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 enum {
 101         IOV_NESTED = 0,
 102         IOV_DEST,
 103         IOV_DNS,
 104         IOV_DNS_ADDR,
 105         IOV_SEARCH,
 106         IOV_SEARCH_DOMAIN,
 107         IOV_PDBUF,
 108 #define IOV_REFRESH IOV_PDBUF
 109         IOV_CERID,
 110         IOV_DHCPV6_RAW,
 111         IOV_RELAY_MSG,
 112         IOV_TOTAL
 113 };
 114
 115 static void handle_nested_message(uint8_t *data, size_t len,
 116                 uint8_t **opts, uint8_t **end, struct iovec iov[IOV_TOTAL - 1])
 117 {
 118         struct dhcpv6_relay_header *hdr = (struct dhcpv6_relay_header*)data;
 119         if (iov[IOV_NESTED].iov_base == NULL) {
 120                 iov[IOV_NESTED].iov_base = data;
 121                 iov[IOV_NESTED].iov_len = len;
 122         }
 123
 124         if (len < sizeof(struct dhcpv6_client_header))
 125                 return;
 126
 127         if (hdr->msg_type != DHCPV6_MSG_RELAY_FORW) {
 128                 iov[IOV_NESTED].iov_len = data - (uint8_t*)iov[IOV_NESTED].iov_base;
 129                 struct dhcpv6_client_header *hdr = (void*)data;
 130                 *opts = (uint8_t*)&hdr[1];
 131                 *end = data + len;
 132                 return;
 133         }
 134
 135         uint16_t otype, olen;
 136         uint8_t *odata;
 137         dhcpv6_for_each_option(hdr->options, data + len, otype, olen, odata) {
 138                 if (otype == DHCPV6_OPT_RELAY_MSG) {
 139                         iov[IOV_RELAY_MSG].iov_base = odata + olen;
 140                         iov[IOV_RELAY_MSG].iov_len = (((uint8_t*)iov[IOV_NESTED].iov_base) +
 141                                         iov[IOV_NESTED].iov_len) - (odata + olen);
 142                         handle_nested_message(odata, olen, opts, end, iov);
 143                         return;
 144                 }
 145         }
 146 }
 147
 148
 149 static void update_nested_message(uint8_t *data, size_t len, ssize_t pdiff)
 150 {
 151         struct dhcpv6_relay_header *hdr = (struct dhcpv6_relay_header*)data;
 152         if (hdr->msg_type != DHCPV6_MSG_RELAY_FORW)
 153                 return;
 154
 155         hdr->msg_type = DHCPV6_MSG_RELAY_REPL;
 156
 157         uint16_t otype, olen;
 158         uint8_t *odata;
 159         dhcpv6_for_each_option(hdr->options, data + len, otype, olen, odata) {
 160                 if (otype == DHCPV6_OPT_RELAY_MSG) {
 161                         olen += pdiff;
 162                         odata[-2] = (olen >> 8) & 0xff;
 163                         odata[-1] = olen & 0xff;
 164                         update_nested_message(odata, olen - pdiff, pdiff);
 165                         return;
 166                 }
 167         }
 168 }
 169
 170
 171 // Simple DHCPv6-server for information requests
 172 static void handle_client_request(void *addr, void *data, size_t len,
 173                 struct interface *iface)
 174 {
 175         struct dhcpv6_client_header *hdr = data;
 176         if (len < sizeof(*hdr))
 177                 return;
 178
 179         syslog(LOG_NOTICE, "Got DHCPv6 request");
 180
 181         // Construct reply message
 182         struct __attribute__((packed)) {
 183                 uint8_t msg_type;
 184                 uint8_t tr_id[3];
 185                 uint16_t serverid_type;
 186                 uint16_t serverid_length;
 187                 uint16_t duid_type;
 188                 uint16_t hardware_type;
 189                 uint8_t mac[6];
 190                 uint16_t solmaxrt_type;
 191                 uint16_t solmaxrt_length;
 192                 uint32_t solmaxrt_value;
 193                 uint16_t clientid_type;
 194                 uint16_t clientid_length;
 195                 uint8_t clientid_buf[130];
