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 <net/route.h>
  24
  25 #include "router.h"
  26 #include "odhcpd.h"
  27
  28
  29 static void forward_router_solicitation(const struct interface *iface);
  30 static void forward_router_advertisement(uint8_t *data, size_t len);
  31
  32 static void handle_icmpv6(void *addr, void *data, size_t len,
  33                 struct interface *iface, void *dest);
  34 static void trigger_router_advert(struct uloop_timeout *event);
  35 static void sigusr1_refresh(int signal);
  36
  37 static struct odhcpd_event router_event = {{.fd = -1}, handle_icmpv6};
  38
  39 static FILE *fp_route = NULL;
  40 #define RA_IOV_LEN 6
  41
  42
  43 int init_router(void)
  44 {
  45         // Open ICMPv6 socket
  46         int sock = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
  47         if (sock < 0 && errno != EAFNOSUPPORT) {
  48                 syslog(LOG_ERR, "Failed to open RAW-socket: %s", strerror(errno));
  49                 return -1;
  50         }
  51
  52         // Let the kernel compute our checksums
  53         int val = 2;
  54         setsockopt(sock, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
  55
  56         // This is required by RFC 4861
  57         val = 255;
  58         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
  59         setsockopt(sock, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &val, sizeof(val));
  60
  61         // We need to know the source interface
  62         val = 1;
  63         setsockopt(sock, IPPROTO_IPV6, IPV6_RECVPKTINFO, &val, sizeof(val));
  64         setsockopt(sock, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &val, sizeof(val));
  65
  66         // Don't loop back
  67         val = 0;
  68         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &val, sizeof(val));
  69
  70         // Filter ICMPv6 package types
  71         struct icmp6_filter filt;
  72         ICMP6_FILTER_SETBLOCKALL(&filt);
  73         ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filt);
  74         ICMP6_FILTER_SETPASS(ND_ROUTER_SOLICIT, &filt);
  75         setsockopt(sock, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
  76
  77         // Register socket
  78         router_event.uloop.fd = sock;
  79         odhcpd_register(&router_event);
  80
  81         if (!(fp_route = fopen("/proc/net/ipv6_route", "r")))
  82                 syslog(LOG_ERR, "Failed to open routing table: %s",
  83                                 strerror(errno));
  84
  85         signal(SIGUSR1, sigusr1_refresh);
  86         return 0;
  87 }
  88
  89
  90 int setup_router_interface(struct interface *iface, bool enable)
  91 {
  92         if (!fp_route || router_event.uloop.fd < 0)
  93                 return -1;
  94
  95         struct ipv6_mreq all_nodes = {ALL_IPV6_NODES, iface->ifindex};
  96         struct ipv6_mreq all_routers = {ALL_IPV6_ROUTERS, iface->ifindex};
  97
  98         uloop_timeout_cancel(&iface->timer_rs);
  99         iface->timer_rs.cb = NULL;
 100
 101         setsockopt(router_event.uloop.fd, IPPROTO_IPV6, IPV6_DROP_MEMBERSHIP,
 102                         &all_nodes, sizeof(all_nodes));
 103         setsockopt(router_event.uloop.fd, IPPROTO_IPV6, IPV6_DROP_MEMBERSHIP,
 104                         &all_routers, sizeof(all_routers));
 105
 106         if (!enable) {
 107                 if (iface->ra)
 108                         trigger_router_advert(&iface->timer_rs);
 109         } else {
 110                 void *mreq = &all_routers;
 111
 112                 if (iface->ra == RELAYD_RELAY && iface->master) {
 113                         mreq = &all_nodes;
 114                         forward_router_solicitation(iface);
 115                 } else if (iface->ra == RELAYD_SERVER && !iface->master) {
 116                         iface->timer_rs.cb = trigger_router_advert;
 117                         trigger_router_advert(&iface->timer_rs);
 118                 }
 119
 120                 if (iface->ra == RELAYD_RELAY || (iface->ra == RELAYD_SERVER && !iface->master))
 121                         setsockopt(router_event.uloop.fd, IPPROTO_IPV6,
