src/libsystemd-dhcp/dhcp-client.c

   1 /***
   2   This file is part of systemd.
   3
   4   Copyright (C) 2013 Intel Corporation. All rights reserved.
   5
   6   systemd is free software; you can redistribute it and/or modify it
   7   under the terms of the GNU Lesser General Public License as published by
   8   the Free Software Foundation; either version 2.1 of the License, or
   9   (at your option) any later version.
  10
  11   systemd is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   Lesser General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public License
  17   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  18 ***/
  19
  20 #include <stdlib.h>
  21 #include <errno.h>
  22 #include <string.h>
  23 #include <stdio.h>
  24 #include <net/ethernet.h>
  25
  26 #include "util.h"
  27 #include "list.h"
  28
  29 #include "dhcp-protocol.h"
  30 #include "dhcp-internal.h"
  31 #include "sd-dhcp-client.h"
  32
  33 #define DHCP_CLIENT_MIN_OPTIONS_SIZE            312
  34
  35 struct DHCPLease {
  36         uint32_t lifetime;
  37         uint32_t address;
  38         uint32_t server_address;
  39         uint32_t subnet_mask;
  40         uint32_t router;
  41 };
  42
  43 typedef struct DHCPLease DHCPLease;
  44
  45 struct sd_dhcp_client {
  46         DHCPState state;
  47         sd_event *event;
  48         sd_event_source *timeout_resend;
  49         int index;
  50         int fd;
  51         union sockaddr_union link;
  52         sd_event_source *receive_message;
  53         uint8_t *req_opts;
  54         size_t req_opts_size;
  55         uint32_t last_addr;
  56         struct ether_addr mac_addr;
  57         uint32_t xid;
  58         usec_t start_time;
  59         unsigned int attempt;
  60         DHCPLease *lease;
  61 };
  62
  63 static const uint8_t default_req_opts[] = {
  64         DHCP_OPTION_SUBNET_MASK,
  65         DHCP_OPTION_ROUTER,
  66         DHCP_OPTION_HOST_NAME,
  67         DHCP_OPTION_DOMAIN_NAME,
  68         DHCP_OPTION_DOMAIN_NAME_SERVER,
  69         DHCP_OPTION_NTP_SERVER,
  70 };
  71
  72 int sd_dhcp_client_set_request_option(sd_dhcp_client *client, uint8_t option)
  73 {
  74         size_t i;
  75
  76         assert_return(client, -EINVAL);
  77         assert_return (client->state == DHCP_STATE_INIT, -EBUSY);
  78
  79         switch(option) {
  80         case DHCP_OPTION_PAD:
  81         case DHCP_OPTION_OVERLOAD:
  82         case DHCP_OPTION_MESSAGE_TYPE:
  83         case DHCP_OPTION_PARAMETER_REQUEST_LIST:
  84         case DHCP_OPTION_END:
  85                 return -EINVAL;
  86
  87         default:
  88                 break;
  89         }
  90
  91         for (i = 0; i < client->req_opts_size; i++)
  92                 if (client->req_opts[i] == option)
  93                         return -EEXIST;
  94
  95         if (!GREEDY_REALLOC(client->req_opts, client->req_opts_size,
  96                             client->req_opts_size + 1))
  97                 return -ENOMEM;
  98
  99         client->req_opts[client->req_opts_size - 1] = option;
 100
 101         return 0;
 102 }
 103
 104 int sd_dhcp_client_set_request_address(sd_dhcp_client *client,
 105                                        const struct in_addr *last_addr)
 106 {
 107         assert_return(client, -EINVAL);
 108         assert_return(client->state == DHCP_STATE_INIT, -EBUSY);
 109
 110         if (last_addr)
 111                 client->last_addr = last_addr->s_addr;
 112         else
 113                 client->last_addr = INADDR_ANY;
 114
 115         return 0;
 116 }
 117
 118 int sd_dhcp_client_set_index(sd_dhcp_client *client, int interface_index)
 119 {
 120         assert_return(client, -EINVAL);
 121         assert_return(client->state == DHCP_STATE_INIT, -EBUSY);
 122         assert_return(interface_index >= -1, -EINVAL);
 123
 124         client->index = interface_index;
 125
 126         return 0;
 127 }
 128
 129 int sd_dhcp_client_set_mac(sd_dhcp_client *client,
 130                            const struct ether_addr *addr)
 131 {
 132         assert_return(client, -EINVAL);
 133         assert_return(client->state == DHCP_STATE_INIT, -EBUSY);
 134
 135         memcpy(&client->mac_addr, addr, ETH_ALEN);
