src/dhcpv6.c

   1 /**
   2  * Copyright (C) 2012-2013 Steven Barth <steven@midlink.org>
   3  * Copyright (C) 2018 Hans Dedecker <dedeckeh@gmail.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License v2 as published by
   7  * the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  *
  15  */
  16
  17 #include <errno.h>
  18 #include <unistd.h>
  19 #include <stddef.h>
  20 #include <resolv.h>
  21 #include <sys/timerfd.h>
  22 #include <arpa/inet.h>
  23
  24 #include <libubox/utils.h>
  25
  26 #include "odhcpd.h"
  27 #include "dhcpv6.h"
  28
  29
  30 static void relay_client_request(struct sockaddr_in6 *source,
  31                 const void *data, size_t len, struct interface *iface);
  32 static void relay_server_response(uint8_t *data, size_t len);
  33
  34 static void handle_dhcpv6(void *addr, void *data, size_t len,
  35                 struct interface *iface, void *dest);
  36 static void handle_client_request(void *addr, void *data, size_t len,
  37                 struct interface *iface, void *dest_addr);
  38
  39
  40 /* Create socket and register events */
  41 int dhcpv6_init(void)
  42 {
  43         return dhcpv6_ia_init();
  44 }
  45
  46 int dhcpv6_setup_interface(struct interface *iface, bool enable)
  47 {
  48         int ret = 0;
  49
  50         enable = enable && (iface->dhcpv6 != MODE_DISABLED);
  51
  52         if (iface->dhcpv6_event.uloop.fd >= 0) {
  53                 uloop_fd_delete(&iface->dhcpv6_event.uloop);
  54                 close(iface->dhcpv6_event.uloop.fd);
  55                 iface->dhcpv6_event.uloop.fd = -1;
  56         }
  57
  58         /* Configure multicast settings */
  59         if (enable) {
  60                 struct sockaddr_in6 bind_addr = {AF_INET6, htons(DHCPV6_SERVER_PORT),
  61                                         0, IN6ADDR_ANY_INIT, 0};
  62                 struct ipv6_mreq mreq;
  63                 int val = 1;
  64
  65                 iface->dhcpv6_event.uloop.fd = socket(AF_INET6, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
  66                 if (iface->dhcpv6_event.uloop.fd < 0) {
  67                         syslog(LOG_ERR, "socket(AF_INET6): %m");
  68                         ret = -1;
  69                         goto out;
  70                 }
  71
  72                 /* Basic IPv6 configuration */
  73                 if (setsockopt(iface->dhcpv6_event.uloop.fd, SOL_SOCKET, SO_BINDTODEVICE,
  74                                         iface->ifname, strlen(iface->ifname)) < 0) {
  75                         syslog(LOG_ERR, "setsockopt(SO_BINDTODEVICE): %m");
  76                         ret = -1;
  77                         goto out;
  78                 }
  79
  80                 if (setsockopt(iface->dhcpv6_event.uloop.fd, IPPROTO_IPV6, IPV6_V6ONLY,
  81                                         &val, sizeof(val)) < 0) {
  82                         syslog(LOG_ERR, "setsockopt(IPV6_V6ONLY): %m");
  83                         ret = -1;
  84                         goto out;
  85                 }
  86
  87                 if (setsockopt(iface->dhcpv6_event.uloop.fd, SOL_SOCKET, SO_REUSEADDR,
  88                                         &val, sizeof(val)) < 0) {
  89                         syslog(LOG_ERR, "setsockopt(SO_REUSEADDR): %m");
  90                         ret = -1;
  91                         goto out;
  92                 }
  93
  94                 if (setsockopt(iface->dhcpv6_event.uloop.fd, IPPROTO_IPV6, IPV6_RECVPKTINFO,
  95                                         &val, sizeof(val)) < 0) {
  96                         syslog(LOG_ERR, "setsockopt(IPV6_RECVPKTINFO): %m");
