src/libsystemd-network/sd-ndisc.c

   1 /***
   2   This file is part of systemd.
   3
   4   Copyright (C) 2014 Intel Corporation. All rights reserved.
   5
   6   systemd is free software; you can redistribute it and/or modify it
   7   under the terms of the GNU Lesser General Public License as published by
   8   the Free Software Foundation; either version 2.1 of the License, or
   9   (at your option) any later version.
  10
  11   systemd is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   Lesser General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public License
  17   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  18 ***/
  19
  20 #include <netinet/icmp6.h>
  21 #include <netinet/ip6.h>
  22 #include <string.h>
  23 #include <stdbool.h>
  24 #include <netinet/in.h>
  25 #include <sys/ioctl.h>
  26
  27 #include "async.h"
  28 #include "list.h"
  29 #include "socket-util.h"
  30
  31 #include "icmp6-util.h"
  32 #include "sd-ndisc.h"
  33
  34 #define NDISC_ROUTER_SOLICITATION_INTERVAL      4 * USEC_PER_SEC
  35 #define NDISC_MAX_ROUTER_SOLICITATIONS          3
  36
  37 enum NDiscState {
  38         NDISC_STATE_IDLE,
  39         NDISC_STATE_SOLICITATION_SENT,
  40         NDISC_STATE_ADVERTISMENT_LISTEN,
  41         _NDISC_STATE_MAX,
  42         _NDISC_STATE_INVALID = -1,
  43 };
  44
  45 #define IP6_MIN_MTU (unsigned)1280
  46 #define ICMP6_RECV_SIZE (IP6_MIN_MTU - sizeof(struct ip6_hdr))
  47 #define NDISC_OPT_LEN_UNITS 8
  48
  49 typedef struct NDiscPrefix NDiscPrefix;
  50
  51 struct NDiscPrefix {
  52         unsigned n_ref;
  53
  54         sd_ndisc *nd;
  55
  56         LIST_FIELDS(NDiscPrefix, prefixes);
  57
  58         uint8_t len;
  59         usec_t valid_until;
  60         struct in6_addr addr;
  61 };
  62
  63 struct sd_ndisc {
  64         unsigned n_ref;
  65
  66         enum NDiscState state;
  67         sd_event *event;
  68         int event_priority;
  69         int index;
  70         struct ether_addr mac_addr;
  71         uint32_t mtu;
  72         LIST_HEAD(NDiscPrefix, prefixes);
  73         int fd;
  74         sd_event_source *recv;
  75         sd_event_source *timeout;
  76         int nd_sent;
  77         sd_ndisc_callback_t callback;
  78         void *userdata;
  79 };
  80
  81 #define log_ndisc(p, fmt, ...) log_internal(LOG_DEBUG, 0, __FILE__, __LINE__, __func__, "NDisc CLIENT: " fmt, ##__VA_ARGS__)
  82
  83 static NDiscPrefix *ndisc_prefix_unref(NDiscPrefix *prefix) {
  84
  85         if (!prefix)
  86                 return NULL;
  87
  88         assert(prefix->n_ref > 0);
  89         prefix->n_ref--;
  90
  91         if (prefix->n_ref > 0)
  92                 return NULL;
  93
  94         if (prefix->nd)
  95                 LIST_REMOVE(prefixes, prefix->nd->prefixes, prefix);
  96
  97         free(prefix);
  98
  99         return NULL;
 100 }
 101
 102 static int ndisc_prefix_new(sd_ndisc *nd, NDiscPrefix **ret) {
 103         _cleanup_free_ NDiscPrefix *prefix = NULL;
 104
 105         assert(ret);
 106
 107         prefix = new0(NDiscPrefix, 1);
 108         if (!prefix)
 109                 return -ENOMEM;
 110
 111         prefix->n_ref = 1;
 112         LIST_INIT(prefixes, prefix);
 113         prefix->nd = nd;
 114
 115         *ret = prefix;
 116         prefix = NULL;
 117
 118         return 0;
 119 }
 120
 121 static void ndisc_notify(sd_ndisc *nd, int event) {
 122         if (nd->callback)
 123                 nd->callback(nd, event, nd->userdata);
 124 }
 125
 126 int sd_ndisc_set_callback(sd_ndisc *nd, sd_ndisc_callback_t callback,
