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