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)
 124 {
 125         struct dhcp_packet packet;
 126         uint32_t req_nip;
 127         uint32_t lease_time_sec = server_config.max_lease_sec;
 128         uint32_t static_lease_ip;
 129         uint8_t *req_ip_opt;
 130         const char *p_host_name;
 131         struct option_set *curr;
 132         struct in_addr addr;
 133
 134         init_packet(&packet, oldpacket, DHCPOFFER);
 135
 136         static_lease_ip = get_static_nip_by_mac(server_config.static_leases, oldpacket->chaddr);
 137
 138         /* ADDME: if static, short circuit */
 139         if (!static_lease_ip) {
 140                 struct dyn_lease *lease;
 141
 142                 lease = find_lease_by_mac(oldpacket->chaddr);
 143                 /* The client is in our lease/offered table */
 144                 if (lease) {
 145                         signed_leasetime_t tmp = lease->expires - time(NULL);
 146                         if (tmp >= 0)
 147                                 lease_time_sec = tmp;
 148                         packet.yiaddr = lease->lease_nip;
 149                 }
 150                 /* Or the client has requested an IP */
 151                 else if ((req_ip_opt = get_option(oldpacket, DHCP_REQUESTED_IP)) != NULL
 152                  /* (read IP) */
 153                  && (move_from_unaligned32(req_nip, req_ip_opt), 1)
 154                  /* and the IP is in the lease range */
 155                  && ntohl(req_nip) >= server_config.start_ip
 156                  && ntohl(req_nip) <= server_config.end_ip
 157                  /* and is not already taken/offered */
 158                  && (!(lease = find_lease_by_nip(req_nip))
 159                         /* or its taken, but expired */
 160                         || is_expired_lease(lease))
 161                 ) {
 162                         packet.yiaddr = req_nip;
 163                 }
 164                 /* Otherwise, find a free IP */
 165                 else {
 166                         packet.yiaddr = find_free_or_expired_nip(oldpacket->chaddr);
 167                 }
 168
 169                 if (!packet.yiaddr) {
 170                         bb_error_msg("no IP addresses to give - OFFER abandoned");
 171                         return -1;
 172                 }
 173                 p_host_name = (const char*) get_option(oldpacket, DHCP_HOST_NAME);
 174                 if (add_lease(packet.chaddr, packet.yiaddr,
 175                                 server_config.offer_time,
 176                                 p_host_name,
 177                                 p_host_name ? (unsigned char)p_host_name[OPT_LEN - OPT_DATA] : 0
 178                         ) == 0
 179                 ) {
 180                         bb_error_msg("lease pool is full - OFFER abandoned");
 181                         return -1;
 182                 }
 183                 lease_time_sec = select_lease_time(oldpacket);
 184         } else {
 185                 /* It is a static lease... use it */
 186                 packet.yiaddr = static_lease_ip;
 187         }
 188
 189         add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_sec));
 190
 191         curr = server_config.options;
 192         while (curr) {
 193                 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
 194                         add_option_string(packet.options, curr->data);
 195                 curr = curr->next;
 196         }
 197
 198         add_bootp_options(&packet);
 199
 200         addr.s_addr = packet.yiaddr;
 201         bb_info_msg("Sending OFFER of %s", inet_ntoa(addr));
 202         return send_packet(&packet, 0);
 203 }
 204
 205 static int send_NAK(struct dhcp_packet *oldpacket)
 206 {
 207         struct dhcp_packet packet;
 208
 209         init_packet(&packet, oldpacket, DHCPNAK);
 210
 211         log1("Sending NAK");
 212         return send_packet(&packet, 1);
 213 }
 214
 215 static int send_ACK(struct dhcp_packet *oldpacket, uint32_t yiaddr)
 216 {
 217         struct dhcp_packet packet;
 218         struct option_set *curr;
 219         uint32_t lease_time_sec;
 220         struct in_addr addr;
 221         const char *p_host_name;
 222
 223         init_packet(&packet, oldpacket, DHCPACK);
 224         packet.yiaddr = yiaddr;
 225
 226         lease_time_sec = select_lease_time(oldpacket);
 227
 228         add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_sec));
 229
 230         curr = server_config.options;
 231         while (curr) {
 232                 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
 233                         add_option_string(packet.options, curr->data);
 234                 curr = curr->next;
 235         }
 236
 237         add_bootp_options(&packet);
