src/resolve/resolved-dns-query.c

   1 /***
   2   This file is part of systemd.
   3
   4   Copyright 2014 Lennart Poettering
   5
   6   systemd is free software; you can redistribute it and/or modify it
   7   under the terms of the GNU Lesser General Public License as published by
   8   the Free Software Foundation; either version 2.1 of the License, or
   9   (at your option) any later version.
  10
  11   systemd is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   Lesser General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public License
  17   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  18 ***/
  19
  20 #include "alloc-util.h"
  21 #include "dns-domain.h"
  22 #include "dns-type.h"
  23 #include "hostname-util.h"
  24 #include "local-addresses.h"
  25 #include "resolved-dns-query.h"
  26 #include "resolved-dns-synthesize.h"
  27 #include "resolved-etc-hosts.h"
  28 #include "string-util.h"
  29
  30 /* How long to wait for the query in total */
  31 #define QUERY_TIMEOUT_USEC (30 * USEC_PER_SEC)
  32
  33 #define CNAME_MAX 8
  34 #define QUERIES_MAX 2048
  35 #define AUXILIARY_QUERIES_MAX 64
  36
  37 static int dns_query_candidate_new(DnsQueryCandidate **ret, DnsQuery *q, DnsScope *s) {
  38         DnsQueryCandidate *c;
  39
  40         assert(ret);
  41         assert(q);
  42         assert(s);
  43
  44         c = new0(DnsQueryCandidate, 1);
  45         if (!c)
  46                 return -ENOMEM;
  47
  48         c->query = q;
  49         c->scope = s;
  50
  51         LIST_PREPEND(candidates_by_query, q->candidates, c);
  52         LIST_PREPEND(candidates_by_scope, s->query_candidates, c);
  53
  54         *ret = c;
  55         return 0;
  56 }
  57
  58 static void dns_query_candidate_stop(DnsQueryCandidate *c) {
  59         DnsTransaction *t;
  60
  61         assert(c);
  62
  63         while ((t = set_steal_first(c->transactions))) {
  64                 set_remove(t->notify_query_candidates, c);
  65                 dns_transaction_gc(t);
  66         }
  67 }
  68
  69 DnsQueryCandidate* dns_query_candidate_free(DnsQueryCandidate *c) {
  70
  71         if (!c)
  72                 return NULL;
  73
  74         dns_query_candidate_stop(c);
  75
  76         set_free(c->transactions);
  77         dns_search_domain_unref(c->search_domain);
  78
  79         if (c->query)
  80                 LIST_REMOVE(candidates_by_query, c->query->candidates, c);
  81
  82         if (c->scope)
  83                 LIST_REMOVE(candidates_by_scope, c->scope->query_candidates, c);
  84
  85         free(c);
  86
  87         return NULL;
  88 }
  89
  90 static int dns_query_candidate_next_search_domain(DnsQueryCandidate *c) {
  91         DnsSearchDomain *next = NULL;
  92
  93         assert(c);
  94
  95         if (c->search_domain && c->search_domain->linked)
  96                 next = c->search_domain->domains_next;
  97         else
  98                 next = dns_scope_get_search_domains(c->scope);
  99
 100         for (;;) {
 101                 if (!next) /* We hit the end of the list */
 102                         return 0;
 103
 104                 if (!next->route_only)
 105                         break;
 106
 107                 /* Skip over route-only domains */
 108                 next = next->domains_next;
 109         }
 110
 111         dns_search_domain_unref(c->search_domain);
 112         c->search_domain = dns_search_domain_ref(next);
 113
 114         return 1;
 115 }
 116
 117 static int dns_query_candidate_add_transaction(DnsQueryCandidate *c, DnsResourceKey *key) {
 118         DnsTransaction *t;
 119         int r;
 120
 121         assert(c);
 122         assert(key);
 123
 124         t = dns_scope_find_transaction(c->scope, key, true);
 125         if (!t) {
 126                 r = dns_transaction_new(&t, c->scope, key);
 127                 if (r < 0)
 128                         return r;
 129         } else {
 130                 if (set_contains(c->transactions, t))
 131                         return 0;
 132         }
 133
 134         r = set_ensure_allocated(&c->transactions, NULL);
 135         if (r < 0)
 136                 goto gc;
 137
 138         r = set_ensure_allocated(&t->notify_query_candidates, NULL);
 139         if (r < 0)
 140                 goto gc;
 141
 142         r = set_put(t->notify_query_candidates, c);
 143         if (r < 0)
 144                 goto gc;
 145
 146         r = set_put(c->transactions, t);
 147         if (r < 0) {
 148                 (void) set_remove(t->notify_query_candidates, c);
 149                 goto gc;
 150         }
 151
 152         return 1;
 153
 154 gc:
 155         dns_transaction_gc(t);
 156         return r;
 157 }
 158
 159 static int dns_query_candidate_go(DnsQueryCandidate *c) {
 160         DnsTransaction *t;
