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[6])
 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[7].iov_base = odata + olen;
 126                         iov[7].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 clientid_type;
 177                 uint16_t clientid_length;
 178                 uint8_t clientid_buf[130];
 179         } dest = {
 180                 .msg_type = DHCPV6_MSG_REPLY,
 181                 .serverid_type = htons(DHCPV6_OPT_SERVERID),
 182                 .serverid_length = htons(10),
 183                 .duid_type = htons(3),
 184                 .hardware_type = htons(1),
 185                 .clientid_type = htons(DHCPV6_OPT_CLIENTID),
 186                 .clientid_buf = {0}
 187         };
 188         odhcpd_get_mac(iface, dest.mac);
 189
 190         struct __attribute__((packed)) {
 191                 uint16_t type;
 192                 uint16_t len;
 193                 uint16_t value;
 194         } stat = {htons(DHCPV6_OPT_STATUS), htons(sizeof(stat) - 4),
 195                         htons(DHCPV6_STATUS_NOADDRSAVAIL)};
 196
 197         struct __attribute__((packed)) {
 198                 uint16_t type;
 199                 uint16_t len;
 200                 uint32_t value;
 201         } refresh = {htons(DHCPV6_OPT_INFO_REFRESH), htons(sizeof(uint32_t)),
 202                         htonl(600)};
 203
 204         struct odhcpd_ipaddr ipaddr;
 205         struct in6_addr *dns_addr = iface->dns;
 206         size_t dns_cnt = iface->dns_cnt;
 207
 208         if (dns_cnt == 0 && odhcpd_get_interface_addresses(iface->ifindex, &ipaddr, 1) == 1) {
 209                 dns_addr = &ipaddr.addr;
 210                 dns_cnt = 1;
 211         }
 212
 213         struct {
 214                 uint16_t type;
 215                 uint16_t len;
 216         } dns = {htons(DHCPV6_OPT_DNS_SERVERS), htons(dns_cnt * sizeof(*dns_addr))};
 217
 218
 219
 220         // DNS Search options
 221         uint8_t search_buf[256], *search_domain = iface->search;
 222         size_t search_len = iface->search_len;
 223
 224         if (!search_domain && !res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 225                 int len = dn_comp(_res.dnsrch[0], search_buf,
 226                                 sizeof(search_buf), NULL, NULL);
 227                 if (len > 0) {
 228                         search_domain = search_buf;
 229                         search_len = len;
 230                 }
 231         }
 232
 233         struct {
 234                 uint16_t type;
 235                 uint16_t len;
 236         } search = {htons(DHCPV6_OPT_DNS_DOMAIN), htons(search_len)};
 237
 238
 239
 240         uint8_t pdbuf[512];
 241         struct iovec iov[] = {{NULL, 0},
 242                         {&dest, (uint8_t*)&dest.clientid_type - (uint8_t*)&dest},
 243                         {&dns, (dns_cnt) ? sizeof(dns) : 0},
 244                         {dns_addr, dns_cnt * sizeof(*dns_addr)},
 245                         {&search, (search_len) ? sizeof(search) : 0},
 246                         {search_domain, search_len},
 247                         {pdbuf, 0},
 248                         {NULL, 0}};
 249
 250         uint8_t *opts = (uint8_t*)&hdr[1], *opts_end = (uint8_t*)data + len;
 251         if (hdr->msg_type == DHCPV6_MSG_RELAY_FORW)
 252                 handle_nested_message(data, len, &opts, &opts_end, iov);
 253
 254         memcpy(dest.tr_id, &opts[-3], sizeof(dest.tr_id));
 255
 256         if (opts[-4] == DHCPV6_MSG_ADVERTISE || opts[-4] == DHCPV6_MSG_REPLY || opts[-4] == DHCPV6_MSG_RELAY_REPL)
 257                 return;
 258
 259         if (opts[-4] == DHCPV6_MSG_SOLICIT) {
 260                 dest.msg_type = DHCPV6_MSG_ADVERTISE;
 261         } else if (opts[-4] == DHCPV6_MSG_INFORMATION_REQUEST) {
 262                 iov[6].iov_base = &refresh;
 263                 iov[6].iov_len = sizeof(refresh);
 264         }
 265
 266         // Go through options and find what we need
 267         uint16_t otype, olen;
 268         uint8_t *odata;
 269         dhcpv6_for_each_option(opts, opts_end, otype, olen, odata) {
 270                 if (otype == DHCPV6_OPT_CLIENTID && olen <= 130) {
 271                         dest.clientid_length = htons(olen);
 272                         memcpy(dest.clientid_buf, odata, olen);
