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);
  34 static void send_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
  41
  42 int init_router(void)
  43 {
  44         // Open ICMPv6 socket
  45         int sock = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
  46         if (sock < 0 && errno != EAFNOSUPPORT) {
  47                 syslog(LOG_ERR, "Failed to open RAW-socket: %s", strerror(errno));
  48                 return -1;
  49         }
  50
  51         // Let the kernel compute our checksums
  52         int val = 2;
  53         setsockopt(sock, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
  54
  55         // This is required by RFC 4861
  56         val = 255;
  57         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
  58         setsockopt(sock, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &val, sizeof(val));
  59
  60         // We need to know the source interface
  61         val = 1;
  62         setsockopt(sock, IPPROTO_IPV6, IPV6_RECVPKTINFO, &val, sizeof(val));
  63         setsockopt(sock, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &val, sizeof(val));
  64
  65         // Don't loop back
  66         val = 0;
  67         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &val, sizeof(val));
  68
  69         // Filter ICMPv6 package types
  70         struct icmp6_filter filt;
  71         ICMP6_FILTER_SETBLOCKALL(&filt);
  72         ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filt);
  73         ICMP6_FILTER_SETPASS(ND_ROUTER_SOLICIT, &filt);
  74         setsockopt(sock, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
  75
  76         // Register socket
  77         router_event.uloop.fd = sock;
  78         odhcpd_register(&router_event);
  79
  80         if (!(fp_route = fopen("/proc/net/ipv6_route", "r")))
  81                 syslog(LOG_ERR, "Failed to open routing table: %s",
  82                                 strerror(errno));
  83
  84         signal(SIGUSR1, sigusr1_refresh);
  85         return 0;
  86 }
  87
  88
  89 int setup_router_interface(struct interface *iface, bool enable)
  90 {
  91         struct ipv6_mreq all_nodes = {ALL_IPV6_NODES, iface->ifindex};
  92         struct ipv6_mreq all_routers = {ALL_IPV6_ROUTERS, iface->ifindex};
  93
  94         uloop_timeout_cancel(&iface->timer_rs);
  95         iface->timer_rs.cb = NULL;
  96
  97         setsockopt(router_event.uloop.fd, IPPROTO_IPV6, IPV6_DROP_MEMBERSHIP,
  98                         &all_nodes, sizeof(all_nodes));
  99         setsockopt(router_event.uloop.fd, IPPROTO_IPV6, IPV6_DROP_MEMBERSHIP,
 100                         &all_routers, sizeof(all_routers));
 101
 102         if (!enable) {
 103                 if (iface->ra)
 104                         send_router_advert(&iface->timer_rs);
 105         } else {
 106                 void *mreq = &all_routers;
 107
 108                 if (iface->ra == RELAYD_RELAY && iface->master) {
 109                         mreq = &all_nodes;
 110                         forward_router_solicitation(iface);
 111                 } else if (iface->ra == RELAYD_SERVER && !iface->master) {
 112                         iface->timer_rs.cb = send_router_advert;
 113                         send_router_advert(&iface->timer_rs);
 114                 }
 115
 116                 if (iface->ra == RELAYD_RELAY || (iface->ra == RELAYD_SERVER && !iface->master))
 117                         setsockopt(router_event.uloop.fd, IPPROTO_IPV6,
 118                                         IPV6_ADD_MEMBERSHIP, mreq, sizeof(all_nodes));
 119         }
 120         return 0;
 121 }
 122
 123
 124 // Signal handler to resend all RDs
 125 static void sigusr1_refresh(_unused int signal)
 126 {
 127         struct interface *iface;
 128         list_for_each_entry(iface, &interfaces, head)
