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         if (client_config.hostname)
 366                 udhcp_add_binary_option(packet, client_config.hostname);
 367         if (client_config.fqdn)
 368                 udhcp_add_binary_option(packet, client_config.fqdn);
 369         if (client_config.vendorclass)
 370                 udhcp_add_binary_option(packet, client_config.vendorclass);
 371
 372         /* Add a "param req" option with the list of options we'd like to have
 373          * from stubborn DHCP servers. Pull the data from the struct in common.c.
 374          * No bounds checking because it goes towards the head of the packet. */
 375         end = udhcp_end_option(packet->options);
 376         len = 0;
 377         for (i = 0; (c = dhcp_optflags[i].code) != 0; i++) {
 378                 if ((   (dhcp_optflags[i].flags & OPTION_REQ)
 379                      && !client_config.no_default_options
 380                     )
 381                  || (client_config.opt_mask[c >> 3] & (1 << (c & 7)))
 382                 ) {
 383                         packet->options[end + OPT_DATA + len] = c;
 384                         len++;
 385                 }
 386         }
 387         if (len) {
 388                 packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
 389                 packet->options[end + OPT_LEN] = len;
 390                 packet->options[end + OPT_DATA + len] = DHCP_END;
 391         }
 392
 393         /* Add -x options if any */
 394         {
 395                 struct option_set *curr = client_config.options;
 396                 while (curr) {
 397                         udhcp_add_binary_option(packet, curr->data);
 398                         curr = curr->next;
 399                 }
 400 //              if (client_config.sname)
 401 //                      strncpy((char*)packet->sname, client_config.sname, sizeof(packet->sname) - 1);
 402 //              if (client_config.boot_file)
 403 //                      strncpy((char*)packet->file, client_config.boot_file, sizeof(packet->file) - 1);
 404         }
 405 }
 406
 407 /* RFC 2131
 408  * 4.4.4 Use of broadcast and unicast
 409  *
 410  * The DHCP client broadcasts DHCPDISCOVER, DHCPREQUEST and DHCPINFORM
 411  * messages, unless the client knows the address of a DHCP server.
 412  * The client unicasts DHCPRELEASE messages to the server. Because
 413  * the client is declining the use of the IP address supplied by the server,
 414  * the client broadcasts DHCPDECLINE messages.
 415  *
 416  * When the DHCP client knows the address of a DHCP server, in either
 417  * INIT or REBOOTING state, the client may use that address
 418  * in the DHCPDISCOVER or DHCPREQUEST rather than the IP broadcast address.
 419  * The client may also use unicast to send DHCPINFORM messages
 420  * to a known DHCP server. If the client receives no response to DHCP
 421  * messages sent to the IP address of a known DHCP server, the DHCP
 422  * client reverts to using the IP broadcast address.
 423  */
 424
 425 static int raw_bcast_from_client_config_ifindex(struct dhcp_packet *packet)
 426 {
 427         return udhcp_send_raw_packet(packet,
 428                 /*src*/ INADDR_ANY, CLIENT_PORT,
 429                 /*dst*/ INADDR_BROADCAST, SERVER_PORT, MAC_BCAST_ADDR,
 430                 client_config.ifindex);
 431 }
 432
 433 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
 434 static int send_discover(uint32_t xid, uint32_t requested)
 435 {
 436         struct dhcp_packet packet;
 437
 438         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 439          * random xid field (we override it below),
 440          * client-id option (unless -C), message type option:
 441          */
 442         init_packet(&packet, DHCPDISCOVER);
 443
 444         packet.xid = xid;
 445         if (requested)
 446                 udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 447
 448         /* Add options: maxsize,
 449          * optionally: hostname, fqdn, vendorclass,
 450          * "param req" option according to -O, options specified with -x
 451          */
 452         add_client_options(&packet);
 453
 454         bb_info_msg("Sending discover...");
 455         return raw_bcast_from_client_config_ifindex(&packet);
 456 }
 457
 458 /* Broadcast a DHCP request message */
 459 /* RFC 2131 3.1 paragraph 3:
 460  * "The client _broadcasts_ a DHCPREQUEST message..."
 461  */
 462 static int send_select(uint32_t xid, uint32_t server, uint32_t requested)
 463 {
 464         struct dhcp_packet packet;
 465         struct in_addr addr;
 466
 467 /*
 468  * RFC 2131 4.3.2 DHCPREQUEST message
 469  * ...
 470  * If the DHCPREQUEST message contains a 'server identifier'
 471  * option, the message is in response to a DHCPOFFER message.
 472  * Otherwise, the message is a request to verify or extend an
 473  * existing lease. If the client uses a 'client identifier'
 474  * in a DHCPREQUEST message, it MUST use that same 'client identifier'
 475  * in all subsequent messages. If the client included a list
 476  * of requested parameters in a DHCPDISCOVER message, it MUST
 477  * include that list in all subsequent messages.