 127                              void *userdata) {
 128         assert(nd);
 129
 130         nd->callback = callback;
 131         nd->userdata = userdata;
 132
 133         return 0;
 134 }
 135
 136 int sd_ndisc_set_index(sd_ndisc *nd, int interface_index) {
 137         assert(nd);
 138         assert(interface_index >= -1);
 139
 140         nd->index = interface_index;
 141
 142         return 0;
 143 }
 144
 145 int sd_ndisc_set_mac(sd_ndisc *nd, const struct ether_addr *mac_addr) {
 146         assert(nd);
 147
 148         if (mac_addr)
 149                 memcpy(&nd->mac_addr, mac_addr, sizeof(nd->mac_addr));
 150         else
 151                 zero(nd->mac_addr);
 152
 153         return 0;
 154
 155 }
 156
 157 int sd_ndisc_attach_event(sd_ndisc *nd, sd_event *event, int priority) {
 158         int r;
 159
 160         assert_return(nd, -EINVAL);
 161         assert_return(!nd->event, -EBUSY);
 162
 163         if (event)
 164                 nd->event = sd_event_ref(event);
 165         else {
 166                 r = sd_event_default(&nd->event);
 167                 if (r < 0)
 168                         return 0;
 169         }
 170
 171         nd->event_priority = priority;
 172
 173         return 0;
 174 }
 175
 176 int sd_ndisc_detach_event(sd_ndisc *nd) {
 177         assert_return(nd, -EINVAL);
 178
 179         nd->event = sd_event_unref(nd->event);
 180
 181         return 0;
 182 }
 183
 184 sd_event *sd_ndisc_get_event(sd_ndisc *nd) {
 185         assert(nd);
 186
 187         return nd->event;
 188 }
 189
 190 sd_ndisc *sd_ndisc_ref(sd_ndisc *nd) {
 191
 192         if (!nd)
 193                 return NULL;
 194
 195         assert(nd->n_ref > 0);
 196         nd->n_ref++;
 197
 198         return nd;
 199 }
 200
 201 static int ndisc_init(sd_ndisc *nd) {
 202         assert(nd);
 203
 204         nd->recv = sd_event_source_unref(nd->recv);
 205         nd->fd = asynchronous_close(nd->fd);
 206         nd->timeout = sd_event_source_unref(nd->timeout);
 207
 208         return 0;
 209 }
 210
 211 sd_ndisc *sd_ndisc_unref(sd_ndisc *nd) {
 212         NDiscPrefix *prefix, *p;
 213
 214         if (!nd)
 215                 return NULL;
 216
 217         assert(nd->n_ref > 0);
 218         nd->n_ref--;
 219
 220         if (nd->n_ref > 0)
 221                 return NULL;
 222
 223         ndisc_init(nd);
 224         sd_ndisc_detach_event(nd);
 225
 226         LIST_FOREACH_SAFE(prefixes, prefix, p, nd->prefixes)
 227                 prefix = ndisc_prefix_unref(prefix);
 228
 229         free(nd);
 230
 231         return NULL;
 232 }
 233
 234 DEFINE_TRIVIAL_CLEANUP_FUNC(sd_ndisc*, sd_ndisc_unref);
 235 #define _cleanup_sd_ndisc_free_ _cleanup_(sd_ndisc_unrefp)
 236
 237 int sd_ndisc_new(sd_ndisc **ret) {
 238         _cleanup_sd_ndisc_free_ sd_ndisc *nd = NULL;
 239
 240         assert(ret);
 241
 242         nd = new0(sd_ndisc, 1);
 243         if (!nd)
 244                 return -ENOMEM;
 245
 246         nd->n_ref = 1;
 247
 248         nd->index = -1;
 249         nd->fd = -1;
 250
 251         LIST_HEAD_INIT(nd->prefixes);
 252
 253         *ret = nd;
 254         nd = NULL;
 255
 256         return 0;
 257 }
 258
 259 int sd_ndisc_get_mtu(sd_ndisc *nd, uint32_t *mtu) {
 260         assert_return(nd, -EINVAL);
 261         assert_return(mtu, -EINVAL);
 262
 263         if (nd->mtu == 0)
 264                 return -ENOMSG;
 265
 266         *mtu = nd->mtu;
 267
 268         return 0;
 269 }
 270
