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 static void client_background(void)
 102 {
 103 #if !BB_MMU
 104         bb_error_msg("cannot background in uclinux (yet)");
 105 /* ... mainly because udhcpc calls client_background()
 106  * in _the _middle _of _udhcpc _run_, not at the start!
 107  * If that will be properly disabled for NOMMU, client_background()
 108  * will work on NOMMU too */
 109 #else
 110         bb_daemonize(0);
 111         logmode &= ~LOGMODE_STDIO;
 112         /* rewrite pidfile, as our pid is different now */
 113         write_pidfile(client_config.pidfile);
 114 #endif
 115         /* Do not fork again. */
 116         client_config.foreground = 1;
 117         client_config.background_if_no_lease = 0;
 118 }
 119
 120
 121 static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
 122 {
 123         uint8_t *storage;
 124         int len = strlen(str);
 125         if (len > 255) len = 255;
 126         storage = xzalloc(len + extra + OPT_DATA);
 127         storage[OPT_CODE] = code;
 128         storage[OPT_LEN] = len + extra;
 129         memcpy(storage + extra + OPT_DATA, str, len);
 130         return storage;
 131 }
 132
 133
 134 int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 135 int udhcpc_main(int argc ATTRIBUTE_UNUSED, char **argv)
 136 {
 137         uint8_t *temp, *message;
 138         char *str_c, *str_V, *str_h, *str_F, *str_r;
 139         USE_FEATURE_UDHCP_PORT(char *str_P;)
 140         llist_t *list_O = NULL;
 141 #if ENABLE_FEATURE_UDHCPC_ARPING
 142         char *str_W;
 143 #endif
 144         int tryagain_timeout = 20;
 145         int discover_timeout = 3;
 146         int discover_retries = 3;
 147         uint32_t server_addr = server_addr; /* for compiler */
 148         uint32_t requested_ip = 0;
 149         uint32_t xid = 0;
 150         uint32_t lease_seconds = 0; /* can be given as 32-bit quantity */
 151         int packet_num;
 152         int timeout; /* must be signed */
 153         unsigned already_waited_sec;
 154         unsigned opt;
 155         int max_fd;
 156         int retval;
 157         struct timeval tv;
 158         struct dhcpMessage packet;
 159         fd_set rfds;
 160
 161         enum {
 162                 OPT_c = 1 << 0,
 163                 OPT_C = 1 << 1,
 164                 OPT_V = 1 << 2,
 165                 OPT_f = 1 << 3,
 166                 OPT_b = 1 << 4,
 167                 OPT_H = 1 << 5,
 168                 OPT_h = 1 << 6,
 169                 OPT_F = 1 << 7,
 170                 OPT_i = 1 << 8,
 171                 OPT_n = 1 << 9,
 172                 OPT_p = 1 << 10,
 173                 OPT_q = 1 << 11,
 174                 OPT_R = 1 << 12,
 175                 OPT_r = 1 << 13,
 176                 OPT_s = 1 << 14,
 177                 OPT_T = 1 << 15,
 178                 OPT_t = 1 << 16,
 179                 OPT_v = 1 << 17,
 180                 OPT_S = 1 << 18,
 181                 OPT_A = 1 << 19,
 182 #if ENABLE_FEATURE_UDHCPC_ARPING
 183                 OPT_a = 1 << 20,
 184                 OPT_W = 1 << 21,
 185 #endif
 186                 OPT_P = 1 << 22,
 187                 OPT_o = 1 << 23,
 188         };
 189 #if ENABLE_GETOPT_LONG
 190         static const char udhcpc_longopts[] ALIGN1 =
 191                 "clientid\0"       Required_argument "c"
 192                 "clientid-none\0"  No_argument       "C"
 193                 "vendorclass\0"    Required_argument "V"
 194                 "foreground\0"     No_argument       "f"
 195                 "background\0"     No_argument       "b"
 196                 "hostname\0"       Required_argument "H"
 197                 "fqdn\0"           Required_argument "F"
 198                 "interface\0"      Required_argument "i"
