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Asterisk developer's documentation :: Codename Pineapple

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dnsmgr.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2005-2006, Kevin P. Fleming
 *
 * Kevin P. Fleming <kpfleming@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 Background DNS update manager
 *
 * \author Kevin P. Fleming <kpfleming@digium.com> 
 */

#include "asterisk.h"

ASTERISK_FILE_VERSION(__FILE__, "$Revision: 49116 $")

#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <resolv.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <regex.h>
#include <signal.h>

#include "asterisk/dnsmgr.h"
#include "asterisk/linkedlists.h"
#include "asterisk/utils.h"
#include "asterisk/config.h"
#include "asterisk/logger.h"
#include "asterisk/sched.h"
#include "asterisk/options.h"
#include "asterisk/cli.h"

static struct sched_context *sched;
static int refresh_sched = -1;
static pthread_t refresh_thread = AST_PTHREADT_NULL;

struct ast_dnsmgr_entry {
   /*! where we will store the resulting address */
   struct in_addr *result;
   /*! the last result, used to check if address has changed */
   struct in_addr last;
   /*! Set to 1 if the entry changes */
   int changed:1;
   ast_mutex_t lock;
   AST_LIST_ENTRY(ast_dnsmgr_entry) list;
   /*! just 1 here, but we use calloc to allocate the correct size */
   char name[1];
};

static AST_LIST_HEAD_STATIC(entry_list, ast_dnsmgr_entry);

AST_MUTEX_DEFINE_STATIC(refresh_lock);

#define REFRESH_DEFAULT 300

static int enabled;
static int refresh_interval;

struct refresh_info {
   struct entry_list *entries;
   int verbose;
   unsigned int regex_present:1;
   regex_t filter;
};

static struct refresh_info master_refresh_info = {
   .entries = &entry_list,
   .verbose = 0,
};

struct ast_dnsmgr_entry *ast_dnsmgr_get(const char *name, struct in_addr *result)
{
   struct ast_dnsmgr_entry *entry;

   if (!result || ast_strlen_zero(name) || !(entry = ast_calloc(1, sizeof(*entry) + strlen(name))))
      return NULL;

   entry->result = result;
   ast_mutex_init(&entry->lock);
   strcpy(entry->name, name);

   AST_LIST_LOCK(&entry_list);
   AST_LIST_INSERT_HEAD(&entry_list, entry, list);
   AST_LIST_UNLOCK(&entry_list);

   return entry;
}

void ast_dnsmgr_release(struct ast_dnsmgr_entry *entry)
{
   if (!entry)
      return;

   AST_LIST_LOCK(&entry_list);
   AST_LIST_REMOVE(&entry_list, entry, list);
   AST_LIST_UNLOCK(&entry_list);
   if (option_verbose > 3)
      ast_verbose(VERBOSE_PREFIX_4 "removing dns manager for '%s'\n", entry->name);

   ast_mutex_destroy(&entry->lock);
   free(entry);
}

int ast_dnsmgr_lookup(const char *name, struct in_addr *result, struct ast_dnsmgr_entry **dnsmgr)
{
   if (ast_strlen_zero(name) || !result || !dnsmgr)
      return -1;

   if (*dnsmgr && !strcasecmp((*dnsmgr)->name, name))
      return 0;

   if (option_verbose > 3)
      ast_verbose(VERBOSE_PREFIX_4 "doing dnsmgr_lookup for '%s'\n", name);

   /* if it's actually an IP address and not a name,
      there's no need for a managed lookup */
   if (inet_aton(name, result))
      return 0;

   /* if the manager is disabled, do a direct lookup and return the result,
      otherwise register a managed lookup for the name */
   if (!enabled) {
      struct ast_hostent ahp;
      struct hostent *hp;

      if ((hp = ast_gethostbyname(name, &ahp)))
         memcpy(result, hp->h_addr, sizeof(result));
      return 0;
   } else {
      if (option_verbose > 2)
         ast_verbose(VERBOSE_PREFIX_2 "adding dns manager for '%s'\n", name);
      *dnsmgr = ast_dnsmgr_get(name, result);
      return !*dnsmgr;
   }
}

