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 #include <syslog.h>
  11 /* Override ENABLE_FEATURE_PIDFILE - ifupdown needs our pidfile to always exist */
  12 #define WANT_PIDFILE 1
  13 #include "common.h"
  14 #include "dhcpd.h"
  15 #include "dhcpc.h"
  16 #include "options.h"
  17
  18
  19 static int sockfd = -1;
  20
  21 #define LISTEN_NONE   0
  22 #define LISTEN_KERNEL 1
  23 #define LISTEN_RAW    2
  24 static smallint listen_mode;
  25
  26 /* initial state: (re)start DHCP negotiation */
  27 #define INIT_SELECTING  0
  28 /* discover was sent, DHCPOFFER reply received */
  29 #define REQUESTING      1
  30 /* select/renew was sent, DHCPACK reply received */
  31 #define BOUND           2
  32 /* half of lease passed, want to renew it by sending unicast renew requests */
  33 #define RENEWING        3
  34 /* renew requests were not answered, lease is almost over, send broadcast renew */
  35 #define REBINDING       4
  36 /* manually requested renew (SIGUSR1) */
  37 #define RENEW_REQUESTED 5
  38 /* release, possibly manually requested (SIGUSR2) */
  39 #define RELEASED        6
  40 static smallint state;
  41
  42 /* struct client_config_t client_config is in bb_common_bufsiz1 */
  43
  44
  45 /* just a little helper */
  46 static void change_listen_mode(int new_mode)
  47 {
  48         log1("Entering listen mode: %s",
  49                 new_mode != LISTEN_NONE
  50                         ? (new_mode == LISTEN_KERNEL ? "kernel" : "raw")
  51                         : "none"
  52         );
  53
  54         listen_mode = new_mode;
  55         if (sockfd >= 0) {
  56                 close(sockfd);
  57                 sockfd = -1;
  58         }
  59         if (new_mode == LISTEN_KERNEL)
  60                 sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
  61         else if (new_mode != LISTEN_NONE)
  62                 sockfd = udhcp_raw_socket(client_config.ifindex);
  63         /* else LISTEN_NONE: sockfd stay closed */
  64 }
  65
  66
  67 /* perform a renew */
  68 static void perform_renew(void)
  69 {
  70         bb_info_msg("Performing a DHCP renew");
  71         switch (state) {
  72         case BOUND:
  73                 change_listen_mode(LISTEN_KERNEL);
  74         case RENEWING:
  75         case REBINDING:
  76                 state = RENEW_REQUESTED;
  77                 break;
  78         case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
  79                 udhcp_run_script(NULL, "deconfig");
  80         case REQUESTING:
  81         case RELEASED:
  82                 change_listen_mode(LISTEN_RAW);
  83                 state = INIT_SELECTING;
  84                 break;
  85         case INIT_SELECTING:
  86                 break;
  87         }
  88 }
  89
  90
  91 /* perform a release */
  92 static void perform_release(uint32_t requested_ip, uint32_t server_addr)
  93 {
  94         char buffer[sizeof("255.255.255.255")];
  95         struct in_addr temp_addr;
  96
  97         /* send release packet */
  98         if (state == BOUND || state == RENEWING || state == REBINDING) {
  99                 temp_addr.s_addr = server_addr;
 100                 strcpy(buffer, inet_ntoa(temp_addr));
 101                 temp_addr.s_addr = requested_ip;
 102                 bb_info_msg("Unicasting a release of %s to %s",
 103                                 inet_ntoa(temp_addr), buffer);
 104                 send_release(server_addr, requested_ip); /* unicast */
 105                 udhcp_run_script(NULL, "deconfig");
 106         }
 107         bb_info_msg("Entering released state");
 108
 109         change_listen_mode(LISTEN_NONE);
 110         state = RELEASED;
 111 }
 112
 113
 114 #if BB_MMU
 115 static void client_background(void)
 116 {
 117         bb_daemonize(0);
 118         logmode &= ~LOGMODE_STDIO;
 119         /* rewrite pidfile, as our pid is different now */
 120         write_pidfile(client_config.pidfile);
 121 }
 122 #endif
 123
 124
 125 static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
 126 {
 127         uint8_t *storage;
 128         int len = strlen(str);
 129         if (len > 255) len = 255;
 130         storage = xzalloc(len + extra + OPT_DATA);
 131         storage[OPT_CODE] = code;
 132         storage[OPT_LEN] = len + extra;
 133         memcpy(storage + extra + OPT_DATA, str, len);
 134         return storage;
 135 }
 136
 137
 138 int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 139 int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 140 {
