src/resolve/resolved-dns-scope.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright 2014 Lennart Poettering
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU Lesser General Public License as published by
  10   the Free Software Foundation; either version 2.1 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   Lesser General Public License for more details.
  17
  18   You should have received a copy of the GNU Lesser General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20 ***/
  21
  22 #include <netinet/tcp.h>
  23
  24 #include "af-list.h"
  25 #include "alloc-util.h"
  26 #include "dns-domain.h"
  27 #include "fd-util.h"
  28 #include "hostname-util.h"
  29 #include "missing.h"
  30 #include "random-util.h"
  31 #include "resolved-dns-scope.h"
  32 #include "resolved-llmnr.h"
  33 #include "resolved-mdns.h"
  34 #include "socket-util.h"
  35 #include "strv.h"
  36
  37 #define MULTICAST_RATELIMIT_INTERVAL_USEC (1*USEC_PER_SEC)
  38 #define MULTICAST_RATELIMIT_BURST 1000
  39
  40 /* After how much time to repeat LLMNR requests, see RFC 4795 Section 7 */
  41 #define MULTICAST_RESEND_TIMEOUT_MIN_USEC (100 * USEC_PER_MSEC)
  42 #define MULTICAST_RESEND_TIMEOUT_MAX_USEC (1 * USEC_PER_SEC)
  43
  44 int dns_scope_new(Manager *m, DnsScope **ret, Link *l, DnsProtocol protocol, int family) {
  45         DnsScope *s;
  46
  47         assert(m);
  48         assert(ret);
  49
  50         s = new0(DnsScope, 1);
  51         if (!s)
  52                 return -ENOMEM;
  53
  54         s->manager = m;
  55         s->link = l;
  56         s->protocol = protocol;
  57         s->family = family;
  58         s->resend_timeout = MULTICAST_RESEND_TIMEOUT_MIN_USEC;
  59
  60         s->dnssec_mode = _DNSSEC_MODE_INVALID;
  61
  62         if (protocol == DNS_PROTOCOL_DNS) {
  63                 /* Copy DNSSEC mode from the link if it is set there,
  64                  * otherwise take the manager's DNSSEC mode. Note that
  65                  * we copy this only at scope creation time, and do
  66                  * not update it from the on, even if the setting
  67                  * changes. */
  68
  69                 if (l)
  70                         s->dnssec_mode = l->dnssec_mode;
  71                 if (s->dnssec_mode == _DNSSEC_MODE_INVALID)
  72                         s->dnssec_mode = m->dnssec_mode;
  73                 if (s->dnssec_mode == _DNSSEC_MODE_INVALID)
  74                         s->dnssec_mode = DNSSEC_NO;
  75         }
  76
  77         LIST_PREPEND(scopes, m->dns_scopes, s);
  78
  79         dns_scope_llmnr_membership(s, true);
  80         dns_scope_mdns_membership(s, true);
  81
  82         log_debug("New scope on link %s, protocol %s, family %s", l ? l->name : "*", dns_protocol_to_string(protocol), family == AF_UNSPEC ? "*" : af_to_name(family));
  83
  84         /* Enforce ratelimiting for the multicast protocols */
  85         RATELIMIT_INIT(s->ratelimit, MULTICAST_RATELIMIT_INTERVAL_USEC, MULTICAST_RATELIMIT_BURST);
  86
  87         *ret = s;
  88         return 0;
  89 }
  90
  91 static void dns_scope_abort_transactions(DnsScope *s) {
  92         assert(s);
  93
  94         while (s->transactions) {
  95                 DnsTransaction *t = s->transactions;
  96
  97                 /* Abort the transaction, but make sure it is not
  98                  * freed while we still look at it */
  99
 100                 t->block_gc++;
 101                 if (DNS_TRANSACTION_IS_LIVE(t->state))
 102                         dns_transaction_complete(t, DNS_TRANSACTION_ABORTED);
 103                 t->block_gc--;
 104
 105                 dns_transaction_free(t);
 106         }
 107 }
 108
 109 DnsScope* dns_scope_free(DnsScope *s) {
 110         DnsResourceRecord *rr;
 111
 112         if (!s)
 113                 return NULL;
 114
 115         log_debug("Removing scope on link %s, protocol %s, family %s", s->link ? s->link->name : "*", dns_protocol_to_string(s->protocol), s->family == AF_UNSPEC ? "*" : af_to_name(s->family));
 116
 117         dns_scope_llmnr_membership(s, false);
 118         dns_scope_mdns_membership(s, false);
 119         dns_scope_abort_transactions(s);
 120
 121         while (s->query_candidates)
 122                 dns_query_candidate_free(s->query_candidates);
 123
 124         hashmap_free(s->transactions_by_key);
 125
 126         while ((rr = ordered_hashmap_steal_first(s->conflict_queue)))
 127                 dns_resource_record_unref(rr);
 128
 129         ordered_hashmap_free(s->conflict_queue);
 130         sd_event_source_unref(s->conflict_event_source);
 131
 132         dns_cache_flush(&s->cache);
 133         dns_zone_flush(&s->zone);
 134
 135         LIST_REMOVE(scopes, s->manager->dns_scopes, s);
 136         free(s);
 137
 138         return NULL;
 139 }
 140
 141 DnsServer *dns_scope_get_dns_server(DnsScope *s) {
 142         assert(s);
 143
