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 clientid_type;
 179                 uint16_t clientid_length;
 180                 uint8_t clientid_buf[130];
 181         } dest = {
 182                 .msg_type = DHCPV6_MSG_REPLY,
 183                 .serverid_type = htons(DHCPV6_OPT_SERVERID),
 184                 .serverid_length = htons(10),
 185                 .duid_type = htons(3),
 186                 .hardware_type = htons(1),
 187                 .clientid_type = htons(DHCPV6_OPT_CLIENTID),
 188                 .clientid_buf = {0}
 189         };
 190         odhcpd_get_mac(iface, dest.mac);
 191
 192         struct __attribute__((packed)) {
 193                 uint16_t type;
 194                 uint16_t len;
 195                 uint16_t value;
 196         } stat = {htons(DHCPV6_OPT_STATUS), htons(sizeof(stat) - 4),
 197                         htons(DHCPV6_STATUS_NOADDRSAVAIL)};
 198
 199         struct __attribute__((packed)) {
 200                 uint16_t type;
 201                 uint16_t len;
 202                 uint32_t value;
 203         } refresh = {htons(DHCPV6_OPT_INFO_REFRESH), htons(sizeof(uint32_t)),
 204                         htonl(600)};
 205
 206         struct odhcpd_ipaddr ipaddr;
 207         struct in6_addr *dns_addr = iface->dns;
 208         size_t dns_cnt = iface->dns_cnt;
 209
 210         if (dns_cnt == 0 && odhcpd_get_interface_addresses(iface->ifindex, &ipaddr, 1) == 1) {
 211                 dns_addr = &ipaddr.addr;
 212                 dns_cnt = 1;
 213         }
 214
 215         struct {
 216                 uint16_t type;
 217                 uint16_t len;
 218         } dns = {htons(DHCPV6_OPT_DNS_SERVERS), htons(dns_cnt * sizeof(*dns_addr))};
 219
 220
 221
 222         // DNS Search options
 223         uint8_t search_buf[256], *search_domain = iface->search;
 224         size_t search_len = iface->search_len;
 225
 226         if (!search_domain && !res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 227                 int len = dn_comp(_res.dnsrch[0], search_buf,
 228                                 sizeof(search_buf), NULL, NULL);
 229                 if (len > 0) {
 230                         search_domain = search_buf;
 231                         search_len = len;
 232                 }
 233         }
 234
 235         struct {
 236                 uint16_t type;
 237                 uint16_t len;
 238         } search = {htons(DHCPV6_OPT_DNS_DOMAIN), htons(search_len)};
 239
 240
 241
 242         uint8_t pdbuf[512];
 243         struct iovec iov[] = {{NULL, 0},
 244                         {&dest, (uint8_t*)&dest.clientid_type - (uint8_t*)&dest},
 245                         {&dns, (dns_cnt) ? sizeof(dns) : 0},
 246                         {dns_addr, dns_cnt * sizeof(*dns_addr)},
 247                         {&search, (search_len) ? sizeof(search) : 0},
 248                         {search_domain, search_len},
 249                         {pdbuf, 0},
 250                         {NULL, 0}};
 251
 252         uint8_t *opts = (uint8_t*)&hdr[1], *opts_end = (uint8_t*)data + len;
 253         if (hdr->msg_type == DHCPV6_MSG_RELAY_FORW)
 254                 handle_nested_message(data, len, &opts, &opts_end, iov);
 255
 256         memcpy(dest.tr_id, &opts[-3], sizeof(dest.tr_id));
 257
 258         if (opts[-4] == DHCPV6_MSG_ADVERTISE || opts[-4] == DHCPV6_MSG_REPLY || opts[-4] == DHCPV6_MSG_RELAY_REPL)
 259                 return;
 260
 261         if (opts[-4] == DHCPV6_MSG_SOLICIT) {
 262                 dest.msg_type = DHCPV6_MSG_ADVERTISE;
 263         } else if (opts[-4] == DHCPV6_MSG_INFORMATION_REQUEST) {
 264                 iov[6].iov_base = &refresh;
 265                 iov[6].iov_len = sizeof(refresh);
 266         }
 267
 268         // Go through options and find what we need
 269         uint16_t otype, olen;
 270         uint8_t *odata;
 271         dhcpv6_for_each_option(opts, opts_end, otype, olen, odata) {
 272                 if (otype == DHCPV6_OPT_CLIENTID && olen <= 130) {
 273                         dest.clientid_length = htons(olen);
 274                         memcpy(dest.clientid_buf, odata, olen);
 275                         iov[1].iov_len += 4 + olen;
 276                 } else if (otype == DHCPV6_OPT_SERVERID) {
 277                         if (olen != ntohs(dest.serverid_length) ||
 278                                         memcmp(odata, &dest.duid_type, olen))
