src/ra.c

   1 /**
   2  * Copyright (C) 2012-2014 Steven Barth <steven@midlink.org>
   3  * Copyright (C) 2017-2018 Hans Dedecker <dedeckeh@gmail.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License v2 as published by
   7  * the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  */
  15
  16 #include <errno.h>
  17 #include <fcntl.h>
  18 #include <stdio.h>
  19 #include <signal.h>
  20 #include <string.h>
  21 #include <stddef.h>
  22 #include <stdbool.h>
  23 #include <syslog.h>
  24 #include <unistd.h>
  25 #include <resolv.h>
  26 #include <alloca.h>
  27
  28 #include <net/if.h>
  29 #include <arpa/inet.h>
  30 #include <sys/ioctl.h>
  31 #include <sys/socket.h>
  32 #include <sys/types.h>
  33 #include <netinet/in.h>
  34 #include <netinet/icmp6.h>
  35
  36 #include <linux/rtnetlink.h>
  37
  38 #ifndef SOL_NETLINK
  39 #define SOL_NETLINK 270
  40 #endif
  41
  42 #ifndef NETLINK_ADD_MEMBERSHIP
  43 #define NETLINK_ADD_MEMBERSHIP 1
  44 #endif
  45
  46 #ifndef IFF_LOWER_UP
  47 #define IFF_LOWER_UP 0x10000
  48 #endif
  49
  50 #include "odhcp6c.h"
  51 #include "ra.h"
  52
  53 static bool nocarrier = false;
  54
  55 static int sock = -1, rtnl = -1;
  56 static int if_index = 0;
  57 static char if_name[IF_NAMESIZE] = {0};
  58 static volatile int rs_attempt = 0;
  59 static struct in6_addr lladdr = IN6ADDR_ANY_INIT;
  60 static unsigned int ra_options = 0;
  61 static unsigned int ra_holdoff_interval = 0;
  62 static int ra_hoplimit = 0;
  63 static int ra_mtu = 0;
  64 static int ra_reachable = 0;
  65 static int ra_retransmit = 0;
  66
  67 struct {
  68         struct icmp6_hdr hdr;
  69         struct icmpv6_opt lladdr;
  70 } rs = {
  71         .hdr = {ND_ROUTER_SOLICIT, 0, 0, {{0}}},
  72         .lladdr = {ND_OPT_SOURCE_LINKADDR, 1, {0}},
  73 };
  74
  75 static void ra_send_rs(int signal __attribute__((unused)));
  76
  77 int ra_init(const char *ifname, const struct in6_addr *ifid,
  78                 unsigned int options, unsigned int holdoff_interval)
  79 {
  80         struct ifreq ifr;
  81
  82         ra_options = options;
  83         ra_holdoff_interval = holdoff_interval;
  84
  85         const pid_t ourpid = getpid();
  86         sock = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
  87         if (sock < 0)
  88                 goto failure;
  89
  90         memset(&ifr, 0, sizeof(ifr));
  91         strncpy(ifr.ifr_name, ifname, sizeof(ifr.ifr_name) - 1);
  92         if (ioctl(sock, SIOCGIFINDEX, &ifr) < 0)
  93                 goto failure;
  94
  95         if_index = ifr.ifr_ifindex;
  96         lladdr = *ifid;
  97
  98         rtnl = socket(AF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_ROUTE);
  99         if (rtnl < 0)
 100                 goto failure;
 101
 102         struct sockaddr_nl rtnl_kernel = { .nl_family = AF_NETLINK };
 103         if (connect(rtnl, (const struct sockaddr*)&rtnl_kernel, sizeof(rtnl_kernel)) < 0)
 104                 goto failure;
 105
 106         int val = RTNLGRP_LINK;
 107         if (setsockopt(rtnl, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &val, sizeof(val)) < 0)
 108                 goto failure;
 109
 110         if (fcntl(rtnl, F_SETOWN, ourpid) < 0)
 111                 goto failure;
 112
 113         if (fcntl(rtnl, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC) < 0)
 114                 goto failure;
 115
 116         struct {
 117                 struct nlmsghdr hdr;
 118                 struct ifinfomsg ifi;
 119         } req = {
 120                 .hdr = {sizeof(req), RTM_GETLINK, NLM_F_REQUEST, 1, 0},
 121                 .ifi = {.ifi_index = if_index}
 122         };
 123         if (send(rtnl, &req, sizeof(req), 0) < 0)
 124                 goto failure;
 125
 126         ra_link_up();
 127
 128         // Filter ICMPv6 package types
 129         struct icmp6_filter filt;
 130         ICMP6_FILTER_SETBLOCKALL(&filt);
 131         ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filt);
 132         if (setsockopt(sock, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt)) < 0)
 133                 goto failure;
 134
 135         // Bind to all-nodes
 136         struct ipv6_mreq an = {ALL_IPV6_NODES, if_index};
 137         if (setsockopt(sock, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &an, sizeof(an)) < 0)
 138                 goto failure;
 139
 140         // Let the kernel compute our checksums
 141         val = 2;
 142         if (setsockopt(sock, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val)) < 0)
 143                 goto failure;
 144
 145         // This is required by RFC 4861
