res_stun_monitor.c

Go to the documentation of this file.

/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2010, Digium, Inc.
 *
 * David Vossel <dvossel@digium.com>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*!
 * \file
 * \brief STUN Network Monitor
 *
 * \author David Vossel <dvossel@digium.com>
 */

/*** MODULEINFO
   <support_level>core</support_level>
 ***/

#include "asterisk.h"

ASTERISK_FILE_VERSION(__FILE__, "$Revision: 369681 $")

#include "asterisk/module.h"
#include "asterisk/event.h"
#include "asterisk/sched.h"
#include "asterisk/config.h"
#include "asterisk/stun.h"
#include "asterisk/netsock2.h"
#include "asterisk/lock.h"
#include "asterisk/acl.h"
#include "asterisk/cli.h"

#include <fcntl.h>

#define DEFAULT_MONITOR_REFRESH 30  /*!< Default refresh period in seconds */
#define DEFAULT_RETRIES 3     /*!< retries shown in stun show status
                    matching static retries in stun.c */

static const char stun_conf_file[] = "res_stun_monitor.conf";
static struct ast_sched_context *sched;

static struct {
   /*! STUN monitor protection lock. */
   ast_mutex_t lock;
   /*! Current perceived external address. */
   struct sockaddr_in external_addr;
   /*! STUN server host name. */
   const char *server_hostname;
   /*! Port of STUN server to use */
   unsigned int stun_port;
   /*! Number of seconds between polls to the STUN server for the external address. */
   unsigned int refresh;
   /*! Monitoring STUN socket. */
   int stun_sock;
   /*! TRUE if the STUN monitor is enabled. */
   unsigned int monitor_enabled:1;
   /*! TRUE if the perceived external address is valid/known. */
   unsigned int external_addr_known:1;
   /*! TRUE if we have already griped about a STUN poll failing. */
   unsigned int stun_poll_failed_gripe:1;
} args;

static void stun_close_sock(void)
{
   if (0 <= args.stun_sock) {
      close(args.stun_sock);
      args.stun_sock = -1;
   }
}

/* \brief called by scheduler to send STUN request */
static int stun_monitor_request(const void *blarg)
{
   int res;
   struct sockaddr_in answer;
   static const struct sockaddr_in no_addr = { 0, };

   ast_mutex_lock(&args.lock);
   if (!args.monitor_enabled) {
      goto monitor_request_cleanup;
   }

   if (args.stun_sock < 0) {
      struct ast_sockaddr stun_addr;

      /* STUN socket not open.  Refresh the server DNS address resolution. */
      if (!args.server_hostname) {
         /* No STUN hostname? */
         goto monitor_request_cleanup;
      }

      /* Lookup STUN address. */
      memset(&stun_addr, 0, sizeof(stun_addr));
      stun_addr.ss.ss_family = AF_INET;
      if (ast_get_ip(&stun_addr, args.server_hostname)) {
         /* Lookup failed. */
         ast_log(LOG_WARNING, "Unable to lookup STUN server '%s'\n",
            args.server_hostname);
         goto monitor_request_cleanup;
      }
      ast_sockaddr_set_port(&stun_addr, args.stun_port);

      /* open socket binding */
      args.stun_sock = socket(AF_INET, SOCK_DGRAM, 0);
      if (args.stun_sock < 0) {
         ast_log(LOG_WARNING, "Unable to create STUN socket: %s\n", strerror(errno));
         goto monitor_request_cleanup;
      }
      if (ast_connect(args.stun_sock, &stun_addr)) {
         ast_log(LOG_WARNING, "STUN Failed to connect to %s: %s\n",
            ast_sockaddr_stringify(&stun_addr), strerror(errno));
         stun_close_sock();
         goto monitor_request_cleanup;
      }
   }

   res = ast_stun_request(args.stun_sock, NULL, NULL, &answer);
   if (res) {
      /*
       * STUN request timed out or errored.
       *
       * Refresh the server DNS address resolution next time around.
       */
      if (!args.stun_poll_failed_gripe) {
         args.stun_poll_failed_gripe = 1;
         ast_log(LOG_WARNING, "STUN poll %s. Re-evaluating STUN server address.\n",
            res < 0 ? "failed" : "got no response");
      }
      stun_close_sock();
   } else {
      args.stun_poll_failed_gripe = 0;
      if (memcmp(&no_addr, &answer, sizeof(no_addr))
         && memcmp(&args.external_addr, &answer, sizeof(args.external_addr))) {
         const char *newaddr = ast_strdupa(ast_inet_ntoa(answer.sin_addr));
         int newport = ntohs(answer.sin_port);

         ast_log(LOG_NOTICE, "Old external address/port %s:%d now seen as %s:%d.\n",
            ast_inet_ntoa(args.external_addr.sin_addr),
            ntohs(args.external_addr.sin_port), newaddr, newport);

         args.external_addr = answer;

         if (args.external_addr_known) {
            struct ast_event *event;

