src/network/dns.c

   1 /* Domain Name System Resolver Department */
   2
   3 #ifdef HAVE_CONFIG_H
   4 #include "config.h"
   5 #endif
   6
   7 #include <stdlib.h>
   8 #include <string.h>
   9 #include <sys/types.h>
  10 #ifdef HAVE_NETDB_H
  11 #include <netdb.h> /* OS/2 needs this after sys/types.h */
  12 #endif
  13 #ifdef HAVE_SYS_SOCKET_H
  14 #include <sys/socket.h> /* OS/2 needs this after sys/types.h */
  15 #endif
  16 #ifdef HAVE_FCNTL_H
  17 #include <fcntl.h> /* OS/2 needs this after sys/types.h */
  18 #endif
  19 #ifdef HAVE_UNISTD_H
  20 #include <unistd.h>
  21 #endif
  22
  23 /* Go and say 'thanks' to BSD. */
  24 #ifdef HAVE_NETINET_IN_H
  25 #include <netinet/in.h>
  26 #endif
  27 #ifdef HAVE_ARPA_INET_H
  28 #include <arpa/inet.h>
  29 #endif
  30
  31 #include "elinks.h"
  32
  33 #include "config/options.h"
  34 #include "main/select.h"
  35 #include "network/dns.h"
  36 #include "osdep/osdep.h"
  37 #include "protocol/uri.h"
  38 #include "util/error.h"
  39 #include "util/memory.h"
  40 #include "util/time.h"
  41
  42
  43 struct dnsentry {
  44         LIST_HEAD(struct dnsentry);
  45
  46         struct sockaddr_storage *addr;  /* Pointer to array of addresses. */
  47         int addrno;                     /* Adress array length. */
  48         timeval_T creation_time;        /* Creation time; let us do timeouts. */
  49         unsigned char name[1];          /* Associated host; XXX: Must be last. */
  50 };
  51
  52 struct dnsquery {
  53 #ifdef THREAD_SAFE_LOOKUP
  54         struct dnsquery *next_in_queue; /* Got queued? */
  55 #endif
  56         dns_callback_T done;            /* Used for reporting back DNS result. */
  57         void *data;                     /* Private callback data. */
  58
  59         /* The @done callback is called with these members. Thus, when
  60          * free()ing, *always* set pointer to NULL ! */
  61         struct sockaddr_storage *addr;  /* Reference to array of addresses. */
  62         int addrno;                     /* Reference to array len. */
  63
  64         /* As with the two members above, when stopping a DNS query *always* set
  65          * this pointer to NULL. */
  66         struct dnsquery **queryref;     /* Reference to callers DNS member. */
  67
  68 #ifndef NO_ASYNC_LOOKUP
  69         int h;                          /* One end of the async thread pipe. */
  70 #endif
  71         unsigned char name[1];          /* Associated host; XXX: Must be last. */
  72 };
  73
  74
  75 #ifdef THREAD_SAFE_LOOKUP
  76 static struct dnsquery *dns_queue = NULL;
  77 #endif
  78
  79 static INIT_LIST_OF(struct dnsentry, dns_cache);
  80
  81 static void done_dns_lookup(struct dnsquery *query, enum dns_result res);
  82
  83
  84 /* DNS cache management: */
  85
  86 static struct dnsentry *
  87 find_in_dns_cache(unsigned char *name)
  88 {
  89         struct dnsentry *dnsentry;
  90
  91         foreach (dnsentry, dns_cache)
  92                 if (!c_strcasecmp(dnsentry->name, name)) {
  93                         move_to_top_of_list(dns_cache, dnsentry);
  94                         return dnsentry;
  95                 }
  96
  97         return NULL;
  98 }
  99
