src/resolve/resolved-dns-stub.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <net/if_arp.h>
   4
   5 #include "errno-util.h"
   6 #include "fd-util.h"
   7 #include "missing_network.h"
   8 #include "missing_socket.h"
   9 #include "resolved-dns-stub.h"
  10 #include "socket-netlink.h"
  11 #include "socket-util.h"
  12 #include "string-table.h"
  13
  14 /* The MTU of the loopback device is 64K on Linux, advertise that as maximum datagram size, but subtract the Ethernet,
  15  * IP and UDP header sizes */
  16 #define ADVERTISE_DATAGRAM_SIZE_MAX (65536U-14U-20U-8U)
  17
  18 static int manager_dns_stub_fd_extra(Manager *m, DnsStubListenerExtra *l, int type);
  19
  20 static void dns_stub_listener_extra_hash_func(const DnsStubListenerExtra *a, struct siphash *state) {
  21         assert(a);
  22
  23         siphash24_compress(&a->mode, sizeof(a->mode), state);
  24         siphash24_compress(&a->family, sizeof(a->family), state);
  25         siphash24_compress(&a->address, FAMILY_ADDRESS_SIZE(a->family), state);
  26         siphash24_compress(&a->port, sizeof(a->port), state);
  27 }
  28
  29 static int dns_stub_listener_extra_compare_func(const DnsStubListenerExtra *a, const DnsStubListenerExtra *b) {
  30         int r;
  31
  32         assert(a);
  33         assert(b);
  34
  35         r = CMP(a->mode, b->mode);
  36         if (r != 0)
  37                 return r;
  38
  39         r = CMP(a->family, b->family);
  40         if (r != 0)
  41                 return r;
  42
  43         r = memcmp(&a->address, &b->address, FAMILY_ADDRESS_SIZE(a->family));
  44         if (r != 0)
  45                 return r;
  46
  47         return CMP(a->port, b->port);
  48 }
  49
  50 DEFINE_HASH_OPS_WITH_KEY_DESTRUCTOR(
  51                 dns_stub_listener_extra_hash_ops,
  52                 DnsStubListenerExtra,
  53                 dns_stub_listener_extra_hash_func,
  54                 dns_stub_listener_extra_compare_func,
  55                 dns_stub_listener_extra_free);
  56
  57 int dns_stub_listener_extra_new(
  58                 Manager *m,
  59                 DnsStubListenerExtra **ret) {
  60
  61         DnsStubListenerExtra *l;
  62
  63         l = new(DnsStubListenerExtra, 1);
  64         if (!l)
  65                 return -ENOMEM;
  66
  67         *l = (DnsStubListenerExtra) {
  68                 .manager = m,
  69         };
  70
  71         *ret = TAKE_PTR(l);
  72         return 0;
  73 }
  74
  75 DnsStubListenerExtra *dns_stub_listener_extra_free(DnsStubListenerExtra *p) {
  76         if (!p)
  77                 return NULL;
  78
  79         p->udp_event_source = sd_event_source_unref(p->udp_event_source);
  80         p->tcp_event_source = sd_event_source_unref(p->tcp_event_source);
  81
  82         return mfree(p);
  83 }
  84
  85 static int dns_stub_make_reply_packet(
  86                 DnsPacket **p,
  87                 size_t max_size,
  88                 DnsQuestion *q,
  89                 DnsAnswer *answer,
  90                 bool *ret_truncated) {
  91
  92         bool truncated = false;
  93         DnsResourceRecord *rr;
  94         unsigned c = 0;
  95         int r;
  96
  97         assert(p);
  98
  99         /* Note that we don't bother with any additional RRs, as this is stub is for local lookups only, and hence
 100          * roundtrips aren't expensive. */
 101
 102         if (!*p) {
 103                 r = dns_packet_new(p, DNS_PROTOCOL_DNS, 0, max_size);
 104                 if (r < 0)
 105                         return r;
 106
 107                 r = dns_packet_append_question(*p, q);
 108                 if (r < 0)
 109                         return r;
 110
 111                 DNS_PACKET_HEADER(*p)->qdcount = htobe16(dns_question_size(q));
 112         }
 113