 141         uint8_t *temp, *message;
 142         char *str_c, *str_V, *str_h, *str_F, *str_r;
 143         IF_FEATURE_UDHCP_PORT(char *str_P;)
 144         llist_t *list_O = NULL;
 145         int tryagain_timeout = 20;
 146         int discover_timeout = 3;
 147         int discover_retries = 3;
 148         uint32_t server_addr = server_addr; /* for compiler */
 149         uint32_t requested_ip = 0;
 150         uint32_t xid = 0;
 151         uint32_t lease_seconds = 0; /* can be given as 32-bit quantity */
 152         int packet_num;
 153         int timeout; /* must be signed */
 154         unsigned already_waited_sec;
 155         unsigned opt;
 156         int max_fd;
 157         int retval;
 158         struct timeval tv;
 159         struct dhcp_packet packet;
 160         fd_set rfds;
 161
 162 #if ENABLE_LONG_OPTS
 163         static const char udhcpc_longopts[] ALIGN1 =
 164                 "clientid\0"       Required_argument "c"
 165                 "clientid-none\0"  No_argument       "C"
 166                 "vendorclass\0"    Required_argument "V"
 167                 "hostname\0"       Required_argument "H"
 168                 "fqdn\0"           Required_argument "F"
 169                 "interface\0"      Required_argument "i"
 170                 "now\0"            No_argument       "n"
 171                 "pidfile\0"        Required_argument "p"
 172                 "quit\0"           No_argument       "q"
 173                 "release\0"        No_argument       "R"
 174                 "request\0"        Required_argument "r"
 175                 "script\0"         Required_argument "s"
 176                 "timeout\0"        Required_argument "T"
 177                 "version\0"        No_argument       "v"
 178                 "retries\0"        Required_argument "t"
 179                 "tryagain\0"       Required_argument "A"
 180                 "syslog\0"         No_argument       "S"
 181                 "request-option\0" Required_argument "O"
 182                 "no-default-options\0" No_argument   "o"
 183                 "foreground\0"     No_argument       "f"
 184                 "background\0"     No_argument       "b"
 185                 IF_FEATURE_UDHCPC_ARPING("arping\0"     No_argument       "a")
 186                 IF_FEATURE_UDHCP_PORT("client-port\0"   Required_argument "P")
 187                 ;
 188 #endif
 189         enum {
 190                 OPT_c = 1 << 0,
 191                 OPT_C = 1 << 1,
 192                 OPT_V = 1 << 2,
 193                 OPT_H = 1 << 3,
 194                 OPT_h = 1 << 4,
 195                 OPT_F = 1 << 5,
 196                 OPT_i = 1 << 6,
 197                 OPT_n = 1 << 7,
 198                 OPT_p = 1 << 8,
 199                 OPT_q = 1 << 9,
 200                 OPT_R = 1 << 10,
 201                 OPT_r = 1 << 11,
 202                 OPT_s = 1 << 12,
 203                 OPT_T = 1 << 13,
 204                 OPT_t = 1 << 14,
 205                 OPT_S = 1 << 15,
 206                 OPT_A = 1 << 16,
 207                 OPT_O = 1 << 17,
 208                 OPT_o = 1 << 18,
 209                 OPT_f = 1 << 19,
 210 /* The rest has variable bit positions, need to be clever */
 211                 OPTBIT_f = 19,
 212                 USE_FOR_MMU(             OPTBIT_b,)
 213                 IF_FEATURE_UDHCPC_ARPING(OPTBIT_a,)
 214                 IF_FEATURE_UDHCP_PORT(   OPTBIT_P,)
 215                 USE_FOR_MMU(             OPT_b = 1 << OPTBIT_b,)
 216                 IF_FEATURE_UDHCPC_ARPING(OPT_a = 1 << OPTBIT_a,)
 217                 IF_FEATURE_UDHCP_PORT(   OPT_P = 1 << OPTBIT_P,)
 218         };
 219
 220         /* Default options. */
 221         IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;)
 222         IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
 223         client_config.interface = "eth0";
 224         client_config.script = DEFAULT_SCRIPT;
 225
 226         /* Parse command line */
 227         /* Cc: mutually exclusive; O: list; -T,-t,-A take numeric param */
 228         opt_complementary = "c--C:C--c:O::T+:t+:A+"
 229 #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
 230                 ":vv"
 231 #endif
 232                 ;
 233         IF_LONG_OPTS(applet_long_options = udhcpc_longopts;)
 234         opt = getopt32(argv, "c:CV:H:h:F:i:np:qRr:s:T:t:SA:O:of"
 235                 USE_FOR_MMU("b")
 236                 IF_FEATURE_UDHCPC_ARPING("a")
 237                 IF_FEATURE_UDHCP_PORT("P:")