  97                         ret = -1;
  98                         goto out;
  99                 }
 100
 101                 val = DHCPV6_HOP_COUNT_LIMIT;
 102                 if (setsockopt(iface->dhcpv6_event.uloop.fd, IPPROTO_IPV6, IPV6_MULTICAST_HOPS,
 103                                         &val, sizeof(val)) < 0) {
 104                         syslog(LOG_ERR, "setsockopt(IPV6_MULTICAST_HOPS): %m");
 105                         ret = -1;
 106                         goto out;
 107                 }
 108
 109                 val = 0;
 110                 if (setsockopt(iface->dhcpv6_event.uloop.fd, IPPROTO_IPV6, IPV6_MULTICAST_LOOP,
 111                                         &val, sizeof(val)) < 0) {
 112                         syslog(LOG_ERR, "setsockopt(IPV6_MULTICAST_LOOP): %m");
 113                         ret = -1;
 114                         goto out;
 115                 }
 116
 117                 if (bind(iface->dhcpv6_event.uloop.fd, (struct sockaddr*)&bind_addr,
 118                                         sizeof(bind_addr)) < 0) {
 119                         syslog(LOG_ERR, "bind(): %m");
 120                         ret = -1;
 121                         goto out;
 122                 }
 123
 124                 memset(&mreq, 0, sizeof(mreq));
 125                 inet_pton(AF_INET6, ALL_DHCPV6_RELAYS, &mreq.ipv6mr_multiaddr);
 126                 mreq.ipv6mr_interface = iface->ifindex;
 127
 128                 if (setsockopt(iface->dhcpv6_event.uloop.fd, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP,
 129                                         &mreq, sizeof(mreq)) < 0) {
 130                         syslog(LOG_ERR, "setsockopt(IPV6_ADD_MEMBERSHIP): %m");
 131                         ret = -1;
 132                         goto out;
 133                 }
 134
 135                 if (iface->dhcpv6 == MODE_SERVER) {
 136                         memset(&mreq, 0, sizeof(mreq));
 137                         inet_pton(AF_INET6, ALL_DHCPV6_SERVERS, &mreq.ipv6mr_multiaddr);
 138                         mreq.ipv6mr_interface = iface->ifindex;
 139
 140                         if (setsockopt(iface->dhcpv6_event.uloop.fd, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP,
 141                                                 &mreq, sizeof(mreq)) < 0) {
 142                                 syslog(LOG_ERR, "setsockopt(IPV6_ADD_MEMBERSHIP): %m");
 143                                 ret = -1;
 144                                 goto out;
 145                         }
 146                 }
 147
 148                 iface->dhcpv6_event.handle_dgram = handle_dhcpv6;
 149                 odhcpd_register(&iface->dhcpv6_event);
 150         }
 151
 152         ret = dhcpv6_ia_setup_interface(iface, enable);
 153
 154 out:
 155         if (ret < 0 && iface->dhcpv6_event.uloop.fd >= 0) {
 156                 close(iface->dhcpv6_event.uloop.fd);
 157                 iface->dhcpv6_event.uloop.fd = -1;
 158         }
 159
 160         return ret;
 161 }
 162
 163 enum {
 164         IOV_NESTED = 0,
 165         IOV_DEST,
 166         IOV_MAXRT,
 167 #define IOV_STAT IOV_MAXRT
 168         IOV_RAPID_COMMIT,
 169         IOV_DNS,
 170         IOV_DNS_ADDR,
 171         IOV_SEARCH,
 172         IOV_SEARCH_DOMAIN,
 173         IOV_PDBUF,
 174 #define IOV_REFRESH IOV_PDBUF
 175         IOV_CERID,
 176         IOV_DHCPV6_RAW,
 177         IOV_RELAY_MSG,
 178         IOV_TOTAL
 179 };
 180
 181 static void handle_nested_message(uint8_t *data, size_t len,
 182                                   struct dhcpv6_client_header **c_hdr, uint8_t **opts,
