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 #include <sys/param.h>
  26
  27 #include "util.h"
  28 #include "list.h"
  29
  30 #include "dhcp-protocol.h"
  31 #include "dhcp-internal.h"
  32 #include "sd-dhcp-client.h"
  33
  34 #define DHCP_CLIENT_MIN_OPTIONS_SIZE            312
  35
  36 struct DHCPLease {
  37         uint32_t t1;
  38         uint32_t t2;
  39         uint32_t lifetime;
  40         be32_t address;
  41         be32_t server_address;
  42         be32_t subnet_mask;
  43         be32_t router;
  44 };
  45
  46 typedef struct DHCPLease DHCPLease;
  47
  48 struct sd_dhcp_client {
  49         DHCPState state;
  50         sd_event *event;
  51         sd_event_source *timeout_resend;
  52         int index;
  53         int fd;
  54         union sockaddr_union link;
  55         sd_event_source *receive_message;
  56         uint8_t *req_opts;
  57         size_t req_opts_size;
  58         be32_t last_addr;
  59         struct ether_addr mac_addr;
  60         uint32_t xid;
  61         usec_t start_time;
  62         unsigned int attempt;
  63         usec_t request_sent;
  64         sd_event_source *timeout_t1;
  65         sd_event_source *timeout_t2;
  66         sd_event_source *timeout_expire;
  67         sd_dhcp_client_cb_t cb;
  68         void *userdata;
  69         DHCPLease *lease;
  70 };
  71
  72 static const uint8_t default_req_opts[] = {
  73         DHCP_OPTION_SUBNET_MASK,
  74         DHCP_OPTION_ROUTER,
  75         DHCP_OPTION_HOST_NAME,
  76         DHCP_OPTION_DOMAIN_NAME,
  77         DHCP_OPTION_DOMAIN_NAME_SERVER,
  78         DHCP_OPTION_NTP_SERVER,
  79 };
  80
  81 static int client_receive_message(sd_event_source *s, int fd,
  82                                   uint32_t revents, void *userdata);
  83
  84 int sd_dhcp_client_set_callback(sd_dhcp_client *client, sd_dhcp_client_cb_t cb,
  85                                 void *userdata)
  86 {
  87         assert_return(client, -EINVAL);
  88
  89         client->cb = cb;
  90         client->userdata = userdata;
  91
  92         return 0;
  93 }
  94
  95 int sd_dhcp_client_set_request_option(sd_dhcp_client *client, uint8_t option)
  96 {
  97         size_t i;
  98
  99         assert_return(client, -EINVAL);
 100         assert_return (client->state == DHCP_STATE_INIT, -EBUSY);
 101
 102         switch(option) {
 103         case DHCP_OPTION_PAD:
 104         case DHCP_OPTION_OVERLOAD:
 105         case DHCP_OPTION_MESSAGE_TYPE:
 106         case DHCP_OPTION_PARAMETER_REQUEST_LIST:
 107         case DHCP_OPTION_END:
 108                 return -EINVAL;
 109
 110         default:
 111                 break;
 112         }
 113
 114         for (i = 0; i < client->req_opts_size; i++)
 115                 if (client->req_opts[i] == option)
 116                         return -EEXIST;
 117
 118         if (!GREEDY_REALLOC(client->req_opts, client->req_opts_size,
 119                             client->req_opts_size + 1))
 120                 return -ENOMEM;
 121
 122         client->req_opts[client->req_opts_size - 1] = option;
 123
 124         return 0;
 125 }
 126
 127 int sd_dhcp_client_set_request_address(sd_dhcp_client *client,
 128                                        const struct in_addr *last_addr)
 129 {
 130         assert_return(client, -EINVAL);
 131         assert_return(client->state == DHCP_STATE_INIT, -EBUSY);
 132
 133         if (last_addr)
 134                 client->last_addr = last_addr->s_addr;
 135         else
 136                 client->last_addr = INADDR_ANY;
 137
 138         return 0;
 139 }
 140
 141 int sd_dhcp_client_set_index(sd_dhcp_client *client, int interface_index)
 142 {
 143         assert_return(client, -EINVAL);
 144         assert_return(client->state == DHCP_STATE_INIT, -EBUSY);
 145         assert_return(interface_index >= -1, -EINVAL);
 146
 147         client->index = interface_index;
 148
 149         return 0;
 150 }
 151
 152 int sd_dhcp_client_set_mac(sd_dhcp_client *client,
 153                            const struct ether_addr *addr)
 154 {
 155         assert_return(client, -EINVAL);
 156         assert_return(client->state == DHCP_STATE_INIT, -EBUSY);
 157
 158         memcpy(&client->mac_addr, addr, ETH_ALEN);
 159
 160         return 0;
 161 }
 162
 163 int sd_dhcp_client_get_address(sd_dhcp_client *client, struct in_addr *addr)
 164 {
 165         assert_return(client, -EINVAL);
 166         assert_return(addr, -EINVAL);
 167
 168         switch (client->state) {
 169         case DHCP_STATE_INIT:
 170         case DHCP_STATE_SELECTING:
