gnunet-service-nat-auto_legacy.c

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/*
     This file is part of GNUnet.
     Copyright (C) 2015 GNUnet e.V.
 
     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_resolver_service.h"
#include "gnunet_nat_lib.h"
#include "nat.h"
 
#define LOG(kind, ...) GNUNET_log_from (kind, "nat", __VA_ARGS__)
 
 
#define TIMEOUT GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, 15)
 
#define NAT_SERVER_TIMEOUT GNUNET_TIME_relative_multiply ( \
    GNUNET_TIME_UNIT_SECONDS, 10)
 
enum AutoPhase
{
  AUTO_INIT = 0,
 
  AUTO_EXTERNAL_IP,
 
  AUTO_STUN,
 
  AUTO_LOCAL_IP,
 
  AUTO_NAT_PUNCHED,
 
  AUTO_UPNPC,
 
  AUTO_ICMP_SERVER,
 
  AUTO_ICMP_CLIENT,
 
  AUTO_DONE
};
 
 
struct GNUNET_NAT_AutoHandle
{
  struct GNUNET_NAT_Test *tst;
 
  GNUNET_NAT_AutoResultCallback fin_cb;
 
  void *fin_cb_cls;
 
  struct GNUNET_NAT_ExternalHandle *eh;
 
  struct GNUNET_CONFIGURATION_Handle *cfg;
 
  struct GNUNET_CONFIGURATION_Handle *initial_cfg;
 
  struct GNUNET_SCHEDULER_Task *task;
 
  struct GNUNET_MQ_Handle *mq;
 
  enum AutoPhase phase;
 
  enum GNUNET_NAT_Type type;
 
  int have_v6;
 
  int upnp_set_external_address;
 
  int connected_back;
 
  char *stun_ip;
 
  unsigned int stun_port;
 
  int internal_ip_is_public;
 
  enum GNUNET_NAT_StatusCode ret;
};
 
 
static struct GNUNET_NETWORK_Handle *lsock4;
 
static struct GNUNET_SCHEDULER_Task *ltask4;
 
static unsigned long long port = 7895;
 
static char *stun_server = "stun.ekiga.net";
 
static unsigned int stun_port = 3478;
 
 
static void
next_phase (struct GNUNET_NAT_AutoHandle *ah);
 
 
static void
process_stun_reply (struct sockaddr_in *answer,
                    struct GNUNET_NAT_AutoHandle *ah)
{
  ah->stun_ip = inet_ntoa (answer->sin_addr);
  ah->stun_port = ntohs (answer->sin_port);
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              "External IP is: %s , with port %u\n",
              ah->stun_ip,
              ah->stun_port);
  next_phase (ah);
}
 
 
static void
stop_stun ()
{
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              "Stopping STUN and quitting...\n");
  /* Clean task */
  if (NULL != ltask4)
  {
    GNUNET_SCHEDULER_cancel (ltask4);
    ltask4 = NULL;
  }
  /* Clean socket */
  if (NULL != lsock4)
  {
    GNUNET_NETWORK_socket_close (lsock4);
    lsock4 = NULL;
  }
}
 
 
static void
do_udp_read (void *cls)
{
  struct GNUNET_NAT_AutoHandle *ah = cls;
  unsigned char reply_buf[1024];
  ssize_t rlen;
  struct sockaddr_in answer;
  const struct GNUNET_SCHEDULER_TaskContext *tc;
 
  tc = GNUNET_SCHEDULER_get_task_context ();
  if ((0 != (tc->reason & GNUNET_SCHEDULER_REASON_READ_READY)) &&
      (GNUNET_NETWORK_fdset_isset (tc->read_ready,
                                   lsock4)))
  {
    rlen = GNUNET_NETWORK_socket_recv (lsock4,
                                       reply_buf,
                                       sizeof(reply_buf));
 