 100 static void
 101 add_to_dns_cache(unsigned char *name, struct sockaddr_storage *addr, int addrno)
 102 {
 103         int namelen = strlen(name);
 104         struct dnsentry *dnsentry;
 105         int size;
 106
 107         assert(addrno > 0);
 108
 109         dnsentry = mem_calloc(1, sizeof(*dnsentry) + namelen);
 110         if (!dnsentry) return;
 111
 112         size = addrno * sizeof(*dnsentry->addr);
 113         dnsentry->addr = mem_alloc(size);
 114         if (!dnsentry->addr) {
 115                 mem_free(dnsentry);
 116                 return;
 117         }
 118
 119         /* calloc() sets NUL char for us. */
 120         memcpy(dnsentry->name, name, namelen);
 121         memcpy(dnsentry->addr, addr, size);;
 122
 123         dnsentry->addrno = addrno;
 124
 125         timeval_now(&dnsentry->creation_time);
 126         add_to_list(dns_cache, dnsentry);
 127 }
 128
 129 static void
 130 del_dns_cache_entry(struct dnsentry *dnsentry)
 131 {
 132         del_from_list(dnsentry);
 133         mem_free_if(dnsentry->addr);
 134         mem_free(dnsentry);
 135 }
 136
 137
 138 /* Synchronous DNS lookup management: */
 139
 140 enum dns_result
 141 do_real_lookup(unsigned char *name, struct sockaddr_storage **addrs, int *addrno,
 142                int in_thread)
 143 {
 144 #ifdef CONFIG_IPV6
 145         struct addrinfo hint, *ai, *ai_cur;
 146 #else
 147         struct hostent *hostent = NULL;
 148 #endif
 149         int i;
 150
 151         if (!name || !addrs || !addrno)
 152                 return DNS_ERROR;
 153
 154 #ifdef CONFIG_IPV6
 155         /* I had a strong preference for the following, but the glibc is really
 156          * obsolete so I had to rather use much more complicated getaddrinfo().
 157          * But we duplicate the code terribly here :|. */
 158         /* hostent = getipnodebyname(name, AF_INET6, AI_ALL | AI_ADDRCONFIG, NULL); */
 159         memset(&hint, 0, sizeof(hint));
 160         hint.ai_family = AF_UNSPEC;
 161         hint.ai_socktype = SOCK_STREAM;
 162         if (getaddrinfo(name, NULL, &hint, &ai) != 0) return DNS_ERROR;
 163
 164 #else
 165         /* Seems there are problems on Mac, so we first need to try
 166          * gethostbyaddr(), but there are problems with gethostbyaddr on Cygwin,
 167          * so we do not use gethostbyaddr there. */
 168 #if defined(HAVE_GETHOSTBYADDR) && !defined(HAVE_SYS_CYGWIN_H)
 169         {
 170                 struct in_addr inp;
 171
 172                 if (is_ip_address(name, strlen(name)) && inet_aton(name, &inp))
 173                         hostent = gethostbyaddr(&inp, sizeof(inp), AF_INET);
 174         }
 175         if (!hostent)
 176 #endif
 177         {
 178                 hostent = gethostbyname(name);
 179                 if (!hostent) return DNS_ERROR;
 180         }
 181 #endif
 182
 183 #ifdef CONFIG_IPV6
 184         for (i = 0, ai_cur = ai; ai_cur; i++, ai_cur = ai_cur->ai_next);
 185 #else
 186         for (i = 0; hostent->h_addr_list[i] != NULL; i++);
 187 #endif
 188
 189         /* We cannot use mem_*() in thread ("It will chew memory on OS/2 and
 190          * BeOS because there are no locks around the memory debugging code."
