main/dnsmgr.c

   1 /*
   2  * Asterisk -- An open source telephony toolkit.
   3  *
   4  * Copyright (C) 2005-2006, Kevin P. Fleming
   5  *
   6  * Kevin P. Fleming <kpfleming@digium.com>
   7  *
   8  * See http://www.asterisk.org for more information about
   9  * the Asterisk project. Please do not directly contact
  10  * any of the maintainers of this project for assistance;
  11  * the project provides a web site, mailing lists and IRC
  12  * channels for your use.
  13  *
  14  * This program is free software, distributed under the terms of
  15  * the GNU General Public License Version 2. See the LICENSE file
  16  * at the top of the source tree.
  17  */
  18
  19 /*! \file
  20  *
  21  * \brief Background DNS update manager
  22  *
  23  * \author Kevin P. Fleming <kpfleming@digium.com>
  24  *
  25  * \bug There is a minor race condition.  In the event that an IP address
  26  * of a dnsmgr managed host changes, there is the potential for the consumer
  27  * of that address to access the in_addr data at the same time that the dnsmgr
  28  * thread is in the middle of updating it to the new address.
  29  */
  30
  31 #include "asterisk.h"
  32
  33 ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
  34
  35 #include "asterisk/_private.h"
  36 #include <regex.h>
  37 #include <signal.h>
  38
  39 #include "asterisk/dnsmgr.h"
  40 #include "asterisk/linkedlists.h"
  41 #include "asterisk/utils.h"
  42 #include "asterisk/config.h"
  43 #include "asterisk/sched.h"
  44 #include "asterisk/cli.h"
  45 #include "asterisk/manager.h"
  46 #include "asterisk/acl.h"
  47
  48 static struct sched_context *sched;
  49 static int refresh_sched = -1;
  50 static pthread_t refresh_thread = AST_PTHREADT_NULL;
  51
  52 struct ast_dnsmgr_entry {
  53         /*! where we will store the resulting IP address and port number */
  54         struct sockaddr_in *result;
  55         /*! the last result, used to check if address/port has changed */
  56         struct sockaddr_in last;
  57         /*! SRV record to lookup, if provided. Composed of service, protocol, and domain name: _Service._Proto.Name */
  58         char *service;
  59         /*! Set to 1 if the entry changes */
  60         int changed:1;
  61         ast_mutex_t lock;
  62         AST_RWLIST_ENTRY(ast_dnsmgr_entry) list;
  63         /*! just 1 here, but we use calloc to allocate the correct size */
  64         char name[1];
  65 };
  66
  67 static AST_RWLIST_HEAD_STATIC(entry_list, ast_dnsmgr_entry);
  68
  69 AST_MUTEX_DEFINE_STATIC(refresh_lock);
  70
  71 #define REFRESH_DEFAULT 300
  72
  73 static int enabled;
  74 static int refresh_interval;
  75
  76 struct refresh_info {
  77         struct entry_list *entries;
  78         int verbose;
  79         unsigned int regex_present:1;
  80         regex_t filter;
  81 };
  82
  83 static struct refresh_info master_refresh_info = {
  84         .entries = &entry_list,
  85         .verbose = 0,
  86 };
  87
  88 struct ast_dnsmgr_entry *ast_dnsmgr_get(const char *name, struct sockaddr_in *result, const char *service)
  89 {
  90         struct ast_dnsmgr_entry *entry;
  91         int total_size = sizeof(*entry) + strlen(name) + (service ? strlen(service) + 1 : 0);
  92
  93         if (!result || ast_strlen_zero(name) || !(entry = ast_calloc(1, total_size)))
  94                 return NULL;
  95
  96         entry->result = result;
  97         ast_mutex_init(&entry->lock);
  98         strcpy(entry->name, name);
  99         memcpy(&entry->last, result, sizeof(entry->last));
 100         if (service) {
 101                 entry->service = ((char *) entry) + sizeof(*entry) + strlen(name);
 102                 strcpy(entry->service, service);
 103         }
 104
 105         AST_RWLIST_WRLOCK(&entry_list);
 106         AST_RWLIST_INSERT_HEAD(&entry_list, entry, list);
 107         AST_RWLIST_UNLOCK(&entry_list);
 108
 109         return entry;
 110 }
 111
 112 void ast_dnsmgr_release(struct ast_dnsmgr_entry *entry)
 113 {
 114         if (!entry)
 115                 return;
 116
