gnunet-daemon-pt.c

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/*
     This file is part of GNUnet.
     Copyright (C) 2010, 2012, 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_dns_service.h"
#include "gnunet_cadet_service.h"
#include "gnunet_dht_service.h"
#include "gnunet_vpn_service.h"
#include "gnunet_statistics_service.h"
#include "gnunet_applications.h"
#include "block_dns.h"
 
 
#define TIMEOUT GNUNET_TIME_UNIT_MINUTES
 
#define MAX_DNS_SIZE (8 * 1024)
 
#define MAX_OPEN_TUNNELS 4
 
 
enum RequestGroup
{
  ANSWERS = 0,
 
  AUTHORITY_RECORDS = 1,
 
  ADDITIONAL_RECORDS = 2,
 
  END = 3
};
 
 
struct ReplyContext
{
  struct GNUNET_DNS_RequestHandle *rh;
 
  struct GNUNET_DNSPARSER_Packet *dns;
 
  struct GNUNET_VPN_RedirectionRequest *rr;
 
  struct GNUNET_DNSPARSER_Record *rec;
 
  unsigned int offset;
 
  enum RequestGroup group;
};
 
 
struct CadetExit
{
  struct CadetExit *next;
 
  struct CadetExit *prev;
 
  struct GNUNET_CADET_Channel *cadet_channel;
 
  struct GNUNET_TIME_Absolute expiration;
 
  struct RequestContext *receive_queue_head;
 
  struct RequestContext *receive_queue_tail;
 
  struct GNUNET_PeerIdentity peer;
 
  unsigned int num_transmitted;
 
  unsigned int num_answered;
 
  /* unsigned */ int idle;
};
 
 
struct RequestContext
{
  struct RequestContext *next;
 
  struct RequestContext *prev;
 
  struct CadetExit *exit;
 
  struct GNUNET_DNS_RequestHandle *rh;
 
  struct GNUNET_MQ_Envelope *env;
 
  struct GNUNET_SCHEDULER_Task *timeout_task;
 
  uint16_t mlen;
 
  uint16_t dns_id;
};
 
 
static struct CadetExit *exit_head;
 
static struct CadetExit *exit_tail;
 
static const struct GNUNET_CONFIGURATION_Handle *cfg;
 
static struct GNUNET_VPN_Handle *vpn_handle;
 
static struct GNUNET_CADET_Handle *cadet_handle;
 
static struct GNUNET_STATISTICS_Handle *stats;
 
static struct GNUNET_DNS_Handle *dns_post_handle;
 
static struct GNUNET_DNS_Handle *dns_pre_handle;
 
static struct GNUNET_DHT_Handle *dht;
 
static struct GNUNET_DHT_GetHandle *dht_get;
 
static int ipv4_pt;
 
static int ipv6_pt;
 
static int dns_channel;
 
static unsigned int dns_exit_available;
 
 
static void
try_open_exit (void);
 
 
static uint32_t
get_channel_weight (struct CadetExit *exit)
{
  uint32_t dropped;
  uint32_t drop_percent;
  uint32_t good_percent;
 
  GNUNET_assert (exit->num_transmitted >= exit->num_answered);
  dropped = exit->num_transmitted - exit->num_answered;
  if (exit->num_transmitted > 0)
    drop_percent = (uint32_t) ((100LL * dropped) / exit->num_transmitted);
  else
    drop_percent = 50; /* no data */
  if ((exit->num_transmitted > 20) &&
      (drop_percent > 25))
    return 0; /* statistically significant, and > 25% loss, die */
  good_percent = 100 - drop_percent;
  GNUNET_assert (0 != good_percent);
  if (UINT32_MAX / good_percent / good_percent < exit->num_transmitted)
    return UINT32_MAX; /* formula below would overflow */
  return 1 + good_percent * good_percent * exit->num_transmitted;
}
 
