src/dhcpv6.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
  16 #include <errno.h>
  17 #include <unistd.h>
  18 #include <stddef.h>
  19 #include <resolv.h>
  20 #include <sys/timerfd.h>
  21 #include <arpa/inet.h>
  22
  23 #include "odhcpd.h"
  24 #include "dhcpv6.h"
  25
  26
  27 static void relay_client_request(struct sockaddr_in6 *source,
  28                 const void *data, size_t len, struct interface *iface);
  29 static void relay_server_response(uint8_t *data, size_t len);
  30
  31 static void handle_dhcpv6(void *addr, void *data, size_t len,
  32                 struct interface *iface, void *dest);
  33 static void handle_client_request(void *addr, void *data, size_t len,
  34                 struct interface *iface, void *dest_addr);
  35
  36
  37 /* Create socket and register events */
  38 int dhcpv6_init(void)
  39 {
  40         dhcpv6_ia_init();
  41         return 0;
  42 }
  43
  44 int dhcpv6_setup_interface(struct interface *iface, bool enable)
  45 {
  46         int ret = 0;
  47
  48         if (iface->dhcpv6_event.uloop.fd > 0) {
  49                 uloop_fd_delete(&iface->dhcpv6_event.uloop);
  50                 close(iface->dhcpv6_event.uloop.fd);
  51                 iface->dhcpv6_event.uloop.fd = -1;
  52         }
  53
  54         /* Configure multicast settings */
  55         if (enable && iface->dhcpv6) {
  56                 struct sockaddr_in6 bind_addr = {AF_INET6, htons(DHCPV6_SERVER_PORT),
  57                                         0, IN6ADDR_ANY_INIT, 0};
  58                 struct ipv6_mreq mreq;
  59                 int val = 1;
  60
  61                 iface->dhcpv6_event.uloop.fd = socket(AF_INET6, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
  62                 if (iface->dhcpv6_event.uloop.fd < 0) {
  63                         syslog(LOG_ERR, "socket(AF_INET6): %m");
  64                         ret = -1;
  65                         goto out;
  66                 }
  67
  68                 /* Basic IPv6 configuration */
  69                 if (setsockopt(iface->dhcpv6_event.uloop.fd, SOL_SOCKET, SO_BINDTODEVICE,
  70                                         iface->ifname, strlen(iface->ifname)) < 0) {
  71                         syslog(LOG_ERR, "setsockopt(SO_BINDTODEVICE): %m");
  72                         ret = -1;
  73                         goto out;
  74                 }
  75
  76                 if (setsockopt(iface->dhcpv6_event.uloop.fd, IPPROTO_IPV6, IPV6_V6ONLY,
  77                                         &val, sizeof(val)) < 0) {
  78                         syslog(LOG_ERR, "setsockopt(IPV6_V6ONLY): %m");
  79                         ret = -1;
  80                         goto out;
  81                 }
  82
  83                 if (setsockopt(iface->dhcpv6_event.uloop.fd, SOL_SOCKET, SO_REUSEADDR,
  84                                         &val, sizeof(val)) < 0) {
  85                         syslog(LOG_ERR, "setsockopt(SO_REUSEADDR): %m");
  86                         ret = -1;
  87                         goto out;
  88                 }
  89
  90                 if (setsockopt(iface->dhcpv6_event.uloop.fd, IPPROTO_IPV6, IPV6_RECVPKTINFO,
  91                                         &val, sizeof(val)) < 0) {
  92                         syslog(LOG_ERR, "setsockopt(IPV6_RECVPKTINFO): %m");
  93                         ret = -1;
  94                         goto out;
  95                 }
  96
  97                 val = DHCPV6_HOP_COUNT_LIMIT;
  98                 if (setsockopt(iface->dhcpv6_event.uloop.fd, IPPROTO_IPV6, IPV6_MULTICAST_HOPS,
  99                                         &val, sizeof(val)) < 0) {
 100                         syslog(LOG_ERR, "setsockopt(IPV6_MULTICAST_HOPS): %m");
 101                         ret = -1;
 102                         goto out;
 103                 }
 104
 105                 val = 0;