 271 static int prefix_match(const struct in6_addr *prefix, uint8_t prefixlen,
 272                         const struct in6_addr *addr,
 273                         uint8_t addr_prefixlen) {
 274         uint8_t bytes, mask, len;
 275
 276         assert_return(prefix, -EINVAL);
 277         assert_return(addr, -EINVAL);
 278
 279         len = MIN(prefixlen, addr_prefixlen);
 280
 281         bytes = len / 8;
 282         mask = 0xff << (8 - len % 8);
 283
 284         if (memcmp(prefix, addr, bytes) != 0 ||
 285             (prefix->s6_addr[bytes] & mask) != (addr->s6_addr[bytes] & mask))
 286                 return -EADDRNOTAVAIL;
 287
 288         return 0;
 289 }
 290
 291 static int ndisc_prefix_match(sd_ndisc *nd, const struct in6_addr *addr,
 292                               uint8_t addr_len, NDiscPrefix **result) {
 293         NDiscPrefix *prefix, *p;
 294         usec_t time_now;
 295         int r;
 296
 297         assert(nd);
 298
 299         r = sd_event_now(nd->event, clock_boottime_or_monotonic(), &time_now);
 300         if (r < 0)
 301                 return r;
 302
 303         LIST_FOREACH_SAFE(prefixes, prefix, p, nd->prefixes) {
 304                 if (prefix->valid_until < time_now) {
 305                         prefix = ndisc_prefix_unref(prefix);
 306
 307                         continue;
 308                 }
 309
 310                 if (prefix_match(&prefix->addr, prefix->len, addr, addr_len) >= 0) {
 311                         *result = prefix;
 312                         return 0;
 313                 }
 314         }
 315
 316         return -EADDRNOTAVAIL;
 317 }
 318
 319 int sd_ndisc_prefix_match(struct in6_addr *prefix, uint8_t prefixlen,
 320                           struct in6_addr *addr) {
 321         return prefix_match(prefix, prefixlen, addr, sizeof(addr->s6_addr) * 8);
 322 }
 323
 324 int sd_ndisc_get_prefixlen(sd_ndisc *nd, const struct in6_addr *addr,
 325                               uint8_t *prefixlen) {
 326         int r;
 327         NDiscPrefix *prefix;
 328
 329         assert_return(nd, -EINVAL);
 330         assert_return(addr, -EINVAL);
 331         assert_return(prefixlen, -EINVAL);
 332
 333         r = ndisc_prefix_match(nd, addr, sizeof(addr->s6_addr) * 8, &prefix);
 334         if (r < 0)
 335                 return r;
 336
 337         *prefixlen = prefix->len;
 338
 339         return 0;
 340 }
 341
 342 static int ndisc_prefix_update(sd_ndisc *nd, ssize_t len,
 343                                const struct nd_opt_prefix_info *prefix_opt) {
 344         NDiscPrefix *prefix;
 345         uint32_t lifetime;
 346         usec_t time_now;
 347         char time_string[FORMAT_TIMESPAN_MAX];
 348         int r;
 349
 350         assert(nd);
 351         assert(prefix_opt);
 352
 353         if (len < prefix_opt->nd_opt_pi_len)
 354                 return -ENOMSG;
 355
 356         if (!(prefix_opt->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_ONLINK))
 357                 return 0;
 358
 359         lifetime = be32toh(prefix_opt->nd_opt_pi_valid_time);
 360
 361         r = ndisc_prefix_match(nd, &prefix_opt->nd_opt_pi_prefix,
 362                                prefix_opt->nd_opt_pi_prefix_len, &prefix);
 363
 364         if (r < 0 && r != -EADDRNOTAVAIL)
 365                 return r;
 366
 367         /* if router advertisment prefix valid timeout is zero, the timeout
 368            callback will be called immediately to clean up the prefix */
 369
 370         if (r == -EADDRNOTAVAIL) {
 371                 r = ndisc_prefix_new(nd, &prefix);
