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
 425         assert(m);
 426
 427         if (dns_question_size(question_utf8) > 0) {
 428                 r = dns_question_is_valid_for_query(question_utf8);
 429                 if (r < 0)
 430                         return r;
 431                 if (r == 0)
 432                         return -EINVAL;
 433
 434                 good = true;
 435         }
 436
 437         /* If the IDNA and UTF8 questions are the same, merge their references */
 438         r = dns_question_is_equal(question_idna, question_utf8);
 439         if (r < 0)
 440                 return r;
 441         if (r > 0)
 442                 question_idna = question_utf8;
 443         else {
 444                 if (dns_question_size(question_idna) > 0) {
 445                         r = dns_question_is_valid_for_query(question_idna);
 446                         if (r < 0)
 447                                 return r;
 448                         if (r == 0)
 449                                 return -EINVAL;
 450
 451                         good = true;
 452                 }
 453         }
 454
 455         if (!good) /* don't allow empty queries */
 456                 return -EINVAL;
 457
 458         if (m->n_dns_queries >= QUERIES_MAX)
 459                 return -EBUSY;
 460
 461         q = new0(DnsQuery, 1);
 462         if (!q)
 463                 return -ENOMEM;
 464
 465         q->question_utf8 = dns_question_ref(question_utf8);
 466         q->question_idna = dns_question_ref(question_idna);
 467         q->ifindex = ifindex;
 468         q->flags = flags;
 469         q->answer_dnssec_result = _DNSSEC_RESULT_INVALID;
 470         q->answer_protocol = _DNS_PROTOCOL_INVALID;
 471         q->answer_family = AF_UNSPEC;
 472
 473         /* First dump UTF8  question */
 474         DNS_QUESTION_FOREACH(key, question_utf8) {
 475                 _cleanup_free_ char *p = NULL;
 476
 477                 r = dns_resource_key_to_string(key, &p);
 478                 if (r < 0)
 479                         return r;
 480
 481                 log_debug("Looking up RR for %s.", strstrip(p));
 482         }
 483
 484         /* And then dump the IDNA question, but only what hasn't been dumped already through the UTF8 question. */
 485         DNS_QUESTION_FOREACH(key, question_idna) {
 486                 _cleanup_free_ char *p = NULL;
 487
 488                 r = dns_question_contains(question_utf8, key);
 489                 if (r < 0)
 490                         return r;
 491                 if (r > 0)
 492                         continue;
 493
 494                 r = dns_resource_key_to_string(key, &p);
 495                 if (r < 0)
 496                         return r;
 497
 498                 log_debug("Looking up IDNA RR for %s.", strstrip(p));
 499         }
 500
 501         LIST_PREPEND(queries, m->dns_queries, q);
 502         m->n_dns_queries++;
 503         q->manager = m;
 504
 505         if (ret)
 506                 *ret = q;
 507         q = NULL;
 508
 509         return 0;
 510 }
 511
 512 int dns_query_make_auxiliary(DnsQuery *q, DnsQuery *auxiliary_for) {
 513         assert(q);
 514         assert(auxiliary_for);
 515
 516         /* Ensure that that the query is not auxiliary yet, and
 517          * nothing else is auxiliary to it either */
 518         assert(!q->auxiliary_for);
 519         assert(!q->auxiliary_queries);
 520
 521         /* Ensure that the unit we shall be made auxiliary for isn't
 522          * auxiliary itself */
 523         assert(!auxiliary_for->auxiliary_for);
 524
 525         if (auxiliary_for->n_auxiliary_queries >= AUXILIARY_QUERIES_MAX)
 526                 return -EAGAIN;
 527
 528         LIST_PREPEND(auxiliary_queries, auxiliary_for->auxiliary_queries, q);
 529         q->auxiliary_for = auxiliary_for;
 530
 531         auxiliary_for->n_auxiliary_queries++;
 532         return 0;
 533 }
 534
 535 static void dns_query_complete(DnsQuery *q, DnsTransactionState state) {
 536         assert(q);
 537         assert(!DNS_TRANSACTION_IS_LIVE(state));
 538         assert(DNS_TRANSACTION_IS_LIVE(q->state));
 539