 122                                         IPV6_ADD_MEMBERSHIP, mreq, sizeof(all_nodes));
 123         }
 124         return 0;
 125 }
 126
 127
 128 // Signal handler to resend all RDs
 129 static void sigusr1_refresh(_unused int signal)
 130 {
 131         struct interface *iface;
 132         list_for_each_entry(iface, &interfaces, head)
 133                 if (iface->ra == RELAYD_SERVER && !iface->master)
 134                         uloop_timeout_set(&iface->timer_rs, 1000);
 135 }
 136
 137 static bool router_icmpv6_valid(struct sockaddr_in6 *source, uint8_t *data, size_t len)
 138 {
 139         struct icmp6_hdr *hdr = (struct icmp6_hdr *)data;
 140         struct icmpv6_opt *opt, *end = (struct icmpv6_opt*)&data[len];
 141
 142         /* Hoplimit is already checked in odhcpd_receive_packets */
 143         if (len < sizeof(*hdr) || hdr->icmp6_code)
 144                 return false;
 145
 146         switch (hdr->icmp6_type) {
 147         case ND_ROUTER_ADVERT:
 148                 if (!IN6_IS_ADDR_LINKLOCAL(&source->sin6_addr))
 149                         return false;
 150
 151                 opt = (struct icmpv6_opt *)((struct nd_router_advert *)data + 1);
 152                 break;
 153
 154         case ND_ROUTER_SOLICIT:
 155                 opt = (struct icmpv6_opt *)((struct nd_router_solicit *)data + 1);
 156                 break;
 157
 158         default:
 159                 return false;
 160         }
 161
 162         icmpv6_for_each_option(opt, opt, end)
 163                 if (opt->type == ND_OPT_SOURCE_LINKADDR &&
 164                                 IN6_IS_ADDR_UNSPECIFIED(&source->sin6_addr) &&
 165                                 hdr->icmp6_type == ND_ROUTER_SOLICIT)
 166                         return false;
 167
 168         // Check all options parsed successfully
 169         return opt == end;
 170 }
 171
 172
 173 // Detect whether a default route exists, also find the source prefixes
 174 static bool parse_routes(struct odhcpd_ipaddr *n, ssize_t len)
 175 {
 176         rewind(fp_route);
 177
 178         char line[512], ifname[16];
 179         bool found_default = false;
 180         struct odhcpd_ipaddr p = {IN6ADDR_ANY_INIT, 0, 0, 0, 0};
 181         while (fgets(line, sizeof(line), fp_route)) {
 182                 uint32_t rflags;
 183                 if (sscanf(line, "00000000000000000000000000000000 00 "
 184                                 "%*s %*s %*s %*s %*s %*s %*s %15s", ifname) &&
 185                                 strcmp(ifname, "lo")) {
 186                         found_default = true;
 187                 } else if (sscanf(line, "%8" SCNx32 "%8" SCNx32 "%*8" SCNx32 "%*8" SCNx32 " %hhx %*s "
 188                                 "%*s 00000000000000000000000000000000 %*s %*s %*s %" SCNx32 " lo",
 189                                 &p.addr.s6_addr32[0], &p.addr.s6_addr32[1], &p.prefix, &rflags) &&
 190                                 p.prefix > 0 && (rflags & RTF_NONEXTHOP) && (rflags & RTF_REJECT)) {
 191                         // Find source prefixes by scanning through unreachable-routes
 192                         p.addr.s6_addr32[0] = htonl(p.addr.s6_addr32[0]);
 193                         p.addr.s6_addr32[1] = htonl(p.addr.s6_addr32[1]);
 194
 195                         for (ssize_t i = 0; i < len; ++i) {
 196                                 if (n[i].prefix <= 64 && n[i].prefix >= p.prefix &&
 197                                                 !odhcpd_bmemcmp(&p.addr, &n[i].addr, p.prefix)) {
 198                                         n[i].dprefix = p.prefix;
 199                                         break;
 200                                 }
 201                         }
 202
 203                 }
 204         }
 205
 206         return found_default;
 207 }
 208
 209 // Unicsat RAs
 210 static void send_neigh_ra(const struct in6_addr *addr,
 211                 const struct interface *iface, void *data)
 212 {
 213         struct sockaddr_in6 dest = {
 214                 .sin6_family = AF_INET6,
 215                 .sin6_addr = *addr,