 171         case DHCP_STATE_INIT_REBOOT:
 172         case DHCP_STATE_REBOOTING:
 173         case DHCP_STATE_REQUESTING:
 174                 return -EADDRNOTAVAIL;
 175
 176         case DHCP_STATE_BOUND:
 177         case DHCP_STATE_RENEWING:
 178         case DHCP_STATE_REBINDING:
 179                 addr->s_addr = client->lease->address;
 180
 181                 break;
 182         }
 183
 184         return 0;
 185 }
 186
 187 int sd_dhcp_client_get_netmask(sd_dhcp_client *client, struct in_addr *addr)
 188 {
 189         assert_return(client, -EINVAL);
 190         assert_return(addr, -EINVAL);
 191
 192         switch (client->state) {
 193         case DHCP_STATE_INIT:
 194         case DHCP_STATE_SELECTING:
 195         case DHCP_STATE_INIT_REBOOT:
 196         case DHCP_STATE_REBOOTING:
 197         case DHCP_STATE_REQUESTING:
 198                 return -EADDRNOTAVAIL;
 199
 200         case DHCP_STATE_BOUND:
 201         case DHCP_STATE_RENEWING:
 202         case DHCP_STATE_REBINDING:
 203                 addr->s_addr = client->lease->subnet_mask;
 204
 205                 break;
 206         }
 207
 208         return 0;
 209 }
 210
 211 int sd_dhcp_client_prefixlen(const struct in_addr *addr)
 212 {
 213         int len = 0;
 214         uint32_t mask;
 215
 216         assert_return(addr, -EADDRNOTAVAIL);
 217
 218         mask = be32toh(addr->s_addr);
 219         while (mask) {
 220                 len++;
 221                 mask = mask << 1;
 222         }
 223
 224         return len;
 225 }
 226
 227 int sd_dhcp_client_get_router(sd_dhcp_client *client, struct in_addr *addr)
 228 {
 229         assert_return(client, -EINVAL);
 230         assert_return(addr, -EINVAL);
 231
 232         switch (client->state) {
 233         case DHCP_STATE_INIT:
 234         case DHCP_STATE_SELECTING:
 235         case DHCP_STATE_INIT_REBOOT:
 236         case DHCP_STATE_REBOOTING:
 237         case DHCP_STATE_REQUESTING:
 238                 return -EADDRNOTAVAIL;
 239
 240         case DHCP_STATE_BOUND:
 241         case DHCP_STATE_RENEWING:
 242         case DHCP_STATE_REBINDING:
 243                 addr->s_addr = client->lease->router;
 244
 245                 break;
 246         }
 247
 248         return 0;
 249 }
 250
 251 static int client_notify(sd_dhcp_client *client, int event)
 252 {
 253         if (client->cb)
 254                 client->cb(client, event, client->userdata);
 255
 256         return 0;
 257 }
 258
 259 static int client_stop(sd_dhcp_client *client, int error)
 260 {
 261         assert_return(client, -EINVAL);
 262         assert_return(client->state != DHCP_STATE_INIT &&
 263                       client->state != DHCP_STATE_INIT_REBOOT, -EALREADY);
 264
 265         client->receive_message =
 266                 sd_event_source_unref(client->receive_message);
 267
 268         if (client->fd >= 0)
 269                 close(client->fd);
 270         client->fd = -1;
 271
 272         client->timeout_resend = sd_event_source_unref(client->timeout_resend);
 273
 274         client->timeout_t1 = sd_event_source_unref(client->timeout_t1);
 275         client->timeout_t2 = sd_event_source_unref(client->timeout_t2);
 276         client->timeout_expire = sd_event_source_unref(client->timeout_expire);
 277
 278         client->attempt = 1;
 279
 280         client_notify(client, error);
 281
 282         switch (client->state) {
 283
 284         case DHCP_STATE_INIT:
 285         case DHCP_STATE_SELECTING:
 286         case DHCP_STATE_REQUESTING:
 287         case DHCP_STATE_BOUND:
 288
 289                 client->start_time = 0;
 290                 client->state = DHCP_STATE_INIT;
 291                 break;
 292
 293         case DHCP_STATE_INIT_REBOOT:
 294         case DHCP_STATE_REBOOTING:
 295         case DHCP_STATE_RENEWING:
 296         case DHCP_STATE_REBINDING:
 297
 298                 break;
 299         }
 300
 301         if (client->lease) {
 302                 free(client->lease);
 303                 client->lease = NULL;
 304         }
 305
 306         return 0;
 307 }
 308
 309 static int client_packet_init(sd_dhcp_client *client, uint8_t type,
 310                               DHCPMessage *message, uint16_t secs,
 311                               uint8_t **opt, size_t *optlen)
 312 {
 313         int err;
 314         be16_t max_size;
 315
 316         *opt = (uint8_t *)(message + 1);
 317
 318         if (*optlen < 4)
 319                 return -ENOBUFS;
 320         *optlen -= 4;
 321
 322         message->op = BOOTREQUEST;
 323         message->htype = 1;