 196         } dest = {
 197                 .msg_type = DHCPV6_MSG_REPLY,
 198                 .serverid_type = htons(DHCPV6_OPT_SERVERID),
 199                 .serverid_length = htons(10),
 200                 .duid_type = htons(3),
 201                 .hardware_type = htons(1),
 202                 .solmaxrt_type = htons(DHCPV6_OPT_SOL_MAX_RT),
 203                 .solmaxrt_length = htons(4),
 204                 .solmaxrt_value = htonl(60),
 205                 .clientid_type = htons(DHCPV6_OPT_CLIENTID),
 206                 .clientid_buf = {0}
 207         };
 208         odhcpd_get_mac(iface, dest.mac);
 209
 210         struct __attribute__((packed)) {
 211                 uint16_t type;
 212                 uint16_t len;
 213                 uint16_t value;
 214         } stat = {htons(DHCPV6_OPT_STATUS), htons(sizeof(stat) - 4),
 215                         htons(DHCPV6_STATUS_NOADDRSAVAIL)};
 216
 217         struct __attribute__((packed)) {
 218                 uint16_t type;
 219                 uint16_t len;
 220                 uint32_t value;
 221         } refresh = {htons(DHCPV6_OPT_INFO_REFRESH), htons(sizeof(uint32_t)),
 222                         htonl(600)};
 223
 224         struct odhcpd_ipaddr ipaddr;
 225         struct in6_addr *dns_addr = iface->dns;
 226         size_t dns_cnt = iface->dns_cnt;
 227
 228         if (dns_cnt == 0 && odhcpd_get_interface_addresses(iface->ifindex, &ipaddr, 1) == 1) {
 229                 dns_addr = &ipaddr.addr;
 230                 dns_cnt = 1;
 231         }
 232
 233         struct {
 234                 uint16_t type;
 235                 uint16_t len;
 236         } dns = {htons(DHCPV6_OPT_DNS_SERVERS), htons(dns_cnt * sizeof(*dns_addr))};
 237
 238
 239
 240         // DNS Search options
 241         uint8_t search_buf[256], *search_domain = iface->search;
 242         size_t search_len = iface->search_len;
 243
 244         if (!search_domain && !res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 245                 int len = dn_comp(_res.dnsrch[0], search_buf,
 246                                 sizeof(search_buf), NULL, NULL);
 247                 if (len > 0) {
 248                         search_domain = search_buf;
 249                         search_len = len;
 250                 }
 251         }
 252
 253         struct {
 254                 uint16_t type;
 255                 uint16_t len;
 256         } search = {htons(DHCPV6_OPT_DNS_DOMAIN), htons(search_len)};
 257
 258
 259         struct dhcpv6_cer_id cerid = {
 260 #ifdef EXT_CER_ID
 261                 .type = htons(EXT_CER_ID),
 262 #endif
 263                 .len = htons(36),
 264                 .addr = iface->dhcpv6_pd_cer,
 265         };
 266
 267
 268         uint8_t pdbuf[512];
 269         struct iovec iov[IOV_TOTAL] = {
 270                 [IOV_NESTED] = {NULL, 0},
 271                 [IOV_DEST] = {&dest, (uint8_t*)&dest.clientid_type - (uint8_t*)&dest},
 272                 [IOV_DNS] = {&dns, (dns_cnt) ? sizeof(dns) : 0},
 273                 [IOV_DNS_ADDR] = {dns_addr, dns_cnt * sizeof(*dns_addr)},
 274                 [IOV_SEARCH] = {&search, (search_len) ? sizeof(search) : 0},
 275                 [IOV_SEARCH_DOMAIN] = {search_domain, search_len},
 276                 [IOV_PDBUF] = {pdbuf, 0},
 277                 [IOV_CERID] = {&cerid, 0},
 278                 [IOV_DHCPV6_RAW] = {iface->dhcpv6_raw, iface->dhcpv6_raw_len},
 279                 [IOV_RELAY_MSG] = {NULL, 0}
 280         };
 281
 282         uint8_t *opts = (uint8_t*)&hdr[1], *opts_end = (uint8_t*)data + len;
 283         if (hdr->msg_type == DHCPV6_MSG_RELAY_FORW)
 284                 handle_nested_message(data, len, &opts, &opts_end, iov);
 285
