asterisk/main/dnsmgr.c

528 lines
14 KiB
C

/*
* 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>
*
* \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.
*/
/*! \li \ref dnsmgr.c uses the configuration file \ref dnsmgr.conf
* \addtogroup configuration_file Configuration Files
*/
/*!
* \page dnsmgr.conf dnsmgr.conf
* \verbinclude dnsmgr.conf.sample
*/
/*** MODULEINFO
<support_level>core</support_level>
***/
#include "asterisk.h"
#include "asterisk/_private.h"
#include <regex.h>
#include <signal.h>
#include "asterisk/module.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"
static struct ast_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 IP address and port number */
struct ast_sockaddr *result;
/*! SRV record to lookup, if provided. Composed of service, protocol, and domain name: _Service._Proto.Name */
char *service;
/*! Address family to filter DNS responses. */
unsigned int family;
/*! Set to 1 if the entry changes */
unsigned int changed:1;
/*! Data to pass back to update_func */
void *data;
/*! The callback function to execute on address update */
dns_update_func update_func;
ast_mutex_t lock;
AST_RWLIST_ENTRY(ast_dnsmgr_entry) list;
/*! just 1 here, but we use calloc to allocate the correct size */
char name[1];
};
static AST_RWLIST_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_family(const char *name, struct ast_sockaddr *result, const char *service, unsigned int family)
{
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);
}
entry->family = family;
AST_RWLIST_WRLOCK(&entry_list);
AST_RWLIST_INSERT_HEAD(&entry_list, entry, list);
AST_RWLIST_UNLOCK(&entry_list);
return entry;
}
struct ast_dnsmgr_entry *ast_dnsmgr_get(const char *name, struct ast_sockaddr *result, const char *service)
{
return ast_dnsmgr_get_family(name, result, service, 0);
}
void ast_dnsmgr_release(struct ast_dnsmgr_entry *entry)
{
if (!entry) {
return;
}
AST_RWLIST_WRLOCK(&entry_list);
AST_RWLIST_REMOVE(&entry_list, entry, list);
AST_RWLIST_UNLOCK(&entry_list);
ast_debug(6, "removing dns manager for '%s'\n", entry->name);
ast_mutex_destroy(&entry->lock);
ast_free(entry);
}
static int internal_dnsmgr_lookup(const char *name, struct ast_sockaddr *result, struct ast_dnsmgr_entry **dnsmgr, const char *service, dns_update_func func, void *data)
{
unsigned int family;
if (ast_strlen_zero(name) || !result || !dnsmgr) {
return -1;
}
if (*dnsmgr && !strcasecmp((*dnsmgr)->name, name)) {
return 0;
}
/* Lookup address family filter. */
family = result->ss.ss_family;
/*
* If it's actually an IP address and not a name, there's no
* need for a managed lookup.