    // Lets handle the packet
    memset (&answer, 0, sizeof(struct sockaddr_in));
    if (ah->phase == AUTO_NAT_PUNCHED)
    {
      // Destroy the connection
      GNUNET_NETWORK_socket_close (lsock4);
      GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                  "The external server was able to connect back");
      ah->connected_back = GNUNET_YES;
      next_phase (ah);
    }
    else
    {
      if (GNUNET_OK ==
          GNUNET_NAT_stun_handle_packet (reply_buf, rlen, &answer))
      {
        // Process the answer
        process_stun_reply (&answer, ah);
      }
      else
      {
        next_phase (ah);
      }
    }
  }
  else
  {
    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                "TIMEOUT while waiting for an answer\n");
    if (ah->phase == AUTO_NAT_PUNCHED)
    {
      stop_stun ();
    }
 
    next_phase (ah);
  }
}
 
 
static struct GNUNET_NETWORK_Handle *
bind_v4 ()
{
  struct GNUNET_NETWORK_Handle *ls;
  struct sockaddr_in sa4;
  int eno;
 
  memset (&sa4, 0, sizeof(sa4));
  sa4.sin_family = AF_INET;
  sa4.sin_port = htons (port);
#if HAVE_SOCKADDR_IN_SIN_LEN
  sa4.sin_len = sizeof(sa4);
#endif
  ls = GNUNET_NETWORK_socket_create (AF_INET,
                                     SOCK_DGRAM,
                                     0);
  if (NULL == ls)
    return NULL;
  if (GNUNET_OK !=
      GNUNET_NETWORK_socket_bind (ls, (const struct sockaddr *) &sa4,
                                  sizeof(sa4)))
  {
    eno = errno;
    GNUNET_NETWORK_socket_close (ls);
    errno = eno;
    return NULL;
  }
  return ls;
}
 
 
static void
request_callback (void *cls,
                  enum GNUNET_NAT_StatusCode result)
{
  // struct GNUNET_NAT_AutoHandle *ah = cls;
 
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              "Request callback: stop and quit\n");
  stop_stun ();
 
  // next_phase (ah); FIXME this always will be NULL, as called in test_stun()
}
 
 
static void
result_callback (void *cls,
                 enum GNUNET_NAT_StatusCode ret)
{
  struct GNUNET_NAT_AutoHandle *ah = cls;
 
  if (GNUNET_NAT_ERROR_SUCCESS == ret)
    GNUNET_NAT_test_stop (ah->tst);
  ah->tst = NULL;
  ah->ret = ret;
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              GNUNET_NAT_ERROR_SUCCESS == ret
              ? _ ("NAT traversal with ICMP Server succeeded.\n")
              : _ ("NAT traversal with ICMP Server failed.\n"));
  GNUNET_CONFIGURATION_set_value_string (ah->cfg, "nat", "ENABLE_ICMP_SERVER",
                                         GNUNET_NAT_ERROR_SUCCESS == ret ?
                                         "NO" : "YES");
  next_phase (ah);
}
 
 
static void
reversal_test (void *cls)
{
  struct GNUNET_NAT_AutoHandle *ah = cls;
 
  ah->task = NULL;
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              _ ("Testing connection reversal with ICMP server.\n"));
  GNUNET_RESOLVER_connect (ah->cfg);
  ah->tst = GNUNET_NAT_test_start (ah->cfg, GNUNET_YES, 0, 0, TIMEOUT,
                                   &result_callback, ah);
}
 
 
static void
set_external_ipv4 (void *cls,
                   const struct in_addr *addr,
                   enum GNUNET_NAT_StatusCode ret)
{
  struct GNUNET_NAT_AutoHandle *ah = cls;
  char buf[INET_ADDRSTRLEN];
 
  ah->eh = NULL;
  ah->ret = ret;
  if (GNUNET_NAT_ERROR_SUCCESS != ret)
  {
    next_phase (ah);
    return;
  }
  /* enable 'behind nat' */
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              _ ("Detected external IP `%s'\n"),
              inet_ntop (AF_INET,
                         addr,
                         buf,
                         sizeof(buf)));
  GNUNET_CONFIGURATION_set_value_string (ah->cfg, "nat", "BEHIND_NAT", "YES");
 
  /* set external IP address */
  if (NULL == inet_ntop (AF_INET, addr, buf, sizeof(buf)))
  {
    GNUNET_break (0);
    /* actually, this should never happen, as the caller already executed just
     * this check, but for consistency (eg: future changes in the caller)
     * we still need to report this error...
     */
    ah->ret = GNUNET_NAT_ERROR_EXTERNAL_IP_ADDRESS_INVALID;
    next_phase (ah);
    return;
  }
  GNUNET_CONFIGURATION_set_value_string (ah->cfg, "nat", "EXTERNAL_ADDRESS",
                                         buf);
  ah->upnp_set_external_address = GNUNET_YES;
  next_phase (ah);
}
 
 
static void
test_external_ip (struct GNUNET_NAT_AutoHandle *ah)
{
  if (GNUNET_NAT_ERROR_SUCCESS != ah->ret)
    next_phase (ah);
 
