Sat Sep 16 05:47:45 2006

Asterisk developer's documentation


dnsmgr.c

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00001 /*
00002  * Asterisk -- An open source telephony toolkit.
00003  *
00004  * Copyright (C) 2005-2006, Kevin P. Fleming
00005  *
00006  * Kevin P. Fleming <kpfleming@digium.com>
00007  *
00008  * See http://www.asterisk.org for more information about
00009  * the Asterisk project. Please do not directly contact
00010  * any of the maintainers of this project for assistance;
00011  * the project provides a web site, mailing lists and IRC
00012  * channels for your use.
00013  *
00014  * This program is free software, distributed under the terms of
00015  * the GNU General Public License Version 2. See the LICENSE file
00016  * at the top of the source tree.
00017  */
00018 
00019 /*! \file
00020  *
00021  * \brief Background DNS update manager
00022  * 
00023  */
00024 
00025 #include <sys/types.h>
00026 #include <netinet/in.h>
00027 #include <sys/socket.h>
00028 #include <arpa/inet.h>
00029 #include <resolv.h>
00030 #include <stdio.h>
00031 #include <string.h>
00032 #include <unistd.h>
00033 #include <stdlib.h>
00034 #include <regex.h>
00035 #include <signal.h>
00036 
00037 #include "asterisk.h"
00038 
00039 ASTERISK_FILE_VERSION(__FILE__, "$Revision: 29732 $")
00040 
00041 #include "asterisk/dnsmgr.h"
00042 #include "asterisk/linkedlists.h"
00043 #include "asterisk/utils.h"
00044 #include "asterisk/config.h"
00045 #include "asterisk/logger.h"
00046 #include "asterisk/sched.h"
00047 #include "asterisk/options.h"
00048 #include "asterisk/cli.h"
00049 
00050 static struct sched_context *sched;
00051 static int refresh_sched = -1;
00052 static pthread_t refresh_thread = AST_PTHREADT_NULL;
00053 
00054 struct ast_dnsmgr_entry {
00055    struct in_addr *result;
00056    AST_LIST_ENTRY(ast_dnsmgr_entry) list;
00057    char name[1];
00058 };
00059 
00060 static AST_LIST_HEAD_STATIC(entry_list, ast_dnsmgr_entry);
00061 
00062 AST_MUTEX_DEFINE_STATIC(refresh_lock);
00063 
00064 #define REFRESH_DEFAULT 300
00065 
00066 static int enabled = 0;
00067 static int refresh_interval;
00068 
00069 struct refresh_info {
00070    struct entry_list *entries;
00071    int verbose;
00072    unsigned int regex_present:1;
00073    regex_t filter;
00074 };
00075 
00076 static struct refresh_info master_refresh_info = {
00077    .entries = &entry_list,
00078    .verbose = 0,
00079 };
00080 
00081 struct ast_dnsmgr_entry *ast_dnsmgr_get(const char *name, struct in_addr *result)
00082 {
00083    struct ast_dnsmgr_entry *entry;
00084 
00085    if (!result || ast_strlen_zero(name))
00086       return NULL;
00087 
00088    entry = calloc(1, sizeof(*entry) + strlen(name));
00089    if (!entry)
00090       return NULL;
00091 
00092    entry->result = result;
00093    strcpy(entry->name, name);
00094 
00095    AST_LIST_LOCK(&entry_list);
00096    AST_LIST_INSERT_HEAD(&entry_list, entry, list);
00097    AST_LIST_UNLOCK(&entry_list);
00098 
00099    return entry;
00100 }
00101 
00102 void ast_dnsmgr_release(struct ast_dnsmgr_entry *entry)
00103 {
00104    if (!entry)
00105       return;
00106 
00107    AST_LIST_LOCK(&entry_list);
00108    AST_LIST_REMOVE(&entry_list, entry, list);
00109    AST_LIST_UNLOCK(&entry_list);
00110    free(entry);
00111 }
00112 
00113 int ast_dnsmgr_lookup(const char *name, struct in_addr *result, struct ast_dnsmgr_entry **dnsmgr)
00114 {
00115    if (ast_strlen_zero(name) || !result || !dnsmgr)
00116       return -1;
00117 
00118    if (*dnsmgr && !strcasecmp((*dnsmgr)->name, name))
00119       return 0;
00120 
00121    if (option_verbose > 3)
00122       ast_verbose(VERBOSE_PREFIX_3 "doing lookup for '%s'\n", name);
00123 
00124    /* if it's actually an IP address and not a name,
00125       there's no need for a managed lookup */
00126    if (inet_aton(name, result))
00127       return 0;
00128 
00129    /* if the manager is disabled, do a direct lookup and return the result,
00130       otherwise register a managed lookup for the name */
00131    if (!enabled) {
00132       struct ast_hostent ahp;
