gdhcp/common.c

   1 /*
   2  *  DHCP library with GLib integration
   3  *
   4  *  Copyright (C) 2007-2010  Intel Corporation. All rights reserved.
   5  *
   6  *  This program is free software; you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License version 2 as
   8  *  published by the Free Software Foundation.
   9  *
  10  *  This program is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU General Public License
  16  *  along with this program; if not, write to the Free Software
  17  *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  18  *
  19  */
  20
  21 #ifdef HAVE_CONFIG_H
  22 #include <config.h>
  23 #endif
  24
  25 #include <errno.h>
  26 #include <unistd.h>
  27 #include <stdint.h>
  28 #include <string.h>
  29 #include <endian.h>
  30 #include <netpacket/packet.h>
  31 #include <net/ethernet.h>
  32
  33 #include "gdhcp.h"
  34 #include "common.h"
  35
  36 static const DHCPOption client_options[] = {
  37         { OPTION_IP,                    0x01 }, /* subnet-mask */
  38         { OPTION_IP | OPTION_LIST,      0x03 }, /* routers */
  39         { OPTION_IP | OPTION_LIST,      0x06 }, /* domain-name-servers */
  40         { OPTION_STRING,                0x0f }, /* domain-name */
  41         { OPTION_IP | OPTION_LIST,      0x2a }, /* ntp-servers */
  42         { OPTION_U32,                   0x33 }, /* dhcp-lease-time */
  43         /* Options below will not be exposed to user */
  44         { OPTION_IP,                    0x32 }, /* requested-ip */
  45         { OPTION_U8,                    0x35 }, /* message-type */
  46         { OPTION_U16,                   0x39 }, /* max-size */
  47         { OPTION_STRING,                0x3c }, /* vendor */
  48         { OPTION_STRING,                0x3d }, /* client-id */
  49         { OPTION_UNKNOWN,               0x00 },
  50 };
  51
  52 GDHCPOptionType dhcp_get_code_type(uint8_t code)
  53 {
  54         int i;
  55
  56         for (i = 0; client_options[i].code; i++) {
  57                 if (client_options[i].code == code)
  58                         return client_options[i].type;
  59         }
  60
  61         return OPTION_UNKNOWN;
  62 }
  63
  64 uint8_t *dhcp_get_option(struct dhcp_packet *packet, int code)
  65 {
  66         int len, rem;
  67         uint8_t *optionptr;
  68         uint8_t overload = 0;
  69
  70         /* option bytes: [code][len][data1][data2]..[dataLEN] */
  71         optionptr = packet->options;
  72         rem = sizeof(packet->options);
  73
  74         while (1) {
  75                 if (rem <= 0)
  76                         /* Bad packet, malformed option field */
  77                         return NULL;
  78
  79                 if (optionptr[OPT_CODE] == DHCP_PADDING) {
  80                         rem--;
  81                         optionptr++;
  82
  83                         continue;
  84                 }
  85
  86                 if (optionptr[OPT_CODE] == DHCP_END) {
  87                         if (overload & FILE_FIELD) {
  88                                 overload &= ~FILE_FIELD;
  89
  90                                 optionptr = packet->file;
  91                                 rem = sizeof(packet->file);
  92
  93                                 continue;
  94                         } else if (overload & SNAME_FIELD) {
  95                                 overload &= ~SNAME_FIELD;
  96
  97                                 optionptr = packet->sname;
  98                                 rem = sizeof(packet->sname);
  99
 100                                 continue;
 101                         }
 102
 103                         break;
 104                 }
 105
 106                 len = 2 + optionptr[OPT_LEN];
 107
 108                 rem -= len;
 109                 if (rem < 0)
 110                         continue; /* complain and return NULL */
 111
 112                 if (optionptr[OPT_CODE] == code)
 113                         return optionptr + OPT_DATA;
 114
 115                 if (optionptr[OPT_CODE] == DHCP_OPTION_OVERLOAD)
 116                         overload |= optionptr[OPT_DATA];
 117
 118                 optionptr += len;
 119         }
 120
 121         return NULL;
 122 }
 123
 124 int dhcp_end_option(uint8_t *optionptr)
 125 {
 126         int i = 0;
 127
 128         while (optionptr[i] != DHCP_END) {
 129                 if (optionptr[i] != DHCP_PADDING)
 130                         i += optionptr[i + OPT_LEN] + OPT_DATA - 1;
 131
 132                 i++;
 133         }
 134
 135         return i;
 136 }
 137
 138 /*
 139  * Add an option (supplied in binary form) to the options.