 106                 if (setsockopt(iface->dhcpv6_event.uloop.fd, IPPROTO_IPV6, IPV6_MULTICAST_LOOP,
 107                                         &val, sizeof(val)) < 0) {
 108                         syslog(LOG_ERR, "setsockopt(IPV6_MULTICAST_LOOP): %m");
 109                         ret = -1;
 110                         goto out;
 111                 }
 112
 113                 if (bind(iface->dhcpv6_event.uloop.fd, (struct sockaddr*)&bind_addr,
 114                                         sizeof(bind_addr)) < 0) {
 115                         syslog(LOG_ERR, "bind(): %m");
 116                         ret = -1;
 117                         goto out;
 118                 }
 119
 120                 memset(&mreq, 0, sizeof(mreq));
 121                 inet_pton(AF_INET6, ALL_DHCPV6_RELAYS, &mreq.ipv6mr_multiaddr);
 122                 mreq.ipv6mr_interface = iface->ifindex;
 123
 124                 if (setsockopt(iface->dhcpv6_event.uloop.fd, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP,
 125                                         &mreq, sizeof(mreq)) < 0) {
 126                         syslog(LOG_ERR, "setsockopt(IPV6_ADD_MEMBERSHIP): %m");
 127                         ret = -1;
 128                         goto out;
 129                 }
 130
 131                 if (iface->dhcpv6 == MODE_SERVER) {
 132                         memset(&mreq, 0, sizeof(mreq));
 133                         inet_pton(AF_INET6, ALL_DHCPV6_SERVERS, &mreq.ipv6mr_multiaddr);
 134                         mreq.ipv6mr_interface = iface->ifindex;
 135
 136                         if (setsockopt(iface->dhcpv6_event.uloop.fd, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP,
 137                                                 &mreq, sizeof(mreq)) < 0) {
 138                                 syslog(LOG_ERR, "setsockopt(IPV6_ADD_MEMBERSHIP): %m");
 139                                 ret = -1;
 140                                 goto out;
 141                         }
 142                 }
 143
 144                 iface->dhcpv6_event.handle_dgram = handle_dhcpv6;
 145                 odhcpd_register(&iface->dhcpv6_event);
 146         }
 147
 148         ret = dhcpv6_setup_ia_interface(iface, enable);
 149
 150 out:
 151         if (ret < 0 && iface->dhcpv6_event.uloop.fd > 0) {
 152                 close(iface->dhcpv6_event.uloop.fd);
 153                 iface->dhcpv6_event.uloop.fd = -1;
 154         }
 155
 156         return ret;
 157 }
 158
 159 enum {
 160         IOV_NESTED = 0,
 161         IOV_DEST,
 162         IOV_MAXRT,
 163 #define IOV_STAT IOV_MAXRT
 164         IOV_DNS,
 165         IOV_DNS_ADDR,
 166         IOV_SEARCH,
 167         IOV_SEARCH_DOMAIN,
 168         IOV_PDBUF,
 169 #define IOV_REFRESH IOV_PDBUF
 170         IOV_CERID,
 171         IOV_DHCPV6_RAW,
 172         IOV_RELAY_MSG,
 173         IOV_TOTAL
 174 };
 175
 176 static void handle_nested_message(uint8_t *data, size_t len,
 177                 uint8_t **opts, uint8_t **end, struct iovec iov[IOV_TOTAL - 1])
 178 {
 179         struct dhcpv6_relay_header *hdr = (struct dhcpv6_relay_header*)data;
 180         if (iov[IOV_NESTED].iov_base == NULL) {
 181                 iov[IOV_NESTED].iov_base = data;
 182                 iov[IOV_NESTED].iov_len = len;
 183         }
 184
 185         if (len < sizeof(struct dhcpv6_client_header))
 186                 return;
 187
 188         if (hdr->msg_type != DHCPV6_MSG_RELAY_FORW) {
 189                 iov[IOV_NESTED].iov_len = data - (uint8_t*)iov[IOV_NESTED].iov_base;
 190                 struct dhcpv6_client_header *hdr = (void*)data;
 191                 *opts = (uint8_t*)&hdr[1];
 192                 *end = data + len;
 193                 return;
 194         }
 195
 196         uint16_t otype, olen;
 197         uint8_t *odata;
 198         dhcpv6_for_each_option(hdr->options, data + len, otype, olen, odata) {
