Sun Dec 18 20:55:40 2011

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  * \author Kevin P. Fleming <kpfleming@digium.com> 
00024  */
00025 
00026 #include "asterisk.h"
00027 
00028 ASTERISK_FILE_VERSION(__FILE__, "$Revision: 100465 $")
00029 
00030 #include <sys/types.h>
00031 #include <netinet/in.h>
00032 #include <sys/socket.h>
00033 #include <arpa/inet.h>
00034 #include <resolv.h>
00035 #include <stdio.h>
00036 #include <string.h>
00037 #include <unistd.h>
00038 #include <stdlib.h>
00039 #include <regex.h>
00040 #include <signal.h>
00041 
00042 #include "asterisk/dnsmgr.h"
00043 #include "asterisk/linkedlists.h"
00044 #include "asterisk/utils.h"
00045 #include "asterisk/config.h"
00046 #include "asterisk/logger.h"
00047 #include "asterisk/sched.h"
00048 #include "asterisk/options.h"
00049 #include "asterisk/cli.h"
00050 
00051 static struct sched_context *sched;
00052 static int refresh_sched = -1;
00053 static pthread_t refresh_thread = AST_PTHREADT_NULL;
00054 
00055 struct ast_dnsmgr_entry {
00056    /*! where we will store the resulting address */
00057    struct in_addr *result;
00058    /*! the last result, used to check if address has changed */
00059    struct in_addr last;
00060    /*! Set to 1 if the entry changes */
00061    int changed:1;
00062    ast_mutex_t lock;
00063    AST_LIST_ENTRY(ast_dnsmgr_entry) list;
00064    /*! just 1 here, but we use calloc to allocate the correct size */
00065    char name[1];
00066 };
00067 
00068 static AST_LIST_HEAD_STATIC(entry_list, ast_dnsmgr_entry);
00069 
00070 AST_MUTEX_DEFINE_STATIC(refresh_lock);
00071 
00072 #define REFRESH_DEFAULT 300
00073 
00074 static int enabled;
00075 static int refresh_interval;
00076 
00077 struct refresh_info {
00078    struct entry_list *entries;
00079    int verbose;
00080    unsigned int regex_present:1;
00081    regex_t filter;
00082 };
00083 
00084 static struct refresh_info master_refresh_info = {
00085    .entries = &entry_list,
00086    .verbose = 0,
00087 };
00088 
00089 struct ast_dnsmgr_entry *ast_dnsmgr_get(const char *name, struct in_addr *result)
00090 {
00091    struct ast_dnsmgr_entry *entry;
00092 
00093    if (!result || ast_strlen_zero(name) || !(entry = ast_calloc(1, sizeof(*entry) + strlen(name))))
00094       return NULL;
00095 
00096    entry->result = result;
00097    ast_mutex_init(&entry->lock);
00098    strcpy(entry->name, name);
00099    memcpy(&entry->last, result, sizeof(entry->last));
00100 
00101    AST_LIST_LOCK(&entry_list);
00102    AST_LIST_INSERT_HEAD(&entry_list, entry, list);
00103    AST_LIST_UNLOCK(&entry_list);
00104 
00105    return entry;
00106 }
00107 
00108 void ast_dnsmgr_release(struct ast_dnsmgr_entry *entry)
00109 {
00110    if (!entry)
00111       return;
00112 
00113    AST_LIST_LOCK(&entry_list);
00114    AST_LIST_REMOVE(&entry_list, entry, list);
00115    AST_LIST_UNLOCK(&entry_list);
00116    if (option_verbose > 3)
00117       ast_verbose(VERBOSE_PREFIX_4 "removing dns manager for '%s'\n", entry->name);
00118 
00119    ast_mutex_destroy(&entry->lock);
00120    free(entry);
00121 }
00122 
00123 int ast_dnsmgr_lookup(const char *name, struct in_addr *result, struct ast_dnsmgr_entry **dnsmgr)
00124 {
00125    struct ast_hostent ahp;
00126    struct hostent *hp;
00127 
00128    if (ast_strlen_zero(name) || !result || !dnsmgr)
00129       return -1;
