networking/udhcp/dhcpc.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * udhcp client
   4  *
   5  * Russ Dill <Russ.Dill@asu.edu> July 2001
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20  */
  21 #include <syslog.h>
  22 /* Override ENABLE_FEATURE_PIDFILE - ifupdown needs our pidfile to always exist */
  23 #define WANT_PIDFILE 1
  24 #include "common.h"
  25 #include "dhcpd.h"
  26 #include "dhcpc.h"
  27
  28 #include <asm/types.h>
  29 #if (defined(__GLIBC__) && __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 1) || defined(_NEWLIB_VERSION)
  30 # include <netpacket/packet.h>
  31 # include <net/ethernet.h>
  32 #else
  33 # include <linux/if_packet.h>
  34 # include <linux/if_ether.h>
  35 #endif
  36 #include <linux/filter.h>
  37
  38 /* struct client_config_t client_config is in bb_common_bufsiz1 */
  39
  40
  41 /*** Script execution code ***/
  42
  43 /* get a rough idea of how long an option will be (rounding up...) */
  44 static const uint8_t len_of_option_as_string[] = {
  45         [OPTION_IP              ] = sizeof("255.255.255.255 "),
  46         [OPTION_IP_PAIR         ] = sizeof("255.255.255.255 ") * 2,
  47         [OPTION_STATIC_ROUTES   ] = sizeof("255.255.255.255/32 255.255.255.255 "),
  48         [OPTION_STRING          ] = 1,
  49 #if ENABLE_FEATURE_UDHCP_RFC3397
  50         [OPTION_DNS_STRING      ] = 1, /* unused */
  51         /* Hmmm, this severely overestimates size if SIP_SERVERS option
  52          * is in domain name form: N-byte option in binary form
  53          * mallocs ~16*N bytes. But it is freed almost at once.
  54          */
  55         [OPTION_SIP_SERVERS     ] = sizeof("255.255.255.255 "),
  56 #endif
  57 //      [OPTION_BOOLEAN         ] = sizeof("yes "),
  58         [OPTION_U8              ] = sizeof("255 "),
  59         [OPTION_U16             ] = sizeof("65535 "),
  60 //      [OPTION_S16             ] = sizeof("-32768 "),
  61         [OPTION_U32             ] = sizeof("4294967295 "),
  62         [OPTION_S32             ] = sizeof("-2147483684 "),
  63 };
  64
  65 /* note: ip is a pointer to an IP in network order, possibly misaliged */
  66 static int sprint_nip(char *dest, const char *pre, const uint8_t *ip)
  67 {
  68         return sprintf(dest, "%s%u.%u.%u.%u", pre, ip[0], ip[1], ip[2], ip[3]);
  69 }
  70
  71 /* really simple implementation, just count the bits */
  72 static int mton(uint32_t mask)
  73 {
  74         int i = 0;
  75         mask = ntohl(mask); /* 111110000-like bit pattern */
  76         while (mask) {
  77                 i++;
  78                 mask <<= 1;
  79         }
  80         return i;
  81 }
  82
  83 /* Create "opt_name=opt_value" string */
  84 static NOINLINE char *xmalloc_optname_optval(uint8_t *option, const struct dhcp_optflag *optflag, const char *opt_name)
  85 {
  86         unsigned upper_length;
  87         int len, type, optlen;
  88         char *dest, *ret;
  89
  90         /* option points to OPT_DATA, need to go back and get OPT_LEN */
  91         len = option[OPT_LEN - OPT_DATA];
  92
  93         type = optflag->flags & OPTION_TYPE_MASK;
  94         optlen = dhcp_option_lengths[type];
  95         upper_length = len_of_option_as_string[type] * ((unsigned)len / (unsigned)optlen);
  96
  97         dest = ret = xmalloc(upper_length + strlen(opt_name) + 2);
  98         dest += sprintf(ret, "%s=", opt_name);
  99
 100         while (len >= optlen) {
 101                 unsigned ip_ofs = 0;
 102
 103                 switch (type) {
 104                 case OPTION_IP_PAIR:
 105                         dest += sprint_nip(dest, "", option);
 106                         *dest++ = '/';
 107                         ip_ofs = 4;
 108                         /* fall through */
 109                 case OPTION_IP:
 110                         dest += sprint_nip(dest, "", option + ip_ofs);
 111                         break;
 112 //              case OPTION_BOOLEAN:
 113 //                      dest += sprintf(dest, *option ? "yes" : "no");
 114 //                      break;
 115                 case OPTION_U8:
 116                         dest += sprintf(dest, "%u", *option);
 117                         break;
 118 //              case OPTION_S16:
 119                 case OPTION_U16: {
 120                         uint16_t val_u16;
 121                         move_from_unaligned16(val_u16, option);
 122                         dest += sprintf(dest, "%u", ntohs(val_u16));
 123                         break;
 124                 }
 125                 case OPTION_S32:
 126                 case OPTION_U32: {
 127                         uint32_t val_u32;
 128                         move_from_unaligned32(val_u32, option);
 129                         dest += sprintf(dest, type == OPTION_U32 ? "%lu" : "%ld", (unsigned long) ntohl(val_u32));
 130                         break;
 131                 }
 132                 case OPTION_STRING:
 133                         memcpy(dest, option, len);
 134                         dest[len] = '\0';
 135                         return ret;      /* Short circuit this case */
 136                 case OPTION_STATIC_ROUTES: {
 137                         /* Option binary format:
 138                          * mask [one byte, 0..32]
 139                          * ip [big endian, 0..4 bytes depending on mask]
 140                          * router [big endian, 4 bytes]
 141                          * may be repeated
 142                          *
 143                          * We convert it to a string "IP/MASK ROUTER IP2/MASK2 ROUTER2"
 144                          */
 145                         const char *pfx = "";
 146
 147                         while (len >= 1 + 4) { /* mask + 0-byte ip + router */
 148                                 uint32_t nip;
 149                                 uint8_t *p;
 150                                 unsigned mask;
 151                                 int bytes;
 152
 153                                 mask = *option++;
 154                                 if (mask > 32)
 155                                         break;
 156                                 len--;
 157
 158                                 nip = 0;
 159                                 p = (void*) &nip;
 160                                 bytes = (mask + 7) / 8; /* 0 -> 0, 1..8 -> 1, 9..16 -> 2 etc */
 161                                 while (--bytes >= 0) {
 162                                         *p++ = *option++;
 163                                         len--;
 164                                 }
 165                                 if (len < 4)
 166                                         break;
 167
 168                                 /* print ip/mask */
 169                                 dest += sprint_nip(dest, pfx, (void*) &nip);
 170                                 pfx = " ";
 171                                 dest += sprintf(dest, "/%u ", mask);
 172                                 /* print router */
 173                                 dest += sprint_nip(dest, "", option);
 174                                 option += 4;
 175                                 len -= 4;
 176                         }
 177
 178                         return ret;
 179                 }
 180 #if ENABLE_FEATURE_UDHCP_RFC3397
 181                 case OPTION_DNS_STRING:
 182                         /* unpack option into dest; use ret for prefix (i.e., "optname=") */
 183                         dest = dname_dec(option, len, ret);
 184                         if (dest) {
 185                                 free(ret);
 186                                 return dest;
 187                         }
 188                         /* error. return "optname=" string */
 189                         return ret;
 190                 case OPTION_SIP_SERVERS:
 191                         /* Option binary format:
 192                          * type: byte
 193                          * type=0: domain names, dns-compressed
 194                          * type=1: IP addrs
 195                          */
 196                         option++;
 197                         len--;
 198                         if (option[-1] == 0) {
 199                                 dest = dname_dec(option, len, ret);
 200                                 if (dest) {
 201                                         free(ret);
 202                                         return dest;
 203                                 }
 204                         } else
 205                         if (option[-1] == 1) {
 206                                 const char *pfx = "";
 207                                 while (1) {
 208                                         len -= 4;
 209                                         if (len < 0)
 210                                                 break;
 211                                         dest += sprint_nip(dest, pfx, option);
 212                                         pfx = " ";
 213                                         option += 4;
 214                                 }
 215                         }
 216                         return ret;
 217 #endif
 218                 } /* switch */
 219                 option += optlen;
 220                 len -= optlen;
 221 // TODO: it can be a list only if (optflag->flags & OPTION_LIST).