  // FIXME: CPS?
  /* try to detect external IP */
  ah->eh = GNUNET_NAT_mini_get_external_ipv4 (TIMEOUT,
                                              &set_external_ipv4, ah);
}
 
 
static void
test_stun (struct GNUNET_NAT_AutoHandle *ah)
{
  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "Running STUN test\n");
 
  /* Get port from the configuration */
  if (GNUNET_OK !=
      GNUNET_CONFIGURATION_get_value_number (ah->cfg,
                                             "transport-udp",
                                             "PORT",
                                             &port))
  {
    port = 2086;
  }
 
  // Lets create the socket
  lsock4 = bind_v4 ();
  if (NULL == lsock4)
  {
    GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR, "bind");
    next_phase (ah);
    return;
  }
  else
  {
    // Lets call our function now when it accepts
    ltask4 = GNUNET_SCHEDULER_add_read_net (NAT_SERVER_TIMEOUT,
                                            lsock4,
                                            &do_udp_read,
                                            ah);
  }
 
 
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "STUN service listens on port %u\n",
              (unsigned int) port);
  if (GNUNET_NO ==
      GNUNET_NAT_stun_make_request (stun_server,
                                    stun_port,
                                    lsock4,
                                    &request_callback,
                                    NULL))
  {
    /*An error happened*/
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "STUN error, stopping\n");
    stop_stun ();
    next_phase (ah);
  }
}
 
 
static int
process_if (void *cls,
            const char *name,
            int isDefault,
            const struct sockaddr *addr,
            const struct sockaddr *broadcast_addr,
            const struct sockaddr *netmask,
            socklen_t addrlen)
{
  struct GNUNET_NAT_AutoHandle *ah = cls;
  const struct sockaddr_in *in;
  char buf[INET_ADDRSTRLEN];
 
 
  if ((sizeof(struct sockaddr_in6) == addrlen) &&
      (0 != GNUNET_memcmp (&in6addr_loopback, &((const struct
                                                 sockaddr_in6 *) addr)->
                           sin6_addr)) &&
      (! IN6_IS_ADDR_LINKLOCAL (&((const struct
                                   sockaddr_in6 *) addr)->sin6_addr)))
  {
    ah->have_v6 = GNUNET_YES;
    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                _ (
                  "This system has a global IPv6 address, setting IPv6 to supported.\n"));
 
    return GNUNET_OK;
  }
  if (addrlen != sizeof(struct sockaddr_in))
    return GNUNET_OK;
  in = (const struct sockaddr_in *) addr;
 
 
  /* set internal IP address */
  if (NULL == inet_ntop (AF_INET, &in->sin_addr, buf, sizeof(buf)))
  {
    GNUNET_break (0);
    return GNUNET_OK;
  }
  GNUNET_CONFIGURATION_set_value_string (ah->cfg, "nat", "INTERNAL_ADDRESS",
                                         buf);
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              _ ("Detected internal network address `%s'.\n"),
              buf);
 
 
  ah->ret = GNUNET_NAT_ERROR_SUCCESS;
 
  /* Check if our internal IP is the same as the External detect by STUN*/
  if (ah->stun_ip && (strcmp (buf, ah->stun_ip) == 0))
  {
    ah->internal_ip_is_public = GNUNET_YES;
    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                "A internal IP is the sameas the external");
    /* No need to continue*/
    return GNUNET_SYSERR;
  }
 
  /* no need to continue iteration if we found the default */
  if (! isDefault)
    return GNUNET_OK;
  else
    return GNUNET_SYSERR;
}
 
 
static void
test_local_ip (struct GNUNET_NAT_AutoHandle *ah)
{
  ah->have_v6 = GNUNET_NO;
  ah->ret = GNUNET_NAT_ERROR_NO_VALID_IF_IP_COMBO; // reset to success if any of the IFs in below iterator has a valid IP
  GNUNET_OS_network_interfaces_list (&process_if, ah);
 