 161         Iterator i;
 162         int r;
 163         unsigned n = 0;
 164
 165         assert(c);
 166
 167         /* Start the transactions that are not started yet */
 168         SET_FOREACH(t, c->transactions, i) {
 169                 if (t->state != DNS_TRANSACTION_NULL)
 170                         continue;
 171
 172                 r = dns_transaction_go(t);
 173                 if (r < 0)
 174                         return r;
 175
 176                 n++;
 177         }
 178
 179         /* If there was nothing to start, then let's proceed immediately */
 180         if (n == 0)
 181                 dns_query_candidate_notify(c);
 182
 183         return 0;
 184 }
 185
 186 static DnsTransactionState dns_query_candidate_state(DnsQueryCandidate *c) {
 187         DnsTransactionState state = DNS_TRANSACTION_NO_SERVERS;
 188         DnsTransaction *t;
 189         Iterator i;
 190
 191         assert(c);
 192
 193         if (c->error_code != 0)
 194                 return DNS_TRANSACTION_ERRNO;
 195
 196         SET_FOREACH(t, c->transactions, i) {
 197
 198                 switch (t->state) {
 199
 200                 case DNS_TRANSACTION_NULL:
 201                         /* If there's a NULL transaction pending, then
 202                          * this means not all transactions where
 203                          * started yet, and we were called from within
 204                          * the stackframe that is supposed to start
 205                          * remaining transactions. In this case,
 206                          * simply claim the candidate is pending. */
 207
 208                 case DNS_TRANSACTION_PENDING:
 209                 case DNS_TRANSACTION_VALIDATING:
 210                         /* If there's one transaction currently in
 211                          * VALIDATING state, then this means there's
 212                          * also one in PENDING state, hence we can
 213                          * return PENDING immediately. */
 214                         return DNS_TRANSACTION_PENDING;
 215
 216                 case DNS_TRANSACTION_SUCCESS:
 217                         state = t->state;
 218                         break;
 219
 220                 default:
 221                         if (state != DNS_TRANSACTION_SUCCESS)
 222                                 state = t->state;
 223
 224                         break;
 225                 }
 226         }
 227
 228         return state;
 229 }
 230
 231 static bool dns_query_candidate_is_routable(DnsQueryCandidate *c, uint16_t type) {
 232         int family;
 233
 234         assert(c);
 235
 236         /* Checks whether the specified RR type matches an address family that is routable on the link(s) the scope of
 237          * this candidate belongs to. Specifically, whether there's a routable IPv4 address on it if we query an A RR,
 238          * or a routable IPv6 address if we query an AAAA RR. */
 239
 240         if (!c->query->suppress_unroutable_family)
 241                 return true;
 242
 243         if (c->scope->protocol != DNS_PROTOCOL_DNS)
 244                 return true;
 245
 246         family = dns_type_to_af(type);
 247         if (family < 0)
 248                 return true;
 249
 250         if (c->scope->link)
 251                 return link_relevant(c->scope->link, family, false);
 252         else
 253                 return manager_routable(c->scope->manager, family);
 254 }
 255
 256 static int dns_query_candidate_setup_transactions(DnsQueryCandidate *c) {
 257         DnsQuestion *question;
 258         DnsResourceKey *key;
 259         int n = 0, r;
 260
 261         assert(c);
 262
 263         dns_query_candidate_stop(c);
 264
 265         question = dns_query_question_for_protocol(c->query, c->scope->protocol);
 266
 267         /* Create one transaction per question key */
 268         DNS_QUESTION_FOREACH(key, question) {
 269                 _cleanup_(dns_resource_key_unrefp) DnsResourceKey *new_key = NULL;
 270                 DnsResourceKey *qkey;
 271
 272                 if (!dns_query_candidate_is_routable(c, key->type))
 273                         continue;
 274
 275                 if (c->search_domain) {
 276                         r = dns_resource_key_new_append_suffix(&new_key, key, c->search_domain->name);
 277                         if (r < 0)
 278                                 goto fail;
 279
 280                         qkey = new_key;
 281                 } else
 282                         qkey = key;
 283
 284                 if (!dns_scope_good_key(c->scope, qkey))
 285                         continue;
 286
 287                 r = dns_query_candidate_add_transaction(c, qkey);
 288                 if (r < 0)
 289                         goto fail;
 290
 291                 n++;
 292         }
