/*
     This file is part of GNUnet.
     Copyright (C) 2011-2014, 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 nat/gnunet-service-nat_mini.c
 * @brief functions for interaction with miniupnp; tested with miniupnpc 1.5
 * @author Christian Grothoff
 */
#include "platform.h"
#include "gnunet_util_lib.h"
#include "gnunet_nat_service.h"
#include "gnunet-service-nat_mini.h"
#include "nat.h"

#define LOG(kind, ...) GNUNET_log_from (kind, "nat", __VA_ARGS__)

/**
 * How long do we give upnpc to create a mapping?
 */
#define MAP_TIMEOUT GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, 15)

/**
 * How long do we give upnpc to remove a mapping?
 */
#define UNMAP_TIMEOUT \
  GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, 1)

/**
 * How often do we check for changes in the mapping?
 */
#define MAP_REFRESH_FREQ \
  GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MINUTES, 5)


/* ************************* external-ip calling ************************ */

/**
 * Opaque handle to cancel "GNUNET_NAT_mini_get_external_ipv4" operation.
 */
struct GNUNET_NAT_ExternalHandle
{
  /**
   * Function to call with the result.
   */
  GNUNET_NAT_IPCallback cb;

  /**
   * Closure for @e cb.
   */
  void *cb_cls;

  /**
   * Read task.
   */
  struct GNUNET_SCHEDULER_Task *task;

  /**
   * Handle to `external-ip` process.
   */
  struct GNUNET_OS_Process *eip;

  /**
   * Handle to stdout pipe of `external-ip`.
   */
  struct GNUNET_DISK_PipeHandle *opipe;

  /**
   * Read handle of @e opipe.
   */
  const struct GNUNET_DISK_FileHandle *r;

  /**
   * Number of bytes in @e buf that are valid.
   */
  size_t off;

  /**
   * Destination of our read operation (output of 'external-ip').
   */
  char buf[17];

  /**
   * Error code for better debugging and user feedback
   */
  enum GNUNET_NAT_StatusCode ret;
};


/**
 * Read the output of `external-ip` into `buf`.  When complete, parse
 * the address and call our callback.
 *
 * @param cls the `struct GNUNET_NAT_ExternalHandle`
 */
static void
read_external_ipv4 (void *cls)
{
  struct GNUNET_NAT_ExternalHandle *eh = cls;
  ssize_t ret;
  struct in_addr addr;

  eh->task = NULL;
  ret = GNUNET_DISK_file_read (eh->r,
                               &eh->buf[eh->off],
                               sizeof(eh->buf) - eh->off);
  if (ret > 0)
  {
    /* try to read more */
    eh->off += ret;
    eh->task = GNUNET_SCHEDULER_add_read_file (GNUNET_TIME_UNIT_FOREVER_REL,
                                               eh->r,
                                               &read_external_ipv4,
                                               eh);
    return;
  }
  eh->ret = GNUNET_NAT_ERROR_EXTERNAL_IP_UTILITY_OUTPUT_INVALID;
  if ((eh->off > 7) && (eh->buf[eh->off - 1] == '\n'))
  {
    eh->buf[eh->off - 1] = '\0';
    if (1 == inet_pton (AF_INET, eh->buf, &addr))
    {
      if (0 == addr.s_addr)
        eh->ret =
          GNUNET_NAT_ERROR_EXTERNAL_IP_ADDRESS_INVALID;     /* got 0.0.0.0 */
      else
        eh->ret = GNUNET_NAT_ERROR_SUCCESS;
    }
  }
  eh->cb (eh->cb_cls,
          (GNUNET_NAT_ERROR_SUCCESS == eh->ret) ? &addr : NULL,
          eh->ret);
  GNUNET_NAT_mini_get_external_ipv4_cancel_ (eh);
}


/**
 * (Asynchronously) signal error invoking `external-ip` to client.
 *
 * @param cls the `struct GNUNET_NAT_ExternalHandle` (freed)
 */
static void
signal_external_ip_error (void *cls)
{
  struct GNUNET_NAT_ExternalHandle *eh = cls;

  eh->task = NULL;
  eh->cb (eh->cb_cls, NULL, eh->ret);
  GNUNET_free (eh);
}


/**
 * Try to get the external IPv4 address of this peer.
 *
 * @param cb function to call with result
 * @param cb_cls closure for @a cb
 * @return handle for cancellation (can only be used until @a cb is called), never NULL
 */
struct GNUNET_NAT_ExternalHandle *
GNUNET_NAT_mini_get_external_ipv4_ (GNUNET_NAT_IPCallback cb, void *cb_cls)
{
  struct GNUNET_NAT_ExternalHandle *eh;

