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 timeout; /* = 0. Must be signed */
  22 static uint32_t requested_ip; /* = 0 */
  23 static uint32_t server_addr;
  24 static int sockfd = -1;
  25
  26 #define LISTEN_NONE 0
  27 #define LISTEN_KERNEL 1
  28 #define LISTEN_RAW 2
  29 static smallint listen_mode;
  30
  31 static smallint state;
  32
  33 /* struct client_config_t client_config is in bb_common_bufsiz1 */
  34
  35
  36 /* just a little helper */
  37 static void change_listen_mode(int new_mode)
  38 {
  39         DEBUG("entering %s listen mode",
  40                 new_mode ? (new_mode == 1 ? "kernel" : "raw") : "none");
  41         if (sockfd >= 0) {
  42                 close(sockfd);
  43                 sockfd = -1;
  44         }
  45         listen_mode = new_mode;
  46 }
  47
  48
  49 /* perform a renew */
  50 static void perform_renew(void)
  51 {
  52         bb_info_msg("Performing a DHCP renew");
  53         switch (state) {
  54         case BOUND:
  55                 change_listen_mode(LISTEN_KERNEL);
  56         case RENEWING:
  57         case REBINDING:
  58                 state = RENEW_REQUESTED;
  59                 break;
  60         case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
  61                 udhcp_run_script(NULL, "deconfig");
  62         case REQUESTING:
  63         case RELEASED:
  64                 change_listen_mode(LISTEN_RAW);
  65                 state = INIT_SELECTING;
  66                 break;
  67         case INIT_SELECTING:
  68                 break;
  69         }
  70 }
  71
  72
  73 /* perform a release */
  74 static void perform_release(void)
  75 {
  76         char buffer[sizeof("255.255.255.255")];
  77         struct in_addr temp_addr;
  78
  79         /* send release packet */
  80         if (state == BOUND || state == RENEWING || state == REBINDING) {
  81                 temp_addr.s_addr = server_addr;
  82                 strcpy(buffer, inet_ntoa(temp_addr));
  83                 temp_addr.s_addr = requested_ip;
  84                 bb_info_msg("Unicasting a release of %s to %s",
  85                                 inet_ntoa(temp_addr), buffer);
  86                 send_release(server_addr, requested_ip); /* unicast */
  87                 udhcp_run_script(NULL, "deconfig");
  88         }
  89         bb_info_msg("Entering released state");
  90
  91         change_listen_mode(LISTEN_NONE);
  92         state = RELEASED;
  93         timeout = INT_MAX;
  94 }
  95
  96
  97 static void client_background(void)
  98 {
  99 #if !BB_MMU
 100         bb_error_msg("cannot background in uclinux (yet)");
 101 /* ... mainly because udhcpc calls client_background()
 102  * in _the _middle _of _udhcpc _run_, not at the start!
