gnunet-daemon-exit.c

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/*
     This file is part of GNUnet.
     Copyright (C) 2010-2013, 2017 Christian Grothoff

     GNUnet is free software: you can redistribute it and/or modify it
     under the terms of the GNU Affero General Public License as published
     by the Free Software Foundation, either version 3 of the License,
     or (at your option) any later version.

     GNUnet is distributed in the hope that it will be useful, but
     WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     Affero General Public License for more details.

     You should have received a copy of the GNU Affero General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.

     SPDX-License-Identifier: AGPL3.0-or-later
 */

#include "platform.h"
#include "gnunet_util_lib.h"
#include "gnunet_protocols.h"
#include "gnunet_applications.h"
#include "gnunet_dht_service.h"
#include "gnunet_cadet_service.h"
#include "gnunet_dnsparser_lib.h"
#include "gnunet_dnsstub_lib.h"
#include "gnunet_statistics_service.h"
#include "gnunet_constants.h"
#include "gnunet_signatures.h"
#include "gnunet_tun_lib.h"
#include "gnunet_regex_service.h"
#include "exit.h"
#include "block_dns.h"


#define REGEX_MAX_PATH_LEN_IPV4 4

#define REGEX_MAX_PATH_LEN_IPV6 8

#define REGEX_REFRESH_FREQUENCY GNUNET_TIME_relative_multiply ( \
    GNUNET_TIME_UNIT_MINUTES, 30)

#define DHT_PUT_FREQUENCY GNUNET_TIME_relative_multiply ( \
    GNUNET_TIME_UNIT_MINUTES, 15)

#define DNS_ADVERTISEMENT_TIMEOUT GNUNET_TIME_relative_multiply ( \
    GNUNET_TIME_UNIT_HOURS, 3)


#define LOG(kind, ...)                          \
  GNUNET_log_from (kind, "exit", __VA_ARGS__);


struct SocketAddress
{
  int af;

  union
  {
    struct in_addr ipv4;

    struct in6_addr ipv6;
  } address;

  uint8_t proto;

  uint16_t port;
};


struct LocalService
{
  struct SocketAddress address;

  struct GNUNET_HashCode descriptor;

  char *name;

  struct GNUNET_CADET_Port *port;

  int16_t is_udp;
};


struct RedirectInformation
{
  struct SocketAddress remote_address;

  struct SocketAddress local_address;

  /*
     Note 1: additional information might be added here in the
     future to support protocols that require special handling,
     such as ftp/tftp

     Note 2: we might also sometimes not match on all components
     of the tuple, to support protocols where things do not always
     fully map.
   */
};


struct ChannelState
{
  struct GNUNET_CADET_Channel *channel;

  struct GNUNET_PeerIdentity peer;

  int is_dns;

  union
  {
    struct
    {
      struct GNUNET_CONTAINER_HeapNode *heap_node;

      struct GNUNET_HashCode state_key;

      struct LocalService *serv;

      struct RedirectInformation ri;
    } tcp_udp;

    struct
    {
      struct GNUNET_DNSSTUB_RequestSocket *rs;

      uint16_t original_id;

      uint16_t my_id;
    } dns;
  } specifics;
};


static int global_ret;

static struct GNUNET_REGEX_Announcement *regex4;

static struct GNUNET_REGEX_Announcement *regex6;

static const struct GNUNET_CONFIGURATION_Handle *cfg;

static struct GNUNET_HELPER_Handle *helper_handle;

static char *exit_argv[8];

static struct in6_addr exit_ipv6addr;

static unsigned long long ipv6prefix;

static struct in_addr exit_ipv4addr;

static struct in_addr exit_ipv4mask;

static struct GNUNET_STATISTICS_Handle *stats;

static struct GNUNET_CADET_Handle *cadet_handle;

static struct GNUNET_CONTAINER_MultiHashMap *connections_map;

static struct GNUNET_CONTAINER_Heap *connections_heap;

static unsigned long long max_connections;

static struct GNUNET_CONTAINER_MultiHashMap *services;

static struct ChannelState *channels[UINT16_MAX + 1];

static struct GNUNET_DNSSTUB_Context *dnsstub;

static struct GNUNET_DHT_PutHandle *dht_put;

static struct GNUNET_DHT_Handle *dht;

static struct GNUNET_SCHEDULER_Task *dht_task;

static struct GNUNET_DNS_Advertisement dns_advertisement;

static struct GNUNET_HashCode dht_put_key;

static struct GNUNET_CRYPTO_EddsaPrivateKey *peer_key;

static struct GNUNET_CADET_Port *dns_port;

static struct GNUNET_CADET_Port *cadet_port4;

static struct GNUNET_CADET_Port *cadet_port6;

static int ipv4_exit;

static int ipv6_exit;

static int ipv4_enabled;

static int ipv6_enabled;


GNUNET_NETWORK_STRUCT_BEGIN

struct DnsResponseMessage
{
  struct GNUNET_MessageHeader header;

  struct GNUNET_TUN_DnsHeader dns;

  /* Followed by more DNS payload */
};

GNUNET_NETWORK_STRUCT_END


static void
process_dns_result (void *cls,
                    const struct GNUNET_TUN_DnsHeader *dns,
                    size_t r)
{
  struct ChannelState *ts;
  struct GNUNET_MQ_Envelope *env;
  struct DnsResponseMessage *resp;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Processing DNS result from stub resolver\n");
  GNUNET_assert (NULL == cls);
  if (NULL == dns)
    return;
  /* Handle case that this is a reply to a request from a CADET DNS channel */
  ts = channels[dns->id];
  if (NULL == ts)
    return;
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Got a response from the stub resolver for DNS request received via CADET!\n");
  channels[dns->id] = NULL;
  env = GNUNET_MQ_msg_extra (resp,
                             r - sizeof(struct GNUNET_TUN_DnsHeader),
                             GNUNET_MESSAGE_TYPE_VPN_DNS_FROM_INTERNET);
  GNUNET_memcpy (&resp->dns,
                 dns,
                 r);
  resp->dns.id = ts->specifics.dns.original_id;
  GNUNET_MQ_send (GNUNET_CADET_get_mq (ts->channel),
                  env);
}


static int
check_dns_request (void *cls,
                   const struct DnsResponseMessage *msg)
{
  struct ChannelState *ts = cls;

  if (NULL == dnsstub)
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  if (GNUNET_NO == ts->is_dns)
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


static void
handle_dns_request (void *cls,
                    const struct DnsResponseMessage *msg)
{
  struct ChannelState *ts = cls;
  size_t mlen = ntohs (msg->header.size);
  size_t dlen = mlen - sizeof(struct GNUNET_MessageHeader);
  char buf[dlen] GNUNET_ALIGN;
  struct GNUNET_TUN_DnsHeader *dout;

  if (GNUNET_SYSERR == ts->is_dns)
  {
    /* channel is DNS from now on */
    ts->is_dns = GNUNET_YES;
  }
  ts->specifics.dns.original_id = msg->dns.id;
  if (channels[ts->specifics.dns.my_id] == ts)
    channels[ts->specifics.dns.my_id] = NULL;
  ts->specifics.dns.my_id = (uint16_t) GNUNET_CRYPTO_random_u32 (
    GNUNET_CRYPTO_QUALITY_WEAK,
    UINT16_MAX
    + 1);
  channels[ts->specifics.dns.my_id] = ts;
  GNUNET_memcpy (buf,
                 &msg->dns,
                 dlen);
  dout = (struct GNUNET_TUN_DnsHeader *) buf;
  dout->id = ts->specifics.dns.my_id;
  ts->specifics.dns.rs = GNUNET_DNSSTUB_resolve (dnsstub,
                                                 buf,
                                                 dlen,
                                                 &process_dns_result,
                                                 NULL);
  if (NULL == ts->specifics.dns.rs)
  {
    GNUNET_break_op (0);
    return;
  }
  GNUNET_CADET_receive_done (ts->channel);
}


static void
hash_redirect_info (struct GNUNET_HashCode *hash,
                    const struct RedirectInformation *ri)
{
  char *off;

  memset (hash,
          0,
          sizeof(struct GNUNET_HashCode));
  /* the GNUnet hashmap only uses the first sizeof(unsigned int) of the hash,
     so we put the IP address in there (and hope for few collisions) */
  off = (char *) hash;
  switch (ri->remote_address.af)
  {
  case AF_INET:
    GNUNET_memcpy (off,
                   &ri->remote_address.address.ipv4,
                   sizeof(struct in_addr));
    off += sizeof(struct in_addr);
    break;

  case AF_INET6:
    GNUNET_memcpy (off,
                   &ri->remote_address.address.ipv6,
                   sizeof(struct in6_addr));
    off += sizeof(struct in_addr);
    break;

  default:
    GNUNET_assert (0);
  }
  GNUNET_memcpy (off,
                 &ri->remote_address.port,
                 sizeof(uint16_t));
  off += sizeof(uint16_t);
  switch (ri->local_address.af)
  {
  case AF_INET:
    GNUNET_memcpy (off,
                   &ri->local_address.address.ipv4,
                   sizeof(struct in_addr));
    off += sizeof(struct in_addr);
    break;

  case AF_INET6:
    GNUNET_memcpy (off,
                   &ri->local_address.address.ipv6,
                   sizeof(struct in6_addr));
    off += sizeof(struct in_addr);
    break;

  default:
    GNUNET_assert (0);
  }
  GNUNET_memcpy (off,
                 &ri->local_address.port,
                 sizeof(uint16_t));
  off += sizeof(uint16_t);
  GNUNET_memcpy (off,
                 &ri->remote_address.proto,
                 sizeof(uint8_t));
  /* off += sizeof (uint8_t); */
}


static struct ChannelState *
get_redirect_state (int af,
                    int protocol,
                    const void *destination_ip,
                    uint16_t destination_port,
                    const void *local_ip,
                    uint16_t local_port,
                    struct GNUNET_HashCode *state_key)
{
  struct RedirectInformation ri;
  struct GNUNET_HashCode key;
  struct ChannelState *state;

  if (((af == AF_INET) && (protocol == IPPROTO_ICMP)) ||
      ((af == AF_INET6) && (protocol == IPPROTO_ICMPV6)))
  {
    /* ignore ports */
    destination_port = 0;
    local_port = 0;
  }
  ri.remote_address.af = af;
  if (af == AF_INET)
    ri.remote_address.address.ipv4 = *((struct in_addr*) destination_ip);
  else
    ri.remote_address.address.ipv6 = *((struct in6_addr*) destination_ip);
  ri.remote_address.port = destination_port;
  ri.remote_address.proto = protocol;
  ri.local_address.af = af;
  if (af == AF_INET)
    ri.local_address.address.ipv4 = *((struct in_addr*) local_ip);
  else
    ri.local_address.address.ipv6 = *((struct in6_addr*) local_ip);
  ri.local_address.port = local_port;
  ri.local_address.proto = protocol;
  hash_redirect_info (&key,
                      &ri);
  if (NULL != state_key)
    *state_key = key;
  state = GNUNET_CONTAINER_multihashmap_get (connections_map,
                                             &key);
  if (NULL == state)
    return NULL;
  /* Mark this connection as freshly used */
  if (NULL == state_key)
    GNUNET_CONTAINER_heap_update_cost (state->specifics.tcp_udp.heap_node,
                                       GNUNET_TIME_absolute_get ().abs_value_us);
  return state;
}


static int
check_tcp_service (void *cls,
                   const struct GNUNET_EXIT_TcpServiceStartMessage *start)
{
  struct ChannelState *state = cls;

  if (NULL == state)
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  if (GNUNET_YES == state->is_dns)
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  if (NULL == state->specifics.tcp_udp.serv)
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  if (NULL != state->specifics.tcp_udp.heap_node)
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  if (start->tcp_header.off * 4 < sizeof(struct GNUNET_TUN_TcpHeader))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


static void
prepare_ipv4_packet (const void *payload,
                     size_t payload_length,
                     int protocol,
                     const struct GNUNET_TUN_TcpHeader *tcp_header,
                     const struct SocketAddress *src_address,
                     const struct SocketAddress *dst_address,
                     struct GNUNET_TUN_IPv4Header *pkt4)
{
  size_t len;

  len = payload_length;
  switch (protocol)
  {
  case IPPROTO_UDP:
    len += sizeof(struct GNUNET_TUN_UdpHeader);
    break;

  case IPPROTO_TCP:
    len += sizeof(struct GNUNET_TUN_TcpHeader);
    GNUNET_assert (NULL != tcp_header);
    break;

  default:
    GNUNET_break (0);
    return;
  }
  if (len + sizeof(struct GNUNET_TUN_IPv4Header) > UINT16_MAX)
  {
    GNUNET_break (0);
    return;
  }