 286         memcpy(dest.tr_id, &opts[-3], sizeof(dest.tr_id));
 287
 288         if (opts[-4] == DHCPV6_MSG_ADVERTISE || opts[-4] == DHCPV6_MSG_REPLY || opts[-4] == DHCPV6_MSG_RELAY_REPL)
 289                 return;
 290
 291         if (opts[-4] == DHCPV6_MSG_SOLICIT) {
 292                 dest.msg_type = DHCPV6_MSG_ADVERTISE;
 293         } else if (opts[-4] == DHCPV6_MSG_INFORMATION_REQUEST) {
 294                 iov[IOV_REFRESH].iov_base = &refresh;
 295                 iov[IOV_REFRESH].iov_len = sizeof(refresh);
 296         }
 297
 298         // Go through options and find what we need
 299         uint16_t otype, olen;
 300         uint8_t *odata;
 301         dhcpv6_for_each_option(opts, opts_end, otype, olen, odata) {
 302                 if (otype == DHCPV6_OPT_CLIENTID && olen <= 130) {
 303                         dest.clientid_length = htons(olen);
 304                         memcpy(dest.clientid_buf, odata, olen);
 305                         iov[IOV_DEST].iov_len += 4 + olen;
 306                 } else if (otype == DHCPV6_OPT_SERVERID) {
 307                         if (olen != ntohs(dest.serverid_length) ||
 308                                         memcmp(odata, &dest.duid_type, olen))
 309                                 return; // Not for us
 310                 } else if (iface->filter_class && otype == DHCPV6_OPT_USER_CLASS) {
 311                         uint8_t *c = odata, *cend = &odata[olen];
 312                         for (; &c[2] <= cend && &c[2 + (c[0] << 8) + c[1]] <= cend; c = &c[2 + (c[0] << 8) + c[1]]) {
 313                                 size_t elen = strlen(iface->filter_class);
 314                                 if (((((size_t)c[0]) << 8) | c[1]) == elen && !memcmp(&c[2], iface->filter_class, elen))
 315                                         return; // Ignore from homenet
 316                         }
 317                 } else if (otype == DHCPV6_OPT_IA_PD) {
 318 #ifdef EXT_CER_ID
 319                         iov[IOV_CERID].iov_len = sizeof(cerid);
 320
 321                         if (IN6_IS_ADDR_UNSPECIFIED(&cerid.addr)) {
 322                                 struct odhcpd_ipaddr addrs[32];
 323                                 ssize_t len = odhcpd_get_interface_addresses(0, addrs,
 324                                                 sizeof(addrs) / sizeof(*addrs));
 325
 326                                 for (ssize_t i = 0; i < len; ++i)
 327                                         if (IN6_IS_ADDR_UNSPECIFIED(&cerid.addr)
 328                                                         || memcmp(&addrs[i].addr, &cerid.addr, sizeof(cerid.addr)) < 0)
 329                                                 cerid.addr = addrs[i].addr;
 330                         }
 331 #endif
 332                 }
 333         }
 334
 335         if (opts[-4] != DHCPV6_MSG_INFORMATION_REQUEST) {
 336                 ssize_t ialen = dhcpv6_handle_ia(pdbuf, sizeof(pdbuf), iface, addr, &opts[-4], opts_end);
 337                 iov[IOV_PDBUF].iov_len = ialen;
 338                 if (ialen < 0 || (ialen == 0 && (opts[-4] == DHCPV6_MSG_REBIND || opts[-4] == DHCPV6_MSG_CONFIRM)))
 339                         return;
 340         }
 341
 342         if (iov[IOV_NESTED].iov_len > 0) // Update length
 343                 update_nested_message(data, len, iov[IOV_DEST].iov_len + iov[IOV_DNS].iov_len +
 344                                 iov[IOV_DNS_ADDR].iov_len + iov[IOV_SEARCH].iov_len +
 345                                 iov[IOV_SEARCH_DOMAIN].iov_len + iov[IOV_PDBUF].iov_len +
 346                                 iov[IOV_CERID].iov_len + iov[IOV_DHCPV6_RAW].iov_len - (4 + opts_end - opts));
 347
 348         odhcpd_send(iface->dhcpv6_event.uloop.fd, addr, iov, ARRAY_SIZE(iov), iface);
 349 }
 350
 351