 191          * -- Mikulas).  So we don't if in_thread != 0. */
 192         *addrs = in_thread ? calloc(i, sizeof(**addrs))
 193                            : mem_calloc(i, sizeof(**addrs));
 194         if (!*addrs) return DNS_ERROR;
 195         *addrno = i;
 196
 197 #ifdef CONFIG_IPV6
 198         for (i = 0, ai_cur = ai; ai_cur; i++, ai_cur = ai_cur->ai_next) {
 199                 /* Don't use struct sockaddr_in6 here: because we
 200                  * called getaddrinfo with AF_UNSPEC, the address
 201                  * might not be for IP at all.  */
 202                 struct sockaddr_storage *addr = &(*addrs)[i];
 203
 204                 /* RFC 3493 says struct sockaddr_storage is supposed
 205                  * to be "Large enough to accommodate all supported
 206                  * protocol-specific address structures."  So if
 207                  * getaddrinfo supports an address that does not fit
 208                  * in struct sockaddr_storage, then it is a bug in the
 209                  * library.  In this case, fail the whole lookup, to
 210                  * make the bug more likely to be noticed.  */
 211                 assert(ai_cur->ai_addrlen <= sizeof(*addr));
 212                 if_assert_failed {
 213                         freeaddrinfo(ai);
 214                         if (in_thread)
 215                                 free(*addrs);
 216                         else
 217                                 mem_free(*addrs);
 218                         *addrs = NULL;
 219                         *addrno = 0;
 220                         return DNS_ERROR;
 221                 }
 222
 223                 memcpy(addr, ai_cur->ai_addr, ai_cur->ai_addrlen);
 224         }
 225
 226         freeaddrinfo(ai);
 227
 228 #else
 229         for (i = 0; hostent->h_addr_list[i] != NULL; i++) {
 230                 struct sockaddr_in *addr = (struct sockaddr_in *) &(*addrs)[i];
 231
 232                 addr->sin_family = hostent->h_addrtype;
 233                 memcpy(&addr->sin_addr.s_addr, hostent->h_addr_list[i], hostent->h_length);
 234         }
 235 #endif
 236
 237         return DNS_SUCCESS;
 238 }
 239
 240
 241 /* Asynchronous DNS lookup management: */
 242
 243 #ifndef NO_ASYNC_LOOKUP
 244 static enum dns_result
 245 write_dns_data(int h, void *data, size_t datalen)
 246 {
 247         size_t done = 0;
 248
 249         do {
 250                 int w = safe_write(h, data + done, datalen - done);
 251
 252                 if (w < 0) return DNS_ERROR;
 253                 done += w;
 254         } while (done < datalen);
 255
 256         assert(done == datalen);
 257
 258         return DNS_SUCCESS;
 259 }
 260
 261 static void
 262 async_dns_writer(void *data, int h)
 263 {
 264         unsigned char *name = (unsigned char *) data;
 265         struct sockaddr_storage *addrs;
 266         int addrno, i;
 267
 268         if (do_real_lookup(name, &addrs, &addrno, 1) == DNS_ERROR)
 269                 return;
 270
 271         /* We will do blocking I/O here, however it's only local communication
 272          * and it's supposed to be just a flash talk, so it shouldn't matter.
 273          * And it would be incredibly more complicated and messy (and mainly
 274          * useless) to do this in non-blocking way. */
 275         if (set_blocking_fd(h) < 0) return;
 276
 277         if (write_dns_data(h, &addrno, sizeof(addrno)) == DNS_ERROR)
 278                 return;
 279
 280         for (i = 0; i < addrno; i++) {
 281                 struct sockaddr_storage *addr = &addrs[i];
 282
 283                 if (write_dns_data(h, addr, sizeof(*addr)) == DNS_ERROR)
 284                         return;
 285         }
 286
 287         /* We're in thread, thus we must do plain free(). */
 288         free(addrs);
 289 }
 290
 291 static enum dns_result
 292 read_dns_data(int h, void *data, size_t datalen)
 293 {
 294         size_t done = 0;
 295
 296         do {
 297                 ssize_t r = safe_read(h, data + done, datalen - done);
 298
 299                 if (r <= 0) return DNS_ERROR;
 300                 done += r;
 301         } while (done < datalen);
 302
 303         assert(done == datalen);
 304
 305         return DNS_SUCCESS;
 306 }
 307
 308 static void
 309 async_dns_reader(struct dnsquery *query)
 310 {
 311         enum dns_result result = DNS_ERROR;
 312         int i;
 313
 314         /* We will do blocking I/O here, however it's only local communication
 315          * and it's supposed to be just a flash talk, so it shouldn't matter.