  GNUNET_TUN_initialize_ipv4_header (pkt4,
                                     protocol,
                                     len,
                                     &src_address->address.ipv4,
                                     &dst_address->address.ipv4);
  switch (protocol)
  {
  case IPPROTO_UDP:
    {
      struct GNUNET_TUN_UdpHeader *pkt4_udp = (struct
                                               GNUNET_TUN_UdpHeader *) &pkt4[1];

      pkt4_udp->source_port = htons (src_address->port);
      pkt4_udp->destination_port = htons (dst_address->port);
      pkt4_udp->len = htons ((uint16_t) payload_length);
      GNUNET_TUN_calculate_udp4_checksum (pkt4,
                                          pkt4_udp,
                                          payload,
                                          payload_length);
      GNUNET_memcpy (&pkt4_udp[1],
                     payload,
                     payload_length);
    }
    break;

  case IPPROTO_TCP:
    {
      struct GNUNET_TUN_TcpHeader *pkt4_tcp = (struct
                                               GNUNET_TUN_TcpHeader *) &pkt4[1];

      *pkt4_tcp = *tcp_header;
      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                  "Sending TCP packet from port %u to port %u\n",
                  src_address->port,
                  dst_address->port);
      pkt4_tcp->source_port = htons (src_address->port);
      pkt4_tcp->destination_port = htons (dst_address->port);
      GNUNET_TUN_calculate_tcp4_checksum (pkt4,
                                          pkt4_tcp,
                                          payload,
                                          payload_length);
      GNUNET_memcpy (&pkt4_tcp[1],
                     payload,
                     payload_length);
    }
    break;

  default:
    GNUNET_assert (0);
  }
}


static void
prepare_ipv6_packet (const void *payload,
                     size_t payload_length,
                     int protocol,
                     const struct GNUNET_TUN_TcpHeader *tcp_header,
                     const struct SocketAddress *src_address,
                     const struct SocketAddress *dst_address,
                     struct GNUNET_TUN_IPv6Header *pkt6)
{
  size_t len;

  len = payload_length;
  switch (protocol)
  {
  case IPPROTO_UDP:
    len += sizeof(struct GNUNET_TUN_UdpHeader);
    break;

  case IPPROTO_TCP:
    len += sizeof(struct GNUNET_TUN_TcpHeader);
    break;

  default:
    GNUNET_break (0);
    return;
  }
  if (len > UINT16_MAX)
  {
    GNUNET_break (0);
    return;
  }

  GNUNET_TUN_initialize_ipv6_header (pkt6,
                                     protocol,
                                     len,
                                     &src_address->address.ipv6,
                                     &dst_address->address.ipv6);

  switch (protocol)
  {
  case IPPROTO_UDP:
    {
      struct GNUNET_TUN_UdpHeader *pkt6_udp = (struct
                                               GNUNET_TUN_UdpHeader *) &pkt6[1];

      pkt6_udp->source_port = htons (src_address->port);
      pkt6_udp->destination_port = htons (dst_address->port);
      pkt6_udp->len = htons ((uint16_t) payload_length);
      GNUNET_TUN_calculate_udp6_checksum (pkt6,
                                          pkt6_udp,
                                          payload,
                                          payload_length);
      GNUNET_memcpy (&pkt6_udp[1],
                     payload,
                     payload_length);
    }
    break;

  case IPPROTO_TCP:
    {
      struct GNUNET_TUN_TcpHeader *pkt6_tcp = (struct
                                               GNUNET_TUN_TcpHeader *) &pkt6[1];

      /* GNUNET_memcpy first here as some TCP header fields are initialized this way! */
      *pkt6_tcp = *tcp_header;
      pkt6_tcp->source_port = htons (src_address->port);
      pkt6_tcp->destination_port = htons (dst_address->port);
      GNUNET_TUN_calculate_tcp6_checksum (pkt6,
                                          pkt6_tcp,
                                          payload,
                                          payload_length);
      GNUNET_memcpy (&pkt6_tcp[1],
                     payload,
                     payload_length);
    }
    break;

  default:
    GNUNET_assert (0);
    break;
  }
}


static void
send_tcp_packet_via_tun (const struct SocketAddress *destination_address,
                         const struct SocketAddress *source_address,
                         const struct GNUNET_TUN_TcpHeader *tcp_header,
                         const void *payload,
                         size_t payload_length)
{
  size_t len;

  GNUNET_STATISTICS_update (stats,
                            gettext_noop ("# TCP packets sent via TUN"),
                            1,
                            GNUNET_NO);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Sending packet with %u bytes TCP payload via TUN\n",
              (unsigned int) payload_length);
  len = sizeof(struct GNUNET_MessageHeader) + sizeof(struct
                                                     GNUNET_TUN_Layer2PacketHeader);
  switch (source_address->af)
  {
  case AF_INET:
    len += sizeof(struct GNUNET_TUN_IPv4Header);
    break;

  case AF_INET6:
    len += sizeof(struct GNUNET_TUN_IPv6Header);
    break;

  default:
    GNUNET_break (0);
    return;
  }
  len += sizeof(struct GNUNET_TUN_TcpHeader);
  len += payload_length;
  if (len >= GNUNET_MAX_MESSAGE_SIZE)
  {
    GNUNET_break (0);
    return;
  }
  {
    char buf[len] GNUNET_ALIGN;
    struct GNUNET_MessageHeader *hdr;
    struct GNUNET_TUN_Layer2PacketHeader *tun;

    hdr = (struct GNUNET_MessageHeader *) buf;
    hdr->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
    hdr->size = htons (len);
    tun = (struct GNUNET_TUN_Layer2PacketHeader*) &hdr[1];
    tun->flags = htons (0);
    switch (source_address->af)
    {
    case AF_INET:
      {
        struct GNUNET_TUN_IPv4Header *ipv4
          = (struct GNUNET_TUN_IPv4Header*) &tun[1];

        tun->proto = htons (ETH_P_IPV4);
        prepare_ipv4_packet (payload,
                             payload_length,
                             IPPROTO_TCP,
                             tcp_header,
                             source_address,
                             destination_address,
                             ipv4);
      }
      break;

    case AF_INET6:
      {
        struct GNUNET_TUN_IPv6Header *ipv6
          = (struct GNUNET_TUN_IPv6Header*) &tun[1];

        tun->proto = htons (ETH_P_IPV6);
        prepare_ipv6_packet (payload,
                             payload_length,
                             IPPROTO_TCP,
                             tcp_header,
                             source_address,
                             destination_address,
                             ipv6);
      }
      break;

    default:
      GNUNET_assert (0);
      break;
    }
    if (NULL != helper_handle)
      (void) GNUNET_HELPER_send (helper_handle,
                                 (const struct GNUNET_MessageHeader*) buf,
                                 GNUNET_YES,
                                 NULL,
                                 NULL);
  }
}


static void
send_icmp_packet_via_tun (const struct SocketAddress *destination_address,
                          const struct SocketAddress *source_address,
                          const struct GNUNET_TUN_IcmpHeader *icmp_header,
                          const void *payload, size_t payload_length)
{
  size_t len;
  struct GNUNET_TUN_IcmpHeader *icmp;

  GNUNET_STATISTICS_update (stats,
                            gettext_noop ("# ICMP packets sent via TUN"),
                            1, GNUNET_NO);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Sending packet with %u bytes ICMP payload via TUN\n",
              (unsigned int) payload_length);
  len = sizeof(struct GNUNET_MessageHeader) + sizeof(struct
                                                     GNUNET_TUN_Layer2PacketHeader);
  switch (destination_address->af)
  {
  case AF_INET:
    len += sizeof(struct GNUNET_TUN_IPv4Header);
    break;

  case AF_INET6:
    len += sizeof(struct GNUNET_TUN_IPv6Header);
    break;

  default:
    GNUNET_break (0);
    return;
  }
  len += sizeof(struct GNUNET_TUN_IcmpHeader);
  len += payload_length;
  if (len >= GNUNET_MAX_MESSAGE_SIZE)
  {
    GNUNET_break (0);
    return;
  }
  {
    char buf[len] GNUNET_ALIGN;
    struct GNUNET_MessageHeader *hdr;
    struct GNUNET_TUN_Layer2PacketHeader *tun;

    hdr = (struct GNUNET_MessageHeader *) buf;
    hdr->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
    hdr->size = htons (len);
    tun = (struct GNUNET_TUN_Layer2PacketHeader*) &hdr[1];
    tun->flags = htons (0);
    switch (source_address->af)
    {
    case AF_INET:
      {
        struct GNUNET_TUN_IPv4Header *ipv4 = (struct
                                              GNUNET_TUN_IPv4Header*) &tun[1];

        tun->proto = htons (ETH_P_IPV4);
        GNUNET_TUN_initialize_ipv4_header (ipv4,
                                           IPPROTO_ICMP,
                                           sizeof(struct
                                                  GNUNET_TUN_IcmpHeader)
                                           + payload_length,
                                           &source_address->address.ipv4,
                                           &destination_address->address.ipv4);
        icmp = (struct GNUNET_TUN_IcmpHeader*) &ipv4[1];
      }
      break;

    case AF_INET6:
      {
        struct GNUNET_TUN_IPv6Header *ipv6 = (struct
                                              GNUNET_TUN_IPv6Header*) &tun[1];

        tun->proto = htons (ETH_P_IPV6);
        GNUNET_TUN_initialize_ipv6_header (ipv6,
                                           IPPROTO_ICMPV6,
                                           sizeof(struct
                                                  GNUNET_TUN_IcmpHeader)
                                           + payload_length,
                                           &source_address->address.ipv6,
                                           &destination_address->address.ipv6);
        icmp = (struct GNUNET_TUN_IcmpHeader*) &ipv6[1];
      }
      break;

    default:
      GNUNET_assert (0);
      break;
    }
    *icmp = *icmp_header;
    GNUNET_memcpy (&icmp[1],
                   payload,
                   payload_length);
    GNUNET_TUN_calculate_icmp_checksum (icmp,
                                        payload,
                                        payload_length);
    if (NULL != helper_handle)
      (void) GNUNET_HELPER_send (helper_handle,
                                 (const struct GNUNET_MessageHeader*) buf,
                                 GNUNET_YES,
                                 NULL, NULL);
  }
}


static void
setup_fresh_address (int af,
                     uint8_t proto,
                     struct SocketAddress *local_address)
{
  local_address->af = af;
  local_address->proto = (uint8_t) proto;
  /* default "local" port range is often 32768--61000,
     so we pick a random value in that range */
  if (((af == AF_INET) && (proto == IPPROTO_ICMP)) ||
      ((af == AF_INET6) && (proto == IPPROTO_ICMPV6)))
    local_address->port = 0;
  else
    local_address->port
      = (uint16_t) 32768 + GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK,
                                                     28232);
  switch (af)
  {
  case AF_INET:
    {
      struct in_addr addr;
      struct in_addr mask;
      struct in_addr rnd;

      addr = exit_ipv4addr;
      mask = exit_ipv4mask;
      if (0 == ~mask.s_addr)
      {
        /* only one valid IP anyway */
        local_address->address.ipv4 = addr;
        return;
      }
      /* Given 192.168.0.1/255.255.0.0, we want a mask
         of '192.168.255.255', thus:  */
      mask.s_addr = addr.s_addr | ~mask.s_addr;
      /* Pick random IPv4 address within the subnet, except 'addr' or 'mask' itself */
      do
      {
        rnd.s_addr = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK,
                                               UINT32_MAX);
        local_address->address.ipv4.s_addr = (addr.s_addr | rnd.s_addr)
                                             & mask.s_addr;
      }
      while ((local_address->address.ipv4.s_addr == addr.s_addr) ||
             (local_address->address.ipv4.s_addr == mask.s_addr));
    }
    break;

  case AF_INET6:
    {
      struct in6_addr addr;
      struct in6_addr mask;
      struct in6_addr rnd;
      int i;

      addr = exit_ipv6addr;
      GNUNET_assert (ipv6prefix < 128);
      if (ipv6prefix == 127)
      {
        /* only one valid IP anyway */
        local_address->address.ipv6 = addr;
        return;
      }
      /* Given ABCD::/96, we want a mask of 'ABCD::FFFF:FFFF,
         thus: */
      mask = addr;
      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 */
      do
      {
        for (i = 0; i < 16; i++)
        {
          rnd.s6_addr[i] = (unsigned char) GNUNET_CRYPTO_random_u32 (
            GNUNET_CRYPTO_QUALITY_WEAK,
            256);
          local_address->address.ipv6.s6_addr[i]
            = (addr.s6_addr[i] | rnd.s6_addr[i]) & mask.s6_addr[i];
        }
      }
      while ((0 == GNUNET_memcmp (&local_address->address.ipv6,
                                  &addr)) ||
             (0 == GNUNET_memcmp (&local_address->address.ipv6,
                                  &mask)));
    }
    break;

  default:
    GNUNET_assert (0);
  }
}


static void
setup_state_record (struct ChannelState *state)
{
  struct GNUNET_HashCode key;
  struct ChannelState *s;

