GNUNET_NO), or did we exchange messages with the
+   * other side already (#GNUNET_YES)?
    */
-  int af;
+  int is_established;
 
   /**
    * Length of the doubly linked 'tmq_head/tmq_tail' list.
@@ -245,7 +274,7 @@ struct TunnelState
      * Address if af is AF_INET.
      */
     struct in_addr v4;
-    
+
     /**
      * Address if af is AF_INET6.
      */
@@ -255,7 +284,7 @@ struct TunnelState
 
   /**
    * 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).
+   * that we pick freely within the VPN's channel IP range).
    */
   union
   {
@@ -263,7 +292,7 @@ struct TunnelState
      * Address if af is AF_INET.
      */
     struct in_addr v4;
-    
+
     /**
      * Address if af is AF_INET6.
      */
@@ -285,7 +314,7 @@ struct TunnelState
 
 
 /**
- * Return value from 'main'.
+ * Return value from #main().
  */
 static int global_ret;
 
@@ -295,13 +324,13 @@ static int global_ret;
 static const struct GNUNET_CONFIGURATION_Handle *cfg;
 
 /**
- * Handle to the mesh service.
+ * Handle to the cadet service.
  */
-static struct GNUNET_MESH_Handle *mesh_handle;
+static struct GNUNET_CADET_Handle *cadet_handle;
 
 /**
  * Map from IP address to destination information (possibly with a
- * MESH tunnel handle for fast setup).
+ * CADET channel handle for fast setup).
  */
 static struct GNUNET_CONTAINER_MultiHashMap *destination_map;
 
@@ -312,15 +341,15 @@ static struct GNUNET_CONTAINER_Heap *destination_heap;
 
 /**
  * Map from source and destination address (IP+port) to connection
- * information (mostly with the respective MESH tunnel handle).
+ * information (mostly with the respective CADET channel handle).
  */
-static struct GNUNET_CONTAINER_MultiHashMap *tunnel_map;
+static struct GNUNET_CONTAINER_MultiHashMap *channel_map;
 
 /**
  * Min-Heap sorted by activity time to expire old mappings; values are
- * of type 'struct TunnelState'.
+ * of type 'struct ChannelState'.
  */
-static struct GNUNET_CONTAINER_Heap *tunnel_heap;
+static struct GNUNET_CONTAINER_Heap *channel_heap;
 
 /**
  * Statistics.
@@ -342,11 +371,6 @@ static char *vpn_argv[7];
  */
 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
@@ -354,15 +378,15 @@ static struct GNUNET_SERVER_NotificationContext *nc;
 static unsigned long long max_destination_mappings;
 
 /**
- * If there are more than this number of open tunnels, old ones
+ * If there are more than this number of open channels, old ones
  * will be removed
  */
-static unsigned long long max_tunnel_mappings;
+static unsigned long long max_channel_mappings;
 
 
 /**
  * Compute the key under which we would store an entry in the
- * destination_map for the given IP address.
+ * #destination_map for the given IP address.
  *
  * @param af address family (AF_INET or AF_INET6)
  * @param address IP address, struct in_addr or struct in6_addr
@@ -371,7 +395,7 @@ static unsigned long long max_tunnel_mappings;
 static void
 get_destination_key_from_ip (int af,
                             const void *address,
-                            GNUNET_HashCode *key)
+                            struct GNUNET_HashCode *key)
 {
   switch (af)
   {
@@ -394,7 +418,7 @@ get_destination_key_from_ip (int af,
 
 /**
  * Compute the key under which we would store an entry in the
- * tunnel_map for the given socket address pair.
+ * channel_map for the given socket address pair.
  *
  * @param af address family (AF_INET or AF_INET6)
  * @param protocol IPPROTO_TCP or IPPROTO_UDP
@@ -405,44 +429,44 @@ get_destination_key_from_ip (int af,
  * @param key where to store the key
  */
 static void
-get_tunnel_key_from_ips (int af,
-                        uint8_t protocol,
-                        const void *source_ip,
-                        uint16_t source_port,
-                        const void *destination_ip,
-                        uint16_t destination_port,
-                        GNUNET_HashCode *key)
+get_channel_key_from_ips (int af,
+                          uint8_t protocol,
+                          const void *source_ip,
+                          uint16_t source_port,
+                          const void *destination_ip,
+                          uint16_t destination_port,
+                          struct GNUNET_HashCode *key)
 {
   char *off;
 
-  memset (key, 0, sizeof (GNUNET_HashCode));
+  memset (key, 0, sizeof (struct GNUNET_HashCode));
   /* the GNUnet hashmap only uses the first sizeof(unsigned int) of the hash,
      so we put the ports in there (and hope for few collisions) */
   off = (char*) key;
-  memcpy (off, &source_port, sizeof (uint16_t));
+  GNUNET_memcpy (off, &source_port, sizeof (uint16_t));
   off += sizeof (uint16_t);
-  memcpy (off, &destination_port, sizeof (uint16_t));
+  GNUNET_memcpy (off, &destination_port, sizeof (uint16_t));
   off += sizeof (uint16_t);
   switch (af)
   {
   case AF_INET:
-    memcpy (off, source_ip, sizeof (struct in_addr));
+    GNUNET_memcpy (off, source_ip, sizeof (struct in_addr));
     off += sizeof (struct in_addr);
-    memcpy (off, destination_ip, sizeof (struct in_addr));
+    GNUNET_memcpy (off, destination_ip, sizeof (struct in_addr));
     off += sizeof (struct in_addr);
     break;
   case AF_INET6:
-    memcpy (off, source_ip, sizeof (struct in6_addr));
+    GNUNET_memcpy (off, source_ip, sizeof (struct in6_addr));
     off += sizeof (struct in6_addr);
-    memcpy (off, destination_ip, sizeof (struct in6_addr));
+    GNUNET_memcpy (off, destination_ip, sizeof (struct in6_addr));
     off += sizeof (struct in6_addr);
     break;
   default:
     GNUNET_assert (0);
     break;
   }
-  memcpy (off, &protocol, sizeof (uint8_t));
-  off += sizeof (uint8_t);  
+  GNUNET_memcpy (off, &protocol, sizeof (uint8_t));
+  /* off += sizeof (uint8_t);  */
 }
 
 
@@ -455,19 +479,19 @@ get_tunnel_key_from_ips (int af,
  * @param addr resulting IP address
  */
 static void
-send_client_reply (struct GNUNET_SERVER_Client *client,
+send_client_reply (struct GNUNET_SERVICE_Client *client,
                   uint64_t request_id,
                   int result_af,
                   const void *addr)
 {
-  char buf[sizeof (struct RedirectToIpResponseMessage) + sizeof (struct in6_addr)];
+  struct GNUNET_MQ_Envelope *env;
   struct RedirectToIpResponseMessage *res;
   size_t rlen;
 
   switch (result_af)
   {
   case AF_INET:
-    rlen = sizeof (struct in_addr);    
+    rlen = sizeof (struct in_addr);
     break;
   case AF_INET6:
     rlen = sizeof (struct in6_addr);
@@ -479,36 +503,41 @@ send_client_reply (struct GNUNET_SERVER_Client *client,
     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);
+  env = GNUNET_MQ_msg_extra (res,
+                             rlen,
+                             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);
+  GNUNET_memcpy (&res[1],
+                 addr,
+                 rlen);
+  GNUNET_MQ_send (GNUNET_SERVICE_client_get_mq (client),
+                  env);
 }
 
 
 /**
- * Free resources associated with a tunnel state.
+ * Free resources associated with a channel state.
  *
  * @param ts state to free
  */
 static void
-free_tunnel_state (struct TunnelState *ts)
+free_channel_state (struct ChannelState *ts)
 {
-  GNUNET_HashCode key;
-  struct TunnelMessageQueueEntry *tnq;
-  struct GNUNET_MESH_Tunnel *tunnel;
+  struct GNUNET_HashCode key;
+  struct ChannelMessageQueueEntry *tnq;
+  struct GNUNET_CADET_Channel *channel;
 
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-             "Cleaning up tunnel state\n");
+             "Cleaning up channel state\n");
+  if (NULL != (channel = ts->channel))
+  {
+    ts->channel = NULL;
+    GNUNET_CADET_channel_destroy (channel);
+    return;
+  }
   GNUNET_STATISTICS_update (stats,
-                           gettext_noop ("# Active tunnels"),
+                           gettext_noop ("# Active channels"),
                            -1, GNUNET_NO);
   while (NULL != (tnq = ts->tmq_head))
   {
@@ -519,32 +548,17 @@ free_tunnel_state (struct TunnelState *ts)
     GNUNET_free (tnq);
   }
   GNUNET_assert (0 == ts->tmq_length);
-  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 != (tunnel = ts->tunnel))
-  {
-    ts->tunnel = NULL;
-    GNUNET_MESH_tunnel_destroy (tunnel);
-  }
-  if (GNUNET_SCHEDULER_NO_TASK != ts->destroy_task)
+  if (NULL != ts->search)
   {
-    GNUNET_SCHEDULER_cancel (ts->destroy_task);
-    ts->destroy_task = GNUNET_SCHEDULER_NO_TASK;
+    GNUNET_REGEX_search_cancel (ts->search);
+    ts->search = 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,
+    get_channel_key_from_ips (ts->af,
                             ts->protocol,
                             &ts->source_ip,
                             ts->source_port,
@@ -552,1763 +566,1777 @@ free_tunnel_state (struct TunnelState *ts)
                             ts->destination_port,
                             &key);
     GNUNET_assert (GNUNET_YES ==
-                  GNUNET_CONTAINER_multihashmap_remove (tunnel_map,
+                  GNUNET_CONTAINER_multihashmap_remove (channel_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);
 }
 
 
 /**
- * Destroy the mesh tunnel.
+ * Add the given message to the given channel and trigger the
+ * transmission process.
  *
- * @param cls the 'struct TunnelState' with the tunnel to destroy
- * @param tc scheduler context
+ * @param ts channel to queue the message for
+ * @param env message to queue
  */
 static void
-destroy_tunnel_task (void *cls,
-                    const struct GNUNET_SCHEDULER_TaskContext *tc)
+send_to_channel (struct ChannelState *ts,
+                 struct GNUNET_MQ_Envelope *env)
 {
-  struct TunnelState *ts = cls;
-  struct GNUNET_MESH_Tunnel *tunnel;
-
-  ts->destroy_task = GNUNET_SCHEDULER_NO_TASK;
-  GNUNET_assert (NULL != ts->tunnel);
-  tunnel = ts->tunnel;
-  ts->tunnel = NULL;
-  GNUNET_MESH_tunnel_destroy (tunnel);
-  free_tunnel_state (ts);
+  struct GNUNET_MQ_Handle *mq;
+
+  GNUNET_assert (NULL != ts->channel);
+  mq = GNUNET_CADET_get_mq (ts->channel);
+  GNUNET_MQ_send (mq,
+                  env);
+  if (GNUNET_MQ_get_length (mq) > MAX_MESSAGE_QUEUE_SIZE)
+  {
+    env = GNUNET_MQ_unsent_head (mq);
+    GNUNET_assert (NULL != env);
+    GNUNET_STATISTICS_update (stats,
+                             gettext_noop ("# Messages dropped in cadet queue (overflow)"),
+                             1,
+                             GNUNET_NO);
+    GNUNET_MQ_discard (env);
+  }
 }
 
 
 /**
- * Method called whenever a peer has disconnected from the tunnel.
+ * Output destination of a channel for diagnostics.
  *
- * @param cls closure
- * @param peer peer identity the tunnel stopped working with
+ * @param de destination to process
+ * @return diagnostic string describing destination
  */
-static void
-tunnel_peer_disconnect_handler (void *cls,
-                               const struct
-                               GNUNET_PeerIdentity * peer)
+static const char *
+print_channel_destination (const struct DestinationEntry *de)
 {
-  struct TunnelState *ts = cls;
+  static char dest[256];
 
-  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)
+  if (de->is_service)
+  {
+    GNUNET_snprintf (dest,
+                     sizeof (dest),
+                     "HS: %s-%s",
+                     GNUNET_i2s (&de->details.service_destination.target),
+                     GNUNET_h2s (&de->details.service_destination.service_descriptor));
+  }
+  else
   {
-    GNUNET_MESH_notify_transmit_ready_cancel (ts->th);
-    ts->th = NULL;
+    inet_ntop (de->details.exit_destination.af,
+               &de->details.exit_destination.ip,
+               dest,
+               sizeof (dest));
   }
-  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... */
-  if (GNUNET_SCHEDULER_NO_TASK == ts->destroy_task)
-    ts->destroy_task = GNUNET_SCHEDULER_add_now (&destroy_tunnel_task, ts);
+  return dest;
 }
 
 
 /**
- * Method called whenever a peer has connected to the tunnel.  Notifies
- * the waiting client that the tunnel is now up.
+ * Function called whenever a channel is destroyed.  Should clean up
+ * any associated state.
  *
- * @param cls closure
- * @param peer peer identity the tunnel was created to, NULL on timeout
- * @param atsi performance data for the connection
+ * @param cls our `struct ChannelState`
+ * @param channel connection to the other end (henceforth invalid)
  */
 static void
-tunnel_peer_connect_handler (void *cls,
-                            const struct GNUNET_PeerIdentity
-                            * peer,
-                            const struct
-                            GNUNET_ATS_Information * atsi)
+channel_cleaner (void *cls,
+                 const struct GNUNET_CADET_Channel *channel)
 {
-  struct TunnelState *ts = cls;
+  struct ChannelState *ts = cls;
 
+  ts->channel = NULL; /* we must not call GNUNET_CADET_channel_destroy() anymore */
   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;
+             "CADET notified us about death of channel to `%s'\n",
+              print_channel_destination (&ts->destination));
+  free_channel_state (ts);
 }
 
 
 /**
- * Send a message from the message queue via mesh.
+ * Synthesize a plausible ICMP payload for an ICMP error
+ * response on the given channel.
  *
- * @param cls the 'struct TunnelState' with the message queue
- * @param size number of bytes available in buf
- * @param buf where to copy the message
- * @return number of bytes copied to buf
+ * @param ts channel information
+ * @param ipp IPv4 header to fill in (ICMP payload)
+ * @param udp "UDP" header to fill in (ICMP payload); might actually
+ *            also be the first 8 bytes of the TCP header
  */
-static size_t
-send_to_peer_notify_callback (void *cls, size_t size, void *buf)
+static void
+make_up_icmpv4_payload (struct ChannelState *ts,
+                       struct GNUNET_TUN_IPv4Header *ipp,
+                       struct GNUNET_TUN_UdpHeader *udp)
 {
-  struct TunnelState *ts = cls;
-  struct TunnelMessageQueueEntry *tnq;
-  size_t ret;
-
-  ts->th = NULL;
-  if (NULL == buf)
-    return 0;
-  tnq = ts->tmq_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->tmq_head,
-                              ts->tmq_tail,
-                              tnq);
-  ts->tmq_length--;
-  memcpy (buf, tnq->msg, tnq->len);
-  ret = tnq->len;
-  GNUNET_free (tnq);
-  if (NULL != (tnq = ts->tmq_head))
-    ts->th = GNUNET_MESH_notify_transmit_ready (ts->tunnel, 
-                                               GNUNET_NO /* cork */, 
-                                               42 /* priority */,
-                                               GNUNET_TIME_UNIT_FOREVER_REL,
-                                               NULL, 
-                                               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;
+  GNUNET_TUN_initialize_ipv4_header (ipp,
+                                    ts->protocol,
+                                    sizeof (struct GNUNET_TUN_TcpHeader),
+                                    &ts->source_ip.v4,
+                                    &ts->destination_ip.v4);
+  udp->source_port = htons (ts->source_port);
+  udp->destination_port = htons (ts->destination_port);
+  udp->len = htons (0);
+  udp->crc = htons (0);
 }
 
 
 /**
- * Add the given message to the given tunnel and trigger the
- * transmission process.
+ * Synthesize a plausible ICMP payload for an ICMP error
+ * response on the given channel.
  *
- * @param tnq message to queue
- * @param ts tunnel to queue the message for
+ * @param ts channel information
+ * @param ipp IPv6 header to fill in (ICMP payload)
+ * @param udp "UDP" header to fill in (ICMP payload); might actually
+ *            also be the first 8 bytes of the TCP header
  */
 static void
-send_to_tunnel (struct TunnelMessageQueueEntry *tnq,
-               struct TunnelState *ts)
+make_up_icmpv6_payload (struct ChannelState *ts,
+                       struct GNUNET_TUN_IPv6Header *ipp,
+                       struct GNUNET_TUN_UdpHeader *udp)
 {
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-             "Queueing %u bytes for transmission via mesh tunnel\n",
-             tnq->len);
-  GNUNET_assert (NULL != ts->tunnel);
-  GNUNET_CONTAINER_DLL_insert_tail (ts->tmq_head,
-                                   ts->tmq_tail,
-                                   tnq);
-  ts->tmq_length++;
-  if (ts->tmq_length > MAX_MESSAGE_QUEUE_SIZE)
-  {
-    struct TunnelMessageQueueEntry *dq;
-
-    dq = ts->tmq_head;
-    GNUNET_assert (dq != tnq);
-    GNUNET_CONTAINER_DLL_remove (ts->tmq_head,
-                                ts->tmq_tail,
-                                dq);
-    ts->tmq_length--;
-    GNUNET_MESH_notify_transmit_ready_cancel (ts->th);
-    ts->th = NULL;
-    GNUNET_STATISTICS_update (stats,
-                             gettext_noop ("# Bytes dropped in mesh queue (overflow)"),
-                             dq->len, 
-                             GNUNET_NO);
-    GNUNET_free (dq);
-  }
-  if (NULL == ts->th)
-    ts->th = GNUNET_MESH_notify_transmit_ready (ts->tunnel, 
-                                               GNUNET_NO /* cork */,
-                                               42 /* priority */,
-                                               GNUNET_TIME_UNIT_FOREVER_REL,
-                                               NULL, 
-                                               tnq->len,
-                                               &send_to_peer_notify_callback,
-                                               ts);
+  GNUNET_TUN_initialize_ipv6_header (ipp,
+                                    ts->protocol,
+                                    sizeof (struct GNUNET_TUN_TcpHeader),
+                                    &ts->source_ip.v6,
+                                    &ts->destination_ip.v6);
+  udp->source_port = htons (ts->source_port);
+  udp->destination_port = htons (ts->destination_port);
+  udp->len = htons (0);
+  udp->crc = htons (0);
 }
 
 
 /**
- * Initialize the given destination entry's mesh tunnel.
+ * We got an ICMP packet back from the CADET channel.  Check it is OK.
  *
- * @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 client_af address family of the address returned to the client
- * @param request_id request ID to send in client notification (unused if client is NULL)
- * @return tunnel state of the tunnel that was created
+ * @param cls our `struct ChannelState *`
+ * @param message the actual message
+ * @return #GNUNET_OK to keep the connection open,
+ *         #GNUNET_SYSERR to close it (signal serious error)
  */
-static struct TunnelState *
-create_tunnel_to_destination (struct DestinationEntry *de,
-                             struct GNUNET_SERVER_Client *client,
-                             int client_af,
-                             uint64_t request_id)
+static int
+check_icmp_back (void *cls,
+                 const struct GNUNET_EXIT_IcmpToVPNMessage *i2v)
 {
-  struct TunnelState *ts;
+  struct ChannelState *ts = cls;
 
