src/resolve/resolved-llmnr.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <netinet/in.h>
   4 #include <resolv.h>
   5
   6 #include "fd-util.h"
   7 #include "resolved-llmnr.h"
   8 #include "resolved-manager.h"
   9
  10 void manager_llmnr_stop(Manager *m) {
  11         assert(m);
  12
  13         m->llmnr_ipv4_udp_event_source = sd_event_source_unref(m->llmnr_ipv4_udp_event_source);
  14         m->llmnr_ipv4_udp_fd = safe_close(m->llmnr_ipv4_udp_fd);
  15
  16         m->llmnr_ipv6_udp_event_source = sd_event_source_unref(m->llmnr_ipv6_udp_event_source);
  17         m->llmnr_ipv6_udp_fd = safe_close(m->llmnr_ipv6_udp_fd);
  18
  19         m->llmnr_ipv4_tcp_event_source = sd_event_source_unref(m->llmnr_ipv4_tcp_event_source);
  20         m->llmnr_ipv4_tcp_fd = safe_close(m->llmnr_ipv4_tcp_fd);
  21
  22         m->llmnr_ipv6_tcp_event_source = sd_event_source_unref(m->llmnr_ipv6_tcp_event_source);
  23         m->llmnr_ipv6_tcp_fd = safe_close(m->llmnr_ipv6_tcp_fd);
  24 }
  25
  26 int manager_llmnr_start(Manager *m) {
  27         int r;
  28
  29         assert(m);
  30
  31         if (m->llmnr_support == RESOLVE_SUPPORT_NO)
  32                 return 0;
  33
  34         r = manager_llmnr_ipv4_udp_fd(m);
  35         if (r == -EADDRINUSE)
  36                 goto eaddrinuse;
  37         if (r < 0)
  38                 return r;
  39
  40         r = manager_llmnr_ipv4_tcp_fd(m);
  41         if (r == -EADDRINUSE)
  42                 goto eaddrinuse;
  43         if (r < 0)
  44                 return r;
  45
  46         if (socket_ipv6_is_supported()) {
  47                 r = manager_llmnr_ipv6_udp_fd(m);
  48                 if (r == -EADDRINUSE)
  49                         goto eaddrinuse;
  50                 if (r < 0)
  51                         return r;
  52
  53                 r = manager_llmnr_ipv6_tcp_fd(m);
  54                 if (r == -EADDRINUSE)
  55                         goto eaddrinuse;
  56                 if (r < 0)
  57                         return r;
  58         }
  59
  60         return 0;
  61
  62 eaddrinuse:
  63         log_warning("Another LLMNR responder prohibits binding the socket to the same port. Turning off LLMNR support.");
  64         m->llmnr_support = RESOLVE_SUPPORT_NO;
  65         manager_llmnr_stop(m);
  66
  67         return 0;
  68 }
  69
  70 static int on_llmnr_packet(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
  71         _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
  72         DnsTransaction *t = NULL;
  73         Manager *m = userdata;
  74         DnsScope *scope;
  75         int r;
  76
  77         assert(s);
  78         assert(fd >= 0);
  79         assert(m);
  80
  81         r = manager_recv(m, fd, DNS_PROTOCOL_LLMNR, &p);
  82         if (r <= 0)
  83                 return r;
  84
  85         if (manager_our_packet(m, p))
  86                 return 0;
  87
  88         scope = manager_find_scope(m, p);
  89         if (!scope) {
  90                 log_debug("Got LLMNR UDP packet on unknown scope. Ignoring.");
  91                 return 0;
  92         }
  93
  94         if (dns_packet_validate_reply(p) > 0) {
  95                 log_debug("Got LLMNR UDP reply packet for id %u", DNS_PACKET_ID(p));
  96
  97                 dns_scope_check_conflicts(scope, p);
  98
  99                 t = hashmap_get(m->dns_transactions, UINT_TO_PTR(DNS_PACKET_ID(p)));
 100                 if (t)
 101                         dns_transaction_process_reply(t, p);
 102
 103         } else if (dns_packet_validate_query(p) > 0)  {
 104                 log_debug("Got LLMNR UDP query packet for id %u", DNS_PACKET_ID(p));
 105
 106                 dns_scope_process_query(scope, NULL, p);
 107         } else
 108                 log_debug("Invalid LLMNR UDP packet, ignoring.");
 109
 110         return 0;
 111 }
 112
 113 int manager_llmnr_ipv4_udp_fd(Manager *m) {
 114         union sockaddr_union sa = {
 115                 .in.sin_family = AF_INET,
