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 sd_dhcp_client {
  36         DHCPState state;
  37         sd_event *event;
  38         sd_event_source *timeout_resend;
  39         int index;
  40         uint8_t *req_opts;
  41         size_t req_opts_size;
  42         uint32_t last_addr;
  43         struct ether_addr mac_addr;
  44         uint32_t xid;
  45         usec_t start_time;
  46 };
  47
  48 static const uint8_t default_req_opts[] = {
  49         DHCP_OPTION_SUBNET_MASK,
  50         DHCP_OPTION_ROUTER,
  51         DHCP_OPTION_HOST_NAME,
  52         DHCP_OPTION_DOMAIN_NAME,
  53         DHCP_OPTION_DOMAIN_NAME_SERVER,
  54         DHCP_OPTION_NTP_SERVER,
  55 };
  56
  57 int sd_dhcp_client_set_request_option(sd_dhcp_client *client, uint8_t option)
  58 {
  59         size_t i;
  60
  61         assert_return(client, -EINVAL);
  62         assert_return (client->state == DHCP_STATE_INIT, -EBUSY);
  63
  64         switch(option) {
  65         case DHCP_OPTION_PAD:
  66         case DHCP_OPTION_OVERLOAD:
  67         case DHCP_OPTION_MESSAGE_TYPE:
  68         case DHCP_OPTION_PARAMETER_REQUEST_LIST:
  69         case DHCP_OPTION_END:
  70                 return -EINVAL;
  71
  72         default:
  73                 break;
  74         }
  75
  76         for (i = 0; i < client->req_opts_size; i++)
  77                 if (client->req_opts[i] == option)
  78                         return -EEXIST;
  79
  80         if (!GREEDY_REALLOC(client->req_opts, client->req_opts_size,
  81                             client->req_opts_size + 1))
  82                 return -ENOMEM;
  83
  84         client->req_opts[client->req_opts_size - 1] = option;
  85
  86         return 0;
  87 }
  88
  89 int sd_dhcp_client_set_request_address(sd_dhcp_client *client,
  90                                        const struct in_addr *last_addr)
  91 {
  92         assert_return(client, -EINVAL);
  93         assert_return(client->state == DHCP_STATE_INIT, -EBUSY);
  94
  95         if (last_addr)
  96                 client->last_addr = last_addr->s_addr;
  97         else
  98                 client->last_addr = INADDR_ANY;
  99
 100         return 0;
 101 }
 102
 103 int sd_dhcp_client_set_index(sd_dhcp_client *client, int interface_index)
 104 {
 105         assert_return(client, -EINVAL);
 106         assert_return(client->state == DHCP_STATE_INIT, -EBUSY);
 107         assert_return(interface_index >= -1, -EINVAL);
 108
 109         client->index = interface_index;
 110
 111         return 0;
 112 }
 113
 114 int sd_dhcp_client_set_mac(sd_dhcp_client *client,
 115                            const struct ether_addr *addr)
 116 {
 117         assert_return(client, -EINVAL);
 118         assert_return(client->state == DHCP_STATE_INIT, -EBUSY);
 119
 120         memcpy(&client->mac_addr, addr, ETH_ALEN);
 121
 122         return 0;
 123 }
 124
 125 static int client_stop(sd_dhcp_client *client, int error)
 126 {
 127         assert_return(client, -EINVAL);
 128         assert_return(client->state != DHCP_STATE_INIT &&
 129                       client->state != DHCP_STATE_INIT_REBOOT, -EALREADY);
 130
 131         client->timeout_resend = sd_event_source_unref(client->timeout_resend);
 132
 133         switch (client->state) {
 134
 135         case DHCP_STATE_INIT:
 136         case DHCP_STATE_SELECTING:
 137
 138                 client->state = DHCP_STATE_INIT;
 139                 break;
 140
 141         case DHCP_STATE_INIT_REBOOT:
 142         case DHCP_STATE_REBOOTING:
 143         case DHCP_STATE_REQUESTING:
 144         case DHCP_STATE_BOUND:
 145         case DHCP_STATE_RENEWING:
 146         case DHCP_STATE_REBINDING:
 147
 148                 break;
 149         }
 150
 151         return 0;
 152 }
 153
 154 static int client_packet_init(sd_dhcp_client *client, uint8_t type,
 155                               DHCPMessage *message, uint16_t secs,
