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 <syslog.h>
  12
  13 /* Override ENABLE_FEATURE_PIDFILE - ifupdown needs our pidfile to always exist */
  14 #define WANT_PIDFILE 1
  15 #include "common.h"
  16 #include "dhcpd.h"
  17 #include "dhcpc.h"
  18 #include "options.h"
  19
  20
  21 static int sockfd = -1;
  22
  23 #define LISTEN_NONE 0
  24 #define LISTEN_KERNEL 1
  25 #define LISTEN_RAW 2
  26 static smallint listen_mode;
  27
  28 #define INIT_SELECTING  0
  29 #define REQUESTING      1
  30 #define BOUND           2
  31 #define RENEWING        3
  32 #define REBINDING       4
  33 #define INIT_REBOOT     5
  34 #define RENEW_REQUESTED 6
  35 #define RELEASED        7
  36 static smallint state;
  37
  38 /* struct client_config_t client_config is in bb_common_bufsiz1 */
  39
  40
  41 /* just a little helper */
  42 static void change_listen_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_listen_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_listen_mode(LISTEN_RAW);
  70                 state = INIT_SELECTING;
  71                 break;
  72         case INIT_SELECTING:
  73                 break;
  74         }
  75 }
  76
  77
  78 /* perform a release */
  79 static void perform_release(uint32_t requested_ip, uint32_t server_addr)
  80 {
  81         char buffer[sizeof("255.255.255.255")];
  82         struct in_addr temp_addr;
  83
  84         /* send release packet */
  85         if (state == BOUND || state == RENEWING || state == REBINDING) {
  86                 temp_addr.s_addr = server_addr;
  87                 strcpy(buffer, inet_ntoa(temp_addr));
  88                 temp_addr.s_addr = requested_ip;
  89                 bb_info_msg("Unicasting a release of %s to %s",
  90                                 inet_ntoa(temp_addr), buffer);
  91                 send_release(server_addr, requested_ip); /* unicast */
  92                 udhcp_run_script(NULL, "deconfig");
  93         }
  94         bb_info_msg("Entering released state");
  95
  96         change_listen_mode(LISTEN_NONE);
  97         state = RELEASED;
  98 }
  99
 100
 101 #if BB_MMU
 102 static void client_background(void)
 103 {
 104         bb_daemonize(0);
 105         logmode &= ~LOGMODE_STDIO;
 106         /* rewrite pidfile, as our pid is different now */
 107         write_pidfile(client_config.pidfile);
 108 }
 109 #endif
 110
 111
 112 static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
 113 {
 114         uint8_t *storage;
 115         int len = strlen(str);
 116         if (len > 255) len = 255;
 117         storage = xzalloc(len + extra + OPT_DATA);
 118         storage[OPT_CODE] = code;
 119         storage[OPT_LEN] = len + extra;
 120         memcpy(storage + extra + OPT_DATA, str, len);
 121         return storage;
 122 }
 123
 124
 125 int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 126 int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 127 {
 128         uint8_t *temp, *message;
 129         char *str_c, *str_V, *str_h, *str_F, *str_r;
 130         USE_FEATURE_UDHCP_PORT(char *str_P;)
 131         llist_t *list_O = NULL;
 132         int tryagain_timeout = 20;
 133         int discover_timeout = 3;
 134         int discover_retries = 3;
 135         uint32_t server_addr = server_addr; /* for compiler */
 136         uint32_t requested_ip = 0;
 137         uint32_t xid = 0;
 138         uint32_t lease_seconds = 0; /* can be given as 32-bit quantity */
 139         int packet_num;
 140         int timeout; /* must be signed */
 141         unsigned already_waited_sec;
 142         unsigned opt;
 143         int max_fd;
 144         int retval;
 145         struct timeval tv;
 146         struct dhcpMessage packet;
 147         fd_set rfds;
 148
 149 #if ENABLE_GETOPT_LONG
 150         static const char udhcpc_longopts[] ALIGN1 =
 151                 "clientid\0"       Required_argument "c"