 279                                 return; // Not for us
 280                 } else if (otype == DHCPV6_OPT_USER_CLASS) {
 281                         uint8_t *c = odata, *cend = &odata[olen];
 282                         for (; &c[2] <= cend && &c[2 + (c[0] << 8) + c[1]] <= cend; c = &c[2 + (c[0] << 8) + c[1]]) {
 283                                 size_t elen = strlen(excluded_class);
 284                                 if (((((size_t)c[0]) << 8) | c[1]) == elen && !memcmp(&c[2], excluded_class, elen))
 285                                         return; // Ignore from homenet
 286                         }
 287                 }
 288         }
 289
 290         if (opts[-4] != DHCPV6_MSG_INFORMATION_REQUEST) {
 291                 iov[6].iov_len = dhcpv6_handle_ia(pdbuf, sizeof(pdbuf), iface, addr, &opts[-4], opts_end);
 292                 if (iov[6].iov_len == 0 && opts[-4] == DHCPV6_MSG_REBIND)
 293                         return;
 294         }
 295
 296         if (iov[0].iov_len > 0) // Update length
 297                 update_nested_message(data, len, iov[1].iov_len + iov[2].iov_len +
 298                                 iov[3].iov_len + iov[4].iov_len + iov[5].iov_len +
 299                                 iov[6].iov_len - (4 + opts_end - opts));
 300
 301         odhcpd_send(iface->dhcpv6_event.uloop.fd, addr, iov, ARRAY_SIZE(iov), iface);
 302 }
 303
 304
 305 // Central DHCPv6-relay handler
 306 static void handle_dhcpv6(void *addr, void *data, size_t len,
 307                 struct interface *iface)
 308 {
 309         if (iface->dhcpv6 == RELAYD_SERVER) {
 310                 handle_client_request(addr, data, len, iface);
 311         } else if (iface->dhcpv6 == RELAYD_RELAY) {
 312                 if (iface->master)
 313                         relay_server_response(data, len);
 314                 else
 315                         relay_client_request(addr, data, len, iface);
 316         }
 317 }
 318
 319
 320 // Relay server response (regular relay server handling)
 321 static void relay_server_response(uint8_t *data, size_t len)
 322 {
 323         // Information we need to gather
 324         uint8_t *payload_data = NULL;
 325         size_t payload_len = 0;
 326         int32_t ifaceidx = 0;
 327         struct sockaddr_in6 target = {AF_INET6, htons(DHCPV6_CLIENT_PORT),
 328                 0, IN6ADDR_ANY_INIT, 0};
 329
 330         syslog(LOG_NOTICE, "Got a DHCPv6-reply");
 331
 332         int otype, olen;
 333         uint8_t *odata, *end = data + len;
 334
 335         // Relay DHCPv6 reply from server to client
 336         struct dhcpv6_relay_header *h = (void*)data;
 337         if (len < sizeof(*h) || h->msg_type != DHCPV6_MSG_RELAY_REPL)
 338                 return;
 339
 340         memcpy(&target.sin6_addr, &h->peer_address,
 341                         sizeof(struct in6_addr));
 342
 343         // Go through options and find what we need
 344         dhcpv6_for_each_option(h->options, end, otype, olen, odata) {
 345                 if (otype == DHCPV6_OPT_INTERFACE_ID
 346                                 && olen == sizeof(ifaceidx)) {
 347                         memcpy(&ifaceidx, odata, sizeof(ifaceidx));
 348                 } else if (otype == DHCPV6_OPT_RELAY_MSG) {
 349                         payload_data = odata;
 350                         payload_len = olen;
 351                 }
 352         }
 353
 354         // Invalid interface-id or basic payload
 355         struct interface *iface = odhcpd_get_interface_by_index(ifaceidx);
 356         if (!iface || iface->master || !payload_data || payload_len < 4)
 357                 return;
 358
 359         bool is_authenticated = false;
 360         struct in6_addr *dns_ptr = NULL;
 361         size_t dns_count = 0;
 362
 363         // If the payload is relay-reply we have to send to the server port
 364         if (payload_data[0] == DHCPV6_MSG_RELAY_REPL) {
 365                 target.sin6_port = htons(DHCPV6_SERVER_PORT);
 366         } else { // Go through the payload data
 367                 struct dhcpv6_client_header *h = (void*)payload_data;
 368                 end = payload_data + payload_len;
 369
 370                 dhcpv6_for_each_option(&h[1], end, otype, olen, odata) {
 371                         if (otype == DHCPV6_OPT_DNS_SERVERS && olen >= 16) {
 372                                 dns_ptr = (struct in6_addr*)odata;
 373                                 dns_count = olen / 16;