 478  */
 479         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 480          * random xid field (we override it below),
 481          * client-id option (unless -C), message type option:
 482          */
 483         init_packet(&packet, DHCPREQUEST);
 484
 485         packet.xid = xid;
 486         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 487
 488         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 489
 490         /* Add options: maxsize,
 491          * optionally: hostname, fqdn, vendorclass,
 492          * "param req" option according to -O, and options specified with -x
 493          */
 494         add_client_options(&packet);
 495
 496         addr.s_addr = requested;
 497         bb_info_msg("Sending select for %s...", inet_ntoa(addr));
 498         return raw_bcast_from_client_config_ifindex(&packet);
 499 }
 500
 501 /* Unicast or broadcast a DHCP renew message */
 502 static int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
 503 {
 504         struct dhcp_packet packet;
 505
 506 /*
 507  * RFC 2131 4.3.2 DHCPREQUEST message
 508  * ...
 509  * DHCPREQUEST generated during RENEWING state:
 510  *
 511  * 'server identifier' MUST NOT be filled in, 'requested IP address'
 512  * option MUST NOT be filled in, 'ciaddr' MUST be filled in with
 513  * client's IP address. In this situation, the client is completely
 514  * configured, and is trying to extend its lease. This message will
 515  * be unicast, so no relay agents will be involved in its
 516  * transmission.  Because 'giaddr' is therefore not filled in, the
 517  * DHCP server will trust the value in 'ciaddr', and use it when
 518  * replying to the client.
 519  */
 520         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 521          * random xid field (we override it below),
 522          * client-id option (unless -C), message type option:
 523          */
 524         init_packet(&packet, DHCPREQUEST);
 525
 526         packet.xid = xid;
 527         packet.ciaddr = ciaddr;
 528
 529         /* Add options: maxsize,
 530          * optionally: hostname, fqdn, vendorclass,
 531          * "param req" option according to -O, and options specified with -x
 532          */
 533         add_client_options(&packet);
 534
 535         bb_info_msg("Sending renew...");
 536         if (server)
 537                 return udhcp_send_kernel_packet(&packet,
 538                         ciaddr, CLIENT_PORT,
 539                         server, SERVER_PORT);
 540         return raw_bcast_from_client_config_ifindex(&packet);
 541 }
 542
 543 #if ENABLE_FEATURE_UDHCPC_ARPING
 544 /* Broadcast a DHCP decline message */
 545 static int send_decline(uint32_t xid, uint32_t server, uint32_t requested)
 546 {
 547         struct dhcp_packet packet;
 548
 549         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 550          * client-id option (unless -C), message type option:
 551          */
 552         init_packet(&packet, DHCPDECLINE);
 553
 554         /* RFC 2131 says DHCPDECLINE's xid is randomly selected by client,
 555          * but in case the server is buggy and wants DHCPDECLINE's xid
 556          * to match the xid which started entire handshake,
 557          * we use the same xid we used in initial DHCPDISCOVER:
 558          */
 559         packet.xid = xid;
 560         /* DHCPDECLINE uses "requested ip", not ciaddr, to store offered IP */
 561         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 562
 563         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 564
 565         bb_info_msg("Sending decline...");
 566         return raw_bcast_from_client_config_ifindex(&packet);
 567 }
 568 #endif
 569
 570 /* Unicast a DHCP release message */
 571 static int send_release(uint32_t server, uint32_t ciaddr)
 572 {
 573         struct dhcp_packet packet;
 574
 575         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 576          * client-id option (unless -C), message type option:
 577          */
 578         init_packet(&packet, DHCPRELEASE);
 579
 580         /* DHCPRELEASE uses ciaddr, not "requested ip", to store IP being released */
 581         packet.ciaddr = ciaddr;
 582
 583         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 584
 585         bb_info_msg("Sending release...");
 586         return udhcp_send_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
 587 }
 588
 589 /* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */
 590 static NOINLINE int udhcp_recv_raw_packet(struct dhcp_packet *dhcp_pkt, int fd)
 591 {
 592         int bytes;
 593         struct ip_udp_dhcp_packet packet;
 594         uint16_t check;
 595
 596         memset(&packet, 0, sizeof(packet));
 597         bytes = safe_read(fd, &packet, sizeof(packet));
 598         if (bytes < 0) {
 599                 log1("Packet read error, ignoring");
 600                 /* NB: possible down interface, etc. Caller should pause. */
 601                 return bytes; /* returns -1 */
 602         }
 603
 604         if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) {
 605                 log1("Packet is too short, ignoring");
 606                 return -2;
 607         }
 608
 609         if (bytes < ntohs(packet.ip.tot_len)) {
 610                 /* packet is bigger than sizeof(packet), we did partial read */
 611                 log1("Oversized packet, ignoring");
 612                 return -2;
 613         }
 614
 615         /* ignore any extra garbage bytes */
