networking/udhcp/dhcpc.c

   1 /* dhcpc.c
   2  *
   3  * udhcp DHCP client
   4  *
   5  * Russ Dill <Russ.Dill@asu.edu> July 2001
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20  */
  21
  22 #include <stdio.h>
  23 #include <sys/time.h>
  24 #include <sys/types.h>
  25 #include <sys/file.h>
  26 #include <unistd.h>
  27 #include <getopt.h>
  28 #include <stdlib.h>
  29 #include <sys/socket.h>
  30 #include <netinet/in.h>
  31 #include <arpa/inet.h>
  32 #include <signal.h>
  33 #include <time.h>
  34 #include <string.h>
  35 #include <sys/ioctl.h>
  36 #include <net/if.h>
  37 #include <errno.h>
  38
  39 #include "dhcpd.h"
  40 #include "dhcpc.h"
  41 #include "options.h"
  42 #include "clientpacket.h"
  43 #include "packet.h"
  44 #include "script.h"
  45 #include "socket.h"
  46 #include "debug.h"
  47 #include "pidfile.h"
  48
  49 static int state;
  50 static unsigned long requested_ip; /* = 0 */
  51 static unsigned long server_addr;
  52 static unsigned long timeout;
  53 static int packet_num; /* = 0 */
  54 static int fd = -1;
  55 static int signal_pipe[2];
  56
  57 #define LISTEN_NONE 0
  58 #define LISTEN_KERNEL 1
  59 #define LISTEN_RAW 2
  60 static int listen_mode;
  61
  62 #define DEFAULT_SCRIPT  "/usr/share/udhcpc/default.script"
  63
  64 struct client_config_t client_config = {
  65         /* Default options. */
  66         abort_if_no_lease: 0,
  67         foreground: 0,
  68         quit_after_lease: 0,
  69         background_if_no_lease: 0,
  70         interface: "eth0",
  71         pidfile: NULL,
  72         script: DEFAULT_SCRIPT,
  73         clientid: NULL,
  74         hostname: NULL,
  75         ifindex: 0,
  76         arp: "\0\0\0\0\0\0",            /* appease gcc-3.0 */
  77 };
  78
  79 #ifndef IN_BUSYBOX
  80 static void __attribute__ ((noreturn)) show_usage(void)
  81 {
  82         printf(
  83 "Usage: udhcpc [OPTIONS]\n\n"
  84 "  -c, --clientid=CLIENTID         Client identifier\n"
  85 "  -H, --hostname=HOSTNAME         Client hostname\n"
  86 "  -h                              Alias for -H\n"
  87 "  -f, --foreground                Do not fork after getting lease\n"
  88 "  -b, --background                Fork to background if lease cannot be\n"
  89 "                                  immediately negotiated.\n"
  90 "  -i, --interface=INTERFACE       Interface to use (default: eth0)\n"
  91 "  -n, --now                       Exit with failure if lease cannot be\n"
  92 "                                  immediately negotiated.\n"
  93 "  -p, --pidfile=file              Store process ID of daemon in file\n"
  94 "  -q, --quit                      Quit after obtaining lease\n"
  95 "  -r, --request=IP                IP address to request (default: none)\n"
  96 "  -s, --script=file               Run file at dhcp events (default:\n"
  97 "                                  " DEFAULT_SCRIPT ")\n"
  98 "  -v, --version                   Display version\n"
  99         );
 100         exit(0);
 101 }
 102 #else
 103 extern void show_usage(void) __attribute__ ((noreturn));
 104 #endif
 105
 106
 107 /* just a little helper */
 108 static void change_mode(int new_mode)
 109 {
 110         DEBUG(LOG_INFO, "entering %s listen mode",
 111                 new_mode ? (new_mode == 1 ? "kernel" : "raw") : "none");
 112         if (fd >= 0) close(fd);
 113         fd = -1;
 114         listen_mode = new_mode;
 115 }
 116
 117
 118 /* perform a renew */
 119 static void perform_renew(void)
 120 {
 121         LOG(LOG_INFO, "Performing a DHCP renew");
 122         switch (state) {
 123         case BOUND:
 124                 change_mode(LISTEN_KERNEL);
 125         case RENEWING:
 126         case REBINDING:
 127                 state = RENEW_REQUESTED;
 128                 break;
 129         case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
 130                 run_script(NULL, "deconfig");
 131         case REQUESTING:
 132         case RELEASED:
 133                 change_mode(LISTEN_RAW);
 134                 state = INIT_SELECTING;
 135                 break;
 136         case INIT_SELECTING:
 137         }
 138
 139         /* start things over */
 140         packet_num = 0;
 141
 142         /* Kill any timeouts because the user wants this to hurry along */
 143         timeout = 0;
 144 }
 145
 146
 147 /* perform a release */
 148 static void perform_release(void)
 149 {
 150         char buffer[16];
 151         struct in_addr temp_addr;
 152
 153         /* send release packet */
 154         if (state == BOUND || state == RENEWING || state == REBINDING) {
 155                 temp_addr.s_addr = server_addr;
 156                 sprintf(buffer, "%s", inet_ntoa(temp_addr));
 157                 temp_addr.s_addr = requested_ip;
 158                 LOG(LOG_INFO, "Unicasting a release of %s to %s",
 159                                 inet_ntoa(temp_addr), buffer);
 160                 send_release(server_addr, requested_ip); /* unicast */
 161                 run_script(NULL, "deconfig");
 162         }
 163         LOG(LOG_INFO, "Entering released state");
 164
 165         change_mode(LISTEN_NONE);