 372                 if (r < 0)
 373                         return r;
 374
 375                 prefix->len = prefix_opt->nd_opt_pi_prefix_len;
 376
 377                 memcpy(&prefix->addr, &prefix_opt->nd_opt_pi_prefix,
 378                         sizeof(prefix->addr));
 379
 380                 log_ndisc(nd, "New prefix "SD_NDISC_ADDRESS_FORMAT_STR"/%d lifetime %d expires in %s",
 381                              SD_NDISC_ADDRESS_FORMAT_VAL(prefix->addr),
 382                              prefix->len, lifetime,
 383                              format_timespan(time_string, FORMAT_TIMESPAN_MAX, lifetime * USEC_PER_SEC, USEC_PER_SEC));
 384
 385                 LIST_PREPEND(prefixes, nd->prefixes, prefix);
 386
 387         } else {
 388                 if (prefix->len != prefix_opt->nd_opt_pi_prefix_len) {
 389                         uint8_t prefixlen;
 390
 391                         prefixlen = MIN(prefix->len, prefix_opt->nd_opt_pi_prefix_len);
 392
 393                         log_ndisc(nd, "Prefix length mismatch %d/%d using %d",
 394                                      prefix->len,
 395                                      prefix_opt->nd_opt_pi_prefix_len,
 396                                      prefixlen);
 397
 398                         prefix->len = prefixlen;
 399                 }
 400
 401                 log_ndisc(nd, "Update prefix "SD_NDISC_ADDRESS_FORMAT_STR"/%d lifetime %d expires in %s",
 402                              SD_NDISC_ADDRESS_FORMAT_VAL(prefix->addr),
 403                              prefix->len, lifetime,
 404                              format_timespan(time_string, FORMAT_TIMESPAN_MAX, lifetime * USEC_PER_SEC, USEC_PER_SEC));
 405         }
 406
 407         r = sd_event_now(nd->event, clock_boottime_or_monotonic(), &time_now);
 408         if (r < 0)
 409                 return r;
 410
 411         prefix->valid_until = time_now + lifetime * USEC_PER_SEC;
 412
 413         return r;
 414 }
 415
 416 static int ndisc_ra_parse(sd_ndisc *nd, struct nd_router_advert *ra,
 417                           ssize_t len) {
 418         void *opt;
 419         struct nd_opt_hdr *opt_hdr;
 420
 421         assert_return(nd, -EINVAL);
 422         assert_return(ra, -EINVAL);
 423
 424         len -= sizeof(*ra);
 425         if (len < NDISC_OPT_LEN_UNITS) {
 426                 log_ndisc(nd, "Router Advertisement below minimum length");
 427
 428                 return -ENOMSG;
 429         }
 430
 431         opt = ra + 1;
 432         opt_hdr = opt;
 433
 434         while (len != 0 && len >= opt_hdr->nd_opt_len * NDISC_OPT_LEN_UNITS) {
 435                 struct nd_opt_mtu *opt_mtu;
 436                 uint32_t mtu;
 437                 struct nd_opt_prefix_info *opt_prefix;
 438
 439                 if (opt_hdr->nd_opt_len == 0)
 440                         return -ENOMSG;
 441
 442                 switch (opt_hdr->nd_opt_type) {
 443                 case ND_OPT_MTU:
 444                         opt_mtu = opt;
 445
 446                         mtu = be32toh(opt_mtu->nd_opt_mtu_mtu);
 447
 448                         if (mtu != nd->mtu) {
 449                                 nd->mtu = MAX(mtu, IP6_MIN_MTU);
 450
 451                                 log_ndisc(nd, "Router Advertisement link MTU %d using %d",
 452                                              mtu, nd->mtu);
 453                         }
 454
 455                         break;
 456
 457                 case ND_OPT_PREFIX_INFORMATION:
 458                         opt_prefix = opt;
 459
