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
  22 #include "odhcpd.h"
  23 #include "dhcpv6.h"
  24
  25
  26 static void relay_client_request(struct sockaddr_in6 *source,
  27                 const void *data, size_t len, struct interface *iface);
  28 static void relay_server_response(uint8_t *data, size_t len);
  29
  30 static void handle_dhcpv6(void *addr, void *data, size_t len,
  31                 struct interface *iface);
  32 static void handle_client_request(void *addr, void *data, size_t len,
  33                 struct interface *iface);
  34
  35
  36
  37 // Create socket and register events
  38 int init_dhcpv6(void)
  39 {
  40         dhcpv6_ia_init();
  41         return 0;
  42 }
  43
  44
  45 int setup_dhcpv6_interface(struct interface *iface, bool enable)
  46 {
  47         if (iface->dhcpv6_event.uloop.fd > 0) {
  48                 uloop_fd_delete(&iface->dhcpv6_event.uloop);
  49                 close(iface->dhcpv6_event.uloop.fd);
  50                 iface->dhcpv6_event.uloop.fd = -1;
  51         }
  52
  53         // Configure multicast settings
  54         if (enable && iface->dhcpv6 && !iface->master) {
  55                 int sock = socket(AF_INET6, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
  56                 if (sock < 0) {
  57                         syslog(LOG_ERR, "Failed to create DHCPv6 server socket: %s",
  58                                         strerror(errno));
  59                         return -1;
  60                 }
  61
  62                 // Basic IPv6 configuration
  63                 setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, iface->ifname, strlen(iface->ifname));
  64
  65                 int val = 1;
  66                 setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, &val, sizeof(val));
  67                 setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
  68                 setsockopt(sock, IPPROTO_IPV6, IPV6_RECVPKTINFO, &val, sizeof(val));
  69
  70                 val = DHCPV6_HOP_COUNT_LIMIT;
  71                 setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
  72
  73                 val = 0;
  74                 setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &val, sizeof(val));
  75
  76                 struct sockaddr_in6 bind_addr = {AF_INET6, htons(DHCPV6_SERVER_PORT),
  77                                         0, IN6ADDR_ANY_INIT, 0};
  78
  79                 if (bind(sock, (struct sockaddr*)&bind_addr, sizeof(bind_addr))) {
  80                         syslog(LOG_ERR, "Failed to open DHCPv6 server socket: %s",
  81                                         strerror(errno));
  82                         return -1;
  83                 }
  84
  85                 struct ipv6_mreq relay = {ALL_DHCPV6_RELAYS, iface->ifindex};
  86                 struct ipv6_mreq server = {ALL_DHCPV6_SERVERS, iface->ifindex};
  87                 setsockopt(sock, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &relay, sizeof(relay));
  88
  89                 if (iface->dhcpv6 == RELAYD_SERVER)
  90                         setsockopt(sock, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &server, sizeof(server));
  91
  92                 iface->dhcpv6_event.uloop.fd = sock;
  93                 iface->dhcpv6_event.handle_dgram = handle_dhcpv6;
  94                 odhcpd_register(&iface->dhcpv6_event);
  95         }
  96
  97         return setup_dhcpv6_ia_interface(iface, enable);
  98 }
  99
 100
 101 static void handle_nested_message(uint8_t *data, size_t len,
 102                 uint8_t **opts, uint8_t **end, struct iovec iov[9])
 103 {
 104         struct dhcpv6_relay_header *hdr = (struct dhcpv6_relay_header*)data;
 105         if (iov[0].iov_base == NULL) {
 106                 iov[0].iov_base = data;
 107                 iov[0].iov_len = len;
 108         }
 109
 110         if (len < sizeof(struct dhcpv6_client_header))
 111                 return;
 112
 113         if (hdr->msg_type != DHCPV6_MSG_RELAY_FORW) {
 114                 iov[0].iov_len = data - (uint8_t*)iov[0].iov_base;
 115                 struct dhcpv6_client_header *hdr = (void*)data;
 116                 *opts = (uint8_t*)&hdr[1];
 117                 *end = data + len;
 118                 return;
 119         }