 166         state = RELEASED;
 167         timeout = 0x7fffffff;
 168 }
 169
 170
 171 /* Exit and cleanup */
 172 static void exit_client(int retval)
 173 {
 174         pidfile_delete(client_config.pidfile);
 175         CLOSE_LOG();
 176         exit(retval);
 177 }
 178
 179
 180 /* Signal handler */
 181 static void signal_handler(int sig)
 182 {
 183         if (send(signal_pipe[1], &sig, sizeof(sig), MSG_DONTWAIT) < 0) {
 184                 LOG(LOG_ERR, "Could not send signal: %s",
 185                         strerror(errno));
 186         }
 187 }
 188
 189
 190 static void background(void)
 191 {
 192         int pid_fd;
 193
 194         pid_fd = pidfile_acquire(client_config.pidfile); /* hold lock during fork. */
 195         while (pid_fd >= 0 && pid_fd < 3) pid_fd = dup(pid_fd); /* don't let daemon close it */
 196         if (daemon(0, 0) == -1) {
 197                 perror("fork");
 198                 exit_client(1);
 199         }
 200         client_config.foreground = 1; /* Do not fork again. */
 201         client_config.background_if_no_lease = 0;
 202         pidfile_write_release(pid_fd);
 203 }
 204
 205
 206 #ifdef COMBINED_BINARY
 207 int udhcpc_main(int argc, char *argv[])
 208 #else
 209 int main(int argc, char *argv[])
 210 #endif
 211 {
 212         unsigned char *temp, *message;
 213         unsigned long t1 = 0, t2 = 0, xid = 0;
 214         unsigned long start = 0, lease;
 215         fd_set rfds;
 216         int retval;
 217         struct timeval tv;
 218         int c, len;
 219         struct dhcpMessage packet;
 220         struct in_addr temp_addr;
 221         int pid_fd;
 222         time_t now;
 223         int max_fd;
 224         int sig;
 225
 226         static struct option arg_options[] = {
 227                 {"clientid",    required_argument,      0, 'c'},
 228                 {"foreground",  no_argument,            0, 'f'},
 229                 {"background",  no_argument,            0, 'b'},
 230                 {"hostname",    required_argument,      0, 'H'},
 231                 {"hostname",    required_argument,      0, 'h'},
 232                 {"interface",   required_argument,      0, 'i'},
 233                 {"now",         no_argument,            0, 'n'},
 234                 {"pidfile",     required_argument,      0, 'p'},
 235                 {"quit",        no_argument,            0, 'q'},
 236                 {"request",     required_argument,      0, 'r'},
 237                 {"script",      required_argument,      0, 's'},
 238                 {"version",     no_argument,            0, 'v'},
 239                 {"help",        no_argument,            0, '?'},
 240                 {0, 0, 0, 0}
 241         };
 242
 243         /* get options */
 244         while (1) {
 245                 int option_index = 0;
 246                 c = getopt_long(argc, argv, "c:fbH:h:i:np:qr:s:v", arg_options, &option_index);
 247                 if (c == -1) break;
 248
 249                 switch (c) {
 250                 case 'c':
 251                         len = strlen(optarg) > 255 ? 255 : strlen(optarg);
 252                         if (client_config.clientid) free(client_config.clientid);
 253                         client_config.clientid = xmalloc(len + 2);
 254                         client_config.clientid[OPT_CODE] = DHCP_CLIENT_ID;
 255                         client_config.clientid[OPT_LEN] = len;
 256                         client_config.clientid[OPT_DATA] = '\0';
 257                         strncpy(client_config.clientid + OPT_DATA, optarg, len);
 258                         break;
 259                 case 'f':
 260                         client_config.foreground = 1;
 261                         break;
 262                 case 'b':
 263                         client_config.background_if_no_lease = 1;
 264                         break;
 265                 case 'h':
 266                 case 'H':
 267                         len = strlen(optarg) > 255 ? 255 : strlen(optarg);
 268                         if (client_config.hostname) free(client_config.hostname);
 269                         client_config.hostname = xmalloc(len + 2);
 270                         client_config.hostname[OPT_CODE] = DHCP_HOST_NAME;
 271                         client_config.hostname[OPT_LEN] = len;
 272                         strncpy(client_config.hostname + 2, optarg, len);
 273                         break;
 274                 case 'i':
 275                         client_config.interface =  optarg;
 276                         break;
 277                 case 'n':
 278                         client_config.abort_if_no_lease = 1;
 279                         break;
 280                 case 'p':
 281                         client_config.pidfile = optarg;
 282                         break;
 283                 case 'q':
 284                         client_config.quit_after_lease = 1;
 285                         break;
 286                 case 'r':
 287                         requested_ip = inet_addr(optarg);
 288                         break;
 289                 case 's':