 216                 .sin6_scope_id = iface->ifindex,
 217         };
 218         odhcpd_send(router_event.uloop.fd, &dest, data, RA_IOV_LEN, iface);
 219 }
 220
 221
 222 // Router Advert server mode
 223 static uint64_t send_router_advert(struct interface *iface, const struct in6_addr *from)
 224 {
 225         int mtu = odhcpd_get_interface_config(iface->ifname, "mtu");
 226         int hlim = odhcpd_get_interface_config(iface->ifname, "hop_limit");
 227
 228         if (mtu < 1280)
 229                 mtu = 1280;
 230
 231         struct {
 232                 struct nd_router_advert h;
 233                 struct icmpv6_opt lladdr;
 234                 struct nd_opt_mtu mtu;
 235                 struct nd_opt_prefix_info prefix[RELAYD_MAX_PREFIXES];
 236         } adv = {
 237                 .h = {{.icmp6_type = ND_ROUTER_ADVERT, .icmp6_code = 0}, 0, 0},
 238                 .lladdr = {ND_OPT_SOURCE_LINKADDR, 1, {0}},
 239                 .mtu = {ND_OPT_MTU, 1, 0, htonl(mtu)},
 240         };
 241
 242         if (hlim > 0)
 243                 adv.h.nd_ra_curhoplimit = hlim;
 244
 245         if (iface->dhcpv6)
 246                 adv.h.nd_ra_flags_reserved = ND_RA_FLAG_OTHER;
 247
 248         if (iface->managed >= RELAYD_MANAGED_MFLAG)
 249                 adv.h.nd_ra_flags_reserved |= ND_RA_FLAG_MANAGED;
 250
 251         if (iface->route_preference < 0)
 252                 adv.h.nd_ra_flags_reserved |= ND_RA_PREF_LOW;
 253         else if (iface->route_preference > 0)
 254                 adv.h.nd_ra_flags_reserved |= ND_RA_PREF_HIGH;
 255         odhcpd_get_mac(iface, adv.lladdr.data);
 256
 257         // If not currently shutting down
 258         struct odhcpd_ipaddr addrs[RELAYD_MAX_PREFIXES];
 259         ssize_t ipcnt = 0;
 260         uint64_t maxpreferred = 0;
 261
 262         // If not shutdown
 263         if (iface->timer_rs.cb) {
 264                 ipcnt = odhcpd_get_interface_addresses(iface->ifindex,
 265                                 addrs, ARRAY_SIZE(addrs));
 266
 267                 // Check default route
 268                 if (parse_routes(addrs, ipcnt) || iface->default_router > 1)
 269                         adv.h.nd_ra_router_lifetime =
 270                                         htons(3 * MaxRtrAdvInterval);
 271         }
 272
 273         // Construct Prefix Information options
 274         bool have_public = false;
 275         size_t cnt = 0;
 276
 277         struct in6_addr dns_pref = IN6ADDR_ANY_INIT, *dns_addr = &dns_pref;
 278         uint32_t dns_time = 0;
 279         size_t dns_cnt = 1;
 280
 281         for (ssize_t i = 0; i < ipcnt; ++i) {
 282                 struct odhcpd_ipaddr *addr = &addrs[i];
 283                 if (addr->prefix > 96)
 284                         continue; // Address not suitable
 285
 286                 if (addr->preferred > MaxPreferredTime)
 287                         addr->preferred = MaxPreferredTime;
 288
 289                 if (addr->valid > MaxValidTime)
 290                         addr->valid = MaxValidTime;
 291
 292                 struct nd_opt_prefix_info *p = NULL;
 293                 for (size_t i = 0; i < cnt; ++i) {
 294                         if (addr->prefix == adv.prefix[i].nd_opt_pi_prefix_len &&
 295                                         !odhcpd_bmemcmp(&adv.prefix[i].nd_opt_pi_prefix,
 296                                         &addr->addr, addr->prefix))
 297                                 p = &adv.prefix[i];
 298                 }
 299
 300                 if (!p) {
 301                         if (cnt >= ARRAY_SIZE(adv.prefix))
 302                                 break;
 303
 304                         p = &adv.prefix[cnt++];
 305                 }
 306
 307                 if ((addr->addr.s6_addr[0] & 0xfe) != 0xfc && addr->preferred > 0) {
 308                         have_public = true;
 309
 310                         if (maxpreferred < 1000 * addr->preferred)
 311                                 maxpreferred = 1000 * addr->preferred;
 312                 }
 313
 314                 odhcpd_bmemcpy(&p->nd_opt_pi_prefix, &addr->addr,
