src/resolve/resolved-dns-scope.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2
   3 #include <netinet/tcp.h>
   4
   5 #include "af-list.h"
   6 #include "alloc-util.h"
   7 #include "dns-domain.h"
   8 #include "errno-util.h"
   9 #include "fd-util.h"
  10 #include "hostname-util.h"
  11 #include "missing_network.h"
  12 #include "random-util.h"
  13 #include "resolved-dnssd.h"
  14 #include "resolved-dns-scope.h"
  15 #include "resolved-dns-zone.h"
  16 #include "resolved-llmnr.h"
  17 #include "resolved-mdns.h"
  18 #include "socket-util.h"
  19 #include "strv.h"
  20
  21 #define MULTICAST_RATELIMIT_INTERVAL_USEC (1*USEC_PER_SEC)
  22 #define MULTICAST_RATELIMIT_BURST 1000
  23
  24 /* After how much time to repeat LLMNR requests, see RFC 4795 Section 7 */
  25 #define MULTICAST_RESEND_TIMEOUT_MIN_USEC (100 * USEC_PER_MSEC)
  26 #define MULTICAST_RESEND_TIMEOUT_MAX_USEC (1 * USEC_PER_SEC)
  27
  28 int dns_scope_new(Manager *m, DnsScope **ret, Link *l, DnsProtocol protocol, int family) {
  29         DnsScope *s;
  30
  31         assert(m);
  32         assert(ret);
  33
  34         s = new(DnsScope, 1);
  35         if (!s)
  36                 return -ENOMEM;
  37
  38         *s = (DnsScope) {
  39                 .manager = m,
  40                 .link = l,
  41                 .protocol = protocol,
  42                 .family = family,
  43                 .resend_timeout = MULTICAST_RESEND_TIMEOUT_MIN_USEC,
  44         };
  45
  46         if (protocol == DNS_PROTOCOL_DNS) {
  47                 /* Copy DNSSEC mode from the link if it is set there,
  48                  * otherwise take the manager's DNSSEC mode. Note that
  49                  * we copy this only at scope creation time, and do
  50                  * not update it from the on, even if the setting
  51                  * changes. */
  52
  53                 if (l) {
  54                         s->dnssec_mode = link_get_dnssec_mode(l);
  55                         s->dns_over_tls_mode = link_get_dns_over_tls_mode(l);
  56                 } else {
  57                         s->dnssec_mode = manager_get_dnssec_mode(m);
  58                         s->dns_over_tls_mode = manager_get_dns_over_tls_mode(m);
  59                 }
  60
  61         } else {
  62                 s->dnssec_mode = DNSSEC_NO;
  63                 s->dns_over_tls_mode = DNS_OVER_TLS_NO;
  64         }
  65
  66         LIST_PREPEND(scopes, m->dns_scopes, s);
  67
  68         dns_scope_llmnr_membership(s, true);
  69         dns_scope_mdns_membership(s, true);
  70
  71         log_debug("New scope on link %s, protocol %s, family %s", l ? l->ifname : "*", dns_protocol_to_string(protocol), family == AF_UNSPEC ? "*" : af_to_name(family));
  72
  73         /* Enforce ratelimiting for the multicast protocols */
  74         s->ratelimit = (RateLimit) { MULTICAST_RATELIMIT_INTERVAL_USEC, MULTICAST_RATELIMIT_BURST };
  75
  76         *ret = s;
  77         return 0;
  78 }
  79
  80 static void dns_scope_abort_transactions(DnsScope *s) {
  81         assert(s);
  82
  83         while (s->transactions) {
  84                 DnsTransaction *t = s->transactions;
  85
  86                 /* Abort the transaction, but make sure it is not
  87                  * freed while we still look at it */
  88
  89                 t->block_gc++;
  90                 if (DNS_TRANSACTION_IS_LIVE(t->state))
  91                         dns_transaction_complete(t, DNS_TRANSACTION_ABORTED);
  92                 t->block_gc--;
  93
  94                 dns_transaction_free(t);
  95         }
  96 }
  97
  98 DnsScope* dns_scope_free(DnsScope *s) {
  99         if (!s)
 100                 return NULL;
 101
 102         log_debug("Removing scope on link %s, protocol %s, family %s", s->link ? s->link->ifname : "*", dns_protocol_to_string(s->protocol), s->family == AF_UNSPEC ? "*" : af_to_name(s->family));
 103
 104         dns_scope_llmnr_membership(s, false);
 105         dns_scope_mdns_membership(s, false);
 106         dns_scope_abort_transactions(s);
 107
 108         while (s->query_candidates)
 109                 dns_query_candidate_unref(s->query_candidates);
 110
 111         hashmap_free(s->transactions_by_key);
 112
 113         ordered_hashmap_free_with_destructor(s->conflict_queue, dns_resource_record_unref);
 114         sd_event_source_disable_unref(s->conflict_event_source);
 115
 116         sd_event_source_disable_unref(s->announce_event_source);
 117
 118         dns_cache_flush(&s->cache);
 119         dns_zone_flush(&s->zone);
 120
 121         LIST_REMOVE(scopes, s->manager->dns_scopes, s);
 122         return mfree(s);
 123 }
 124
 125 DnsServer *dns_scope_get_dns_server(DnsScope *s) {
 126         assert(s);
 127
 128         if (s->protocol != DNS_PROTOCOL_DNS)
 129                 return NULL;
 130
 131         if (s->link)
 132                 return link_get_dns_server(s->link);
 133         else
 134                 return manager_get_dns_server(s->manager);
 135 }
 136
 137 unsigned dns_scope_get_n_dns_servers(DnsScope *s) {
 138         unsigned n = 0;
 139         DnsServer *i;
 140
 141         assert(s);
 142
 143         if (s->protocol != DNS_PROTOCOL_DNS)
 144                 return 0;
 145
 146         if (s->link)
 147                 i = s->link->dns_servers;
 148         else
 149                 i = s->manager->dns_servers;
 150
 151         for (; i; i = i->servers_next)
 152                 n++;
 153
 154         return n;
 155 }
 156
 157 void dns_scope_next_dns_server(DnsScope *s, DnsServer *if_current) {
 158         assert(s);
 159
 160         if (s->protocol != DNS_PROTOCOL_DNS)
 161                 return;
 162
 163         /* Changes to the next DNS server in the list. If 'if_current' is passed will do so only if the
 164          * current DNS server still matches it. */
 165
 166         if (s->link)
 167                 link_next_dns_server(s->link, if_current);
 168         else
 169                 manager_next_dns_server(s->manager, if_current);
 170 }
 171
 172 void dns_scope_packet_received(DnsScope *s, usec_t rtt) {
 173         assert(s);
 174
 175         if (rtt <= s->max_rtt)
 176                 return;
 177
 178         s->max_rtt = rtt;
 179         s->resend_timeout = MIN(MAX(MULTICAST_RESEND_TIMEOUT_MIN_USEC, s->max_rtt * 2), MULTICAST_RESEND_TIMEOUT_MAX_USEC);
 180 }
 181
 182 void dns_scope_packet_lost(DnsScope *s, usec_t usec) {
 183         assert(s);
 184
 185         if (s->resend_timeout <= usec)
 186                 s->resend_timeout = MIN(s->resend_timeout * 2, MULTICAST_RESEND_TIMEOUT_MAX_USEC);
 187 }
 188
 189 static int dns_scope_emit_one(DnsScope *s, int fd, int family, DnsPacket *p) {
 190         int r;
 191
 192         assert(s);
 193         assert(p);
 194         assert(p->protocol == s->protocol);
 195
 196         if (family == AF_UNSPEC) {
 197                 if (s->family == AF_UNSPEC)
 198                         return -EAFNOSUPPORT;
 199
 200                 family = s->family;
 201         }
 202
 203         switch (s->protocol) {
 204
 205         case DNS_PROTOCOL_DNS: {
 206                 size_t mtu, udp_size, min_mtu, socket_mtu = 0;
 207
 208                 assert(fd >= 0);
 209
 210                 if (DNS_PACKET_QDCOUNT(p) > 1) /* Classic DNS only allows one question per packet */
 211                         return -EOPNOTSUPP;
 212
 213                 if (p->size > DNS_PACKET_UNICAST_SIZE_MAX)
 214                         return -EMSGSIZE;
 215
 216                 /* Determine the local most accurate MTU */
 217                 if (s->link)
 218                         mtu = s->link->mtu;
 219                 else
 220                         mtu = manager_find_mtu(s->manager);
 221
 222                 /* Acquire the socket's PMDU MTU */
 223                 r = socket_get_mtu(fd, family, &socket_mtu);
 224                 if (r < 0 && !ERRNO_IS_DISCONNECT(r)) /* Will return ENOTCONN if no information is available yet */
 225                         return log_debug_errno(r, "Failed to read socket MTU: %m");
 226
 227                 /* Determine the appropriate UDP header size */
 228                 udp_size = udp_header_size(family);
 229                 min_mtu = udp_size + DNS_PACKET_HEADER_SIZE;
 230
 231                 log_debug("Emitting UDP, link MTU is %zu, socket MTU is %zu, minimal MTU is %zu",
 232                           mtu, socket_mtu, min_mtu);
 233
 234                 /* Clamp by the kernel's idea of the (path) MTU */
 235                 if (socket_mtu != 0 && socket_mtu < mtu)
 236                         mtu = socket_mtu;
 237
 238                 /* Put a lower limit, in case all MTU data we acquired was rubbish */
 239                 if (mtu < min_mtu)
 240                         mtu = min_mtu;
 241
 242                 /* Now check our packet size against the MTU we determined */
 243                 if (udp_size + p->size > mtu)
 244                         return -EMSGSIZE; /* This means: try TCP instead */
 245
 246                 r = manager_write(s->manager, fd, p);