/*
 * Refresh a dnsmgr entry
 */
static int dnsmgr_refresh(struct ast_dnsmgr_entry *entry, int verbose)
{
   struct ast_hostent ahp;
   struct hostent *hp;
   char iabuf[INET_ADDRSTRLEN];
   char iabuf2[INET_ADDRSTRLEN];
   struct in_addr tmp;
   int changed = 0;
        
   ast_mutex_lock(&entry->lock);
   if (verbose && (option_verbose > 2))
      ast_verbose(VERBOSE_PREFIX_2 "refreshing '%s'\n", entry->name);

   if ((hp = ast_gethostbyname(entry->name, &ahp))) {
      /* check to see if it has changed, do callback if requested (where de callback is defined ????) */
      memcpy(&tmp, hp->h_addr, sizeof(tmp));
      if (tmp.s_addr != entry->last.s_addr) {
         ast_copy_string(iabuf, ast_inet_ntoa(entry->last), sizeof(iabuf));
         ast_copy_string(iabuf2, ast_inet_ntoa(tmp), sizeof(iabuf2));
         ast_log(LOG_NOTICE, "host '%s' changed from %s to %s\n", 
            entry->name, iabuf, iabuf2);
         memcpy(entry->result, hp->h_addr, sizeof(entry->result));
         memcpy(&entry->last, hp->h_addr, sizeof(entry->last));
         changed = entry->changed = 1;
      } 
      
   }
   ast_mutex_unlock(&entry->lock);
   return changed;
}

int ast_dnsmgr_refresh(struct ast_dnsmgr_entry *entry)
{
   return dnsmgr_refresh(entry, 0);
}

/*
 * Check if dnsmgr entry has changed from since last call to this function
 */
int ast_dnsmgr_changed(struct ast_dnsmgr_entry *entry) 
{
   int changed;

   ast_mutex_lock(&entry->lock);

   changed = entry->changed;
   entry->changed = 0;

   ast_mutex_unlock(&entry->lock);
   
   return changed;
}

static void *do_refresh(void *data)
{
   for (;;) {
      pthread_testcancel();
      usleep((ast_sched_wait(sched)*1000));
      pthread_testcancel();
      ast_sched_runq(sched);
   }
   return NULL;
}

static int refresh_list(void *data)
{
   struct refresh_info *info = data;
   struct ast_dnsmgr_entry *entry;

   /* if a refresh or reload is already in progress, exit now */
   if (ast_mutex_trylock(&refresh_lock)) {
      if (info->verbose)
         ast_log(LOG_WARNING, "DNS Manager refresh already in progress.\n");
      return -1;
   }

   if (option_verbose > 2)
      ast_verbose(VERBOSE_PREFIX_2 "Refreshing DNS lookups.\n");
   AST_LIST_LOCK(info->entries);
   AST_LIST_TRAVERSE(info->entries, entry, list) {
      if (info->regex_present && regexec(&info->filter, entry->name, 0, NULL, 0))
          continue;

      dnsmgr_refresh(entry, info->verbose);
   }
   AST_LIST_UNLOCK(info->entries);

   ast_mutex_unlock(&refresh_lock);

   /* automatically reschedule based on the interval */
   return refresh_interval * 1000;
}

void dnsmgr_start_refresh(void)
{
   if (refresh_sched > -1) {
      ast_sched_del(sched, refresh_sched);
      refresh_sched = ast_sched_add_variable(sched, 100, refresh_list, &master_refresh_info, 1);
   }
}

static int do_reload(int loading);

static int handle_cli_reload(int fd, int argc, char *argv[])
{
   if (argc > 2)
      return RESULT_SHOWUSAGE;

   do_reload(0);
   return 0;
}

static int handle_cli_refresh(int fd, int argc, char *argv[])
{
   struct refresh_info info = {
      .entries = &entry_list,
      .verbose = 1,
   };

   if (argc > 3)
      return RESULT_SHOWUSAGE;

   if (argc == 3) {
      if (regcomp(&info.filter, argv[2], REG_EXTENDED | REG_NOSUB))
         return RESULT_SHOWUSAGE;
      else
         info.regex_present = 1;
   }

   refresh_list(&info);

   if (info.regex_present)
      regfree(&info.filter);

   return 0;
}

static int handle_cli_status(int fd, int argc, char *argv[])
{
   int count = 0;
   struct ast_dnsmgr_entry *entry;

   if (argc > 2)
      return RESULT_SHOWUSAGE;