*/
if (ast_sockaddr_parse(result, name, PARSE_PORT_FORBID)) {
return 0;
}
ast_debug(6, "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_debug(6, "adding dns manager for '%s'\n", name);
*dnsmgr = ast_dnsmgr_get_family(name, result, service, family);
(*dnsmgr)->update_func = func;
(*dnsmgr)->data = data;
return !*dnsmgr;
}
int ast_dnsmgr_lookup(const char *name, struct ast_sockaddr *result, struct ast_dnsmgr_entry **dnsmgr, const char *service)
{
return internal_dnsmgr_lookup(name, result, dnsmgr, service, NULL, NULL);
}
int ast_dnsmgr_lookup_cb(const char *name, struct ast_sockaddr *result, struct ast_dnsmgr_entry **dnsmgr, const char *service, dns_update_func func, void *data)
{
return internal_dnsmgr_lookup(name, result, dnsmgr, service, func, data);
}
/*
* Refresh a dnsmgr entry
*/
static int dnsmgr_refresh(struct ast_dnsmgr_entry *entry, int verbose)
{
struct ast_sockaddr tmp = { .len = 0, };
int changed = 0;
ast_mutex_lock(&entry->lock);
ast_debug(6, "refreshing '%s'\n", entry->name);
tmp.ss.ss_family = entry->family;
if (!ast_get_ip_or_srv(&tmp, entry->name, entry->service)) {
if (!ast_sockaddr_port(&tmp)) {
ast_sockaddr_set_port(&tmp, ast_sockaddr_port(entry->result));
}
if (ast_sockaddr_cmp(&tmp, entry->result)) {
const char *old_addr = ast_strdupa(ast_sockaddr_stringify(entry->result));
const char *new_addr = ast_strdupa(ast_sockaddr_stringify(&tmp));
if (entry->update_func) {
entry->update_func(entry->result, &tmp, entry->data);
} else {
ast_log(LOG_NOTICE, "dnssrv: host '%s' changed from %s to %s\n",
entry->name, old_addr, new_addr);
ast_sockaddr_copy(entry->result, &tmp);
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(const void *data)
{
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_debug(6, "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;
}
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 char *handle_cli_reload(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
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_refresh(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
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"
" Performs 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_status(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
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 struct ast_cli_entry cli_reload = AST_CLI_DEFINE(handle_cli_reload, "Reloads the DNS manager configuration");
static struct ast_cli_entry cli_refresh = AST_CLI_DEFINE(handle_cli_refresh, "Performs an immediate refresh");
static struct ast_cli_entry cli_status = AST_CLI_DEFINE(handle_cli_status, "Display the DNS manager status");
static int unload_module(void)
{
ast_cli_unregister(&cli_reload);
ast_cli_unregister(&cli_status);
ast_cli_unregister(&cli_refresh);
/* Destroy refresh thread. */
ast_mutex_lock(&refresh_lock);
if (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_mutex_unlock(&refresh_lock);
ast_sched_context_destroy(sched);
return 0;
}
static int load_module(void)
{
if (!(sched = ast_sched_context_create())) {
ast_log(LOG_ERROR, "Unable to create schedule context.\n");
return AST_MODULE_LOAD_FAILURE;
}
ast_cli_register(&cli_reload);
ast_cli_register(&cli_status);
ast_cli_register(&cli_refresh);
return do_reload(1) ? AST_MODULE_LOAD_FAILURE : AST_MODULE_LOAD_SUCCESS;
}
static int reload_module(void)
{
return do_reload(0);
}
static int do_reload(int loading)
{
struct ast_config *config;
struct ast_variable *v;
struct ast_flags config_flags = { loading ? 0 : CONFIG_FLAG_FILEUNCHANGED };
int interval;
int was_enabled;
if ((config = ast_config_load2("dnsmgr.conf", "dnsmgr", config_flags)) == CONFIG_STATUS_FILEUNCHANGED) {
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;
if (config == CONFIG_STATUS_FILEMISSING || config == CONFIG_STATUS_FILEINVALID) {
ast_mutex_unlock(&refresh_lock);
return 0;
}
AST_SCHED_DEL(sched, refresh_sched);
for (v = ast_variable_browse(config, "general"); v; v = v->next) {
if (!strcasecmp(v->name, "enable")) {
enabled = ast_true(v->value);
} else if (!strcasecmp(v->name, "refreshinterval")) {
if (sscanf(v->value, "%30d", &interval) < 1) {
ast_log(LOG_WARNING, "Unable to convert '%s' to a numeric value.\n", v->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);
/* 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_mutex_unlock(&refresh_lock);
return 0;
}
AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_GLOBAL_SYMBOLS | AST_MODFLAG_LOAD_ORDER, "DNS Manager",
.support_level = AST_MODULE_SUPPORT_CORE,
.load = load_module,
.unload = unload_module,
.reload = reload_module,
.load_pri = AST_MODPRI_CORE,
.requires = "extconfig",
);