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                         ndp_rqs_addr6_dump();
 124                 }
 125
 126                 if (iface->ra == RELAYD_RELAY || (iface->ra == RELAYD_SERVER && !iface->master))
 127                         setsockopt(router_event.uloop.fd, IPPROTO_IPV6,
 128                                         IPV6_ADD_MEMBERSHIP, mreq, sizeof(all_nodes));
 129         }
 130         return 0;
 131 }
 132
 133
 134 // Signal handler to resend all RDs
 135 static void sigusr1_refresh(_unused int signal)
 136 {
 137         struct interface *iface;
 138         list_for_each_entry(iface, &interfaces, head)
 139                 if (iface->ra == RELAYD_SERVER && !iface->master)
 140                         uloop_timeout_set(&iface->timer_rs, 1000);
 141 }
 142
 143 static bool router_icmpv6_valid(struct sockaddr_in6 *source, uint8_t *data, size_t len)
 144 {
 145         struct icmp6_hdr *hdr = (struct icmp6_hdr *)data;
 146         struct icmpv6_opt *opt, *end = (struct icmpv6_opt*)&data[len];
 147
 148         /* Hoplimit is already checked in odhcpd_receive_packets */
 149         if (len < sizeof(*hdr) || hdr->icmp6_code)
 150                 return false;
 151
 152         switch (hdr->icmp6_type) {
 153         case ND_ROUTER_ADVERT:
 154                 if (!IN6_IS_ADDR_LINKLOCAL(&source->sin6_addr))
 155                         return false;
 156
 157                 opt = (struct icmpv6_opt *)((struct nd_router_advert *)data + 1);
 158                 break;
 159
 160         case ND_ROUTER_SOLICIT:
 161                 opt = (struct icmpv6_opt *)((struct nd_router_solicit *)data + 1);
 162                 break;
 163
 164         default:
 165                 return false;
 166         }
 167
 168         icmpv6_for_each_option(opt, opt, end)
 169                 if (opt->type == ND_OPT_SOURCE_LINKADDR &&
 170                                 IN6_IS_ADDR_UNSPECIFIED(&source->sin6_addr) &&
 171                                 hdr->icmp6_type == ND_ROUTER_SOLICIT)
 172                         return false;
 173
 174         // Check all options parsed successfully
 175         return opt == end;
 176 }
 177
 178
 179 // Detect whether a default route exists, also find the source prefixes
 180 static bool parse_routes(struct odhcpd_ipaddr *n, ssize_t len)
 181 {
 182         rewind(fp_route);
 183
 184         char line[512], ifname[16];
 185         bool found_default = false;
 186         struct odhcpd_ipaddr p = {IN6ADDR_ANY_INIT, 0, 0, 0, 0};
 187         while (fgets(line, sizeof(line), fp_route)) {
 188                 uint32_t rflags;
 189                 if (sscanf(line, "00000000000000000000000000000000 00 "
 190                                 "%*s %*s %*s %*s %*s %*s %*s %15s", ifname) &&
 191                                 strcmp(ifname, "lo")) {
 192                         found_default = true;
 193                 } else if (sscanf(line, "%8" SCNx32 "%8" SCNx32 "%*8" SCNx32 "%*8" SCNx32 " %hhx %*s "
 194                                 "%*s 00000000000000000000000000000000 %*s %*s %*s %" SCNx32 " lo",
 195                                 &p.addr.s6_addr32[0], &p.addr.s6_addr32[1], &p.prefix, &rflags) &&
 196                                 p.prefix > 0 && (rflags & RTF_NONEXTHOP) && (rflags & RTF_REJECT)) {
 197                         // Find source prefixes by scanning through unreachable-routes
 198                         p.addr.s6_addr32[0] = htonl(p.addr.s6_addr32[0]);
 199                         p.addr.s6_addr32[1] = htonl(p.addr.s6_addr32[1]);
 200
 201                         for (ssize_t i = 0; i < len; ++i) {
 202                                 if (n[i].prefix <= 64 && n[i].prefix >= p.prefix &&