  /* generate fresh, unique address */
  do
  {
    if (NULL == state->specifics.tcp_udp.serv)
      setup_fresh_address (state->specifics.tcp_udp.ri.remote_address.af,
                           state->specifics.tcp_udp.ri.remote_address.proto,
                           &state->specifics.tcp_udp.ri.local_address);
    else
      setup_fresh_address (state->specifics.tcp_udp.serv->address.af,
                           state->specifics.tcp_udp.serv->address.proto,
                           &state->specifics.tcp_udp.ri.local_address);
  }
  while (NULL !=
         get_redirect_state (state->specifics.tcp_udp.ri.remote_address.af,
                             state->specifics.tcp_udp.ri.remote_address.proto,
                             &state->specifics.tcp_udp.ri.remote_address.address,
                             state->specifics.tcp_udp.ri.remote_address.port,
                             &state->specifics.tcp_udp.ri.local_address.address,
                             state->specifics.tcp_udp.ri.local_address.port,
                             &key));
  {
    char buf[INET6_ADDRSTRLEN];
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Picked local address %s:%u for new connection\n",
                inet_ntop (state->specifics.tcp_udp.ri.local_address.af,
                           &state->specifics.tcp_udp.ri.local_address.address,
                           buf,
                           sizeof(buf)),
                (unsigned int) state->specifics.tcp_udp.ri.local_address.port);
  }
  state->specifics.tcp_udp.state_key = key;
  GNUNET_assert (GNUNET_OK ==
                 GNUNET_CONTAINER_multihashmap_put (connections_map,
                                                    &key, state,
                                                    GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
  state->specifics.tcp_udp.heap_node
    = GNUNET_CONTAINER_heap_insert (connections_heap,
                                    state,
                                    GNUNET_TIME_absolute_get ().abs_value_us);
  while (GNUNET_CONTAINER_heap_get_size (connections_heap) > max_connections)
  {
    s = GNUNET_CONTAINER_heap_remove_root (connections_heap);
    GNUNET_assert (state != s);
    s->specifics.tcp_udp.heap_node = NULL;
    GNUNET_CADET_channel_destroy (s->channel);
    GNUNET_assert (GNUNET_OK ==
                   GNUNET_CONTAINER_multihashmap_remove (connections_map,
                                                         &s->specifics.tcp_udp.
                                                         state_key,
                                                         s));
    GNUNET_free (s);
  }
}


static void
send_udp_packet_via_tun (const struct SocketAddress *destination_address,
                         const struct SocketAddress *source_address,
                         const void *payload, size_t payload_length)
{
  size_t len;

  GNUNET_STATISTICS_update (stats,
                            gettext_noop ("# UDP packets sent via TUN"),
                            1, GNUNET_NO);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Sending packet with %u bytes UDP payload via TUN\n",
              (unsigned int) payload_length);
  len = sizeof(struct GNUNET_MessageHeader) + sizeof(struct
                                                     GNUNET_TUN_Layer2PacketHeader);
  switch (source_address->af)
  {
  case AF_INET:
    len += sizeof(struct GNUNET_TUN_IPv4Header);
    break;

  case AF_INET6:
    len += sizeof(struct GNUNET_TUN_IPv6Header);
    break;

  default:
    GNUNET_break (0);
    return;
  }
  len += sizeof(struct GNUNET_TUN_UdpHeader);
  len += payload_length;
  if (len >= GNUNET_MAX_MESSAGE_SIZE)
  {
    GNUNET_break (0);
    return;
  }
  {
    char buf[len] GNUNET_ALIGN;
    struct GNUNET_MessageHeader *hdr;
    struct GNUNET_TUN_Layer2PacketHeader *tun;

    hdr = (struct GNUNET_MessageHeader *) buf;
    hdr->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
    hdr->size = htons (len);
    tun = (struct GNUNET_TUN_Layer2PacketHeader*) &hdr[1];
    tun->flags = htons (0);
    switch (source_address->af)
    {
    case AF_INET:
      {
        struct GNUNET_TUN_IPv4Header *ipv4 = (struct
                                              GNUNET_TUN_IPv4Header*) &tun[1];

        tun->proto = htons (ETH_P_IPV4);
        prepare_ipv4_packet (payload,
                             payload_length,
                             IPPROTO_UDP,
                             NULL,
                             source_address,
                             destination_address,
                             ipv4);
      }
      break;

    case AF_INET6:
      {
        struct GNUNET_TUN_IPv6Header *ipv6 = (struct
                                              GNUNET_TUN_IPv6Header*) &tun[1];

        tun->proto = htons (ETH_P_IPV6);
        prepare_ipv6_packet (payload,
                             payload_length,
                             IPPROTO_UDP,
                             NULL,
                             source_address,
                             destination_address,
                             ipv6);
      }
      break;

    default:
      GNUNET_assert (0);
      break;
    }
    if (NULL != helper_handle)
      (void) GNUNET_HELPER_send (helper_handle,
                                 (const struct GNUNET_MessageHeader*) buf,
                                 GNUNET_YES,
                                 NULL, NULL);
  }
}


static int
check_udp_remote (void *cls,
                  const struct GNUNET_EXIT_UdpInternetMessage *msg)
{
  struct ChannelState *state = cls;

  if (GNUNET_YES == state->is_dns)
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


static void
handle_udp_remote (void *cls,
                   const struct GNUNET_EXIT_UdpInternetMessage *msg)
{
  struct ChannelState *state = cls;
  uint16_t pkt_len = ntohs (msg->header.size) - sizeof(struct
                                                       GNUNET_EXIT_UdpInternetMessage);
  const struct in_addr *v4;
  const struct in6_addr *v6;
  const void *payload;
  int af;

  if (GNUNET_SYSERR == state->is_dns)
  {
    /* channel is UDP/TCP from now on */
    state->is_dns = GNUNET_NO;
  }
  GNUNET_STATISTICS_update (stats,
                            gettext_noop ("# Bytes received from CADET"),
                            pkt_len, GNUNET_NO);
  GNUNET_STATISTICS_update (stats,
                            gettext_noop (
                              "# UDP IP-exit requests received via cadet"),
                            1, GNUNET_NO);
  af = (int) ntohl (msg->af);
  state->specifics.tcp_udp.ri.remote_address.af = af;
  switch (af)
  {
  case AF_INET:
    if (pkt_len < sizeof(struct in_addr))
    {
      GNUNET_break_op (0);
      return;
    }
    if (! ipv4_exit)
    {
      GNUNET_break_op (0);
      return;
    }
    v4 = (const struct in_addr*) &msg[1];
    payload = &v4[1];
    pkt_len -= sizeof(struct in_addr);
    state->specifics.tcp_udp.ri.remote_address.address.ipv4 = *v4;
    break;

  case AF_INET6:
    if (pkt_len < sizeof(struct in6_addr))
    {
      GNUNET_break_op (0);
      return;
    }
    if (! ipv6_exit)
    {
      GNUNET_break_op (0);
      return;
    }
    v6 = (const struct in6_addr*) &msg[1];
    payload = &v6[1];
    pkt_len -= sizeof(struct in6_addr);
    state->specifics.tcp_udp.ri.remote_address.address.ipv6 = *v6;
    break;

  default:
    GNUNET_break_op (0);
    return;
  }
  {
    char buf[INET6_ADDRSTRLEN];
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Received data from %s for forwarding to UDP %s:%u\n",
                GNUNET_i2s (&state->peer),
                inet_ntop (af,
                           &state->specifics.tcp_udp.ri.remote_address.address,
                           buf, sizeof(buf)),
                (unsigned int) ntohs (msg->destination_port));
  }
  state->specifics.tcp_udp.ri.remote_address.proto = IPPROTO_UDP;
  state->specifics.tcp_udp.ri.remote_address.port = msg->destination_port;
  if (NULL == state->specifics.tcp_udp.heap_node)
    setup_state_record (state);
  if (0 != ntohs (msg->source_port))
    state->specifics.tcp_udp.ri.local_address.port = msg->source_port;
  send_udp_packet_via_tun (&state->specifics.tcp_udp.ri.remote_address,
                           &state->specifics.tcp_udp.ri.local_address,
                           payload,
                           pkt_len);
  GNUNET_CADET_receive_done (state->channel);
}


static int
check_udp_service (void *cls,
                   const struct GNUNET_EXIT_UdpServiceMessage *msg)
{
  struct ChannelState *state = cls;

  if (NULL == state->specifics.tcp_udp.serv)
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


static void
handle_udp_service (void *cls,
                    const struct GNUNET_EXIT_UdpServiceMessage *msg)
{
  struct ChannelState *state = cls;
  uint16_t pkt_len = ntohs (msg->header.size) - sizeof(struct
                                                       GNUNET_EXIT_UdpServiceMessage);

  GNUNET_STATISTICS_update (stats,
                            gettext_noop ("# Bytes received from CADET"),
                            pkt_len, GNUNET_NO);
  GNUNET_STATISTICS_update (stats,
                            gettext_noop (
                              "# UDP service requests received via cadet"),
                            1, GNUNET_NO);
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Received data from %s for forwarding to UDP service %s on port %u\n",
       GNUNET_i2s (&state->peer),
       GNUNET_h2s (&state->specifics.tcp_udp.serv->descriptor),
       (unsigned int) ntohs (msg->destination_port));
  setup_state_record (state);
  if (0 != ntohs (msg->source_port))
    state->specifics.tcp_udp.ri.local_address.port = msg->source_port;
  send_udp_packet_via_tun (&state->specifics.tcp_udp.ri.remote_address,
                           &state->specifics.tcp_udp.ri.local_address,
                           &msg[1],
                           pkt_len);
  GNUNET_CADET_receive_done (state->channel);
}


static void
handle_tcp_service (void *cls,
                    const struct GNUNET_EXIT_TcpServiceStartMessage *start)
{
  struct ChannelState *state = cls;
  uint16_t pkt_len = ntohs (start->header.size) - sizeof(struct
                                                         GNUNET_EXIT_TcpServiceStartMessage);

  if (GNUNET_SYSERR == state->is_dns)
  {
    /* channel is UDP/TCP from now on */
    state->is_dns = GNUNET_NO;
  }
  GNUNET_STATISTICS_update (stats,
                            gettext_noop (
                              "# TCP service creation requests received via cadet"),
                            1,
                            GNUNET_NO);
  GNUNET_STATISTICS_update (stats,
                            gettext_noop ("# Bytes received from CADET"),
                            pkt_len,
                            GNUNET_NO);
  GNUNET_break_op (ntohl (start->reserved) == 0);
  /* setup fresh connection */
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Received data from %s for forwarding to TCP service %s on port %u\n",
              GNUNET_i2s (&state->peer),
              GNUNET_h2s (&state->specifics.tcp_udp.serv->descriptor),
              (unsigned int) ntohs (start->tcp_header.destination_port));
  setup_state_record (state);
  send_tcp_packet_via_tun (&state->specifics.tcp_udp.ri.remote_address,
                           &state->specifics.tcp_udp.ri.local_address,
                           &start->tcp_header,
                           &start[1],
                           pkt_len);
  GNUNET_CADET_receive_done (state->channel);
}


static int
check_tcp_remote (void *cls,
                  const struct GNUNET_EXIT_TcpInternetStartMessage *start)
{
  struct ChannelState *state = cls;

  if (NULL == state)
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  if (GNUNET_YES == state->is_dns)
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  if ((NULL != state->specifics.tcp_udp.serv) ||
      (NULL != state->specifics.tcp_udp.heap_node))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  if (start->tcp_header.off * 4 < sizeof(struct GNUNET_TUN_TcpHeader))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


static void
handle_tcp_remote (void *cls,
                   const struct GNUNET_EXIT_TcpInternetStartMessage *start)
{
  struct ChannelState *state = cls;
  uint16_t pkt_len = ntohs (start->header.size) - sizeof(struct
                                                         GNUNET_EXIT_TcpInternetStartMessage);
  const struct in_addr *v4;
  const struct in6_addr *v6;
  const void *payload;
  int af;

  if (GNUNET_SYSERR == state->is_dns)
  {
    /* channel is UDP/TCP from now on */
    state->is_dns = GNUNET_NO;
  }
  GNUNET_STATISTICS_update (stats,
                            gettext_noop ("# Bytes received from CADET"),
                            pkt_len, GNUNET_NO);
  GNUNET_STATISTICS_update (stats,
                            gettext_noop (
                              "# TCP IP-exit creation requests received via cadet"),
                            1, GNUNET_NO);
  af = (int) ntohl (start->af);
  state->specifics.tcp_udp.ri.remote_address.af = af;
  switch (af)
  {
  case AF_INET:
    if (pkt_len < sizeof(struct in_addr))
    {
      GNUNET_break_op (0);
      return;
    }
    if (! ipv4_exit)
    {
      GNUNET_break_op (0);
      return;
    }
    v4 = (const struct in_addr*) &start[1];
    payload = &v4[1];
    pkt_len -= sizeof(struct in_addr);
    state->specifics.tcp_udp.ri.remote_address.address.ipv4 = *v4;
    break;