  eh = GNUNET_new (struct GNUNET_NAT_ExternalHandle);
  eh->cb = cb;
  eh->cb_cls = cb_cls;
  eh->ret = GNUNET_NAT_ERROR_SUCCESS;
  if (GNUNET_SYSERR ==
      GNUNET_OS_check_helper_binary ("external-ip", GNUNET_NO, NULL))
  {
    LOG (GNUNET_ERROR_TYPE_INFO, _ ("`external-ip' command not found\n"));
    eh->ret = GNUNET_NAT_ERROR_EXTERNAL_IP_UTILITY_NOT_FOUND;
    eh->task = GNUNET_SCHEDULER_add_now (&signal_external_ip_error, eh);
    return eh;
  }
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Running `external-ip' to determine our external IP\n");
  eh->opipe = GNUNET_DISK_pipe (GNUNET_YES, GNUNET_YES, GNUNET_NO, GNUNET_YES);
  if (NULL == eh->opipe)
  {
    eh->ret = GNUNET_NAT_ERROR_IPC_FAILURE;
    eh->task = GNUNET_SCHEDULER_add_now (&signal_external_ip_error, eh);
    return eh;
  }
  eh->eip = GNUNET_OS_start_process (GNUNET_NO,
                                     0,
                                     NULL,
                                     eh->opipe,
                                     NULL,
                                     "external-ip",
                                     "external-ip",
                                     NULL);
  if (NULL == eh->eip)
  {
    GNUNET_DISK_pipe_close (eh->opipe);
    eh->ret = GNUNET_NAT_ERROR_EXTERNAL_IP_UTILITY_FAILED;
    eh->task = GNUNET_SCHEDULER_add_now (&signal_external_ip_error, eh);
    return eh;
  }
  GNUNET_DISK_pipe_close_end (eh->opipe, GNUNET_DISK_PIPE_END_WRITE);
  eh->r = GNUNET_DISK_pipe_handle (eh->opipe, GNUNET_DISK_PIPE_END_READ);
  eh->task = GNUNET_SCHEDULER_add_read_file (GNUNET_TIME_UNIT_FOREVER_REL,
                                             eh->r,
                                             &read_external_ipv4,
                                             eh);
  return eh;
}


/**
 * Cancel operation.
 *
 * @param eh operation to cancel
 */
void
GNUNET_NAT_mini_get_external_ipv4_cancel_ (struct GNUNET_NAT_ExternalHandle *eh)
{
  if (NULL != eh->eip)
  {
    (void) GNUNET_OS_process_kill (eh->eip, SIGKILL);
    GNUNET_break (GNUNET_OK == GNUNET_OS_process_wait (eh->eip));
    GNUNET_OS_process_destroy (eh->eip);
  }
  if (NULL != eh->opipe)
  {
    GNUNET_DISK_pipe_close (eh->opipe);
    eh->opipe = NULL;
  }
  if (NULL != eh->task)
  {
    GNUNET_SCHEDULER_cancel (eh->task);
    eh->task = NULL;
  }
  GNUNET_free (eh);
}


/* ************************* upnpc calling ************************ */


/**
 * Handle to a mapping created with upnpc.
 */
struct GNUNET_NAT_MiniHandle
{
  /**
   * Function to call on mapping changes.
   */
  GNUNET_NAT_MiniAddressCallback ac;

  /**
   * Closure for @e ac.
   */
  void *ac_cls;

  /**
   * Command used to install the map.
   */
  struct GNUNET_OS_CommandHandle *map_cmd;

  /**
   * Command used to refresh our map information.
   */
  struct GNUNET_OS_CommandHandle *refresh_cmd;

  /**
   * Command used to remove the mapping.
   */
  struct GNUNET_OS_CommandHandle *unmap_cmd;

  /**
   * Our current external mapping (if we have one).
   */
  struct sockaddr_in current_addr;

  /**
   * We check the mapping periodically to see if it
   * still works.  This task triggers the check.
   */
  struct GNUNET_SCHEDULER_Task *refresh_task;

  /**
   * Are we mapping TCP or UDP?
   */
  int is_tcp;

  /**
   * Did we succeed with creating a mapping?
   */
  int did_map;