 316          * And it would be incredibly more complicated and messy (and mainly
 317          * useless) to do this in non-blocking way. */
 318         if (set_blocking_fd(query->h) < 0) goto done;
 319
 320         if (read_dns_data(query->h, &query->addrno, sizeof(query->addrno)) == DNS_ERROR)
 321                 goto done;
 322
 323         query->addr = mem_calloc(query->addrno, sizeof(*query->addr));
 324         if (!query->addr) goto done;
 325
 326         for (i = 0; i < query->addrno; i++) {
 327                 struct sockaddr_storage *addr = &query->addr[i];
 328
 329                 if (read_dns_data(query->h, addr, sizeof(*addr)) == DNS_ERROR)
 330                         goto done;
 331         }
 332
 333         result = DNS_SUCCESS;
 334
 335 done:
 336         if (result == DNS_ERROR)
 337                 mem_free_set(&query->addr, NULL);
 338
 339         done_dns_lookup(query, result);
 340 }
 341
 342 static void
 343 async_dns_error(struct dnsquery *query)
 344 {
 345         done_dns_lookup(query, DNS_ERROR);
 346 }
 347
 348 static int
 349 init_async_dns_lookup(struct dnsquery *dnsquery, int force_async)
 350 {
 351         if (!force_async && !get_opt_bool("connection.async_dns", NULL)) {
 352                 dnsquery->h = -1;
 353                 return 0;
 354         }
 355
 356         dnsquery->h = start_thread(async_dns_writer, dnsquery->name,
 357                                    strlen(dnsquery->name) + 1);
 358         if (dnsquery->h == -1)
 359                 return 0;
 360
 361         set_handlers(dnsquery->h, (select_handler_T) async_dns_reader, NULL,
 362                      (select_handler_T) async_dns_error, dnsquery);
 363
 364         return 1;
 365 }
 366
 367 static void
 368 done_async_dns_lookup(struct dnsquery *dnsquery)
 369 {
 370         if (dnsquery->h == -1) return;
 371
 372         clear_handlers(dnsquery->h);
 373         close(dnsquery->h);
 374         dnsquery->h = -1;
 375 }
 376 #else
 377 #define init_async_dns_lookup(dnsquery, force)  (0)
 378 #define done_async_dns_lookup(dnsquery)         /* Nada. */
 379 #endif /* NO_ASYNC_LOOKUP */
 380
 381
 382 static enum dns_result
 383 do_lookup(struct dnsquery *query, int force_async)
 384 {
 385         enum dns_result result;
 386
 387         /* DBG("starting lookup for %s", query->name); */
 388
 389         /* Async lookup */
 390         if (init_async_dns_lookup(query, force_async))
 391                 return DNS_ASYNC;
 392
 393         /* Sync lookup */
 394         result = do_real_lookup(query->name, &query->addr, &query->addrno, 0);
 395         done_dns_lookup(query, result);
 396
 397         return result;
 398 }
 399
 400 static enum dns_result
 401 do_queued_lookup(struct dnsquery *query)
 402 {
 403 #ifdef THREAD_SAFE_LOOKUP
 404         query->next_in_queue = NULL;
 405
 406         if (dns_queue) {
 407                 /* DBG("queuing lookup for %s", q->name); */
 408                 assertm(!dns_queue->next_in_queue, "DNS queue corrupted");
 409                 dns_queue->next_in_queue = query;
 410                 dns_queue = query;
 411                 return DNS_ERROR;
 412         }
 413
 414         dns_queue = query;
 415 #endif
 416         /* DBG("direct lookup"); */
 417         return do_lookup(query, 0);
 418 }
 419
 420
 421 static void
 422 done_dns_lookup(struct dnsquery *query, enum dns_result result)
 423 {
 424         struct dnsentry *dnsentry;
 425
 426         /* DBG("end lookup %s (%d)", query->name, res); */
 427
 428         /* do_lookup() might start a new async thread */
 429         done_async_dns_lookup(query);
 430
 431 #ifdef THREAD_SAFE_LOOKUP
 432         if (query->next_in_queue) {
 433                 /* DBG("processing next in queue: %s", query->next_in_queue->name); */
 434                 do_lookup(query->next_in_queue, 1);
 435         } else {
 436                 dns_queue = NULL;
 437         }
 438 #endif
 439
 440         /* Make sure the query is unregister _before_ calling any callbacks. */