 222 // Should we bail out/warn if we see multi-ip option which is
 223 // not allowed to be such (for example, DHCP_BROADCAST)? -
 224                 if (len <= 0 /* || !(optflag->flags & OPTION_LIST) */)
 225                         break;
 226                 *dest++ = ' ';
 227                 *dest = '\0';
 228         }
 229         return ret;
 230 }
 231
 232 /* put all the parameters into the environment */
 233 static char **fill_envp(struct dhcp_packet *packet)
 234 {
 235         int envc;
 236         int i;
 237         char **envp, **curr;
 238         const char *opt_name;
 239         uint8_t *temp;
 240         uint8_t overload = 0;
 241
 242         /* We need 6 elements for:
 243          * "interface=IFACE"
 244          * "ip=N.N.N.N" from packet->yiaddr
 245          * "siaddr=IP" from packet->siaddr_nip (unless 0)
 246          * "boot_file=FILE" from packet->file (unless overloaded)
 247          * "sname=SERVER_HOSTNAME" from packet->sname (unless overloaded)
 248          * terminating NULL
 249          */
 250         envc = 6;
 251         /* +1 element for each option, +2 for subnet option: */
 252         if (packet) {
 253                 for (i = 0; dhcp_optflags[i].code; i++) {
 254                         if (udhcp_get_option(packet, dhcp_optflags[i].code)) {
 255                                 if (dhcp_optflags[i].code == DHCP_SUBNET)
 256                                         envc++; /* for mton */
 257                                 envc++;
 258                         }
 259                 }
 260                 temp = udhcp_get_option(packet, DHCP_OPTION_OVERLOAD);
 261                 if (temp)
 262                         overload = *temp;
 263         }
 264         curr = envp = xzalloc(sizeof(char *) * envc);
 265
 266         *curr = xasprintf("interface=%s", client_config.interface);
 267         putenv(*curr++);
 268
 269         if (!packet)
 270                 return envp;
 271
 272         *curr = xmalloc(sizeof("ip=255.255.255.255"));
 273         sprint_nip(*curr, "ip=", (uint8_t *) &packet->yiaddr);
 274         putenv(*curr++);
 275
 276         opt_name = dhcp_option_strings;
 277         i = 0;
 278         while (*opt_name) {
 279                 temp = udhcp_get_option(packet, dhcp_optflags[i].code);
 280                 if (!temp)
 281                         goto next;
 282                 *curr = xmalloc_optname_optval(temp, &dhcp_optflags[i], opt_name);
 283                 putenv(*curr++);
 284                 if (dhcp_optflags[i].code == DHCP_SUBNET) {
 285                         /* Subnet option: make things like "$ip/$mask" possible */
 286                         uint32_t subnet;
 287                         move_from_unaligned32(subnet, temp);
 288                         *curr = xasprintf("mask=%d", mton(subnet));
 289                         putenv(*curr++);
 290                 }
 291  next:
 292                 opt_name += strlen(opt_name) + 1;
 293                 i++;
 294         }
 295         if (packet->siaddr_nip) {
 296                 *curr = xmalloc(sizeof("siaddr=255.255.255.255"));
 297                 sprint_nip(*curr, "siaddr=", (uint8_t *) &packet->siaddr_nip);
 298                 putenv(*curr++);
 299         }
 300         if (!(overload & FILE_FIELD) && packet->file[0]) {
 301                 /* watch out for invalid packets */
 302                 *curr = xasprintf("boot_file=%."DHCP_PKT_FILE_LEN_STR"s", packet->file);
 303                 putenv(*curr++);
 304         }
 305         if (!(overload & SNAME_FIELD) && packet->sname[0]) {
 306                 /* watch out for invalid packets */
 307                 *curr = xasprintf("sname=%."DHCP_PKT_SNAME_LEN_STR"s", packet->sname);
 308                 putenv(*curr++);
 309         }
 310         return envp;
 311 }
 312
 313 /* Call a script with a par file and env vars */
 314 static void udhcp_run_script(struct dhcp_packet *packet, const char *name)
 315 {
 316         char **envp, **curr;
 317         char *argv[3];
 318
 319         if (client_config.script == NULL)
 320                 return;
 321
 322         envp = fill_envp(packet);
 323
 324         /* call script */
 325         log1("Executing %s %s", client_config.script, name);
 326         argv[0] = (char*) client_config.script;
 327         argv[1] = (char*) name;
 328         argv[2] = NULL;
 329         spawn_and_wait(argv);
 330
 331         for (curr = envp; *curr; curr++) {
 332                 log2(" %s", *curr);
 333                 bb_unsetenv_and_free(*curr);
 334         }
 335         free(envp);
 336 }
 337
 338
 339 /*** Sending/receiving packets ***/
 340
 341 static ALWAYS_INLINE uint32_t random_xid(void)
 342 {
 343         return rand();
 344 }
 345
 346 /* Initialize the packet with the proper defaults */
 347 static void init_packet(struct dhcp_packet *packet, char type)
 348 {
 349         /* Fill in: op, htype, hlen, cookie fields; message type option: */
 350         udhcp_init_header(packet, type);
 351
 352         packet->xid = random_xid();
 353
 354         memcpy(packet->chaddr, client_config.client_mac, 6);
 355         if (client_config.clientid)
 356                 udhcp_add_binary_option(packet, client_config.clientid);
 357 }
 358
 359 static void add_client_options(struct dhcp_packet *packet)
 360 {
 361         uint8_t c;
 362         int i, end, len;
 363
 364         udhcp_add_simple_option(packet, DHCP_MAX_SIZE, htons(IP_UDP_DHCP_SIZE));
 365
 366         /* Add a "param req" option with the list of options we'd like to have
 367          * from stubborn DHCP servers. Pull the data from the struct in common.c.
 368          * No bounds checking because it goes towards the head of the packet. */
 369         end = udhcp_end_option(packet->options);
 370         len = 0;
 371         for (i = 0; (c = dhcp_optflags[i].code) != 0; i++) {
 372                 if ((   (dhcp_optflags[i].flags & OPTION_REQ)
 373                      && !client_config.no_default_options
 374                     )
 375                  || (client_config.opt_mask[c >> 3] & (1 << (c & 7)))
 376                 ) {
 377                         packet->options[end + OPT_DATA + len] = c;
 378                         len++;
 379                 }
 380         }
 381         if (len) {
 382                 packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
 383                 packet->options[end + OPT_LEN] = len;
 384                 packet->options[end + OPT_DATA + len] = DHCP_END;
 385         }
 386
 387         if (client_config.vendorclass)
 388                 udhcp_add_binary_option(packet, client_config.vendorclass);
 389         if (client_config.hostname)
 390                 udhcp_add_binary_option(packet, client_config.hostname);
 391         if (client_config.fqdn)
 392                 udhcp_add_binary_option(packet, client_config.fqdn);
 393
 394         /* Add -x options if any */
 395         {
 396                 struct option_set *curr = client_config.options;
 397                 while (curr) {
 398                         udhcp_add_binary_option(packet, curr->data);
 399                         curr = curr->next;
 400                 }
 401 //              if (client_config.sname)
 402 //                      strncpy((char*)packet->sname, client_config.sname, sizeof(packet->sname) - 1);
 403 //              if (client_config.boot_file)
 404 //                      strncpy((char*)packet->file, client_config.boot_file, sizeof(packet->file) - 1);
 405         }
 406 }
 407
 408 /* RFC 2131
 409  * 4.4.4 Use of broadcast and unicast
 410  *
 411  * The DHCP client broadcasts DHCPDISCOVER, DHCPREQUEST and DHCPINFORM
 412  * messages, unless the client knows the address of a DHCP server.