 293
 294         return n;
 295
 296 fail:
 297         dns_query_candidate_stop(c);
 298         return r;
 299 }
 300
 301 void dns_query_candidate_notify(DnsQueryCandidate *c) {
 302         DnsTransactionState state;
 303         int r;
 304
 305         assert(c);
 306
 307         state = dns_query_candidate_state(c);
 308
 309         if (DNS_TRANSACTION_IS_LIVE(state))
 310                 return;
 311
 312         if (state != DNS_TRANSACTION_SUCCESS && c->search_domain) {
 313
 314                 r = dns_query_candidate_next_search_domain(c);
 315                 if (r < 0)
 316                         goto fail;
 317
 318                 if (r > 0) {
 319                         /* OK, there's another search domain to try, let's do so. */
 320
 321                         r = dns_query_candidate_setup_transactions(c);
 322                         if (r < 0)
 323                                 goto fail;
 324
 325                         if (r > 0) {
 326                                 /* New transactions where queued. Start them and wait */
 327
 328                                 r = dns_query_candidate_go(c);
 329                                 if (r < 0)
 330                                         goto fail;
 331
 332                                 return;
 333                         }
 334                 }
 335
 336         }
 337
 338         dns_query_ready(c->query);
 339         return;
 340
 341 fail:
 342         log_warning_errno(r, "Failed to follow search domains: %m");
 343         c->error_code = r;
 344         dns_query_ready(c->query);
 345 }
 346
 347 static void dns_query_stop(DnsQuery *q) {
 348         DnsQueryCandidate *c;
 349
 350         assert(q);
 351
 352         q->timeout_event_source = sd_event_source_unref(q->timeout_event_source);
 353
 354         LIST_FOREACH(candidates_by_query, c, q->candidates)
 355                 dns_query_candidate_stop(c);
 356 }
 357
 358 static void dns_query_free_candidates(DnsQuery *q) {
 359         assert(q);
 360
 361         while (q->candidates)
 362                 dns_query_candidate_free(q->candidates);
 363 }
 364
 365 static void dns_query_reset_answer(DnsQuery *q) {
 366         assert(q);
 367
 368         q->answer = dns_answer_unref(q->answer);
 369         q->answer_rcode = 0;
 370         q->answer_dnssec_result = _DNSSEC_RESULT_INVALID;
 371         q->answer_errno = 0;
 372         q->answer_authenticated = false;
 373         q->answer_protocol = _DNS_PROTOCOL_INVALID;
 374         q->answer_family = AF_UNSPEC;
 375         q->answer_search_domain = dns_search_domain_unref(q->answer_search_domain);
 376 }
 377
 378 DnsQuery *dns_query_free(DnsQuery *q) {
 379         if (!q)
 380                 return NULL;
 381
 382         while (q->auxiliary_queries)
 383                 dns_query_free(q->auxiliary_queries);
 384
 385         if (q->auxiliary_for) {
 386                 assert(q->auxiliary_for->n_auxiliary_queries > 0);
 387                 q->auxiliary_for->n_auxiliary_queries--;
 388                 LIST_REMOVE(auxiliary_queries, q->auxiliary_for->auxiliary_queries, q);
 389         }
 390
 391         dns_query_free_candidates(q);
 392
 393         dns_question_unref(q->question_idna);
 394         dns_question_unref(q->question_utf8);
 395
 396         dns_query_reset_answer(q);
 397
 398         sd_bus_message_unref(q->request);
 399         sd_bus_track_unref(q->bus_track);
 400
 401         free(q->request_address_string);
 402
 403         if (q->manager) {
 404                 LIST_REMOVE(queries, q->manager->dns_queries, q);
 405                 q->manager->n_dns_queries--;
 406         }
 407
 408         free(q);
 409
 410         return NULL;
 411 }
 412
 413 int dns_query_new(
 414                 Manager *m,
 415                 DnsQuery **ret,
 416                 DnsQuestion *question_utf8,
 417                 DnsQuestion *question_idna,
 418                 int ifindex, uint64_t flags) {
 419
 420         _cleanup_(dns_query_freep) DnsQuery *q = NULL;
 421         DnsResourceKey *key;
 422         bool good = false;
 423         int r;
 424         char key_str[DNS_RESOURCE_KEY_STRING_MAX];
 425
 426         assert(m);
 427
 428         if (dns_question_size(question_utf8) > 0) {
 429                 r = dns_question_is_valid_for_query(question_utf8);
 430                 if (r < 0)
 431                         return r;
 432                 if (r == 0)
 433                         return -EINVAL;
 434
 435                 good = true;
 436         }
 437
 438         /* If the IDNA and UTF8 questions are the same, merge their references */
 439         r = dns_question_is_equal(question_idna, question_utf8);
 440         if (r < 0)
 441                 return r;
 442         if (r > 0)
 443                 question_idna = question_utf8;
