remove 'nac' option from VPN, always return IP immediately, always build mesh tunnel...
[oweals/gnunet.git] / src / vpn / gnunet-service-vpn.c
index 6b89c46ae2277a250b5bf560de4634ed08076c88..2b5b41e14fc2bf0c28d37aef9c119ff5fcbdb826 100644 (file)
  * @author Christian Grothoff
  *
  * TODO:
- * Basics:
- * - test!
- *
- * Features:
- * - add back ICMP support (especially needed for IPv6)
+ * - keep multiple peers/mesh tunnels ready as alternative exits /
+ *   recover from tunnel-to-exit failure gracefully
  */
 #include "platform.h"
 #include "gnunet_util_lib.h"
@@ -42,6 +39,7 @@
 #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"
 
@@ -52,6 +50,8 @@
 #define MAX_MESSAGE_QUEUE_SIZE 4
 
 
+#define PORT_VPN 42
+
 /**
  * State we keep for each of our tunnels.
  */
@@ -69,7 +69,7 @@ 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.
@@ -82,8 +82,8 @@ 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 tunnel to an Internet-exit,
+   * #GNUNET_YES if this tunnel is to a service.
    */
   int is_service;
 
@@ -98,7 +98,7 @@ struct DestinationEntry
       /**
        * The description of the service (only used for service tunnels).
        */
-      GNUNET_HashCode service_descriptor;
+      struct GNUNET_HashCode service_descriptor;
 
       /**
        * Peer offering the service.
@@ -177,6 +177,11 @@ struct TunnelState
    */
   struct GNUNET_MESH_Tunnel *tunnel;
 
+  /**
+   * Active query with REGEX to locate exit.
+   */
+  struct GNUNET_REGEX_Search *search;
+
   /**
    * Active transmission handle, NULL for none.
    */
@@ -198,23 +203,12 @@ struct TunnelState
    */
   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;
-
   /**
    * Destination to which this tunnel leads.  Note that
    * this struct is NOT in the destination_map (but a
@@ -291,6 +285,11 @@ struct TunnelState
 };
 
 
+/**
+ * Return value from 'main'.
+ */
+static int global_ret;
+
 /**
  * Configuration we use.
  */
@@ -373,7 +372,7 @@ 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)
   {
@@ -413,11 +412,11 @@ get_tunnel_key_from_ips (int af,
                         uint16_t source_port,
                         const void *destination_ip,
                         uint16_t destination_port,
-                        GNUNET_HashCode *key)
+                        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;
@@ -444,7 +443,7 @@ get_tunnel_key_from_ips (int af,
     break;
   }
   memcpy (off, &protocol, sizeof (uint8_t));
-  off += sizeof (uint8_t);  
+  /* off += sizeof (uint8_t);  */
 }
 
 
@@ -462,7 +461,7 @@ send_client_reply (struct GNUNET_SERVER_Client *client,
                   int result_af,
                   const void *addr)
 {
-  char buf[sizeof (struct RedirectToIpResponseMessage) + sizeof (struct in6_addr)];
+  char buf[sizeof (struct RedirectToIpResponseMessage) + sizeof (struct in6_addr)] GNUNET_ALIGN;
   struct RedirectToIpResponseMessage *res;
   size_t rlen;
 
@@ -503,7 +502,7 @@ send_client_reply (struct GNUNET_SERVER_Client *client,
 static void
 free_tunnel_state (struct TunnelState *ts)
 {
-  GNUNET_HashCode key;
+  struct GNUNET_HashCode key;
   struct TunnelMessageQueueEntry *tnq;
   struct GNUNET_MESH_Tunnel *tunnel;
 
@@ -521,11 +520,6 @@ 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);
@@ -537,6 +531,11 @@ free_tunnel_state (struct TunnelState *ts)
     ts->tunnel = NULL;
     GNUNET_MESH_tunnel_destroy (tunnel);
   }
+  if (NULL != ts->search)
+  {
+    GNUNET_REGEX_search_cancel (ts->search);
+    ts->search = NULL;
+  }
   if (GNUNET_SCHEDULER_NO_TASK != ts->destroy_task)
   {
     GNUNET_SCHEDULER_cancel (ts->destroy_task);
@@ -571,8 +570,8 @@ free_tunnel_state (struct TunnelState *ts)
 /**
  * Destroy the mesh tunnel.
  *
- * @param cls the 'struct TunnelState' with the tunnel to destroy
- * @param ts schedule context
+ * @param cls the `struct TunnelState` with the tunnel to destroy
+ * @param tc scheduler context
  */
 static void
 destroy_tunnel_task (void *cls,
@@ -593,13 +592,15 @@ destroy_tunnel_task (void *cls,
 /**
  * Method called whenever a peer has disconnected from the tunnel.
  *
+ * FIXME merge with inbound_cleaner
+ * 
  * @param cls closure
  * @param peer peer identity the tunnel stopped working with
  */
-static void
+void
 tunnel_peer_disconnect_handler (void *cls,
                                const struct
-                               GNUNET_PeerIdentity * peer)
+                               GNUNET_PeerIdentity *peer)
 {
   struct TunnelState *ts = cls;
 