 413  * The client unicasts DHCPRELEASE messages to the server. Because
 414  * the client is declining the use of the IP address supplied by the server,
 415  * the client broadcasts DHCPDECLINE messages.
 416  *
 417  * When the DHCP client knows the address of a DHCP server, in either
 418  * INIT or REBOOTING state, the client may use that address
 419  * in the DHCPDISCOVER or DHCPREQUEST rather than the IP broadcast address.
 420  * The client may also use unicast to send DHCPINFORM messages
 421  * to a known DHCP server. If the client receives no response to DHCP
 422  * messages sent to the IP address of a known DHCP server, the DHCP
 423  * client reverts to using the IP broadcast address.
 424  */
 425
 426 static int raw_bcast_from_client_config_ifindex(struct dhcp_packet *packet)
 427 {
 428         return udhcp_send_raw_packet(packet,
 429                 /*src*/ INADDR_ANY, CLIENT_PORT,
 430                 /*dst*/ INADDR_BROADCAST, SERVER_PORT, MAC_BCAST_ADDR,
 431                 client_config.ifindex);
 432 }
 433
 434 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
 435 /* NOINLINE: limit stack usage in caller */
 436 static NOINLINE int send_discover(uint32_t xid, uint32_t requested)
 437 {
 438         struct dhcp_packet packet;
 439
 440         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 441          * random xid field (we override it below),
 442          * client-id option (unless -C), message type option:
 443          */
 444         init_packet(&packet, DHCPDISCOVER);
 445
 446         packet.xid = xid;
 447         if (requested)
 448                 udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 449
 450         /* Add options: maxsize,
 451          * optionally: hostname, fqdn, vendorclass,
 452          * "param req" option according to -O, options specified with -x
 453          */
 454         add_client_options(&packet);
 455
 456         bb_info_msg("Sending discover...");
 457         return raw_bcast_from_client_config_ifindex(&packet);
 458 }
 459
 460 /* Broadcast a DHCP request message */
 461 /* RFC 2131 3.1 paragraph 3:
 462  * "The client _broadcasts_ a DHCPREQUEST message..."
 463  */
 464 /* NOINLINE: limit stack usage in caller */
 465 static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requested)
 466 {
 467         struct dhcp_packet packet;
 468         struct in_addr addr;
 469
 470 /*
 471  * RFC 2131 4.3.2 DHCPREQUEST message
 472  * ...
 473  * If the DHCPREQUEST message contains a 'server identifier'
 474  * option, the message is in response to a DHCPOFFER message.
 475  * Otherwise, the message is a request to verify or extend an
 476  * existing lease. If the client uses a 'client identifier'
 477  * in a DHCPREQUEST message, it MUST use that same 'client identifier'
 478  * in all subsequent messages. If the client included a list
 479  * of requested parameters in a DHCPDISCOVER message, it MUST
 480  * include that list in all subsequent messages.
 481  */
 482         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 483          * random xid field (we override it below),
 484          * client-id option (unless -C), message type option:
 485          */
 486         init_packet(&packet, DHCPREQUEST);
 487
 488         packet.xid = xid;
 489         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 490
 491         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 492
 493         /* Add options: maxsize,
 494          * optionally: hostname, fqdn, vendorclass,
 495          * "param req" option according to -O, and options specified with -x
 496          */
 497         add_client_options(&packet);
 498
 499         addr.s_addr = requested;
 500         bb_info_msg("Sending select for %s...", inet_ntoa(addr));
 501         return raw_bcast_from_client_config_ifindex(&packet);
 502 }
 503
 504 /* Unicast or broadcast a DHCP renew message */
 505 /* NOINLINE: limit stack usage in caller */
 506 static NOINLINE int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
 507 {
 508         struct dhcp_packet packet;
 509
 510 /*
 511  * RFC 2131 4.3.2 DHCPREQUEST message
 512  * ...
 513  * DHCPREQUEST generated during RENEWING state:
 514  *
 515  * 'server identifier' MUST NOT be filled in, 'requested IP address'
 516  * option MUST NOT be filled in, 'ciaddr' MUST be filled in with
 517  * client's IP address. In this situation, the client is completely
 518  * configured, and is trying to extend its lease. This message will
 519  * be unicast, so no relay agents will be involved in its
 520  * transmission.  Because 'giaddr' is therefore not filled in, the
 521  * DHCP server will trust the value in 'ciaddr', and use it when
 522  * replying to the client.
 523  */
 524         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 525          * random xid field (we override it below),
 526          * client-id option (unless -C), message type option:
 527          */
 528         init_packet(&packet, DHCPREQUEST);
 529
 530         packet.xid = xid;
 531         packet.ciaddr = ciaddr;
 532
 533         /* Add options: maxsize,
 534          * optionally: hostname, fqdn, vendorclass,
 535          * "param req" option according to -O, and options specified with -x
 536          */
 537         add_client_options(&packet);
 538
 539         bb_info_msg("Sending renew...");
 540         if (server)
 541                 return udhcp_send_kernel_packet(&packet,
 542                         ciaddr, CLIENT_PORT,
 543                         server, SERVER_PORT);
 544         return raw_bcast_from_client_config_ifindex(&packet);
 545 }
 546
 547 #if ENABLE_FEATURE_UDHCPC_ARPING
 548 /* Broadcast a DHCP decline message */
 549 /* NOINLINE: limit stack usage in caller */
 550 static NOINLINE int send_decline(uint32_t xid, uint32_t server, uint32_t requested)
 551 {
 552         struct dhcp_packet packet;
 553
 554         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 555          * client-id option (unless -C), message type option:
 556          */
 557         init_packet(&packet, DHCPDECLINE);
 558
 559         /* RFC 2131 says DHCPDECLINE's xid is randomly selected by client,
 560          * but in case the server is buggy and wants DHCPDECLINE's xid
 561          * to match the xid which started entire handshake,
 562          * we use the same xid we used in initial DHCPDISCOVER:
 563          */
 564         packet.xid = xid;
 565         /* DHCPDECLINE uses "requested ip", not ciaddr, to store offered IP */
 566         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 567
 568         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 569
 570         bb_info_msg("Sending decline...");
 571         return raw_bcast_from_client_config_ifindex(&packet);
 572 }
 573 #endif
 574
 575 /* Unicast a DHCP release message */
 576 static int send_release(uint32_t server, uint32_t ciaddr)
 577 {
 578         struct dhcp_packet packet;
 579
 580         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 581          * client-id option (unless -C), message type option:
 582          */
 583         init_packet(&packet, DHCPRELEASE);
 584
 585         /* DHCPRELEASE uses ciaddr, not "requested ip", to store IP being released */
 586         packet.ciaddr = ciaddr;
 587
 588         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 589
 590         bb_info_msg("Sending release...");
 591         return udhcp_send_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
 592 }
 593
 594 /* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */
 595 /* NOINLINE: limit stack usage in caller */
 596 static NOINLINE int udhcp_recv_raw_packet(struct dhcp_packet *dhcp_pkt, int fd)
 597 {
 598         int bytes;
 599         struct ip_udp_dhcp_packet packet;
 600         uint16_t check;
 601
 602         memset(&packet, 0, sizeof(packet));
 603         bytes = safe_read(fd, &packet, sizeof(packet));
 604         if (bytes < 0) {
 605                 log1("Packet read error, ignoring");
 606                 /* NB: possible down interface, etc. Caller should pause. */
 607                 return bytes; /* returns -1 */
 608         }
 609
 610         if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) {
 611                 log1("Packet is too short, ignoring");
 612                 return -2;
 613         }
 614
 615         if (bytes < ntohs(packet.ip.tot_len)) {
 616                 /* packet is bigger than sizeof(packet), we did partial read */
 617                 log1("Oversized packet, ignoring");
 618                 return -2;
 619         }
 620
 621         /* ignore any extra garbage bytes */
 622         bytes = ntohs(packet.ip.tot_len);
 623
 624         /* make sure its the right packet for us, and that it passes sanity checks */
 625         if (packet.ip.protocol != IPPROTO_UDP || packet.ip.version != IPVERSION
 626          || packet.ip.ihl != (sizeof(packet.ip) >> 2)
 627          || packet.udp.dest != htons(CLIENT_PORT)
 628         /* || bytes > (int) sizeof(packet) - can't happen */
 629          || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