 247                 if (r < 0)
 248                         return r;
 249
 250                 break;
 251         }
 252
 253         case DNS_PROTOCOL_LLMNR: {
 254                 union in_addr_union addr;
 255
 256                 assert(fd < 0);
 257
 258                 if (DNS_PACKET_QDCOUNT(p) > 1)
 259                         return -EOPNOTSUPP;
 260
 261                 if (!ratelimit_below(&s->ratelimit))
 262                         return -EBUSY;
 263
 264                 if (family == AF_INET) {
 265                         addr.in = LLMNR_MULTICAST_IPV4_ADDRESS;
 266                         fd = manager_llmnr_ipv4_udp_fd(s->manager);
 267                 } else if (family == AF_INET6) {
 268                         addr.in6 = LLMNR_MULTICAST_IPV6_ADDRESS;
 269                         fd = manager_llmnr_ipv6_udp_fd(s->manager);
 270                 } else
 271                         return -EAFNOSUPPORT;
 272                 if (fd < 0)
 273                         return fd;
 274
 275                 r = manager_send(s->manager, fd, s->link->ifindex, family, &addr, LLMNR_PORT, NULL, p);
 276                 if (r < 0)
 277                         return r;
 278
 279                 break;
 280         }
 281
 282         case DNS_PROTOCOL_MDNS: {
 283                 union in_addr_union addr;
 284                 assert(fd < 0);
 285
 286                 if (!ratelimit_below(&s->ratelimit))
 287                         return -EBUSY;
 288
 289                 if (family == AF_INET) {
 290                         if (in4_addr_is_null(&p->destination.in))
 291                                 addr.in = MDNS_MULTICAST_IPV4_ADDRESS;
 292                         else
 293                                 addr = p->destination;
 294                         fd = manager_mdns_ipv4_fd(s->manager);
 295                 } else if (family == AF_INET6) {
 296                         if (in6_addr_is_null(&p->destination.in6))
 297                                 addr.in6 = MDNS_MULTICAST_IPV6_ADDRESS;
 298                         else
 299                                 addr = p->destination;
 300                         fd = manager_mdns_ipv6_fd(s->manager);
 301                 } else
 302                         return -EAFNOSUPPORT;
 303                 if (fd < 0)
 304                         return fd;
 305
 306                 r = manager_send(s->manager, fd, s->link->ifindex, family, &addr, p->destination_port ?: MDNS_PORT, NULL, p);
 307                 if (r < 0)
 308                         return r;
 309
 310                 break;
 311         }
 312
 313         default:
 314                 return -EAFNOSUPPORT;
 315         }
 316
 317         return 1;
 318 }
 319
 320 int dns_scope_emit_udp(DnsScope *s, int fd, int af, DnsPacket *p) {
 321         int r;
 322
 323         assert(s);
 324         assert(p);
 325         assert(p->protocol == s->protocol);
 326         assert((s->protocol == DNS_PROTOCOL_DNS) == (fd >= 0));
 327
 328         do {
 329                 /* If there are multiple linked packets, set the TC bit in all but the last of them */
 330                 if (p->more) {
 331                         assert(p->protocol == DNS_PROTOCOL_MDNS);
 332                         dns_packet_set_flags(p, true, true);
 333                 }
 334
 335                 r = dns_scope_emit_one(s, fd, af, p);
 336                 if (r < 0)
 337                         return r;
 338
 339                 p = p->more;
 340         } while (p);
 341
 342         return 0;
 343 }
 344
 345 static int dns_scope_socket(
 346                 DnsScope *s,
 347                 int type,
 348                 int family,
 349                 const union in_addr_union *address,
 350                 DnsServer *server,
 351                 uint16_t port,
 352                 union sockaddr_union *ret_socket_address) {
 353
 354         _cleanup_close_ int fd = -1;
 355         union sockaddr_union sa;
 356         socklen_t salen;
 357         int r, ifindex;
 358
 359         assert(s);
 360
 361         if (server) {
 362                 assert(family == AF_UNSPEC);
 363                 assert(!address);
 364
 365                 ifindex = dns_server_ifindex(server);
 366
 367                 switch (server->family) {
 368                 case AF_INET:
 369                         sa = (union sockaddr_union) {
 370                                 .in.sin_family = server->family,
 371                                 .in.sin_port = htobe16(port),
 372                                 .in.sin_addr = server->address.in,
 373                         };
 374                         salen = sizeof(sa.in);
 375                         break;
 376                 case AF_INET6:
 377                         sa = (union sockaddr_union) {
 378                                 .in6.sin6_family = server->family,
 379                                 .in6.sin6_port = htobe16(port),
 380                                 .in6.sin6_addr = server->address.in6,
 381                                 .in6.sin6_scope_id = ifindex,
 382                         };
 383                         salen = sizeof(sa.in6);
 384                         break;
 385                 default:
 386                         return -EAFNOSUPPORT;
 387                 }
 388         } else {
 389                 assert(family != AF_UNSPEC);
 390                 assert(address);
 391
 392                 ifindex = s->link ? s->link->ifindex : 0;
 393
 394                 switch (family) {
 395                 case AF_INET:
 396                         sa = (union sockaddr_union) {
 397                                 .in.sin_family = family,
 398                                 .in.sin_port = htobe16(port),
 399                                 .in.sin_addr = address->in,
 400                         };
 401                         salen = sizeof(sa.in);
 402                         break;
 403                 case AF_INET6:
 404                         sa = (union sockaddr_union) {
 405                                 .in6.sin6_family = family,
 406                                 .in6.sin6_port = htobe16(port),
 407                                 .in6.sin6_addr = address->in6,
 408                                 .in6.sin6_scope_id = ifindex,
 409                         };
 410                         salen = sizeof(sa.in6);
 411                         break;
 412                 default:
 413                         return -EAFNOSUPPORT;
 414                 }
 415         }
 416
 417         fd = socket(sa.sa.sa_family, type|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
 418         if (fd < 0)
 419                 return -errno;
 420
 421         if (type == SOCK_STREAM) {
 422                 r = setsockopt_int(fd, IPPROTO_TCP, TCP_NODELAY, true);
 423                 if (r < 0)
 424                         return r;
 425         }
 426
 427         if (s->link) {
 428                 r = socket_set_unicast_if(fd, sa.sa.sa_family, ifindex);
 429                 if (r < 0)
 430                         return r;
 431         }
 432
 433         if (s->protocol == DNS_PROTOCOL_LLMNR) {
 434                 /* RFC 4795, section 2.5 requires the TTL to be set to 1 */
 435                 r = socket_set_ttl(fd, sa.sa.sa_family, 1);
 436                 if (r < 0)
 437                         return r;
 438         }
 439
 440         if (type == SOCK_DGRAM) {
 441                 /* Set IP_RECVERR or IPV6_RECVERR to get ICMP error feedback. See discussion in #10345. */
 442                 r = socket_set_recverr(fd, sa.sa.sa_family, true);
 443                 if (r < 0)
 444                         return r;
 445
 446                 r = socket_set_recvpktinfo(fd, sa.sa.sa_family, true);
 447                 if (r < 0)
 448                         return r;
 449
 450                 /* Turn of path MTU discovery for security reasons */
 451                 r = socket_disable_pmtud(fd, sa.sa.sa_family);
 452                 if (r < 0)
 453                         log_debug_errno(r, "Failed to disable UDP PMTUD, ignoring: %m");
 454
 455                 /* Learn about fragmentation taking place */
 456                 r = socket_set_recvfragsize(fd, sa.sa.sa_family, true);
 457                 if (r < 0)
 458                         log_debug_errno(r, "Failed to enable fragment size reception, ignoring: %m");
 459         }
 460
 461         if (ret_socket_address)
 462                 *ret_socket_address = sa;
 463         else {
 464                 bool bound = false;
 465
 466                 /* Let's temporarily bind the socket to the specified ifindex. The kernel currently takes
 467                  * only the SO_BINDTODEVICE/SO_BINDTOINDEX ifindex into account when making routing decisions
 468                  * in connect() — and not IP_UNICAST_IF. We don't really want any of the other semantics of
 469                  * SO_BINDTODEVICE/SO_BINDTOINDEX, hence we immediately unbind the socket after the fact
 470                  * again.