 156                               uint8_t **opt, size_t *optlen)
 157 {
 158         int err;
 159
 160         *opt = (uint8_t *)(message + 1);
 161
 162         if (*optlen < 4)
 163                 return -ENOBUFS;
 164         *optlen -= 4;
 165
 166         message->op = BOOTREQUEST;
 167         message->htype = 1;
 168         message->hlen = ETHER_ADDR_LEN;
 169         message->xid = htobe32(client->xid);
 170
 171         /* Although 'secs' field is a SHOULD in RFC 2131, certain DHCP servers
 172            refuse to issue an DHCP lease if 'secs' is set to zero */
 173         message->secs = htobe16(secs);
 174
 175         memcpy(&message->chaddr, &client->mac_addr, ETH_ALEN);
 176         (*opt)[0] = 0x63;
 177         (*opt)[1] = 0x82;
 178         (*opt)[2] = 0x53;
 179         (*opt)[3] = 0x63;
 180
 181         *opt += 4;
 182
 183         err = dhcp_option_append(opt, optlen, DHCP_OPTION_MESSAGE_TYPE, 1,
 184                                  &type);
 185         if (err < 0)
 186                 return err;
 187
 188         /* Some DHCP servers will refuse to issue an DHCP lease if the Cliient
 189            Identifier option is not set */
 190         err = dhcp_option_append(opt, optlen, DHCP_OPTION_CLIENT_IDENTIFIER,
 191                                  ETH_ALEN, &client->mac_addr);
 192         if (err < 0)
 193                 return err;
 194
 195         if (type == DHCP_DISCOVER || type == DHCP_REQUEST) {
 196                 err = dhcp_option_append(opt, optlen,
 197                                          DHCP_OPTION_PARAMETER_REQUEST_LIST,
 198                                          client->req_opts_size,
 199                                          client->req_opts);
 200                 if (err < 0)
 201                         return err;
 202         }
 203
 204         return 0;
 205 }
 206
 207 static uint16_t client_checksum(void *buf, int len)
 208 {
 209         uint32_t sum;
 210         uint16_t *check;
 211         int i;
 212         uint8_t *odd;
 213
 214         sum = 0;
 215         check = buf;
 216
 217         for (i = 0; i < len / 2 ; i++)
 218                 sum += check[i];
 219
 220         if (len & 0x01) {
 221                 odd = buf;
 222                 sum += odd[len];
 223         }
 224
 225         return ~((sum & 0xffff) + (sum >> 16));
 226 }
 227
 228 static int client_send_discover(sd_dhcp_client *client, uint16_t secs)
 229 {
 230         int err = 0;
 231         _cleanup_free_ DHCPPacket *discover;
 232         size_t optlen, len;
 233         uint8_t *opt;
 234
 235         optlen = DHCP_CLIENT_MIN_OPTIONS_SIZE;
 236         len = sizeof(DHCPPacket) + optlen;
 237
 238         discover = malloc0(len);
 239
 240         if (!discover)
 241                 return -ENOMEM;
 242
 243         err = client_packet_init(client, DHCP_DISCOVER, &discover->dhcp,
 244                                  secs, &opt, &optlen);
 245         if (err < 0)
 246                 return err;
 247
 248         if (client->last_addr != INADDR_ANY) {
 249                 err = dhcp_option_append(&opt, &optlen,
 250                                          DHCP_OPTION_REQUESTED_IP_ADDRESS,
 251                                          4, &client->last_addr);
 252                 if (err < 0)
 253                         return err;
 254         }
 255
 256         err = dhcp_option_append(&opt, &optlen, DHCP_OPTION_END, 0, NULL);
 257         if (err < 0)
 258                 return err;
 259
 260         discover->ip.version = IPVERSION;
 261         discover->ip.ihl = sizeof(discover->ip) >> 2;
 262         discover->ip.tot_len = htobe16(len);
 263
 264         discover->ip.protocol = IPPROTO_UDP;
 265         discover->ip.saddr = INADDR_ANY;
 266         discover->ip.daddr = INADDR_BROADCAST;
 267
 268         discover->udp.source = htobe16(DHCP_PORT_CLIENT);
 269         discover->udp.dest = htobe16(DHCP_PORT_SERVER);