 199                 "now\0"            No_argument       "n"
 200                 "pidfile\0"        Required_argument "p"
 201                 "quit\0"           No_argument       "q"
 202                 "release\0"        No_argument       "R"
 203                 "request\0"        Required_argument "r"
 204                 "script\0"         Required_argument "s"
 205                 "timeout\0"        Required_argument "T"
 206                 "version\0"        No_argument       "v"
 207                 "retries\0"        Required_argument "t"
 208                 "tryagain\0"       Required_argument "A"
 209                 "syslog\0"         No_argument       "S"
 210 #if ENABLE_FEATURE_UDHCPC_ARPING
 211                 "arping\0"         No_argument       "a"
 212 #endif
 213                 "request-option\0" Required_argument "O"
 214 #if ENABLE_FEATURE_UDHCP_PORT
 215                 "client-port\0"    Required_argument "P"
 216 #endif
 217                 "no-default-options\0" No_argument   "o"
 218                 ;
 219 #endif
 220         /* Default options. */
 221 #if ENABLE_FEATURE_UDHCP_PORT
 222         SERVER_PORT = 67;
 223         CLIENT_PORT = 68;
 224 #endif
 225         client_config.interface = "eth0";
 226         client_config.script = DEFAULT_SCRIPT;
 227
 228         /* Parse command line */
 229         /* Cc: mutually exclusive; O: list; -T,-t,-A take numeric param */
 230         opt_complementary = "c--C:C--c:O::T+:t+:A+";
 231 #if ENABLE_GETOPT_LONG
 232         applet_long_options = udhcpc_longopts;
 233 #endif
 234         opt = getopt32(argv, "c:CV:fbH:h:F:i:np:qRr:s:T:t:vSA:"
 235                 USE_FEATURE_UDHCPC_ARPING("aW:")
 236                 USE_FEATURE_UDHCP_PORT("P:")
 237                 "O:o"
 238                 , &str_c, &str_V, &str_h, &str_h, &str_F
 239                 , &client_config.interface, &client_config.pidfile, &str_r
 240                 , &client_config.script
 241                 , &discover_timeout, &discover_retries, &tryagain_timeout
 242                 USE_FEATURE_UDHCPC_ARPING(, &str_W)
 243                 USE_FEATURE_UDHCP_PORT(, &str_P)
 244                 , &list_O
 245                 );
 246
 247         if (opt & OPT_c)
 248                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, str_c, 0);
 249         //if (opt & OPT_C)
 250         if (opt & OPT_V)
 251                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
 252         if (opt & OPT_f)
 253                 client_config.foreground = 1;
 254         if (opt & OPT_b)
 255                 client_config.background_if_no_lease = 1;
 256         if (opt & (OPT_h|OPT_H))
 257                 client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
 258         if (opt & OPT_F) {
 259                 client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
 260                 /* Flags: 0000NEOS
 261                 S: 1 => Client requests Server to update A RR in DNS as well as PTR
 262                 O: 1 => Server indicates to client that DNS has been updated regardless
 263                 E: 1 => Name data is DNS format, i.e. <4>host<6>domain<4>com<0> not "host.domain.com"
 264                 N: 1 => Client requests Server to not update DNS
 265                 */
 266                 client_config.fqdn[OPT_DATA + 0] = 0x1;
 267                 /* client_config.fqdn[OPT_DATA + 1] = 0; - redundant */
 268                 /* client_config.fqdn[OPT_DATA + 2] = 0; - redundant */
 269         }
 270         // if (opt & OPT_i) client_config.interface = ...
 271         if (opt & OPT_n)
 272                 client_config.abort_if_no_lease = 1;
 273         // if (opt & OPT_p) client_config.pidfile = ...