 460                         ndisc_prefix_update(nd, len, opt_prefix);
 461
 462                         break;
 463                 }
 464
 465                 len -= opt_hdr->nd_opt_len * NDISC_OPT_LEN_UNITS;
 466                 opt = (void *)((char *)opt +
 467                         opt_hdr->nd_opt_len * NDISC_OPT_LEN_UNITS);
 468                 opt_hdr = opt;
 469         }
 470
 471         if (len > 0)
 472                 log_ndisc(nd, "Router Advertisement contains %zd bytes of trailing garbage", len);
 473
 474         return 0;
 475 }
 476
 477 static int ndisc_router_advertisment_recv(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
 478         sd_ndisc *nd = userdata;
 479         int r, buflen = 0;
 480         ssize_t len;
 481         _cleanup_free_ struct nd_router_advert *ra = NULL;
 482         int event = SD_NDISC_EVENT_ROUTER_ADVERTISMENT_NONE;
 483
 484         assert(s);
 485         assert(nd);
 486         assert(nd->event);
 487
 488         r = ioctl(fd, FIONREAD, &buflen);
 489         if (r < 0 || buflen <= 0)
 490                 buflen = ICMP6_RECV_SIZE;
 491
 492         ra = malloc(buflen);
 493         if (!ra)
 494                 return -ENOMEM;
 495
 496         len = read(fd, ra, buflen);
 497         if (len < 0) {
 498                 log_ndisc(nd, "Could not receive message from UDP socket: %m");
 499                 return 0;
 500         }
 501
 502         if (ra->nd_ra_type != ND_ROUTER_ADVERT)
 503                 return 0;
 504
 505         if (ra->nd_ra_code != 0)
 506                 return 0;
 507
 508         nd->timeout = sd_event_source_unref(nd->timeout);
 509
 510         nd->state = NDISC_STATE_ADVERTISMENT_LISTEN;
 511
 512         if (ra->nd_ra_flags_reserved & ND_RA_FLAG_OTHER )
 513                 event = SD_NDISC_EVENT_ROUTER_ADVERTISMENT_OTHER;
 514
 515         if (ra->nd_ra_flags_reserved & ND_RA_FLAG_MANAGED)
 516                 event = SD_NDISC_EVENT_ROUTER_ADVERTISMENT_MANAGED;
 517
 518         log_ndisc(nd, "Received Router Advertisement flags %s/%s",
 519                      ra->nd_ra_flags_reserved & ND_RA_FLAG_MANAGED? "MANAGED": "none",
 520                      ra->nd_ra_flags_reserved & ND_RA_FLAG_OTHER? "OTHER": "none");
 521
 522         if (event != SD_NDISC_EVENT_ROUTER_ADVERTISMENT_NONE) {
 523                 r = ndisc_ra_parse(nd, ra, len);
 524                 if (r < 0) {
 525                         log_ndisc(nd, "Could not parse Router Advertisement: %s",
 526                                      strerror(-r));
 527                         return 0;
 528                 }
 529         }
 530
 531         ndisc_notify(nd, event);
 532
 533         return 0;
 534 }
 535
 536 static int ndisc_router_solicitation_timeout(sd_event_source *s, uint64_t usec, void *userdata) {
 537         sd_ndisc *nd = userdata;
 538         uint64_t time_now, next_timeout;
 539         struct ether_addr unset = { };
 540         struct ether_addr *addr = NULL;
 541         int r;
 542
 543         assert(s);
 544         assert(nd);
 545         assert(nd->event);
 546
 547         nd->timeout = sd_event_source_unref(nd->timeout);
 548
 549         if (nd->nd_sent >= NDISC_MAX_ROUTER_SOLICITATIONS) {
 550                 ndisc_notify(nd, SD_NDISC_EVENT_ROUTER_ADVERTISMENT_TIMEOUT);
 551                 nd->state = NDISC_STATE_ADVERTISMENT_LISTEN;
 552         } else {
 553                 if (memcmp(&nd->mac_addr, &unset, sizeof(struct ether_addr)))
 554                         addr = &nd->mac_addr;
 555
 556                 r = icmp6_send_router_solicitation(nd->fd, addr);