 616         bytes = ntohs(packet.ip.tot_len);
 617
 618         /* make sure its the right packet for us, and that it passes sanity checks */
 619         if (packet.ip.protocol != IPPROTO_UDP || packet.ip.version != IPVERSION
 620          || packet.ip.ihl != (sizeof(packet.ip) >> 2)
 621          || packet.udp.dest != htons(CLIENT_PORT)
 622         /* || bytes > (int) sizeof(packet) - can't happen */
 623          || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
 624         ) {
 625                 log1("Unrelated/bogus packet, ignoring");
 626                 return -2;
 627         }
 628
 629         /* verify IP checksum */
 630         check = packet.ip.check;
 631         packet.ip.check = 0;
 632         if (check != udhcp_checksum(&packet.ip, sizeof(packet.ip))) {
 633                 log1("Bad IP header checksum, ignoring");
 634                 return -2;
 635         }
 636
 637         /* verify UDP checksum. IP header has to be modified for this */
 638         memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
 639         /* ip.xx fields which are not memset: protocol, check, saddr, daddr */
 640         packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
 641         check = packet.udp.check;
 642         packet.udp.check = 0;
 643         if (check && check != udhcp_checksum(&packet, bytes)) {
 644                 log1("Packet with bad UDP checksum received, ignoring");
 645                 return -2;
 646         }
 647
 648         memcpy(dhcp_pkt, &packet.data, bytes - (sizeof(packet.ip) + sizeof(packet.udp)));
 649
 650         if (dhcp_pkt->cookie != htonl(DHCP_MAGIC)) {
 651                 bb_info_msg("Packet with bad magic, ignoring");
 652                 return -2;
 653         }
 654         log1("Got valid DHCP packet");
 655         udhcp_dump_packet(dhcp_pkt);
 656         return bytes - (sizeof(packet.ip) + sizeof(packet.udp));
 657 }
 658
 659
 660 /*** Main ***/
 661
 662 static int sockfd = -1;
 663
 664 #define LISTEN_NONE   0
 665 #define LISTEN_KERNEL 1
 666 #define LISTEN_RAW    2
 667 static smallint listen_mode;
 668
 669 /* initial state: (re)start DHCP negotiation */
 670 #define INIT_SELECTING  0
 671 /* discover was sent, DHCPOFFER reply received */
 672 #define REQUESTING      1
 673 /* select/renew was sent, DHCPACK reply received */
 674 #define BOUND           2
 675 /* half of lease passed, want to renew it by sending unicast renew requests */
 676 #define RENEWING        3
 677 /* renew requests were not answered, lease is almost over, send broadcast renew */
 678 #define REBINDING       4
 679 /* manually requested renew (SIGUSR1) */
 680 #define RENEW_REQUESTED 5
 681 /* release, possibly manually requested (SIGUSR2) */
 682 #define RELEASED        6
 683 static smallint state;
 684
 685 static int udhcp_raw_socket(int ifindex)
 686 {
 687         int fd;
 688         struct sockaddr_ll sock;
 689
 690         /*
 691          * Comment:
 692          *
 693          *      I've selected not to see LL header, so BPF doesn't see it, too.
 694          *      The filter may also pass non-IP and non-ARP packets, but we do
 695          *      a more complete check when receiving the message in userspace.
 696          *
 697          * and filter shamelessly stolen from:
 698          *
 699          *      http://www.flamewarmaster.de/software/dhcpclient/
 700          *
 701          * There are a few other interesting ideas on that page (look under
 702          * "Motivation").  Use of netlink events is most interesting.  Think
 703          * of various network servers listening for events and reconfiguring.
 704          * That would obsolete sending HUP signals and/or make use of restarts.
 705          *
 706          * Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
 707          * License: GPL v2.
 708          *
 709          * TODO: make conditional?
 710          */
 711 #define SERVER_AND_CLIENT_PORTS  ((67 << 16) + 68)
 712         static const struct sock_filter filter_instr[] = {
 713                 /* check for udp */
 714                 BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
 715                 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 2, 0),     /* L5, L1, is UDP? */
 716                 /* ugly check for arp on ethernet-like and IPv4 */
 717                 BPF_STMT(BPF_LD|BPF_W|BPF_ABS, 2),                      /* L1: */
 718                 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 0x08000604, 3, 4),      /* L3, L4 */
 719                 /* skip IP header */
 720                 BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0),                     /* L5: */
 721                 /* check udp source and destination ports */
 722                 BPF_STMT(BPF_LD|BPF_W|BPF_IND, 0),
 723                 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, SERVER_AND_CLIENT_PORTS, 0, 1), /* L3, L4 */
 724                 /* returns */
 725                 BPF_STMT(BPF_RET|BPF_K, 0x0fffffff ),                   /* L3: pass */
 726                 BPF_STMT(BPF_RET|BPF_K, 0),                             /* L4: reject */
 727         };
 728         static const struct sock_fprog filter_prog = {
 729                 .len = sizeof(filter_instr) / sizeof(filter_instr[0]),
 730                 /* casting const away: */
 731                 .filter = (struct sock_filter *) filter_instr,
 732         };
 733
 734         log1("Opening raw socket on ifindex %d", ifindex); //log2?