 274         if (opt & OPT_q)
 275                 client_config.quit_after_lease = 1;
 276         if (opt & OPT_R)
 277                 client_config.release_on_quit = 1;
 278         if (opt & OPT_r)
 279                 requested_ip = inet_addr(str_r);
 280         // if (opt & OPT_s) client_config.script = ...
 281         // if (opt & OPT_T) discover_timeout = xatoi_u(str_T);
 282         // if (opt & OPT_t) discover_retries = xatoi_u(str_t);
 283         // if (opt & OPT_A) tryagain_timeout = xatoi_u(str_A);
 284         if (opt & OPT_v) {
 285                 puts("version "BB_VER);
 286                 return 0;
 287         }
 288         if (opt & OPT_S) {
 289                 openlog(applet_name, LOG_PID, LOG_LOCAL0);
 290                 logmode |= LOGMODE_SYSLOG;
 291         }
 292 #if ENABLE_FEATURE_UDHCP_PORT
 293         if (opt & OPT_P) {
 294                 CLIENT_PORT = xatou16(str_P);
 295                 SERVER_PORT = CLIENT_PORT - 1;
 296         }
 297 #endif
 298         if (opt & OPT_o)
 299                 client_config.no_default_options = 1;
 300         while (list_O) {
 301                 int n = index_in_strings(dhcp_option_strings, list_O->data);
 302                 if (n < 0)
 303                         bb_error_msg_and_die("unknown option '%s'", list_O->data);
 304                 n = dhcp_options[n].code;
 305                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
 306                 list_O = list_O->link;
 307         }
 308
 309         if (read_interface(client_config.interface, &client_config.ifindex,
 310                            NULL, client_config.arp))
 311                 return 1;
 312
 313         /* Make sure fd 0,1,2 are open */
 314         bb_sanitize_stdio();
 315         /* Equivalent of doing a fflush after every \n */
 316         setlinebuf(stdout);
 317
 318         /* Create pidfile */
 319         write_pidfile(client_config.pidfile);
 320         /* if (!..) bb_perror_msg("cannot create pidfile %s", pidfile); */
 321
 322         /* Goes to stdout and possibly syslog */
 323         bb_info_msg("%s (v"BB_VER") started", applet_name);
 324
 325         /* if not set, and not suppressed, setup the default client ID */
 326         if (!client_config.clientid && !(opt & OPT_C)) {
 327                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
 328                 client_config.clientid[OPT_DATA] = 1;
 329                 memcpy(client_config.clientid + OPT_DATA+1, client_config.arp, 6);
 330         }
 331
 332         if (!client_config.vendorclass)
 333                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, "udhcp "BB_VER, 0);
 334
 335         /* setup the signal pipe */
 336         udhcp_sp_setup();
 337
 338         state = INIT_SELECTING;
 339         udhcp_run_script(NULL, "deconfig");
 340         change_listen_mode(LISTEN_RAW);
 341         packet_num = 0;
 342         timeout = 0;
 343         already_waited_sec = 0;
 344
 345         /* Main event loop. select() waits on signal pipe and possibly
 346          * on sockfd.
 347          * "continue" statements in code below jump to the top of the loop.