 238
 239         addr.s_addr = packet.yiaddr;
 240         bb_info_msg("Sending ACK to %s", inet_ntoa(addr));
 241
 242         if (send_packet(&packet, 0) < 0)
 243                 return -1;
 244
 245         p_host_name = (const char*) get_option(oldpacket, DHCP_HOST_NAME);
 246         add_lease(packet.chaddr, packet.yiaddr,
 247                 lease_time_sec,
 248                 p_host_name,
 249                 p_host_name ? (unsigned char)p_host_name[OPT_LEN - OPT_DATA] : 0
 250         );
 251         if (ENABLE_FEATURE_UDHCPD_WRITE_LEASES_EARLY) {
 252                 /* rewrite the file with leases at every new acceptance */
 253                 write_leases();
 254         }
 255
 256         return 0;
 257 }
 258
 259 static int send_inform(struct dhcp_packet *oldpacket)
 260 {
 261         struct dhcp_packet packet;
 262         struct option_set *curr;
 263
 264         init_packet(&packet, oldpacket, DHCPACK);
 265
 266         curr = server_config.options;
 267         while (curr) {
 268                 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
 269                         add_option_string(packet.options, curr->data);
 270                 curr = curr->next;
 271         }
 272
 273         add_bootp_options(&packet);
 274
 275         return send_packet(&packet, 0);
 276 }
 277
 278
 279 /* globals */
 280 struct dyn_lease *g_leases;
 281 /* struct server_config_t server_config is in bb_common_bufsiz1 */
 282
 283
 284 int udhcpd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 285 int udhcpd_main(int argc UNUSED_PARAM, char **argv)
 286 {
 287         fd_set rfds;
 288         int server_socket = -1, retval, max_sock;
 289         struct dhcp_packet packet;
 290         uint8_t *state;
 291         uint32_t static_lease_ip;
 292         unsigned timeout_end;
 293         unsigned num_ips;
 294         unsigned opt;
 295         struct option_set *option;
 296         struct dyn_lease *lease, fake_lease;
 297         IF_FEATURE_UDHCP_PORT(char *str_P;)
 298
 299 #if ENABLE_FEATURE_UDHCP_PORT
 300         SERVER_PORT = 67;
 301         CLIENT_PORT = 68;
 302 #endif
 303
 304 #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
 305         opt_complementary = "vv";
 306 #endif
 307         opt = getopt32(argv, "fSv"
 308                 IF_FEATURE_UDHCP_PORT("P:", &str_P)
 309 #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
 310                 , &dhcp_verbose
 311 #endif
 312                 );
 313         argv += optind;
 314         if (!(opt & 1)) { /* no -f */
 315                 bb_daemonize_or_rexec(0, argv);
 316                 logmode = LOGMODE_NONE;
 317         }
 318         if (opt & 2) { /* -S */
 319                 openlog(applet_name, LOG_PID, LOG_DAEMON);
 320                 logmode |= LOGMODE_SYSLOG;
 321         }
 322 #if ENABLE_FEATURE_UDHCP_PORT
 323         if (opt & 4) { /* -P */
 324                 SERVER_PORT = xatou16(str_P);
 325                 CLIENT_PORT = SERVER_PORT + 1;
 326         }
 327 #endif
 328         /* Would rather not do read_config before daemonization -
 329          * otherwise NOMMU machines will parse config twice */
 330         read_config(argv[0] ? argv[0] : DHCPD_CONF_FILE);
 331
 332         /* Make sure fd 0,1,2 are open */
 333         bb_sanitize_stdio();
 334         /* Equivalent of doing a fflush after every \n */
 335         setlinebuf(stdout);
 336
 337         /* Create pidfile */
 338         write_pidfile(server_config.pidfile);
 339         /* if (!..) bb_perror_msg("can't create pidfile %s", pidfile); */
 340
 341         bb_info_msg("%s (v"BB_VER") started", applet_name);
 342
 343         option = find_option(server_config.options, DHCP_LEASE_TIME);
 344         server_config.max_lease_sec = LEASE_TIME;
 345         if (option) {
 346                 move_from_unaligned32(server_config.max_lease_sec, option->data + OPT_DATA);
 347                 server_config.max_lease_sec = ntohl(server_config.max_lease_sec);
 348         }
 349
 350         /* Sanity check */
 351         num_ips = server_config.end_ip - server_config.start_ip + 1;
 352         if (server_config.max_leases > num_ips) {
 353                 bb_error_msg("max_leases=%u is too big, setting to %u",
 354                         (unsigned)server_config.max_leases, num_ips);
 355                 server_config.max_leases = num_ips;
 356         }
 357
 358         g_leases = xzalloc(server_config.max_leases * sizeof(g_leases[0]));
 359         read_leases(server_config.lease_file);
 360
 361         if (udhcp_read_interface(server_config.interface,
 362                         &server_config.ifindex,
 363                         &server_config.server_nip,
 364                         server_config.server_mac)
 365         ) {