 630         ) {
 631                 log1("Unrelated/bogus packet, ignoring");
 632                 return -2;
 633         }
 634
 635         /* verify IP checksum */
 636         check = packet.ip.check;
 637         packet.ip.check = 0;
 638         if (check != udhcp_checksum(&packet.ip, sizeof(packet.ip))) {
 639                 log1("Bad IP header checksum, ignoring");
 640                 return -2;
 641         }
 642
 643         /* verify UDP checksum. IP header has to be modified for this */
 644         memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
 645         /* ip.xx fields which are not memset: protocol, check, saddr, daddr */
 646         packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
 647         check = packet.udp.check;
 648         packet.udp.check = 0;
 649         if (check && check != udhcp_checksum(&packet, bytes)) {
 650                 log1("Packet with bad UDP checksum received, ignoring");
 651                 return -2;
 652         }
 653
 654         memcpy(dhcp_pkt, &packet.data, bytes - (sizeof(packet.ip) + sizeof(packet.udp)));
 655
 656         if (dhcp_pkt->cookie != htonl(DHCP_MAGIC)) {
 657                 bb_info_msg("Packet with bad magic, ignoring");
 658                 return -2;
 659         }
 660         log1("Got valid DHCP packet");
 661         udhcp_dump_packet(dhcp_pkt);
 662         return bytes - (sizeof(packet.ip) + sizeof(packet.udp));
 663 }
 664
 665
 666 /*** Main ***/
 667
 668 static int sockfd = -1;
 669
 670 #define LISTEN_NONE   0
 671 #define LISTEN_KERNEL 1
 672 #define LISTEN_RAW    2
 673 static smallint listen_mode;
 674
 675 /* initial state: (re)start DHCP negotiation */
 676 #define INIT_SELECTING  0
 677 /* discover was sent, DHCPOFFER reply received */
 678 #define REQUESTING      1
 679 /* select/renew was sent, DHCPACK reply received */
 680 #define BOUND           2
 681 /* half of lease passed, want to renew it by sending unicast renew requests */
 682 #define RENEWING        3
 683 /* renew requests were not answered, lease is almost over, send broadcast renew */
 684 #define REBINDING       4
 685 /* manually requested renew (SIGUSR1) */
 686 #define RENEW_REQUESTED 5
 687 /* release, possibly manually requested (SIGUSR2) */
 688 #define RELEASED        6
 689 static smallint state;
 690
 691 static int udhcp_raw_socket(int ifindex)
 692 {
 693         int fd;
 694         struct sockaddr_ll sock;
 695
 696         /*
 697          * Comment:
 698          *
 699          *      I've selected not to see LL header, so BPF doesn't see it, too.
 700          *      The filter may also pass non-IP and non-ARP packets, but we do
 701          *      a more complete check when receiving the message in userspace.
 702          *
 703          * and filter shamelessly stolen from:
 704          *
 705          *      http://www.flamewarmaster.de/software/dhcpclient/
 706          *
 707          * There are a few other interesting ideas on that page (look under
 708          * "Motivation").  Use of netlink events is most interesting.  Think
 709          * of various network servers listening for events and reconfiguring.
 710          * That would obsolete sending HUP signals and/or make use of restarts.
 711          *
 712          * Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
 713          * License: GPL v2.
 714          *
 715          * TODO: make conditional?
 716          */
 717 #define SERVER_AND_CLIENT_PORTS  ((67 << 16) + 68)
 718         static const struct sock_filter filter_instr[] = {
 719                 /* check for udp */
 720                 BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
 721                 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 2, 0),     /* L5, L1, is UDP? */
 722                 /* ugly check for arp on ethernet-like and IPv4 */
 723                 BPF_STMT(BPF_LD|BPF_W|BPF_ABS, 2),                      /* L1: */
 724                 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 0x08000604, 3, 4),      /* L3, L4 */
 725                 /* skip IP header */
 726                 BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0),                     /* L5: */
 727                 /* check udp source and destination ports */
 728                 BPF_STMT(BPF_LD|BPF_W|BPF_IND, 0),
 729                 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, SERVER_AND_CLIENT_PORTS, 0, 1), /* L3, L4 */
 730                 /* returns */
 731                 BPF_STMT(BPF_RET|BPF_K, 0x0fffffff ),                   /* L3: pass */
 732                 BPF_STMT(BPF_RET|BPF_K, 0),                             /* L4: reject */
 733         };
 734         static const struct sock_fprog filter_prog = {
 735                 .len = sizeof(filter_instr) / sizeof(filter_instr[0]),
 736                 /* casting const away: */
 737                 .filter = (struct sock_filter *) filter_instr,
 738         };
 739
 740         log1("Opening raw socket on ifindex %d", ifindex); //log2?
 741
 742         fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
 743         log1("Got raw socket fd %d", fd); //log2?
 744
 745         if (SERVER_PORT == 67 && CLIENT_PORT == 68) {
 746                 /* Use only if standard ports are in use */
 747                 /* Ignoring error (kernel may lack support for this) */
 748                 if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
 749                                 sizeof(filter_prog)) >= 0)
 750                         log1("Attached filter to raw socket fd %d", fd); // log?
 751         }
 752
 753         sock.sll_family = AF_PACKET;
 754         sock.sll_protocol = htons(ETH_P_IP);
 755         sock.sll_ifindex = ifindex;
 756         xbind(fd, (struct sockaddr *) &sock, sizeof(sock));
 757         log1("Created raw socket");
 758
 759         return fd;
 760 }
 761
 762 static void change_listen_mode(int new_mode)
 763 {
 764         log1("Entering listen mode: %s",
 765                 new_mode != LISTEN_NONE
 766                         ? (new_mode == LISTEN_KERNEL ? "kernel" : "raw")
 767                         : "none"
 768         );
 769
 770         listen_mode = new_mode;
 771         if (sockfd >= 0) {
 772                 close(sockfd);
 773                 sockfd = -1;
 774         }
 775         if (new_mode == LISTEN_KERNEL)
 776                 sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
 777         else if (new_mode != LISTEN_NONE)
 778                 sockfd = udhcp_raw_socket(client_config.ifindex);
 779         /* else LISTEN_NONE: sockfd stays closed */
 780 }
 781
 782 static void perform_renew(void)
 783 {
 784         bb_info_msg("Performing a DHCP renew");
 785         switch (state) {
 786         case BOUND:
 787                 change_listen_mode(LISTEN_KERNEL);
 788         case RENEWING:
 789         case REBINDING:
 790                 state = RENEW_REQUESTED;
 791                 break;
 792         case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
 793                 udhcp_run_script(NULL, "deconfig");
 794         case REQUESTING:
 795         case RELEASED:
 796                 change_listen_mode(LISTEN_RAW);
 797                 state = INIT_SELECTING;
 798                 break;
 799         case INIT_SELECTING:
 800                 break;
 801         }
 802 }
 803
 804 static void perform_release(uint32_t requested_ip, uint32_t server_addr)
 805 {
 806         char buffer[sizeof("255.255.255.255")];
 807         struct in_addr temp_addr;
 808
 809         /* send release packet */
 810         if (state == BOUND || state == RENEWING || state == REBINDING) {
 811                 temp_addr.s_addr = server_addr;
 812                 strcpy(buffer, inet_ntoa(temp_addr));
 813                 temp_addr.s_addr = requested_ip;
 814                 bb_info_msg("Unicasting a release of %s to %s",
 815                                 inet_ntoa(temp_addr), buffer);
 816                 send_release(server_addr, requested_ip); /* unicast */
 817                 udhcp_run_script(NULL, "deconfig");
 818         }
 819         bb_info_msg("Entering released state");
 820
 821         change_listen_mode(LISTEN_NONE);
 822         state = RELEASED;
 823 }
 824
 825 static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
 826 {
 827         uint8_t *storage;
 828         int len = strnlen(str, 255);
 829         storage = xzalloc(len + extra + OPT_DATA);
 830         storage[OPT_CODE] = code;
 831         storage[OPT_LEN] = len + extra;
 832         memcpy(storage + extra + OPT_DATA, str, len);
 833         return storage;
 834 }
 835
 836 #if BB_MMU
 837 static void client_background(void)
 838 {
 839         bb_daemonize(0);
 840         logmode &= ~LOGMODE_STDIO;
 841         /* rewrite pidfile, as our pid is different now */
 842         write_pidfile(client_config.pidfile);
 843 }
 844 #endif
 845
 846 //usage:#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
 847 //usage:# define IF_UDHCP_VERBOSE(...) __VA_ARGS__
 848 //usage:#else
 849 //usage:# define IF_UDHCP_VERBOSE(...)