 540         /* Note that this call might invalidate the query. Callers
 541          * should hence not attempt to access the query or transaction
 542          * after calling this function. */
 543
 544         q->state = state;
 545
 546         dns_query_stop(q);
 547         if (q->complete)
 548                 q->complete(q);
 549 }
 550
 551 static int on_query_timeout(sd_event_source *s, usec_t usec, void *userdata) {
 552         DnsQuery *q = userdata;
 553
 554         assert(s);
 555         assert(q);
 556
 557         dns_query_complete(q, DNS_TRANSACTION_TIMEOUT);
 558         return 0;
 559 }
 560
 561 static int dns_query_add_candidate(DnsQuery *q, DnsScope *s) {
 562         DnsQueryCandidate *c;
 563         int r;
 564
 565         assert(q);
 566         assert(s);
 567
 568         r = dns_query_candidate_new(&c, q, s);
 569         if (r < 0)
 570                 return r;
 571
 572         /* If this a single-label domain on DNS, we might append a suitable search domain first. */
 573         if ((q->flags & SD_RESOLVED_NO_SEARCH) == 0)  {
 574                 r = dns_scope_name_needs_search_domain(s, dns_question_first_name(q->question_idna));
 575                 if (r < 0)
 576                         goto fail;
 577                 if (r > 0) {
 578                         /* OK, we need a search domain now. Let's find one for this scope */
 579
 580                         r = dns_query_candidate_next_search_domain(c);
 581                         if (r <= 0) /* if there's no search domain, then we won't add any transaction. */
 582                                 goto fail;
 583                 }
 584         }
 585
 586         r = dns_query_candidate_setup_transactions(c);
 587         if (r < 0)
 588                 goto fail;
 589
 590         return 0;
 591
 592 fail:
 593         dns_query_candidate_free(c);
 594         return r;
 595 }
 596
 597 static int dns_query_synthesize_reply(DnsQuery *q, DnsTransactionState *state) {
 598         _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
 599         int r;
 600
 601         assert(q);
 602         assert(state);
 603
 604         /* Tries to synthesize localhost RR replies (and others) where appropriate. Note that this is done *after* the
 605          * the normal lookup finished. The data from the network hence takes precedence over the data we
 606          * synthesize. (But note that many scopes refuse to resolve certain domain names) */
 607
 608         if (!IN_SET(*state,
 609                     DNS_TRANSACTION_RCODE_FAILURE,
 610                     DNS_TRANSACTION_NO_SERVERS,
 611                     DNS_TRANSACTION_TIMEOUT,
 612                     DNS_TRANSACTION_ATTEMPTS_MAX_REACHED,
 613                     DNS_TRANSACTION_NETWORK_DOWN,
 614                     DNS_TRANSACTION_NOT_FOUND))
 615                 return 0;
 616
 617         r = dns_synthesize_answer(
 618                         q->manager,
 619                         q->question_utf8,
 620                         q->ifindex,
 621                         &answer);
 622
 623         if (r <= 0)
 624                 return r;
 625
 626         dns_query_reset_answer(q);
 627
 628         q->answer = answer;
 629         answer = NULL;
 630         q->answer_rcode = DNS_RCODE_SUCCESS;
 631         q->answer_protocol = dns_synthesize_protocol(q->flags);
 632         q->answer_family = dns_synthesize_family(q->flags);
 633         q->answer_authenticated = true;
 634
 635         *state = DNS_TRANSACTION_SUCCESS;
 636
 637         return 1;
 638 }
 639
 640 static int dns_query_try_etc_hosts(DnsQuery *q) {
 641         _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
 642         int r;
 643
 644         assert(q);
 645
 646         /* Looks in /etc/hosts for matching entries. Note that this is done *before* the normal lookup is done. The
 647          * data from /etc/hosts hence takes precedence over the network. */
 648
 649         r = manager_etc_hosts_lookup(
 650                         q->manager,
 651                         q->question_utf8,
 652                         &answer);
 653         if (r <= 0)
 654                 return r;
 655