 140  * Option format: [code][len][data1][data2]..[dataLEN]
 141  */
 142 void dhcp_add_binary_option(struct dhcp_packet *packet, uint8_t *addopt)
 143 {
 144         unsigned len;
 145         uint8_t *optionptr = packet->options;
 146         unsigned end = dhcp_end_option(optionptr);
 147
 148         len = OPT_DATA + addopt[OPT_LEN];
 149
 150         /* end position + (option code/length + addopt length) + end option */
 151         if (end + len + 1 >= DHCP_OPTIONS_BUFSIZE)
 152                 /* option did not fit into the packet */
 153                 return;
 154
 155         memcpy(optionptr + end, addopt, len);
 156
 157         optionptr[end + len] = DHCP_END;
 158 }
 159
 160 void dhcp_add_simple_option(struct dhcp_packet *packet, uint8_t code,
 161                                                         uint32_t data)
 162 {
 163         uint8_t option[6], len;
 164         GDHCPOptionType type = dhcp_get_code_type(code);
 165
 166         if (type == OPTION_UNKNOWN)
 167                 return;
 168
 169         option[OPT_CODE] = code;
 170
 171         len = dhcp_option_lengths[type & OPTION_TYPE_MASK];
 172         option[OPT_LEN] = len;
 173
 174 #if __BYTE_ORDER == __BIG_ENDIAN
 175         data <<= 8 * (4 - len);
 176 #endif
 177
 178         dhcp_put_unaligned(data, (uint32_t *) &option[OPT_DATA]);
 179         dhcp_add_binary_option(packet, option);
 180
 181         return;
 182 }
 183
 184 void dhcp_init_header(struct dhcp_packet *packet, char type)
 185 {
 186         memset(packet, 0, sizeof(*packet));
 187
 188         packet->op = BOOTREQUEST;
 189
 190         switch (type) {
 191         case DHCPOFFER:
 192         case DHCPACK:
 193         case DHCPNAK:
 194                 packet->op = BOOTREPLY;
 195         }
 196
 197         packet->htype = 1;
 198         packet->hlen = 6;
 199         packet->cookie = htonl(DHCP_MAGIC);
 200         packet->options[0] = DHCP_END;
 201
 202         dhcp_add_simple_option(packet, DHCP_MESSAGE_TYPE, type);
 203 }
 204
 205 static gboolean check_vendor(uint8_t  *option_vendor, const char *vendor)
 206 {
 207         uint8_t vendor_length = sizeof(vendor) - 1;
 208
 209         if (option_vendor[OPT_LEN - OPT_DATA] != vendor_length)
 210                 return FALSE;
 211
 212         if (memcmp(option_vendor, vendor, vendor_length) != 0)
 213                 return FALSE;
 214
 215         return TRUE;
 216 }
 217
 218 static void check_broken_vendor(struct dhcp_packet *packet)
 219 {
 220         uint8_t *vendor;
 221
 222         if (packet->op != BOOTREQUEST)
 223                 return;
 224
 225         vendor = dhcp_get_option(packet, DHCP_VENDOR);
 226         if (vendor == NULL)
 227                 return;
 228
 229         if (check_vendor(vendor, "MSFT 98") == TRUE)
 230                 packet->flags |= htons(BROADCAST_FLAG);
 231 }
 232
 233 int dhcp_recv_l3_packet(struct dhcp_packet *packet, int fd)
 234 {
 235         int n;
 236
 237         memset(packet, 0, sizeof(*packet));
 238
 239         n = read(fd, packet, sizeof(*packet));
 240         if (n < 0)
 241                 return -errno;
 242
 243         if (packet->cookie != htonl(DHCP_MAGIC))
 244                 return -EPROTO;
 245
 246         check_broken_vendor(packet);
 247
 248         return n;
 249 }
 250
 251 /* TODO: Use glib checksum */
 252 uint16_t dhcp_checksum(void *addr, int count)
 253 {
 254         /*
 255          * Compute Internet Checksum for "count" bytes
 256          * beginning at location "addr".
