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 // Router Advert server mode
 210 static uint64_t send_router_advert(struct interface *iface, const struct in6_addr *from)
 211 {
 212         int mtu = odhcpd_get_interface_config(iface->ifname, "mtu");
 213         int hlim = odhcpd_get_interface_config(iface->ifname, "hop_limit");
 214
 215         if (mtu < 1280)
 216                 mtu = 1280;
 217
 218         struct {
 219                 struct nd_router_advert h;
 220                 struct icmpv6_opt lladdr;
 221                 struct nd_opt_mtu mtu;
 222                 struct nd_opt_prefix_info prefix[RELAYD_MAX_PREFIXES];
 223         } adv = {
 224                 .h = {{.icmp6_type = ND_ROUTER_ADVERT, .icmp6_code = 0}, 0, 0},
 225                 .lladdr = {ND_OPT_SOURCE_LINKADDR, 1, {0}},
 226                 .mtu = {ND_OPT_MTU, 1, 0, htonl(mtu)},
 227         };
 228
 229         if (hlim > 0)
 230                 adv.h.nd_ra_curhoplimit = hlim;
 231
 232         if (iface->dhcpv6)
 233                 adv.h.nd_ra_flags_reserved = ND_RA_FLAG_OTHER;
 234
 235         if (iface->managed >= RELAYD_MANAGED_MFLAG)
 236                 adv.h.nd_ra_flags_reserved |= ND_RA_FLAG_MANAGED;
 237
 238         if (iface->route_preference < 0)
 239                 adv.h.nd_ra_flags_reserved |= ND_RA_PREF_LOW;
 240         else if (iface->route_preference > 0)
 241                 adv.h.nd_ra_flags_reserved |= ND_RA_PREF_HIGH;
 242         odhcpd_get_mac(iface, adv.lladdr.data);
 243
 244         // If not currently shutting down
 245         struct odhcpd_ipaddr addrs[RELAYD_MAX_PREFIXES];
 246         ssize_t ipcnt = 0;
 247         uint64_t minvalid = UINT64_MAX;
 248         uint64_t maxvalid = 0;
 249
 250         // If not shutdown
 251         if (iface->timer_rs.cb) {
 252                 ipcnt = odhcpd_get_interface_addresses(iface->ifindex,
 253                                 addrs, ARRAY_SIZE(addrs));
 254
 255                 // Check default route
 256                 if (parse_routes(addrs, ipcnt) || iface->default_router > 1)
 257                         adv.h.nd_ra_router_lifetime = 1;
 258         }
 259
 260         // Construct Prefix Information options
 261         size_t cnt = 0;
 262
 263         struct in6_addr dns_pref = IN6ADDR_ANY_INIT, *dns_addr = &dns_pref;
 264         uint32_t dns_time = 0;
 265         size_t dns_cnt = 1;
 266
 267         for (ssize_t i = 0; i < ipcnt; ++i) {
 268                 struct odhcpd_ipaddr *addr = &addrs[i];
 269                 if (addr->prefix > 96)
 270                         continue; // Address not suitable
 271
 272                 if (addr->preferred > MaxValidTime)
 273                         addr->preferred = MaxValidTime;
 274
 275                 if (addr->valid > MaxValidTime)
 276                         addr->valid = MaxValidTime;
 277
 278                 struct nd_opt_prefix_info *p = NULL;
 279                 for (size_t i = 0; i < cnt; ++i) {
 280                         if (addr->prefix == adv.prefix[i].nd_opt_pi_prefix_len &&
 281                                         !odhcpd_bmemcmp(&adv.prefix[i].nd_opt_pi_prefix,
 282                                         &addr->addr, addr->prefix))
 283                                 p = &adv.prefix[i];
 284                 }
 285
 286                 if (!p) {
 287                         if (cnt >= ARRAY_SIZE(adv.prefix))
 288                                 break;
 289
 290                         p = &adv.prefix[cnt++];
 291                 }
 292
 293                 if (addr->preferred > 0) {
 294                         if (minvalid > 1000ULL * addr->valid)
 295                                 minvalid = 1000ULL * addr->valid;
 296
 297                         if (maxvalid < 1000ULL * addr->valid && (iface->default_router ||
 298                                         (addr->addr.s6_addr[0] & 0xfe) != 0xfc))
 299                                 maxvalid = 1000ULL * addr->valid;
 300                 }
 301
 302
 303                 odhcpd_bmemcpy(&p->nd_opt_pi_prefix, &addr->addr,
