networking/udhcp/dhcpd.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * udhcp Server
   4  * Copyright (C) 1999 Matthew Ramsay <matthewr@moreton.com.au>
   5  *                      Chris Trew <ctrew@moreton.com.au>
   6  *
   7  * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation; either version 2 of the License, or
  12  * (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License
  20  * along with this program; if not, write to the Free Software
  21  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  22  */
  23
  24 #include <syslog.h>
  25 #include "common.h"
  26 #include "dhcpc.h"
  27 #include "dhcpd.h"
  28 #include "options.h"
  29
  30
  31 /* send a packet to gateway_nip using the kernel ip stack */
  32 static int send_packet_to_relay(struct dhcp_packet *dhcp_pkt)
  33 {
  34         log1("Forwarding packet to relay");
  35
  36         return udhcp_send_kernel_packet(dhcp_pkt,
  37                         server_config.server_nip, SERVER_PORT,
  38                         dhcp_pkt->gateway_nip, SERVER_PORT);
  39 }
  40
  41 /* send a packet to a specific mac address and ip address by creating our own ip packet */
  42 static int send_packet_to_client(struct dhcp_packet *dhcp_pkt, int force_broadcast)
  43 {
  44         const uint8_t *chaddr;
  45         uint32_t ciaddr;
  46
  47         // Was:
  48         //if (force_broadcast) { /* broadcast */ }
  49         //else if (dhcp_pkt->ciaddr) { /* unicast to dhcp_pkt->ciaddr */ }
  50         //else if (dhcp_pkt->flags & htons(BROADCAST_FLAG)) { /* broadcast */ }
  51         //else { /* unicast to dhcp_pkt->yiaddr */ }
  52         // But this is wrong: yiaddr is _our_ idea what client's IP is
  53         // (for example, from lease file). Client may not know that,
  54         // and may not have UDP socket listening on that IP!
  55         // We should never unicast to dhcp_pkt->yiaddr!
  56         // dhcp_pkt->ciaddr, OTOH, comes from client's request packet,
  57         // and can be used.
  58
  59         if (force_broadcast
  60          || (dhcp_pkt->flags & htons(BROADCAST_FLAG))
  61          || !dhcp_pkt->ciaddr
  62         ) {
  63                 log1("Broadcasting packet to client");
  64                 ciaddr = INADDR_BROADCAST;
  65                 chaddr = MAC_BCAST_ADDR;
  66         } else {
  67                 log1("Unicasting packet to client ciaddr");
  68                 ciaddr = dhcp_pkt->ciaddr;
  69                 chaddr = dhcp_pkt->chaddr;
  70         }
  71
  72         return udhcp_send_raw_packet(dhcp_pkt,
  73                 /*src*/ server_config.server_nip, SERVER_PORT,
  74                 /*dst*/ ciaddr, CLIENT_PORT, chaddr,
  75                 server_config.ifindex);
  76 }
  77
  78 /* send a dhcp packet, if force broadcast is set, the packet will be broadcast to the client */
  79 static int send_packet(struct dhcp_packet *dhcp_pkt, int force_broadcast)
  80 {
  81         if (dhcp_pkt->gateway_nip)
  82                 return send_packet_to_relay(dhcp_pkt);
  83         return send_packet_to_client(dhcp_pkt, force_broadcast);
  84 }
  85
  86 static void init_packet(struct dhcp_packet *packet, struct dhcp_packet *oldpacket, char type)
  87 {
  88         udhcp_init_header(packet, type);
  89         packet->xid = oldpacket->xid;
  90         memcpy(packet->chaddr, oldpacket->chaddr, sizeof(oldpacket->chaddr));
  91         packet->flags = oldpacket->flags;
  92         packet->gateway_nip = oldpacket->gateway_nip;
  93         packet->ciaddr = oldpacket->ciaddr;
  94         add_simple_option(packet->options, DHCP_SERVER_ID, server_config.server_nip);
  95 }
  96
  97 /* add in the bootp options */
  98 static void add_bootp_options(struct dhcp_packet *packet)
  99 {
 100         packet->siaddr_nip = server_config.siaddr_nip;
 101         if (server_config.sname)
 102                 strncpy((char*)packet->sname, server_config.sname, sizeof(packet->sname) - 1);
 103         if (server_config.boot_file)
 104                 strncpy((char*)packet->file, server_config.boot_file, sizeof(packet->file) - 1);
 105 }
 106
 107 static uint32_t select_lease_time(struct dhcp_packet *packet)
 108 {
 109         uint32_t lease_time_sec = server_config.max_lease_sec;
 110         uint8_t *lease_time_opt = get_option(packet, DHCP_LEASE_TIME);
 111         if (lease_time_opt) {
 112                 move_from_unaligned32(lease_time_sec, lease_time_opt);
 113                 lease_time_sec = ntohl(lease_time_sec);
 114                 if (lease_time_sec > server_config.max_lease_sec)
 115                         lease_time_sec = server_config.max_lease_sec;
 116                 if (lease_time_sec < server_config.min_lease_sec)