 444         else {
 445                 if (dns_question_size(question_idna) > 0) {
 446                         r = dns_question_is_valid_for_query(question_idna);
 447                         if (r < 0)
 448                                 return r;
 449                         if (r == 0)
 450                                 return -EINVAL;
 451
 452                         good = true;
 453                 }
 454         }
 455
 456         if (!good) /* don't allow empty queries */
 457                 return -EINVAL;
 458
 459         if (m->n_dns_queries >= QUERIES_MAX)
 460                 return -EBUSY;
 461
 462         q = new0(DnsQuery, 1);
 463         if (!q)
 464                 return -ENOMEM;
 465
 466         q->question_utf8 = dns_question_ref(question_utf8);
 467         q->question_idna = dns_question_ref(question_idna);
 468         q->ifindex = ifindex;
 469         q->flags = flags;
 470         q->answer_dnssec_result = _DNSSEC_RESULT_INVALID;
 471         q->answer_protocol = _DNS_PROTOCOL_INVALID;
 472         q->answer_family = AF_UNSPEC;
 473
 474         /* First dump UTF8  question */
 475         DNS_QUESTION_FOREACH(key, question_utf8)
 476                 log_debug("Looking up RR for %s.",
 477                           dns_resource_key_to_string(key, key_str, sizeof key_str));
 478
 479         /* And then dump the IDNA question, but only what hasn't been dumped already through the UTF8 question. */
 480         DNS_QUESTION_FOREACH(key, question_idna) {
 481                 r = dns_question_contains(question_utf8, key);
 482                 if (r < 0)
 483                         return r;
 484                 if (r > 0)
 485                         continue;
 486
 487                 log_debug("Looking up IDNA RR for %s.",
 488                           dns_resource_key_to_string(key, key_str, sizeof key_str));
 489         }
 490
 491         LIST_PREPEND(queries, m->dns_queries, q);
 492         m->n_dns_queries++;
 493         q->manager = m;
 494
 495         if (ret)
 496                 *ret = q;
 497         q = NULL;
 498
 499         return 0;
 500 }
 501
 502 int dns_query_make_auxiliary(DnsQuery *q, DnsQuery *auxiliary_for) {
 503         assert(q);
 504         assert(auxiliary_for);
 505
 506         /* Ensure that that the query is not auxiliary yet, and
 507          * nothing else is auxiliary to it either */
 508         assert(!q->auxiliary_for);
 509         assert(!q->auxiliary_queries);
 510
 511         /* Ensure that the unit we shall be made auxiliary for isn't
 512          * auxiliary itself */
 513         assert(!auxiliary_for->auxiliary_for);
 514
 515         if (auxiliary_for->n_auxiliary_queries >= AUXILIARY_QUERIES_MAX)
 516                 return -EAGAIN;
 517
 518         LIST_PREPEND(auxiliary_queries, auxiliary_for->auxiliary_queries, q);
 519         q->auxiliary_for = auxiliary_for;
 520
 521         auxiliary_for->n_auxiliary_queries++;
 522         return 0;
 523 }
 524
 525 static void dns_query_complete(DnsQuery *q, DnsTransactionState state) {
 526         assert(q);
 527         assert(!DNS_TRANSACTION_IS_LIVE(state));
 528         assert(DNS_TRANSACTION_IS_LIVE(q->state));
 529
 530         /* Note that this call might invalidate the query. Callers
 531          * should hence not attempt to access the query or transaction
 532          * after calling this function. */
 533
 534         q->state = state;
 535
 536         dns_query_stop(q);
 537         if (q->complete)
 538                 q->complete(q);
 539 }
 540
 541 static int on_query_timeout(sd_event_source *s, usec_t usec, void *userdata) {
 542         DnsQuery *q = userdata;
 543
 544         assert(s);
 545         assert(q);
 546
 547         dns_query_complete(q, DNS_TRANSACTION_TIMEOUT);
 548         return 0;
 549 }
 550
 551 static int dns_query_add_candidate(DnsQuery *q, DnsScope *s) {
 552         DnsQueryCandidate *c;
 553         int r;
 554
 555         assert(q);
 556         assert(s);
 557
 558         r = dns_query_candidate_new(&c, q, s);
 559         if (r < 0)
 560                 return r;
 561
 562         /* If this a single-label domain on DNS, we might append a suitable search domain first. */
 563         if ((q->flags & SD_RESOLVED_NO_SEARCH) == 0)  {
 564                 r = dns_scope_name_needs_search_domain(s, dns_question_first_name(q->question_idna));
 565                 if (r < 0)
 566                         goto fail;
 567                 if (r > 0) {
 568                         /* OK, we need a search domain now. Let's find one for this scope */
 569
 570                         r = dns_query_candidate_next_search_domain(c);
 571                         if (r <= 0) /* if there's no search domain, then we won't add any transaction. */
 572                                 goto fail;