-  GNUNET_STATISTICS_update (stats,
-                           gettext_noop ("# Mesh tunnels created"),
-                           1, GNUNET_NO);
-  GNUNET_assert (NULL == de->ts);
-  ts = GNUNET_malloc (sizeof (struct TunnelState));
-  ts->af = client_af;
-  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->tunnel = GNUNET_MESH_tunnel_create (mesh_handle,
-                                         ts,
-                                         &tunnel_peer_connect_handler,
-                                         &tunnel_peer_disconnect_handler,
-                                         ts);
-  if (NULL == ts->tunnel)
+  if (NULL == ts->heap_node)
   {
-    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-               _("Failed to setup mesh tunnel!\n"));
-    if (NULL != client)
-      GNUNET_SERVER_client_drop (client);
-    GNUNET_free (ts);
-    return NULL;
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
   }
-  if (de->is_service)
+  if (AF_UNSPEC == ts->af)
   {
-    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);  
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
   }
-  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;
-}
-
-
-/**
- * We have too many active tunnels.  Clean up the oldest tunnel.
- *
- * @param except tunnel that must NOT be cleaned up, even if it is the oldest
- */
-static void
-expire_tunnel (struct TunnelState *except)
-{
-  struct TunnelState *ts;
-
-  ts = GNUNET_CONTAINER_heap_peek (tunnel_heap);
-  GNUNET_assert (NULL != ts);
-  if (except == ts)
-    return; /* can't do this */
-  free_tunnel_state (ts);
+  return GNUNET_OK;
 }
 
 
 /**
- * Route a packet via mesh to the given destination.  
+ * We got an ICMP packet back from the CADET channel.  Pass it on to the
+ * local virtual interface via the helper.
  *
- * @param destination description of the destination
- * @param af address family on this end (AF_INET or AF_INET6)
- * @param protocol IPPROTO_TCP or IPPROTO_UDP
- * @param source_ip source IP used by the sender (struct in_addr or struct in6_addr)
- * @param destination_ip destination IP used by the sender (struct in_addr or struct in6_addr)
- * @param payload payload of the packet after the IP header
- * @param payload_length number of bytes in payload
+ * @param cls our `struct ChannelState *`
+ * @param message the actual message
  */
 static void
-route_packet (struct DestinationEntry *destination,
-             int af,
-             uint8_t protocol,
-             const void *source_ip,
-             const void *destination_ip,
-             const void *payload,
-             size_t payload_length)
+handle_icmp_back (void *cls,
+                  const struct GNUNET_EXIT_IcmpToVPNMessage *i2v)
 {
-  GNUNET_HashCode key;
-  struct TunnelState *ts;
-  struct TunnelMessageQueueEntry *tnq;
-  size_t alen;
+  struct ChannelState *ts = cls;
   size_t mlen;
-  int is_new;
-  const struct GNUNET_TUN_UdpHeader *udp;
-  const struct GNUNET_TUN_TcpHeader *tcp;
-  const struct GNUNET_TUN_IcmpHeader *icmp;
-  uint16_t spt;
-  uint16_t dpt;
 
-  switch (protocol)
+  GNUNET_STATISTICS_update (stats,
+                           gettext_noop ("# ICMP packets received from cadet"),
+                           1,
+                            GNUNET_NO);
+  mlen = ntohs (i2v->header.size) - sizeof (struct GNUNET_EXIT_IcmpToVPNMessage);
   {
-  case IPPROTO_UDP:
-    {
-      if (payload_length < sizeof (struct GNUNET_TUN_UdpHeader))
-      {
-       /* blame kernel? */
-       GNUNET_break (0);
-       return;
-      }
-      udp = payload;
-      if (udp->len < sizeof (struct GNUNET_TUN_UdpHeader))
-      {
-       GNUNET_break_op (0);
-       return GNUNET_SYSERR;
-      }
-      spt = ntohs (udp->spt);
-      dpt = ntohs (udp->dpt);
-      get_tunnel_key_from_ips (af,
-                              IPPROTO_UDP,
-                              source_ip,
-                              spt,
-                              destination_ip,
-                              dpt,
-                              &key);
-    }
-    break;
-  case IPPROTO_TCP:
-    {
-      if (payload_length < sizeof (struct GNUNET_TUN_TcpHeader))
-      {
-       /* blame kernel? */
-       GNUNET_break (0);
-       return;
-      }
-      tcp = payload;
-      if (tcp->off * 4 < sizeof (struct GNUNET_TUN_TcpHeader))
-      {
-       GNUNET_break_op (0);
-       return GNUNET_SYSERR;
-      }
-      spt = ntohs (tcp->spt);
-      dpt = ntohs (tcp->dpt);
-      get_tunnel_key_from_ips (af,
-                              IPPROTO_TCP,
-                              source_ip,
-                              spt,
-                              destination_ip,
-                              dpt,
-                              &key);
-    }
-    break;
-  case IPPROTO_ICMP:
-    {
-      if (payload_length < sizeof (struct GNUNET_TUN_IcmpHeader))
-      {
-       /* blame kernel? */
-       GNUNET_break (0);
-       return;
-      }
-      icmp = payload;
-      spt = 0;
-      dpt = 0;
-      get_tunnel_key_from_ips (af,
-                              IPPROTO_ICMP,
-                              source_ip,
-                              0,
-                              destination_ip,
-                              0,
-                              &key);
-    }
-    break;
-  default:
-    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-               _("Protocol %u not supported, dropping\n"),
-               (unsigned int) protocol);
-    return;
+    char sbuf[INET6_ADDRSTRLEN];
+    char dbuf[INET6_ADDRSTRLEN];
+
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+               "Received ICMP packet from cadet, sending %u bytes from %s -> %s via TUN\n",
+               (unsigned int) mlen,
+               inet_ntop (ts->af, &ts->destination_ip, sbuf, sizeof (sbuf)),
+               inet_ntop (ts->af, &ts->source_ip, dbuf, sizeof (dbuf)));
   }
-  if (! destination->is_service)
-  {  
-    switch (destination->details.exit_destination.af)
+  switch (ts->af)
+  {
+  case AF_INET:
     {
-    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)),
-                 dpt);
-    }
-  }
-  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));
-    }
-
-  }
-
-  /* see if we have an existing tunnel for this destination */
-  ts = GNUNET_CONTAINER_multihashmap_get (tunnel_map,
-                                         &key);
-  if (NULL == ts)
-  {
-    /* 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, af, 0);
-    else
-      ts = destination->ts;
-    if (NULL == ts)
-      return;
-    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);
-    while (GNUNET_CONTAINER_multihashmap_size (tunnel_map) > max_tunnel_mappings)
-      expire_tunnel (ts);
-  }
-  else
-  {
-    is_new = GNUNET_NO;
-    GNUNET_CONTAINER_heap_update_cost (tunnel_heap, 
-                                      ts->heap_node,
-                                      GNUNET_TIME_absolute_get ().abs_value);
-  }
-  GNUNET_assert (NULL != ts->tunnel);
-  
-  /* send via tunnel */
-  switch (protocol)
-  {
-  case IPPROTO_UDP:
-    if (destination->is_service)
-    {
-      struct GNUNET_EXIT_UdpServiceMessage *usm;
-
-      mlen = sizeof (struct GNUNET_EXIT_UdpServiceMessage) + 
-       payload_length - sizeof (struct GNUNET_TUN_UdpHeader);
-      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 GNUNET_TUN_UdpHeader));
-    }
-    else
-    {
-      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 GNUNET_TUN_UdpHeader);
-      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 GNUNET_TUN_UdpHeader));
-    }
-    break;
-  case IPPROTO_TCP:
-    if (is_new)
-    {
-      if (destination->is_service)
-      {
-       struct GNUNET_EXIT_TcpServiceStartMessage *tsm;
-
-       mlen = sizeof (struct GNUNET_EXIT_TcpServiceStartMessage) + 
-         payload_length - sizeof (struct GNUNET_TUN_TcpHeader);
-       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 GNUNET_TUN_TcpHeader));
-      }
-      else
+      size_t size = sizeof (struct GNUNET_TUN_IPv4Header)
+       + sizeof (struct GNUNET_TUN_IcmpHeader)
+       + sizeof (struct GNUNET_MessageHeader) +
+       sizeof (struct GNUNET_TUN_Layer2PacketHeader) +
+       mlen;
       {
-       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 GNUNET_TUN_TcpHeader);
-       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)
+       /* reserve some extra space in case we have an ICMP type here where
+          we will need to make up the payload ourselves */
+       char buf[size + sizeof (struct GNUNET_TUN_IPv4Header) + 8] GNUNET_ALIGN;
+       struct GNUNET_MessageHeader *msg = (struct GNUNET_MessageHeader *) buf;
+       struct GNUNET_TUN_Layer2PacketHeader *tun = (struct GNUNET_TUN_Layer2PacketHeader*) &msg[1];
+       struct GNUNET_TUN_IPv4Header *ipv4 = (struct GNUNET_TUN_IPv4Header *) &tun[1];
+       struct GNUNET_TUN_IcmpHeader *icmp = (struct GNUNET_TUN_IcmpHeader *) &ipv4[1];
+       msg->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
+       tun->flags = htons (0);
+       tun->proto = htons (ETH_P_IPV4);
+       GNUNET_TUN_initialize_ipv4_header (ipv4,
+                                          IPPROTO_ICMP,
+                                          sizeof (struct GNUNET_TUN_IcmpHeader) + mlen,
+                                          &ts->destination_ip.v4,
+                                          &ts->source_ip.v4);
+       *icmp = i2v->icmp_header;
+       GNUNET_memcpy (&icmp[1],
+                       &i2v[1],
+                       mlen);
+       /* For some ICMP types, we need to adjust (make up) the payload here.
+          Also, depending on the AF used on the other side, we have to
+          do ICMP PT (translate ICMP types) */
+       switch (ntohl (i2v->af))
        {
        case AF_INET:
-         ip4dst = (struct in_addr *) &tim[1];
-         *ip4dst = destination->details.exit_destination.ip.v4;
-         payload = &ip4dst[1];
+         switch (icmp->type)
+         {
+         case GNUNET_TUN_ICMPTYPE_ECHO_REPLY:
+         case GNUNET_TUN_ICMPTYPE_ECHO_REQUEST:
+           break;
+         case GNUNET_TUN_ICMPTYPE_DESTINATION_UNREACHABLE:
+         case GNUNET_TUN_ICMPTYPE_SOURCE_QUENCH:
+         case GNUNET_TUN_ICMPTYPE_TIME_EXCEEDED:
+           {
+             struct GNUNET_TUN_IPv4Header *ipp = (struct GNUNET_TUN_IPv4Header *) &icmp[1];
+             struct GNUNET_TUN_UdpHeader *udp = (struct GNUNET_TUN_UdpHeader *) &ipp[1];
+
+             if (mlen != 0)
+               {
+                 /* sender did not strip ICMP payload? */
+                 GNUNET_break_op (0);
+                 return;
+               }
+             size += sizeof (struct GNUNET_TUN_IPv4Header) + 8;
+             GNUNET_assert (8 == sizeof (struct GNUNET_TUN_UdpHeader));
+             make_up_icmpv4_payload (ts, ipp, udp);
+           }
+           break;
+         default:
+           GNUNET_break_op (0);
+           GNUNET_STATISTICS_update (stats,
+                                     gettext_noop ("# ICMPv4 packets dropped (type not allowed)"),
+                                     1, GNUNET_NO);
+           return;
+         }
+         /* end AF_INET */
          break;
        case AF_INET6:
-         ip6dst = (struct in6_addr *) &tim[1];
-         *ip6dst = destination->details.exit_destination.ip.v6;
-         payload = &ip6dst[1];
+         /* ICMP PT 6-to-4 and possibly making up payloads */
+         switch (icmp->type)
+         {
+         case GNUNET_TUN_ICMPTYPE6_DESTINATION_UNREACHABLE:
+           icmp->type = GNUNET_TUN_ICMPTYPE_DESTINATION_UNREACHABLE;
+           {
+             struct GNUNET_TUN_IPv4Header *ipp = (struct GNUNET_TUN_IPv4Header *) &icmp[1];
+             struct GNUNET_TUN_UdpHeader *udp = (struct GNUNET_TUN_UdpHeader *) &ipp[1];
+
+             if (mlen != 0)
+               {
+                 /* sender did not strip ICMP payload? */
+                 GNUNET_break_op (0);
+                 return;
+               }
+             size += sizeof (struct GNUNET_TUN_IPv4Header) + 8;
+             GNUNET_assert (8 == sizeof (struct GNUNET_TUN_UdpHeader));
+             make_up_icmpv4_payload (ts, ipp, udp);
+           }
+           break;
+         case GNUNET_TUN_ICMPTYPE6_TIME_EXCEEDED:
+           icmp->type = GNUNET_TUN_ICMPTYPE_TIME_EXCEEDED;
+           {
+             struct GNUNET_TUN_IPv4Header *ipp = (struct GNUNET_TUN_IPv4Header *) &icmp[1];
+             struct GNUNET_TUN_UdpHeader *udp = (struct GNUNET_TUN_UdpHeader *) &ipp[1];
+
+             if (mlen != 0)
+               {
+                 /* sender did not strip ICMP payload? */
+                 GNUNET_break_op (0);
+                 return;
+               }
+             size += sizeof (struct GNUNET_TUN_IPv4Header) + 8;
+             GNUNET_assert (8 == sizeof (struct GNUNET_TUN_UdpHeader));
+             make_up_icmpv4_payload (ts, ipp, udp);
+           }
+           break;
+         case GNUNET_TUN_ICMPTYPE6_PACKET_TOO_BIG:
+         case GNUNET_TUN_ICMPTYPE6_PARAMETER_PROBLEM:
+           GNUNET_STATISTICS_update (stats,
+                                     gettext_noop ("# ICMPv6 packets dropped (impossible PT to v4)"),
+                                     1, GNUNET_NO);
+           return;
+         case GNUNET_TUN_ICMPTYPE6_ECHO_REQUEST:
+           icmp->type = GNUNET_TUN_ICMPTYPE_ECHO_REQUEST;
+           break;
+         case GNUNET_TUN_ICMPTYPE6_ECHO_REPLY:
+           icmp->type = GNUNET_TUN_ICMPTYPE_ECHO_REPLY;
+           break;
+         default:
+           GNUNET_break_op (0);
+           GNUNET_STATISTICS_update (stats,
+                                     gettext_noop ("# ICMPv6 packets dropped (type not allowed)"),
+                                     1, GNUNET_NO);
+           return;
+         }
+         /* end AF_INET6 */
          break;
        default:
-         GNUNET_assert (0);
+         GNUNET_break_op (0);
+         return;
        }
-       memcpy (payload,
-               &tcp[1],
-               payload_length - sizeof (struct GNUNET_TUN_TcpHeader));
+       msg->size = htons (size);
+       GNUNET_TUN_calculate_icmp_checksum (icmp,
+                                           &i2v[1],
+                                           mlen);
+       (void) GNUNET_HELPER_send (helper_handle,
+                                  msg,
+                                  GNUNET_YES,
+                                  NULL, NULL);
       }
     }
-    else
+    break;
+  case AF_INET6:
     {
-      struct GNUNET_EXIT_TcpDataMessage *tdm;
-
-      mlen = sizeof (struct GNUNET_EXIT_TcpDataMessage) + 
-       payload_length - sizeof (struct GNUNET_TUN_TcpHeader);
-      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_TO_EXIT);
-      tdm->reserved = htonl (0);
-      tdm->tcp_header = *tcp;
-      memcpy (&tdm[1],
-             &tcp[1],
-             payload_length - sizeof (struct GNUNET_TUN_TcpHeader));
-     }
-    break;
-  case IPPROTO_ICMP:
-    if (destination->is_service)
-    {
-      struct GNUNET_EXIT_IcmpServiceMessage *ism;
-
-      mlen = sizeof (struct GNUNET_EXIT_IcmpServiceMessage) + 
-       payload_length - sizeof (struct GNUNET_TUN_IcmpHeader);
-      if (mlen >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
-      {
-       GNUNET_break (0);
-       return;
-      }
-      tnq = GNUNET_malloc (sizeof (struct TunnelMessageQueueEntry) + mlen);
-      tnq->msg = &tnq[1];
-      ism = (struct GNUNET_EXIT_IcmpServiceMessage *) &tnq[1];
-      ism->header.type = htons (GNUNET_MESSAGE_TYPE_VPN_ICMP_TO_SERVICE);
-      ism->af = htonl (af); /* need to tell destination ICMP protocol family! */
-      ism->service_descriptor = destination->details.service_destination.service_descriptor;
-      ism->icmp_header = *icmp;
-      /* ICMP protocol translation will be done by the receiver (as we don't know
-        the target AF); however, we still need to possibly discard the payload
-        depending on the ICMP type */
-      switch (af)
+      size_t size = sizeof (struct GNUNET_TUN_IPv6Header)
+       + sizeof (struct GNUNET_TUN_IcmpHeader)
+       + sizeof (struct GNUNET_MessageHeader) +
+       sizeof (struct GNUNET_TUN_Layer2PacketHeader) +
+       mlen;
       {
-      case AF_INET:
-       switch (icmp->type)
-       {
-       case GNUNET_TUN_ICMPTYPE_ECHO_REPLY:
-       case GNUNET_TUN_ICMPTYPE_ECHO_REQUEST:
-         break;
-       case GNUNET_TUN_ICMPTYPE_DESTINATION_UNREACHABLE:
-       case GNUNET_TUN_ICMPTYPE_SOURCE_QUENCH:
-       case GNUNET_TUN_ICMPTYPE_TIME_EXCEEDED:
-         /* throw away ICMP payload, won't be useful for the other side anyway */
-         payload_length = sizeof (struct GNUNET_TUN_IcmpHeader); 
-         break;
-       default:
-         GNUNET_STATISTICS_update (stats,
-                                   gettext_noop ("# ICMPv4 packets dropped (not allowed)"),
-                                   1, GNUNET_NO);
-         return;
-       }
-       /* end of AF_INET */
-       break;
-      case AF_INET6:
-       switch (icmp->type)
-       {
-       case GNUNET_TUN_ICMPTYPE6_DESTINATION_UNREACHABLE:
-       case GNUNET_TUN_ICMPTYPE6_PACKET_TOO_BIG:
-       case GNUNET_TUN_ICMPTYPE6_TIME_EXCEEDED:
-       case GNUNET_TUN_ICMPTYPE6_PARAMETER_PROBLEM:
-         /* throw away ICMP payload, won't be useful for the other side anyway */
-         payload_length = sizeof (struct GNUNET_TUN_IcmpHeader); 
-         break;
-       case GNUNET_TUN_ICMPTYPE6_ECHO_REQUEST:
-       case GNUNET_TUN_ICMPTYPE6_ECHO_REPLY:
-         break;
-       default:
-         GNUNET_STATISTICS_update (stats,
-                                   gettext_noop ("# ICMPv6 packets dropped (not allowed)"),
-                                   1, GNUNET_NO);
-         return;
-       }       
-       /* end of AF_INET6 */
-       break;
-      default:
-       GNUNET_assert (0);
-       break;
-      }
-
-      /* update length calculations, as payload_length may have changed */
-      mlen = sizeof (struct GNUNET_EXIT_IcmpServiceMessage) + 
-       alen + payload_length - sizeof (struct GNUNET_TUN_IcmpHeader);      
-      tnq->len = mlen;
-      ism->header.size = htons ((uint16_t) mlen);
-      /* finally, copy payload (if there is any left...) */
-      memcpy (&ism[1],
-             &icmp[1],
-             payload_length - sizeof (struct GNUNET_TUN_IcmpHeader));
-    }
-    else
-    {
-      struct GNUNET_EXIT_IcmpInternetMessage *iim;
-      struct in_addr *ip4dst;
-      struct in6_addr *ip6dst;
-      void *payload;
+       char buf[size + sizeof (struct GNUNET_TUN_IPv6Header) + 8] GNUNET_ALIGN;
+       struct GNUNET_MessageHeader *msg = (struct GNUNET_MessageHeader *) buf;
+       struct GNUNET_TUN_Layer2PacketHeader *tun = (struct GNUNET_TUN_Layer2PacketHeader*) &msg[1];
+       struct GNUNET_TUN_IPv6Header *ipv6 = (struct GNUNET_TUN_IPv6Header *) &tun[1];
+       struct GNUNET_TUN_IcmpHeader *icmp = (struct GNUNET_TUN_IcmpHeader *) &ipv6[1];
+       msg->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
+       tun->flags = htons (0);
+       tun->proto = htons (ETH_P_IPV6);
+       GNUNET_TUN_initialize_ipv6_header (ipv6,
+                                          IPPROTO_ICMPV6,
+                                          sizeof (struct GNUNET_TUN_IcmpHeader) + mlen,
+                                          &ts->destination_ip.v6,
+                                          &ts->source_ip.v6);
+       *icmp = i2v->icmp_header;
+       GNUNET_memcpy (&icmp[1],
+               &i2v[1],
+               mlen);
 