 656         dns_query_reset_answer(q);
 657
 658         q->answer = answer;
 659         answer = NULL;
 660         q->answer_rcode = DNS_RCODE_SUCCESS;
 661         q->answer_protocol = dns_synthesize_protocol(q->flags);
 662         q->answer_family = dns_synthesize_family(q->flags);
 663         q->answer_authenticated = true;
 664
 665         return 1;
 666 }
 667
 668 int dns_query_go(DnsQuery *q) {
 669         DnsScopeMatch found = DNS_SCOPE_NO;
 670         DnsScope *s, *first = NULL;
 671         DnsQueryCandidate *c;
 672         int r;
 673
 674         assert(q);
 675
 676         if (q->state != DNS_TRANSACTION_NULL)
 677                 return 0;
 678
 679         r = dns_query_try_etc_hosts(q);
 680         if (r < 0)
 681                 return r;
 682         if (r > 0) {
 683                 dns_query_complete(q, DNS_TRANSACTION_SUCCESS);
 684                 return 1;
 685         }
 686
 687         LIST_FOREACH(scopes, s, q->manager->dns_scopes) {
 688                 DnsScopeMatch match;
 689                 const char *name;
 690
 691                 name = dns_question_first_name(dns_query_question_for_protocol(q, s->protocol));
 692                 if (!name)
 693                         continue;
 694
 695                 match = dns_scope_good_domain(s, q->ifindex, q->flags, name);
 696                 if (match < 0)
 697                         return match;
 698
 699                 if (match == DNS_SCOPE_NO)
 700                         continue;
 701
 702                 found = match;
 703
 704                 if (match == DNS_SCOPE_YES) {
 705                         first = s;
 706                         break;
 707                 } else {
 708                         assert(match == DNS_SCOPE_MAYBE);
 709
 710                         if (!first)
 711                                 first = s;
 712                 }
 713         }
 714
 715         if (found == DNS_SCOPE_NO) {
 716                 DnsTransactionState state = DNS_TRANSACTION_NO_SERVERS;
 717
 718                 r = dns_query_synthesize_reply(q, &state);
 719                 if (r < 0)
 720                         return r;
 721
 722                 dns_query_complete(q, state);
 723                 return 1;
 724         }
 725
 726         r = dns_query_add_candidate(q, first);
 727         if (r < 0)
 728                 goto fail;
 729
 730         LIST_FOREACH(scopes, s, first->scopes_next) {
 731                 DnsScopeMatch match;
 732                 const char *name;
 733
 734                 name = dns_question_first_name(dns_query_question_for_protocol(q, s->protocol));
 735                 if (!name)
 736                         continue;
 737
 738                 match = dns_scope_good_domain(s, q->ifindex, q->flags, name);
 739                 if (match < 0)
 740                         goto fail;
 741
 742                 if (match != found)
 743                         continue;
 744
 745                 r = dns_query_add_candidate(q, s);
 746                 if (r < 0)
 747                         goto fail;
 748         }
 749
 750         dns_query_reset_answer(q);
 751
 752         r = sd_event_add_time(
 753                         q->manager->event,
 754                         &q->timeout_event_source,
 755                         clock_boottime_or_monotonic(),
 756                         now(clock_boottime_or_monotonic()) + QUERY_TIMEOUT_USEC, 0,
 757                         on_query_timeout, q);
 758         if (r < 0)
 759                 goto fail;
 760
 761         (void) sd_event_source_set_description(q->timeout_event_source, "query-timeout");
 762
 763         q->state = DNS_TRANSACTION_PENDING;
 764         q->block_ready++;
 765
 766         /* Start the transactions */
 767         LIST_FOREACH(candidates_by_query, c, q->candidates) {
 768                 r = dns_query_candidate_go(c);
 769                 if (r < 0) {
 770                         q->block_ready--;
 771                         goto fail;
 772                 }
 773         }
 774
 775         q->block_ready--;
 776         dns_query_ready(q);
 777
 778         return 1;
 779
 780 fail:
 781         dns_query_stop(q);