 117                         lease_time_sec = server_config.min_lease_sec;
 118         }
 119         return lease_time_sec;
 120 }
 121
 122 /* send a DHCP OFFER to a DHCP DISCOVER */
 123 static int send_offer(struct dhcp_packet *oldpacket, uint32_t static_lease_nip, struct dyn_lease *lease)
 124 {
 125         struct dhcp_packet packet;
 126         uint32_t req_nip;
 127         uint32_t lease_time_sec = server_config.max_lease_sec;
 128         uint8_t *req_ip_opt;
 129         const char *p_host_name;
 130         struct option_set *curr;
 131         struct in_addr addr;
 132
 133         init_packet(&packet, oldpacket, DHCPOFFER);
 134
 135         /* ADDME: if static, short circuit */
 136         if (!static_lease_nip) {
 137                 /* The client is in our lease/offered table */
 138                 if (lease) {
 139                         packet.yiaddr = lease->lease_nip;
 140                 }
 141                 /* Or the client has requested an IP */
 142                 else if ((req_ip_opt = get_option(oldpacket, DHCP_REQUESTED_IP)) != NULL
 143                  /* (read IP) */
 144                  && (move_from_unaligned32(req_nip, req_ip_opt), 1)
 145                  /* and the IP is in the lease range */
 146                  && ntohl(req_nip) >= server_config.start_ip
 147                  && ntohl(req_nip) <= server_config.end_ip
 148                  /* and is not already taken/offered */
 149                  && (!(lease = find_lease_by_nip(req_nip))
 150                         /* or its taken, but expired */
 151                         || is_expired_lease(lease))
 152                 ) {
 153                         packet.yiaddr = req_nip;
 154                 }
 155                 /* Otherwise, find a free IP */
 156                 else {
 157                         packet.yiaddr = find_free_or_expired_nip(oldpacket->chaddr);
 158                 }
 159
 160                 if (!packet.yiaddr) {
 161                         bb_error_msg("no IP addresses to give - OFFER abandoned");
 162                         return -1;
 163                 }
 164                 p_host_name = (const char*) get_option(oldpacket, DHCP_HOST_NAME);
 165                 if (add_lease(packet.chaddr, packet.yiaddr,
 166                                 server_config.offer_time,
 167                                 p_host_name,
 168                                 p_host_name ? (unsigned char)p_host_name[OPT_LEN - OPT_DATA] : 0
 169                         ) == 0
 170                 ) {
 171                         bb_error_msg("lease pool is full - OFFER abandoned");
 172                         return -1;
 173                 }
 174                 lease_time_sec = select_lease_time(oldpacket);
 175         } else {
 176                 /* It is a static lease... use it */
 177                 packet.yiaddr = static_lease_nip;
 178         }
 179
 180         add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_sec));
 181
 182         curr = server_config.options;
 183         while (curr) {
 184                 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
 185                         add_option_string(packet.options, curr->data);
 186                 curr = curr->next;
 187         }
 188
 189         add_bootp_options(&packet);
 190
 191         addr.s_addr = packet.yiaddr;
 192         bb_info_msg("Sending OFFER of %s", inet_ntoa(addr));
 193         return send_packet(&packet, 0);
 194 }
 195
 196 static int send_NAK(struct dhcp_packet *oldpacket)
 197 {
 198         struct dhcp_packet packet;
 199
 200         init_packet(&packet, oldpacket, DHCPNAK);
 201
 202         log1("Sending NAK");
 203         return send_packet(&packet, 1);
 204 }
 205
 206 static int send_ACK(struct dhcp_packet *oldpacket, uint32_t yiaddr)
 207 {
 208         struct dhcp_packet packet;
 209         struct option_set *curr;
 210         uint32_t lease_time_sec;
 211         struct in_addr addr;
 212         const char *p_host_name;
 213
 214         init_packet(&packet, oldpacket, DHCPACK);
 215         packet.yiaddr = yiaddr;
 216
 217         lease_time_sec = select_lease_time(oldpacket);
 218
 219         add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_sec));
 220
 221         curr = server_config.options;
 222         while (curr) {
 223                 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
 224                         add_option_string(packet.options, curr->data);
 225                 curr = curr->next;
 226         }
 227
 228         add_bootp_options(&packet);
 229
 230         addr.s_addr = packet.yiaddr;
 231         bb_info_msg("Sending ACK to %s", inet_ntoa(addr));
 232
 233         if (send_packet(&packet, 0) < 0)