 850 //usage:#endif
 851 //usage:#define udhcpc_trivial_usage
 852 //usage:       "[-fbnq"IF_UDHCP_VERBOSE("v")"oCR] [-i IFACE] [-r IP] [-s PROG] [-p PIDFILE]\n"
 853 //usage:       "        [-H HOSTNAME] [-V VENDOR] [-x OPT:VAL]... [-O OPT]..." IF_FEATURE_UDHCP_PORT(" [-P N]")
 854 //usage:#define udhcpc_full_usage "\n"
 855 //usage:        IF_LONG_OPTS(
 856 //usage:     "\n        -i,--interface IFACE    Interface to use (default eth0)"
 857 //usage:     "\n        -p,--pidfile FILE       Create pidfile"
 858 //usage:     "\n        -s,--script PROG        Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
 859 //usage:     "\n        -t,--retries N          Send up to N discover packets"
 860 //usage:     "\n        -T,--timeout N          Pause between packets (default 3 seconds)"
 861 //usage:     "\n        -A,--tryagain N         Wait N seconds after failure (default 20)"
 862 //usage:     "\n        -f,--foreground         Run in foreground"
 863 //usage:        USE_FOR_MMU(
 864 //usage:     "\n        -b,--background         Background if lease is not obtained"
 865 //usage:        )
 866 //usage:     "\n        -n,--now                Exit if lease is not obtained"
 867 //usage:     "\n        -q,--quit               Exit after obtaining lease"
 868 //usage:     "\n        -R,--release            Release IP on exit"
 869 //usage:     "\n        -S,--syslog             Log to syslog too"
 870 //usage:        IF_FEATURE_UDHCP_PORT(
 871 //usage:     "\n        -P,--client-port N      Use port N (default 68)"
 872 //usage:        )
 873 //usage:        IF_FEATURE_UDHCPC_ARPING(
 874 //usage:     "\n        -a,--arping             Use arping to validate offered address"
 875 //usage:        )
 876 //usage:     "\n        -O,--request-option OPT Request option OPT from server (cumulative)"
 877 //usage:     "\n        -o,--no-default-options Don't request any options (unless -O is given)"
 878 //usage:     "\n        -r,--request IP         Request this IP address"
 879 //usage:     "\n        -x OPT:VAL              Include option OPT in sent packets (cumulative)"
 880 //usage:     "\n                                Examples of string, numeric, and hex byte opts:"
 881 //usage:     "\n                                -x hostname:bbox - option 12"
 882 //usage:     "\n                                -x lease:3600 - option 51 (lease time)"
 883 //usage:     "\n                                -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
 884 //usage:     "\n        -F,--fqdn NAME          Ask server to update DNS mapping for NAME"
 885 //usage:     "\n        -H,-h,--hostname NAME   Send NAME as client hostname (default none)"
 886 //usage:     "\n        -V,--vendorclass VENDOR Vendor identifier (default 'udhcp VERSION')"
 887 //usage:     "\n        -C,--clientid-none      Don't send MAC as client identifier"
 888 //usage:        IF_UDHCP_VERBOSE(
 889 //usage:     "\n        -v                      Verbose"
 890 //usage:        )
 891 //usage:        )
 892 //usage:        IF_NOT_LONG_OPTS(
 893 //usage:     "\n        -i IFACE        Interface to use (default eth0)"
 894 //usage:     "\n        -p FILE         Create pidfile"
 895 //usage:     "\n        -s PROG         Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
 896 //usage:     "\n        -t N            Send up to N discover packets"
 897 //usage:     "\n        -T N            Pause between packets (default 3 seconds)"
 898 //usage:     "\n        -A N            Wait N seconds (default 20) after failure"
 899 //usage:     "\n        -f              Run in foreground"
 900 //usage:        USE_FOR_MMU(
 901 //usage:     "\n        -b              Background if lease is not obtained"
 902 //usage:        )
 903 //usage:     "\n        -n              Exit if lease is not obtained"
 904 //usage:     "\n        -q              Exit after obtaining lease"
 905 //usage:     "\n        -R              Release IP on exit"
 906 //usage:     "\n        -S              Log to syslog too"
 907 //usage:        IF_FEATURE_UDHCP_PORT(
 908 //usage:     "\n        -P N            Use port N (default 68)"
 909 //usage:        )
 910 //usage:        IF_FEATURE_UDHCPC_ARPING(
 911 //usage:     "\n        -a              Use arping to validate offered address"
 912 //usage:        )
 913 //usage:     "\n        -O OPT          Request option OPT from server (cumulative)"
 914 //usage:     "\n        -o              Don't request any options (unless -O is given)"
 915 //usage:     "\n        -r IP           Request this IP address"
 916 //usage:     "\n        -x OPT:VAL      Include option OPT in sent packets (cumulative)"
 917 //usage:     "\n                        Examples of string, numeric, and hex byte opts:"
 918 //usage:     "\n                        -x hostname:bbox - option 12"
 919 //usage:     "\n                        -x lease:3600 - option 51 (lease time)"
 920 //usage:     "\n                        -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
 921 //usage:     "\n        -F NAME         Ask server to update DNS mapping for NAME"
 922 //usage:     "\n        -H,-h NAME      Send NAME as client hostname (default none)"
 923 //usage:     "\n        -V VENDOR       Vendor identifier (default 'udhcp VERSION')"
 924 //usage:     "\n        -C              Don't send MAC as client identifier"
 925 //usage:        IF_UDHCP_VERBOSE(
 926 //usage:     "\n        -v              Verbose"
 927 //usage:        )
 928 //usage:        )
 929 //usage:     "\nSignals:"
 930 //usage:     "\n        USR1    Renew current lease"
 931 //usage:     "\n        USR2    Release current lease"
 932
 933
 934 int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 935 int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 936 {
 937         uint8_t *temp, *message;
 938         const char *str_V, *str_h, *str_F, *str_r;
 939         IF_FEATURE_UDHCP_PORT(char *str_P;)
 940         void *clientid_mac_ptr;
 941         llist_t *list_O = NULL;
 942         llist_t *list_x = NULL;
 943         int tryagain_timeout = 20;
 944         int discover_timeout = 3;
 945         int discover_retries = 3;
 946         uint32_t server_addr = server_addr; /* for compiler */
 947         uint32_t requested_ip = 0;
 948         uint32_t xid = 0;
 949         uint32_t lease_seconds = 0; /* can be given as 32-bit quantity */
 950         int packet_num;
 951         int timeout; /* must be signed */
 952         unsigned already_waited_sec;
 953         unsigned opt;
 954         int max_fd;
 955         int retval;
 956         struct timeval tv;
 957         struct dhcp_packet packet;
 958         fd_set rfds;
 959
 960 #if ENABLE_LONG_OPTS
 961         static const char udhcpc_longopts[] ALIGN1 =
 962                 "clientid-none\0"  No_argument       "C"
 963                 "vendorclass\0"    Required_argument "V"
 964                 "hostname\0"       Required_argument "H"
 965                 "fqdn\0"           Required_argument "F"
 966                 "interface\0"      Required_argument "i"
 967                 "now\0"            No_argument       "n"
 968                 "pidfile\0"        Required_argument "p"
 969                 "quit\0"           No_argument       "q"
 970                 "release\0"        No_argument       "R"
 971                 "request\0"        Required_argument "r"
 972                 "script\0"         Required_argument "s"
 973                 "timeout\0"        Required_argument "T"
 974                 "version\0"        No_argument       "v"
 975                 "retries\0"        Required_argument "t"
 976                 "tryagain\0"       Required_argument "A"
