networking/udhcp/dhcpc.c

   1 /* vi: set sw=4 ts=4: */
   2 /* dhcpc.c
   3  *
   4  * udhcp DHCP client
   5  *
   6  * Russ Dill <Russ.Dill@asu.edu> July 2001
   7  *
   8  * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
   9  */
  10
  11 #include <getopt.h>
  12 #include <syslog.h>
  13
  14 #include "common.h"
  15 #include "dhcpd.h"
  16 #include "dhcpc.h"
  17 #include "options.h"
  18
  19
  20 /* Something is definitely wrong here. IPv4 addresses
  21  * in variables of type long?? BTW, we use inet_ntoa()
  22  * in the code. Manpage says that struct in_addr has a member of type long (!)
  23  * which holds IPv4 address, and the struct is passed by value (!!)
  24  */
  25 static unsigned timeout;
  26 static uint32_t requested_ip; /* = 0 */
  27 static uint32_t server_addr;
  28 static int packet_num; /* = 0 */
  29 static int sockfd = -1;
  30
  31 #define LISTEN_NONE 0
  32 #define LISTEN_KERNEL 1
  33 #define LISTEN_RAW 2
  34 static smallint listen_mode;
  35
  36 static smallint state;
  37
  38 struct client_config_t client_config;
  39
  40
  41 /* just a little helper */
  42 static void change_mode(int new_mode)
  43 {
  44         DEBUG("entering %s listen mode",
  45                 new_mode ? (new_mode == 1 ? "kernel" : "raw") : "none");
  46         if (sockfd >= 0) {
  47                 close(sockfd);
  48                 sockfd = -1;
  49         }
  50         listen_mode = new_mode;
  51 }
  52
  53
  54 /* perform a renew */
  55 static void perform_renew(void)
  56 {
  57         bb_info_msg("Performing a DHCP renew");
  58         switch (state) {
  59         case BOUND:
  60                 change_mode(LISTEN_KERNEL);
  61         case RENEWING:
  62         case REBINDING:
  63                 state = RENEW_REQUESTED;
  64                 break;
  65         case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
  66                 udhcp_run_script(NULL, "deconfig");
  67         case REQUESTING:
  68         case RELEASED:
  69                 change_mode(LISTEN_RAW);
  70                 state = INIT_SELECTING;
  71                 break;
  72         case INIT_SELECTING:
  73                 break;
  74         }
  75
  76         /* start things over */
  77         packet_num = 0;
  78
  79         /* Kill any timeouts because the user wants this to hurry along */
  80         timeout = 0;
  81 }
  82
  83
  84 /* perform a release */
  85 static void perform_release(void)
  86 {
  87         char buffer[sizeof("255.255.255.255")];
  88         struct in_addr temp_addr;
  89
  90         /* send release packet */
  91         if (state == BOUND || state == RENEWING || state == REBINDING) {
  92                 temp_addr.s_addr = server_addr;
  93                 strcpy(buffer, inet_ntoa(temp_addr));
  94                 temp_addr.s_addr = requested_ip;
  95                 bb_info_msg("Unicasting a release of %s to %s",
  96                                 inet_ntoa(temp_addr), buffer);
  97                 send_release(server_addr, requested_ip); /* unicast */
  98                 udhcp_run_script(NULL, "deconfig");
  99         }
 100         bb_info_msg("Entering released state");
 101
 102         change_mode(LISTEN_NONE);
 103         state = RELEASED;
 104         timeout = INT_MAX;
 105 }
 106
 107
 108 static void client_background(void)
 109 {
 110 #ifdef __uClinux__
 111         bb_error_msg("cannot background in uclinux (yet)");
 112 /* ... mainly because udhcpc calls client_background()
 113  * in _the _middle _of _udhcpc _run_, not at the start!