 324         message->hlen = ETHER_ADDR_LEN;
 325         message->xid = htobe32(client->xid);
 326
 327         /* Although 'secs' field is a SHOULD in RFC 2131, certain DHCP servers
 328            refuse to issue an DHCP lease if 'secs' is set to zero */
 329         message->secs = htobe16(secs);
 330
 331         if (client->state == DHCP_STATE_RENEWING ||
 332             client->state == DHCP_STATE_REBINDING)
 333                 message->ciaddr = client->lease->address;
 334
 335         memcpy(&message->chaddr, &client->mac_addr, ETH_ALEN);
 336         (*opt)[0] = 0x63;
 337         (*opt)[1] = 0x82;
 338         (*opt)[2] = 0x53;
 339         (*opt)[3] = 0x63;
 340
 341         *opt += 4;
 342
 343         err = dhcp_option_append(opt, optlen, DHCP_OPTION_MESSAGE_TYPE, 1,
 344                                  &type);
 345         if (err < 0)
 346                 return err;
 347
 348         /* Some DHCP servers will refuse to issue an DHCP lease if the Cliient
 349            Identifier option is not set */
 350         err = dhcp_option_append(opt, optlen, DHCP_OPTION_CLIENT_IDENTIFIER,
 351                                  ETH_ALEN, &client->mac_addr);
 352         if (err < 0)
 353                 return err;
 354
 355         if (type == DHCP_DISCOVER || type == DHCP_REQUEST) {
 356                 err = dhcp_option_append(opt, optlen,
 357                                          DHCP_OPTION_PARAMETER_REQUEST_LIST,
 358                                          client->req_opts_size,
 359                                          client->req_opts);
 360                 if (err < 0)
 361                         return err;
 362
 363                 /* Some DHCP servers will send bigger DHCP packets than the
 364                    defined default size unless the Maximum Messge Size option
 365                    is explicitely set */
 366                 max_size = htobe16(DHCP_IP_UDP_SIZE + DHCP_MESSAGE_SIZE +
 367                                    DHCP_CLIENT_MIN_OPTIONS_SIZE);
 368                 err = dhcp_option_append(opt, optlen,
 369                                          DHCP_OPTION_MAXIMUM_MESSAGE_SIZE,
 370                                          2, &max_size);
 371                 if (err < 0)
 372                         return err;
 373         }
 374
 375         return 0;
 376 }
 377
 378 static uint16_t client_checksum(void *buf, int len)
 379 {
 380         uint32_t sum;
 381         uint16_t *check;
 382         int i;
 383         uint8_t *odd;
 384
 385         sum = 0;
 386         check = buf;
 387
 388         for (i = 0; i < len / 2 ; i++)
 389                 sum += check[i];
 390
 391         if (len & 0x01) {
 392                 odd = buf;
 393                 sum += odd[len - 1];
 394         }
 395
 396         while (sum >> 16)
 397                 sum = (sum & 0xffff) + (sum >> 16);
 398
 399         return ~sum;
 400 }
 401
 402 static void client_append_ip_headers(DHCPPacket *packet, uint16_t len)
 403 {
 404         packet->ip.version = IPVERSION;
 405         packet->ip.ihl = DHCP_IP_SIZE / 4;
 406         packet->ip.tot_len = htobe16(len);
 407
 408         packet->ip.protocol = IPPROTO_UDP;
 409         packet->ip.saddr = INADDR_ANY;
 410         packet->ip.daddr = INADDR_BROADCAST;
 411
 412         packet->udp.source = htobe16(DHCP_PORT_CLIENT);
 413         packet->udp.dest = htobe16(DHCP_PORT_SERVER);
 414         packet->udp.len = htobe16(len - DHCP_IP_SIZE);
 415
 416         packet->ip.check = packet->udp.len;
 417         packet->udp.check = client_checksum(&packet->ip.ttl, len - 8);
 418
 419         packet->ip.ttl = IPDEFTTL;
 420         packet->ip.check = 0;
 421         packet->ip.check = client_checksum(&packet->ip, DHCP_IP_SIZE);
 422 }
 423
 424 static int client_send_discover(sd_dhcp_client *client, uint16_t secs)
 425 {
 426         int err = 0;
 427         _cleanup_free_ DHCPPacket *discover;
 428         size_t optlen, len;
 429         uint8_t *opt;
 430
 431         optlen = DHCP_CLIENT_MIN_OPTIONS_SIZE;
 432         len = sizeof(DHCPPacket) + optlen;
 433
 434         discover = malloc0(len);
 435
 436         if (!discover)
 437                 return -ENOMEM;
 438
 439         err = client_packet_init(client, DHCP_DISCOVER, &discover->dhcp,
 440                                  secs, &opt, &optlen);
 441         if (err < 0)
 442                 return err;
 443
 444         if (client->last_addr != INADDR_ANY) {
 445                 err = dhcp_option_append(&opt, &optlen,
 446                                          DHCP_OPTION_REQUESTED_IP_ADDRESS,
