Thu Apr 28 2011 16:57:09

Asterisk developer's documentation


dnsmgr.c File Reference

Background DNS update manager. More...

#include "asterisk.h"
#include "asterisk/_private.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/sched.h"
#include "asterisk/cli.h"
#include "asterisk/manager.h"
#include "asterisk/acl.h"
Include dependency graph for dnsmgr.c:

Go to the source code of this file.

Data Structures

struct  ast_dnsmgr_entry
struct  entry_list
struct  refresh_info

Defines

#define REFRESH_DEFAULT   300

Functions

static void __fini_entry_list (void)
static void __init_entry_list (void)
int ast_dnsmgr_changed (struct ast_dnsmgr_entry *entry)
 Check is see if a dnsmgr entry has changed.
struct ast_dnsmgr_entryast_dnsmgr_get (const char *name, struct sockaddr_in *result, const char *service)
 Allocate a new DNS manager entry.
int ast_dnsmgr_lookup (const char *name, struct sockaddr_in *result, struct ast_dnsmgr_entry **dnsmgr, const char *service)
 Allocate and initialize a DNS manager entry.
int ast_dnsmgr_refresh (struct ast_dnsmgr_entry *entry)
 Force a refresh of a dnsmgr entry.
void ast_dnsmgr_release (struct ast_dnsmgr_entry *entry)
 Free a DNS manager entry.
int dnsmgr_init (void)
static int dnsmgr_refresh (struct ast_dnsmgr_entry *entry, int verbose)
int dnsmgr_reload (void)
void dnsmgr_start_refresh (void)
static void * do_refresh (void *data)
static int do_reload (int loading)
static char * handle_cli_refresh (struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
static char * handle_cli_reload (struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
static char * handle_cli_status (struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
static int refresh_list (const void *data)

Variables

static struct ast_cli_entry cli_refresh = AST_CLI_DEFINE(handle_cli_refresh, "Performs an immediate refresh")
static struct ast_cli_entry cli_reload = AST_CLI_DEFINE(handle_cli_reload, "Reloads the DNS manager configuration")
static struct ast_cli_entry cli_status = AST_CLI_DEFINE(handle_cli_status, "Display the DNS manager status")
static int enabled
static struct entry_list entry_list
static struct refresh_info master_refresh_info
static int refresh_interval
static ast_mutex_t refresh_lock = AST_MUTEX_INIT_VALUE
static int refresh_sched = -1
static pthread_t refresh_thread = AST_PTHREADT_NULL
static struct sched_contextsched

Detailed Description

Background DNS update manager.

Author:
Kevin P. Fleming <kpfleming@digium.com>
Bug:
There is a minor race condition. In the event that an IP address of a dnsmgr managed host changes, there is the potential for the consumer of that address to access the in_addr data at the same time that the dnsmgr thread is in the middle of updating it to the new address.

Definition in file dnsmgr.c.


Define Documentation

#define REFRESH_DEFAULT   300

Definition at line 69 of file dnsmgr.c.

Referenced by do_reload().


Function Documentation

static void __fini_entry_list ( void  ) [static]

Definition at line 65 of file dnsmgr.c.

{
static void __init_entry_list ( void  ) [static]

Definition at line 65 of file dnsmgr.c.

{
int ast_dnsmgr_changed ( struct ast_dnsmgr_entry entry)

Check is see if a dnsmgr entry has changed.

Return values:
non-zeroif the dnsmgr entry has changed since the last call to this function
zeroif the dnsmgr entry has not changed since the last call to this function

Definition at line 193 of file dnsmgr.c.

References ast_mutex_lock(), ast_mutex_unlock(), ast_dnsmgr_entry::changed, and ast_dnsmgr_entry::lock.

Referenced by iax2_do_register().