 471                  *
 472                  * As a special exception we don't do this if we notice that the specified IP address is on
 473                  * the local host. SO_BINDTODEVICE in combination with destination addresses on the local
 474                  * host result in EHOSTUNREACH, since Linux won't send the packets out of the specified
 475                  * interface, but delivers them directly to the local socket. */
 476                 if (s->link &&
 477                     !manager_find_link_address(s->manager, sa.sa.sa_family, sockaddr_in_addr(&sa.sa))) {
 478                         r = socket_bind_to_ifindex(fd, ifindex);
 479                         if (r < 0)
 480                                 return r;
 481
 482                         bound = true;
 483                 }
 484
 485                 r = connect(fd, &sa.sa, salen);
 486                 if (r < 0 && errno != EINPROGRESS)
 487                         return -errno;
 488
 489                 if (bound) {
 490                         r = socket_bind_to_ifindex(fd, 0);
 491                         if (r < 0)
 492                                 return r;
 493                 }
 494         }
 495
 496         return TAKE_FD(fd);
 497 }
 498
 499 int dns_scope_socket_udp(DnsScope *s, DnsServer *server) {
 500         return dns_scope_socket(s, SOCK_DGRAM, AF_UNSPEC, NULL, server, dns_server_port(server), NULL);
 501 }
 502
 503 int dns_scope_socket_tcp(DnsScope *s, int family, const union in_addr_union *address, DnsServer *server, uint16_t port, union sockaddr_union *ret_socket_address) {
 504         /* If ret_socket_address is not NULL, the caller is responsible
 505          * for calling connect() or sendmsg(). This is required by TCP
 506          * Fast Open, to be able to send the initial SYN packet along
 507          * with the first data packet. */
 508         return dns_scope_socket(s, SOCK_STREAM, family, address, server, port, ret_socket_address);
 509 }
 510
 511 static DnsScopeMatch match_link_local_reverse_lookups(const char *domain) {
 512         assert(domain);
 513
 514         if (dns_name_endswith(domain, "254.169.in-addr.arpa") > 0)
 515                 return DNS_SCOPE_YES_BASE + 4; /* 4 labels match */
 516
 517         if (dns_name_endswith(domain, "8.e.f.ip6.arpa") > 0 ||
 518             dns_name_endswith(domain, "9.e.f.ip6.arpa") > 0 ||
 519             dns_name_endswith(domain, "a.e.f.ip6.arpa") > 0 ||
 520             dns_name_endswith(domain, "b.e.f.ip6.arpa") > 0)
 521                 return DNS_SCOPE_YES_BASE + 5; /* 5 labels match */
 522
 523         return _DNS_SCOPE_MATCH_INVALID;
 524 }
 525
 526 static DnsScopeMatch match_subnet_reverse_lookups(
 527                 DnsScope *s,
 528                 const char *domain,
 529                 bool exclude_own) {
 530
 531         union in_addr_union ia;
 532         int f, r;
 533
 534         assert(s);
 535         assert(domain);
 536
 537         /* Checks whether the specified domain is a reverse address domain (i.e. in the .in-addr.arpa or
 538          * .ip6.arpa area), and if so, whether the address matches any of the local subnets of the link the
 539          * scope is associated with. If so, our scope should consider itself relevant for any lookup in the
 540          * domain, since it apparently refers to hosts on this link's subnet.
 541          *
 542          * If 'exclude_own' is true this will return DNS_SCOPE_NO for any IP addresses assigned locally. This
 543          * is useful for LLMNR/mDNS as we never want to look up our own hostname on LLMNR/mDNS but always use
 544          * the locally synthesized one. */
 545
 546         if (!s->link)
 547                 return _DNS_SCOPE_MATCH_INVALID; /* No link, hence no local addresses to check */
 548
 549         r = dns_name_address(domain, &f, &ia);
 550         if (r < 0)
 551                 log_debug_errno(r, "Failed to determine whether '%s' is an address domain: %m", domain);
 552         if (r <= 0)
 553                 return _DNS_SCOPE_MATCH_INVALID;
 554
 555         if (s->family != AF_UNSPEC && f != s->family)
 556                 return _DNS_SCOPE_MATCH_INVALID; /* Don't look for IPv4 addresses on LLMNR/mDNS over IPv6 and vice versa */
 557
 558         LIST_FOREACH(addresses, a, s->link->addresses) {
 559
 560                 if (a->family != f)
 561                         continue;
 562
 563                 /* Equals our own address? nah, let's not use this scope. The local synthesizer will pick it up for us. */
 564                 if (exclude_own &&
 565                     in_addr_equal(f, &a->in_addr, &ia) > 0)
 566                         return DNS_SCOPE_NO;
 567
 568                 if (a->prefixlen == UCHAR_MAX) /* don't know subnet mask */
 569                         continue;
 570
 571                 /* Check if the address is in the local subnet */
 572                 r = in_addr_prefix_covers(f, &a->in_addr, a->prefixlen, &ia);
 573                 if (r < 0)
 574                         log_debug_errno(r, "Failed to determine whether link address covers lookup address '%s': %m", domain);
 575                 if (r > 0)
 576                         /* Note that we only claim zero labels match. This is so that this is at the same
 577                          * priority a DNS scope with "." as routing domain is. */
 578                         return DNS_SCOPE_YES_BASE + 0;
 579         }
 580
 581         return _DNS_SCOPE_MATCH_INVALID;
 582 }
 583
 584 DnsScopeMatch dns_scope_good_domain(
 585                 DnsScope *s,
 586                 DnsQuery *q) {
 587
 588         DnsQuestion *question;
 589         const char *domain;
 590         uint64_t flags;
 591         int ifindex;
 592
 593         /* This returns the following return values:
 594          *
 595          *    DNS_SCOPE_NO         → This scope is not suitable for lookups of this domain, at all
 596          *    DNS_SCOPE_MAYBE      → This scope is suitable, but only if nothing else wants it
 597          *    DNS_SCOPE_YES_BASE+n → This scope is suitable, and 'n' suffix labels match
 598          *
 599          *  (The idea is that the caller will only use the scopes with the longest 'n' returned. If no scopes return
 600          *  DNS_SCOPE_YES_BASE+n, then it should use those which returned DNS_SCOPE_MAYBE. It should never use those
 601          *  which returned DNS_SCOPE_NO.)