 103  * If that will be properly disabled for NOMMU, client_background()
 104  * will work on NOMMU too */
 105 #else
 106         bb_daemonize(0);
 107         logmode &= ~LOGMODE_STDIO;
 108         /* rewrite pidfile, as our pid is different now */
 109         write_pidfile(client_config.pidfile);
 110 #endif
 111         /* Do not fork again. */
 112         client_config.foreground = 1;
 113         client_config.background_if_no_lease = 0;
 114 }
 115
 116
 117 static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
 118 {
 119         uint8_t *storage;
 120         int len = strlen(str);
 121         if (len > 255) len = 255;
 122         storage = xzalloc(len + extra + OPT_DATA);
 123         storage[OPT_CODE] = code;
 124         storage[OPT_LEN] = len + extra;
 125         memcpy(storage + extra + OPT_DATA, str, len);
 126         return storage;
 127 }
 128
 129
 130 int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 131 int udhcpc_main(int argc ATTRIBUTE_UNUSED, char **argv)
 132 {
 133         uint8_t *temp, *message;
 134         char *str_c, *str_V, *str_h, *str_F, *str_r;
 135         USE_FEATURE_UDHCP_PORT(char *str_P;)
 136         llist_t *list_O = NULL;
 137 #if ENABLE_FEATURE_UDHCPC_ARPING
 138         char *str_W;
 139 #endif
 140         int tryagain_timeout = 20;
 141         int discover_timeout = 3;
 142         int discover_retries = 3;
 143         uint32_t xid = 0;
 144         uint32_t lease_seconds = 0; /* can be given as 32-bit quantity */
 145         int packet_num;
 146         unsigned already_waited_sec;
 147         unsigned opt;
 148         int max_fd;
 149         int retval;
 150         struct timeval tv;
 151         struct dhcpMessage packet;
 152         fd_set rfds;
 153
 154         enum {
 155                 OPT_c = 1 << 0,
 156                 OPT_C = 1 << 1,
 157                 OPT_V = 1 << 2,
 158                 OPT_f = 1 << 3,
 159                 OPT_b = 1 << 4,
 160                 OPT_H = 1 << 5,
 161                 OPT_h = 1 << 6,
 162                 OPT_F = 1 << 7,
 163                 OPT_i = 1 << 8,
 164                 OPT_n = 1 << 9,
 165                 OPT_p = 1 << 10,
 166                 OPT_q = 1 << 11,
 167                 OPT_R = 1 << 12,
 168                 OPT_r = 1 << 13,
 169                 OPT_s = 1 << 14,
 170                 OPT_T = 1 << 15,
 171                 OPT_t = 1 << 16,
 172                 OPT_v = 1 << 17,
 173                 OPT_S = 1 << 18,
 174                 OPT_A = 1 << 19,
 175 #if ENABLE_FEATURE_UDHCPC_ARPING
 176                 OPT_a = 1 << 20,
 177                 OPT_W = 1 << 21,
 178 #endif
 179                 OPT_P = 1 << 22,
 180                 OPT_o = 1 << 23,
 181         };
 182 #if ENABLE_GETOPT_LONG
 183         static const char udhcpc_longopts[] ALIGN1 =
 184                 "clientid\0"       Required_argument "c"
 185                 "clientid-none\0"  No_argument       "C"
 186                 "vendorclass\0"    Required_argument "V"
 187                 "foreground\0"     No_argument       "f"
 188                 "background\0"     No_argument       "b"
 189                 "hostname\0"       Required_argument "H"
 190                 "fqdn\0"           Required_argument "F"
 191                 "interface\0"      Required_argument "i"
 192                 "now\0"            No_argument       "n"
 193                 "pidfile\0"        Required_argument "p"
 194                 "quit\0"           No_argument       "q"
 195                 "release\0"        No_argument       "R"
 196                 "request\0"        Required_argument "r"
 197                 "script\0"         Required_argument "s"
 198                 "timeout\0"        Required_argument "T"
 199                 "version\0"        No_argument       "v"
 200                 "retries\0"        Required_argument "t"
 201                 "tryagain\0"       Required_argument "A"
 202                 "syslog\0"         No_argument       "S"
 203 #if ENABLE_FEATURE_UDHCPC_ARPING
 204                 "arping\0"         No_argument       "a"
 205 #endif
 206                 "request-option\0" Required_argument "O"
 207 #if ENABLE_FEATURE_UDHCP_PORT
 208                 "client-port\0"    Required_argument "P"
 209 #endif
 210                 "no-default-options\0" No_argument   "o"
 211                 ;
 212 #endif
 213         /* Default options. */
 214 #if ENABLE_FEATURE_UDHCP_PORT
 215         SERVER_PORT = 67;