 129                 if (iface->ra == RELAYD_SERVER && !iface->master)
 130                         uloop_timeout_set(&iface->timer_rs, 1000);
 131 }
 132
 133 static bool router_icmpv6_valid(struct sockaddr_in6 *source, uint8_t *data, size_t len)
 134 {
 135         struct icmp6_hdr *hdr = (struct icmp6_hdr *)data;
 136         struct icmpv6_opt *opt, *end = (struct icmpv6_opt*)&data[len];
 137
 138         /* Hoplimit is already checked in odhcpd_receive_packets */
 139         if (len < sizeof(*hdr) || hdr->icmp6_code)
 140                 return false;
 141
 142         switch (hdr->icmp6_type) {
 143         case ND_ROUTER_ADVERT:
 144                 if (!IN6_IS_ADDR_LINKLOCAL(&source->sin6_addr))
 145                         return false;
 146
 147                 opt = (struct icmpv6_opt *)((struct nd_router_advert *)data + 1);
 148                 break;
 149
 150         case ND_ROUTER_SOLICIT:
 151                 opt = (struct icmpv6_opt *)((struct nd_router_solicit *)data + 1);
 152                 break;
 153
 154         default:
 155                 return false;
 156         }
 157
 158         icmpv6_for_each_option(opt, opt, end)
 159                 if (opt->type == ND_OPT_SOURCE_LINKADDR &&
 160                                 IN6_IS_ADDR_UNSPECIFIED(&source->sin6_addr) &&
 161                                 hdr->icmp6_type == ND_ROUTER_SOLICIT)
 162                         return false;
 163
 164         // Check all options parsed successfully
 165         return opt == end;
 166 }
 167
 168 // Event handler for incoming ICMPv6 packets
 169 static void handle_icmpv6(void *addr, void *data, size_t len,
 170                 struct interface *iface)
 171 {
 172         struct icmp6_hdr *hdr = data;
 173
 174         if (!router_icmpv6_valid(addr, data, len))
 175                 return;
 176
 177         if ((iface->ra == RELAYD_SERVER && !iface->master)) { // Server mode
 178                 if (hdr->icmp6_type == ND_ROUTER_SOLICIT)
 179                         send_router_advert(&iface->timer_rs);
 180         } else if (iface->ra == RELAYD_RELAY) { // Relay mode
 181                 if (hdr->icmp6_type == ND_ROUTER_ADVERT && iface->master)
 182                         forward_router_advertisement(data, len);
 183                 else if (hdr->icmp6_type == ND_ROUTER_SOLICIT && !iface->master)
 184                         forward_router_solicitation(odhcpd_get_master_interface());
 185         }
 186 }
 187
 188
 189 static bool match_route(const struct odhcpd_ipaddr *n, const struct in6_addr *addr)
 190 {
 191         if (n->prefix <= 32)
 192                 return ntohl(n->addr.s6_addr32[0]) >> (32 - n->prefix) ==
 193                                 ntohl(addr->s6_addr32[0]) >> (32 - n->prefix);
 194
 195         if (n->addr.s6_addr32[0] != addr->s6_addr32[0])
 196                 return false;
 197
 198         return ntohl(n->addr.s6_addr32[1]) >> (64 - n->prefix) ==
 199                         ntohl(addr->s6_addr32[1]) >> (64 - n->prefix);
 200 }
 201
 202
 203 // Detect whether a default route exists, also find the source prefixes
 204 static bool parse_routes(struct odhcpd_ipaddr *n, ssize_t len)
 205 {
 206         rewind(fp_route);
 207
 208         char line[512], ifname[16];
 209         bool found_default = false;
 210         struct odhcpd_ipaddr p = {IN6ADDR_ANY_INIT, 0, false, 0, 0, 0};
 211         while (fgets(line, sizeof(line), fp_route)) {
 212                 uint32_t rflags;
 213                 if (sscanf(line, "00000000000000000000000000000000 00 "
 214                                 "%*s %*s %*s %*s %*s %*s %*s %15s", ifname) &&
 215                                 strcmp(ifname, "lo")) {
 216                         found_default = true;
 217                 } else if (sscanf(line, "%8" SCNx32 "%8" SCNx32 "%*8" SCNx32 "%*8" SCNx32 " %hhx %*s "