 144         if (s->protocol != DNS_PROTOCOL_DNS)
 145                 return NULL;
 146
 147         if (s->link)
 148                 return link_get_dns_server(s->link);
 149         else
 150                 return manager_get_dns_server(s->manager);
 151 }
 152
 153 void dns_scope_next_dns_server(DnsScope *s) {
 154         assert(s);
 155
 156         if (s->protocol != DNS_PROTOCOL_DNS)
 157                 return;
 158
 159         if (s->link)
 160                 link_next_dns_server(s->link);
 161         else
 162                 manager_next_dns_server(s->manager);
 163 }
 164
 165 void dns_scope_packet_received(DnsScope *s, usec_t rtt) {
 166         assert(s);
 167
 168         if (rtt <= s->max_rtt)
 169                 return;
 170
 171         s->max_rtt = rtt;
 172         s->resend_timeout = MIN(MAX(MULTICAST_RESEND_TIMEOUT_MIN_USEC, s->max_rtt * 2), MULTICAST_RESEND_TIMEOUT_MAX_USEC);
 173 }
 174
 175 void dns_scope_packet_lost(DnsScope *s, usec_t usec) {
 176         assert(s);
 177
 178         if (s->resend_timeout <= usec)
 179                 s->resend_timeout = MIN(s->resend_timeout * 2, MULTICAST_RESEND_TIMEOUT_MAX_USEC);
 180 }
 181
 182 static int dns_scope_emit_one(DnsScope *s, int fd, DnsPacket *p) {
 183         union in_addr_union addr;
 184         int ifindex = 0, r;
 185         int family;
 186         uint32_t mtu;
 187
 188         assert(s);
 189         assert(p);
 190         assert(p->protocol == s->protocol);
 191
 192         if (s->link) {
 193                 mtu = s->link->mtu;
 194                 ifindex = s->link->ifindex;
 195         } else
 196                 mtu = manager_find_mtu(s->manager);
 197
 198         switch (s->protocol) {
 199
 200         case DNS_PROTOCOL_DNS:
 201                 assert(fd >= 0);
 202
 203                 if (DNS_PACKET_QDCOUNT(p) > 1)
 204                         return -EOPNOTSUPP;
 205
 206                 if (p->size > DNS_PACKET_UNICAST_SIZE_MAX)
 207                         return -EMSGSIZE;
 208
 209                 if (p->size + UDP_PACKET_HEADER_SIZE > mtu)
 210                         return -EMSGSIZE;
 211
 212                 r = manager_write(s->manager, fd, p);
 213                 if (r < 0)
 214                         return r;
 215
 216                 break;
 217
 218         case DNS_PROTOCOL_LLMNR:
 219                 assert(fd < 0);
 220
 221                 if (DNS_PACKET_QDCOUNT(p) > 1)
 222                         return -EOPNOTSUPP;
 223
 224                 if (!ratelimit_test(&s->ratelimit))
 225                         return -EBUSY;
 226
 227                 family = s->family;
 228
 229                 if (family == AF_INET) {
 230                         addr.in = LLMNR_MULTICAST_IPV4_ADDRESS;
 231                         fd = manager_llmnr_ipv4_udp_fd(s->manager);
 232                 } else if (family == AF_INET6) {
 233                         addr.in6 = LLMNR_MULTICAST_IPV6_ADDRESS;
 234                         fd = manager_llmnr_ipv6_udp_fd(s->manager);
 235                 } else
 236                         return -EAFNOSUPPORT;
 237                 if (fd < 0)
 238                         return fd;
 239
 240                 r = manager_send(s->manager, fd, ifindex, family, &addr, LLMNR_PORT, p);
 241                 if (r < 0)
 242                         return r;
 243
 244                 break;
 245
 246         case DNS_PROTOCOL_MDNS:
 247                 assert(fd < 0);
 248
 249                 if (!ratelimit_test(&s->ratelimit))
 250                         return -EBUSY;
 251
 252                 family = s->family;
 253
 254                 if (family == AF_INET) {
 255                         addr.in = MDNS_MULTICAST_IPV4_ADDRESS;
 256                         fd = manager_mdns_ipv4_fd(s->manager);
 257                 } else if (family == AF_INET6) {
 258                         addr.in6 = MDNS_MULTICAST_IPV6_ADDRESS;
 259                         fd = manager_mdns_ipv6_fd(s->manager);
 260                 } else
 261                         return -EAFNOSUPPORT;
 262                 if (fd < 0)
 263                         return fd;
 264
 265                 r = manager_send(s->manager, fd, ifindex, family, &addr, MDNS_PORT, p);
 266                 if (r < 0)
 267                         return r;
 268
 269                 break;
 270
 271         default:
 272                 return -EAFNOSUPPORT;
 273         }
 274
 275         return 1;
 276 }
 277
 278 int dns_scope_emit_udp(DnsScope *s, int fd, DnsPacket *p) {
 279         int r;
 280
 281         assert(s);
 282         assert(p);
 283         assert(p->protocol == s->protocol);
 284         assert((s->protocol == DNS_PROTOCOL_DNS) == (fd >= 0));
 285
 286         do {
 287                 /* If there are multiple linked packets, set the TC bit in all but the last of them */
 288                 if (p->more) {
