src/router.c

   1 /**
   2  * Copyright (C) 2012-2013 Steven Barth <steven@midlink.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License v2 as published by
   6  * the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  */
  14
  15 #include <errno.h>
  16 #include <fcntl.h>
  17 #include <signal.h>
  18 #include <resolv.h>
  19 #include <stdio.h>
  20 #include <stdlib.h>
  21 #include <unistd.h>
  22 #include <stdbool.h>
  23 #include <arpa/inet.h>
  24 #include <net/route.h>
  25
  26 #include "router.h"
  27 #include "odhcpd.h"
  28
  29
  30 static void forward_router_solicitation(const struct interface *iface);
  31 static void forward_router_advertisement(uint8_t *data, size_t len);
  32
  33 static void handle_icmpv6(void *addr, void *data, size_t len,
  34                 struct interface *iface, void *dest);
  35 static void trigger_router_advert(struct uloop_timeout *event);
  36 static void sigusr1_refresh(int signal);
  37
  38 static struct odhcpd_event router_event = {.uloop = {.fd = -1}, .handle_dgram = handle_icmpv6, };
  39
  40 static FILE *fp_route = NULL;
  41 #define RA_IOV_LEN 6
  42
  43 #define TIME_LEFT(t1, now) ((t1) != UINT32_MAX ? (t1) - (now) : UINT32_MAX)
  44
  45 int init_router(void)
  46 {
  47         // Open ICMPv6 socket
  48         int sock = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
  49         if (sock < 0 && errno != EAFNOSUPPORT) {
  50                 syslog(LOG_ERR, "Failed to open RAW-socket: %s", strerror(errno));
  51                 return -1;
  52         }
  53
  54         // Let the kernel compute our checksums
  55         int val = 2;
  56         setsockopt(sock, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
  57
  58         // This is required by RFC 4861
  59         val = 255;
  60         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
  61         setsockopt(sock, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &val, sizeof(val));
  62
  63         // We need to know the source interface
  64         val = 1;
  65         setsockopt(sock, IPPROTO_IPV6, IPV6_RECVPKTINFO, &val, sizeof(val));
  66         setsockopt(sock, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &val, sizeof(val));
  67
  68         // Don't loop back
  69         val = 0;
  70         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &val, sizeof(val));
  71
  72         // Filter ICMPv6 package types
  73         struct icmp6_filter filt;
  74         ICMP6_FILTER_SETBLOCKALL(&filt);
  75         ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filt);
  76         ICMP6_FILTER_SETPASS(ND_ROUTER_SOLICIT, &filt);
  77         setsockopt(sock, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
  78
  79         // Register socket
  80         router_event.uloop.fd = sock;
  81         odhcpd_register(&router_event);
  82
  83         if (!(fp_route = fopen("/proc/net/ipv6_route", "r")))
  84                 syslog(LOG_ERR, "Failed to open routing table: %s",
  85                                 strerror(errno));
  86
  87         signal(SIGUSR1, sigusr1_refresh);
  88         return 0;
  89 }
  90
  91
  92 int setup_router_interface(struct interface *iface, bool enable)
  93 {
  94         if (!fp_route || router_event.uloop.fd < 0)
  95                 return -1;
  96
  97         struct ipv6_mreq all_nodes = {ALL_IPV6_NODES, iface->ifindex};
  98         struct ipv6_mreq all_routers = {ALL_IPV6_ROUTERS, iface->ifindex};
  99
 100         uloop_timeout_cancel(&iface->timer_rs);
 101         iface->timer_rs.cb = NULL;
 102
 103         if (iface->ifindex <= 0)
 104                 return -1;
 105
 106         setsockopt(router_event.uloop.fd, IPPROTO_IPV6, IPV6_DROP_MEMBERSHIP,
 107                         &all_nodes, sizeof(all_nodes));
 108         setsockopt(router_event.uloop.fd, IPPROTO_IPV6, IPV6_DROP_MEMBERSHIP,
 109                         &all_routers, sizeof(all_routers));
 110
 111         if (!enable) {
 112                 if (iface->ra)
 113                         trigger_router_advert(&iface->timer_rs);
 114         } else {
 115                 void *mreq = &all_routers;
 116
 117                 if (iface->ra == RELAYD_RELAY && iface->master) {
 118                         mreq = &all_nodes;
 119                         forward_router_solicitation(iface);