 573                 }
 574         }
 575
 576         r = dns_query_candidate_setup_transactions(c);
 577         if (r < 0)
 578                 goto fail;
 579
 580         return 0;
 581
 582 fail:
 583         dns_query_candidate_free(c);
 584         return r;
 585 }
 586
 587 static int dns_query_synthesize_reply(DnsQuery *q, DnsTransactionState *state) {
 588         _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
 589         int r;
 590
 591         assert(q);
 592         assert(state);
 593
 594         /* Tries to synthesize localhost RR replies (and others) where appropriate. Note that this is done *after* the
 595          * the normal lookup finished. The data from the network hence takes precedence over the data we
 596          * synthesize. (But note that many scopes refuse to resolve certain domain names) */
 597
 598         if (!IN_SET(*state,
 599                     DNS_TRANSACTION_RCODE_FAILURE,
 600                     DNS_TRANSACTION_NO_SERVERS,
 601                     DNS_TRANSACTION_TIMEOUT,
 602                     DNS_TRANSACTION_ATTEMPTS_MAX_REACHED,
 603                     DNS_TRANSACTION_NETWORK_DOWN,
 604                     DNS_TRANSACTION_NOT_FOUND))
 605                 return 0;
 606
 607         r = dns_synthesize_answer(
 608                         q->manager,
 609                         q->question_utf8,
 610                         q->ifindex,
 611                         &answer);
 612
 613         if (r <= 0)
 614                 return r;
 615
 616         dns_query_reset_answer(q);
 617
 618         q->answer = answer;
 619         answer = NULL;
 620         q->answer_rcode = DNS_RCODE_SUCCESS;
 621         q->answer_protocol = dns_synthesize_protocol(q->flags);
 622         q->answer_family = dns_synthesize_family(q->flags);
 623         q->answer_authenticated = true;
 624
 625         *state = DNS_TRANSACTION_SUCCESS;
 626
 627         return 1;
 628 }
 629
 630 static int dns_query_try_etc_hosts(DnsQuery *q) {
 631         _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
 632         int r;
 633
 634         assert(q);
 635
 636         /* Looks in /etc/hosts for matching entries. Note that this is done *before* the normal lookup is done. The
 637          * data from /etc/hosts hence takes precedence over the network. */
 638
 639         r = manager_etc_hosts_lookup(
 640                         q->manager,
 641                         q->question_utf8,
 642                         &answer);
 643         if (r <= 0)
 644                 return r;
 645
 646         dns_query_reset_answer(q);
 647
 648         q->answer = answer;
 649         answer = NULL;
 650         q->answer_rcode = DNS_RCODE_SUCCESS;
 651         q->answer_protocol = dns_synthesize_protocol(q->flags);
 652         q->answer_family = dns_synthesize_family(q->flags);
 653         q->answer_authenticated = true;
 654
 655         return 1;
 656 }
 657
 658 int dns_query_go(DnsQuery *q) {
 659         DnsScopeMatch found = DNS_SCOPE_NO;
 660         DnsScope *s, *first = NULL;
 661         DnsQueryCandidate *c;
 662         int r;
 663
 664         assert(q);
 665
 666         if (q->state != DNS_TRANSACTION_NULL)
 667                 return 0;
 668
 669         r = dns_query_try_etc_hosts(q);
 670         if (r < 0)
 671                 return r;
 672         if (r > 0) {
 673                 dns_query_complete(q, DNS_TRANSACTION_SUCCESS);
 674                 return 1;
 675         }
 676
 677         LIST_FOREACH(scopes, s, q->manager->dns_scopes) {
 678                 DnsScopeMatch match;
 679                 const char *name;
 680
 681                 name = dns_question_first_name(dns_query_question_for_protocol(q, s->protocol));
 682                 if (!name)
 683                         continue;
 684
 685                 match = dns_scope_good_domain(s, q->ifindex, q->flags, name);
 686                 if (match < 0)
 687                         return match;
 688
 689                 if (match == DNS_SCOPE_NO)
 690                         continue;
 691
 692                 found = match;
 693
 694                 if (match == DNS_SCOPE_YES) {
 695                         first = s;
 696                         break;
 697                 } else {
 698                         assert(match == DNS_SCOPE_MAYBE);
 699
 700                         if (!first)
 701                                 first = s;
 702                 }
 703         }
 704
 705         if (found == DNS_SCOPE_NO) {
 706                 DnsTransactionState state = DNS_TRANSACTION_NO_SERVERS;
 707
 708                 r = dns_query_synthesize_reply(q, &state);
 709                 if (r < 0)
 710                         return r;
 711
 712                 dns_query_complete(q, state);
 713                 return 1;