 114         DNS_ANSWER_FOREACH(rr, answer) {
 115
 116                 r = dns_question_matches_rr(q, rr, NULL);
 117                 if (r < 0)
 118                         return r;
 119                 if (r > 0)
 120                         goto add;
 121
 122                 r = dns_question_matches_cname_or_dname(q, rr, NULL);
 123                 if (r < 0)
 124                         return r;
 125                 if (r > 0)
 126                         goto add;
 127
 128                 continue;
 129         add:
 130                 r = dns_packet_append_rr(*p, rr, 0, NULL, NULL);
 131                 if (r == -EMSGSIZE) {
 132                         truncated = true;
 133                         break;
 134                 }
 135                 if (r < 0)
 136                         return r;
 137
 138                 c++;
 139         }
 140
 141         if (ret_truncated)
 142                 *ret_truncated = truncated;
 143         else if (truncated)
 144                 return -EMSGSIZE;
 145
 146         DNS_PACKET_HEADER(*p)->ancount = htobe16(be16toh(DNS_PACKET_HEADER(*p)->ancount) + c);
 147
 148         return 0;
 149 }
 150
 151 static int dns_stub_finish_reply_packet(
 152                 DnsPacket *p,
 153                 uint16_t id,
 154                 int rcode,
 155                 bool tc,        /* set the Truncated bit? */
 156                 bool add_opt,   /* add an OPT RR to this packet? */
 157                 bool edns0_do,  /* set the EDNS0 DNSSEC OK bit? */
 158                 bool ad) {      /* set the DNSSEC authenticated data bit? */
 159
 160         int r;
 161
 162         assert(p);
 163
 164         if (add_opt) {
 165                 r = dns_packet_append_opt(p, ADVERTISE_DATAGRAM_SIZE_MAX, edns0_do, /* include_rfc6975 = */ false, rcode, NULL);
 166                 if (r == -EMSGSIZE) /* Hit the size limit? then indicate truncation */
 167                         tc = true;
 168                 else if (r < 0)
 169                         return r;
 170
 171         } else {
 172                 /* If the client can't to EDNS0, don't do DO either */
 173                 edns0_do = false;
 174
 175                 /* If the client didn't do EDNS, clamp the rcode to 4 bit */
 176                 if (rcode > 0xF)
 177                         rcode = DNS_RCODE_SERVFAIL;
 178         }
 179
 180         /* Don't set the AD bit unless DO is on, too */
 181         if (!edns0_do)
 182                 ad = false;
 183
 184         DNS_PACKET_HEADER(p)->id = id;
 185
 186         DNS_PACKET_HEADER(p)->flags = htobe16(DNS_PACKET_MAKE_FLAGS(
 187                                                               1  /* qr */,
 188                                                               0  /* opcode */,
 189                                                               0  /* aa */,
 190                                                               tc /* tc */,
 191                                                               1  /* rd */,
 192                                                               1  /* ra */,
 193                                                               ad /* ad */,
 194                                                               0  /* cd */,
 195                                                               rcode));
 196
 197         return 0;
 198 }
 199
 200 static int dns_stub_send(
 201                 Manager *m,
 202                 DnsStubListenerExtra *l,
 203                 DnsStream *s,
 204                 DnsPacket *p,
 205                 DnsPacket *reply) {
 206
 207         int r;
 208
 209         assert(m);
 210         assert(p);
 211         assert(reply);
 212
 213         if (s)
 214                 r = dns_stream_write_packet(s, reply);
 215         else