 735
 736         fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
 737         log1("Got raw socket fd %d", fd); //log2?
 738
 739         if (SERVER_PORT == 67 && CLIENT_PORT == 68) {
 740                 /* Use only if standard ports are in use */
 741                 /* Ignoring error (kernel may lack support for this) */
 742                 if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
 743                                 sizeof(filter_prog)) >= 0)
 744                         log1("Attached filter to raw socket fd %d", fd); // log?
 745         }
 746
 747         sock.sll_family = AF_PACKET;
 748         sock.sll_protocol = htons(ETH_P_IP);
 749         sock.sll_ifindex = ifindex;
 750         xbind(fd, (struct sockaddr *) &sock, sizeof(sock));
 751         log1("Created raw socket");
 752
 753         return fd;
 754 }
 755
 756 static void change_listen_mode(int new_mode)
 757 {
 758         log1("Entering listen mode: %s",
 759                 new_mode != LISTEN_NONE
 760                         ? (new_mode == LISTEN_KERNEL ? "kernel" : "raw")
 761                         : "none"
 762         );
 763
 764         listen_mode = new_mode;
 765         if (sockfd >= 0) {
 766                 close(sockfd);
 767                 sockfd = -1;
 768         }
 769         if (new_mode == LISTEN_KERNEL)
 770                 sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
 771         else if (new_mode != LISTEN_NONE)
 772                 sockfd = udhcp_raw_socket(client_config.ifindex);
 773         /* else LISTEN_NONE: sockfd stays closed */
 774 }
 775
 776 static void perform_renew(void)
 777 {
 778         bb_info_msg("Performing a DHCP renew");
 779         switch (state) {
 780         case BOUND:
 781                 change_listen_mode(LISTEN_KERNEL);
 782         case RENEWING:
 783         case REBINDING:
 784                 state = RENEW_REQUESTED;
 785                 break;
 786         case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
 787                 udhcp_run_script(NULL, "deconfig");
 788         case REQUESTING:
 789         case RELEASED:
 790                 change_listen_mode(LISTEN_RAW);
 791                 state = INIT_SELECTING;
 792                 break;
 793         case INIT_SELECTING:
 794                 break;
 795         }
 796 }
 797
 798 static void perform_release(uint32_t requested_ip, uint32_t server_addr)
 799 {
 800         char buffer[sizeof("255.255.255.255")];
 801         struct in_addr temp_addr;
 802
 803         /* send release packet */
 804         if (state == BOUND || state == RENEWING || state == REBINDING) {
 805                 temp_addr.s_addr = server_addr;
 806                 strcpy(buffer, inet_ntoa(temp_addr));
 807                 temp_addr.s_addr = requested_ip;
 808                 bb_info_msg("Unicasting a release of %s to %s",
 809                                 inet_ntoa(temp_addr), buffer);
 810                 send_release(server_addr, requested_ip); /* unicast */
 811                 udhcp_run_script(NULL, "deconfig");
 812         }
 813         bb_info_msg("Entering released state");
 814
 815         change_listen_mode(LISTEN_NONE);
 816         state = RELEASED;
 817 }
 818
 819 static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
 820 {
 821         uint8_t *storage;
 822         int len = strnlen(str, 255);
 823         storage = xzalloc(len + extra + OPT_DATA);
 824         storage[OPT_CODE] = code;
 825         storage[OPT_LEN] = len + extra;
 826         memcpy(storage + extra + OPT_DATA, str, len);
 827         return storage;
 828 }
 829
 830 #if BB_MMU
 831 static void client_background(void)
 832 {
 833         bb_daemonize(0);
 834         logmode &= ~LOGMODE_STDIO;
 835         /* rewrite pidfile, as our pid is different now */
 836         write_pidfile(client_config.pidfile);
 837 }
 838 #endif
 839
 840 //usage:#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
 841 //usage:# define IF_UDHCP_VERBOSE(...) __VA_ARGS__
 842 //usage:#else
 843 //usage:# define IF_UDHCP_VERBOSE(...)