{
   int changed;

   ast_mutex_lock(&entry->lock);

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

   ast_mutex_unlock(&entry->lock);
   
   return changed;
}
struct ast_dnsmgr_entry* ast_dnsmgr_get ( const char *  name,
struct sockaddr_in *  result,
const char *  service 
) [read]

Allocate a new DNS manager entry.

Parameters:
namethe hostname
resultwhere the DNS manager should store the IP address as it refreshes it. it.

This function allocates a new DNS manager entry object, and fills it with the provided hostname and IP address. This function does not force an initial lookup of the IP address. So, generally, this should be used when the initial address is already known.

Returns:
a DNS manager entry
Version:
1.6.1 result changed from struct in_addr to struct sockaddr_in to store port number

Definition at line 86 of file dnsmgr.c.

References ast_calloc, ast_mutex_init(), AST_RWLIST_INSERT_HEAD, AST_RWLIST_UNLOCK, AST_RWLIST_WRLOCK, ast_strlen_zero(), ast_dnsmgr_entry::lock, ast_dnsmgr_entry::result, and ast_dnsmgr_entry::service.

Referenced by ast_dnsmgr_lookup().

{
   struct ast_dnsmgr_entry *entry;
   int total_size = sizeof(*entry) + strlen(name) + (service ? strlen(service) + 1 : 0);

   if (!result || ast_strlen_zero(name) || !(entry = ast_calloc(1, total_size)))
      return NULL;

   entry->result = result;
   ast_mutex_init(&entry->lock);
   strcpy(entry->name, name);
   if (service) {
      entry->service = ((char *) entry) + sizeof(*entry) + strlen(name);
      strcpy(entry->service, service);
   }

   AST_RWLIST_WRLOCK(&entry_list);
   AST_RWLIST_INSERT_HEAD(&entry_list, entry, list);
   AST_RWLIST_UNLOCK(&entry_list);

   return entry;
}
int ast_dnsmgr_lookup ( const char *  name,
struct sockaddr_in *  result,
struct ast_dnsmgr_entry **  dnsmgr,
const char *  service 
)

Allocate and initialize a DNS manager entry.

Parameters:
namethe hostname
resultwhere to store the IP address as the DNS manager refreshes it
dnsmgrWhere to store the allocate DNS manager entry

This function allocates a new DNS manager entry object, and fills it with the provided hostname and IP address. This function _does_ force an initial lookup, so it may block for some period of time.

Return values:
0success
non-zerofailure
Version:
1.6.1 result changed from struct in_addr to struct aockaddr_in to store port number

Definition at line 126 of file dnsmgr.c.

References ast_dnsmgr_get(), ast_get_ip_or_srv(), ast_strlen_zero(), ast_verb, enabled, and inet_aton().

Referenced by __sip_subscribe_mwi_do(), build_peer(), iax2_append_register(), and transmit_register().

{
   if (ast_strlen_zero(name) || !result || !dnsmgr)
      return -1;

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

   /* if it's actually an IP address and not a name,
      there's no need for a managed lookup */
   if (inet_aton(name, &result->sin_addr)) {
      result->sin_family = AF_INET;
      return 0;
      }

   ast_verb(4, "doing dnsmgr_lookup for '%s'\n", name);

   /* do a lookup now but add a manager so it will automagically get updated in the background */
   ast_get_ip_or_srv(result, name, service);
   
   /* if dnsmgr is not enable don't bother adding an entry */
   if (!enabled)
      return 0;
   
   ast_verb(3, "adding dns manager for '%s'\n", name);
   *dnsmgr = ast_dnsmgr_get(name, result, service);
   return !*dnsmgr;
}
int ast_dnsmgr_refresh ( struct ast_dnsmgr_entry entry)

Force a refresh of a dnsmgr entry.

Return values:
non-zeroif the result is different than the previous result
zeroif the result is the same as the previous result

Definition at line 185 of file dnsmgr.c.

References dnsmgr_refresh().

Referenced by iax2_do_register(), and sip_reg_timeout().