@@ -607,7 +608,7 @@ tunnel_peer_disconnect_handler (void *cls,
              "Peer %s disconnected from tunnel.\n",
              GNUNET_i2s (peer));
   GNUNET_STATISTICS_update (stats,
-                           gettext_noop ("# Peers connected to mesh tunnels"),
+                           gettext_noop ("# peers connected to mesh tunnels"),
                            -1, GNUNET_NO);
   if (NULL != ts->th)
   {
@@ -623,47 +624,13 @@ tunnel_peer_disconnect_handler (void *cls,
 }
 
 
-/**
- * Method called whenever a peer has connected to the tunnel.  Notifies
- * the waiting client that the tunnel is now up.
- *
- * @param cls closure
- * @param peer peer identity the tunnel was created to, NULL on timeout
- * @param atsi performance data for the connection
- */
-static void
-tunnel_peer_connect_handler (void *cls,
-                            const struct GNUNET_PeerIdentity
-                            * peer,
-                            const struct
-                            GNUNET_ATS_Information * atsi)
-{
-  struct TunnelState *ts = cls;
-
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-             "Peer %s connected to tunnel.\n",
-             GNUNET_i2s (peer));
-  GNUNET_STATISTICS_update (stats,
-                           gettext_noop ("# Peers connected to mesh tunnels"),
-                           1, GNUNET_NO);
-  if (NULL == ts->client)
-    return; /* nothing to do */
-  send_client_reply (ts->client,
-                    ts->request_id,
-                    ts->af,
-                    &ts->destination_ip);
-  GNUNET_SERVER_client_drop (ts->client);
-  ts->client = NULL;
-}
-
-
 /**
  * Send a message from the message queue via mesh.
  *
- * @param cls the 'struct TunnelState' with the message queue
- * @param size number of bytes available in buf
+ * @param cls the `struct TunnelState` with the message queue
+ * @param size number of bytes available in @a buf
  * @param buf where to copy the message
- * @return number of bytes copied to buf
+ * @return number of bytes copied to @a buf
  */
 static size_t
 send_to_peer_notify_callback (void *cls, size_t size, void *buf)
@@ -691,9 +658,7 @@ send_to_peer_notify_callback (void *cls, size_t size, void *buf)
   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);
@@ -732,6 +697,7 @@ send_to_tunnel (struct TunnelMessageQueueEntry *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,
@@ -743,26 +709,55 @@ send_to_tunnel (struct TunnelMessageQueueEntry *tnq,
   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);
 }
 
 
+/**
+ * Regex has found a potential exit peer for us; consider using it.
+ *
+ * @param cls the 'struct TunnelState'
+ * @param id Peer providing a regex that matches the string.
+ * @param get_path Path of the get request.
+ * @param get_path_length Lenght of get_path.
+ * @param put_path Path of the put request.
+ * @param put_path_length Length of the 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 TunnelState *ts = cls;
+
+  GNUNET_REGEX_search_cancel (ts->search);
+  ts->search = NULL;
+  ts->tunnel = GNUNET_MESH_tunnel_create (mesh_handle,
+                                          ts,
+                                          id,
+                                          PORT_VPN,
+                                          GNUNET_YES,
+                                          GNUNET_NO);
+}
+
+
 /**
  * Initialize the given destination entry's mesh tunnel.
  *
  * @param de destination entry for which we need to setup a tunnel
- * @param client client to notify on successful tunnel setup, or NULL for none
+ * @param 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
  */
 static struct TunnelState *
 create_tunnel_to_destination (struct DestinationEntry *de,
-                             struct GNUNET_SERVER_Client *client,
+                             int client_af,
                              uint64_t request_id)
 {
   struct TunnelState *ts;
@@ -771,64 +766,76 @@ create_tunnel_to_destination (struct DestinationEntry *de,
                            gettext_noop ("# Mesh tunnels created"),
                            1, GNUNET_NO);
   GNUNET_assert (NULL == de->ts);
-  ts = GNUNET_malloc (sizeof (struct TunnelState));
-  if (NULL != client)
-  {
-    ts->request_id = request_id;
-    ts->client = client;
-    GNUNET_SERVER_client_keep (client);
-  }
+  ts = GNUNET_new (struct TunnelState);
+  ts->af = client_af;
   ts->destination = *de;
   ts->destination.heap_node = NULL; /* copy is NOT in destination heap */
   de->ts = ts;
   ts->destination_container = de; /* we are referenced from de */
-  ts->af = AF_UNSPEC; /* so far, unknown */
-  ts->tunnel = GNUNET_MESH_tunnel_create (mesh_handle,
-                                         ts,
-                                         &tunnel_peer_connect_handler,
-                                         &tunnel_peer_disconnect_handler,
-                                         ts);
-  if (NULL == ts->tunnel)
-  {
-    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;
-  }
   if (de->is_service)
   {
+    ts->tunnel = GNUNET_MESH_tunnel_create (mesh_handle,
+                                           ts,
+                                           &de->details.service_destination.target,
+                                           PORT_VPN,
+                                           GNUNET_YES,
+                                           GNUNET_NO);
+    if (NULL == ts->tunnel)
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                 _("Failed to setup mesh tunnel!\n"));
+      GNUNET_free (ts);
+      return NULL;
+    }
     GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Creating tunnel to peer %s offering service %s\n",
                GNUNET_i2s (&de->details.service_destination.target),
                GNUNET_h2s (&de->details.service_destination.service_descriptor));
-    GNUNET_MESH_peer_request_connect_add (ts->tunnel,
-                                         &de->details.service_destination.target);  
   }
   else
   {
+    char *policy;
+
     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;
+    {
+      char address[GNUNET_TUN_IPV4_REGEXLEN];
+
+      GNUNET_TUN_ipv4toregexsearch (&de->details.exit_destination.ip.v4,
+                  "255.255.255.255", address);
+      GNUNET_asprintf (&policy, "%s%s%s",
+                       GNUNET_APPLICATION_TYPE_EXIT_REGEX_PREFIX,
+                       "4",
+                       address);
+      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");
+    {
+      char address[GNUNET_TUN_IPV6_REGEXLEN];
+      
+      GNUNET_TUN_ipv6toregexsearch (&de->details.exit_destination.ip.v6,
+                  128, address);
+      GNUNET_asprintf (&policy, "%s%s%s",
+                       GNUNET_APPLICATION_TYPE_EXIT_REGEX_PREFIX,
+                       "6",
+                       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;
 }
 