  GNUNET_CONFIGURATION_set_value_string (ah->cfg, "nat", "DISABLEV6",
                                         (GNUNET_YES == ah->have_v6) ? "NO" :
                                         "YES");
  next_phase (ah);
}
 
 
static void
mq_error_handler (void *cls,
                  enum GNUNET_MQ_Error error)
{
  struct GNUNET_NAT_AutoHandle *ah = cls;
 
  GNUNET_MQ_destroy (ah->mq);
  ah->mq = NULL;
  /* wait a bit first? */
  next_phase (ah);
}
 
 
static void
test_nat_punched (struct GNUNET_NAT_AutoHandle *ah)
{
  struct GNUNET_NAT_TestMessage *msg;
  struct GNUNET_MQ_Envelope *env;
 
  if (! ah->stun_ip)
  {
    LOG (GNUNET_ERROR_TYPE_INFO,
         "We don't have a STUN IP");
    next_phase (ah);
    return;
  }
 
  LOG (GNUNET_ERROR_TYPE_INFO,
       "Asking gnunet-nat-server to connect to `%s'\n",
       ah->stun_ip);
  ah->mq = GNUNET_CLIENT_connect (ah->cfg,
                                  "gnunet-nat-server",
                                  NULL,
                                  &mq_error_handler,
                                  ah);
  if (NULL == ah->mq)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                _ ("Failed to connect to `gnunet-nat-server'\n"));
    next_phase (ah);
    return;
  }
  env = GNUNET_MQ_msg (msg,
                       GNUNET_MESSAGE_TYPE_NAT_TEST);
  msg->dst_ipv4 = inet_addr (ah->stun_ip);
  msg->dport = htons (ah->stun_port);
  msg->data = port;
  msg->is_tcp = htonl ((uint32_t) GNUNET_NO);
  GNUNET_MQ_send (ah->mq,
                  env);
  if (NULL != ltask4)
  {
    GNUNET_SCHEDULER_cancel (ltask4);
    ltask4 = GNUNET_SCHEDULER_add_read_net (NAT_SERVER_TIMEOUT,
                                            lsock4,
                                            &do_udp_read,
                                            ah);
  }
}
 
 
static void
test_upnpc (struct GNUNET_NAT_AutoHandle *ah)
{
  int have_upnpc;
 
  if (GNUNET_NAT_ERROR_SUCCESS != ah->ret)
    next_phase (ah);
 
  // test if upnpc is available
  have_upnpc = (GNUNET_SYSERR !=
                GNUNET_OS_check_helper_binary ("upnpc", GNUNET_NO, NULL));
  // FIXME: test if upnpc is actually working, that is, if transports start to work once we use UPnP
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              (have_upnpc)
              ? _ ("upnpc found, enabling its use\n")
              : _ ("upnpc not found\n"));
  GNUNET_CONFIGURATION_set_value_string (ah->cfg, "nat", "ENABLE_UPNP",
                                         (GNUNET_YES == have_upnpc) ? "YES" :
                                         "NO");
  next_phase (ah);
}
 
 
static void
test_icmp_server (struct GNUNET_NAT_AutoHandle *ah)
{
  int ext_ip;
  int nated;
  int binary;
  char *tmp;
  char *helper;
 
  ext_ip = GNUNET_NO;
  nated = GNUNET_NO;
  binary = GNUNET_NO;
 
  tmp = NULL;
  helper = GNUNET_OS_get_libexec_binary_path ("gnunet-helper-nat-server");
  if ((GNUNET_OK ==
       GNUNET_CONFIGURATION_get_value_string (ah->cfg,
                                              "nat",
                                              "EXTERNAL_ADDRESS",
                                              &tmp)) &&
      (0 < strlen (tmp)))
  {
    ext_ip = GNUNET_OK;
    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                _ (
                  "test_icmp_server not possible, as we have no public IPv4 address\n"));
  }
  else
    goto err;
 
  if (GNUNET_YES ==
      GNUNET_CONFIGURATION_get_value_yesno (ah->cfg,
                                            "nat",
                                            "BEHIND_NAT"))
  {
    nated = GNUNET_YES;
    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                _ (
                  "test_icmp_server not possible, as we are not behind NAT\n"));
  }
  else
    goto err;
 