 146         val = 255;
 147         if (setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val)) < 0)
 148                 goto failure;
 149
 150         // Receive multicast hops
 151         val = 1;
 152         if (setsockopt(sock, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &val, sizeof(val)) < 0)
 153                 goto failure;
 154
 155         // Bind to one device
 156         if (setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname)) < 0)
 157                 goto failure;
 158
 159         // Add async-mode
 160         if (fcntl(sock, F_SETOWN, ourpid) < 0)
 161                 goto failure;
 162
 163         val = fcntl(sock, F_GETFL);
 164         if (val < 0)
 165                 goto failure;
 166
 167         if (fcntl(sock, F_SETFL, val | O_ASYNC) < 0)
 168                 goto failure;
 169
 170         // Send RS
 171         signal(SIGALRM, ra_send_rs);
 172         ra_send_rs(SIGALRM);
 173
 174         return 0;
 175
 176 failure:
 177         if (sock >= 0)
 178                 close(sock);
 179
 180         if (rtnl >= 0)
 181                 close(rtnl);
 182
 183         return -1;
 184 }
 185
 186 static void ra_send_rs(int signal __attribute__((unused)))
 187 {
 188         const struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
 189         const struct icmpv6_opt llnull = {ND_OPT_SOURCE_LINKADDR, 1, {0}};
 190         size_t len;
 191
 192         if ((rs_attempt % 2 == 0) && memcmp(&rs.lladdr, &llnull, sizeof(llnull)))
 193                 len = sizeof(rs);
 194         else
 195                 len = sizeof(struct icmp6_hdr);
 196
 197         if (sendto(sock, &rs, len, MSG_DONTWAIT, (struct sockaddr*)&dest, sizeof(dest)) < 0)
 198                 syslog(LOG_ERR, "Failed to send RS (%s)",  strerror(errno));
 199
 200         if (++rs_attempt <= 3)
 201                 alarm(4);
 202 }
 203
 204 static int16_t pref_to_priority(uint8_t flags)
 205 {
 206         flags = (flags >> 3) & 0x03;
 207
 208         return (flags == 0x0) ? 512 : (flags == 0x1) ? 384 :
 209                         (flags == 0x3) ? 640 : -1;
 210 }
 211
 212 bool ra_link_up(void)
 213 {
 214         static bool firstcall = true;
 215         struct {
 216                 struct nlmsghdr hdr;
 217                 struct ifinfomsg msg;
 218                 uint8_t pad[4000];
 219         } resp;
 220         bool ret = false;
 221         ssize_t read;
 222
 223         do {
 224                 read = recv(rtnl, &resp, sizeof(resp), MSG_DONTWAIT);
 225
 226                 if (read < 0 || !NLMSG_OK(&resp.hdr, (size_t)read) ||
 227                                 resp.hdr.nlmsg_type != RTM_NEWLINK ||
 228                                 resp.msg.ifi_index != if_index)
 229                         continue;
 230
 231                 ssize_t alen = NLMSG_PAYLOAD(&resp.hdr, sizeof(resp.msg));
 232                 for (struct rtattr *rta = (struct rtattr*)(resp.pad);
 233                                 RTA_OK(rta, alen); rta = RTA_NEXT(rta, alen)) {
 234                         if (rta->rta_type == IFLA_ADDRESS &&
 235                                         RTA_PAYLOAD(rta) >= sizeof(rs.lladdr.data))
 236                                 memcpy(rs.lladdr.data, RTA_DATA(rta), sizeof(rs.lladdr.data));
 237                 }
 238
 239                 bool hascarrier = resp.msg.ifi_flags & IFF_LOWER_UP;
 240                 if (!firstcall && nocarrier != !hascarrier)
 241                         ret = true;
 242
 243                 nocarrier = !hascarrier;
 244                 firstcall = false;
 245         } while (read > 0);
 246
 247         if (ret) {
 248                 syslog(LOG_NOTICE, "carrier => %i event on %s", (int)!nocarrier, if_name);
 249
 250                 rs_attempt = 0;
 251                 ra_send_rs(SIGALRM);
 252         }
 253
 254         return ret;
 255 }
 256
 257 static bool ra_icmpv6_valid(struct sockaddr_in6 *source, int hlim, uint8_t *data, size_t len)
 258 {
 259         struct icmp6_hdr *hdr = (struct icmp6_hdr*)data;
 260         struct icmpv6_opt *opt, *end = (struct icmpv6_opt*)&data[len];
 261
 262         if (hlim != 255 || len < sizeof(*hdr) || hdr->icmp6_code)
 263                 return false;
 264
 265         switch (hdr->icmp6_type) {
 266         case ND_ROUTER_ADVERT:
 267                 if (!IN6_IS_ADDR_LINKLOCAL(&source->sin6_addr))
 268                         return false;
 269
 270                 opt = (struct icmpv6_opt*)((struct nd_router_advert*)data + 1);
 271                 break;
 272
 273         default:
 274                 return false;