 290                         client_config.script = optarg;
 291                         break;
 292                 case 'v':
 293                         printf("udhcpcd, version %s\n\n", VERSION);
 294                         exit_client(0);
 295                         break;
 296                 default:
 297                         show_usage();
 298                 }
 299         }
 300
 301         OPEN_LOG("udhcpc");
 302         LOG(LOG_INFO, "udhcp client (v%s) started", VERSION);
 303
 304         pid_fd = pidfile_acquire(client_config.pidfile);
 305         pidfile_write_release(pid_fd);
 306
 307         if (read_interface(client_config.interface, &client_config.ifindex,
 308                            NULL, client_config.arp) < 0)
 309                 exit_client(1);
 310
 311         if (!client_config.clientid) {
 312                 client_config.clientid = xmalloc(6 + 3);
 313                 client_config.clientid[OPT_CODE] = DHCP_CLIENT_ID;
 314                 client_config.clientid[OPT_LEN] = 7;
 315                 client_config.clientid[OPT_DATA] = 1;
 316                 memcpy(client_config.clientid + 3, client_config.arp, 6);
 317         }
 318
 319         /* setup signal handlers */
 320         socketpair(AF_UNIX, SOCK_STREAM, 0, signal_pipe);
 321         signal(SIGUSR1, signal_handler);
 322         signal(SIGUSR2, signal_handler);
 323         signal(SIGTERM, signal_handler);
 324
 325         state = INIT_SELECTING;
 326         run_script(NULL, "deconfig");
 327         change_mode(LISTEN_RAW);
 328
 329         for (;;) {
 330
 331                 tv.tv_sec = timeout - time(0);
 332                 tv.tv_usec = 0;
 333                 FD_ZERO(&rfds);
 334
 335                 if (listen_mode != LISTEN_NONE && fd < 0) {
 336                         if (listen_mode == LISTEN_KERNEL)
 337                                 fd = listen_socket(INADDR_ANY, CLIENT_PORT, client_config.interface);
 338                         else
 339                                 fd = raw_socket(client_config.ifindex);
 340                         if (fd < 0) {
 341                                 LOG(LOG_ERR, "FATAL: couldn't listen on socket, %s", strerror(errno));
 342                                 exit_client(0);
 343                         }
 344                 }
 345                 if (fd >= 0) FD_SET(fd, &rfds);
 346                 FD_SET(signal_pipe[0], &rfds);
 347
 348                 if (tv.tv_sec > 0) {
 349                         DEBUG(LOG_INFO, "Waiting on select...\n");
 350                         max_fd = signal_pipe[0] > fd ? signal_pipe[0] : fd;
 351                         retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
 352                 } else retval = 0; /* If we already timed out, fall through */
 353
 354                 now = time(0);
 355                 if (retval == 0) {
 356                         /* timeout dropped to zero */
 357                         switch (state) {
 358                         case INIT_SELECTING:
 359                                 if (packet_num < 3) {
 360                                         if (packet_num == 0)
 361                                                 xid = random_xid();
 362
 363                                         /* send discover packet */
 364                                         send_discover(xid, requested_ip); /* broadcast */
 365
 366                                         timeout = now + ((packet_num == 2) ? 4 : 2);
 367                                         packet_num++;
 368                                 } else {
 369                                         if (client_config.background_if_no_lease) {
 370                                                 LOG(LOG_INFO, "No lease, forking to background.");
 371                                                 background();
 372                                         } else if (client_config.abort_if_no_lease) {
 373                                                 LOG(LOG_INFO, "No lease, failing.");
 374                                                 exit_client(1);
 375                                         }
 376                                         /* wait to try again */
 377                                         packet_num = 0;
 378                                         timeout = now + 60;
 379                                 }
 380                                 break;
 381                         case RENEW_REQUESTED:
 382                         case REQUESTING:
 383                                 if (packet_num < 3) {
 384                                         /* send request packet */
 385                                         if (state == RENEW_REQUESTED)
 386                                                 send_renew(xid, server_addr, requested_ip); /* unicast */
 387                                         else send_selecting(xid, server_addr, requested_ip); /* broadcast */
 388
 389                                         timeout = now + ((packet_num == 2) ? 10 : 2);
 390                                         packet_num++;
 391                                 } else {