 203                                                 !odhcpd_bmemcmp(&p.addr, &n[i].addr, p.prefix)) {
 204                                         n[i].dprefix = p.prefix;
 205                                         break;
 206                                 }
 207                         }
 208
 209                 }
 210         }
 211
 212         return found_default;
 213 }
 214
 215 static int calc_adv_interval(struct interface *iface, uint32_t minvalid,
 216                 uint32_t *maxival)
 217 {
 218         uint32_t minival = iface->ra_mininterval;
 219         int msecs;
 220
 221         *maxival = iface->ra_maxinterval;
 222
 223         if (*maxival > minvalid/3)
 224                 *maxival = minvalid/3;
 225
 226         if (*maxival > MaxRtrAdvInterval)
 227                 *maxival = MaxRtrAdvInterval;
 228         else if (*maxival < 4)
 229                 *maxival = 4;
 230
 231         if (minival < MinRtrAdvInterval)
 232                 minival = MinRtrAdvInterval;
 233         else if (minival > (*maxival * 3)/4)
 234                 minival = (*maxival >= 9 ? *maxival/3 : *maxival);
 235
 236         odhcpd_urandom(&msecs, sizeof(msecs));
 237         msecs = (labs(msecs) % ((*maxival != minival) ? (*maxival - minival)*1000 : 500)) +
 238                         minival*1000;
 239
 240         return msecs;
 241 }
 242
 243 static uint16_t calc_ra_lifetime(struct interface *iface, uint32_t maxival)
 244 {
 245         uint16_t lifetime = 3*maxival;
 246
 247         if (iface->ra_lifetime >= 0) {
 248                 lifetime = iface->ra_lifetime;
 249                 if (lifetime < maxival)
 250                         lifetime = maxival;
 251                 else if (lifetime > 9000)
 252                         lifetime = 9000;
 253         }
 254
 255         return lifetime;
 256 }
 257
 258 // Router Advert server mode
 259 static uint64_t send_router_advert(struct interface *iface, const struct in6_addr *from)
 260 {
 261         time_t now = odhcpd_time();
 262         uint32_t mtu = iface->ra_mtu;
 263         int hlim = iface->ra_hoplimit;
 264
 265         if (mtu == 0)
 266                  mtu = odhcpd_get_interface_config(iface->ifname, "mtu");
 267
 268         if (mtu < 1280)
 269                 mtu = 1280;
 270
 271         if (hlim == 0)
 272                 hlim = odhcpd_get_interface_config(iface->ifname, "hop_limit");
 273
 274         struct {
 275                 struct nd_router_advert h;
 276                 struct icmpv6_opt lladdr;
 277                 struct nd_opt_mtu mtu;
 278                 struct nd_opt_prefix_info prefix[sizeof(iface->ia_addr) / sizeof(*iface->ia_addr)];
 279         } adv = {
 280                 .h = {{.icmp6_type = ND_ROUTER_ADVERT, .icmp6_code = 0}, 0, 0},
 281                 .lladdr = {ND_OPT_SOURCE_LINKADDR, 1, {0}},
 282                 .mtu = {ND_OPT_MTU, 1, 0, htonl(mtu)},
 283         };
 284
 285         if (hlim > 0)
 286                 adv.h.nd_ra_curhoplimit = hlim;
 287
 288         if (iface->dhcpv6)
 289                 adv.h.nd_ra_flags_reserved = ND_RA_FLAG_OTHER;
 290
 291         if (iface->managed >= RELAYD_MANAGED_MFLAG)
 292                 adv.h.nd_ra_flags_reserved |= ND_RA_FLAG_MANAGED;
 293
 294         if (iface->route_preference < 0)
 295                 adv.h.nd_ra_flags_reserved |= ND_RA_PREF_LOW;
 296         else if (iface->route_preference > 0)
 297                 adv.h.nd_ra_flags_reserved |= ND_RA_PREF_HIGH;
 298
 299         adv.h.nd_ra_reachable = htonl(iface->ra_reachabletime);
 300
 301         odhcpd_get_mac(iface, adv.lladdr.data);
 302
 303         // If not currently shutting down
 304         struct odhcpd_ipaddr addrs[RELAYD_MAX_ADDRS];
 305         ssize_t ipcnt = 0;
 306         uint32_t minvalid = UINT32_MAX;
