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,                0x0c }, /* hostname */
  41         { OPTION_STRING,                0x0f }, /* domain-name */
  42         { OPTION_IP | OPTION_LIST,      0x2a }, /* ntp-servers */
  43         { OPTION_U32,                   0x33 }, /* dhcp-lease-time */
  44         /* Options below will not be exposed to user */
  45         { OPTION_IP,                    0x32 }, /* requested-ip */
  46         { OPTION_U8,                    0x35 }, /* message-type */
  47         { OPTION_U16,                   0x39 }, /* max-size */
  48         { OPTION_STRING,                0x3c }, /* vendor */
  49         { OPTION_STRING,                0x3d }, /* client-id */
  50         { OPTION_UNKNOWN,               0x00 },
  51 };
  52
  53 GDHCPOptionType dhcp_get_code_type(uint8_t code)
  54 {
  55         int i;
  56
  57         for (i = 0; client_options[i].code; i++) {
  58                 if (client_options[i].code == code)
  59                         return client_options[i].type;
  60         }
  61
  62         return OPTION_UNKNOWN;
  63 }
  64
  65 uint8_t *dhcp_get_option(struct dhcp_packet *packet, int code)
  66 {
  67         int len, rem;
  68         uint8_t *optionptr;
  69         uint8_t overload = 0;
  70
  71         /* option bytes: [code][len][data1][data2]..[dataLEN] */
  72         optionptr = packet->options;
  73         rem = sizeof(packet->options);
  74
  75         while (1) {
  76                 if (rem <= 0)
  77                         /* Bad packet, malformed option field */
  78                         return NULL;
  79
  80                 if (optionptr[OPT_CODE] == DHCP_PADDING) {
  81                         rem--;
  82                         optionptr++;
  83
  84                         continue;
  85                 }
  86
  87                 if (optionptr[OPT_CODE] == DHCP_END) {
  88                         if (overload & FILE_FIELD) {
  89                                 overload &= ~FILE_FIELD;
  90
  91                                 optionptr = packet->file;
  92                                 rem = sizeof(packet->file);
  93
  94                                 continue;
  95                         } else if (overload & SNAME_FIELD) {
  96                                 overload &= ~SNAME_FIELD;
  97
  98                                 optionptr = packet->sname;
  99                                 rem = sizeof(packet->sname);
 100
 101                                 continue;
 102                         }
 103
 104                         break;
 105                 }
 106
 107                 len = 2 + optionptr[OPT_LEN];
 108
 109                 rem -= len;
 110                 if (rem < 0)
 111                         continue; /* complain and return NULL */
 112
 113                 if (optionptr[OPT_CODE] == code)
 114                         return optionptr + OPT_DATA;
 115
 116                 if (optionptr[OPT_CODE] == DHCP_OPTION_OVERLOAD)
 117                         overload |= optionptr[OPT_DATA];
 118
 119                 optionptr += len;
 120         }
 121
 122         return NULL;
 123 }
 124
 125 int dhcp_end_option(uint8_t *optionptr)
 126 {
 127         int i = 0;
 128
 129         while (optionptr[i] != DHCP_END) {
 130                 if (optionptr[i] != DHCP_PADDING)
 131                         i += optionptr[i + OPT_LEN] + OPT_DATA - 1;
 132
 133                 i++;
 134         }
 135
 136         return i;
 137 }
 138
 139 /*
 140  * Add an option (supplied in binary form) to the options.