-      mlen = sizeof (struct GNUNET_EXIT_IcmpInternetMessage) + 
-       alen + payload_length - sizeof (struct GNUNET_TUN_IcmpHeader);
-      if (mlen >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
-      {
-       GNUNET_break (0);
-       return;
-      }
-      tnq = GNUNET_malloc (sizeof (struct TunnelMessageQueueEntry) + 
-                          mlen);
-      tnq->msg = &tnq[1];
-      iim = (struct GNUNET_EXIT_IcmpInternetMessage *) &tnq[1];
-      iim->header.type = htons (GNUNET_MESSAGE_TYPE_VPN_ICMP_TO_INTERNET); 
-      iim->icmp_header = *icmp;
-      /* Perform ICMP protocol-translation (depending on destination AF and source AF)
-        and throw away ICMP payload depending on ICMP message type */
-      switch (af)
-      {
-      case AF_INET:
-       switch (icmp->type)
+       /* For some ICMP types, we need to adjust (make up) the payload here.
+          Also, depending on the AF used on the other side, we have to
+          do ICMP PT (translate ICMP types) */
+       switch (ntohl (i2v->af))
        {
-       case GNUNET_TUN_ICMPTYPE_ECHO_REPLY:      
-         if (destination->details.exit_destination.af == AF_INET6)
-           iim->icmp_header.type = GNUNET_TUN_ICMPTYPE6_ECHO_REPLY;
-         break;
-       case GNUNET_TUN_ICMPTYPE_ECHO_REQUEST:    
-         if (destination->details.exit_destination.af == AF_INET6)
-           iim->icmp_header.type = GNUNET_TUN_ICMPTYPE6_ECHO_REQUEST;
-         break;
-       case GNUNET_TUN_ICMPTYPE_DESTINATION_UNREACHABLE:
-         if (destination->details.exit_destination.af == AF_INET6)
-           iim->icmp_header.type = GNUNET_TUN_ICMPTYPE6_DESTINATION_UNREACHABLE;
-         /* throw away IP-payload, exit will have to make it up anyway */
-         payload_length = sizeof (struct GNUNET_TUN_IcmpHeader);
-         break;
-       case GNUNET_TUN_ICMPTYPE_TIME_EXCEEDED: 
-         if (destination->details.exit_destination.af == AF_INET6)
-           iim->icmp_header.type = GNUNET_TUN_ICMPTYPE6_TIME_EXCEEDED;
-         /* throw away IP-payload, exit will have to make it up anyway */
-         payload_length = sizeof (struct GNUNET_TUN_IcmpHeader);
-         break;
-       case GNUNET_TUN_ICMPTYPE_SOURCE_QUENCH:
-         if (destination->details.exit_destination.af == AF_INET6)
+       case AF_INET:
+         /* ICMP PT 4-to-6 and possibly making up payloads */
+         switch (icmp->type)
+         {
+         case GNUNET_TUN_ICMPTYPE_ECHO_REPLY:
+           icmp->type = GNUNET_TUN_ICMPTYPE6_ECHO_REPLY;
+           break;
+         case GNUNET_TUN_ICMPTYPE_ECHO_REQUEST:
+           icmp->type = GNUNET_TUN_ICMPTYPE6_ECHO_REQUEST;
+           break;
+         case GNUNET_TUN_ICMPTYPE_DESTINATION_UNREACHABLE:
+           icmp->type = GNUNET_TUN_ICMPTYPE6_DESTINATION_UNREACHABLE;
            {
-             GNUNET_STATISTICS_update (stats,
-                                       gettext_noop ("# ICMPv4 packets dropped (impossible PT to v6)"),
-                                       1, GNUNET_NO);
-             GNUNET_free (tnq);
-             return;
+             struct GNUNET_TUN_IPv6Header *ipp = (struct GNUNET_TUN_IPv6Header *) &icmp[1];
+             struct GNUNET_TUN_UdpHeader *udp = (struct GNUNET_TUN_UdpHeader *) &ipp[1];
+
+             if (mlen != 0)
+               {
+                 /* sender did not strip ICMP payload? */
+                 GNUNET_break_op (0);
+                 return;
+               }
+             size += sizeof (struct GNUNET_TUN_IPv6Header) + 8;
+             GNUNET_assert (8 == sizeof (struct GNUNET_TUN_UdpHeader));
+             make_up_icmpv6_payload (ts, ipp, udp);
            }
-         /* throw away IP-payload, exit will have to make it up anyway */
-         payload_length = sizeof (struct GNUNET_TUN_IcmpHeader);
+           break;
+         case GNUNET_TUN_ICMPTYPE_TIME_EXCEEDED:
+           icmp->type = GNUNET_TUN_ICMPTYPE6_TIME_EXCEEDED;
+           {
+             struct GNUNET_TUN_IPv6Header *ipp = (struct GNUNET_TUN_IPv6Header *) &icmp[1];
+             struct GNUNET_TUN_UdpHeader *udp = (struct GNUNET_TUN_UdpHeader *) &ipp[1];
+
+             if (mlen != 0)
+               {
+                 /* sender did not strip ICMP payload? */
+                 GNUNET_break_op (0);
+                 return;
+               }
+             size += sizeof (struct GNUNET_TUN_IPv6Header) + 8;
+             GNUNET_assert (8 == sizeof (struct GNUNET_TUN_UdpHeader));
+             make_up_icmpv6_payload (ts, ipp, udp);
+           }
+           break;
+         case GNUNET_TUN_ICMPTYPE_SOURCE_QUENCH:
+           GNUNET_STATISTICS_update (stats,
+                                     gettext_noop ("# ICMPv4 packets dropped (impossible PT to v6)"),
+                                     1, GNUNET_NO);
+           return;
+         default:
+           GNUNET_break_op (0);
+           GNUNET_STATISTICS_update (stats,
+                                     gettext_noop ("# ICMPv4 packets dropped (type not allowed)"),
+                                     1, GNUNET_NO);
+           return;
+         }
+         /* end AF_INET */
          break;
-       default:
-         GNUNET_STATISTICS_update (stats,
-                                   gettext_noop ("# ICMPv4 packets dropped (type not allowed)"),
-                                   1, GNUNET_NO);
-         GNUNET_free (tnq);        
-         return;
-       }
-       /* end of AF_INET */
-       break;
-      case AF_INET6:
-       switch (icmp->type)
+       case AF_INET6:
+         switch (icmp->type)
          {
          case GNUNET_TUN_ICMPTYPE6_DESTINATION_UNREACHABLE:
-           if (destination->details.exit_destination.af == AF_INET6)
-             iim->icmp_header.type = GNUNET_TUN_ICMPTYPE6_DESTINATION_UNREACHABLE;
-           /* throw away IP-payload, exit will have to make it up anyway */
-           payload_length = sizeof (struct GNUNET_TUN_IcmpHeader);
-           break;
          case GNUNET_TUN_ICMPTYPE6_TIME_EXCEEDED:
-           if (destination->details.exit_destination.af == AF_INET)
-             iim->icmp_header.type = GNUNET_TUN_ICMPTYPE_TIME_EXCEEDED;
-           /* throw away IP-payload, exit will have to make it up anyway */
-           payload_length = sizeof (struct GNUNET_TUN_IcmpHeader);
-           break;
          case GNUNET_TUN_ICMPTYPE6_PACKET_TOO_BIG:
-           if (destination->details.exit_destination.af == AF_INET)
-           {
-             GNUNET_STATISTICS_update (stats,
-                                       gettext_noop ("# ICMPv6 packets dropped (impossible PT to v4)"),
-                                       1, GNUNET_NO);
-             GNUNET_free (tnq);
-             return;
-           }
-           /* throw away IP-payload, exit will have to make it up anyway */
-           payload_length = sizeof (struct GNUNET_TUN_IcmpHeader);
-           break;
          case GNUNET_TUN_ICMPTYPE6_PARAMETER_PROBLEM:
-           if (destination->details.exit_destination.af == AF_INET)
            {
-             GNUNET_STATISTICS_update (stats,
-                                       gettext_noop ("# ICMPv6 packets dropped (impossible PT to v4)"),
-                                       1, GNUNET_NO);
-             GNUNET_free (tnq);
-             return;
+             struct GNUNET_TUN_IPv6Header *ipp = (struct GNUNET_TUN_IPv6Header *) &icmp[1];
+             struct GNUNET_TUN_UdpHeader *udp = (struct GNUNET_TUN_UdpHeader *) &ipp[1];
+
+             if (mlen != 0)
+               {
+                 /* sender did not strip ICMP payload? */
+                 GNUNET_break_op (0);
+                 return;
+               }
+             size += sizeof (struct GNUNET_TUN_IPv6Header) + 8;
+             GNUNET_assert (8 == sizeof (struct GNUNET_TUN_UdpHeader));
+             make_up_icmpv6_payload (ts, ipp, udp);
            }
-           /* throw away IP-payload, exit will have to make it up anyway */
-           payload_length = sizeof (struct GNUNET_TUN_IcmpHeader);
            break;
          case GNUNET_TUN_ICMPTYPE6_ECHO_REQUEST:
-           if (destination->details.exit_destination.af == AF_INET)
-             iim->icmp_header.type = GNUNET_TUN_ICMPTYPE_ECHO_REQUEST;
-           break;
-         case GNUNET_TUN_ICMPTYPE6_ECHO_REPLY:
-           if (destination->details.exit_destination.af == AF_INET)
-             iim->icmp_header.type = GNUNET_TUN_ICMPTYPE_ECHO_REPLY;
            break;
          default:
+           GNUNET_break_op (0);
            GNUNET_STATISTICS_update (stats,
                                      gettext_noop ("# ICMPv6 packets dropped (type not allowed)"),
                                      1, GNUNET_NO);
-           GNUNET_free (tnq);      
            return;
          }
-       /* end of AF_INET6 */
-       break;
-      default:
-       GNUNET_assert (0);
-      } 
-      /* update length calculations, as payload_length may have changed */
-      mlen = sizeof (struct GNUNET_EXIT_IcmpInternetMessage) + 
-       alen + payload_length - sizeof (struct GNUNET_TUN_IcmpHeader);      
-      tnq->len = mlen;
-      iim->header.size = htons ((uint16_t) mlen);
+         /* end AF_INET6 */
+         break;
+       default:
+         GNUNET_break_op (0);
+         return;
+       }
+       msg->size = htons (size);
+       GNUNET_TUN_calculate_icmp_checksum (icmp,
+                                           &i2v[1], mlen);
+       (void) GNUNET_HELPER_send (helper_handle,
+                                  msg,
+                                  GNUNET_YES,
+                                  NULL, NULL);
+      }
+    }
+    break;
+  default:
+    GNUNET_assert (0);
+  }
+  GNUNET_CONTAINER_heap_update_cost (ts->heap_node,
+                                    GNUNET_TIME_absolute_get ().abs_value_us);
+  GNUNET_CADET_receive_done (ts->channel);
+}
 
-      /* need to tell destination ICMP protocol family! */
-      iim->af = htonl (destination->details.exit_destination.af);
-      switch (destination->details.exit_destination.af)
+
+/**
+ * We got a UDP packet back from the CADET channel.  Check that it is OK.
+ *
+ * @param cls our `struct ChannelState *`
+ * @param reply the actual message
+ * @return #GNUNET_OK to keep the connection open,
+ *         #GNUNET_SYSERR to close it (signal serious error)
+ */
+static int
+check_udp_back (void *cls,
+                  const struct GNUNET_EXIT_UdpReplyMessage *reply)
+{
+  struct ChannelState *ts = cls;
+
+  if (NULL == ts->heap_node)
+  {
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
+  }
+  if (AF_UNSPEC == ts->af)
+  {
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
+  }
+  return GNUNET_OK;
+}
+
+
+/**
+ * We got a UDP packet back from the CADET channel.  Pass it on to the
+ * local virtual interface via the helper.
+ *
+ * @param cls our `struct ChannelState *`
+ * @param reply the actual message
+ */
+static void
+handle_udp_back (void *cls,
+                 const struct GNUNET_EXIT_UdpReplyMessage *reply)
+{
+  struct ChannelState *ts = cls;
+  size_t mlen;
+
+  GNUNET_STATISTICS_update (stats,
+                           gettext_noop ("# UDP packets received from cadet"),
+                           1,
+                            GNUNET_NO);
+  mlen = ntohs (reply->header.size) - sizeof (struct GNUNET_EXIT_UdpReplyMessage);
+  {
+    char sbuf[INET6_ADDRSTRLEN];
+    char dbuf[INET6_ADDRSTRLEN];
+
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+               "Received UDP reply from cadet, 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:
+    {
+      size_t size = sizeof (struct GNUNET_TUN_IPv4Header)
+       + sizeof (struct GNUNET_TUN_UdpHeader)
+       + sizeof (struct GNUNET_MessageHeader) +
+       sizeof (struct GNUNET_TUN_Layer2PacketHeader) +
+       mlen;
       {
-      case AF_INET:
-       ip4dst = (struct in_addr *) &iim[1];
-       *ip4dst = destination->details.exit_destination.ip.v4;
-       payload = &ip4dst[1];
-       break;
-      case AF_INET6:
-       ip6dst = (struct in6_addr *) &iim[1];
-       *ip6dst = destination->details.exit_destination.ip.v6;
-       payload = &ip6dst[1];
-       break;
-      default:
-       GNUNET_assert (0);
+       char buf[size] GNUNET_ALIGN;
+       struct GNUNET_MessageHeader *msg = (struct GNUNET_MessageHeader *) buf;
+       struct GNUNET_TUN_Layer2PacketHeader *tun = (struct GNUNET_TUN_Layer2PacketHeader*) &msg[1];
+       struct GNUNET_TUN_IPv4Header *ipv4 = (struct GNUNET_TUN_IPv4Header *) &tun[1];
+       struct GNUNET_TUN_UdpHeader *udp = (struct GNUNET_TUN_UdpHeader *) &ipv4[1];
+       msg->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
+       msg->size = htons (size);
+       tun->flags = htons (0);
+       tun->proto = htons (ETH_P_IPV4);
+       GNUNET_TUN_initialize_ipv4_header (ipv4,
+                                          IPPROTO_UDP,
+                                          sizeof (struct GNUNET_TUN_UdpHeader) + mlen,
+                                          &ts->destination_ip.v4,
+                                          &ts->source_ip.v4);
+       if (0 == ntohs (reply->source_port))
+         udp->source_port = htons (ts->destination_port);
+       else
+         udp->source_port = reply->source_port;
+       if (0 == ntohs (reply->destination_port))
+         udp->destination_port = htons (ts->source_port);
+       else
+         udp->destination_port = reply->destination_port;
+       udp->len = htons (mlen + sizeof (struct GNUNET_TUN_UdpHeader));
+       GNUNET_TUN_calculate_udp4_checksum (ipv4,
+                                           udp,
+                                           &reply[1],
+                                           mlen);
+       GNUNET_memcpy (&udp[1],
+               &reply[1],
+               mlen);
+       (void) GNUNET_HELPER_send (helper_handle,
+                                  msg,
+                                  GNUNET_YES,
+                                  NULL, NULL);
+      }
+    }
+    break;
+  case AF_INET6:
+    {
+      size_t size = sizeof (struct GNUNET_TUN_IPv6Header)
+       + sizeof (struct GNUNET_TUN_UdpHeader)
+       + sizeof (struct GNUNET_MessageHeader) +
+       sizeof (struct GNUNET_TUN_Layer2PacketHeader) +
+       mlen;
+      {
+       char buf[size] GNUNET_ALIGN;
+       struct GNUNET_MessageHeader *msg = (struct GNUNET_MessageHeader *) buf;
+       struct GNUNET_TUN_Layer2PacketHeader *tun = (struct GNUNET_TUN_Layer2PacketHeader*) &msg[1];
+       struct GNUNET_TUN_IPv6Header *ipv6 = (struct GNUNET_TUN_IPv6Header *) &tun[1];
+       struct GNUNET_TUN_UdpHeader *udp = (struct GNUNET_TUN_UdpHeader *) &ipv6[1];
+       msg->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
+       msg->size = htons (size);
+       tun->flags = htons (0);
+       tun->proto = htons (ETH_P_IPV6);
+       GNUNET_TUN_initialize_ipv6_header (ipv6,
+                                          IPPROTO_UDP,
+                                          sizeof (struct GNUNET_TUN_UdpHeader) + mlen,
+                                          &ts->destination_ip.v6,
+                                          &ts->source_ip.v6);
+       if (0 == ntohs (reply->source_port))
+         udp->source_port = htons (ts->destination_port);
+       else
+         udp->source_port = reply->source_port;
+       if (0 == ntohs (reply->destination_port))
+         udp->destination_port = htons (ts->source_port);
+       else
+         udp->destination_port = reply->destination_port;
+       udp->len = htons (mlen + sizeof (struct GNUNET_TUN_UdpHeader));
+       GNUNET_TUN_calculate_udp6_checksum (ipv6,
+                                           udp,
+                                           &reply[1], mlen);
+       GNUNET_memcpy (&udp[1],
+               &reply[1],
+               mlen);
+       (void) GNUNET_HELPER_send (helper_handle,
+                                  msg,
+                                  GNUNET_YES,
+                                  NULL, NULL);
+      }
+    }
+    break;
+  default:
+    GNUNET_assert (0);
+  }
+  GNUNET_CONTAINER_heap_update_cost (ts->heap_node,
+                                    GNUNET_TIME_absolute_get ().abs_value_us);
+  GNUNET_CADET_receive_done (ts->channel);
+}
+
+
+/**
+ * We got a TCP packet back from the CADET channel.  Check it is OK.
+ *
+ * @param cls our `struct ChannelState *`
+ * @param data the actual message
+ * @return #GNUNET_OK to keep the connection open,
+ *         #GNUNET_SYSERR to close it (signal serious error)
+ */
+static int
+check_tcp_back (void *cls,
+                  const struct GNUNET_EXIT_TcpDataMessage *data)
+{
+  struct ChannelState *ts = cls;
+
+  if (NULL == ts->heap_node)
+  {
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
+  }
+  if (data->tcp_header.off * 4 < sizeof (struct GNUNET_TUN_TcpHeader))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
+  }
+  return GNUNET_OK;
+}
+
+
+/**
+ * We got a TCP packet back from the CADET channel.  Pass it on to the
+ * local virtual interface via the helper.
+ *
+ * @param cls our `struct ChannelState *`
+ * @param data the actual message
+ */
+static void
+handle_tcp_back (void *cls,
+                 const struct GNUNET_EXIT_TcpDataMessage *data)
+{
+  struct ChannelState *ts = cls;
+  size_t mlen;
+
+  GNUNET_STATISTICS_update (stats,
+                           gettext_noop ("# TCP packets received from cadet"),
+                           1,
+                            GNUNET_NO);
+  mlen = ntohs (data->header.size) - sizeof (struct GNUNET_EXIT_TcpDataMessage);
+  {
+    char sbuf[INET6_ADDRSTRLEN];
+    char dbuf[INET6_ADDRSTRLEN];
+
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+               "Received TCP reply from cadet, 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:
+    {
+      size_t size = sizeof (struct GNUNET_TUN_IPv4Header)
+       + sizeof (struct GNUNET_TUN_TcpHeader)
+       + sizeof (struct GNUNET_MessageHeader) +
+       sizeof (struct GNUNET_TUN_Layer2PacketHeader) +
+       mlen;
+      {
+       char buf[size] GNUNET_ALIGN;
+       struct GNUNET_MessageHeader *msg = (struct GNUNET_MessageHeader *) buf;
+       struct GNUNET_TUN_Layer2PacketHeader *tun = (struct GNUNET_TUN_Layer2PacketHeader*) &msg[1];
+       struct GNUNET_TUN_IPv4Header *ipv4 = (struct GNUNET_TUN_IPv4Header *) &tun[1];
+       struct GNUNET_TUN_TcpHeader *tcp = (struct GNUNET_TUN_TcpHeader *) &ipv4[1];
+       msg->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
+       msg->size = htons (size);
+       tun->flags = htons (0);
+       tun->proto = htons (ETH_P_IPV4);
+       GNUNET_TUN_initialize_ipv4_header (ipv4,
+                                          IPPROTO_TCP,
+                                          sizeof (struct GNUNET_TUN_TcpHeader) + mlen,
+                                          &ts->destination_ip.v4,
+                                          &ts->source_ip.v4);
+       *tcp = data->tcp_header;
+       tcp->source_port = htons (ts->destination_port);
+       tcp->destination_port = htons (ts->source_port);
+       GNUNET_TUN_calculate_tcp4_checksum (ipv4,
+                                           tcp,
+                                           &data[1],
+                                           mlen);
+       GNUNET_memcpy (&tcp[1],
+                       &data[1],
+                       mlen);
+       (void) GNUNET_HELPER_send (helper_handle,
+                                  msg,
+                                  GNUNET_YES,
+                                  NULL, NULL);
       }
-      memcpy (payload,
-             &icmp[1],
-             payload_length - sizeof (struct GNUNET_TUN_IcmpHeader));
     }
     break;
+  case AF_INET6:
+    {
+      size_t size = sizeof (struct GNUNET_TUN_IPv6Header)
+       + sizeof (struct GNUNET_TUN_TcpHeader)
+       + sizeof (struct GNUNET_MessageHeader) +
+       sizeof (struct GNUNET_TUN_Layer2PacketHeader) +
+       mlen;
+      {
+       char buf[size] GNUNET_ALIGN;
+       struct GNUNET_MessageHeader *msg = (struct GNUNET_MessageHeader *) buf;
+       struct GNUNET_TUN_Layer2PacketHeader *tun = (struct GNUNET_TUN_Layer2PacketHeader*) &msg[1];
+       struct GNUNET_TUN_IPv6Header *ipv6 = (struct GNUNET_TUN_IPv6Header *) &tun[1];
+       struct GNUNET_TUN_TcpHeader *tcp = (struct GNUNET_TUN_TcpHeader *) &ipv6[1];
+       msg->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
+       msg->size = htons (size);
+       tun->flags = htons (0);
+       tun->proto = htons (ETH_P_IPV6);
+       GNUNET_TUN_initialize_ipv6_header (ipv6,
+                                          IPPROTO_TCP,
+                                          sizeof (struct GNUNET_TUN_TcpHeader) + mlen,
+                                          &ts->destination_ip.v6,
+                                          &ts->source_ip.v6);
+       *tcp = data->tcp_header;
+       tcp->source_port = htons (ts->destination_port);
+       tcp->destination_port = htons (ts->source_port);
+       GNUNET_TUN_calculate_tcp6_checksum (ipv6,
+                                           tcp,
+                                           &data[1],
+                                           mlen);
+       GNUNET_memcpy (&tcp[1],
+                       &data[1],
+                       mlen);
+       (void) GNUNET_HELPER_send (helper_handle,
+                                  msg,
+                                  GNUNET_YES,
+                                  NULL, NULL);
+      }
+    }
+    break;
+  }
+  GNUNET_CONTAINER_heap_update_cost (ts->heap_node,
+                                    GNUNET_TIME_absolute_get ().abs_value_us);
+  GNUNET_CADET_receive_done (ts->channel);
+}
+
+
+/**
+ * Create a channel for @a ts to @a target at @a port
+ *
+ * @param ts channel state to create the channel for
+ * @param target peer to connect to
+ * @param port destination port
+ * @return the channel handle
+ */
+static struct GNUNET_CADET_Channel *
+create_channel (struct ChannelState *ts,
+                const struct GNUNET_PeerIdentity *target,
+                const struct GNUNET_HashCode *port)
+{
+  struct GNUNET_MQ_MessageHandler cadet_handlers[] = {
+    GNUNET_MQ_hd_var_size (udp_back,
+                           GNUNET_MESSAGE_TYPE_VPN_UDP_REPLY,
+                           struct GNUNET_EXIT_UdpReplyMessage,
+                           ts),
+    GNUNET_MQ_hd_var_size (tcp_back,
+                           GNUNET_MESSAGE_TYPE_VPN_TCP_DATA_TO_VPN,
+                           struct GNUNET_EXIT_TcpDataMessage,
+                           ts),
+    GNUNET_MQ_hd_var_size (icmp_back,
+                           GNUNET_MESSAGE_TYPE_VPN_ICMP_TO_VPN,
+                           struct GNUNET_EXIT_IcmpToVPNMessage,
+                           ts),
+    GNUNET_MQ_handler_end()
+  };
+
+  return GNUNET_CADET_channel_create (cadet_handle,
+                                      ts,
+                                      target,
+                                      port,
+                                      GNUNET_CADET_OPTION_DEFAULT,
+                                      NULL,
+                                      &channel_cleaner,
+                                      cadet_handlers);
+}
+
+
+/**
+ * Regex has found a potential exit peer for us; consider using it.
+ *
+ * @param cls the `struct ChannelState`
+ * @param id Peer providing a regex that matches the string.
+ * @param get_path Path of the get request.
+ * @param get_path_length Lenght of @a get_path.
+ * @param put_path Path of the put request.
+ * @param put_path_length Length of the @a put_path.
+ */
+static void
+handle_regex_result (void *cls,
+                    const struct GNUNET_PeerIdentity *id,
+                    const struct GNUNET_PeerIdentity *get_path,
+                    unsigned int get_path_length,
+                    const struct GNUNET_PeerIdentity *put_path,
+                    unsigned int put_path_length)
+{
+  struct ChannelState *ts = cls;
+  struct GNUNET_HashCode port;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+              "Exit %s found for destination %s!\n",
+              GNUNET_i2s (id),
+              print_channel_destination (&ts->destination));
+  GNUNET_REGEX_search_cancel (ts->search);
+  ts->search = NULL;
+  switch (ts->af)
+  {
+  case AF_INET:
+    /* these must match the strings used in gnunet-daemon-exit */
+    GNUNET_CRYPTO_hash (GNUNET_APPLICATION_PORT_IPV4_GATEWAY,
+                        strlen (GNUNET_APPLICATION_PORT_IPV4_GATEWAY),
+                        &port);
+    break;
+  case AF_INET6:
+    /* these must match the strings used in gnunet-daemon-exit */
+    GNUNET_CRYPTO_hash (GNUNET_APPLICATION_PORT_IPV6_GATEWAY,
+                        strlen (GNUNET_APPLICATION_PORT_IPV6_GATEWAY),
+                        &port);
+    break;
   default:
-    /* not supported above, how can we get here !? */
-    GNUNET_assert (0);
-    break;
+    GNUNET_break (0);
+    return;
   }
-  send_to_tunnel (tnq, ts);
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+              "Creating tunnel to %s for destination %s!\n",
+              GNUNET_i2s (id),
+              print_channel_destination (&ts->destination));
+  ts->channel = create_channel (ts,
+                                id,
+                                &port);
 }
 