 120
 121         uint16_t otype, olen;
 122         uint8_t *odata;
 123         dhcpv6_for_each_option(hdr->options, data + len, otype, olen, odata) {
 124                 if (otype == DHCPV6_OPT_RELAY_MSG) {
 125                         iov[9].iov_base = odata + olen;
 126                         iov[9].iov_len = (((uint8_t*)iov[0].iov_base) + iov[0].iov_len)
 127                                         - (odata + olen);
 128                         handle_nested_message(odata, olen, opts, end, iov);
 129                         return;
 130                 }
 131         }
 132 }
 133
 134
 135 static void update_nested_message(uint8_t *data, size_t len, ssize_t pdiff)
 136 {
 137         struct dhcpv6_relay_header *hdr = (struct dhcpv6_relay_header*)data;
 138         if (hdr->msg_type != DHCPV6_MSG_RELAY_FORW)
 139                 return;
 140
 141         hdr->msg_type = DHCPV6_MSG_RELAY_REPL;
 142
 143         uint16_t otype, olen;
 144         uint8_t *odata;
 145         dhcpv6_for_each_option(hdr->options, data + len, otype, olen, odata) {
 146                 if (otype == DHCPV6_OPT_RELAY_MSG) {
 147                         olen += pdiff;
 148                         odata[-2] = (olen >> 8) & 0xff;
 149                         odata[-1] = olen & 0xff;
 150                         update_nested_message(odata, olen - pdiff, pdiff);
 151                         return;
 152                 }
 153         }
 154 }
 155
 156
 157 // Simple DHCPv6-server for information requests
 158 static void handle_client_request(void *addr, void *data, size_t len,
 159                 struct interface *iface)
 160 {
 161         struct dhcpv6_client_header *hdr = data;
 162         if (len < sizeof(*hdr))
 163                 return;
 164
 165         syslog(LOG_NOTICE, "Got DHCPv6 request");
 166
 167         // Construct reply message
 168         struct __attribute__((packed)) {
 169                 uint8_t msg_type;
 170                 uint8_t tr_id[3];
 171                 uint16_t serverid_type;
 172                 uint16_t serverid_length;
 173                 uint16_t duid_type;
 174                 uint16_t hardware_type;
 175                 uint8_t mac[6];
 176                 uint16_t solmaxrt_type;
 177                 uint16_t solmaxrt_length;
 178                 uint32_t solmaxrt_value;
 179                 uint16_t clientid_type;
 180                 uint16_t clientid_length;
 181                 uint8_t clientid_buf[130];
 182         } dest = {
 183                 .msg_type = DHCPV6_MSG_REPLY,
 184                 .serverid_type = htons(DHCPV6_OPT_SERVERID),
 185                 .serverid_length = htons(10),
 186                 .duid_type = htons(3),
 187                 .hardware_type = htons(1),
 188                 .solmaxrt_type = htons(DHCPV6_OPT_SOL_MAX_RT),
 189                 .solmaxrt_length = htons(4),
 190                 .solmaxrt_value = htonl(60),
 191                 .clientid_type = htons(DHCPV6_OPT_CLIENTID),
 192                 .clientid_buf = {0}
 193         };
 194         odhcpd_get_mac(iface, dest.mac);
 195
 196         struct __attribute__((packed)) {
 197                 uint16_t type;
 198                 uint16_t len;
 199                 uint16_t value;
 200         } stat = {htons(DHCPV6_OPT_STATUS), htons(sizeof(stat) - 4),
 201                         htons(DHCPV6_STATUS_NOADDRSAVAIL)};
 202
 203         struct __attribute__((packed)) {
 204                 uint16_t type;
 205                 uint16_t len;
 206                 uint32_t value;
 207         } refresh = {htons(DHCPV6_OPT_INFO_REFRESH), htons(sizeof(uint32_t)),
 208                         htonl(600)};
 209
 210         struct odhcpd_ipaddr ipaddr;
 211         struct in6_addr *dns_addr = iface->dns;
 212         size_t dns_cnt = iface->dns_cnt;
 213
 214         if (dns_cnt == 0 && odhcpd_get_interface_addresses(iface->ifindex, &ipaddr, 1) == 1) {
 215                 dns_addr = &ipaddr.addr;
 216                 dns_cnt = 1;
 217         }
 218
 219         struct {
 220                 uint16_t type;
 221                 uint16_t len;
 222         } dns = {htons(DHCPV6_OPT_DNS_SERVERS), htons(dns_cnt * sizeof(*dns_addr))};
 223
 224
 225
 226         // DNS Search options
 227         uint8_t search_buf[256], *search_domain = iface->search;