 216                 /* Note that it is essential here that we explicitly choose the source IP address for this packet. This
 217                  * is because otherwise the kernel will choose it automatically based on the routing table and will
 218                  * thus pick 127.0.0.1 rather than 127.0.0.53. */
 219                 r = manager_send(m,
 220                                  manager_dns_stub_fd_extra(m, l, SOCK_DGRAM),
 221                                  l ? p->ifindex : LOOPBACK_IFINDEX, /* force loopback iface if this is the main listener stub */
 222                                  p->family, &p->sender, p->sender_port, &p->destination,
 223                                  reply);
 224         if (r < 0)
 225                 return log_debug_errno(r, "Failed to send reply packet: %m");
 226
 227         return 0;
 228 }
 229
 230 static int dns_stub_send_failure(
 231                 Manager *m,
 232                 DnsStubListenerExtra *l,
 233                 DnsStream *s,
 234                 DnsPacket *p,
 235                 int rcode,
 236                 bool authenticated) {
 237
 238         _cleanup_(dns_packet_unrefp) DnsPacket *reply = NULL;
 239         int r;
 240
 241         assert(m);
 242         assert(p);
 243
 244         r = dns_stub_make_reply_packet(&reply, DNS_PACKET_PAYLOAD_SIZE_MAX(p), p->question, NULL, NULL);
 245         if (r < 0)
 246                 return log_debug_errno(r, "Failed to make failure packet: %m");
 247
 248         r = dns_stub_finish_reply_packet(reply, DNS_PACKET_ID(p), rcode, false, !!p->opt, DNS_PACKET_DO(p), authenticated);
 249         if (r < 0)
 250                 return log_debug_errno(r, "Failed to build failure packet: %m");
 251
 252         return dns_stub_send(m, l, s, p, reply);
 253 }
 254
 255 static void dns_stub_query_complete(DnsQuery *q) {
 256         int r;
 257
 258         assert(q);
 259         assert(q->request_dns_packet);
 260
 261         switch (q->state) {
 262
 263         case DNS_TRANSACTION_SUCCESS: {
 264                 bool truncated;
 265
 266                 r = dns_stub_make_reply_packet(&q->reply_dns_packet, DNS_PACKET_PAYLOAD_SIZE_MAX(q->request_dns_packet), q->question_idna, q->answer, &truncated);
 267                 if (r < 0) {
 268                         log_debug_errno(r, "Failed to build reply packet: %m");
 269                         break;
 270                 }
 271
 272                 if (!truncated) {
 273                         r = dns_query_process_cname(q);
 274                         if (r == -ELOOP) {
 275                                 (void) dns_stub_send_failure(q->manager, q->stub_listener_extra, q->request_dns_stream, q->request_dns_packet, DNS_RCODE_SERVFAIL, false);
 276                                 break;
 277                         }
 278                         if (r < 0) {
 279                                 log_debug_errno(r, "Failed to process CNAME: %m");
 280                                 break;
 281                         }
 282                         if (r == DNS_QUERY_RESTARTED)
 283                                 return;
 284                 }
 285
 286                 r = dns_stub_finish_reply_packet(
 287                                 q->reply_dns_packet,
 288                                 DNS_PACKET_ID(q->request_dns_packet),
 289                                 q->answer_rcode,
 290                                 truncated,
 291                                 !!q->request_dns_packet->opt,
 292                                 DNS_PACKET_DO(q->request_dns_packet),
 293                                 dns_query_fully_authenticated(q));
 294                 if (r < 0) {
 295                         log_debug_errno(r, "Failed to finish reply packet: %m");
 296                         break;
 297                 }
 298