 447                                          4, &client->last_addr);
 448                 if (err < 0)
 449                         return err;
 450         }
 451
 452         err = dhcp_option_append(&opt, &optlen, DHCP_OPTION_END, 0, NULL);
 453         if (err < 0)
 454                 return err;
 455
 456         client_append_ip_headers(discover, len);
 457
 458         err = dhcp_network_send_raw_socket(client->fd, &client->link,
 459                                            discover, len);
 460
 461         return err;
 462 }
 463
 464 static int client_send_request(sd_dhcp_client *client, uint16_t secs)
 465 {
 466         _cleanup_free_ DHCPPacket *request;
 467         size_t optlen, len;
 468         int err;
 469         uint8_t *opt;
 470
 471         optlen = DHCP_CLIENT_MIN_OPTIONS_SIZE;
 472         len = DHCP_MESSAGE_SIZE + optlen;
 473
 474         request = malloc0(len);
 475         if (!request)
 476                 return -ENOMEM;
 477
 478         err = client_packet_init(client, DHCP_REQUEST, &request->dhcp, secs,
 479                                  &opt, &optlen);
 480         if (err < 0)
 481                 return err;
 482
 483         if (client->state == DHCP_STATE_REQUESTING) {
 484                 err = dhcp_option_append(&opt, &optlen,
 485                                          DHCP_OPTION_REQUESTED_IP_ADDRESS,
 486                                          4, &client->lease->address);
 487                 if (err < 0)
 488                         return err;
 489
 490                 err = dhcp_option_append(&opt, &optlen,
 491                                          DHCP_OPTION_SERVER_IDENTIFIER,
 492                                          4, &client->lease->server_address);
 493                 if (err < 0)
 494                         return err;
 495         }
 496
 497         err = dhcp_option_append(&opt, &optlen, DHCP_OPTION_END, 0, NULL);
 498         if (err < 0)
 499                 return err;
 500
 501         if (client->state == DHCP_STATE_RENEWING) {
 502                 err = dhcp_network_send_udp_socket(client->fd,
 503                                                    client->lease->server_address,
 504                                                    &request->dhcp,
 505                                                    len - DHCP_IP_UDP_SIZE);
 506         } else {
 507                 client_append_ip_headers(request, len);
 508
 509                 err = dhcp_network_send_raw_socket(client->fd, &client->link,
 510                                                    request, len);
 511         }
 512
 513         return err;
 514 }
 515
 516 static int client_timeout_resend(sd_event_source *s, uint64_t usec,
 517                                  void *userdata)
 518 {
 519         sd_dhcp_client *client = userdata;
 520         usec_t next_timeout = 0;
 521         uint32_t time_left;
 522         uint16_t secs;
 523         int err = 0;
 524
 525         switch (client->state) {
 526         case DHCP_STATE_RENEWING:
 527
 528                 time_left = (client->lease->t2 - client->lease->t1)/2;
 529                 if (time_left < 60)
 530                         time_left = 60;
 531
 532                 next_timeout = usec + time_left * USEC_PER_SEC;
 533
 534                 break;
 535
 536         case DHCP_STATE_REBINDING:
 537
 538                 time_left = (client->lease->lifetime - client->lease->t2)/2;
 539                 if (time_left < 60)
 540                         time_left = 60;
 541
 542                 next_timeout = usec + time_left * USEC_PER_SEC;
 543
 544                 break;
 545
 546         case DHCP_STATE_INIT:
 547         case DHCP_STATE_INIT_REBOOT:
 548         case DHCP_STATE_REBOOTING:
 549         case DHCP_STATE_SELECTING:
 550         case DHCP_STATE_REQUESTING:
 551         case DHCP_STATE_BOUND:
 552
 553                 if (client->attempt < 64)
 554                         client->attempt *= 2;
 555
 556                 next_timeout = usec + (client->attempt - 1) * USEC_PER_SEC;
 557
 558                 break;
 559         }
 560
 561         next_timeout += (random_u() & 0x1fffff);
 562
 563         err = sd_event_add_monotonic(client->event, next_timeout,
 564                                      10 * USEC_PER_MSEC,
 565                                      client_timeout_resend, client,
 566                                      &client->timeout_resend);
 567         if (err < 0)
 568                 goto error;
 569
 570         secs = (usec - client->start_time) / USEC_PER_SEC;
 571