  case AF_INET6:
    if (pkt_len < sizeof(struct in6_addr))
    {
      GNUNET_break_op (0);
      return;
    }
    if (! ipv6_exit)
    {
      GNUNET_break_op (0);
      return;
    }
    v6 = (const struct in6_addr*) &start[1];
    payload = &v6[1];
    pkt_len -= sizeof(struct in6_addr);
    state->specifics.tcp_udp.ri.remote_address.address.ipv6 = *v6;
    break;

  default:
    GNUNET_break_op (0);
    return;
  }
  {
    char buf[INET6_ADDRSTRLEN];
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Received payload from %s for existing TCP stream to %s:%u\n",
                GNUNET_i2s (&state->peer),
                inet_ntop (af,
                           &state->specifics.tcp_udp.ri.remote_address.address,
                           buf, sizeof(buf)),
                (unsigned int) ntohs (start->tcp_header.destination_port));
  }
  state->specifics.tcp_udp.ri.remote_address.proto = IPPROTO_TCP;
  state->specifics.tcp_udp.ri.remote_address.port = ntohs (
    start->tcp_header.destination_port);
  setup_state_record (state);
  send_tcp_packet_via_tun (&state->specifics.tcp_udp.ri.remote_address,
                           &state->specifics.tcp_udp.ri.local_address,
                           &start->tcp_header,
                           payload,
                           pkt_len);
  GNUNET_CADET_receive_done (state->channel);
}


static int
check_tcp_data (void *cls,
                const struct GNUNET_EXIT_TcpDataMessage *data)
{
  struct ChannelState *state = cls;

  if ((NULL == state) ||
      (NULL == state->specifics.tcp_udp.heap_node))
  {
    /* connection should have been up! */
    GNUNET_STATISTICS_update (stats,
                              gettext_noop (
                                "# TCP DATA requests dropped (no session)"),
                              1, GNUNET_NO);
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  if (data->tcp_header.off * 4 < sizeof(struct GNUNET_TUN_TcpHeader))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  if (GNUNET_YES == state->is_dns)
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


static void
handle_tcp_data (void *cls,
                 const struct GNUNET_EXIT_TcpDataMessage *data)
{
  struct ChannelState *state = cls;
  uint16_t pkt_len = ntohs (data->header.size) - sizeof(struct
                                                        GNUNET_EXIT_TcpDataMessage);

  GNUNET_STATISTICS_update (stats,
                            gettext_noop ("# Bytes received from CADET"),
                            pkt_len, GNUNET_NO);
  GNUNET_STATISTICS_update (stats,
                            gettext_noop (
                              "# TCP data requests received via cadet"),
                            1, GNUNET_NO);
  if (GNUNET_SYSERR == state->is_dns)
  {
    /* channel is UDP/TCP from now on */
    state->is_dns = GNUNET_NO;
  }

  GNUNET_break_op (ntohl (data->reserved) == 0);
  {
    char buf[INET6_ADDRSTRLEN];
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Received additional %u bytes of data from %s for TCP stream to %s:%u\n",
                pkt_len,
                GNUNET_i2s (&state->peer),
                inet_ntop (state->specifics.tcp_udp.ri.remote_address.af,
                           &state->specifics.tcp_udp.ri.remote_address.address,
                           buf, sizeof(buf)),
                (unsigned int) state->specifics.tcp_udp.ri.remote_address.port);
  }

  send_tcp_packet_via_tun (&state->specifics.tcp_udp.ri.remote_address,
                           &state->specifics.tcp_udp.ri.local_address,
                           &data->tcp_header,
                           &data[1], pkt_len);
  GNUNET_CADET_receive_done (state->channel);
}


static void
make_up_icmpv4_payload (struct ChannelState *state,
                        struct GNUNET_TUN_IPv4Header *ipp,
                        struct GNUNET_TUN_UdpHeader *udp)
{
  GNUNET_TUN_initialize_ipv4_header (ipp,
                                     state->specifics.tcp_udp.ri.remote_address.
                                     proto,
                                     sizeof(struct GNUNET_TUN_TcpHeader),
                                     &state->specifics.tcp_udp.ri.remote_address
                                     .address.ipv4,
                                     &state->specifics.tcp_udp.ri.local_address.
                                     address.ipv4);
  udp->source_port = htons (state->specifics.tcp_udp.ri.remote_address.port);
  udp->destination_port = htons (
    state->specifics.tcp_udp.ri.local_address.port);
  udp->len = htons (0);
  udp->crc = htons (0);
}


static void
make_up_icmpv6_payload (struct ChannelState *state,
                        struct GNUNET_TUN_IPv6Header *ipp,
                        struct GNUNET_TUN_UdpHeader *udp)
{
  GNUNET_TUN_initialize_ipv6_header (ipp,
                                     state->specifics.tcp_udp.ri.remote_address.
                                     proto,
                                     sizeof(struct GNUNET_TUN_TcpHeader),
                                     &state->specifics.tcp_udp.ri.remote_address
                                     .address.ipv6,
                                     &state->specifics.tcp_udp.ri.local_address.
                                     address.ipv6);
  udp->source_port = htons (state->specifics.tcp_udp.ri.remote_address.port);
  udp->destination_port = htons (
    state->specifics.tcp_udp.ri.local_address.port);
  udp->len = htons (0);
  udp->crc = htons (0);
}


static int
check_icmp_remote (void *cls,
                   const struct GNUNET_EXIT_IcmpInternetMessage *msg)
{
  struct ChannelState *state = cls;

  if (GNUNET_YES == state->is_dns)
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


static void
handle_icmp_remote (void *cls,
                    const struct GNUNET_EXIT_IcmpInternetMessage *msg)
{
  struct ChannelState *state = cls;
  uint16_t pkt_len = ntohs (msg->header.size) - sizeof(struct
                                                       GNUNET_EXIT_IcmpInternetMessage);
  const struct in_addr *v4;
  const struct in6_addr *v6;
  const void *payload;
  char buf[sizeof(struct GNUNET_TUN_IPv6Header) + 8] GNUNET_ALIGN;
  int af;

  if (GNUNET_SYSERR == state->is_dns)
  {
    /* channel is UDP/TCP from now on */
    state->is_dns = GNUNET_NO;
  }
  GNUNET_STATISTICS_update (stats,
                            gettext_noop ("# Bytes received from CADET"),
                            pkt_len, GNUNET_NO);
  GNUNET_STATISTICS_update (stats,
                            gettext_noop (
                              "# ICMP IP-exit requests received via cadet"),
                            1, GNUNET_NO);

  af = (int) ntohl (msg->af);
  if ((NULL != state->specifics.tcp_udp.heap_node) &&
      (af != state->specifics.tcp_udp.ri.remote_address.af))
  {
    /* other peer switched AF on this channel; not allowed */
    GNUNET_break_op (0);
    return;
  }

  switch (af)
  {
  case AF_INET:
    if (pkt_len < sizeof(struct in_addr))
    {
      GNUNET_break_op (0);
      return;
    }
    if (! ipv4_exit)
    {
      GNUNET_break_op (0);
      return;
    }
    v4 = (const struct in_addr*) &msg[1];
    payload = &v4[1];
    pkt_len -= sizeof(struct in_addr);
    state->specifics.tcp_udp.ri.remote_address.address.ipv4 = *v4;
    if (NULL == state->specifics.tcp_udp.heap_node)
    {
      state->specifics.tcp_udp.ri.remote_address.af = af;
      state->specifics.tcp_udp.ri.remote_address.proto = IPPROTO_ICMP;
      setup_state_record (state);
    }
    /* check that ICMP type is something we want to support
       and possibly make up payload! */
    switch (msg->icmp_header.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:
      if (0 != pkt_len)
      {
        GNUNET_break_op (0);
        return;
      }
      /* make up payload */
      {
        struct GNUNET_TUN_IPv4Header *ipp = (struct
                                             GNUNET_TUN_IPv4Header *) buf;
        struct GNUNET_TUN_UdpHeader *udp = (struct
                                            GNUNET_TUN_UdpHeader *) &ipp[1];

        GNUNET_assert (8 == sizeof(struct GNUNET_TUN_UdpHeader));
        pkt_len = sizeof(struct GNUNET_TUN_IPv4Header) + 8;
        make_up_icmpv4_payload (state,
                                ipp,
                                udp);
        payload = ipp;
      }
      break;

    default:
      GNUNET_break_op (0);
      GNUNET_STATISTICS_update (stats,
                                gettext_noop (
                                  "# ICMPv4 packets dropped (type not allowed)"),
                                1, GNUNET_NO);
      return;
    }
    /* end AF_INET */
    break;

  case AF_INET6:
    if (pkt_len < sizeof(struct in6_addr))
    {
      GNUNET_break_op (0);
      return;
    }
    if (! ipv6_exit)
    {
      GNUNET_break_op (0);
      return;
    }
    v6 = (const struct in6_addr*) &msg[1];
    payload = &v6[1];
    pkt_len -= sizeof(struct in6_addr);
    state->specifics.tcp_udp.ri.remote_address.address.ipv6 = *v6;
    if (NULL == state->specifics.tcp_udp.heap_node)
    {
      state->specifics.tcp_udp.ri.remote_address.af = af;
      state->specifics.tcp_udp.ri.remote_address.proto = IPPROTO_ICMPV6;
      setup_state_record (state);
    }
    /* check that ICMP type is something we want to support
       and possibly make up payload! */
    switch (msg->icmp_header.type)
    {
    case GNUNET_TUN_ICMPTYPE6_ECHO_REPLY:
    case GNUNET_TUN_ICMPTYPE6_ECHO_REQUEST:
      break;

    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:
      if (0 != pkt_len)
      {
        GNUNET_break_op (0);
        return;
      }
      /* make up payload */
      {
        struct GNUNET_TUN_IPv6Header *ipp = (struct
                                             GNUNET_TUN_IPv6Header *) buf;
        struct GNUNET_TUN_UdpHeader *udp = (struct
                                            GNUNET_TUN_UdpHeader *) &ipp[1];

        GNUNET_assert (8 == sizeof(struct GNUNET_TUN_UdpHeader));
        pkt_len = sizeof(struct GNUNET_TUN_IPv6Header) + 8;
        make_up_icmpv6_payload (state,
                                ipp,
                                udp);
        payload = ipp;
      }
      break;

    default:
      GNUNET_break_op (0);
      GNUNET_STATISTICS_update (stats,
                                gettext_noop (
                                  "# ICMPv6 packets dropped (type not allowed)"),
                                1, GNUNET_NO);
      return;
    }
    /* end AF_INET6 */
    break;

  default:
    /* bad AF */
    GNUNET_break_op (0);
    return;
  }

  {
    char buf[INET6_ADDRSTRLEN];
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Received ICMP data from %s for forwarding to %s\n",
                GNUNET_i2s (&state->peer),
                inet_ntop (af,
                           &state->specifics.tcp_udp.ri.remote_address.address,
                           buf, sizeof(buf)));
  }
  send_icmp_packet_via_tun (&state->specifics.tcp_udp.ri.remote_address,
                            &state->specifics.tcp_udp.ri.local_address,
                            &msg->icmp_header,
                            payload, pkt_len);
  GNUNET_CADET_receive_done (state->channel);
}


static uint16_t
make_up_icmp_service_payload (struct ChannelState *state,
                              char *buf)
{
  switch (state->specifics.tcp_udp.serv->address.af)
  {
  case AF_INET:
    {
      struct GNUNET_TUN_IPv4Header *ipv4;
      struct GNUNET_TUN_UdpHeader *udp;

      ipv4 = (struct GNUNET_TUN_IPv4Header *) buf;
      udp = (struct GNUNET_TUN_UdpHeader *) &ipv4[1];
      make_up_icmpv4_payload (state,
                              ipv4,
                              udp);
      GNUNET_assert (8 == sizeof(struct GNUNET_TUN_UdpHeader));
      return sizeof(struct GNUNET_TUN_IPv4Header) + 8;
    }
    break;

  case AF_INET6:
    {
      struct GNUNET_TUN_IPv6Header *ipv6;
      struct GNUNET_TUN_UdpHeader *udp;

      ipv6 = (struct GNUNET_TUN_IPv6Header *) buf;
      udp = (struct GNUNET_TUN_UdpHeader *) &ipv6[1];
      make_up_icmpv6_payload (state,
                              ipv6,
                              udp);
      GNUNET_assert (8 == sizeof(struct GNUNET_TUN_UdpHeader));
      return sizeof(struct GNUNET_TUN_IPv6Header) + 8;
    }
    break;

  default:
    GNUNET_break (0);
  }
  return 0;
}


static int
check_icmp_service (void *cls,
                    const struct GNUNET_EXIT_IcmpServiceMessage *msg)
{
  struct ChannelState *state = cls;

  if (GNUNET_YES == state->is_dns)
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  if (NULL == state->specifics.tcp_udp.serv)
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


static void
handle_icmp_service (void *cls,
                     const struct GNUNET_EXIT_IcmpServiceMessage *msg)
{
  struct ChannelState *state = cls;
  uint16_t pkt_len = ntohs (msg->header.size) - sizeof(struct
                                                       GNUNET_EXIT_IcmpServiceMessage);
  struct GNUNET_TUN_IcmpHeader icmp;
  char buf[sizeof(struct GNUNET_TUN_IPv6Header) + 8] GNUNET_ALIGN;
  const void *payload;