{
   return dnsmgr_refresh(entry, 0);
}
void ast_dnsmgr_release ( struct ast_dnsmgr_entry entry)

Free a DNS manager entry.

Parameters:
entrythe DNS manager entry to free
Returns:
nothing

Definition at line 109 of file dnsmgr.c.

References ast_free, ast_mutex_destroy(), AST_RWLIST_REMOVE, AST_RWLIST_UNLOCK, AST_RWLIST_WRLOCK, ast_verb, and ast_dnsmgr_entry::lock.

Referenced by delete_users(), peer_destructor(), sip_destroy_peer(), sip_registry_destroy(), and sip_subscribe_mwi_destroy().

{
   if (!entry)
      return;

   AST_RWLIST_WRLOCK(&entry_list);
   AST_RWLIST_REMOVE(&entry_list, entry, list);
   AST_RWLIST_UNLOCK(&entry_list);
   ast_verb(4, "removing dns manager for '%s'\n", entry->name);

   ast_mutex_destroy(&entry->lock);
   ast_free(entry);
}
int dnsmgr_init ( void  )

Provided by dnsmgr.c

Definition at line 352 of file dnsmgr.c.

References ast_cli_register(), ast_log(), cli_refresh, cli_reload, cli_status, do_reload(), LOG_ERROR, and sched_context_create().

Referenced by main().

{
   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);
   ast_cli_register(&cli_refresh);
   return do_reload(1);
}
static int dnsmgr_refresh ( struct ast_dnsmgr_entry entry,
int  verbose 
) [static]

Definition at line 158 of file dnsmgr.c.

References ast_copy_string(), ast_get_ip_or_srv(), ast_inet_ntoa(), ast_log(), ast_mutex_lock(), ast_mutex_unlock(), ast_verb, ast_dnsmgr_entry::changed, inaddrcmp(), ast_dnsmgr_entry::lock, LOG_NOTICE, ast_dnsmgr_entry::result, and ast_dnsmgr_entry::service.

Referenced by ast_dnsmgr_refresh(), and refresh_list().

{
   char iabuf[INET_ADDRSTRLEN];
   char iabuf2[INET_ADDRSTRLEN];
   struct sockaddr_in tmp;
   int changed = 0;
        
   ast_mutex_lock(&entry->lock);
   if (verbose)
      ast_verb(3, "refreshing '%s'\n", entry->name);

   memset(&tmp, 0, sizeof(tmp));
   tmp.sin_port = entry->result->sin_port;
   
   if (!ast_get_ip_or_srv(&tmp, entry->name, entry->service) && inaddrcmp(&tmp, entry->result)) {
      ast_copy_string(iabuf, ast_inet_ntoa(entry->result->sin_addr), sizeof(iabuf));
      ast_copy_string(iabuf2, ast_inet_ntoa(tmp.sin_addr), sizeof(iabuf2));
      ast_log(LOG_NOTICE, "dnssrv: host '%s' changed from %s:%d to %s:%d\n", 
         entry->name, iabuf, ntohs(entry->result->sin_port), iabuf2, ntohs(tmp.sin_port));
      *entry->result = tmp;
      changed = entry->changed = 1;
   }

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

Provided by dnsmgr.c

Definition at line 364 of file dnsmgr.c.

References do_reload().

{
   return do_reload(0);
}
void dnsmgr_start_refresh ( void  )
static void* do_refresh ( void *  data) [static]

Definition at line 207 of file dnsmgr.c.

References ast_sched_runq(), and ast_sched_wait().

Referenced by do_reload().

{
   for (;;) {
      pthread_testcancel();
      usleep((ast_sched_wait(sched)*1000));
      pthread_testcancel();
      ast_sched_runq(sched);
   }
   return NULL;
}
static int do_reload ( int  loading) [static]

Definition at line 369 of file dnsmgr.c.