 366                 retval = 1;
 367                 goto ret;
 368         }
 369
 370         /* Setup the signal pipe */
 371         udhcp_sp_setup();
 372
 373         timeout_end = monotonic_sec() + server_config.auto_time;
 374         while (1) { /* loop until universe collapses */
 375                 int bytes;
 376                 struct timeval tv;
 377
 378                 if (server_socket < 0) {
 379                         server_socket = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT,
 380                                         server_config.interface);
 381                 }
 382
 383                 max_sock = udhcp_sp_fd_set(&rfds, server_socket);
 384                 if (server_config.auto_time) {
 385                         tv.tv_sec = timeout_end - monotonic_sec();
 386                         tv.tv_usec = 0;
 387                 }
 388                 retval = 0;
 389                 if (!server_config.auto_time || tv.tv_sec > 0) {
 390                         retval = select(max_sock + 1, &rfds, NULL, NULL,
 391                                         server_config.auto_time ? &tv : NULL);
 392                 }
 393                 if (retval == 0) {
 394                         write_leases();
 395                         timeout_end = monotonic_sec() + server_config.auto_time;
 396                         continue;
 397                 }
 398                 if (retval < 0 && errno != EINTR) {
 399                         log1("Error on select");
 400                         continue;
 401                 }
 402
 403                 switch (udhcp_sp_read(&rfds)) {
 404                 case SIGUSR1:
 405                         bb_info_msg("Received a SIGUSR1");
 406                         write_leases();
 407                         /* why not just reset the timeout, eh */
 408                         timeout_end = monotonic_sec() + server_config.auto_time;
 409                         continue;
 410                 case SIGTERM:
 411                         bb_info_msg("Received a SIGTERM");
 412                         goto ret0;
 413                 case 0: /* no signal: read a packet */
 414                         break;
 415                 default: /* signal or error (probably EINTR): back to select */
 416                         continue;
 417                 }
 418
 419                 bytes = udhcp_recv_kernel_packet(&packet, server_socket);
 420                 if (bytes < 0) {
 421                         /* bytes can also be -2 ("bad packet data") */
 422                         if (bytes == -1 && errno != EINTR) {
 423                                 log1("Read error: %s, reopening socket", strerror(errno));
 424                                 close(server_socket);
 425                                 server_socket = -1;
 426                         }
 427                         continue;
 428                 }
 429
 430                 if (packet.hlen != 6) {
 431                         bb_error_msg("MAC length != 6, ignoring packet");
 432                         continue;
 433                 }
 434
 435                 state = get_option(&packet, DHCP_MESSAGE_TYPE);
 436                 if (state == NULL) {
 437                         bb_error_msg("no message type option, ignoring packet");
 438                         continue;
 439                 }
 440
 441                 /* Look for a static lease */
 442                 static_lease_ip = get_static_nip_by_mac(server_config.static_leases, &packet.chaddr);
 443                 if (static_lease_ip) {
 444                         bb_info_msg("Found static lease: %x", static_lease_ip);
 445
 446                         memcpy(&fake_lease.lease_mac, &packet.chaddr, 6);
 447                         fake_lease.lease_nip = static_lease_ip;
 448                         fake_lease.expires = 0;
 449
 450                         lease = &fake_lease;
 451                 } else {
 452                         lease = find_lease_by_mac(packet.chaddr);
 453                 }
 454
 455                 switch (state[0]) {
 456                 case DHCPDISCOVER:
 457                         log1("Received DISCOVER");
 458
 459                         if (send_offer(&packet) < 0) {
 460                                 bb_error_msg("send OFFER failed");
 461                         }
 462                         break;
 463                 case DHCPREQUEST: {
 464                         uint8_t *server_id_opt, *requested_opt;
 465                         uint32_t server_id_net = server_id_net; /* for compiler */
 466                         uint32_t requested_nip = requested_nip; /* for compiler */
 467
 468                         log1("Received REQUEST");
 469
 470                         requested_opt = get_option(&packet, DHCP_REQUESTED_IP);