 136
 137         return 0;
 138 }
 139
 140 static int client_notify(sd_dhcp_client *client, int event)
 141 {
 142         return 0;
 143 }
 144
 145 static int client_stop(sd_dhcp_client *client, int error)
 146 {
 147         assert_return(client, -EINVAL);
 148         assert_return(client->state != DHCP_STATE_INIT &&
 149                       client->state != DHCP_STATE_INIT_REBOOT, -EALREADY);
 150
 151         client->receive_message =
 152                 sd_event_source_unref(client->receive_message);
 153
 154         if (client->fd >= 0)
 155                 close(client->fd);
 156         client->fd = -1;
 157
 158         client->timeout_resend = sd_event_source_unref(client->timeout_resend);
 159
 160         client->attempt = 1;
 161
 162         switch (client->state) {
 163
 164         case DHCP_STATE_INIT:
 165         case DHCP_STATE_SELECTING:
 166         case DHCP_STATE_REQUESTING:
 167
 168                 client->start_time = 0;
 169                 client->state = DHCP_STATE_INIT;
 170                 break;
 171
 172         case DHCP_STATE_INIT_REBOOT:
 173         case DHCP_STATE_REBOOTING:
 174         case DHCP_STATE_BOUND:
 175         case DHCP_STATE_RENEWING:
 176         case DHCP_STATE_REBINDING:
 177
 178                 break;
 179         }
 180
 181         if (client->lease) {
 182                 free(client->lease);
 183                 client->lease = NULL;
 184         }
 185
 186         return 0;
 187 }
 188
 189 static int client_packet_init(sd_dhcp_client *client, uint8_t type,
 190                               DHCPMessage *message, uint16_t secs,
 191                               uint8_t **opt, size_t *optlen)
 192 {
 193         int err;
 194         be16_t max_size;
 195
 196         *opt = (uint8_t *)(message + 1);
 197
 198         if (*optlen < 4)
 199                 return -ENOBUFS;
 200         *optlen -= 4;
 201
 202         message->op = BOOTREQUEST;
 203         message->htype = 1;
 204         message->hlen = ETHER_ADDR_LEN;
 205         message->xid = htobe32(client->xid);
 206
 207         /* Although 'secs' field is a SHOULD in RFC 2131, certain DHCP servers
 208            refuse to issue an DHCP lease if 'secs' is set to zero */
 209         message->secs = htobe16(secs);
 210
 211         memcpy(&message->chaddr, &client->mac_addr, ETH_ALEN);
 212         (*opt)[0] = 0x63;
 213         (*opt)[1] = 0x82;
 214         (*opt)[2] = 0x53;
 215         (*opt)[3] = 0x63;
 216
 217         *opt += 4;
 218
 219         err = dhcp_option_append(opt, optlen, DHCP_OPTION_MESSAGE_TYPE, 1,
 220                                  &type);
 221         if (err < 0)
 222                 return err;
 223
 224         /* Some DHCP servers will refuse to issue an DHCP lease if the Cliient
 225            Identifier option is not set */
 226         err = dhcp_option_append(opt, optlen, DHCP_OPTION_CLIENT_IDENTIFIER,
 227                                  ETH_ALEN, &client->mac_addr);
 228         if (err < 0)
 229                 return err;
 230
 231         if (type == DHCP_DISCOVER || type == DHCP_REQUEST) {
 232                 err = dhcp_option_append(opt, optlen,
 233                                          DHCP_OPTION_PARAMETER_REQUEST_LIST,
 234                                          client->req_opts_size,
 235                                          client->req_opts);
 236                 if (err < 0)
 237                         return err;
 238
 239                 /* Some DHCP servers will send bigger DHCP packets than the
 240                    defined default size unless the Maximum Messge Size option
 241                    is explicitely set */
 242                 max_size = htobe16(DHCP_IP_UDP_SIZE + DHCP_MESSAGE_SIZE +
 243                                    DHCP_CLIENT_MIN_OPTIONS_SIZE);
 244                 err = dhcp_option_append(opt, optlen,
 245                                          DHCP_OPTION_MAXIMUM_MESSAGE_SIZE,
 246                                          2, &max_size);
 247                 if (err < 0)
 248                         return err;
 249         }
 250
 251         return 0;
 252 }
 253
 254 static uint16_t client_checksum(void *buf, int len)
 255 {
 256         uint32_t sum;