 844 //usage:#endif
 845 //usage:#define udhcpc_trivial_usage
 846 //usage:       "[-fbnq"IF_UDHCP_VERBOSE("v")"oCR] [-i IFACE] [-r IP] [-s PROG] [-p PIDFILE]\n"
 847 //usage:       "        [-H HOSTNAME] [-V VENDOR] [-x OPT:VAL]... [-O OPT]..." IF_FEATURE_UDHCP_PORT(" [-P N]")
 848 //usage:#define udhcpc_full_usage "\n"
 849 //usage:        IF_LONG_OPTS(
 850 //usage:     "\n        -i,--interface IFACE    Interface to use (default eth0)"
 851 //usage:     "\n        -p,--pidfile FILE       Create pidfile"
 852 //usage:     "\n        -s,--script PROG        Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
 853 //usage:     "\n        -t,--retries N          Send up to N discover packets"
 854 //usage:     "\n        -T,--timeout N          Pause between packets (default 3 seconds)"
 855 //usage:     "\n        -A,--tryagain N         Wait N seconds after failure (default 20)"
 856 //usage:     "\n        -f,--foreground         Run in foreground"
 857 //usage:        USE_FOR_MMU(
 858 //usage:     "\n        -b,--background         Background if lease is not obtained"
 859 //usage:        )
 860 //usage:     "\n        -n,--now                Exit if lease is not obtained"
 861 //usage:     "\n        -q,--quit               Exit after obtaining lease"
 862 //usage:     "\n        -R,--release            Release IP on exit"
 863 //usage:     "\n        -S,--syslog             Log to syslog too"
 864 //usage:        IF_FEATURE_UDHCP_PORT(
 865 //usage:     "\n        -P,--client-port N      Use port N (default 68)"
 866 //usage:        )
 867 //usage:        IF_FEATURE_UDHCPC_ARPING(
 868 //usage:     "\n        -a,--arping             Use arping to validate offered address"
 869 //usage:        )
 870 //usage:     "\n        -O,--request-option OPT Request option OPT from server (cumulative)"
 871 //usage:     "\n        -o,--no-default-options Don't request any options (unless -O is given)"
 872 //usage:     "\n        -r,--request IP         Request this IP address"
 873 //usage:     "\n        -x OPT:VAL              Include option OPT in sent packets (cumulative)"
 874 //usage:     "\n                                Examples of string, numeric, and hex byte opts:"
 875 //usage:     "\n                                -x hostname:bbox - option 12"
 876 //usage:     "\n                                -x lease:3600 - option 51 (lease time)"
 877 //usage:     "\n                                -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
 878 //usage:     "\n        -F,--fqdn NAME          Ask server to update DNS mapping for NAME"
 879 //usage:     "\n        -H,-h,--hostname NAME   Send NAME as client hostname (default none)"
 880 //usage:     "\n        -V,--vendorclass VENDOR Vendor identifier (default 'udhcp VERSION')"
 881 //usage:     "\n        -C,--clientid-none      Don't send MAC as client identifier"
 882 //usage:        IF_UDHCP_VERBOSE(
 883 //usage:     "\n        -v                      Verbose"
 884 //usage:        )
 885 //usage:        )
 886 //usage:        IF_NOT_LONG_OPTS(
 887 //usage:     "\n        -i IFACE        Interface to use (default eth0)"
 888 //usage:     "\n        -p FILE         Create pidfile"
 889 //usage:     "\n        -s PROG         Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
 890 //usage:     "\n        -t N            Send up to N discover packets"
 891 //usage:     "\n        -T N            Pause between packets (default 3 seconds)"
 892 //usage:     "\n        -A N            Wait N seconds (default 20) after failure"
 893 //usage:     "\n        -f              Run in foreground"
 894 //usage:        USE_FOR_MMU(
 895 //usage:     "\n        -b              Background if lease is not obtained"
 896 //usage:        )
 897 //usage:     "\n        -n              Exit if lease is not obtained"
 898 //usage:     "\n        -q              Exit after obtaining lease"
 899 //usage:     "\n        -R              Release IP on exit"
 900 //usage:     "\n        -S              Log to syslog too"
 901 //usage:        IF_FEATURE_UDHCP_PORT(
 902 //usage:     "\n        -P N            Use port N (default 68)"
 903 //usage:        )
 904 //usage:        IF_FEATURE_UDHCPC_ARPING(
 905 //usage:     "\n        -a              Use arping to validate offered address"
 906 //usage:        )
 907 //usage:     "\n        -O OPT          Request option OPT from server (cumulative)"
 908 //usage:     "\n        -o              Don't request any options (unless -O is given)"
 909 //usage:     "\n        -r IP           Request this IP address"
 910 //usage:     "\n        -x OPT:VAL      Include option OPT in sent packets (cumulative)"
 911 //usage:     "\n                        Examples of string, numeric, and hex byte opts:"
 912 //usage:     "\n                        -x hostname:bbox - option 12"
 913 //usage:     "\n                        -x lease:3600 - option 51 (lease time)"
 914 //usage:     "\n                        -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
 915 //usage:     "\n        -F NAME         Ask server to update DNS mapping for NAME"
 916 //usage:     "\n        -H,-h NAME      Send NAME as client hostname (default none)"
 917 //usage:     "\n        -V VENDOR       Vendor identifier (default 'udhcp VERSION')"
 918 //usage:     "\n        -C              Don't send MAC as client identifier"
 919 //usage:        IF_UDHCP_VERBOSE(
 920 //usage:     "\n        -v              Verbose"
 921 //usage:        )
 922 //usage:        )
 923
 924 int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 925 int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 926 {
 927         uint8_t *temp, *message;