00133       struct hostent *hp;
00134 
00135       if ((hp = ast_gethostbyname(name, &ahp)))
00136          memcpy(result, hp->h_addr, sizeof(result));
00137       return 0;
00138    } else {
00139       if (option_verbose > 2)
00140          ast_verbose(VERBOSE_PREFIX_2 "adding manager for '%s'\n", name);
00141       *dnsmgr = ast_dnsmgr_get(name, result);
00142       return !*dnsmgr;
00143    }
00144 }
00145 
00146 static void *do_refresh(void *data)
00147 {
00148    for (;;) {
00149       pthread_testcancel();
00150       usleep(ast_sched_wait(sched));
00151       pthread_testcancel();
00152       ast_sched_runq(sched);
00153    }
00154    return NULL;
00155 }
00156 
00157 static int refresh_list(void *data)
00158 {
00159    struct refresh_info *info = data;
00160    struct ast_dnsmgr_entry *entry;
00161    struct ast_hostent ahp;
00162    struct hostent *hp;
00163 
00164    /* if a refresh or reload is already in progress, exit now */
00165    if (ast_mutex_trylock(&refresh_lock)) {
00166       if (info->verbose)
00167          ast_log(LOG_WARNING, "DNS Manager refresh already in progress.\n");
00168       return -1;
00169    }
00170 
00171    if (option_verbose > 2)
00172       ast_verbose(VERBOSE_PREFIX_2 "Refreshing DNS lookups.\n");
00173    AST_LIST_LOCK(info->entries);
00174    AST_LIST_TRAVERSE(info->entries, entry, list) {
00175       if (info->regex_present && regexec(&info->filter, entry->name, 0, NULL, 0))
00176           continue;
00177 
00178       if (info->verbose && (option_verbose > 2))
00179          ast_verbose(VERBOSE_PREFIX_2 "refreshing '%s'\n", entry->name);
00180 
00181       if ((hp = ast_gethostbyname(entry->name, &ahp))) {
00182          /* check to see if it has changed, do callback if requested */
00183          memcpy(entry->result, hp->h_addr, sizeof(entry->result));
00184       }
00185    }
00186    AST_LIST_UNLOCK(info->entries);
00187 
00188    ast_mutex_unlock(&refresh_lock);
00189 
00190    /* automatically reschedule based on the interval */
00191    return refresh_interval * 1000;
00192 }
00193 
00194 void dnsmgr_start_refresh(void)
00195 {
00196    if (refresh_sched > -1) {
00197       ast_sched_del(sched, refresh_sched);
00198       refresh_sched = ast_sched_add_variable(sched, 100, refresh_list, &master_refresh_info, 1);
00199    }
00200 }
00201 
00202 static int do_reload(int loading);
00203 
00204 static int handle_cli_reload(int fd, int argc, char *argv[])
00205 {
00206    if (argc > 2)
00207       return RESULT_SHOWUSAGE;
00208 
00209    do_reload(0);
00210    return 0;
00211 }
00212 
00213 static int handle_cli_refresh(int fd, int argc, char *argv[])
00214 {
00215    struct refresh_info info = {
00216       .entries = &entry_list,
00217       .verbose = 1,
00218    };
00219 
00220    if (argc > 3)
00221       return RESULT_SHOWUSAGE;
00222 
00223    if (argc == 3) {
00224       if (regcomp(&info.filter, argv[2], REG_EXTENDED | REG_NOSUB))
00225          return RESULT_SHOWUSAGE;
00226       else
00227          info.regex_present = 1;
00228    }
00229 
00230    refresh_list(&info);
00231 
00232    if (info.regex_present)
00233       regfree(&info.filter);
00234 
00235    return 0;
00236 }
00237 
00238 static int handle_cli_status(int fd, int argc, char *argv[])
00239 {
00240    int count = 0;
00241    struct ast_dnsmgr_entry *entry;
00242 
00243    if (argc > 2)
00244       return RESULT_SHOWUSAGE;
00245 
00246    ast_cli(fd, "DNS Manager: %s\n", enabled ? "enabled" : "disabled");
00247    ast_cli(fd, "Refresh Interval: %d seconds\n", refresh_interval);
00248    AST_LIST_LOCK(&entry_list);
00249    AST_LIST_TRAVERSE(&entry_list, entry, list)
00250       count++;
00251    AST_LIST_UNLOCK(&entry_list);
00252    ast_cli(fd, "Number of entries: %d\n", count);
00253 
00254    return 0;
00255 }
00256 
00257 static struct ast_cli_entry cli_reload = {
00258    .cmda = { "dnsmgr", "reload", NULL },
00259    .handler = handle_cli_reload,
00260    .summary = "Reloads the DNS manager configuration",
00261    .usage = 
00262    "Usage: dnsmgr reload\n"
00263    "       Reloads the DNS manager configuration.\n"