 116                 .in.sin_port = htobe16(LLMNR_PORT),
 117         };
 118         _cleanup_close_ int s = -1;
 119         int r;
 120
 121         assert(m);
 122
 123         if (m->llmnr_ipv4_udp_fd >= 0)
 124                 return m->llmnr_ipv4_udp_fd;
 125
 126         s = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
 127         if (s < 0)
 128                 return log_error_errno(errno, "LLMNR-IPv4(UDP): Failed to create socket: %m");
 129
 130         /* RFC 4795, section 2.5 recommends setting the TTL of UDP packets to 255. */
 131         r = setsockopt_int(s, IPPROTO_IP, IP_TTL, 255);
 132         if (r < 0)
 133                 return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set IP_TTL: %m");
 134
 135         r = setsockopt_int(s, IPPROTO_IP, IP_MULTICAST_TTL, 255);
 136         if (r < 0)
 137                 return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set IP_MULTICAST_TTL: %m");
 138
 139         r = setsockopt_int(s, IPPROTO_IP, IP_MULTICAST_LOOP, true);
 140         if (r < 0)
 141                 return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set IP_MULTICAST_LOOP: %m");
 142
 143         r = setsockopt_int(s, IPPROTO_IP, IP_PKTINFO, true);
 144         if (r < 0)
 145                 return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set IP_PKTINFO: %m");
 146
 147         r = setsockopt_int(s, IPPROTO_IP, IP_RECVTTL, true);
 148         if (r < 0)
 149                 return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set IP_RECVTTL: %m");
 150
 151         /* Disable Don't-Fragment bit in the IP header */
 152         r = setsockopt_int(s, IPPROTO_IP, IP_MTU_DISCOVER, IP_PMTUDISC_DONT);
 153         if (r < 0)
 154                 return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set IP_MTU_DISCOVER: %m");
 155
 156         /* first try to bind without SO_REUSEADDR to detect another LLMNR responder */
 157         r = bind(s, &sa.sa, sizeof(sa.in));
 158         if (r < 0) {
 159                 if (errno != EADDRINUSE)
 160                         return log_error_errno(errno, "LLMNR-IPv4(UDP): Failed to bind socket: %m");
 161
 162                 log_warning("LLMNR-IPv4(UDP): There appears to be another LLMNR responder running, or previously systemd-resolved crashed with some outstanding transfers.");
 163
 164                 /* try again with SO_REUSEADDR */
 165                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 166                 if (r < 0)
 167                         return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set SO_REUSEADDR: %m");
 168
 169                 r = bind(s, &sa.sa, sizeof(sa.in));
 170                 if (r < 0)
 171                         return log_error_errno(errno, "LLMNR-IPv4(UDP): Failed to bind socket: %m");
 172         } else {
 173                 /* enable SO_REUSEADDR for the case that the user really wants multiple LLMNR responders */
 174                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 175                 if (r < 0)
 176                         return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set SO_REUSEADDR: %m");
 177         }
 178
 179         r = sd_event_add_io(m->event, &m->llmnr_ipv4_udp_event_source, s, EPOLLIN, on_llmnr_packet, m);
 180         if (r < 0)
 181                 return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to create event source: %m");
 182
 183         (void) sd_event_source_set_description(m->llmnr_ipv4_udp_event_source, "llmnr-ipv4-udp");
 184
 185         return m->llmnr_ipv4_udp_fd = TAKE_FD(s);
 186 }
 187
 188 int manager_llmnr_ipv6_udp_fd(Manager *m) {
 189         union sockaddr_union sa = {
 190                 .in6.sin6_family = AF_INET6,
 191                 .in6.sin6_port = htobe16(LLMNR_PORT),
 192         };
 193         _cleanup_close_ int s = -1;
 194         int r;
 195
 196         assert(m);
 197
 198         if (m->llmnr_ipv6_udp_fd >= 0)
 199                 return m->llmnr_ipv6_udp_fd;
 200
 201         s = socket(AF_INET6, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
