res_stun_monitor.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2010, Digium, Inc.
 *
 * David Vossel <[email protected]>
 *
 * 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 <[email protected]>
 */

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

#include "asterisk.h"

#include "asterisk/module.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 "asterisk/json.h"
#include "asterisk/stasis.h"
#include "asterisk/stasis_system.h"
#include "asterisk/astobj2.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) {
 RAII_VAR(struct stasis_message *, msg, NULL, ao2_cleanup);
 RAII_VAR(struct ast_json_payload *, json_payload, NULL, ao2_cleanup);
 RAII_VAR(struct ast_json *, json_object, NULL, ast_json_unref);

 if (!ast_network_change_type()) {
 goto publish_failure;
 }

 /* This json_object doesn't actually contain anything yet. We have to reference something
 * for stasis, and this is useful for if we want to ever add data for any reason. */
 json_object = ast_json_object_create();
 if (!json_object) {
 goto publish_failure;
 }

 if (!(json_payload = ast_json_payload_create(json_object))) {
 goto publish_failure;
 }

 msg = stasis_message_create(ast_network_change_type(), json_payload);

publish_failure:
 if (msg) {
 stasis_publish(ast_system_topic(), msg);
 } else {
 ast_log(LOG_ERROR, "Failed to issue network change message.\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, int reload)
{
 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);

 /* Only treat this as fatal if we are reloading */
 if (reload) {
 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, !startup)) {
 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 %-5u %-7u %-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",
 .support_level = AST_MODULE_SUPPORT_CORE,
 .load = load_module,
 .unload = unload_module,
 .reload = reload,
 .load_pri = AST_MODPRI_CHANNEL_DEPEND
);