 602          */
 603
 604         assert(s);
 605         assert(q);
 606
 607         question = dns_query_question_for_protocol(q, s->protocol);
 608         if (!question)
 609                 return DNS_SCOPE_NO;
 610
 611         domain = dns_question_first_name(question);
 612         if (!domain)
 613                 return DNS_SCOPE_NO;
 614
 615         ifindex = q->ifindex;
 616         flags = q->flags;
 617
 618         /* Checks if the specified domain is something to look up on this scope. Note that this accepts
 619          * non-qualified hostnames, i.e. those without any search path suffixed. */
 620
 621         if (ifindex != 0 && (!s->link || s->link->ifindex != ifindex))
 622                 return DNS_SCOPE_NO;
 623
 624         if ((SD_RESOLVED_FLAGS_MAKE(s->protocol, s->family, false, false) & flags) == 0)
 625                 return DNS_SCOPE_NO;
 626
 627         /* Never resolve any loopback hostname or IP address via DNS, LLMNR or mDNS. Instead, always rely on
 628          * synthesized RRs for these. */
 629         if (is_localhost(domain) ||
 630             dns_name_endswith(domain, "127.in-addr.arpa") > 0 ||
 631             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)
 632                 return DNS_SCOPE_NO;
 633
 634         /* Never respond to some of the domains listed in RFC6303 + RFC6761 */
 635         if (dns_name_dont_resolve(domain))
 636                 return DNS_SCOPE_NO;
 637
 638         /* Never go to network for the _gateway or _outbound domain — they're something special, synthesized locally. */
 639         if (is_gateway_hostname(domain) || is_outbound_hostname(domain))
 640                 return DNS_SCOPE_NO;
 641
 642         switch (s->protocol) {
 643
 644         case DNS_PROTOCOL_DNS: {
 645                 bool has_search_domains = false;
 646                 DnsScopeMatch m;
 647                 int n_best = -1;
 648
 649                 if (dns_name_is_empty(domain)) {
 650                         DnsResourceKey *t;
 651                         bool found = false;
 652
 653                         /* Refuse empty name if only A and/or AAAA records are requested. */
 654
 655                         DNS_QUESTION_FOREACH(t, question)
 656                                 if (!IN_SET(t->type, DNS_TYPE_A, DNS_TYPE_AAAA)) {
 657                                         found = true;
 658                                         break;
 659                                 }
 660
 661                         if (!found)
 662                                 return DNS_SCOPE_NO;
 663                 }
 664
 665                 /* Never route things to scopes that lack DNS servers */
 666                 if (!dns_scope_get_dns_server(s))
 667                         return DNS_SCOPE_NO;
 668
 669                 /* Always honour search domains for routing queries, except if this scope lacks DNS servers. Note that
 670                  * we return DNS_SCOPE_YES here, rather than just DNS_SCOPE_MAYBE, which means other wildcard scopes
 671                  * won't be considered anymore. */
 672                 LIST_FOREACH(domains, d, dns_scope_get_search_domains(s)) {
 673
 674                         if (!d->route_only && !dns_name_is_root(d->name))
 675                                 has_search_domains = true;
 676
 677                         if (dns_name_endswith(domain, d->name) > 0) {
 678                                 int c;
 679
 680                                 c = dns_name_count_labels(d->name);
 681                                 if (c < 0)
 682                                         continue;
 683
 684                                 if (c > n_best)
 685                                         n_best = c;
 686                         }
 687                 }
 688
 689                 /* If there's a true search domain defined for this scope, and the query is single-label,
 690                  * then let's resolve things here, prefereably. Note that LLMNR considers itself
 691                  * authoritative for single-label names too, at the same preference, see below. */
 692                 if (has_search_domains && dns_name_is_single_label(domain))
 693                         return DNS_SCOPE_YES_BASE + 1;
 694
 695                 /* Let's return the number of labels in the best matching result */
 696                 if (n_best >= 0) {
 697                         assert(n_best <= DNS_SCOPE_YES_END - DNS_SCOPE_YES_BASE);
 698                         return DNS_SCOPE_YES_BASE + n_best;
 699                 }
 700
 701                 /* Exclude link-local IP ranges */
 702                 if (match_link_local_reverse_lookups(domain) >= DNS_SCOPE_YES_BASE ||
 703                     /* If networks use .local in their private setups, they are supposed to also add .local
 704                      * to their search domains, which we already checked above. Otherwise, we consider .local
 705                      * specific to mDNS and won't send such queries ordinary DNS servers. */
 706                     dns_name_endswith(domain, "local") > 0)
 707                         return DNS_SCOPE_NO;
 708
 709                 /* If the IP address to look up matches the local subnet, then implicitly synthesizes
 710                  * DNS_SCOPE_YES_BASE + 0 on this interface, i.e. preferably resolve IP addresses via the DNS
 711                  * server belonging to this interface. */
 712                 m = match_subnet_reverse_lookups(s, domain, false);
 713                 if (m >= 0)
 714                         return m;
 715
 716                 /* If there was no match at all, then see if this scope is suitable as default route. */
 717                 if (!dns_scope_is_default_route(s))
 718                         return DNS_SCOPE_NO;
 719
 720                 return DNS_SCOPE_MAYBE;
 721         }
 722
 723         case DNS_PROTOCOL_MDNS: {
 724                 DnsScopeMatch m;
 725
 726                 m = match_link_local_reverse_lookups(domain);
 727                 if (m >= 0)
 728                         return m;
 729
 730                 m = match_subnet_reverse_lookups(s, domain, true);
 731                 if (m >= 0)
 732                         return m;
 733
 734                 if ((s->family == AF_INET && dns_name_endswith(domain, "in-addr.arpa") > 0) ||
 735                     (s->family == AF_INET6 && dns_name_endswith(domain, "ip6.arpa") > 0))
 736                         return DNS_SCOPE_MAYBE;
 737
 738                 if ((dns_name_endswith(domain, "local") > 0 && /* only resolve names ending in .local via mDNS */
 739                      dns_name_equal(domain, "local") == 0 &&   /* but not the single-label "local" name itself */
 740                      manager_is_own_hostname(s->manager, domain) <= 0)) /* never resolve the local hostname via mDNS */
 741                         return DNS_SCOPE_YES_BASE + 1; /* Return +1, as the top-level .local domain matches, i.e. one label */
 742
 743                 return DNS_SCOPE_NO;
 744         }
 745
 746         case DNS_PROTOCOL_LLMNR: {
 747                 DnsScopeMatch m;
 748
 749                 m = match_link_local_reverse_lookups(domain);
 750                 if (m >= 0)
 751                         return m;
 752
 753                 m = match_subnet_reverse_lookups(s, domain, true);
 754                 if (m >= 0)
 755                         return m;
 756
 757                 if ((s->family == AF_INET && dns_name_endswith(domain, "in-addr.arpa") > 0) ||
 758                     (s->family == AF_INET6 && dns_name_endswith(domain, "ip6.arpa") > 0))
 759                         return DNS_SCOPE_MAYBE;
 760
 761                 if ((dns_name_is_single_label(domain) && /* only resolve single label names via LLMNR */
 762                      !is_gateway_hostname(domain) && /* don't resolve "_gateway" with LLMNR, let local synthesizing logic handle that */
 763                      !is_outbound_hostname(domain) && /* similar for "_outbound" */
 764                      dns_name_equal(domain, "local") == 0 && /* don't resolve "local" with LLMNR, it's the top-level domain of mDNS after all, see above */
 765                      manager_is_own_hostname(s->manager, domain) <= 0))  /* never resolve the local hostname via LLMNR */
 766                         return DNS_SCOPE_YES_BASE + 1; /* Return +1, as we consider ourselves authoritative
 767                                                         * for single-label names, i.e. one label. This is
 768                                                         * particularly relevant as it means a "." route on some
 769                                                         * other scope won't pull all traffic away from
 770                                                         * us. (If people actually want to pull traffic away