 234                 return -1;
 235
 236         p_host_name = (const char*) get_option(oldpacket, DHCP_HOST_NAME);
 237         add_lease(packet.chaddr, packet.yiaddr,
 238                 lease_time_sec,
 239                 p_host_name,
 240                 p_host_name ? (unsigned char)p_host_name[OPT_LEN - OPT_DATA] : 0
 241         );
 242         if (ENABLE_FEATURE_UDHCPD_WRITE_LEASES_EARLY) {
 243                 /* rewrite the file with leases at every new acceptance */
 244                 write_leases();
 245         }
 246
 247         return 0;
 248 }
 249
 250 static int send_inform(struct dhcp_packet *oldpacket)
 251 {
 252         struct dhcp_packet packet;
 253         struct option_set *curr;
 254
 255         init_packet(&packet, oldpacket, DHCPACK);
 256
 257         curr = server_config.options;
 258         while (curr) {
 259                 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
 260                         add_option_string(packet.options, curr->data);
 261                 curr = curr->next;
 262         }
 263
 264         add_bootp_options(&packet);
 265
 266         return send_packet(&packet, 0);
 267 }
 268
 269
 270 /* globals */
 271 struct dyn_lease *g_leases;
 272 /* struct server_config_t server_config is in bb_common_bufsiz1 */
 273
 274
 275 int udhcpd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 276 int udhcpd_main(int argc UNUSED_PARAM, char **argv)
 277 {
 278         fd_set rfds;
 279         int server_socket = -1, retval, max_sock;
 280         struct dhcp_packet packet;
 281         uint8_t *state;
 282         uint32_t static_lease_nip;
 283         unsigned timeout_end;
 284         unsigned num_ips;
 285         unsigned opt;
 286         struct option_set *option;
 287         struct dyn_lease *lease, fake_lease;
 288         IF_FEATURE_UDHCP_PORT(char *str_P;)
 289
 290 #if ENABLE_FEATURE_UDHCP_PORT
 291         SERVER_PORT = 67;
 292         CLIENT_PORT = 68;
 293 #endif
 294
 295 #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
 296         opt_complementary = "vv";
 297 #endif
 298         opt = getopt32(argv, "fSv"
 299                 IF_FEATURE_UDHCP_PORT("P:", &str_P)
 300 #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
 301                 , &dhcp_verbose
 302 #endif
 303                 );
 304         argv += optind;
 305         if (!(opt & 1)) { /* no -f */
 306                 bb_daemonize_or_rexec(0, argv);
 307                 logmode = LOGMODE_NONE;
 308         }
 309         if (opt & 2) { /* -S */
 310                 openlog(applet_name, LOG_PID, LOG_DAEMON);
 311                 logmode |= LOGMODE_SYSLOG;
 312         }
 313 #if ENABLE_FEATURE_UDHCP_PORT
 314         if (opt & 4) { /* -P */
 315                 SERVER_PORT = xatou16(str_P);
 316                 CLIENT_PORT = SERVER_PORT + 1;
 317         }
 318 #endif
 319         /* Would rather not do read_config before daemonization -
 320          * otherwise NOMMU machines will parse config twice */
 321         read_config(argv[0] ? argv[0] : DHCPD_CONF_FILE);
 322
 323         /* Make sure fd 0,1,2 are open */
 324         bb_sanitize_stdio();
 325         /* Equivalent of doing a fflush after every \n */
 326         setlinebuf(stdout);
 327
 328         /* Create pidfile */
 329         write_pidfile(server_config.pidfile);
 330         /* if (!..) bb_perror_msg("can't create pidfile %s", pidfile); */
 331
 332         bb_info_msg("%s (v"BB_VER") started", applet_name);
 333
 334         option = find_option(server_config.options, DHCP_LEASE_TIME);
 335         server_config.max_lease_sec = LEASE_TIME;
 336         if (option) {
 337                 move_from_unaligned32(server_config.max_lease_sec, option->data + OPT_DATA);
 338                 server_config.max_lease_sec = ntohl(server_config.max_lease_sec);
 339         }
 340
 341         /* Sanity check */
 342         num_ips = server_config.end_ip - server_config.start_ip + 1;
 343         if (server_config.max_leases > num_ips) {
 344                 bb_error_msg("max_leases=%u is too big, setting to %u",
 345                         (unsigned)server_config.max_leases, num_ips);
 346                 server_config.max_leases = num_ips;
 347         }
 348
 349         g_leases = xzalloc(server_config.max_leases * sizeof(g_leases[0]));
 350         read_leases(server_config.lease_file);
 351
 352         if (udhcp_read_interface(server_config.interface,
 353                         &server_config.ifindex,
 354                         &server_config.server_nip,
 355                         server_config.server_mac)
 356         ) {
 357                 retval = 1;
 358                 goto ret;
 359         }
 360
 361         /* Setup the signal pipe */