@@ -844,6 +851,7 @@ 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);
@@ -855,7 +863,7 @@ expire_tunnel (struct TunnelState *except)
  *
  * @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 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
@@ -870,7 +878,7 @@ route_packet (struct DestinationEntry *destination,
              const void *payload,
              size_t payload_length)
 {
-  GNUNET_HashCode key;
+  struct GNUNET_HashCode key;
   struct TunnelState *ts;
   struct TunnelMessageQueueEntry *tnq;
   size_t alen;
@@ -878,8 +886,9 @@ route_packet (struct DestinationEntry *destination,
   int is_new;
   const struct GNUNET_TUN_UdpHeader *udp;
   const struct GNUNET_TUN_TcpHeader *tcp;
-  uint16_t spt;
-  uint16_t dpt;
+  const struct GNUNET_TUN_IcmpHeader *icmp;
+  uint16_t source_port;
+  uint16_t destination_port;
 
   switch (protocol)
   {
@@ -891,15 +900,22 @@ route_packet (struct DestinationEntry *destination,
        GNUNET_break (0);
        return;
       }
+      tcp = NULL; /* make compiler happy */
+      icmp = NULL;  /* make compiler happy */
       udp = payload;
-      spt = ntohs (udp->spt);
-      dpt = ntohs (udp->dpt);
+      if (udp->len < sizeof (struct GNUNET_TUN_UdpHeader))
+      {
+       GNUNET_break_op (0);
+       return;
+      }
+      source_port = ntohs (udp->source_port);
+      destination_port = ntohs (udp->destination_port);
       get_tunnel_key_from_ips (af,
                               IPPROTO_UDP,
                               source_ip,
-                              spt,
+                              source_port,
                               destination_ip,
-                              dpt,
+                              destination_port,
                               &key);
     }
     break;
@@ -910,16 +926,51 @@ route_packet (struct DestinationEntry *destination,
        /* blame kernel? */
        GNUNET_break (0);
        return;
-      }
+      }      
+      udp = NULL; /* make compiler happy */
+      icmp = NULL;  /* make compiler happy */
       tcp = payload;
-      spt = ntohs (tcp->spt);
-      dpt = ntohs (tcp->dpt);
+      if (tcp->off * 4 < sizeof (struct GNUNET_TUN_TcpHeader))
+      {
+       GNUNET_break_op (0);
+       return;
+      }
+      source_port = ntohs (tcp->source_port);
+      destination_port = ntohs (tcp->destination_port);
       get_tunnel_key_from_ips (af,
                               IPPROTO_TCP,
                               source_ip,
-                              spt,
+                              source_port,
+                              destination_ip,
+                              destination_port,
+                              &key);
+    }
+    break;
+  case IPPROTO_ICMP:  
+  case IPPROTO_ICMPV6:  
+    {
+      if ( (AF_INET == af) ^ (protocol == IPPROTO_ICMP) )
+      {
+       GNUNET_break (0);
+       return;
+      }
+      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_tunnel_key_from_ips (af,
+                              protocol,
+                              source_ip,
+                              0,
                               destination_ip,
-                              dpt,
+                              0,
                               &key);
     }
     break;
@@ -929,6 +980,7 @@ route_packet (struct DestinationEntry *destination,
                (unsigned int) protocol);
     return;
   }
+  alen = 0;
   if (! destination->is_service)
   {  
     switch (destination->details.exit_destination.af)
@@ -940,7 +992,6 @@ route_packet (struct DestinationEntry *destination,
       alen = sizeof (struct in6_addr);
       break;
     default:
-      alen = 0;
       GNUNET_assert (0);
     }
 