 299                 (void) dns_stub_send(q->manager, q->stub_listener_extra, q->request_dns_stream, q->request_dns_packet, q->reply_dns_packet);
 300                 break;
 301         }
 302
 303         case DNS_TRANSACTION_RCODE_FAILURE:
 304                 (void) dns_stub_send_failure(q->manager, q->stub_listener_extra, q->request_dns_stream, q->request_dns_packet, q->answer_rcode, dns_query_fully_authenticated(q));
 305                 break;
 306
 307         case DNS_TRANSACTION_NOT_FOUND:
 308                 (void) dns_stub_send_failure(q->manager, q->stub_listener_extra, q->request_dns_stream, q->request_dns_packet, DNS_RCODE_NXDOMAIN, dns_query_fully_authenticated(q));
 309                 break;
 310
 311         case DNS_TRANSACTION_TIMEOUT:
 312         case DNS_TRANSACTION_ATTEMPTS_MAX_REACHED:
 313                 /* Propagate a timeout as a no packet, i.e. that the client also gets a timeout */
 314                 break;
 315
 316         case DNS_TRANSACTION_NO_SERVERS:
 317         case DNS_TRANSACTION_INVALID_REPLY:
 318         case DNS_TRANSACTION_ERRNO:
 319         case DNS_TRANSACTION_ABORTED:
 320         case DNS_TRANSACTION_DNSSEC_FAILED:
 321         case DNS_TRANSACTION_NO_TRUST_ANCHOR:
 322         case DNS_TRANSACTION_RR_TYPE_UNSUPPORTED:
 323         case DNS_TRANSACTION_NETWORK_DOWN:
 324                 (void) dns_stub_send_failure(q->manager, q->stub_listener_extra, q->request_dns_stream, q->request_dns_packet, DNS_RCODE_SERVFAIL, false);
 325                 break;
 326
 327         case DNS_TRANSACTION_NULL:
 328         case DNS_TRANSACTION_PENDING:
 329         case DNS_TRANSACTION_VALIDATING:
 330         default:
 331                 assert_not_reached("Impossible state");
 332         }
 333
 334         dns_query_free(q);
 335 }
 336
 337 static int dns_stub_stream_complete(DnsStream *s, int error) {
 338         assert(s);
 339
 340         log_debug_errno(error, "DNS TCP connection terminated, destroying queries: %m");
 341
 342         for (;;) {
 343                 DnsQuery *q;
 344
 345                 q = set_first(s->queries);
 346                 if (!q)
 347                         break;
 348
 349                 dns_query_free(q);
 350         }
 351
 352         /* This drops the implicit ref we keep around since it was allocated, as incoming stub connections
 353          * should be kept as long as the client wants to. */
 354         dns_stream_unref(s);
 355         return 0;
 356 }
 357
 358 static void dns_stub_process_query(Manager *m, DnsStubListenerExtra *l, DnsStream *s, DnsPacket *p) {
 359         _cleanup_(dns_query_freep) DnsQuery *q = NULL;
 360         int r;
 361
 362         assert(m);
 363         assert(p);
 364         assert(p->protocol == DNS_PROTOCOL_DNS);
 365
 366         if (!l && /* l == NULL if this is the main stub */
 367             (in_addr_is_localhost(p->family, &p->sender) <= 0 ||
 368              in_addr_is_localhost(p->family, &p->destination) <= 0)) {
 369                 log_error("Got packet on unexpected IP range, refusing.");
 370                 dns_stub_send_failure(m, l, s, p, DNS_RCODE_SERVFAIL, false);
 371                 return;
 372         }
 373
 374         r = dns_packet_extract(p);
 375         if (r < 0) {
 376                 log_debug_errno(r, "Failed to extract resources from incoming packet, ignoring packet: %m");
 377                 dns_stub_send_failure(m, l, s, p, DNS_RCODE_FORMERR, false);
 378                 return;
 379         }
 380
 381         if (!DNS_PACKET_VERSION_SUPPORTED(p)) {
 382                 log_debug("Got EDNS OPT field with unsupported version number.");
 383                 dns_stub_send_failure(m, l, s, p, DNS_RCODE_BADVERS, false);
 384                 return;
 385         }
 386
 387         if (dns_type_is_obsolete(p->question->keys[0]->type)) {