            /*
             * The external address was already known, and has changed...
             * generate event.
             */
            event = ast_event_new(AST_EVENT_NETWORK_CHANGE, AST_EVENT_IE_END);
            if (!event) {
               ast_log(LOG_ERROR, "Could not create AST_EVENT_NETWORK_CHANGE event.\n");
            } else if (ast_event_queue(event)) {
               ast_event_destroy(event);
               ast_log(LOG_ERROR, "Could not queue AST_EVENT_NETWORK_CHANGE event.\n");
            }
         } else {
            /* this was the first external address we found, do not alert listeners
             * until this address changes to something else. */
            args.external_addr_known = 1;
         }
      }
   }

monitor_request_cleanup:
   /* always refresh this scheduler item.  It will be removed elsewhere when
    * it is supposed to go away */
   res = args.refresh * 1000;
   ast_mutex_unlock(&args.lock);

   return res;
}

/*!
 * \internal
 * \brief Stops the STUN monitor thread.
 *
 * \note do not hold the args->lock while calling this
 *
 * \return Nothing
 */
static void stun_stop_monitor(void)
{
   ast_mutex_lock(&args.lock);
   args.monitor_enabled = 0;
   ast_free((char *) args.server_hostname);
   args.server_hostname = NULL;
   stun_close_sock();
   ast_mutex_unlock(&args.lock);

   if (sched) {
      ast_sched_context_destroy(sched);
      sched = NULL;
      ast_log(LOG_NOTICE, "STUN monitor stopped\n");
   }
}

/*!
 * \internal
 * \brief Starts the STUN monitor thread.
 *
 * \note The args->lock MUST be held when calling this function
 *
 * \return Nothing
 */
static int stun_start_monitor(void)
{
   /* if scheduler thread is not started, make sure to start it now */
   if (sched) {
      return 0; /* already started */
   }

   if (!(sched = ast_sched_context_create())) {
      ast_log(LOG_ERROR, "Failed to create stun monitor scheduler context\n");
      return -1;
   }

   if (ast_sched_start_thread(sched)) {
      ast_sched_context_destroy(sched);
      sched = NULL;
      stun_close_sock();
      return -1;
   }

   if (ast_sched_add_variable(sched, (args.refresh * 1000), stun_monitor_request, NULL, 1) < 0) {
      ast_log(LOG_ERROR, "Unable to schedule STUN network monitor \n");
      ast_sched_context_destroy(sched);
      sched = NULL;
      return -1;
   }

   ast_log(LOG_NOTICE, "STUN monitor started\n");

   return 0;
}

/*!
 * \internal
 * \brief Parse and setup the stunaddr parameter.
 *
 * \param value Configuration parameter variable value.
 *
 * \retval 0 on success.
 * \retval -1 on error.
 */
static int setup_stunaddr(const char *value)
{
   char *val;
   char *host_str;
   char *port_str;
   unsigned int port;
   struct ast_sockaddr stun_addr;

   if (ast_strlen_zero(value)) {
      /* Setting to an empty value disables STUN monitoring. */
      args.monitor_enabled = 0;
      return 0;
   }

   val = ast_strdupa(value);
   if (!ast_sockaddr_split_hostport(val, &host_str, &port_str, 0)
      || ast_strlen_zero(host_str)) {
      return -1;
   }

   /* Determine STUN port */
   if (ast_strlen_zero(port_str)
      || 1 != sscanf(port_str, "%30u", &port)) {
      port = STANDARD_STUN_PORT;
   }

   host_str = ast_strdup(host_str);
   if (!host_str) {
      return -1;
   }

   /* Lookup STUN address. */
   memset(&stun_addr, 0, sizeof(stun_addr));
   stun_addr.ss.ss_family = AF_INET;
   if (ast_get_ip(&stun_addr, host_str)) {
      ast_log(LOG_WARNING, "Unable to lookup STUN server '%s'\n", host_str);
      ast_free(host_str);
      return -1;
   }

   /* Save STUN server information. */
   ast_free((char *) args.server_hostname);
   args.server_hostname = host_str;
   args.stun_port = port;