 307         bool default_route = false;
 308         bool valid_prefix = false;
 309
 310         // If not shutdown
 311         if (iface->timer_rs.cb) {
 312                 ipcnt = iface->ia_addr_len;
 313                 memcpy(addrs, iface->ia_addr, ipcnt * sizeof(*addrs));
 314
 315                 // Check default route
 316                 if (iface->default_router) {
 317                         default_route = true;
 318
 319                         if (iface->default_router > 1)
 320                                 valid_prefix = true;
 321                 } else if (parse_routes(addrs, ipcnt))
 322                         default_route = true;
 323         }
 324
 325         // Construct Prefix Information options
 326         size_t cnt = 0;
 327
 328         struct in6_addr dns_pref, *dns_addr = &dns_pref;
 329         size_t dns_cnt = 1;
 330
 331         odhcpd_get_interface_dns_addr(iface, &dns_pref);
 332
 333         for (ssize_t i = 0; i < ipcnt; ++i) {
 334                 struct odhcpd_ipaddr *addr = &addrs[i];
 335                 uint32_t preferred = 0;
 336                 uint32_t valid = 0;
 337
 338                 if (addr->prefix > 96 || addr->valid <= (uint32_t)now) {
 339                         char namebuf[INET6_ADDRSTRLEN];
 340
 341                         inet_ntop(AF_INET6, addr, namebuf, sizeof(namebuf));
 342                         syslog(LOG_INFO, "Address %s (prefix %d, valid %u) not suitable as RA prefix on %s",
 343                                         namebuf, addr->prefix, addr->valid, iface->ifname);
 344                         continue;
 345                 }
 346
 347                 struct nd_opt_prefix_info *p = NULL;
 348                 for (size_t i = 0; i < cnt; ++i) {
 349                         if (addr->prefix == adv.prefix[i].nd_opt_pi_prefix_len &&
 350                                         !odhcpd_bmemcmp(&adv.prefix[i].nd_opt_pi_prefix,
 351                                         &addr->addr, addr->prefix))
 352                                 p = &adv.prefix[i];
 353                 }
 354
 355                 if (!p) {
 356                         if (cnt >= ARRAY_SIZE(adv.prefix))
 357                                 break;
 358
 359                         p = &adv.prefix[cnt++];
 360                 }
 361
 362                 if (addr->preferred > (uint32_t)now) {
 363                         preferred = TIME_LEFT(addr->preferred, now);
 364
 365                         if (iface->ra_useleasetime &&
 366                                         preferred > iface->dhcpv4_leasetime)
 367                                 preferred = iface->dhcpv4_leasetime;
 368                 }
 369
 370                 valid = TIME_LEFT(addr->valid, now);
 371                 if (iface->ra_useleasetime && valid > iface->dhcpv4_leasetime)
 372                         valid = iface->dhcpv4_leasetime;
 373
 374                 if (minvalid > valid)
 375                         minvalid = valid;
 376
 377                 if (!IN6_IS_ADDR_ULA(&addr->addr) || iface->default_router)
 378                         valid_prefix = true;
 379
 380                 odhcpd_bmemcpy(&p->nd_opt_pi_prefix, &addr->addr,
 381                                 (iface->ra_advrouter) ? 128 : addr->prefix);
 382                 p->nd_opt_pi_type = ND_OPT_PREFIX_INFORMATION;
 383                 p->nd_opt_pi_len = 4;
 384                 p->nd_opt_pi_prefix_len = (addr->prefix < 64) ? 64 : addr->prefix;
 385                 p->nd_opt_pi_flags_reserved = 0;
 386                 if (!iface->ra_not_onlink)
 387                         p->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_ONLINK;
 388                 if (iface->managed < RELAYD_MANAGED_NO_AFLAG && addr->prefix <= 64)