References ast_config_destroy(), ast_config_load2(), ast_log(), ast_mutex_lock(), ast_mutex_unlock(), ast_pthread_create_background, AST_PTHREADT_NULL, ast_sched_add_variable(), AST_SCHED_DEL, ast_true(), ast_variable_retrieve(), config, CONFIG_FLAG_FILEUNCHANGED, CONFIG_STATUS_FILEINVALID, CONFIG_STATUS_FILEMISSING, CONFIG_STATUS_FILEUNCHANGED, do_refresh(), enabled, EVENT_FLAG_SYSTEM, LOG_ERROR, LOG_NOTICE, LOG_WARNING, manager_event, master_refresh_info, REFRESH_DEFAULT, refresh_interval, and refresh_list().

Referenced by dnsmgr_init(), dnsmgr_reload(), and handle_cli_reload().

{
   struct ast_config *config;
   struct ast_flags config_flags = { loading ? 0 : CONFIG_FLAG_FILEUNCHANGED };
   const char *interval_value;
   const char *enabled_value;
   int interval;
   int was_enabled;
   int res = -1;

   config = ast_config_load2("dnsmgr.conf", "dnsmgr", config_flags);
   if (config == CONFIG_STATUS_FILEMISSING || config == CONFIG_STATUS_FILEUNCHANGED || config == CONFIG_STATUS_FILEINVALID) {
      return 0;
   }

   /* 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;

   AST_SCHED_DEL(sched, refresh_sched);

   if (config) {
      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, "%30d", &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");
         }
      }
      /* 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;
      res = 0;
   }
   else
      res = 0;

   ast_mutex_unlock(&refresh_lock);
   manager_event(EVENT_FLAG_SYSTEM, "Reload", "Module: DNSmgr\r\nStatus: %s\r/nMessage: DNSmgr reload Requested\r\n", enabled ? "Enabled" : "Disabled");

   return res;
}
static char* handle_cli_refresh ( struct ast_cli_entry e,
int  cmd,
struct ast_cli_args a 
) [static]

Definition at line 275 of file dnsmgr.c.

References ast_cli_args::argc, ast_cli_args::argv, ast_cli(), CLI_GENERATE, CLI_INIT, CLI_SHOWUSAGE, CLI_SUCCESS, ast_cli_entry::command, enabled, refresh_info::entries, entry_list, ast_cli_args::fd, refresh_info::filter, refresh_list(), refresh_info::regex_present, and ast_cli_entry::usage.

{
   struct refresh_info info = {
      .entries = &entry_list,
      .verbose = 1,
   };
   switch (cmd) {
   case CLI_INIT:
      e->command = "dnsmgr refresh";
      e->usage = 
         "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";
      return NULL;
   case CLI_GENERATE:
      return NULL;   
   }

   if (!enabled) {
      ast_cli(a->fd, "DNS Manager is disabled.\n");
      return 0;
   }

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

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

   refresh_list(&info);

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

   return CLI_SUCCESS;
}
static char* handle_cli_reload ( struct ast_cli_entry e,
int  cmd,
struct ast_cli_args a 
) [static]

Definition at line 256 of file dnsmgr.c.

References ast_cli_args::argc, CLI_GENERATE, CLI_INIT, CLI_SHOWUSAGE, CLI_SUCCESS, ast_cli_entry::command, do_reload(), and ast_cli_entry::usage.

{
   switch (cmd) {
   case CLI_INIT:
      e->command = "dnsmgr reload";
      e->usage = 
         "Usage: dnsmgr reload\n"
         "       Reloads the DNS manager configuration.\n";
      return NULL;
   case CLI_GENERATE:
      return NULL;   
   }
   if (a->argc > 2)
      return CLI_SHOWUSAGE;

   do_reload(0);
   return CLI_SUCCESS;
}
static char* handle_cli_status ( struct ast_cli_entry e,
int  cmd,
struct ast_cli_args a 
) [static]

Definition at line 319 of file dnsmgr.c.

