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 "errno-util.h"
   7 #include "fd-util.h"
   8 #include "resolved-llmnr.h"
   9 #include "resolved-manager.h"
  10
  11 void manager_llmnr_stop(Manager *m) {
  12         assert(m);
  13
  14         m->llmnr_ipv4_udp_event_source = sd_event_source_unref(m->llmnr_ipv4_udp_event_source);
  15         m->llmnr_ipv4_udp_fd = safe_close(m->llmnr_ipv4_udp_fd);
  16
  17         m->llmnr_ipv6_udp_event_source = sd_event_source_unref(m->llmnr_ipv6_udp_event_source);
  18         m->llmnr_ipv6_udp_fd = safe_close(m->llmnr_ipv6_udp_fd);
  19
  20         m->llmnr_ipv4_tcp_event_source = sd_event_source_unref(m->llmnr_ipv4_tcp_event_source);
  21         m->llmnr_ipv4_tcp_fd = safe_close(m->llmnr_ipv4_tcp_fd);
  22
  23         m->llmnr_ipv6_tcp_event_source = sd_event_source_unref(m->llmnr_ipv6_tcp_event_source);
  24         m->llmnr_ipv6_tcp_fd = safe_close(m->llmnr_ipv6_tcp_fd);
  25 }
  26
  27 int manager_llmnr_start(Manager *m) {
  28         int r;
  29
  30         assert(m);
  31
  32         if (m->llmnr_support == RESOLVE_SUPPORT_NO)
  33                 return 0;
  34
  35         r = manager_llmnr_ipv4_udp_fd(m);
  36         if (r == -EADDRINUSE)
  37                 goto eaddrinuse;
  38         if (r < 0)
  39                 return r;
  40
  41         r = manager_llmnr_ipv4_tcp_fd(m);
  42         if (r == -EADDRINUSE)
  43                 goto eaddrinuse;
  44         if (r < 0)
  45                 return r;
  46
  47         if (socket_ipv6_is_supported()) {
  48                 r = manager_llmnr_ipv6_udp_fd(m);
  49                 if (r == -EADDRINUSE)
  50                         goto eaddrinuse;
  51                 if (r < 0)
  52                         return r;
  53
  54                 r = manager_llmnr_ipv6_tcp_fd(m);
  55                 if (r == -EADDRINUSE)
  56                         goto eaddrinuse;
  57                 if (r < 0)
  58                         return r;
  59         }
  60
  61         return 0;
  62
  63 eaddrinuse:
  64         log_warning("Another LLMNR responder prohibits binding the socket to the same port. Turning off LLMNR support.");
  65         m->llmnr_support = RESOLVE_SUPPORT_NO;
  66         manager_llmnr_stop(m);
  67
  68         return 0;
  69 }
  70
  71 static int on_llmnr_packet(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
  72         _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
  73         DnsTransaction *t = NULL;
  74         Manager *m = userdata;
  75         DnsScope *scope;
  76         int r;
  77
  78         assert(s);
  79         assert(fd >= 0);
  80         assert(m);
  81
  82         r = manager_recv(m, fd, DNS_PROTOCOL_LLMNR, &p);
  83         if (r <= 0)
  84                 return r;
  85
  86         if (manager_our_packet(m, p))
  87                 return 0;
  88
  89         scope = manager_find_scope(m, p);
  90         if (!scope) {
  91                 log_debug("Got LLMNR UDP packet on unknown scope. Ignoring.");
  92                 return 0;
  93         }
  94
  95         if (dns_packet_validate_reply(p) > 0) {
  96                 log_debug("Got LLMNR UDP reply packet for id %u", DNS_PACKET_ID(p));
  97
  98                 dns_scope_check_conflicts(scope, p);
  99
 100                 t = hashmap_get(m->dns_transactions, UINT_TO_PTR(DNS_PACKET_ID(p)));
 101                 if (t)
 102                         dns_transaction_process_reply(t, p);
 103
 104         } else if (dns_packet_validate_query(p) > 0)  {
 105                 log_debug("Got LLMNR UDP query packet for id %u", DNS_PACKET_ID(p));
 106
 107                 dns_scope_process_query(scope, NULL, p);
 108         } else
 109                 log_debug("Invalid LLMNR UDP packet, ignoring.");
 110
 111         return 0;
 112 }
 113
 114 int manager_llmnr_ipv4_udp_fd(Manager *m) {
 115         union sockaddr_union sa = {
 116                 .in.sin_family = AF_INET,
 117                 .in.sin_port = htobe16(LLMNR_PORT),
 118         };