 714         }
 715
 716         r = dns_query_add_candidate(q, first);
 717         if (r < 0)
 718                 goto fail;
 719
 720         LIST_FOREACH(scopes, s, first->scopes_next) {
 721                 DnsScopeMatch match;
 722                 const char *name;
 723
 724                 name = dns_question_first_name(dns_query_question_for_protocol(q, s->protocol));
 725                 if (!name)
 726                         continue;
 727
 728                 match = dns_scope_good_domain(s, q->ifindex, q->flags, name);
 729                 if (match < 0)
 730                         goto fail;
 731
 732                 if (match != found)
 733                         continue;
 734
 735                 r = dns_query_add_candidate(q, s);
 736                 if (r < 0)
 737                         goto fail;
 738         }
 739
 740         dns_query_reset_answer(q);
 741
 742         r = sd_event_add_time(
 743                         q->manager->event,
 744                         &q->timeout_event_source,
 745                         clock_boottime_or_monotonic(),
 746                         now(clock_boottime_or_monotonic()) + QUERY_TIMEOUT_USEC, 0,
 747                         on_query_timeout, q);
 748         if (r < 0)
 749                 goto fail;
 750
 751         (void) sd_event_source_set_description(q->timeout_event_source, "query-timeout");
 752
 753         q->state = DNS_TRANSACTION_PENDING;
 754         q->block_ready++;
 755
 756         /* Start the transactions */
 757         LIST_FOREACH(candidates_by_query, c, q->candidates) {
 758                 r = dns_query_candidate_go(c);
 759                 if (r < 0) {
 760                         q->block_ready--;
 761                         goto fail;
 762                 }
 763         }
 764
 765         q->block_ready--;
 766         dns_query_ready(q);
 767
 768         return 1;
 769
 770 fail:
 771         dns_query_stop(q);
 772         return r;
 773 }
 774
 775 static void dns_query_accept(DnsQuery *q, DnsQueryCandidate *c) {
 776         DnsTransactionState state = DNS_TRANSACTION_NO_SERVERS;
 777         bool has_authenticated = false, has_non_authenticated = false;
 778         DnssecResult dnssec_result_authenticated = _DNSSEC_RESULT_INVALID, dnssec_result_non_authenticated = _DNSSEC_RESULT_INVALID;
 779         DnsTransaction *t;
 780         Iterator i;
 781         int r;
 782
 783         assert(q);
 784
 785         if (!c) {
 786                 r = dns_query_synthesize_reply(q, &state);
 787                 if (r < 0)
 788                         goto fail;
 789
 790                 dns_query_complete(q, state);
 791                 return;
 792         }
 793
 794         if (c->error_code != 0) {
 795                 /* If the candidate had an error condition of its own, start with that. */
 796                 state = DNS_TRANSACTION_ERRNO;
 797                 q->answer = dns_answer_unref(q->answer);
 798                 q->answer_rcode = 0;
 799                 q->answer_dnssec_result = _DNSSEC_RESULT_INVALID;
 800                 q->answer_errno = c->error_code;
 801         }
 802
 803         SET_FOREACH(t, c->transactions, i) {
 804
 805                 switch (t->state) {
 806
 807                 case DNS_TRANSACTION_SUCCESS: {
 808                         /* We found a successfuly reply, merge it into the answer */
 809                         r = dns_answer_extend(&q->answer, t->answer);
 810                         if (r < 0)
 811                                 goto fail;
 812
 813                         q->answer_rcode = t->answer_rcode;
 814                         q->answer_errno = 0;
 815
 816                         if (t->answer_authenticated) {
 817                                 has_authenticated = true;
 818                                 dnssec_result_authenticated = t->answer_dnssec_result;
 819                         } else {
 820                                 has_non_authenticated = true;
 821                                 dnssec_result_non_authenticated = t->answer_dnssec_result;
 822                         }
 823
 824                         state = DNS_TRANSACTION_SUCCESS;
 825                         break;
 826                 }
 827
 828                 case DNS_TRANSACTION_NULL:
 829                 case DNS_TRANSACTION_PENDING:
 830                 case DNS_TRANSACTION_VALIDATING:
 831                 case DNS_TRANSACTION_ABORTED:
 832                         /* Ignore transactions that didn't complete */
 833                         continue;
 834
 835                 default:
 836                         /* Any kind of failure? Store the data away,
 837                          * if there's nothing stored yet. */
 838
 839                         if (state == DNS_TRANSACTION_SUCCESS)