 977                 "syslog\0"         No_argument       "S"
 978                 "request-option\0" Required_argument "O"
 979                 "no-default-options\0" No_argument   "o"
 980                 "foreground\0"     No_argument       "f"
 981                 "background\0"     No_argument       "b"
 982                 IF_FEATURE_UDHCPC_ARPING("arping\0"     No_argument       "a")
 983                 IF_FEATURE_UDHCP_PORT("client-port\0"   Required_argument "P")
 984                 ;
 985 #endif
 986         enum {
 987                 OPT_C = 1 << 0,
 988                 OPT_V = 1 << 1,
 989                 OPT_H = 1 << 2,
 990                 OPT_h = 1 << 3,
 991                 OPT_F = 1 << 4,
 992                 OPT_i = 1 << 5,
 993                 OPT_n = 1 << 6,
 994                 OPT_p = 1 << 7,
 995                 OPT_q = 1 << 8,
 996                 OPT_R = 1 << 9,
 997                 OPT_r = 1 << 10,
 998                 OPT_s = 1 << 11,
 999                 OPT_T = 1 << 12,
1000                 OPT_t = 1 << 13,
1001                 OPT_S = 1 << 14,
1002                 OPT_A = 1 << 15,
1003                 OPT_O = 1 << 16,
1004                 OPT_o = 1 << 17,
1005                 OPT_x = 1 << 18,
1006                 OPT_f = 1 << 19,
1007 /* The rest has variable bit positions, need to be clever */
1008                 OPTBIT_f = 19,
1009                 USE_FOR_MMU(             OPTBIT_b,)
1010                 IF_FEATURE_UDHCPC_ARPING(OPTBIT_a,)
1011                 IF_FEATURE_UDHCP_PORT(   OPTBIT_P,)
1012                 USE_FOR_MMU(             OPT_b = 1 << OPTBIT_b,)
1013                 IF_FEATURE_UDHCPC_ARPING(OPT_a = 1 << OPTBIT_a,)
1014                 IF_FEATURE_UDHCP_PORT(   OPT_P = 1 << OPTBIT_P,)
1015         };
1016
1017         /* Default options */
1018         IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;)
1019         IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
1020         client_config.interface = "eth0";
1021         client_config.script = CONFIG_UDHCPC_DEFAULT_SCRIPT;
1022         str_V = "udhcp "BB_VER;
1023
1024         /* Parse command line */
1025         /* O,x: list; -T,-t,-A take numeric param */
1026         opt_complementary = "O::x::T+:t+:A+"
1027 #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
1028                 ":vv"
1029 #endif
1030                 ;
1031         IF_LONG_OPTS(applet_long_options = udhcpc_longopts;)
1032         opt = getopt32(argv, "CV:H:h:F:i:np:qRr:s:T:t:SA:O:ox:f"
1033                 USE_FOR_MMU("b")
1034                 IF_FEATURE_UDHCPC_ARPING("a")
1035                 IF_FEATURE_UDHCP_PORT("P:")
1036                 "v"
1037                 , &str_V, &str_h, &str_h, &str_F
1038                 , &client_config.interface, &client_config.pidfile, &str_r /* i,p */
1039                 , &client_config.script /* s */
1040                 , &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */
1041                 , &list_O
1042                 , &list_x
1043                 IF_FEATURE_UDHCP_PORT(, &str_P)
1044 #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
1045                 , &dhcp_verbose
1046 #endif
1047                 );
1048         if (opt & (OPT_h|OPT_H))
1049                 client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
1050         if (opt & OPT_F) {
1051                 /* FQDN option format: [0x51][len][flags][0][0]<fqdn> */
1052                 client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
1053                 /* Flag bits: 0000NEOS
1054                  * S: 1 = Client requests server to update A RR in DNS as well as PTR
1055                  * O: 1 = Server indicates to client that DNS has been updated regardless
1056                  * E: 1 = Name is in DNS format, i.e. <4>host<6>domain<3>com<0>,
1057                  *    not "host.domain.com". Format 0 is obsolete.
1058                  * N: 1 = Client requests server to not update DNS (S must be 0 then)
1059                  * Two [0] bytes which follow are deprecated and must be 0.
1060                  */
1061                 client_config.fqdn[OPT_DATA + 0] = 0x1;
1062                 /*client_config.fqdn[OPT_DATA + 1] = 0; - xzalloc did it */
1063                 /*client_config.fqdn[OPT_DATA + 2] = 0; */
1064         }
1065         if (opt & OPT_r)
1066                 requested_ip = inet_addr(str_r);
1067 #if ENABLE_FEATURE_UDHCP_PORT
1068         if (opt & OPT_P) {
1069                 CLIENT_PORT = xatou16(str_P);
1070                 SERVER_PORT = CLIENT_PORT - 1;
1071         }
1072 #endif
1073         if (opt & OPT_o)
1074                 client_config.no_default_options = 1;
1075         while (list_O) {
1076                 char *optstr = llist_pop(&list_O);
1077                 unsigned n = udhcp_option_idx(optstr);
1078                 n = dhcp_optflags[n].code;
1079                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
1080         }
1081         while (list_x) {
1082                 char *optstr = llist_pop(&list_x);
1083                 char *colon = strchr(optstr, ':');
1084                 if (colon)
1085                         *colon = ' ';
1086                 /* now it looks similar to udhcpd's config file line:
1087                  * "optname optval", using the common routine: */
1088                 udhcp_str2optset(optstr, &client_config.options);
1089         }
1090
1091         if (udhcp_read_interface(client_config.interface,
1092                         &client_config.ifindex,
1093                         NULL,
1094                         client_config.client_mac)
1095         ) {
1096                 return 1;
1097         }
1098
1099         clientid_mac_ptr = NULL;
1100         if (!(opt & OPT_C) && !udhcp_find_option(client_config.options, DHCP_CLIENT_ID)) {
1101                 /* not suppressed and not set, set the default client ID */
1102                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
1103                 client_config.clientid[OPT_DATA] = 1; /* type: ethernet */
1104                 clientid_mac_ptr = client_config.clientid + OPT_DATA+1;
1105                 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1106         }
1107         if (str_V[0] != '\0')
1108                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
1109 #if !BB_MMU
1110         /* on NOMMU reexec (i.e., background) early */
1111         if (!(opt & OPT_f)) {
1112                 bb_daemonize_or_rexec(0 /* flags */, argv);
1113                 logmode = LOGMODE_NONE;
1114         }
1115 #endif
1116         if (opt & OPT_S) {
1117                 openlog(applet_name, LOG_PID, LOG_DAEMON);
1118                 logmode |= LOGMODE_SYSLOG;
1119         }
1120
1121         /* Make sure fd 0,1,2 are open */
1122         bb_sanitize_stdio();
1123         /* Equivalent of doing a fflush after every \n */
1124         setlinebuf(stdout);
1125         /* Create pidfile */
1126         write_pidfile(client_config.pidfile);
1127         /* Goes to stdout (unless NOMMU) and possibly syslog */
1128         bb_info_msg("%s (v"BB_VER") started", applet_name);
1129         /* Set up the signal pipe */
1130         udhcp_sp_setup();
1131         /* We want random_xid to be random... */
1132         srand(monotonic_us());
1133
1134         state = INIT_SELECTING;
1135         udhcp_run_script(NULL, "deconfig");
1136         change_listen_mode(LISTEN_RAW);
1137         packet_num = 0;
1138         timeout = 0;
1139         already_waited_sec = 0;
1140
1141         /* Main event loop. select() waits on signal pipe and possibly
1142          * on sockfd.