  if (GNUNET_YES ==
      GNUNET_OS_check_helper_binary (helper,
                                     GNUNET_YES,
                                     "-d 127.0.0.1"))
  {
    binary = GNUNET_OK;   // use localhost as source for that one udp-port, ok for testing
    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                _ ("No working gnunet-helper-nat-server found\n"));
  }
err:
  GNUNET_free (tmp);
  GNUNET_free (helper);
 
  if ((GNUNET_OK == ext_ip) &&
      (GNUNET_YES == nated) &&
      (GNUNET_OK == binary))
    ah->task = GNUNET_SCHEDULER_add_now (&reversal_test,
                                         ah);
  else
    next_phase (ah);
}
 
 
static void
test_icmp_client (struct GNUNET_NAT_AutoHandle *ah)
{
  char *tmp;
  char *helper;
 
  tmp = NULL;
  helper = GNUNET_OS_get_libexec_binary_path ("gnunet-helper-nat-client");
  if ((GNUNET_OK ==
       GNUNET_CONFIGURATION_get_value_string (ah->cfg,
                                              "nat",
                                              "INTERNAL_ADDRESS",
                                              &tmp)) &&
      (0 < strlen (tmp)))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                _ (
                  "test_icmp_client not possible, as we have no internal IPv4 address\n"));
  }
  else
    goto err;
 
  if (GNUNET_YES !=
      GNUNET_CONFIGURATION_get_value_yesno (ah->cfg,
                                            "nat",
                                            "BEHIND_NAT"))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                _ (
                  "test_icmp_server not possible, as we are not behind NAT\n"));
  }
  else
    goto err;
 
  if (GNUNET_YES ==
      GNUNET_OS_check_helper_binary (helper,
                                     GNUNET_YES,
                                     "-d 127.0.0.1 127.0.0.2 42"))
  {
    // none of these parameters are actually used in privilege testing mode
    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                _ ("No working gnunet-helper-nat-server found\n"));
  }
err:
  GNUNET_free (tmp);
  GNUNET_free (helper);
 
  next_phase (ah);
}
 
 
static void
next_phase (struct GNUNET_NAT_AutoHandle *ah)
{
  struct GNUNET_CONFIGURATION_Handle *diff;
 
  ah->phase++;
  switch (ah->phase)
  {
  case AUTO_INIT:
    GNUNET_assert (0);
    break;
 
  case AUTO_EXTERNAL_IP:
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Will run AUTO_EXTERNAL_IP\n");
    test_external_ip (ah);
    break;
 
  case AUTO_STUN:
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Will run AUTO_STUN\n");
    test_stun (ah);
    break;
 
  case AUTO_LOCAL_IP:
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Will run AUTO_LOCAL_IP\n");
    test_local_ip (ah);
    break;
 
  case AUTO_NAT_PUNCHED:
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Will run AUTO_NAT_PUNCHED\n");
    test_nat_punched (ah);
    break;
 
  case AUTO_UPNPC:
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Will run AUTO_UPNPC\n");
    test_upnpc (ah);
    break;
 
  case AUTO_ICMP_SERVER:
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Will run AUTO_ICMP_SERVER\n");
    test_icmp_server (ah);
    break;
 
  case AUTO_ICMP_CLIENT:
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Will run AUTO_ICMP_CLIENT\n");
    test_icmp_client (ah);
    break;
 
  case AUTO_DONE:
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Done with tests\n");
    if (! ah->internal_ip_is_public)
    {
      GNUNET_CONFIGURATION_set_value_string (ah->cfg,
                                             "nat",
                                             "BEHIND_NAT",
                                             "YES");
 
      if (ah->connected_back)
      {
        GNUNET_CONFIGURATION_set_value_string (ah->cfg,
                                               "nat",
                                               "PUNCHED_NAT",
                                               "YES");
      }
      else
      {
        GNUNET_CONFIGURATION_set_value_string (ah->cfg,
                                               "nat",
                                               "PUNCHED_NAT",
                                               "NO");
      }
 