 315                                 (iface->ra_advrouter) ? 128 : addr->prefix);
 316                 p->nd_opt_pi_type = ND_OPT_PREFIX_INFORMATION;
 317                 p->nd_opt_pi_len = 4;
 318                 p->nd_opt_pi_prefix_len = (addr->prefix < 64) ? 64 : addr->prefix;
 319                 p->nd_opt_pi_flags_reserved = 0;
 320                 if (!iface->ra_not_onlink)
 321                         p->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_ONLINK;
 322                 if (iface->managed < RELAYD_MANAGED_NO_AFLAG && addr->prefix <= 64)
 323                         p->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_AUTO;
 324                 if (iface->ra_advrouter)
 325                         p->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_RADDR;
 326                 p->nd_opt_pi_valid_time = htonl(addr->valid);
 327                 p->nd_opt_pi_preferred_time = htonl(addr->preferred);
 328
 329                 if (addr->preferred > dns_time) {
 330                         dns_time = addr->preferred;
 331                         dns_pref = addr->addr;
 332                 }
 333         }
 334
 335         if (!have_public && !iface->default_router && adv.h.nd_ra_router_lifetime) {
 336                 syslog(LOG_WARNING, "A default route is present but there is no public prefix "
 337                                 "on %s thus we don't announce a default route!", iface->ifname);
 338                 adv.h.nd_ra_router_lifetime = 0;
 339         }
 340
 341         // DNS Recursive DNS
 342         if (iface->dns_cnt > 0) {
 343                 dns_addr = iface->dns;
 344                 dns_cnt = iface->dns_cnt;
 345                 dns_time = 2 * MaxRtrAdvInterval;
 346         }
 347
 348         if (!dns_addr || IN6_IS_ADDR_UNSPECIFIED(dns_addr))
 349                 dns_cnt = 0;
 350
 351         struct {
 352                 uint8_t type;
 353                 uint8_t len;
 354                 uint8_t pad;
 355                 uint8_t pad2;
 356                 uint32_t lifetime;
 357         } dns = {ND_OPT_RECURSIVE_DNS, (1 + (2 * dns_cnt)), 0, 0, htonl(dns_time)};
 358
 359
 360
 361         // DNS Search options
 362         uint8_t search_buf[256], *search_domain = iface->search;
 363         size_t search_len = iface->search_len, search_padded = 0;
 364
 365         if (!search_domain && !res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 366                 int len = dn_comp(_res.dnsrch[0], search_buf,
 367                                 sizeof(search_buf), NULL, NULL);
 368                 if (len > 0) {
 369                         search_domain = search_buf;
 370                         search_len = len;
 371                 }
 372         }
 373
 374         if (search_len > 0)
 375                 search_padded = ((search_len + 7) & (~7)) + 8;
 376
 377         struct {
 378                 uint8_t type;
 379                 uint8_t len;
 380                 uint8_t pad;
 381                 uint8_t pad2;
 382                 uint32_t lifetime;
 383                 uint8_t name[];
 384         } *search = alloca(sizeof(*search) + search_padded);
 385
 386         search->type = ND_OPT_DNS_SEARCH;
 387         search->len = search_len ? ((sizeof(*search) + search_padded) / 8) : 0;
 388         search->pad = 0;
 389         search->pad2 = 0;
 390         search->lifetime = htonl(2 * MaxRtrAdvInterval);;
 391         memcpy(search->name, search_domain, search_len);
 392         memset(&search->name[search_len], 0, search_padded - search_len);
 393
 394
 395         size_t routes_cnt = 0;
 396         struct {
 397                 uint8_t type;
 398                 uint8_t len;
 399                 uint8_t prefix;
 400                 uint8_t flags;
 401                 uint32_t lifetime;
 402                 uint32_t addr[4];
 403         } routes[RELAYD_MAX_PREFIXES];
 404
 405         for (ssize_t i = 0; i < ipcnt; ++i) {
 406                 struct odhcpd_ipaddr *addr = &addrs[i];
 407                 if (addr->dprefix > 64 || addr->dprefix == 0 ||