 238                 "v"
 239                 , &str_c, &str_V, &str_h, &str_h, &str_F
 240                 , &client_config.interface, &client_config.pidfile, &str_r /* i,p */
 241                 , &client_config.script /* s */
 242                 , &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */
 243                 , &list_O
 244                 IF_FEATURE_UDHCP_PORT(, &str_P)
 245 #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
 246                 , &dhcp_verbose
 247 #endif
 248                 );
 249         if (opt & OPT_c)
 250                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, str_c, 0);
 251         if (opt & OPT_V)
 252                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
 253         if (opt & (OPT_h|OPT_H))
 254                 client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
 255         if (opt & OPT_F) {
 256                 client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
 257                 /* Flags: 0000NEOS
 258                 S: 1 => Client requests Server to update A RR in DNS as well as PTR
 259                 O: 1 => Server indicates to client that DNS has been updated regardless
 260                 E: 1 => Name data is DNS format, i.e. <4>host<6>domain<3>com<0> not "host.domain.com"
 261                 N: 1 => Client requests Server to not update DNS
 262                 */
 263                 client_config.fqdn[OPT_DATA + 0] = 0x1;
 264                 /* client_config.fqdn[OPT_DATA + 1] = 0; - redundant */
 265                 /* client_config.fqdn[OPT_DATA + 2] = 0; - redundant */
 266         }
 267         if (opt & OPT_r)
 268                 requested_ip = inet_addr(str_r);
 269 #if ENABLE_FEATURE_UDHCP_PORT
 270         if (opt & OPT_P) {
 271                 CLIENT_PORT = xatou16(str_P);
 272                 SERVER_PORT = CLIENT_PORT - 1;
 273         }
 274 #endif
 275         if (opt & OPT_o)
 276                 client_config.no_default_options = 1;
 277         while (list_O) {
 278                 char *optstr = llist_pop(&list_O);
 279                 int n = index_in_strings(dhcp_option_strings, optstr);
 280                 if (n < 0)
 281                         bb_error_msg_and_die("unknown option '%s'", optstr);
 282                 n = dhcp_options[n].code;
 283                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
 284         }
 285
 286         if (udhcp_read_interface(client_config.interface,
 287                         &client_config.ifindex,
 288                         NULL,
 289                         client_config.client_mac)
 290         ) {
 291                 return 1;
 292         }
 293
 294 #if !BB_MMU
 295         /* on NOMMU reexec (i.e., background) early */
 296         if (!(opt & OPT_f)) {
 297                 bb_daemonize_or_rexec(0 /* flags */, argv);
 298                 logmode = LOGMODE_NONE;
 299         }
 300 #endif
 301         if (opt & OPT_S) {
 302                 openlog(applet_name, LOG_PID, LOG_DAEMON);
 303                 logmode |= LOGMODE_SYSLOG;
 304         }
 305
 306         /* Make sure fd 0,1,2 are open */
 307         bb_sanitize_stdio();
 308         /* Equivalent of doing a fflush after every \n */
 309         setlinebuf(stdout);
 310
 311         /* Create pidfile */
 312         write_pidfile(client_config.pidfile);
 313
 314         /* Goes to stdout (unless NOMMU) and possibly syslog */
 315         bb_info_msg("%s (v"BB_VER") started", applet_name);
 316
 317         /* If not set, and not suppressed, set up the default client ID */
 318         if (!client_config.clientid && !(opt & OPT_C)) {
 319                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
 320                 client_config.clientid[OPT_DATA] = 1;
 321                 memcpy(client_config.clientid + OPT_DATA+1, client_config.client_mac, 6);
 322         }
 323
 324         if (!client_config.vendorclass)
 325                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, "udhcp "BB_VER, 0);
 326
 327         /* Set up the signal pipe */
 328         udhcp_sp_setup();
 329
 330         state = INIT_SELECTING;
 331         udhcp_run_script(NULL, "deconfig");
 332         change_listen_mode(LISTEN_RAW);
 333         packet_num = 0;
 334         timeout = 0;
 335         already_waited_sec = 0;
 336
 337         /* Main event loop. select() waits on signal pipe and possibly
 338          * on sockfd.
 339          * "continue" statements in code below jump to the top of the loop.