 120                 } else if (iface->ra == RELAYD_SERVER && !iface->master) {
 121                         iface->timer_rs.cb = trigger_router_advert;
 122                         uloop_timeout_set(&iface->timer_rs, 1000);
 123                 }
 124
 125                 if (iface->ra == RELAYD_RELAY || (iface->ra == RELAYD_SERVER && !iface->master))
 126                         setsockopt(router_event.uloop.fd, IPPROTO_IPV6,
 127                                         IPV6_ADD_MEMBERSHIP, mreq, sizeof(all_nodes));
 128         }
 129         return 0;
 130 }
 131
 132
 133 // Signal handler to resend all RDs
 134 static void sigusr1_refresh(_unused int signal)
 135 {
 136         struct interface *iface;
 137         list_for_each_entry(iface, &interfaces, head)
 138                 if (iface->ra == RELAYD_SERVER && !iface->master)
 139                         uloop_timeout_set(&iface->timer_rs, 1000);
 140 }
 141
 142 static bool router_icmpv6_valid(struct sockaddr_in6 *source, uint8_t *data, size_t len)
 143 {
 144         struct icmp6_hdr *hdr = (struct icmp6_hdr *)data;
 145         struct icmpv6_opt *opt, *end = (struct icmpv6_opt*)&data[len];
 146
 147         /* Hoplimit is already checked in odhcpd_receive_packets */
 148         if (len < sizeof(*hdr) || hdr->icmp6_code)
 149                 return false;
 150
 151         switch (hdr->icmp6_type) {
 152         case ND_ROUTER_ADVERT:
 153                 if (!IN6_IS_ADDR_LINKLOCAL(&source->sin6_addr))
 154                         return false;
 155
 156                 opt = (struct icmpv6_opt *)((struct nd_router_advert *)data + 1);
 157                 break;
 158
 159         case ND_ROUTER_SOLICIT:
 160                 opt = (struct icmpv6_opt *)((struct nd_router_solicit *)data + 1);
 161                 break;
 162
 163         default:
 164                 return false;
 165         }
 166
 167         icmpv6_for_each_option(opt, opt, end)
 168                 if (opt->type == ND_OPT_SOURCE_LINKADDR &&
 169                                 IN6_IS_ADDR_UNSPECIFIED(&source->sin6_addr) &&
 170                                 hdr->icmp6_type == ND_ROUTER_SOLICIT)
 171                         return false;
 172
 173         // Check all options parsed successfully
 174         return opt == end;
 175 }
 176
 177
 178 // Detect whether a default route exists, also find the source prefixes
 179 static bool parse_routes(struct odhcpd_ipaddr *n, ssize_t len)
 180 {
 181         rewind(fp_route);
 182
 183         char line[512], ifname[16];
 184         bool found_default = false;
 185         struct odhcpd_ipaddr p = {IN6ADDR_ANY_INIT, 0, 0, 0, 0};
 186         while (fgets(line, sizeof(line), fp_route)) {
 187                 uint32_t rflags;
 188                 if (sscanf(line, "00000000000000000000000000000000 00 "
 189                                 "%*s %*s %*s %*s %*s %*s %*s %15s", ifname) &&
 190                                 strcmp(ifname, "lo")) {
 191                         found_default = true;
 192                 } else if (sscanf(line, "%8" SCNx32 "%8" SCNx32 "%*8" SCNx32 "%*8" SCNx32 " %hhx %*s "
 193                                 "%*s 00000000000000000000000000000000 %*s %*s %*s %" SCNx32 " lo",
 194                                 &p.addr.s6_addr32[0], &p.addr.s6_addr32[1], &p.prefix, &rflags) &&
 195                                 p.prefix > 0 && (rflags & RTF_NONEXTHOP) && (rflags & RTF_REJECT)) {
 196                         // Find source prefixes by scanning through unreachable-routes
 197                         p.addr.s6_addr32[0] = htonl(p.addr.s6_addr32[0]);
 198                         p.addr.s6_addr32[1] = htonl(p.addr.s6_addr32[1]);
 199
 200                         for (ssize_t i = 0; i < len; ++i) {
 201                                 if (n[i].prefix <= 64 && n[i].prefix >= p.prefix &&
 202                                                 !odhcpd_bmemcmp(&p.addr, &n[i].addr, p.prefix)) {
 203                                         n[i].dprefix = p.prefix;
 204                                         break;
 205                                 }
 206                         }
 207
 208                 }
 209         }
 210
 211         return found_default;
 212 }
 213
 214 // Router Advert server mode