  /**
   * Did we find our mapping during refresh scan?
   */
  int found;

  /**
   * Which port are we mapping?
   */
  uint16_t port;
};


/**
 * Run "upnpc -l" to find out if our mapping changed.
 *
 * @param cls the `struct GNUNET_NAT_MiniHandle`
 */
static void
do_refresh (void *cls);


/**
 * Process the output from the "upnpc -r" command.
 *
 * @param cls the `struct GNUNET_NAT_MiniHandle`
 * @param line line of output, NULL at the end
 */
static void
process_map_output (void *cls, const char *line);


/**
 * Run "upnpc -r" to map our internal port.
 *
 * @param mini our handle
 */
static void
run_upnpc_r (struct GNUNET_NAT_MiniHandle *mini)
{
  char pstr[6];

  GNUNET_snprintf (pstr, sizeof(pstr), "%u", (unsigned int) mini->port);
  mini->map_cmd = GNUNET_OS_command_run (&process_map_output,
                                         mini,
                                         MAP_TIMEOUT,
                                         "upnpc",
                                         "upnpc",
                                         "-r",
                                         pstr,
                                         mini->is_tcp ? "tcp" : "udp",
                                         NULL);
  if (NULL == mini->map_cmd)
  {
    mini->ac (mini->ac_cls,
              GNUNET_SYSERR,
              NULL,
              0,
              GNUNET_NAT_ERROR_UPNPC_FAILED);
    return;
  }
}


/**
 * Process the output from "upnpc -l" to see if our
 * external mapping changed.  If so, do the notifications.
 *
 * @param cls the `struct GNUNET_NAT_MiniHandle`
 * @param line line of output, NULL at the end
 */
static void
process_refresh_output (void *cls, const char *line)
{
  struct GNUNET_NAT_MiniHandle *mini = cls;
  char pstr[9];
  const char *s;
  unsigned int nport;
  struct in_addr exip;

  if (NULL == line)
  {
    GNUNET_OS_command_stop (mini->refresh_cmd);
    mini->refresh_cmd = NULL;
    if (GNUNET_NO == mini->found)
    {
      /* mapping disappeared, try to re-create */
      if (GNUNET_YES == mini->did_map)
      {
        mini->ac (mini->ac_cls,
                  GNUNET_NO,
                  (const struct sockaddr *) &mini->current_addr,
                  sizeof(mini->current_addr),
                  GNUNET_NAT_ERROR_SUCCESS);
        mini->did_map = GNUNET_NO;
      }
      run_upnpc_r (mini);
    }
    return;
  }
  if (! mini->did_map)
    return; /* never mapped, won't find our mapping anyway */

  /* we're looking for output of the form:
  * "ExternalIPAddress = 12.134.41.124" */

  s = strstr (line, "ExternalIPAddress = ");
  if (NULL != s)
  {
    s += strlen ("ExternalIPAddress = ");
    if (1 != inet_pton (AF_INET, s, &exip))
      return;   /* skip */
    if (exip.s_addr == mini->current_addr.sin_addr.s_addr)
      return;   /* no change */
    /* update mapping */
    mini->ac (mini->ac_cls,
              GNUNET_NO,
              (const struct sockaddr *) &mini->current_addr,
              sizeof(mini->current_addr),
              GNUNET_NAT_ERROR_SUCCESS);
    mini->current_addr.sin_addr = exip;
    mini->ac (mini->ac_cls,
              GNUNET_YES,
              (const struct sockaddr *) &mini->current_addr,
              sizeof(mini->current_addr),
              GNUNET_NAT_ERROR_SUCCESS);
    return;
  }
  /*
   * we're looking for output of the form:
   *
   * "0 TCP  3000->192.168.2.150:3000  'libminiupnpc' ''"
   * "1 UDP  3001->192.168.2.150:3001  'libminiupnpc' ''"
   *
   * the pattern we look for is:
   *
   * "%s TCP  PORT->STRING:OURPORT *" or
   * "%s UDP  PORT->STRING:OURPORT *"
   */GNUNET_snprintf (pstr, sizeof(pstr), ":%u ", mini->port);
  if (NULL == (s = strstr (line, "->")))
    return; /* skip */
  if (NULL == strstr (s, pstr))
    return; /* skip */
  if (1 != sscanf (line,
                   (mini->is_tcp) ? "%*u TCP  %u->%*s:%*u %*s"
                   : "%*u UDP  %u->%*s:%*u %*s",
                   &nport))
    return; /* skip */
  mini->found = GNUNET_YES;
  if (nport == ntohs (mini->current_addr.sin_port))
    return; /* no change */