 289                         assert(p->protocol == DNS_PROTOCOL_MDNS);
 290                         dns_packet_set_flags(p, true, true);
 291                 }
 292
 293                 r = dns_scope_emit_one(s, fd, p);
 294                 if (r < 0)
 295                         return r;
 296
 297                 p = p->more;
 298         } while (p);
 299
 300         return 0;
 301 }
 302
 303 static int dns_scope_socket(
 304                 DnsScope *s,
 305                 int type,
 306                 int family,
 307                 const union in_addr_union *address,
 308                 DnsServer *server,
 309                 uint16_t port) {
 310
 311         _cleanup_close_ int fd = -1;
 312         union sockaddr_union sa = {};
 313         socklen_t salen;
 314         static const int one = 1;
 315         int ret, r;
 316
 317         assert(s);
 318
 319         if (server) {
 320                 assert(family == AF_UNSPEC);
 321                 assert(!address);
 322
 323                 sa.sa.sa_family = server->family;
 324                 if (server->family == AF_INET) {
 325                         sa.in.sin_port = htobe16(port);
 326                         sa.in.sin_addr = server->address.in;
 327                         salen = sizeof(sa.in);
 328                 } else if (server->family == AF_INET6) {
 329                         sa.in6.sin6_port = htobe16(port);
 330                         sa.in6.sin6_addr = server->address.in6;
 331                         sa.in6.sin6_scope_id = s->link ? s->link->ifindex : 0;
 332                         salen = sizeof(sa.in6);
 333                 } else
 334                         return -EAFNOSUPPORT;
 335         } else {
 336                 assert(family != AF_UNSPEC);
 337                 assert(address);
 338
 339                 sa.sa.sa_family = family;
 340
 341                 if (family == AF_INET) {
 342                         sa.in.sin_port = htobe16(port);
 343                         sa.in.sin_addr = address->in;
 344                         salen = sizeof(sa.in);
 345                 } else if (family == AF_INET6) {
 346                         sa.in6.sin6_port = htobe16(port);
 347                         sa.in6.sin6_addr = address->in6;
 348                         sa.in6.sin6_scope_id = s->link ? s->link->ifindex : 0;
 349                         salen = sizeof(sa.in6);
 350                 } else
 351                         return -EAFNOSUPPORT;
 352         }
 353
 354         fd = socket(sa.sa.sa_family, type|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
 355         if (fd < 0)
 356                 return -errno;
 357
 358         if (type == SOCK_STREAM) {
 359                 r = setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &one, sizeof(one));
 360                 if (r < 0)
 361                         return -errno;
 362         }
 363
 364         if (s->link) {
 365                 uint32_t ifindex = htobe32(s->link->ifindex);
 366
 367                 if (sa.sa.sa_family == AF_INET) {
 368                         r = setsockopt(fd, IPPROTO_IP, IP_UNICAST_IF, &ifindex, sizeof(ifindex));
 369                         if (r < 0)
 370                                 return -errno;
 371                 } else if (sa.sa.sa_family == AF_INET6) {
 372                         r = setsockopt(fd, IPPROTO_IPV6, IPV6_UNICAST_IF, &ifindex, sizeof(ifindex));
 373                         if (r < 0)
 374                                 return -errno;
 375                 }
 376         }
 377
 378         if (s->protocol == DNS_PROTOCOL_LLMNR) {
 379                 /* RFC 4795, section 2.5 requires the TTL to be set to 1 */
 380
 381                 if (sa.sa.sa_family == AF_INET) {
 382                         r = setsockopt(fd, IPPROTO_IP, IP_TTL, &one, sizeof(one));
 383                         if (r < 0)
 384                                 return -errno;
 385                 } else if (sa.sa.sa_family == AF_INET6) {
 386                         r = setsockopt(fd, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &one, sizeof(one));
 387                         if (r < 0)
 388                                 return -errno;
 389                 }
 390         }
 391
 392         r = connect(fd, &sa.sa, salen);
 393         if (r < 0 && errno != EINPROGRESS)
 394                 return -errno;
 395
 396         ret = fd;
 397         fd = -1;
 398
 399         return ret;
 400 }
 401
 402 int dns_scope_socket_udp(DnsScope *s, DnsServer *server, uint16_t port) {
 403         return dns_scope_socket(s, SOCK_DGRAM, AF_UNSPEC, NULL, server, port);
 404 }
 405
 406 int dns_scope_socket_tcp(DnsScope *s, int family, const union in_addr_union *address, DnsServer *server, uint16_t port) {
 407         return dns_scope_socket(s, SOCK_STREAM, family, address, server, port);
 408 }
 409
 410 DnsScopeMatch dns_scope_good_domain(DnsScope *s, int ifindex, uint64_t flags, const char *domain) {