 215 static uint64_t send_router_advert(struct interface *iface, const struct in6_addr *from)
 216 {
 217         time_t now = odhcpd_time();
 218         int mtu = odhcpd_get_interface_config(iface->ifname, "mtu");
 219         int hlim = odhcpd_get_interface_config(iface->ifname, "hop_limit");
 220
 221         if (mtu < 1280)
 222                 mtu = 1280;
 223
 224         struct {
 225                 struct nd_router_advert h;
 226                 struct icmpv6_opt lladdr;
 227                 struct nd_opt_mtu mtu;
 228                 struct nd_opt_prefix_info prefix[sizeof(iface->ia_addr) / sizeof(*iface->ia_addr)];
 229         } adv = {
 230                 .h = {{.icmp6_type = ND_ROUTER_ADVERT, .icmp6_code = 0}, 0, 0},
 231                 .lladdr = {ND_OPT_SOURCE_LINKADDR, 1, {0}},
 232                 .mtu = {ND_OPT_MTU, 1, 0, htonl(mtu)},
 233         };
 234
 235         if (hlim > 0)
 236                 adv.h.nd_ra_curhoplimit = hlim;
 237
 238         if (iface->dhcpv6)
 239                 adv.h.nd_ra_flags_reserved = ND_RA_FLAG_OTHER;
 240
 241         if (iface->managed >= RELAYD_MANAGED_MFLAG)
 242                 adv.h.nd_ra_flags_reserved |= ND_RA_FLAG_MANAGED;
 243
 244         if (iface->route_preference < 0)
 245                 adv.h.nd_ra_flags_reserved |= ND_RA_PREF_LOW;
 246         else if (iface->route_preference > 0)
 247                 adv.h.nd_ra_flags_reserved |= ND_RA_PREF_HIGH;
 248         odhcpd_get_mac(iface, adv.lladdr.data);
 249
 250         // If not currently shutting down
 251         struct odhcpd_ipaddr addrs[RELAYD_MAX_ADDRS];
 252         ssize_t ipcnt = 0;
 253         int64_t minvalid = INT64_MAX;
 254
 255         // If not shutdown
 256         if (iface->timer_rs.cb) {
 257                 ipcnt = iface->ia_addr_len;
 258                 memcpy(addrs, iface->ia_addr, ipcnt * sizeof(*addrs));
 259
 260                 // Check default route
 261                 if (iface->default_router > 1)
 262                         adv.h.nd_ra_router_lifetime = htons(iface->default_router);
 263                 else if (parse_routes(addrs, ipcnt))
 264                         adv.h.nd_ra_router_lifetime = htons(1);
 265
 266                 syslog(LOG_INFO, "Initial RA router lifetime %d, %d address(es) available on %s",
 267                                 ntohs(adv.h.nd_ra_router_lifetime), (int)ipcnt, iface->ifname);
 268         }
 269
 270         // Construct Prefix Information options
 271         size_t cnt = 0;
 272
 273         struct in6_addr dns_pref, *dns_addr = &dns_pref;
 274         size_t dns_cnt = 1;
 275
 276         odhcpd_get_linklocal_interface_address(iface->ifindex, &dns_pref);
 277
 278         for (ssize_t i = 0; i < ipcnt; ++i) {
 279                 struct odhcpd_ipaddr *addr = &addrs[i];
 280
 281                 if (addr->prefix > 96 || addr->valid <= (uint32_t)now) {
 282                         char namebuf[INET6_ADDRSTRLEN];
 283
 284                         inet_ntop(AF_INET6, addr, namebuf, sizeof(namebuf));
 285                         syslog(LOG_INFO, "Address %s (prefix %d, valid %u) not suitable as RA prefix on %s",
 286                                         namebuf, addr->prefix, addr->valid, iface->ifname);
 287                         continue;
 288                 }
 289
 290                 struct nd_opt_prefix_info *p = NULL;
 291                 for (size_t i = 0; i < cnt; ++i) {
 292                         if (addr->prefix == adv.prefix[i].nd_opt_pi_prefix_len &&
 293                                         !odhcpd_bmemcmp(&adv.prefix[i].nd_opt_pi_prefix,
 294                                         &addr->addr, addr->prefix))
 295                                 p = &adv.prefix[i];
 296                 }
 297
 298                 if (!p) {
 299                         if (cnt >= ARRAY_SIZE(adv.prefix))
 300                                 break;
 301
 302                         p = &adv.prefix[cnt++];
 303                 }
 304
 305                 if (addr->preferred > (uint32_t)now &&
 306                                 minvalid > 1000LL * TIME_LEFT(addr->valid, now))
 307                         minvalid = 1000LL * TIME_LEFT(addr->valid, now);
 308
 309                 uint32_t this_lifetime = TIME_LEFT(addr->valid, now);