00130 
00131    if (*dnsmgr && !strcasecmp((*dnsmgr)->name, name))
00132       return 0;
00133 
00134    if (option_verbose > 3)
00135       ast_verbose(VERBOSE_PREFIX_4 "doing dnsmgr_lookup for '%s'\n", name);
00136 
00137    /* if it's actually an IP address and not a name,
00138       there's no need for a managed lookup */
00139    if (inet_aton(name, result))
00140       return 0;
00141 
00142    /* do a lookup now but add a manager so it will automagically get updated in the background */
00143    if ((hp = ast_gethostbyname(name, &ahp)))
00144       memcpy(result, hp->h_addr, sizeof(result));
00145    
00146    /* if dnsmgr is not enable don't bother adding an entry */
00147    if (!enabled)
00148       return 0;
00149    
00150    if (option_verbose > 2)
00151       ast_verbose(VERBOSE_PREFIX_2 "adding dns manager for '%s'\n", name);
00152    *dnsmgr = ast_dnsmgr_get(name, result);
00153    return !*dnsmgr;
00154 }
00155 
00156 /*
00157  * Refresh a dnsmgr entry
00158  */
00159 static int dnsmgr_refresh(struct ast_dnsmgr_entry *entry, int verbose)
00160 {
00161    struct ast_hostent ahp;
00162    struct hostent *hp;
00163    char iabuf[INET_ADDRSTRLEN];
00164    char iabuf2[INET_ADDRSTRLEN];
00165    struct in_addr tmp;
00166    int changed = 0;
00167         
00168    ast_mutex_lock(&entry->lock);
00169    if (verbose && (option_verbose > 2))
00170       ast_verbose(VERBOSE_PREFIX_2 "refreshing '%s'\n", entry->name);
00171 
00172    if ((hp = ast_gethostbyname(entry->name, &ahp))) {
00173       /* check to see if it has changed, do callback if requested (where de callback is defined ????) */
00174       memcpy(&tmp, hp->h_addr, sizeof(tmp));
00175       if (tmp.s_addr != entry->last.s_addr) {
00176          ast_copy_string(iabuf, ast_inet_ntoa(entry->last), sizeof(iabuf));
00177          ast_copy_string(iabuf2, ast_inet_ntoa(tmp), sizeof(iabuf2));
00178          ast_log(LOG_NOTICE, "host '%s' changed from %s to %s\n", 
00179             entry->name, iabuf, iabuf2);
00180          memcpy(entry->result, hp->h_addr, sizeof(entry->result));
00181          memcpy(&entry->last, hp->h_addr, sizeof(entry->last));
00182          changed = entry->changed = 1;
00183       } 
00184       
00185    }
00186    ast_mutex_unlock(&entry->lock);
00187    return changed;
00188 }
00189 
00190 int ast_dnsmgr_refresh(struct ast_dnsmgr_entry *entry)
00191 {
00192    return dnsmgr_refresh(entry, 0);
00193 }
00194 
00195 /*
00196  * Check if dnsmgr entry has changed from since last call to this function
00197  */
00198 int ast_dnsmgr_changed(struct ast_dnsmgr_entry *entry) 
00199 {
00200    int changed;
00201 
00202    ast_mutex_lock(&entry->lock);
00203 
00204    changed = entry->changed;
00205    entry->changed = 0;
00206 
00207    ast_mutex_unlock(&entry->lock);
00208    
00209    return changed;
00210 }
00211 
00212 static void *do_refresh(void *data)
00213 {
00214    for (;;) {
00215       pthread_testcancel();
00216       usleep((ast_sched_wait(sched)*1000));
00217       pthread_testcancel();
00218       ast_sched_runq(sched);
00219    }
00220    return NULL;
00221 }
00222 
00223 static int refresh_list(const void *data)
00224 {
00225    struct refresh_info *info = (struct refresh_info *)data;
00226    struct ast_dnsmgr_entry *entry;
00227 
00228    /* if a refresh or reload is already in progress, exit now */