 572         switch (client->state) {
 573         case DHCP_STATE_INIT:
 574                 err = client_send_discover(client, secs);
 575                 if (err >= 0) {
 576                         client->state = DHCP_STATE_SELECTING;
 577                         client->attempt = 1;
 578                 } else {
 579                         if (client->attempt >= 64)
 580                                 goto error;
 581                 }
 582
 583                 break;
 584
 585         case DHCP_STATE_SELECTING:
 586                 err = client_send_discover(client, secs);
 587                 if (err < 0 && client->attempt >= 64)
 588                         goto error;
 589
 590                 break;
 591
 592         case DHCP_STATE_REQUESTING:
 593         case DHCP_STATE_RENEWING:
 594         case DHCP_STATE_REBINDING:
 595                 err = client_send_request(client, secs);
 596                 if (err < 0 && client->attempt >= 64)
 597                          goto error;
 598
 599                 client->request_sent = usec;
 600
 601                 break;
 602
 603         case DHCP_STATE_INIT_REBOOT:
 604         case DHCP_STATE_REBOOTING:
 605         case DHCP_STATE_BOUND:
 606
 607                 break;
 608         }
 609
 610         return 0;
 611
 612 error:
 613         client_stop(client, err);
 614
 615         /* Errors were dealt with when stopping the client, don't spill
 616            errors into the event loop handler */
 617         return 0;
 618 }
 619
 620 static int client_initialize_events(sd_dhcp_client *client, usec_t usec)
 621 {
 622         int r;
 623
 624         r = sd_event_add_io(client->event, client->fd, EPOLLIN,
 625                             client_receive_message, client,
 626                             &client->receive_message);
 627         if (r < 0)
 628                 goto error;
 629
 630         r = sd_event_add_monotonic(client->event, usec, 0,
 631                                    client_timeout_resend, client,
 632                                    &client->timeout_resend);
 633
 634 error:
 635         if (r < 0)
 636                 client_stop(client, r);
 637
 638         return 0;
 639
 640 }
 641
 642 static int client_timeout_expire(sd_event_source *s, uint64_t usec,
 643                                  void *userdata)
 644 {
 645         sd_dhcp_client *client = userdata;
 646
 647         client_stop(client, DHCP_EVENT_EXPIRED);
 648
 649         return 0;
 650 }
 651
 652 static int client_timeout_t2(sd_event_source *s, uint64_t usec, void *userdata)
 653 {
 654         sd_dhcp_client *client = userdata;
 655         int r;
 656
 657         if (client->fd >= 0) {
 658                 client->receive_message =
 659                         sd_event_source_unref(client->receive_message);
 660                 close(client->fd);
 661                 client->fd = -1;
 662         }
 663
 664         client->state = DHCP_STATE_REBINDING;
 665         client->attempt = 1;
 666
 667         r = dhcp_network_bind_raw_socket(client->index, &client->link);
 668         if (r < 0) {
 669                 client_stop(client, r);
 670                 return 0;
 671         }
 672
 673         client->fd = r;
 674
 675         return client_initialize_events(client, usec);
 676 }
 677
 678 static int client_timeout_t1(sd_event_source *s, uint64_t usec, void *userdata)
 679 {
 680         sd_dhcp_client *client = userdata;
 681         int r;
 682
 683         client->state = DHCP_STATE_RENEWING;
 684         client->attempt = 1;
 685
 686         r = dhcp_network_bind_udp_socket(client->index,
 687                                          client->lease->address);
 688         if (r < 0) {
 689                 client_stop(client, r);
 690                 return 0;
 691         }
 692
 693         client->fd = r;
 694
 695         return client_initialize_events(client, usec);
 696 }
 697
 698 static int client_parse_offer(uint8_t code, uint8_t len, const uint8_t *option,
 699                               void *user_data)
 700 {
 701         DHCPLease *lease = user_data;
 702         be32_t val;
 703
 704         switch(code) {
 705
 706         case DHCP_OPTION_IP_ADDRESS_LEASE_TIME:
 707                 if (len == 4) {
 708                         memcpy(&val, option, 4);
 709                         lease->lifetime = be32toh(val);
 710                 }
 711
 712                 break;
 713
 714         case DHCP_OPTION_SERVER_IDENTIFIER:
 715                 if (len >= 4)
 716                         memcpy(&lease->server_address, option, 4);
 717