 352 // Central DHCPv6-relay handler
 353 static void handle_dhcpv6(void *addr, void *data, size_t len,
 354                 struct interface *iface)
 355 {
 356         if (iface->dhcpv6 == RELAYD_SERVER) {
 357                 handle_client_request(addr, data, len, iface);
 358         } else if (iface->dhcpv6 == RELAYD_RELAY) {
 359                 if (iface->master)
 360                         relay_server_response(data, len);
 361                 else
 362                         relay_client_request(addr, data, len, iface);
 363         }
 364 }
 365
 366
 367 // Relay server response (regular relay server handling)
 368 static void relay_server_response(uint8_t *data, size_t len)
 369 {
 370         // Information we need to gather
 371         uint8_t *payload_data = NULL;
 372         size_t payload_len = 0;
 373         int32_t ifaceidx = 0;
 374         struct sockaddr_in6 target = {AF_INET6, htons(DHCPV6_CLIENT_PORT),
 375                 0, IN6ADDR_ANY_INIT, 0};
 376
 377         syslog(LOG_NOTICE, "Got a DHCPv6-reply");
 378
 379         int otype, olen;
 380         uint8_t *odata, *end = data + len;
 381
 382         // Relay DHCPv6 reply from server to client
 383         struct dhcpv6_relay_header *h = (void*)data;
 384         if (len < sizeof(*h) || h->msg_type != DHCPV6_MSG_RELAY_REPL)
 385                 return;
 386
 387         memcpy(&target.sin6_addr, &h->peer_address,
 388                         sizeof(struct in6_addr));
 389
 390         // Go through options and find what we need
 391         dhcpv6_for_each_option(h->options, end, otype, olen, odata) {
 392                 if (otype == DHCPV6_OPT_INTERFACE_ID
 393                                 && olen == sizeof(ifaceidx)) {
 394                         memcpy(&ifaceidx, odata, sizeof(ifaceidx));
 395                 } else if (otype == DHCPV6_OPT_RELAY_MSG) {
 396                         payload_data = odata;
 397                         payload_len = olen;
 398                 }
 399         }
 400
 401         // Invalid interface-id or basic payload
 402         struct interface *iface = odhcpd_get_interface_by_index(ifaceidx);
 403         if (!iface || iface->master || !payload_data || payload_len < 4)
 404                 return;
 405
 406         bool is_authenticated = false;
 407         struct in6_addr *dns_ptr = NULL;
 408         size_t dns_count = 0;
 409
 410         // If the payload is relay-reply we have to send to the server port
 411         if (payload_data[0] == DHCPV6_MSG_RELAY_REPL) {
 412                 target.sin6_port = htons(DHCPV6_SERVER_PORT);
 413         } else { // Go through the payload data
 414                 struct dhcpv6_client_header *h = (void*)payload_data;
 415                 end = payload_data + payload_len;
 416
 417                 dhcpv6_for_each_option(&h[1], end, otype, olen, odata) {
 418                         if (otype == DHCPV6_OPT_DNS_SERVERS && olen >= 16) {
 419                                 dns_ptr = (struct in6_addr*)odata;
 420                                 dns_count = olen / 16;
 421                         } else if (otype == DHCPV6_OPT_AUTH) {
 422                                 is_authenticated = true;
 423                         }
 424                 }
 425         }
 426
 427         // Rewrite DNS servers if requested
 428         if (iface->always_rewrite_dns && dns_ptr && dns_count > 0) {
 429                 if (is_authenticated)
 430                         return; // Impossible to rewrite
 431
 432                 struct odhcpd_ipaddr ip;
 433                 const struct in6_addr *rewrite = iface->dns;
 434                 size_t rewrite_cnt = iface->dns_cnt;
 435
 436                 if (rewrite_cnt == 0) {
