src/resolve/resolved-llmnr.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2
   3 #include <netinet/in.h>
   4 #include <netinet/tcp.h>
   5 #include <resolv.h>
   6
   7 #include "errno-util.h"
   8 #include "fd-util.h"
   9 #include "resolved-llmnr.h"
  10 #include "resolved-manager.h"
  11
  12 void manager_llmnr_stop(Manager *m) {
  13         assert(m);
  14
  15         m->llmnr_ipv4_udp_event_source = sd_event_source_disable_unref(m->llmnr_ipv4_udp_event_source);
  16         m->llmnr_ipv4_udp_fd = safe_close(m->llmnr_ipv4_udp_fd);
  17
  18         m->llmnr_ipv6_udp_event_source = sd_event_source_disable_unref(m->llmnr_ipv6_udp_event_source);
  19         m->llmnr_ipv6_udp_fd = safe_close(m->llmnr_ipv6_udp_fd);
  20
  21         m->llmnr_ipv4_tcp_event_source = sd_event_source_disable_unref(m->llmnr_ipv4_tcp_event_source);
  22         m->llmnr_ipv4_tcp_fd = safe_close(m->llmnr_ipv4_tcp_fd);
  23
  24         m->llmnr_ipv6_tcp_event_source = sd_event_source_disable_unref(m->llmnr_ipv6_tcp_event_source);
  25         m->llmnr_ipv6_tcp_fd = safe_close(m->llmnr_ipv6_tcp_fd);
  26 }
  27
  28 int manager_llmnr_start(Manager *m) {
  29         int r;
  30
  31         assert(m);
  32
  33         if (m->llmnr_support == RESOLVE_SUPPORT_NO)
  34                 return 0;
  35
  36         r = manager_llmnr_ipv4_udp_fd(m);
  37         if (r == -EADDRINUSE)
  38                 goto eaddrinuse;
  39         if (r < 0)
  40                 return r;
  41
  42         r = manager_llmnr_ipv4_tcp_fd(m);
  43         if (r == -EADDRINUSE)
  44                 goto eaddrinuse;
  45         if (r < 0)
  46                 return r;
  47
  48         if (socket_ipv6_is_supported()) {
  49                 r = manager_llmnr_ipv6_udp_fd(m);
  50                 if (r == -EADDRINUSE)
  51                         goto eaddrinuse;
  52                 if (r < 0)
  53                         return r;
  54
  55                 r = manager_llmnr_ipv6_tcp_fd(m);
  56                 if (r == -EADDRINUSE)
  57                         goto eaddrinuse;
  58                 if (r < 0)
  59                         return r;
  60         }
  61
  62         return 0;
  63
  64 eaddrinuse:
  65         log_warning("Another LLMNR responder prohibits binding the socket to the same port. Turning off LLMNR support.");
  66         m->llmnr_support = RESOLVE_SUPPORT_NO;
  67         manager_llmnr_stop(m);
  68
  69         return 0;
  70 }
  71
  72 static int on_llmnr_packet(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
  73         _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
  74         DnsTransaction *t = NULL;
  75         Manager *m = ASSERT_PTR(userdata);
  76         DnsScope *scope;
  77         int r;
  78
  79         assert(s);
  80         assert(fd >= 0);
  81
  82         r = manager_recv(m, fd, DNS_PROTOCOL_LLMNR, &p);
  83         if (r <= 0)
  84                 return r;
  85
  86         if (manager_packet_from_local_address(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, false);
 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 static int set_llmnr_common_socket_options(int fd, int family) {
 115         int r;
 116
 117         r = socket_set_recvpktinfo(fd, family, true);
 118         if (r < 0)
 119                 return r;
 120
 121         r = socket_set_recvttl(fd, family, true);
 122         if (r < 0)
 123                 return r;
 124
 125         return 0;
 126 }
 127
 128 static int set_llmnr_common_udp_socket_options(int fd, int family) {
 129         int r;
 130
 131         /* RFC 4795, section 2.5 recommends setting the TTL of UDP packets to 255. */
 132         r = socket_set_ttl(fd, family, 255);
 133         if (r < 0)
 134                 return r;
 135
 136         return 0;
 137 }
 138
 139 int manager_llmnr_ipv4_udp_fd(Manager *m) {
 140         union sockaddr_union sa = {
 141                 .in.sin_family = AF_INET,
 142                 .in.sin_port = htobe16(LLMNR_PORT),
 143         };
 144         _cleanup_close_ int s = -EBADF;
 145         int r;
 146
 147         assert(m);
 148
 149         if (m->llmnr_ipv4_udp_fd >= 0)
 150                 return m->llmnr_ipv4_udp_fd;
 151
 152         s = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
 153         if (s < 0)
 154                 return log_error_errno(errno, "LLMNR-IPv4(UDP): Failed to create socket: %m");
 155
 156         r = set_llmnr_common_socket_options(s, AF_INET);
 157         if (r < 0)
 158                 return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set common socket options: %m");
 159
 160         r = set_llmnr_common_udp_socket_options(s, AF_INET);
 161         if (r < 0)
 162                 return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set common UDP socket options: %m");
 163
 164         r = setsockopt_int(s, IPPROTO_IP, IP_MULTICAST_TTL, 255);
 165         if (r < 0)