 411         DnsSearchDomain *d;
 412
 413         assert(s);
 414         assert(domain);
 415
 416         /* Checks if the specified domain is something to look up on
 417          * this scope. Note that this accepts non-qualified hostnames,
 418          * i.e. those without any search path prefixed yet. */
 419
 420         if (ifindex != 0 && (!s->link || s->link->ifindex != ifindex))
 421                 return DNS_SCOPE_NO;
 422
 423         if ((SD_RESOLVED_FLAGS_MAKE(s->protocol, s->family, 0) & flags) == 0)
 424                 return DNS_SCOPE_NO;
 425
 426         /* Never resolve any loopback hostname or IP address via DNS,
 427          * LLMNR or mDNS. Instead, always rely on synthesized RRs for
 428          * these. */
 429         if (is_localhost(domain) ||
 430             dns_name_endswith(domain, "127.in-addr.arpa") > 0 ||
 431             dns_name_equal(domain, "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa") > 0)
 432                 return DNS_SCOPE_NO;
 433
 434         /* Never respond to some of the domains listed in RFC6303 */
 435         if (dns_name_endswith(domain, "0.in-addr.arpa") > 0 ||
 436             dns_name_equal(domain, "255.255.255.255.in-addr.arpa") > 0 ||
 437             dns_name_equal(domain, "0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa") > 0)
 438                 return DNS_SCOPE_NO;
 439
 440         /* Never respond to some of the domains listed in RFC6761 */
 441         if (dns_name_endswith(domain, "invalid") > 0)
 442                 return DNS_SCOPE_NO;
 443
 444         /* Always honour search domains for routing queries. Note that
 445          * we return DNS_SCOPE_YES here, rather than just
 446          * DNS_SCOPE_MAYBE, which means wildcard scopes won't be
 447          * considered anymore. */
 448         LIST_FOREACH(domains, d, dns_scope_get_search_domains(s))
 449                 if (dns_name_endswith(domain, d->name) > 0)
 450                         return DNS_SCOPE_YES;
 451
 452         switch (s->protocol) {
 453
 454         case DNS_PROTOCOL_DNS:
 455
 456                 /* Exclude link-local IP ranges */
 457                 if (dns_name_endswith(domain, "254.169.in-addr.arpa") == 0 &&
 458                     dns_name_endswith(domain, "8.e.f.ip6.arpa") == 0 &&
 459                     dns_name_endswith(domain, "9.e.f.ip6.arpa") == 0 &&
 460                     dns_name_endswith(domain, "a.e.f.ip6.arpa") == 0 &&
 461                     dns_name_endswith(domain, "b.e.f.ip6.arpa") == 0 &&
 462                     /* If networks use .local in their private setups, they are supposed to also add .local to their search
 463                      * domains, which we already checked above. Otherwise, we consider .local specific to mDNS and won't
 464                      * send such queries ordinary DNS servers. */
 465                     dns_name_endswith(domain, "local") == 0)
 466                         return DNS_SCOPE_MAYBE;
 467
 468                 return DNS_SCOPE_NO;
 469
 470         case DNS_PROTOCOL_MDNS:
 471                 if ((s->family == AF_INET && dns_name_endswith(domain, "in-addr.arpa") > 0) ||
 472                     (s->family == AF_INET6 && dns_name_endswith(domain, "ip6.arpa") > 0) ||
 473                     (dns_name_endswith(domain, "local") > 0 && /* only resolve names ending in .local via mDNS */
 474                      dns_name_equal(domain, "local") == 0 &&   /* but not the single-label "local" name itself */
 475                      manager_is_own_hostname(s->manager, domain) <= 0)) /* never resolve the local hostname via mDNS */
 476                         return DNS_SCOPE_MAYBE;
 477
 478                 return DNS_SCOPE_NO;
 479
 480         case DNS_PROTOCOL_LLMNR:
 481                 if ((s->family == AF_INET && dns_name_endswith(domain, "in-addr.arpa") > 0) ||
 482                     (s->family == AF_INET6 && dns_name_endswith(domain, "ip6.arpa") > 0) ||
 483                     (dns_name_is_single_label(domain) && /* only resolve single label names via LLMNR */
 484                      !is_gateway_hostname(domain) && /* don't resolve "gateway" with LLMNR, let nss-myhostname handle this */
 485                      manager_is_own_hostname(s->manager, domain) <= 0))  /* never resolve the local hostname via LLMNR */
 486                         return DNS_SCOPE_MAYBE;
 487
 488                 return DNS_SCOPE_NO;
 489
 490         default:
 491                 assert_not_reached("Unknown scope protocol");
 492         }
 493 }
 494
 495 int dns_scope_good_key(DnsScope *s, DnsResourceKey *key) {
 496         assert(s);
 497         assert(key);
 498
 499         /* Check if it makes sense to resolve the specified key on
 500          * this scope. Note that this call assumes as fully qualified
 501          * name, i.e. the search suffixes already appended. */
 502
 503         if (s->protocol == DNS_PROTOCOL_DNS) {
