networking/udhcp/dhcpc.c

   1 /* vi: set sw=4 ts=4: */
   2 /* dhcpc.c
   3  *
   4  * udhcp DHCP client
   5  *
   6  * Russ Dill <Russ.Dill@asu.edu> July 2001
   7  *
   8  * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
   9  */
  10
  11 #include <getopt.h>
  12 #include <syslog.h>
  13
  14 /* Override ENABLE_FEATURE_PIDFILE - ifupdown needs our pidfile to always exist */
  15 #define WANT_PIDFILE 1
  16 #include "common.h"
  17 #include "dhcpd.h"
  18 #include "dhcpc.h"
  19 #include "options.h"
  20
  21
  22 /* Something is definitely wrong here. IPv4 addresses
  23  * in variables of type long?? BTW, we use inet_ntoa()
  24  * in the code. Manpage says that struct in_addr has a member of type long (!)
  25  * which holds IPv4 address, and the struct is passed by value (!!)
  26  */
  27 static unsigned timeout;
  28 static uint32_t requested_ip; /* = 0 */
  29 static uint32_t server_addr;
  30 static int packet_num; /* = 0 */
  31 static int sockfd = -1;
  32
  33 #define LISTEN_NONE 0
  34 #define LISTEN_KERNEL 1
  35 #define LISTEN_RAW 2
  36 static smallint listen_mode;
  37
  38 static smallint state;
  39
  40 struct client_config_t client_config;
  41
  42
  43 /* just a little helper */
  44 static void change_mode(int new_mode)
  45 {
  46         DEBUG("entering %s listen mode",
  47                 new_mode ? (new_mode == 1 ? "kernel" : "raw") : "none");
  48         if (sockfd >= 0) {
  49                 close(sockfd);
  50                 sockfd = -1;
  51         }
  52         listen_mode = new_mode;
  53 }
  54
  55
  56 /* perform a renew */
  57 static void perform_renew(void)
  58 {
  59         bb_info_msg("Performing a DHCP renew");
  60         switch (state) {
  61         case BOUND:
  62                 change_mode(LISTEN_KERNEL);
  63         case RENEWING:
  64         case REBINDING:
  65                 state = RENEW_REQUESTED;
  66                 break;
  67         case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
  68                 udhcp_run_script(NULL, "deconfig");
  69         case REQUESTING:
  70         case RELEASED:
  71                 change_mode(LISTEN_RAW);
  72                 state = INIT_SELECTING;
  73                 break;
  74         case INIT_SELECTING:
  75                 break;
  76         }
  77
  78         /* start things over */
  79         packet_num = 0;
  80
  81         /* Kill any timeouts because the user wants this to hurry along */
  82         timeout = 0;
  83 }
  84
  85
  86 /* perform a release */
  87 static void perform_release(void)
  88 {
  89         char buffer[sizeof("255.255.255.255")];
  90         struct in_addr temp_addr;
  91
  92         /* send release packet */
  93         if (state == BOUND || state == RENEWING || state == REBINDING) {
  94                 temp_addr.s_addr = server_addr;
  95                 strcpy(buffer, inet_ntoa(temp_addr));
  96                 temp_addr.s_addr = requested_ip;
  97                 bb_info_msg("Unicasting a release of %s to %s",
  98                                 inet_ntoa(temp_addr), buffer);
  99                 send_release(server_addr, requested_ip); /* unicast */
 100                 udhcp_run_script(NULL, "deconfig");
 101         }
 102         bb_info_msg("Entering released state");
 103
 104         change_mode(LISTEN_NONE);
 105         state = RELEASED;
 106         timeout = INT_MAX;
 107 }
 108
 109
 110 static void client_background(void)
 111 {
 112 #ifdef __uClinux__
 113         bb_error_msg("cannot background in uclinux (yet)");
 114 /* ... mainly because udhcpc calls client_background()
 115  * in _the _middle _of _udhcpc _run_, not at the start!
