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