 392                                         /* timed out, go back to init state */
 393                                         if (state == RENEW_REQUESTED) run_script(NULL, "deconfig");
 394                                         state = INIT_SELECTING;
 395                                         timeout = now;
 396                                         packet_num = 0;
 397                                         change_mode(LISTEN_RAW);
 398                                 }
 399                                 break;
 400                         case BOUND:
 401                                 /* Lease is starting to run out, time to enter renewing state */
 402                                 state = RENEWING;
 403                                 change_mode(LISTEN_KERNEL);
 404                                 DEBUG(LOG_INFO, "Entering renew state");
 405                                 /* fall right through */
 406                         case RENEWING:
 407                                 /* Either set a new T1, or enter REBINDING state */
 408                                 if ((t2 - t1) <= (lease / 14400 + 1)) {
 409                                         /* timed out, enter rebinding state */
 410                                         state = REBINDING;
 411                                         timeout = now + (t2 - t1);
 412                                         DEBUG(LOG_INFO, "Entering rebinding state");
 413                                 } else {
 414                                         /* send a request packet */
 415                                         send_renew(xid, server_addr, requested_ip); /* unicast */
 416
 417                                         t1 = (t2 - t1) / 2 + t1;
 418                                         timeout = t1 + start;
 419                                 }
 420                                 break;
 421                         case REBINDING:
 422                                 /* Either set a new T2, or enter INIT state */
 423                                 if ((lease - t2) <= (lease / 14400 + 1)) {
 424                                         /* timed out, enter init state */
 425                                         state = INIT_SELECTING;
 426                                         LOG(LOG_INFO, "Lease lost, entering init state");
 427                                         run_script(NULL, "deconfig");
 428                                         timeout = now;
 429                                         packet_num = 0;
 430                                         change_mode(LISTEN_RAW);
 431                                 } else {
 432                                         /* send a request packet */
 433                                         send_renew(xid, 0, requested_ip); /* broadcast */
 434
 435                                         t2 = (lease - t2) / 2 + t2;
 436                                         timeout = t2 + start;
 437                                 }
 438                                 break;
 439                         case RELEASED:
 440                                 /* yah, I know, *you* say it would never happen */
 441                                 timeout = 0x7fffffff;
 442                                 break;
 443                         }
 444                 } else if (retval > 0 && listen_mode != LISTEN_NONE && FD_ISSET(fd, &rfds)) {
 445                         /* a packet is ready, read it */
 446
 447                         if (listen_mode == LISTEN_KERNEL)
 448                                 len = get_packet(&packet, fd);
 449                         else len = get_raw_packet(&packet, fd);
 450
 451                         if (len == -1 && errno != EINTR) {
 452                                 DEBUG(LOG_INFO, "error on read, %s, reopening socket", strerror(errno));
 453                                 change_mode(listen_mode); /* just close and reopen */
 454                         }
 455                         if (len < 0) continue;
 456
 457                         if (packet.xid != xid) {
 458                                 DEBUG(LOG_INFO, "Ignoring XID %lx (our xid is %lx)",
 459                                         (unsigned long) packet.xid, xid);
 460                                 continue;
 461                         }
 462
 463                         if ((message = get_option(&packet, DHCP_MESSAGE_TYPE)) == NULL) {
 464                                 DEBUG(LOG_ERR, "couldnt get option from packet -- ignoring");
 465                                 continue;
 466                         }
 467
 468                         switch (state) {
 469                         case INIT_SELECTING:
 470                                 /* Must be a DHCPOFFER to one of our xid's */
 471                                 if (*message == DHCPOFFER) {
 472                                         if ((temp = get_option(&packet, DHCP_SERVER_ID))) {
 473                                                 memcpy(&server_addr, temp, 4);
 474                                                 xid = packet.xid;