 304                                 (iface->ra_advrouter) ? 128 : addr->prefix);
 305                 p->nd_opt_pi_type = ND_OPT_PREFIX_INFORMATION;
 306                 p->nd_opt_pi_len = 4;
 307                 p->nd_opt_pi_prefix_len = (addr->prefix < 64) ? 64 : addr->prefix;
 308                 p->nd_opt_pi_flags_reserved = 0;
 309                 if (!iface->ra_not_onlink)
 310                         p->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_ONLINK;
 311                 if (iface->managed < RELAYD_MANAGED_NO_AFLAG && addr->prefix <= 64)
 312                         p->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_AUTO;
 313                 if (iface->ra_advrouter)
 314                         p->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_RADDR;
 315                 p->nd_opt_pi_valid_time = htonl(addr->valid);
 316                 p->nd_opt_pi_preferred_time = htonl(addr->preferred);
 317
 318                 if (addr->preferred > dns_time) {
 319                         dns_time = addr->preferred;
 320                         dns_pref = addr->addr;
 321                 }
 322         }
 323
 324         if (!maxvalid && !iface->default_router && adv.h.nd_ra_router_lifetime) {
 325                 syslog(LOG_WARNING, "A default route is present but there is no public prefix "
 326                                 "on %s thus we don't announce a default route!", iface->ifname);
 327                 adv.h.nd_ra_router_lifetime = 0;
 328         }
 329
 330         // DNS Recursive DNS
 331         if (iface->dns_cnt > 0) {
 332                 dns_addr = iface->dns;
 333                 dns_cnt = iface->dns_cnt;
 334                 dns_time = 2 * MaxRtrAdvInterval;
 335         }
 336
 337         if (!dns_addr || IN6_IS_ADDR_UNSPECIFIED(dns_addr))
 338                 dns_cnt = 0;
 339
 340         struct {
 341                 uint8_t type;
 342                 uint8_t len;
 343                 uint8_t pad;
 344                 uint8_t pad2;
 345                 uint32_t lifetime;
 346         } dns = {ND_OPT_RECURSIVE_DNS, (1 + (2 * dns_cnt)), 0, 0, htonl(dns_time)};
 347
 348
 349
 350         // DNS Search options
 351         uint8_t search_buf[256], *search_domain = iface->search;
 352         size_t search_len = iface->search_len, search_padded = 0;
 353
 354         if (!search_domain && !res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 355                 int len = dn_comp(_res.dnsrch[0], search_buf,
 356                                 sizeof(search_buf), NULL, NULL);
 357                 if (len > 0) {
 358                         search_domain = search_buf;
 359                         search_len = len;
 360                 }
 361         }
 362
 363         if (search_len > 0)
 364                 search_padded = ((search_len + 7) & (~7)) + 8;
 365
 366         struct {
 367                 uint8_t type;
 368                 uint8_t len;
 369                 uint8_t pad;
 370                 uint8_t pad2;
 371                 uint32_t lifetime;
 372                 uint8_t name[];
 373         } *search = alloca(sizeof(*search) + search_padded);
 374
 375         search->type = ND_OPT_DNS_SEARCH;
 376         search->len = search_len ? ((sizeof(*search) + search_padded) / 8) : 0;
 377         search->pad = 0;
 378         search->pad2 = 0;
 379         search->lifetime = htonl(2 * MaxRtrAdvInterval);;
 380         memcpy(search->name, search_domain, search_len);
 381         memset(&search->name[search_len], 0, search_padded - search_len);
 382
 383
 384         size_t routes_cnt = 0;
 385         struct {
 386                 uint8_t type;
 387                 uint8_t len;
 388                 uint8_t prefix;
 389                 uint8_t flags;
 390                 uint32_t lifetime;
 391                 uint32_t addr[4];
 392         } routes[RELAYD_MAX_PREFIXES];
 393
 394         for (ssize_t i = 0; i < ipcnt; ++i) {
 395                 struct odhcpd_ipaddr *addr = &addrs[i];
 396                 if (addr->dprefix > 64 || addr->dprefix == 0 ||