 119         _cleanup_close_ int s = -1;
 120         int r;
 121
 122         assert(m);
 123
 124         if (m->llmnr_ipv4_udp_fd >= 0)
 125                 return m->llmnr_ipv4_udp_fd;
 126
 127         s = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
 128         if (s < 0)
 129                 return log_error_errno(errno, "LLMNR-IPv4(UDP): Failed to create socket: %m");
 130
 131         /* RFC 4795, section 2.5 recommends setting the TTL of UDP packets to 255. */
 132         r = setsockopt_int(s, IPPROTO_IP, IP_TTL, 255);
 133         if (r < 0)
 134                 return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set IP_TTL: %m");
 135
 136         r = setsockopt_int(s, IPPROTO_IP, IP_MULTICAST_TTL, 255);
 137         if (r < 0)
 138                 return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set IP_MULTICAST_TTL: %m");
 139
 140         r = setsockopt_int(s, IPPROTO_IP, IP_MULTICAST_LOOP, true);
 141         if (r < 0)
 142                 return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set IP_MULTICAST_LOOP: %m");
 143
 144         r = setsockopt_int(s, IPPROTO_IP, IP_PKTINFO, true);
 145         if (r < 0)
 146                 return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set IP_PKTINFO: %m");
 147
 148         r = setsockopt_int(s, IPPROTO_IP, IP_RECVTTL, true);
 149         if (r < 0)
 150                 return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set IP_RECVTTL: %m");
 151
 152         /* Disable Don't-Fragment bit in the IP header */
 153         r = setsockopt_int(s, IPPROTO_IP, IP_MTU_DISCOVER, IP_PMTUDISC_DONT);
 154         if (r < 0)
 155                 return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set IP_MTU_DISCOVER: %m");
 156
 157         /* first try to bind without SO_REUSEADDR to detect another LLMNR responder */
 158         r = bind(s, &sa.sa, sizeof(sa.in));
 159         if (r < 0) {
 160                 if (errno != EADDRINUSE)
 161                         return log_error_errno(errno, "LLMNR-IPv4(UDP): Failed to bind socket: %m");
 162
 163                 log_warning("LLMNR-IPv4(UDP): There appears to be another LLMNR responder running, or previously systemd-resolved crashed with some outstanding transfers.");
 164
 165                 /* try again with SO_REUSEADDR */
 166                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 167                 if (r < 0)
 168                         return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set SO_REUSEADDR: %m");
 169
 170                 r = bind(s, &sa.sa, sizeof(sa.in));
 171                 if (r < 0)
 172                         return log_error_errno(errno, "LLMNR-IPv4(UDP): Failed to bind socket: %m");
 173         } else {
 174                 /* enable SO_REUSEADDR for the case that the user really wants multiple LLMNR responders */
 175                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 176                 if (r < 0)
 177                         return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set SO_REUSEADDR: %m");
 178         }
 179
 180         r = sd_event_add_io(m->event, &m->llmnr_ipv4_udp_event_source, s, EPOLLIN, on_llmnr_packet, m);
 181         if (r < 0)
 182                 return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to create event source: %m");
 183
 184         (void) sd_event_source_set_description(m->llmnr_ipv4_udp_event_source, "llmnr-ipv4-udp");
 185
 186         return m->llmnr_ipv4_udp_fd = TAKE_FD(s);
 187 }
 188
 189 int manager_llmnr_ipv6_udp_fd(Manager *m) {
 190         union sockaddr_union sa = {
 191                 .in6.sin6_family = AF_INET6,
 192                 .in6.sin6_port = htobe16(LLMNR_PORT),
 193         };
 194         _cleanup_close_ int s = -1;
 195         int r;
 196
 197         assert(m);
 198
 199         if (m->llmnr_ipv6_udp_fd >= 0)
 200                 return m->llmnr_ipv6_udp_fd;
 201
 202         s = socket(AF_INET6, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