 114  * If that will be properly disabled for NOMMU, client_background()
 115  * will work on NOMMU too */
 116 #else
 117         bb_daemonize(0);
 118         logmode &= ~LOGMODE_STDIO;
 119         /* rewrite pidfile, as our pid is different now */
 120         if (client_config.pidfile)
 121                 write_pidfile(client_config.pidfile);
 122 #endif
 123         /* Do not fork again. */
 124         client_config.foreground = 1;
 125         client_config.background_if_no_lease = 0;
 126 }
 127
 128
 129 static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
 130 {
 131         uint8_t *storage;
 132         int len = strlen(str);
 133         if (len > 255) len = 255;
 134         storage = xzalloc(len + extra + OPT_DATA);
 135         storage[OPT_CODE] = code;
 136         storage[OPT_LEN] = len + extra;
 137         memcpy(storage + extra + OPT_DATA, str, len);
 138         return storage;
 139 }
 140
 141
 142 int udhcpc_main(int argc, char **argv);
 143 int udhcpc_main(int argc, char **argv)
 144 {
 145         uint8_t *temp, *message;
 146         char *str_c, *str_V, *str_h, *str_F, *str_r, *str_T, *str_t;
 147         uint32_t xid = 0;
 148         uint32_t lease = 0; /* can be given as 32-bit quantity */
 149         unsigned t1 = 0, t2 = 0;
 150         unsigned start = 0;
 151         unsigned now;
 152         unsigned opt;
 153         int max_fd;
 154         int sig;
 155         int retval;
 156         int len;
 157         int no_clientid = 0;
 158         fd_set rfds;
 159         struct timeval tv;
 160         struct dhcpMessage packet;
 161         struct in_addr temp_addr;
 162
 163         enum {
 164                 OPT_c = 1 << 0,
 165                 OPT_C = 1 << 1,
 166                 OPT_V = 1 << 2,
 167                 OPT_f = 1 << 3,
 168                 OPT_b = 1 << 4,
 169                 OPT_H = 1 << 5,
 170                 OPT_h = 1 << 6,
 171                 OPT_F = 1 << 7,
 172                 OPT_i = 1 << 8,
 173                 OPT_n = 1 << 9,
 174                 OPT_p = 1 << 10,
 175                 OPT_q = 1 << 11,
 176                 OPT_R = 1 << 12,
 177                 OPT_r = 1 << 13,
 178                 OPT_s = 1 << 14,
 179                 OPT_T = 1 << 15,
 180                 OPT_t = 1 << 16,
 181                 OPT_v = 1 << 17,
 182         };
 183 #if ENABLE_GETOPT_LONG
 184         static const struct option arg_options[] = {
 185                 { "clientid",   required_argument,      0, 'c' },
 186                 { "clientid-none", no_argument,         0, 'C' },
 187                 { "vendorclass", required_argument,     0, 'V' },
 188                 { "foreground", no_argument,            0, 'f' },
 189                 { "background", no_argument,            0, 'b' },
 190                 { "hostname",   required_argument,      0, 'H' },
 191                 { "hostname",   required_argument,      0, 'h' },
 192                 { "fqdn",       required_argument,      0, 'F' },
 193                 { "interface",  required_argument,      0, 'i' },
 194                 { "now",        no_argument,            0, 'n' },
 195                 { "pidfile",    required_argument,      0, 'p' },
 196                 { "quit",       no_argument,            0, 'q' },
 197                 { "release",    no_argument,            0, 'R' },
 198                 { "request",    required_argument,      0, 'r' },
 199                 { "script",     required_argument,      0, 's' },
 200                 { "timeout",    required_argument,      0, 'T' },
 201                 { "version",    no_argument,            0, 'v' },
 202                 { "retries",    required_argument,      0, 't' },
 203                 { 0, 0, 0, 0 }
 204         };
 205 #endif
 206         /* Default options. */
 207         client_config.interface = "eth0";
 208         client_config.script = DEFAULT_SCRIPT;
 209         client_config.retries = 3;
 210         client_config.timeout = 3;
 211
 212         /* Parse command line */
 213         opt_complementary = "?:c--C:C--c" // mutually exclusive
 214                             ":hH:Hh"; // -h and -H are the same
 215 #if ENABLE_GETOPT_LONG
 216         applet_long_options = arg_options;
 217 #endif
 218         opt = getopt32(argc, argv, "c:CV:fbH:h:F:i:np:qRr:s:T:t:v",
 219                 &str_c, &str_V, &str_h, &str_h, &str_F,
 220                 &client_config.interface, &client_config.pidfile, &str_r,
 221                 &client_config.script, &str_T, &str_t
 222                 );
 223
 224         if (opt & OPT_c)
 225                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, str_c, 0);
 226         if (opt & OPT_C)
 227                 no_clientid = 1;
 228         if (opt & OPT_V)
 229                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
 230         if (opt & OPT_f)
 231                 client_config.foreground = 1;
 232         if (opt & OPT_b)
 233                 client_config.background_if_no_lease = 1;
 234         if (opt & OPT_h)
 235                 client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
 236         if (opt & OPT_F) {
 237                 client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
 238                 /* Flags: 0000NEOS
 239                 S: 1 => Client requests Server to update A RR in DNS as well as PTR
 240                 O: 1 => Server indicates to client that DNS has been updated regardless
 241                 E: 1 => Name data is DNS format, i.e. <4>host<6>domain<4>com<0> not "host.domain.com"
 242                 N: 1 => Client requests Server to not update DNS
 243                 */
 244                 client_config.fqdn[OPT_DATA + 0] = 0x1;
 245                 /* client_config.fqdn[OPT_DATA + 1] = 0; - redundant */
 246                 /* client_config.fqdn[OPT_DATA + 2] = 0; - redundant */
 247         }
 248         // if (opt & OPT_i) client_config.interface = ...