 183                                   uint8_t **end, struct iovec iov[IOV_TOTAL])
 184 {
 185         struct dhcpv6_relay_header *r_hdr = (struct dhcpv6_relay_header *)data;
 186         uint16_t otype, olen;
 187         uint8_t *odata;
 188
 189         if (iov[IOV_NESTED].iov_base == NULL) {
 190                 iov[IOV_NESTED].iov_base = data;
 191                 iov[IOV_NESTED].iov_len = len;
 192         }
 193
 194         if (len < sizeof(struct dhcpv6_client_header))
 195                 return;
 196
 197         if (r_hdr->msg_type != DHCPV6_MSG_RELAY_FORW) {
 198                 iov[IOV_NESTED].iov_len = data - (uint8_t *)iov[IOV_NESTED].iov_base;
 199                 *c_hdr = (void *)data;
 200                 *opts = (uint8_t *)&(*c_hdr)[1];
 201                 *end = data + len;
 202                 return;
 203         }
 204
 205         dhcpv6_for_each_option(r_hdr->options, data + len, otype, olen, odata) {
 206                 if (otype == DHCPV6_OPT_RELAY_MSG) {
 207                         iov[IOV_RELAY_MSG].iov_base = odata + olen;
 208                         iov[IOV_RELAY_MSG].iov_len = (((uint8_t *)iov[IOV_NESTED].iov_base) +
 209                                         iov[IOV_NESTED].iov_len) - (odata + olen);
 210                         handle_nested_message(odata, olen, c_hdr, opts, end, iov);
 211                         return;
 212                 }
 213         }
 214 }
 215
 216
 217 static void update_nested_message(uint8_t *data, size_t len, ssize_t pdiff)
 218 {
 219         struct dhcpv6_relay_header *hdr = (struct dhcpv6_relay_header*)data;
 220         if (hdr->msg_type != DHCPV6_MSG_RELAY_FORW)
 221                 return;
 222
 223         hdr->msg_type = DHCPV6_MSG_RELAY_REPL;
 224
 225         uint16_t otype, olen;
 226         uint8_t *odata;
 227         dhcpv6_for_each_option(hdr->options, data + len, otype, olen, odata) {
 228                 if (otype == DHCPV6_OPT_RELAY_MSG) {
 229                         olen += pdiff;
 230                         odata[-2] = (olen >> 8) & 0xff;
 231                         odata[-1] = olen & 0xff;
 232                         update_nested_message(odata, olen - pdiff, pdiff);
 233                         return;
 234                 }
 235         }
 236 }
 237
 238 /* Simple DHCPv6-server for information requests */
 239 static void handle_client_request(void *addr, void *data, size_t len,
 240                 struct interface *iface, void *dest_addr)
 241 {
 242         struct dhcpv6_client_header *hdr = data;
 243         uint8_t *opts = (uint8_t *)&hdr[1], *opts_end = (uint8_t *)data + len;
 244         bool o_rapid_commit = false;
 245
 246         if (len < sizeof(*hdr))
 247                 return;
 248
 249         syslog(LOG_DEBUG, "Got a DHCPv6-request on %s", iface->name);
 250
 251         /* Construct reply message */
 252         struct __attribute__((packed)) {
 253                 uint8_t msg_type;
 254                 uint8_t tr_id[3];
 255                 uint16_t serverid_type;
 256                 uint16_t serverid_length;
 257                 uint16_t duid_type;
 258                 uint16_t hardware_type;
 259                 uint8_t mac[6];
 260                 uint16_t clientid_type;
 261                 uint16_t clientid_length;
 262                 uint8_t clientid_buf[130];
 263         } dest = {
 264                 .msg_type = DHCPV6_MSG_REPLY,
 265                 .serverid_type = htons(DHCPV6_OPT_SERVERID),
 266                 .serverid_length = htons(10),
 267                 .duid_type = htons(3),
 268                 .hardware_type = htons(1),