 216         CLIENT_PORT = 68;
 217 #endif
 218         client_config.interface = "eth0";
 219         client_config.script = DEFAULT_SCRIPT;
 220
 221         /* Parse command line */
 222         /* Cc: mutually exclusive; O: list; -T,-t,-A take numeric param */
 223         opt_complementary = "c--C:C--c:O::T+:t+:A+";
 224 #if ENABLE_GETOPT_LONG
 225         applet_long_options = udhcpc_longopts;
 226 #endif
 227         opt = getopt32(argv, "c:CV:fbH:h:F:i:np:qRr:s:T:t:vSA:"
 228                 USE_FEATURE_UDHCPC_ARPING("aW:")
 229                 USE_FEATURE_UDHCP_PORT("P:")
 230                 "O:o"
 231                 , &str_c, &str_V, &str_h, &str_h, &str_F
 232                 , &client_config.interface, &client_config.pidfile, &str_r
 233                 , &client_config.script
 234                 , &discover_timeout, &discover_retries, &tryagain_timeout
 235                 USE_FEATURE_UDHCPC_ARPING(, &str_W)
 236                 USE_FEATURE_UDHCP_PORT(, &str_P)
 237                 , &list_O
 238                 );
 239
 240         if (opt & OPT_c)
 241                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, str_c, 0);
 242         //if (opt & OPT_C)
 243         if (opt & OPT_V)
 244                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
 245         if (opt & OPT_f)
 246                 client_config.foreground = 1;
 247         if (opt & OPT_b)
 248                 client_config.background_if_no_lease = 1;
 249         if (opt & (OPT_h|OPT_H))
 250                 client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
 251         if (opt & OPT_F) {
 252                 client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
 253                 /* Flags: 0000NEOS
 254                 S: 1 => Client requests Server to update A RR in DNS as well as PTR
 255                 O: 1 => Server indicates to client that DNS has been updated regardless
 256                 E: 1 => Name data is DNS format, i.e. <4>host<6>domain<4>com<0> not "host.domain.com"
 257                 N: 1 => Client requests Server to not update DNS
 258                 */
 259                 client_config.fqdn[OPT_DATA + 0] = 0x1;
 260                 /* client_config.fqdn[OPT_DATA + 1] = 0; - redundant */
 261                 /* client_config.fqdn[OPT_DATA + 2] = 0; - redundant */
 262         }
 263         // if (opt & OPT_i) client_config.interface = ...
 264         if (opt & OPT_n)
 265                 client_config.abort_if_no_lease = 1;
 266         // if (opt & OPT_p) client_config.pidfile = ...
 267         if (opt & OPT_q)
 268                 client_config.quit_after_lease = 1;
 269         if (opt & OPT_R)
 270                 client_config.release_on_quit = 1;
 271         if (opt & OPT_r)
 272                 requested_ip = inet_addr(str_r);
 273         // if (opt & OPT_s) client_config.script = ...
 274         // if (opt & OPT_T) discover_timeout = xatoi_u(str_T);
 275         // if (opt & OPT_t) discover_retries = xatoi_u(str_t);
 276         // if (opt & OPT_A) tryagain_timeout = xatoi_u(str_A);
 277         if (opt & OPT_v) {
 278                 puts("version "BB_VER);
 279                 return 0;
 280         }
 281         if (opt & OPT_S) {
 282                 openlog(applet_name, LOG_PID, LOG_LOCAL0);
 283                 logmode |= LOGMODE_SYSLOG;
 284         }
 285 #if ENABLE_FEATURE_UDHCP_PORT
 286         if (opt & OPT_P) {
 287                 CLIENT_PORT = xatou16(str_P);
 288                 SERVER_PORT = CLIENT_PORT - 1;
 289         }
 290 #endif
 291         if (opt & OPT_o)
 292                 client_config.no_default_options = 1;
 293         while (list_O) {
 294                 int n = index_in_strings(dhcp_option_strings, list_O->data);
 295                 if (n < 0)
 296                         bb_error_msg_and_die("unknown option '%s'", list_O->data);
 297                 n = dhcp_options[n].code;
 298                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
 299                 list_O = list_O->link;
 300         }
 301
 302         if (read_interface(client_config.interface, &client_config.ifindex,
 303                            NULL, client_config.arp))
 304                 return 1;
 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         /* if (!..) bb_perror_msg("cannot create pidfile %s", pidfile); */
 314
 315         /* Goes to stdout and possibly syslog */
 316         bb_info_msg("%s (v"BB_VER") started", applet_name);