@@ -953,19 +1004,17 @@ route_packet (struct DestinationEntry *destination,
                  "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,
+                 source_port,
                  inet_ntop (af, destination_ip, dbuf, sizeof (dbuf)),
-                 dpt,
+                 destination_port,
                  inet_ntop (destination->details.exit_destination.af,
                             &destination->details.exit_destination.ip,
                             xbuf, sizeof (xbuf)),
-                 dpt);
+                 destination_port);
     }
   }
   else
   {
-    /* make compiler happy */
-    alen = 0;
     {
       char sbuf[INET6_ADDRSTRLEN];
       char dbuf[INET6_ADDRSTRLEN];
@@ -974,9 +1023,9 @@ route_packet (struct DestinationEntry *destination,
                  "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,
+                 source_port,
                  inet_ntop (af, destination_ip, dbuf, sizeof (dbuf)),
-                 dpt,
+                 destination_port,
                  GNUNET_h2s (&destination->details.service_destination.service_descriptor),
                  GNUNET_i2s (&destination->details.service_destination.target));
     }
@@ -992,7 +1041,7 @@ route_packet (struct DestinationEntry *destination,
        available) or create a fresh one */
     is_new = GNUNET_YES;
     if (NULL == destination->ts)
-      ts = create_tunnel_to_destination (destination, NULL, 0);
+      ts = create_tunnel_to_destination (destination, af, 0);
     else
       ts = destination->ts;
     if (NULL == ts)
@@ -1012,11 +1061,11 @@ route_packet (struct DestinationEntry *destination,
       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->source_port = source_port;
+    ts->destination_port = destination_port;
     ts->heap_node = GNUNET_CONTAINER_heap_insert (tunnel_heap,
                                                  ts,
-                                                 GNUNET_TIME_absolute_get ().abs_value);
+                                                 GNUNET_TIME_absolute_get ().abs_value_us);
     GNUNET_assert (GNUNET_YES ==
                   GNUNET_CONTAINER_multihashmap_put (tunnel_map,
                                                      &key,
@@ -1033,7 +1082,7 @@ route_packet (struct DestinationEntry *destination,
     is_new = GNUNET_NO;
     GNUNET_CONTAINER_heap_update_cost (tunnel_heap, 
                                       ts->heap_node,
-                                      GNUNET_TIME_absolute_get ().abs_value);
+                                      GNUNET_TIME_absolute_get ().abs_value_us);
   }
   GNUNET_assert (NULL != ts->tunnel);
   
@@ -1060,8 +1109,8 @@ route_packet (struct DestinationEntry *destination,
       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->source_port = (ntohs (udp->source_port) < 32000) ? udp->source_port : 0;
+      usm->destination_port = udp->destination_port;
       usm->service_descriptor = destination->details.service_destination.service_descriptor;
       memcpy (&usm[1],
              &udp[1],
@@ -1089,8 +1138,8 @@ route_packet (struct DestinationEntry *destination,
       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;
+      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:
@@ -1204,6 +1253,242 @@ route_packet (struct DestinationEntry *destination,
              payload_length - sizeof (struct GNUNET_TUN_TcpHeader));
      }
     break;
+  case IPPROTO_ICMP:
+  case IPPROTO_ICMPV6:
+    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)
+      {
+      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;
+
+      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)
+       {
+       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)
+           {
+             GNUNET_STATISTICS_update (stats,
+                                       gettext_noop ("# ICMPv4 packets dropped (impossible PT to v6)"),
+                                       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;
+       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 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;
+           }
+           /* 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_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);
+
+      /* need to tell destination ICMP protocol family! */
+      iim->af = htonl (destination->details.exit_destination.af);
+      switch (destination->details.exit_destination.af)
+      {
+      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);
+      }
+      memcpy (payload,
+             &icmp[1],
+             payload_length - sizeof (struct GNUNET_TUN_IcmpHeader));
+    }
+    break;
   default:
     /* not supported above, how can we get here !? */
     GNUNET_assert (0);
@@ -1223,13 +1508,13 @@ route_packet (struct DestinationEntry *destination,
  * @param client NULL
  * @param message message we got from the client (VPN tunnel interface)
  */
-static void
+static int
 message_token (void *cls GNUNET_UNUSED, void *client GNUNET_UNUSED,
                const struct GNUNET_MessageHeader *message)
 {
   const struct GNUNET_TUN_Layer2PacketHeader *tun;
   size_t mlen;
-  GNUNET_HashCode key;
+  struct GNUNET_HashCode key;
   struct DestinationEntry *de;
 
   GNUNET_STATISTICS_update (stats,
@@ -1240,7 +1525,7 @@ message_token (void *cls GNUNET_UNUSED, void *client GNUNET_UNUSED,
        (mlen < sizeof (struct GNUNET_MessageHeader) + sizeof (struct GNUNET_TUN_Layer2PacketHeader)) )
   {
     GNUNET_break (0);
-    return;
+    return GNUNET_OK;
   }
   tun = (const struct GNUNET_TUN_Layer2PacketHeader *) &message[1];
   mlen -= (sizeof (struct GNUNET_MessageHeader) + sizeof (struct GNUNET_TUN_Layer2PacketHeader));
@@ -1254,18 +1539,13 @@ message_token (void *cls GNUNET_UNUSED, void *client GNUNET_UNUSED,
       {
        /* blame kernel */
        GNUNET_break (0);
-       return;
+        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);
-      /* FIXME: do we need to guard against hash collision? 
-        (if so, we need to also store the local destination IP in the
-        destination entry and then compare here; however, the risk
-        of collision seems minimal AND the impact is unlikely to be
-        super-problematic as well... */
       if (NULL == de)
       {
        char buf[INET6_ADDRSTRLEN];
@@ -1276,7 +1556,7 @@ message_token (void *cls GNUNET_UNUSED, void *client GNUNET_UNUSED,
                               &pkt6->destination_address,
                               buf,
                               sizeof (buf)));
-       return;
+       return GNUNET_OK;
       }
       route_packet (de,
                    AF_INET6,
@@ -1295,18 +1575,13 @@ message_token (void *cls GNUNET_UNUSED, void *client GNUNET_UNUSED,
       {
        /* blame kernel */
        GNUNET_break (0);
-       return;
+       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);
-      /* FIXME: do we need to guard against hash collision? 
-        (if so, we need to also store the local destination IP in the
-        destination entry and then compare here; however, the risk
-        of collision seems minimal AND the impact is unlikely to be
-        super-problematic as well... */
       if (NULL == de)
       {
        char buf[INET_ADDRSTRLEN];
@@ -1317,13 +1592,13 @@ message_token (void *cls GNUNET_UNUSED, void *client GNUNET_UNUSED,
                               &pkt4->destination_address,
                               buf,
                               sizeof (buf)));
-       return;
+        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;
+        return GNUNET_OK;
       }
       route_packet (de,
                    AF_INET,
@@ -1340,37 +1615,87 @@ message_token (void *cls GNUNET_UNUSED, void *client GNUNET_UNUSED,
                (unsigned int) ntohs (tun->proto));
     break;
   }
+  return GNUNET_OK;
 }
 