 782         return r;
 783 }
 784
 785 static void dns_query_accept(DnsQuery *q, DnsQueryCandidate *c) {
 786         DnsTransactionState state = DNS_TRANSACTION_NO_SERVERS;
 787         bool has_authenticated = false, has_non_authenticated = false;
 788         DnssecResult dnssec_result_authenticated = _DNSSEC_RESULT_INVALID, dnssec_result_non_authenticated = _DNSSEC_RESULT_INVALID;
 789         DnsTransaction *t;
 790         Iterator i;
 791         int r;
 792
 793         assert(q);
 794
 795         if (!c) {
 796                 r = dns_query_synthesize_reply(q, &state);
 797                 if (r < 0)
 798                         goto fail;
 799
 800                 dns_query_complete(q, state);
 801                 return;
 802         }
 803
 804         if (c->error_code != 0) {
 805                 /* If the candidate had an error condition of its own, start with that. */
 806                 state = DNS_TRANSACTION_ERRNO;
 807                 q->answer = dns_answer_unref(q->answer);
 808                 q->answer_rcode = 0;
 809                 q->answer_dnssec_result = _DNSSEC_RESULT_INVALID;
 810                 q->answer_errno = c->error_code;
 811         }
 812
 813         SET_FOREACH(t, c->transactions, i) {
 814
 815                 switch (t->state) {
 816
 817                 case DNS_TRANSACTION_SUCCESS: {
 818                         /* We found a successfuly reply, merge it into the answer */
 819                         r = dns_answer_extend(&q->answer, t->answer);
 820                         if (r < 0)
 821                                 goto fail;
 822
 823                         q->answer_rcode = t->answer_rcode;
 824                         q->answer_errno = 0;
 825
 826                         if (t->answer_authenticated) {
 827                                 has_authenticated = true;
 828                                 dnssec_result_authenticated = t->answer_dnssec_result;
 829                         } else {
 830                                 has_non_authenticated = true;
 831                                 dnssec_result_non_authenticated = t->answer_dnssec_result;
 832                         }
 833
 834                         state = DNS_TRANSACTION_SUCCESS;
 835                         break;
 836                 }
 837
 838                 case DNS_TRANSACTION_NULL:
 839                 case DNS_TRANSACTION_PENDING:
 840                 case DNS_TRANSACTION_VALIDATING:
 841                 case DNS_TRANSACTION_ABORTED:
 842                         /* Ignore transactions that didn't complete */
 843                         continue;
 844
 845                 default:
 846                         /* Any kind of failure? Store the data away,
 847                          * if there's nothing stored yet. */
 848
 849                         if (state == DNS_TRANSACTION_SUCCESS)
 850                                 continue;
 851
 852                         q->answer = dns_answer_unref(q->answer);
 853                         q->answer_rcode = t->answer_rcode;
 854                         q->answer_dnssec_result = t->answer_dnssec_result;
 855                         q->answer_errno = t->answer_errno;
 856
 857                         state = t->state;
 858                         break;
 859                 }
 860         }
 861
 862         if (state == DNS_TRANSACTION_SUCCESS) {
 863                 q->answer_authenticated = has_authenticated && !has_non_authenticated;
 864                 q->answer_dnssec_result = q->answer_authenticated ? dnssec_result_authenticated : dnssec_result_non_authenticated;
 865         }
 866
 867         q->answer_protocol = c->scope->protocol;
 868         q->answer_family = c->scope->family;
 869
 870         dns_search_domain_unref(q->answer_search_domain);
 871         q->answer_search_domain = dns_search_domain_ref(c->search_domain);
 872
 873         r = dns_query_synthesize_reply(q, &state);
 874         if (r < 0)
 875                 goto fail;
 876
 877         dns_query_complete(q, state);
 878         return;
 879
 880 fail:
 881         q->answer_errno = -r;
 882         dns_query_complete(q, DNS_TRANSACTION_ERRNO);
 883 }
 884