 141  * Option format: [code][len][data1][data2]..[dataLEN]
 142  */
 143 void dhcp_add_binary_option(struct dhcp_packet *packet, uint8_t *addopt)
 144 {
 145         unsigned len;
 146         uint8_t *optionptr = packet->options;
 147         unsigned end = dhcp_end_option(optionptr);
 148
 149         len = OPT_DATA + addopt[OPT_LEN];
 150
 151         /* end position + (option code/length + addopt length) + end option */
 152         if (end + len + 1 >= DHCP_OPTIONS_BUFSIZE)
 153                 /* option did not fit into the packet */
 154                 return;
 155
 156         memcpy(optionptr + end, addopt, len);
 157
 158         optionptr[end + len] = DHCP_END;
 159 }
 160
 161 void dhcp_add_simple_option(struct dhcp_packet *packet, uint8_t code,
 162                                                         uint32_t data)
 163 {
 164         uint8_t option[6], len;
 165         GDHCPOptionType type = dhcp_get_code_type(code);
 166
 167         if (type == OPTION_UNKNOWN)
 168                 return;
 169
 170         option[OPT_CODE] = code;
 171
 172         len = dhcp_option_lengths[type & OPTION_TYPE_MASK];
 173         option[OPT_LEN] = len;
 174
 175 #if __BYTE_ORDER == __BIG_ENDIAN
 176         data <<= 8 * (4 - len);
 177 #endif
 178
 179         dhcp_put_unaligned(data, (uint32_t *) &option[OPT_DATA]);
 180         dhcp_add_binary_option(packet, option);
 181
 182         return;
 183 }
 184
 185 void dhcp_init_header(struct dhcp_packet *packet, char type)
 186 {
 187         memset(packet, 0, sizeof(*packet));
 188
 189         packet->op = BOOTREQUEST;
 190
 191         switch (type) {
 192         case DHCPOFFER:
 193         case DHCPACK:
 194         case DHCPNAK:
 195                 packet->op = BOOTREPLY;
 196         }
 197
 198         packet->htype = 1;
 199         packet->hlen = 6;
 200         packet->cookie = htonl(DHCP_MAGIC);
 201         packet->options[0] = DHCP_END;
 202
 203         dhcp_add_simple_option(packet, DHCP_MESSAGE_TYPE, type);
 204 }
 205
 206 static gboolean check_vendor(uint8_t  *option_vendor, const char *vendor)
 207 {
 208         uint8_t vendor_length = sizeof(vendor) - 1;
 209
 210         if (option_vendor[OPT_LEN - OPT_DATA] != vendor_length)
 211                 return FALSE;
 212
 213         if (memcmp(option_vendor, vendor, vendor_length) != 0)
 214                 return FALSE;
 215
 216         return TRUE;
 217 }
 218
 219 static void check_broken_vendor(struct dhcp_packet *packet)
 220 {
 221         uint8_t *vendor;
 222
 223         if (packet->op != BOOTREQUEST)
 224                 return;
 225
 226         vendor = dhcp_get_option(packet, DHCP_VENDOR);
 227         if (vendor == NULL)
 228                 return;
 229
 230         if (check_vendor(vendor, "MSFT 98") == TRUE)
 231                 packet->flags |= htons(BROADCAST_FLAG);
 232 }
 233
 234 int dhcp_recv_l3_packet(struct dhcp_packet *packet, int fd)
 235 {
 236         int n;
 237
 238         memset(packet, 0, sizeof(*packet));
 239
 240         n = read(fd, packet, sizeof(*packet));
 241         if (n < 0)
 242                 return -errno;
 243
 244         if (packet->cookie != htonl(DHCP_MAGIC))
 245                 return -EPROTO;
 246
 247         check_broken_vendor(packet);
 248
 249         return n;
 250 }
 251
 252 /* TODO: Use glib checksum */
 253 uint16_t dhcp_checksum(void *addr, int count)
 254 {
 255         /*
 256          * Compute Internet Checksum for "count" bytes
 257          * beginning at location "addr".
 258          */
 259         int32_t sum = 0;
 260         uint16_t *source = (uint16_t *) addr;
 261
 262         while (count > 1)  {
 263                 /*  This is the inner loop */
 264                 sum += *source++;
 265                 count -= 2;
 266         }
 267
 268         /*  Add left-over byte, if any */
 269         if (count > 0) {
 270                 /* Make sure that the left-over byte is added correctly both
 271                  * with little and big endian hosts */
 272                 uint16_t tmp = 0;
 273                 *(uint8_t *) &tmp = *(uint8_t *) source;
 274                 sum += tmp;
 275         }
 276         /*  Fold 32-bit sum to 16 bits */
 277         while (sum >> 16)
 278                 sum = (sum & 0xffff) + (sum >> 16);
 279
 280         return ~sum;
 281 }
 282
 283 int dhcp_send_raw_packet(struct dhcp_packet *dhcp_pkt,
 284                 uint32_t source_ip, int source_port, uint32_t dest_ip,
 285                         int dest_port, const uint8_t *dest_arp, int ifindex)
 286 {
 287         struct sockaddr_ll dest;
 288         struct ip_udp_dhcp_packet packet;
 289         int fd, n;
 290
 291         enum {