 257          */
 258         int32_t sum = 0;
 259         uint16_t *source = (uint16_t *) addr;
 260
 261         while (count > 1)  {
 262                 /*  This is the inner loop */
 263                 sum += *source++;
 264                 count -= 2;
 265         }
 266
 267         /*  Add left-over byte, if any */
 268         if (count > 0) {
 269                 /* Make sure that the left-over byte is added correctly both
 270                  * with little and big endian hosts */
 271                 uint16_t tmp = 0;
 272                 *(uint8_t *) &tmp = *(uint8_t *) source;
 273                 sum += tmp;
 274         }
 275         /*  Fold 32-bit sum to 16 bits */
 276         while (sum >> 16)
 277                 sum = (sum & 0xffff) + (sum >> 16);
 278
 279         return ~sum;
 280 }
 281
 282 int dhcp_send_raw_packet(struct dhcp_packet *dhcp_pkt,
 283                 uint32_t source_ip, int source_port, uint32_t dest_ip,
 284                         int dest_port, const uint8_t *dest_arp, int ifindex)
 285 {
 286         struct sockaddr_ll dest;
 287         struct ip_udp_dhcp_packet packet;
 288         int fd, n;
 289
 290         enum {
 291                 IP_UPD_DHCP_SIZE = sizeof(struct ip_udp_dhcp_packet) -
 292                                                 EXTEND_FOR_BUGGY_SERVERS,
 293                 UPD_DHCP_SIZE = IP_UPD_DHCP_SIZE -
 294                                 offsetof(struct ip_udp_dhcp_packet, udp),
 295         };
 296
 297         fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
 298         if (fd < 0)
 299                 return -errno;
 300
 301         memset(&dest, 0, sizeof(dest));
 302         memset(&packet, 0, sizeof(packet));
 303         packet.data = *dhcp_pkt;
 304
 305         dest.sll_family = AF_PACKET;
 306         dest.sll_protocol = htons(ETH_P_IP);
 307         dest.sll_ifindex = ifindex;
 308         dest.sll_halen = 6;
 309         memcpy(dest.sll_addr, dest_arp, 6);
 310         if (bind(fd, (struct sockaddr *)&dest, sizeof(dest)) < 0) {
 311                 close(fd);
 312                 return -errno;
 313         }
 314
 315         packet.ip.protocol = IPPROTO_UDP;
 316         packet.ip.saddr = source_ip;
 317         packet.ip.daddr = dest_ip;
 318         packet.udp.source = htons(source_port);
 319         packet.udp.dest = htons(dest_port);
 320         /* size, excluding IP header: */
 321         packet.udp.len = htons(UPD_DHCP_SIZE);
 322         /* for UDP checksumming, ip.len is set to UDP packet len */
 323         packet.ip.tot_len = packet.udp.len;
 324         packet.udp.check = dhcp_checksum(&packet, IP_UPD_DHCP_SIZE);
 325         /* but for sending, it is set to IP packet len */
 326         packet.ip.tot_len = htons(IP_UPD_DHCP_SIZE);
 327         packet.ip.ihl = sizeof(packet.ip) >> 2;
 328         packet.ip.version = IPVERSION;
 329         packet.ip.ttl = IPDEFTTL;
 330         packet.ip.check = dhcp_checksum(&packet.ip, sizeof(packet.ip));
 331
 332         /*
 333          * Currently we send full-sized DHCP packets (zero padded).
 334          * If you need to change this: last byte of the packet is
 335          * packet.data.options[dhcp_end_option(packet.data.options)]
 336          */
 337         n = sendto(fd, &packet, IP_UPD_DHCP_SIZE, 0,
 338                         (struct sockaddr *) &dest, sizeof(dest));
 339         if (n < 0)
 340                 return -errno;
 341
 342         close(fd);
 343
 344         return n;
 345 }
 346
 347 int dhcp_send_kernel_packet(struct dhcp_packet *dhcp_pkt,
 348                                 uint32_t source_ip, int source_port,
 349                                 uint32_t dest_ip, int dest_port)
 350 {
 351         struct sockaddr_in client;
 352         int fd, n, opt = 1;
 353
 354         enum {
 355                 DHCP_SIZE = sizeof(struct dhcp_packet) -
 356                                         EXTEND_FOR_BUGGY_SERVERS,
 357         };
 358
 359         fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
 360         if (fd < 0)
 361                 return -errno;
 362
 363         setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
 364
 365         memset(&client, 0, sizeof(client));
 366         client.sin_family = AF_INET;
 367         client.sin_port = htons(source_port);
 368         client.sin_addr.s_addr = source_ip;
 369         if (bind(fd, (struct sockaddr *) &client, sizeof(client)) < 0) {
 370                 close(fd);
 371                 return -errno;
 372         }
 373
 374         memset(&client, 0, sizeof(client));
 375         client.sin_family = AF_INET;
 376         client.sin_port = htons(dest_port);
 377         client.sin_addr.s_addr = dest_ip;
 378         if (connect(fd, (struct sockaddr *) &client, sizeof(client)) < 0) {
 379                 close(fd);
 380                 return -errno;
 381         }
 382
 383         n = write(fd, dhcp_pkt, DHCP_SIZE);
 384
 385         close(fd);
 386
 387         if (n < 0)
 388                 return -errno;
 389
 390         return n;
 391 }
 392
 393 int dhcp_l3_socket(int port, const char *interface)
 394 {
 395         int fd, opt = 1;
 396         struct sockaddr_in addr;
 397
 398         fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
 399
 400         setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
 401
 402         if (setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE,
 403                                 interface, strlen(interface) + 1) < 0) {
 404                 close(fd);
 405                 return -1;
 406         }
 407
 408         memset(&addr, 0, sizeof(addr));
 409         addr.sin_family = AF_INET;
 410         addr.sin_port = htons(port);
 411         if (bind(fd, (struct sockaddr *)&addr, sizeof(addr)) != 0) {
 412                 close(fd);
 413                 return -1;
 414         }
 415
 416         return fd;
 417 }