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 static struct odhcpd_event dhcpv6_event = {{.fd = -1}, handle_dhcpv6};
  36
  37
  38
  39 // Create socket and register events
  40 int init_dhcpv6(void)
  41 {
  42         int sock = socket(AF_INET6, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
  43
  44         // Basic IPv6 configuration
  45         int val = 1;
  46         setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, &val, sizeof(val));
  47         setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
  48         setsockopt(sock, IPPROTO_IPV6, IPV6_RECVPKTINFO, &val, sizeof(val));
  49
  50         val = DHCPV6_HOP_COUNT_LIMIT;
  51         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
  52
  53         val = 0;
  54         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &val, sizeof(val));
  55
  56         struct sockaddr_in6 bind_addr = {AF_INET6, htons(DHCPV6_SERVER_PORT),
  57                                 0, IN6ADDR_ANY_INIT, 0};
  58
  59         if (bind(sock, (struct sockaddr*)&bind_addr, sizeof(bind_addr))) {
  60                 syslog(LOG_ERR, "Failed to open DHCPv6 server socket: %s",
  61                                 strerror(errno));
  62                 return -1;
  63         }
  64
  65         dhcpv6_event.uloop.fd = sock;
  66         odhcpd_register(&dhcpv6_event);
  67
  68         dhcpv6_ia_init(dhcpv6_event.uloop.fd);
  69
  70         return 0;
  71 }
  72
  73
  74 int setup_dhcpv6_interface(struct interface *iface, bool enable)
  75 {
  76         // Configure multicast settings
  77         struct ipv6_mreq relay = {ALL_DHCPV6_RELAYS, iface->ifindex};
  78         struct ipv6_mreq server = {ALL_DHCPV6_SERVERS, iface->ifindex};
  79
  80         setsockopt(dhcpv6_event.uloop.fd, IPPROTO_IPV6,
  81                         IPV6_DROP_MEMBERSHIP, &relay, sizeof(relay));
  82         setsockopt(dhcpv6_event.uloop.fd, IPPROTO_IPV6,
  83                         IPV6_DROP_MEMBERSHIP, &server, sizeof(server));
  84
  85         if (enable && iface->dhcpv6 && !iface->master) {
  86                 setsockopt(dhcpv6_event.uloop.fd, IPPROTO_IPV6,
  87                                 IPV6_ADD_MEMBERSHIP, &relay, sizeof(relay));
  88
  89                 if (iface->dhcpv6 == RELAYD_SERVER)
  90                         setsockopt(dhcpv6_event.uloop.fd, IPPROTO_IPV6,
  91                                         IPV6_ADD_MEMBERSHIP, &server, sizeof(server));
  92         }
  93
  94         setup_dhcpv6_ia_interface(iface, enable);
  95         return 0;
  96 }
  97
  98
  99 static void handle_nested_message(uint8_t *data, size_t len,
 100                 uint8_t **opts, uint8_t **end, struct iovec iov[6])
 101 {
 102         struct dhcpv6_relay_header *hdr = (struct dhcpv6_relay_header*)data;
 103         if (iov[0].iov_base == NULL) {
 104                 iov[0].iov_base = data;
 105                 iov[0].iov_len = len;
 106         }
 107
 108         if (len < sizeof(struct dhcpv6_client_header))
 109                 return;
 110
 111         if (hdr->msg_type != DHCPV6_MSG_RELAY_FORW) {
 112                 iov[0].iov_len = data - (uint8_t*)iov[0].iov_base;
 113                 struct dhcpv6_client_header *hdr = (void*)data;
 114                 *opts = (uint8_t*)&hdr[1];
 115                 *end = data + len;
 116                 return;
 117         }
 118
 119         uint16_t otype, olen;
 120         uint8_t *odata;
 121         dhcpv6_for_each_option(hdr->options, data + len, otype, olen, odata) {
 122                 if (otype == DHCPV6_OPT_RELAY_MSG) {
 123                         iov[7].iov_base = odata + olen;