 388                 log_debug("Got message with obsolete key type, refusing.");
 389                 dns_stub_send_failure(m, l, s, p, DNS_RCODE_NOTIMP, false);
 390                 return;
 391         }
 392
 393         if (dns_type_is_zone_transer(p->question->keys[0]->type)) {
 394                 log_debug("Got request for zone transfer, refusing.");
 395                 dns_stub_send_failure(m, l, s, p, DNS_RCODE_NOTIMP, false);
 396                 return;
 397         }
 398
 399         if (!DNS_PACKET_RD(p))  {
 400                 /* If the "rd" bit is off (i.e. recursion was not requested), then refuse operation */
 401                 log_debug("Got request with recursion disabled, refusing.");
 402                 dns_stub_send_failure(m, l, s, p, DNS_RCODE_REFUSED, false);
 403                 return;
 404         }
 405
 406         if (DNS_PACKET_DO(p) && DNS_PACKET_CD(p)) {
 407                 log_debug("Got request with DNSSEC CD bit set, refusing.");
 408                 dns_stub_send_failure(m, l, s, p, DNS_RCODE_NOTIMP, false);
 409                 return;
 410         }
 411
 412         r = dns_query_new(m, &q, p->question, p->question, 0, SD_RESOLVED_PROTOCOLS_ALL|SD_RESOLVED_NO_SEARCH);
 413         if (r < 0) {
 414                 log_error_errno(r, "Failed to generate query object: %m");
 415                 dns_stub_send_failure(m, l, s, p, DNS_RCODE_SERVFAIL, false);
 416                 return;
 417         }
 418
 419         /* Request that the TTL is corrected by the cached time for this lookup, so that we return vaguely useful TTLs */
 420         q->clamp_ttl = true;
 421
 422         q->request_dns_packet = dns_packet_ref(p);
 423         q->request_dns_stream = dns_stream_ref(s); /* make sure the stream stays around until we can send a reply through it */
 424         q->stub_listener_extra = l;
 425         q->complete = dns_stub_query_complete;
 426
 427         if (s) {
 428                 /* Remember which queries belong to this stream, so that we can cancel them when the stream
 429                  * is disconnected early */
 430
 431                 r = set_ensure_put(&s->queries, NULL, q);
 432                 if (r < 0) {
 433                         log_oom();
 434                         return;
 435                 }
 436                 assert(r > 0);
 437         }
 438
 439         r = dns_query_go(q);
 440         if (r < 0) {
 441                 log_error_errno(r, "Failed to start query: %m");
 442                 dns_stub_send_failure(m, l, s, p, DNS_RCODE_SERVFAIL, false);
 443                 return;
 444         }
 445
 446         log_debug("Processing query...");
 447         TAKE_PTR(q);
 448 }
 449
 450 static int on_dns_stub_packet_internal(sd_event_source *s, int fd, uint32_t revents, Manager *m, DnsStubListenerExtra *l) {
 451         _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
 452         int r;
 453
 454         r = manager_recv(m, fd, DNS_PROTOCOL_DNS, &p);
 455         if (r <= 0)
 456                 return r;
 457
 458         if (dns_packet_validate_query(p) > 0) {
 459                 log_debug("Got DNS stub UDP query packet for id %u", DNS_PACKET_ID(p));
 460
 461                 dns_stub_process_query(m, l, NULL, p);
 462         } else
 463                 log_debug("Invalid DNS stub UDP packet, ignoring.");
 464
 465         return 0;
 466 }
 467
 468 static int on_dns_stub_packet(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
 469         return on_dns_stub_packet_internal(s, fd, revents, userdata, NULL);
 470 }
 471
 472 static int on_dns_stub_packet_extra(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
 473         DnsStubListenerExtra *l = userdata;
 474
 475         assert(l);
 476
 477         return on_dns_stub_packet_internal(s, fd, revents, l->manager, l);
