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