 840                                 continue;
 841
 842                         q->answer = dns_answer_unref(q->answer);
 843                         q->answer_rcode = t->answer_rcode;
 844                         q->answer_dnssec_result = t->answer_dnssec_result;
 845                         q->answer_errno = t->answer_errno;
 846
 847                         state = t->state;
 848                         break;
 849                 }
 850         }
 851
 852         if (state == DNS_TRANSACTION_SUCCESS) {
 853                 q->answer_authenticated = has_authenticated && !has_non_authenticated;
 854                 q->answer_dnssec_result = q->answer_authenticated ? dnssec_result_authenticated : dnssec_result_non_authenticated;
 855         }
 856
 857         q->answer_protocol = c->scope->protocol;
 858         q->answer_family = c->scope->family;
 859
 860         dns_search_domain_unref(q->answer_search_domain);
 861         q->answer_search_domain = dns_search_domain_ref(c->search_domain);
 862
 863         r = dns_query_synthesize_reply(q, &state);
 864         if (r < 0)
 865                 goto fail;
 866
 867         dns_query_complete(q, state);
 868         return;
 869
 870 fail:
 871         q->answer_errno = -r;
 872         dns_query_complete(q, DNS_TRANSACTION_ERRNO);
 873 }
 874
 875 void dns_query_ready(DnsQuery *q) {
 876
 877         DnsQueryCandidate *bad = NULL, *c;
 878         bool pending = false;
 879
 880         assert(q);
 881         assert(DNS_TRANSACTION_IS_LIVE(q->state));
 882
 883         /* Note that this call might invalidate the query. Callers
 884          * should hence not attempt to access the query or transaction
 885          * after calling this function, unless the block_ready
 886          * counter was explicitly bumped before doing so. */
 887
 888         if (q->block_ready > 0)
 889                 return;
 890
 891         LIST_FOREACH(candidates_by_query, c, q->candidates) {
 892                 DnsTransactionState state;
 893
 894                 state = dns_query_candidate_state(c);
 895                 switch (state) {
 896
 897                 case DNS_TRANSACTION_SUCCESS:
 898                         /* One of the candidates is successful,
 899                          * let's use it, and copy its data out */
 900                         dns_query_accept(q, c);
 901                         return;
 902
 903                 case DNS_TRANSACTION_NULL:
 904                 case DNS_TRANSACTION_PENDING:
 905                 case DNS_TRANSACTION_VALIDATING:
 906                         /* One of the candidates is still going on,
 907                          * let's maybe wait for it */
 908                         pending = true;
 909                         break;
 910
 911                 default:
 912                         /* Any kind of failure */
 913                         bad = c;
 914                         break;
 915                 }
 916         }
 917
 918         if (pending)
 919                 return;
 920
 921         dns_query_accept(q, bad);
 922 }
 923
 924 static int dns_query_cname_redirect(DnsQuery *q, const DnsResourceRecord *cname) {
 925         _cleanup_(dns_question_unrefp) DnsQuestion *nq_idna = NULL, *nq_utf8 = NULL;
 926         int r, k;
 927
 928         assert(q);
 929
 930         q->n_cname_redirects++;
 931         if (q->n_cname_redirects > CNAME_MAX)
 932                 return -ELOOP;
 933
 934         r = dns_question_cname_redirect(q->question_idna, cname, &nq_idna);
 935         if (r < 0)
 936                 return r;
 937         else if (r > 0)
 938                 log_debug("Following CNAME/DNAME %s → %s.", dns_question_first_name(q->question_idna), dns_question_first_name(nq_idna));
 939
 940         k = dns_question_is_equal(q->question_idna, q->question_utf8);
 941         if (k < 0)
 942                 return r;
 943         if (k > 0) {
 944                 /* Same question? Shortcut new question generation */
 945                 nq_utf8 = dns_question_ref(nq_idna);
 946                 k = r;
 947         } else {
 948                 k = dns_question_cname_redirect(q->question_utf8, cname, &nq_utf8);
 949                 if (k < 0)
 950                         return k;
 951                 else if (k > 0)
 952                         log_debug("Following UTF8 CNAME/DNAME %s → %s.", dns_question_first_name(q->question_utf8), dns_question_first_name(nq_utf8));
 953         }
 954
 955         if (r == 0 && k == 0) /* No actual cname happened? */
 956                 return -ELOOP;
 957
 958         if (q->answer_protocol == DNS_PROTOCOL_DNS) {
 959                 /* Don't permit CNAME redirects from unicast DNS to LLMNR or MulticastDNS, so that global resources
 960                  * cannot invade the local namespace. The opposite way we permit: local names may redirect to global