 199                 if (otype == DHCPV6_OPT_RELAY_MSG) {
 200                         iov[IOV_RELAY_MSG].iov_base = odata + olen;
 201                         iov[IOV_RELAY_MSG].iov_len = (((uint8_t*)iov[IOV_NESTED].iov_base) +
 202                                         iov[IOV_NESTED].iov_len) - (odata + olen);
 203                         handle_nested_message(odata, olen, opts, end, iov);
 204                         return;
 205                 }
 206         }
 207 }
 208
 209
 210 static void update_nested_message(uint8_t *data, size_t len, ssize_t pdiff)
 211 {
 212         struct dhcpv6_relay_header *hdr = (struct dhcpv6_relay_header*)data;
 213         if (hdr->msg_type != DHCPV6_MSG_RELAY_FORW)
 214                 return;
 215
 216         hdr->msg_type = DHCPV6_MSG_RELAY_REPL;
 217
 218         uint16_t otype, olen;
 219         uint8_t *odata;
 220         dhcpv6_for_each_option(hdr->options, data + len, otype, olen, odata) {
 221                 if (otype == DHCPV6_OPT_RELAY_MSG) {
 222                         olen += pdiff;
 223                         odata[-2] = (olen >> 8) & 0xff;
 224                         odata[-1] = olen & 0xff;
 225                         update_nested_message(odata, olen - pdiff, pdiff);
 226                         return;
 227                 }
 228         }
 229 }
 230
 231 /* Simple DHCPv6-server for information requests */
 232 static void handle_client_request(void *addr, void *data, size_t len,
 233                 struct interface *iface, void *dest_addr)
 234 {
 235         struct dhcpv6_client_header *hdr = data;
 236
 237         if (len < sizeof(*hdr))
 238                 return;
 239
 240         syslog(LOG_NOTICE, "Got DHCPv6 request");
 241
 242         /* Construct reply message */
 243         struct __attribute__((packed)) {
 244                 uint8_t msg_type;
 245                 uint8_t tr_id[3];
 246                 uint16_t serverid_type;
 247                 uint16_t serverid_length;
 248                 uint16_t duid_type;
 249                 uint16_t hardware_type;
 250                 uint8_t mac[6];
 251                 uint16_t clientid_type;
 252                 uint16_t clientid_length;
 253                 uint8_t clientid_buf[130];
 254         } dest = {
 255                 .msg_type = DHCPV6_MSG_REPLY,
 256                 .serverid_type = htons(DHCPV6_OPT_SERVERID),
 257                 .serverid_length = htons(10),
 258                 .duid_type = htons(3),
 259                 .hardware_type = htons(1),
 260                 .clientid_type = htons(DHCPV6_OPT_CLIENTID),
 261                 .clientid_buf = {0}
 262         };
 263         odhcpd_get_mac(iface, dest.mac);
 264
 265         struct __attribute__((packed)) {
 266                 uint16_t type;
 267                 uint16_t len;
 268                 uint32_t value;
 269         } maxrt = {htons(DHCPV6_OPT_SOL_MAX_RT), htons(sizeof(maxrt) - 4),
 270                         htonl(60)};
 271
 272         struct __attribute__((packed)) {
 273                 uint16_t type;
 274                 uint16_t len;
 275                 uint16_t value;
 276         } stat = {htons(DHCPV6_OPT_STATUS), htons(sizeof(stat) - 4),
 277                         htons(DHCPV6_STATUS_USEMULTICAST)};
 278
 279         struct __attribute__((packed)) {
 280                 uint16_t type;
 281                 uint16_t len;
 282                 uint32_t value;
 283         } refresh = {htons(DHCPV6_OPT_INFO_REFRESH), htons(sizeof(uint32_t)),
 284                         htonl(600)};
 285
 286         struct in6_addr dns_addr, *dns_addr_ptr = iface->dns;
 287         size_t dns_cnt = iface->dns_cnt;
 288
 289         if ((dns_cnt == 0) &&
 290                 !odhcpd_get_interface_dns_addr(iface, &dns_addr)) {
 291                 dns_addr_ptr = &dns_addr;
 292                 dns_cnt = 1;
 293         }
 294
 295         struct {