 202         if (s < 0)
 203                 return log_error_errno(errno, "LLMNR-IPv6(UDP): Failed to create socket: %m");
 204
 205         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_UNICAST_HOPS, 255);
 206         if (r < 0)
 207                 return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set IPV6_UNICAST_HOPS: %m");
 208
 209         /* RFC 4795, section 2.5 recommends setting the TTL of UDP packets to 255. */
 210         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, 255);
 211         if (r < 0)
 212                 return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set IPV6_MULTICAST_HOPS: %m");
 213
 214         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, true);
 215         if (r < 0)
 216                 return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set IPV6_MULTICAST_LOOP: %m");
 217
 218         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_V6ONLY, true);
 219         if (r < 0)
 220                 return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set IPV6_V6ONLY: %m");
 221
 222         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_RECVPKTINFO, true);
 223         if (r < 0)
 224                 return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set IPV6_RECVPKTINFO: %m");
 225
 226         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, true);
 227         if (r < 0)
 228                 return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set IPV6_RECVHOPLIMIT: %m");
 229
 230         /* first try to bind without SO_REUSEADDR to detect another LLMNR responder */
 231         r = bind(s, &sa.sa, sizeof(sa.in6));
 232         if (r < 0) {
 233                 if (errno != EADDRINUSE)
 234                         return log_error_errno(errno, "LLMNR-IPv6(UDP): Failed to bind socket: %m");
 235
 236                 log_warning("LLMNR-IPv6(UDP): There appears to be another LLMNR responder running, or previously systemd-resolved crashed with some outstanding transfers.");
 237
 238                 /* try again with SO_REUSEADDR */
 239                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 240                 if (r < 0)
 241                         return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set SO_REUSEADDR: %m");
 242
 243                 r = bind(s, &sa.sa, sizeof(sa.in6));
 244                 if (r < 0)
 245                         return log_error_errno(errno, "LLMNR-IPv6(UDP): Failed to bind socket: %m");
 246         } else {
 247                 /* enable SO_REUSEADDR for the case that the user really wants multiple LLMNR responders */
 248                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 249                 if (r < 0)
 250                         return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set SO_REUSEADDR: %m");
 251         }
 252
 253         r = sd_event_add_io(m->event, &m->llmnr_ipv6_udp_event_source, s, EPOLLIN, on_llmnr_packet, m);
 254         if (r < 0)
 255                 return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to create event source: %m");
 256
 257         (void) sd_event_source_set_description(m->llmnr_ipv6_udp_event_source, "llmnr-ipv6-udp");
 258
 259         return m->llmnr_ipv6_udp_fd = TAKE_FD(s);
 260 }
 261
 262 static int on_llmnr_stream_packet(DnsStream *s) {
 263         _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
 264         DnsScope *scope;
 265
 266         assert(s);
 267
 268         p = dns_stream_take_read_packet(s);
 269         assert(p);
 270
 271         scope = manager_find_scope(s->manager, p);
 272         if (!scope)
 273                 log_debug("Got LLMNR TCP packet on unknown scope. Ignoring.");
 274         else if (dns_packet_validate_query(p) > 0) {
 275                 log_debug("Got LLMNR TCP query packet for id %u", DNS_PACKET_ID(p));
 276
 277                 dns_scope_process_query(scope, s, p);
 278         } else
 279                 log_debug("Invalid LLMNR TCP packet, ignoring.");