 718                 break;
 719
 720         case DHCP_OPTION_SUBNET_MASK:
 721                 if (len >= 4)
 722                         memcpy(&lease->subnet_mask, option, 4);
 723
 724                 break;
 725
 726         case DHCP_OPTION_ROUTER:
 727                 if (len >= 4)
 728                         memcpy(&lease->router, option, 4);
 729
 730                 break;
 731
 732         case DHCP_OPTION_RENEWAL_T1_TIME:
 733                 if (len == 4) {
 734                         memcpy(&val, option, 4);
 735                         lease->t1 = be32toh(val);
 736                 }
 737
 738                 break;
 739
 740         case DHCP_OPTION_REBINDING_T2_TIME:
 741                 if (len == 4) {
 742                         memcpy(&val, option, 4);
 743                         lease->t2 = be32toh(val);
 744                 }
 745
 746                 break;
 747         }
 748
 749         return 0;
 750 }
 751
 752 static int client_verify_headers(sd_dhcp_client *client, DHCPPacket *message,
 753                                  size_t len)
 754 {
 755         size_t hdrlen;
 756
 757         if (len < (DHCP_IP_UDP_SIZE + DHCP_MESSAGE_SIZE))
 758                 return -EINVAL;
 759
 760         hdrlen = message->ip.ihl * 4;
 761         if (hdrlen < 20 || hdrlen > len || client_checksum(&message->ip,
 762                                                            hdrlen))
 763                 return -EINVAL;
 764
 765         message->ip.check = message->udp.len;
 766         message->ip.ttl = 0;
 767
 768         if (hdrlen + be16toh(message->udp.len) > len ||
 769             client_checksum(&message->ip.ttl, be16toh(message->udp.len) + 12))
 770                 return -EINVAL;
 771
 772         if (be16toh(message->udp.source) != DHCP_PORT_SERVER ||
 773             be16toh(message->udp.dest) != DHCP_PORT_CLIENT)
 774                 return -EINVAL;
 775
 776         if (message->dhcp.op != BOOTREPLY)
 777                 return -EINVAL;
 778
 779         if (be32toh(message->dhcp.xid) != client->xid)
 780                 return -EINVAL;
 781
 782         if (memcmp(&message->dhcp.chaddr[0], &client->mac_addr.ether_addr_octet,
 783                     ETHER_ADDR_LEN))
 784                 return -EINVAL;
 785
 786         return 0;
 787 }
 788
 789 static int client_receive_offer(sd_dhcp_client *client, DHCPPacket *offer,
 790                                 size_t len)
 791 {
 792         int err;
 793         DHCPLease *lease;
 794
 795         err = client_verify_headers(client, offer, len);
 796         if (err < 0)
 797                 return err;
 798
 799         lease = new0(DHCPLease, 1);
 800         if (!lease)
 801                 return -ENOMEM;
 802
 803         len = len - DHCP_IP_UDP_SIZE;
 804         if (dhcp_option_parse(&offer->dhcp, len, client_parse_offer,
 805                               lease) != DHCP_OFFER)
 806                 goto error;
 807
 808         lease->address = offer->dhcp.yiaddr;
 809
 810         if (lease->address == INADDR_ANY ||
 811             lease->server_address == INADDR_ANY ||
 812             lease->subnet_mask == INADDR_ANY ||
 813             lease->lifetime == 0)
 814                 goto error;
 815
 816         client->lease = lease;
 817
 818         return 0;
 819
 820 error:
 821         free(lease);
 822
 823         return -ENOMSG;
 824 }
 825
 826 static int client_receive_ack(sd_dhcp_client *client, const uint8_t *buf,
 827                               size_t len)
 828 {
 829         int r;
 830         DHCPPacket *ack;
 831         DHCPMessage *dhcp;
 832         DHCPLease *lease;
 833
 834         if (client->state == DHCP_STATE_RENEWING) {
 835                 dhcp = (DHCPMessage *)buf;
 836         } else {
 837                 ack = (DHCPPacket *)buf;
 838
 839                 r = client_verify_headers(client, ack, len);
 840                 if (r < 0)
 841                         return r;
 842
 843                 dhcp = &ack->dhcp;
 844                 len -= DHCP_IP_UDP_SIZE;
 845         }
 846
 847         lease = new0(DHCPLease, 1);
 848         if (!lease)
 849                 return -ENOMEM;
 850
 851         r = dhcp_option_parse(dhcp, len, client_parse_offer, lease);
 852
 853         if (r == DHCP_NAK) {
 854                 r = DHCP_EVENT_NO_LEASE;
 855                 goto error;
 856         }
 857
 858         if (r != DHCP_ACK) {
 859                 r = -ENOMSG;
 860                 goto error;
 861         }
 862
 863         lease->address = dhcp->yiaddr;
 864
 865         if (lease->address == INADDR_ANY ||