 
static struct CadetExit *
choose_exit ()
{
  struct CadetExit *pos;
  uint64_t total_transmitted;
  uint64_t selected_offset;
  uint32_t channel_weight;
 
  total_transmitted = 0;
  for (pos = exit_head; NULL != pos; pos = pos->next)
  {
    if (NULL == pos->cadet_channel)
      break;
    channel_weight = get_channel_weight (pos);
    total_transmitted += channel_weight;
    /* double weight for idle channels */
    if (0 != pos->idle)
      total_transmitted += channel_weight;
  }
  if (0 == total_transmitted)
  {
    /* no channels available, or only a very bad one... */
    return exit_head;
  }
  selected_offset = GNUNET_CRYPTO_random_u64 (GNUNET_CRYPTO_QUALITY_WEAK,
                                              total_transmitted);
  total_transmitted = 0;
  for (pos = exit_head; NULL != pos; pos = pos->next)
  {
    if (NULL == pos->cadet_channel)
      break;
    channel_weight = get_channel_weight (pos);
    total_transmitted += channel_weight;
    /* double weight for idle channels */
    if (0 != pos->idle)
      total_transmitted += channel_weight;
    if (total_transmitted > selected_offset)
      return pos;
  }
  GNUNET_break (0);
  return NULL;
}
 
 
static void
finish_request (struct ReplyContext *rc)
{
  char *buf;
  size_t buf_len;
 
  if (GNUNET_SYSERR ==
      GNUNET_DNSPARSER_pack (rc->dns,
                             MAX_DNS_SIZE,
                             &buf,
                             &buf_len))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                _ ("Failed to pack DNS request.  Dropping.\n"));
    GNUNET_DNS_request_drop (rc->rh);
  }
  else
  {
    GNUNET_STATISTICS_update (stats,
                              gettext_noop ("# DNS requests mapped to VPN"),
                              1, GNUNET_NO);
    GNUNET_DNS_request_answer (rc->rh,
                               buf_len,
                               buf);
    GNUNET_free (buf);
  }
  GNUNET_DNSPARSER_free_packet (rc->dns);
  GNUNET_free (rc);
}
 
 
static void
submit_request (struct ReplyContext *rc);
 
 
static void
vpn_allocation_callback (void *cls,
                         int af,
                         const void *address)
{
  struct ReplyContext *rc = cls;
 
  rc->rr = NULL;
  if (af == AF_UNSPEC)
  {
    GNUNET_DNS_request_drop (rc->rh);
    GNUNET_DNSPARSER_free_packet (rc->dns);
    GNUNET_free (rc);
    return;
  }
  GNUNET_STATISTICS_update (stats,
                            gettext_noop ("# DNS records modified"),
                            1,
                            GNUNET_NO);
  switch (rc->rec->type)
  {
  case GNUNET_DNSPARSER_TYPE_A:
    GNUNET_assert (AF_INET == af);
    GNUNET_memcpy (rc->rec->data.raw.data,
                   address,
                   sizeof(struct in_addr));
    break;
 
  case GNUNET_DNSPARSER_TYPE_AAAA:
    GNUNET_assert (AF_INET6 == af);
    GNUNET_memcpy (rc->rec->data.raw.data,
                   address,
                   sizeof(struct in6_addr));
    break;
 
  default:
    GNUNET_assert (0);
    return;
  }
  rc->rec = NULL;
  submit_request (rc);
}
 
 
static void
modify_address (struct ReplyContext *rc,
                struct GNUNET_DNSPARSER_Record *rec)
{
  int af;
 
  switch (rec->type)
  {
  case GNUNET_DNSPARSER_TYPE_A:
    af = AF_INET;
    GNUNET_assert (rec->data.raw.data_len == sizeof(struct in_addr));
    break;
 
  case GNUNET_DNSPARSER_TYPE_AAAA:
    af = AF_INET6;
    GNUNET_assert (rec->data.raw.data_len == sizeof(struct in6_addr));
    break;
 