 
 /**
- * We got a UDP packet back from the MESH tunnel.  Pass it on to the
+ * 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->source_port = htons (ts->source_port);
+  udp->destination_port = 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->source_port = htons (ts->source_port);
+  udp->destination_port = htons (ts->destination_port);
+  udp->len = htons (0);
+  udp->crc = htons (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)
+ * @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)
+receive_icmp_back (void *cls GNUNET_UNUSED, struct GNUNET_MESH_Tunnel *tunnel,
+                  void **tunnel_ctx,
+                  const struct GNUNET_MessageHeader *message)
 {
   struct TunnelState *ts = *tunnel_ctx;
-  const struct GNUNET_EXIT_UdpReplyMessage *reply;
+  const struct GNUNET_EXIT_IcmpToVPNMessage *i2v;
   size_t mlen;
 
   GNUNET_STATISTICS_update (stats,
-                           gettext_noop ("# UDP packets received from mesh"),
+                           gettext_noop ("# ICMP packets received from mesh"),
                            1, GNUNET_NO);
   mlen = ntohs (message->size);
-  if (mlen < sizeof (struct GNUNET_EXIT_UdpReplyMessage))
+  if (mlen < sizeof (struct GNUNET_EXIT_IcmpToVPNMessage))
   {
     GNUNET_break_op (0);
     return GNUNET_SYSERR;
@@ -1385,60 +1710,152 @@ receive_udp_back (void *cls GNUNET_UNUSED, struct GNUNET_MESH_Tunnel *tunnel,
     GNUNET_break_op (0);
     return GNUNET_SYSERR;
   }
-  reply = (const struct GNUNET_EXIT_UdpReplyMessage *) message;
-  mlen -= sizeof (struct GNUNET_EXIT_UdpReplyMessage);
+  i2v = (const struct GNUNET_EXIT_IcmpToVPNMessage *) message;
+  mlen -= sizeof (struct GNUNET_EXIT_IcmpToVPNMessage);
   {
     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",
+               "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)),
-               ts->destination_port,
-               inet_ntop (ts->af, &ts->source_ip, dbuf, sizeof (dbuf)),
-               ts->source_port);
+               inet_ntop (ts->af, &ts->source_ip, dbuf, sizeof (dbuf)));
   }
   switch (ts->af)
   {
   case AF_INET:
     {
       size_t size = sizeof (struct GNUNET_TUN_IPv4Header) 
-       + sizeof (struct GNUNET_TUN_UdpHeader) 
+       + sizeof (struct GNUNET_TUN_IcmpHeader) 
        + sizeof (struct GNUNET_MessageHeader) +
        sizeof (struct GNUNET_TUN_Layer2PacketHeader) +
        mlen;
       {
-       char buf[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] 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];
+       struct GNUNET_TUN_IcmpHeader *icmp = (struct GNUNET_TUN_IcmpHeader *) &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,
+                                          IPPROTO_ICMP,
+                                          sizeof (struct GNUNET_TUN_IcmpHeader) + 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],
+       *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))
+       {
+       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 */
+         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 */
+         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,
@@ -1449,76 +1866,318 @@ receive_udp_back (void *cls GNUNET_UNUSED, struct GNUNET_MESH_Tunnel *tunnel,
   case AF_INET6:
     {
       size_t size = sizeof (struct GNUNET_TUN_IPv6Header) 
-       + sizeof (struct GNUNET_TUN_UdpHeader) 
+       + sizeof (struct GNUNET_TUN_IcmpHeader) 
        + sizeof (struct GNUNET_MessageHeader) +
        sizeof (struct GNUNET_TUN_Layer2PacketHeader) +
        mlen;
       {
-       char buf[size];
+       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_UdpHeader *udp = (struct GNUNET_TUN_UdpHeader *) &ipv6[1];
+       struct GNUNET_TUN_IcmpHeader *icmp = (struct GNUNET_TUN_IcmpHeader *) &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,
+                                          IPPROTO_ICMPV6,
+                                          sizeof (struct GNUNET_TUN_IcmpHeader) + 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],
+       *icmp = i2v->icmp_header;
+       memcpy (&icmp[1],
+               &i2v[1],
                mlen);
-       (void) GNUNET_HELPER_send (helper_handle,
-                                  msg,
-                                  GNUNET_YES,
-                                  NULL, NULL);
-      }
-    }
-    break;
+
+       /* 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:     
+         /* 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;
+           {
+             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_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 */
+         break;
+       case AF_INET6:
+         switch (icmp->type)
+         {
+         case GNUNET_TUN_ICMPTYPE6_DESTINATION_UNREACHABLE:
+         case GNUNET_TUN_ICMPTYPE6_TIME_EXCEEDED:
+         case GNUNET_TUN_ICMPTYPE6_PACKET_TOO_BIG:
+         case GNUNET_TUN_ICMPTYPE6_PARAMETER_PROBLEM:
+           {
+             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_ICMPTYPE6_ECHO_REQUEST:
+           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);
+                                    GNUNET_TIME_absolute_get ().abs_value_us);
   return GNUNET_OK;
 }
 