 340          */
 341         for (;;) {
 342                 /* silence "uninitialized!" warning */
 343                 unsigned timestamp_before_wait = timestamp_before_wait;
 344
 345                 //bb_error_msg("sockfd:%d, listen_mode:%d", sockfd, listen_mode);
 346
 347                 /* Was opening raw or udp socket here
 348                  * if (listen_mode != LISTEN_NONE && sockfd < 0),
 349                  * but on fast network renew responses return faster
 350                  * than we open sockets. Thus this code is moved
 351                  * to change_listen_mode(). Thus we open listen socket
 352                  * BEFORE we send renew request (see "case BOUND:"). */
 353
 354                 max_fd = udhcp_sp_fd_set(&rfds, sockfd);
 355
 356                 tv.tv_sec = timeout - already_waited_sec;
 357                 tv.tv_usec = 0;
 358                 retval = 0; /* If we already timed out, fall through, else... */
 359                 if ((int)tv.tv_sec > 0) {
 360                         timestamp_before_wait = (unsigned)monotonic_sec();
 361                         log1("Waiting on select...");
 362                         retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
 363                         if (retval < 0) {
 364                                 /* EINTR? A signal was caught, don't panic */
 365                                 if (errno == EINTR) {
 366                                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
 367                                         continue;
 368                                 }
 369                                 /* Else: an error occured, panic! */
 370                                 bb_perror_msg_and_die("select");
 371                         }
 372                 }
 373
 374                 /* If timeout dropped to zero, time to become active:
 375                  * resend discover/renew/whatever
 376                  */
 377                 if (retval == 0) {
 378                         /* We will restart the wait in any case */
 379                         already_waited_sec = 0;
 380
 381                         switch (state) {
 382                         case INIT_SELECTING:
 383                                 if (packet_num < discover_retries) {
 384                                         if (packet_num == 0)
 385                                                 xid = random_xid();
 386                                         /* broadcast */
 387                                         send_discover(xid, requested_ip);
 388                                         timeout = discover_timeout;
 389                                         packet_num++;
 390                                         continue;
 391                                 }
 392  leasefail:
 393                                 udhcp_run_script(NULL, "leasefail");
 394 #if BB_MMU /* -b is not supported on NOMMU */
 395                                 if (opt & OPT_b) { /* background if no lease */
 396                                         bb_info_msg("No lease, forking to background");
 397                                         client_background();
 398                                         /* do not background again! */
 399                                         opt = ((opt & ~OPT_b) | OPT_f);
 400                                 } else
 401 #endif
 402                                 if (opt & OPT_n) { /* abort if no lease */
 403                                         bb_info_msg("No lease, failing");
 404                                         retval = 1;
 405                                         goto ret;
 406                                 }
 407                                 /* wait before trying again */
 408                                 timeout = tryagain_timeout;
 409                                 packet_num = 0;
 410                                 continue;
 411                         case REQUESTING:
 412                                 if (packet_num < discover_retries) {
 413                                         /* send broadcast select packet */
 414                                         send_select(xid, server_addr, requested_ip);
 415                                         timeout = discover_timeout;
 416                                         packet_num++;
 417                                         continue;
 418                                 }
 419                                 /* Timed out, go back to init state.