 928         const char *str_V, *str_h, *str_F, *str_r;
 929         IF_FEATURE_UDHCP_PORT(char *str_P;)
 930         llist_t *list_O = NULL;
 931         llist_t *list_x = NULL;
 932         int tryagain_timeout = 20;
 933         int discover_timeout = 3;
 934         int discover_retries = 3;
 935         uint32_t server_addr = server_addr; /* for compiler */
 936         uint32_t requested_ip = 0;
 937         uint32_t xid = 0;
 938         uint32_t lease_seconds = 0; /* can be given as 32-bit quantity */
 939         int packet_num;
 940         int timeout; /* must be signed */
 941         unsigned already_waited_sec;
 942         unsigned opt;
 943         int max_fd;
 944         int retval;
 945         struct timeval tv;
 946         struct dhcp_packet packet;
 947         fd_set rfds;
 948
 949 #if ENABLE_LONG_OPTS
 950         static const char udhcpc_longopts[] ALIGN1 =
 951                 "clientid-none\0"  No_argument       "C"
 952                 "vendorclass\0"    Required_argument "V"
 953                 "hostname\0"       Required_argument "H"
 954                 "fqdn\0"           Required_argument "F"
 955                 "interface\0"      Required_argument "i"
 956                 "now\0"            No_argument       "n"
 957                 "pidfile\0"        Required_argument "p"
 958                 "quit\0"           No_argument       "q"
 959                 "release\0"        No_argument       "R"
 960                 "request\0"        Required_argument "r"
 961                 "script\0"         Required_argument "s"
 962                 "timeout\0"        Required_argument "T"
 963                 "version\0"        No_argument       "v"
 964                 "retries\0"        Required_argument "t"
 965                 "tryagain\0"       Required_argument "A"
 966                 "syslog\0"         No_argument       "S"
 967                 "request-option\0" Required_argument "O"
 968                 "no-default-options\0" No_argument   "o"
 969                 "foreground\0"     No_argument       "f"
 970                 "background\0"     No_argument       "b"
 971                 IF_FEATURE_UDHCPC_ARPING("arping\0"     No_argument       "a")
 972                 IF_FEATURE_UDHCP_PORT("client-port\0"   Required_argument "P")
 973                 ;
 974 #endif
 975         enum {
 976                 OPT_C = 1 << 0,
 977                 OPT_V = 1 << 1,
 978                 OPT_H = 1 << 2,
 979                 OPT_h = 1 << 3,
 980                 OPT_F = 1 << 4,
 981                 OPT_i = 1 << 5,
 982                 OPT_n = 1 << 6,
 983                 OPT_p = 1 << 7,
 984                 OPT_q = 1 << 8,
 985                 OPT_R = 1 << 9,
 986                 OPT_r = 1 << 10,
 987                 OPT_s = 1 << 11,
 988                 OPT_T = 1 << 12,
 989                 OPT_t = 1 << 13,
 990                 OPT_S = 1 << 14,
 991                 OPT_A = 1 << 15,
 992                 OPT_O = 1 << 16,
 993                 OPT_o = 1 << 17,
 994                 OPT_x = 1 << 18,
 995                 OPT_f = 1 << 19,
 996 /* The rest has variable bit positions, need to be clever */
 997                 OPTBIT_f = 19,
 998                 USE_FOR_MMU(             OPTBIT_b,)
 999                 IF_FEATURE_UDHCPC_ARPING(OPTBIT_a,)
1000                 IF_FEATURE_UDHCP_PORT(   OPTBIT_P,)
1001                 USE_FOR_MMU(             OPT_b = 1 << OPTBIT_b,)
1002                 IF_FEATURE_UDHCPC_ARPING(OPT_a = 1 << OPTBIT_a,)
1003                 IF_FEATURE_UDHCP_PORT(   OPT_P = 1 << OPTBIT_P,)
1004         };
1005
1006         /* Default options. */
1007         IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;)
1008         IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
1009         client_config.interface = "eth0";
1010         client_config.script = CONFIG_UDHCPC_DEFAULT_SCRIPT;
1011         str_V = "udhcp "BB_VER;
1012
1013         /* Parse command line */
1014         /* O,x: list; -T,-t,-A take numeric param */
1015         opt_complementary = "O::x::T+:t+:A+"
1016 #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
1017                 ":vv"
1018 #endif
1019                 ;
1020         IF_LONG_OPTS(applet_long_options = udhcpc_longopts;)
1021         opt = getopt32(argv, "CV:H:h:F:i:np:qRr:s:T:t:SA:O:ox:f"
1022                 USE_FOR_MMU("b")
1023                 IF_FEATURE_UDHCPC_ARPING("a")
1024                 IF_FEATURE_UDHCP_PORT("P:")
1025                 "v"
1026                 , &str_V, &str_h, &str_h, &str_F
1027                 , &client_config.interface, &client_config.pidfile, &str_r /* i,p */
1028                 , &client_config.script /* s */
1029                 , &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */
1030                 , &list_O
1031                 , &list_x
1032                 IF_FEATURE_UDHCP_PORT(, &str_P)
1033 #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
1034                 , &dhcp_verbose
1035 #endif
1036                 );
1037         if (opt & (OPT_h|OPT_H))
1038                 client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
1039         if (opt & OPT_F) {
1040                 /* FQDN option format: [0x51][len][flags][0][0]<fqdn> */
1041                 client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
1042                 /* Flag bits: 0000NEOS
1043                  * S: 1 = Client requests server to update A RR in DNS as well as PTR
1044                  * O: 1 = Server indicates to client that DNS has been updated regardless
1045                  * E: 1 = Name is in DNS format, i.e. <4>host<6>domain<3>com<0>,
1046                  *    not "host.domain.com". Format 0 is obsolete.