00229    if (ast_mutex_trylock(&refresh_lock)) {
00230       if (info->verbose)
00231          ast_log(LOG_WARNING, "DNS Manager refresh already in progress.\n");
00232       return -1;
00233    }
00234 
00235    if (option_verbose > 2)
00236       ast_verbose(VERBOSE_PREFIX_2 "Refreshing DNS lookups.\n");
00237    AST_LIST_LOCK(info->entries);
00238    AST_LIST_TRAVERSE(info->entries, entry, list) {
00239       if (info->regex_present && regexec(&info->filter, entry->name, 0, NULL, 0))
00240           continue;
00241 
00242       dnsmgr_refresh(entry, info->verbose);
00243    }
00244    AST_LIST_UNLOCK(info->entries);
00245 
00246    ast_mutex_unlock(&refresh_lock);
00247 
00248    /* automatically reschedule based on the interval */
00249    return refresh_interval * 1000;
00250 }
00251 
00252 void dnsmgr_start_refresh(void)
00253 {
00254    if (refresh_sched > -1) {
00255       AST_SCHED_DEL(sched, refresh_sched);
00256       refresh_sched = ast_sched_add_variable(sched, 100, refresh_list, &master_refresh_info, 1);
00257    }
00258 }
00259 
00260 static int do_reload(int loading);
00261 
00262 static int handle_cli_reload(int fd, int argc, char *argv[])
00263 {
00264    if (argc > 2)
00265       return RESULT_SHOWUSAGE;
00266 
00267    do_reload(0);
00268    return 0;
00269 }
00270 
00271 static int handle_cli_refresh(int fd, int argc, char *argv[])
00272 {
00273    struct refresh_info info = {
00274       .entries = &entry_list,
00275       .verbose = 1,
00276    };
00277 
00278    if (argc > 3)
00279       return RESULT_SHOWUSAGE;
00280 
00281    if (argc == 3) {
00282       if (regcomp(&info.filter, argv[2], REG_EXTENDED | REG_NOSUB))
00283          return RESULT_SHOWUSAGE;
00284       else
00285          info.regex_present = 1;
00286    }
00287 
00288    refresh_list(&info);
00289 
00290    if (info.regex_present)
00291       regfree(&info.filter);
00292 
00293    return 0;
00294 }
00295 
00296 static int handle_cli_status(int fd, int argc, char *argv[])
00297 {
00298    int count = 0;
00299    struct ast_dnsmgr_entry *entry;
00300 
00301    if (argc > 2)
00302       return RESULT_SHOWUSAGE;
00303 
00304    ast_cli(fd, "DNS Manager: %s\n", enabled ? "enabled" : "disabled");
00305    ast_cli(fd, "Refresh Interval: %d seconds\n", refresh_interval);
00306    AST_LIST_LOCK(&entry_list);
00307    AST_LIST_TRAVERSE(&entry_list, entry, list)
00308       count++;
00309    AST_LIST_UNLOCK(&entry_list);
00310    ast_cli(fd, "Number of entries: %d\n", count);
00311 
00312    return 0;
00313 }
00314 
00315 static struct ast_cli_entry cli_reload = {
00316    { "dnsmgr", "reload", NULL },
00317    handle_cli_reload, "Reloads the DNS manager configuration",
00318    "Usage: dnsmgr reload\n"
00319    "       Reloads the DNS manager configuration.\n"
00320 };
00321 
00322 static struct ast_cli_entry cli_refresh = {
00323    { "dnsmgr", "refresh", NULL },
00324    handle_cli_refresh, "Performs an immediate refresh",
00325    "Usage: dnsmgr refresh [pattern]\n"
00326    "       Peforms an immediate refresh of the managed DNS entries.\n"
00327    "       Optional regular expression pattern is used to filter the entries to refresh.\n",
00328 };
00329 
00330 static struct ast_cli_entry cli_status = {
00331    { "dnsmgr", "status", NULL },
00332    handle_cli_status, "Display the DNS manager status",