 116  * If that will be properly disabled for NOMMU, client_background()
 117  * will work on NOMMU too */
 118 #else
 119         bb_daemonize(0);
 120         logmode &= ~LOGMODE_STDIO;
 121         /* rewrite pidfile, as our pid is different now */
 122         if (client_config.pidfile)
 123                 write_pidfile(client_config.pidfile);
 124 #endif
 125         /* Do not fork again. */
 126         client_config.foreground = 1;
 127         client_config.background_if_no_lease = 0;
 128 }
 129
 130
 131 static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
 132 {
 133         uint8_t *storage;
 134         int len = strlen(str);
 135         if (len > 255) len = 255;
 136         storage = xzalloc(len + extra + OPT_DATA);
 137         storage[OPT_CODE] = code;
 138         storage[OPT_LEN] = len + extra;
 139         memcpy(storage + extra + OPT_DATA, str, len);
 140         return storage;
 141 }
 142
 143
 144 int udhcpc_main(int argc, char **argv);
 145 int udhcpc_main(int argc, char **argv)
 146 {
 147         uint8_t *temp, *message;
 148         char *str_c, *str_V, *str_h, *str_F, *str_r, *str_T, *str_t;
 149         uint32_t xid = 0;
 150         uint32_t lease = 0; /* can be given as 32-bit quantity */
 151         unsigned t1 = 0, t2 = 0;
 152         unsigned start = 0;
 153         unsigned now;
 154         unsigned opt;
 155         int max_fd;
 156         int sig;
 157         int retval;
 158         int len;
 159         int no_clientid = 0;
 160         fd_set rfds;
 161         struct timeval tv;
 162         struct dhcpMessage packet;
 163         struct in_addr temp_addr;
 164
 165         enum {
 166                 OPT_c = 1 << 0,
 167                 OPT_C = 1 << 1,
 168                 OPT_V = 1 << 2,
 169                 OPT_f = 1 << 3,
 170                 OPT_b = 1 << 4,
 171                 OPT_H = 1 << 5,
 172                 OPT_h = 1 << 6,
 173                 OPT_F = 1 << 7,
 174                 OPT_i = 1 << 8,
 175                 OPT_n = 1 << 9,
 176                 OPT_p = 1 << 10,
 177                 OPT_q = 1 << 11,
 178                 OPT_R = 1 << 12,
 179                 OPT_r = 1 << 13,
 180                 OPT_s = 1 << 14,
 181                 OPT_T = 1 << 15,
 182                 OPT_t = 1 << 16,
 183                 OPT_v = 1 << 17,
 184         };
 185 #if ENABLE_GETOPT_LONG
 186         static const char udhcpc_longopts[] =
 187                 "clientid\0"      Required_argument "c"
 188                 "clientid-none\0" No_argument       "C"
 189                 "vendorclass\0"   Required_argument "V"
 190                 "foreground\0"    No_argument       "f"
 191                 "background\0"    No_argument       "b"
 192                 "hostname\0"      Required_argument "H"
 193                 "hostname\0"      Required_argument "h"
 194                 "fqdn\0"          Required_argument "F"
 195                 "interface\0"     Required_argument "i"
 196                 "now\0"           No_argument       "n"
 197                 "pidfile\0"       Required_argument "p"
 198                 "quit\0"          No_argument       "q"
 199                 "release\0"       No_argument       "R"
 200                 "request\0"       Required_argument "r"
 201                 "script\0"        Required_argument "s"
 202                 "timeout\0"       Required_argument "T"
 203                 "version\0"       No_argument       "v"
 204                 "retries\0"       Required_argument "t"
 205                 ;
 206 #endif
 207         /* Default options. */
 208         client_config.interface = "eth0";
 209         client_config.script = DEFAULT_SCRIPT;
 210         client_config.retries = 3;
 211         client_config.timeout = 3;
 212
 213         /* Parse command line */
 214         opt_complementary = "c--C:C--c" // mutually exclusive
 215                             ":hH:Hh"; // -h and -H are the same
 216 #if ENABLE_GETOPT_LONG
 217         applet_long_options = udhcpc_longopts;
 218 #endif
 219         opt = getopt32(argc, argv, "c:CV:fbH:h:F:i:np:qRr:s:T:t:v",
 220                 &str_c, &str_V, &str_h, &str_h, &str_F,
 221                 &client_config.interface, &client_config.pidfile, &str_r,
 222                 &client_config.script, &str_T, &str_t
 223                 );
 224
 225         if (opt & OPT_c)
 226                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, str_c, 0);
 227         if (opt & OPT_C)
 228                 no_clientid = 1;
 229         if (opt & OPT_V)
 230                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
 231         if (opt & OPT_f)
 232                 client_config.foreground = 1;
 233         if (opt & OPT_b)
 234                 client_config.background_if_no_lease = 1;
 235         if (opt & OPT_h)
 236                 client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
 237         if (opt & OPT_F) {
 238                 client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
 239                 /* Flags: 0000NEOS
 240                 S: 1 => Client requests Server to update A RR in DNS as well as PTR
 241                 O: 1 => Server indicates to client that DNS has been updated regardless
 242                 E: 1 => Name data is DNS format, i.e. <4>host<6>domain<4>com<0> not "host.domain.com"
 243                 N: 1 => Client requests Server to not update DNS
 244                 */
 245                 client_config.fqdn[OPT_DATA + 0] = 0x1;
 246                 /* client_config.fqdn[OPT_DATA + 1] = 0; - redundant */
 247                 /* client_config.fqdn[OPT_DATA + 2] = 0; - redundant */
 248         }
 249         // if (opt & OPT_i) client_config.interface = ...