 389                         p->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_AUTO;
 390                 if (iface->ra_advrouter)
 391                         p->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_RADDR;
 392                 p->nd_opt_pi_preferred_time = htonl(preferred);
 393                 p->nd_opt_pi_valid_time = htonl(valid);
 394         }
 395
 396         // Calculate periodic transmit
 397         uint32_t maxival;
 398         int msecs = calc_adv_interval(iface, minvalid, &maxival);
 399
 400         if (default_route) {
 401                 if (!valid_prefix) {
 402                         syslog(LOG_WARNING, "A default route is present but there is no public prefix "
 403                                         "on %s thus we don't announce a default route!", iface->ifname);
 404                         adv.h.nd_ra_router_lifetime = 0;
 405                 } else
 406                         adv.h.nd_ra_router_lifetime = htons(calc_ra_lifetime(iface, maxival));
 407
 408         } else
 409                 adv.h.nd_ra_router_lifetime = 0;
 410
 411         syslog(LOG_INFO, "Using a RA lifetime of %d seconds on %s", ntohs(adv.h.nd_ra_router_lifetime), iface->ifname);
 412
 413         // DNS Recursive DNS
 414         if (iface->dns_cnt > 0) {
 415                 dns_addr = iface->dns;
 416                 dns_cnt = iface->dns_cnt;
 417         }
 418
 419         if (!dns_addr || IN6_IS_ADDR_UNSPECIFIED(dns_addr))
 420                 dns_cnt = 0;
 421
 422         struct {
 423                 uint8_t type;
 424                 uint8_t len;
 425                 uint8_t pad;
 426                 uint8_t pad2;
 427                 uint32_t lifetime;
 428         } dns = {ND_OPT_RECURSIVE_DNS, (1 + (2 * dns_cnt)), 0, 0, 0};
 429
 430
 431
 432         // DNS Search options
 433         uint8_t search_buf[256], *search_domain = iface->search;
 434         size_t search_len = iface->search_len, search_padded = 0;
 435
 436         if (!search_domain && !res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 437                 int len = dn_comp(_res.dnsrch[0], search_buf,
 438                                 sizeof(search_buf), NULL, NULL);
 439                 if (len > 0) {
 440                         search_domain = search_buf;
 441                         search_len = len;
 442                 }
 443         }
 444
 445         if (search_len > 0)
 446                 search_padded = ((search_len + 7) & (~7)) + 8;
 447
 448         struct {
 449                 uint8_t type;
 450                 uint8_t len;
 451                 uint8_t pad;
 452                 uint8_t pad2;
 453                 uint32_t lifetime;
 454                 uint8_t name[];
 455         } *search = alloca(sizeof(*search) + search_padded);
 456
 457         search->type = ND_OPT_DNS_SEARCH;
 458         search->len = search_len ? ((sizeof(*search) + search_padded) / 8) : 0;
 459         search->pad = 0;
 460         search->pad2 = 0;
 461         memcpy(search->name, search_domain, search_len);
 462         memset(&search->name[search_len], 0, search_padded - search_len);
 463
 464
 465         size_t routes_cnt = 0;
 466         struct {
 467                 uint8_t type;
 468                 uint8_t len;
 469                 uint8_t prefix;
 470                 uint8_t flags;
 471                 uint32_t lifetime;
 472                 uint32_t addr[4];
 473         } routes[RELAYD_MAX_PREFIXES];
 474
 475         for (ssize_t i = 0; i < ipcnt; ++i) {
 476                 struct odhcpd_ipaddr *addr = &addrs[i];
 477                 if (addr->dprefix > 64 || addr->dprefix == 0 || addr->valid <= (uint32_t)now ||