  default:
    GNUNET_assert (0);
    return;
  }
  rc->rec = rec;
  rc->rr = GNUNET_VPN_redirect_to_ip (vpn_handle,
                                      af,
                                      af,
                                      rec->data.raw.data,
                                      GNUNET_TIME_relative_to_absolute (
                                        TIMEOUT),
                                      &vpn_allocation_callback,
                                      rc);
}
 
 
static void
submit_request (struct ReplyContext *rc)
{
  struct GNUNET_DNSPARSER_Record *ra;
  unsigned int ra_len;
  unsigned int i;
 
  while (1)
  {
    switch (rc->group)
    {
    case ANSWERS:
      ra = rc->dns->answers;
      ra_len = rc->dns->num_answers;
      break;
 
    case AUTHORITY_RECORDS:
      ra = rc->dns->authority_records;
      ra_len = rc->dns->num_authority_records;
      break;
 
    case ADDITIONAL_RECORDS:
      ra = rc->dns->additional_records;
      ra_len = rc->dns->num_additional_records;
      break;
 
    case END:
      finish_request (rc);
      return;
 
    default:
      GNUNET_assert (0);
    }
    for (i = rc->offset; i < ra_len; i++)
    {
      switch (ra[i].type)
      {
      case GNUNET_DNSPARSER_TYPE_A:
        if (ipv4_pt)
        {
          rc->offset = i + 1;
          modify_address (rc,
                          &ra[i]);
          return;
        }
        break;
 
      case GNUNET_DNSPARSER_TYPE_AAAA:
        if (ipv6_pt)
        {
          rc->offset = i + 1;
          modify_address (rc,
                          &ra[i]);
          return;
        }
        break;
      }
    }
    rc->group++;
  }
}
 
 
static int
work_test (const struct GNUNET_DNSPARSER_Record *ra,
           unsigned int ra_len)
{
  unsigned int i;
 
  for (i = 0; i < ra_len; i++)
  {
    switch (ra[i].type)
    {
    case GNUNET_DNSPARSER_TYPE_A:
      if (ipv4_pt)
        return GNUNET_YES;
      break;
 
    case GNUNET_DNSPARSER_TYPE_AAAA:
      if (ipv6_pt)
        return GNUNET_YES;
      break;
    }
  }
  return GNUNET_NO;
}
 
 
static void
dns_post_request_handler (void *cls,
                          struct GNUNET_DNS_RequestHandle *rh,
                          size_t request_length,
                          const char *request)
{
  struct GNUNET_DNSPARSER_Packet *dns;
  struct ReplyContext *rc;
  int work;
 
  GNUNET_STATISTICS_update (stats,
                            gettext_noop ("# DNS replies intercepted"),
                            1, GNUNET_NO);
  dns = GNUNET_DNSPARSER_parse (request,
                                request_length);
  if (NULL == dns)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                _ ("Failed to parse DNS request.  Dropping.\n"));
    GNUNET_DNS_request_drop (rh);
    return;
  }
  work = GNUNET_NO;
  work |= work_test (dns->answers,
                     dns->num_answers);
  work |= work_test (dns->authority_records,
                     dns->num_authority_records);
  work |= work_test (dns->additional_records,
                     dns->num_additional_records);
  if (! work)
  {
    GNUNET_DNS_request_forward (rh);
    GNUNET_DNSPARSER_free_packet (dns);
    return;
  }
  rc = GNUNET_new (struct ReplyContext);
  rc->rh = rh;
  rc->dns = dns;
  rc->offset = 0;
  rc->group = ANSWERS;
  submit_request (rc);
}
 
 
static void
timeout_request (void *cls)
{
  struct RequestContext *rc = cls;
  struct CadetExit *exit = rc->exit;
 