 771                                                         * from us they should turn off LLMNR on the
 772                                                         * link). Note that unicast DNS scopes with search
 773                                                         * domains also consider themselves authoritative for
 774                                                         * single-label domains, at the same preference (see
 775                                                         * above). */
 776
 777                 return DNS_SCOPE_NO;
 778         }
 779
 780         default:
 781                 assert_not_reached();
 782         }
 783 }
 784
 785 bool dns_scope_good_key(DnsScope *s, const DnsResourceKey *key) {
 786         int key_family;
 787
 788         assert(s);
 789         assert(key);
 790
 791         /* Check if it makes sense to resolve the specified key on this scope. Note that this call assumes a
 792          * fully qualified name, i.e. the search suffixes already appended. */
 793
 794         if (!IN_SET(key->class, DNS_CLASS_IN, DNS_CLASS_ANY))
 795                 return false;
 796
 797         if (s->protocol == DNS_PROTOCOL_DNS) {
 798
 799                 /* On classic DNS, looking up non-address RRs is always fine. (Specifically, we want to
 800                  * permit looking up DNSKEY and DS records on the root and top-level domains.) */
 801                 if (!dns_resource_key_is_address(key))
 802                         return true;
 803
 804                 /* Unless explicitly overridden, we refuse to look up A and AAAA RRs on the root and
 805                  * single-label domains, under the assumption that those should be resolved via LLMNR or
 806                  * search path only, and should not be leaked onto the internet. */
 807                 const char* name = dns_resource_key_name(key);
 808
 809                 if (!s->manager->resolve_unicast_single_label &&
 810                     dns_name_is_single_label(name))
 811                         return false;
 812
 813                 return !dns_name_is_root(name);
 814         }
 815
 816         /* Never route DNSSEC RR queries to LLMNR/mDNS scopes */
 817         if (dns_type_is_dnssec(key->type))
 818                 return false;
 819
 820         /* On mDNS and LLMNR, send A and AAAA queries only on the respective scopes */
 821
 822         key_family = dns_type_to_af(key->type);
 823         if (key_family < 0)
 824                 return true;
 825
 826         return key_family == s->family;
 827 }
 828
 829 static int dns_scope_multicast_membership(DnsScope *s, bool b, struct in_addr in, struct in6_addr in6) {
 830         int fd;
 831
 832         assert(s);
 833         assert(s->link);
 834
 835         if (s->family == AF_INET) {
 836                 struct ip_mreqn mreqn = {
 837                         .imr_multiaddr = in,
 838                         .imr_ifindex = s->link->ifindex,
 839                 };
 840
 841                 if (s->protocol == DNS_PROTOCOL_LLMNR)
 842                         fd = manager_llmnr_ipv4_udp_fd(s->manager);
 843                 else
 844                         fd = manager_mdns_ipv4_fd(s->manager);
 845
 846                 if (fd < 0)
 847                         return fd;
 848
 849                 /* Always first try to drop membership before we add
 850                  * one. This is necessary on some devices, such as
 851                  * veth. */
 852                 if (b)
 853                         (void) setsockopt(fd, IPPROTO_IP, IP_DROP_MEMBERSHIP, &mreqn, sizeof(mreqn));
 854
 855                 if (setsockopt(fd, IPPROTO_IP, b ? IP_ADD_MEMBERSHIP : IP_DROP_MEMBERSHIP, &mreqn, sizeof(mreqn)) < 0)
 856                         return -errno;
 857
 858         } else if (s->family == AF_INET6) {
 859                 struct ipv6_mreq mreq = {
 860                         .ipv6mr_multiaddr = in6,
 861                         .ipv6mr_interface = s->link->ifindex,
 862                 };
 863
 864                 if (s->protocol == DNS_PROTOCOL_LLMNR)
 865                         fd = manager_llmnr_ipv6_udp_fd(s->manager);
 866                 else
 867                         fd = manager_mdns_ipv6_fd(s->manager);
 868
 869                 if (fd < 0)
 870                         return fd;
 871
 872                 if (b)
 873                         (void) setsockopt(fd, IPPROTO_IPV6, IPV6_DROP_MEMBERSHIP, &mreq, sizeof(mreq));
 874
 875                 if (setsockopt(fd, IPPROTO_IPV6, b ? IPV6_ADD_MEMBERSHIP : IPV6_DROP_MEMBERSHIP, &mreq, sizeof(mreq)) < 0)
 876                         return -errno;
 877         } else
 878                 return -EAFNOSUPPORT;
 879
 880         return 0;
 881 }
 882
 883 int dns_scope_llmnr_membership(DnsScope *s, bool b) {
 884         assert(s);
 885
 886         if (s->protocol != DNS_PROTOCOL_LLMNR)
 887                 return 0;
 888
 889         return dns_scope_multicast_membership(s, b, LLMNR_MULTICAST_IPV4_ADDRESS, LLMNR_MULTICAST_IPV6_ADDRESS);
 890 }
 891
 892 int dns_scope_mdns_membership(DnsScope *s, bool b) {
 893         assert(s);
 894
 895         if (s->protocol != DNS_PROTOCOL_MDNS)
 896                 return 0;
 897
 898         return dns_scope_multicast_membership(s, b, MDNS_MULTICAST_IPV4_ADDRESS, MDNS_MULTICAST_IPV6_ADDRESS);
 899 }
 900
 901 int dns_scope_make_reply_packet(
 902                 DnsScope *s,
 903                 uint16_t id,
 904                 int rcode,
 905                 DnsQuestion *q,
 906                 DnsAnswer *answer,
 907                 DnsAnswer *soa,
 908                 bool tentative,
 909                 DnsPacket **ret) {
 910
 911         _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
 912         unsigned n_answer = 0, n_soa = 0;
 913         int r;
 914         bool c_or_aa;
 915
 916         assert(s);
 917         assert(ret);
 918
 919         if (dns_question_isempty(q) &&
 920             dns_answer_isempty(answer) &&
 921             dns_answer_isempty(soa))
 922                 return -EINVAL;
 923
 924         r = dns_packet_new(&p, s->protocol, 0, DNS_PACKET_SIZE_MAX);
 925         if (r < 0)
 926                 return r;
 927
 928         /* mDNS answers must have the Authoritative Answer bit set, see RFC 6762, section 18.4. */
 929         c_or_aa = s->protocol == DNS_PROTOCOL_MDNS;
 930
 931         DNS_PACKET_HEADER(p)->id = id;
 932         DNS_PACKET_HEADER(p)->flags = htobe16(DNS_PACKET_MAKE_FLAGS(
 933                                                               1 /* qr */,
 934                                                               0 /* opcode */,
 935                                                               c_or_aa,
 936                                                               0 /* tc */,
 937                                                               tentative,
 938                                                               0 /* (ra) */,
 939                                                               0 /* (ad) */,
 940                                                               0 /* (cd) */,
 941                                                               rcode));
 942
 943         r = dns_packet_append_question(p, q);
 944         if (r < 0)
 945                 return r;
 946         DNS_PACKET_HEADER(p)->qdcount = htobe16(dns_question_size(q));
 947
 948         r = dns_packet_append_answer(p, answer, &n_answer);
 949         if (r < 0)
 950                 return r;
 951         DNS_PACKET_HEADER(p)->ancount = htobe16(n_answer);
 952
 953         r = dns_packet_append_answer(p, soa, &n_soa);
 954         if (r < 0)
 955                 return r;
 956         DNS_PACKET_HEADER(p)->arcount = htobe16(n_soa);
 957
 958         *ret = TAKE_PTR(p);
 959
 960         return 0;
 961 }
 962
 963 static void dns_scope_verify_conflicts(DnsScope *s, DnsPacket *p) {
 964         DnsResourceRecord *rr;
 965         DnsResourceKey *key;
 966
 967         assert(s);
 968         assert(p);
 969
 970         DNS_QUESTION_FOREACH(key, p->question)
 971                 dns_zone_verify_conflicts(&s->zone, key);
 972
 973         DNS_ANSWER_FOREACH(rr, p->answer)
 974                 dns_zone_verify_conflicts(&s->zone, rr->key);
 975 }
 976
 977 void dns_scope_process_query(DnsScope *s, DnsStream *stream, DnsPacket *p) {
 978         _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL, *soa = NULL;
 979         _cleanup_(dns_packet_unrefp) DnsPacket *reply = NULL;
 980         DnsResourceKey *key = NULL;
 981         bool tentative = false;
 982         int r;
 983
 984         assert(s);
 985         assert(p);
 986
 987         if (p->protocol != DNS_PROTOCOL_LLMNR)
 988                 return;
 989