 475                                                 requested_ip = packet.yiaddr;
 476
 477                                                 /* enter requesting state */
 478                                                 state = REQUESTING;
 479                                                 timeout = now;
 480                                                 packet_num = 0;
 481                                         } else {
 482                                                 DEBUG(LOG_ERR, "No server ID in message");
 483                                         }
 484                                 }
 485                                 break;
 486                         case RENEW_REQUESTED:
 487                         case REQUESTING:
 488                         case RENEWING:
 489                         case REBINDING:
 490                                 if (*message == DHCPACK) {
 491                                         if (!(temp = get_option(&packet, DHCP_LEASE_TIME))) {
 492                                                 LOG(LOG_ERR, "No lease time with ACK, using 1 hour lease");
 493                                                 lease = 60 * 60;
 494                                         } else {
 495                                                 memcpy(&lease, temp, 4);
 496                                                 lease = ntohl(lease);
 497                                         }
 498
 499                                         /* enter bound state */
 500                                         t1 = lease / 2;
 501
 502                                         /* little fixed point for n * .875 */
 503                                         t2 = (lease * 0x7) >> 3;
 504                                         temp_addr.s_addr = packet.yiaddr;
 505                                         LOG(LOG_INFO, "Lease of %s obtained, lease time %ld",
 506                                                 inet_ntoa(temp_addr), lease);
 507                                         start = now;
 508                                         timeout = t1 + start;
 509                                         requested_ip = packet.yiaddr;
 510                                         run_script(&packet,
 511                                                    ((state == RENEWING || state == REBINDING) ? "renew" : "bound"));
 512
 513                                         state = BOUND;
 514                                         change_mode(LISTEN_NONE);
 515                                         if (client_config.quit_after_lease)
 516                                                 exit_client(0);
 517                                         if (!client_config.foreground)
 518                                                 background();
 519
 520                                 } else if (*message == DHCPNAK) {
 521                                         /* return to init state */
 522                                         LOG(LOG_INFO, "Received DHCP NAK");
 523                                         run_script(&packet, "nak");
 524                                         if (state != REQUESTING)
 525                                                 run_script(NULL, "deconfig");
 526                                         state = INIT_SELECTING;
 527                                         timeout = now;
 528                                         requested_ip = 0;
 529                                         packet_num = 0;
 530                                         change_mode(LISTEN_RAW);
 531                                         sleep(3); /* avoid excessive network traffic */
 532                                 }
 533                                 break;
 534                         /* case BOUND, RELEASED: - ignore all packets */
 535                         }
 536                 } else if (retval > 0 && FD_ISSET(signal_pipe[0], &rfds)) {
 537                         if (read(signal_pipe[0], &sig, sizeof(sig)) < 0) {
 538                                 DEBUG(LOG_ERR, "Could not read signal: %s",
 539                                         strerror(errno));
 540                                 continue; /* probably just EINTR */
 541                         }
 542                         switch (sig) {
 543                         case SIGUSR1:
 544                                 perform_renew();
 545                                 break;
 546                         case SIGUSR2:
 547                                 perform_release();
 548                                 break;
 549                         case SIGTERM:
 550                                 LOG(LOG_INFO, "Received SIGTERM");
 551                                 exit_client(0);
 552                         }
 553                 } else if (retval == -1 && errno == EINTR) {
 554                         /* a signal was caught */
 555                 } else {
 556                         /* An error occured */
 557                         DEBUG(LOG_ERR, "Error on select");
 558                 }
 559
 560         }
 561         return 0;
 562 }
 563