  GNUNET_STATISTICS_update (stats,
                            gettext_noop ("# DNS requests dropped (timeout)"),
                            1,
                            GNUNET_NO);
  GNUNET_DNS_request_drop (rc->rh);
  GNUNET_free (rc);
  if ((0 == get_channel_weight (exit)) &&
      (NULL == exit->receive_queue_head))
  {
    /* this straw broke the camel's back: this channel now has
       such a low score that it will not be used; close it! */
    GNUNET_CADET_channel_destroy (exit->cadet_channel);
    exit->cadet_channel = NULL;
    GNUNET_CONTAINER_DLL_remove (exit_head,
                                 exit_tail,
                                 exit);
    GNUNET_CONTAINER_DLL_insert_tail (exit_head,
                                      exit_tail,
                                      exit);
    /* go back to semi-innocent: mark as not great, but
       avoid a prohibitively negative score (see
     #get_channel_weight(), which checks for a certain
       minimum number of transmissions before making
       up an opinion) */exit->num_transmitted = 5;
    exit->num_answered = 0;
    dns_exit_available--;
    /* now try to open an alternative exit */
    try_open_exit ();
  }
}
 
 
static void
dns_pre_request_handler (void *cls,
                         struct GNUNET_DNS_RequestHandle *rh,
                         size_t request_length,
                         const char *request)
{
  struct RequestContext *rc;
  struct GNUNET_MQ_Envelope *env;
  struct GNUNET_MessageHeader *hdr;
  struct GNUNET_TUN_DnsHeader dns;
  struct CadetExit *exit;
 
  GNUNET_STATISTICS_update (stats,
                            gettext_noop ("# DNS requests intercepted"),
                            1, GNUNET_NO);
  if (0 == dns_exit_available)
  {
    GNUNET_STATISTICS_update (stats,
                              gettext_noop (
                                "# DNS requests dropped (DNS cadet channel down)"),
                              1, GNUNET_NO);
    GNUNET_DNS_request_drop (rh);
    return;
  }
  if (request_length < sizeof(dns))
  {
    GNUNET_STATISTICS_update (stats,
                              gettext_noop (
                                "# DNS requests dropped (malformed)"),
                              1, GNUNET_NO);
    GNUNET_DNS_request_drop (rh);
    return;
  }
  exit = choose_exit ();
  GNUNET_assert (NULL != exit);
  GNUNET_assert (NULL != exit->cadet_channel);
 
  env = GNUNET_MQ_msg_extra (hdr,
                             request_length,
                             GNUNET_MESSAGE_TYPE_VPN_DNS_TO_INTERNET);
  GNUNET_memcpy (&hdr[1],
                 request,
                 request_length);
  rc = GNUNET_new (struct RequestContext);
  rc->exit = exit;
  rc->rh = rh;
  rc->timeout_task = GNUNET_SCHEDULER_add_delayed (TIMEOUT,
                                                   &timeout_request,
                                                   rc);
  GNUNET_memcpy (&dns,
                 request,
                 sizeof(dns));
  rc->dns_id = dns.id;
  rc->env = env;
  GNUNET_CONTAINER_DLL_remove (exit->receive_queue_head,
                               exit->receive_queue_tail,
                               rc);
  if (0 < exit->idle)
    exit->idle--;
  exit->num_transmitted++;
  GNUNET_MQ_send (GNUNET_CADET_get_mq (exit->cadet_channel),
                  GNUNET_MQ_env_copy (env));
}
 
 
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 int
check_dns_response (void *cls,
                    const struct DnsResponseMessage *msg)
{
  return GNUNET_OK; /* all OK */
}
 
 
static void
handle_dns_response (void *cls,
                     const struct DnsResponseMessage *msg)
{
  struct CadetExit *exit = cls;
  size_t mlen;
  struct RequestContext *rc;
 