 292                 IP_UPD_DHCP_SIZE = sizeof(struct ip_udp_dhcp_packet) -
 293                                                 EXTEND_FOR_BUGGY_SERVERS,
 294                 UPD_DHCP_SIZE = IP_UPD_DHCP_SIZE -
 295                                 offsetof(struct ip_udp_dhcp_packet, udp),
 296         };
 297
 298         fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
 299         if (fd < 0)
 300                 return -errno;
 301
 302         memset(&dest, 0, sizeof(dest));
 303         memset(&packet, 0, sizeof(packet));
 304         packet.data = *dhcp_pkt;
 305
 306         dest.sll_family = AF_PACKET;
 307         dest.sll_protocol = htons(ETH_P_IP);
 308         dest.sll_ifindex = ifindex;
 309         dest.sll_halen = 6;
 310         memcpy(dest.sll_addr, dest_arp, 6);
 311         if (bind(fd, (struct sockaddr *)&dest, sizeof(dest)) < 0) {
 312                 close(fd);
 313                 return -errno;
 314         }
 315
 316         packet.ip.protocol = IPPROTO_UDP;
 317         packet.ip.saddr = source_ip;
 318         packet.ip.daddr = dest_ip;
 319         packet.udp.source = htons(source_port);
 320         packet.udp.dest = htons(dest_port);
 321         /* size, excluding IP header: */
 322         packet.udp.len = htons(UPD_DHCP_SIZE);
 323         /* for UDP checksumming, ip.len is set to UDP packet len */
 324         packet.ip.tot_len = packet.udp.len;
 325         packet.udp.check = dhcp_checksum(&packet, IP_UPD_DHCP_SIZE);
 326         /* but for sending, it is set to IP packet len */
 327         packet.ip.tot_len = htons(IP_UPD_DHCP_SIZE);
 328         packet.ip.ihl = sizeof(packet.ip) >> 2;
 329         packet.ip.version = IPVERSION;
 330         packet.ip.ttl = IPDEFTTL;
 331         packet.ip.check = dhcp_checksum(&packet.ip, sizeof(packet.ip));
 332
 333         /*
 334          * Currently we send full-sized DHCP packets (zero padded).
 335          * If you need to change this: last byte of the packet is
 336          * packet.data.options[dhcp_end_option(packet.data.options)]
 337          */
 338         n = sendto(fd, &packet, IP_UPD_DHCP_SIZE, 0,
 339                         (struct sockaddr *) &dest, sizeof(dest));
 340         if (n < 0)
 341                 return -errno;
 342
 343         close(fd);
 344
 345         return n;
 346 }
 347
 348 int dhcp_send_kernel_packet(struct dhcp_packet *dhcp_pkt,
 349                                 uint32_t source_ip, int source_port,
 350                                 uint32_t dest_ip, int dest_port)
 351 {
 352         struct sockaddr_in client;
 353         int fd, n, opt = 1;
 354
 355         enum {
 356                 DHCP_SIZE = sizeof(struct dhcp_packet) -
 357                                         EXTEND_FOR_BUGGY_SERVERS,
 358         };
 359
 360         fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
 361         if (fd < 0)
 362                 return -errno;
 363
 364         setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
 365
 366         memset(&client, 0, sizeof(client));
 367         client.sin_family = AF_INET;
 368         client.sin_port = htons(source_port);
 369         client.sin_addr.s_addr = source_ip;
 370         if (bind(fd, (struct sockaddr *) &client, sizeof(client)) < 0) {
 371                 close(fd);
 372                 return -errno;
 373         }
 374
 375         memset(&client, 0, sizeof(client));
 376         client.sin_family = AF_INET;
 377         client.sin_port = htons(dest_port);
 378         client.sin_addr.s_addr = dest_ip;
 379         if (connect(fd, (struct sockaddr *) &client, sizeof(client)) < 0) {
 380                 close(fd);
 381                 return -errno;
 382         }
 383
 384         n = write(fd, dhcp_pkt, DHCP_SIZE);
 385
 386         close(fd);
 387
 388         if (n < 0)
 389                 return -errno;
 390
 391         return n;
 392 }
 393
 394 int dhcp_l3_socket(int port, const char *interface)
 395 {
 396         int fd, opt = 1;
 397         struct sockaddr_in addr;
 398
 399         fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
 400
 401         setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
 402
 403         if (setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE,
 404                                 interface, strlen(interface) + 1) < 0) {
 405                 close(fd);
 406                 return -1;
 407         }
 408
 409         memset(&addr, 0, sizeof(addr));
 410         addr.sin_family = AF_INET;
 411         addr.sin_port = htons(port);
 412         if (bind(fd, (struct sockaddr *)&addr, sizeof(addr)) != 0) {
 413                 close(fd);
 414                 return -1;
 415         }
 416
 417         return fd;
 418 }