 557                 if (r < 0)
 558                         log_ndisc(nd, "Error sending Router Solicitation");
 559                 else {
 560                         nd->state = NDISC_STATE_SOLICITATION_SENT;
 561                         log_ndisc(nd, "Sent Router Solicitation");
 562                 }
 563
 564                 nd->nd_sent++;
 565
 566                 r = sd_event_now(nd->event, clock_boottime_or_monotonic(), &time_now);
 567                 if (r < 0) {
 568                         ndisc_notify(nd, r);
 569                         return 0;
 570                 }
 571
 572                 next_timeout = time_now + NDISC_ROUTER_SOLICITATION_INTERVAL;
 573
 574                 r = sd_event_add_time(nd->event, &nd->timeout, clock_boottime_or_monotonic(),
 575                                       next_timeout, 0,
 576                                       ndisc_router_solicitation_timeout, nd);
 577                 if (r < 0) {
 578                         ndisc_notify(nd, r);
 579                         return 0;
 580                 }
 581
 582                 r = sd_event_source_set_priority(nd->timeout,
 583                                                  nd->event_priority);
 584                 if (r < 0) {
 585                         ndisc_notify(nd, r);
 586                         return 0;
 587                 }
 588
 589                 r = sd_event_source_set_description(nd->timeout, "ndisc-timeout");
 590                 if (r < 0) {
 591                         ndisc_notify(nd, r);
 592                         return 0;
 593                 }
 594         }
 595
 596         return 0;
 597 }
 598
 599 int sd_ndisc_stop(sd_ndisc *nd) {
 600         assert_return(nd, -EINVAL);
 601         assert_return(nd->event, -EINVAL);
 602
 603         log_ndisc(client, "Stop NDisc");
 604
 605         ndisc_init(nd);
 606
 607         nd->state = NDISC_STATE_IDLE;
 608
 609         return 0;
 610 }
 611
 612 int sd_ndisc_router_discovery_start(sd_ndisc *nd) {
 613         int r;
 614
 615         assert(nd);
 616         assert(nd->event);
 617
 618         if (nd->state != NDISC_STATE_IDLE)
 619                 return -EINVAL;
 620
 621         if (nd->index < 1)
 622                 return -EINVAL;
 623
 624         r = icmp6_bind_router_solicitation(nd->index);
 625         if (r < 0)
 626                 return r;
 627
 628         nd->fd = r;
 629
 630         r = sd_event_add_io(nd->event, &nd->recv, nd->fd, EPOLLIN,
 631                             ndisc_router_advertisment_recv, nd);
 632         if (r < 0)
 633                 goto error;
 634
 635         r = sd_event_source_set_priority(nd->recv, nd->event_priority);
 636         if (r < 0)
 637                 goto error;
 638
 639         r = sd_event_source_set_description(nd->recv, "ndisc-receive-message");
 640         if (r < 0)
 641                 goto error;
 642
 643         r = sd_event_add_time(nd->event, &nd->timeout, clock_boottime_or_monotonic(),
 644                               0, 0, ndisc_router_solicitation_timeout, nd);
 645         if (r < 0)
 646                 goto error;
 647
 648         r = sd_event_source_set_priority(nd->timeout, nd->event_priority);
 649         if (r < 0)
 650                 goto error;
 651
 652         r = sd_event_source_set_description(nd->timeout, "ndisc-timeout");
 653 error:
 654         if (r < 0)
 655                 ndisc_init(nd);
 656         else
 657                 log_ndisc(client, "Start Router Solicitation");
 658
 659         return r;
 660 }