 348          */
 349         for (;;) {
 350                 unsigned timestamp_before_wait;
 351
 352                 if (listen_mode != LISTEN_NONE && sockfd < 0) {
 353                         if (listen_mode == LISTEN_KERNEL)
 354                                 sockfd = listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
 355                         else
 356                                 sockfd = raw_socket(client_config.ifindex);
 357                 }
 358                 max_fd = udhcp_sp_fd_set(&rfds, sockfd);
 359
 360                 tv.tv_sec = timeout - already_waited_sec;
 361                 tv.tv_usec = 0;
 362                 retval = 0; /* If we already timed out, fall through, else... */
 363                 if (tv.tv_sec > 0) {
 364                         timestamp_before_wait = (unsigned)monotonic_sec();
 365                         DEBUG("Waiting on select...");
 366                         retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
 367                         if (retval < 0) {
 368                                 /* EINTR? A signal was caught, don't panic */
 369                                 if (errno == EINTR)
 370                                         continue;
 371                                 /* Else: an error occured, panic! */
 372                                 bb_perror_msg_and_die("select");
 373                         }
 374                 }
 375
 376                 /* If timeout dropped to zero, time to become active:
 377                  * resend discover/renew/whatever
 378                  */
 379                 if (retval == 0) {
 380                         /* We will restart wait afresh in any case */
 381                         already_waited_sec = 0;
 382
 383                         switch (state) {
 384                         case INIT_SELECTING:
 385                                 if (packet_num < discover_retries) {
 386                                         if (packet_num == 0)
 387                                                 xid = random_xid();
 388
 389                                         send_discover(xid, requested_ip); /* broadcast */
 390
 391                                         timeout = discover_timeout;
 392                                         packet_num++;
 393                                         continue;
 394                                 }
 395                                 udhcp_run_script(NULL, "leasefail");
 396                                 if (client_config.background_if_no_lease) {
 397                                         bb_info_msg("No lease, forking to background");
 398                                         client_background();
 399                                 } else if (client_config.abort_if_no_lease) {
 400                                         bb_info_msg("No lease, failing");
 401                                         retval = 1;
 402                                         goto ret;
 403                                 }
 404                                 /* wait before trying again */
 405                                 timeout = tryagain_timeout;
 406                                 packet_num = 0;
 407                                 continue;
 408                         case RENEW_REQUESTED:
 409                         case REQUESTING:
 410                                 if (packet_num < discover_retries) {
 411                                         /* send request packet */
 412                                         if (state == RENEW_REQUESTED) /* unicast */
 413                                                 send_renew(xid, server_addr, requested_ip);
 414                                         else /* broadcast */
 415                                                 send_selecting(xid, server_addr, requested_ip);
 416
 417                                         timeout = discover_timeout;
 418                                         packet_num++;
 419                                         continue;
 420                                 }
 421                                 /* timed out, go back to init state */
 422                                 if (state == RENEW_REQUESTED)
 423                                         udhcp_run_script(NULL, "deconfig");
 424                                 change_listen_mode(LISTEN_RAW);
 425                                 state = INIT_SELECTING;
 426                                 timeout = 0;
 427                                 packet_num = 0;
 428                                 continue;
 429                         case BOUND:
 430                                 /* Half of the lease passed, time to enter renewing state */
 431                                 change_listen_mode(LISTEN_KERNEL);
 432                                 DEBUG("Entering renew state");
 433                                 state = RENEWING;
 434                                 /* fall right through */
 435                         case RENEWING:
 436                                 if (timeout > 60) {
 437                                         /* send a request packet */
 438                                         send_renew(xid, server_addr, requested_ip); /* unicast */
 439                                         timeout >>= 1;
 440                                         continue;
 441                                 }
 442                                 /* Timed out, enter rebinding state */
 443                                 DEBUG("Entering rebinding state");
 444                                 state = REBINDING;
 445                                 /* fall right through */
 446                         case REBINDING:
 447                                 /* Lease is *really* about to run out,
 448                                  * try to find DHCP server using broadcast */
 449                                 if (timeout > 0) {
 450                                         /* send a request packet */
 451                                         send_renew(xid, 0, requested_ip); /* broadcast */
 452                                         timeout >>= 1;
 453                                         continue;
 454                                 }
 455                                 /* Timed out, enter init state */
 456                                 bb_info_msg("Lease lost, entering init state");
 457                                 udhcp_run_script(NULL, "deconfig");
 458                                 change_listen_mode(LISTEN_RAW);
 459                                 state = INIT_SELECTING;
 460                                 /*timeout = 0; - already is */
 461                                 packet_num = 0;
 462                                 continue;
 463                         /* case RELEASED: */
 464                         }
 465                         /* yah, I know, *you* say it would never happen */
 466                         timeout = INT_MAX;
 467                         continue; /* back to main loop */
 468                 }
 469
 470                 /* select() didn't timeout, something did happen. */
 471                 /* Is is a packet? */
 472                 if (listen_mode != LISTEN_NONE && FD_ISSET(sockfd, &rfds)) {
 473                         int len;
 474                         /* A packet is ready, read it */
 475
 476                         if (listen_mode == LISTEN_KERNEL)
 477                                 len = udhcp_recv_kernel_packet(&packet, sockfd);
 478                         else
 479                                 len = udhcp_recv_raw_packet(&packet, sockfd);
 480                         if (len == -1) { /* error is severe, reopen socket */
 481                                 DEBUG("error on read, %s, reopening socket", strerror(errno));
 482                                 sleep(discover_timeout); /* 3 seconds by default */
 483                                 change_listen_mode(listen_mode); /* just close and reopen */
 484                         }
 485                         /* If this packet will turn out to be unrelated/bogus,
 486                          * we will go back and wait for next one.