 203         if (s < 0)
 204                 return log_error_errno(errno, "LLMNR-IPv6(UDP): Failed to create socket: %m");
 205
 206         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_UNICAST_HOPS, 255);
 207         if (r < 0)
 208                 return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set IPV6_UNICAST_HOPS: %m");
 209
 210         /* RFC 4795, section 2.5 recommends setting the TTL of UDP packets to 255. */
 211         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, 255);
 212         if (r < 0)
 213                 return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set IPV6_MULTICAST_HOPS: %m");
 214
 215         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, true);
 216         if (r < 0)
 217                 return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set IPV6_MULTICAST_LOOP: %m");
 218
 219         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_V6ONLY, true);
 220         if (r < 0)
 221                 return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set IPV6_V6ONLY: %m");
 222
 223         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_RECVPKTINFO, true);
 224         if (r < 0)
 225                 return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set IPV6_RECVPKTINFO: %m");
 226
 227         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, true);
 228         if (r < 0)
 229                 return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set IPV6_RECVHOPLIMIT: %m");
 230
 231         /* first try to bind without SO_REUSEADDR to detect another LLMNR responder */
 232         r = bind(s, &sa.sa, sizeof(sa.in6));
 233         if (r < 0) {
 234                 if (errno != EADDRINUSE)
 235                         return log_error_errno(errno, "LLMNR-IPv6(UDP): Failed to bind socket: %m");
 236
 237                 log_warning("LLMNR-IPv6(UDP): There appears to be another LLMNR responder running, or previously systemd-resolved crashed with some outstanding transfers.");
 238
 239                 /* try again with SO_REUSEADDR */
 240                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 241                 if (r < 0)
 242                         return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set SO_REUSEADDR: %m");
 243
 244                 r = bind(s, &sa.sa, sizeof(sa.in6));
 245                 if (r < 0)
 246                         return log_error_errno(errno, "LLMNR-IPv6(UDP): Failed to bind socket: %m");
 247         } else {
 248                 /* enable SO_REUSEADDR for the case that the user really wants multiple LLMNR responders */
 249                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 250                 if (r < 0)
 251                         return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set SO_REUSEADDR: %m");
 252         }
 253
 254         r = sd_event_add_io(m->event, &m->llmnr_ipv6_udp_event_source, s, EPOLLIN, on_llmnr_packet, m);
 255         if (r < 0)
 256                 return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to create event source: %m");
 257
 258         (void) sd_event_source_set_description(m->llmnr_ipv6_udp_event_source, "llmnr-ipv6-udp");
 259
 260         return m->llmnr_ipv6_udp_fd = TAKE_FD(s);
 261 }
 262
 263 static int on_llmnr_stream_packet(DnsStream *s) {
 264         _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
 265         DnsScope *scope;
 266
 267         assert(s);
 268
 269         p = dns_stream_take_read_packet(s);
 270         assert(p);
 271
 272         scope = manager_find_scope(s->manager, p);
 273         if (!scope)
 274                 log_debug("Got LLMNR TCP packet on unknown scope. Ignoring.");
 275         else if (dns_packet_validate_query(p) > 0) {
 276                 log_debug("Got LLMNR TCP query packet for id %u", DNS_PACKET_ID(p));
 277
 278                 dns_scope_process_query(scope, s, p);
 279         } else
 280                 log_debug("Invalid LLMNR TCP packet, ignoring.");
 281