1143          * "continue" statements in code below jump to the top of the loop.
1144          */
1145         for (;;) {
1146                 /* silence "uninitialized!" warning */
1147                 unsigned timestamp_before_wait = timestamp_before_wait;
1148
1149                 //bb_error_msg("sockfd:%d, listen_mode:%d", sockfd, listen_mode);
1150
1151                 /* Was opening raw or udp socket here
1152                  * if (listen_mode != LISTEN_NONE && sockfd < 0),
1153                  * but on fast network renew responses return faster
1154                  * than we open sockets. Thus this code is moved
1155                  * to change_listen_mode(). Thus we open listen socket
1156                  * BEFORE we send renew request (see "case BOUND:"). */
1157
1158                 max_fd = udhcp_sp_fd_set(&rfds, sockfd);
1159
1160                 tv.tv_sec = timeout - already_waited_sec;
1161                 tv.tv_usec = 0;
1162                 retval = 0;
1163                 /* If we already timed out, fall through with retval = 0, else... */
1164                 if ((int)tv.tv_sec > 0) {
1165                         timestamp_before_wait = (unsigned)monotonic_sec();
1166                         log1("Waiting on select...");
1167                         retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
1168                         if (retval < 0) {
1169                                 /* EINTR? A signal was caught, don't panic */
1170                                 if (errno == EINTR) {
1171                                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1172                                         continue;
1173                                 }
1174                                 /* Else: an error occured, panic! */
1175                                 bb_perror_msg_and_die("select");
1176                         }
1177                 }
1178
1179                 /* If timeout dropped to zero, time to become active:
1180                  * resend discover/renew/whatever
1181                  */
1182                 if (retval == 0) {
1183                         /* When running on a bridge, the ifindex may have changed
1184                          * (e.g. if member interfaces were added/removed
1185                          * or if the status of the bridge changed).
1186                          * Refresh ifindex and client_mac:
1187                          */
1188                         if (udhcp_read_interface(client_config.interface,
1189                                         &client_config.ifindex,
1190                                         NULL,
1191                                         client_config.client_mac)
1192                         ) {
1193                                 return 1; /* iface is gone? */
1194                         }
1195                         if (clientid_mac_ptr)
1196                                 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1197
1198                         /* We will restart the wait in any case */
1199                         already_waited_sec = 0;
1200
1201                         switch (state) {
1202                         case INIT_SELECTING:
1203                                 if (packet_num < discover_retries) {
1204                                         if (packet_num == 0)
1205                                                 xid = random_xid();
1206                                         /* broadcast */
1207                                         send_discover(xid, requested_ip);
1208                                         timeout = discover_timeout;
1209                                         packet_num++;
1210                                         continue;
1211                                 }
1212  leasefail:
1213                                 udhcp_run_script(NULL, "leasefail");
1214 #if BB_MMU /* -b is not supported on NOMMU */
1215                                 if (opt & OPT_b) { /* background if no lease */
1216                                         bb_info_msg("No lease, forking to background");
1217                                         client_background();
1218                                         /* do not background again! */
1219                                         opt = ((opt & ~OPT_b) | OPT_f);
1220                                 } else
1221 #endif
1222                                 if (opt & OPT_n) { /* abort if no lease */
1223                                         bb_info_msg("No lease, failing");
1224                                         retval = 1;
1225                                         goto ret;
1226                                 }
1227                                 /* wait before trying again */
1228                                 timeout = tryagain_timeout;
1229                                 packet_num = 0;
1230                                 continue;
1231                         case REQUESTING:
1232                                 if (packet_num < discover_retries) {
1233                                         /* send broadcast select packet */
1234                                         send_select(xid, server_addr, requested_ip);
1235                                         timeout = discover_timeout;
1236                                         packet_num++;
1237                                         continue;
1238                                 }
1239                                 /* Timed out, go back to init state.
1240                                  * "discover...select...discover..." loops
1241                                  * were seen in the wild. Treat them similarly
1242                                  * to "no response to discover" case */
1243                                 change_listen_mode(LISTEN_RAW);
1244                                 state = INIT_SELECTING;
1245                                 goto leasefail;
1246                         case BOUND:
1247                                 /* 1/2 lease passed, enter renewing state */
1248                                 state = RENEWING;
1249                                 change_listen_mode(LISTEN_KERNEL);
1250                                 log1("Entering renew state");
1251                                 /* fall right through */
1252                         case RENEW_REQUESTED: /* manual (SIGUSR1) renew */
1253                         case_RENEW_REQUESTED:
1254                         case RENEWING:
1255                                 if (timeout > 60) {
1256                                         /* send an unicast renew request */
1257                         /* Sometimes observed to fail (EADDRNOTAVAIL) to bind
1258                          * a new UDP socket for sending inside send_renew.
1259                          * I hazard to guess existing listening socket
1260                          * is somehow conflicting with it, but why is it
1261                          * not deterministic then?! Strange.
1262                          * Anyway, it does recover by eventually failing through
1263                          * into INIT_SELECTING state.
1264                          */
1265                                         send_renew(xid, server_addr, requested_ip);
1266                                         timeout >>= 1;
1267                                         continue;
1268                                 }
1269                                 /* Timed out, enter rebinding state */
1270                                 log1("Entering rebinding state");
1271                                 state = REBINDING;
1272                                 /* fall right through */
1273                         case REBINDING:
1274                                 /* Switch to bcast receive */
1275                                 change_listen_mode(LISTEN_RAW);
1276                                 /* Lease is *really* about to run out,
1277                                  * try to find DHCP server using broadcast */
1278                                 if (timeout > 0) {
1279                                         /* send a broadcast renew request */
1280                                         send_renew(xid, 0 /*INADDR_ANY*/, requested_ip);
1281                                         timeout >>= 1;
1282                                         continue;
1283                                 }
1284                                 /* Timed out, enter init state */
1285                                 bb_info_msg("Lease lost, entering init state");
1286                                 udhcp_run_script(NULL, "deconfig");
1287                                 state = INIT_SELECTING;
1288                                 /*timeout = 0; - already is */
1289                                 packet_num = 0;
1290                                 continue;
1291                         /* case RELEASED: */
1292                         }
1293                         /* yah, I know, *you* say it would never happen */
1294                         timeout = INT_MAX;
1295                         continue; /* back to main loop */
1296                 } /* if select timed out */
1297
1298                 /* select() didn't timeout, something happened */
1299
1300                 /* Is it a signal? */
1301                 /* note: udhcp_sp_read checks FD_ISSET before reading */
1302                 switch (udhcp_sp_read(&rfds)) {
1303                 case SIGUSR1:
1304                         perform_renew();
1305                         if (state == RENEW_REQUESTED)
1306                                 goto case_RENEW_REQUESTED;
1307                         /* Start things over */
1308                         packet_num = 0;
1309                         /* Kill any timeouts, user wants this to hurry along */
1310                         timeout = 0;
1311                         continue;
1312                 case SIGUSR2:
1313                         perform_release(requested_ip, server_addr);
1314                         timeout = INT_MAX;
1315                         continue;
1316                 case SIGTERM:
1317                         bb_info_msg("Received SIGTERM");
1318                         if (opt & OPT_R) /* release on quit */
1319                                 perform_release(requested_ip, server_addr);
1320                         goto ret0;
1321                 }
1322
1323                 /* Is it a packet? */
1324                 if (listen_mode == LISTEN_NONE || !FD_ISSET(sockfd, &rfds))
1325                         continue; /* no */
1326
1327                 {
1328                         int len;
1329
1330                         /* A packet is ready, read it */
1331                         if (listen_mode == LISTEN_KERNEL)
1332                                 len = udhcp_recv_kernel_packet(&packet, sockfd);
1333                         else
1334                                 len = udhcp_recv_raw_packet(&packet, sockfd);
1335                         if (len == -1) {
1336                                 /* Error is severe, reopen socket */
1337                                 bb_info_msg("Read error: %s, reopening socket", strerror(errno));
1338                                 sleep(discover_timeout); /* 3 seconds by default */
1339                                 change_listen_mode(listen_mode); /* just close and reopen */
1340                         }
1341                         /* If this packet will turn out to be unrelated/bogus,
1342                          * we will go back and wait for next one.