References ast_cli_args::argc, ast_cli(), AST_RWLIST_RDLOCK, AST_RWLIST_TRAVERSE, AST_RWLIST_UNLOCK, CLI_GENERATE, CLI_INIT, CLI_SHOWUSAGE, CLI_SUCCESS, ast_cli_entry::command, enabled, ast_cli_args::fd, refresh_interval, and ast_cli_entry::usage.

{
   int count = 0;
   struct ast_dnsmgr_entry *entry;
   switch (cmd) {
   case CLI_INIT:
      e->command = "dnsmgr status";
      e->usage = 
         "Usage: dnsmgr status\n"
         "       Displays the DNS manager status.\n";
      return NULL;
   case CLI_GENERATE:
      return NULL;   
   }

   if (a->argc > 2)
      return CLI_SHOWUSAGE;

   ast_cli(a->fd, "DNS Manager: %s\n", enabled ? "enabled" : "disabled");
   ast_cli(a->fd, "Refresh Interval: %d seconds\n", refresh_interval);
   AST_RWLIST_RDLOCK(&entry_list);
   AST_RWLIST_TRAVERSE(&entry_list, entry, list)
      count++;
   AST_RWLIST_UNLOCK(&entry_list);
   ast_cli(a->fd, "Number of entries: %d\n", count);

   return CLI_SUCCESS;
}
static int refresh_list ( const void *  data) [static]

Definition at line 218 of file dnsmgr.c.

References ast_log(), ast_mutex_trylock(), ast_mutex_unlock(), AST_RWLIST_RDLOCK, AST_RWLIST_TRAVERSE, AST_RWLIST_UNLOCK, ast_verb, dnsmgr_refresh(), refresh_info::entries, refresh_info::filter, LOG_WARNING, refresh_interval, refresh_info::regex_present, and refresh_info::verbose.

Referenced by dnsmgr_start_refresh(), do_reload(), and handle_cli_refresh().

{
   struct refresh_info *info = (struct refresh_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;
   }

   ast_verb(3, "Refreshing DNS lookups.\n");
   AST_RWLIST_RDLOCK(info->entries);
   AST_RWLIST_TRAVERSE(info->entries, entry, list) {
      if (info->regex_present && regexec(&info->filter, entry->name, 0, NULL, 0))
          continue;

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

   ast_mutex_unlock(&refresh_lock);

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

Variable Documentation

struct ast_cli_entry cli_refresh = AST_CLI_DEFINE(handle_cli_refresh, "Performs an immediate refresh") [static]

Definition at line 349 of file dnsmgr.c.

Referenced by dnsmgr_init().

struct ast_cli_entry cli_reload = AST_CLI_DEFINE(handle_cli_reload, "Reloads the DNS manager configuration") [static]

Definition at line 348 of file dnsmgr.c.

Referenced by dnsmgr_init().

struct ast_cli_entry cli_status = AST_CLI_DEFINE(handle_cli_status, "Display the DNS manager status") [static]

Definition at line 350 of file dnsmgr.c.

Referenced by dnsmgr_init().

int enabled [static]

Definition at line 71 of file dnsmgr.c.

struct entry_list entry_list [static]

Referenced by handle_cli_refresh().

Initial value:
 {
   .entries = &entry_list,
   .verbose = 0,
}

Definition at line 81 of file dnsmgr.c.

Referenced by dnsmgr_start_refresh(), and do_reload().

int refresh_interval [static]

Definition at line 72 of file dnsmgr.c.

Referenced by do_reload(), handle_cli_status(), and refresh_list().

ast_mutex_t refresh_lock = AST_MUTEX_INIT_VALUE [static]

Definition at line 67 of file dnsmgr.c.

int refresh_sched = -1 [static]

Definition at line 49 of file dnsmgr.c.

pthread_t refresh_thread = AST_PTHREADT_NULL [static]

Definition at line 50 of file dnsmgr.c.

struct sched_context* sched [static]

Definition at line 48 of file dnsmgr.c.