 280
 281         dns_stream_unref(s);
 282         return 0;
 283 }
 284
 285 static int on_llmnr_stream(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
 286         DnsStream *stream;
 287         Manager *m = userdata;
 288         int cfd, r;
 289
 290         cfd = accept4(fd, NULL, NULL, SOCK_NONBLOCK|SOCK_CLOEXEC);
 291         if (cfd < 0) {
 292                 if (IN_SET(errno, EAGAIN, EINTR))
 293                         return 0;
 294
 295                 return -errno;
 296         }
 297
 298         r = dns_stream_new(m, &stream, DNS_STREAM_LLMNR_RECV, DNS_PROTOCOL_LLMNR, cfd, NULL);
 299         if (r < 0) {
 300                 safe_close(cfd);
 301                 return r;
 302         }
 303
 304         stream->on_packet = on_llmnr_stream_packet;
 305         /* We don't configure a "complete" handler here, we rely on the default handler than simply drops the
 306          * reference to the stream, thus freeing it */
 307         return 0;
 308 }
 309
 310 int manager_llmnr_ipv4_tcp_fd(Manager *m) {
 311         union sockaddr_union sa = {
 312                 .in.sin_family = AF_INET,
 313                 .in.sin_port = htobe16(LLMNR_PORT),
 314         };
 315         _cleanup_close_ int s = -1;
 316         int r;
 317
 318         assert(m);
 319
 320         if (m->llmnr_ipv4_tcp_fd >= 0)
 321                 return m->llmnr_ipv4_tcp_fd;
 322
 323         s = socket(AF_INET, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
 324         if (s < 0)
 325                 return log_error_errno(errno, "LLMNR-IPv4(TCP): Failed to create socket: %m");
 326
 327         /* RFC 4795, section 2.5. requires setting the TTL of TCP streams to 1 */
 328         r = setsockopt_int(s, IPPROTO_IP, IP_TTL, true);
 329         if (r < 0)
 330                 return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to set IP_TTL: %m");
 331
 332         r = setsockopt_int(s, IPPROTO_IP, IP_PKTINFO, true);
 333         if (r < 0)
 334                 return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to set IP_PKTINFO: %m");
 335
 336         r = setsockopt_int(s, IPPROTO_IP, IP_RECVTTL, true);
 337         if (r < 0)
 338                 return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to set IP_RECVTTL: %m");
 339
 340         /* Disable Don't-Fragment bit in the IP header */
 341         r = setsockopt_int(s, IPPROTO_IP, IP_MTU_DISCOVER, IP_PMTUDISC_DONT);
 342         if (r < 0)
 343                 return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to set IP_MTU_DISCOVER: %m");
 344
 345         /* first try to bind without SO_REUSEADDR to detect another LLMNR responder */
 346         r = bind(s, &sa.sa, sizeof(sa.in));
 347         if (r < 0) {
 348                 if (errno != EADDRINUSE)
 349                         return log_error_errno(errno, "LLMNR-IPv4(TCP): Failed to bind socket: %m");
 350
 351                 log_warning("LLMNR-IPv4(TCP): There appears to be another LLMNR responder running, or previously systemd-resolved crashed with some outstanding transfers.");
 352
 353                 /* try again with SO_REUSEADDR */
 354                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 355                 if (r < 0)
 356                         return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to set SO_REUSEADDR: %m");
 357
 358                 r = bind(s, &sa.sa, sizeof(sa.in));
 359                 if (r < 0)
 360                         return log_error_errno(errno, "LLMNR-IPv4(TCP): Failed to bind socket: %m");
 361         } else {
 362                 /* enable SO_REUSEADDR for the case that the user really wants multiple LLMNR responders */
 363                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 364                 if (r < 0)
 365                         return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to set SO_REUSEADDR: %m");
 366         }
 367
 368         r = listen(s, SOMAXCONN);
 369         if (r < 0)