 124                         iov[7].iov_len = (((uint8_t*)iov[0].iov_base) + iov[0].iov_len)
 125                                         - (odata + olen);
 126                         handle_nested_message(odata, olen, opts, end, iov);
 127                         return;
 128                 }
 129         }
 130 }
 131
 132
 133 static void update_nested_message(uint8_t *data, size_t len, ssize_t pdiff)
 134 {
 135         struct dhcpv6_relay_header *hdr = (struct dhcpv6_relay_header*)data;
 136         if (hdr->msg_type != DHCPV6_MSG_RELAY_FORW)
 137                 return;
 138
 139         hdr->msg_type = DHCPV6_MSG_RELAY_REPL;
 140
 141         uint16_t otype, olen;
 142         uint8_t *odata;
 143         dhcpv6_for_each_option(hdr->options, data + len, otype, olen, odata) {
 144                 if (otype == DHCPV6_OPT_RELAY_MSG) {
 145                         olen += pdiff;
 146                         odata[-2] = (olen >> 8) & 0xff;
 147                         odata[-1] = olen & 0xff;
 148                         update_nested_message(odata, olen - pdiff, pdiff);
 149                         return;
 150                 }
 151         }
 152 }
 153
 154
 155 // Simple DHCPv6-server for information requests
 156 static void handle_client_request(void *addr, void *data, size_t len,
 157                 struct interface *iface)
 158 {
 159         struct dhcpv6_client_header *hdr = data;
 160         if (len < sizeof(*hdr))
 161                 return;
 162
 163         syslog(LOG_NOTICE, "Got DHCPv6 request");
 164
 165         // Construct reply message
 166         struct __attribute__((packed)) {
 167                 uint8_t msg_type;
 168                 uint8_t tr_id[3];
 169                 uint16_t serverid_type;
 170                 uint16_t serverid_length;
 171                 uint16_t duid_type;
 172                 uint16_t hardware_type;
 173                 uint8_t mac[6];
 174                 uint16_t clientid_type;
 175                 uint16_t clientid_length;
 176                 uint8_t clientid_buf[130];
 177         } dest = {
 178                 .msg_type = DHCPV6_MSG_REPLY,
 179                 .serverid_type = htons(DHCPV6_OPT_SERVERID),
 180                 .serverid_length = htons(10),
 181                 .duid_type = htons(3),
 182                 .hardware_type = htons(1),
 183                 .clientid_type = htons(DHCPV6_OPT_CLIENTID),
 184                 .clientid_buf = {0}
 185         };
 186         odhcpd_get_mac(iface, dest.mac);
 187
 188         struct __attribute__((packed)) {
 189                 uint16_t type;
 190                 uint16_t len;
 191                 uint16_t value;
 192         } stat = {htons(DHCPV6_OPT_STATUS), htons(sizeof(stat) - 4),
 193                         htons(DHCPV6_STATUS_NOADDRSAVAIL)};
 194
 195         struct __attribute__((packed)) {
 196                 uint16_t type;
 197                 uint16_t len;
 198                 uint32_t value;
 199         } refresh = {htons(DHCPV6_OPT_INFO_REFRESH), htons(sizeof(uint32_t)),
 200                         htonl(600)};
 201
 202         struct odhcpd_ipaddr ipaddr;
 203         struct in6_addr *dns_addr = iface->dns;
 204         size_t dns_cnt = iface->dns_cnt;
 205
 206         if (dns_cnt == 0 && odhcpd_get_interface_addresses(iface->ifindex, &ipaddr, 1) == 1) {
 207                 dns_addr = &ipaddr.addr;
 208                 dns_cnt = 1;
 209         }
 210
 211         struct {
 212                 uint16_t type;
 213                 uint16_t len;
 214         } dns = {htons(DHCPV6_OPT_DNS_SERVERS), htons(dns_cnt * sizeof(*dns_addr))};
 215
 216
 217
 218         // DNS Search options