 269                 .clientid_type = htons(DHCPV6_OPT_CLIENTID),
 270                 .clientid_buf = {0}
 271         };
 272         odhcpd_get_mac(iface, dest.mac);
 273
 274         struct __attribute__((packed)) {
 275                 uint16_t type;
 276                 uint16_t len;
 277                 uint32_t value;
 278         } maxrt = {htons(DHCPV6_OPT_SOL_MAX_RT), htons(sizeof(maxrt) - 4),
 279                         htonl(60)};
 280
 281         struct __attribute__((packed)) {
 282                 uint16_t type;
 283                 uint16_t len;
 284         } rapid_commit = {htons(DHCPV6_OPT_RAPID_COMMIT), 0};
 285
 286         struct __attribute__((packed)) {
 287                 uint16_t type;
 288                 uint16_t len;
 289                 uint16_t value;
 290         } stat = {htons(DHCPV6_OPT_STATUS), htons(sizeof(stat) - 4),
 291                         htons(DHCPV6_STATUS_USEMULTICAST)};
 292
 293         struct __attribute__((packed)) {
 294                 uint16_t type;
 295                 uint16_t len;
 296                 uint32_t value;
 297         } refresh = {htons(DHCPV6_OPT_INFO_REFRESH), htons(sizeof(uint32_t)),
 298                         htonl(600)};
 299
 300         struct in6_addr dns_addr, *dns_addr_ptr = iface->dns;
 301         size_t dns_cnt = iface->dns_cnt;
 302
 303         if ((dns_cnt == 0) &&
 304                 !odhcpd_get_interface_dns_addr(iface, &dns_addr)) {
 305                 dns_addr_ptr = &dns_addr;
 306                 dns_cnt = 1;
 307         }
 308
 309         struct {
 310                 uint16_t type;
 311                 uint16_t len;
 312         } dns = {htons(DHCPV6_OPT_DNS_SERVERS), htons(dns_cnt * sizeof(*dns_addr_ptr))};
 313
 314
 315
 316         /* DNS Search options */
 317         uint8_t search_buf[256], *search_domain = iface->search;
 318         size_t search_len = iface->search_len;
 319
 320         if (!search_domain && !res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 321                 int len = dn_comp(_res.dnsrch[0], search_buf,
 322                                 sizeof(search_buf), NULL, NULL);
 323                 if (len > 0) {
 324                         search_domain = search_buf;
 325                         search_len = len;
 326                 }
 327         }
 328
 329         struct {
 330                 uint16_t type;
 331                 uint16_t len;
 332         } search = {htons(DHCPV6_OPT_DNS_DOMAIN), htons(search_len)};
 333
 334
 335         struct dhcpv6_cer_id cerid = {
 336 #ifdef EXT_CER_ID
 337                 .type = htons(EXT_CER_ID),
 338 #endif
 339                 .len = htons(36),
 340                 .addr = iface->dhcpv6_pd_cer,
 341         };
 342
 343
 344         uint8_t pdbuf[512];
 345         struct iovec iov[IOV_TOTAL] = {
 346                 [IOV_NESTED] = {NULL, 0},
 347                 [IOV_DEST] = {&dest, (uint8_t*)&dest.clientid_type - (uint8_t*)&dest},
 348                 [IOV_MAXRT] = {&maxrt, sizeof(maxrt)},
 349                 [IOV_RAPID_COMMIT] = {&rapid_commit, 0},
 350                 [IOV_DNS] = {&dns, (dns_cnt) ? sizeof(dns) : 0},
 351                 [IOV_DNS_ADDR] = {dns_addr_ptr, dns_cnt * sizeof(*dns_addr_ptr)},
 352                 [IOV_SEARCH] = {&search, (search_len) ? sizeof(search) : 0},
 353                 [IOV_SEARCH_DOMAIN] = {search_domain, search_len},
 354                 [IOV_PDBUF] = {pdbuf, 0},
 355                 [IOV_CERID] = {&cerid, 0},
 356                 [IOV_DHCPV6_RAW] = {iface->dhcpv6_raw, iface->dhcpv6_raw_len},
 357                 [IOV_RELAY_MSG] = {NULL, 0}
 358         };
 359