 408                                 (addr->dprefix == 64 && addr->prefix == 64)) {
 409                         continue; // Address not suitable
 410                 } else if (addr->dprefix > 32) {
 411                         addr->addr.s6_addr32[1] &= htonl(~((1U << (64 - addr->dprefix)) - 1));
 412                 } else if (addr->dprefix <= 32) {
 413                         addr->addr.s6_addr32[0] &= htonl(~((1U << (32 - addr->dprefix)) - 1));
 414                         addr->addr.s6_addr32[1] = 0;
 415                 }
 416
 417                 routes[routes_cnt].type = ND_OPT_ROUTE_INFO;
 418                 routes[routes_cnt].len = sizeof(*routes) / 8;
 419                 routes[routes_cnt].prefix = addr->dprefix;
 420                 routes[routes_cnt].flags = 0;
 421                 if (iface->route_preference < 0)
 422                         routes[routes_cnt].flags |= ND_RA_PREF_LOW;
 423                 else if (iface->route_preference > 0)
 424                         routes[routes_cnt].flags |= ND_RA_PREF_HIGH;
 425                 routes[routes_cnt].lifetime = htonl(addr->valid);
 426                 routes[routes_cnt].addr[0] = addr->addr.s6_addr32[0];
 427                 routes[routes_cnt].addr[1] = addr->addr.s6_addr32[1];
 428                 routes[routes_cnt].addr[2] = 0;
 429                 routes[routes_cnt].addr[3] = 0;
 430
 431                 ++routes_cnt;
 432         }
 433
 434         // Calculate periodic transmit
 435         int msecs = 0;
 436         uint32_t maxival = MaxRtrAdvInterval * 1000;
 437         uint32_t minival = MinRtrAdvInterval * 1000;
 438
 439         if (maxpreferred > 0 && maxival > maxpreferred / 2) {
 440                 maxival = maxpreferred / 2;
 441                 if (maxival < 4000)
 442                         maxival = 4000;
 443
 444                 if (maxival >= 9000)
 445                         minival = maxival / 3;
 446                 else
 447                         minival = (maxival * 3) / 4;
 448         }
 449
 450         odhcpd_urandom(&msecs, sizeof(msecs));
 451         msecs = (labs(msecs) % (maxival - minival)) + minival;
 452
 453         struct icmpv6_opt adv_interval = {
 454                 .type = ND_OPT_RTR_ADV_INTERVAL,
 455                 .len = 1,
 456                 .data = {0, 0, maxival >> 24, maxival >> 16, maxival >> 8, maxival}
 457         };
 458
 459         struct iovec iov[RA_IOV_LEN] = {
 460                         {&adv, (uint8_t*)&adv.prefix[cnt] - (uint8_t*)&adv},
 461                         {&routes, routes_cnt * sizeof(*routes)},
 462                         {&dns, (dns_cnt) ? sizeof(dns) : 0},
 463                         {dns_addr, dns_cnt * sizeof(*dns_addr)},
 464                         {search, search->len * 8},
 465                         {&adv_interval, adv_interval.len * 8}};
 466         struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_NODES, 0};
 467
 468         if (from && !IN6_IS_ADDR_UNSPECIFIED(from))
 469                 dest.sin6_addr = *from;
 470
 471         odhcpd_send(router_event.uloop.fd,
 472                         &dest, iov, ARRAY_SIZE(iov), iface);
 473
 474         odhcpd_iterate_interface_neighbors(iface, send_neigh_ra, iov);
 475         return msecs;
 476 }
 477
 478
 479 static void trigger_router_advert(struct uloop_timeout *event)
 480 {
 481         struct interface *iface = container_of(event, struct interface, timer_rs);
 482         int msecs = send_router_advert(iface, NULL);
 483
 484         // Rearm timer if not shut down
 485         if (event->cb)
 486                 uloop_timeout_set(event, msecs);
 487 }
 488
 489
 490 // Event handler for incoming ICMPv6 packets
 491 static void handle_icmpv6(void *addr, void *data, size_t len,
 492                 struct interface *iface, _unused void *dest)
 493 {
 494         struct icmp6_hdr *hdr = data;
 495         struct sockaddr_in6 *from = addr;
 496
 497         if (!router_icmpv6_valid(addr, data, len))
 498                 return;
 499
 500         if ((iface->ra == RELAYD_SERVER && !iface->master)) { // Server mode