 317
 318         /* if not set, and not suppressed, setup the default client ID */
 319         if (!client_config.clientid && !(opt & OPT_C)) {
 320                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
 321                 client_config.clientid[OPT_DATA] = 1;
 322                 memcpy(client_config.clientid + OPT_DATA+1, client_config.arp, 6);
 323         }
 324
 325         if (!client_config.vendorclass)
 326                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, "udhcp "BB_VER, 0);
 327
 328         /* setup the signal pipe */
 329         udhcp_sp_setup();
 330
 331         state = INIT_SELECTING;
 332         udhcp_run_script(NULL, "deconfig");
 333         change_listen_mode(LISTEN_RAW);
 334         packet_num = 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                 unsigned timestamp_before_wait;
 343
 344                 if (listen_mode != LISTEN_NONE && sockfd < 0) {
 345                         if (listen_mode == LISTEN_KERNEL)
 346                                 sockfd = listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
 347                         else
 348                                 sockfd = raw_socket(client_config.ifindex);
 349                 }
 350                 max_fd = udhcp_sp_fd_set(&rfds, sockfd);
 351
 352                 tv.tv_sec = timeout - already_waited_sec;
 353                 tv.tv_usec = 0;
 354                 retval = 0; /* If we already timed out, fall through, else... */
 355                 if (tv.tv_sec > 0) {
 356                         timestamp_before_wait = (unsigned)monotonic_sec();
 357                         DEBUG("Waiting on select...");
 358                         retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
 359                         if (retval < 0) {
 360                                 /* EINTR? A signal was caught, don't panic */
 361                                 if (errno == EINTR)
 362                                         continue;
 363                                 /* Else: an error occured, panic! */
 364                                 bb_perror_msg_and_die("select");
 365                         }
 366                 }
 367
 368                 /* If timeout dropped to zero, time to become active:
 369                  * resend discover/renew/whatever
 370                  */
 371                 if (retval == 0) {
 372                         /* We will restart wait afresh in any case */
 373                         already_waited_sec = 0;
 374
 375                         switch (state) {
 376                         case INIT_SELECTING:
 377                                 if (packet_num < discover_retries) {
 378                                         if (packet_num == 0)
 379                                                 xid = random_xid();
 380
 381                                         send_discover(xid, requested_ip); /* broadcast */
 382
 383                                         timeout = discover_timeout;
 384                                         packet_num++;
 385                                         continue;
 386                                 }
 387                                 udhcp_run_script(NULL, "leasefail");
 388                                 if (client_config.background_if_no_lease) {
 389                                         bb_info_msg("No lease, forking to background");
 390                                         client_background();
 391                                 } else if (client_config.abort_if_no_lease) {
 392                                         bb_info_msg("No lease, failing");
 393                                         retval = 1;
 394                                         goto ret;
 395                                 }
 396                                 /* wait before trying again */
 397                                 timeout = tryagain_timeout;
 398                                 packet_num = 0;
 399                                 continue;
 400                         case RENEW_REQUESTED:
 401                         case REQUESTING:
 402                                 if (packet_num < discover_retries) {
 403                                         /* send request packet */
 404                                         if (state == RENEW_REQUESTED) /* unicast */
 405                                                 send_renew(xid, server_addr, requested_ip);