 478 }
 479
 480 static int on_dns_stub_stream_packet(DnsStream *s) {
 481         _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
 482
 483         assert(s);
 484
 485         p = dns_stream_take_read_packet(s);
 486         assert(p);
 487
 488         if (dns_packet_validate_query(p) > 0) {
 489                 log_debug("Got DNS stub TCP query packet for id %u", DNS_PACKET_ID(p));
 490
 491                 dns_stub_process_query(s->manager, s->stub_listener_extra, s, p);
 492         } else
 493                 log_debug("Invalid DNS stub TCP packet, ignoring.");
 494
 495         return 0;
 496 }
 497
 498 static int on_dns_stub_stream_internal(sd_event_source *s, int fd, uint32_t revents, Manager *m, DnsStubListenerExtra *l) {
 499         DnsStream *stream;
 500         int cfd, r;
 501
 502         cfd = accept4(fd, NULL, NULL, SOCK_NONBLOCK|SOCK_CLOEXEC);
 503         if (cfd < 0) {
 504                 if (ERRNO_IS_ACCEPT_AGAIN(errno))
 505                         return 0;
 506
 507                 return -errno;
 508         }
 509
 510         r = dns_stream_new(m, &stream, DNS_STREAM_STUB, DNS_PROTOCOL_DNS, cfd, NULL);
 511         if (r < 0) {
 512                 safe_close(cfd);
 513                 return r;
 514         }
 515
 516         stream->stub_listener_extra = l;
 517         stream->on_packet = on_dns_stub_stream_packet;
 518         stream->complete = dns_stub_stream_complete;
 519
 520         /* We let the reference to the stream dangle here, it will be dropped later by the complete callback. */
 521
 522         return 0;
 523 }
 524
 525 static int on_dns_stub_stream(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
 526         return on_dns_stub_stream_internal(s, fd, revents, userdata, NULL);
 527 }
 528
 529 static int on_dns_stub_stream_extra(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
 530         DnsStubListenerExtra *l = userdata;
 531
 532         assert(l);
 533         return on_dns_stub_stream_internal(s, fd, revents, l->manager, l);
 534 }
 535
 536 static int set_dns_stub_common_socket_options(int fd, int family) {
 537         int r;
 538
 539         assert(fd >= 0);
 540         assert(IN_SET(family, AF_INET, AF_INET6));
 541
 542         r = setsockopt_int(fd, SOL_SOCKET, SO_REUSEADDR, true);
 543         if (r < 0)
 544                 return r;
 545
 546         r = socket_set_recvpktinfo(fd, family, true);
 547         if (r < 0)
 548                 return r;
 549
 550         r = socket_set_recvttl(fd, family, true);
 551         if (r < 0)
 552                 return r;
 553
 554         return 0;
 555 }
 556
 557 static int manager_dns_stub_fd(Manager *m, int type) {
 558         union sockaddr_union sa = {
 559                 .in.sin_family = AF_INET,
 560                 .in.sin_addr.s_addr = htobe32(INADDR_DNS_STUB),
 561                 .in.sin_port = htobe16(53),
 562         };
 563         _cleanup_close_ int fd = -1;
 564         int r;
 565
 566         assert(IN_SET(type, SOCK_DGRAM, SOCK_STREAM));
 567
 568         sd_event_source **event_source = type == SOCK_DGRAM ? &m->dns_stub_udp_event_source : &m->dns_stub_tcp_event_source;
 569         if (*event_source)
 570                 return sd_event_source_get_io_fd(*event_source);
 571
 572         fd = socket(AF_INET, type | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
 573         if (fd < 0)
 574                 return -errno;
 575
 576         r = set_dns_stub_common_socket_options(fd, AF_INET);
 577         if (r < 0)
 578                 return r;
 579
 580         /* Make sure no traffic from outside the local host can leak to onto this socket */
 581         r = socket_bind_to_ifindex(fd, LOOPBACK_IFINDEX);
 582         if (r < 0)
 583                 return r;
 584
