/*
     This file is part of GNUnet.
     Copyright (C) 2015, 2016 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
 */

/**
 * @file src/nat/gnunet-nat.c
 * @brief Command-line tool to interact with the NAT service
 * @author Christian Grothoff
 * @author Bruno Cabral
 */
#include "platform.h"
#include "gnunet_util_lib.h"
#include "gnunet_nat_service.h"

/**
 * Value to return from #main().
 */
static int global_ret;

/**
 * Name of section in configuration file to use for
 * additional options.
 */
static char *section_name;

/**
 * Flag set to 1 if we use IPPROTO_UDP.
 */
static int use_udp;

/**
 * Flag set to 1 if we are to listen for connection reversal requests.
 */
static int listen_reversal;

/**
 * Flag set to 1 if we use IPPROTO_TCP.
 */
static int use_tcp;

/**
 * Protocol to use.
 */
static uint8_t proto;

/**
 * Local address to use for connection reversal request.
 */
static char *local_addr;

/**
 * Remote address to use for connection reversal request.
 */
static char *remote_addr;

/**
 * Should we actually bind to #bind_addr and receive and process STUN requests?
 */
static int do_stun;

/**
 * Handle to NAT operation.
 */
static struct GNUNET_NAT_Handle *nh;

/**
 * Listen socket for STUN processing.
 */
static struct GNUNET_NETWORK_Handle *ls;

/**
 * Task for reading STUN packets.
 */
static struct GNUNET_SCHEDULER_Task *rtask;


/**
 * Test if all activities have finished, and if so,
 * terminate.
 */
static void
test_finished ()
{
  if (NULL != nh)
    return;
  if (NULL != rtask)
    return;
  GNUNET_SCHEDULER_shutdown ();
}


/**
 * Signature of the callback passed to #GNUNET_NAT_register() for
 * a function to call whenever our set of 'valid' addresses changes.
 *
 * @param cls closure, NULL
 * @param[in,out] app_ctx location where the app can store stuff
 *                  on add and retrieve it on remove
 * @param add_remove #GNUNET_YES to add a new public IP address,
 *                   #GNUNET_NO to remove a previous (now invalid) one
 * @param ac address class the address belongs to
 * @param addr either the previous or the new public IP address
 * @param addrlen actual length of the @a addr
 */
static void
address_cb (void *cls,
            void **app_ctx,
            int add_remove,
            enum GNUNET_NAT_AddressClass ac,
            const struct sockaddr *addr,
            socklen_t addrlen)
{
  (void) cls;
  (void) app_ctx;

  fprintf (stdout,
           "%s %s (%d)\n",
           add_remove ? "+" : "-",
           GNUNET_a2s (addr, addrlen),
           (int) ac);
}


/**
 * Signature of the callback passed to #GNUNET_NAT_register().
 * for a function to call whenever someone asks us to do connection
 * reversal.
 *
 * @param cls closure, NULL
 * @param remote_addr public IP address of the other peer
 * @param remote_addrlen actual length of the @a remote_addr
 */
static void
reversal_cb (void *cls,
             const struct sockaddr *remote_addr,
             socklen_t remote_addrlen)
{
  GNUNET_log (GNUNET_ERROR_TYPE_MESSAGE,
              "Connection reversal requested by %s\n",
              GNUNET_a2s (remote_addr, remote_addrlen));
}


/**
 * Task run on shutdown.
 *
 * @param cls NULL
 */
static void
do_shutdown (void *cls)
{
  if (NULL != nh)
  {
    GNUNET_NAT_unregister (nh);
    nh = NULL;
  }
  if (NULL != ls)
  {
    GNUNET_NETWORK_socket_close (ls);
    ls = NULL;
  }
  if (NULL != rtask)
  {
    GNUNET_SCHEDULER_cancel (rtask);
    rtask = NULL;
  }
}