 296                 uint16_t type;
 297                 uint16_t len;
 298         } dns = {htons(DHCPV6_OPT_DNS_SERVERS), htons(dns_cnt * sizeof(*dns_addr_ptr))};
 299
 300
 301
 302         /* DNS Search options */
 303         uint8_t search_buf[256], *search_domain = iface->search;
 304         size_t search_len = iface->search_len;
 305
 306         if (!search_domain && !res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 307                 int len = dn_comp(_res.dnsrch[0], search_buf,
 308                                 sizeof(search_buf), NULL, NULL);
 309                 if (len > 0) {
 310                         search_domain = search_buf;
 311                         search_len = len;
 312                 }
 313         }
 314
 315         struct {
 316                 uint16_t type;
 317                 uint16_t len;
 318         } search = {htons(DHCPV6_OPT_DNS_DOMAIN), htons(search_len)};
 319
 320
 321         struct dhcpv6_cer_id cerid = {
 322 #ifdef EXT_CER_ID
 323                 .type = htons(EXT_CER_ID),
 324 #endif
 325                 .len = htons(36),
 326                 .addr = iface->dhcpv6_pd_cer,
 327         };
 328
 329
 330         uint8_t pdbuf[512];
 331         struct iovec iov[IOV_TOTAL] = {
 332                 [IOV_NESTED] = {NULL, 0},
 333                 [IOV_DEST] = {&dest, (uint8_t*)&dest.clientid_type - (uint8_t*)&dest},
 334                 [IOV_MAXRT] = {&maxrt, sizeof(maxrt)},
 335                 [IOV_DNS] = {&dns, (dns_cnt) ? sizeof(dns) : 0},
 336                 [IOV_DNS_ADDR] = {dns_addr_ptr, dns_cnt * sizeof(*dns_addr_ptr)},
 337                 [IOV_SEARCH] = {&search, (search_len) ? sizeof(search) : 0},
 338                 [IOV_SEARCH_DOMAIN] = {search_domain, search_len},
 339                 [IOV_PDBUF] = {pdbuf, 0},
 340                 [IOV_CERID] = {&cerid, 0},
 341                 [IOV_DHCPV6_RAW] = {iface->dhcpv6_raw, iface->dhcpv6_raw_len},
 342                 [IOV_RELAY_MSG] = {NULL, 0}
 343         };
 344
 345         uint8_t *opts = (uint8_t*)&hdr[1], *opts_end = (uint8_t*)data + len;
 346         if (hdr->msg_type == DHCPV6_MSG_RELAY_FORW)
 347                 handle_nested_message(data, len, &opts, &opts_end, iov);
 348
 349         memcpy(dest.tr_id, &opts[-3], sizeof(dest.tr_id));
 350
 351         if (opts[-4] == DHCPV6_MSG_ADVERTISE || opts[-4] == DHCPV6_MSG_REPLY || opts[-4] == DHCPV6_MSG_RELAY_REPL)
 352                 return;
 353
 354         if (!IN6_IS_ADDR_MULTICAST((struct in6_addr *)dest_addr) && iov[IOV_NESTED].iov_len == 0 &&
 355                 (opts[-4] == DHCPV6_MSG_SOLICIT || opts[-4] == DHCPV6_MSG_CONFIRM ||
 356                  opts[-4] == DHCPV6_MSG_REBIND || opts[-4] == DHCPV6_MSG_INFORMATION_REQUEST))
 357                 return;
 358
 359         if (opts[-4] == DHCPV6_MSG_SOLICIT) {
 360                 dest.msg_type = DHCPV6_MSG_ADVERTISE;
 361         } else if (opts[-4] == DHCPV6_MSG_INFORMATION_REQUEST) {
 362                 iov[IOV_REFRESH].iov_base = &refresh;
 363                 iov[IOV_REFRESH].iov_len = sizeof(refresh);
 364
 365                 /* Return inf max rt option in reply to information request */
 366                 maxrt.type = htons(DHCPV6_OPT_INF_MAX_RT);
 367         }
 368
 369         /* Go through options and find what we need */
 370         uint16_t otype, olen;
 371         uint8_t *odata;
 372         dhcpv6_for_each_option(opts, opts_end, otype, olen, odata) {
 373                 if (otype == DHCPV6_OPT_CLIENTID && olen <= 130) {
 374                         dest.clientid_length = htons(olen);
 375                         memcpy(dest.clientid_buf, odata, olen);
 376                         iov[IOV_DEST].iov_len += 4 + olen;
 377                 } else if (otype == DHCPV6_OPT_SERVERID) {
 378                         if (olen != ntohs(dest.serverid_length) ||