 218                                 "%*s 00000000000000000000000000000000 %*s %*s %*s %" SCNx32 " lo",
 219                                 &p.addr.s6_addr32[0], &p.addr.s6_addr32[1], &p.prefix, &rflags) &&
 220                                 p.prefix > 0 && (rflags & RTF_NONEXTHOP) && (rflags & RTF_REJECT)) {
 221                         // Find source prefixes by scanning through unreachable-routes
 222                         p.addr.s6_addr32[0] = htonl(p.addr.s6_addr32[0]);
 223                         p.addr.s6_addr32[1] = htonl(p.addr.s6_addr32[1]);
 224
 225                         for (ssize_t i = 0; i < len; ++i) {
 226                                 if (n[i].prefix <= 64 && n[i].prefix >= p.prefix &&
 227                                                 match_route(&p, &n[i].addr)) {
 228                                         n[i].prefix = p.prefix;
 229                                         break;
 230                                 }
 231                         }
 232
 233                 }
 234         }
 235
 236         return found_default;
 237 }
 238
 239
 240 // Router Advert server mode
 241 static void send_router_advert(struct uloop_timeout *event)
 242 {
 243         struct interface *iface =
 244                         container_of(event, struct interface, timer_rs);
 245
 246         int mtu = odhcpd_get_interface_mtu(iface->ifname);
 247         if (mtu < 0)
 248                 mtu = 1500;
 249
 250         struct {
 251                 struct nd_router_advert h;
 252                 struct icmpv6_opt lladdr;
 253                 struct nd_opt_mtu mtu;
 254                 struct nd_opt_prefix_info prefix[RELAYD_MAX_PREFIXES];
 255         } adv = {
 256                 .h = {{.icmp6_type = ND_ROUTER_ADVERT, .icmp6_code = 0}, 0, 0},
 257                 .lladdr = {ND_OPT_SOURCE_LINKADDR, 1, {0}},
 258                 .mtu = {ND_OPT_MTU, 1, 0, htonl(mtu)},
 259         };
 260
 261         if (iface->dhcpv6)
 262                 adv.h.nd_ra_flags_reserved = ND_RA_FLAG_OTHER;
 263
 264         if (iface->managed >= RELAYD_MANAGED_MFLAG)
 265                 adv.h.nd_ra_flags_reserved |= ND_RA_FLAG_MANAGED;
 266
 267         if (iface->route_preference < 0)
 268                 adv.h.nd_ra_flags_reserved |= ND_RA_PREF_LOW;
 269         else if (iface->route_preference > 0)
 270                 adv.h.nd_ra_flags_reserved |= ND_RA_PREF_HIGH;
 271         odhcpd_get_mac(iface, adv.lladdr.data);
 272
 273         // If not currently shutting down
 274         struct odhcpd_ipaddr addrs[RELAYD_MAX_PREFIXES];
 275         ssize_t ipcnt = 0;
 276         uint64_t maxpreferred = 0;
 277
 278         // If not shutdown
 279         if (event->cb) {
 280                 ipcnt = odhcpd_get_interface_addresses(iface->ifindex,
 281                                 addrs, ARRAY_SIZE(addrs));
 282
 283                 // Check default route
 284                 if (parse_routes(addrs, ipcnt) || iface->default_router > 1)
 285                         adv.h.nd_ra_router_lifetime =
 286                                         htons(3 * MaxRtrAdvInterval);
 287         }
 288
 289         // Construct Prefix Information options
 290         bool have_public = false;
 291         size_t cnt = 0;
 292
 293         struct in6_addr *dns_addr = NULL;
 294         uint32_t dns_time = 0;
 295         size_t dns_cnt = 1;
 296
 297         for (ssize_t i = 0; i < ipcnt; ++i) {
 298                 struct odhcpd_ipaddr *addr = &addrs[i];
 299                 if (addr->prefix > 96 || addr->has_class)
 300                         continue; // Address not suitable
 301
 302                 if (addr->preferred > MaxPreferredTime)
 303                         addr->preferred = MaxPreferredTime;
 304
 305                 if (addr->valid > MaxValidTime)
 306                         addr->valid = MaxValidTime;
 307