 478                                 (addr->dprefix == 64 && addr->prefix == 64)) {
 479                         continue; // Address not suitable
 480                 } else if (addr->dprefix > 32) {
 481                         addr->addr.s6_addr32[1] &= htonl(~((1U << (64 - addr->dprefix)) - 1));
 482                 } else if (addr->dprefix <= 32) {
 483                         addr->addr.s6_addr32[0] &= htonl(~((1U << (32 - addr->dprefix)) - 1));
 484                         addr->addr.s6_addr32[1] = 0;
 485                 }
 486
 487                 routes[routes_cnt].type = ND_OPT_ROUTE_INFO;
 488                 routes[routes_cnt].len = sizeof(*routes) / 8;
 489                 routes[routes_cnt].prefix = addr->dprefix;
 490                 routes[routes_cnt].flags = 0;
 491                 if (iface->route_preference < 0)
 492                         routes[routes_cnt].flags |= ND_RA_PREF_LOW;
 493                 else if (iface->route_preference > 0)
 494                         routes[routes_cnt].flags |= ND_RA_PREF_HIGH;
 495                 routes[routes_cnt].lifetime = htonl(TIME_LEFT(addr->valid, now));
 496                 routes[routes_cnt].addr[0] = addr->addr.s6_addr32[0];
 497                 routes[routes_cnt].addr[1] = addr->addr.s6_addr32[1];
 498                 routes[routes_cnt].addr[2] = 0;
 499                 routes[routes_cnt].addr[3] = 0;
 500
 501                 ++routes_cnt;
 502         }
 503
 504         search->lifetime = htonl(maxival*10);
 505         dns.lifetime = search->lifetime;
 506
 507         struct icmpv6_opt adv_interval = {
 508                 .type = ND_OPT_RTR_ADV_INTERVAL,
 509                 .len = 1,
 510                 .data = {0, 0, (maxival*1000) >> 24, (maxival*1000) >> 16, (maxival*1000) >> 8, maxival*1000}
 511         };
 512
 513         struct iovec iov[RA_IOV_LEN] = {
 514                         {&adv, (uint8_t*)&adv.prefix[cnt] - (uint8_t*)&adv},
 515                         {&routes, routes_cnt * sizeof(*routes)},
 516                         {&dns, (dns_cnt) ? sizeof(dns) : 0},
 517                         {dns_addr, dns_cnt * sizeof(*dns_addr)},
 518                         {search, search->len * 8},
 519                         {&adv_interval, adv_interval.len * 8}};
 520         struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_NODES, 0};
 521
 522         if (from && !IN6_IS_ADDR_UNSPECIFIED(from))
 523                 dest.sin6_addr = *from;
 524
 525         odhcpd_send(router_event.uloop.fd,
 526                         &dest, iov, ARRAY_SIZE(iov), iface);
 527
 528         return msecs;
 529 }
 530
 531
 532 static void trigger_router_advert(struct uloop_timeout *event)
 533 {
 534         struct interface *iface = container_of(event, struct interface, timer_rs);
 535         int msecs = send_router_advert(iface, NULL);
 536
 537         // Rearm timer if not shut down
 538         if (event->cb)
 539                 uloop_timeout_set(event, msecs);
 540 }
 541
 542
 543 // Event handler for incoming ICMPv6 packets
 544 static void handle_icmpv6(void *addr, void *data, size_t len,
 545                 struct interface *iface, _unused void *dest)
 546 {
 547         struct icmp6_hdr *hdr = data;
 548         struct sockaddr_in6 *from = addr;
 549
 550         if (!router_icmpv6_valid(addr, data, len))
 551                 return;
 552
 553         if ((iface->ra == RELAYD_SERVER && !iface->master)) { // Server mode
 554                 if (hdr->icmp6_type == ND_ROUTER_SOLICIT)
 555                         send_router_advert(iface, &from->sin6_addr);
 556         } else if (iface->ra == RELAYD_RELAY) { // Relay mode
 557                 if (hdr->icmp6_type == ND_ROUTER_ADVERT && iface->master)
 558                         forward_router_advertisement(data, len);