 374                         } else if (otype == DHCPV6_OPT_AUTH) {
 375                                 is_authenticated = true;
 376                         }
 377                 }
 378         }
 379
 380         // Rewrite DNS servers if requested
 381         if (iface->always_rewrite_dns && dns_ptr && dns_count > 0) {
 382                 if (is_authenticated)
 383                         return; // Impossible to rewrite
 384
 385                 struct odhcpd_ipaddr ip;
 386                 const struct in6_addr *rewrite = iface->dns;
 387                 size_t rewrite_cnt = iface->dns_cnt;
 388
 389                 if (rewrite_cnt == 0) {
 390                         if (odhcpd_get_interface_addresses(iface->ifindex, &ip, 1) < 1)
 391                                 return; // Unable to get interface address
 392
 393                         rewrite = &ip.addr;
 394                         rewrite_cnt = 1;
 395                 }
 396
 397                 // Copy over any other addresses
 398                 for (size_t i = 0; i < dns_count; ++i) {
 399                         size_t j = (i < rewrite_cnt) ? i : rewrite_cnt - 1;
 400                         memcpy(&dns_ptr[i], &rewrite[j], sizeof(*rewrite));
 401                 }
 402         }
 403
 404         struct iovec iov = {payload_data, payload_len};
 405         odhcpd_send(iface->dhcpv6_event.uloop.fd, &target, &iov, 1, iface);
 406 }
 407
 408
 409 // Relay client request (regular DHCPv6-relay)
 410 static void relay_client_request(struct sockaddr_in6 *source,
 411                 const void *data, size_t len, struct interface *iface)
 412 {
 413         struct interface *master = odhcpd_get_master_interface();
 414         const struct dhcpv6_relay_header *h = data;
 415         if (!master || master->dhcpv6 != RELAYD_RELAY ||
 416                         h->msg_type == DHCPV6_MSG_RELAY_REPL ||
 417                         h->msg_type == DHCPV6_MSG_RECONFIGURE ||
 418                         h->msg_type == DHCPV6_MSG_REPLY ||
 419                         h->msg_type == DHCPV6_MSG_ADVERTISE)
 420                 return; // Invalid message types for client
 421
 422         syslog(LOG_NOTICE, "Got a DHCPv6-request");
 423
 424         // Construct our forwarding envelope
 425         struct dhcpv6_relay_forward_envelope hdr = {
 426                 .msg_type = DHCPV6_MSG_RELAY_FORW,
 427                 .hop_count = 0,
 428                 .interface_id_type = htons(DHCPV6_OPT_INTERFACE_ID),
 429                 .interface_id_len = htons(sizeof(uint32_t)),
 430                 .relay_message_type = htons(DHCPV6_OPT_RELAY_MSG),
 431                 .relay_message_len = htons(len),
 432         };
 433
 434         if (h->msg_type == DHCPV6_MSG_RELAY_FORW) { // handle relay-forward
 435                 if (h->hop_count >= DHCPV6_HOP_COUNT_LIMIT)
 436                         return; // Invalid hop count
 437                 else
 438                         hdr.hop_count = h->hop_count + 1;
 439         }
 440
 441         // use memcpy here as the destination fields are unaligned
 442         uint32_t ifindex = iface->ifindex;
 443         memcpy(&hdr.peer_address, &source->sin6_addr, sizeof(struct in6_addr));
 444         memcpy(&hdr.interface_id_data, &ifindex, sizeof(ifindex));
 445
 446         // Detect public IP of slave interface to use as link-address
 447         struct odhcpd_ipaddr ip;
 448         if (odhcpd_get_interface_addresses(iface->ifindex, &ip, 1) < 1) {
 449                 // No suitable address! Is the slave not configured yet?
 450                 // Detect public IP of master interface and use it instead
 451                 // This is WRONG and probably violates the RFC. However
 452                 // otherwise we have a hen and egg problem because the
 453                 // slave-interface cannot be auto-configured.
 454                 if (odhcpd_get_interface_addresses(master->ifindex, &ip, 1) < 1)
 455                         return; // Could not obtain a suitable address
 456         }
 457         memcpy(&hdr.link_address, &ip.addr, sizeof(hdr.link_address));
 458
 459         struct sockaddr_in6 dhcpv6_servers = {AF_INET6,
 460                         htons(DHCPV6_SERVER_PORT), 0, ALL_DHCPV6_SERVERS, 0};
 461         struct iovec iov[2] = {{&hdr, sizeof(hdr)}, {(void*)data, len}};
 462         odhcpd_send(iface->dhcpv6_event.uloop.fd, &dhcpv6_servers, iov, 2, master);
 463 }