 420                                  * "discover...select...discover..." loops
 421                                  * were seen in the wild. Treat them similarly
 422                                  * to "no response to discover" case */
 423                                 change_listen_mode(LISTEN_RAW);
 424                                 state = INIT_SELECTING;
 425                                 goto leasefail;
 426                         case BOUND:
 427                                 /* 1/2 lease passed, enter renewing state */
 428                                 state = RENEWING;
 429                                 change_listen_mode(LISTEN_KERNEL);
 430                                 log1("Entering renew state");
 431                                 /* fall right through */
 432                         case RENEW_REQUESTED: /* manual (SIGUSR1) renew */
 433                         case_RENEW_REQUESTED:
 434                         case RENEWING:
 435                                 if (timeout > 60) {
 436                                         /* send an unicast renew request */
 437                         /* Sometimes observed to fail (EADDRNOTAVAIL) to bind
 438                          * a new UDP socket for sending inside send_renew.
 439                          * I hazard to guess existing listening socket
 440                          * is somehow conflicting with it, but why is it
 441                          * not deterministic then?! Strange.
 442                          * Anyway, it does recover by eventually failing through
 443                          * into INIT_SELECTING state.
 444                          */
 445                                         send_renew(xid, server_addr, requested_ip);
 446                                         timeout >>= 1;
 447                                         continue;
 448                                 }
 449                                 /* Timed out, enter rebinding state */
 450                                 log1("Entering rebinding state");
 451                                 state = REBINDING;
 452                                 /* fall right through */
 453                         case REBINDING:
 454                                 /* Lease is *really* about to run out,
 455                                  * try to find DHCP server using broadcast */
 456                                 if (timeout > 0) {
 457                                         /* send a broadcast renew request */
 458                                         send_renew(xid, 0 /*INADDR_ANY*/, requested_ip);
 459                                         timeout >>= 1;
 460                                         continue;
 461                                 }
 462                                 /* Timed out, enter init state */
 463                                 bb_info_msg("Lease lost, entering init state");
 464                                 udhcp_run_script(NULL, "deconfig");
 465                                 change_listen_mode(LISTEN_RAW);
 466                                 state = INIT_SELECTING;
 467                                 /*timeout = 0; - already is */
 468                                 packet_num = 0;
 469                                 continue;
 470                         /* case RELEASED: */
 471                         }
 472                         /* yah, I know, *you* say it would never happen */
 473                         timeout = INT_MAX;
 474                         continue; /* back to main loop */
 475                 } /* if select timed out */
 476
 477                 /* select() didn't timeout, something happened */
 478
 479                 /* Is it a signal? */
 480                 /* note: udhcp_sp_read checks FD_ISSET before reading */
 481                 switch (udhcp_sp_read(&rfds)) {
 482                 case SIGUSR1:
 483                         perform_renew();
 484                         if (state == RENEW_REQUESTED)
 485                                 goto case_RENEW_REQUESTED;
 486                         /* Start things over */
 487                         packet_num = 0;
 488                         /* Kill any timeouts, user wants this to hurry along */
 489                         timeout = 0;
 490                         continue;
 491                 case SIGUSR2:
 492                         perform_release(requested_ip, server_addr);
 493                         timeout = INT_MAX;
 494                         continue;
 495                 case SIGTERM:
 496                         bb_info_msg("Received SIGTERM");
 497                         if (opt & OPT_R) /* release on quit */
 498                                 perform_release(requested_ip, server_addr);
 499                         goto ret0;
 500                 }
 501
 502                 /* Is it a packet? */
 503                 if (listen_mode == LISTEN_NONE || !FD_ISSET(sockfd, &rfds))
 504                         continue; /* no */
 505
 506                 {
 507                         int len;