 990         if (p->ipproto == IPPROTO_UDP) {
 991                 /* Don't accept UDP queries directed to anything but
 992                  * the LLMNR multicast addresses. See RFC 4795,
 993                  * section 2.5. */
 994
 995                 if (p->family == AF_INET && !in4_addr_equal(&p->destination.in, &LLMNR_MULTICAST_IPV4_ADDRESS))
 996                         return;
 997
 998                 if (p->family == AF_INET6 && !in6_addr_equal(&p->destination.in6, &LLMNR_MULTICAST_IPV6_ADDRESS))
 999                         return;
1000         }
1001
1002         r = dns_packet_extract(p);
1003         if (r < 0) {
1004                 log_debug_errno(r, "Failed to extract resource records from incoming packet: %m");
1005                 return;
1006         }
1007
1008         if (DNS_PACKET_LLMNR_C(p)) {
1009                 /* Somebody notified us about a possible conflict */
1010                 dns_scope_verify_conflicts(s, p);
1011                 return;
1012         }
1013
1014         assert(dns_question_size(p->question) == 1);
1015         key = dns_question_first_key(p->question);
1016
1017         r = dns_zone_lookup(&s->zone, key, 0, &answer, &soa, &tentative);
1018         if (r < 0) {
1019                 log_debug_errno(r, "Failed to look up key: %m");
1020                 return;
1021         }
1022         if (r == 0)
1023                 return;
1024
1025         if (answer)
1026                 dns_answer_order_by_scope(answer, in_addr_is_link_local(p->family, &p->sender) > 0);
1027
1028         r = dns_scope_make_reply_packet(s, DNS_PACKET_ID(p), DNS_RCODE_SUCCESS, p->question, answer, soa, tentative, &reply);
1029         if (r < 0) {
1030                 log_debug_errno(r, "Failed to build reply packet: %m");
1031                 return;
1032         }
1033
1034         if (stream) {
1035                 r = dns_stream_write_packet(stream, reply);
1036                 if (r < 0) {
1037                         log_debug_errno(r, "Failed to enqueue reply packet: %m");
1038                         return;
1039                 }
1040
1041                 /* Let's take an extra reference on this stream, so that it stays around after returning. The reference
1042                  * will be dangling until the stream is disconnected, and the default completion handler of the stream
1043                  * will then unref the stream and destroy it */
1044                 if (DNS_STREAM_QUEUED(stream))
1045                         dns_stream_ref(stream);
1046         } else {
1047                 int fd;
1048
1049                 if (!ratelimit_below(&s->ratelimit))
1050                         return;
1051
1052                 if (p->family == AF_INET)
1053                         fd = manager_llmnr_ipv4_udp_fd(s->manager);
1054                 else if (p->family == AF_INET6)
1055                         fd = manager_llmnr_ipv6_udp_fd(s->manager);
1056                 else {
1057                         log_debug("Unknown protocol");
1058                         return;
1059                 }
1060                 if (fd < 0) {
1061                         log_debug_errno(fd, "Failed to get reply socket: %m");
1062                         return;
1063                 }
1064
1065                 /* Note that we always immediately reply to all LLMNR
1066                  * requests, and do not wait any time, since we
1067                  * verified uniqueness for all records. Also see RFC
1068                  * 4795, Section 2.7 */
1069
1070                 r = manager_send(s->manager, fd, p->ifindex, p->family, &p->sender, p->sender_port, NULL, reply);
1071                 if (r < 0) {
1072                         log_debug_errno(r, "Failed to send reply packet: %m");
1073                         return;
1074                 }
1075         }
1076 }
1077
1078 DnsTransaction *dns_scope_find_transaction(
1079                 DnsScope *scope,
1080                 DnsResourceKey *key,
1081                 uint64_t query_flags) {
1082
1083         DnsTransaction *first;
1084
1085         assert(scope);
1086         assert(key);
1087
1088         /* Iterate through the list of transactions with a matching key */
1089         first = hashmap_get(scope->transactions_by_key, key);
1090         LIST_FOREACH(transactions_by_key, t, first) {
1091
1092                 /* These four flags must match exactly: we cannot use a validated response for a
1093                  * non-validating client, and we cannot use a non-validated response for a validating
1094                  * client. Similar, if the sources don't match things aren't usable either. */
1095                 if (((query_flags ^ t->query_flags) &
1096                      (SD_RESOLVED_NO_VALIDATE|
1097                      SD_RESOLVED_NO_ZONE|
1098                       SD_RESOLVED_NO_TRUST_ANCHOR|
1099                       SD_RESOLVED_NO_NETWORK)) != 0)
1100                         continue;
1101
1102                 /* We can reuse a primary query if a regular one is requested, but not vice versa */
1103                 if ((query_flags & SD_RESOLVED_REQUIRE_PRIMARY) &&
1104                     !(t->query_flags & SD_RESOLVED_REQUIRE_PRIMARY))
1105                         continue;
1106
1107                 /* Don't reuse a transaction that allowed caching when we got told not to use it */
1108                 if ((query_flags & SD_RESOLVED_NO_CACHE) &&
1109                     !(t->query_flags & SD_RESOLVED_NO_CACHE))
1110                         continue;
1111
1112                 /* If we are asked to clamp ttls an the existing transaction doesn't do it, we can't
1113                  * reuse */
1114                 if ((query_flags & SD_RESOLVED_CLAMP_TTL) &&
1115                     !(t->query_flags & SD_RESOLVED_CLAMP_TTL))
1116                         continue;
1117
1118                 return t;
1119         }
1120
1121         return NULL;
1122 }
1123
1124 static int dns_scope_make_conflict_packet(
1125                 DnsScope *s,
1126                 DnsResourceRecord *rr,
1127                 DnsPacket **ret) {
1128
1129         _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
1130         int r;
1131
1132         assert(s);
1133         assert(rr);
1134         assert(ret);
1135
1136         r = dns_packet_new(&p, s->protocol, 0, DNS_PACKET_SIZE_MAX);
1137         if (r < 0)
1138                 return r;
1139
1140         DNS_PACKET_HEADER(p)->flags = htobe16(DNS_PACKET_MAKE_FLAGS(
1141                                                               0 /* qr */,
1142                                                               0 /* opcode */,
1143                                                               1 /* conflict */,
1144                                                               0 /* tc */,
1145                                                               0 /* t */,
1146                                                               0 /* (ra) */,
1147                                                               0 /* (ad) */,
1148                                                               0 /* (cd) */,
1149                                                               0));
1150
1151         /* For mDNS, the transaction ID should always be 0 */
1152         if (s->protocol != DNS_PROTOCOL_MDNS)
1153                 random_bytes(&DNS_PACKET_HEADER(p)->id, sizeof(uint16_t));
1154
1155         DNS_PACKET_HEADER(p)->qdcount = htobe16(1);
1156         DNS_PACKET_HEADER(p)->arcount = htobe16(1);
1157
1158         r = dns_packet_append_key(p, rr->key, 0, NULL);
1159         if (r < 0)
1160                 return r;
1161
1162         r = dns_packet_append_rr(p, rr, 0, NULL, NULL);
1163         if (r < 0)
1164                 return r;
1165
1166         *ret = TAKE_PTR(p);
1167
1168         return 0;
1169 }
1170
1171 static int on_conflict_dispatch(sd_event_source *es, usec_t usec, void *userdata) {
1172         DnsScope *scope = userdata;
1173         int r;
1174
1175         assert(es);
1176         assert(scope);
1177
1178         scope->conflict_event_source = sd_event_source_disable_unref(scope->conflict_event_source);
1179
1180         for (;;) {
1181                 _cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
1182                 _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
1183                 _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
1184
1185                 key = ordered_hashmap_first_key(scope->conflict_queue);
1186                 if (!key)
1187                         break;
1188
1189                 rr = ordered_hashmap_remove(scope->conflict_queue, key);
1190                 assert(rr);
1191
1192                 r = dns_scope_make_conflict_packet(scope, rr, &p);
1193                 if (r < 0) {
1194                         log_error_errno(r, "Failed to make conflict packet: %m");