 166                 return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set IP_MULTICAST_TTL: %m");
 167
 168         r = setsockopt_int(s, IPPROTO_IP, IP_MULTICAST_LOOP, true);
 169         if (r < 0)
 170                 return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set IP_MULTICAST_LOOP: %m");
 171
 172         /* Disable Don't-Fragment bit in the IP header */
 173         r = setsockopt_int(s, IPPROTO_IP, IP_MTU_DISCOVER, IP_PMTUDISC_DONT);
 174         if (r < 0)
 175                 return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set IP_MTU_DISCOVER: %m");
 176
 177         /* first try to bind without SO_REUSEADDR to detect another LLMNR responder */
 178         r = bind(s, &sa.sa, sizeof(sa.in));
 179         if (r < 0) {
 180                 if (errno != EADDRINUSE)
 181                         return log_error_errno(errno, "LLMNR-IPv4(UDP): Failed to bind socket: %m");
 182
 183                 log_warning("LLMNR-IPv4(UDP): There appears to be another LLMNR responder running, or previously systemd-resolved crashed with some outstanding transfers.");
 184
 185                 /* try again with SO_REUSEADDR */
 186                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 187                 if (r < 0)
 188                         return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set SO_REUSEADDR: %m");
 189
 190                 r = bind(s, &sa.sa, sizeof(sa.in));
 191                 if (r < 0)
 192                         return log_error_errno(errno, "LLMNR-IPv4(UDP): Failed to bind socket: %m");
 193         } else {
 194                 /* enable SO_REUSEADDR for the case that the user really wants multiple LLMNR responders */
 195                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 196                 if (r < 0)
 197                         return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set SO_REUSEADDR: %m");
 198         }
 199
 200         r = sd_event_add_io(m->event, &m->llmnr_ipv4_udp_event_source, s, EPOLLIN, on_llmnr_packet, m);
 201         if (r < 0)
 202                 return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to create event source: %m");
 203
 204         (void) sd_event_source_set_description(m->llmnr_ipv4_udp_event_source, "llmnr-ipv4-udp");
 205
 206         return m->llmnr_ipv4_udp_fd = TAKE_FD(s);
 207 }
 208
 209 int manager_llmnr_ipv6_udp_fd(Manager *m) {
 210         union sockaddr_union sa = {
 211                 .in6.sin6_family = AF_INET6,
 212                 .in6.sin6_port = htobe16(LLMNR_PORT),
 213         };
 214         _cleanup_close_ int s = -EBADF;
 215         int r;
 216
 217         assert(m);
 218
 219         if (m->llmnr_ipv6_udp_fd >= 0)
 220                 return m->llmnr_ipv6_udp_fd;
 221
 222         s = socket(AF_INET6, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
 223         if (s < 0)
 224                 return log_error_errno(errno, "LLMNR-IPv6(UDP): Failed to create socket: %m");
 225
 226         r = set_llmnr_common_socket_options(s, AF_INET6);
 227         if (r < 0)
 228                 return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set common socket options: %m");
 229
 230         r = set_llmnr_common_udp_socket_options(s, AF_INET6);
 231         if (r < 0)
 232                 return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set common UDP socket options: %m");
 233
 234         /* RFC 4795, section 2.5 recommends setting the TTL of UDP packets to 255. */
 235         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, 255);
 236         if (r < 0)
 237                 return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set IPV6_MULTICAST_HOPS: %m");
 238
 239         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, true);
 240         if (r < 0)
 241                 return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set IPV6_MULTICAST_LOOP: %m");
 242
 243         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_V6ONLY, true);
 244         if (r < 0)
 245                 return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set IPV6_V6ONLY: %m");
 246
 247         /* first try to bind without SO_REUSEADDR to detect another LLMNR responder */
 248         r = bind(s, &sa.sa, sizeof(sa.in6));
 249         if (r < 0) {
 250                 if (errno != EADDRINUSE)
 251                         return log_error_errno(errno, "LLMNR-IPv6(UDP): Failed to bind socket: %m");
 252
 253                 log_warning("LLMNR-IPv6(UDP): There appears to be another LLMNR responder running, or previously systemd-resolved crashed with some outstanding transfers.");
 254
 255                 /* try again with SO_REUSEADDR */
 256                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 257                 if (r < 0)
 258                         return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set SO_REUSEADDR: %m");
 259