 559                 else if (hdr->icmp6_type == ND_ROUTER_SOLICIT && !iface->master)
 560                         forward_router_solicitation(odhcpd_get_master_interface());
 561         }
 562 }
 563
 564
 565 // Forward router solicitation
 566 static void forward_router_solicitation(const struct interface *iface)
 567 {
 568         if (!iface)
 569                 return;
 570
 571         struct icmp6_hdr rs = {ND_ROUTER_SOLICIT, 0, 0, {{0}}};
 572         struct iovec iov = {&rs, sizeof(rs)};
 573         struct sockaddr_in6 all_routers =
 574                 {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, iface->ifindex};
 575
 576         syslog(LOG_NOTICE, "Sending RS to %s", iface->ifname);
 577         odhcpd_send(router_event.uloop.fd, &all_routers, &iov, 1, iface);
 578 }
 579
 580
 581 // Handler for incoming router solicitations on slave interfaces
 582 static void forward_router_advertisement(uint8_t *data, size_t len)
 583 {
 584         struct nd_router_advert *adv = (struct nd_router_advert *)data;
 585
 586         // Rewrite options
 587         uint8_t *end = data + len;
 588         uint8_t *mac_ptr = NULL;
 589         struct in6_addr *dns_ptr = NULL;
 590         size_t dns_count = 0;
 591
 592         struct icmpv6_opt *opt;
 593         icmpv6_for_each_option(opt, &adv[1], end) {
 594                 if (opt->type == ND_OPT_SOURCE_LINKADDR) {
 595                         // Store address of source MAC-address
 596                         mac_ptr = opt->data;
 597                 } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 1) {
 598                         // Check if we have to rewrite DNS
 599                         dns_ptr = (struct in6_addr*)&opt->data[6];
 600                         dns_count = (opt->len - 1) / 2;
 601                 }
 602         }
 603
 604         syslog(LOG_NOTICE, "Got a RA");
 605
 606         // Indicate a proxy, however we don't follow the rest of RFC 4389 yet
 607         adv->nd_ra_flags_reserved |= ND_RA_FLAG_PROXY;
 608
 609         // Forward advertisement to all slave interfaces
 610         struct sockaddr_in6 all_nodes = {AF_INET6, 0, 0, ALL_IPV6_NODES, 0};
 611         struct iovec iov = {data, len};
 612
 613         struct interface *iface;
 614         list_for_each_entry(iface, &interfaces, head) {
 615                 if (iface->ra != RELAYD_RELAY || iface->master)
 616                         continue;
 617
 618                 // Fixup source hardware address option
 619                 if (mac_ptr)
 620                         odhcpd_get_mac(iface, mac_ptr);
 621
 622                 // If we have to rewrite DNS entries
 623                 if (iface->always_rewrite_dns && dns_ptr && dns_count > 0) {
 624                         const struct in6_addr *rewrite = iface->dns;
 625                         struct in6_addr addr;
 626                         size_t rewrite_cnt = iface->dns_cnt;
 627
 628                         if (rewrite_cnt == 0) {
 629                                 if (odhcpd_get_interface_dns_addr(iface, &addr))
 630                                         continue; // Unable to comply
 631
 632                                 rewrite = &addr;
 633                                 rewrite_cnt = 1;
 634                         }
 635
 636                         // Copy over any other addresses
 637                         for (size_t i = 0; i < dns_count; ++i) {
 638                                 size_t j = (i < rewrite_cnt) ? i : rewrite_cnt - 1;
 639                                 dns_ptr[i] = rewrite[j];
 640                         }
 641                 }
 642
 643                 odhcpd_send(router_event.uloop.fd, &all_nodes, &iov, 1, iface);
 644         }
 645 }