 866             lease->server_address == INADDR_ANY ||
 867             lease->subnet_mask == INADDR_ANY || lease->lifetime == 0) {
 868                 r = -ENOMSG;
 869                 goto error;
 870         }
 871
 872         r = DHCP_EVENT_IP_ACQUIRE;
 873         if (client->lease) {
 874                 if (client->lease->address != lease->address ||
 875                     client->lease->subnet_mask != lease->subnet_mask ||
 876                     client->lease->router != lease->router) {
 877                         r = DHCP_EVENT_IP_CHANGE;
 878                 }
 879
 880                 free(client->lease);
 881         }
 882
 883         client->lease = lease;
 884
 885         return r;
 886
 887 error:
 888         free(lease);
 889
 890         return r;
 891 }
 892
 893 static uint64_t client_compute_timeout(uint64_t request_sent,
 894                                        uint32_t lifetime)
 895 {
 896         return request_sent + (lifetime - 3) * USEC_PER_SEC +
 897                 + (random_u() & 0x1fffff);
 898 }
 899
 900 static int client_set_lease_timeouts(sd_dhcp_client *client, uint64_t usec)
 901 {
 902         int err;
 903         uint64_t next_timeout;
 904
 905         if (client->lease->lifetime < 10)
 906                 return -EINVAL;
 907
 908         client->timeout_t1 = sd_event_source_unref(client->timeout_t1);
 909         client->timeout_t2 = sd_event_source_unref(client->timeout_t2);
 910         client->timeout_expire = sd_event_source_unref(client->timeout_expire);
 911
 912         if (!client->lease->t1)
 913                 client->lease->t1 = client->lease->lifetime / 2;
 914
 915         next_timeout = client_compute_timeout(client->request_sent,
 916                                               client->lease->t1);
 917         if (next_timeout < usec)
 918                 return -EINVAL;
 919
 920         err = sd_event_add_monotonic(client->event, next_timeout,
 921                                      10 * USEC_PER_MSEC,
 922                                      client_timeout_t1, client,
 923                                      &client->timeout_t1);
 924         if (err < 0)
 925                 return err;
 926
 927         if (!client->lease->t2)
 928                 client->lease->t2 = client->lease->lifetime * 7 / 8;
 929
 930         if (client->lease->t2 < client->lease->t1)
 931                 return -EINVAL;
 932
 933         if (client->lease->lifetime < client->lease->t2)
 934                 return -EINVAL;
 935
 936         next_timeout = client_compute_timeout(client->request_sent,
 937                                               client->lease->t2);
 938         if (next_timeout < usec)
 939                 return -EINVAL;
 940
 941         err = sd_event_add_monotonic(client->event, next_timeout,
 942                                      10 * USEC_PER_MSEC,
 943                                      client_timeout_t2, client,
 944                                      &client->timeout_t2);
 945         if (err < 0)
 946                 return err;
 947
 948         next_timeout = client_compute_timeout(client->request_sent,
 949                                               client->lease->lifetime);
 950         if (next_timeout < usec)
 951                 return -EINVAL;
 952
 953         err = sd_event_add_monotonic(client->event, next_timeout,
 954                                      10 * USEC_PER_MSEC,
 955                                      client_timeout_expire, client,
 956                                      &client->timeout_expire);
 957         if (err < 0)
 958                 return err;
 959
 960         return 0;
 961 }
 962
 963 static int client_receive_message(sd_event_source *s, int fd,
 964                                   uint32_t revents, void *userdata)
 965 {
 966         sd_dhcp_client *client = userdata;
 967         uint8_t buf[sizeof(DHCPPacket) + DHCP_CLIENT_MIN_OPTIONS_SIZE];
 968         int buflen = sizeof(buf);
 969         int len, r = 0, notify_event = 0;
 970         DHCPPacket *message;
 971         usec_t time_now;
 972
 973         len = read(fd, &buf, buflen);
 974         if (len < 0)
 975                 return 0;
 976
 977         r = sd_event_get_now_monotonic(client->event, &time_now);
 978         if (r < 0)
 979                 goto error;
 980
 981         switch (client->state) {
 982         case DHCP_STATE_SELECTING:
 983
 984                 message = (DHCPPacket *)&buf;
 985
 986                 if (client_receive_offer(client, message, len) >= 0) {
 987