 282         dns_stream_unref(s);
 283         return 0;
 284 }
 285
 286 static int on_llmnr_stream(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
 287         DnsStream *stream;
 288         Manager *m = userdata;
 289         int cfd, r;
 290
 291         cfd = accept4(fd, NULL, NULL, SOCK_NONBLOCK|SOCK_CLOEXEC);
 292         if (cfd < 0) {
 293                 if (ERRNO_IS_ACCEPT_AGAIN(errno))
 294                         return 0;
 295
 296                 return -errno;
 297         }
 298
 299         r = dns_stream_new(m, &stream, DNS_STREAM_LLMNR_RECV, DNS_PROTOCOL_LLMNR, cfd, NULL);
 300         if (r < 0) {
 301                 safe_close(cfd);
 302                 return r;
 303         }
 304
 305         stream->on_packet = on_llmnr_stream_packet;
 306         /* We don't configure a "complete" handler here, we rely on the default handler than simply drops the
 307          * reference to the stream, thus freeing it */
 308         return 0;
 309 }
 310
 311 int manager_llmnr_ipv4_tcp_fd(Manager *m) {
 312         union sockaddr_union sa = {
 313                 .in.sin_family = AF_INET,
 314                 .in.sin_port = htobe16(LLMNR_PORT),
 315         };
 316         _cleanup_close_ int s = -1;
 317         int r;
 318
 319         assert(m);
 320
 321         if (m->llmnr_ipv4_tcp_fd >= 0)
 322                 return m->llmnr_ipv4_tcp_fd;
 323
 324         s = socket(AF_INET, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
 325         if (s < 0)
 326                 return log_error_errno(errno, "LLMNR-IPv4(TCP): Failed to create socket: %m");
 327
 328         /* RFC 4795, section 2.5. requires setting the TTL of TCP streams to 1 */
 329         r = setsockopt_int(s, IPPROTO_IP, IP_TTL, true);
 330         if (r < 0)
 331                 return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to set IP_TTL: %m");
 332
 333         r = setsockopt_int(s, IPPROTO_IP, IP_PKTINFO, true);
 334         if (r < 0)
 335                 return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to set IP_PKTINFO: %m");
 336
 337         r = setsockopt_int(s, IPPROTO_IP, IP_RECVTTL, true);
 338         if (r < 0)
 339                 return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to set IP_RECVTTL: %m");
 340
 341         /* Disable Don't-Fragment bit in the IP header */
 342         r = setsockopt_int(s, IPPROTO_IP, IP_MTU_DISCOVER, IP_PMTUDISC_DONT);
 343         if (r < 0)
 344                 return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to set IP_MTU_DISCOVER: %m");
 345
 346         /* first try to bind without SO_REUSEADDR to detect another LLMNR responder */
 347         r = bind(s, &sa.sa, sizeof(sa.in));
 348         if (r < 0) {
 349                 if (errno != EADDRINUSE)
 350                         return log_error_errno(errno, "LLMNR-IPv4(TCP): Failed to bind socket: %m");
 351
 352                 log_warning("LLMNR-IPv4(TCP): There appears to be another LLMNR responder running, or previously systemd-resolved crashed with some outstanding transfers.");
 353
 354                 /* try again with SO_REUSEADDR */
 355                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 356                 if (r < 0)
 357                         return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to set SO_REUSEADDR: %m");
 358
 359                 r = bind(s, &sa.sa, sizeof(sa.in));
 360                 if (r < 0)
 361                         return log_error_errno(errno, "LLMNR-IPv4(TCP): Failed to bind socket: %m");
 362         } else {
 363                 /* enable SO_REUSEADDR for the case that the user really wants multiple LLMNR responders */
 364                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 365                 if (r < 0)
 366                         return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to set SO_REUSEADDR: %m");
 367         }
 368
 369         r = listen(s, SOMAXCONN);
 370         if (r < 0)