 308                 struct nd_opt_prefix_info *p = NULL;
 309                 for (size_t i = 0; i < cnt; ++i) {
 310                         if (addr->prefix == adv.prefix[i].nd_opt_pi_prefix_len &&
 311                                         !odhcpd_bmemcmp(&adv.prefix[i].nd_opt_pi_prefix,
 312                                         &addr->addr, addr->prefix))
 313                                 p = &adv.prefix[i];
 314                 }
 315
 316                 if (!p) {
 317                         if (cnt >= ARRAY_SIZE(adv.prefix))
 318                                 break;
 319
 320                         p = &adv.prefix[cnt++];
 321                 }
 322
 323                 if ((addr->addr.s6_addr[0] & 0xfe) != 0xfc && addr->preferred > 0) {
 324                         have_public = true;
 325
 326                         if (maxpreferred < 1000 * addr->preferred)
 327                                 maxpreferred = 1000 * addr->preferred;
 328                 }
 329
 330                 odhcpd_bmemcpy(&p->nd_opt_pi_prefix, &addr->addr, addr->prefix);
 331                 p->nd_opt_pi_type = ND_OPT_PREFIX_INFORMATION;
 332                 p->nd_opt_pi_len = 4;
 333                 p->nd_opt_pi_prefix_len = (addr->prefix < 64) ? 64 : addr->prefix;
 334                 p->nd_opt_pi_flags_reserved = 0;
 335                 if (!iface->ra_not_onlink)
 336                         p->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_ONLINK;
 337                 if (iface->managed < RELAYD_MANAGED_NO_AFLAG && addr->prefix <= 64)
 338                         p->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_AUTO;
 339                 p->nd_opt_pi_valid_time = htonl(addr->valid);
 340                 p->nd_opt_pi_preferred_time = htonl(addr->preferred);
 341
 342                 if (addr->preferred > dns_time) {
 343                         dns_time = addr->preferred;
 344                         dns_addr = &addr->addr;
 345                 }
 346         }
 347
 348         if (!have_public && !iface->default_router && adv.h.nd_ra_router_lifetime) {
 349                 syslog(LOG_WARNING, "A default route is present but there is no public prefix "
 350                                 "on %s thus we don't announce a default route!", iface->ifname);
 351                 adv.h.nd_ra_router_lifetime = 0;
 352         }
 353
 354         // DNS Recursive DNS
 355         if (iface->dns_cnt > 0) {
 356                 dns_addr = iface->dns;
 357                 dns_cnt = iface->dns_cnt;
 358                 dns_time = 2 * MaxRtrAdvInterval;
 359         }
 360
 361         if (!dns_addr)
 362                 dns_cnt = 0;
 363
 364         struct {
 365                 uint8_t type;
 366                 uint8_t len;
 367                 uint8_t pad;
 368                 uint8_t pad2;
 369                 uint32_t lifetime;
 370         } dns = {ND_OPT_RECURSIVE_DNS, (1 + (2 * dns_cnt)), 0, 0, htonl(dns_time)};
 371
 372
 373
 374         // DNS Search options
 375         uint8_t search_buf[256], *search_domain = iface->search;
 376         size_t search_len = iface->search_len, search_padded = 0;
 377
 378         if (!search_domain && !res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 379                 int len = dn_comp(_res.dnsrch[0], search_buf,
 380                                 sizeof(search_buf), NULL, NULL);
 381                 if (len > 0) {
 382                         search_domain = search_buf;
 383                         search_len = len;
 384                 }
 385         }
 386
 387         if (search_len > 0)
 388                 search_padded = ((search_len + 7) & (~7)) + 8;
 389
 390         struct {
 391                 uint8_t type;
 392                 uint8_t len;
 393                 uint8_t pad;
 394                 uint8_t pad2;