 310                 if (this_lifetime > UINT16_MAX)
 311                         this_lifetime = UINT16_MAX;
 312                 if ((!IN6_IS_ADDR_ULA(&addr->addr) || iface->default_router)
 313                                 && adv.h.nd_ra_router_lifetime
 314                                 && ntohs(adv.h.nd_ra_router_lifetime) < this_lifetime) {
 315                         adv.h.nd_ra_router_lifetime = htons(this_lifetime);
 316
 317                         syslog(LOG_INFO, "Updating RA router lifetime to %d on %s", this_lifetime, iface->ifname);
 318                 }
 319
 320                 odhcpd_bmemcpy(&p->nd_opt_pi_prefix, &addr->addr,
 321                                 (iface->ra_advrouter) ? 128 : addr->prefix);
 322                 p->nd_opt_pi_type = ND_OPT_PREFIX_INFORMATION;
 323                 p->nd_opt_pi_len = 4;
 324                 p->nd_opt_pi_prefix_len = (addr->prefix < 64) ? 64 : addr->prefix;
 325                 p->nd_opt_pi_flags_reserved = 0;
 326                 if (!iface->ra_not_onlink)
 327                         p->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_ONLINK;
 328                 if (iface->managed < RELAYD_MANAGED_NO_AFLAG && addr->prefix <= 64)
 329                         p->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_AUTO;
 330                 if (iface->ra_advrouter)
 331                         p->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_RADDR;
 332                 p->nd_opt_pi_valid_time = htonl(TIME_LEFT(addr->valid, now));
 333                 if (addr->preferred > (uint32_t)now)
 334                         p->nd_opt_pi_preferred_time = htonl(TIME_LEFT(addr->preferred, now));
 335                 else if (addr->valid - now < 7200)
 336                         p->nd_opt_pi_valid_time = 0;
 337         }
 338
 339         if (!iface->default_router && adv.h.nd_ra_router_lifetime == htons(1)) {
 340                 syslog(LOG_WARNING, "A default route is present but there is no public prefix "
 341                                 "on %s thus we don't announce a default route!", iface->ifname);
 342                 adv.h.nd_ra_router_lifetime = 0;
 343         }
 344
 345         // DNS Recursive DNS
 346         if (iface->dns_cnt > 0) {
 347                 dns_addr = iface->dns;
 348                 dns_cnt = iface->dns_cnt;
 349         }
 350
 351         if (!dns_addr || IN6_IS_ADDR_UNSPECIFIED(dns_addr))
 352                 dns_cnt = 0;
 353
 354         struct {
 355                 uint8_t type;
 356                 uint8_t len;
 357                 uint8_t pad;
 358                 uint8_t pad2;
 359                 uint32_t lifetime;
 360         } dns = {ND_OPT_RECURSIVE_DNS, (1 + (2 * dns_cnt)), 0, 0, 0};
 361
 362
 363
 364         // DNS Search options
 365         uint8_t search_buf[256], *search_domain = iface->search;
 366         size_t search_len = iface->search_len, search_padded = 0;
 367
 368         if (!search_domain && !res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 369                 int len = dn_comp(_res.dnsrch[0], search_buf,
 370                                 sizeof(search_buf), NULL, NULL);
 371                 if (len > 0) {
 372                         search_domain = search_buf;
 373                         search_len = len;
 374                 }
 375         }
 376
 377         if (search_len > 0)
 378                 search_padded = ((search_len + 7) & (~7)) + 8;
 379
 380         struct {
 381                 uint8_t type;
 382                 uint8_t len;
 383                 uint8_t pad;
 384                 uint8_t pad2;
 385                 uint32_t lifetime;
 386                 uint8_t name[];
 387         } *search = alloca(sizeof(*search) + search_padded);
 388
 389         search->type = ND_OPT_DNS_SEARCH;
 390         search->len = search_len ? ((sizeof(*search) + search_padded) / 8) : 0;
 391         search->pad = 0;
 392         search->pad2 = 0;
 393         memcpy(search->name, search_domain, search_len);
 394         memset(&search->name[search_len], 0, search_padded - search_len);
 395
 396
 397         size_t routes_cnt = 0;
 398         struct {
 399                 uint8_t type;
 400                 uint8_t len;
 401                 uint8_t prefix;