 152                 "clientid-none\0"  No_argument       "C"
 153                 "vendorclass\0"    Required_argument "V"
 154                 "hostname\0"       Required_argument "H"
 155                 "fqdn\0"           Required_argument "F"
 156                 "interface\0"      Required_argument "i"
 157                 "now\0"            No_argument       "n"
 158                 "pidfile\0"        Required_argument "p"
 159                 "quit\0"           No_argument       "q"
 160                 "release\0"        No_argument       "R"
 161                 "request\0"        Required_argument "r"
 162                 "script\0"         Required_argument "s"
 163                 "timeout\0"        Required_argument "T"
 164                 "version\0"        No_argument       "v"
 165                 "retries\0"        Required_argument "t"
 166                 "tryagain\0"       Required_argument "A"
 167                 "syslog\0"         No_argument       "S"
 168                 "request-option\0" Required_argument "O"
 169                 "no-default-options\0" No_argument   "o"
 170                 "foreground\0"     No_argument       "f"
 171                 "background\0"     No_argument       "b"
 172                 USE_FEATURE_UDHCPC_ARPING("arping\0"    No_argument       "a")
 173                 USE_FEATURE_UDHCP_PORT("client-port\0"  Required_argument "P")
 174                 ;
 175 #endif
 176         enum {
 177                 OPT_c = 1 << 0,
 178                 OPT_C = 1 << 1,
 179                 OPT_V = 1 << 2,
 180                 OPT_H = 1 << 3,
 181                 OPT_h = 1 << 4,
 182                 OPT_F = 1 << 5,
 183                 OPT_i = 1 << 6,
 184                 OPT_n = 1 << 7,
 185                 OPT_p = 1 << 8,
 186                 OPT_q = 1 << 9,
 187                 OPT_R = 1 << 10,
 188                 OPT_r = 1 << 11,
 189                 OPT_s = 1 << 12,
 190                 OPT_T = 1 << 13,
 191                 OPT_t = 1 << 14,
 192                 OPT_v = 1 << 15,
 193                 OPT_S = 1 << 16,
 194                 OPT_A = 1 << 17,
 195                 OPT_O = 1 << 18,
 196                 OPT_o = 1 << 19,
 197                 OPT_f = 1 << 20,
 198 /* The rest has variable bit positions, need to be clever */
 199                 OPTBIT_f = 20,
 200                 USE_FOR_MMU(              OPTBIT_b,)
 201                 USE_FEATURE_UDHCPC_ARPING(OPTBIT_a,)
 202                 USE_FEATURE_UDHCP_PORT(   OPTBIT_P,)
 203                 USE_FOR_MMU(              OPT_b = 1 << OPTBIT_b,)
 204                 USE_FEATURE_UDHCPC_ARPING(OPT_a = 1 << OPTBIT_a,)
 205                 USE_FEATURE_UDHCP_PORT(   OPT_P = 1 << OPTBIT_P,)
 206         };
 207
 208         /* Default options. */
 209         USE_FEATURE_UDHCP_PORT(SERVER_PORT = 67;)
 210         USE_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
 211         client_config.interface = "eth0";
 212         client_config.script = DEFAULT_SCRIPT;
 213
 214         /* Parse command line */
 215         /* Cc: mutually exclusive; O: list; -T,-t,-A take numeric param */
 216         opt_complementary = "c--C:C--c:O::T+:t+:A+";
 217         USE_GETOPT_LONG(applet_long_options = udhcpc_longopts;)
 218         opt = getopt32(argv, "c:CV:H:h:F:i:np:qRr:s:T:t:vSA:O:of"
 219                 USE_FOR_MMU("b")
 220                 USE_FEATURE_UDHCPC_ARPING("a")
 221                 USE_FEATURE_UDHCP_PORT("P:")
 222                 , &str_c, &str_V, &str_h, &str_h, &str_F
 223                 , &client_config.interface, &client_config.pidfile, &str_r /* i,p */
 224                 , &client_config.script /* s */
 225                 , &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */
 226                 , &list_O
 227                 USE_FEATURE_UDHCP_PORT(, &str_P)
 228                 );
 229         if (opt & OPT_c)
 230                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, str_c, 0);