 228         size_t search_len = iface->search_len;
 229
 230         if (!search_domain && !res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 231                 int len = dn_comp(_res.dnsrch[0], search_buf,
 232                                 sizeof(search_buf), NULL, NULL);
 233                 if (len > 0) {
 234                         search_domain = search_buf;
 235                         search_len = len;
 236                 }
 237         }
 238
 239         struct {
 240                 uint16_t type;
 241                 uint16_t len;
 242         } search = {htons(DHCPV6_OPT_DNS_DOMAIN), htons(search_len)};
 243
 244
 245         struct dhcpv6_cer_id cerid = {
 246 #ifdef EXT_CER_ID
 247                 .type = htons(EXT_CER_ID),
 248 #endif
 249                 .len = htons(36),
 250                 .addr = iface->dhcpv6_pd_cer,
 251         };
 252
 253
 254         uint8_t pdbuf[512];
 255         struct iovec iov[] = {{NULL, 0},
 256                         {&dest, (uint8_t*)&dest.clientid_type - (uint8_t*)&dest},
 257                         {&dns, (dns_cnt) ? sizeof(dns) : 0},
 258                         {dns_addr, dns_cnt * sizeof(*dns_addr)},
 259                         {&search, (search_len) ? sizeof(search) : 0},
 260                         {search_domain, search_len},
 261                         {pdbuf, 0},
 262                         {&cerid, 0},
 263                         {iface->dhcpv6_raw, iface->dhcpv6_raw_len},
 264                         {NULL, 0}};
 265
 266         uint8_t *opts = (uint8_t*)&hdr[1], *opts_end = (uint8_t*)data + len;
 267         if (hdr->msg_type == DHCPV6_MSG_RELAY_FORW)
 268                 handle_nested_message(data, len, &opts, &opts_end, iov);
 269
 270         memcpy(dest.tr_id, &opts[-3], sizeof(dest.tr_id));
 271
 272         if (opts[-4] == DHCPV6_MSG_ADVERTISE || opts[-4] == DHCPV6_MSG_REPLY || opts[-4] == DHCPV6_MSG_RELAY_REPL)
 273                 return;
 274
 275         if (opts[-4] == DHCPV6_MSG_SOLICIT) {
 276                 dest.msg_type = DHCPV6_MSG_ADVERTISE;
 277         } else if (opts[-4] == DHCPV6_MSG_INFORMATION_REQUEST) {
 278                 iov[6].iov_base = &refresh;
 279                 iov[6].iov_len = sizeof(refresh);
 280         }
 281
 282         // Go through options and find what we need
 283         uint16_t otype, olen;
 284         uint8_t *odata;
 285         dhcpv6_for_each_option(opts, opts_end, otype, olen, odata) {
 286                 if (otype == DHCPV6_OPT_CLIENTID && olen <= 130) {
 287                         dest.clientid_length = htons(olen);
 288                         memcpy(dest.clientid_buf, odata, olen);
 289                         iov[1].iov_len += 4 + olen;
 290                 } else if (otype == DHCPV6_OPT_SERVERID) {
 291                         if (olen != ntohs(dest.serverid_length) ||
 292                                         memcmp(odata, &dest.duid_type, olen))
 293                                 return; // Not for us
 294                 } else if (iface->filter_class && otype == DHCPV6_OPT_USER_CLASS) {
 295                         uint8_t *c = odata, *cend = &odata[olen];
 296                         for (; &c[2] <= cend && &c[2 + (c[0] << 8) + c[1]] <= cend; c = &c[2 + (c[0] << 8) + c[1]]) {
 297                                 size_t elen = strlen(iface->filter_class);
 298                                 if (((((size_t)c[0]) << 8) | c[1]) == elen && !memcmp(&c[2], iface->filter_class, elen))
 299                                         return; // Ignore from homenet
 300                         }
 301                 } else if (otype == DHCPV6_OPT_IA_PD) {
 302 #ifdef EXT_CER_ID
 303                         iov[7].iov_len = sizeof(cerid);
 304
 305                         if (IN6_IS_ADDR_UNSPECIFIED(&cerid.addr)) {
 306                                 struct odhcpd_ipaddr addrs[32];
 307                                 ssize_t len = odhcpd_get_interface_addresses(0, addrs,
 308                                                 sizeof(addrs) / sizeof(*addrs));
 309
 310                                 for (ssize_t i = 0; i < len; ++i)
 311                                         if (IN6_IS_ADDR_UNSPECIFIED(&cerid.addr)