00333    "Usage: dnsmgr status\n"
00334    "       Displays the DNS manager status.\n"
00335 };
00336 
00337 int dnsmgr_init(void)
00338 {
00339    if (!(sched = sched_context_create())) {
00340       ast_log(LOG_ERROR, "Unable to create schedule context.\n");
00341       return -1;
00342    }
00343    ast_cli_register(&cli_reload);
00344    ast_cli_register(&cli_status);
00345    return do_reload(1);
00346 }
00347 
00348 int dnsmgr_reload(void)
00349 {
00350    return do_reload(0);
00351 }
00352 
00353 static int do_reload(int loading)
00354 {
00355    struct ast_config *config;
00356    const char *interval_value;
00357    const char *enabled_value;
00358    int interval;
00359    int was_enabled;
00360    int res = -1;
00361 
00362    /* ensure that no refresh cycles run while the reload is in progress */
00363    ast_mutex_lock(&refresh_lock);
00364 
00365    /* reset defaults in preparation for reading config file */
00366    refresh_interval = REFRESH_DEFAULT;
00367    was_enabled = enabled;
00368    enabled = 0;
00369 
00370    AST_SCHED_DEL(sched, refresh_sched);
00371 
00372    if ((config = ast_config_load("dnsmgr.conf"))) {
00373       if ((enabled_value = ast_variable_retrieve(config, "general", "enable"))) {
00374          enabled = ast_true(enabled_value);
00375       }
00376       if ((interval_value = ast_variable_retrieve(config, "general", "refreshinterval"))) {
00377          if (sscanf(interval_value, "%d", &interval) < 1)
00378             ast_log(LOG_WARNING, "Unable to convert '%s' to a numeric value.\n", interval_value);
00379          else if (interval < 0)
00380             ast_log(LOG_WARNING, "Invalid refresh interval '%d' specified, using default\n", interval);
00381          else
00382             refresh_interval = interval;
00383       }
00384       ast_config_destroy(config);
00385    }
00386 
00387    if (enabled && refresh_interval)
00388       ast_log(LOG_NOTICE, "Managed DNS entries will be refreshed every %d seconds.\n", refresh_interval);
00389 
00390    /* if this reload enabled the manager, create the background thread
00391       if it does not exist */
00392    if (enabled) {
00393       if (!was_enabled && (refresh_thread == AST_PTHREADT_NULL)) {
00394          if (ast_pthread_create_background(&refresh_thread, NULL, do_refresh, NULL) < 0) {
00395             ast_log(LOG_ERROR, "Unable to start refresh thread.\n");
00396          }
00397          ast_cli_register(&cli_refresh);
00398       }
00399       /* make a background refresh happen right away */
00400       refresh_sched = ast_sched_add_variable(sched, 100, refresh_list, &master_refresh_info, 1);
00401       res = 0;
00402    }
00403    /* if this reload disabled the manager and there is a background thread,
00404       kill it */
00405    else if (!enabled && was_enabled && (refresh_thread != AST_PTHREADT_NULL)) {
00406       /* wake up the thread so it will exit */
00407       pthread_cancel(refresh_thread);
00408       pthread_kill(refresh_thread, SIGURG);
00409       pthread_join(refresh_thread, NULL);
00410       refresh_thread = AST_PTHREADT_NULL;
00411       ast_cli_unregister(&cli_refresh);
00412       res = 0;
00413    }
00414    else
00415       res = 0;
00416 
00417    ast_mutex_unlock(&refresh_lock);
00418 
00419    return res;
00420 }

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