 250         if (opt & OPT_n)
 251                 client_config.abort_if_no_lease = 1;
 252         // if (opt & OPT_p) client_config.pidfile = ...
 253         if (opt & OPT_q)
 254                 client_config.quit_after_lease = 1;
 255         if (opt & OPT_R)
 256                 client_config.release_on_quit = 1;
 257         if (opt & OPT_r)
 258                 requested_ip = inet_addr(str_r);
 259         // if (opt & OPT_s) client_config.script = ...
 260         if (opt & OPT_T)
 261                 client_config.timeout = xatoi_u(str_T);
 262         if (opt & OPT_t)
 263                 client_config.retries = xatoi_u(str_t);
 264         if (opt & OPT_v) {
 265                 printf("version %s\n\n", BB_VER);
 266                 return 0;
 267         }
 268
 269         if (ENABLE_FEATURE_UDHCP_SYSLOG) {
 270                 openlog(applet_name, LOG_PID, LOG_LOCAL0);
 271                 logmode |= LOGMODE_SYSLOG;
 272         }
 273
 274         if (read_interface(client_config.interface, &client_config.ifindex,
 275                            NULL, client_config.arp) < 0)
 276                 return 1;
 277
 278         /* Sanitize fd's and write pidfile */
 279         udhcp_make_pidfile(client_config.pidfile);
 280
 281         /* if not set, and not suppressed, setup the default client ID */
 282         if (!client_config.clientid && !no_clientid) {
 283                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
 284                 client_config.clientid[OPT_DATA] = 1;
 285                 memcpy(client_config.clientid + OPT_DATA+1, client_config.arp, 6);
 286         }
 287
 288         if (!client_config.vendorclass)
 289                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, "udhcp "BB_VER, 0);
 290
 291         /* setup the signal pipe */
 292         udhcp_sp_setup();
 293
 294         state = INIT_SELECTING;
 295         udhcp_run_script(NULL, "deconfig");
 296         change_mode(LISTEN_RAW);
 297
 298         for (;;) {
 299                 tv.tv_sec = timeout - monotonic_sec();
 300                 tv.tv_usec = 0;
 301
 302                 if (listen_mode != LISTEN_NONE && sockfd < 0) {
 303                         if (listen_mode == LISTEN_KERNEL)
 304                                 sockfd = listen_socket(INADDR_ANY, CLIENT_PORT, client_config.interface);
 305                         else
 306                                 sockfd = raw_socket(client_config.ifindex);
 307                 }
 308                 max_fd = udhcp_sp_fd_set(&rfds, sockfd);
 309
 310                 if (tv.tv_sec > 0) {
 311                         DEBUG("Waiting on select...");
 312                         retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
 313                 } else retval = 0; /* If we already timed out, fall through */
 314
 315                 now = monotonic_sec();
 316                 if (retval == 0) {
 317                         /* timeout dropped to zero */
 318                         switch (state) {
 319                         case INIT_SELECTING:
 320                                 if (packet_num < client_config.retries) {
 321                                         if (packet_num == 0)
 322                                                 xid = random_xid();
 323
 324                                         /* send discover packet */
 325                                         send_discover(xid, requested_ip); /* broadcast */
 326
 327                                         timeout = now + client_config.timeout;
 328                                         packet_num++;
 329                                 } else {
 330                                         udhcp_run_script(NULL, "leasefail");
 331                                         if (client_config.background_if_no_lease) {
 332                                                 bb_info_msg("No lease, forking to background");
 333                                                 client_background();
 334                                         } else if (client_config.abort_if_no_lease) {
 335                                                 bb_info_msg("No lease, failing");
 336                                                 retval = 1;
 337                                                 goto ret;
 338                                         }
 339                                         /* wait to try again */
 340                                         packet_num = 0;
 341                                         timeout = now + 60;
 342                                 }
 343                                 break;
 344                         case RENEW_REQUESTED:
 345                         case REQUESTING:
 346                                 if (packet_num < client_config.retries) {
 347                                         /* send request packet */
 348                                         if (state == RENEW_REQUESTED)
 349                                                 send_renew(xid, server_addr, requested_ip); /* unicast */
 350                                         else send_selecting(xid, server_addr, requested_ip); /* broadcast */
 351
 352                                         timeout = now + ((packet_num == 2) ? 10 : 2);
 353                                         packet_num++;
 354                                 } else {
 355                                         /* timed out, go back to init state */
 356                                         if (state == RENEW_REQUESTED)