 117         AST_RWLIST_WRLOCK(&entry_list);
 118         AST_RWLIST_REMOVE(&entry_list, entry, list);
 119         AST_RWLIST_UNLOCK(&entry_list);
 120         ast_verb(4, "removing dns manager for '%s'\n", entry->name);
 121
 122         ast_mutex_destroy(&entry->lock);
 123         ast_free(entry);
 124 }
 125
 126 int ast_dnsmgr_lookup(const char *name, struct sockaddr_in *result, struct ast_dnsmgr_entry **dnsmgr, const char *service)
 127 {
 128         if (ast_strlen_zero(name) || !result || !dnsmgr)
 129                 return -1;
 130
 131         if (*dnsmgr && !strcasecmp((*dnsmgr)->name, name))
 132                 return 0;
 133
 134         /* if it's actually an IP address and not a name,
 135            there's no need for a managed lookup */
 136         if (inet_aton(name, &result->sin_addr))
 137                 return 0;
 138
 139         ast_verb(4, "doing dnsmgr_lookup for '%s'\n", name);
 140
 141         /* do a lookup now but add a manager so it will automagically get updated in the background */
 142         ast_get_ip_or_srv(result, name, service);
 143
 144         /* if dnsmgr is not enable don't bother adding an entry */
 145         if (!enabled)
 146                 return 0;
 147
 148         ast_verb(3, "adding dns manager for '%s'\n", name);
 149         *dnsmgr = ast_dnsmgr_get(name, result, service);
 150         return !*dnsmgr;
 151 }
 152
 153 /*
 154  * Refresh a dnsmgr entry
 155  */
 156 static int dnsmgr_refresh(struct ast_dnsmgr_entry *entry, int verbose)
 157 {
 158         char iabuf[INET_ADDRSTRLEN];
 159         char iabuf2[INET_ADDRSTRLEN];
 160         struct sockaddr_in tmp;
 161         int changed = 0;
 162
 163         ast_mutex_lock(&entry->lock);
 164         if (verbose)
 165                 ast_verb(3, "refreshing '%s'\n", entry->name);
 166
 167         ast_get_ip_or_srv(&tmp, entry->name, entry->service);
 168         if (inaddrcmp(&tmp, &entry->last)) {
 169                 ast_copy_string(iabuf, ast_inet_ntoa(entry->last.sin_addr), sizeof(iabuf));
 170                 ast_copy_string(iabuf2, ast_inet_ntoa(tmp.sin_addr), sizeof(iabuf2));
 171                 ast_log(LOG_NOTICE, "dnssrv: host '%s' changed from %s:%d to %s:%d\n",
 172                         entry->name, iabuf, ntohs(entry->last.sin_port), iabuf2, ntohs(tmp.sin_port));
 173                 *entry->result = tmp;
 174                 entry->last = tmp;
 175                 changed = entry->changed = 1;
 176         }
 177
 178         ast_mutex_unlock(&entry->lock);
 179         return changed;
 180 }
 181
 182 int ast_dnsmgr_refresh(struct ast_dnsmgr_entry *entry)
 183 {
 184         return dnsmgr_refresh(entry, 0);
 185 }
 186
 187 /*
 188  * Check if dnsmgr entry has changed from since last call to this function
 189  */
 190 int ast_dnsmgr_changed(struct ast_dnsmgr_entry *entry)
 191 {
 192         int changed;
 193
 194         ast_mutex_lock(&entry->lock);
 195
 196         changed = entry->changed;
 197         entry->changed = 0;
 198
 199         ast_mutex_unlock(&entry->lock);
 200
 201         return changed;
 202 }
 203
 204 static void *do_refresh(void *data)
 205 {
 206         for (;;) {
 207                 pthread_testcancel();
 208                 usleep((ast_sched_wait(sched)*1000));
 209                 pthread_testcancel();
 210                 ast_sched_runq(sched);
 211         }
 212         return NULL;
 213 }
 214
 215 static int refresh_list(const void *data)
 216 {
 217         struct refresh_info *info = (struct refresh_info *)data;
 218         struct ast_dnsmgr_entry *entry;
 219
 220         /* if a refresh or reload is already in progress, exit now */
 221         if (ast_mutex_trylock(&refresh_lock)) {
 222                 if (info->verbose)
 223                         ast_log(LOG_WARNING, "DNS Manager refresh already in progress.\n");
 224                 return -1;
 225         }
 226
 227         ast_verb(3, "Refreshing DNS lookups.\n");
 228         AST_RWLIST_RDLOCK(info->entries);
 229         AST_RWLIST_TRAVERSE(info->entries, entry, list) {