 257         uint16_t *check;
 258         int i;
 259         uint8_t *odd;
 260
 261         sum = 0;
 262         check = buf;
 263
 264         for (i = 0; i < len / 2 ; i++)
 265                 sum += check[i];
 266
 267         if (len & 0x01) {
 268                 odd = buf;
 269                 sum += odd[len];
 270         }
 271
 272         return ~((sum & 0xffff) + (sum >> 16));
 273 }
 274
 275 static void client_append_ip_headers(DHCPPacket *packet, uint16_t len)
 276 {
 277         packet->ip.version = IPVERSION;
 278         packet->ip.ihl = DHCP_IP_SIZE / 4;
 279         packet->ip.tot_len = htobe16(len);
 280
 281         packet->ip.protocol = IPPROTO_UDP;
 282         packet->ip.saddr = INADDR_ANY;
 283         packet->ip.daddr = INADDR_BROADCAST;
 284
 285         packet->udp.source = htobe16(DHCP_PORT_CLIENT);
 286         packet->udp.dest = htobe16(DHCP_PORT_SERVER);
 287         packet->udp.len = htobe16(len - DHCP_IP_SIZE);
 288
 289         packet->ip.check = packet->udp.len;
 290         packet->udp.check = client_checksum(&packet->ip.ttl, len - 8);
 291
 292         packet->ip.ttl = IPDEFTTL;
 293         packet->ip.check = 0;
 294         packet->ip.check = client_checksum(&packet->ip, DHCP_IP_SIZE);
 295 }
 296
 297 static int client_send_discover(sd_dhcp_client *client, uint16_t secs)
 298 {
 299         int err = 0;
 300         _cleanup_free_ DHCPPacket *discover;
 301         size_t optlen, len;
 302         uint8_t *opt;
 303
 304         optlen = DHCP_CLIENT_MIN_OPTIONS_SIZE;
 305         len = sizeof(DHCPPacket) + optlen;
 306
 307         discover = malloc0(len);
 308
 309         if (!discover)
 310                 return -ENOMEM;
 311
 312         err = client_packet_init(client, DHCP_DISCOVER, &discover->dhcp,
 313                                  secs, &opt, &optlen);
 314         if (err < 0)
 315                 return err;
 316
 317         if (client->last_addr != INADDR_ANY) {
 318                 err = dhcp_option_append(&opt, &optlen,
 319                                          DHCP_OPTION_REQUESTED_IP_ADDRESS,
 320                                          4, &client->last_addr);
 321                 if (err < 0)
 322                         return err;
 323         }
 324
 325         err = dhcp_option_append(&opt, &optlen, DHCP_OPTION_END, 0, NULL);
 326         if (err < 0)
 327                 return err;
 328
 329         client_append_ip_headers(discover, len);
 330
 331         err = dhcp_network_send_raw_socket(client->fd, &client->link,
 332                                            discover, len);
 333
 334         return err;
 335 }
 336
 337 static int client_send_request(sd_dhcp_client *client, uint16_t secs)
 338 {
 339         _cleanup_free_ DHCPPacket *request;
 340         size_t optlen, len;
 341         int err;
 342         uint8_t *opt;
 343
 344         optlen = DHCP_CLIENT_MIN_OPTIONS_SIZE;
 345         len = DHCP_MESSAGE_SIZE + optlen;
 346
 347         request = malloc0(len);
 348         if (!request)
 349                 return -ENOMEM;
 350
 351         err = client_packet_init(client, DHCP_REQUEST, &request->dhcp, secs,
 352                                  &opt, &optlen);
 353         if (err < 0)
 354                 return err;
 355
 356         if (client->state == DHCP_STATE_REQUESTING) {
 357                 err = dhcp_option_append(&opt, &optlen,
 358                                          DHCP_OPTION_REQUESTED_IP_ADDRESS,
 359                                          4, &client->lease->address);
 360                 if (err < 0)
 361                         return err;
 362
 363                 err = dhcp_option_append(&opt, &optlen,
 364                                          DHCP_OPTION_SERVER_IDENTIFIER,
 365                                          4, &client->lease->server_address);
 366                 if (err < 0)
 367                         return err;
 368         }
 369
 370         err = dhcp_option_append(&opt, &optlen, DHCP_OPTION_END, 0, NULL);
 371         if (err < 0)
 372                 return err;
 373
 374         client_append_ip_headers(request, len);
 375
 376         err = dhcp_network_send_raw_socket(client->fd, &client->link,