  /* external port changed, update mapping */
  mini->ac (mini->ac_cls,
            GNUNET_NO,
            (const struct sockaddr *) &mini->current_addr,
            sizeof(mini->current_addr),
            GNUNET_NAT_ERROR_SUCCESS);
  mini->current_addr.sin_port = htons ((uint16_t) nport);
  mini->ac (mini->ac_cls,
            GNUNET_YES,
            (const struct sockaddr *) &mini->current_addr,
            sizeof(mini->current_addr),
            GNUNET_NAT_ERROR_SUCCESS);
}


/**
 * Run "upnpc -l" to find out if our mapping changed.
 *
 * @param cls the 'struct GNUNET_NAT_MiniHandle'
 */
static void
do_refresh (void *cls)
{
  struct GNUNET_NAT_MiniHandle *mini = cls;
  int ac;

  mini->refresh_task =
    GNUNET_SCHEDULER_add_delayed (MAP_REFRESH_FREQ, &do_refresh, mini);
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Running `upnpc' to check if our mapping still exists\n");
  mini->found = GNUNET_NO;
  ac = GNUNET_NO;
  if (NULL != mini->map_cmd)
  {
    /* took way too long, abort it! */
    GNUNET_OS_command_stop (mini->map_cmd);
    mini->map_cmd = NULL;
    ac = GNUNET_YES;
  }
  if (NULL != mini->refresh_cmd)
  {
    /* took way too long, abort it! */
    GNUNET_OS_command_stop (mini->refresh_cmd);
    mini->refresh_cmd = NULL;
    ac = GNUNET_YES;
  }
  mini->refresh_cmd = GNUNET_OS_command_run (&process_refresh_output,
                                             mini,
                                             MAP_TIMEOUT,
                                             "upnpc",
                                             "upnpc",
                                             "-l",
                                             NULL);
  if (GNUNET_YES == ac)
    mini->ac (mini->ac_cls,
              GNUNET_SYSERR,
              NULL,
              0,
              GNUNET_NAT_ERROR_UPNPC_TIMEOUT);
}


/**
 * Process the output from the 'upnpc -r' command.
 *
 * @param cls the `struct GNUNET_NAT_MiniHandle`
 * @param line line of output, NULL at the end
 */
static void
process_map_output (void *cls, const char *line)
{
  struct GNUNET_NAT_MiniHandle *mini = cls;
  const char *ipaddr;
  char *ipa;
  const char *pstr;
  unsigned int port;

  if (NULL == line)
  {
    GNUNET_OS_command_stop (mini->map_cmd);
    mini->map_cmd = NULL;
    if (GNUNET_YES != mini->did_map)
      mini->ac (mini->ac_cls,
                GNUNET_SYSERR,
                NULL,
                0,
                GNUNET_NAT_ERROR_UPNPC_PORTMAP_FAILED);
    if (NULL == mini->refresh_task)
      mini->refresh_task =
        GNUNET_SCHEDULER_add_delayed (MAP_REFRESH_FREQ, &do_refresh, mini);
    return;
  }
  /*
   * The upnpc output we're after looks like this:
   *
   * "external 87.123.42.204:3000 TCP is redirected to internal 192.168.2.150:3000"
   */if ((NULL == (ipaddr = strstr (line, " "))) ||
      (NULL == (pstr = strstr (ipaddr, ":"))) ||
      (1 != sscanf (pstr + 1, "%u", &port)))
  {
    return;   /* skip line */
  }
  ipa = GNUNET_strdup (ipaddr + 1);
  strstr (ipa, ":")[0] = '\0';
  if (1 != inet_pton (AF_INET, ipa, &mini->current_addr.sin_addr))
  {
    GNUNET_free (ipa);
    return;   /* skip line */
  }
  GNUNET_free (ipa);

  mini->current_addr.sin_port = htons (port);
  mini->current_addr.sin_family = AF_INET;
#if HAVE_SOCKADDR_IN_SIN_LEN
  mini->current_addr.sin_len = sizeof(struct sockaddr_in);
#endif
  mini->did_map = GNUNET_YES;
  mini->ac (mini->ac_cls,
            GNUNET_YES,
            (const struct sockaddr *) &mini->current_addr,
            sizeof(mini->current_addr),
            GNUNET_NAT_ERROR_SUCCESS);
}