 362         udhcp_sp_setup();
 363
 364         timeout_end = monotonic_sec() + server_config.auto_time;
 365         while (1) { /* loop until universe collapses */
 366                 int bytes;
 367                 struct timeval tv;
 368
 369                 if (server_socket < 0) {
 370                         server_socket = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT,
 371                                         server_config.interface);
 372                 }
 373
 374                 max_sock = udhcp_sp_fd_set(&rfds, server_socket);
 375                 if (server_config.auto_time) {
 376                         tv.tv_sec = timeout_end - monotonic_sec();
 377                         tv.tv_usec = 0;
 378                 }
 379                 retval = 0;
 380                 if (!server_config.auto_time || tv.tv_sec > 0) {
 381                         retval = select(max_sock + 1, &rfds, NULL, NULL,
 382                                         server_config.auto_time ? &tv : NULL);
 383                 }
 384                 if (retval == 0) {
 385                         write_leases();
 386                         timeout_end = monotonic_sec() + server_config.auto_time;
 387                         continue;
 388                 }
 389                 if (retval < 0 && errno != EINTR) {
 390                         log1("Error on select");
 391                         continue;
 392                 }
 393
 394                 switch (udhcp_sp_read(&rfds)) {
 395                 case SIGUSR1:
 396                         bb_info_msg("Received a SIGUSR1");
 397                         write_leases();
 398                         /* why not just reset the timeout, eh */
 399                         timeout_end = monotonic_sec() + server_config.auto_time;
 400                         continue;
 401                 case SIGTERM:
 402                         bb_info_msg("Received a SIGTERM");
 403                         goto ret0;
 404                 case 0: /* no signal: read a packet */
 405                         break;
 406                 default: /* signal or error (probably EINTR): back to select */
 407                         continue;
 408                 }
 409
 410                 bytes = udhcp_recv_kernel_packet(&packet, server_socket);
 411                 if (bytes < 0) {
 412                         /* bytes can also be -2 ("bad packet data") */
 413                         if (bytes == -1 && errno != EINTR) {
 414                                 log1("Read error: %s, reopening socket", strerror(errno));
 415                                 close(server_socket);
 416                                 server_socket = -1;
 417                         }
 418                         continue;
 419                 }
 420
 421                 if (packet.hlen != 6) {
 422                         bb_error_msg("MAC length != 6, ignoring packet");
 423                         continue;
 424                 }
 425
 426                 state = get_option(&packet, DHCP_MESSAGE_TYPE);
 427                 if (state == NULL) {
 428                         bb_error_msg("no message type option, ignoring packet");
 429                         continue;
 430                 }
 431
 432                 /* Look for a static lease */
 433                 static_lease_nip = get_static_nip_by_mac(server_config.static_leases, &packet.chaddr);
 434                 if (static_lease_nip) {
 435                         bb_info_msg("Found static lease: %x", static_lease_nip);
 436
 437                         memcpy(&fake_lease.lease_mac, &packet.chaddr, 6);
 438                         fake_lease.lease_nip = static_lease_nip;
 439                         fake_lease.expires = 0;
 440
 441                         lease = &fake_lease;
 442                 } else {
 443                         lease = find_lease_by_mac(packet.chaddr);
 444                 }
 445
 446                 switch (state[0]) {
 447                 case DHCPDISCOVER:
 448                         log1("Received DISCOVER");
 449
 450                         if (send_offer(&packet, static_lease_nip, lease) < 0) {
 451                                 bb_error_msg("send OFFER failed");
 452                         }
 453                         break;
 454                 case DHCPREQUEST: {
 455                         uint8_t *server_id_opt, *requested_opt;
 456                         uint32_t server_id_net = server_id_net; /* for compiler */
 457                         uint32_t requested_nip = requested_nip; /* for compiler */
 458
 459                         log1("Received REQUEST");
 460
 461                         requested_opt = get_option(&packet, DHCP_REQUESTED_IP);