 
 /**
- * Receive packets from the helper-process (someone send to the local
- * virtual tunnel interface).  Find the destination mapping, and if it
- * exists, identify the correct MESH tunnel (or possibly create it)
- * and forward the packet.
+ * Initialize the given destination entry's cadet channel.
  *
- * @param cls closure, NULL
- * @param client NULL
- * @param message message we got from the client (VPN tunnel interface)
+ * @param dt destination channel for which we need to setup a channel
+ * @param client_af address family of the address returned to the client
+ * @return channel state of the channel that was created
  */
-static void
-message_token (void *cls GNUNET_UNUSED, void *client GNUNET_UNUSED,
-               const struct GNUNET_MessageHeader *message)
+static struct ChannelState *
+create_channel_to_destination (struct DestinationChannel *dt,
+                               int client_af)
 {
-  const struct GNUNET_TUN_Layer2PacketHeader *tun;
-  size_t mlen;
-  GNUNET_HashCode key;
-  struct DestinationEntry *de;
+  struct ChannelState *ts;
 
   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 GNUNET_TUN_Layer2PacketHeader)) )
+                           gettext_noop ("# Cadet channels created"),
+                           1,
+                            GNUNET_NO);
+  ts = GNUNET_new (struct ChannelState);
+  ts->af = client_af;
+  ts->destination = *dt->destination;
+  ts->destination.heap_node = NULL; /* copy is NOT in destination heap */
+  ts->destination_port = dt->destination_port;
+  if (dt->destination->is_service)
   {
-    GNUNET_break (0);
-    return;
+    struct GNUNET_HashCode cadet_port;
+
+    GNUNET_TUN_compute_service_cadet_port (&ts->destination.details.service_destination.service_descriptor,
+                                           ts->destination_port,
+                                           &cadet_port);
+    ts->channel = create_channel (ts,
+                                  &dt->destination->details.service_destination.target,
+                                  &cadet_port);
+
+    if (NULL == ts->channel)
+    {
+      GNUNET_break (0);
+      GNUNET_free (ts);
+      return NULL;
+    }
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+               "Creating channel to peer %s offering service %s on port %u\n",
+               GNUNET_i2s (&dt->destination->details.service_destination.target),
+               GNUNET_h2s (&ts->destination.details.service_destination.service_descriptor),
+                (unsigned int) ts->destination_port);
   }
-  tun = (const struct GNUNET_TUN_Layer2PacketHeader *) &message[1];
-  mlen -= (sizeof (struct GNUNET_MessageHeader) + sizeof (struct GNUNET_TUN_Layer2PacketHeader));
-  switch (ntohs (tun->proto))
+  else
   {
-  case ETH_P_IPV6:
+    char *policy;
+
+    switch (dt->destination->details.exit_destination.af)
     {
-      const struct GNUNET_TUN_IPv6Header *pkt6;
-      
-      if (mlen < sizeof (struct GNUNET_TUN_IPv6Header))
+    case AF_INET:
+    {
+      char address[GNUNET_TUN_IPV4_REGEXLEN];
+
+      GNUNET_TUN_ipv4toregexsearch (&dt->destination->details.exit_destination.ip.v4,
+                                   dt->destination_port,
+                                   address);
+      GNUNET_asprintf (&policy,
+                       "%s%s",
+                       GNUNET_APPLICATION_TYPE_EXIT_REGEX_PREFIX,
+                       address);
+      break;
+    }
+    case AF_INET6:
+    {
+      char address[GNUNET_TUN_IPV6_REGEXLEN];
+
+      GNUNET_TUN_ipv6toregexsearch (&dt->destination->details.exit_destination.ip.v6,
+                                   dt->destination_port,
+                                    address);
+      GNUNET_asprintf (&policy,
+                       "%s%s",
+                       GNUNET_APPLICATION_TYPE_EXIT_REGEX_PREFIX,
+                       address);
+      break;
+    }
+    default:
+      GNUNET_assert (0);
+      break;
+    }
+
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+               "Requesting connect by string: %s\n",
+               policy);
+    ts->search = GNUNET_REGEX_search (cfg,
+                                     policy,
+                                     &handle_regex_result,
+                                     ts);
+    GNUNET_free (policy);
+  }
+  return ts;
+}
+
+
+/**
+ * We have too many active channels.  Clean up the oldest channel.
+ *
+ * @param except channel that must NOT be cleaned up, even if it is the oldest
+ */
+static void
+expire_channel (struct ChannelState *except)
+{
+  struct ChannelState *ts;
+
+  ts = GNUNET_CONTAINER_heap_peek (channel_heap);
+  GNUNET_assert (NULL != ts);
+  if (except == ts)
+    return; /* can't do this */
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Tearing down expired channel to %s\n",
+              print_channel_destination (&except->destination));
+  free_channel_state (ts);
+}
+
+
+/**
+ * Route a packet via cadet to the given destination.
+ *
+ * @param destination description of the destination
+ * @param af address family on this end (AF_INET or AF_INET6)
+ * @param protocol IPPROTO_TCP or IPPROTO_UDP or IPPROTO_ICMP or IPPROTO_ICMPV6
+ * @param source_ip source IP used by the sender (struct in_addr or struct in6_addr)
+ * @param destination_ip destination IP used by the sender (struct in_addr or struct in6_addr)
+ * @param payload payload of the packet after the IP header
+ * @param payload_length number of bytes in @a payload
+ */
+static void
+route_packet (struct DestinationEntry *destination,
+             int af,
+             uint8_t protocol,
+             const void *source_ip,
+             const void *destination_ip,
+             const void *payload,
+             size_t payload_length)
+{
+  struct GNUNET_HashCode key;
+  struct ChannelState *ts;
+  size_t alen;
+  size_t mlen;
+  struct GNUNET_MQ_Envelope *env;
+  const struct GNUNET_TUN_UdpHeader *udp;
+  const struct GNUNET_TUN_TcpHeader *tcp;
+  const struct GNUNET_TUN_IcmpHeader *icmp;
+  struct DestinationChannel *dt;
+  uint16_t source_port;
+  uint16_t destination_port;
+
+  switch (protocol)
+  {
+  case IPPROTO_UDP:
+    {
+      if (payload_length < sizeof (struct GNUNET_TUN_UdpHeader))
       {
-       /* blame kernel */
+       /* blame kernel? */
        GNUNET_break (0);
        return;
       }
-      pkt6 = (const struct GNUNET_TUN_IPv6Header *) &tun[1];
-      get_destination_key_from_ip (AF_INET6,
-                                  &pkt6->destination_address,
-                                  &key);
-      de = GNUNET_CONTAINER_multihashmap_get (destination_map, &key);
-      /* 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)
+      tcp = NULL; /* make compiler happy */
+      icmp = NULL;  /* make compiler happy */
+      udp = payload;
+      if (udp->len < sizeof (struct GNUNET_TUN_UdpHeader))
       {
-       char buf[INET6_ADDRSTRLEN];
-       
-       GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                   _("Packet received for unmapped destination `%s' (dropping it)\n"),
-                   inet_ntop (AF_INET6,
-                              &pkt6->destination_address,
-                              buf,
-                              sizeof (buf)));
+       GNUNET_break_op (0);
        return;
       }
-      route_packet (de,
-                   AF_INET6,
-                   pkt6->next_header,
-                   &pkt6->source_address,                  
-                   &pkt6->destination_address,             
-                   &pkt6[1],
-                   mlen - sizeof (struct GNUNET_TUN_IPv6Header));
+      source_port = ntohs (udp->source_port);
+      destination_port = ntohs (udp->destination_port);
+      get_channel_key_from_ips (af,
+                                IPPROTO_UDP,
+                                source_ip,
+                                source_port,
+                                destination_ip,
+                                destination_port,
+                                &key);
     }
     break;
-  case ETH_P_IPV4:
+  case IPPROTO_TCP:
     {
-      struct GNUNET_TUN_IPv4Header *pkt4;
-
-      if (mlen < sizeof (struct GNUNET_TUN_IPv4Header))
+      if (payload_length < sizeof (struct GNUNET_TUN_TcpHeader))
       {
-       /* blame kernel */
+       /* blame kernel? */
        GNUNET_break (0);
        return;
       }
-      pkt4 = (struct GNUNET_TUN_IPv4Header *) &tun[1];
-      get_destination_key_from_ip (AF_INET,
-                                  &pkt4->destination_address,
-                                  &key);
-      de = GNUNET_CONTAINER_multihashmap_get (destination_map, &key);
-      /* 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)
+      udp = NULL; /* make compiler happy */
+      icmp = NULL;  /* make compiler happy */
+      tcp = payload;
+      if (tcp->off * 4 < sizeof (struct GNUNET_TUN_TcpHeader))
       {
-       char buf[INET_ADDRSTRLEN];
-       
-       GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                   _("Packet received for unmapped destination `%s' (dropping it)\n"),
-                   inet_ntop (AF_INET,
-                              &pkt4->destination_address,
-                              buf,
-                              sizeof (buf)));
+       GNUNET_break_op (0);
        return;
       }
-      if (pkt4->header_length * 4 != sizeof (struct GNUNET_TUN_IPv4Header))
+      source_port = ntohs (tcp->source_port);
+      destination_port = ntohs (tcp->destination_port);
+      get_channel_key_from_ips (af,
+                                IPPROTO_TCP,
+                                source_ip,
+                                source_port,
+                                destination_ip,
+                                destination_port,
+                                &key);
+    }
+    break;
+  case IPPROTO_ICMP:
+  case IPPROTO_ICMPV6:
+    {
+      if ( (AF_INET == af) ^ (protocol == IPPROTO_ICMP) )
       {
-       GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                   _("Received IPv4 packet with options (dropping it)\n"));                
+       GNUNET_break (0);
        return;
       }
-      route_packet (de,
-                   AF_INET,
-                   pkt4->protocol,
-                   &pkt4->source_address,                  
-                   &pkt4->destination_address,             
-                   &pkt4[1],
-                   mlen - sizeof (struct GNUNET_TUN_IPv4Header));
+      if (payload_length < sizeof (struct GNUNET_TUN_IcmpHeader))
+      {
+       /* blame kernel? */
+       GNUNET_break (0);
+       return;
+      }
+      tcp = NULL; /* make compiler happy */
+      udp = NULL;  /* make compiler happy */
+      icmp = payload;
+      source_port = 0;
+      destination_port = 0;
+      get_channel_key_from_ips (af,
+                                protocol,
+                                source_ip,
+                                0,
+                                destination_ip,
+                                0,
+                                &key);
     }
     break;
   default:
     GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-               _("Received packet of unknown protocol %d from TUN (dropping it)\n"),
-               (unsigned int) ntohs (tun->proto));
-    break;
+               _("Protocol %u not supported, dropping\n"),
+               (unsigned int) protocol);
+    return;
   }
-}
-
-
-/**
- * Synthesize a plausible ICMP payload for an ICMP error
- * response on the given tunnel.
- *
- * @param ts tunnel information
- * @param ipp IPv4 header to fill in (ICMP payload)
- * @param udp "UDP" header to fill in (ICMP payload); might actually
- *            also be the first 8 bytes of the TCP header
- */
-static void
-make_up_icmpv4_payload (struct TunnelState *ts,
-                       struct GNUNET_TUN_IPv4Header *ipp,
-                       struct GNUNET_TUN_UdpHeader *udp)
-{
-  GNUNET_TUN_initialize_ipv4_header (ipp,
-                                    ts->protocol,
-                                    sizeof (struct GNUNET_TUN_TcpHeader),
-                                    &ts->source_ip.v4,
-                                    &ts->destination_ip.v4);
-  udp->spt = htons (ts->source_port);
-  udp->dpt = htons (ts->destination_port);
-  udp->len = htons (0);
-  udp->crc = htons (0);
-}
-
-
-/**
- * Synthesize a plausible ICMP payload for an ICMP error
- * response on the given tunnel.
- *
- * @param ts tunnel information
- * @param ipp IPv6 header to fill in (ICMP payload)
- * @param udp "UDP" header to fill in (ICMP payload); might actually
- *            also be the first 8 bytes of the TCP header
- */
-static void
-make_up_icmpv6_payload (struct TunnelState *ts,
-                       struct GNUNET_TUN_IPv6Header *ipp,
-                       struct GNUNET_TUN_UdpHeader *udp)
-{
-  GNUNET_TUN_initialize_ipv6_header (ipp,
-                                    ts->protocol,
-                                    sizeof (struct GNUNET_TUN_TcpHeader),
-                                    &ts->source_ip.v6,
-                                    &ts->destination_ip.v6);
-  udp->spt = htons (ts->source_port);
-  udp->dpt = htons (ts->destination_port);
-  udp->len = htons (0);
-  udp->crc = htons (0);
-}
-
+  alen = 0;
+  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:
+      GNUNET_assert (0);
+    }
 