1195                         return 0;
1196                 }
1197
1198                 r = dns_scope_emit_udp(scope, -1, AF_UNSPEC, p);
1199                 if (r < 0)
1200                         log_debug_errno(r, "Failed to send conflict packet: %m");
1201         }
1202
1203         return 0;
1204 }
1205
1206 int dns_scope_notify_conflict(DnsScope *scope, DnsResourceRecord *rr) {
1207         usec_t jitter;
1208         int r;
1209
1210         assert(scope);
1211         assert(rr);
1212
1213         /* We don't send these queries immediately. Instead, we queue
1214          * them, and send them after some jitter delay. */
1215         r = ordered_hashmap_ensure_allocated(&scope->conflict_queue, &dns_resource_key_hash_ops);
1216         if (r < 0) {
1217                 log_oom();
1218                 return r;
1219         }
1220
1221         /* We only place one RR per key in the conflict
1222          * messages, not all of them. That should be enough to
1223          * indicate where there might be a conflict */
1224         r = ordered_hashmap_put(scope->conflict_queue, rr->key, rr);
1225         if (IN_SET(r, 0, -EEXIST))
1226                 return 0;
1227         if (r < 0)
1228                 return log_debug_errno(r, "Failed to queue conflicting RR: %m");
1229
1230         dns_resource_key_ref(rr->key);
1231         dns_resource_record_ref(rr);
1232
1233         if (scope->conflict_event_source)
1234                 return 0;
1235
1236         random_bytes(&jitter, sizeof(jitter));
1237         jitter %= LLMNR_JITTER_INTERVAL_USEC;
1238
1239         r = sd_event_add_time_relative(
1240                         scope->manager->event,
1241                         &scope->conflict_event_source,
1242                         clock_boottime_or_monotonic(),
1243                         jitter,
1244                         LLMNR_JITTER_INTERVAL_USEC,
1245                         on_conflict_dispatch, scope);
1246         if (r < 0)
1247                 return log_debug_errno(r, "Failed to add conflict dispatch event: %m");
1248
1249         (void) sd_event_source_set_description(scope->conflict_event_source, "scope-conflict");
1250
1251         return 0;
1252 }
1253
1254 void dns_scope_check_conflicts(DnsScope *scope, DnsPacket *p) {
1255         DnsResourceRecord *rr;
1256         int r;
1257
1258         assert(scope);
1259         assert(p);
1260
1261         if (!IN_SET(p->protocol, DNS_PROTOCOL_LLMNR, DNS_PROTOCOL_MDNS))
1262                 return;
1263
1264         if (DNS_PACKET_RRCOUNT(p) <= 0)
1265                 return;
1266
1267         if (p->protocol == DNS_PROTOCOL_LLMNR) {
1268                 if (DNS_PACKET_LLMNR_C(p) != 0)
1269                         return;
1270
1271                 if (DNS_PACKET_LLMNR_T(p) != 0)
1272                         return;
1273         }
1274
1275         if (manager_packet_from_local_address(scope->manager, p))
1276                 return;
1277
1278         r = dns_packet_extract(p);
1279         if (r < 0) {
1280                 log_debug_errno(r, "Failed to extract packet: %m");
1281                 return;
1282         }
1283
1284         log_debug("Checking for conflicts...");
1285
1286         DNS_ANSWER_FOREACH(rr, p->answer) {
1287                 /* No conflict if it is DNS-SD RR used for service enumeration. */
1288                 if (dns_resource_key_is_dnssd_ptr(rr->key))
1289                         continue;
1290
1291                 /* Check for conflicts against the local zone. If we
1292                  * found one, we won't check any further */
1293                 r = dns_zone_check_conflicts(&scope->zone, rr);
1294                 if (r != 0)
1295                         continue;
1296
1297                 /* Check for conflicts against the local cache. If so,
1298                  * send out an advisory query, to inform everybody */
1299                 r = dns_cache_check_conflicts(&scope->cache, rr, p->family, &p->sender);
1300                 if (r <= 0)
1301                         continue;
1302
1303                 dns_scope_notify_conflict(scope, rr);
1304         }
1305 }
1306
1307 void dns_scope_dump(DnsScope *s, FILE *f) {
1308         assert(s);
1309
1310         if (!f)
1311                 f = stdout;
1312
1313         fputs("[Scope protocol=", f);
1314         fputs(dns_protocol_to_string(s->protocol), f);
1315
1316         if (s->link) {
1317                 fputs(" interface=", f);
1318                 fputs(s->link->ifname, f);
1319         }
1320
1321         if (s->family != AF_UNSPEC) {
1322                 fputs(" family=", f);
1323                 fputs(af_to_name(s->family), f);
1324         }
1325
1326         fputs("]\n", f);
1327
1328         if (!dns_zone_is_empty(&s->zone)) {
1329                 fputs("ZONE:\n", f);
1330                 dns_zone_dump(&s->zone, f);
1331         }
1332
1333         if (!dns_cache_is_empty(&s->cache)) {
1334                 fputs("CACHE:\n", f);
1335                 dns_cache_dump(&s->cache, f);
1336         }
1337 }
1338
1339 DnsSearchDomain *dns_scope_get_search_domains(DnsScope *s) {
1340         assert(s);
1341
1342         if (s->protocol != DNS_PROTOCOL_DNS)
1343                 return NULL;
1344
1345         if (s->link)
1346                 return s->link->search_domains;
1347
1348         return s->manager->search_domains;
1349 }
1350
1351 bool dns_scope_name_wants_search_domain(DnsScope *s, const char *name) {
1352         assert(s);
1353
1354         if (s->protocol != DNS_PROTOCOL_DNS)
1355                 return false;
1356
1357         return dns_name_is_single_label(name);
1358 }
1359
1360 bool dns_scope_network_good(DnsScope *s) {
1361         /* Checks whether the network is in good state for lookups on this scope. For mDNS/LLMNR/Classic DNS scopes
1362          * bound to links this is easy, as they don't even exist if the link isn't in a suitable state. For the global
1363          * DNS scope we check whether there are any links that are up and have an address.
1364          *
1365          * Note that Linux routing is complex and even systems that superficially have no IPv4 address might
1366          * be able to route IPv4 (and similar for IPv6), hence let's make a check here independent of address
1367          * family. */
1368
1369         if (s->link)
1370                 return true;
1371
1372         return manager_routable(s->manager);
1373 }
1374
1375 int dns_scope_ifindex(DnsScope *s) {
1376         assert(s);
1377
1378         if (s->link)
1379                 return s->link->ifindex;
1380
1381         return 0;
1382 }
1383
1384 static int on_announcement_timeout(sd_event_source *s, usec_t usec, void *userdata) {
1385         DnsScope *scope = userdata;
1386
1387         assert(s);
1388
1389         scope->announce_event_source = sd_event_source_disable_unref(scope->announce_event_source);
1390
1391         (void) dns_scope_announce(scope, false);
1392         return 0;
1393 }
1394
1395 int dns_scope_announce(DnsScope *scope, bool goodbye) {
1396         _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
1397         _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
1398         _cleanup_set_free_ Set *types = NULL;
1399         DnsZoneItem *z;
1400         unsigned size = 0;
1401         char *service_type;
1402         int r;
1403
1404         if (!scope)
1405                 return 0;
1406
1407         if (scope->protocol != DNS_PROTOCOL_MDNS)
1408                 return 0;
1409
1410         /* Check if we're done with probing. */
1411         LIST_FOREACH(transactions_by_scope, t, scope->transactions)
1412                 if (DNS_TRANSACTION_IS_LIVE(t->state))
1413                         return 0;
1414
1415         /* Check if there're services pending conflict resolution. */
1416         if (manager_next_dnssd_names(scope->manager))
1417                 return 0; /* we reach this point only if changing hostname didn't help */
1418
1419         /* Calculate answer's size. */
1420         HASHMAP_FOREACH(z, scope->zone.by_key) {
1421                 if (z->state != DNS_ZONE_ITEM_ESTABLISHED)
1422                         continue;
1423
1424                 if (z->rr->key->type == DNS_TYPE_PTR &&
1425                     !dns_zone_contains_name(&scope->zone, z->rr->ptr.name)) {
1426                         char key_str[DNS_RESOURCE_KEY_STRING_MAX];
1427
1428                         log_debug("Skip PTR RR <%s> since its counterparts seem to be withdrawn", dns_resource_key_to_string(z->rr->key, key_str, sizeof key_str));
1429                         z->state = DNS_ZONE_ITEM_WITHDRAWN;
1430                         continue;
1431                 }
1432
1433                 /* Collect service types for _services._dns-sd._udp.local RRs in a set */
1434                 if (!scope->announced &&