 357                                                 udhcp_run_script(NULL, "deconfig");
 358                                         state = INIT_SELECTING;
 359                                         timeout = now;
 360                                         packet_num = 0;
 361                                         change_mode(LISTEN_RAW);
 362                                 }
 363                                 break;
 364                         case BOUND:
 365                                 /* Lease is starting to run out, time to enter renewing state */
 366                                 state = RENEWING;
 367                                 change_mode(LISTEN_KERNEL);
 368                                 DEBUG("Entering renew state");
 369                                 /* fall right through */
 370                         case RENEWING:
 371                                 /* Either set a new T1, or enter REBINDING state */
 372                                 if ((t2 - t1) <= (lease / 14400 + 1)) {
 373                                         /* timed out, enter rebinding state */
 374                                         state = REBINDING;
 375                                         timeout = now + (t2 - t1);
 376                                         DEBUG("Entering rebinding state");
 377                                 } else {
 378                                         /* send a request packet */
 379                                         send_renew(xid, server_addr, requested_ip); /* unicast */
 380
 381                                         t1 = (t2 - t1) / 2 + t1;
 382                                         timeout = t1 + start;
 383                                 }
 384                                 break;
 385                         case REBINDING:
 386                                 /* Either set a new T2, or enter INIT state */
 387                                 if ((lease - t2) <= (lease / 14400 + 1)) {
 388                                         /* timed out, enter init state */
 389                                         state = INIT_SELECTING;
 390                                         bb_info_msg("Lease lost, entering init state");
 391                                         udhcp_run_script(NULL, "deconfig");
 392                                         timeout = now;
 393                                         packet_num = 0;
 394                                         change_mode(LISTEN_RAW);
 395                                 } else {
 396                                         /* send a request packet */
 397                                         send_renew(xid, 0, requested_ip); /* broadcast */
 398
 399                                         t2 = (lease - t2) / 2 + t2;
 400                                         timeout = t2 + start;
 401                                 }
 402                                 break;
 403                         case RELEASED:
 404                                 /* yah, I know, *you* say it would never happen */
 405                                 timeout = INT_MAX;
 406                                 break;
 407                         }
 408                 } else if (retval > 0 && listen_mode != LISTEN_NONE && FD_ISSET(sockfd, &rfds)) {
 409                         /* a packet is ready, read it */
 410
 411                         if (listen_mode == LISTEN_KERNEL)
 412                                 len = udhcp_get_packet(&packet, sockfd);
 413                         else len = get_raw_packet(&packet, sockfd);
 414
 415                         if (len == -1 && errno != EINTR) {
 416                                 DEBUG("error on read, %s, reopening socket", strerror(errno));
 417                                 change_mode(listen_mode); /* just close and reopen */
 418                         }
 419                         if (len < 0) continue;
 420
 421                         if (packet.xid != xid) {
 422                                 DEBUG("Ignoring XID %x (our xid is %x)",
 423                                         (unsigned)packet.xid, (unsigned)xid);
 424                                 continue;
 425                         }
 426
 427                         /* Ignore packets that aren't for us */
 428                         if (memcmp(packet.chaddr, client_config.arp, 6)) {
 429                                 DEBUG("Packet does not have our chaddr - ignoring");
 430                                 continue;
 431                         }
 432
 433                         message = get_option(&packet, DHCP_MESSAGE_TYPE);
 434                         if (message == NULL) {
 435                                 bb_error_msg("cannot get option from packet - ignoring");
 436                                 continue;
 437                         }
 438
 439                         switch (state) {
 440                         case INIT_SELECTING:
 441                                 /* Must be a DHCPOFFER to one of our xid's */
 442                                 if (*message == DHCPOFFER) {
 443                                         temp = get_option(&packet, DHCP_SERVER_ID);
 444                                         if (temp) {
 445                                                 /* can be misaligned, thus memcpy */
 446                                                 memcpy(&server_addr, temp, 4);
 447                                                 xid = packet.xid;