 219         uint8_t search_buf[256], *search_domain = iface->search;
 220         size_t search_len = iface->search_len;
 221
 222         if (!search_domain && !res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 223                 int len = dn_comp(_res.dnsrch[0], search_buf,
 224                                 sizeof(search_buf), NULL, NULL);
 225                 if (len > 0) {
 226                         search_domain = search_buf;
 227                         search_len = len;
 228                 }
 229         }
 230
 231         struct {
 232                 uint16_t type;
 233                 uint16_t len;
 234         } search = {htons(DHCPV6_OPT_DNS_DOMAIN), htons(search_len)};
 235
 236
 237
 238         uint8_t pdbuf[512];
 239         struct iovec iov[] = {{NULL, 0},
 240                         {&dest, (uint8_t*)&dest.clientid_type - (uint8_t*)&dest},
 241                         {&dns, (dns_cnt) ? sizeof(dns) : 0},
 242                         {dns_addr, dns_cnt * sizeof(*dns_addr)},
 243                         {&search, (search_len) ? sizeof(search) : 0},
 244                         {search_domain, search_len},
 245                         {pdbuf, 0},
 246                         {NULL, 0}};
 247
 248         uint8_t *opts = (uint8_t*)&hdr[1], *opts_end = (uint8_t*)data + len;
 249         if (hdr->msg_type == DHCPV6_MSG_RELAY_FORW)
 250                 handle_nested_message(data, len, &opts, &opts_end, iov);
 251
 252         memcpy(dest.tr_id, &opts[-3], sizeof(dest.tr_id));
 253
 254         if (opts[-4] == DHCPV6_MSG_ADVERTISE || opts[-4] == DHCPV6_MSG_REPLY || opts[-4] == DHCPV6_MSG_RELAY_REPL)
 255                 return;
 256
 257         if (opts[-4] == DHCPV6_MSG_SOLICIT) {
 258                 dest.msg_type = DHCPV6_MSG_ADVERTISE;
 259         } else if (opts[-4] == DHCPV6_MSG_INFORMATION_REQUEST) {
 260                 iov[6].iov_base = &refresh;
 261                 iov[6].iov_len = sizeof(refresh);
 262         }
 263
 264         // Go through options and find what we need
 265         uint16_t otype, olen;
 266         uint8_t *odata;
 267         dhcpv6_for_each_option(opts, opts_end, otype, olen, odata) {
 268                 if (otype == DHCPV6_OPT_CLIENTID && olen <= 130) {
 269                         dest.clientid_length = htons(olen);
 270                         memcpy(dest.clientid_buf, odata, olen);
 271                         iov[1].iov_len += 4 + olen;
 272                 } else if (otype == DHCPV6_OPT_SERVERID) {
 273                         if (olen != ntohs(dest.serverid_length) ||
 274                                         memcmp(odata, &dest.duid_type, olen))
 275                                 return; // Not for us
 276                 }
 277         }
 278
 279         if (opts[-4] != DHCPV6_MSG_INFORMATION_REQUEST) {
 280                 iov[6].iov_len = dhcpv6_handle_ia(pdbuf, sizeof(pdbuf), iface, addr, &opts[-4], opts_end);
 281                 if (iov[6].iov_len == 0 && opts[-4] == DHCPV6_MSG_REBIND)
 282                         return;
 283         }
 284
 285         if (iov[0].iov_len > 0) // Update length
 286                 update_nested_message(data, len, iov[1].iov_len + iov[2].iov_len +
 287                                 iov[3].iov_len + iov[4].iov_len + iov[5].iov_len +
 288                                 iov[6].iov_len - (4 + opts_end - opts));
 289
 290         odhcpd_send(dhcpv6_event.uloop.fd, addr, iov, ARRAY_SIZE(iov), iface);
 291 }
 292
 293
 294 // Central DHCPv6-relay handler
 295 static void handle_dhcpv6(void *addr, void *data, size_t len,
 296                 struct interface *iface)
 297 {