  GNUNET_STATISTICS_update (stats,
                            gettext_noop ("# Bytes received from CADET"),
                            pkt_len, GNUNET_NO);
  GNUNET_STATISTICS_update (stats,
                            gettext_noop (
                              "# ICMP service requests received via cadet"),
                            1, GNUNET_NO);
  /* check that we got at least a valid header */
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Received data from %s for forwarding to ICMP service %s\n",
              GNUNET_i2s (&state->peer),
              GNUNET_h2s (&state->specifics.tcp_udp.serv->descriptor));
  icmp = msg->icmp_header;
  payload = &msg[1];
  state->specifics.tcp_udp.ri.remote_address
    = state->specifics.tcp_udp.serv->address;
  setup_state_record (state);

  /* check that ICMP type is something we want to support,
     perform ICMP PT if needed ans possibly make up payload */
  switch (msg->af)
  {
  case AF_INET:
    switch (msg->icmp_header.type)
    {
    case GNUNET_TUN_ICMPTYPE_ECHO_REPLY:
      if (state->specifics.tcp_udp.serv->address.af == AF_INET6)
        icmp.type = GNUNET_TUN_ICMPTYPE6_ECHO_REPLY;
      break;

    case GNUNET_TUN_ICMPTYPE_ECHO_REQUEST:
      if (state->specifics.tcp_udp.serv->address.af == AF_INET6)
        icmp.type = GNUNET_TUN_ICMPTYPE6_ECHO_REQUEST;
      break;

    case GNUNET_TUN_ICMPTYPE_DESTINATION_UNREACHABLE:
      if (state->specifics.tcp_udp.serv->address.af == AF_INET6)
        icmp.type = GNUNET_TUN_ICMPTYPE6_DESTINATION_UNREACHABLE;
      if (0 != pkt_len)
      {
        GNUNET_break_op (0);
        return;
      }
      payload = buf;
      pkt_len = make_up_icmp_service_payload (state, buf);
      break;

    case GNUNET_TUN_ICMPTYPE_TIME_EXCEEDED:
      if (state->specifics.tcp_udp.serv->address.af == AF_INET6)
        icmp.type = GNUNET_TUN_ICMPTYPE6_TIME_EXCEEDED;
      if (0 != pkt_len)
      {
        GNUNET_break_op (0);
        return;
      }
      payload = buf;
      pkt_len = make_up_icmp_service_payload (state, buf);
      break;

    case GNUNET_TUN_ICMPTYPE_SOURCE_QUENCH:
      if (state->specifics.tcp_udp.serv->address.af == AF_INET6)
      {
        GNUNET_STATISTICS_update (stats,
                                  gettext_noop (
                                    "# ICMPv4 packets dropped (impossible PT to v6)"),
                                  1, GNUNET_NO);
        return;
      }
      if (0 != pkt_len)
      {
        GNUNET_break_op (0);
        return;
      }
      payload = buf;
      pkt_len = make_up_icmp_service_payload (state, buf);
      break;

    default:
      GNUNET_break_op (0);
      GNUNET_STATISTICS_update (stats,
                                gettext_noop (
                                  "# ICMPv4 packets dropped (type not allowed)"),
                                1, GNUNET_NO);
      return;
    }
    /* end of AF_INET */
    break;

  case AF_INET6:
    switch (msg->icmp_header.type)
    {
    case GNUNET_TUN_ICMPTYPE6_ECHO_REPLY:
      if (state->specifics.tcp_udp.serv->address.af == AF_INET)
        icmp.type = GNUNET_TUN_ICMPTYPE_ECHO_REPLY;
      break;

    case GNUNET_TUN_ICMPTYPE6_ECHO_REQUEST:
      if (state->specifics.tcp_udp.serv->address.af == AF_INET)
        icmp.type = GNUNET_TUN_ICMPTYPE_ECHO_REQUEST;
      break;

    case GNUNET_TUN_ICMPTYPE6_DESTINATION_UNREACHABLE:
      if (state->specifics.tcp_udp.serv->address.af == AF_INET)
        icmp.type = GNUNET_TUN_ICMPTYPE_DESTINATION_UNREACHABLE;
      if (0 != pkt_len)
      {
        GNUNET_break_op (0);
        return;
      }
      payload = buf;
      pkt_len = make_up_icmp_service_payload (state, buf);
      break;

    case GNUNET_TUN_ICMPTYPE6_TIME_EXCEEDED:
      if (state->specifics.tcp_udp.serv->address.af == AF_INET)
        icmp.type = GNUNET_TUN_ICMPTYPE_TIME_EXCEEDED;
      if (0 != pkt_len)
      {
        GNUNET_break_op (0);
        return;
      }
      payload = buf;
      pkt_len = make_up_icmp_service_payload (state, buf);
      break;

    case GNUNET_TUN_ICMPTYPE6_PACKET_TOO_BIG:
    case GNUNET_TUN_ICMPTYPE6_PARAMETER_PROBLEM:
      if (state->specifics.tcp_udp.serv->address.af == AF_INET)
      {
        GNUNET_STATISTICS_update (stats,
                                  gettext_noop (
                                    "# ICMPv6 packets dropped (impossible PT to v4)"),
                                  1, GNUNET_NO);
        return;
      }
      if (0 != pkt_len)
      {
        GNUNET_break_op (0);
        return;
      }
      payload = buf;
      pkt_len = make_up_icmp_service_payload (state, buf);
      break;

    default:
      GNUNET_break_op (0);
      GNUNET_STATISTICS_update (stats,
                                gettext_noop (
                                  "# ICMPv6 packets dropped (type not allowed)"),
                                1, GNUNET_NO);
      return;
    }
    /* end of AF_INET6 */
    break;

  default:
    GNUNET_break_op (0);
    return;
  }

  send_icmp_packet_via_tun (&state->specifics.tcp_udp.ri.remote_address,
                            &state->specifics.tcp_udp.ri.local_address,
                            &icmp,
                            payload,
                            pkt_len);
  GNUNET_CADET_receive_done (state->channel);
}


static int
free_service_record (void *cls,
                     const struct GNUNET_HashCode *key,
                     void *value)
{
  struct LocalService *service = value;

  GNUNET_assert (GNUNET_YES ==
                 GNUNET_CONTAINER_multihashmap_remove (services,
                                                       key,
                                                       service));
  GNUNET_CADET_close_port (service->port);
  GNUNET_free (service->name);
  GNUNET_free (service);
  return GNUNET_OK;
}


static void *
new_service_channel (void *cls,
                     struct GNUNET_CADET_Channel *channel,
                     const struct GNUNET_PeerIdentity *initiator)
{
  struct LocalService *ls = cls;
  struct ChannelState *s = GNUNET_new (struct ChannelState);

  s->peer = *initiator;
  GNUNET_STATISTICS_update (stats,
                            gettext_noop ("# Inbound CADET channels created"),
                            1,
                            GNUNET_NO);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Received inbound channel from `%s'\n",
              GNUNET_i2s (initiator));
  s->channel = channel;
  s->specifics.tcp_udp.serv = ls;
  s->specifics.tcp_udp.ri.remote_address = ls->address;
  return s;
}


static void
clean_channel (void *cls,
               const struct GNUNET_CADET_Channel *channel)
{
  struct ChannelState *s = cls;

  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Channel destroyed\n");
  if (GNUNET_SYSERR == s->is_dns)
  {
    GNUNET_free (s);
    return;
  }
  if (GNUNET_YES == s->is_dns)
  {
    if (channels[s->specifics.dns.my_id] == s)
      channels[s->specifics.dns.my_id] = NULL;
  }
  else
  {
    if (NULL != s->specifics.tcp_udp.heap_node)
    {
      GNUNET_assert (GNUNET_YES ==
                     GNUNET_CONTAINER_multihashmap_remove (connections_map,
                                                           &s->specifics.tcp_udp
                                                           .state_key,
                                                           s));
      GNUNET_CONTAINER_heap_remove_node (s->specifics.tcp_udp.heap_node);
      s->specifics.tcp_udp.heap_node = NULL;
    }
  }
  GNUNET_free (s);
}


static void
store_service (int proto,
               const char *name,
               uint16_t destination_port,
               struct LocalService *service)
{
  struct GNUNET_MQ_MessageHandler handlers[] = {
    GNUNET_MQ_hd_var_size (icmp_service,
                           GNUNET_MESSAGE_TYPE_VPN_ICMP_TO_SERVICE,
                           struct GNUNET_EXIT_IcmpServiceMessage,
                           service),
    GNUNET_MQ_hd_var_size (udp_service,
                           GNUNET_MESSAGE_TYPE_VPN_UDP_TO_SERVICE,
                           struct GNUNET_EXIT_UdpServiceMessage,
                           service),
    GNUNET_MQ_hd_var_size (tcp_service,
                           GNUNET_MESSAGE_TYPE_VPN_TCP_TO_SERVICE_START,
                           struct GNUNET_EXIT_TcpServiceStartMessage,
                           service),
    GNUNET_MQ_hd_var_size (tcp_data,
                           GNUNET_MESSAGE_TYPE_VPN_TCP_DATA_TO_EXIT,
                           struct GNUNET_EXIT_TcpDataMessage,
                           service),
    GNUNET_MQ_handler_end ()
  };

  struct GNUNET_HashCode cadet_port;

  service->name = GNUNET_strdup (name);
  GNUNET_TUN_service_name_to_hash (name,
                                   &service->descriptor);
  GNUNET_TUN_compute_service_cadet_port (&service->descriptor,
                                         destination_port,
                                         &cadet_port);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Opening CADET port %s for SERVICE exit %s on port %u\n",
              GNUNET_h2s (&cadet_port),
              name,
              (unsigned int) destination_port);
  service->port = GNUNET_CADET_open_port (cadet_handle,
                                          &cadet_port,
                                          &new_service_channel,
                                          service,
                                          NULL,
                                          &clean_channel,
                                          handlers);
  service->is_udp = (IPPROTO_UDP == proto);
  if (GNUNET_OK !=
      GNUNET_CONTAINER_multihashmap_put (services,
                                         &cadet_port,
                                         service,
                                         GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY))
  {
    GNUNET_CADET_close_port (service->port);
    GNUNET_free (service->name);
    GNUNET_free (service);
    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                _ ("Got duplicate service records for `%s:%u'\n"),
                name,
                (unsigned int) destination_port);
  }
}


static void
send_packet_to_cadet_channel (struct ChannelState *s,
                              struct GNUNET_MQ_Envelope *env)
{
  GNUNET_assert (NULL != s);
  GNUNET_STATISTICS_update (stats,
                            gettext_noop (
                              "# Messages transmitted via cadet channels"),
                            1,
                            GNUNET_NO);
  GNUNET_MQ_send (GNUNET_CADET_get_mq (s->channel),
                  env);
}


static void
icmp_from_helper (const struct GNUNET_TUN_IcmpHeader *icmp,
                  size_t pktlen,
                  int af,
                  const void *destination_ip,
                  const void *source_ip)
{
  struct ChannelState *state;
  struct GNUNET_MQ_Envelope *env;
  struct GNUNET_EXIT_IcmpToVPNMessage *i2v;
  const struct GNUNET_TUN_IPv4Header *ipv4;
  const struct GNUNET_TUN_IPv6Header *ipv6;
  const struct GNUNET_TUN_UdpHeader *udp;
  uint16_t source_port;
  uint16_t destination_port;
  uint8_t protocol;

  {
    char sbuf[INET6_ADDRSTRLEN];
    char dbuf[INET6_ADDRSTRLEN];
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Received ICMP packet going from %s to %s\n",
                inet_ntop (af,
                           source_ip,
                           sbuf, sizeof(sbuf)),
                inet_ntop (af,
                           destination_ip,
                           dbuf, sizeof(dbuf)));
  }

  if (pktlen < sizeof(struct GNUNET_TUN_IcmpHeader))
  {
    /* blame kernel */
    GNUNET_break (0);
    return;
  }