 441         *query->queryref = NULL;
 442
 443         /* If the callback was cleared skip to the freeing part. */
 444         if (!query->done)
 445                 goto done;
 446
 447         dnsentry = find_in_dns_cache(query->name);
 448         if (dnsentry) {
 449                 /* If the query failed, use the existing DNS cache entry even if
 450                  * it is too old. */
 451                 if (result == DNS_ERROR) {
 452                         query->done(query->data, dnsentry->addr, dnsentry->addrno);
 453                         goto done;
 454                 }
 455
 456                 del_dns_cache_entry(dnsentry);
 457         }
 458
 459         if (result == DNS_SUCCESS)
 460                 add_to_dns_cache(query->name, query->addr, query->addrno);
 461
 462         query->done(query->data, query->addr, query->addrno);
 463
 464 done:
 465         mem_free_set(&query->addr, NULL);
 466         mem_free(query);
 467 }
 468
 469 static enum dns_result
 470 init_dns_lookup(unsigned char *name, void **queryref,
 471                 dns_callback_T done, void *data)
 472 {
 473         struct dnsquery *query;
 474         int namelen = strlen(name);
 475
 476         query = mem_calloc(1, sizeof(*query) + namelen);
 477         if (!query) {
 478                 done(data, NULL, 0);
 479                 return DNS_ERROR;
 480         }
 481
 482         query->done = done;
 483         query->data = data;
 484
 485         /* calloc() sets NUL char for us. */
 486         memcpy(query->name, name, namelen);
 487
 488         query->queryref = (struct dnsquery **) queryref;
 489         *(query->queryref) = query;
 490
 491         return do_queued_lookup(query);
 492 }
 493
 494
 495 enum dns_result
 496 find_host(unsigned char *name, void **queryref,
 497           dns_callback_T done, void *data, int no_cache)
 498 {
 499         struct dnsentry *dnsentry;
 500
 501         assert(queryref);
 502         *queryref = NULL;
 503
 504         if (no_cache)
 505                 return init_dns_lookup(name, queryref, done, data);
 506
 507         /* Check if the DNS name is in the cache. If the cache entry is too old
 508          * do a new lookup. However, old cache entries will be used as a
 509          * fallback if the new lookup fails. */
 510         dnsentry = find_in_dns_cache(name);
 511         if (dnsentry) {
 512                 timeval_T age, now, max_age;
 513
 514                 assert(dnsentry && dnsentry->addrno > 0);
 515
 516                 timeval_from_seconds(&max_age, DNS_CACHE_TIMEOUT);
 517                 timeval_now(&now);
 518                 timeval_sub(&age, &dnsentry->creation_time, &now);
 519
 520                 if (timeval_cmp(&age, &max_age) <= 0) {
 521                         done(data, dnsentry->addr, dnsentry->addrno);
 522                         return DNS_SUCCESS;
 523                 }
 524         }
 525
 526         return init_dns_lookup(name, queryref, done, data);
 527 }
 528
 529 void
 530 kill_dns_request(void **queryref)
 531 {
 532         struct dnsquery *query = *queryref;
 533
 534         assert(query);
 535
 536         query->done = NULL;
 537         done_dns_lookup(query, DNS_ERROR);
 538 }
 539
 540 void
 541 shrink_dns_cache(int whole)
 542 {
 543         struct dnsentry *dnsentry, *next;
 544
 545         if (whole) {
 546                 foreachsafe (dnsentry, next, dns_cache)
 547                         del_dns_cache_entry(dnsentry);
 548
 549         } else {
 550                 timeval_T now, max_age;
 551
 552                 timeval_from_seconds(&max_age, DNS_CACHE_TIMEOUT);
 553                 timeval_now(&now);
 554
 555                 foreachsafe (dnsentry, next, dns_cache) {
 556                         timeval_T age;
 557
 558                         timeval_sub(&age, &dnsentry->creation_time, &now);
 559
 560                         if (timeval_cmp(&age, &max_age) > 0)
 561                                 del_dns_cache_entry(dnsentry);
 562                 }
 563         }
 564 }