  mlen = ntohs (msg->header.size) - sizeof(*msg);
  for (rc = exit->receive_queue_head; NULL != rc; rc = rc->next)
  {
    if (msg->dns.id == rc->dns_id)
    {
      GNUNET_STATISTICS_update (stats,
                                gettext_noop ("# DNS replies received"),
                                1,
                                GNUNET_NO);
      GNUNET_DNS_request_answer (rc->rh,
                                 mlen + sizeof(struct GNUNET_TUN_DnsHeader),
                                 (const void *) &msg->dns);
      GNUNET_CONTAINER_DLL_remove (exit->receive_queue_head,
                                   exit->receive_queue_tail,
                                   rc);
      GNUNET_SCHEDULER_cancel (rc->timeout_task);
      GNUNET_MQ_discard (rc->env);
      GNUNET_free (rc);
      exit->num_answered++;
      return;
    }
  }
  GNUNET_STATISTICS_update (stats,
                            gettext_noop ("# DNS replies dropped (too late?)"),
                            1, GNUNET_NO);
}
 
 
static void
abort_all_requests (struct CadetExit *exit)
{
  struct RequestContext *rc;
 
  while (NULL != (rc = exit->receive_queue_head))
  {
    GNUNET_CONTAINER_DLL_remove (exit->receive_queue_head,
                                 exit->receive_queue_tail,
                                 rc);
    GNUNET_DNS_request_drop (rc->rh);
    GNUNET_SCHEDULER_cancel (rc->timeout_task);
    GNUNET_MQ_discard (rc->env);
    GNUNET_free (rc);
  }
}
 
 
static void
cleanup (void *cls)
{
  struct CadetExit *exit;
 
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Protocol translation daemon is shutting down now\n");
  if (NULL != vpn_handle)
  {
    GNUNET_VPN_disconnect (vpn_handle);
    vpn_handle = NULL;
  }
  while (NULL != (exit = exit_head))
  {
    GNUNET_CONTAINER_DLL_remove (exit_head,
                                 exit_tail,
                                 exit);
    if (NULL != exit->cadet_channel)
    {
      GNUNET_CADET_channel_destroy (exit->cadet_channel);
      exit->cadet_channel = NULL;
    }
    abort_all_requests (exit);
    GNUNET_free (exit);
  }
  if (NULL != cadet_handle)
  {
    GNUNET_CADET_disconnect (cadet_handle);
    cadet_handle = NULL;
  }
  if (NULL != dns_post_handle)
  {
    GNUNET_DNS_disconnect (dns_post_handle);
    dns_post_handle = NULL;
  }
  if (NULL != dns_pre_handle)
  {
    GNUNET_DNS_disconnect (dns_pre_handle);
    dns_pre_handle = NULL;
  }
  if (NULL != stats)
  {
    GNUNET_STATISTICS_destroy (stats, GNUNET_YES);
    stats = NULL;
  }
  if (NULL != dht_get)
  {
    GNUNET_DHT_get_stop (dht_get);
    dht_get = NULL;
  }
  if (NULL != dht)
  {
    GNUNET_DHT_disconnect (dht);
    dht = NULL;
  }
}
 
 
static void
cadet_channel_end_cb (void *cls,
                      const struct GNUNET_CADET_Channel *channel)
{
  struct CadetExit *exit = cls;
  struct CadetExit *alt;
  struct RequestContext *rc;
 
  exit->cadet_channel = NULL;
  dns_exit_available--;
  /* open alternative channels */
  /* our channel is now closed, move our requests to an alternative
     channel */
  alt = choose_exit ();
  while (NULL != (rc = exit->receive_queue_head))
  {
    GNUNET_CONTAINER_DLL_remove (exit->receive_queue_head,
                                 exit->receive_queue_tail,
                                 rc);
    rc->exit = alt;
    GNUNET_CONTAINER_DLL_insert (alt->receive_queue_head,
                                 alt->receive_queue_tail,
                                 rc);
    GNUNET_MQ_send (GNUNET_CADET_get_mq (alt->cadet_channel),
                    GNUNET_MQ_env_copy (rc->env));
  }
  try_open_exit ();
}
 
 
static void
channel_idle_notify_cb (void *cls,
                        const struct GNUNET_CADET_Channel *channel,
                        int window_size)
{
  struct CadetExit *pos = cls;
 
  pos->idle = window_size;
}
 
 
static void
try_open_exit ()
{
  struct CadetExit *pos;
  uint32_t candidate_count;
  uint32_t candidate_selected;
  struct GNUNET_HashCode port;
 