 312                                                         || memcmp(&addrs[i].addr, &cerid.addr, sizeof(cerid.addr)) < 0)
 313                                                 cerid.addr = addrs[i].addr;
 314                         }
 315 #endif
 316                 }
 317         }
 318
 319         if (opts[-4] != DHCPV6_MSG_INFORMATION_REQUEST) {
 320                 ssize_t ialen = dhcpv6_handle_ia(pdbuf, sizeof(pdbuf), iface, addr, &opts[-4], opts_end);
 321                 iov[6].iov_len = ialen;
 322                 if (ialen < 0 || (ialen == 0 && (opts[-4] == DHCPV6_MSG_REBIND || opts[-4] == DHCPV6_MSG_CONFIRM)))
 323                         return;
 324         }
 325
 326         if (iov[0].iov_len > 0) // Update length
 327                 update_nested_message(data, len, iov[1].iov_len + iov[2].iov_len +
 328                                 iov[3].iov_len + iov[4].iov_len + iov[5].iov_len +
 329                                 iov[6].iov_len + iov[7].iov_len - (4 + opts_end - opts));
 330
 331         odhcpd_send(iface->dhcpv6_event.uloop.fd, addr, iov, ARRAY_SIZE(iov), iface);
 332 }
 333
 334
 335 // Central DHCPv6-relay handler
 336 static void handle_dhcpv6(void *addr, void *data, size_t len,
 337                 struct interface *iface)
 338 {
 339         if (iface->dhcpv6 == RELAYD_SERVER) {
 340                 handle_client_request(addr, data, len, iface);
 341         } else if (iface->dhcpv6 == RELAYD_RELAY) {
 342                 if (iface->master)
 343                         relay_server_response(data, len);
 344                 else
 345                         relay_client_request(addr, data, len, iface);
 346         }
 347 }
 348
 349
 350 // Relay server response (regular relay server handling)
 351 static void relay_server_response(uint8_t *data, size_t len)
 352 {
 353         // Information we need to gather
 354         uint8_t *payload_data = NULL;
 355         size_t payload_len = 0;
 356         int32_t ifaceidx = 0;
 357         struct sockaddr_in6 target = {AF_INET6, htons(DHCPV6_CLIENT_PORT),
 358                 0, IN6ADDR_ANY_INIT, 0};
 359
 360         syslog(LOG_NOTICE, "Got a DHCPv6-reply");
 361
 362         int otype, olen;
 363         uint8_t *odata, *end = data + len;
 364
 365         // Relay DHCPv6 reply from server to client
 366         struct dhcpv6_relay_header *h = (void*)data;
 367         if (len < sizeof(*h) || h->msg_type != DHCPV6_MSG_RELAY_REPL)
 368                 return;
 369
 370         memcpy(&target.sin6_addr, &h->peer_address,
 371                         sizeof(struct in6_addr));
 372
 373         // Go through options and find what we need
 374         dhcpv6_for_each_option(h->options, end, otype, olen, odata) {
 375                 if (otype == DHCPV6_OPT_INTERFACE_ID
 376                                 && olen == sizeof(ifaceidx)) {
 377                         memcpy(&ifaceidx, odata, sizeof(ifaceidx));
 378                 } else if (otype == DHCPV6_OPT_RELAY_MSG) {
 379                         payload_data = odata;
 380                         payload_len = olen;
 381                 }
 382         }
 383
 384         // Invalid interface-id or basic payload
 385         struct interface *iface = odhcpd_get_interface_by_index(ifaceidx);
 386         if (!iface || iface->master || !payload_data || payload_len < 4)
 387                 return;
 388
 389         bool is_authenticated = false;
 390         struct in6_addr *dns_ptr = NULL;
 391         size_t dns_count = 0;
 392
 393         // If the payload is relay-reply we have to send to the server port
 394         if (payload_data[0] == DHCPV6_MSG_RELAY_REPL) {
 395                 target.sin6_port = htons(DHCPV6_SERVER_PORT);
 396         } else { // Go through the payload data
 397                 struct dhcpv6_client_header *h = (void*)payload_data;
 398                 end = payload_data + payload_len;
 399
 400                 dhcpv6_for_each_option(&h[1], end, otype, olen, odata) {
 401                         if (otype == DHCPV6_OPT_DNS_SERVERS && olen >= 16) {
 402                                 dns_ptr = (struct in6_addr*)odata;
 403                                 dns_count = olen / 16;
 404                         } else if (otype == DHCPV6_OPT_AUTH) {
 405                                 is_authenticated = true;
 406                         }