 298         if (iface->dhcpv6 == RELAYD_SERVER) {
 299                 handle_client_request(addr, data, len, iface);
 300         } else if (iface->dhcpv6 == RELAYD_RELAY) {
 301                 if (iface->master)
 302                         relay_server_response(data, len);
 303                 else
 304                         relay_client_request(addr, data, len, iface);
 305         }
 306 }
 307
 308
 309 // Relay server response (regular relay server handling)
 310 static void relay_server_response(uint8_t *data, size_t len)
 311 {
 312         // Information we need to gather
 313         uint8_t *payload_data = NULL;
 314         size_t payload_len = 0;
 315         int32_t ifaceidx = 0;
 316         struct sockaddr_in6 target = {AF_INET6, htons(DHCPV6_CLIENT_PORT),
 317                 0, IN6ADDR_ANY_INIT, 0};
 318
 319         syslog(LOG_NOTICE, "Got a DHCPv6-reply");
 320
 321         int otype, olen;
 322         uint8_t *odata, *end = data + len;
 323
 324         // Relay DHCPv6 reply from server to client
 325         struct dhcpv6_relay_header *h = (void*)data;
 326         if (len < sizeof(*h) || h->msg_type != DHCPV6_MSG_RELAY_REPL)
 327                 return;
 328
 329         memcpy(&target.sin6_addr, &h->peer_address,
 330                         sizeof(struct in6_addr));
 331
 332         // Go through options and find what we need
 333         dhcpv6_for_each_option(h->options, end, otype, olen, odata) {
 334                 if (otype == DHCPV6_OPT_INTERFACE_ID
 335                                 && olen == sizeof(ifaceidx)) {
 336                         memcpy(&ifaceidx, odata, sizeof(ifaceidx));
 337                 } else if (otype == DHCPV6_OPT_RELAY_MSG) {
 338                         payload_data = odata;
 339                         payload_len = olen;
 340                 }
 341         }
 342
 343         // Invalid interface-id or basic payload
 344         struct interface *iface = odhcpd_get_interface_by_index(ifaceidx);
 345         if (!iface || iface->master || !payload_data || payload_len < 4)
 346                 return;
 347
 348         bool is_authenticated = false;
 349         struct in6_addr *dns_ptr = NULL;
 350         size_t dns_count = 0;
 351
 352         // If the payload is relay-reply we have to send to the server port
 353         if (payload_data[0] == DHCPV6_MSG_RELAY_REPL) {
 354                 target.sin6_port = htons(DHCPV6_SERVER_PORT);
 355         } else { // Go through the payload data
 356                 struct dhcpv6_client_header *h = (void*)payload_data;
 357                 end = payload_data + payload_len;
 358
 359                 dhcpv6_for_each_option(&h[1], end, otype, olen, odata) {
 360                         if (otype == DHCPV6_OPT_DNS_SERVERS && olen >= 16) {
 361                                 dns_ptr = (struct in6_addr*)odata;
 362                                 dns_count = olen / 16;
 363                         } else if (otype == DHCPV6_OPT_AUTH) {
 364                                 is_authenticated = true;
 365                         }
 366                 }
 367         }
 368
 369         // Rewrite DNS servers if requested
 370         if (iface->always_rewrite_dns && dns_ptr && dns_count > 0) {
 371                 if (is_authenticated)
 372                         return; // Impossible to rewrite
 373
 374                 struct odhcpd_ipaddr ip;
 375                 const struct in6_addr *rewrite = iface->dns;
 376                 size_t rewrite_cnt = iface->dns_cnt;
 377
 378                 if (rewrite_cnt == 0) {
 379                         if (odhcpd_get_interface_addresses(iface->ifindex, &ip, 1) < 1)