 260                 r = bind(s, &sa.sa, sizeof(sa.in6));
 261                 if (r < 0)
 262                         return log_error_errno(errno, "LLMNR-IPv6(UDP): Failed to bind socket: %m");
 263         } else {
 264                 /* enable SO_REUSEADDR for the case that the user really wants multiple LLMNR responders */
 265                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 266                 if (r < 0)
 267                         return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set SO_REUSEADDR: %m");
 268         }
 269
 270         r = sd_event_add_io(m->event, &m->llmnr_ipv6_udp_event_source, s, EPOLLIN, on_llmnr_packet, m);
 271         if (r < 0)
 272                 return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to create event source: %m");
 273
 274         (void) sd_event_source_set_description(m->llmnr_ipv6_udp_event_source, "llmnr-ipv6-udp");
 275
 276         return m->llmnr_ipv6_udp_fd = TAKE_FD(s);
 277 }
 278
 279 static int on_llmnr_stream_packet(DnsStream *s, DnsPacket *p) {
 280         DnsScope *scope;
 281
 282         assert(s);
 283         assert(s->manager);
 284         assert(p);
 285
 286         scope = manager_find_scope(s->manager, p);
 287         if (!scope)
 288                 log_debug("Got LLMNR TCP packet on unknown scope. Ignoring.");
 289         else if (dns_packet_validate_query(p) > 0) {
 290                 log_debug("Got LLMNR TCP query packet for id %u", DNS_PACKET_ID(p));
 291
 292                 dns_scope_process_query(scope, s, p);
 293         } else
 294                 log_debug("Invalid LLMNR TCP packet, ignoring.");
 295
 296         return 0;
 297 }
 298
 299 static int on_llmnr_stream(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
 300         DnsStream *stream;
 301         Manager *m = userdata;
 302         int cfd, r;
 303
 304         cfd = accept4(fd, NULL, NULL, SOCK_NONBLOCK|SOCK_CLOEXEC);
 305         if (cfd < 0) {
 306                 if (ERRNO_IS_ACCEPT_AGAIN(errno))
 307                         return 0;
 308
 309                 return -errno;
 310         }
 311
 312         /* We don't configure a "complete" handler here, we rely on the default handler, thus freeing it */
 313         r = dns_stream_new(m, &stream, DNS_STREAM_LLMNR_RECV, DNS_PROTOCOL_LLMNR, cfd, NULL,
 314                            on_llmnr_stream_packet, NULL, DNS_STREAM_DEFAULT_TIMEOUT_USEC);
 315         if (r < 0) {
 316                 safe_close(cfd);
 317                 return r;
 318         }
 319
 320         return 0;
 321 }
 322
 323 static int set_llmnr_common_tcp_socket_options(int fd, int family) {
 324         int r;
 325
 326         /* RFC 4795, section 2.5. requires setting the TTL of TCP streams to 1 */
 327         r = socket_set_ttl(fd, family, 1);
 328         if (r < 0)
 329                 return r;
 330
 331         r = setsockopt_int(fd, IPPROTO_TCP, TCP_FASTOPEN, 5); /* Everybody appears to pick qlen=5, let's do the same here. */
 332         if (r < 0)
 333                 log_debug_errno(r, "Failed to enable TCP_FASTOPEN on TCP listening socket, ignoring: %m");
 334
 335         r = setsockopt_int(fd, IPPROTO_TCP, TCP_NODELAY, true);
 336         if (r < 0)
 337                 log_debug_errno(r, "Failed to enable TCP_NODELAY mode, ignoring: %m");
 338
 339         return 0;
 340 }
 341
 342 int manager_llmnr_ipv4_tcp_fd(Manager *m) {
 343         union sockaddr_union sa = {
 344                 .in.sin_family = AF_INET,
 345                 .in.sin_port = htobe16(LLMNR_PORT),
 346         };
 347         _cleanup_close_ int s = -EBADF;
 348         int r;
 349
 350         assert(m);
 351
 352         if (m->llmnr_ipv4_tcp_fd >= 0)
 353                 return m->llmnr_ipv4_tcp_fd;
 354
 355         s = socket(AF_INET, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
 356         if (s < 0)
 357                 return log_error_errno(errno, "LLMNR-IPv4(TCP): Failed to create socket: %m");
 358
 359         r = set_llmnr_common_socket_options(s, AF_INET);
 360         if (r < 0)
 361                 return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to set common socket options: %m");
 362
 363         r = set_llmnr_common_tcp_socket_options(s, AF_INET);
 364         if (r < 0)
 365                 return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to set common TCP socket options: %m");
 366
 367         /* Disable Don't-Fragment bit in the IP header */
 368         r = setsockopt_int(s, IPPROTO_IP, IP_MTU_DISCOVER, IP_PMTUDISC_DONT);
 369         if (r < 0)
 370                 return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to set IP_MTU_DISCOVER: %m");
 371
 372         /* first try to bind without SO_REUSEADDR to detect another LLMNR responder */
 373         r = bind(s, &sa.sa, sizeof(sa.in));
 374         if (r < 0) {
 375                 if (errno != EADDRINUSE)