-/**
- * We got an ICMP packet back from the MESH tunnel.  Pass it on to the
- * local virtual interface via the helper.
- *
- * @param cls closure, NULL
- * @param tunnel connection to the other end
- * @param tunnel_ctx pointer to our 'struct TunnelState *'
- * @param sender who sent the message
- * @param message the actual message
- * @param atsi performance data for the connection
- * @return GNUNET_OK to keep the connection open,
- *         GNUNET_SYSERR to close it (signal serious error)
- */ 
-static int
-receive_icmp_back (void *cls GNUNET_UNUSED, struct GNUNET_MESH_Tunnel *tunnel,
-                  void **tunnel_ctx, const struct GNUNET_PeerIdentity *sender,
-                  const struct GNUNET_MessageHeader *message,
-                  const struct GNUNET_ATS_Information *atsi GNUNET_UNUSED)
-{
-  struct TunnelState *ts = *tunnel_ctx;
-  const struct GNUNET_EXIT_IcmpToVPNMessage *i2v;
-  size_t mlen;
+    {
+      char sbuf[INET6_ADDRSTRLEN];
+      char dbuf[INET6_ADDRSTRLEN];
+      char xbuf[INET6_ADDRSTRLEN];
 
-  GNUNET_STATISTICS_update (stats,
-                           gettext_noop ("# ICMP packets received from mesh"),
-                           1, GNUNET_NO);
-  mlen = ntohs (message->size);
-  if (mlen < sizeof (struct GNUNET_EXIT_IcmpToVPNMessage))
+      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)),
+                 source_port,
+                 inet_ntop (af,
+                             destination_ip,
+                             dbuf,
+                             sizeof (dbuf)),
+                 destination_port,
+                 inet_ntop (destination->details.exit_destination.af,
+                            &destination->details.exit_destination.ip,
+                            xbuf, sizeof (xbuf)),
+                 destination_port);
+    }
+    for (dt = destination->dt_head; NULL != dt; dt = dt->next)
+      if (dt->destination_port == destination_port)
+       break;
+  }
+  else
+  {
+    {
+      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)),
+                 source_port,
+                 inet_ntop (af,
+                             destination_ip,
+                             dbuf,
+                             sizeof (dbuf)),
+                 destination_port,
+                 GNUNET_h2s (&destination->details.service_destination.service_descriptor),
+                 GNUNET_i2s (&destination->details.service_destination.target));
+    }
+    for (dt = destination->dt_head; NULL != dt; dt = dt->next)
+      if (dt->destination_port == destination_port)
+       break;
+  }
+  if (NULL == dt)
   {
-    GNUNET_break_op (0);
-    return GNUNET_SYSERR;
+    dt = GNUNET_new (struct DestinationChannel);
+    dt->destination = destination;
+    GNUNET_CONTAINER_DLL_insert (destination->dt_head,
+                                destination->dt_tail,
+                                dt);
+    dt->destination_port = destination_port;
   }
-  if (NULL == ts->heap_node)
+
+  /* see if we have an existing channel for this destination */
+  ts = GNUNET_CONTAINER_multihashmap_get (channel_map,
+                                         &key);
+  if (NULL == ts)
   {
-    GNUNET_break_op (0);
-    return GNUNET_SYSERR;
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Creating new channel for key %s\n",
+                GNUNET_h2s (&key));
+    /* need to either use the existing channel from the destination (if still
+       available) or create a fresh one */
+    ts = create_channel_to_destination (dt,
+                                        af);
+    if (NULL == ts)
+      return;
+    /* now bind existing "unbound" channel to our IP/port tuple */
+    ts->protocol = protocol;
+    ts->af = af;
+    if (AF_INET == af)
+    {
+      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 = source_port;
+    ts->destination_port = destination_port;
+    ts->heap_node = GNUNET_CONTAINER_heap_insert (channel_heap,
+                                                 ts,
+                                                 GNUNET_TIME_absolute_get ().abs_value_us);
+    GNUNET_assert (GNUNET_YES ==
+                  GNUNET_CONTAINER_multihashmap_put (channel_map,
+                                                     &key,
+                                                     ts,
+                                                     GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
+    GNUNET_STATISTICS_update (stats,
+                             gettext_noop ("# Active channels"),
+                             1, GNUNET_NO);
+    while (GNUNET_CONTAINER_multihashmap_size (channel_map) > max_channel_mappings)
+      expire_channel (ts);
   }
-  if (AF_UNSPEC == ts->af)
+  else
   {
-    GNUNET_break_op (0);
-    return GNUNET_SYSERR;
+    GNUNET_CONTAINER_heap_update_cost (ts->heap_node,
+                                      GNUNET_TIME_absolute_get ().abs_value_us);
   }
-  i2v = (const struct GNUNET_EXIT_IcmpToVPNMessage *) message;
-  mlen -= sizeof (struct GNUNET_EXIT_IcmpToVPNMessage);
+  if (NULL == ts->channel)
   {
-    char sbuf[INET6_ADDRSTRLEN];
-    char dbuf[INET6_ADDRSTRLEN];
-    
-    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-               "Received ICMP packet from mesh, sending %u bytes from %s -> %s via TUN\n",
-               (unsigned int) mlen,
-               inet_ntop (ts->af, &ts->destination_ip, sbuf, sizeof (sbuf)),
-               inet_ntop (ts->af, &ts->source_ip, dbuf, sizeof (dbuf)));
+    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                "Packet dropped, channel to %s not yet ready (%s)\n",
+                print_channel_destination (&ts->destination),
+                (NULL == ts->search)
+                ? "EXIT search failed"
+                : "EXIT search active");
+    GNUNET_STATISTICS_update (stats,
+                             gettext_noop ("# Packets dropped (channel not yet online)"),
+                             1,
+                              GNUNET_NO);
+    return;
   }
-  switch (ts->af)
+
+  /* send via channel */
+  switch (protocol)
   {
-  case AF_INET:
+  case IPPROTO_UDP:
+    if (destination->is_service)
     {
-      size_t size = sizeof (struct GNUNET_TUN_IPv4Header) 
-       + sizeof (struct GNUNET_TUN_IcmpHeader) 
-       + sizeof (struct GNUNET_MessageHeader) +
-       sizeof (struct GNUNET_TUN_Layer2PacketHeader) +
-       mlen;
+      struct GNUNET_EXIT_UdpServiceMessage *usm;
+
+      mlen = sizeof (struct GNUNET_EXIT_UdpServiceMessage) +
+       payload_length - sizeof (struct GNUNET_TUN_UdpHeader);
+      if (mlen >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
       {
-       /* reserve some extra space in case we have an ICMP type here where
-          we will need to make up the payload ourselves */
-       char buf[size + sizeof (struct GNUNET_TUN_IPv4Header) + 8];
-       struct GNUNET_MessageHeader *msg = (struct GNUNET_MessageHeader *) buf;
-       struct GNUNET_TUN_Layer2PacketHeader *tun = (struct GNUNET_TUN_Layer2PacketHeader*) &msg[1];
-       struct GNUNET_TUN_IPv4Header *ipv4 = (struct GNUNET_TUN_IPv4Header *) &tun[1];
-       struct GNUNET_TUN_IcmpHeader *icmp = (struct GNUNET_TUN_IcmpHeader *) &ipv4[1];
-       msg->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
-       tun->flags = htons (0);
-       tun->proto = htons (ETH_P_IPV4);
-       GNUNET_TUN_initialize_ipv4_header (ipv4,
-                                          IPPROTO_ICMP,
-                                          sizeof (struct GNUNET_TUN_IcmpHeader) + mlen,
-                                          &ts->destination_ip.v4,
-                                          &ts->source_ip.v4);
-       *icmp = i2v->icmp_header;
-       memcpy (&icmp[1],
-               &i2v[1],
-               mlen);
-       /* For some ICMP types, we need to adjust (make up) the payload here. 
-          Also, depending on the AF used on the other side, we have to 
-          do ICMP PT (translate ICMP types) */
-       switch (ntohl (i2v->af))
+       GNUNET_break (0);
+       return;
+      }
+      env = GNUNET_MQ_msg_extra (usm,
+                                 payload_length - sizeof (struct GNUNET_TUN_UdpHeader),
+                                 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->source_port) < 32000) ? udp->source_port : 0;
+      usm->destination_port = udp->destination_port;
+      GNUNET_memcpy (&usm[1],
+                     &udp[1],
+                     payload_length - sizeof (struct GNUNET_TUN_UdpHeader));
+    }
+    else
+    {
+      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 GNUNET_TUN_UdpHeader);
+      if (mlen >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
+      {
+       GNUNET_break (0);
+       return;
+      }
+      env = GNUNET_MQ_msg_extra (uim,
+                                 payload_length + alen - sizeof (struct GNUNET_TUN_UdpHeader),
+                                 GNUNET_MESSAGE_TYPE_VPN_UDP_TO_INTERNET);
+      uim->af = htonl (destination->details.exit_destination.af);
+      uim->source_port = (ntohs (udp->source_port) < 32000) ? udp->source_port : 0;
+      uim->destination_port = udp->destination_port;
+      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);
+      }
+      GNUNET_memcpy (payload,
+                     &udp[1],
+                     payload_length - sizeof (struct GNUNET_TUN_UdpHeader));
+    }
+    break;
+  case IPPROTO_TCP:
+    if (GNUNET_NO == ts->is_established)
+    {
+      if (destination->is_service)
+      {
+       struct GNUNET_EXIT_TcpServiceStartMessage *tsm;
+
+       mlen = sizeof (struct GNUNET_EXIT_TcpServiceStartMessage) +
+         payload_length - sizeof (struct GNUNET_TUN_TcpHeader);
+       if (mlen >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
        {
-       case AF_INET:     
-         switch (icmp->type)
-         {
-         case GNUNET_TUN_ICMPTYPE_ECHO_REPLY:
-         case GNUNET_TUN_ICMPTYPE_ECHO_REQUEST:
-           break;
-         case GNUNET_TUN_ICMPTYPE_DESTINATION_UNREACHABLE:
-         case GNUNET_TUN_ICMPTYPE_SOURCE_QUENCH:
-         case GNUNET_TUN_ICMPTYPE_TIME_EXCEEDED:         
-           {
-             struct GNUNET_TUN_IPv4Header *ipp = (struct GNUNET_TUN_IPv4Header *) &icmp[1];
-             struct GNUNET_TUN_UdpHeader *udp = (struct GNUNET_TUN_UdpHeader *) &ipp[1];
-             
-             if (mlen != 0)
-               {
-                 /* sender did not strip ICMP payload? */
-                 GNUNET_break_op (0);
-                 return GNUNET_SYSERR;
-               }
-             size += sizeof (struct GNUNET_TUN_IPv4Header) + 8;
-             GNUNET_assert (8 == sizeof (struct GNUNET_TUN_UdpHeader));
-             make_up_icmpv4_payload (ts, ipp, udp);
-           }
-           break;
-         default:
-           GNUNET_break_op (0);
-           GNUNET_STATISTICS_update (stats,
-                                     gettext_noop ("# ICMPv4 packets dropped (type not allowed)"),
-                                     1, GNUNET_NO);
-           return GNUNET_SYSERR;
-         }
-         /* end AF_INET */
+         GNUNET_break (0);
+         return;
+       }
+       env = GNUNET_MQ_msg_extra (tsm,
+                                   payload_length - sizeof (struct GNUNET_TUN_TcpHeader),
+                                   GNUNET_MESSAGE_TYPE_VPN_TCP_TO_SERVICE_START);
+       tsm->reserved = htonl (0);
+       tsm->tcp_header = *tcp;
+       GNUNET_memcpy (&tsm[1],
+                       &tcp[1],
+                       payload_length - sizeof (struct GNUNET_TUN_TcpHeader));
+      }
+      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 GNUNET_TUN_TcpHeader);
+       if (mlen >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
+       {
+         GNUNET_break (0);
+         return;
+       }
+        env = GNUNET_MQ_msg_extra (tim,
+                                   payload_length + alen - sizeof (struct GNUNET_TUN_TcpHeader),
+                                   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:
-         /* ICMP PT 6-to-4 and possibly making up payloads */
-         switch (icmp->type)
-         {
-         case GNUNET_TUN_ICMPTYPE6_DESTINATION_UNREACHABLE:
-           icmp->type = GNUNET_TUN_ICMPTYPE_DESTINATION_UNREACHABLE;
-           {
-             struct GNUNET_TUN_IPv4Header *ipp = (struct GNUNET_TUN_IPv4Header *) &icmp[1];
-             struct GNUNET_TUN_UdpHeader *udp = (struct GNUNET_TUN_UdpHeader *) &ipp[1];
-             
-             if (mlen != 0)
-               {
-                 /* sender did not strip ICMP payload? */
-                 GNUNET_break_op (0);
-                 return GNUNET_SYSERR;
-               }
-             size += sizeof (struct GNUNET_TUN_IPv4Header) + 8;
-             GNUNET_assert (8 == sizeof (struct GNUNET_TUN_UdpHeader));
-             make_up_icmpv4_payload (ts, ipp, udp);
-           }
-           break;
-         case GNUNET_TUN_ICMPTYPE6_TIME_EXCEEDED:
-           icmp->type = GNUNET_TUN_ICMPTYPE_TIME_EXCEEDED;
-           {
-             struct GNUNET_TUN_IPv4Header *ipp = (struct GNUNET_TUN_IPv4Header *) &icmp[1];
-             struct GNUNET_TUN_UdpHeader *udp = (struct GNUNET_TUN_UdpHeader *) &ipp[1];
-             
-             if (mlen != 0)
-               {
-                 /* sender did not strip ICMP payload? */
-                 GNUNET_break_op (0);
-                 return GNUNET_SYSERR;
-               }
-             size += sizeof (struct GNUNET_TUN_IPv4Header) + 8;
-             GNUNET_assert (8 == sizeof (struct GNUNET_TUN_UdpHeader));
-             make_up_icmpv4_payload (ts, ipp, udp);
-           }
-           break;
-         case GNUNET_TUN_ICMPTYPE6_PACKET_TOO_BIG:
-         case GNUNET_TUN_ICMPTYPE6_PARAMETER_PROBLEM:
-           GNUNET_STATISTICS_update (stats,
-                                     gettext_noop ("# ICMPv6 packets dropped (impossible PT to v4)"),
-                                     1, GNUNET_NO);
-           return GNUNET_OK;
-         case GNUNET_TUN_ICMPTYPE6_ECHO_REQUEST:
-           icmp->type = GNUNET_TUN_ICMPTYPE_ECHO_REQUEST;
-           break;
-         case GNUNET_TUN_ICMPTYPE6_ECHO_REPLY:
-           icmp->type = GNUNET_TUN_ICMPTYPE_ECHO_REPLY;
-           break;
-         default:
-           GNUNET_break_op (0);
-           GNUNET_STATISTICS_update (stats,
-                                     gettext_noop ("# ICMPv6 packets dropped (type not allowed)"),
-                                     1, GNUNET_NO);
-           return GNUNET_SYSERR;
-         }
-         /* end AF_INET6 */
+         ip6dst = (struct in6_addr *) &tim[1];
+         *ip6dst = destination->details.exit_destination.ip.v6;
+         payload = &ip6dst[1];
+         break;
+       default:
+         GNUNET_assert (0);
+       }
+       GNUNET_memcpy (payload,
+                       &tcp[1],
+                       payload_length - sizeof (struct GNUNET_TUN_TcpHeader));
+      }
+    }
+    else
+    {
+      struct GNUNET_EXIT_TcpDataMessage *tdm;
+
+      mlen = sizeof (struct GNUNET_EXIT_TcpDataMessage) +
+       payload_length - sizeof (struct GNUNET_TUN_TcpHeader);
+      if (mlen >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
+      {
+       GNUNET_break (0);
+       return;
+      }
+      env = GNUNET_MQ_msg_extra (tdm,
+                                 payload_length - sizeof (struct GNUNET_TUN_TcpHeader),
+                                 GNUNET_MESSAGE_TYPE_VPN_TCP_DATA_TO_EXIT);
+      tdm->reserved = htonl (0);
+      tdm->tcp_header = *tcp;
+      GNUNET_memcpy (&tdm[1],
+                     &tcp[1],
+                     payload_length - sizeof (struct GNUNET_TUN_TcpHeader));
+     }
+    break;
+  case IPPROTO_ICMP:
+  case IPPROTO_ICMPV6:
+    if (destination->is_service)
+    {
+      struct GNUNET_EXIT_IcmpServiceMessage *ism;
+
+      /* ICMP protocol translation will be done by the receiver (as we don't know
+        the target AF); however, we still need to possibly discard the payload
+        depending on the ICMP type */
+      switch (af)
+      {
+      case AF_INET:
+       switch (icmp->type)
+       {
+       case GNUNET_TUN_ICMPTYPE_ECHO_REPLY:
+       case GNUNET_TUN_ICMPTYPE_ECHO_REQUEST:
+         break;
+       case GNUNET_TUN_ICMPTYPE_DESTINATION_UNREACHABLE:
+       case GNUNET_TUN_ICMPTYPE_SOURCE_QUENCH:
+       case GNUNET_TUN_ICMPTYPE_TIME_EXCEEDED:
+         /* throw away ICMP payload, won't be useful for the other side anyway */
+         payload_length = sizeof (struct GNUNET_TUN_IcmpHeader);
          break;
        default:
-         GNUNET_break_op (0);
-         return GNUNET_SYSERR;
-       }       
-       msg->size = htons (size);
-       GNUNET_TUN_calculate_icmp_checksum (icmp,
-                                           &i2v[1],
-                                           mlen);
-       (void) GNUNET_HELPER_send (helper_handle,
-                                  msg,
-                                  GNUNET_YES,
-                                  NULL, NULL);
+         GNUNET_STATISTICS_update (stats,
+                                   gettext_noop ("# ICMPv4 packets dropped (not allowed)"),
+                                   1, GNUNET_NO);
+         return;
+       }
+       /* end of AF_INET */
+       break;
+      case AF_INET6:
+       switch (icmp->type)
+       {
+       case GNUNET_TUN_ICMPTYPE6_DESTINATION_UNREACHABLE:
+       case GNUNET_TUN_ICMPTYPE6_PACKET_TOO_BIG:
+       case GNUNET_TUN_ICMPTYPE6_TIME_EXCEEDED:
+       case GNUNET_TUN_ICMPTYPE6_PARAMETER_PROBLEM:
+         /* throw away ICMP payload, won't be useful for the other side anyway */
+         payload_length = sizeof (struct GNUNET_TUN_IcmpHeader);
+         break;
+       case GNUNET_TUN_ICMPTYPE6_ECHO_REQUEST:
+       case GNUNET_TUN_ICMPTYPE6_ECHO_REPLY:
+         break;
+       default:
+         GNUNET_STATISTICS_update (stats,
+                                   gettext_noop ("# ICMPv6 packets dropped (not allowed)"),
+                                   1, GNUNET_NO);
+         return;
+       }
+       /* end of AF_INET6 */
+       break;
+      default:
+       GNUNET_assert (0);
+       break;
+      }
+
+      /* update length calculations, as payload_length may have changed */
+      mlen = sizeof (struct GNUNET_EXIT_IcmpServiceMessage) +
+       alen + payload_length - sizeof (struct GNUNET_TUN_IcmpHeader);
+      if (mlen >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
+      {
+       GNUNET_break (0);
+       return;
       }
+
+      env = GNUNET_MQ_msg_extra (ism,
+                                 payload_length - sizeof (struct GNUNET_TUN_IcmpHeader),
+                                 GNUNET_MESSAGE_TYPE_VPN_ICMP_TO_SERVICE);
+      ism->af = htonl (af); /* need to tell destination ICMP protocol family! */
+      ism->icmp_header = *icmp;
+      GNUNET_memcpy (&ism[1],
+                     &icmp[1],
+                     payload_length - sizeof (struct GNUNET_TUN_IcmpHeader));
     }
-    break;
-  case AF_INET6:
+    else
     {
-      size_t size = sizeof (struct GNUNET_TUN_IPv6Header) 
-       + sizeof (struct GNUNET_TUN_IcmpHeader) 
-       + sizeof (struct GNUNET_MessageHeader) +
-       sizeof (struct GNUNET_TUN_Layer2PacketHeader) +
-       mlen;
-      {
-       char buf[size + sizeof (struct GNUNET_TUN_IPv6Header) + 8];
-       struct GNUNET_MessageHeader *msg = (struct GNUNET_MessageHeader *) buf;
-       struct GNUNET_TUN_Layer2PacketHeader *tun = (struct GNUNET_TUN_Layer2PacketHeader*) &msg[1];
-       struct GNUNET_TUN_IPv6Header *ipv6 = (struct GNUNET_TUN_IPv6Header *) &tun[1];
-       struct GNUNET_TUN_IcmpHeader *icmp = (struct GNUNET_TUN_IcmpHeader *) &ipv6[1];
-       msg->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
-       tun->flags = htons (0);
-       tun->proto = htons (ETH_P_IPV6);
-       GNUNET_TUN_initialize_ipv6_header (ipv6,
-                                          IPPROTO_ICMP,
-                                          sizeof (struct GNUNET_TUN_IcmpHeader) + mlen,
-                                          &ts->destination_ip.v6,
-                                          &ts->source_ip.v6);
-       *icmp = i2v->icmp_header;
-       memcpy (&icmp[1],
-               &i2v[1],
-               mlen);
+      struct GNUNET_EXIT_IcmpInternetMessage *iim;
+      struct in_addr *ip4dst;
+      struct in6_addr *ip6dst;
+      void *payload;
+      uint8_t new_type;
 