 380                                 return; // Unable to get interface address
 381
 382                         rewrite = &ip.addr;
 383                         rewrite_cnt = 1;
 384                 }
 385
 386                 // Copy over any other addresses
 387                 for (size_t i = 0; i < dns_count; ++i) {
 388                         size_t j = (i < rewrite_cnt) ? i : rewrite_cnt - 1;
 389                         memcpy(&dns_ptr[i], &rewrite[j], sizeof(*rewrite));
 390                 }
 391         }
 392
 393         struct iovec iov = {payload_data, payload_len};
 394         odhcpd_send(dhcpv6_event.uloop.fd, &target, &iov, 1, iface);
 395 }
 396
 397
 398 // Relay client request (regular DHCPv6-relay)
 399 static void relay_client_request(struct sockaddr_in6 *source,
 400                 const void *data, size_t len, struct interface *iface)
 401 {
 402         struct interface *master = odhcpd_get_master_interface();
 403         const struct dhcpv6_relay_header *h = data;
 404         if (!master || master->dhcpv6 != RELAYD_RELAY ||
 405                         h->msg_type == DHCPV6_MSG_RELAY_REPL ||
 406                         h->msg_type == DHCPV6_MSG_RECONFIGURE ||
 407                         h->msg_type == DHCPV6_MSG_REPLY ||
 408                         h->msg_type == DHCPV6_MSG_ADVERTISE)
 409                 return; // Invalid message types for client
 410
 411         syslog(LOG_NOTICE, "Got a DHCPv6-request");
 412
 413         // Construct our forwarding envelope
 414         struct dhcpv6_relay_forward_envelope hdr = {
 415                 .msg_type = DHCPV6_MSG_RELAY_FORW,
 416                 .hop_count = 0,
 417                 .interface_id_type = htons(DHCPV6_OPT_INTERFACE_ID),
 418                 .interface_id_len = htons(sizeof(uint32_t)),
 419                 .relay_message_type = htons(DHCPV6_OPT_RELAY_MSG),
 420                 .relay_message_len = htons(len),
 421         };
 422
 423         if (h->msg_type == DHCPV6_MSG_RELAY_FORW) { // handle relay-forward
 424                 if (h->hop_count >= DHCPV6_HOP_COUNT_LIMIT)
 425                         return; // Invalid hop count
 426                 else
 427                         hdr.hop_count = h->hop_count + 1;
 428         }
 429
 430         // use memcpy here as the destination fields are unaligned
 431         uint32_t ifindex = iface->ifindex;
 432         memcpy(&hdr.peer_address, &source->sin6_addr, sizeof(struct in6_addr));
 433         memcpy(&hdr.interface_id_data, &ifindex, sizeof(ifindex));
 434
 435         // Detect public IP of slave interface to use as link-address
 436         struct odhcpd_ipaddr ip;
 437         if (odhcpd_get_interface_addresses(iface->ifindex, &ip, 1) < 1) {
 438                 // No suitable address! Is the slave not configured yet?
 439                 // Detect public IP of master interface and use it instead
 440                 // This is WRONG and probably violates the RFC. However
 441                 // otherwise we have a hen and egg problem because the
 442                 // slave-interface cannot be auto-configured.
 443                 if (odhcpd_get_interface_addresses(master->ifindex, &ip, 1) < 1)
 444                         return; // Could not obtain a suitable address
 445         }
 446         memcpy(&hdr.link_address, &ip.addr, sizeof(hdr.link_address));
 447
 448         struct sockaddr_in6 dhcpv6_servers = {AF_INET6,
 449                         htons(DHCPV6_SERVER_PORT), 0, ALL_DHCPV6_SERVERS, 0};
 450         struct iovec iov[2] = {{&hdr, sizeof(hdr)}, {(void*)data, len}};
 451         odhcpd_send(dhcpv6_event.uloop.fd, &dhcpv6_servers, iov, 2, master);
 452 }