  GNUNET_CRYPTO_hash (GNUNET_APPLICATION_PORT_INTERNET_RESOLVER,
                      strlen (GNUNET_APPLICATION_PORT_INTERNET_RESOLVER),
                      &port);
  candidate_count = 0;
  for (pos = exit_head; NULL != pos; pos = pos->next)
    if (NULL == pos->cadet_channel)
      candidate_count++;
  if (0 == candidate_count)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                "No DNS exits available yet.\n");
    return;
  }
  candidate_selected = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK,
                                                 candidate_count);
  candidate_count = 0;
  for (pos = exit_head; NULL != pos; pos = pos->next)
    if (NULL == pos->cadet_channel)
    {
      candidate_count++;
      if (candidate_selected < candidate_count)
      {
        struct GNUNET_MQ_MessageHandler cadet_handlers[] = {
          GNUNET_MQ_hd_var_size (dns_response,
                                 GNUNET_MESSAGE_TYPE_VPN_DNS_FROM_INTERNET,
                                 struct DnsResponseMessage,
                                 pos),
          GNUNET_MQ_handler_end ()
        };
 
 
        /* move to the head of the DLL */
        pos->cadet_channel
          = GNUNET_CADET_channel_create (cadet_handle,
                                         pos,
                                         &pos->peer,
                                         &port,
                                         &channel_idle_notify_cb,
                                         &cadet_channel_end_cb,
                                         cadet_handlers);
        if (NULL == pos->cadet_channel)
        {
          GNUNET_break (0);
          continue;
        }
        GNUNET_CONTAINER_DLL_remove (exit_head,
                                     exit_tail,
                                     pos);
        GNUNET_CONTAINER_DLL_insert (exit_head,
                                     exit_tail,
                                     pos);
        dns_exit_available++;
        return;
      }
    }
  GNUNET_assert (NULL == exit_head);
}
 
 
static void
handle_dht_result (void *cls,
                   struct GNUNET_TIME_Absolute exp,
                   const struct GNUNET_HashCode *key,
                   const struct GNUNET_PeerIdentity *trunc_peer,
                   const struct GNUNET_DHT_PathElement *get_path,
                   unsigned int get_path_length,
                   const struct GNUNET_DHT_PathElement *put_path,
                   unsigned int put_path_length,
                   enum GNUNET_BLOCK_Type type,
                   size_t size, const void *data)
{
  const struct GNUNET_DNS_Advertisement *ad;
  struct CadetExit *exit;
 
  if (sizeof(struct GNUNET_DNS_Advertisement) != size)
  {
    GNUNET_break (0);
    return;
  }
  ad = data;
  for (exit = exit_head; NULL != exit; exit = exit->next)
    if (0 == GNUNET_memcmp (&ad->peer,
                            &exit->peer))
      break;
  if (NULL == exit)
  {
    exit = GNUNET_new (struct CadetExit);
    exit->peer = ad->peer;
    /* channel is closed, so insert at the end */
    GNUNET_CONTAINER_DLL_insert_tail (exit_head,
                                      exit_tail,
                                      exit);
  }
  exit->expiration = GNUNET_TIME_absolute_max (exit->expiration,
                                               GNUNET_TIME_absolute_ntoh (
                                                 ad->expiration_time));
  if (dns_exit_available < MAX_OPEN_TUNNELS)
    try_open_exit ();
}
 