 231         if (opt & OPT_V)
 232                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
 233         if (opt & (OPT_h|OPT_H))
 234                 client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
 235         if (opt & OPT_F) {
 236                 client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
 237                 /* Flags: 0000NEOS
 238                 S: 1 => Client requests Server to update A RR in DNS as well as PTR
 239                 O: 1 => Server indicates to client that DNS has been updated regardless
 240                 E: 1 => Name data is DNS format, i.e. <4>host<6>domain<3>com<0> not "host.domain.com"
 241                 N: 1 => Client requests Server to not update DNS
 242                 */
 243                 client_config.fqdn[OPT_DATA + 0] = 0x1;
 244                 /* client_config.fqdn[OPT_DATA + 1] = 0; - redundant */
 245                 /* client_config.fqdn[OPT_DATA + 2] = 0; - redundant */
 246         }
 247         if (opt & OPT_r)
 248                 requested_ip = inet_addr(str_r);
 249         if (opt & OPT_v) {
 250                 puts("version "BB_VER);
 251                 return 0;
 252         }
 253 #if ENABLE_FEATURE_UDHCP_PORT
 254         if (opt & OPT_P) {
 255                 CLIENT_PORT = xatou16(str_P);
 256                 SERVER_PORT = CLIENT_PORT - 1;
 257         }
 258 #endif
 259         if (opt & OPT_o)
 260                 client_config.no_default_options = 1;
 261         while (list_O) {
 262                 char *optstr = llist_pop(&list_O);
 263                 int n = index_in_strings(dhcp_option_strings, optstr);
 264                 if (n < 0)
 265                         bb_error_msg_and_die("unknown option '%s'", optstr);
 266                 n = dhcp_options[n].code;
 267                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
 268         }
 269
 270         if (udhcp_read_interface(client_config.interface, &client_config.ifindex,
 271                            NULL, client_config.arp))
 272                 return 1;
 273 #if !BB_MMU
 274         /* on NOMMU reexec (i.e., background) early */
 275         if (!(opt & OPT_f)) {
 276                 bb_daemonize_or_rexec(0 /* flags */, argv);
 277                 logmode = 0;
 278         }
 279 #endif
 280         if (opt & OPT_S) {
 281                 openlog(applet_name, LOG_PID, LOG_LOCAL0);
 282                 logmode |= LOGMODE_SYSLOG;
 283         }
 284
 285         /* Make sure fd 0,1,2 are open */
 286         bb_sanitize_stdio();
 287         /* Equivalent of doing a fflush after every \n */
 288         setlinebuf(stdout);
 289
 290         /* Create pidfile */
 291         write_pidfile(client_config.pidfile);
 292
 293         /* Goes to stdout (unless NOMMU) and possibly syslog */
 294         bb_info_msg("%s (v"BB_VER") started", applet_name);
 295
 296         /* if not set, and not suppressed, setup the default client ID */
 297         if (!client_config.clientid && !(opt & OPT_C)) {
 298                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
 299                 client_config.clientid[OPT_DATA] = 1;
 300                 memcpy(client_config.clientid + OPT_DATA+1, client_config.arp, 6);
 301         }
 302
 303         if (!client_config.vendorclass)
 304                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, "udhcp "BB_VER, 0);
 305
 306         /* setup the signal pipe */
 307         udhcp_sp_setup();
 308
 309         state = INIT_SELECTING;
 310         udhcp_run_script(NULL, "deconfig");
 311         change_listen_mode(LISTEN_RAW);
 312         packet_num = 0;
 313         timeout = 0;
 314         already_waited_sec = 0;
 315
 316         /* Main event loop. select() waits on signal pipe and possibly
 317          * on sockfd.
 318          * "continue" statements in code below jump to the top of the loop.