 406                                         else /* broadcast */
 407                                                 send_selecting(xid, server_addr, requested_ip);
 408
 409                                         timeout = discover_timeout;
 410                                         packet_num++;
 411                                         continue;
 412                                 }
 413                                 /* timed out, go back to init state */
 414                                 if (state == RENEW_REQUESTED)
 415                                         udhcp_run_script(NULL, "deconfig");
 416                                 change_listen_mode(LISTEN_RAW);
 417                                 state = INIT_SELECTING;
 418                                 timeout = 0;
 419                                 packet_num = 0;
 420                                 continue;
 421                         case BOUND:
 422                                 /* Half of the lease passed, time to enter renewing state */
 423                                 change_listen_mode(LISTEN_KERNEL);
 424                                 DEBUG("Entering renew state");
 425                                 state = RENEWING;
 426                                 /* fall right through */
 427                         case RENEWING:
 428                                 if (timeout > 60) {
 429                                         /* send a request packet */
 430                                         send_renew(xid, server_addr, requested_ip); /* unicast */
 431                                         timeout >>= 1;
 432                                         continue;
 433                                 }
 434                                 /* Timed out, enter rebinding state */
 435                                 DEBUG("Entering rebinding state");
 436                                 state = REBINDING;
 437                                 /* fall right through */
 438                         case REBINDING:
 439                                 /* Lease is *really* about to run out,
 440                                  * try to find DHCP server using broadcast */
 441                                 if (timeout > 0) {
 442                                         /* send a request packet */
 443                                         send_renew(xid, 0, requested_ip); /* broadcast */
 444                                         timeout >>= 1;
 445                                         continue;
 446                                 }
 447                                 /* Timed out, enter init state */
 448                                 bb_info_msg("Lease lost, entering init state");
 449                                 udhcp_run_script(NULL, "deconfig");
 450                                 change_listen_mode(LISTEN_RAW);
 451                                 state = INIT_SELECTING;
 452                                 /*timeout = 0; - already is */
 453                                 packet_num = 0;
 454                                 continue;
 455                         /* case RELEASED: */
 456                         }
 457                         /* yah, I know, *you* say it would never happen */
 458                         timeout = INT_MAX;
 459                         continue; /* back to main loop */
 460                 }
 461
 462                 /* select() didn't timeout, something did happen. */
 463                 /* Is is a packet? */
 464                 if (listen_mode != LISTEN_NONE && FD_ISSET(sockfd, &rfds)) {
 465                         int len;
 466                         /* A packet is ready, read it */
 467
 468                         if (listen_mode == LISTEN_KERNEL)
 469                                 len = udhcp_recv_kernel_packet(&packet, sockfd);
 470                         else
 471                                 len = udhcp_recv_raw_packet(&packet, sockfd);
 472                         if (len == -1) { /* error is severe, reopen socket */
 473                                 DEBUG("error on read, %s, reopening socket", strerror(errno));
 474                                 sleep(discover_timeout); /* 3 seconds by default */
 475                                 change_listen_mode(listen_mode); /* just close and reopen */
 476                         }
 477                         /* If this packet will turn out to be unrelated/bogus,
 478                          * we will go back and wait for next one.
