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