1047                  * N: 1 = Client requests server to not update DNS (S must be 0 then)
1048                  * Two [0] bytes which follow are deprecated and must be 0.
1049                  */
1050                 client_config.fqdn[OPT_DATA + 0] = 0x1;
1051                 /*client_config.fqdn[OPT_DATA + 1] = 0; - xzalloc did it */
1052                 /*client_config.fqdn[OPT_DATA + 2] = 0; */
1053         }
1054         if (opt & OPT_r)
1055                 requested_ip = inet_addr(str_r);
1056 #if ENABLE_FEATURE_UDHCP_PORT
1057         if (opt & OPT_P) {
1058                 CLIENT_PORT = xatou16(str_P);
1059                 SERVER_PORT = CLIENT_PORT - 1;
1060         }
1061 #endif
1062         if (opt & OPT_o)
1063                 client_config.no_default_options = 1;
1064         while (list_O) {
1065                 char *optstr = llist_pop(&list_O);
1066                 unsigned n = udhcp_option_idx(optstr);
1067                 n = dhcp_optflags[n].code;
1068                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
1069         }
1070         while (list_x) {
1071                 char *optstr = llist_pop(&list_x);
1072                 char *colon = strchr(optstr, ':');
1073                 if (colon)
1074                         *colon = ' ';
1075                 /* now it looks similar to udhcpd's config file line:
1076                  * "optname optval", using the common routine: */
1077                 udhcp_str2optset(optstr, &client_config.options);
1078         }
1079
1080         if (udhcp_read_interface(client_config.interface,
1081                         &client_config.ifindex,
1082                         NULL,
1083                         client_config.client_mac)
1084         ) {
1085                 return 1;
1086         }
1087
1088         if (!(opt & OPT_C) && !udhcp_find_option(client_config.options, DHCP_CLIENT_ID)) {
1089                 /* not suppressed and not set, set the default client ID */
1090                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
1091                 client_config.clientid[OPT_DATA] = 1; /* type: ethernet */
1092                 memcpy(client_config.clientid + OPT_DATA+1, client_config.client_mac, 6);
1093         }
1094         if (str_V[0] != '\0')
1095                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
1096 #if !BB_MMU
1097         /* on NOMMU reexec (i.e., background) early */
1098         if (!(opt & OPT_f)) {
1099                 bb_daemonize_or_rexec(0 /* flags */, argv);
1100                 logmode = LOGMODE_NONE;
1101         }
1102 #endif
1103         if (opt & OPT_S) {
1104                 openlog(applet_name, LOG_PID, LOG_DAEMON);
1105                 logmode |= LOGMODE_SYSLOG;
1106         }
1107
1108         /* Make sure fd 0,1,2 are open */
1109         bb_sanitize_stdio();
1110         /* Equivalent of doing a fflush after every \n */
1111         setlinebuf(stdout);
1112         /* Create pidfile */
1113         write_pidfile(client_config.pidfile);
1114         /* Goes to stdout (unless NOMMU) and possibly syslog */
1115         bb_info_msg("%s (v"BB_VER") started", applet_name);
1116         /* Set up the signal pipe */
1117         udhcp_sp_setup();
1118         /* We want random_xid to be random... */
1119         srand(monotonic_us());
1120
1121         state = INIT_SELECTING;
1122         udhcp_run_script(NULL, "deconfig");
1123         change_listen_mode(LISTEN_RAW);
1124         packet_num = 0;
1125         timeout = 0;
1126         already_waited_sec = 0;
1127
1128         /* Main event loop. select() waits on signal pipe and possibly
1129          * on sockfd.
1130          * "continue" statements in code below jump to the top of the loop.