 
 /**
- * We got a TCP packet back from the MESH tunnel.  Pass it on to the
+ * 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)
+ * @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_MessageHeader *message)
+{
+  struct TunnelState *ts = *tunnel_ctx;
+  const struct GNUNET_EXIT_UdpReplyMessage *reply;
+  size_t mlen;
+
+  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;
+      {
+       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);
+       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);
+       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 (tunnel_heap, 
+                                    ts->heap_node,
+                                    GNUNET_TIME_absolute_get ().abs_value_us);
+  return GNUNET_OK;
+}
+
+
+/**
+ * We got a TCP 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 message the actual message
+ * @return #GNUNET_OK to keep the connection open,
+ *         #GNUNET_SYSERR to close it (signal serious error)
  */ 
 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)
+                  const struct GNUNET_MessageHeader *message)
 {
   struct TunnelState *ts = *tunnel_ctx;
   const struct GNUNET_EXIT_TcpDataMessage *data;
@@ -1552,6 +2211,11 @@ receive_tcp_back (void *cls GNUNET_UNUSED, struct GNUNET_MESH_Tunnel *tunnel,
                inet_ntop (ts->af, &ts->source_ip, dbuf, sizeof (dbuf)),
                ts->source_port);
   }
+  if (data->tcp_header.off * 4 < sizeof (struct GNUNET_TUN_TcpHeader))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
+  }
   switch (ts->af)
   {
   case AF_INET:
@@ -1562,7 +2226,7 @@ receive_tcp_back (void *cls GNUNET_UNUSED, struct GNUNET_MESH_Tunnel *tunnel,
        sizeof (struct GNUNET_TUN_Layer2PacketHeader) +
        mlen;
       {
-       char buf[size];
+       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];
@@ -1577,8 +2241,8 @@ receive_tcp_back (void *cls GNUNET_UNUSED, struct GNUNET_MESH_Tunnel *tunnel,
                                           &ts->destination_ip.v4,
                                           &ts->source_ip.v4);
        *tcp = data->tcp_header;
-       tcp->spt = htons (ts->destination_port);
-       tcp->dpt = htons (ts->source_port);
+       tcp->source_port = htons (ts->destination_port);
+       tcp->destination_port = htons (ts->source_port);
        GNUNET_TUN_calculate_tcp4_checksum (ipv4,
                                            tcp,
                                            &data[1],
@@ -1601,7 +2265,7 @@ receive_tcp_back (void *cls GNUNET_UNUSED, struct GNUNET_MESH_Tunnel *tunnel,
        sizeof (struct GNUNET_TUN_Layer2PacketHeader) +
        mlen;
       {
-       char buf[size];
+       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];
@@ -1615,12 +2279,16 @@ receive_tcp_back (void *cls GNUNET_UNUSED, struct GNUNET_MESH_Tunnel *tunnel,
                                           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);
+       *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,
-                                           &tcp[1],
+                                           &data[1],
                                            mlen);
+       memcpy (&tcp[1],
+               &data[1],
+               mlen);
        (void) GNUNET_HELPER_send (helper_handle,
                                   msg,
                                   GNUNET_YES,
@@ -1631,7 +2299,7 @@ receive_tcp_back (void *cls GNUNET_UNUSED, struct GNUNET_MESH_Tunnel *tunnel,
   }
   GNUNET_CONTAINER_heap_update_cost (tunnel_heap, 
                                     ts->heap_node,
-                                    GNUNET_TIME_absolute_get ().abs_value);
+                                    GNUNET_TIME_absolute_get ().abs_value_us);
   return GNUNET_OK;
 }
 