 275         }
 276
 277         icmpv6_for_each_option(opt, opt, end)
 278                 ;
 279
 280         return opt == end;
 281 }
 282
 283 static bool ra_set_hoplimit(int val)
 284 {
 285         if (val > 0 && val != ra_hoplimit) {
 286                 ra_hoplimit = val;
 287                 return true;
 288         }
 289
 290         return false;
 291 }
 292
 293 static bool ra_set_mtu(int val)
 294 {
 295         if (val >= 1280 && val <= 65535 && ra_mtu != val) {
 296                 ra_mtu = val;
 297                 return true;
 298         }
 299
 300         return false;
 301 }
 302
 303 static bool ra_set_reachable(int val)
 304 {
 305         if (val > 0 && val <= 3600000 && ra_reachable != val) {
 306                 ra_reachable = val;
 307                 return true;
 308         }
 309
 310         return false;
 311 }
 312
 313 static bool ra_set_retransmit(int val)
 314 {
 315         if (val > 0 && val <= 60000 && ra_retransmit != val) {
 316                 ra_retransmit = val;
 317                 return true;
 318         }
 319
 320         return false;
 321 }
 322
 323 int ra_get_hoplimit(void)
 324 {
 325         return ra_hoplimit;
 326 }
 327
 328 int ra_get_mtu(void)
 329 {
 330         return ra_mtu;
 331 }
 332
 333 int ra_get_reachable(void)
 334 {
 335         return ra_reachable;
 336 }
 337
 338 int ra_get_retransmit(void)
 339 {
 340         return ra_retransmit;
 341 }
 342
 343 bool ra_process(void)
 344 {
 345         bool found = false;
 346         bool changed = false;
 347         uint8_t buf[1500] _aligned(4);
 348         union {
 349                 struct cmsghdr hdr;
 350                 uint8_t buf[CMSG_SPACE(sizeof(int))];
 351         } cmsg_buf;
 352         struct nd_router_advert *adv = (struct nd_router_advert*)buf;
 353         struct odhcp6c_entry *entry = alloca(sizeof(*entry) + 256);
 354         const struct in6_addr any = IN6ADDR_ANY_INIT;
 355
 356         memset(entry, 0, sizeof(*entry));
 357
 358         if (IN6_IS_ADDR_UNSPECIFIED(&lladdr)) {
 359                 struct sockaddr_in6 addr = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
 360                 socklen_t alen = sizeof(addr);
 361                 int sock = socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);
 362
 363                 if (sock >= 0) {
 364                         if (!connect(sock, (struct sockaddr*)&addr, sizeof(addr)) &&
 365                                         !getsockname(sock, (struct sockaddr*)&addr, &alen))
 366                                 lladdr = addr.sin6_addr;
 367
 368                         close(sock);
 369                 }
 370         }
 371
 372         while (true) {
 373                 struct sockaddr_in6 from;
 374                 struct iovec iov = {buf, sizeof(buf)};
 375                 struct msghdr msg = {
 376                         .msg_name = (void *) &from,
 377                         .msg_namelen = sizeof(from),
 378                         .msg_iov = &iov,
 379                         .msg_iovlen = 1,
 380                         .msg_control = cmsg_buf.buf,
 381                         .msg_controllen = sizeof(cmsg_buf),
 382                         .msg_flags = 0
 383                 };
 384                 struct icmpv6_opt *opt;
 385                 uint32_t router_valid;
 386                 int hlim = 0;
 387
 388                 ssize_t len = recvmsg(sock, &msg, MSG_DONTWAIT);
 389                 if (len <= 0)
 390                         break;
 391
 392                 if (IN6_IS_ADDR_UNSPECIFIED(&lladdr))
 393                         continue;
 394
 395                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL;
 396                                 ch = CMSG_NXTHDR(&msg, ch))
 397                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 398                                         ch->cmsg_type == IPV6_HOPLIMIT)
 399                                 memcpy(&hlim, CMSG_DATA(ch), sizeof(hlim));
 400
 401                 if (!ra_icmpv6_valid(&from, hlim, buf, len))
 402                         continue;
 403
 404                 if (!found) {
 405                         odhcp6c_expire();
 406                         found = true;
 407                 }
 408
 409                 router_valid = ntohs(adv->nd_ra_router_lifetime);
 410
 411                 /* RFC4861 §6.3.7
 412                  * Once the host sends a Router Solicitation, and receives a valid
 413                  * Router Advertisement with a non-zero Router Lifetime, the host MUST
 414                  * desist from sending additional solicitations on that interface