 319          */
 320         for (;;) {
 321                 unsigned timestamp_before_wait;
 322
 323                 if (listen_mode != LISTEN_NONE && sockfd < 0) {
 324                         if (listen_mode == LISTEN_KERNEL)
 325                                 sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
 326                         else
 327                                 sockfd = udhcp_raw_socket(client_config.ifindex);
 328                 }
 329                 max_fd = udhcp_sp_fd_set(&rfds, sockfd);
 330
 331                 tv.tv_sec = timeout - already_waited_sec;
 332                 tv.tv_usec = 0;
 333                 retval = 0; /* If we already timed out, fall through, else... */
 334                 if (tv.tv_sec > 0) {
 335                         timestamp_before_wait = (unsigned)monotonic_sec();
 336                         DEBUG("Waiting on select...");
 337                         retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
 338                         if (retval < 0) {
 339                                 /* EINTR? A signal was caught, don't panic */
 340                                 if (errno == EINTR)
 341                                         continue;
 342                                 /* Else: an error occured, panic! */
 343                                 bb_perror_msg_and_die("select");
 344                         }
 345                 }
 346
 347                 /* If timeout dropped to zero, time to become active:
 348                  * resend discover/renew/whatever
 349                  */
 350                 if (retval == 0) {
 351                         /* We will restart the wait in any case */
 352                         already_waited_sec = 0;
 353
 354                         switch (state) {
 355                         case INIT_SELECTING:
 356                                 if (packet_num < discover_retries) {
 357                                         if (packet_num == 0)
 358                                                 xid = random_xid();
 359
 360                                         send_discover(xid, requested_ip); /* broadcast */
 361
 362                                         timeout = discover_timeout;
 363                                         packet_num++;
 364                                         continue;
 365                                 }
 366  leasefail:
 367                                 udhcp_run_script(NULL, "leasefail");
 368 #if BB_MMU /* -b is not supported on NOMMU */
 369                                 if (opt & OPT_b) { /* background if no lease */
 370                                         bb_info_msg("No lease, forking to background");
 371                                         client_background();
 372                                         /* do not background again! */
 373                                         opt = ((opt & ~OPT_b) | OPT_f);
 374                                 } else
 375 #endif
 376                                 if (opt & OPT_n) { /* abort if no lease */
 377                                         bb_info_msg("No lease, failing");
 378                                         retval = 1;
 379                                         goto ret;
 380                                 }
 381                                 /* wait before trying again */
 382                                 timeout = tryagain_timeout;
 383                                 packet_num = 0;
 384                                 continue;
 385                         case RENEW_REQUESTED:
 386                         case REQUESTING:
 387                                 if (packet_num < discover_retries) {
 388                                         /* send request packet */
 389                                         if (state == RENEW_REQUESTED) /* unicast */
 390                                                 send_renew(xid, server_addr, requested_ip);
 391                                         else /* broadcast */
 392                                                 send_select(xid, server_addr, requested_ip);
 393
 394                                         timeout = discover_timeout;
 395                                         packet_num++;
 396                                         continue;
 397                                 }
 398                                 /* timed out, go back to init state */
 399                                 if (state == RENEW_REQUESTED)
 400                                         udhcp_run_script(NULL, "deconfig");
 401                                 change_listen_mode(LISTEN_RAW);
 402                                 state = INIT_SELECTING;
 403                                 /* "discover...select...discover..." loops
 404                                  * were seen in the wild. Treat then similarly
 405                                  * to "no response to discover" case */
 406                                 if (state == REQUESTING)
 407                                         goto leasefail;
 408                                 timeout = 0;
 409                                 packet_num = 0;
 410                                 continue;
 411                         case BOUND:
 412                                 /* Half of the lease passed, time to enter renewing state */
 413                                 change_listen_mode(LISTEN_KERNEL);
 414                                 DEBUG("Entering renew state");
 415                                 state = RENEWING;
 416                                 /* fall right through */
 417                         case RENEWING:
 418                                 if (timeout > 60) {
 419                                         /* send a request packet */
 420                                         send_renew(xid, server_addr, requested_ip); /* unicast */
 421                                         timeout >>= 1;
 422                                         continue;
 423                                 }
 424                                 /* Timed out, enter rebinding state */
 425                                 DEBUG("Entering rebinding state");
 426                                 state = REBINDING;
 427                                 /* fall right through */
 428                         case REBINDING:
 429                                 /* Lease is *really* about to run out,
 430                                  * try to find DHCP server using broadcast */
 431                                 if (timeout > 0) {
 432                                         /* send a request packet */
 433                                         send_renew(xid, 0 /* INADDR_ANY*/, requested_ip); /* broadcast */
 434                                         timeout >>= 1;
 435                                         continue;
 436                                 }
 437                                 /* Timed out, enter init state */
 438                                 bb_info_msg("Lease lost, entering init state");
 439                                 udhcp_run_script(NULL, "deconfig");
 440                                 change_listen_mode(LISTEN_RAW);
 441                                 state = INIT_SELECTING;
 442                                 /*timeout = 0; - already is */
 443                                 packet_num = 0;
 444                                 continue;
 445                         /* case RELEASED: */
 446                         }
 447                         /* yah, I know, *you* say it would never happen */
 448                         timeout = INT_MAX;
 449                         continue; /* back to main loop */
 450                 }
 451
 452                 /* select() didn't timeout, something did happen. */
 453                 /* Is is a packet? */
 454                 if (listen_mode != LISTEN_NONE && FD_ISSET(sockfd, &rfds)) {
 455                         int len;
 456                         /* A packet is ready, read it */
 457
 458                         if (listen_mode == LISTEN_KERNEL)
 459                                 len = udhcp_recv_kernel_packet(&packet, sockfd);
 460                         else
 461                                 len = udhcp_recv_raw_packet(&packet, sockfd);
 462                         if (len == -1) { /* error is severe, reopen socket */
 463                                 DEBUG("error on read, %s, reopening socket", strerror(errno));
 464                                 sleep(discover_timeout); /* 3 seconds by default */
 465                                 change_listen_mode(listen_mode); /* just close and reopen */
 466                         }
 467                         /* If this packet will turn out to be unrelated/bogus,
 468                          * we will go back and wait for next one.