  /* Find out if this is an ICMP packet in response to an existing
     TCP/UDP packet and if so, figure out ports / protocol of the
     existing session from the IP data in the ICMP payload */
  source_port = 0;
  destination_port = 0;
  switch (af)
  {
  case AF_INET:
    protocol = IPPROTO_ICMP;
    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:
      if (pktlen <
          sizeof(struct GNUNET_TUN_IcmpHeader)
          + sizeof(struct GNUNET_TUN_IPv4Header) + 8)
      {
        /* blame kernel */
        GNUNET_break (0);
        return;
      }
      ipv4 = (const struct GNUNET_TUN_IPv4Header *) &icmp[1];
      protocol = ipv4->protocol;
      /* could be TCP or UDP, but both have the ports in the right
         place, so that doesn't matter here */
      udp = (const struct GNUNET_TUN_UdpHeader *) &ipv4[1];
      /* swap ports, as they are from the original message */
      destination_port = ntohs (udp->source_port);
      source_port = ntohs (udp->destination_port);
      /* throw away ICMP payload, won't be useful for the other side anyway */
      pktlen = sizeof(struct GNUNET_TUN_IcmpHeader);
      break;

    default:
      GNUNET_STATISTICS_update (stats,
                                gettext_noop (
                                  "# ICMPv4 packets dropped (type not allowed)"),
                                1, GNUNET_NO);
      return;
    }
    break;

  case AF_INET6:
    protocol = IPPROTO_ICMPV6;
    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:
      if (pktlen <
          sizeof(struct GNUNET_TUN_IcmpHeader)
          + sizeof(struct GNUNET_TUN_IPv6Header) + 8)
      {
        /* blame kernel */
        GNUNET_break (0);
        return;
      }
      ipv6 = (const struct GNUNET_TUN_IPv6Header *) &icmp[1];
      protocol = ipv6->next_header;
      /* could be TCP or UDP, but both have the ports in the right
         place, so that doesn't matter here */
      udp = (const struct GNUNET_TUN_UdpHeader *) &ipv6[1];
      /* swap ports, as they are from the original message */
      destination_port = ntohs (udp->source_port);
      source_port = ntohs (udp->destination_port);
      /* throw away ICMP payload, won't be useful for the other side anyway */
      pktlen = 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 (type not allowed)"),
                                1, GNUNET_NO);
      return;
    }
    break;

  default:
    GNUNET_assert (0);
  }
  switch (protocol)
  {
  case IPPROTO_ICMP:
    state = get_redirect_state (af,
                                IPPROTO_ICMP,
                                source_ip,
                                0,
                                destination_ip,
                                0,
                                NULL);
    break;

  case IPPROTO_ICMPV6:
    state = get_redirect_state (af,
                                IPPROTO_ICMPV6,
                                source_ip,
                                0,
                                destination_ip,
                                0,
                                NULL);
    break;

  case IPPROTO_UDP:
    state = get_redirect_state (af,
                                IPPROTO_UDP,
                                source_ip,
                                source_port,
                                destination_ip,
                                destination_port,
                                NULL);
    break;

  case IPPROTO_TCP:
    state = get_redirect_state (af,
                                IPPROTO_TCP,
                                source_ip,
                                source_port,
                                destination_ip,
                                destination_port,
                                NULL);
    break;

  default:
    GNUNET_STATISTICS_update (stats,
                              gettext_noop (
                                "# ICMP packets dropped (not allowed)"),
                              1,
                              GNUNET_NO);
    return;
  }
  if (NULL == state)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                _ (
                  "ICMP Packet dropped, have no matching connection information\n"));
    return;
  }
  env = GNUNET_MQ_msg_extra (i2v,
                             pktlen - sizeof(struct GNUNET_TUN_IcmpHeader),
                             GNUNET_MESSAGE_TYPE_VPN_ICMP_TO_VPN);
  i2v->af = htonl (af);
  GNUNET_memcpy (&i2v->icmp_header,
                 icmp,
                 pktlen);
  send_packet_to_cadet_channel (state,
                                env);
}


static void
udp_from_helper (const struct GNUNET_TUN_UdpHeader *udp,
                 size_t pktlen,
                 int af,
                 const void *destination_ip,
                 const void *source_ip)
{
  struct ChannelState *state;
  struct GNUNET_MQ_Envelope *env;
  struct GNUNET_EXIT_UdpReplyMessage *urm;

  {
    char sbuf[INET6_ADDRSTRLEN];
    char dbuf[INET6_ADDRSTRLEN];

    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Received UDP packet going from %s:%u to %s:%u\n",
                inet_ntop (af,
                           source_ip,
                           sbuf, sizeof(sbuf)),
                (unsigned int) ntohs (udp->source_port),
                inet_ntop (af,
                           destination_ip,
                           dbuf, sizeof(dbuf)),
                (unsigned int) ntohs (udp->destination_port));
  }

  if (pktlen < sizeof(struct GNUNET_TUN_UdpHeader))
  {
    /* blame kernel */
    GNUNET_break (0);
    return;
  }
  if (pktlen != ntohs (udp->len))
  {
    /* blame kernel */
    GNUNET_break (0);
    return;
  }
  state = get_redirect_state (af,
                              IPPROTO_UDP,
                              source_ip,
                              ntohs (udp->source_port),
                              destination_ip,
                              ntohs (udp->destination_port),
                              NULL);
  if (NULL == state)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                _ (
                  "UDP Packet dropped, have no matching connection information\n"));
    return;
  }
  env = GNUNET_MQ_msg_extra (urm,
                             pktlen - sizeof(struct GNUNET_TUN_UdpHeader),
                             GNUNET_MESSAGE_TYPE_VPN_UDP_REPLY);
  urm->source_port = htons (0);
  urm->destination_port = htons (0);
  GNUNET_memcpy (&urm[1],
                 &udp[1],
                 pktlen - sizeof(struct GNUNET_TUN_UdpHeader));
  send_packet_to_cadet_channel (state,
                                env);
}


static void
tcp_from_helper (const struct GNUNET_TUN_TcpHeader *tcp,
                 size_t pktlen,
                 int af,
                 const void *destination_ip,
                 const void *source_ip)
{
  struct ChannelState *state;
  char buf[pktlen] GNUNET_ALIGN;
  struct GNUNET_TUN_TcpHeader *mtcp;
  struct GNUNET_EXIT_TcpDataMessage *tdm;
  struct GNUNET_MQ_Envelope *env;
  size_t mlen;

  {
    char sbuf[INET6_ADDRSTRLEN];
    char dbuf[INET6_ADDRSTRLEN];
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Received TCP packet with %u bytes going from %s:%u to %s:%u\n",
                (unsigned int) (pktlen - sizeof(struct GNUNET_TUN_TcpHeader)),
                inet_ntop (af,
                           source_ip,
                           sbuf, sizeof(sbuf)),
                (unsigned int) ntohs (tcp->source_port),
                inet_ntop (af,
                           destination_ip,
                           dbuf, sizeof(dbuf)),
                (unsigned int) ntohs (tcp->destination_port));
  }

  if (pktlen < sizeof(struct GNUNET_TUN_TcpHeader))
  {
    /* blame kernel */
    GNUNET_break (0);
    return;
  }
  state = get_redirect_state (af,
                              IPPROTO_TCP,
                              source_ip,
                              ntohs (tcp->source_port),
                              destination_ip,
                              ntohs (tcp->destination_port),
                              NULL);
  if (NULL == state)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                _ (
                  "TCP Packet dropped, have no matching connection information\n"));

    return;
  }
  /* mug port numbers and crc to avoid information leakage;
     sender will need to lookup the correct values anyway */
  GNUNET_memcpy (buf, tcp, pktlen);
  mtcp = (struct GNUNET_TUN_TcpHeader *) buf;
  mtcp->source_port = 0;
  mtcp->destination_port = 0;
  mtcp->crc = 0;

  mlen = sizeof(struct GNUNET_EXIT_TcpDataMessage) + (pktlen - sizeof(struct
                                                                      GNUNET_TUN_TcpHeader));
  if (mlen >= GNUNET_MAX_MESSAGE_SIZE)
  {
    GNUNET_break (0);
    return;
  }
  env = GNUNET_MQ_msg_extra (tdm,
                             pktlen - sizeof(struct GNUNET_TUN_TcpHeader),
                             GNUNET_MESSAGE_TYPE_VPN_TCP_DATA_TO_VPN);
  tdm->reserved = htonl (0);
  GNUNET_memcpy (&tdm->tcp_header,
                 buf,
                 pktlen);
  send_packet_to_cadet_channel (state,
                                env);
}


static int
message_token (void *cls GNUNET_UNUSED,
               const struct GNUNET_MessageHeader *message)
{
  const struct GNUNET_TUN_Layer2PacketHeader *pkt_tun;
  size_t size;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Got %u-byte message of type %u from gnunet-helper-exit\n",
              ntohs (message->size),
              ntohs (message->type));
  GNUNET_STATISTICS_update (stats,
                            gettext_noop ("# Packets received from TUN"),
                            1, GNUNET_NO);
  if (ntohs (message->type) != GNUNET_MESSAGE_TYPE_VPN_HELPER)
  {
    GNUNET_break (0);
    return GNUNET_OK;
  }
  size = ntohs (message->size);
  if (size < sizeof(struct GNUNET_TUN_Layer2PacketHeader) + sizeof(struct
                                                                   GNUNET_MessageHeader))
  {
    GNUNET_break (0);
    return GNUNET_OK;
  }
  GNUNET_STATISTICS_update (stats,
                            gettext_noop ("# Bytes received from TUN"),
                            size, GNUNET_NO);
  pkt_tun = (const struct GNUNET_TUN_Layer2PacketHeader *) &message[1];
  size -= sizeof(struct GNUNET_TUN_Layer2PacketHeader) + sizeof(struct
                                                                GNUNET_MessageHeader);
  switch (ntohs (pkt_tun->proto))
  {
  case ETH_P_IPV4:
    {
      const struct GNUNET_TUN_IPv4Header *pkt4;

      if (size < sizeof(struct GNUNET_TUN_IPv4Header))
      {
        /* Kernel to blame? */
        GNUNET_break (0);
        return GNUNET_OK;
      }
      pkt4 = (const struct GNUNET_TUN_IPv4Header *) &pkt_tun[1];
      if (size != ntohs (pkt4->total_length))
      {
        /* Kernel to blame? */
        GNUNET_break (0);
        return GNUNET_OK;
      }
      if (pkt4->header_length * 4 != sizeof(struct GNUNET_TUN_IPv4Header))
      {
        GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                    _ ("IPv4 packet options received.  Ignored.\n"));
        return GNUNET_OK;
      }

      size -= sizeof(struct GNUNET_TUN_IPv4Header);
      switch (pkt4->protocol)
      {
      case IPPROTO_UDP:
        udp_from_helper ((const struct GNUNET_TUN_UdpHeader *) &pkt4[1], size,
                         AF_INET,
                         &pkt4->destination_address,
                         &pkt4->source_address);
        break;

      case IPPROTO_TCP:
        tcp_from_helper ((const struct GNUNET_TUN_TcpHeader *) &pkt4[1], size,
                         AF_INET,
                         &pkt4->destination_address,
                         &pkt4->source_address);
        break;

      case IPPROTO_ICMP:
        icmp_from_helper ((const struct GNUNET_TUN_IcmpHeader *) &pkt4[1], size,
                          AF_INET,
                          &pkt4->destination_address,
                          &pkt4->source_address);
        break;

      default:
        GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                    _ (
                      "IPv4 packet with unsupported next header %u received.  Ignored.\n"),
                    (int) pkt4->protocol);
        return GNUNET_OK;
      }
    }
    break;

  case ETH_P_IPV6:
    {
      const struct GNUNET_TUN_IPv6Header *pkt6;

      if (size < sizeof(struct GNUNET_TUN_IPv6Header))
      {
        /* Kernel to blame? */
        GNUNET_break (0);
        return GNUNET_OK;
      }
      pkt6 = (struct GNUNET_TUN_IPv6Header *) &pkt_tun[1];
      if (size != ntohs (pkt6->payload_length) + sizeof(struct
                                                        GNUNET_TUN_IPv6Header))
      {
        /* Kernel to blame? */
        GNUNET_break (0);
        return GNUNET_OK;
      }
      size -= sizeof(struct GNUNET_TUN_IPv6Header);
      switch (pkt6->next_header)
      {
      case IPPROTO_UDP:
        udp_from_helper ((const struct GNUNET_TUN_UdpHeader *) &pkt6[1], size,
                         AF_INET6,
                         &pkt6->destination_address,
                         &pkt6->source_address);
        break;

      case IPPROTO_TCP:
        tcp_from_helper ((const struct GNUNET_TUN_TcpHeader *) &pkt6[1], size,
                         AF_INET6,
                         &pkt6->destination_address,
                         &pkt6->source_address);
        break;

      case IPPROTO_ICMPV6:
        icmp_from_helper ((const struct GNUNET_TUN_IcmpHeader *) &pkt6[1], size,
                          AF_INET6,
                          &pkt6->destination_address,
                          &pkt6->source_address);
        break;

      default:
        GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                    _ (
                      "IPv6 packet with unsupported next header %d received.  Ignored.\n"),
                    pkt6->next_header);
        return GNUNET_OK;
      }
    }
    break;

  default:
    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                _ ("Packet from unknown protocol %u received.  Ignored.\n"),
                ntohs (pkt_tun->proto));
    break;
  }
  return GNUNET_OK;
}


static void *
new_channel (void *cls,
             struct GNUNET_CADET_Channel *channel,
             const struct GNUNET_PeerIdentity *initiator)
{
  struct ChannelState *s = GNUNET_new (struct ChannelState);