1343                          * Be sure timeout is properly decreased. */
1344                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1345                         if (len < 0)
1346                                 continue;
1347                 }
1348
1349                 if (packet.xid != xid) {
1350                         log1("xid %x (our is %x), ignoring packet",
1351                                 (unsigned)packet.xid, (unsigned)xid);
1352                         continue;
1353                 }
1354
1355                 /* Ignore packets that aren't for us */
1356                 if (packet.hlen != 6
1357                  || memcmp(packet.chaddr, client_config.client_mac, 6) != 0
1358                 ) {
1359 //FIXME: need to also check that last 10 bytes are zero
1360                         log1("chaddr does not match, ignoring packet"); // log2?
1361                         continue;
1362                 }
1363
1364                 message = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
1365                 if (message == NULL) {
1366                         bb_error_msg("no message type option, ignoring packet");
1367                         continue;
1368                 }
1369
1370                 switch (state) {
1371                 case INIT_SELECTING:
1372                         /* Must be a DHCPOFFER to one of our xid's */
1373                         if (*message == DHCPOFFER) {
1374                 /* TODO: why we don't just fetch server's IP from IP header? */
1375                                 temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
1376                                 if (!temp) {
1377                                         bb_error_msg("no server ID, ignoring packet");
1378                                         continue;
1379                                         /* still selecting - this server looks bad */
1380                                 }
1381                                 /* it IS unaligned sometimes, don't "optimize" */
1382                                 move_from_unaligned32(server_addr, temp);
1383                                 /*xid = packet.xid; - already is */
1384                                 requested_ip = packet.yiaddr;
1385
1386                                 /* enter requesting state */
1387                                 state = REQUESTING;
1388                                 timeout = 0;
1389                                 packet_num = 0;
1390                                 already_waited_sec = 0;
1391                         }
1392                         continue;
1393                 case REQUESTING:
1394                 case RENEWING:
1395                 case RENEW_REQUESTED:
1396                 case REBINDING:
1397                         if (*message == DHCPACK) {
1398                                 temp = udhcp_get_option(&packet, DHCP_LEASE_TIME);
1399                                 if (!temp) {
1400                                         bb_error_msg("no lease time with ACK, using 1 hour lease");
1401                                         lease_seconds = 60 * 60;
1402                                 } else {
1403                                         /* it IS unaligned sometimes, don't "optimize" */
1404                                         move_from_unaligned32(lease_seconds, temp);
1405                                         lease_seconds = ntohl(lease_seconds);
1406                                         lease_seconds &= 0x0fffffff; /* paranoia: must not be prone to overflows */
1407                                         if (lease_seconds < 10) /* and not too small */
1408                                                 lease_seconds = 10;
1409                                 }
1410 #if ENABLE_FEATURE_UDHCPC_ARPING
1411                                 if (opt & OPT_a) {
1412 /* RFC 2131 3.1 paragraph 5:
1413  * "The client receives the DHCPACK message with configuration
1414  * parameters. The client SHOULD perform a final check on the
1415  * parameters (e.g., ARP for allocated network address), and notes
1416  * the duration of the lease specified in the DHCPACK message. At this
1417  * point, the client is configured. If the client detects that the
1418  * address is already in use (e.g., through the use of ARP),
1419  * the client MUST send a DHCPDECLINE message to the server and restarts
1420  * the configuration process..." */
1421                                         if (!arpping(packet.yiaddr,
1422                                                         NULL,
1423                                                         (uint32_t) 0,
1424                                                         client_config.client_mac,
1425                                                         client_config.interface)
1426                                         ) {
1427                                                 bb_info_msg("Offered address is in use "
1428                                                         "(got ARP reply), declining");
1429                                                 send_decline(xid, server_addr, packet.yiaddr);
1430
1431                                                 if (state != REQUESTING)
1432                                                         udhcp_run_script(NULL, "deconfig");
1433                                                 change_listen_mode(LISTEN_RAW);
1434                                                 state = INIT_SELECTING;
1435                                                 requested_ip = 0;
1436                                                 timeout = tryagain_timeout;
1437                                                 packet_num = 0;
1438                                                 already_waited_sec = 0;
1439                                                 continue; /* back to main loop */
1440                                         }
1441                                 }
1442 #endif
1443                                 /* enter bound state */
1444                                 timeout = lease_seconds / 2;
1445                                 {
1446                                         struct in_addr temp_addr;
1447                                         temp_addr.s_addr = packet.yiaddr;
1448                                         bb_info_msg("Lease of %s obtained, lease time %u",
1449                                                 inet_ntoa(temp_addr), (unsigned)lease_seconds);
1450                                 }
1451                                 requested_ip = packet.yiaddr;
1452                                 udhcp_run_script(&packet, state == REQUESTING ? "bound" : "renew");
1453
1454                                 state = BOUND;
1455                                 change_listen_mode(LISTEN_NONE);
1456                                 if (opt & OPT_q) { /* quit after lease */
1457                                         if (opt & OPT_R) /* release on quit */
1458                                                 perform_release(requested_ip, server_addr);
1459                                         goto ret0;
1460                                 }
1461                                 /* future renew failures should not exit (JM) */
1462                                 opt &= ~OPT_n;
1463 #if BB_MMU /* NOMMU case backgrounded earlier */
1464                                 if (!(opt & OPT_f)) {
1465                                         client_background();
1466                                         /* do not background again! */
1467                                         opt = ((opt & ~OPT_b) | OPT_f);
1468                                 }
1469 #endif
1470                                 already_waited_sec = 0;
1471                                 continue; /* back to main loop */
1472                         }
1473                         if (*message == DHCPNAK) {
1474                                 /* return to init state */
1475                                 bb_info_msg("Received DHCP NAK");
1476                                 udhcp_run_script(&packet, "nak");
1477                                 if (state != REQUESTING)
1478                                         udhcp_run_script(NULL, "deconfig");
1479                                 change_listen_mode(LISTEN_RAW);
1480                                 sleep(3); /* avoid excessive network traffic */
1481                                 state = INIT_SELECTING;
1482                                 requested_ip = 0;
1483                                 timeout = 0;
1484                                 packet_num = 0;
1485                                 already_waited_sec = 0;
1486                         }
1487                         continue;
1488                 /* case BOUND: - ignore all packets */
1489                 /* case RELEASED: - ignore all packets */
1490                 }
1491                 /* back to main loop */
1492         } /* for (;;) - main loop ends */
1493
1494  ret0:
1495         retval = 0;
1496  ret:
1497         /*if (client_config.pidfile) - remove_pidfile has its own check */
1498                 remove_pidfile(client_config.pidfile);
1499         return retval;
1500 }