 
static void
run (void *cls, char *const *args GNUNET_UNUSED,
     const char *cfgfile GNUNET_UNUSED,
     const struct GNUNET_CONFIGURATION_Handle *cfg_)
{
  struct GNUNET_HashCode dns_key;
 
  cfg = cfg_;
  stats = GNUNET_STATISTICS_create ("pt",
                                    cfg);
  ipv4_pt = GNUNET_CONFIGURATION_get_value_yesno (cfg,
                                                  "pt",
                                                  "TUNNEL_IPV4");
  ipv6_pt = GNUNET_CONFIGURATION_get_value_yesno (cfg,
                                                  "pt",
                                                  "TUNNEL_IPV6");
  dns_channel = GNUNET_CONFIGURATION_get_value_yesno (cfg,
                                                      "pt",
                                                      "TUNNEL_DNS");
  if (! (ipv4_pt || ipv6_pt || dns_channel))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                _ ("No useful service enabled.  Exiting.\n"));
    GNUNET_SCHEDULER_shutdown ();
    return;
  }
  GNUNET_SCHEDULER_add_shutdown (&cleanup, cls);
  if (ipv4_pt || ipv6_pt)
  {
    dns_post_handle
      = GNUNET_DNS_connect (cfg,
                            GNUNET_DNS_FLAG_POST_RESOLUTION,
                            &dns_post_request_handler,
                            NULL);
    if (NULL == dns_post_handle)
    {
      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                  _ ("Failed to connect to %s service.  Exiting.\n"),
                  "DNS");
      GNUNET_SCHEDULER_shutdown ();
      return;
    }
    vpn_handle = GNUNET_VPN_connect (cfg);
    if (NULL == vpn_handle)
    {
      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                  _ ("Failed to connect to %s service.  Exiting.\n"),
                  "VPN");
      GNUNET_SCHEDULER_shutdown ();
      return;
    }
  }
  if (dns_channel)
  {
    dns_pre_handle
      = GNUNET_DNS_connect (cfg,
                            GNUNET_DNS_FLAG_PRE_RESOLUTION,
                            &dns_pre_request_handler,
                            NULL);
    if (NULL == dns_pre_handle)
    {
      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                  _ ("Failed to connect to %s service.  Exiting.\n"),
                  "DNS");
      GNUNET_SCHEDULER_shutdown ();
      return;
    }
    cadet_handle = GNUNET_CADET_connect (cfg);
    if (NULL == cadet_handle)
    {
      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                  _ ("Failed to connect to %s service.  Exiting.\n"),
                  "CADET");
      GNUNET_SCHEDULER_shutdown ();
      return;
    }
    dht = GNUNET_DHT_connect (cfg, 1);
    if (NULL == dht)
    {
      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                  _ ("Failed to connect to %s service.  Exiting.\n"),
                  "DHT");
      GNUNET_SCHEDULER_shutdown ();
      return;
    }
    GNUNET_CRYPTO_hash ("dns",
                        strlen ("dns"),
                        &dns_key);
    dht_get = GNUNET_DHT_get_start (dht,
                                    GNUNET_BLOCK_TYPE_DNS,
                                    &dns_key,
                                    1,
                                    GNUNET_DHT_RO_DEMULTIPLEX_EVERYWHERE,
                                    NULL, 0,
                                    &handle_dht_result,
                                    NULL);
  }
}
 
 
int
main (int argc,
      char *const *argv)
{
  static const struct GNUNET_GETOPT_CommandLineOption options[] = {
    GNUNET_GETOPT_OPTION_END
  };
  int ret;
 
  ret = (GNUNET_OK ==
         GNUNET_PROGRAM_run (GNUNET_OS_project_data_gnunet (),
                             argc,
                             argv,
                             "gnunet-daemon-pt",
                             gettext_noop (
                               "Daemon to run to perform IP protocol translation to GNUnet"),
                             options,
                             &run,
                             NULL))
        ? 0
        : 1;
  return ret;
}
 
 
/* end of gnunet-daemon-pt.c */