 395                 uint32_t lifetime;
 396                 uint8_t name[];
 397         } *search = alloca(sizeof(*search) + search_padded);
 398
 399         if (!search) {
 400                 syslog(LOG_ERR, "Alloca failed for dns search on interface %s", iface->ifname);
 401                 return;
 402         }
 403         search->type = ND_OPT_DNS_SEARCH;
 404         search->len = search_len ? ((sizeof(*search) + search_padded) / 8) : 0;
 405         search->pad = 0;
 406         search->pad2 = 0;
 407         search->lifetime = htonl(2 * MaxRtrAdvInterval);;
 408         memcpy(search->name, search_domain, search_len);
 409         memset(&search->name[search_len], 0, search_padded - search_len);
 410
 411
 412         size_t routes_cnt = 0;
 413         struct {
 414                 uint8_t type;
 415                 uint8_t len;
 416                 uint8_t prefix;
 417                 uint8_t flags;
 418                 uint32_t lifetime;
 419                 uint32_t addr[4];
 420         } routes[RELAYD_MAX_PREFIXES];
 421
 422         for (ssize_t i = 0; i < ipcnt; ++i) {
 423                 struct odhcpd_ipaddr *addr = &addrs[i];
 424                 if (addr->prefix > 64 || addr->prefix == 0) {
 425                         continue; // Address not suitable
 426                 } else if (addr->prefix > 32) {
 427                         addr->addr.s6_addr32[1] &= htonl(~((1U << (64 - addr->prefix)) - 1));
 428                 } else if (addr->prefix <= 32) {
 429                         addr->addr.s6_addr32[0] &= htonl(~((1U << (32 - addr->prefix)) - 1));
 430                         addr->addr.s6_addr32[1] = 0;
 431                 }
 432
 433                 routes[routes_cnt].type = ND_OPT_ROUTE_INFO;
 434                 routes[routes_cnt].len = sizeof(*routes) / 8;
 435                 routes[routes_cnt].prefix = addr->prefix;
 436                 routes[routes_cnt].flags = 0;
 437                 if (iface->route_preference < 0)
 438                         routes[routes_cnt].flags |= ND_RA_PREF_LOW;
 439                 else if (iface->route_preference > 0)
 440                         routes[routes_cnt].flags |= ND_RA_PREF_HIGH;
 441                 routes[routes_cnt].lifetime = htonl(addr->valid);
 442                 routes[routes_cnt].addr[0] = addr->addr.s6_addr32[0];
 443                 routes[routes_cnt].addr[1] = addr->addr.s6_addr32[1];
 444                 routes[routes_cnt].addr[2] = addr->addr.s6_addr32[2];
 445                 routes[routes_cnt].addr[3] = addr->addr.s6_addr32[3];
 446
 447                 ++routes_cnt;
 448         }
 449
 450
 451         struct iovec iov[] = {{&adv, (uint8_t*)&adv.prefix[cnt] - (uint8_t*)&adv},
 452                         {&routes, routes_cnt * sizeof(*routes)},
 453                         {&dns, (dns_cnt) ? sizeof(dns) : 0},
 454                         {dns_addr, dns_cnt * sizeof(*dns_addr)},
 455                         {search, search->len * 8}};
 456         struct sockaddr_in6 all_nodes = {AF_INET6, 0, 0, ALL_IPV6_NODES, 0};
 457         odhcpd_send(router_event.uloop.fd,
 458                         &all_nodes, iov, ARRAY_SIZE(iov), iface);
 459
 460         // Rearm timer if not shut down
 461         if (event->cb) {
 462                 uint32_t maxinterval = MaxRtrAdvInterval * 1000;
 463                 uint32_t mininterval = MinRtrAdvInterval * 1000;
 464
 465                 if (maxpreferred > 0 && maxinterval > maxpreferred / 2) {
 466                         maxinterval = maxpreferred / 2;
 467                         if (maxinterval < 4000)
 468                                 maxinterval = 4000;
 469
 470                         if (maxinterval >= 9000)
 471                                 mininterval = maxinterval / 3;
 472                         else
 473                                 mininterval = (maxinterval * 3) / 4;