 469                          * Be sure timeout is properly decreased. */
 470                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
 471                         if (len < 0)
 472                                 continue;
 473
 474                         if (packet.xid != xid) {
 475                                 DEBUG("Ignoring XID %x (our xid is %x)",
 476                                         (unsigned)packet.xid, (unsigned)xid);
 477                                 continue;
 478                         }
 479
 480                         /* Ignore packets that aren't for us */
 481                         if (memcmp(packet.chaddr, client_config.arp, 6)) {
 482                                 DEBUG("Packet does not have our chaddr - ignoring");
 483                                 continue;
 484                         }
 485
 486                         message = get_option(&packet, DHCP_MESSAGE_TYPE);
 487                         if (message == NULL) {
 488                                 bb_error_msg("cannot get message type from packet - ignoring");
 489                                 continue;
 490                         }
 491
 492                         switch (state) {
 493                         case INIT_SELECTING:
 494                                 /* Must be a DHCPOFFER to one of our xid's */
 495                                 if (*message == DHCPOFFER) {
 496                         /* TODO: why we don't just fetch server's IP from IP header? */
 497                                         temp = get_option(&packet, DHCP_SERVER_ID);
 498                                         if (!temp) {
 499                                                 bb_error_msg("no server ID in message");
 500                                                 continue;
 501                                                 /* still selecting - this server looks bad */
 502                                         }
 503                                         /* it IS unaligned sometimes, don't "optimize" */
 504                                         server_addr = get_unaligned_u32p((uint32_t*)temp);
 505                                         xid = packet.xid;
 506                                         requested_ip = packet.yiaddr;
 507
 508                                         /* enter requesting state */
 509                                         state = REQUESTING;
 510                                         timeout = 0;
 511                                         packet_num = 0;
 512                                         already_waited_sec = 0;
 513                                 }
 514                                 continue;
 515                         case RENEW_REQUESTED:
 516                         case REQUESTING:
 517                         case RENEWING:
 518                         case REBINDING:
 519                                 if (*message == DHCPACK) {
 520                                         temp = get_option(&packet, DHCP_LEASE_TIME);
 521                                         if (!temp) {
 522                                                 bb_error_msg("no lease time with ACK, using 1 hour lease");
 523                                                 lease_seconds = 60 * 60;
 524                                         } else {
 525                                                 /* can be misaligned, thus memcpy */
 526                                                 memcpy(&lease_seconds, temp, 4);
 527                                                 lease_seconds = ntohl(lease_seconds);
 528                                                 lease_seconds &= 0x0fffffff; /* paranoia: must not be prone to overflows */
 529                                                 if (lease_seconds < 10) /* and not too small */
 530                                                         lease_seconds = 10;
 531                                         }
 532 //FIXME: why do we check ARP only after we've got DHCPACK?
 533 //Shouldn't we do it immediately after DHCPOFFER?