 988                         client->timeout_resend =
 989                                 sd_event_source_unref(client->timeout_resend);
 990
 991                         client->state = DHCP_STATE_REQUESTING;
 992                         client->attempt = 1;
 993
 994                         r = sd_event_add_monotonic(client->event, time_now, 0,
 995                                                    client_timeout_resend,
 996                                                    client,
 997                                                    &client->timeout_resend);
 998                         if (r < 0)
 999                                 goto error;
1000                 }
1001
1002                 break;
1003
1004         case DHCP_STATE_REQUESTING:
1005         case DHCP_STATE_RENEWING:
1006         case DHCP_STATE_REBINDING:
1007
1008                 r = client_receive_ack(client, buf, len);
1009
1010                 if (r == DHCP_EVENT_NO_LEASE)
1011                         goto error;
1012
1013                 if (r >= 0) {
1014                         client->timeout_resend =
1015                                 sd_event_source_unref(client->timeout_resend);
1016
1017                         if (client->state == DHCP_STATE_REQUESTING)
1018                                 notify_event = DHCP_EVENT_IP_ACQUIRE;
1019                         else if (r != DHCP_EVENT_IP_ACQUIRE)
1020                                 notify_event = r;
1021
1022                         client->state = DHCP_STATE_BOUND;
1023                         client->attempt = 1;
1024
1025                         client->last_addr = client->lease->address;
1026
1027                         r = client_set_lease_timeouts(client, time_now);
1028                         if (r < 0)
1029                                 goto error;
1030
1031                         if (notify_event)
1032                                 client_notify(client, notify_event);
1033
1034                         client->receive_message =
1035                                 sd_event_source_unref(client->receive_message);
1036                         close(client->fd);
1037                         client->fd = -1;
1038                 }
1039
1040                 r = 0;
1041
1042                 break;
1043
1044         case DHCP_STATE_INIT:
1045         case DHCP_STATE_INIT_REBOOT:
1046         case DHCP_STATE_REBOOTING:
1047         case DHCP_STATE_BOUND:
1048
1049                 break;
1050         }
1051
1052 error:
1053         if (r < 0 || r == DHCP_EVENT_NO_LEASE)
1054                 return client_stop(client, r);
1055
1056         return 0;
1057 }
1058
1059 int sd_dhcp_client_start(sd_dhcp_client *client)
1060 {
1061         int r;
1062
1063         assert_return(client, -EINVAL);
1064         assert_return(client->index > 0, -EINVAL);
1065         assert_return(client->state == DHCP_STATE_INIT ||
1066                       client->state == DHCP_STATE_INIT_REBOOT, -EBUSY);
1067
1068         client->xid = random_u();
1069
1070         r = dhcp_network_bind_raw_socket(client->index, &client->link);
1071
1072         if (r < 0) {
1073                 client_stop(client, r);
1074                 return r;
1075         }
1076
1077         client->fd = r;
1078         client->start_time = now(CLOCK_MONOTONIC);
1079
1080         return client_initialize_events(client, client->start_time);
1081 }
1082
1083 int sd_dhcp_client_stop(sd_dhcp_client *client)
1084 {
1085         return client_stop(client, DHCP_EVENT_STOP);
1086 }
1087
1088 sd_dhcp_client *sd_dhcp_client_free(sd_dhcp_client *client)
1089 {
1090         assert_return(client, NULL);
1091
1092         sd_dhcp_client_stop(client);
1093
1094         sd_event_unref(client->event);
1095         free(client->req_opts);
1096         free(client);
1097
1098         return NULL;
1099 }
1100
1101 sd_dhcp_client *sd_dhcp_client_new(sd_event *event)
1102 {
1103         sd_dhcp_client *client;
1104
1105         assert_return(event, NULL);
1106
1107         client = new0(sd_dhcp_client, 1);
1108         if (!client)
1109                 return NULL;
1110
1111         client->event = sd_event_ref(event);
1112         client->state = DHCP_STATE_INIT;
1113         client->index = -1;
1114         client->fd = -1;
1115         client->attempt = 1;
1116
1117         client->req_opts_size = ELEMENTSOF(default_req_opts);
1118
1119         client->req_opts = memdup(default_req_opts, client->req_opts_size);
1120         if (!client->req_opts) {
1121                 free(client);
1122                 return NULL;
1123         }
1124
1125         return client;
1126 }