 885 void dns_query_ready(DnsQuery *q) {
 886
 887         DnsQueryCandidate *bad = NULL, *c;
 888         bool pending = false;
 889
 890         assert(q);
 891         assert(DNS_TRANSACTION_IS_LIVE(q->state));
 892
 893         /* Note that this call might invalidate the query. Callers
 894          * should hence not attempt to access the query or transaction
 895          * after calling this function, unless the block_ready
 896          * counter was explicitly bumped before doing so. */
 897
 898         if (q->block_ready > 0)
 899                 return;
 900
 901         LIST_FOREACH(candidates_by_query, c, q->candidates) {
 902                 DnsTransactionState state;
 903
 904                 state = dns_query_candidate_state(c);
 905                 switch (state) {
 906
 907                 case DNS_TRANSACTION_SUCCESS:
 908                         /* One of the candidates is successful,
 909                          * let's use it, and copy its data out */
 910                         dns_query_accept(q, c);
 911                         return;
 912
 913                 case DNS_TRANSACTION_NULL:
 914                 case DNS_TRANSACTION_PENDING:
 915                 case DNS_TRANSACTION_VALIDATING:
 916                         /* One of the candidates is still going on,
 917                          * let's maybe wait for it */
 918                         pending = true;
 919                         break;
 920
 921                 default:
 922                         /* Any kind of failure */
 923                         bad = c;
 924                         break;
 925                 }
 926         }
 927
 928         if (pending)
 929                 return;
 930
 931         dns_query_accept(q, bad);
 932 }
 933
 934 static int dns_query_cname_redirect(DnsQuery *q, const DnsResourceRecord *cname) {
 935         _cleanup_(dns_question_unrefp) DnsQuestion *nq_idna = NULL, *nq_utf8 = NULL;
 936         int r, k;
 937
 938         assert(q);
 939
 940         q->n_cname_redirects ++;
 941         if (q->n_cname_redirects > CNAME_MAX)
 942                 return -ELOOP;
 943
 944         r = dns_question_cname_redirect(q->question_idna, cname, &nq_idna);
 945         if (r < 0)
 946                 return r;
 947         else if (r > 0)
 948                 log_debug("Following CNAME/DNAME %s → %s.", dns_question_first_name(q->question_idna), dns_question_first_name(nq_idna));
 949
 950         k = dns_question_is_equal(q->question_idna, q->question_utf8);
 951         if (k < 0)
 952                 return r;
 953         if (k > 0) {
 954                 /* Same question? Shortcut new question generation */
 955                 nq_utf8 = dns_question_ref(nq_idna);
 956                 k = r;
 957         } else {
 958                 k = dns_question_cname_redirect(q->question_utf8, cname, &nq_utf8);
 959                 if (k < 0)
 960                         return k;
 961                 else if (k > 0)
 962                         log_debug("Following UTF8 CNAME/DNAME %s → %s.", dns_question_first_name(q->question_utf8), dns_question_first_name(nq_utf8));
 963         }
 964
 965         if (r == 0 && k == 0) /* No actual cname happened? */
 966                 return -ELOOP;
 967
 968         if (q->answer_protocol == DNS_PROTOCOL_DNS) {
 969                 /* Don't permit CNAME redirects from unicast DNS to LLMNR or MulticastDNS, so that global resources
 970                  * cannot invade the local namespace. The opposite way we permit: local names may redirect to global
 971                  * ones. */
 972
 973                 q->flags &= ~(SD_RESOLVED_LLMNR|SD_RESOLVED_MDNS); /* mask away the local protocols */
 974         }
 975
 976         /* Turn off searching for the new name */
 977         q->flags |= SD_RESOLVED_NO_SEARCH;
 978
 979         dns_question_unref(q->question_idna);
 980         q->question_idna = nq_idna;
 981         nq_idna = NULL;
 982
 983         dns_question_unref(q->question_utf8);
 984         q->question_utf8 = nq_utf8;
 985         nq_utf8 = NULL;
 986
 987         dns_query_free_candidates(q);
 988         dns_query_reset_answer(q);
 989