 249         if (opt & OPT_n)
 250                 client_config.abort_if_no_lease = 1;
 251         // if (opt & OPT_p) client_config.pidfile = ...
 252         if (opt & OPT_q)
 253                 client_config.quit_after_lease = 1;
 254         if (opt & OPT_R)
 255                 client_config.release_on_quit = 1;
 256         if (opt & OPT_r)
 257                 requested_ip = inet_addr(str_r);
 258         // if (opt & OPT_s) client_config.script = ...
 259         if (opt & OPT_T)
 260                 client_config.timeout = xatoi_u(str_T);
 261         if (opt & OPT_t)
 262                 client_config.retries = xatoi_u(str_t);
 263         if (opt & OPT_v) {
 264                 printf("version %s\n\n", BB_VER);
 265                 return 0;
 266         }
 267
 268         if (ENABLE_FEATURE_UDHCP_SYSLOG) {
 269                 openlog(applet_name, LOG_PID, LOG_LOCAL0);
 270                 logmode |= LOGMODE_SYSLOG;
 271         }
 272
 273         if (read_interface(client_config.interface, &client_config.ifindex,
 274                            NULL, client_config.arp) < 0)
 275                 return 1;
 276
 277         /* Sanitize fd's and write pidfile */
 278         udhcp_make_pidfile(client_config.pidfile);
 279
 280         /* if not set, and not suppressed, setup the default client ID */
 281         if (!client_config.clientid && !no_clientid) {
 282                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
 283                 client_config.clientid[OPT_DATA] = 1;
 284                 memcpy(client_config.clientid + OPT_DATA+1, client_config.arp, 6);
 285         }
 286
 287         if (!client_config.vendorclass)
 288                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, "udhcp "BB_VER, 0);
 289
 290         /* setup the signal pipe */
 291         udhcp_sp_setup();
 292
 293         state = INIT_SELECTING;
 294         udhcp_run_script(NULL, "deconfig");
 295         change_mode(LISTEN_RAW);
 296
 297         for (;;) {
 298                 tv.tv_sec = timeout - monotonic_sec();
 299                 tv.tv_usec = 0;
 300
 301                 if (listen_mode != LISTEN_NONE && sockfd < 0) {
 302                         if (listen_mode == LISTEN_KERNEL)
 303                                 sockfd = listen_socket(INADDR_ANY, CLIENT_PORT, client_config.interface);
 304                         else
 305                                 sockfd = raw_socket(client_config.ifindex);
 306                 }
 307                 max_fd = udhcp_sp_fd_set(&rfds, sockfd);
 308
 309                 if (tv.tv_sec > 0) {
 310                         DEBUG("Waiting on select...");
 311                         retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
 312                 } else retval = 0; /* If we already timed out, fall through */
 313
 314                 now = monotonic_sec();
 315                 if (retval == 0) {
 316                         /* timeout dropped to zero */
 317                         switch (state) {
 318                         case INIT_SELECTING:
 319                                 if (packet_num < client_config.retries) {
 320                                         if (packet_num == 0)
 321                                                 xid = random_xid();
 322
 323                                         /* send discover packet */
 324                                         send_discover(xid, requested_ip); /* broadcast */
 325
 326                                         timeout = now + client_config.timeout;
 327                                         packet_num++;
 328                                 } else {
 329                                         udhcp_run_script(NULL, "leasefail");
 330                                         if (client_config.background_if_no_lease) {
 331                                                 bb_info_msg("No lease, forking to background");
 332                                                 client_background();
 333                                         } else if (client_config.abort_if_no_lease) {
 334                                                 bb_info_msg("No lease, failing");
 335                                                 retval = 1;
 336                                                 goto ret;
 337                                         }
 338                                         /* wait to try again */
 339                                         packet_num = 0;
 340                                         timeout = now + 60;
 341                                 }
 342                                 break;
 343                         case RENEW_REQUESTED:
 344                         case REQUESTING:
 345                                 if (packet_num < client_config.retries) {
 346                                         /* send request packet */
 347                                         if (state == RENEW_REQUESTED)
 348                                                 send_renew(xid, server_addr, requested_ip); /* unicast */
 349                                         else send_selecting(xid, server_addr, requested_ip); /* broadcast */
 350
 351                                         timeout = now + ((packet_num == 2) ? 10 : 2);
 352                                         packet_num++;
 353                                 } else {
 354                                         /* timed out, go back to init state */
 355                                         if (state == RENEW_REQUESTED)