 479                          * Be sure timeout is properly decreased. */
 480                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
 481                         if (len < 0)
 482                                 continue;
 483
 484                         if (packet.xid != xid) {
 485                                 DEBUG("Ignoring XID %x (our xid is %x)",
 486                                         (unsigned)packet.xid, (unsigned)xid);
 487                                 continue;
 488                         }
 489
 490                         /* Ignore packets that aren't for us */
 491                         if (memcmp(packet.chaddr, client_config.arp, 6)) {
 492                                 DEBUG("Packet does not have our chaddr - ignoring");
 493                                 continue;
 494                         }
 495
 496                         message = get_option(&packet, DHCP_MESSAGE_TYPE);
 497                         if (message == NULL) {
 498                                 bb_error_msg("cannot get message type from packet - ignoring");
 499                                 continue;
 500                         }
 501
 502                         switch (state) {
 503                         case INIT_SELECTING:
 504                                 /* Must be a DHCPOFFER to one of our xid's */
 505                                 if (*message == DHCPOFFER) {
 506                         /* TODO: why we don't just fetch server's IP from IP header? */
 507                                         temp = get_option(&packet, DHCP_SERVER_ID);
 508                                         if (!temp) {
 509                                                 bb_error_msg("no server ID in message");
 510                                                 continue;
 511                                                 /* still selecting - this server looks bad */
 512                                         }
 513                                         /* can be misaligned, thus memcpy */
 514                                         memcpy(&server_addr, temp, 4);
 515                                         xid = packet.xid;
 516                                         requested_ip = packet.yiaddr;
 517
 518                                         /* enter requesting state */
 519                                         state = REQUESTING;
 520                                         timeout = 0;
 521                                         packet_num = 0;
 522                                         already_waited_sec = 0;
 523                                 }
 524                                 continue;
 525                         case RENEW_REQUESTED:
 526                         case REQUESTING:
 527                         case RENEWING:
 528                         case REBINDING:
 529                                 if (*message == DHCPACK) {
 530                                         temp = get_option(&packet, DHCP_LEASE_TIME);
 531                                         if (!temp) {
 532                                                 bb_error_msg("no lease time with ACK, using 1 hour lease");
 533                                                 lease_seconds = 60 * 60;
 534                                         } else {
 535                                                 /* can be misaligned, thus memcpy */
 536                                                 memcpy(&lease_seconds, temp, 4);
 537                                                 lease_seconds = ntohl(lease_seconds);
 538                                                 lease_seconds &= 0x0fffffff; /* paranoia: must not be negative */
 539                                         }
 540 #if ENABLE_FEATURE_UDHCPC_ARPING
 541                                         if (opt & OPT_a) {
 542                                                 if (!arpping(packet.yiaddr,
 543                                                             (uint32_t) 0,
 544                                                             client_config.arp,
 545                                                             client_config.interface)
 546                                                 ) {
 547                                                         bb_info_msg("offered address is in use "
 548                                                                 "(got ARP reply), declining");
 549                                                         send_decline(xid, server_addr, packet.yiaddr);
 550
 551                                                         if (state != REQUESTING)
 552                                                                 udhcp_run_script(NULL, "deconfig");
 553                                                         change_listen_mode(LISTEN_RAW);
 554                                                         state = INIT_SELECTING;
 555                                                         requested_ip = 0;
 556                                                         timeout = tryagain_timeout;
 557                                                         packet_num = 0;
 558                                                         already_waited_sec = 0;
 559                                                         continue; /* back to main loop */
 560                                                 }
 561                                         }
 562 #endif
 563                                         /* enter bound state */
 564                                         timeout = lease_seconds / 2;
 565                                         {
 566                                                 struct in_addr temp_addr;
 567                                                 temp_addr.s_addr = packet.yiaddr;
 568                                                 bb_info_msg("Lease of %s obtained, lease time %u",
 569                                                         inet_ntoa(temp_addr), (unsigned)lease_seconds);
 570                                         }
 571                                         requested_ip = packet.yiaddr;
 572                                         udhcp_run_script(&packet,
 573                                                    ((state == RENEWING || state == REBINDING) ? "renew" : "bound"));
 574
 575                                         state = BOUND;
 576                                         change_listen_mode(LISTEN_NONE);
 577                                         if (client_config.quit_after_lease) {
 578                                                 if (client_config.release_on_quit)
 579                                                         perform_release();
 580                                                 goto ret0;
 581                                         }
 582                                         if (!client_config.foreground)
 583                                                 client_background();
 584
 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();
 622                                 break;
 623                         case SIGTERM:
 624                                 bb_info_msg("Received SIGTERM");
 625                                 if (client_config.release_on_quit)
 626                                         perform_release();
 627                                 goto ret0;
 628                         }
 629                 }
 630         } /* for (;;) - main loop ends */
 631
 632  ret0:
 633         retval = 0;
 634  ret:
 635         /*if (client_config.pidfile) - remove_pidfile has its own check */
 636                 remove_pidfile(client_config.pidfile);
 637         return retval;
 638 }