  s->is_dns = GNUNET_SYSERR;
  s->peer = *initiator;
  GNUNET_STATISTICS_update (stats,
                            gettext_noop ("# Inbound CADET channels created"),
                            1,
                            GNUNET_NO);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Received inbound channel from `%s'\n",
              GNUNET_i2s (initiator));
  s->channel = channel;
  return s;
}


static int
free_iterate (void *cls,
              const struct GNUNET_HashCode *hash,
              void *value)
{
  GNUNET_free (value);
  return GNUNET_YES;
}


static void
dummy_task (void *cls)
{
  /* just terminate */
}


static void
cleanup (void *cls)
{
  unsigned int i;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Exit service is shutting down now\n");

  if (NULL != helper_handle)
  {
    GNUNET_HELPER_stop (helper_handle, GNUNET_NO);
    helper_handle = NULL;
  }
  if (NULL != regex4)
  {
    GNUNET_REGEX_announce_cancel (regex4);
    regex4 = NULL;
  }
  if (NULL != regex6)
  {
    GNUNET_REGEX_announce_cancel (regex6);
    regex6 = NULL;
  }
  if (NULL != services)
  {
    GNUNET_CONTAINER_multihashmap_iterate (services,
                                           &free_service_record,
                                           NULL);
    GNUNET_CONTAINER_multihashmap_destroy (services);
  }
  if (NULL != dns_port)
  {
    GNUNET_CADET_close_port (dns_port);
    dns_port = NULL;
  }
  if (NULL != cadet_port4)
  {
    GNUNET_CADET_close_port (cadet_port4);
    cadet_port4 = NULL;
  }
  if (NULL != cadet_port6)
  {
    GNUNET_CADET_close_port (cadet_port6);
    cadet_port6 = NULL;
  }
  if (NULL != cadet_handle)
  {
    GNUNET_CADET_disconnect (cadet_handle);
    cadet_handle = NULL;
  }
  if (NULL != connections_map)
  {
    GNUNET_CONTAINER_multihashmap_iterate (connections_map,
                                           &free_iterate,
                                           NULL);
    GNUNET_CONTAINER_multihashmap_destroy (connections_map);
    connections_map = NULL;
  }
  if (NULL != connections_heap)
  {
    GNUNET_CONTAINER_heap_destroy (connections_heap);
    connections_heap = NULL;
  }
  if (NULL != dnsstub)
  {
    GNUNET_DNSSTUB_stop (dnsstub);
    dnsstub = NULL;
  }
  if (NULL != peer_key)
  {
    GNUNET_free (peer_key);
    peer_key = NULL;
  }
  if (NULL != dht_task)
  {
    GNUNET_SCHEDULER_cancel (dht_task);
    dht_task = NULL;
  }
  if (NULL != dht_put)
  {
    GNUNET_DHT_put_cancel (dht_put);
    dht_put = NULL;
  }
  if (NULL != dht)
  {
    GNUNET_DHT_disconnect (dht);
    dht = NULL;
  }
  if (NULL != stats)
  {
    GNUNET_STATISTICS_destroy (stats,
                               GNUNET_NO);
    stats = NULL;
  }
  for (i = 0; i < 8; i++)
    GNUNET_free (exit_argv[i]);
}


static void
add_services (int proto,
              char *cpy,
              const char *name)
{
  char *redirect;
  char *hostname;
  char *hostport;
  struct LocalService *serv;
  char *n;
  size_t slen;

  slen = strlen (name);
  GNUNET_assert (slen >= 8);
  n = GNUNET_strndup (name, slen - 8 /* remove .gnunet. */);

  for (redirect = strtok (cpy, " ;"); redirect != NULL;
       redirect = strtok (NULL, " ;"))
  {
    if (NULL == (hostname = strstr (redirect, ":")))
    {
      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                  _ (
                    "Option `%s' for domain `%s' is not formatted correctly!\n"),
                  redirect,
                  name);
      continue;
    }
    hostname[0] = '\0';
    hostname++;
    if (NULL == (hostport = strstr (hostname, ":")))
    {
      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                  _ (
                    "Option `%s' for domain `%s' is not formatted correctly!\n"),
                  redirect,
                  name);
      continue;
    }
    hostport[0] = '\0';
    hostport++;

    int local_port = atoi (redirect);
    int remote_port = atoi (hostport);

    if (! ((local_port > 0) && (local_port < 65536)))
    {
      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                  _ ("`%s' is not a valid port number (for domain `%s')!"),
                  redirect,
                  name);
      continue;
    }
    if (! ((remote_port > 0) && (remote_port < 65536)))
    {
      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                  _ ("`%s' is not a valid port number (for domain `%s')!"),
                  hostport,
                  name);
      continue;
    }

    serv = GNUNET_new (struct LocalService);
    serv->address.proto = proto;
    serv->address.port = remote_port;
    if (0 == strcmp ("localhost4",
                     hostname))
    {
      const char *ip4addr = exit_argv[5];

      serv->address.af = AF_INET;
      GNUNET_assert (1 == inet_pton (AF_INET,
                                     ip4addr,
                                     &serv->address.address.ipv4));
    }
    else if (0 == strcmp ("localhost6",
                          hostname))
    {
      const char *ip6addr = exit_argv[3];

      serv->address.af = AF_INET6;
      GNUNET_assert (1 == inet_pton (AF_INET6,
                                     ip6addr,
                                     &serv->address.address.ipv6));
    }
    else
    {
      struct addrinfo *res;
      int ret;

      ret = getaddrinfo (hostname,
                         NULL,
                         NULL,
                         &res);
      if ((0 != ret) || (NULL == res))
      {
        GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                    _ (
                      "No addresses found for hostname `%s' of service `%s'!\n"),
                    hostname,
                    n);
        GNUNET_free (serv);
        continue;
      }

      serv->address.af = res->ai_family;
      switch (res->ai_family)
      {
      case AF_INET:
        if (! ipv4_enabled)
        {
          GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                      _ (
                        "Service `%s' configured for IPv4, but IPv4 is disabled!\n"),
                      n);
          freeaddrinfo (res);
          GNUNET_free (serv);
          continue;
        }
        serv->address.address.ipv4
          = ((struct sockaddr_in *) res->ai_addr)->sin_addr;
        break;

      case AF_INET6:
        if (! ipv6_enabled)
        {
          GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                      _ (
                        "Service `%s' configured for IPv4, but IPv4 is disabled!\n"),
                      n);
          freeaddrinfo (res);
          GNUNET_free (serv);
          continue;
        }
        serv->address.address.ipv6
          = ((struct sockaddr_in6 *) res->ai_addr)->sin6_addr;
        break;

      default:
        freeaddrinfo (res);
        GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                    _ (
                      "No IP addresses found for hostname `%s' of service `%s'!\n"),
                    hostname,
                    n);
        GNUNET_free (serv);
        continue;
      }
      freeaddrinfo (res);
    }
    store_service (proto,
                   n,
                   local_port,
                   serv);
  }
  GNUNET_free (n);
}


static void
read_service_conf (void *cls,
                   const char *section)
{
  char *cpy;

  if ((strlen (section) < 8) ||
      (0 != strcmp (".gnunet.", section + (strlen (section) - 8))))
    return;
  if (GNUNET_OK ==
      GNUNET_CONFIGURATION_get_value_string (cfg,
                                             section,
                                             "UDP_REDIRECTS",
                                             &cpy))
  {
    add_services (IPPROTO_UDP,
                  cpy,
                  section);
    GNUNET_free (cpy);
  }
  if (GNUNET_OK ==
      GNUNET_CONFIGURATION_get_value_string (cfg,
                                             section,
                                             "TCP_REDIRECTS",
                                             &cpy))
  {
    add_services (IPPROTO_TCP,
                  cpy,
                  section);
    GNUNET_free (cpy);
  }
}


static void
do_dht_put (void *cls);


static void
dht_put_cont (void *cls)
{
  dht_put = NULL;
}


static void
do_dht_put (void *cls)
{
  struct GNUNET_TIME_Absolute expiration;

  dht_task = GNUNET_SCHEDULER_add_delayed (DHT_PUT_FREQUENCY,
                                           &do_dht_put,
                                           NULL);
  expiration = GNUNET_TIME_absolute_ntoh (dns_advertisement.expiration_time);
  if (GNUNET_TIME_absolute_get_remaining (expiration).rel_value_us <
      GNUNET_TIME_UNIT_HOURS.rel_value_us)
  {
    /* refresh advertisement */
    expiration = GNUNET_TIME_relative_to_absolute (DNS_ADVERTISEMENT_TIMEOUT);
    dns_advertisement.expiration_time = GNUNET_TIME_absolute_hton (expiration);
    GNUNET_assert (GNUNET_OK ==
                   GNUNET_CRYPTO_eddsa_sign_ (peer_key,
                                              &dns_advertisement.purpose,
                                              &dns_advertisement.signature));
  }
  if (NULL != dht_put)
    GNUNET_DHT_put_cancel (dht_put);
  dht_put = GNUNET_DHT_put (dht,
                            &dht_put_key,
                            1 /* replication */,
                            GNUNET_DHT_RO_NONE,
                            GNUNET_BLOCK_TYPE_DNS,
                            sizeof(struct GNUNET_DNS_Advertisement),
                            &dns_advertisement,
                            expiration,
                            &dht_put_cont,
                            NULL);
}


static void
parse_ip_options ()
{
  ipv4_exit = GNUNET_CONFIGURATION_get_value_yesno (cfg,
                                                    "exit",
                                                    "EXIT_IPV4");
  ipv6_exit = GNUNET_CONFIGURATION_get_value_yesno (cfg,
                                                    "exit",
                                                    "EXIT_IPV6");
  ipv4_enabled = GNUNET_CONFIGURATION_get_value_yesno (cfg,
                                                       "exit",
                                                       "ENABLE_IPV4");
  ipv6_enabled = GNUNET_CONFIGURATION_get_value_yesno (cfg,
                                                       "exit",
                                                       "ENABLE_IPV6");
  if ((ipv4_exit || ipv4_enabled) &&
      (GNUNET_OK != GNUNET_NETWORK_test_pf (PF_INET)) )
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                _ (
                  "This system does not support IPv4, will disable IPv4 functions despite them being enabled in the configuration\n"));
    ipv4_exit = GNUNET_NO;
    ipv4_enabled = GNUNET_NO;
  }
  if ((ipv6_exit || ipv6_enabled) &&
      (GNUNET_OK != GNUNET_NETWORK_test_pf (PF_INET6)) )
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                _ (
                  "This system does not support IPv6, will disable IPv6 functions despite them being enabled in the configuration\n"));
    ipv6_exit = GNUNET_NO;
    ipv6_enabled = GNUNET_NO;
  }
  if (ipv4_exit && (! ipv4_enabled))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                _ (
                  "Cannot enable IPv4 exit but disable IPv4 on TUN interface, will use ENABLE_IPv4=YES\n"));
    ipv4_enabled = GNUNET_YES;
  }
  if (ipv6_exit && (! ipv6_enabled))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                _ (
                  "Cannot enable IPv6 exit but disable IPv6 on TUN interface, will use ENABLE_IPv6=YES\n"));
    ipv6_enabled = GNUNET_YES;
  }
}


static void
advertise_dns_exit ()
{
  struct GNUNET_MQ_MessageHandler handlers[] = {
    GNUNET_MQ_hd_var_size (dns_request,
                           GNUNET_MESSAGE_TYPE_VPN_DNS_TO_INTERNET,
                           struct DnsResponseMessage,
                           NULL),
    GNUNET_MQ_handler_end ()
  };
  char *dns_exit;
  struct GNUNET_HashCode port;

  if (GNUNET_YES !=
      GNUNET_CONFIGURATION_get_value_yesno (cfg,
                                            "exit",
                                            "EXIT_DNS"))
    return;
  GNUNET_assert (NULL != (dnsstub = GNUNET_DNSSTUB_start (128)));
  dns_exit = NULL;
  /* TODO: support using multiple DNS resolvers */
  if ((GNUNET_OK !=
       GNUNET_CONFIGURATION_get_value_string (cfg,
                                              "exit",
                                              "DNS_RESOLVER",
                                              &dns_exit)) ||
      (GNUNET_OK !=
       GNUNET_DNSSTUB_add_dns_ip (dnsstub,
                                  dns_exit)))
  {
    GNUNET_log_config_invalid (GNUNET_ERROR_TYPE_ERROR,
                               "dns",
                               "DNS_RESOLVER",
                               _ ("need a valid IPv4 or IPv6 address\n"));
    GNUNET_free (dns_exit);
    return;
  }
  /* open port */
  GNUNET_CRYPTO_hash (GNUNET_APPLICATION_PORT_INTERNET_RESOLVER,
                      strlen (GNUNET_APPLICATION_PORT_INTERNET_RESOLVER),
                      &port);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Opening CADET port %s for DNS exit service\n",
              GNUNET_h2s (&port));
  dns_port = GNUNET_CADET_open_port (cadet_handle,
                                     &port,
                                     &new_channel,
                                     NULL,
                                     NULL,
                                     &clean_channel,
                                     handlers);
  /* advertise exit */
  dht = GNUNET_DHT_connect (cfg,
                            1);
  peer_key = GNUNET_CRYPTO_eddsa_key_create_from_configuration (cfg);
  GNUNET_CRYPTO_eddsa_key_get_public (peer_key,
                                      &dns_advertisement.peer.public_key);
  dns_advertisement.purpose.size = htonl (sizeof(struct
                                                 GNUNET_DNS_Advertisement)
                                          - sizeof(struct
                                                   GNUNET_CRYPTO_EddsaSignature));
  dns_advertisement.purpose.purpose = htonl (
    GNUNET_SIGNATURE_PURPOSE_DNS_RECORD);
  GNUNET_CRYPTO_hash ("dns",
                      strlen ("dns"),
                      &dht_put_key);
  dht_task = GNUNET_SCHEDULER_add_now (&do_dht_put,
                                       NULL);
  GNUNET_free (dns_exit);
}