@@ -1641,8 +2309,8 @@ receive_tcp_back (void *cls GNUNET_UNUSED, struct GNUNET_MESH_Tunnel *tunnel,
  * 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)
@@ -1652,7 +2320,7 @@ 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));
@@ -1692,8 +2360,8 @@ allocate_v4_address (struct in_addr *v4)
  * 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)
@@ -1703,7 +2371,7 @@ 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));
@@ -1711,7 +2379,7 @@ 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 */
@@ -1792,6 +2460,7 @@ expire_destination (struct DestinationEntry *except)
   struct DestinationEntry *de;
 
   de = GNUNET_CONTAINER_heap_peek (destination_heap);
+  GNUNET_assert (NULL != de);
   if (except == de)
     return; /* can't do this */
   free_destination_entry (de);
@@ -1799,16 +2468,76 @@ 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 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 int
+allocate_response_ip (int *result_af,
+                     void **addr,
+                     struct in_addr *v4,
+                     struct in6_addr *v6)
+{
+  *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);
+    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 unused
  * @param client requesting client
- * @param message redirection request (a 'struct RedirectToIpRequestMessage')
+ * @param message redirection request (a `struct RedirectToIpRequestMessage`)
  */
 static void
-service_redirect_to_ip (void *cls GNUNET_UNUSED, struct GNUNET_SERVER_Client *client,
+service_redirect_to_ip (void *cls,
+                       struct GNUNET_SERVER_Client *client,
                        const struct GNUNET_MessageHeader *message)
 {
   size_t mlen;
@@ -1820,7 +2549,8 @@ service_redirect_to_ip (void *cls GNUNET_UNUSED, struct GNUNET_SERVER_Client *cl
   struct in6_addr v6;
   void *addr;
   struct DestinationEntry *de;
-  GNUNET_HashCode key;
+  struct GNUNET_HashCode key;
+  struct TunnelState *ts;
   
   /* validate and parse request */
   mlen = ntohs (message->size);
@@ -1858,52 +2588,19 @@ service_redirect_to_ip (void *cls GNUNET_UNUSED, struct GNUNET_SERVER_Client *cl
   }
 
   /* 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);
-  }
+  /* 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 */
@@ -1923,7 +2620,7 @@ service_redirect_to_ip (void *cls GNUNET_UNUSED, struct GNUNET_SERVER_Client *cl
   }
   
   /* 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,
@@ -1940,17 +2637,28 @@ 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 */
-  (void) create_tunnel_to_destination (de, 
-                                      (GNUNET_NO == ntohl (msg->nac)) ? NULL : client,
-                                      msg->request_id);
+  ts = create_tunnel_to_destination (de, 
+                                    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);
 }
@@ -1963,7 +2671,7 @@ service_redirect_to_ip (void *cls GNUNET_UNUSED, struct GNUNET_SERVER_Client *cl
  *
  * @param cls unused
  * @param client requesting client
- * @param message redirection request (a 'struct RedirectToPeerRequestMessage')
+ * @param message redirection request (a `struct RedirectToPeerRequestMessage`)
  */
 static void
 service_redirect_to_service (void *cls GNUNET_UNUSED, struct GNUNET_SERVER_Client *client,
@@ -1975,58 +2683,25 @@ service_redirect_to_service (void *cls GNUNET_UNUSED, struct GNUNET_SERVER_Clien
   struct in6_addr v6;
   void *addr;
   struct DestinationEntry *de;
-  GNUNET_HashCode key;
+  struct GNUNET_HashCode key;
+  struct TunnelState *ts;
   
   /*  parse request */
   msg = (const struct RedirectToServiceRequestMessage *) message;
 
   /* 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);
-  }
+  send_client_reply (client,
+                    msg->request_id,
+                    result_af,
+                    addr);  
   if (result_af == AF_UNSPEC)
   {
     /* failure, we're done */
@@ -2047,7 +2722,7 @@ service_redirect_to_service (void *cls GNUNET_UNUSED, struct GNUNET_SERVER_Clien
   }
   
   /* 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;
@@ -2062,61 +2737,45 @@ service_redirect_to_service (void *cls GNUNET_UNUSED, struct GNUNET_SERVER_Clien
                                                    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);
   while (GNUNET_CONTAINER_multihashmap_size (destination_map) > max_destination_mappings)
     expire_destination (de);
-  (void) create_tunnel_to_destination (de,
-                                      (GNUNET_NO == ntohl (msg->nac)) ? NULL : client,
-                                      msg->request_id);
+  ts = create_tunnel_to_destination (de,
+                                    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;
-}
-
-
 /**
- * Function called whenever an inbound tunnel is destroyed.  Should clean up
+ * Function called whenever a tunnel is destroyed.  Should clean up
  * any associated state.
- *
- * @param cls closure (set from GNUNET_MESH_connect)
+ * 
+ * @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')
+ *                   with the tunnel is stored (our `struct TunnelState`)
  */ 
 static void
-tunnel_cleaner (void *cls, const struct GNUNET_MESH_Tunnel *tunnel, void *tunnel_ctx)
+tunnel_cleaner (void *cls, 
+               const struct GNUNET_MESH_Tunnel *tunnel, 
+               void *tunnel_ctx)
 {
   struct TunnelState *ts = tunnel_ctx;
 
-  if (NULL == ts)
-  {
-    GNUNET_break (0);
-    return;     
-  }
-  GNUNET_assert (ts->tunnel == tunnel);
-  ts->tunnel = NULL;
+  ts->tunnel = NULL; /* we must not call GNUNET_MESH_tunnel_destroy() anymore */
   free_tunnel_state (ts);
 }
 