/**
 * Task to receive incoming packets for STUN processing.
 */
static void
stun_read_task (void *cls)
{
  ssize_t size;

  rtask = GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_UNIT_FOREVER_REL,
                                         ls,
                                         &stun_read_task,
                                         NULL);
  size = GNUNET_NETWORK_socket_recvfrom_amount (ls);
  if (size > 0)
  {
    GNUNET_break (0);
    GNUNET_SCHEDULER_shutdown ();
    global_ret = 1;
    return;
  }
  {
    char buf[size + 1];
    struct sockaddr_storage sa;
    socklen_t salen = sizeof(sa);
    ssize_t ret;

    ret = GNUNET_NETWORK_socket_recvfrom (ls,
                                          buf,
                                          size + 1,
                                          (struct sockaddr *) &sa,
                                          &salen);
    if (ret != size)
    {
      GNUNET_break (0);
      GNUNET_SCHEDULER_shutdown ();
      global_ret = 1;
      return;
    }
    (void) GNUNET_NAT_stun_handle_packet (nh,
                                          (const struct sockaddr *) &sa,
                                          salen,
                                          buf,
                                          ret);
  }
}


/**
 * Main function that will be run.
 *
 * @param cls closure
 * @param args remaining command-line arguments
 * @param cfgfile name of the configuration file used (for saving, can be NULL!)
 * @param c configuration
 */
static void
run (void *cls,
     char *const *args,
     const char *cfgfile,
     const struct GNUNET_CONFIGURATION_Handle *c)
{
  uint8_t af;
  struct sockaddr *local_sa;
  struct sockaddr *remote_sa;
  socklen_t local_len;
  size_t remote_len;

  if (use_tcp && use_udp)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_MESSAGE, "Cannot use TCP and UDP\n");
    global_ret = 1;
    return;
  }
  proto = 0;
  if (use_tcp)
    proto = IPPROTO_TCP;
  if (use_udp)
    proto = IPPROTO_UDP;

  GNUNET_SCHEDULER_add_shutdown (&do_shutdown, NULL);

  if (0 == proto)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_MESSAGE, "Must specify either TCP or UDP\n");
    global_ret = 1;
    return;
  }
  local_len = 0;
  local_sa = NULL;
  remote_len = 0;
  remote_sa = NULL;
  if (NULL != local_addr)
  {
    local_len =
      (socklen_t) GNUNET_STRINGS_parse_socket_addr (local_addr, &af, &local_sa);
    if (0 == local_len)
    {
      GNUNET_log (GNUNET_ERROR_TYPE_MESSAGE,
                  "Invalid socket address `%s'\n",
                  local_addr);
      goto fail_and_shutdown;
    }
  }

  if (NULL != remote_addr)
  {
    remote_len =
      GNUNET_STRINGS_parse_socket_addr (remote_addr, &af, &remote_sa);
    if (0 == remote_len)
    {
      GNUNET_log (GNUNET_ERROR_TYPE_MESSAGE,
                  "Invalid socket address `%s'\n",
                  remote_addr);
      goto fail_and_shutdown;
    }
  }

  if (NULL != local_addr)
  {
    if (NULL == section_name)
      section_name = GNUNET_strdup ("undefined");
    nh = GNUNET_NAT_register (c,
                              section_name,
                              proto,
                              1,
                              (const struct sockaddr **) &local_sa,
                              &local_len,
                              &address_cb,
                              (listen_reversal) ? &reversal_cb : NULL,
                              NULL);
  }
  else if (listen_reversal)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_MESSAGE,
                "Use of `-W` only effective in combination with `-i`\n");
    goto fail_and_shutdown;
  }

  if (NULL != remote_addr)
  {
    int ret;

    if ((NULL == nh) || (sizeof(struct sockaddr_in) != local_len))
    {
      GNUNET_log (GNUNET_ERROR_TYPE_MESSAGE,
                  "Require IPv4 local address to initiate connection reversal\n");
      goto fail_and_shutdown;
    }
    if (sizeof(struct sockaddr_in) != remote_len)
    {
      GNUNET_log (GNUNET_ERROR_TYPE_MESSAGE,
                  "Require IPv4 reversal target address\n");
      goto fail_and_shutdown;
    }
    GNUNET_assert (AF_INET == local_sa->sa_family);
    GNUNET_assert (AF_INET == remote_sa->sa_family);
    ret = GNUNET_NAT_request_reversal (nh,
                                       (const struct sockaddr_in *) local_sa,
                                       (const struct sockaddr_in *) remote_sa);
    switch (ret)
    {
    case GNUNET_SYSERR:
      GNUNET_log (GNUNET_ERROR_TYPE_MESSAGE,
                  "Connection reversal internal error\n");
      break;