 379                                         memcmp(odata, &dest.duid_type, olen))
 380                                 return; /* Not for us */
 381                 } else if (iface->filter_class && otype == DHCPV6_OPT_USER_CLASS) {
 382                         uint8_t *c = odata, *cend = &odata[olen];
 383                         for (; &c[2] <= cend && &c[2 + (c[0] << 8) + c[1]] <= cend; c = &c[2 + (c[0] << 8) + c[1]]) {
 384                                 size_t elen = strlen(iface->filter_class);
 385                                 if (((((size_t)c[0]) << 8) | c[1]) == elen && !memcmp(&c[2], iface->filter_class, elen))
 386                                         return; /* Ignore from homenet */
 387                         }
 388                 } else if (otype == DHCPV6_OPT_IA_PD) {
 389 #ifdef EXT_CER_ID
 390                         iov[IOV_CERID].iov_len = sizeof(cerid);
 391
 392                         if (IN6_IS_ADDR_UNSPECIFIED(&cerid.addr)) {
 393                                 struct odhcpd_ipaddr *addrs;
 394                                 ssize_t len = netlink_get_interface_addrs(0, true, &addrs);
 395
 396                                 for (ssize_t i = 0; i < len; ++i)
 397                                         if (IN6_IS_ADDR_UNSPECIFIED(&cerid.addr)
 398                                                         || memcmp(&addrs[i].addr, &cerid.addr, sizeof(cerid.addr)) < 0)
 399                                                 cerid.addr = addrs[i].addr.in6;
 400
 401                                 free(addrs);
 402                         }
 403 #endif
 404                 }
 405         }
 406
 407         if (!IN6_IS_ADDR_MULTICAST((struct in6_addr *)dest_addr) && iov[IOV_NESTED].iov_len == 0 &&
 408                 (opts[-4] == DHCPV6_MSG_REQUEST || opts[-4] == DHCPV6_MSG_RENEW ||
 409                  opts[-4] == DHCPV6_MSG_RELEASE || opts[-4] == DHCPV6_MSG_DECLINE)) {
 410                 iov[IOV_STAT].iov_base = &stat;
 411                 iov[IOV_STAT].iov_len = sizeof(stat);
 412
 413                 for (ssize_t i = IOV_STAT + 1; i < IOV_TOTAL; ++i)
 414                         iov[i].iov_len = 0;
 415
 416                 odhcpd_send(iface->dhcpv6_event.uloop.fd, addr, iov, ARRAY_SIZE(iov), iface);
 417                 return;
 418         }
 419
 420         if (opts[-4] != DHCPV6_MSG_INFORMATION_REQUEST) {
 421                 ssize_t ialen = dhcpv6_handle_ia(pdbuf, sizeof(pdbuf), iface, addr, &opts[-4], opts_end);
 422                 iov[IOV_PDBUF].iov_len = ialen;
 423                 if (ialen < 0 || (ialen == 0 && (opts[-4] == DHCPV6_MSG_REBIND || opts[-4] == DHCPV6_MSG_CONFIRM)))
 424                         return;
 425         }
 426
 427         if (iov[IOV_NESTED].iov_len > 0) /* Update length */
 428                 update_nested_message(data, len, iov[IOV_DEST].iov_len + iov[IOV_MAXRT].iov_len +
 429                                 iov[IOV_DNS].iov_len + iov[IOV_DNS_ADDR].iov_len +
 430                                 iov[IOV_SEARCH].iov_len + iov[IOV_SEARCH_DOMAIN].iov_len +
 431                                 iov[IOV_PDBUF].iov_len + iov[IOV_CERID].iov_len +
 432                                 iov[IOV_DHCPV6_RAW].iov_len - (4 + opts_end - opts));
 433
 434         odhcpd_send(iface->dhcpv6_event.uloop.fd, addr, iov, ARRAY_SIZE(iov), iface);
 435 }
 436
 437
 438 /* Central DHCPv6-relay handler */
 439 static void handle_dhcpv6(void *addr, void *data, size_t len,
 440                 struct interface *iface, void *dest_addr)
 441 {
 442         if (iface->dhcpv6 == MODE_SERVER) {
 443                 handle_client_request(addr, data, len, iface, dest_addr);
 444         } else if (iface->dhcpv6 == MODE_RELAY) {
 445                 if (iface->master)
 446                         relay_server_response(data, len);
 447                 else
 448                         relay_client_request(addr, data, len, iface);
 449         }