 402                 uint8_t flags;
 403                 uint32_t lifetime;
 404                 uint32_t addr[4];
 405         } routes[RELAYD_MAX_PREFIXES];
 406
 407         for (ssize_t i = 0; i < ipcnt; ++i) {
 408                 struct odhcpd_ipaddr *addr = &addrs[i];
 409                 if (addr->dprefix > 64 || addr->dprefix == 0 || addr->valid <= (uint32_t)now ||
 410                                 (addr->dprefix == 64 && addr->prefix == 64)) {
 411                         continue; // Address not suitable
 412                 } else if (addr->dprefix > 32) {
 413                         addr->addr.s6_addr32[1] &= htonl(~((1U << (64 - addr->dprefix)) - 1));
 414                 } else if (addr->dprefix <= 32) {
 415                         addr->addr.s6_addr32[0] &= htonl(~((1U << (32 - addr->dprefix)) - 1));
 416                         addr->addr.s6_addr32[1] = 0;
 417                 }
 418
 419                 routes[routes_cnt].type = ND_OPT_ROUTE_INFO;
 420                 routes[routes_cnt].len = sizeof(*routes) / 8;
 421                 routes[routes_cnt].prefix = addr->dprefix;
 422                 routes[routes_cnt].flags = 0;
 423                 if (iface->route_preference < 0)
 424                         routes[routes_cnt].flags |= ND_RA_PREF_LOW;
 425                 else if (iface->route_preference > 0)
 426                         routes[routes_cnt].flags |= ND_RA_PREF_HIGH;
 427                 routes[routes_cnt].lifetime = htonl(TIME_LEFT(addr->valid, now));
 428                 routes[routes_cnt].addr[0] = addr->addr.s6_addr32[0];
 429                 routes[routes_cnt].addr[1] = addr->addr.s6_addr32[1];
 430                 routes[routes_cnt].addr[2] = 0;
 431                 routes[routes_cnt].addr[3] = 0;
 432
 433                 ++routes_cnt;
 434         }
 435
 436         // Calculate periodic transmit
 437         int msecs = 0;
 438         uint32_t maxival = iface->ra_maxinterval * 1000;
 439         uint32_t minival;
 440
 441         if (maxival < 4000 || maxival > MaxRtrAdvInterval * 1000)
 442                 maxival = MaxRtrAdvInterval * 1000;
 443
 444         if (maxival > minvalid / 3) {
 445                 maxival = minvalid / 3;
 446
 447                 if (maxival < 4000)
 448                         maxival = 4000;
 449         }
 450
 451         minival = (maxival * 3) / 4;
 452
 453         search->lifetime = htonl(maxival / 100);
 454         dns.lifetime = search->lifetime;
 455
 456         odhcpd_urandom(&msecs, sizeof(msecs));
 457         msecs = (labs(msecs) % (maxival - minival)) + minival;
 458
 459         struct icmpv6_opt adv_interval = {
 460                 .type = ND_OPT_RTR_ADV_INTERVAL,
 461                 .len = 1,
 462                 .data = {0, 0, maxival >> 24, maxival >> 16, maxival >> 8, maxival}
 463         };
 464
 465         struct iovec iov[RA_IOV_LEN] = {
 466                         {&adv, (uint8_t*)&adv.prefix[cnt] - (uint8_t*)&adv},
 467                         {&routes, routes_cnt * sizeof(*routes)},
 468                         {&dns, (dns_cnt) ? sizeof(dns) : 0},
 469                         {dns_addr, dns_cnt * sizeof(*dns_addr)},
 470                         {search, search->len * 8},
 471                         {&adv_interval, adv_interval.len * 8}};
 472         struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_NODES, 0};
 473
 474         if (from && !IN6_IS_ADDR_UNSPECIFIED(from))
 475                 dest.sin6_addr = *from;
 476
 477         odhcpd_send(router_event.uloop.fd,
 478                         &dest, iov, ARRAY_SIZE(iov), iface);
 479
 480         return msecs;
 481 }
 482
 483
 484 static void trigger_router_advert(struct uloop_timeout *event)
 485 {
 486         struct interface *iface = container_of(event, struct interface, timer_rs);
 487         int msecs = send_router_advert(iface, NULL);
 488
 489         // Rearm timer if not shut down
 490         if (event->cb)
 491                 uloop_timeout_set(event, msecs);
 492 }
 493
 494
 495 // Event handler for incoming ICMPv6 packets
 496 static void handle_icmpv6(void *addr, void *data, size_t len,
 497                 struct interface *iface, _unused void *dest)
 498 {
 499         struct icmp6_hdr *hdr = data;
 500         struct sockaddr_in6 *from = addr;