 474                 }
 475
 476                 int msecs;
 477                 odhcpd_urandom(&msecs, sizeof(msecs));
 478                 msecs = (labs(msecs) % (maxinterval - mininterval)) + mininterval;
 479                 uloop_timeout_set(&iface->timer_rs, msecs);
 480         }
 481 }
 482
 483
 484 // Forward router solicitation
 485 static void forward_router_solicitation(const struct interface *iface)
 486 {
 487         if (!iface)
 488                 return;
 489
 490         struct icmp6_hdr rs = {ND_ROUTER_SOLICIT, 0, 0, {{0}}};
 491         struct iovec iov = {&rs, sizeof(rs)};
 492         struct sockaddr_in6 all_routers =
 493                 {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, iface->ifindex};
 494
 495         syslog(LOG_NOTICE, "Sending RS to %s", iface->ifname);
 496         odhcpd_send(router_event.uloop.fd, &all_routers, &iov, 1, iface);
 497 }
 498
 499
 500 // Handler for incoming router solicitations on slave interfaces
 501 static void forward_router_advertisement(uint8_t *data, size_t len)
 502 {
 503         struct nd_router_advert *adv = (struct nd_router_advert *)data;
 504
 505         // Rewrite options
 506         uint8_t *end = data + len;
 507         uint8_t *mac_ptr = NULL;
 508         struct in6_addr *dns_ptr = NULL;
 509         size_t dns_count = 0;
 510
 511         struct icmpv6_opt *opt;
 512         icmpv6_for_each_option(opt, &adv[1], end) {
 513                 if (opt->type == ND_OPT_SOURCE_LINKADDR) {
 514                         // Store address of source MAC-address
 515                         mac_ptr = opt->data;
 516                 } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 1) {
 517                         // Check if we have to rewrite DNS
 518                         dns_ptr = (struct in6_addr*)&opt->data[6];
 519                         dns_count = (opt->len - 1) / 2;
 520                 }
 521         }
 522
 523         syslog(LOG_NOTICE, "Got a RA");
 524
 525         // Indicate a proxy, however we don't follow the rest of RFC 4389 yet
 526         adv->nd_ra_flags_reserved |= ND_RA_FLAG_PROXY;
 527
 528         // Forward advertisement to all slave interfaces
 529         struct sockaddr_in6 all_nodes = {AF_INET6, 0, 0, ALL_IPV6_NODES, 0};
 530         struct iovec iov = {data, len};
 531
 532         struct odhcpd_ipaddr addr;
 533         struct interface *iface;
 534         list_for_each_entry(iface, &interfaces, head) {
 535                 if (iface->ra != RELAYD_RELAY || iface->master)
 536                         continue;
 537
 538                 // Fixup source hardware address option
 539                 if (mac_ptr)
 540                         odhcpd_get_mac(iface, mac_ptr);
 541
 542                 // If we have to rewrite DNS entries
 543                 if (iface->always_rewrite_dns && dns_ptr && dns_count > 0) {
 544                         const struct in6_addr *rewrite = iface->dns;
 545                         size_t rewrite_cnt = iface->dns_cnt;
 546
 547                         if (rewrite_cnt == 0) {
 548                                 if (odhcpd_get_interface_addresses(iface->ifindex, &addr, 1) < 1)
 549                                         continue; // Unable to comply
 550
 551                                 rewrite = &addr.addr;
 552                                 rewrite_cnt = 1;
 553                         }
 554
 555                         // Copy over any other addresses
 556                         for (size_t i = 0; i < dns_count; ++i) {
 557                                 size_t j = (i < rewrite_cnt) ? i : rewrite_cnt - 1;
 558                                 dns_ptr[i] = rewrite[j];
 559                         }
 560                 }
 561
 562                 odhcpd_send(router_event.uloop.fd, &all_nodes, &iov, 1, iface);
 563         }
 564 }