 370                 return log_error_errno(errno, "LLMNR-IPv4(TCP): Failed to listen the stream: %m");
 371
 372         r = sd_event_add_io(m->event, &m->llmnr_ipv4_tcp_event_source, s, EPOLLIN, on_llmnr_stream, m);
 373         if (r < 0)
 374                 return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to create event source: %m");
 375
 376         (void) sd_event_source_set_description(m->llmnr_ipv4_tcp_event_source, "llmnr-ipv4-tcp");
 377
 378         return m->llmnr_ipv4_tcp_fd = TAKE_FD(s);
 379 }
 380
 381 int manager_llmnr_ipv6_tcp_fd(Manager *m) {
 382         union sockaddr_union sa = {
 383                 .in6.sin6_family = AF_INET6,
 384                 .in6.sin6_port = htobe16(LLMNR_PORT),
 385         };
 386         _cleanup_close_ int s = -1;
 387         int r;
 388
 389         assert(m);
 390
 391         if (m->llmnr_ipv6_tcp_fd >= 0)
 392                 return m->llmnr_ipv6_tcp_fd;
 393
 394         s = socket(AF_INET6, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
 395         if (s < 0)
 396                 return log_error_errno(errno, "LLMNR-IPv6(TCP): Failed to create socket: %m");
 397
 398         /* RFC 4795, section 2.5. requires setting the TTL of TCP streams to 1 */
 399         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_UNICAST_HOPS, true);
 400         if (r < 0)
 401                 return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to set IPV6_UNICAST_HOPS: %m");
 402
 403         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_V6ONLY, true);
 404         if (r < 0)
 405                 return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to set IPV6_V6ONLY: %m");
 406
 407         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_RECVPKTINFO, true);
 408         if (r < 0)
 409                 return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to set IPV6_RECVPKTINFO: %m");
 410
 411         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, true);
 412         if (r < 0)
 413                 return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to set IPV6_RECVHOPLIMIT: %m");
 414
 415         /* first try to bind without SO_REUSEADDR to detect another LLMNR responder */
 416         r = bind(s, &sa.sa, sizeof(sa.in6));
 417         if (r < 0) {
 418                 if (errno != EADDRINUSE)
 419                         return log_error_errno(errno, "LLMNR-IPv6(TCP): Failed to bind socket: %m");
 420
 421                 log_warning("LLMNR-IPv6(TCP): There appears to be another LLMNR responder running, or previously systemd-resolved crashed with some outstanding transfers.");
 422
 423                 /* try again with SO_REUSEADDR */
 424                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 425                 if (r < 0)
 426                         return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to set SO_REUSEADDR: %m");
 427
 428                 r = bind(s, &sa.sa, sizeof(sa.in6));
 429                 if (r < 0)
 430                         return log_error_errno(errno, "LLMNR-IPv6(TCP): Failed to bind socket: %m");
 431         } else {
 432                 /* enable SO_REUSEADDR for the case that the user really wants multiple LLMNR responders */
 433                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 434                 if (r < 0)
 435                         return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to set SO_REUSEADDR: %m");
 436         }
 437
 438         r = listen(s, SOMAXCONN);
 439         if (r < 0)
 440                 return log_error_errno(errno, "LLMNR-IPv6(TCP): Failed to listen the stream: %m");
 441
 442         r = sd_event_add_io(m->event, &m->llmnr_ipv6_tcp_event_source, s, EPOLLIN, on_llmnr_stream, m);
 443         if (r < 0)
 444                 return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to create event source: %m");
 445
 446         (void) sd_event_source_set_description(m->llmnr_ipv6_tcp_event_source, "llmnr-ipv6-tcp");
 447
 448         return m->llmnr_ipv6_tcp_fd = TAKE_FD(s);
 449 }