 230                 if (info->regex_present && regexec(&info->filter, entry->name, 0, NULL, 0))
 231                     continue;
 232
 233                 dnsmgr_refresh(entry, info->verbose);
 234         }
 235         AST_RWLIST_UNLOCK(info->entries);
 236
 237         ast_mutex_unlock(&refresh_lock);
 238
 239         /* automatically reschedule based on the interval */
 240         return refresh_interval * 1000;
 241 }
 242
 243 void dnsmgr_start_refresh(void)
 244 {
 245         if (refresh_sched > -1) {
 246                 AST_SCHED_DEL(sched, refresh_sched);
 247                 refresh_sched = ast_sched_add_variable(sched, 100, refresh_list, &master_refresh_info, 1);
 248         }
 249 }
 250
 251 static int do_reload(int loading);
 252
 253 static char *handle_cli_reload(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
 254 {
 255         switch (cmd) {
 256         case CLI_INIT:
 257                 e->command = "dnsmgr reload";
 258                 e->usage =
 259                         "Usage: dnsmgr reload\n"
 260                         "       Reloads the DNS manager configuration.\n";
 261                 return NULL;
 262         case CLI_GENERATE:
 263                 return NULL;
 264         }
 265         if (a->argc > 2)
 266                 return CLI_SHOWUSAGE;
 267
 268         do_reload(0);
 269         return CLI_SUCCESS;
 270 }
 271
 272 static char *handle_cli_refresh(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
 273 {
 274         struct refresh_info info = {
 275                 .entries = &entry_list,
 276                 .verbose = 1,
 277         };
 278         switch (cmd) {
 279         case CLI_INIT:
 280                 e->command = "dnsmgr refresh";
 281                 e->usage =
 282                         "Usage: dnsmgr refresh [pattern]\n"
 283                         "       Peforms an immediate refresh of the managed DNS entries.\n"
 284                         "       Optional regular expression pattern is used to filter the entries to refresh.\n";
 285                 return NULL;
 286         case CLI_GENERATE:
 287                 return NULL;
 288         }
 289         if (a->argc > 3)
 290                 return CLI_SHOWUSAGE;
 291
 292         if (a->argc == 3) {
 293                 if ( regcomp(&info.filter, a->argv[2], REG_EXTENDED | REG_NOSUB) )
 294                         return CLI_SHOWUSAGE;
 295                 else
 296                         info.regex_present = 1;
 297         }
 298
 299         refresh_list(&info);
 300
 301         if (info.regex_present)
 302                 regfree(&info.filter);
 303
 304         return CLI_SUCCESS;
 305 }
 306
 307 static char *handle_cli_status(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
 308 {
 309         int count = 0;
 310         struct ast_dnsmgr_entry *entry;
 311         switch (cmd) {
 312         case CLI_INIT:
 313                 e->command = "dnsmgr status";
 314                 e->usage =
 315                         "Usage: dnsmgr status\n"
 316                         "       Displays the DNS manager status.\n";
 317                 return NULL;
 318         case CLI_GENERATE:
 319                 return NULL;
 320         }
 321
 322         if (a->argc > 2)
 323                 return CLI_SHOWUSAGE;
 324
 325         ast_cli(a->fd, "DNS Manager: %s\n", enabled ? "enabled" : "disabled");
 326         ast_cli(a->fd, "Refresh Interval: %d seconds\n", refresh_interval);
 327         AST_RWLIST_RDLOCK(&entry_list);
 328         AST_RWLIST_TRAVERSE(&entry_list, entry, list)
 329                 count++;
 330         AST_RWLIST_UNLOCK(&entry_list);
 331         ast_cli(a->fd, "Number of entries: %d\n", count);
 332
 333         return CLI_SUCCESS;
 334 }
 335
 336 static struct ast_cli_entry cli_reload = AST_CLI_DEFINE(handle_cli_reload, "Reloads the DNS manager configuration");
 337 static struct ast_cli_entry cli_refresh = AST_CLI_DEFINE(handle_cli_refresh, "Performs an immediate refresh");
 338 static struct ast_cli_entry cli_status = AST_CLI_DEFINE(handle_cli_status, "Display the DNS manager status");