 504
 505                 /* On classic DNS, looking up non-address RRs is always
 506                  * fine. (Specifically, we want to permit looking up
 507                  * DNSKEY and DS records on the root and top-level
 508                  * domains.) */
 509                 if (!dns_resource_key_is_address(key))
 510                         return true;
 511
 512                 /* However, we refuse to look up A and AAAA RRs on the
 513                  * root and single-label domains, under the assumption
 514                  * that those should be resolved via LLMNR or search
 515                  * path only, and should not be leaked onto the
 516                  * internet. */
 517                 return !(dns_name_is_single_label(DNS_RESOURCE_KEY_NAME(key)) ||
 518                          dns_name_is_root(DNS_RESOURCE_KEY_NAME(key)));
 519         }
 520
 521         /* On mDNS and LLMNR, send A and AAAA queries only on the
 522          * respective scopes */
 523
 524         if (s->family == AF_INET && key->class == DNS_CLASS_IN && key->type == DNS_TYPE_AAAA)
 525                 return false;
 526
 527         if (s->family == AF_INET6 && key->class == DNS_CLASS_IN && key->type == DNS_TYPE_A)
 528                 return false;
 529
 530         return true;
 531 }
 532
 533 static int dns_scope_multicast_membership(DnsScope *s, bool b, struct in_addr in, struct in6_addr in6) {
 534         int fd;
 535
 536         assert(s);
 537         assert(s->link);
 538
 539         if (s->family == AF_INET) {
 540                 struct ip_mreqn mreqn = {
 541                         .imr_multiaddr = in,
 542                         .imr_ifindex = s->link->ifindex,
 543                 };
 544
 545                 fd = manager_llmnr_ipv4_udp_fd(s->manager);
 546                 if (fd < 0)
 547                         return fd;
 548
 549                 /* Always first try to drop membership before we add
 550                  * one. This is necessary on some devices, such as
 551                  * veth. */
 552                 if (b)
 553                         (void) setsockopt(fd, IPPROTO_IP, IP_DROP_MEMBERSHIP, &mreqn, sizeof(mreqn));
 554
 555                 if (setsockopt(fd, IPPROTO_IP, b ? IP_ADD_MEMBERSHIP : IP_DROP_MEMBERSHIP, &mreqn, sizeof(mreqn)) < 0)
 556                         return -errno;
 557
 558         } else if (s->family == AF_INET6) {
 559                 struct ipv6_mreq mreq = {
 560                         .ipv6mr_multiaddr = in6,
 561                         .ipv6mr_interface = s->link->ifindex,
 562                 };
 563
 564                 fd = manager_llmnr_ipv6_udp_fd(s->manager);
 565                 if (fd < 0)
 566                         return fd;
 567
 568                 if (b)
 569                         (void) setsockopt(fd, IPPROTO_IPV6, IPV6_DROP_MEMBERSHIP, &mreq, sizeof(mreq));
 570
 571                 if (setsockopt(fd, IPPROTO_IPV6, b ? IPV6_ADD_MEMBERSHIP : IPV6_DROP_MEMBERSHIP, &mreq, sizeof(mreq)) < 0)
 572                         return -errno;
 573         } else
 574                 return -EAFNOSUPPORT;
 575
 576         return 0;
 577 }
 578
 579 int dns_scope_llmnr_membership(DnsScope *s, bool b) {
 580
 581         if (s->protocol != DNS_PROTOCOL_LLMNR)
 582                 return 0;
 583
 584         return dns_scope_multicast_membership(s, b, LLMNR_MULTICAST_IPV4_ADDRESS, LLMNR_MULTICAST_IPV6_ADDRESS);
 585 }
 586
 587 int dns_scope_mdns_membership(DnsScope *s, bool b) {
 588
 589         if (s->protocol != DNS_PROTOCOL_MDNS)
 590                 return 0;
 591
 592         return dns_scope_multicast_membership(s, b, MDNS_MULTICAST_IPV4_ADDRESS, MDNS_MULTICAST_IPV6_ADDRESS);
 593 }
 594
 595 static int dns_scope_make_reply_packet(
 596                 DnsScope *s,
 597                 uint16_t id,
 598                 int rcode,
 599                 DnsQuestion *q,
 600                 DnsAnswer *answer,
 601                 DnsAnswer *soa,
 602                 bool tentative,
 603                 DnsPacket **ret) {
 604
 605         _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
 606         unsigned i;
 607         int r;
 608
 609         assert(s);
 610         assert(ret);
 611
 612         if ((!q || q->n_keys <= 0)
 613             && (!answer || answer->n_rrs <= 0)
 614             && (!soa || soa->n_rrs <= 0))
 615                 return -EINVAL;
 616
 617         r = dns_packet_new(&p, s->protocol, 0);
 618         if (r < 0)
 619                 return r;
 620
 621         DNS_PACKET_HEADER(p)->id = id;
 622         DNS_PACKET_HEADER(p)->flags = htobe16(DNS_PACKET_MAKE_FLAGS(
 623                                                               1 /* qr */,
 624                                                               0 /* opcode */,
 625                                                               0 /* c */,