 356                                                 udhcp_run_script(NULL, "deconfig");
 357                                         state = INIT_SELECTING;
 358                                         timeout = now;
 359                                         packet_num = 0;
 360                                         change_mode(LISTEN_RAW);
 361                                 }
 362                                 break;
 363                         case BOUND:
 364                                 /* Lease is starting to run out, time to enter renewing state */
 365                                 state = RENEWING;
 366                                 change_mode(LISTEN_KERNEL);
 367                                 DEBUG("Entering renew state");
 368                                 /* fall right through */
 369                         case RENEWING:
 370                                 /* Either set a new T1, or enter REBINDING state */
 371                                 if ((t2 - t1) <= (lease / 14400 + 1)) {
 372                                         /* timed out, enter rebinding state */
 373                                         state = REBINDING;
 374                                         timeout = now + (t2 - t1);
 375                                         DEBUG("Entering rebinding state");
 376                                 } else {
 377                                         /* send a request packet */
 378                                         send_renew(xid, server_addr, requested_ip); /* unicast */
 379
 380                                         t1 = (t2 - t1) / 2 + t1;
 381                                         timeout = t1 + start;
 382                                 }
 383                                 break;
 384                         case REBINDING:
 385                                 /* Either set a new T2, or enter INIT state */
 386                                 if ((lease - t2) <= (lease / 14400 + 1)) {
 387                                         /* timed out, enter init state */
 388                                         state = INIT_SELECTING;
 389                                         bb_info_msg("Lease lost, entering init state");
 390                                         udhcp_run_script(NULL, "deconfig");
 391                                         timeout = now;
 392                                         packet_num = 0;
 393                                         change_mode(LISTEN_RAW);
 394                                 } else {
 395                                         /* send a request packet */
 396                                         send_renew(xid, 0, requested_ip); /* broadcast */
 397
 398                                         t2 = (lease - t2) / 2 + t2;
 399                                         timeout = t2 + start;
 400                                 }
 401                                 break;
 402                         case RELEASED:
 403                                 /* yah, I know, *you* say it would never happen */
 404                                 timeout = INT_MAX;
 405                                 break;
 406                         }
 407                 } else if (retval > 0 && listen_mode != LISTEN_NONE && FD_ISSET(sockfd, &rfds)) {
 408                         /* a packet is ready, read it */
 409
 410                         if (listen_mode == LISTEN_KERNEL)
 411                                 len = udhcp_get_packet(&packet, sockfd);
 412                         else len = get_raw_packet(&packet, sockfd);
 413
 414                         if (len == -1 && errno != EINTR) {
 415                                 DEBUG("error on read, %s, reopening socket", strerror(errno));
 416                                 change_mode(listen_mode); /* just close and reopen */
 417                         }
 418                         if (len < 0) continue;
 419
 420                         if (packet.xid != xid) {
 421                                 DEBUG("Ignoring XID %x (our xid is %x)",
 422                                         (unsigned)packet.xid, (unsigned)xid);
 423                                 continue;
 424                         }
 425
 426                         /* Ignore packets that aren't for us */
 427                         if (memcmp(packet.chaddr, client_config.arp, 6)) {
 428                                 DEBUG("Packet does not have our chaddr - ignoring");
 429                                 continue;
 430                         }
 431
 432                         message = get_option(&packet, DHCP_MESSAGE_TYPE);
 433                         if (message == NULL) {
 434                                 bb_error_msg("cannot get option from packet - ignoring");
 435                                 continue;
 436                         }
 437
 438                         switch (state) {
 439                         case INIT_SELECTING:
 440                                 /* Must be a DHCPOFFER to one of our xid's */
 441                                 if (*message == DHCPOFFER) {
 442                                         temp = get_option(&packet, DHCP_SERVER_ID);
 443                                         if (temp) {
 444                                                 /* can be misaligned, thus memcpy */
 445                                                 memcpy(&server_addr, temp, 4);
 446                                                 xid = packet.xid;