 508
 509                         /* A packet is ready, read it */
 510                         if (listen_mode == LISTEN_KERNEL)
 511                                 len = udhcp_recv_kernel_packet(&packet, sockfd);
 512                         else
 513                                 len = udhcp_recv_raw_packet(&packet, sockfd);
 514                         if (len == -1) {
 515                                 /* Error is severe, reopen socket */
 516                                 bb_info_msg("Read error: %s, reopening socket", strerror(errno));
 517                                 sleep(discover_timeout); /* 3 seconds by default */
 518                                 change_listen_mode(listen_mode); /* just close and reopen */
 519                         }
 520                         /* If this packet will turn out to be unrelated/bogus,
 521                          * we will go back and wait for next one.
 522                          * Be sure timeout is properly decreased. */
 523                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
 524                         if (len < 0)
 525                                 continue;
 526                 }
 527
 528                 if (packet.xid != xid) {
 529                         log1("xid %x (our is %x), ignoring packet",
 530                                 (unsigned)packet.xid, (unsigned)xid);
 531                         continue;
 532                 }
 533
 534                 /* Ignore packets that aren't for us */
 535                 if (packet.hlen != 6
 536                  || memcmp(packet.chaddr, client_config.client_mac, 6)
 537                 ) {
 538 //FIXME: need to also check that last 10 bytes are zero
 539                         log1("chaddr does not match, ignoring packet"); // log2?
 540                         continue;
 541                 }
 542
 543                 message = get_option(&packet, DHCP_MESSAGE_TYPE);
 544                 if (message == NULL) {
 545                         bb_error_msg("no message type option, ignoring packet");
 546                         continue;
 547                 }
 548
 549                 switch (state) {
 550                 case INIT_SELECTING:
 551                         /* Must be a DHCPOFFER to one of our xid's */
 552                         if (*message == DHCPOFFER) {
 553                 /* TODO: why we don't just fetch server's IP from IP header? */
 554                                 temp = get_option(&packet, DHCP_SERVER_ID);
 555                                 if (!temp) {
 556                                         bb_error_msg("no server ID in message");
 557                                         continue;
 558                                         /* still selecting - this server looks bad */
 559                                 }
 560                                 /* it IS unaligned sometimes, don't "optimize" */
 561                                 move_from_unaligned32(server_addr, temp);
 562                                 xid = packet.xid;
 563                                 requested_ip = packet.yiaddr;
 564
 565                                 /* enter requesting state */
 566                                 state = REQUESTING;
 567                                 timeout = 0;
 568                                 packet_num = 0;
 569                                 already_waited_sec = 0;
 570                         }
 571                         continue;
 572                 case REQUESTING:
 573                 case RENEWING:
 574                 case RENEW_REQUESTED:
 575                 case REBINDING:
 576                         if (*message == DHCPACK) {
 577                                 temp = get_option(&packet, DHCP_LEASE_TIME);
 578                                 if (!temp) {
 579                                         bb_error_msg("no lease time with ACK, using 1 hour lease");
 580                                         lease_seconds = 60 * 60;
 581                                 } else {
 582                                         /* it IS unaligned sometimes, don't "optimize" */
 583                                         move_from_unaligned32(lease_seconds, temp);
 584                                         lease_seconds = ntohl(lease_seconds);
 585                                         lease_seconds &= 0x0fffffff; /* paranoia: must not be prone to overflows */
 586                                         if (lease_seconds < 10) /* and not too small */
 587                                                 lease_seconds = 10;
 588                                 }
 589 #if ENABLE_FEATURE_UDHCPC_ARPING
 590                                 if (opt & OPT_a) {
 591 /* RFC 2131 3.1 paragraph 5:
 592  * "The client receives the DHCPACK message with configuration
 593  * parameters. The client SHOULD perform a final check on the
 594  * parameters (e.g., ARP for allocated network address), and notes
 595  * the duration of the lease specified in the DHCPACK message. At this