 415                  * Moreover, a host SHOULD send at least one solicitation in the case
 416                  * where an advertisement is received prior to having sent a solicitation.
 417                  */
 418                 if (rs_attempt > 0 && router_valid > 0) {
 419                         alarm(0);
 420                         rs_attempt = 0;
 421                 }
 422
 423                 // Parse default route
 424                 entry->target = any;
 425                 entry->length = 0;
 426                 entry->router = from.sin6_addr;
 427                 entry->priority = pref_to_priority(adv->nd_ra_flags_reserved);
 428                 if (entry->priority < 0)
 429                         entry->priority = pref_to_priority(0);
 430
 431                 entry->valid = router_valid;
 432                 entry->preferred = entry->valid;
 433                 changed |= odhcp6c_update_entry(STATE_RA_ROUTE, entry,
 434                                                 0, ra_holdoff_interval);
 435
 436                 // Parse hoplimit
 437                 changed |= ra_set_hoplimit(adv->nd_ra_curhoplimit);
 438
 439                 // Parse ND parameters
 440                 changed |= ra_set_reachable(ntohl(adv->nd_ra_reachable));
 441                 changed |= ra_set_retransmit(ntohl(adv->nd_ra_retransmit));
 442
 443                 // Evaluate options
 444                 icmpv6_for_each_option(opt, &adv[1], &buf[len]) {
 445                         if (opt->type == ND_OPT_MTU) {
 446                                 uint32_t *mtu = (uint32_t*)&opt->data[2];
 447                                 changed |= ra_set_mtu(ntohl(*mtu));
 448                         } else if (opt->type == ND_OPT_ROUTE_INFORMATION && opt->len <= 3) {
 449                                 struct icmpv6_opt_route_info *ri = (struct icmpv6_opt_route_info *)opt;
 450
 451                                 if (ri->prefix_len > 128) {
 452                                         continue;
 453                                 } else if (ri->prefix_len > 64) {
 454                                         if (ri->len < 2)
 455                                                 continue;
 456                                 } else if (ri->prefix_len > 0) {
 457                                         if (ri->len < 1)
 458                                                 continue;
 459                                 }
 460
 461                                 entry->router = from.sin6_addr;
 462                                 entry->target = any;
 463                                 entry->priority = pref_to_priority(ri->flags);
 464                                 entry->length = ri->prefix_len;
 465                                 entry->valid = ntohl(ri->lifetime);
 466                                 memcpy(&entry->target, ri->prefix, (ri->len - 1) * 8);
 467
 468                                 if (IN6_IS_ADDR_LINKLOCAL(&entry->target)
 469                                                 || IN6_IS_ADDR_LOOPBACK(&entry->target)
 470                                                 || IN6_IS_ADDR_MULTICAST(&entry->target))
 471                                         continue;
 472
 473                                 if (entry->priority > 0)
 474                                         changed |= odhcp6c_update_entry(STATE_RA_ROUTE, entry,
 475                                                                         0, ra_holdoff_interval);
 476                         } else if (opt->type == ND_OPT_PREFIX_INFORMATION && opt->len == 4) {
 477                                 struct nd_opt_prefix_info *pinfo = (struct nd_opt_prefix_info*)opt;
 478                                 entry->router = any;
 479                                 entry->target = pinfo->nd_opt_pi_prefix;
 480                                 entry->priority = 256;
 481                                 entry->length = pinfo->nd_opt_pi_prefix_len;
 482                                 entry->valid = ntohl(pinfo->nd_opt_pi_valid_time);
 483                                 entry->preferred = ntohl(pinfo->nd_opt_pi_preferred_time);
 484
 485                                 if (entry->length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry->target)
 486                                                 || IN6_IS_ADDR_LOOPBACK(&entry->target)
 487                                                 || IN6_IS_ADDR_MULTICAST(&entry->target)
 488                                                 || entry->valid < entry->preferred)
 489                                         continue;