 377                                            request, len);
 378
 379         return err;
 380 }
 381
 382 static int client_timeout_resend(sd_event_source *s, uint64_t usec,
 383                                  void *userdata)
 384 {
 385         sd_dhcp_client *client = userdata;
 386         usec_t next_timeout;
 387         uint16_t secs;
 388         int err = 0;
 389
 390         secs = (usec - client->start_time) / USEC_PER_SEC;
 391
 392         if (client->attempt < 64)
 393                 client->attempt *= 2;
 394
 395         next_timeout = usec + (client->attempt - 1) * USEC_PER_SEC +
 396                 (random_u() & 0x1fffff);
 397
 398         err = sd_event_add_monotonic(client->event, next_timeout,
 399                                      10 * USEC_PER_MSEC,
 400                                      client_timeout_resend, client,
 401                                      &client->timeout_resend);
 402         if (err < 0)
 403                 goto error;
 404
 405         switch (client->state) {
 406         case DHCP_STATE_INIT:
 407                 err = client_send_discover(client, secs);
 408                 if (err >= 0) {
 409                         client->state = DHCP_STATE_SELECTING;
 410                         client->attempt = 1;
 411                 } else {
 412                         if (client->attempt >= 64)
 413                                 goto error;
 414                 }
 415
 416                 break;
 417
 418         case DHCP_STATE_SELECTING:
 419                 err = client_send_discover(client, secs);
 420                 if (err < 0 && client->attempt >= 64)
 421                         goto error;
 422
 423                 break;
 424
 425         case DHCP_STATE_REQUESTING:
 426                 err = client_send_request(client, secs);
 427                 if (err < 0 && client->attempt >= 64)
 428                          goto error;
 429
 430                 break;
 431
 432         case DHCP_STATE_INIT_REBOOT:
 433         case DHCP_STATE_REBOOTING:
 434         case DHCP_STATE_BOUND:
 435         case DHCP_STATE_RENEWING:
 436         case DHCP_STATE_REBINDING:
 437
 438                 break;
 439         }
 440
 441         return 0;
 442
 443 error:
 444         client_stop(client, err);
 445
 446         /* Errors were dealt with when stopping the client, don't spill
 447            errors into the event loop handler */
 448         return 0;
 449 }
 450
 451 static int client_parse_offer(uint8_t code, uint8_t len, const uint8_t *option,
 452                               void *user_data)
 453 {
 454         DHCPLease *lease = user_data;
 455         be32_t val;
 456
 457         switch(code) {
 458
 459         case DHCP_OPTION_IP_ADDRESS_LEASE_TIME:
 460                 if (len == 4) {
 461                         memcpy(&val, option, 4);
 462                         lease->lifetime = be32toh(val);
 463                 }
 464
 465                 break;
 466
 467         case DHCP_OPTION_SERVER_IDENTIFIER:
 468                 if (len >= 4)
 469                         memcpy(&lease->server_address, option, 4);
 470
 471                 break;
 472
 473         case DHCP_OPTION_SUBNET_MASK:
 474                 if (len >= 4)
 475                         memcpy(&lease->subnet_mask, option, 4);
 476
 477                 break;
 478
 479         case DHCP_OPTION_ROUTER:
 480                 if (len >= 4)
 481                         memcpy(&lease->router, option, 4);
 482
 483                 break;
 484         }
 485
 486         return 0;
 487 }
 488
 489 static int client_verify_headers(sd_dhcp_client *client, DHCPPacket *message,
 490                                  size_t len)
 491 {
 492         size_t hdrlen;
 493
 494         if (len < (DHCP_IP_UDP_SIZE + DHCP_MESSAGE_SIZE))
 495                 return -EINVAL;
 496
 497         hdrlen = message->ip.ihl * 4;
 498         if (hdrlen < 20 || hdrlen > len || client_checksum(&message->ip,
 499                                                            hdrlen))
 500                 return -EINVAL;
 501
 502         message->ip.check = message->udp.len;
 503         message->ip.ttl = 0;
 504
 505         if (hdrlen + be16toh(message->udp.len) > len ||