@@ -2126,12 +2785,12 @@ tunnel_cleaner (void *cls, const struct GNUNET_MESH_Tunnel *tunnel, void *tunnel
  *
  * @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;
@@ -2146,12 +2805,12 @@ cleanup_destination (void *cls,
  *
  * @param cls unused
  * @param key unused
- * @param value a 'struct TunnelState *'
- * @return GNUNET_OK (continue to iterate)
+ * @param value a `struct TunnelState *`
+ * @return #GNUNET_OK (continue to iterate)
  */
 static int
 cleanup_tunnel (void *cls,
-               const GNUNET_HashCode *key,
+               const struct GNUNET_HashCode *key,
                void *value)
 {
   struct TunnelState *ts = value;
@@ -2168,7 +2827,7 @@ cleanup_tunnel (void *cls,
  * @param tc unused
  */
 static void
-cleanup (void *cls GNUNET_UNUSED,
+cleanup (void *cls,
          const struct GNUNET_SCHEDULER_TaskContext *tc)
 {
   unsigned int i;
@@ -2207,8 +2866,8 @@ cleanup (void *cls GNUNET_UNUSED,
     mesh_handle = NULL;
   }
   if (NULL != helper_handle)
-    {
-    GNUNET_HELPER_stop (helper_handle);
+  {
+    GNUNET_HELPER_stop (helper_handle, GNUNET_NO);
     helper_handle = NULL;
   }
   if (NULL != nc)
@@ -2216,9 +2875,9 @@ cleanup (void *cls GNUNET_UNUSED,
     GNUNET_SERVER_notification_context_destroy (nc);
     nc = NULL;
   }
-  if (stats != NULL)
+  if (NULL != stats)
   {
-    GNUNET_STATISTICS_destroy (stats, GNUNET_YES);
+    GNUNET_STATISTICS_destroy (stats, GNUNET_NO);
     stats = NULL;
   }
   for (i=0;i<5;i++)
@@ -2226,80 +2885,6 @@ cleanup (void *cls GNUNET_UNUSED,
 }
 
 
-/**
- * A client disconnected, clean up all references to it.
- *
- * @param cls the client that disconnected
- * @param key unused
- * @param value a 'struct TunnelState *'
- * @return GNUNET_OK (continue to iterate)
- */
-static int
-cleanup_tunnel_client (void *cls,
-                      const GNUNET_HashCode *key,
-                      void *value)
-{
-  struct GNUNET_SERVER_Client *client = cls;
-  struct TunnelState *ts = value;
-
-  if (client == ts->client)
-  {
-    GNUNET_SERVER_client_drop (ts->client);
-    ts->client = NULL;
-  }
-  return GNUNET_OK;
-}
-
-
-/**
- * A client disconnected, clean up all references to it.
- *
- * @param cls the client that disconnected
- * @param key unused
- * @param value a 'struct DestinationEntry *'
- * @return GNUNET_OK (continue to iterate)
- */
-static int
-cleanup_destination_client (void *cls,
-                           const GNUNET_HashCode *key,
-                           void *value)
-{
-  struct GNUNET_SERVER_Client *client = cls;
-  struct DestinationEntry *de = value;
-  struct TunnelState *ts;
-
-  if (NULL == (ts = de->ts))
-    return GNUNET_OK;
-  if (client == ts->client)
-  {
-    GNUNET_SERVER_client_drop (ts->client);
-    ts->client = NULL;
-  }
-  return GNUNET_OK;
-}
-
-  
-/**
- * A client has disconnected from us.  If we are currently building
- * a tunnel for it, cancel the operation.
- *
- * @param cls unused
- * @param client handle to the client that disconnected
- */
-static void
-client_disconnect (void *cls, struct GNUNET_SERVER_Client *client)
-{
-  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);
-}
-
-
 /**
  * Main function that will be run by the scheduler.
  *
@@ -2323,11 +2908,9 @@ run (void *cls,
   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;
@@ -2335,100 +2918,133 @@ 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 (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_free (binary);
+    global_ret = 1;
+    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",
+      GNUNET_CONFIGURATION_get_value_number (cfg, "VPN", "MAX_TUNNELS",
                                             &max_tunnel_mappings))
     max_tunnel_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_map = GNUNET_CONTAINER_multihashmap_create (max_tunnel_mappings * 2, GNUNET_NO);
   tunnel_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))) )
+  if (GNUNET_OK == GNUNET_NETWORK_test_pf (PF_INET6))
   {
-    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))
-  {
-    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 ();
+      return;
+    }
+    vpn_argv[2] = ipv6addr;
+    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 ();
+      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;
+    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 ();
+      return;
+    }
+    vpn_argv[4] = ipv4addr;
+    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 ();
+      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
+    GNUNET_MESH_connect (cfg_, NULL, 
+                        NULL
                         &tunnel_cleaner, 
                         mesh_handlers,
-                        types);
-  helper_handle = GNUNET_HELPER_start ("gnunet-helper-vpn", vpn_argv,
-                                      &message_token, NULL);
+                        NULL);
+  helper_handle = GNUNET_HELPER_start (GNUNET_NO,
+                                      "gnunet-helper-vpn", vpn_argv,
+                                      &message_token, NULL, 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);
 }
 
@@ -2446,7 +3062,7 @@ main (int argc, char *const *argv)
   return (GNUNET_OK ==
           GNUNET_SERVICE_run (argc, argv, "vpn", 
                              GNUNET_SERVICE_OPTION_NONE,
-                              &run, NULL)) ? 0 : 1;
+                              &run, NULL)) ? global_ret : 1;
 }
 
 /* end of gnunet-service-vpn.c */