 450 }
 451
 452
 453 /* Relay server response (regular relay server handling) */
 454 static void relay_server_response(uint8_t *data, size_t len)
 455 {
 456         /* Information we need to gather */
 457         uint8_t *payload_data = NULL;
 458         size_t payload_len = 0;
 459         int32_t ifaceidx = 0;
 460         struct sockaddr_in6 target = {AF_INET6, htons(DHCPV6_CLIENT_PORT),
 461                 0, IN6ADDR_ANY_INIT, 0};
 462
 463         syslog(LOG_NOTICE, "Got a DHCPv6-reply");
 464
 465         int otype, olen;
 466         uint8_t *odata, *end = data + len;
 467
 468         /* Relay DHCPv6 reply from server to client */
 469         struct dhcpv6_relay_header *h = (void*)data;
 470         if (len < sizeof(*h) || h->msg_type != DHCPV6_MSG_RELAY_REPL)
 471                 return;
 472
 473         memcpy(&target.sin6_addr, &h->peer_address,
 474                         sizeof(struct in6_addr));
 475
 476         /* Go through options and find what we need */
 477         dhcpv6_for_each_option(h->options, end, otype, olen, odata) {
 478                 if (otype == DHCPV6_OPT_INTERFACE_ID
 479                                 && olen == sizeof(ifaceidx)) {
 480                         memcpy(&ifaceidx, odata, sizeof(ifaceidx));
 481                 } else if (otype == DHCPV6_OPT_RELAY_MSG) {
 482                         payload_data = odata;
 483                         payload_len = olen;
 484                 }
 485         }
 486
 487         /* Invalid interface-id or basic payload */
 488         struct interface *iface = odhcpd_get_interface_by_index(ifaceidx);
 489         if (!iface || iface->master || !payload_data || payload_len < 4)
 490                 return;
 491
 492         bool is_authenticated = false;
 493         struct in6_addr *dns_ptr = NULL;
 494         size_t dns_count = 0;
 495
 496         /* If the payload is relay-reply we have to send to the server port */
 497         if (payload_data[0] == DHCPV6_MSG_RELAY_REPL) {
 498                 target.sin6_port = htons(DHCPV6_SERVER_PORT);
 499         } else { /* Go through the payload data */
 500                 struct dhcpv6_client_header *h = (void*)payload_data;
 501                 end = payload_data + payload_len;
 502
 503                 dhcpv6_for_each_option(&h[1], end, otype, olen, odata) {
 504                         if (otype == DHCPV6_OPT_DNS_SERVERS && olen >= 16) {
 505                                 dns_ptr = (struct in6_addr*)odata;
 506                                 dns_count = olen / 16;
 507                         } else if (otype == DHCPV6_OPT_AUTH) {
 508                                 is_authenticated = true;
 509                         }
 510                 }
 511         }
 512
 513         /* Rewrite DNS servers if requested */
 514         if (iface->always_rewrite_dns && dns_ptr && dns_count > 0) {
 515                 if (is_authenticated)
 516                         return; /* Impossible to rewrite */
 517
 518                 const struct in6_addr *rewrite = iface->dns;
 519                 struct in6_addr addr;
 520                 size_t rewrite_cnt = iface->dns_cnt;
 521
 522                 if (rewrite_cnt == 0) {
 523                         if (odhcpd_get_interface_dns_addr(iface, &addr))
 524                                 return; // Unable to get interface address
 525
 526                         rewrite = &addr;
 527                         rewrite_cnt = 1;
 528                 }
 529
 530                 /* Copy over any other addresses */
 531                 for (size_t i = 0; i < dns_count; ++i) {
 532                         size_t j = (i < rewrite_cnt) ? i : rewrite_cnt - 1;
 533                         memcpy(&dns_ptr[i], &rewrite[j], sizeof(*rewrite));
 534                 }
 535         }
 536
 537         struct iovec iov = {payload_data, payload_len};