 585         r = setsockopt_int(fd, IPPROTO_IP, IP_TTL, 1);
 586         if (r < 0)
 587                 return r;
 588
 589         if (bind(fd, &sa.sa, sizeof(sa.in)) < 0)
 590                 return -errno;
 591
 592         if (type == SOCK_STREAM &&
 593             listen(fd, SOMAXCONN) < 0)
 594                 return -errno;
 595
 596         r = sd_event_add_io(m->event, event_source, fd, EPOLLIN,
 597                             type == SOCK_DGRAM ? on_dns_stub_packet : on_dns_stub_stream,
 598                             m);
 599         if (r < 0)
 600                 return r;
 601
 602         r = sd_event_source_set_io_fd_own(*event_source, true);
 603         if (r < 0)
 604                 return r;
 605
 606         (void) sd_event_source_set_description(*event_source,
 607                                                type == SOCK_DGRAM ? "dns-stub-udp" : "dns-stub-tcp");
 608
 609         return TAKE_FD(fd);
 610 }
 611
 612 static int manager_dns_stub_fd_extra(Manager *m, DnsStubListenerExtra *l, int type) {
 613         _cleanup_free_ char *pretty = NULL;
 614         _cleanup_close_ int fd = -1;
 615         union sockaddr_union sa;
 616         int r;
 617
 618         assert(m);
 619         assert(IN_SET(type, SOCK_DGRAM, SOCK_STREAM));
 620
 621         if (!l)
 622                 return manager_dns_stub_fd(m, type);
 623
 624         sd_event_source **event_source = type == SOCK_DGRAM ? &l->udp_event_source : &l->tcp_event_source;
 625         if (*event_source)
 626                 return sd_event_source_get_io_fd(*event_source);
 627
 628         if (l->family == AF_INET)
 629                 sa = (union sockaddr_union) {
 630                         .in.sin_family = l->family,
 631                         .in.sin_port = htobe16(l->port != 0 ? l->port : 53U),
 632                         .in.sin_addr = l->address.in,
 633                 };
 634         else
 635                 sa = (union sockaddr_union) {
 636                         .in6.sin6_family = l->family,
 637                         .in6.sin6_port = htobe16(l->port != 0 ? l->port : 53U),
 638                         .in6.sin6_addr = l->address.in6,
 639                 };
 640
 641         fd = socket(l->family, type | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
 642         if (fd < 0) {
 643                 r = -errno;
 644                 goto fail;
 645         }
 646
 647         r = set_dns_stub_common_socket_options(fd, l->family);
 648         if (r < 0)
 649                 goto fail;
 650
 651         /* Do not set IP_TTL for extra DNS stub listeners, as the address may not be local and in that case
 652          * people may want ttl > 1. */
 653
 654         r = socket_set_freebind(fd, l->family, true);
 655         if (r < 0)
 656                 goto fail;
 657
 658         if (bind(fd, &sa.sa, SOCKADDR_LEN(sa)) < 0) {
 659                 r = -errno;
 660                 goto fail;
 661         }
 662
 663         if (type == SOCK_STREAM &&
 664             listen(fd, SOMAXCONN) < 0) {
 665                 r = -errno;
 666                 goto fail;
 667         }
 668
 669         r = sd_event_add_io(m->event, event_source, fd, EPOLLIN,
 670                             type == SOCK_DGRAM ? on_dns_stub_packet_extra : on_dns_stub_stream_extra,
 671                             l);
 672         if (r < 0)
 673                 goto fail;
 674
 675         r = sd_event_source_set_io_fd_own(*event_source, true);
 676         if (r < 0)
 677                 goto fail;
 678
 679         (void) sd_event_source_set_description(*event_source,
 680                                                type == SOCK_DGRAM ? "dns-stub-udp-extra" : "dns-stub-tcp-extra");
 681
 682         if (DEBUG_LOGGING) {
 683                 (void) in_addr_port_to_string(l->family, &l->address, l->port, &pretty);