    case GNUNET_NO:
      GNUNET_log (GNUNET_ERROR_TYPE_MESSAGE,
                  "Connection reversal unavailable\n");
      break;

    case GNUNET_OK:
      /* operation in progress */
      break;
    }
  }

  if (do_stun)
  {
    if (NULL == local_addr)
    {
      GNUNET_log (GNUNET_ERROR_TYPE_MESSAGE,
                  "Require local address to support STUN requests\n");
      goto fail_and_shutdown;
    }
    if (IPPROTO_UDP != proto)
    {
      GNUNET_log (GNUNET_ERROR_TYPE_MESSAGE, "STUN only supported over UDP\n");
      goto fail_and_shutdown;
    }
    ls = GNUNET_NETWORK_socket_create (af, SOCK_DGRAM, IPPROTO_UDP);
    if (NULL == ls)
    {
      GNUNET_log (GNUNET_ERROR_TYPE_MESSAGE, "Failed to create socket\n");
      goto fail_and_shutdown;
    }
    if (GNUNET_OK != GNUNET_NETWORK_socket_bind (ls, local_sa, local_len))
    {
      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                  "Failed to bind to %s: %s\n",
                  GNUNET_a2s (local_sa, local_len),
                  strerror (errno));
      goto fail_and_shutdown;
    }
    rtask = GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_UNIT_FOREVER_REL,
                                           ls,
                                           &stun_read_task,
                                           NULL);
  }
  GNUNET_free (remote_sa);
  GNUNET_free (local_sa);
  test_finished ();
  return;
fail_and_shutdown:
  global_ret = 1;
  GNUNET_SCHEDULER_shutdown ();
  GNUNET_free (remote_sa);
  GNUNET_free (local_sa);
}


/**
 * Main function of gnunet-nat
 *
 * @param argc number of command-line arguments
 * @param argv command line
 * @return 0 on success, -1 on error
 */
int
main (int argc, char *const argv[])
{
  struct GNUNET_GETOPT_CommandLineOption options[] = {
    GNUNET_GETOPT_option_string (
      'i',
      "in",
      "ADDRESS",
      gettext_noop ("which IP and port are we locally using to bind/listen to"),
      &local_addr),

    GNUNET_GETOPT_option_string (
      'r',
      "remote",
      "ADDRESS",
      gettext_noop (
        "which remote IP and port should be asked for connection reversal"),
      &remote_addr),

    GNUNET_GETOPT_option_string (
      'S',
      "section",
      NULL,
      gettext_noop (
        "name of configuration section to find additional options, such as manual host punching data"),
      &section_name),

    GNUNET_GETOPT_option_flag ('s',
                               "stun",
                               gettext_noop ("enable STUN processing"),
                               &do_stun),

    GNUNET_GETOPT_option_flag ('t', "tcp", gettext_noop ("use TCP"), &use_tcp),

    GNUNET_GETOPT_option_flag ('u', "udp", gettext_noop ("use UDP"), &use_udp),

    GNUNET_GETOPT_option_flag ('W',
                               "watch",
                               gettext_noop (
                                 "watch for connection reversal requests"),
                               &listen_reversal),
    GNUNET_GETOPT_OPTION_END
  };

  if (GNUNET_OK != GNUNET_STRINGS_get_utf8_args (argc, argv, &argc, &argv))
    return 2;
  if (GNUNET_OK !=
      GNUNET_PROGRAM_run (argc,
                          argv,
                          "gnunet-nat [options]",
                          _ ("GNUnet NAT traversal autoconfigure daemon"),
                          options,
                          &run,
                          NULL))
  {
    global_ret = 1;
  }
  GNUNET_free_nz ((void *) argv);
  return global_ret;
}


/* end of gnunet-nat.c */