 534 #if ENABLE_FEATURE_UDHCPC_ARPING
 535                                         if (opt & OPT_a) {
 536                                                 if (!arpping(packet.yiaddr,
 537                                                             (uint32_t) 0,
 538                                                             client_config.arp,
 539                                                             client_config.interface)
 540                                                 ) {
 541                                                         bb_info_msg("offered address is in use "
 542                                                                 "(got ARP reply), declining");
 543 //NB: not clear whether it should be unicast or bcast.
 544 //Currently it is a bcast. Why?
 545                                                         send_decline(xid, server_addr, packet.yiaddr);
 546
 547                                                         if (state != REQUESTING)
 548                                                                 udhcp_run_script(NULL, "deconfig");
 549                                                         change_listen_mode(LISTEN_RAW);
 550                                                         state = INIT_SELECTING;
 551                                                         requested_ip = 0;
 552                                                         timeout = tryagain_timeout;
 553                                                         packet_num = 0;
 554                                                         already_waited_sec = 0;
 555                                                         continue; /* back to main loop */
 556                                                 }
 557                                         }
 558 #endif
 559                                         /* enter bound state */
 560                                         timeout = lease_seconds / 2;
 561                                         {
 562                                                 struct in_addr temp_addr;
 563                                                 temp_addr.s_addr = packet.yiaddr;
 564                                                 bb_info_msg("Lease of %s obtained, lease time %u",
 565                                                         inet_ntoa(temp_addr), (unsigned)lease_seconds);
 566                                         }
 567                                         requested_ip = packet.yiaddr;
 568                                         udhcp_run_script(&packet,
 569                                                    ((state == RENEWING || state == REBINDING) ? "renew" : "bound"));
 570
 571                                         state = BOUND;
 572                                         change_listen_mode(LISTEN_NONE);
 573                                         if (opt & OPT_q) { /* quit after lease */
 574                                                 if (opt & OPT_R) /* release on quit */
 575                                                         perform_release(requested_ip, server_addr);
 576                                                 goto ret0;
 577                                         }
 578 #if BB_MMU /* NOMMU case backgrounded earlier */
 579                                         if (!(opt & OPT_f)) {
 580                                                 client_background();
 581                                                 /* do not background again! */
 582                                                 opt = ((opt & ~OPT_b) | OPT_f);
 583                                         }
 584 #endif
 585                                         already_waited_sec = 0;
 586                                         continue; /* back to main loop */
 587                                 }
 588                                 if (*message == DHCPNAK) {
 589                                         /* return to init state */
 590                                         bb_info_msg("Received DHCP NAK");
 591                                         udhcp_run_script(&packet, "nak");
 592                                         if (state != REQUESTING)
 593                                                 udhcp_run_script(NULL, "deconfig");
 594                                         change_listen_mode(LISTEN_RAW);
 595                                         sleep(3); /* avoid excessive network traffic */
 596                                         state = INIT_SELECTING;
 597                                         requested_ip = 0;
 598                                         timeout = 0;
 599                                         packet_num = 0;
 600                                         already_waited_sec = 0;
 601                                 }
 602                                 continue;
 603                         /* case BOUND, RELEASED: - ignore all packets */
 604                         }
 605                         continue; /* back to main loop */
 606                 }
 607
 608                 /* select() didn't timeout, something did happen.
 609                  * But it wasn't a packet. It's a signal pipe then. */
 610                 {
 611                         int signo = udhcp_sp_read(&rfds);
 612                         switch (signo) {
 613                         case SIGUSR1:
 614                                 perform_renew();
 615                                 /* start things over */
 616                                 packet_num = 0;
 617                                 /* Kill any timeouts because the user wants this to hurry along */
 618                                 timeout = 0;
 619                                 break;
 620                         case SIGUSR2:
 621                                 perform_release(requested_ip, server_addr);
 622                                 timeout = INT_MAX;
 623                                 break;
 624                         case SIGTERM:
 625                                 bb_info_msg("Received SIGTERM");
 626                                 if (opt & OPT_R) /* release on quit */
 627                                         perform_release(requested_ip, server_addr);
 628                                 goto ret0;
 629                         }
 630                 }
 631         } /* for (;;) - main loop ends */
 632
 633  ret0:
 634         retval = 0;
 635  ret:
 636         /*if (client_config.pidfile) - remove_pidfile has its own check */
 637                 remove_pidfile(client_config.pidfile);
 638         return retval;
 639 }