-       /* For some ICMP types, we need to adjust (make up) the payload here. 
-          Also, depending on the AF used on the other side, we have to 
-          do ICMP PT (translate ICMP types) */
-       switch (ntohl (i2v->af))
+      new_type = icmp->type;
+      /* Perform ICMP protocol-translation (depending on destination AF and source AF)
+        and throw away ICMP payload depending on ICMP message type */
+      switch (af)
+      {
+      case AF_INET:
+       switch (icmp->type)
        {
-       case AF_INET:     
-         /* ICMP PT 4-to-6 and possibly making up payloads */
-         switch (icmp->type)
-         {
-         case GNUNET_TUN_ICMPTYPE_ECHO_REPLY:
-           icmp->type = GNUNET_TUN_ICMPTYPE6_ECHO_REPLY;
-           break;
-         case GNUNET_TUN_ICMPTYPE_ECHO_REQUEST:
-           icmp->type = GNUNET_TUN_ICMPTYPE6_ECHO_REQUEST;
-           break;
-         case GNUNET_TUN_ICMPTYPE_DESTINATION_UNREACHABLE:
-           icmp->type = GNUNET_TUN_ICMPTYPE6_DESTINATION_UNREACHABLE;
-           {
-             struct GNUNET_TUN_IPv6Header *ipp = (struct GNUNET_TUN_IPv6Header *) &icmp[1];
-             struct GNUNET_TUN_UdpHeader *udp = (struct GNUNET_TUN_UdpHeader *) &ipp[1];
-             
-             if (mlen != 0)
-               {
-                 /* sender did not strip ICMP payload? */
-                 GNUNET_break_op (0);
-                 return GNUNET_SYSERR;
-               }
-             size += sizeof (struct GNUNET_TUN_IPv6Header) + 8;
-             GNUNET_assert (8 == sizeof (struct GNUNET_TUN_UdpHeader));
-             make_up_icmpv6_payload (ts, ipp, udp);
-           }
-           break;
-         case GNUNET_TUN_ICMPTYPE_TIME_EXCEEDED:         
-           icmp->type = GNUNET_TUN_ICMPTYPE6_TIME_EXCEEDED;
+       case GNUNET_TUN_ICMPTYPE_ECHO_REPLY:
+         if (destination->details.exit_destination.af == AF_INET6)
+           new_type = GNUNET_TUN_ICMPTYPE6_ECHO_REPLY;
+         break;
+       case GNUNET_TUN_ICMPTYPE_ECHO_REQUEST:
+         if (destination->details.exit_destination.af == AF_INET6)
+           new_type = GNUNET_TUN_ICMPTYPE6_ECHO_REQUEST;
+         break;
+       case GNUNET_TUN_ICMPTYPE_DESTINATION_UNREACHABLE:
+         if (destination->details.exit_destination.af == AF_INET6)
+           new_type = GNUNET_TUN_ICMPTYPE6_DESTINATION_UNREACHABLE;
+         /* throw away IP-payload, exit will have to make it up anyway */
+         payload_length = sizeof (struct GNUNET_TUN_IcmpHeader);
+         break;
+       case GNUNET_TUN_ICMPTYPE_TIME_EXCEEDED:
+         if (destination->details.exit_destination.af == AF_INET6)
+           new_type = GNUNET_TUN_ICMPTYPE6_TIME_EXCEEDED;
+         /* throw away IP-payload, exit will have to make it up anyway */
+         payload_length = sizeof (struct GNUNET_TUN_IcmpHeader);
+         break;
+       case GNUNET_TUN_ICMPTYPE_SOURCE_QUENCH:
+         if (destination->details.exit_destination.af == AF_INET6)
            {
-             struct GNUNET_TUN_IPv6Header *ipp = (struct GNUNET_TUN_IPv6Header *) &icmp[1];
-             struct GNUNET_TUN_UdpHeader *udp = (struct GNUNET_TUN_UdpHeader *) &ipp[1];
-             
-             if (mlen != 0)
-               {
-                 /* sender did not strip ICMP payload? */
-                 GNUNET_break_op (0);
-                 return GNUNET_SYSERR;
-               }
-             size += sizeof (struct GNUNET_TUN_IPv6Header) + 8;
-             GNUNET_assert (8 == sizeof (struct GNUNET_TUN_UdpHeader));
-             make_up_icmpv6_payload (ts, ipp, udp);
+             GNUNET_STATISTICS_update (stats,
+                                       gettext_noop ("# ICMPv4 packets dropped (impossible PT to v6)"),
+                                       1, GNUNET_NO);
+             return;
            }
-           break;
-         case GNUNET_TUN_ICMPTYPE_SOURCE_QUENCH:
-           GNUNET_STATISTICS_update (stats,
-                                     gettext_noop ("# ICMPv4 packets dropped (impossible PT to v6)"),
-                                     1, GNUNET_NO);        
-           return GNUNET_OK;
-         default:
-           GNUNET_break_op (0);
-           GNUNET_STATISTICS_update (stats,
-                                     gettext_noop ("# ICMPv4 packets dropped (type not allowed)"),
-                                     1, GNUNET_NO);
-           return GNUNET_SYSERR;
-         }
-         /* end AF_INET */
+         /* throw away IP-payload, exit will have to make it up anyway */
+         payload_length = sizeof (struct GNUNET_TUN_IcmpHeader);
          break;
-       case AF_INET6:
-         switch (icmp->type)
+       default:
+         GNUNET_STATISTICS_update (stats,
+                                   gettext_noop ("# ICMPv4 packets dropped (type not allowed)"),
+                                   1, GNUNET_NO);
+         return;
+       }
+       /* end of AF_INET */
+       break;
+      case AF_INET6:
+       switch (icmp->type)
          {
          case GNUNET_TUN_ICMPTYPE6_DESTINATION_UNREACHABLE:
+           if (destination->details.exit_destination.af == AF_INET)
+             new_type = GNUNET_TUN_ICMPTYPE_DESTINATION_UNREACHABLE;
+           /* throw away IP-payload, exit will have to make it up anyway */
+           payload_length = sizeof (struct GNUNET_TUN_IcmpHeader);
+           break;
          case GNUNET_TUN_ICMPTYPE6_TIME_EXCEEDED:
+           if (destination->details.exit_destination.af == AF_INET)
+             new_type = GNUNET_TUN_ICMPTYPE_TIME_EXCEEDED;
+           /* throw away IP-payload, exit will have to make it up anyway */
+           payload_length = sizeof (struct GNUNET_TUN_IcmpHeader);
+           break;
          case GNUNET_TUN_ICMPTYPE6_PACKET_TOO_BIG:
+           if (destination->details.exit_destination.af == AF_INET)
+           {
+             GNUNET_STATISTICS_update (stats,
+                                       gettext_noop ("# ICMPv6 packets dropped (impossible PT to v4)"),
+                                       1, GNUNET_NO);
+             return;
+           }
+           /* throw away IP-payload, exit will have to make it up anyway */
+           payload_length = sizeof (struct GNUNET_TUN_IcmpHeader);
+           break;
          case GNUNET_TUN_ICMPTYPE6_PARAMETER_PROBLEM:
+           if (destination->details.exit_destination.af == AF_INET)
            {
-             struct GNUNET_TUN_IPv6Header *ipp = (struct GNUNET_TUN_IPv6Header *) &icmp[1];
-             struct GNUNET_TUN_UdpHeader *udp = (struct GNUNET_TUN_UdpHeader *) &ipp[1];
-             
-             if (mlen != 0)
-               {
-                 /* sender did not strip ICMP payload? */
-                 GNUNET_break_op (0);
-                 return GNUNET_SYSERR;
-               }
-             size += sizeof (struct GNUNET_TUN_IPv6Header) + 8;
-             GNUNET_assert (8 == sizeof (struct GNUNET_TUN_UdpHeader));
-             make_up_icmpv6_payload (ts, ipp, udp);
+             GNUNET_STATISTICS_update (stats,
+                                       gettext_noop ("# ICMPv6 packets dropped (impossible PT to v4)"),
+                                       1, GNUNET_NO);
+             return;
            }
+           /* throw away IP-payload, exit will have to make it up anyway */
+           payload_length = sizeof (struct GNUNET_TUN_IcmpHeader);
            break;
          case GNUNET_TUN_ICMPTYPE6_ECHO_REQUEST:
+           if (destination->details.exit_destination.af == AF_INET)
+             new_type = GNUNET_TUN_ICMPTYPE_ECHO_REQUEST;
+           break;
+         case GNUNET_TUN_ICMPTYPE6_ECHO_REPLY:
+           if (destination->details.exit_destination.af == AF_INET)
+             new_type = GNUNET_TUN_ICMPTYPE_ECHO_REPLY;
            break;
          default:
-           GNUNET_break_op (0);
            GNUNET_STATISTICS_update (stats,
                                      gettext_noop ("# ICMPv6 packets dropped (type not allowed)"),
                                      1, GNUNET_NO);
-           return GNUNET_SYSERR;
-         }
-         /* end AF_INET6 */
-         break;
-       default:
-         GNUNET_break_op (0);
-         return GNUNET_SYSERR;
-       }
-       msg->size = htons (size);
-       GNUNET_TUN_calculate_icmp_checksum (icmp,
-                                           &i2v[1], mlen);
-       (void) GNUNET_HELPER_send (helper_handle,
-                                  msg,
-                                  GNUNET_YES,
-                                  NULL, NULL);
-      }
-    }
-    break;
-  default:
-    GNUNET_assert (0);
-  }
-  GNUNET_CONTAINER_heap_update_cost (tunnel_heap, 
-                                    ts->heap_node,
-                                    GNUNET_TIME_absolute_get ().abs_value);
-  return GNUNET_OK;
-}
-
-
-/**
- * We got a UDP packet back from the MESH tunnel.  Pass it on to the
- * local virtual interface via the helper.
- *
- * @param cls closure, NULL
- * @param tunnel connection to the other end
- * @param tunnel_ctx pointer to our 'struct TunnelState *'
- * @param sender who sent the message
- * @param message the actual message
- * @param atsi performance data for the connection
- * @return GNUNET_OK to keep the connection open,
- *         GNUNET_SYSERR to close it (signal serious error)
- */ 
-static int
-receive_udp_back (void *cls GNUNET_UNUSED, struct GNUNET_MESH_Tunnel *tunnel,
-                  void **tunnel_ctx, const struct GNUNET_PeerIdentity *sender,
-                  const struct GNUNET_MessageHeader *message,
-                  const struct GNUNET_ATS_Information *atsi GNUNET_UNUSED)
-{
-  struct TunnelState *ts = *tunnel_ctx;
-  const struct GNUNET_EXIT_UdpReplyMessage *reply;
-  size_t mlen;
+           return;
+         }
+       /* end of AF_INET6 */
+       break;
+      default:
+       GNUNET_assert (0);
+      }
 
-  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))
-  {
-    GNUNET_break_op (0);
-    return GNUNET_SYSERR;
-  }
-  if (NULL == ts->heap_node)
-  {
-    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,
-               "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:
-    {
-      size_t size = sizeof (struct GNUNET_TUN_IPv4Header) 
-       + sizeof (struct GNUNET_TUN_UdpHeader) 
-       + sizeof (struct GNUNET_MessageHeader) +
-       sizeof (struct GNUNET_TUN_Layer2PacketHeader) +
-       mlen;
+      /* update length calculations, as payload_length may have changed */
+      mlen = sizeof (struct GNUNET_EXIT_IcmpInternetMessage) +
+       alen + payload_length - sizeof (struct GNUNET_TUN_IcmpHeader);
+      if (mlen >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
       {
-       char buf[size];
-       struct GNUNET_MessageHeader *msg = (struct GNUNET_MessageHeader *) buf;
-       struct GNUNET_TUN_Layer2PacketHeader *tun = (struct GNUNET_TUN_Layer2PacketHeader*) &msg[1];
-       struct GNUNET_TUN_IPv4Header *ipv4 = (struct GNUNET_TUN_IPv4Header *) &tun[1];
-       struct GNUNET_TUN_UdpHeader *udp = (struct GNUNET_TUN_UdpHeader *) &ipv4[1];
-       msg->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
-       msg->size = htons (size);
-       tun->flags = htons (0);
-       tun->proto = htons (ETH_P_IPV4);
-       GNUNET_TUN_initialize_ipv4_header (ipv4,
-                                          IPPROTO_UDP,
-                                          sizeof (struct GNUNET_TUN_UdpHeader) + mlen,
-                                          &ts->destination_ip.v4,
-                                          &ts->source_ip.v4);
-       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 GNUNET_TUN_UdpHeader));
-       GNUNET_TUN_calculate_udp4_checksum (ipv4,
-                                           udp,
-                                           &reply[1],
-                                           mlen);
-       memcpy (&udp[1],
-               &reply[1],
-               mlen);
-       (void) GNUNET_HELPER_send (helper_handle,
-                                  msg,
-                                  GNUNET_YES,
-                                  NULL, NULL);
+       GNUNET_break (0);
+       return;
       }
-    }
-    break;
-  case AF_INET6:
-    {
-      size_t size = sizeof (struct GNUNET_TUN_IPv6Header) 
-       + sizeof (struct GNUNET_TUN_UdpHeader) 
-       + sizeof (struct GNUNET_MessageHeader) +
-       sizeof (struct GNUNET_TUN_Layer2PacketHeader) +
-       mlen;
+      env = GNUNET_MQ_msg_extra (iim,
+                                 alen + payload_length - sizeof (struct GNUNET_TUN_IcmpHeader),
+                                 GNUNET_MESSAGE_TYPE_VPN_ICMP_TO_INTERNET);
+      iim->icmp_header = *icmp;
+      iim->icmp_header.type = new_type;
+      iim->af = htonl (destination->details.exit_destination.af);
+      switch (destination->details.exit_destination.af)
       {
-       char buf[size];
-       struct GNUNET_MessageHeader *msg = (struct GNUNET_MessageHeader *) buf;
-       struct GNUNET_TUN_Layer2PacketHeader *tun = (struct GNUNET_TUN_Layer2PacketHeader*) &msg[1];
-       struct GNUNET_TUN_IPv6Header *ipv6 = (struct GNUNET_TUN_IPv6Header *) &tun[1];
-       struct GNUNET_TUN_UdpHeader *udp = (struct GNUNET_TUN_UdpHeader *) &ipv6[1];
-       msg->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
-       msg->size = htons (size);
-       tun->flags = htons (0);
-       tun->proto = htons (ETH_P_IPV6);
-       GNUNET_TUN_initialize_ipv6_header (ipv6,
-                                          IPPROTO_UDP,
-                                          sizeof (struct GNUNET_TUN_UdpHeader) + mlen,
-                                          &ts->destination_ip.v6,
-                                          &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 GNUNET_TUN_UdpHeader));
-       GNUNET_TUN_calculate_udp6_checksum (ipv6,
-                                           udp,
-                                           &reply[1], mlen);
-       memcpy (&udp[1],
-               &reply[1],
-               mlen);
-       (void) GNUNET_HELPER_send (helper_handle,
-                                  msg,
-                                  GNUNET_YES,
-                                  NULL, NULL);
+      case AF_INET:
+       ip4dst = (struct in_addr *) &iim[1];
+       *ip4dst = destination->details.exit_destination.ip.v4;
+       payload = &ip4dst[1];
+       break;
+      case AF_INET6:
+       ip6dst = (struct in6_addr *) &iim[1];
+       *ip6dst = destination->details.exit_destination.ip.v6;
+       payload = &ip6dst[1];
+       break;
+      default:
+       GNUNET_assert (0);
       }
+      GNUNET_memcpy (payload,
+                     &icmp[1],
+                     payload_length - sizeof (struct GNUNET_TUN_IcmpHeader));
     }
     break;
   default:
+    /* not supported above, how can we get here !? */
     GNUNET_assert (0);
+    break;
   }
-  GNUNET_CONTAINER_heap_update_cost (tunnel_heap, 
-                                    ts->heap_node,
-                                    GNUNET_TIME_absolute_get ().abs_value);
-  return GNUNET_OK;
+  ts->is_established = GNUNET_YES;
+  send_to_channel (ts,
+                   env);
 }
 
 
 /**
- * We got a TCP packet back from the MESH tunnel.  Pass it on to the
- * local virtual interface via the helper.
+ * Receive packets from the helper-process (someone send to the local
+ * virtual channel interface).  Find the destination mapping, and if it
+ * exists, identify the correct CADET channel (or possibly create it)
+ * and forward the packet.
  *
  * @param cls closure, NULL
- * @param tunnel connection to the other end
- * @param tunnel_ctx pointer to our 'struct TunnelState *'
- * @param sender who sent the message
- * @param message the actual message
- * @param atsi performance data for the connection
- * @return GNUNET_OK to keep the connection open,
- *         GNUNET_SYSERR to close it (signal serious error)
- */ 
+ * @param message message we got from the client (VPN channel interface)
+ */
 static int
-receive_tcp_back (void *cls GNUNET_UNUSED, struct GNUNET_MESH_Tunnel *tunnel,
-                  void **tunnel_ctx,
-                  const struct GNUNET_PeerIdentity *sender GNUNET_UNUSED,
-                  const struct GNUNET_MessageHeader *message,
-                  const struct GNUNET_ATS_Information *atsi GNUNET_UNUSED)
+message_token (void *cls,
+               const struct GNUNET_MessageHeader *message)
 {
-  struct TunnelState *ts = *tunnel_ctx;
-  const struct GNUNET_EXIT_TcpDataMessage *data;
+  const struct GNUNET_TUN_Layer2PacketHeader *tun;
   size_t mlen;
+  struct GNUNET_HashCode key;
+  struct DestinationEntry *de;
 