 447                                                 requested_ip = packet.yiaddr;
 448
 449                                                 /* enter requesting state */
 450                                                 state = REQUESTING;
 451                                                 timeout = now;
 452                                                 packet_num = 0;
 453                                         } else {
 454                                                 bb_error_msg("no server ID in message");
 455                                         }
 456                                 }
 457                                 break;
 458                         case RENEW_REQUESTED:
 459                         case REQUESTING:
 460                         case RENEWING:
 461                         case REBINDING:
 462                                 if (*message == DHCPACK) {
 463                                         temp = get_option(&packet, DHCP_LEASE_TIME);
 464                                         if (!temp) {
 465                                                 bb_error_msg("no lease time with ACK, using 1 hour lease");
 466                                                 lease = 60 * 60;
 467                                         } else {
 468                                                 /* can be misaligned, thus memcpy */
 469                                                 memcpy(&lease, temp, 4);
 470                                                 lease = ntohl(lease);
 471                                         }
 472
 473                                         /* enter bound state */
 474                                         t1 = lease / 2;
 475
 476                                         /* little fixed point for n * .875 */
 477                                         t2 = (lease * 7) >> 3;
 478                                         temp_addr.s_addr = packet.yiaddr;
 479                                         bb_info_msg("Lease of %s obtained, lease time %u",
 480                                                 inet_ntoa(temp_addr), (unsigned)lease);
 481                                         start = now;
 482                                         timeout = t1 + start;
 483                                         requested_ip = packet.yiaddr;
 484                                         udhcp_run_script(&packet,
 485                                                    ((state == RENEWING || state == REBINDING) ? "renew" : "bound"));
 486
 487                                         state = BOUND;
 488                                         change_mode(LISTEN_NONE);
 489                                         if (client_config.quit_after_lease) {
 490                                                 if (client_config.release_on_quit)
 491                                                         perform_release();
 492                                                 goto ret0;
 493                                         }
 494                                         if (!client_config.foreground)
 495                                                 client_background();
 496
 497                                 } else if (*message == DHCPNAK) {
 498                                         /* return to init state */
 499                                         bb_info_msg("Received DHCP NAK");
 500                                         udhcp_run_script(&packet, "nak");
 501                                         if (state != REQUESTING)
 502                                                 udhcp_run_script(NULL, "deconfig");
 503                                         state = INIT_SELECTING;
 504                                         timeout = now;
 505                                         requested_ip = 0;
 506                                         packet_num = 0;
 507                                         change_mode(LISTEN_RAW);
 508                                         sleep(3); /* avoid excessive network traffic */
 509                                 }
 510                                 break;
 511                         /* case BOUND, RELEASED: - ignore all packets */
 512                         }
 513                 } else if (retval > 0 && (sig = udhcp_sp_read(&rfds))) {
 514                         switch (sig) {
 515                         case SIGUSR1:
 516                                 perform_renew();
 517                                 break;
 518                         case SIGUSR2:
 519                                 perform_release();
 520                                 break;
 521                         case SIGTERM:
 522                                 bb_info_msg("Received SIGTERM");
 523                                 if (client_config.release_on_quit)
 524                                         perform_release();
 525                                 goto ret0;
 526                         }
 527                 } else if (retval == -1 && errno == EINTR) {
 528                         /* a signal was caught */
 529                 } else {
 530                         /* An error occured */
 531                         bb_perror_msg("select");
 532                 }
 533         } /* for (;;) */
 534  ret0:
 535         retval = 0;
 536  ret:
 537         if (client_config.pidfile)
 538                 remove_pidfile(client_config.pidfile);
 539         return retval;
 540 }