 490
 491                                 if (pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_ONLINK)
 492                                         changed |= odhcp6c_update_entry(STATE_RA_ROUTE, entry,
 493                                                                         7200, ra_holdoff_interval);
 494
 495                                 if (!(pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_AUTO) ||
 496                                                 pinfo->nd_opt_pi_prefix_len != 64)
 497                                         continue;
 498
 499                                 entry->target.s6_addr32[2] = lladdr.s6_addr32[2];
 500                                 entry->target.s6_addr32[3] = lladdr.s6_addr32[3];
 501
 502                                 changed |= odhcp6c_update_entry(STATE_RA_PREFIX, entry,
 503                                                                 7200, ra_holdoff_interval);
 504                         } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 2) {
 505                                 entry->router = from.sin6_addr;
 506                                 entry->priority = 0;
 507                                 entry->length = 128;
 508                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 509                                 entry->valid = ntohl(*valid);
 510                                 entry->preferred = 0;
 511
 512                                 for (ssize_t i = 0; i < (opt->len - 1) / 2; ++i) {
 513                                         memcpy(&entry->target, &opt->data[6 + i * sizeof(entry->target)],
 514                                                         sizeof(entry->target));
 515                                         changed |= odhcp6c_update_entry(STATE_RA_DNS, entry,
 516                                                                         0, ra_holdoff_interval);
 517                                 }
 518                         } else if (opt->type == ND_OPT_DNSSL && opt->len > 1) {
 519                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 520                                 uint8_t *buf = &opt->data[6];
 521                                 uint8_t *end = &buf[(opt->len - 1) * 8];
 522
 523                                 entry->router = from.sin6_addr;
 524                                 entry->valid = ntohl(*valid);
 525
 526                                 while (buf < end) {
 527                                         int len = dn_expand(buf, end, buf, (char*)entry->auxtarget, 256);
 528                                         if (len < 1)
 529                                                 break;
 530
 531                                         buf = &buf[len];
 532                                         entry->auxlen = strlen((char*)entry->auxtarget);
 533
 534                                         if (entry->auxlen == 0)
 535                                                 continue;
 536
 537                                         changed |= odhcp6c_update_entry(STATE_RA_SEARCH, entry,
 538                                                                         0, ra_holdoff_interval);
 539                                         entry->auxlen = 0;
 540                                 }
 541                         }
 542                 }
 543
 544                 if (ra_options & RA_RDNSS_DEFAULT_LIFETIME) {
 545                         int states[2] = {STATE_RA_DNS, STATE_RA_SEARCH};
 546
 547                         for (size_t i = 0; i < 2; ++i) {
 548                                 size_t ra_dns_len;
 549                                 uint8_t *start = odhcp6c_get_state(states[i], &ra_dns_len);
 550
 551                                 for (struct odhcp6c_entry *c = (struct odhcp6c_entry*)start;
 552                                                         (uint8_t*)c < &start[ra_dns_len] &&
 553                                                         (uint8_t*)odhcp6c_next_entry(c) <= &start[ra_dns_len];
 554                                                         c = odhcp6c_next_entry(c)) {
 555                                         if (IN6_ARE_ADDR_EQUAL(&c->router, &from.sin6_addr) &&
 556                                                         c->valid > router_valid)
 557                                                 c->valid = router_valid;
 558                                 }
 559                         }
 560                 }
 561         }
 562
 563         if (found)
 564                 odhcp6c_expire();
 565
 566         return found && changed;
 567 }