1435                     dns_resource_key_is_dnssd_ptr(z->rr->key)) {
1436                         if (!set_contains(types, dns_resource_key_name(z->rr->key))) {
1437                                 r = set_ensure_put(&types, &dns_name_hash_ops, dns_resource_key_name(z->rr->key));
1438                                 if (r < 0)
1439                                         return log_debug_errno(r, "Failed to add item to set: %m");
1440                         }
1441                 }
1442
1443                 LIST_FOREACH(by_key, i, z)
1444                         size++;
1445         }
1446
1447         answer = dns_answer_new(size + set_size(types));
1448         if (!answer)
1449                 return log_oom();
1450
1451         /* Second iteration, actually add RRs to the answer. */
1452         HASHMAP_FOREACH(z, scope->zone.by_key)
1453                 LIST_FOREACH (by_key, i, z) {
1454                         DnsAnswerFlags flags;
1455
1456                         if (i->state != DNS_ZONE_ITEM_ESTABLISHED)
1457                                 continue;
1458
1459                         if (dns_resource_key_is_dnssd_ptr(i->rr->key))
1460                                 flags = goodbye ? DNS_ANSWER_GOODBYE : 0;
1461                         else
1462                                 flags = goodbye ? (DNS_ANSWER_GOODBYE|DNS_ANSWER_CACHE_FLUSH) : DNS_ANSWER_CACHE_FLUSH;
1463
1464                         r = dns_answer_add(answer, i->rr, 0, flags, NULL);
1465                         if (r < 0)
1466                                 return log_debug_errno(r, "Failed to add RR to announce: %m");
1467                 }
1468
1469         /* Since all the active services are in the zone make them discoverable now. */
1470         SET_FOREACH(service_type, types) {
1471                 _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
1472
1473                 rr = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_PTR,
1474                                                   "_services._dns-sd._udp.local");
1475                 if (!rr)
1476                         return log_oom();
1477
1478                 rr->ptr.name = strdup(service_type);
1479                 if (!rr->ptr.name)
1480                         return log_oom();
1481
1482                 rr->ttl = MDNS_DEFAULT_TTL;
1483
1484                 r = dns_zone_put(&scope->zone, scope, rr, false);
1485                 if (r < 0)
1486                         log_warning_errno(r, "Failed to add DNS-SD PTR record to MDNS zone, ignoring: %m");
1487
1488                 r = dns_answer_add(answer, rr, 0, 0, NULL);
1489                 if (r < 0)
1490                         return log_debug_errno(r, "Failed to add RR to announce: %m");
1491         }
1492
1493         if (dns_answer_isempty(answer))
1494                 return 0;
1495
1496         r = dns_scope_make_reply_packet(scope, 0, DNS_RCODE_SUCCESS, NULL, answer, NULL, false, &p);
1497         if (r < 0)
1498                 return log_debug_errno(r, "Failed to build reply packet: %m");
1499
1500         r = dns_scope_emit_udp(scope, -1, AF_UNSPEC, p);
1501         if (r < 0)
1502                 return log_debug_errno(r, "Failed to send reply packet: %m");
1503
1504         /* In section 8.3 of RFC6762: "The Multicast DNS responder MUST send at least two unsolicited
1505          * responses, one second apart." */
1506         if (!scope->announced) {
1507                 scope->announced = true;
1508
1509                 r = sd_event_add_time_relative(
1510                                 scope->manager->event,
1511                                 &scope->announce_event_source,
1512                                 clock_boottime_or_monotonic(),
1513                                 MDNS_ANNOUNCE_DELAY,
1514                                 MDNS_JITTER_RANGE_USEC,
1515                                 on_announcement_timeout, scope);
1516                 if (r < 0)
1517                         return log_debug_errno(r, "Failed to schedule second announcement: %m");
1518
1519                 (void) sd_event_source_set_description(scope->announce_event_source, "mdns-announce");
1520         }
1521
1522         return 0;
1523 }
1524
1525 int dns_scope_add_dnssd_services(DnsScope *scope) {
1526         DnssdService *service;
1527         int r;
1528
1529         assert(scope);
1530
1531         if (hashmap_size(scope->manager->dnssd_services) == 0)
1532                 return 0;
1533
1534         scope->announced = false;
1535
1536         HASHMAP_FOREACH(service, scope->manager->dnssd_services) {
1537                 service->withdrawn = false;
1538
1539                 r = dns_zone_put(&scope->zone, scope, service->ptr_rr, false);
1540                 if (r < 0)
1541                         log_warning_errno(r, "Failed to add PTR record to MDNS zone: %m");
1542
1543                 r = dns_zone_put(&scope->zone, scope, service->srv_rr, true);
1544                 if (r < 0)
1545                         log_warning_errno(r, "Failed to add SRV record to MDNS zone: %m");
1546
1547                 LIST_FOREACH(items, txt_data, service->txt_data_items) {
1548                         r = dns_zone_put(&scope->zone, scope, txt_data->rr, true);
1549                         if (r < 0)
1550                                 log_warning_errno(r, "Failed to add TXT record to MDNS zone: %m");
1551                 }
1552         }
1553
1554         return 0;
1555 }
1556
1557 int dns_scope_remove_dnssd_services(DnsScope *scope) {
1558         _cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
1559         DnssdService *service;
1560         int r;
1561
1562         assert(scope);
1563
1564         key = dns_resource_key_new(DNS_CLASS_IN, DNS_TYPE_PTR,
1565                                    "_services._dns-sd._udp.local");
1566         if (!key)
1567                 return log_oom();
1568
1569         r = dns_zone_remove_rrs_by_key(&scope->zone, key);
1570         if (r < 0)
1571                 return r;
1572
1573         HASHMAP_FOREACH(service, scope->manager->dnssd_services) {
1574                 dns_zone_remove_rr(&scope->zone, service->ptr_rr);
1575                 dns_zone_remove_rr(&scope->zone, service->srv_rr);
1576                 LIST_FOREACH(items, txt_data, service->txt_data_items)
1577                         dns_zone_remove_rr(&scope->zone, txt_data->rr);
1578         }
1579
1580         return 0;
1581 }
1582
1583 static bool dns_scope_has_route_only_domains(DnsScope *scope) {
1584         DnsSearchDomain *first;
1585         bool route_only = false;
1586
1587         assert(scope);
1588         assert(scope->protocol == DNS_PROTOCOL_DNS);
1589
1590         /* Returns 'true' if this scope is suitable for queries to specific domains only. For that we check
1591          * if there are any route-only domains on this interface, as a heuristic to discern VPN-style links
1592          * from non-VPN-style links. Returns 'false' for all other cases, i.e. if the scope is intended to
1593          * take queries to arbitrary domains, i.e. has no routing domains set. */
1594
1595         if (scope->link)
1596                 first = scope->link->search_domains;
1597         else
1598                 first = scope->manager->search_domains;
1599
1600         LIST_FOREACH(domains, domain, first) {
1601                 /* "." means "any domain", thus the interface takes any kind of traffic. Thus, we exit early
1602                  * here, as it doesn't really matter whether this link has any route-only domains or not,
1603                  * "~."  really trumps everything and clearly indicates that this interface shall receive all
1604                  * traffic it can get. */
1605                 if (dns_name_is_root(DNS_SEARCH_DOMAIN_NAME(domain)))
1606                         return false;
1607
1608                 if (domain->route_only)
1609                         route_only = true;
1610         }
1611
1612         return route_only;
1613 }
1614
1615 bool dns_scope_is_default_route(DnsScope *scope) {
1616         assert(scope);
1617
1618         /* Only use DNS scopes as default routes */
1619         if (scope->protocol != DNS_PROTOCOL_DNS)
1620                 return false;
1621
1622         /* The global DNS scope is always suitable as default route */
1623         if (!scope->link)
1624                 return true;
1625
1626         /* Honour whatever is explicitly configured. This is really the best approach, and trumps any
1627          * automatic logic. */
1628         if (scope->link->default_route >= 0)
1629                 return scope->link->default_route;
1630
1631         /* Otherwise check if we have any route-only domains, as a sensible heuristic: if so, let's not
1632          * volunteer as default route. */
1633         return !dns_scope_has_route_only_domains(scope);
1634 }