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 static int ndisc_prefix_update(sd_ndisc *nd, ssize_t len,
 320                                const struct nd_opt_prefix_info *prefix_opt) {
 321         NDiscPrefix *prefix;
 322         uint32_t lifetime;
 323         usec_t time_now;
 324         char time_string[FORMAT_TIMESPAN_MAX];
 325         int r;
 326
 327         assert(nd);
 328         assert(prefix_opt);
 329
 330         if (len < prefix_opt->nd_opt_pi_len)
 331                 return -ENOMSG;
 332
 333         if (!(prefix_opt->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_ONLINK))
 334                 return 0;
 335
 336         lifetime = be32toh(prefix_opt->nd_opt_pi_valid_time);
 337
 338         r = ndisc_prefix_match(nd, &prefix_opt->nd_opt_pi_prefix,
 339                                prefix_opt->nd_opt_pi_prefix_len, &prefix);
 340
 341         if (r < 0 && r != -EADDRNOTAVAIL)
 342                 return r;
 343
 344         /* if router advertisment prefix valid timeout is zero, the timeout
 345            callback will be called immediately to clean up the prefix */
 346
 347         if (r == -EADDRNOTAVAIL) {
 348                 r = ndisc_prefix_new(nd, &prefix);
 349                 if (r < 0)
 350                         return r;
 351
 352                 prefix->len = prefix_opt->nd_opt_pi_prefix_len;
 353
 354                 memcpy(&prefix->addr, &prefix_opt->nd_opt_pi_prefix,
 355                         sizeof(prefix->addr));
 356
 357                 log_ndisc(nd, "New prefix "SD_NDISC_ADDRESS_FORMAT_STR"/%d lifetime %d expires in %s",
 358                              SD_NDISC_ADDRESS_FORMAT_VAL(prefix->addr),
 359                              prefix->len, lifetime,
 360                              format_timespan(time_string, FORMAT_TIMESPAN_MAX, lifetime * USEC_PER_SEC, USEC_PER_SEC));
 361
 362                 LIST_PREPEND(prefixes, nd->prefixes, prefix);
 363
 364         } else {
 365                 if (prefix->len != prefix_opt->nd_opt_pi_prefix_len) {
 366                         uint8_t prefixlen;
 367
 368                         prefixlen = MIN(prefix->len, prefix_opt->nd_opt_pi_prefix_len);
 369
 370                         log_ndisc(nd, "Prefix length mismatch %d/%d using %d",
 371                                      prefix->len,
 372                                      prefix_opt->nd_opt_pi_prefix_len,
 373                                      prefixlen);
 374
 375                         prefix->len = prefixlen;
 376                 }
 377
 378                 log_ndisc(nd, "Update prefix "SD_NDISC_ADDRESS_FORMAT_STR"/%d lifetime %d expires in %s",
 379                              SD_NDISC_ADDRESS_FORMAT_VAL(prefix->addr),
 380                              prefix->len, lifetime,
 381                              format_timespan(time_string, FORMAT_TIMESPAN_MAX, lifetime * USEC_PER_SEC, USEC_PER_SEC));
 382         }
 383
 384         r = sd_event_now(nd->event, clock_boottime_or_monotonic(), &time_now);
 385         if (r < 0)
 386                 return r;
 387
 388         prefix->valid_until = time_now + lifetime * USEC_PER_SEC;
 389
 390         return r;
 391 }
 392
 393 static int ndisc_ra_parse(sd_ndisc *nd, struct nd_router_advert *ra,
 394                           ssize_t len) {
 395         void *opt;
 396         struct nd_opt_hdr *opt_hdr;
 397
 398         assert_return(nd, -EINVAL);
 399         assert_return(ra, -EINVAL);
 400
 401         len -= sizeof(*ra);
 402         if (len < NDISC_OPT_LEN_UNITS) {
 403                 log_ndisc(nd, "Router Advertisement below minimum length");
 404
 405                 return -ENOMSG;
 406         }
 407
 408         opt = ra + 1;
 409         opt_hdr = opt;
 410
 411         while (len != 0 && len >= opt_hdr->nd_opt_len * NDISC_OPT_LEN_UNITS) {
 412                 struct nd_opt_mtu *opt_mtu;