 626                                                               0 /* tc */,
 627                                                               tentative,
 628                                                               0 /* (ra) */,
 629                                                               0 /* (ad) */,
 630                                                               0 /* (cd) */,
 631                                                               rcode));
 632
 633         if (q) {
 634                 for (i = 0; i < q->n_keys; i++) {
 635                         r = dns_packet_append_key(p, q->keys[i], NULL);
 636                         if (r < 0)
 637                                 return r;
 638                 }
 639
 640                 DNS_PACKET_HEADER(p)->qdcount = htobe16(q->n_keys);
 641         }
 642
 643         if (answer) {
 644                 for (i = 0; i < answer->n_rrs; i++) {
 645                         r = dns_packet_append_rr(p, answer->items[i].rr, NULL, NULL);
 646                         if (r < 0)
 647                                 return r;
 648                 }
 649
 650                 DNS_PACKET_HEADER(p)->ancount = htobe16(answer->n_rrs);
 651         }
 652
 653         if (soa) {
 654                 for (i = 0; i < soa->n_rrs; i++) {
 655                         r = dns_packet_append_rr(p, soa->items[i].rr, NULL, NULL);
 656                         if (r < 0)
 657                                 return r;
 658                 }
 659
 660                 DNS_PACKET_HEADER(p)->arcount = htobe16(soa->n_rrs);
 661         }
 662
 663         *ret = p;
 664         p = NULL;
 665
 666         return 0;
 667 }
 668
 669 static void dns_scope_verify_conflicts(DnsScope *s, DnsPacket *p) {
 670         unsigned n;
 671
 672         assert(s);
 673         assert(p);
 674
 675         if (p->question)
 676                 for (n = 0; n < p->question->n_keys; n++)
 677                         dns_zone_verify_conflicts(&s->zone, p->question->keys[n]);
 678         if (p->answer)
 679                 for (n = 0; n < p->answer->n_rrs; n++)
 680                         dns_zone_verify_conflicts(&s->zone, p->answer->items[n].rr->key);
 681 }
 682
 683 void dns_scope_process_query(DnsScope *s, DnsStream *stream, DnsPacket *p) {
 684         _cleanup_(dns_packet_unrefp) DnsPacket *reply = NULL;
 685         _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL, *soa = NULL;
 686         DnsResourceKey *key = NULL;
 687         bool tentative = false;
 688         int r, fd;
 689
 690         assert(s);
 691         assert(p);
 692
 693         if (p->protocol != DNS_PROTOCOL_LLMNR)
 694                 return;
 695
 696         if (p->ipproto == IPPROTO_UDP) {
 697                 /* Don't accept UDP queries directed to anything but
 698                  * the LLMNR multicast addresses. See RFC 4795,
 699                  * section 2.5. */
 700
 701                 if (p->family == AF_INET && !in_addr_equal(AF_INET, &p->destination, (union in_addr_union*) &LLMNR_MULTICAST_IPV4_ADDRESS))
 702                         return;
 703
 704                 if (p->family == AF_INET6 && !in_addr_equal(AF_INET6, &p->destination, (union in_addr_union*) &LLMNR_MULTICAST_IPV6_ADDRESS))
 705                         return;
 706         }
 707
 708         r = dns_packet_extract(p);
 709         if (r < 0) {
 710                 log_debug_errno(r, "Failed to extract resources from incoming packet: %m");
 711                 return;
 712         }
 713
 714         if (DNS_PACKET_LLMNR_C(p)) {
 715                 /* Somebody notified us about a possible conflict */
 716                 dns_scope_verify_conflicts(s, p);
 717                 return;
 718         }
 719
 720         assert(p->question->n_keys == 1);
 721         key = p->question->keys[0];
 722
 723         r = dns_zone_lookup(&s->zone, key, &answer, &soa, &tentative);
 724         if (r < 0) {
 725                 log_debug_errno(r, "Failed to lookup key: %m");
 726                 return;
 727         }
 728         if (r == 0)
 729                 return;
 730
 731         if (answer)
 732                 dns_answer_order_by_scope(answer, in_addr_is_link_local(p->family, &p->sender) > 0);
 733
 734         r = dns_scope_make_reply_packet(s, DNS_PACKET_ID(p), DNS_RCODE_SUCCESS, p->question, answer, soa, tentative, &reply);
 735         if (r < 0) {
 736                 log_debug_errno(r, "Failed to build reply packet: %m");
 737                 return;
 738         }
 739
 740         if (stream)
 741                 r = dns_stream_write_packet(stream, reply);
 742         else {
 743                 if (!ratelimit_test(&s->ratelimit))
 744                         return;
 745
 746                 if (p->family == AF_INET)
 747                         fd = manager_llmnr_ipv4_udp_fd(s->manager);
 748                 else if (p->family == AF_INET6)