 487                          * Be sure timeout is properly decreased. */
 488                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
 489                         if (len < 0)
 490                                 continue;
 491
 492                         if (packet.xid != xid) {
 493                                 DEBUG("Ignoring XID %x (our xid is %x)",
 494                                         (unsigned)packet.xid, (unsigned)xid);
 495                                 continue;
 496                         }
 497
 498                         /* Ignore packets that aren't for us */
 499                         if (memcmp(packet.chaddr, client_config.arp, 6)) {
 500                                 DEBUG("Packet does not have our chaddr - ignoring");
 501                                 continue;
 502                         }
 503
 504                         message = get_option(&packet, DHCP_MESSAGE_TYPE);
 505                         if (message == NULL) {
 506                                 bb_error_msg("cannot get message type from packet - ignoring");
 507                                 continue;
 508                         }
 509
 510                         switch (state) {
 511                         case INIT_SELECTING:
 512                                 /* Must be a DHCPOFFER to one of our xid's */
 513                                 if (*message == DHCPOFFER) {
 514                         /* TODO: why we don't just fetch server's IP from IP header? */
 515                                         temp = get_option(&packet, DHCP_SERVER_ID);
 516                                         if (!temp) {
 517                                                 bb_error_msg("no server ID in message");
 518                                                 continue;
 519                                                 /* still selecting - this server looks bad */
 520                                         }
 521                                         /* it IS unaligned sometimes, don't "optimize" */
 522                                         server_addr = get_unaligned_u32p((uint32_t*)temp);
 523                                         xid = packet.xid;
 524                                         requested_ip = packet.yiaddr;
 525
 526                                         /* enter requesting state */
 527                                         state = REQUESTING;
 528                                         timeout = 0;
 529                                         packet_num = 0;
 530                                         already_waited_sec = 0;
 531                                 }
 532                                 continue;
 533                         case RENEW_REQUESTED:
 534                         case REQUESTING:
 535                         case RENEWING:
 536                         case REBINDING:
 537                                 if (*message == DHCPACK) {
 538                                         temp = get_option(&packet, DHCP_LEASE_TIME);
 539                                         if (!temp) {
 540                                                 bb_error_msg("no lease time with ACK, using 1 hour lease");
 541                                                 lease_seconds = 60 * 60;
 542                                         } else {
 543                                                 /* can be misaligned, thus memcpy */
 544                                                 memcpy(&lease_seconds, temp, 4);
 545                                                 lease_seconds = ntohl(lease_seconds);
 546                                                 lease_seconds &= 0x0fffffff; /* paranoia: must not be prone to overflows */
 547                                                 if (lease_seconds < 10) /* and not too small */
 548                                                         lease_seconds = 10;
 549                                         }
 550 #if ENABLE_FEATURE_UDHCPC_ARPING
 551                                         if (opt & OPT_a) {
 552                                                 if (!arpping(packet.yiaddr,
 553                                                             (uint32_t) 0,
 554                                                             client_config.arp,
 555                                                             client_config.interface)
 556                                                 ) {
 557                                                         bb_info_msg("offered address is in use "
 558                                                                 "(got ARP reply), declining");
 559                                                         send_decline(xid, server_addr, packet.yiaddr);
 560
 561                                                         if (state != REQUESTING)
 562                                                                 udhcp_run_script(NULL, "deconfig");
 563                                                         change_listen_mode(LISTEN_RAW);
 564                                                         state = INIT_SELECTING;