static int
setup_exit_helper_args ()
{
  char *exit_ifname;
  char *tun_ifname;
  char *ipv6addr;
  char *ipv6prefix_s;
  char *ipv4addr;
  char *ipv4mask;

  exit_argv[0] = GNUNET_strdup ("exit-gnunet");
  if (GNUNET_SYSERR ==
      GNUNET_CONFIGURATION_get_value_string (cfg,
                                             "exit",
                                             "TUN_IFNAME",
                                             &tun_ifname))
  {
    GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
                               "EXIT",
                               "TUN_IFNAME");
    return GNUNET_SYSERR;
  }
  exit_argv[1] = tun_ifname;
  if (ipv4_enabled)
  {
    if (GNUNET_SYSERR ==
        GNUNET_CONFIGURATION_get_value_string (cfg,
                                               "exit",
                                               "EXIT_IFNAME",
                                               &exit_ifname))
    {
      GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
                                 "EXIT",
                                 "EXIT_IFNAME");
      return GNUNET_SYSERR;
    }
    exit_argv[2] = exit_ifname;
  }
  else
  {
    exit_argv[2] = GNUNET_strdup ("-");
  }

  if (GNUNET_YES == ipv6_enabled)
  {
    ipv6addr = NULL;
    if (((GNUNET_SYSERR ==
          GNUNET_CONFIGURATION_get_value_string (cfg,
                                                 "exit",
                                                 "IPV6ADDR",
                                                 &ipv6addr)) ||
         (1 != inet_pton (AF_INET6,
                          ipv6addr,
                          &exit_ipv6addr))))
    {
      GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
                                 "EXIT",
                                 "IPV6ADDR");
      GNUNET_free (ipv6addr);
      return GNUNET_SYSERR;
    }
    exit_argv[3] = ipv6addr;
    if (GNUNET_SYSERR ==
        GNUNET_CONFIGURATION_get_value_string (cfg,
                                               "exit",
                                               "IPV6PREFIX",
                                               &ipv6prefix_s))
    {
      GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
                                 "EXIT",
                                 "IPV6PREFIX");
      return GNUNET_SYSERR;
    }
    exit_argv[4] = ipv6prefix_s;
    if ((GNUNET_OK !=
         GNUNET_CONFIGURATION_get_value_number (cfg,
                                                "exit",
                                                "IPV6PREFIX",
                                                &ipv6prefix)) ||
        (ipv6prefix >= 127))
    {
      GNUNET_log_config_invalid (GNUNET_ERROR_TYPE_ERROR,
                                 "EXIT",
                                 "IPV6PREFIX",
                                 _ ("Must be a number"));
      return GNUNET_SYSERR;
    }
  }
  else
  {
    /* IPv6 explicitly disabled */
    exit_argv[3] = GNUNET_strdup ("-");
    exit_argv[4] = GNUNET_strdup ("-");
  }
  if (GNUNET_YES == ipv4_enabled)
  {
    ipv4addr = NULL;
    if (((GNUNET_SYSERR ==
          GNUNET_CONFIGURATION_get_value_string (cfg,
                                                 "exit",
                                                 "IPV4ADDR",
                                                 &ipv4addr)) ||
         (1 != inet_pton (AF_INET,
                          ipv4addr,
                          &exit_ipv4addr))))
    {
      GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
                                 "EXIT",
                                 "IPV4ADDR");
      GNUNET_free (ipv4addr);
      return GNUNET_SYSERR;
    }
    exit_argv[5] = ipv4addr;
    ipv4mask = NULL;
    if (((GNUNET_SYSERR ==
          GNUNET_CONFIGURATION_get_value_string (cfg,
                                                 "exit",
                                                 "IPV4MASK",
                                                 &ipv4mask)) ||
         (1 != inet_pton (AF_INET,
                          ipv4mask,
                          &exit_ipv4mask))))
    {
      GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
                                 "EXIT",
                                 "IPV4MASK");
      GNUNET_free (ipv4mask);
      return GNUNET_SYSERR;
    }
    exit_argv[6] = ipv4mask;
  }
  else
  {
    /* IPv4 explicitly disabled */
    exit_argv[5] = GNUNET_strdup ("-");
    exit_argv[6] = GNUNET_strdup ("-");
  }
  exit_argv[7] = NULL;
  return GNUNET_OK;
}


static void
run (void *cls,
     char *const *args,
     const char *cfgfile,
     const struct GNUNET_CONFIGURATION_Handle *cfg_)
{
  struct GNUNET_MQ_MessageHandler handlers[] = {
    GNUNET_MQ_hd_var_size (icmp_remote,
                           GNUNET_MESSAGE_TYPE_VPN_ICMP_TO_INTERNET,
                           struct GNUNET_EXIT_IcmpInternetMessage,
                           NULL),
    GNUNET_MQ_hd_var_size (udp_remote,
                           GNUNET_MESSAGE_TYPE_VPN_UDP_TO_INTERNET,
                           struct GNUNET_EXIT_UdpInternetMessage,
                           NULL),
    GNUNET_MQ_hd_var_size (tcp_remote,
                           GNUNET_MESSAGE_TYPE_VPN_TCP_TO_INTERNET_START,
                           struct GNUNET_EXIT_TcpInternetStartMessage,
                           NULL),
    GNUNET_MQ_hd_var_size (tcp_data,
                           GNUNET_MESSAGE_TYPE_VPN_TCP_DATA_TO_EXIT,
                           struct GNUNET_EXIT_TcpDataMessage,
                           NULL),
    GNUNET_MQ_handler_end ()
  };
  struct GNUNET_HashCode port;
  char *policy;
  char *binary;
  char *regex;
  char *prefixed_regex;

  cfg = cfg_;
  if (GNUNET_OK !=
      GNUNET_CONFIGURATION_get_value_number (cfg,
                                             "exit",
                                             "MAX_CONNECTIONS",
                                             &max_connections))
    max_connections = 1024;
  parse_ip_options ();
  binary = GNUNET_OS_get_suid_binary_path (cfg, "gnunet-helper-exit");
  if ((ipv4_exit) || (ipv6_exit))
  {
    if (GNUNET_YES !=
        GNUNET_OS_check_helper_binary (binary,
                                       GNUNET_YES,
                                       "gnunet-vpn - - - 169.1.3.7 255.255.255.0"))  // no nat, ipv4 only
    {
      GNUNET_free (binary);
      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                  _ (
                    "`%s' is not SUID or the path is invalid, EXIT will not work\n"),
                  "gnunet-helper-exit");
      GNUNET_SCHEDULER_add_shutdown (&dummy_task,
                                     NULL);
      global_ret = 1;
      return;
    }
  }
  if (! (ipv4_enabled || ipv6_enabled))
  {
    GNUNET_free (binary);
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                _ ("No useful service enabled.  Exiting.\n"));
    GNUNET_SCHEDULER_shutdown ();
    return;
  }

  GNUNET_SCHEDULER_add_shutdown (&cleanup,
                                 NULL);
  stats = GNUNET_STATISTICS_create ("exit",
                                    cfg);
  cadet_handle = GNUNET_CADET_connect (cfg);
  if (NULL == cadet_handle)
  {
    GNUNET_free (binary);
    GNUNET_SCHEDULER_shutdown ();
    return;
  }
  advertise_dns_exit ();
  if (GNUNET_OK !=
      setup_exit_helper_args ())
  {
    GNUNET_free (binary);
    GNUNET_SCHEDULER_shutdown ();
    return;
  }

  services = GNUNET_CONTAINER_multihashmap_create (65536,
                                                   GNUNET_NO);
  connections_map = GNUNET_CONTAINER_multihashmap_create (65536,
                                                          GNUNET_NO);
  connections_heap = GNUNET_CONTAINER_heap_create (
    GNUNET_CONTAINER_HEAP_ORDER_MIN);
  GNUNET_CONFIGURATION_iterate_sections (cfg,
                                         &read_service_conf,
                                         NULL);

  /* Cadet handle acquired, now open ports and announce regular
     expressions matching our exit */
  if ((GNUNET_YES == ipv4_enabled) &&
      (GNUNET_YES == ipv4_exit))
  {
    GNUNET_CRYPTO_hash (GNUNET_APPLICATION_PORT_IPV4_GATEWAY,
                        strlen (GNUNET_APPLICATION_PORT_IPV4_GATEWAY),
                        &port);
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Opening CADET port %s for IPv4 gateway service\n",
                GNUNET_h2s (&port));
    cadet_port4 = GNUNET_CADET_open_port (cadet_handle,
                                          &port,
                                          &new_channel,
                                          NULL,
                                          NULL,
                                          &clean_channel,
                                          handlers);
    policy = NULL;
    if (GNUNET_OK !=
        GNUNET_CONFIGURATION_get_value_string (cfg,
                                               "exit",
                                               "EXIT_RANGE_IPV4_POLICY",
                                               &policy))
      regex = NULL;
    else
      regex = GNUNET_TUN_ipv4policy2regex (policy);
    GNUNET_free (policy);
    if (NULL != regex)
    {
      (void) GNUNET_asprintf (&prefixed_regex,
                              "%s%s",
                              GNUNET_APPLICATION_TYPE_EXIT_REGEX_PREFIX,
                              regex);
      regex4 = GNUNET_REGEX_announce (cfg,
                                      prefixed_regex,
                                      REGEX_REFRESH_FREQUENCY,
                                      REGEX_MAX_PATH_LEN_IPV4);
      GNUNET_free (regex);
      GNUNET_free (prefixed_regex);
    }
  }

  if ((GNUNET_YES == ipv6_enabled) && (GNUNET_YES == ipv6_exit))
  {
    GNUNET_CRYPTO_hash (GNUNET_APPLICATION_PORT_IPV6_GATEWAY,
                        strlen (GNUNET_APPLICATION_PORT_IPV6_GATEWAY),
                        &port);
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Opening CADET port %s for IPv6 gateway service\n",
                GNUNET_h2s (&port));
    cadet_port6 = GNUNET_CADET_open_port (cadet_handle,
                                          &port,
                                          &new_channel,
                                          NULL,
                                          NULL,
                                          &clean_channel,
                                          handlers);
    policy = NULL;
    if (GNUNET_OK !=
        GNUNET_CONFIGURATION_get_value_string (cfg,
                                               "exit",
                                               "EXIT_RANGE_IPV6_POLICY",
                                               &policy))
      regex = NULL;
    else
      regex = GNUNET_TUN_ipv6policy2regex (policy);
    GNUNET_free (policy);
    if (NULL != regex)
    {
      (void) GNUNET_asprintf (&prefixed_regex,
                              "%s%s",
                              GNUNET_APPLICATION_TYPE_EXIT_REGEX_PREFIX,
                              regex);
      regex6 = GNUNET_REGEX_announce (cfg,
                                      prefixed_regex,
                                      REGEX_REFRESH_FREQUENCY,
                                      REGEX_MAX_PATH_LEN_IPV6);
      GNUNET_free (regex);
      GNUNET_free (prefixed_regex);
    }
  }
  helper_handle = GNUNET_HELPER_start (GNUNET_NO,
                                       binary,
                                       exit_argv,
                                       &message_token,
                                       NULL,
                                       NULL);
  GNUNET_free (binary);
}


int
main (int argc,
      char *const *argv)
{
  static const struct GNUNET_GETOPT_CommandLineOption options[] = {
    GNUNET_GETOPT_OPTION_END
  };

  if (GNUNET_OK !=
      GNUNET_STRINGS_get_utf8_args (argc,
                                    argv,
                                    &argc,
                                    &argv))
    return 2;

  return (GNUNET_OK ==
          GNUNET_PROGRAM_run (argc,
                              argv,
                              "gnunet-daemon-exit",
                              gettext_noop (
                                "Daemon to run to provide an IP exit node for the VPN"),
                              options,
                              &run,
                              NULL)) ? global_ret : 1;
}


/* end of gnunet-daemon-exit.c */