 749                         fd = manager_llmnr_ipv6_udp_fd(s->manager);
 750                 else {
 751                         log_debug("Unknown protocol");
 752                         return;
 753                 }
 754                 if (fd < 0) {
 755                         log_debug_errno(fd, "Failed to get reply socket: %m");
 756                         return;
 757                 }
 758
 759                 /* Note that we always immediately reply to all LLMNR
 760                  * requests, and do not wait any time, since we
 761                  * verified uniqueness for all records. Also see RFC
 762                  * 4795, Section 2.7 */
 763
 764                 r = manager_send(s->manager, fd, p->ifindex, p->family, &p->sender, p->sender_port, reply);
 765         }
 766
 767         if (r < 0) {
 768                 log_debug_errno(r, "Failed to send reply packet: %m");
 769                 return;
 770         }
 771 }
 772
 773 DnsTransaction *dns_scope_find_transaction(DnsScope *scope, DnsResourceKey *key, bool cache_ok) {
 774         DnsTransaction *t;
 775
 776         assert(scope);
 777         assert(key);
 778
 779         /* Try to find an ongoing transaction that is a equal to the
 780          * specified question */
 781         t = hashmap_get(scope->transactions_by_key, key);
 782         if (!t)
 783                 return NULL;
 784
 785         /* Refuse reusing transactions that completed based on cached
 786          * data instead of a real packet, if that's requested. */
 787         if (!cache_ok &&
 788             IN_SET(t->state, DNS_TRANSACTION_SUCCESS, DNS_TRANSACTION_RCODE_FAILURE) &&
 789             t->answer_source != DNS_TRANSACTION_NETWORK)
 790                 return NULL;
 791
 792         return t;
 793 }
 794
 795 static int dns_scope_make_conflict_packet(
 796                 DnsScope *s,
 797                 DnsResourceRecord *rr,
 798                 DnsPacket **ret) {
 799
 800         _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
 801         int r;
 802
 803         assert(s);
 804         assert(rr);
 805         assert(ret);
 806
 807         r = dns_packet_new(&p, s->protocol, 0);
 808         if (r < 0)
 809                 return r;
 810
 811         DNS_PACKET_HEADER(p)->flags = htobe16(DNS_PACKET_MAKE_FLAGS(
 812                                                               0 /* qr */,
 813                                                               0 /* opcode */,
 814                                                               1 /* conflict */,
 815                                                               0 /* tc */,
 816                                                               0 /* t */,
 817                                                               0 /* (ra) */,
 818                                                               0 /* (ad) */,
 819                                                               0 /* (cd) */,
 820                                                               0));
 821
 822         /* For mDNS, the transaction ID should always be 0 */
 823         if (s->protocol != DNS_PROTOCOL_MDNS)
 824                 random_bytes(&DNS_PACKET_HEADER(p)->id, sizeof(uint16_t));
 825
 826         DNS_PACKET_HEADER(p)->qdcount = htobe16(1);
 827         DNS_PACKET_HEADER(p)->arcount = htobe16(1);
 828
 829         r = dns_packet_append_key(p, rr->key, NULL);
 830         if (r < 0)
 831                 return r;
 832
 833         r = dns_packet_append_rr(p, rr, NULL, NULL);
 834         if (r < 0)
 835                 return r;
 836
 837         *ret = p;
 838         p = NULL;
 839
 840         return 0;
 841 }
 842
 843 static int on_conflict_dispatch(sd_event_source *es, usec_t usec, void *userdata) {
 844         DnsScope *scope = userdata;
 845         int r;
 846
 847         assert(es);
 848         assert(scope);
 849
 850         scope->conflict_event_source = sd_event_source_unref(scope->conflict_event_source);
 851
 852         for (;;) {
 853                 _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
 854                 _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
 855
 856                 rr = ordered_hashmap_steal_first(scope->conflict_queue);
 857                 if (!rr)
 858                         break;
 859
 860                 r = dns_scope_make_conflict_packet(scope, rr, &p);
 861                 if (r < 0) {
 862                         log_error_errno(r, "Failed to make conflict packet: %m");
 863                         return 0;
 864                 }
 865
 866                 r = dns_scope_emit_udp(scope, -1, p);
 867                 if (r < 0)
 868                         log_debug_errno(r, "Failed to send conflict packet: %m");
 869         }
 870
 871         return 0;
 872 }
 873
 874 int dns_scope_notify_conflict(DnsScope *scope, DnsResourceRecord *rr) {
 875         usec_t jitter;