 538         odhcpd_send(iface->dhcpv6_event.uloop.fd, &target, &iov, 1, iface);
 539 }
 540
 541 static struct odhcpd_ipaddr *relay_link_address(struct interface *iface)
 542 {
 543         struct odhcpd_ipaddr *addr = NULL;
 544         time_t now = odhcpd_time();
 545
 546         for (size_t i = 0; i < iface->addr6_len; i++) {
 547                 if (iface->addr6[i].valid <= (uint32_t)now)
 548                         continue;
 549
 550                 if (iface->addr6[i].preferred > (uint32_t)now) {
 551                         addr = &iface->addr6[i];
 552                         break;
 553                 }
 554
 555                 if (!addr || (iface->addr6[i].valid > addr->valid))
 556                         addr = &iface->addr6[i];
 557         }
 558
 559         return addr;
 560 }
 561
 562 /* Relay client request (regular DHCPv6-relay) */
 563 static void relay_client_request(struct sockaddr_in6 *source,
 564                 const void *data, size_t len, struct interface *iface)
 565 {
 566         struct interface *master = odhcpd_get_master_interface();
 567         const struct dhcpv6_relay_header *h = data;
 568         struct sockaddr_in6 s;
 569
 570         if (!master || master->dhcpv6 != MODE_RELAY ||
 571                         h->msg_type == DHCPV6_MSG_RELAY_REPL ||
 572                         h->msg_type == DHCPV6_MSG_RECONFIGURE ||
 573                         h->msg_type == DHCPV6_MSG_REPLY ||
 574                         h->msg_type == DHCPV6_MSG_ADVERTISE)
 575                 return; /* Invalid message types for client */
 576
 577         syslog(LOG_NOTICE, "Got a DHCPv6-request");
 578
 579         /* Construct our forwarding envelope */
 580         struct dhcpv6_relay_forward_envelope hdr = {
 581                 .msg_type = DHCPV6_MSG_RELAY_FORW,
 582                 .hop_count = 0,
 583                 .interface_id_type = htons(DHCPV6_OPT_INTERFACE_ID),
 584                 .interface_id_len = htons(sizeof(uint32_t)),
 585                 .relay_message_type = htons(DHCPV6_OPT_RELAY_MSG),
 586                 .relay_message_len = htons(len),
 587         };
 588
 589         if (h->msg_type == DHCPV6_MSG_RELAY_FORW) { /* handle relay-forward */
 590                 if (h->hop_count >= DHCPV6_HOP_COUNT_LIMIT)
 591                         return; // Invalid hop count
 592                 else
 593                         hdr.hop_count = h->hop_count + 1;
 594         }
 595
 596         /* use memcpy here as the destination fields are unaligned */
 597         uint32_t ifindex = iface->ifindex;
 598         memcpy(&hdr.peer_address, &source->sin6_addr, sizeof(struct in6_addr));
 599         memcpy(&hdr.interface_id_data, &ifindex, sizeof(ifindex));
 600
 601         /* Detect public IP of slave interface to use as link-address */
 602         struct odhcpd_ipaddr *ip = relay_link_address(iface);
 603         if (!ip) {
 604                 /* No suitable address! Is the slave not configured yet?
 605                  * Detect public IP of master interface and use it instead
 606                  * This is WRONG and probably violates the RFC. However
 607                  * otherwise we have a hen and egg problem because the
 608                  * slave-interface cannot be auto-configured. */
 609                 ip = relay_link_address(master);
 610                 if (!ip)
 611                         return; /* Could not obtain a suitable address */
 612         }
 613
 614         memcpy(&hdr.link_address, &ip->addr.in6, sizeof(hdr.link_address));
 615
 616         memset(&s, 0, sizeof(s));
 617         s.sin6_family = AF_INET6;
 618         s.sin6_port = htons(DHCPV6_SERVER_PORT);
 619         inet_pton(AF_INET6, ALL_DHCPV6_SERVERS, &s.sin6_addr);
 620
 621         struct iovec iov[2] = {{&hdr, sizeof(hdr)}, {(void*)data, len}};
 622         odhcpd_send(master->dhcpv6_event.uloop.fd, &s, iov, 2, master);
 623 }