 371                 return log_error_errno(errno, "LLMNR-IPv4(TCP): Failed to listen the stream: %m");
 372
 373         r = sd_event_add_io(m->event, &m->llmnr_ipv4_tcp_event_source, s, EPOLLIN, on_llmnr_stream, m);
 374         if (r < 0)
 375                 return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to create event source: %m");
 376
 377         (void) sd_event_source_set_description(m->llmnr_ipv4_tcp_event_source, "llmnr-ipv4-tcp");
 378
 379         return m->llmnr_ipv4_tcp_fd = TAKE_FD(s);
 380 }
 381
 382 int manager_llmnr_ipv6_tcp_fd(Manager *m) {
 383         union sockaddr_union sa = {
 384                 .in6.sin6_family = AF_INET6,
 385                 .in6.sin6_port = htobe16(LLMNR_PORT),
 386         };
 387         _cleanup_close_ int s = -1;
 388         int r;
 389
 390         assert(m);
 391
 392         if (m->llmnr_ipv6_tcp_fd >= 0)
 393                 return m->llmnr_ipv6_tcp_fd;
 394
 395         s = socket(AF_INET6, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
 396         if (s < 0)
 397                 return log_error_errno(errno, "LLMNR-IPv6(TCP): Failed to create socket: %m");
 398
 399         /* RFC 4795, section 2.5. requires setting the TTL of TCP streams to 1 */
 400         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_UNICAST_HOPS, true);
 401         if (r < 0)
 402                 return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to set IPV6_UNICAST_HOPS: %m");
 403
 404         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_V6ONLY, true);
 405         if (r < 0)
 406                 return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to set IPV6_V6ONLY: %m");
 407
 408         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_RECVPKTINFO, true);
 409         if (r < 0)
 410                 return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to set IPV6_RECVPKTINFO: %m");
 411
 412         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, true);
 413         if (r < 0)
 414                 return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to set IPV6_RECVHOPLIMIT: %m");
 415
 416         /* first try to bind without SO_REUSEADDR to detect another LLMNR responder */
 417         r = bind(s, &sa.sa, sizeof(sa.in6));
 418         if (r < 0) {
 419                 if (errno != EADDRINUSE)
 420                         return log_error_errno(errno, "LLMNR-IPv6(TCP): Failed to bind socket: %m");
 421
 422                 log_warning("LLMNR-IPv6(TCP): There appears to be another LLMNR responder running, or previously systemd-resolved crashed with some outstanding transfers.");
 423
 424                 /* try again with SO_REUSEADDR */
 425                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 426                 if (r < 0)
 427                         return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to set SO_REUSEADDR: %m");
 428
 429                 r = bind(s, &sa.sa, sizeof(sa.in6));
 430                 if (r < 0)
 431                         return log_error_errno(errno, "LLMNR-IPv6(TCP): Failed to bind socket: %m");
 432         } else {
 433                 /* enable SO_REUSEADDR for the case that the user really wants multiple LLMNR responders */
 434                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 435                 if (r < 0)
 436                         return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to set SO_REUSEADDR: %m");
 437         }
 438
 439         r = listen(s, SOMAXCONN);
 440         if (r < 0)
 441                 return log_error_errno(errno, "LLMNR-IPv6(TCP): Failed to listen the stream: %m");
 442
 443         r = sd_event_add_io(m->event, &m->llmnr_ipv6_tcp_event_source, s, EPOLLIN, on_llmnr_stream, m);
 444         if (r < 0)
 445                 return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to create event source: %m");
 446
 447         (void) sd_event_source_set_description(m->llmnr_ipv6_tcp_event_source, "llmnr-ipv6-tcp");
 448
 449         return m->llmnr_ipv6_tcp_fd = TAKE_FD(s);
 450 }