 360         if (hdr->msg_type == DHCPV6_MSG_RELAY_FORW)
 361                 handle_nested_message(data, len, &hdr, &opts, &opts_end, iov);
 362
 363         if (hdr->msg_type == DHCPV6_MSG_ADVERTISE || hdr->msg_type == DHCPV6_MSG_REPLY ||
 364             hdr->msg_type == DHCPV6_MSG_RELAY_REPL)
 365                 return;
 366
 367         if (!IN6_IS_ADDR_MULTICAST((struct in6_addr *)dest_addr) && iov[IOV_NESTED].iov_len == 0 &&
 368             (hdr->msg_type == DHCPV6_MSG_SOLICIT || hdr->msg_type == DHCPV6_MSG_CONFIRM ||
 369              hdr->msg_type == DHCPV6_MSG_REBIND || hdr->msg_type == DHCPV6_MSG_INFORMATION_REQUEST))
 370                 return;
 371
 372         memcpy(dest.tr_id, hdr->transaction_id, sizeof(dest.tr_id));
 373
 374         /* Go through options and find what we need */
 375         uint16_t otype, olen;
 376         uint8_t *odata;
 377         dhcpv6_for_each_option(opts, opts_end, otype, olen, odata) {
 378                 if (otype == DHCPV6_OPT_CLIENTID && olen <= 130) {
 379                         dest.clientid_length = htons(olen);
 380                         memcpy(dest.clientid_buf, odata, olen);
 381                         iov[IOV_DEST].iov_len += 4 + olen;
 382                 } else if (otype == DHCPV6_OPT_SERVERID) {
 383                         if (olen != ntohs(dest.serverid_length) ||
 384                                         memcmp(odata, &dest.duid_type, olen))
 385                                 return; /* Not for us */
 386                 } else if (iface->filter_class && otype == DHCPV6_OPT_USER_CLASS) {
 387                         uint8_t *c = odata, *cend = &odata[olen];
 388                         for (; &c[2] <= cend && &c[2 + (c[0] << 8) + c[1]] <= cend; c = &c[2 + (c[0] << 8) + c[1]]) {
 389                                 size_t elen = strlen(iface->filter_class);
 390                                 if (((((size_t)c[0]) << 8) | c[1]) == elen && !memcmp(&c[2], iface->filter_class, elen))
 391                                         return; /* Ignore from homenet */
 392                         }
 393                 } else if (otype == DHCPV6_OPT_IA_PD) {
 394 #ifdef EXT_CER_ID
 395                         iov[IOV_CERID].iov_len = sizeof(cerid);
 396
 397                         if (IN6_IS_ADDR_UNSPECIFIED(&cerid.addr)) {
 398                                 struct odhcpd_ipaddr *addrs;
 399                                 ssize_t len = netlink_get_interface_addrs(0, true, &addrs);
 400
 401                                 for (ssize_t i = 0; i < len; ++i)
 402                                         if (IN6_IS_ADDR_UNSPECIFIED(&cerid.addr)
 403                                                         || memcmp(&addrs[i].addr, &cerid.addr, sizeof(cerid.addr)) < 0)
 404                                                 cerid.addr = addrs[i].addr.in6;
 405
 406                                 free(addrs);
 407                         }
 408 #endif
 409                 } else if (otype == DHCPV6_OPT_RAPID_COMMIT && hdr->msg_type == DHCPV6_MSG_SOLICIT) {
 410                         iov[IOV_RAPID_COMMIT].iov_len = sizeof(rapid_commit);
 411                         o_rapid_commit = true;
 412                 }
 413         }
 414
 415         if (!IN6_IS_ADDR_MULTICAST((struct in6_addr *)dest_addr) && iov[IOV_NESTED].iov_len == 0 &&
 416             (hdr->msg_type == DHCPV6_MSG_REQUEST || hdr->msg_type == DHCPV6_MSG_RENEW ||
 417              hdr->msg_type == DHCPV6_MSG_RELEASE || hdr->msg_type == DHCPV6_MSG_DECLINE)) {
 418                 iov[IOV_STAT].iov_base = &stat;
 419                 iov[IOV_STAT].iov_len = sizeof(stat);