 684                 log_debug("Listening on %s socket %s.",
 685                           type == SOCK_DGRAM ? "UDP" : "TCP",
 686                           strnull(pretty));
 687         }
 688
 689         return TAKE_FD(fd);
 690
 691 fail:
 692         assert(r < 0);
 693         (void) in_addr_port_to_string(l->family, &l->address, l->port, &pretty);
 694         return log_warning_errno(r,
 695                                  r == -EADDRINUSE ? "Another process is already listening on %s socket %s: %m" :
 696                                                     "Failed to listen on %s socket %s: %m",
 697                                  type == SOCK_DGRAM ? "UDP" : "TCP",
 698                                  strnull(pretty));
 699 }
 700
 701 int manager_dns_stub_start(Manager *m) {
 702         const char *t = "UDP";
 703         int r = 0;
 704
 705         assert(m);
 706
 707         if (m->dns_stub_listener_mode == DNS_STUB_LISTENER_NO)
 708                 log_debug("Not creating stub listener.");
 709         else
 710                 log_debug("Creating stub listener using %s.",
 711                           m->dns_stub_listener_mode == DNS_STUB_LISTENER_UDP ? "UDP" :
 712                           m->dns_stub_listener_mode == DNS_STUB_LISTENER_TCP ? "TCP" :
 713                           "UDP/TCP");
 714
 715         if (FLAGS_SET(m->dns_stub_listener_mode, DNS_STUB_LISTENER_UDP))
 716                 r = manager_dns_stub_fd(m, SOCK_DGRAM);
 717
 718         if (r >= 0 &&
 719             FLAGS_SET(m->dns_stub_listener_mode, DNS_STUB_LISTENER_TCP)) {
 720                 t = "TCP";
 721                 r = manager_dns_stub_fd(m, SOCK_STREAM);
 722         }
 723
 724         if (IN_SET(r, -EADDRINUSE, -EPERM)) {
 725                 log_warning_errno(r,
 726                                   r == -EADDRINUSE ? "Another process is already listening on %s socket 127.0.0.53:53.\n"
 727                                                      "Turning off local DNS stub support." :
 728                                                      "Failed to listen on %s socket 127.0.0.53:53: %m.\n"
 729                                                      "Turning off local DNS stub support.",
 730                                   t);
 731                 manager_dns_stub_stop(m);
 732         } else if (r < 0)
 733                 return log_error_errno(r, "Failed to listen on %s socket 127.0.0.53:53: %m", t);
 734
 735         if (!ordered_set_isempty(m->dns_extra_stub_listeners)) {
 736                 DnsStubListenerExtra *l;
 737
 738                 log_debug("Creating extra stub listeners.");
 739
 740                 ORDERED_SET_FOREACH(l, m->dns_extra_stub_listeners) {
 741                         if (FLAGS_SET(l->mode, DNS_STUB_LISTENER_UDP))
 742                                 (void) manager_dns_stub_fd_extra(m, l, SOCK_DGRAM);
 743                         if (FLAGS_SET(l->mode, DNS_STUB_LISTENER_TCP))
 744                                 (void) manager_dns_stub_fd_extra(m, l, SOCK_STREAM);
 745                 }
 746         }
 747
 748         return 0;
 749 }
 750
 751 void manager_dns_stub_stop(Manager *m) {
 752         assert(m);
 753
 754         m->dns_stub_udp_event_source = sd_event_source_unref(m->dns_stub_udp_event_source);
 755         m->dns_stub_tcp_event_source = sd_event_source_unref(m->dns_stub_tcp_event_source);
 756 }
 757
 758 static const char* const dns_stub_listener_mode_table[_DNS_STUB_LISTENER_MODE_MAX] = {
 759         [DNS_STUB_LISTENER_NO] = "no",
 760         [DNS_STUB_LISTENER_UDP] = "udp",
 761         [DNS_STUB_LISTENER_TCP] = "tcp",
 762         [DNS_STUB_LISTENER_YES] = "yes",
 763 };
 764 DEFINE_STRING_TABLE_LOOKUP_WITH_BOOLEAN(dns_stub_listener_mode, DnsStubListenerMode, DNS_STUB_LISTENER_YES);