 448                                                 requested_ip = packet.yiaddr;
 449
 450                                                 /* enter requesting state */
 451                                                 state = REQUESTING;
 452                                                 timeout = now;
 453                                                 packet_num = 0;
 454                                         } else {
 455                                                 bb_error_msg("no server ID in message");
 456                                         }
 457                                 }
 458                                 break;
 459                         case RENEW_REQUESTED:
 460                         case REQUESTING:
 461                         case RENEWING:
 462                         case REBINDING:
 463                                 if (*message == DHCPACK) {
 464                                         temp = get_option(&packet, DHCP_LEASE_TIME);
 465                                         if (!temp) {
 466                                                 bb_error_msg("no lease time with ACK, using 1 hour lease");
 467                                                 lease = 60 * 60;
 468                                         } else {
 469                                                 /* can be misaligned, thus memcpy */
 470                                                 memcpy(&lease, temp, 4);
 471                                                 lease = ntohl(lease);
 472                                         }
 473
 474                                         /* enter bound state */
 475                                         t1 = lease / 2;
 476
 477                                         /* little fixed point for n * .875 */
 478                                         t2 = (lease * 7) >> 3;
 479                                         temp_addr.s_addr = packet.yiaddr;
 480                                         bb_info_msg("Lease of %s obtained, lease time %u",
 481                                                 inet_ntoa(temp_addr), (unsigned)lease);
 482                                         start = now;
 483                                         timeout = t1 + start;
 484                                         requested_ip = packet.yiaddr;
 485                                         udhcp_run_script(&packet,
 486                                                    ((state == RENEWING || state == REBINDING) ? "renew" : "bound"));
 487
 488                                         state = BOUND;
 489                                         change_mode(LISTEN_NONE);
 490                                         if (client_config.quit_after_lease) {
 491                                                 if (client_config.release_on_quit)
 492                                                         perform_release();
 493                                                 goto ret0;
 494                                         }
 495                                         if (!client_config.foreground)
 496                                                 client_background();
 497
 498                                 } else if (*message == DHCPNAK) {
 499                                         /* return to init state */
 500                                         bb_info_msg("Received DHCP NAK");
 501                                         udhcp_run_script(&packet, "nak");
 502                                         if (state != REQUESTING)
 503                                                 udhcp_run_script(NULL, "deconfig");
 504                                         state = INIT_SELECTING;
 505                                         timeout = now;
 506                                         requested_ip = 0;
 507                                         packet_num = 0;
 508                                         change_mode(LISTEN_RAW);
 509                                         sleep(3); /* avoid excessive network traffic */
 510                                 }
 511                                 break;
 512                         /* case BOUND, RELEASED: - ignore all packets */
 513                         }
 514                 } else if (retval > 0 && (sig = udhcp_sp_read(&rfds))) {
 515                         switch (sig) {
 516                         case SIGUSR1:
 517                                 perform_renew();
 518                                 break;
 519                         case SIGUSR2:
 520                                 perform_release();
 521                                 break;
 522                         case SIGTERM:
 523                                 bb_info_msg("Received SIGTERM");
 524                                 if (client_config.release_on_quit)
 525                                         perform_release();
 526                                 goto ret0;
 527                         }
 528                 } else if (retval == -1 && errno == EINTR) {
 529                         /* a signal was caught */
 530                 } else {
 531                         /* An error occured */
 532                         bb_perror_msg("select");
 533                 }
 534         } /* for (;;) */
 535  ret0:
 536         retval = 0;
 537  ret:
 538         if (client_config.pidfile)
 539                 remove_pidfile(client_config.pidfile);
 540         return retval;
 541 }