 471                         server_id_opt = get_option(&packet, DHCP_SERVER_ID);
 472                         if (requested_opt)
 473                                 move_from_unaligned32(requested_nip, requested_opt);
 474                         if (server_id_opt)
 475                                 move_from_unaligned32(server_id_net, server_id_opt);
 476
 477                         if (lease) {
 478                                 if (server_id_opt) {
 479                                         /* SELECTING State */
 480                                         if (server_id_net == server_config.server_nip
 481                                          && requested_opt
 482                                          && requested_nip == lease->lease_nip
 483                                         ) {
 484                                                 send_ACK(&packet, lease->lease_nip);
 485                                         }
 486                                 } else if (requested_opt) {
 487                                         /* INIT-REBOOT State */
 488                                         if (lease->lease_nip == requested_nip)
 489                                                 send_ACK(&packet, lease->lease_nip);
 490                                         else
 491                                                 send_NAK(&packet);
 492                                 } else if (lease->lease_nip == packet.ciaddr) {
 493                                         /* RENEWING or REBINDING State */
 494                                         send_ACK(&packet, lease->lease_nip);
 495                                 } else { /* don't know what to do!!!! */
 496                                         send_NAK(&packet);
 497                                 }
 498
 499                         /* what to do if we have no record of the client */
 500                         } else if (server_id_opt) {
 501                                 /* SELECTING State */
 502
 503                         } else if (requested_opt) {
 504                                 /* INIT-REBOOT State */
 505                                 lease = find_lease_by_nip(requested_nip);
 506                                 if (lease) {
 507                                         if (is_expired_lease(lease)) {
 508                                                 /* probably best if we drop this lease */
 509                                                 memset(lease->lease_mac, 0, sizeof(lease->lease_mac));
 510                                         } else {
 511                                                 /* make some contention for this address */
 512                                                 send_NAK(&packet);
 513                                         }
 514                                 } else {
 515                                         uint32_t r = ntohl(requested_nip);
 516                                         if (r < server_config.start_ip
 517                                          || r > server_config.end_ip
 518                                         ) {
 519                                                 send_NAK(&packet);
 520                                         }
 521                                         /* else remain silent */
 522                                 }
 523
 524                         } else {
 525                                 /* RENEWING or REBINDING State */
 526                         }
 527                         break;
 528                 }
 529                 case DHCPDECLINE:
 530                         log1("Received DECLINE");
 531                         if (lease) {
 532                                 memset(lease->lease_mac, 0, sizeof(lease->lease_mac));
 533                                 lease->expires = time(NULL) + server_config.decline_time;
 534                         }
 535                         break;
 536                 case DHCPRELEASE:
 537                         log1("Received RELEASE");
 538                         if (lease)
 539                                 lease->expires = time(NULL);
 540                         break;
 541                 case DHCPINFORM:
 542                         log1("Received INFORM");
 543                         send_inform(&packet);
 544                         break;
 545                 default:
 546                         bb_info_msg("Unsupported DHCP message (%02x) - ignoring", state[0]);
 547                 }
 548         }
 549  ret0:
 550         retval = 0;
 551  ret:
 552         /*if (server_config.pidfile) - server_config.pidfile is never NULL */
 553                 remove_pidfile(server_config.pidfile);
 554         return retval;
 555 }