 420
 421                 for (ssize_t i = IOV_STAT + 1; i < IOV_TOTAL; ++i)
 422                         iov[i].iov_len = 0;
 423
 424                 odhcpd_send(iface->dhcpv6_event.uloop.fd, addr, iov, ARRAY_SIZE(iov), iface);
 425                 return;
 426         }
 427
 428         if (hdr->msg_type == DHCPV6_MSG_SOLICIT && !o_rapid_commit) {
 429                 dest.msg_type = DHCPV6_MSG_ADVERTISE;
 430         } else if (hdr->msg_type == DHCPV6_MSG_INFORMATION_REQUEST) {
 431                 iov[IOV_REFRESH].iov_base = &refresh;
 432                 iov[IOV_REFRESH].iov_len = sizeof(refresh);
 433
 434                 /* Return inf max rt option in reply to information request */
 435                 maxrt.type = htons(DHCPV6_OPT_INF_MAX_RT);
 436         }
 437
 438         if (hdr->msg_type != DHCPV6_MSG_INFORMATION_REQUEST) {
 439                 ssize_t ialen = dhcpv6_ia_handle_IAs(pdbuf, sizeof(pdbuf), iface, addr, (const void *)hdr, opts_end);
 440
 441                 iov[IOV_PDBUF].iov_len = ialen;
 442                 if (ialen < 0 ||
 443                     (ialen == 0 && (hdr->msg_type == DHCPV6_MSG_REBIND || hdr->msg_type == DHCPV6_MSG_CONFIRM)))
 444                         return;
 445         }
 446
 447         if (iov[IOV_NESTED].iov_len > 0) /* Update length */
 448                 update_nested_message(data, len, iov[IOV_DEST].iov_len + iov[IOV_MAXRT].iov_len +
 449                                       iov[IOV_RAPID_COMMIT].iov_len + iov[IOV_DNS].iov_len +
 450                                       iov[IOV_DNS_ADDR].iov_len + iov[IOV_SEARCH].iov_len +
 451                                       iov[IOV_SEARCH_DOMAIN].iov_len + iov[IOV_PDBUF].iov_len +
 452                                       iov[IOV_CERID].iov_len + iov[IOV_DHCPV6_RAW].iov_len -
 453                                       (4 + opts_end - opts));
 454
 455         syslog(LOG_DEBUG, "Sending a DHCPv6-%s on %s", iov[IOV_NESTED].iov_len ? "relay-reply" : "reply", iface->name);
 456
 457         odhcpd_send(iface->dhcpv6_event.uloop.fd, addr, iov, ARRAY_SIZE(iov), iface);
 458 }
 459
 460
 461 /* Central DHCPv6-relay handler */
 462 static void handle_dhcpv6(void *addr, void *data, size_t len,
 463                 struct interface *iface, void *dest_addr)
 464 {
 465         if (iface->dhcpv6 == MODE_SERVER) {
 466                 handle_client_request(addr, data, len, iface, dest_addr);
 467         } else if (iface->dhcpv6 == MODE_RELAY) {
 468                 if (iface->master)
 469                         relay_server_response(data, len);
 470                 else
 471                         relay_client_request(addr, data, len, iface);
 472         }
 473 }
 474
 475
 476 /* Relay server response (regular relay server handling) */
 477 static void relay_server_response(uint8_t *data, size_t len)
 478 {
 479         /* Information we need to gather */
 480         uint8_t *payload_data = NULL;
 481         size_t payload_len = 0;
 482         int32_t ifaceidx = 0;
 483         struct sockaddr_in6 target = {AF_INET6, htons(DHCPV6_CLIENT_PORT),
 484                 0, IN6ADDR_ANY_INIT, 0};
 485         int otype, olen;
 486         uint8_t *odata, *end = data + len;
 487         /* Relay DHCPv6 reply from server to client */
 488         struct dhcpv6_relay_header *h = (void*)data;
 489
 490         syslog(LOG_DEBUG, "Got a DHCPv6-relay-reply");
 491
 492         if (len < sizeof(*h) || h->msg_type != DHCPV6_MSG_RELAY_REPL)
 493                 return;
 494
 495         memcpy(&target.sin6_addr, &h->peer_address, sizeof(struct in6_addr));
 496