 270         discover->udp.len = htobe16(len - sizeof(discover->ip));
 271
 272         discover->ip.check = discover->udp.len;
 273         discover->udp.check = client_checksum(&discover->ip.ttl,
 274                                               len - 8);
 275
 276         discover->ip.ttl = IPDEFTTL;
 277         discover->ip.check = 0;
 278         discover->ip.check = client_checksum(&discover->ip,
 279                                              sizeof(discover->ip));
 280
 281         err = dhcp_network_send_raw_packet(client->index, discover, len);
 282
 283         return 0;
 284 }
 285
 286 static int client_timeout_resend(sd_event_source *s, uint64_t usec,
 287                                  void *userdata)
 288 {
 289         sd_dhcp_client *client = userdata;
 290         usec_t next_timeout;
 291         uint16_t secs;
 292         int err = 0;
 293
 294         switch (client->state) {
 295         case DHCP_STATE_INIT:
 296         case DHCP_STATE_SELECTING:
 297
 298                 if (!client->start_time)
 299                         client->start_time = usec;
 300
 301                 secs = (usec - client->start_time) / USEC_PER_SEC;
 302
 303                 next_timeout = usec + 2 * USEC_PER_SEC + (random() & 0x1fffff);
 304
 305                 err = sd_event_add_monotonic(client->event, next_timeout,
 306                                              10 * USEC_PER_MSEC,
 307                                              client_timeout_resend, client,
 308                                              &client->timeout_resend);
 309                 if (err < 0)
 310                         goto error;
 311
 312                 if (client_send_discover(client, secs) >= 0)
 313                         client->state = DHCP_STATE_SELECTING;
 314
 315                 break;
 316
 317         case DHCP_STATE_INIT_REBOOT:
 318         case DHCP_STATE_REBOOTING:
 319         case DHCP_STATE_REQUESTING:
 320         case DHCP_STATE_BOUND:
 321         case DHCP_STATE_RENEWING:
 322         case DHCP_STATE_REBINDING:
 323
 324                 break;
 325         }
 326
 327         return 0;
 328
 329 error:
 330         client_stop(client, err);
 331
 332         /* Errors were dealt with when stopping the client, don't spill
 333            errors into the event loop handler */
 334         return 0;
 335 }
 336
 337 int sd_dhcp_client_start(sd_dhcp_client *client)
 338 {
 339         int err;
 340
 341         assert_return(client, -EINVAL);
 342         assert_return(client->index >= 0, -EINVAL);
 343         assert_return(client->state == DHCP_STATE_INIT ||
 344                       client->state == DHCP_STATE_INIT_REBOOT, -EBUSY);
 345
 346         client->xid = random_u();
 347
 348         err = sd_event_add_monotonic(client->event, now(CLOCK_MONOTONIC), 0,
 349                                      client_timeout_resend, client,
 350                                      &client->timeout_resend);
 351         if (err < 0)
 352                 goto error;
 353
 354         return 0;
 355
 356 error:
 357         client_stop(client, err);
 358
 359         return err;
 360 }
 361
 362 int sd_dhcp_client_stop(sd_dhcp_client *client)
 363 {
 364         return client_stop(client, 0);
 365 }
 366
 367 sd_dhcp_client *sd_dhcp_client_new(sd_event *event)
 368 {
 369         sd_dhcp_client *client;
 370
 371         assert_return(event, NULL);
 372
 373         client = new0(sd_dhcp_client, 1);
 374         if (!client)
 375                 return NULL;
 376
 377         client->event = sd_event_ref(event);
 378         client->state = DHCP_STATE_INIT;
 379         client->index = -1;
 380
 381         client->req_opts_size = ELEMENTSOF(default_req_opts);
 382
 383         client->req_opts = memdup(default_req_opts, client->req_opts_size);
 384         if (!client->req_opts) {
 385                 free(client);
 386                 return NULL;
 387         }
 388
 389         return client;
 390 }