   GNUNET_STATISTICS_update (stats,
-                           gettext_noop ("# TCP packets received from mesh"),
+                           gettext_noop ("# Packets received from TUN interface"),
                            1, GNUNET_NO);
   mlen = ntohs (message->size);
-  if (mlen < sizeof (struct GNUNET_EXIT_TcpDataMessage))
-  {
-    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);
-  }
-  if (data->tcp_header.off * 4 < sizeof (struct GNUNET_TUN_TcpHeader))
+  if ( (ntohs (message->type) != GNUNET_MESSAGE_TYPE_VPN_HELPER) ||
+       (mlen < sizeof (struct GNUNET_MessageHeader) + sizeof (struct GNUNET_TUN_Layer2PacketHeader)) )
   {
-    GNUNET_break_op (0);
-    return GNUNET_SYSERR;
+    GNUNET_break (0);
+    return GNUNET_OK;
   }
-  switch (ts->af)
+  tun = (const struct GNUNET_TUN_Layer2PacketHeader *) &message[1];
+  mlen -= (sizeof (struct GNUNET_MessageHeader) + sizeof (struct GNUNET_TUN_Layer2PacketHeader));
+  switch (ntohs (tun->proto))
   {
-  case AF_INET:
+  case ETH_P_IPV6:
     {
-      size_t size = sizeof (struct GNUNET_TUN_IPv4Header) 
-       + sizeof (struct GNUNET_TUN_TcpHeader) 
-       + sizeof (struct GNUNET_MessageHeader) +
-       sizeof (struct GNUNET_TUN_Layer2PacketHeader) +
-       mlen;
+      const struct GNUNET_TUN_IPv6Header *pkt6;
+
+      if (mlen < sizeof (struct GNUNET_TUN_IPv6Header))
       {
-       char buf[size];
-       struct GNUNET_MessageHeader *msg = (struct GNUNET_MessageHeader *) buf;
-       struct GNUNET_TUN_Layer2PacketHeader *tun = (struct GNUNET_TUN_Layer2PacketHeader*) &msg[1];
-       struct GNUNET_TUN_IPv4Header *ipv4 = (struct GNUNET_TUN_IPv4Header *) &tun[1];
-       struct GNUNET_TUN_TcpHeader *tcp = (struct GNUNET_TUN_TcpHeader *) &ipv4[1];
-       msg->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
-       msg->size = htons (size);
-       tun->flags = htons (0);
-       tun->proto = htons (ETH_P_IPV4);
-       GNUNET_TUN_initialize_ipv4_header (ipv4,
-                                          IPPROTO_TCP,
-                                          sizeof (struct GNUNET_TUN_TcpHeader) + mlen,
-                                          &ts->destination_ip.v4,
-                                          &ts->source_ip.v4);
-       *tcp = data->tcp_header;
-       tcp->spt = htons (ts->destination_port);
-       tcp->dpt = htons (ts->source_port);
-       GNUNET_TUN_calculate_tcp4_checksum (ipv4,
-                                           tcp,
-                                           &data[1],
-                                           mlen);
-       memcpy (&tcp[1],
-               &data[1],
-               mlen);
-       (void) GNUNET_HELPER_send (helper_handle,
-                                  msg,
-                                  GNUNET_YES,
-                                  NULL, NULL);
+       /* blame kernel */
+       GNUNET_break (0);
+        return GNUNET_OK;
+      }
+      pkt6 = (const struct GNUNET_TUN_IPv6Header *) &tun[1];
+      get_destination_key_from_ip (AF_INET6,
+                                  &pkt6->destination_address,
+                                  &key);
+      de = GNUNET_CONTAINER_multihashmap_get (destination_map, &key);
+      if (NULL == de)
+      {
+       char buf[INET6_ADDRSTRLEN];
+
+       GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+                   _("Packet received for unmapped destination `%s' (dropping it)\n"),
+                   inet_ntop (AF_INET6,
+                              &pkt6->destination_address,
+                              buf,
+                              sizeof (buf)));
+       return GNUNET_OK;
       }
+      route_packet (de,
+                   AF_INET6,
+                   pkt6->next_header,
+                   &pkt6->source_address,
+                   &pkt6->destination_address,
+                   &pkt6[1],
+                   mlen - sizeof (struct GNUNET_TUN_IPv6Header));
     }
     break;
-  case AF_INET6:
+  case ETH_P_IPV4:
     {
-      size_t size = sizeof (struct GNUNET_TUN_IPv6Header) 
-       + sizeof (struct GNUNET_TUN_TcpHeader) 
-       + sizeof (struct GNUNET_MessageHeader) +
-       sizeof (struct GNUNET_TUN_Layer2PacketHeader) +
-       mlen;
+      struct GNUNET_TUN_IPv4Header *pkt4;
+
+      if (mlen < sizeof (struct GNUNET_TUN_IPv4Header))
       {
-       char buf[size];
-       struct GNUNET_MessageHeader *msg = (struct GNUNET_MessageHeader *) buf;
-       struct GNUNET_TUN_Layer2PacketHeader *tun = (struct GNUNET_TUN_Layer2PacketHeader*) &msg[1];
-       struct GNUNET_TUN_IPv6Header *ipv6 = (struct GNUNET_TUN_IPv6Header *) &tun[1];
-       struct GNUNET_TUN_TcpHeader *tcp = (struct GNUNET_TUN_TcpHeader *) &ipv6[1];
-       msg->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
-       msg->size = htons (size);
-       tun->flags = htons (0);
-       tun->proto = htons (ETH_P_IPV6);
-       GNUNET_TUN_initialize_ipv6_header (ipv6,
-                                          IPPROTO_TCP,
-                                          sizeof (struct GNUNET_TUN_TcpHeader) + mlen,
-                                          &ts->destination_ip.v6,
-                                          &ts->source_ip.v6);
-       tcp->spt = htons (ts->destination_port);
-       tcp->dpt = htons (ts->source_port);
-       GNUNET_TUN_calculate_tcp6_checksum (ipv6,
-                                           tcp,
-                                           &tcp[1],
-                                           mlen);
-       (void) GNUNET_HELPER_send (helper_handle,
-                                  msg,
-                                  GNUNET_YES,
-                                  NULL, NULL);
+       /* blame kernel */
+       GNUNET_break (0);
+       return GNUNET_OK;
+      }
+      pkt4 = (struct GNUNET_TUN_IPv4Header *) &tun[1];
+      get_destination_key_from_ip (AF_INET,
+                                  &pkt4->destination_address,
+                                  &key);
+      de = GNUNET_CONTAINER_multihashmap_get (destination_map, &key);
+      if (NULL == de)
+      {
+       char buf[INET_ADDRSTRLEN];
+
+       GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+                   _("Packet received for unmapped destination `%s' (dropping it)\n"),
+                   inet_ntop (AF_INET,
+                              &pkt4->destination_address,
+                              buf,
+                              sizeof (buf)));
+        return GNUNET_OK;
+      }
+      if (pkt4->header_length * 4 != sizeof (struct GNUNET_TUN_IPv4Header))
+      {
+       GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+                   _("Received IPv4 packet with options (dropping it)\n"));
+        return GNUNET_OK;
       }
+      route_packet (de,
+                   AF_INET,
+                   pkt4->protocol,
+                   &pkt4->source_address,
+                   &pkt4->destination_address,
+                   &pkt4[1],
+                   mlen - sizeof (struct GNUNET_TUN_IPv4Header));
     }
     break;
+  default:
+    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+               _("Received packet of unknown protocol %d from TUN (dropping it)\n"),
+               (unsigned int) ntohs (tun->proto));
+    break;
   }
-  GNUNET_CONTAINER_heap_update_cost (tunnel_heap, 
-                                    ts->heap_node,
-                                    GNUNET_TIME_absolute_get ().abs_value);
   return GNUNET_OK;
 }
 
 
 /**
- * Allocate an IPv4 address from the range of the tunnel
+ * Allocate an IPv4 address from the range of the channel
  * for a new redirection.
  *
  * @param v4 where to store the address
- * @return GNUNET_OK on success,
- *         GNUNET_SYSERR on error
+ * @return #GNUNET_OK on success,
+ *         #GNUNET_SYSERR on error
  */
 static int
 allocate_v4_address (struct in_addr *v4)
@@ -2318,14 +2346,14 @@ allocate_v4_address (struct in_addr *v4)
   struct in_addr addr;
   struct in_addr mask;
   struct in_addr rnd;
-  GNUNET_HashCode key;
+  struct 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 
+  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;  
+  mask.s_addr = addr.s_addr | ~mask.s_addr;
   tries = 0;
   do
     {
@@ -2337,9 +2365,9 @@ allocate_v4_address (struct in_addr *v4)
        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;          
+      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);
@@ -2354,12 +2382,12 @@ allocate_v4_address (struct in_addr *v4)
 
 
 /**
- * Allocate an IPv6 address from the range of the tunnel
+ * Allocate an IPv6 address from the range of the channel
  * for a new redirection.
  *
  * @param v6 where to store the address
- * @return GNUNET_OK on success,
- *         GNUNET_SYSERR on error
+ * @return #GNUNET_OK on success,
+ *         #GNUNET_SYSERR on error
  */
 static int
 allocate_v6_address (struct in6_addr *v6)
@@ -2369,7 +2397,7 @@ allocate_v6_address (struct in6_addr *v6)
   struct in6_addr mask;
   struct in6_addr rnd;
   int i;
-  GNUNET_HashCode key;
+  struct GNUNET_HashCode key;
   unsigned int tries;
 
   GNUNET_assert (1 == inet_pton (AF_INET6, ipv6addr, &addr));
@@ -2377,9 +2405,9 @@ allocate_v6_address (struct in6_addr *v6)
   /* Given ABCD::/96, we want a mask of 'ABCD::FFFF:FFFF,
      thus: */
   mask = addr;
-  for (i=127;i>=128-ipv6prefix;i--)
+  for (i=127;i>=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
@@ -2394,7 +2422,7 @@ allocate_v6_address (struct in6_addr *v6)
        }
       for (i=0;i<16;i++)
        {
-         rnd.s6_addr[i] = (unsigned char) GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK, 
+         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];
@@ -2424,20 +2452,25 @@ allocate_v6_address (struct in6_addr *v6)
 static void
 free_destination_entry (struct DestinationEntry *de)
 {
+  struct DestinationChannel *dt;
+
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-             "Cleaning up destination entry\n");
+             "Cleaning up destination entry `%s'\n",
+              print_channel_destination (de));
   GNUNET_STATISTICS_update (stats,
                            gettext_noop ("# Active destinations"),
                            -1, GNUNET_NO);
-  if (NULL != de->ts)
+  while (NULL != (dt = de->dt_head))
   {
-    free_tunnel_state (de->ts);
-    GNUNET_assert (NULL == de->ts);
+    GNUNET_CONTAINER_DLL_remove (de->dt_head,
+                                de->dt_tail,
+                                dt);
+    GNUNET_free (dt);
   }
   if (NULL != de->heap_node)
   {
     GNUNET_CONTAINER_heap_remove_node (de->heap_node);
-    de->heap_node = NULL;  
+    de->heap_node = NULL;
     GNUNET_assert (GNUNET_YES ==
                   GNUNET_CONTAINER_multihashmap_remove (destination_map,
                                                         &de->key,
@@ -2452,7 +2485,7 @@ free_destination_entry (struct DestinationEntry *de)
  *
  * @param except destination that must NOT be cleaned up, even if it is the oldest
  */
-static void 
+static void
 expire_destination (struct DestinationEntry *except)
 {
   struct DestinationEntry *de;
@@ -2466,40 +2499,81 @@ expire_destination (struct DestinationEntry *except)
 
 
 /**
- * A client asks us to setup a redirection via some exit
- * node to a particular IP.  Setup the redirection and
- * give the client the allocated IP.
+ * Allocate an IP address for the response.
  *
- * @param cls unused
- * @param client requesting client
- * @param message redirection request (a 'struct RedirectToIpRequestMessage')
+ * @param result_af desired address family; set to the actual
+ *        address family; can initially be AF_UNSPEC if there
+ *        is no preference; will be set to AF_UNSPEC if the
+ *        allocation failed
+ * @param addr set to either v4 or v6 depending on which
+ *         storage location was used; set to NULL if allocation failed
+ * @param v4 storage space for an IPv4 address
+ * @param v6 storage space for an IPv6 address
+ * @return #GNUNET_OK normally, #GNUNET_SYSERR if `* result_af` was
+ *         an unsupported address family (not AF_INET, AF_INET6 or AF_UNSPEC)
  */
-static void
-service_redirect_to_ip (void *cls GNUNET_UNUSED, struct GNUNET_SERVER_Client *client,
-                       const struct GNUNET_MessageHeader *message)
+static int
+allocate_response_ip (int *result_af,
+                     void **addr,
+                     struct in_addr *v4,
+                     struct in6_addr *v6)
 {
-  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;
-  struct TunnelState *ts;
-  
-  /* validate and parse request */
-  mlen = ntohs (message->size);
-  if (mlen < sizeof (struct RedirectToIpRequestMessage))
+  *addr = NULL;
+  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;
+    return GNUNET_SYSERR;
   }
-  alen = mlen - sizeof (struct RedirectToIpRequestMessage);
-  msg = (const struct RedirectToIpRequestMessage *) message;
+  return GNUNET_OK;
+}
+
+
+/**
+ * A client asks us to setup a redirection via some exit node to a
+ * particular IP.  Check if @a msg is well-formed.
+ * allocated IP.
+ *
+ * @param cls client requesting client
+ * @param msg redirection request
+ * @return #GNUNET_OK if @a msg is well-formed
+ */
+static int
+check_client_redirect_to_ip (void *cls,
+                             const struct RedirectToIpRequestMessage *msg)
+{
+  size_t alen;
+  int addr_af;
+
+  alen = ntohs (msg->header.size) - sizeof (struct RedirectToIpRequestMessage);
   addr_af = (int) htonl (msg->addr_af);
   switch (addr_af)
   {
@@ -2507,96 +2581,92 @@ service_redirect_to_ip (void *cls GNUNET_UNUSED, struct GNUNET_SERVER_Client *cl
     if (alen != sizeof (struct in_addr))
     {
       GNUNET_break (0);
-      GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
-      return;      
+      return GNUNET_SYSERR;
     }
     break;
   case AF_INET6:
     if (alen != sizeof (struct in6_addr))
     {
       GNUNET_break (0);
-      GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
-      return;      
+      return GNUNET_SYSERR;
     }
     break;
   default:
     GNUNET_break (0);
-    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
-    return;      
+    return GNUNET_SYSERR;
   }
+  return GNUNET_OK;
+}
+
+
+/**
+ * A client asks us to setup a redirection via some exit node to a
+ * particular IP.  Setup the redirection and give the client the
+ * allocated IP.
+ *
+ * @param cls client requesting client
+ * @param msg redirection request
+ */
+static void
+handle_client_redirect_to_ip (void *cls,
+                              const struct RedirectToIpRequestMessage *msg)
+{
+  struct GNUNET_SERVICE_Client *client = cls;
+  size_t alen;
+  int addr_af;
+  int result_af;
+  struct in_addr v4;
+  struct in6_addr v6;
+  void *addr;
+  struct DestinationEntry *de;
+  struct GNUNET_HashCode key;
 
+  alen = ntohs (msg->header.size) - sizeof (struct RedirectToIpRequestMessage);
+  addr_af = (int) htonl (msg->addr_af);
   /* 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)) )
+  if (GNUNET_OK != allocate_response_ip (&result_af,
+                                        &addr,
+                                        &v4, &v6))
   {
-    /* send reply "instantly" */
-    send_client_reply (client,
-                      msg->request_id,
-                      result_af,
-                      addr);
+    GNUNET_SERVICE_client_drop (client);
+    return;
   }
+  /* send reply with our IP address */
+  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);
+    GNUNET_SERVICE_client_continue (client);
     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 (result_af,
+                           addr,
+                           sbuf,
+                           sizeof (sbuf)),
                inet_ntop (addr_af,
-                          &msg[1], dbuf, sizeof (dbuf)));
+                          &msg[1],
+                           dbuf,
+                           sizeof (dbuf)));
   }
-  
+
   /* setup destination record */
-  de = GNUNET_malloc (sizeof (struct DestinationEntry));
+  de = GNUNET_new (struct DestinationEntry);
   de->is_service = GNUNET_NO;
   de->details.exit_destination.af = addr_af;
-  memcpy (&de->details.exit_destination.ip,
-         &msg[1],
-         alen);
+  GNUNET_memcpy (&de->details.exit_destination.ip,
+                 &msg[1],
+                 alen);
   get_destination_key_from_ip (result_af,
                               addr,
                               &key);
@@ -2608,31 +2678,13 @@ service_redirect_to_ip (void *cls GNUNET_UNUSED, struct GNUNET_SERVER_Client *cl
                                                    GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE));
   de->heap_node = GNUNET_CONTAINER_heap_insert (destination_heap,
                                                de,
-                                               GNUNET_TIME_absolute_ntoh (msg->expiration_time).abs_value);
+                                               GNUNET_TIME_absolute_ntoh (msg->expiration_time).abs_value_us);
   GNUNET_STATISTICS_update (stats,
                            gettext_noop ("# Active destinations"),
                            1, GNUNET_NO);
   while (GNUNET_CONTAINER_multihashmap_size (destination_map) > max_destination_mappings)
     expire_destination (de);
-  
-  /* setup tunnel to destination */
-  ts = create_tunnel_to_destination (de, 
-                                    (GNUNET_NO == ntohl (msg->nac)) ? NULL : client,
-                                    result_af,
-                                    msg->request_id);
-  switch (result_af)
-  {
-  case AF_INET:
-    ts->destination_ip.v4 = v4;
-    break;
-  case AF_INET6:
-    ts->destination_ip.v6 = v6;
-    break;
-  default:
-    GNUNET_assert (0);
-  }
-  /* we're done */
-  GNUNET_SERVER_receive_done (client, GNUNET_OK);
+  GNUNET_SERVICE_client_continue (client);
 }
 
 
@@ -2641,97 +2693,65 @@ service_redirect_to_ip (void *cls GNUNET_UNUSED, struct GNUNET_SERVER_Client *cl
  * offering a service.  Setup the redirection and give the client the
  * allocated IP.
  *
- * @param cls unused
- * @param client requesting client
- * @param message redirection request (a 'struct RedirectToPeerRequestMessage')
+ * @param cls requesting client
+ * @param msg redirection request
  */
 static void
-service_redirect_to_service (void *cls GNUNET_UNUSED, struct GNUNET_SERVER_Client *client,
-                            const struct GNUNET_MessageHeader *message)
+handle_client_redirect_to_service (void *cls,
+                                   const struct RedirectToServiceRequestMessage *msg)
 {
-  const struct RedirectToServiceRequestMessage *msg;
+  struct GNUNET_SERVICE_Client *client = cls;
   int result_af;
   struct in_addr v4;
   struct in6_addr v6;
   void *addr;
   struct DestinationEntry *de;
-  GNUNET_HashCode key;
-  struct TunnelState *ts;
-  
-  /*  parse request */
-  msg = (const struct RedirectToServiceRequestMessage *) message;
+  struct GNUNET_HashCode key;
+  struct DestinationChannel *dt;
 