 497         /* Go through options and find what we need */
 498         dhcpv6_for_each_option(h->options, end, otype, olen, odata) {
 499                 if (otype == DHCPV6_OPT_INTERFACE_ID
 500                                 && olen == sizeof(ifaceidx)) {
 501                         memcpy(&ifaceidx, odata, sizeof(ifaceidx));
 502                 } else if (otype == DHCPV6_OPT_RELAY_MSG) {
 503                         payload_data = odata;
 504                         payload_len = olen;
 505                 }
 506         }
 507
 508         /* Invalid interface-id or basic payload */
 509         struct interface *iface = odhcpd_get_interface_by_index(ifaceidx);
 510         if (!iface || iface->master || !payload_data || payload_len < 4)
 511                 return;
 512
 513         bool is_authenticated = false;
 514         struct in6_addr *dns_ptr = NULL;
 515         size_t dns_count = 0;
 516
 517         /* If the payload is relay-reply we have to send to the server port */
 518         if (payload_data[0] == DHCPV6_MSG_RELAY_REPL) {
 519                 target.sin6_port = htons(DHCPV6_SERVER_PORT);
 520         } else { /* Go through the payload data */
 521                 struct dhcpv6_client_header *h = (void*)payload_data;
 522                 end = payload_data + payload_len;
 523
 524                 dhcpv6_for_each_option(&h[1], end, otype, olen, odata) {
 525                         if (otype == DHCPV6_OPT_DNS_SERVERS && olen >= 16) {
 526                                 dns_ptr = (struct in6_addr*)odata;
 527                                 dns_count = olen / 16;
 528                         } else if (otype == DHCPV6_OPT_AUTH) {
 529                                 is_authenticated = true;
 530                         }
 531                 }
 532         }
 533
 534         /* Rewrite DNS servers if requested */
 535         if (iface->always_rewrite_dns && dns_ptr && dns_count > 0) {
 536                 if (is_authenticated)
 537                         return; /* Impossible to rewrite */
 538
 539                 const struct in6_addr *rewrite = iface->dns;
 540                 struct in6_addr addr;
 541                 size_t rewrite_cnt = iface->dns_cnt;
 542
 543                 if (rewrite_cnt == 0) {
 544                         if (odhcpd_get_interface_dns_addr(iface, &addr))
 545                                 return; /* Unable to get interface address */
 546
 547                         rewrite = &addr;
 548                         rewrite_cnt = 1;
 549                 }
 550
 551                 /* Copy over any other addresses */
 552                 for (size_t i = 0; i < dns_count; ++i) {
 553                         size_t j = (i < rewrite_cnt) ? i : rewrite_cnt - 1;
 554                         memcpy(&dns_ptr[i], &rewrite[j], sizeof(*rewrite));
 555                 }
 556         }
 557
 558         struct iovec iov = {payload_data, payload_len};
 559
 560         syslog(LOG_DEBUG, "Sending a DHCPv6-reply on %s", iface->name);
 561
 562         odhcpd_send(iface->dhcpv6_event.uloop.fd, &target, &iov, 1, iface);
 563 }
 564
 565 static struct odhcpd_ipaddr *relay_link_address(struct interface *iface)
 566 {
 567         struct odhcpd_ipaddr *addr = NULL;
 568         time_t now = odhcpd_time();
 569
 570         for (size_t i = 0; i < iface->addr6_len; i++) {
 571                 if (iface->addr6[i].valid <= (uint32_t)now)
 572                         continue;
 573
 574                 if (iface->addr6[i].preferred > (uint32_t)now) {
 575                         addr = &iface->addr6[i];
 576                         break;
 577                 }
 578