   ast_cli(fd, "DNS Manager: %s\n", enabled ? "enabled" : "disabled");
   ast_cli(fd, "Refresh Interval: %d seconds\n", refresh_interval);
   AST_LIST_LOCK(&entry_list);
   AST_LIST_TRAVERSE(&entry_list, entry, list)
      count++;
   AST_LIST_UNLOCK(&entry_list);
   ast_cli(fd, "Number of entries: %d\n", count);

   return 0;
}

static struct ast_cli_entry cli_reload = {
   { "dnsmgr", "reload", NULL },
   handle_cli_reload, "Reloads the DNS manager configuration",
   "Usage: dnsmgr reload\n"
   "       Reloads the DNS manager configuration.\n"
};

static struct ast_cli_entry cli_refresh = {
   { "dnsmgr", "refresh", NULL },
   handle_cli_refresh, "Performs an immediate refresh",
   "Usage: dnsmgr refresh [pattern]\n"
   "       Peforms an immediate refresh of the managed DNS entries.\n"
   "       Optional regular expression pattern is used to filter the entries to refresh.\n",
};

static struct ast_cli_entry cli_status = {
   { "dnsmgr", "status", NULL },
   handle_cli_status, "Display the DNS manager status",
   "Usage: dnsmgr status\n"
   "       Displays the DNS manager status.\n"
};

int dnsmgr_init(void)
{
   if (!(sched = sched_context_create())) {
      ast_log(LOG_ERROR, "Unable to create schedule context.\n");
      return -1;
   }
   ast_cli_register(&cli_reload);
   ast_cli_register(&cli_status);
   return do_reload(1);
}

int dnsmgr_reload(void)
{
   return do_reload(0);
}

static int do_reload(int loading)
{
   struct ast_config *config;
   const char *interval_value;
   const char *enabled_value;
   int interval;
   int was_enabled;
   int res = -1;

   /* ensure that no refresh cycles run while the reload is in progress */
   ast_mutex_lock(&refresh_lock);

   /* reset defaults in preparation for reading config file */
   refresh_interval = REFRESH_DEFAULT;
   was_enabled = enabled;
   enabled = 0;

   if (refresh_sched > -1)
      ast_sched_del(sched, refresh_sched);

   if ((config = ast_config_load("dnsmgr.conf"))) {
      if ((enabled_value = ast_variable_retrieve(config, "general", "enable"))) {
         enabled = ast_true(enabled_value);
      }
      if ((interval_value = ast_variable_retrieve(config, "general", "refreshinterval"))) {
         if (sscanf(interval_value, "%d", &interval) < 1)
            ast_log(LOG_WARNING, "Unable to convert '%s' to a numeric value.\n", interval_value);
         else if (interval < 0)
            ast_log(LOG_WARNING, "Invalid refresh interval '%d' specified, using default\n", interval);
         else
            refresh_interval = interval;
      }
      ast_config_destroy(config);
   }

   if (enabled && refresh_interval)
      ast_log(LOG_NOTICE, "Managed DNS entries will be refreshed every %d seconds.\n", refresh_interval);

   /* if this reload enabled the manager, create the background thread
      if it does not exist */
   if (enabled) {
      if (!was_enabled && (refresh_thread == AST_PTHREADT_NULL)) {
         if (ast_pthread_create_background(&refresh_thread, NULL, do_refresh, NULL) < 0) {
            ast_log(LOG_ERROR, "Unable to start refresh thread.\n");
         }
         ast_cli_register(&cli_refresh);
      }
      /* make a background refresh happen right away */
      refresh_sched = ast_sched_add_variable(sched, 100, refresh_list, &master_refresh_info, 1);
      res = 0;
   }
   /* if this reload disabled the manager and there is a background thread,
      kill it */
   else if (!enabled && was_enabled && (refresh_thread != AST_PTHREADT_NULL)) {
      /* wake up the thread so it will exit */
      pthread_cancel(refresh_thread);
      pthread_kill(refresh_thread, SIGURG);
      pthread_join(refresh_thread, NULL);
      refresh_thread = AST_PTHREADT_NULL;
      ast_cli_unregister(&cli_refresh);
      res = 0;
   }
   else
      res = 0;

   ast_mutex_unlock(&refresh_lock);

   return res;
}

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