 596  * point, the client is configured. If the client detects that the
 597  * address is already in use (e.g., through the use of ARP),
 598  * the client MUST send a DHCPDECLINE message to the server and restarts
 599  * the configuration process..." */
 600                                         if (!arpping(packet.yiaddr,
 601                                                         NULL,
 602                                                         (uint32_t) 0,
 603                                                         client_config.client_mac,
 604                                                         client_config.interface)
 605                                         ) {
 606                                                 bb_info_msg("Offered address is in use "
 607                                                         "(got ARP reply), declining");
 608                                                 send_decline(xid, server_addr, packet.yiaddr);
 609
 610                                                 if (state != REQUESTING)
 611                                                         udhcp_run_script(NULL, "deconfig");
 612                                                 change_listen_mode(LISTEN_RAW);
 613                                                 state = INIT_SELECTING;
 614                                                 requested_ip = 0;
 615                                                 timeout = tryagain_timeout;
 616                                                 packet_num = 0;
 617                                                 already_waited_sec = 0;
 618                                                 continue; /* back to main loop */
 619                                         }
 620                                 }
 621 #endif
 622                                 /* enter bound state */
 623                                 timeout = lease_seconds / 2;
 624                                 {
 625                                         struct in_addr temp_addr;
 626                                         temp_addr.s_addr = packet.yiaddr;
 627                                         bb_info_msg("Lease of %s obtained, lease time %u",
 628                                                 inet_ntoa(temp_addr), (unsigned)lease_seconds);
 629                                 }
 630                                 requested_ip = packet.yiaddr;
 631                                 udhcp_run_script(&packet,
 632                                         ((state >= RENEWING && state <= RENEW_REQUESTED)
 633                                         ? "renew" : "bound")
 634                                 );
 635
 636                                 state = BOUND;
 637                                 change_listen_mode(LISTEN_NONE);
 638                                 if (opt & OPT_q) { /* quit after lease */
 639                                         if (opt & OPT_R) /* release on quit */
 640                                                 perform_release(requested_ip, server_addr);
 641                                         goto ret0;
 642                                 }
 643 #if BB_MMU /* NOMMU case backgrounded earlier */
 644                                 if (!(opt & OPT_f)) {
 645                                         client_background();
 646                                         /* do not background again! */
 647                                         opt = ((opt & ~OPT_b) | OPT_f);
 648                                 }
 649 #endif
 650                                 already_waited_sec = 0;
 651                                 continue; /* back to main loop */
 652                         }
 653                         if (*message == DHCPNAK) {
 654                                 /* return to init state */
 655                                 bb_info_msg("Received DHCP NAK");
 656                                 udhcp_run_script(&packet, "nak");
 657                                 if (state != REQUESTING)
 658                                         udhcp_run_script(NULL, "deconfig");
 659                                 change_listen_mode(LISTEN_RAW);
 660                                 sleep(3); /* avoid excessive network traffic */
 661                                 state = INIT_SELECTING;
 662                                 requested_ip = 0;
 663                                 timeout = 0;
 664                                 packet_num = 0;
 665                                 already_waited_sec = 0;
 666                         }
 667                         continue;
 668                 /* case BOUND: - ignore all packets */
 669                 /* case RELEASED: - ignore all packets */
 670                 }
 671                 /* back to main loop */
 672         } /* for (;;) - main loop ends */
 673
 674  ret0:
 675         retval = 0;
 676  ret:
 677         /*if (client_config.pidfile) - remove_pidfile has its own check */
 678                 remove_pidfile(client_config.pidfile);
 679         return retval;
 680 }