00264 };
00265 
00266 static struct ast_cli_entry cli_refresh = {
00267    .cmda = { "dnsmgr", "refresh", NULL },
00268    .handler = handle_cli_refresh,
00269    .summary = "Performs an immediate refresh",
00270    .usage = 
00271    "Usage: dnsmgr refresh [pattern]\n"
00272    "       Peforms an immediate refresh of the managed DNS entries.\n"
00273    "       Optional regular expression pattern is used to filter the entries to refresh.\n",
00274 };
00275 
00276 static struct ast_cli_entry cli_status = {
00277    .cmda = { "dnsmgr", "status", NULL },
00278    .handler = handle_cli_status,
00279    .summary = "Display the DNS manager status",
00280    .usage =
00281    "Usage: dnsmgr status\n"
00282    "       Displays the DNS manager status.\n"
00283 };
00284 
00285 int dnsmgr_init(void)
00286 {
00287    sched = sched_context_create();
00288    if (!sched) {
00289       ast_log(LOG_ERROR, "Unable to create schedule context.\n");
00290       return -1;
00291    }
00292    ast_cli_register(&cli_reload);
00293    ast_cli_register(&cli_status);
00294    return do_reload(1);
00295 }
00296 
00297 void dnsmgr_reload(void)
00298 {
00299    do_reload(0);
00300 }
00301 
00302 static int do_reload(int loading)
00303 {
00304    struct ast_config *config;
00305    const char *interval_value;
00306    const char *enabled_value;
00307    int interval;
00308    int was_enabled;
00309    int res = -1;
00310 
00311    /* ensure that no refresh cycles run while the reload is in progress */
00312    ast_mutex_lock(&refresh_lock);
00313 
00314    /* reset defaults in preparation for reading config file */
00315    refresh_interval = REFRESH_DEFAULT;
00316    was_enabled = enabled;
00317    enabled = 0;
00318 
00319    if (refresh_sched > -1)
00320       ast_sched_del(sched, refresh_sched);
00321 
00322    if ((config = ast_config_load("dnsmgr.conf"))) {
00323       if ((enabled_value = ast_variable_retrieve(config, "general", "enable"))) {
00324          enabled = ast_true(enabled_value);
00325       }
00326       if ((interval_value = ast_variable_retrieve(config, "general", "refreshinterval"))) {
00327          if (sscanf(interval_value, "%d", &interval) < 1)
00328             ast_log(LOG_WARNING, "Unable to convert '%s' to a numeric value.\n", interval_value);
00329          else if (interval < 0)
00330             ast_log(LOG_WARNING, "Invalid refresh interval '%d' specified, using default\n", interval);
00331          else
00332             refresh_interval = interval;
00333       }
00334       ast_config_destroy(config);
00335    }
00336 
00337    if (enabled && refresh_interval)
00338       ast_log(LOG_NOTICE, "Managed DNS entries will be refreshed every %d seconds.\n", refresh_interval);
00339 
00340    /* if this reload enabled the manager, create the background thread
00341       if it does not exist */
00342    if (enabled && !was_enabled && (refresh_thread == AST_PTHREADT_NULL)) {
00343       if (ast_pthread_create(&refresh_thread, NULL, do_refresh, NULL) < 0) {
00344          ast_log(LOG_ERROR, "Unable to start refresh thread.\n");
00345       }
00346       else {
00347          ast_cli_register(&cli_refresh);
00348          /* make a background refresh happen right away */
00349          refresh_sched = ast_sched_add_variable(sched, 100, refresh_list, &master_refresh_info, 1);
00350          res = 0;
00351       }
00352    }
00353    /* if this reload disabled the manager and there is a background thread,
00354       kill it */
00355    else if (!enabled && was_enabled && (refresh_thread != AST_PTHREADT_NULL)) {
00356       /* wake up the thread so it will exit */
00357       pthread_cancel(refresh_thread);
00358       pthread_kill(refresh_thread, SIGURG);
00359       pthread_join(refresh_thread, NULL);
00360       refresh_thread = AST_PTHREADT_NULL;
00361       ast_cli_unregister(&cli_refresh);
00362       res = 0;
00363    }
00364    else
00365       res = 0;
00366 
00367    ast_mutex_unlock(&refresh_lock);
00368 
00369    return res;
00370 }

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