 397                                 (addr->dprefix == 64 && addr->prefix == 64)) {
 398                         continue; // Address not suitable
 399                 } else if (addr->dprefix > 32) {
 400                         addr->addr.s6_addr32[1] &= htonl(~((1U << (64 - addr->dprefix)) - 1));
 401                 } else if (addr->dprefix <= 32) {
 402                         addr->addr.s6_addr32[0] &= htonl(~((1U << (32 - addr->dprefix)) - 1));
 403                         addr->addr.s6_addr32[1] = 0;
 404                 }
 405
 406                 routes[routes_cnt].type = ND_OPT_ROUTE_INFO;
 407                 routes[routes_cnt].len = sizeof(*routes) / 8;
 408                 routes[routes_cnt].prefix = addr->dprefix;
 409                 routes[routes_cnt].flags = 0;
 410                 if (iface->route_preference < 0)
 411                         routes[routes_cnt].flags |= ND_RA_PREF_LOW;
 412                 else if (iface->route_preference > 0)
 413                         routes[routes_cnt].flags |= ND_RA_PREF_HIGH;
 414                 routes[routes_cnt].lifetime = htonl(addr->valid);
 415                 routes[routes_cnt].addr[0] = addr->addr.s6_addr32[0];
 416                 routes[routes_cnt].addr[1] = addr->addr.s6_addr32[1];
 417                 routes[routes_cnt].addr[2] = 0;
 418                 routes[routes_cnt].addr[3] = 0;
 419
 420                 ++routes_cnt;
 421         }
 422
 423         // Calculate periodic transmit
 424         int msecs = 0;
 425         uint32_t maxival = iface->ra_maxinterval * 1000;
 426         uint32_t minival;
 427
 428         if (maxival < 4000 || maxival > MaxRtrAdvInterval * 1000)
 429                 maxival = MaxRtrAdvInterval * 1000;
 430
 431         if (minvalid < maxival / 3) {
 432                 maxival = minvalid / 3;
 433
 434                 if (maxival < 4000)
 435                         maxival = 4000;
 436         }
 437
 438         minival = (maxival * 3) / 4;
 439         if (adv.h.nd_ra_router_lifetime)
 440                 adv.h.nd_ra_router_lifetime = htons(maxvalid);
 441
 442         odhcpd_urandom(&msecs, sizeof(msecs));
 443         msecs = (labs(msecs) % (maxival - minival)) + minival;
 444
 445         struct icmpv6_opt adv_interval = {
 446                 .type = ND_OPT_RTR_ADV_INTERVAL,
 447                 .len = 1,
 448                 .data = {0, 0, maxival >> 24, maxival >> 16, maxival >> 8, maxival}
 449         };
 450
 451         struct iovec iov[RA_IOV_LEN] = {
 452                         {&adv, (uint8_t*)&adv.prefix[cnt] - (uint8_t*)&adv},
 453                         {&routes, routes_cnt * sizeof(*routes)},
 454                         {&dns, (dns_cnt) ? sizeof(dns) : 0},
 455                         {dns_addr, dns_cnt * sizeof(*dns_addr)},
 456                         {search, search->len * 8},
 457                         {&adv_interval, adv_interval.len * 8}};
 458         struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_NODES, 0};
 459
 460         if (from && !IN6_IS_ADDR_UNSPECIFIED(from))
 461                 dest.sin6_addr = *from;
 462
 463         odhcpd_send(router_event.uloop.fd,
 464                         &dest, iov, ARRAY_SIZE(iov), iface);
 465
 466         return msecs;
 467 }
 468
 469
 470 static void trigger_router_advert(struct uloop_timeout *event)
 471 {
 472         struct interface *iface = container_of(event, struct interface, timer_rs);
 473         int msecs = send_router_advert(iface, NULL);
 474
 475         // Rearm timer if not shut down
 476         if (event->cb)
 477                 uloop_timeout_set(event, msecs);
 478 }
 479
 480
 481 // Event handler for incoming ICMPv6 packets
 482 static void handle_icmpv6(void *addr, void *data, size_t len,
 483                 struct interface *iface, _unused void *dest)
 484 {
 485         struct icmp6_hdr *hdr = data;
 486         struct sockaddr_in6 *from = addr;
 487
 488         if (!router_icmpv6_valid(addr, data, len))
 489                 return;
 490
 491         if ((iface->ra == RELAYD_SERVER && !iface->master)) { // Server mode