 506             client_checksum(&message->ip.ttl, be16toh(message->udp.len) + 12))
 507                 return -EINVAL;
 508
 509         if (be16toh(message->udp.source) != DHCP_PORT_SERVER ||
 510             be16toh(message->udp.dest) != DHCP_PORT_CLIENT)
 511                 return -EINVAL;
 512
 513         if (message->dhcp.op != BOOTREPLY)
 514                 return -EINVAL;
 515
 516         if (be32toh(message->dhcp.xid) != client->xid)
 517                 return -EINVAL;
 518
 519         if (memcmp(&message->dhcp.chaddr[0], &client->mac_addr.ether_addr_octet,
 520                     ETHER_ADDR_LEN))
 521                 return -EINVAL;
 522
 523         return 0;
 524 }
 525
 526 static int client_receive_offer(sd_dhcp_client *client, DHCPPacket *offer,
 527                                 size_t len)
 528 {
 529         int err;
 530         DHCPLease *lease;
 531
 532         err = client_verify_headers(client, offer, len);
 533         if (err < 0)
 534                 return err;
 535
 536         lease = new0(DHCPLease, 1);
 537         if (!lease)
 538                 return -ENOMEM;
 539
 540         len = len - DHCP_IP_UDP_SIZE;
 541         if (dhcp_option_parse(&offer->dhcp, len, client_parse_offer,
 542                               lease) != DHCP_OFFER)
 543                 goto error;
 544
 545         lease->address = offer->dhcp.yiaddr;
 546
 547         if (lease->address == INADDR_ANY ||
 548             lease->server_address == INADDR_ANY ||
 549             lease->subnet_mask == INADDR_ANY ||
 550             lease->lifetime == 0)
 551                 goto error;
 552
 553         client->lease = lease;
 554
 555         return 0;
 556
 557 error:
 558         free(lease);
 559
 560         return -ENOMSG;
 561 }
 562
 563 static int client_receive_ack(sd_dhcp_client *client, DHCPPacket *offer,
 564                               size_t len)
 565 {
 566         int r;
 567         DHCPLease *lease;
 568
 569         r = client_verify_headers(client, offer, len);
 570         if (r < 0)
 571                 return r;
 572
 573         lease = new0(DHCPLease, 1);
 574         if (!lease)
 575                 return -ENOBUFS;
 576
 577         len = len - DHCP_IP_UDP_SIZE;
 578         r = dhcp_option_parse(&offer->dhcp, len, client_parse_offer, lease);
 579
 580         if (r != DHCP_ACK)
 581                 goto error;
 582
 583         lease->address = offer->dhcp.yiaddr;
 584
 585         if (lease->address == INADDR_ANY ||
 586             lease->server_address == INADDR_ANY ||
 587             lease->subnet_mask == INADDR_ANY || lease->lifetime == 0) {
 588                 r = -ENOMSG;
 589                 goto error;
 590         }
 591
 592         r = DHCP_EVENT_IP_ACQUIRE;
 593         if (client->lease) {
 594                 if (client->lease->address != lease->address ||
 595                     client->lease->subnet_mask != lease->subnet_mask ||
 596                     client->lease->router != lease->router) {
 597                         r = DHCP_EVENT_IP_CHANGE;
 598                 }
 599
 600                 free(client->lease);
 601         }
 602
 603         client->lease = lease;
 604
 605         return r;
 606
 607 error:
 608         free(lease);
 609
 610         return r;
 611 }
 612
 613 static int client_receive_raw_message(sd_event_source *s, int fd,
 614                                       uint32_t revents, void *userdata)
 615 {
 616         sd_dhcp_client *client = userdata;
 617         uint8_t buf[sizeof(DHCPPacket) + DHCP_CLIENT_MIN_OPTIONS_SIZE];
 618         int buflen = sizeof(buf);
 619         int len, r = 0;
 620         DHCPPacket *message;
 621         usec_t time_now;
 622
 623         len = read(fd, &buf, buflen);
 624         if (len < 0)
 625                 return 0;
 626
 627         r = sd_event_get_now_monotonic(client->event, &time_now);
 628         if (r < 0)
 629                 goto error;
 630
 631         message = (DHCPPacket *)&buf;
 632
 633         switch (client->state) {
 634         case DHCP_STATE_SELECTING:
 635
 636                 if (client_receive_offer(client, message, len) >= 0) {
 637
 638                         client->timeout_resend =
 639                                 sd_event_source_unref(client->timeout_resend);