 876         int r;
 877
 878         assert(scope);
 879         assert(rr);
 880
 881         /* We don't send these queries immediately. Instead, we queue
 882          * them, and send them after some jitter delay. */
 883         r = ordered_hashmap_ensure_allocated(&scope->conflict_queue, &dns_resource_key_hash_ops);
 884         if (r < 0) {
 885                 log_oom();
 886                 return r;
 887         }
 888
 889         /* We only place one RR per key in the conflict
 890          * messages, not all of them. That should be enough to
 891          * indicate where there might be a conflict */
 892         r = ordered_hashmap_put(scope->conflict_queue, rr->key, rr);
 893         if (r == -EEXIST || r == 0)
 894                 return 0;
 895         if (r < 0)
 896                 return log_debug_errno(r, "Failed to queue conflicting RR: %m");
 897
 898         dns_resource_record_ref(rr);
 899
 900         if (scope->conflict_event_source)
 901                 return 0;
 902
 903         random_bytes(&jitter, sizeof(jitter));
 904         jitter %= LLMNR_JITTER_INTERVAL_USEC;
 905
 906         r = sd_event_add_time(scope->manager->event,
 907                               &scope->conflict_event_source,
 908                               clock_boottime_or_monotonic(),
 909                               now(clock_boottime_or_monotonic()) + jitter,
 910                               LLMNR_JITTER_INTERVAL_USEC,
 911                               on_conflict_dispatch, scope);
 912         if (r < 0)
 913                 return log_debug_errno(r, "Failed to add conflict dispatch event: %m");
 914
 915         (void) sd_event_source_set_description(scope->conflict_event_source, "scope-conflict");
 916
 917         return 0;
 918 }
 919
 920 void dns_scope_check_conflicts(DnsScope *scope, DnsPacket *p) {
 921         unsigned i;
 922         int r;
 923
 924         assert(scope);
 925         assert(p);
 926
 927         if (p->protocol != DNS_PROTOCOL_LLMNR)
 928                 return;
 929
 930         if (DNS_PACKET_RRCOUNT(p) <= 0)
 931                 return;
 932
 933         if (DNS_PACKET_LLMNR_C(p) != 0)
 934                 return;
 935
 936         if (DNS_PACKET_LLMNR_T(p) != 0)
 937                 return;
 938
 939         if (manager_our_packet(scope->manager, p))
 940                 return;
 941
 942         r = dns_packet_extract(p);
 943         if (r < 0) {
 944                 log_debug_errno(r, "Failed to extract packet: %m");
 945                 return;
 946         }
 947
 948         log_debug("Checking for conflicts...");
 949
 950         for (i = 0; i < p->answer->n_rrs; i++) {
 951
 952                 /* Check for conflicts against the local zone. If we
 953                  * found one, we won't check any further */
 954                 r = dns_zone_check_conflicts(&scope->zone, p->answer->items[i].rr);
 955                 if (r != 0)
 956                         continue;
 957
 958                 /* Check for conflicts against the local cache. If so,
 959                  * send out an advisory query, to inform everybody */
 960                 r = dns_cache_check_conflicts(&scope->cache, p->answer->items[i].rr, p->family, &p->sender);
 961                 if (r <= 0)
 962                         continue;
 963
 964                 dns_scope_notify_conflict(scope, p->answer->items[i].rr);
 965         }
 966 }
 967
 968 void dns_scope_dump(DnsScope *s, FILE *f) {
 969         assert(s);
 970
 971         if (!f)
 972                 f = stdout;
 973
 974         fputs("[Scope protocol=", f);
 975         fputs(dns_protocol_to_string(s->protocol), f);
 976
 977         if (s->link) {
 978                 fputs(" interface=", f);
 979                 fputs(s->link->name, f);
 980         }
 981
 982         if (s->family != AF_UNSPEC) {
 983                 fputs(" family=", f);
 984                 fputs(af_to_name(s->family), f);
 985         }
 986
 987         fputs("]\n", f);
 988
 989         if (!dns_zone_is_empty(&s->zone)) {
 990                 fputs("ZONE:\n", f);
 991                 dns_zone_dump(&s->zone, f);
 992         }
 993
 994         if (!dns_cache_is_empty(&s->cache)) {
 995                 fputs("CACHE:\n", f);
 996                 dns_cache_dump(&s->cache, f);
 997         }
 998 }
 999
1000 DnsSearchDomain *dns_scope_get_search_domains(DnsScope *s) {
1001         assert(s);
1002
1003         if (s->protocol != DNS_PROTOCOL_DNS)
1004                 return NULL;
1005
1006         if (s->link)
1007                 return s->link->search_domains;
1008
1009         return s->manager->search_domains;
1010 }
1011
1012 bool dns_scope_name_needs_search_domain(DnsScope *s, const char *name) {
1013         assert(s);
1014
1015         if (s->protocol != DNS_PROTOCOL_DNS)
1016                 return false;
1017
1018         return dns_name_is_single_label(name);
1019 }