 990         q->state = DNS_TRANSACTION_NULL;
 991
 992         return 0;
 993 }
 994
 995 int dns_query_process_cname(DnsQuery *q) {
 996         _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *cname = NULL;
 997         DnsQuestion *question;
 998         DnsResourceRecord *rr;
 999         int r;
1000
1001         assert(q);
1002
1003         if (!IN_SET(q->state, DNS_TRANSACTION_SUCCESS, DNS_TRANSACTION_NULL))
1004                 return DNS_QUERY_NOMATCH;
1005
1006         question = dns_query_question_for_protocol(q, q->answer_protocol);
1007
1008         DNS_ANSWER_FOREACH(rr, q->answer) {
1009                 r = dns_question_matches_rr(question, rr, DNS_SEARCH_DOMAIN_NAME(q->answer_search_domain));
1010                 if (r < 0)
1011                         return r;
1012                 if (r > 0)
1013                         return DNS_QUERY_MATCH; /* The answer matches directly, no need to follow cnames */
1014
1015                 r = dns_question_matches_cname_or_dname(question, rr, DNS_SEARCH_DOMAIN_NAME(q->answer_search_domain));
1016                 if (r < 0)
1017                         return r;
1018                 if (r > 0 && !cname)
1019                         cname = dns_resource_record_ref(rr);
1020         }
1021
1022         if (!cname)
1023                 return DNS_QUERY_NOMATCH; /* No match and no cname to follow */
1024
1025         if (q->flags & SD_RESOLVED_NO_CNAME)
1026                 return -ELOOP;
1027
1028         /* OK, let's actually follow the CNAME */
1029         r = dns_query_cname_redirect(q, cname);
1030         if (r < 0)
1031                 return r;
1032
1033         /* Let's see if the answer can already answer the new
1034          * redirected question */
1035         r = dns_query_process_cname(q);
1036         if (r != DNS_QUERY_NOMATCH)
1037                 return r;
1038
1039         /* OK, it cannot, let's begin with the new query */
1040         r = dns_query_go(q);
1041         if (r < 0)
1042                 return r;
1043
1044         return DNS_QUERY_RESTARTED; /* We restarted the query for a new cname */
1045 }
1046
1047 static int on_bus_track(sd_bus_track *t, void *userdata) {
1048         DnsQuery *q = userdata;
1049
1050         assert(t);
1051         assert(q);
1052
1053         log_debug("Client of active query vanished, aborting query.");
1054         dns_query_complete(q, DNS_TRANSACTION_ABORTED);
1055         return 0;
1056 }
1057
1058 int dns_query_bus_track(DnsQuery *q, sd_bus_message *m) {
1059         int r;
1060
1061         assert(q);
1062         assert(m);
1063
1064         if (!q->bus_track) {
1065                 r = sd_bus_track_new(sd_bus_message_get_bus(m), &q->bus_track, on_bus_track, q);
1066                 if (r < 0)
1067                         return r;
1068         }
1069
1070         r = sd_bus_track_add_sender(q->bus_track, m);
1071         if (r < 0)
1072                 return r;
1073
1074         return 0;
1075 }
1076
1077 DnsQuestion* dns_query_question_for_protocol(DnsQuery *q, DnsProtocol protocol) {
1078         assert(q);
1079
1080         switch (protocol) {
1081
1082         case DNS_PROTOCOL_DNS:
1083                 return q->question_idna;
1084
1085         case DNS_PROTOCOL_MDNS:
1086         case DNS_PROTOCOL_LLMNR:
1087                 return q->question_utf8;
1088
1089         default:
1090                 return NULL;
1091         }
1092 }
1093
1094 const char *dns_query_string(DnsQuery *q) {
1095         const char *name;
1096         int r;
1097
1098         /* Returns a somewhat useful human-readable lookup key string for this query */
1099
1100         if (q->request_address_string)
1101                 return q->request_address_string;
1102
1103         if (q->request_address_valid) {
1104                 r = in_addr_to_string(q->request_family, &q->request_address, &q->request_address_string);
1105                 if (r >= 0)
1106                         return q->request_address_string;
1107         }
1108
1109         name = dns_question_first_name(q->question_utf8);
1110         if (name)
1111                 return name;
1112
1113         return dns_question_first_name(q->question_idna);
1114 }