 501
 502         if (!router_icmpv6_valid(addr, data, len))
 503                 return;
 504
 505         if ((iface->ra == RELAYD_SERVER && !iface->master)) { // Server mode
 506                 if (hdr->icmp6_type == ND_ROUTER_SOLICIT)
 507                         send_router_advert(iface, &from->sin6_addr);
 508         } else if (iface->ra == RELAYD_RELAY) { // Relay mode
 509                 if (hdr->icmp6_type == ND_ROUTER_ADVERT && iface->master)
 510                         forward_router_advertisement(data, len);
 511                 else if (hdr->icmp6_type == ND_ROUTER_SOLICIT && !iface->master)
 512                         forward_router_solicitation(odhcpd_get_master_interface());
 513         }
 514 }
 515
 516
 517 // Forward router solicitation
 518 static void forward_router_solicitation(const struct interface *iface)
 519 {
 520         if (!iface)
 521                 return;
 522
 523         struct icmp6_hdr rs = {ND_ROUTER_SOLICIT, 0, 0, {{0}}};
 524         struct iovec iov = {&rs, sizeof(rs)};
 525         struct sockaddr_in6 all_routers =
 526                 {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, iface->ifindex};
 527
 528         syslog(LOG_NOTICE, "Sending RS to %s", iface->ifname);
 529         odhcpd_send(router_event.uloop.fd, &all_routers, &iov, 1, iface);
 530 }
 531
 532
 533 // Handler for incoming router solicitations on slave interfaces
 534 static void forward_router_advertisement(uint8_t *data, size_t len)
 535 {
 536         struct nd_router_advert *adv = (struct nd_router_advert *)data;
 537
 538         // Rewrite options
 539         uint8_t *end = data + len;
 540         uint8_t *mac_ptr = NULL;
 541         struct in6_addr *dns_ptr = NULL;
 542         size_t dns_count = 0;
 543
 544         struct icmpv6_opt *opt;
 545         icmpv6_for_each_option(opt, &adv[1], end) {
 546                 if (opt->type == ND_OPT_SOURCE_LINKADDR) {
 547                         // Store address of source MAC-address
 548                         mac_ptr = opt->data;
 549                 } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 1) {
 550                         // Check if we have to rewrite DNS
 551                         dns_ptr = (struct in6_addr*)&opt->data[6];
 552                         dns_count = (opt->len - 1) / 2;
 553                 }
 554         }
 555
 556         syslog(LOG_NOTICE, "Got a RA");
 557
 558         // Indicate a proxy, however we don't follow the rest of RFC 4389 yet
 559         adv->nd_ra_flags_reserved |= ND_RA_FLAG_PROXY;
 560
 561         // Forward advertisement to all slave interfaces
 562         struct sockaddr_in6 all_nodes = {AF_INET6, 0, 0, ALL_IPV6_NODES, 0};
 563         struct iovec iov = {data, len};
 564
 565         struct interface *iface;
 566         list_for_each_entry(iface, &interfaces, head) {
 567                 if (iface->ra != RELAYD_RELAY || iface->master)
 568                         continue;
 569
 570                 // Fixup source hardware address option
 571                 if (mac_ptr)
 572                         odhcpd_get_mac(iface, mac_ptr);
 573
 574                 // If we have to rewrite DNS entries
 575                 if (iface->always_rewrite_dns && dns_ptr && dns_count > 0) {
 576                         const struct in6_addr *rewrite = iface->dns;
 577                         struct in6_addr addr;
 578                         size_t rewrite_cnt = iface->dns_cnt;
 579
 580                         if (rewrite_cnt == 0) {
 581                                 if (odhcpd_get_linklocal_interface_address(iface->ifindex, &addr))
 582                                         continue; // Unable to comply
 583
 584                                 rewrite = &addr;
 585                                 rewrite_cnt = 1;
 586                         }
 587
 588                         // Copy over any other addresses
 589                         for (size_t i = 0; i < dns_count; ++i) {
 590                                 size_t j = (i < rewrite_cnt) ? i : rewrite_cnt - 1;
 591                                 dns_ptr[i] = rewrite[j];
 592                         }
 593                 }
 594
 595                 odhcpd_send(router_event.uloop.fd, &all_nodes, &iov, 1, iface);
 596         }
 597 }