 565                                                         requested_ip = 0;
 566                                                         timeout = tryagain_timeout;
 567                                                         packet_num = 0;
 568                                                         already_waited_sec = 0;
 569                                                         continue; /* back to main loop */
 570                                                 }
 571                                         }
 572 #endif
 573                                         /* enter bound state */
 574                                         timeout = lease_seconds / 2;
 575                                         {
 576                                                 struct in_addr temp_addr;
 577                                                 temp_addr.s_addr = packet.yiaddr;
 578                                                 bb_info_msg("Lease of %s obtained, lease time %u",
 579                                                         inet_ntoa(temp_addr), (unsigned)lease_seconds);
 580                                         }
 581                                         requested_ip = packet.yiaddr;
 582                                         udhcp_run_script(&packet,
 583                                                    ((state == RENEWING || state == REBINDING) ? "renew" : "bound"));
 584
 585                                         state = BOUND;
 586                                         change_listen_mode(LISTEN_NONE);
 587                                         if (client_config.quit_after_lease) {
 588                                                 if (client_config.release_on_quit)
 589                                                         perform_release(requested_ip, server_addr);
 590                                                 goto ret0;
 591                                         }
 592                                         if (!client_config.foreground)
 593                                                 client_background();
 594
 595                                         already_waited_sec = 0;
 596                                         continue; /* back to main loop */
 597                                 }
 598                                 if (*message == DHCPNAK) {
 599                                         /* return to init state */
 600                                         bb_info_msg("Received DHCP NAK");
 601                                         udhcp_run_script(&packet, "nak");
 602                                         if (state != REQUESTING)
 603                                                 udhcp_run_script(NULL, "deconfig");
 604                                         change_listen_mode(LISTEN_RAW);
 605                                         sleep(3); /* avoid excessive network traffic */
 606                                         state = INIT_SELECTING;
 607                                         requested_ip = 0;
 608                                         timeout = 0;
 609                                         packet_num = 0;
 610                                         already_waited_sec = 0;
 611                                 }
 612                                 continue;
 613                         /* case BOUND, RELEASED: - ignore all packets */
 614                         }
 615                         continue; /* back to main loop */
 616                 }
 617
 618                 /* select() didn't timeout, something did happen.
 619                  * But it wasn't a packet. It's a signal pipe then. */
 620                 {
 621                         int signo = udhcp_sp_read(&rfds);
 622                         switch (signo) {
 623                         case SIGUSR1:
 624                                 perform_renew();
 625                                 /* start things over */
 626                                 packet_num = 0;
 627                                 /* Kill any timeouts because the user wants this to hurry along */
 628                                 timeout = 0;
 629                                 break;
 630                         case SIGUSR2:
 631                                 perform_release(requested_ip, server_addr);
 632                                 timeout = INT_MAX;
 633                                 break;
 634                         case SIGTERM:
 635                                 bb_info_msg("Received SIGTERM");
 636                                 if (client_config.release_on_quit)
 637                                         perform_release(requested_ip, server_addr);
 638                                 goto ret0;
 639                         }
 640                 }
 641         } /* for (;;) - main loop ends */
 642
 643  ret0:
 644         retval = 0;
 645  ret:
 646         /*if (client_config.pidfile) - remove_pidfile has its own check */
 647                 remove_pidfile(client_config.pidfile);
 648         return retval;
 649 }