      if (ah->stun_ip)
      {
        GNUNET_CONFIGURATION_set_value_string (ah->cfg,
                                               "nat",
                                               "EXTERNAL_ADDRESS",
                                               ah->stun_ip);
        if (ah->connected_back)
        {
          ah->type = GNUNET_NAT_TYPE_STUN_PUNCHED_NAT;
          GNUNET_CONFIGURATION_set_value_string (ah->cfg,
                                                 "nat",
                                                 "USE_STUN",
                                                 "YES");
        }
        else
        {
          ah->type = GNUNET_NAT_TYPE_UNREACHABLE_NAT;
          GNUNET_CONFIGURATION_set_value_string (ah->cfg,
                                                 "nat",
                                                 "USE_STUN",
                                                 "NO");
        }
      }
      if (0 != ah->stun_port)
      {
        GNUNET_CONFIGURATION_set_value_number (ah->cfg,
                                               "transport-udp",
                                               "ADVERTISED_PORT",
                                               ah->stun_port);
      }
    }
    else
    {
      // The internal IP is the same as public, but we didn't got a incoming connection
      if (ah->connected_back)
      {
        ah->type = GNUNET_NAT_TYPE_NO_NAT;
        GNUNET_CONFIGURATION_set_value_string (ah->cfg,
                                               "nat",
                                               "BEHIND_NAT",
                                               "NO");
      }
      else
      {
        GNUNET_CONFIGURATION_set_value_string (ah->cfg,
                                               "nat",
                                               "BEHIND_NAT",
                                               "YES");
        ah->type = GNUNET_NAT_TYPE_UNREACHABLE_NAT;
        if (ah->stun_ip)
        {
          GNUNET_CONFIGURATION_set_value_string (ah->cfg,
                                                 "nat",
                                                 "EXTERNAL_ADDRESS",
                                                 ah->stun_ip);
        }
        if (0 != ah->stun_port)
        {
          GNUNET_CONFIGURATION_set_value_number (ah->cfg,
                                                 "transport-udp",
                                                 "ADVERTISED_PORT",
                                                 ah->stun_port);
        }
      }
    }
 
    diff = GNUNET_CONFIGURATION_get_diff (ah->initial_cfg,
                                          ah->cfg);
 
 
    ah->fin_cb (ah->fin_cb_cls,
                diff,
                ah->ret,
                ah->type);
    GNUNET_CONFIGURATION_destroy (diff);
    GNUNET_NAT_autoconfig_cancel (ah);
  }
}
 
 
struct GNUNET_NAT_AutoHandle *
GNUNET_NAT_autoconfig_start (const struct GNUNET_CONFIGURATION_Handle *cfg,
                             GNUNET_NAT_AutoResultCallback cb,
                             void *cb_cls)
{
  struct GNUNET_NAT_AutoHandle *ah;
 
  ah = GNUNET_new (struct GNUNET_NAT_AutoHandle);
  ah->fin_cb = cb;
  ah->fin_cb_cls = cb_cls;
  ah->ret = GNUNET_NAT_ERROR_SUCCESS;
  ah->cfg = GNUNET_CONFIGURATION_dup (cfg);
  ah->initial_cfg = GNUNET_CONFIGURATION_dup (cfg);
 
  /* never use loopback addresses if user wanted autoconfiguration */
  GNUNET_CONFIGURATION_set_value_string (ah->cfg,
                                         "nat",
                                         "USE_LOCALADDR",
                                         "NO");
 
  next_phase (ah);
  return ah;
}
 
 
void
GNUNET_NAT_autoconfig_cancel (struct GNUNET_NAT_AutoHandle *ah)
{
  if (NULL != ah->tst)
  {
    GNUNET_NAT_test_stop (ah->tst);
    ah->tst = NULL;
  }
  if (NULL != ah->eh)
  {
    GNUNET_NAT_mini_get_external_ipv4_cancel (ah->eh);
    ah->eh = NULL;
  }
  if (NULL != ah->mq)
  {
    GNUNET_MQ_destroy (ah->mq);
    ah->mq = NULL;
  }
  if (NULL != ah->task)
  {
    GNUNET_SCHEDULER_cancel (ah->task);
    ah->task = NULL;
  }
  GNUNET_CONFIGURATION_destroy (ah->cfg);
  GNUNET_CONFIGURATION_destroy (ah->initial_cfg);
  GNUNET_free (ah);
}
 
 
/* end of nat_auto.c */