   /* Enable STUN monitor */
   args.monitor_enabled = 1;
   return 0;
}

static int load_config(int startup)
{
   struct ast_flags config_flags = { 0, };
   struct ast_config *cfg;
   struct ast_variable *v;

   if (!startup) {
      ast_set_flag(&config_flags, CONFIG_FLAG_FILEUNCHANGED);
   }

   cfg = ast_config_load2(stun_conf_file, "res_stun_monitor", config_flags);
   if (!cfg || cfg == CONFIG_STATUS_FILEINVALID) {
      ast_log(LOG_WARNING, "Unable to load config %s\n", stun_conf_file);
      return -1;
   }
   if (cfg == CONFIG_STATUS_FILEUNCHANGED) {
      return 0;
   }

   /* clean up any previous open socket */
   stun_close_sock();
   args.stun_poll_failed_gripe = 0;

   /* set defaults */
   args.monitor_enabled = 0;
   args.refresh = DEFAULT_MONITOR_REFRESH;

   for (v = ast_variable_browse(cfg, "general"); v; v = v->next) {
      if (!strcasecmp(v->name, "stunaddr")) {
         if (setup_stunaddr(v->value)) {
            ast_log(LOG_WARNING, "Invalid STUN server address: %s at line %d\n",
               v->value, v->lineno);
         }
      } else if (!strcasecmp(v->name, "stunrefresh")) {
         if ((sscanf(v->value, "%30u", &args.refresh) != 1) || !args.refresh) {
            ast_log(LOG_WARNING, "Invalid stunrefresh value '%s', must be an integer > 0 at line %d\n", v->value, v->lineno);
            args.refresh = DEFAULT_MONITOR_REFRESH;
         }
      } else {
         ast_log(LOG_WARNING, "Invalid config option %s at line %d\n",
            v->value, v->lineno);
      }
   }

   ast_config_destroy(cfg);

   return 0;
}

/*! \brief Execute stun show status command */
static void _stun_show_status(int fd)
{
   const char *status;

#define DATALN "%-25s %-5d %-7d %-8d %-7s %-16s %-d\n"
#define HEADER "%-25s %-5s %-7s %-8s %-7s %-16s %-s\n"

   /*! we only have one stun server, but start to play well with more */
   ast_cli(fd, HEADER, "Hostname", "Port", "Period", "Retries", "Status", "ExternAddr", "ExternPort");

   if (args.stun_poll_failed_gripe) {
      status = "FAIL";
   } else if (args.external_addr_known) {
      status = "OK";
   } else {
      status = "INIT";
   }
   ast_cli( fd, DATALN,
           args.server_hostname,
           args.stun_port,
           args.refresh,
           DEFAULT_RETRIES,
           status,
           ast_inet_ntoa(args.external_addr.sin_addr),
           ntohs(args.external_addr.sin_port)
         );

#undef HEADER
#undef DATALN
}

static char *handle_cli_stun_show_status(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
   switch (cmd) {
   case CLI_INIT:
      e->command = "stun show status";
      e->usage =
          "Usage: stun show status\n"
          "       List all known STUN servers and statuses.\n";
      return NULL;
   case CLI_GENERATE:
      return NULL;
   }

   if (a->argc != 3) {
      return CLI_SHOWUSAGE;
   }

   _stun_show_status(a->fd);
   return CLI_SUCCESS;
}

static struct ast_cli_entry cli_stun[] = {
   AST_CLI_DEFINE(handle_cli_stun_show_status, "Show STUN servers and statuses"),
};

static int __reload(int startup)
{
   int res;

   ast_mutex_lock(&args.lock);
   if (!(res = load_config(startup)) && args.monitor_enabled) {
      res = stun_start_monitor();
   }
   ast_mutex_unlock(&args.lock);

   if (res < 0 || !args.monitor_enabled) {
      stun_stop_monitor();
   }

   return res;
}

static int reload(void)
{
   return __reload(0);
}

static int unload_module(void)
{
   stun_stop_monitor();
   ast_mutex_destroy(&args.lock);

   /*! Unregister CLI commands */
   ast_cli_unregister_multiple(cli_stun, ARRAY_LEN(cli_stun));

   return 0;
}

static int load_module(void)
{
   ast_mutex_init(&args.lock);
   args.stun_sock = -1;
   if (__reload(1)) {
      ast_mutex_destroy(&args.lock);
      return AST_MODULE_LOAD_DECLINE;
   }

   /*! Register CLI commands */
   ast_cli_register_multiple(cli_stun, sizeof(cli_stun) / sizeof(struct ast_cli_entry));

   return AST_MODULE_LOAD_SUCCESS;
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_GLOBAL_SYMBOLS | AST_MODFLAG_LOAD_ORDER, "STUN Network Monitor",
      .load = load_module,
      .unload = unload_module,
      .reload = reload,
      .load_pri = AST_MODPRI_CHANNEL_DEPEND
   );