 413                 uint32_t mtu;
 414                 struct nd_opt_prefix_info *opt_prefix;
 415
 416                 if (opt_hdr->nd_opt_len == 0)
 417                         return -ENOMSG;
 418
 419                 switch (opt_hdr->nd_opt_type) {
 420                 case ND_OPT_MTU:
 421                         opt_mtu = opt;
 422
 423                         mtu = be32toh(opt_mtu->nd_opt_mtu_mtu);
 424
 425                         if (mtu != nd->mtu) {
 426                                 nd->mtu = MAX(mtu, IP6_MIN_MTU);
 427
 428                                 log_ndisc(nd, "Router Advertisement link MTU %d using %d",
 429                                              mtu, nd->mtu);
 430                         }
 431
 432                         break;
 433
 434                 case ND_OPT_PREFIX_INFORMATION:
 435                         opt_prefix = opt;
 436
 437                         ndisc_prefix_update(nd, len, opt_prefix);
 438
 439                         break;
 440                 }
 441
 442                 len -= opt_hdr->nd_opt_len * NDISC_OPT_LEN_UNITS;
 443                 opt = (void *)((char *)opt +
 444                         opt_hdr->nd_opt_len * NDISC_OPT_LEN_UNITS);
 445                 opt_hdr = opt;
 446         }
 447
 448         if (len > 0)
 449                 log_ndisc(nd, "Router Advertisement contains %zd bytes of trailing garbage", len);
 450
 451         return 0;
 452 }
 453
 454 static int ndisc_router_advertisment_recv(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
 455         sd_ndisc *nd = userdata;
 456         int r, buflen = 0;
 457         ssize_t len;
 458         _cleanup_free_ struct nd_router_advert *ra = NULL;
 459         int event = SD_NDISC_EVENT_ROUTER_ADVERTISMENT_NONE;
 460
 461         assert(s);
 462         assert(nd);
 463         assert(nd->event);
 464
 465         r = ioctl(fd, FIONREAD, &buflen);
 466         if (r < 0 || buflen <= 0)
 467                 buflen = ICMP6_RECV_SIZE;
 468
 469         ra = malloc(buflen);
 470         if (!ra)
 471                 return -ENOMEM;
 472
 473         len = read(fd, ra, buflen);
 474         if (len < 0) {
 475                 log_ndisc(nd, "Could not receive message from UDP socket: %m");
 476                 return 0;
 477         }
 478
 479         if (ra->nd_ra_type != ND_ROUTER_ADVERT)
 480                 return 0;
 481
 482         if (ra->nd_ra_code != 0)
 483                 return 0;
 484
 485         nd->timeout = sd_event_source_unref(nd->timeout);
 486
 487         nd->state = NDISC_STATE_ADVERTISMENT_LISTEN;
 488
 489         if (ra->nd_ra_flags_reserved & ND_RA_FLAG_OTHER )
 490                 event = SD_NDISC_EVENT_ROUTER_ADVERTISMENT_OTHER;
 491
 492         if (ra->nd_ra_flags_reserved & ND_RA_FLAG_MANAGED)
 493                 event = SD_NDISC_EVENT_ROUTER_ADVERTISMENT_MANAGED;
 494
 495         log_ndisc(nd, "Received Router Advertisement flags %s/%s",
 496                      ra->nd_ra_flags_reserved & ND_RA_FLAG_MANAGED? "MANAGED": "none",
 497                      ra->nd_ra_flags_reserved & ND_RA_FLAG_OTHER? "OTHER": "none");
 498
 499         if (event != SD_NDISC_EVENT_ROUTER_ADVERTISMENT_NONE) {
 500                 r = ndisc_ra_parse(nd, ra, len);
 501                 if (r < 0) {
 502                         log_ndisc(nd, "Could not parse Router Advertisement: %s",
 503                                      strerror(-r));
 504                         return 0;
 505                 }
 506         }
 507
 508         ndisc_notify(nd, event);
 509
 510         return 0;
 511 }
 512
 513 static int ndisc_router_solicitation_timeout(sd_event_source *s, uint64_t usec, void *userdata) {
 514         sd_ndisc *nd = userdata;
 515         uint64_t time_now, next_timeout;
 516         struct ether_addr unset = { };