 273                         iov[1].iov_len += 4 + olen;
 274                 } else if (otype == DHCPV6_OPT_SERVERID) {
 275                         if (olen != ntohs(dest.serverid_length) ||
 276                                         memcmp(odata, &dest.duid_type, olen))
 277                                 return; // Not for us
 278                 }
 279         }
 280
 281         if (opts[-4] != DHCPV6_MSG_INFORMATION_REQUEST) {
 282                 iov[6].iov_len = dhcpv6_handle_ia(pdbuf, sizeof(pdbuf), iface, addr, &opts[-4], opts_end);
 283                 if (iov[6].iov_len == 0 && opts[-4] == DHCPV6_MSG_REBIND)
 284                         return;
 285         }
 286
 287         if (iov[0].iov_len > 0) // Update length
 288                 update_nested_message(data, len, iov[1].iov_len + iov[2].iov_len +
 289                                 iov[3].iov_len + iov[4].iov_len + iov[5].iov_len +
 290                                 iov[6].iov_len - (4 + opts_end - opts));
 291
 292         odhcpd_send(iface->dhcpv6_event.uloop.fd, addr, iov, ARRAY_SIZE(iov), iface);
 293 }
 294
 295
 296 // Central DHCPv6-relay handler
 297 static void handle_dhcpv6(void *addr, void *data, size_t len,
 298                 struct interface *iface)
 299 {
 300         if (iface->dhcpv6 == RELAYD_SERVER) {
 301                 handle_client_request(addr, data, len, iface);
 302         } else if (iface->dhcpv6 == RELAYD_RELAY) {
 303                 if (iface->master)
 304                         relay_server_response(data, len);
 305                 else
 306                         relay_client_request(addr, data, len, iface);
 307         }
 308 }
 309
 310
 311 // Relay server response (regular relay server handling)
 312 static void relay_server_response(uint8_t *data, size_t len)
 313 {
 314         // Information we need to gather
 315         uint8_t *payload_data = NULL;
 316         size_t payload_len = 0;
 317         int32_t ifaceidx = 0;
 318         struct sockaddr_in6 target = {AF_INET6, htons(DHCPV6_CLIENT_PORT),
 319                 0, IN6ADDR_ANY_INIT, 0};
 320
 321         syslog(LOG_NOTICE, "Got a DHCPv6-reply");
 322
 323         int otype, olen;
 324         uint8_t *odata, *end = data + len;
 325
 326         // Relay DHCPv6 reply from server to client
 327         struct dhcpv6_relay_header *h = (void*)data;
 328         if (len < sizeof(*h) || h->msg_type != DHCPV6_MSG_RELAY_REPL)
 329                 return;
 330
 331         memcpy(&target.sin6_addr, &h->peer_address,
 332                         sizeof(struct in6_addr));
 333
 334         // Go through options and find what we need
 335         dhcpv6_for_each_option(h->options, end, otype, olen, odata) {
 336                 if (otype == DHCPV6_OPT_INTERFACE_ID
 337                                 && olen == sizeof(ifaceidx)) {
 338                         memcpy(&ifaceidx, odata, sizeof(ifaceidx));
 339                 } else if (otype == DHCPV6_OPT_RELAY_MSG) {
 340                         payload_data = odata;
 341                         payload_len = olen;
 342                 }
 343         }
 344
 345         // Invalid interface-id or basic payload
 346         struct interface *iface = odhcpd_get_interface_by_index(ifaceidx);
 347         if (!iface || iface->master || !payload_data || payload_len < 4)
 348                 return;
 349
 350         bool is_authenticated = false;
 351         struct in6_addr *dns_ptr = NULL;
 352         size_t dns_count = 0;
 353
 354         // If the payload is relay-reply we have to send to the server port
 355         if (payload_data[0] == DHCPV6_MSG_RELAY_REPL) {
 356                 target.sin6_port = htons(DHCPV6_SERVER_PORT);
 357         } else { // Go through the payload data
 358                 struct dhcpv6_client_header *h = (void*)payload_data;
 359                 end = payload_data + payload_len;
 360
 361                 dhcpv6_for_each_option(&h[1], end, otype, olen, odata) {
 362                         if (otype == DHCPV6_OPT_DNS_SERVERS && olen >= 16) {
 363                                 dns_ptr = (struct in6_addr*)odata;
 364                                 dns_count = olen / 16;
 365                         } else if (otype == DHCPV6_OPT_AUTH) {
 366                                 is_authenticated = true;