 339
 340 int dnsmgr_init(void)
 341 {
 342         if (!(sched = sched_context_create())) {
 343                 ast_log(LOG_ERROR, "Unable to create schedule context.\n");
 344                 return -1;
 345         }
 346         ast_cli_register(&cli_reload);
 347         ast_cli_register(&cli_status);
 348         ast_cli_register(&cli_refresh);
 349         return do_reload(1);
 350 }
 351
 352 int dnsmgr_reload(void)
 353 {
 354         return do_reload(0);
 355 }
 356
 357 static int do_reload(int loading)
 358 {
 359         struct ast_config *config;
 360         struct ast_flags config_flags = { loading ? 0 : CONFIG_FLAG_FILEUNCHANGED };
 361         const char *interval_value;
 362         const char *enabled_value;
 363         int interval;
 364         int was_enabled;
 365         int res = -1;
 366
 367         if ((config = ast_config_load2("dnsmgr.conf", "dnsmgr", config_flags)) == CONFIG_STATUS_FILEUNCHANGED)
 368                 return 0;
 369
 370         /* ensure that no refresh cycles run while the reload is in progress */
 371         ast_mutex_lock(&refresh_lock);
 372
 373         /* reset defaults in preparation for reading config file */
 374         refresh_interval = REFRESH_DEFAULT;
 375         was_enabled = enabled;
 376         enabled = 0;
 377
 378         AST_SCHED_DEL(sched, refresh_sched);
 379
 380         if (config) {
 381                 if ((enabled_value = ast_variable_retrieve(config, "general", "enable"))) {
 382                         enabled = ast_true(enabled_value);
 383                 }
 384                 if ((interval_value = ast_variable_retrieve(config, "general", "refreshinterval"))) {
 385                         if (sscanf(interval_value, "%d", &interval) < 1)
 386                                 ast_log(LOG_WARNING, "Unable to convert '%s' to a numeric value.\n", interval_value);
 387                         else if (interval < 0)
 388                                 ast_log(LOG_WARNING, "Invalid refresh interval '%d' specified, using default\n", interval);
 389                         else
 390                                 refresh_interval = interval;
 391                 }
 392                 ast_config_destroy(config);
 393         }
 394
 395         if (enabled && refresh_interval)
 396                 ast_log(LOG_NOTICE, "Managed DNS entries will be refreshed every %d seconds.\n", refresh_interval);
 397
 398         /* if this reload enabled the manager, create the background thread
 399            if it does not exist */
 400         if (enabled) {
 401                 if (!was_enabled && (refresh_thread == AST_PTHREADT_NULL)) {
 402                         if (ast_pthread_create_background(&refresh_thread, NULL, do_refresh, NULL) < 0) {
 403                                 ast_log(LOG_ERROR, "Unable to start refresh thread.\n");
 404                         }
 405                 }
 406                 /* make a background refresh happen right away */
 407                 refresh_sched = ast_sched_add_variable(sched, 100, refresh_list, &master_refresh_info, 1);
 408                 res = 0;
 409         }
 410         /* if this reload disabled the manager and there is a background thread,
 411            kill it */
 412         else if (!enabled && was_enabled && (refresh_thread != AST_PTHREADT_NULL)) {
 413                 /* wake up the thread so it will exit */
 414                 pthread_cancel(refresh_thread);
 415                 pthread_kill(refresh_thread, SIGURG);
 416                 pthread_join(refresh_thread, NULL);
 417                 refresh_thread = AST_PTHREADT_NULL;
 418                 ast_cli_unregister(&cli_refresh);
 419                 res = 0;
 420         }
 421         else
 422                 res = 0;
 423
 424         ast_mutex_unlock(&refresh_lock);
 425         manager_event(EVENT_FLAG_SYSTEM, "Reload", "Module: DNSmgr\r\nStatus: %s\r/nMessage: DNSmgr reload Requested\r\n", enabled ? "Enabled" : "Disabled");
 426
 427         return res;
 428 }