 961                  * ones. */
 962
 963                 q->flags &= ~(SD_RESOLVED_LLMNR|SD_RESOLVED_MDNS); /* mask away the local protocols */
 964         }
 965
 966         /* Turn off searching for the new name */
 967         q->flags |= SD_RESOLVED_NO_SEARCH;
 968
 969         dns_question_unref(q->question_idna);
 970         q->question_idna = nq_idna;
 971         nq_idna = NULL;
 972
 973         dns_question_unref(q->question_utf8);
 974         q->question_utf8 = nq_utf8;
 975         nq_utf8 = NULL;
 976
 977         dns_query_free_candidates(q);
 978         dns_query_reset_answer(q);
 979
 980         q->state = DNS_TRANSACTION_NULL;
 981
 982         return 0;
 983 }
 984
 985 int dns_query_process_cname(DnsQuery *q) {
 986         _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *cname = NULL;
 987         DnsQuestion *question;
 988         DnsResourceRecord *rr;
 989         int r;
 990
 991         assert(q);
 992
 993         if (!IN_SET(q->state, DNS_TRANSACTION_SUCCESS, DNS_TRANSACTION_NULL))
 994                 return DNS_QUERY_NOMATCH;
 995
 996         question = dns_query_question_for_protocol(q, q->answer_protocol);
 997
 998         DNS_ANSWER_FOREACH(rr, q->answer) {
 999                 r = dns_question_matches_rr(question, rr, DNS_SEARCH_DOMAIN_NAME(q->answer_search_domain));
1000                 if (r < 0)
1001                         return r;
1002                 if (r > 0)
1003                         return DNS_QUERY_MATCH; /* The answer matches directly, no need to follow cnames */
1004
1005                 r = dns_question_matches_cname_or_dname(question, rr, DNS_SEARCH_DOMAIN_NAME(q->answer_search_domain));
1006                 if (r < 0)
1007                         return r;
1008                 if (r > 0 && !cname)
1009                         cname = dns_resource_record_ref(rr);
1010         }
1011
1012         if (!cname)
1013                 return DNS_QUERY_NOMATCH; /* No match and no cname to follow */
1014
1015         if (q->flags & SD_RESOLVED_NO_CNAME)
1016                 return -ELOOP;
1017
1018         /* OK, let's actually follow the CNAME */
1019         r = dns_query_cname_redirect(q, cname);
1020         if (r < 0)
1021                 return r;
1022
1023         /* Let's see if the answer can already answer the new
1024          * redirected question */
1025         r = dns_query_process_cname(q);
1026         if (r != DNS_QUERY_NOMATCH)
1027                 return r;
1028
1029         /* OK, it cannot, let's begin with the new query */
1030         r = dns_query_go(q);
1031         if (r < 0)
1032                 return r;
1033
1034         return DNS_QUERY_RESTARTED; /* We restarted the query for a new cname */
1035 }
1036
1037 static int on_bus_track(sd_bus_track *t, void *userdata) {
1038         DnsQuery *q = userdata;
1039
1040         assert(t);
1041         assert(q);
1042
1043         log_debug("Client of active query vanished, aborting query.");
1044         dns_query_complete(q, DNS_TRANSACTION_ABORTED);
1045         return 0;
1046 }
1047
1048 int dns_query_bus_track(DnsQuery *q, sd_bus_message *m) {
1049         int r;
1050
1051         assert(q);
1052         assert(m);
1053
1054         if (!q->bus_track) {
1055                 r = sd_bus_track_new(sd_bus_message_get_bus(m), &q->bus_track, on_bus_track, q);
1056                 if (r < 0)
1057                         return r;
1058         }
1059
1060         r = sd_bus_track_add_sender(q->bus_track, m);
1061         if (r < 0)
1062                 return r;
1063
1064         return 0;
1065 }
1066
1067 DnsQuestion* dns_query_question_for_protocol(DnsQuery *q, DnsProtocol protocol) {
1068         assert(q);
1069
1070         switch (protocol) {
1071
1072         case DNS_PROTOCOL_DNS:
1073                 return q->question_idna;
1074
1075         case DNS_PROTOCOL_MDNS:
1076         case DNS_PROTOCOL_LLMNR:
1077                 return q->question_utf8;
1078
1079         default:
1080                 return NULL;
1081         }
1082 }
1083
1084 const char *dns_query_string(DnsQuery *q) {
1085         const char *name;
1086         int r;
1087
1088         /* Returns a somewhat useful human-readable lookup key string for this query */
1089
1090         if (q->request_address_string)
1091                 return q->request_address_string;
1092
1093         if (q->request_address_valid) {
1094                 r = in_addr_to_string(q->request_family, &q->request_address, &q->request_address_string);
1095                 if (r >= 0)
1096                         return q->request_address_string;
1097         }
1098
1099         name = dns_question_first_name(q->question_utf8);
1100         if (name)
1101                 return name;
1102
1103         return dns_question_first_name(q->question_idna);
1104 }