 501                 if (hdr->icmp6_type == ND_ROUTER_SOLICIT)
 502                         send_router_advert(iface, &from->sin6_addr);
 503         } else if (iface->ra == RELAYD_RELAY) { // Relay mode
 504                 if (hdr->icmp6_type == ND_ROUTER_ADVERT && iface->master)
 505                         forward_router_advertisement(data, len);
 506                 else if (hdr->icmp6_type == ND_ROUTER_SOLICIT && !iface->master)
 507                         forward_router_solicitation(odhcpd_get_master_interface());
 508         }
 509 }
 510
 511
 512 // Forward router solicitation
 513 static void forward_router_solicitation(const struct interface *iface)
 514 {
 515         if (!iface)
 516                 return;
 517
 518         struct icmp6_hdr rs = {ND_ROUTER_SOLICIT, 0, 0, {{0}}};
 519         struct iovec iov = {&rs, sizeof(rs)};
 520         struct sockaddr_in6 all_routers =
 521                 {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, iface->ifindex};
 522
 523         syslog(LOG_NOTICE, "Sending RS to %s", iface->ifname);
 524         odhcpd_send(router_event.uloop.fd, &all_routers, &iov, 1, iface);
 525 }
 526
 527
 528 // Handler for incoming router solicitations on slave interfaces
 529 static void forward_router_advertisement(uint8_t *data, size_t len)
 530 {
 531         struct nd_router_advert *adv = (struct nd_router_advert *)data;
 532
 533         // Rewrite options
 534         uint8_t *end = data + len;
 535         uint8_t *mac_ptr = NULL;
 536         struct in6_addr *dns_ptr = NULL;
 537         size_t dns_count = 0;
 538
 539         struct icmpv6_opt *opt;
 540         icmpv6_for_each_option(opt, &adv[1], end) {
 541                 if (opt->type == ND_OPT_SOURCE_LINKADDR) {
 542                         // Store address of source MAC-address
 543                         mac_ptr = opt->data;
 544                 } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 1) {
 545                         // Check if we have to rewrite DNS
 546                         dns_ptr = (struct in6_addr*)&opt->data[6];
 547                         dns_count = (opt->len - 1) / 2;
 548                 }
 549         }
 550
 551         syslog(LOG_NOTICE, "Got a RA");
 552
 553         // Indicate a proxy, however we don't follow the rest of RFC 4389 yet
 554         adv->nd_ra_flags_reserved |= ND_RA_FLAG_PROXY;
 555
 556         // Forward advertisement to all slave interfaces
 557         struct sockaddr_in6 all_nodes = {AF_INET6, 0, 0, ALL_IPV6_NODES, 0};
 558         struct iovec iov = {data, len};
 559
 560         struct interface *iface;
 561         list_for_each_entry(iface, &interfaces, head) {
 562                 if (iface->ra != RELAYD_RELAY || iface->master)
 563                         continue;
 564
 565                 // Fixup source hardware address option
 566                 if (mac_ptr)
 567                         odhcpd_get_mac(iface, mac_ptr);
 568
 569                 // If we have to rewrite DNS entries
 570                 if (iface->always_rewrite_dns && dns_ptr && dns_count > 0) {
 571                         const struct in6_addr *rewrite = iface->dns;
 572                         struct in6_addr addr;
 573                         size_t rewrite_cnt = iface->dns_cnt;
 574
 575                         if (rewrite_cnt == 0) {
 576                                 if (odhcpd_get_preferred_interface_address(iface->ifindex, &addr) < 1)
 577                                         continue; // Unable to comply
 578
 579                                 rewrite = &addr;
 580                                 rewrite_cnt = 1;
 581                         }
 582
 583                         // Copy over any other addresses
 584                         for (size_t i = 0; i < dns_count; ++i) {
 585                                 size_t j = (i < rewrite_cnt) ? i : rewrite_cnt - 1;
 586                                 dns_ptr[i] = rewrite[j];
 587                         }
 588                 }
 589
 590                 odhcpd_send(router_event.uloop.fd, &all_nodes, &iov, 1, iface);
 591         }
 592 }