 492                 if (hdr->icmp6_type == ND_ROUTER_SOLICIT)
 493                         send_router_advert(iface, &from->sin6_addr);
 494         } else if (iface->ra == RELAYD_RELAY) { // Relay mode
 495                 if (hdr->icmp6_type == ND_ROUTER_ADVERT && iface->master)
 496                         forward_router_advertisement(data, len);
 497                 else if (hdr->icmp6_type == ND_ROUTER_SOLICIT && !iface->master)
 498                         forward_router_solicitation(odhcpd_get_master_interface());
 499         }
 500 }
 501
 502
 503 // Forward router solicitation
 504 static void forward_router_solicitation(const struct interface *iface)
 505 {
 506         if (!iface)
 507                 return;
 508
 509         struct icmp6_hdr rs = {ND_ROUTER_SOLICIT, 0, 0, {{0}}};
 510         struct iovec iov = {&rs, sizeof(rs)};
 511         struct sockaddr_in6 all_routers =
 512                 {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, iface->ifindex};
 513
 514         syslog(LOG_NOTICE, "Sending RS to %s", iface->ifname);
 515         odhcpd_send(router_event.uloop.fd, &all_routers, &iov, 1, iface);
 516 }
 517
 518
 519 // Handler for incoming router solicitations on slave interfaces
 520 static void forward_router_advertisement(uint8_t *data, size_t len)
 521 {
 522         struct nd_router_advert *adv = (struct nd_router_advert *)data;
 523
 524         // Rewrite options
 525         uint8_t *end = data + len;
 526         uint8_t *mac_ptr = NULL;
 527         struct in6_addr *dns_ptr = NULL;
 528         size_t dns_count = 0;
 529
 530         struct icmpv6_opt *opt;
 531         icmpv6_for_each_option(opt, &adv[1], end) {
 532                 if (opt->type == ND_OPT_SOURCE_LINKADDR) {
 533                         // Store address of source MAC-address
 534                         mac_ptr = opt->data;
 535                 } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 1) {
 536                         // Check if we have to rewrite DNS
 537                         dns_ptr = (struct in6_addr*)&opt->data[6];
 538                         dns_count = (opt->len - 1) / 2;
 539                 }
 540         }
 541
 542         syslog(LOG_NOTICE, "Got a RA");
 543
 544         // Indicate a proxy, however we don't follow the rest of RFC 4389 yet
 545         adv->nd_ra_flags_reserved |= ND_RA_FLAG_PROXY;
 546
 547         // Forward advertisement to all slave interfaces
 548         struct sockaddr_in6 all_nodes = {AF_INET6, 0, 0, ALL_IPV6_NODES, 0};
 549         struct iovec iov = {data, len};
 550
 551         struct interface *iface;
 552         list_for_each_entry(iface, &interfaces, head) {
 553                 if (iface->ra != RELAYD_RELAY || iface->master)
 554                         continue;
 555
 556                 // Fixup source hardware address option
 557                 if (mac_ptr)
 558                         odhcpd_get_mac(iface, mac_ptr);
 559
 560                 // If we have to rewrite DNS entries
 561                 if (iface->always_rewrite_dns && dns_ptr && dns_count > 0) {
 562                         const struct in6_addr *rewrite = iface->dns;
 563                         struct in6_addr addr;
 564                         size_t rewrite_cnt = iface->dns_cnt;
 565
 566                         if (rewrite_cnt == 0) {
 567                                 if (odhcpd_get_preferred_interface_address(iface->ifindex, &addr) < 1)
 568                                         continue; // Unable to comply
 569
 570                                 rewrite = &addr;
 571                                 rewrite_cnt = 1;
 572                         }
 573
 574                         // Copy over any other addresses
 575                         for (size_t i = 0; i < dns_count; ++i) {
 576                                 size_t j = (i < rewrite_cnt) ? i : rewrite_cnt - 1;
 577                                 dns_ptr[i] = rewrite[j];
 578                         }
 579                 }
 580
 581                 odhcpd_send(router_event.uloop.fd, &all_nodes, &iov, 1, iface);
 582         }
 583 }