 517         struct ether_addr *addr = NULL;
 518         int r;
 519
 520         assert(s);
 521         assert(nd);
 522         assert(nd->event);
 523
 524         nd->timeout = sd_event_source_unref(nd->timeout);
 525
 526         if (nd->nd_sent >= NDISC_MAX_ROUTER_SOLICITATIONS) {
 527                 ndisc_notify(nd, SD_NDISC_EVENT_ROUTER_ADVERTISMENT_TIMEOUT);
 528                 nd->state = NDISC_STATE_ADVERTISMENT_LISTEN;
 529         } else {
 530                 if (memcmp(&nd->mac_addr, &unset, sizeof(struct ether_addr)))
 531                         addr = &nd->mac_addr;
 532
 533                 r = icmp6_send_router_solicitation(nd->fd, addr);
 534                 if (r < 0)
 535                         log_ndisc(nd, "Error sending Router Solicitation");
 536                 else {
 537                         nd->state = NDISC_STATE_SOLICITATION_SENT;
 538                         log_ndisc(nd, "Sent Router Solicitation");
 539                 }
 540
 541                 nd->nd_sent++;
 542
 543                 assert_se(sd_event_now(nd->event, clock_boottime_or_monotonic(), &time_now) >= 0);
 544
 545                 next_timeout = time_now + NDISC_ROUTER_SOLICITATION_INTERVAL;
 546
 547                 r = sd_event_add_time(nd->event, &nd->timeout, clock_boottime_or_monotonic(),
 548                                       next_timeout, 0,
 549                                       ndisc_router_solicitation_timeout, nd);
 550                 if (r < 0) {
 551                         ndisc_notify(nd, r);
 552                         return 0;
 553                 }
 554
 555                 r = sd_event_source_set_priority(nd->timeout, nd->event_priority);
 556                 if (r < 0)
 557                         return 0;
 558
 559                 r = sd_event_source_set_description(nd->timeout, "ndisc-timeout");
 560                 if (r < 0)
 561                         return 0;
 562         }
 563
 564         return 0;
 565 }
 566
 567 int sd_ndisc_stop(sd_ndisc *nd) {
 568         assert_return(nd, -EINVAL);
 569         assert_return(nd->event, -EINVAL);
 570
 571         log_ndisc(client, "Stop NDisc");
 572
 573         ndisc_init(nd);
 574
 575         nd->state = NDISC_STATE_IDLE;
 576
 577         return 0;
 578 }
 579
 580 int sd_ndisc_router_discovery_start(sd_ndisc *nd) {
 581         int r;
 582
 583         assert(nd);
 584         assert(nd->event);
 585
 586         if (nd->state != NDISC_STATE_IDLE)
 587                 return -EINVAL;
 588
 589         if (nd->index < 1)
 590                 return -EINVAL;
 591
 592         r = icmp6_bind_router_solicitation(nd->index);
 593         if (r < 0)
 594                 return r;
 595
 596         nd->fd = r;
 597
 598         r = sd_event_add_io(nd->event, &nd->recv, nd->fd, EPOLLIN,
 599                             ndisc_router_advertisment_recv, nd);
 600         if (r < 0)
 601                 goto error;
 602
 603         r = sd_event_source_set_priority(nd->recv, nd->event_priority);
 604         if (r < 0)
 605                 goto error;
 606
 607         r = sd_event_source_set_description(nd->recv, "ndisc-receive-message");
 608         if (r < 0)
 609                 goto error;
 610
 611         r = sd_event_add_time(nd->event, &nd->timeout, clock_boottime_or_monotonic(),
 612                               0, 0, ndisc_router_solicitation_timeout, nd);
 613         if (r < 0)
 614                 goto error;
 615
 616         r = sd_event_source_set_priority(nd->timeout, nd->event_priority);
 617         if (r < 0)
 618                 goto error;
 619
 620         r = sd_event_source_set_description(nd->timeout, "ndisc-timeout");
 621 error:
 622         if (r < 0)
 623                 ndisc_init(nd);
 624         else
 625                 log_ndisc(client, "Start Router Solicitation");
 626
 627         return r;
 628 }