   /* allocate response IP */
-  addr = NULL;
   result_af = (int) htonl (msg->result_af);
-  switch (result_af)
+  if (GNUNET_OK !=
+      allocate_response_ip (&result_af,
+                            &addr,
+                            &v4,
+                            &v6))
   {
-  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);
+    GNUNET_SERVICE_client_drop (client);
+    return;
   }
+  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);
+    GNUNET_SERVICE_client_continue (client);
     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)),
+               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 = GNUNET_new (struct DestinationEntry);
   de->is_service = GNUNET_YES;
-  de->details.service_destination.service_descriptor = msg->service_descriptor;
   de->details.service_destination.target = msg->target;
+  de->details.service_destination.service_descriptor = msg->service_descriptor;
   get_destination_key_from_ip (result_af,
                               addr,
                               &key);
@@ -2741,82 +2761,35 @@ service_redirect_to_service (void *cls GNUNET_UNUSED, struct GNUNET_SERVER_Clien
                                                    &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);
+  de->heap_node
+    = GNUNET_CONTAINER_heap_insert (destination_heap,
+                                    de,
+                                    GNUNET_TIME_absolute_ntoh (msg->expiration_time).abs_value_us);
   while (GNUNET_CONTAINER_multihashmap_size (destination_map) > max_destination_mappings)
     expire_destination (de);
-  ts = create_tunnel_to_destination (de,
-                                    (GNUNET_NO == ntohl (msg->nac)) ? NULL : client,
-                                    result_af,
-                                    msg->request_id);
-  switch (result_af)
-  {
-  case AF_INET:
-    ts->destination_ip.v4 = v4;
-    break;
-  case AF_INET6:
-    ts->destination_ip.v6 = v6;
-    break;
-  default:
-    GNUNET_assert (0);
-  }
-  /* we're done */
-  GNUNET_SERVER_receive_done (client, GNUNET_OK);
-}
-
 
-
-/**
- * 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 *
-inbound_tunnel_cb (void *cls, struct GNUNET_MESH_Tunnel *tunnel,
-                  const struct GNUNET_PeerIdentity *initiator,
-                  const struct GNUNET_ATS_Information *atsi)
-{
-  /* How can and why should anyone open an inbound tunnel to vpn? */
-  GNUNET_break (0);
-  return NULL;
+  dt = GNUNET_new (struct DestinationChannel);
+  dt->destination = de;
+  GNUNET_CONTAINER_DLL_insert (de->dt_head,
+                              de->dt_tail,
+                              dt);
+  /* we're done */
+  GNUNET_SERVICE_client_continue (client);
 }
 
 
-/**
- * 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)
-{
-  /* we don't have inbound tunnels, so this function should never be called */
-  GNUNET_break (0);
-}
-
 
 /**
  * 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)
+ * @param value a `struct DestinationEntry *`
+ * @return #GNUNET_OK (continue to iterate)
  */
 static int
 cleanup_destination (void *cls,
-                    const GNUNET_HashCode *key,
+                    const struct GNUNET_HashCode *key,
                     void *value)
 {
   struct DestinationEntry *de = value;
@@ -2827,21 +2800,24 @@ cleanup_destination (void *cls,
 
 
 /**
- * Free memory occupied by an entry in the tunnel map.
+ * Free memory occupied by an entry in the channel map.
  *
  * @param cls unused
  * @param key unused
- * @param value a 'struct TunnelState *'
- * @return GNUNET_OK (continue to iterate)
+ * @param value a `struct ChannelState *`
+ * @return #GNUNET_OK (continue to iterate)
  */
 static int
-cleanup_tunnel (void *cls,
-               const GNUNET_HashCode *key,
-               void *value)
+cleanup_channel (void *cls,
+                 const struct GNUNET_HashCode *key,
+                 void *value)
 {
-  struct TunnelState *ts = value;
+  struct ChannelState *ts = value;
 
-  free_tunnel_state (ts);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             "Tearing down channel to `%s' during cleanup\n",
+              print_channel_destination (&ts->destination));
+  free_channel_state (ts);
   return GNUNET_OK;
 }
 
@@ -2850,18 +2826,16 @@ cleanup_tunnel (void *cls,
  * 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 *tc)
+cleanup (void *cls)
 {
   unsigned int i;
 
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "VPN is shutting down\n");
   if (NULL != destination_map)
-  {  
+  {
     GNUNET_CONTAINER_multihashmap_iterate (destination_map,
                                           &cleanup_destination,
                                           NULL);
@@ -2873,35 +2847,31 @@ cleanup (void *cls GNUNET_UNUSED,
     GNUNET_CONTAINER_heap_destroy (destination_heap);
     destination_heap = NULL;
   }
-  if (NULL != tunnel_map)
-  {  
-    GNUNET_CONTAINER_multihashmap_iterate (tunnel_map,
-                                          &cleanup_tunnel,
+  if (NULL != channel_map)
+  {
+    GNUNET_CONTAINER_multihashmap_iterate (channel_map,
+                                          &cleanup_channel,
                                           NULL);
-    GNUNET_CONTAINER_multihashmap_destroy (tunnel_map);
-    tunnel_map = NULL;
+    GNUNET_CONTAINER_multihashmap_destroy (channel_map);
+    channel_map = NULL;
   }
-  if (NULL != tunnel_heap)
+  if (NULL != channel_heap)
   {
-    GNUNET_CONTAINER_heap_destroy (tunnel_heap);
-    tunnel_heap = NULL;
+    GNUNET_CONTAINER_heap_destroy (channel_heap);
+    channel_heap = NULL;
   }
-  if (NULL != mesh_handle)
+  if (NULL != cadet_handle)
   {
-    GNUNET_MESH_disconnect (mesh_handle);
-    mesh_handle = NULL;
+    GNUNET_CADET_disconnect (cadet_handle);
+    cadet_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;
+    GNUNET_HELPER_kill (helper_handle, GNUNET_NO);
+    GNUNET_HELPER_wait (helper_handle);
+    helper_handle = NULL;
   }
-  if (stats != NULL)
+  if (NULL != stats)
   {
     GNUNET_STATISTICS_destroy (stats, GNUNET_NO);
     stats = NULL;
@@ -2912,76 +2882,35 @@ cleanup (void *cls GNUNET_UNUSED,
 
 
 /**
- * A client disconnected, clean up all references to it.
+ * Callback called when a client connects to the service.
  *
- * @param cls the client that disconnected
- * @param key unused
- * @param value a 'struct TunnelState *'
- * @return GNUNET_OK (continue to iterate)
+ * @param cls closure for the service
+ * @param c the new client that connected to the service
+ * @param mq the message queue used to send messages to the client
+ * @return @a c
  */
-static int
-cleanup_tunnel_client (void *cls,
-                      const GNUNET_HashCode *key,
-                      void *value)
+static void *
+client_connect_cb (void *cls,
+                  struct GNUNET_SERVICE_Client *c,
+                  struct GNUNET_MQ_Handle *mq)
 {
-  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;
+  return c;
 }
 
 
 /**
- * A client disconnected, clean up all references to it.
+ * Callback called when a client disconnected from the service
  *
- * @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.
- *
- * @param cls unused
- * @param client handle to the client that disconnected
+ * @param cls closure for the service
+ * @param c the client that disconnected
+ * @param internal_cls should be equal to @a c
  */
 static void
-client_disconnect (void *cls, struct GNUNET_SERVER_Client *client)
+client_disconnect_cb (void *cls,
+                     struct GNUNET_SERVICE_Client *c,
+                     void *internal_cls)
 {
-  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);
+  GNUNET_assert (c == internal_cls);
 }
 
 
@@ -2989,31 +2918,14 @@ client_disconnect (void *cls, struct GNUNET_SERVER_Client *client)
  * Main function that will be run by the scheduler.
  *
  * @param cls closure
- * @param server the initialized server
  * @param cfg_ configuration
+ * @param service the initialized service
  */
 static void
 run (void *cls,
-     struct GNUNET_SERVER_Handle *server,
-     const struct GNUNET_CONFIGURATION_Handle *cfg_)
+     const struct GNUNET_CONFIGURATION_Handle *cfg_,
+     struct GNUNET_SERVICE_Handle *service)
 {
-  static const struct GNUNET_SERVER_MessageHandler service_handlers[] = {
-    /* callback, cls, type, size */
-    { &service_redirect_to_ip, NULL, GNUNET_MESSAGE_TYPE_VPN_CLIENT_REDIRECT_TO_IP, 0},
-    { &service_redirect_to_service, NULL, 
-     GNUNET_MESSAGE_TYPE_VPN_CLIENT_REDIRECT_TO_SERVICE, 
-     sizeof (struct RedirectToServiceRequestMessage) },
-    {NULL, NULL, 0, 0}
-  };
-  static const struct GNUNET_MESH_MessageHandler mesh_handlers[] = {
-    { &receive_udp_back, GNUNET_MESSAGE_TYPE_VPN_UDP_REPLY, 0},
-    { &receive_tcp_back, GNUNET_MESSAGE_TYPE_VPN_TCP_DATA_TO_VPN, 0},
-    { &receive_icmp_back, GNUNET_MESSAGE_TYPE_VPN_ICMP_TO_VPN, 0},
-    {NULL, 0, 0}
-  };
-  static const GNUNET_MESH_ApplicationType types[] = {
-    GNUNET_APPLICATION_TYPE_END
-  };
   char *ifname;
   char *ipv6addr;
   char *ipv6prefix_s;
@@ -3021,127 +2933,168 @@ run (void *cls,
   char *ipv4mask;
   struct in_addr v4;
   struct in6_addr v6;
+  char *binary;
+
+  binary = GNUNET_OS_get_libexec_binary_path ("gnunet-helper-vpn");
 
   if (GNUNET_YES !=
-      GNUNET_OS_check_helper_binary ("gnunet-helper-vpn"))
+      GNUNET_OS_check_helper_binary (binary,
+                                     GNUNET_YES,
+                                     "-d gnunet-vpn - - 169.1.3.3.7 255.255.255.0")) //ipv4 only please!
   {
-    fprintf (stderr,
-            "`%s' is not SUID, refusing to run.\n",
-            "gnunet-helper-vpn");
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "`%s' is not SUID, refusing to run.\n",
+                "gnunet-helper-vpn");
+    GNUNET_free (binary);
     global_ret = 1;
+    /* we won't "really" exit here, as the 'service' is still running;
+       however, as no handlers are registered, the service won't do
+       anything either */
     return;
   }
+  GNUNET_free (binary);
   cfg = cfg_;
   stats = GNUNET_STATISTICS_create ("vpn", cfg);
   if (GNUNET_OK !=
-      GNUNET_CONFIGURATION_get_value_number (cfg, "vpn", "MAX_MAPPING",
+      GNUNET_CONFIGURATION_get_value_number (cfg,
+                                             "VPN",
+                                             "MAX_MAPPING",
                                             &max_destination_mappings))
     max_destination_mappings = 200;
   if (GNUNET_OK !=
-      GNUNET_CONFIGURATION_get_value_number (cfg, "vpn", "MAX_TUNNELS",
-                                            &max_tunnel_mappings))
-    max_tunnel_mappings = 200;
+      GNUNET_CONFIGURATION_get_value_number (cfg,
+                                             "VPN",
+                                             "MAX_TUNNELS",
+                                            &max_channel_mappings))
+    max_channel_mappings = 200;
 
-  destination_map = GNUNET_CONTAINER_multihashmap_create (max_destination_mappings * 2);
+  destination_map = GNUNET_CONTAINER_multihashmap_create (max_destination_mappings * 2, GNUNET_NO);
   destination_heap = GNUNET_CONTAINER_heap_create (GNUNET_CONTAINER_HEAP_ORDER_MIN);
-  tunnel_map = GNUNET_CONTAINER_multihashmap_create (max_tunnel_mappings * 2);
-  tunnel_heap = GNUNET_CONTAINER_heap_create (GNUNET_CONTAINER_HEAP_ORDER_MIN);
+  channel_map = GNUNET_CONTAINER_multihashmap_create (max_channel_mappings * 2, GNUNET_NO);
+  channel_heap = GNUNET_CONTAINER_heap_create (GNUNET_CONTAINER_HEAP_ORDER_MIN);
 
 
   vpn_argv[0] = GNUNET_strdup ("vpn-gnunet");
   if (GNUNET_SYSERR ==
-      GNUNET_CONFIGURATION_get_value_string (cfg, "vpn", "IFNAME", &ifname))
+      GNUNET_CONFIGURATION_get_value_string (cfg, "VPN", "IFNAME", &ifname))
   {
-    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                "No entry 'IFNAME' in configuration!\n");
+    GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR, "VPN", "IFNAME");
     GNUNET_SCHEDULER_shutdown ();
     return;
   }
   vpn_argv[1] = ifname;
-  if ( (GNUNET_SYSERR ==
-       GNUNET_CONFIGURATION_get_value_string (cfg, "vpn", "IPV6ADDR",
-                                              &ipv6addr) ||
-       (1 != inet_pton (AF_INET6, ipv6addr, &v6))) )
-  {
-    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                "No valid entry 'IPV6ADDR' in configuration!\n");
-    GNUNET_SCHEDULER_shutdown ();
-    return;
-  }
-  vpn_argv[2] = ipv6addr;
-  if (GNUNET_SYSERR ==
-      GNUNET_CONFIGURATION_get_value_string (cfg, "vpn", "IPV6PREFIX",
-                                             &ipv6prefix_s))
+  ipv6addr = NULL;
+  if (GNUNET_OK == GNUNET_NETWORK_test_pf (PF_INET6))
   {
-    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                "No entry 'IPV6PREFIX' in configuration!\n");
-    GNUNET_SCHEDULER_shutdown ();
-    return;
+    if ( (GNUNET_SYSERR ==
+         GNUNET_CONFIGURATION_get_value_string (cfg, "VPN", "IPV6ADDR",
+                                                &ipv6addr) ||
+         (1 != inet_pton (AF_INET6, ipv6addr, &v6))) )
+    {
+      GNUNET_log_config_invalid (GNUNET_ERROR_TYPE_ERROR, "VPN", "IPV6ADDR",
+                                _("Must specify valid IPv6 address"));
+      GNUNET_SCHEDULER_shutdown ();
+      GNUNET_free_non_null (ipv6addr);
+      return;
+    }
+    vpn_argv[2] = ipv6addr;
+    ipv6prefix_s = NULL;
+    if (GNUNET_SYSERR ==
+       GNUNET_CONFIGURATION_get_value_string (cfg, "VPN", "IPV6PREFIX",
+                                              &ipv6prefix_s))
+    {
+      GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR, "VPN", "IPV6PREFIX");
+      GNUNET_SCHEDULER_shutdown ();
+      GNUNET_free_non_null (ipv6prefix_s);
+      return;
+    }
+    vpn_argv[3] = ipv6prefix_s;
+    if ( (GNUNET_OK !=
+         GNUNET_CONFIGURATION_get_value_number (cfg, "VPN",
+                                                "IPV6PREFIX",
+                                                &ipv6prefix)) ||
+        (ipv6prefix >= 127) )
+    {
+      GNUNET_log_config_invalid (GNUNET_ERROR_TYPE_ERROR, "VPN", "IPV4MASK",
+                                _("Must specify valid IPv6 mask"));
+      GNUNET_SCHEDULER_shutdown ();
+      return;
+    }
   }
-  vpn_argv[3] = ipv6prefix_s;
-  if ( (GNUNET_OK !=
-       GNUNET_CONFIGURATION_get_value_number (cfg, "vpn",
-                                              "IPV6PREFIX",
-                                              &ipv6prefix)) ||
-       (ipv6prefix >= 127) )
+  else
   {
-    GNUNET_SCHEDULER_shutdown ();
-    return;
+    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+               _("IPv6 support disabled as this system does not support IPv6\n"));
+    vpn_argv[2] = GNUNET_strdup ("-");
+    vpn_argv[3] = GNUNET_strdup ("-");
   }
-
-  if ( (GNUNET_SYSERR ==
-       GNUNET_CONFIGURATION_get_value_string (cfg, "vpn", "IPV4ADDR",
-                                              &ipv4addr) ||
-       (1 != inet_pton (AF_INET, ipv4addr, &v4))) )
+  if (GNUNET_OK == GNUNET_NETWORK_test_pf (PF_INET))
   {
-    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                "No valid entry for 'IPV4ADDR' in configuration!\n");
-    GNUNET_SCHEDULER_shutdown ();
-    return;
+    ipv4addr = NULL;
+    if ( (GNUNET_SYSERR ==
+         GNUNET_CONFIGURATION_get_value_string (cfg, "vpn", "IPV4ADDR",
+                                                &ipv4addr) ||
+         (1 != inet_pton (AF_INET, ipv4addr, &v4))) )
+    {
+      GNUNET_log_config_invalid (GNUNET_ERROR_TYPE_ERROR, "VPN", "IPV4ADDR",
+                                _("Must specify valid IPv4 address"));
+      GNUNET_SCHEDULER_shutdown ();
+      GNUNET_free_non_null (ipv4addr);
+      return;
+    }
+    vpn_argv[4] = ipv4addr;
+    ipv4mask = NULL;
+    if ( (GNUNET_SYSERR ==
+         GNUNET_CONFIGURATION_get_value_string (cfg, "vpn", "IPV4MASK",
+                                                &ipv4mask) ||
+         (1 != inet_pton (AF_INET, ipv4mask, &v4))) )
+    {
+      GNUNET_log_config_invalid (GNUNET_ERROR_TYPE_ERROR, "VPN", "IPV4MASK",
+                                _("Must specify valid IPv4 mask"));
+      GNUNET_SCHEDULER_shutdown ();
+      GNUNET_free_non_null (ipv4mask);
+      return;
+    }
+    vpn_argv[5] = ipv4mask;
   }
-  vpn_argv[4] = ipv4addr;
-  if ( (GNUNET_SYSERR ==
-       GNUNET_CONFIGURATION_get_value_string (cfg, "vpn", "IPV4MASK",
-                                              &ipv4mask) ||
-       (1 != inet_pton (AF_INET, ipv4mask, &v4))) )
+  else
   {
-    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                "No valid entry 'IPV4MASK' in configuration!\n");
-    GNUNET_SCHEDULER_shutdown ();
-    return;
+    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+               _("IPv4 support disabled as this system does not support IPv4\n"));
+    vpn_argv[4] = GNUNET_strdup ("-");
+    vpn_argv[5] = GNUNET_strdup ("-");
   }
-  vpn_argv[5] = ipv4mask;
   vpn_argv[6] = NULL;
 
-  mesh_handle =
-    GNUNET_MESH_connect (cfg_, 42 /* queue length */, NULL, 
-                        &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);
+  cadet_handle = GNUNET_CADET_connect (cfg_);
+    // FIXME never opens ports???
+  helper_handle = GNUNET_HELPER_start (GNUNET_NO,
+                                      "gnunet-helper-vpn", vpn_argv,
+                                      &message_token, NULL, NULL);
+  GNUNET_SCHEDULER_add_shutdown (&cleanup,
+                                NULL);
 }
 
 
 /**
- * The main function of the VPN service.
- *
- * @param argc number of arguments from the command line
- * @param argv command line arguments
- * @return 0 ok, 1 on error
+ * Define "main" method using service macro.
  */
-int
-main (int argc, char *const *argv)
-{
-  return (GNUNET_OK ==
-          GNUNET_SERVICE_run (argc, argv, "vpn", 
-                             GNUNET_SERVICE_OPTION_NONE,
-                              &run, NULL)) ? global_ret : 1;
-}
+GNUNET_SERVICE_MAIN
+("vpn",
+ GNUNET_SERVICE_OPTION_NONE,
+ &run,
+ &client_connect_cb,
+ &client_disconnect_cb,
+ NULL,
+ GNUNET_MQ_hd_var_size (client_redirect_to_ip,
+                        GNUNET_MESSAGE_TYPE_VPN_CLIENT_REDIRECT_TO_IP,
+                        struct RedirectToIpRequestMessage,
+                        NULL),
+ GNUNET_MQ_hd_fixed_size (client_redirect_to_service,
+                          GNUNET_MESSAGE_TYPE_VPN_CLIENT_REDIRECT_TO_SERVICE,
+                          struct RedirectToServiceRequestMessage,
+                          NULL),
+ GNUNET_MQ_handler_end ());
+
 
 /* end of gnunet-service-vpn.c */