 376                         return log_error_errno(errno, "LLMNR-IPv4(TCP): Failed to bind socket: %m");
 377
 378                 log_warning("LLMNR-IPv4(TCP): There appears to be another LLMNR responder running, or previously systemd-resolved crashed with some outstanding transfers.");
 379
 380                 /* try again with SO_REUSEADDR */
 381                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 382                 if (r < 0)
 383                         return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to set SO_REUSEADDR: %m");
 384
 385                 r = bind(s, &sa.sa, sizeof(sa.in));
 386                 if (r < 0)
 387                         return log_error_errno(errno, "LLMNR-IPv4(TCP): Failed to bind socket: %m");
 388         } else {
 389                 /* enable SO_REUSEADDR for the case that the user really wants multiple LLMNR responders */
 390                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 391                 if (r < 0)
 392                         return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to set SO_REUSEADDR: %m");
 393         }
 394
 395         r = listen(s, SOMAXCONN_DELUXE);
 396         if (r < 0)
 397                 return log_error_errno(errno, "LLMNR-IPv4(TCP): Failed to listen the stream: %m");
 398
 399         r = sd_event_add_io(m->event, &m->llmnr_ipv4_tcp_event_source, s, EPOLLIN, on_llmnr_stream, m);
 400         if (r < 0)
 401                 return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to create event source: %m");
 402
 403         (void) sd_event_source_set_description(m->llmnr_ipv4_tcp_event_source, "llmnr-ipv4-tcp");
 404
 405         return m->llmnr_ipv4_tcp_fd = TAKE_FD(s);
 406 }
 407
 408 int manager_llmnr_ipv6_tcp_fd(Manager *m) {
 409         union sockaddr_union sa = {
 410                 .in6.sin6_family = AF_INET6,
 411                 .in6.sin6_port = htobe16(LLMNR_PORT),
 412         };
 413         _cleanup_close_ int s = -EBADF;
 414         int r;
 415
 416         assert(m);
 417
 418         if (m->llmnr_ipv6_tcp_fd >= 0)
 419                 return m->llmnr_ipv6_tcp_fd;
 420
 421         s = socket(AF_INET6, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
 422         if (s < 0)
 423                 return log_error_errno(errno, "LLMNR-IPv6(TCP): Failed to create socket: %m");
 424
 425         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_V6ONLY, true);
 426         if (r < 0)
 427                 return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to set IPV6_V6ONLY: %m");
 428
 429         r = set_llmnr_common_socket_options(s, AF_INET6);
 430         if (r < 0)
 431                 return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to set common socket options: %m");
 432
 433         r = set_llmnr_common_tcp_socket_options(s, AF_INET6);
 434         if (r < 0)
 435                 return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to set common TCP socket options: %m");
 436
 437         /* first try to bind without SO_REUSEADDR to detect another LLMNR responder */
 438         r = bind(s, &sa.sa, sizeof(sa.in6));
 439         if (r < 0) {
 440                 if (errno != EADDRINUSE)
 441                         return log_error_errno(errno, "LLMNR-IPv6(TCP): Failed to bind socket: %m");
 442
 443                 log_warning("LLMNR-IPv6(TCP): There appears to be another LLMNR responder running, or previously systemd-resolved crashed with some outstanding transfers.");
 444
 445                 /* try again with SO_REUSEADDR */
 446                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 447                 if (r < 0)
 448                         return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to set SO_REUSEADDR: %m");
 449
 450                 r = bind(s, &sa.sa, sizeof(sa.in6));
 451                 if (r < 0)
 452                         return log_error_errno(errno, "LLMNR-IPv6(TCP): Failed to bind socket: %m");
 453         } else {
 454                 /* enable SO_REUSEADDR for the case that the user really wants multiple LLMNR responders */
 455                 r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 456                 if (r < 0)
 457                         return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to set SO_REUSEADDR: %m");
 458         }
 459
 460         r = listen(s, SOMAXCONN_DELUXE);
 461         if (r < 0)
 462                 return log_error_errno(errno, "LLMNR-IPv6(TCP): Failed to listen the stream: %m");
 463
 464         r = sd_event_add_io(m->event, &m->llmnr_ipv6_tcp_event_source, s, EPOLLIN, on_llmnr_stream, m);
 465         if (r < 0)
 466                 return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to create event source: %m");
 467
 468         (void) sd_event_source_set_description(m->llmnr_ipv6_tcp_event_source, "llmnr-ipv6-tcp");
 469
 470         return m->llmnr_ipv6_tcp_fd = TAKE_FD(s);
 471 }