 640
 641                         client->state = DHCP_STATE_REQUESTING;
 642                         client->attempt = 1;
 643
 644                         r = sd_event_add_monotonic(client->event, time_now, 0,
 645                                                    client_timeout_resend,
 646                                                    client,
 647                                                    &client->timeout_resend);
 648                         if (r < 0)
 649                                 goto error;
 650                 }
 651
 652                 break;
 653
 654         case DHCP_STATE_REQUESTING:
 655
 656                 r = client_receive_ack(client, message, len);
 657                 if (r == DHCP_EVENT_NO_LEASE)
 658                         goto error;
 659
 660                 if (r >= 0) {
 661                         client->timeout_resend =
 662                                 sd_event_source_unref(client->timeout_resend);
 663
 664                         client->state = DHCP_STATE_BOUND;
 665                         client->attempt = 1;
 666
 667                         client->last_addr = client->lease->address;
 668
 669                         client_notify(client, DHCP_EVENT_IP_ACQUIRE);
 670
 671                         close(client->fd);
 672                         client->fd = -1;
 673                         client->receive_message =
 674                                 sd_event_source_unref(client->receive_message);
 675                 }
 676                 break;
 677
 678         case DHCP_STATE_INIT:
 679         case DHCP_STATE_INIT_REBOOT:
 680         case DHCP_STATE_REBOOTING:
 681         case DHCP_STATE_BOUND:
 682         case DHCP_STATE_RENEWING:
 683         case DHCP_STATE_REBINDING:
 684
 685                 break;
 686         }
 687
 688 error:
 689         if (r < 0)
 690                 return client_stop(client, r);
 691
 692         return 0;
 693 }
 694
 695 int sd_dhcp_client_start(sd_dhcp_client *client)
 696 {
 697         int err;
 698
 699         assert_return(client, -EINVAL);
 700         assert_return(client->index >= 0, -EINVAL);
 701         assert_return(client->state == DHCP_STATE_INIT ||
 702                       client->state == DHCP_STATE_INIT_REBOOT, -EBUSY);
 703
 704         client->xid = random_u();
 705
 706         client->fd = dhcp_network_bind_raw_socket(client->index,
 707                                                   &client->link);
 708
 709         if (client->fd < 0) {
 710                 err = client->fd;
 711                 goto error;
 712         }
 713
 714         err = sd_event_add_io(client->event, client->fd, EPOLLIN,
 715                               client_receive_raw_message, client,
 716                               &client->receive_message);
 717         if (err < 0)
 718                 goto error;
 719
 720         client->start_time = now(CLOCK_MONOTONIC);
 721         err = sd_event_add_monotonic(client->event, client->start_time, 0,
 722                                      client_timeout_resend, client,
 723                                      &client->timeout_resend);
 724         if (err < 0)
 725                 goto error;
 726
 727         return 0;
 728
 729 error:
 730         client_stop(client, err);
 731
 732         return err;
 733 }
 734
 735 int sd_dhcp_client_stop(sd_dhcp_client *client)
 736 {
 737         return client_stop(client, 0);
 738 }
 739
 740 sd_dhcp_client *sd_dhcp_client_new(sd_event *event)
 741 {
 742         sd_dhcp_client *client;
 743
 744         assert_return(event, NULL);
 745
 746         client = new0(sd_dhcp_client, 1);
 747         if (!client)
 748                 return NULL;
 749
 750         client->event = sd_event_ref(event);
 751         client->state = DHCP_STATE_INIT;
 752         client->index = -1;
 753         client->fd = -1;
 754         client->attempt = 1;
 755
 756         client->req_opts_size = ELEMENTSOF(default_req_opts);
 757
 758         client->req_opts = memdup(default_req_opts, client->req_opts_size);
 759         if (!client->req_opts) {
 760                 free(client);
 761                 return NULL;
 762         }
 763
 764         return client;
 765 }