 367                         }
 368                 }
 369         }
 370
 371         // Rewrite DNS servers if requested
 372         if (iface->always_rewrite_dns && dns_ptr && dns_count > 0) {
 373                 if (is_authenticated)
 374                         return; // Impossible to rewrite
 375
 376                 struct odhcpd_ipaddr ip;
 377                 const struct in6_addr *rewrite = iface->dns;
 378                 size_t rewrite_cnt = iface->dns_cnt;
 379
 380                 if (rewrite_cnt == 0) {
 381                         if (odhcpd_get_interface_addresses(iface->ifindex, &ip, 1) < 1)
 382                                 return; // Unable to get interface address
 383
 384                         rewrite = &ip.addr;
 385                         rewrite_cnt = 1;
 386                 }
 387
 388                 // Copy over any other addresses
 389                 for (size_t i = 0; i < dns_count; ++i) {
 390                         size_t j = (i < rewrite_cnt) ? i : rewrite_cnt - 1;
 391                         memcpy(&dns_ptr[i], &rewrite[j], sizeof(*rewrite));
 392                 }
 393         }
 394
 395         struct iovec iov = {payload_data, payload_len};
 396         odhcpd_send(iface->dhcpv6_event.uloop.fd, &target, &iov, 1, iface);
 397 }
 398
 399
 400 // Relay client request (regular DHCPv6-relay)
 401 static void relay_client_request(struct sockaddr_in6 *source,
 402                 const void *data, size_t len, struct interface *iface)
 403 {
 404         struct interface *master = odhcpd_get_master_interface();
 405         const struct dhcpv6_relay_header *h = data;
 406         if (!master || master->dhcpv6 != RELAYD_RELAY ||
 407                         h->msg_type == DHCPV6_MSG_RELAY_REPL ||
 408                         h->msg_type == DHCPV6_MSG_RECONFIGURE ||
 409                         h->msg_type == DHCPV6_MSG_REPLY ||
 410                         h->msg_type == DHCPV6_MSG_ADVERTISE)
 411                 return; // Invalid message types for client
 412
 413         syslog(LOG_NOTICE, "Got a DHCPv6-request");
 414
 415         // Construct our forwarding envelope
 416         struct dhcpv6_relay_forward_envelope hdr = {
 417                 .msg_type = DHCPV6_MSG_RELAY_FORW,
 418                 .hop_count = 0,
 419                 .interface_id_type = htons(DHCPV6_OPT_INTERFACE_ID),
 420                 .interface_id_len = htons(sizeof(uint32_t)),
 421                 .relay_message_type = htons(DHCPV6_OPT_RELAY_MSG),
 422                 .relay_message_len = htons(len),
 423         };
 424
 425         if (h->msg_type == DHCPV6_MSG_RELAY_FORW) { // handle relay-forward
 426                 if (h->hop_count >= DHCPV6_HOP_COUNT_LIMIT)
 427                         return; // Invalid hop count
 428                 else
 429                         hdr.hop_count = h->hop_count + 1;
 430         }
 431
 432         // use memcpy here as the destination fields are unaligned
 433         uint32_t ifindex = iface->ifindex;
 434         memcpy(&hdr.peer_address, &source->sin6_addr, sizeof(struct in6_addr));
 435         memcpy(&hdr.interface_id_data, &ifindex, sizeof(ifindex));
 436
 437         // Detect public IP of slave interface to use as link-address
 438         struct odhcpd_ipaddr ip;
 439         if (odhcpd_get_interface_addresses(iface->ifindex, &ip, 1) < 1) {
 440                 // No suitable address! Is the slave not configured yet?
 441                 // Detect public IP of master interface and use it instead
 442                 // This is WRONG and probably violates the RFC. However
 443                 // otherwise we have a hen and egg problem because the
 444                 // slave-interface cannot be auto-configured.
 445                 if (odhcpd_get_interface_addresses(master->ifindex, &ip, 1) < 1)
 446                         return; // Could not obtain a suitable address
 447         }
 448         memcpy(&hdr.link_address, &ip.addr, sizeof(hdr.link_address));
 449
 450         struct sockaddr_in6 dhcpv6_servers = {AF_INET6,
 451                         htons(DHCPV6_SERVER_PORT), 0, ALL_DHCPV6_SERVERS, 0};
 452         struct iovec iov[2] = {{&hdr, sizeof(hdr)}, {(void*)data, len}};
 453         odhcpd_send(iface->dhcpv6_event.uloop.fd, &dhcpv6_servers, iov, 2, master);
 454 }