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