 462                         server_id_opt = get_option(&packet, DHCP_SERVER_ID);
 463                         if (requested_opt)
 464                                 move_from_unaligned32(requested_nip, requested_opt);
 465                         if (server_id_opt)
 466                                 move_from_unaligned32(server_id_net, server_id_opt);
 467
 468                         if (lease) {
 469                                 if (server_id_opt) {
 470                                         /* SELECTING State */
 471                                         if (server_id_net == server_config.server_nip
 472                                          && requested_opt
 473                                          && requested_nip == lease->lease_nip
 474                                         ) {
 475                                                 send_ACK(&packet, lease->lease_nip);
 476                                         }
 477                                 } else if (requested_opt) {
 478                                         /* INIT-REBOOT State */
 479                                         if (lease->lease_nip == requested_nip)
 480                                                 send_ACK(&packet, lease->lease_nip);
 481                                         else
 482                                                 send_NAK(&packet);
 483                                 } else if (lease->lease_nip == packet.ciaddr) {
 484                                         /* RENEWING or REBINDING State */
 485                                         send_ACK(&packet, lease->lease_nip);
 486                                 } else { /* don't know what to do!!!! */
 487                                         send_NAK(&packet);
 488                                 }
 489
 490                         /* what to do if we have no record of the client */
 491                         } else if (server_id_opt) {
 492                                 /* SELECTING State */
 493
 494                         } else if (requested_opt) {
 495                                 /* INIT-REBOOT State */
 496                                 lease = find_lease_by_nip(requested_nip);
 497                                 if (lease) {
 498                                         if (is_expired_lease(lease)) {
 499                                                 /* probably best if we drop this lease */
 500                                                 memset(lease->lease_mac, 0, sizeof(lease->lease_mac));
 501                                         } else {
 502                                                 /* make some contention for this address */
 503                                                 send_NAK(&packet);
 504                                         }
 505                                 } else {
 506                                         uint32_t r = ntohl(requested_nip);
 507                                         if (r < server_config.start_ip
 508                                          || r > server_config.end_ip
 509                                         ) {
 510                                                 send_NAK(&packet);
 511                                         }
 512                                         /* else remain silent */
 513                                 }
 514
 515                         } else {
 516                                 /* RENEWING or REBINDING State */
 517                         }
 518                         break;
 519                 }
 520                 case DHCPDECLINE:
 521                         log1("Received DECLINE");
 522                         if (lease) {
 523                                 memset(lease->lease_mac, 0, sizeof(lease->lease_mac));
 524                                 lease->expires = time(NULL) + server_config.decline_time;
 525                         }
 526                         break;
 527                 case DHCPRELEASE:
 528                         log1("Received RELEASE");
 529                         if (lease)
 530                                 lease->expires = time(NULL);
 531                         break;
 532                 case DHCPINFORM:
 533                         log1("Received INFORM");
 534                         send_inform(&packet);
 535                         break;
 536                 default:
 537                         bb_info_msg("Unsupported DHCP message (%02x) - ignoring", state[0]);
 538                 }
 539         }
 540  ret0:
 541         retval = 0;
 542  ret:
 543         /*if (server_config.pidfile) - server_config.pidfile is never NULL */
 544                 remove_pidfile(server_config.pidfile);
 545         return retval;
 546 }