/**
 * Start mapping the given port using (mini)upnpc.  This function
 * should typically not be used directly (it is used within the
 * general-purpose #GNUNET_NAT_register() code).  However, it can be
 * used if specifically UPnP-based NAT traversal is to be used or
 * tested.
 *
 * @param port port to map
 * @param is_tcp #GNUNET_YES to map TCP, #GNUNET_NO for UDP
 * @param ac function to call with mapping result
 * @param ac_cls closure for @a ac
 * @return NULL on error (no 'upnpc' installed)
 */
struct GNUNET_NAT_MiniHandle *
GNUNET_NAT_mini_map_start (uint16_t port,
                           int is_tcp,
                           GNUNET_NAT_MiniAddressCallback ac,
                           void *ac_cls)
{
  struct GNUNET_NAT_MiniHandle *ret;

  if (GNUNET_SYSERR == GNUNET_OS_check_helper_binary ("upnpc", GNUNET_NO, NULL))
  {
    LOG (GNUNET_ERROR_TYPE_INFO, _ ("`upnpc' command not found\n"));
    ac (ac_cls, GNUNET_SYSERR, NULL, 0, GNUNET_NAT_ERROR_UPNPC_NOT_FOUND);
    return NULL;
  }
  LOG (GNUNET_ERROR_TYPE_DEBUG, "Running `upnpc' to install mapping\n");
  ret = GNUNET_new (struct GNUNET_NAT_MiniHandle);
  ret->ac = ac;
  ret->ac_cls = ac_cls;
  ret->is_tcp = is_tcp;
  ret->port = port;
  ret->refresh_task =
    GNUNET_SCHEDULER_add_delayed (MAP_REFRESH_FREQ, &do_refresh, ret);
  run_upnpc_r (ret);
  return ret;
}


/**
 * Process output from our 'unmap' command.
 *
 * @param cls the `struct GNUNET_NAT_MiniHandle`
 * @param line line of output, NULL at the end
 */
static void
process_unmap_output (void *cls, const char *line)
{
  struct GNUNET_NAT_MiniHandle *mini = cls;

  if (NULL == line)
  {
    LOG (GNUNET_ERROR_TYPE_DEBUG, "UPnP unmap done\n");
    GNUNET_OS_command_stop (mini->unmap_cmd);
    mini->unmap_cmd = NULL;
    GNUNET_free (mini);
    return;
  }
  /* we don't really care about the output... */
}


/**
 * Remove a mapping created with (mini)upnpc.  Calling
 * this function will give 'upnpc' 1s to remove tha mapping,
 * so while this function is non-blocking, a task will be
 * left with the scheduler for up to 1s past this call.
 *
 * @param mini the handle
 */
void
GNUNET_NAT_mini_map_stop (struct GNUNET_NAT_MiniHandle *mini)
{
  char pstr[6];

  if (NULL != mini->refresh_task)
  {
    GNUNET_SCHEDULER_cancel (mini->refresh_task);
    mini->refresh_task = NULL;
  }
  if (NULL != mini->refresh_cmd)
  {
    GNUNET_OS_command_stop (mini->refresh_cmd);
    mini->refresh_cmd = NULL;
  }
  if (NULL != mini->map_cmd)
  {
    GNUNET_OS_command_stop (mini->map_cmd);
    mini->map_cmd = NULL;
  }
  if (GNUNET_NO == mini->did_map)
  {
    GNUNET_free (mini);
    return;
  }
  mini->ac (mini->ac_cls,
            GNUNET_NO,
            (const struct sockaddr *) &mini->current_addr,
            sizeof(mini->current_addr),
            GNUNET_NAT_ERROR_SUCCESS);
  /* Note: oddly enough, deletion uses the external port whereas
   * addition uses the internal port; this rarely matters since they
   * often are the same, but it might... */
  GNUNET_snprintf (pstr,
                   sizeof(pstr),
                   "%u",
                   (unsigned int) ntohs (mini->current_addr.sin_port));
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Unmapping port %u with UPnP\n",
       ntohs (mini->current_addr.sin_port));
  mini->unmap_cmd = GNUNET_OS_command_run (&process_unmap_output,
                                           mini,
                                           UNMAP_TIMEOUT,
                                           "upnpc",
                                           "upnpc",
                                           "-d",
                                           pstr,
                                           mini->is_tcp ? "tcp" : "udp",
                                           NULL);
}


/* end of gnunet-service-nat_mini.c */