 437                         if (odhcpd_get_interface_addresses(iface->ifindex, &ip, 1) < 1)
 438                                 return; // Unable to get interface address
 439
 440                         rewrite = &ip.addr;
 441                         rewrite_cnt = 1;
 442                 }
 443
 444                 // Copy over any other addresses
 445                 for (size_t i = 0; i < dns_count; ++i) {
 446                         size_t j = (i < rewrite_cnt) ? i : rewrite_cnt - 1;
 447                         memcpy(&dns_ptr[i], &rewrite[j], sizeof(*rewrite));
 448                 }
 449         }
 450
 451         struct iovec iov = {payload_data, payload_len};
 452         odhcpd_send(iface->dhcpv6_event.uloop.fd, &target, &iov, 1, iface);
 453 }
 454
 455
 456 // Relay client request (regular DHCPv6-relay)
 457 static void relay_client_request(struct sockaddr_in6 *source,
 458                 const void *data, size_t len, struct interface *iface)
 459 {
 460         struct interface *master = odhcpd_get_master_interface();
 461         const struct dhcpv6_relay_header *h = data;
 462         if (!master || master->dhcpv6 != RELAYD_RELAY ||
 463                         h->msg_type == DHCPV6_MSG_RELAY_REPL ||
 464                         h->msg_type == DHCPV6_MSG_RECONFIGURE ||
 465                         h->msg_type == DHCPV6_MSG_REPLY ||
 466                         h->msg_type == DHCPV6_MSG_ADVERTISE)
 467                 return; // Invalid message types for client
 468
 469         syslog(LOG_NOTICE, "Got a DHCPv6-request");
 470
 471         // Construct our forwarding envelope
 472         struct dhcpv6_relay_forward_envelope hdr = {
 473                 .msg_type = DHCPV6_MSG_RELAY_FORW,
 474                 .hop_count = 0,
 475                 .interface_id_type = htons(DHCPV6_OPT_INTERFACE_ID),
 476                 .interface_id_len = htons(sizeof(uint32_t)),
 477                 .relay_message_type = htons(DHCPV6_OPT_RELAY_MSG),
 478                 .relay_message_len = htons(len),
 479         };
 480
 481         if (h->msg_type == DHCPV6_MSG_RELAY_FORW) { // handle relay-forward
 482                 if (h->hop_count >= DHCPV6_HOP_COUNT_LIMIT)
 483                         return; // Invalid hop count
 484                 else
 485                         hdr.hop_count = h->hop_count + 1;
 486         }
 487
 488         // use memcpy here as the destination fields are unaligned
 489         uint32_t ifindex = iface->ifindex;
 490         memcpy(&hdr.peer_address, &source->sin6_addr, sizeof(struct in6_addr));
 491         memcpy(&hdr.interface_id_data, &ifindex, sizeof(ifindex));
 492
 493         // Detect public IP of slave interface to use as link-address
 494         struct odhcpd_ipaddr ip;
 495         if (odhcpd_get_interface_addresses(iface->ifindex, &ip, 1) < 1) {
 496                 // No suitable address! Is the slave not configured yet?
 497                 // Detect public IP of master interface and use it instead
 498                 // This is WRONG and probably violates the RFC. However
 499                 // otherwise we have a hen and egg problem because the
 500                 // slave-interface cannot be auto-configured.
 501                 if (odhcpd_get_interface_addresses(master->ifindex, &ip, 1) < 1)
 502                         return; // Could not obtain a suitable address
 503         }
 504         memcpy(&hdr.link_address, &ip.addr, sizeof(hdr.link_address));
 505
 506         struct sockaddr_in6 dhcpv6_servers = {AF_INET6,
 507                         htons(DHCPV6_SERVER_PORT), 0, ALL_DHCPV6_SERVERS, 0};
 508         struct iovec iov[2] = {{&hdr, sizeof(hdr)}, {(void*)data, len}};
 509         odhcpd_send(iface->dhcpv6_event.uloop.fd, &dhcpv6_servers, iov, 2, master);
 510 }