 407                 }
 408         }
 409
 410         // Rewrite DNS servers if requested
 411         if (iface->always_rewrite_dns && dns_ptr && dns_count > 0) {
 412                 if (is_authenticated)
 413                         return; // Impossible to rewrite
 414
 415                 struct odhcpd_ipaddr ip;
 416                 const struct in6_addr *rewrite = iface->dns;
 417                 size_t rewrite_cnt = iface->dns_cnt;
 418
 419                 if (rewrite_cnt == 0) {
 420                         if (odhcpd_get_interface_addresses(iface->ifindex, &ip, 1) < 1)
 421                                 return; // Unable to get interface address
 422
 423                         rewrite = &ip.addr;
 424                         rewrite_cnt = 1;
 425                 }
 426
 427                 // Copy over any other addresses
 428                 for (size_t i = 0; i < dns_count; ++i) {
 429                         size_t j = (i < rewrite_cnt) ? i : rewrite_cnt - 1;
 430                         memcpy(&dns_ptr[i], &rewrite[j], sizeof(*rewrite));
 431                 }
 432         }
 433
 434         struct iovec iov = {payload_data, payload_len};
 435         odhcpd_send(iface->dhcpv6_event.uloop.fd, &target, &iov, 1, iface);
 436 }
 437
 438
 439 // Relay client request (regular DHCPv6-relay)
 440 static void relay_client_request(struct sockaddr_in6 *source,
 441                 const void *data, size_t len, struct interface *iface)
 442 {
 443         struct interface *master = odhcpd_get_master_interface();
 444         const struct dhcpv6_relay_header *h = data;
 445         if (!master || master->dhcpv6 != RELAYD_RELAY ||
 446                         h->msg_type == DHCPV6_MSG_RELAY_REPL ||
 447                         h->msg_type == DHCPV6_MSG_RECONFIGURE ||
 448                         h->msg_type == DHCPV6_MSG_REPLY ||
 449                         h->msg_type == DHCPV6_MSG_ADVERTISE)
 450                 return; // Invalid message types for client
 451
 452         syslog(LOG_NOTICE, "Got a DHCPv6-request");
 453
 454         // Construct our forwarding envelope
 455         struct dhcpv6_relay_forward_envelope hdr = {
 456                 .msg_type = DHCPV6_MSG_RELAY_FORW,
 457                 .hop_count = 0,
 458                 .interface_id_type = htons(DHCPV6_OPT_INTERFACE_ID),
 459                 .interface_id_len = htons(sizeof(uint32_t)),
 460                 .relay_message_type = htons(DHCPV6_OPT_RELAY_MSG),
 461                 .relay_message_len = htons(len),
 462         };
 463
 464         if (h->msg_type == DHCPV6_MSG_RELAY_FORW) { // handle relay-forward
 465                 if (h->hop_count >= DHCPV6_HOP_COUNT_LIMIT)
 466                         return; // Invalid hop count
 467                 else
 468                         hdr.hop_count = h->hop_count + 1;
 469         }
 470
 471         // use memcpy here as the destination fields are unaligned
 472         uint32_t ifindex = iface->ifindex;
 473         memcpy(&hdr.peer_address, &source->sin6_addr, sizeof(struct in6_addr));
 474         memcpy(&hdr.interface_id_data, &ifindex, sizeof(ifindex));
 475
 476         // Detect public IP of slave interface to use as link-address
 477         struct odhcpd_ipaddr ip;
 478         if (odhcpd_get_interface_addresses(iface->ifindex, &ip, 1) < 1) {
 479                 // No suitable address! Is the slave not configured yet?
 480                 // Detect public IP of master interface and use it instead
 481                 // This is WRONG and probably violates the RFC. However
 482                 // otherwise we have a hen and egg problem because the
 483                 // slave-interface cannot be auto-configured.
 484                 if (odhcpd_get_interface_addresses(master->ifindex, &ip, 1) < 1)
 485                         return; // Could not obtain a suitable address
 486         }
 487         memcpy(&hdr.link_address, &ip.addr, sizeof(hdr.link_address));
 488
 489         struct sockaddr_in6 dhcpv6_servers = {AF_INET6,
 490                         htons(DHCPV6_SERVER_PORT), 0, ALL_DHCPV6_SERVERS, 0};
 491         struct iovec iov[2] = {{&hdr, sizeof(hdr)}, {(void*)data, len}};
 492         odhcpd_send(iface->dhcpv6_event.uloop.fd, &dhcpv6_servers, iov, 2, master);
 493 }