 579                 if (!addr || (iface->addr6[i].valid > addr->valid))
 580                         addr = &iface->addr6[i];
 581         }
 582
 583         return addr;
 584 }
 585
 586 /* Relay client request (regular DHCPv6-relay) */
 587 static void relay_client_request(struct sockaddr_in6 *source,
 588                 const void *data, size_t len, struct interface *iface)
 589 {
 590         const struct dhcpv6_relay_header *h = data;
 591         /* Construct our forwarding envelope */
 592         struct dhcpv6_relay_forward_envelope hdr = {
 593                 .msg_type = DHCPV6_MSG_RELAY_FORW,
 594                 .hop_count = 0,
 595                 .interface_id_type = htons(DHCPV6_OPT_INTERFACE_ID),
 596                 .interface_id_len = htons(sizeof(uint32_t)),
 597                 .relay_message_type = htons(DHCPV6_OPT_RELAY_MSG),
 598                 .relay_message_len = htons(len),
 599         };
 600         struct iovec iov[2] = {{&hdr, sizeof(hdr)}, {(void *)data, len}};
 601         struct interface *c;
 602         struct odhcpd_ipaddr *ip;
 603         struct sockaddr_in6 s;
 604
 605         if (h->msg_type == DHCPV6_MSG_RELAY_REPL ||
 606             h->msg_type == DHCPV6_MSG_RECONFIGURE ||
 607             h->msg_type == DHCPV6_MSG_REPLY ||
 608             h->msg_type == DHCPV6_MSG_ADVERTISE)
 609                 return; /* Invalid message types for client */
 610
 611         syslog(LOG_DEBUG, "Got a DHCPv6-request on %s", iface->name);
 612
 613         if (h->msg_type == DHCPV6_MSG_RELAY_FORW) { /* handle relay-forward */
 614                 if (h->hop_count >= DHCPV6_HOP_COUNT_LIMIT)
 615                         return; /* Invalid hop count */
 616
 617                 hdr.hop_count = h->hop_count + 1;
 618         }
 619
 620         /* use memcpy here as the destination fields are unaligned */
 621         memcpy(&hdr.peer_address, &source->sin6_addr, sizeof(struct in6_addr));
 622         memcpy(&hdr.interface_id_data, &iface->ifindex, sizeof(iface->ifindex));
 623
 624         /* Detect public IP of slave interface to use as link-address */
 625         ip = relay_link_address(iface);
 626         if (ip)
 627                 memcpy(&hdr.link_address, &ip->addr.in6, sizeof(hdr.link_address));
 628
 629         memset(&s, 0, sizeof(s));
 630         s.sin6_family = AF_INET6;
 631         s.sin6_port = htons(DHCPV6_SERVER_PORT);
 632         inet_pton(AF_INET6, ALL_DHCPV6_SERVERS, &s.sin6_addr);
 633
 634         avl_for_each_element(&interfaces, c, avl) {
 635                 if (!c->master || c->dhcpv6 != MODE_RELAY)
 636                         continue;
 637
 638                 if (!ip) {
 639                         /* No suitable address! Is the slave not configured yet?
 640                          * Detect public IP of master interface and use it instead
 641                          * This is WRONG and probably violates the RFC. However
 642                          * otherwise we have a hen and egg problem because the
 643                          * slave-interface cannot be auto-configured. */
 644                         ip = relay_link_address(c);
 645                         if (!ip)
 646                                 continue; /* Could not obtain a suitable address */
 647
 648                         memcpy(&hdr.link_address, &ip->addr.in6, sizeof(hdr.link_address));
 649                         ip = NULL;
 650                 }
 651
 652                 syslog(LOG_DEBUG, "Sending a DHCPv6-relay-forward on %s", c->name);
 653
 654                 odhcpd_send(c->dhcpv6_event.uloop.fd, &s, iov, 2, c);
 655         }
 656 }