1131          */
1132         for (;;) {
1133                 /* silence "uninitialized!" warning */
1134                 unsigned timestamp_before_wait = timestamp_before_wait;
1135
1136                 //bb_error_msg("sockfd:%d, listen_mode:%d", sockfd, listen_mode);
1137
1138                 /* Was opening raw or udp socket here
1139                  * if (listen_mode != LISTEN_NONE && sockfd < 0),
1140                  * but on fast network renew responses return faster
1141                  * than we open sockets. Thus this code is moved
1142                  * to change_listen_mode(). Thus we open listen socket
1143                  * BEFORE we send renew request (see "case BOUND:"). */
1144
1145                 max_fd = udhcp_sp_fd_set(&rfds, sockfd);
1146
1147                 tv.tv_sec = timeout - already_waited_sec;
1148                 tv.tv_usec = 0;
1149                 retval = 0;
1150                 /* If we already timed out, fall through with retval = 0, else... */
1151                 if ((int)tv.tv_sec > 0) {
1152                         timestamp_before_wait = (unsigned)monotonic_sec();
1153                         log1("Waiting on select...");
1154                         retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
1155                         if (retval < 0) {
1156                                 /* EINTR? A signal was caught, don't panic */
1157                                 if (errno == EINTR) {
1158                                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1159                                         continue;
1160                                 }
1161                                 /* Else: an error occured, panic! */
1162                                 bb_perror_msg_and_die("select");
1163                         }
1164                 }
1165
1166                 /* If timeout dropped to zero, time to become active:
1167                  * resend discover/renew/whatever
1168                  */
1169                 if (retval == 0) {
1170                         /* When running on a bridge, the ifindex may have changed
1171                          * (e.g. if member interfaces were added/removed
1172                          * or if the status of the bridge changed).
1173                          * Refresh ifindex and client_mac:
1174                          */
1175                         udhcp_read_interface(client_config.interface,
1176                                 &client_config.ifindex,
1177                                 NULL,
1178                                 client_config.client_mac);
1179
1180                         /* We will restart the wait in any case */
1181                         already_waited_sec = 0;
1182
1183                         switch (state) {
1184                         case INIT_SELECTING:
1185                                 if (packet_num < discover_retries) {
1186                                         if (packet_num == 0)
1187                                                 xid = random_xid();
1188                                         /* broadcast */
1189                                         send_discover(xid, requested_ip);
1190                                         timeout = discover_timeout;
1191                                         packet_num++;
1192                                         continue;
1193                                 }
1194  leasefail:
1195                                 udhcp_run_script(NULL, "leasefail");
1196 #if BB_MMU /* -b is not supported on NOMMU */
1197                                 if (opt & OPT_b) { /* background if no lease */
1198                                         bb_info_msg("No lease, forking to background");
1199                                         client_background();
1200                                         /* do not background again! */
1201                                         opt = ((opt & ~OPT_b) | OPT_f);
1202                                 } else
1203 #endif
1204                                 if (opt & OPT_n) { /* abort if no lease */
1205                                         bb_info_msg("No lease, failing");
1206                                         retval = 1;
1207                                         goto ret;
1208                                 }
1209                                 /* wait before trying again */
1210                                 timeout = tryagain_timeout;
1211                                 packet_num = 0;
1212                                 continue;
1213                         case REQUESTING:
1214                                 if (packet_num < discover_retries) {
1215                                         /* send broadcast select packet */
1216                                         send_select(xid, server_addr, requested_ip);
1217                                         timeout = discover_timeout;
1218                                         packet_num++;
1219                                         continue;
1220                                 }
1221                                 /* Timed out, go back to init state.
1222                                  * "discover...select...discover..." loops
1223                                  * were seen in the wild. Treat them similarly
1224                                  * to "no response to discover" case */
1225                                 change_listen_mode(LISTEN_RAW);
1226                                 state = INIT_SELECTING;
1227                                 goto leasefail;
1228                         case BOUND:
1229                                 /* 1/2 lease passed, enter renewing state */
1230                                 state = RENEWING;
1231                                 change_listen_mode(LISTEN_KERNEL);
1232                                 log1("Entering renew state");
1233                                 /* fall right through */
1234                         case RENEW_REQUESTED: /* manual (SIGUSR1) renew */
1235                         case_RENEW_REQUESTED:
1236                         case RENEWING:
1237                                 if (timeout > 60) {
1238                                         /* send an unicast renew request */
1239                         /* Sometimes observed to fail (EADDRNOTAVAIL) to bind
1240                          * a new UDP socket for sending inside send_renew.
1241                          * I hazard to guess existing listening socket
1242                          * is somehow conflicting with it, but why is it
1243                          * not deterministic then?! Strange.
1244                          * Anyway, it does recover by eventually failing through
1245                          * into INIT_SELECTING state.
1246                          */
1247                                         send_renew(xid, server_addr, requested_ip);
1248                                         timeout >>= 1;
1249                                         continue;
1250                                 }
1251                                 /* Timed out, enter rebinding state */
1252                                 log1("Entering rebinding state");
1253                                 state = REBINDING;
1254                                 /* fall right through */
1255                         case REBINDING:
1256                                 /* Switch to bcast receive */
1257                                 change_listen_mode(LISTEN_RAW);
1258                                 /* Lease is *really* about to run out,
1259                                  * try to find DHCP server using broadcast */
1260                                 if (timeout > 0) {
1261                                         /* send a broadcast renew request */
1262                                         send_renew(xid, 0 /*INADDR_ANY*/, requested_ip);
1263                                         timeout >>= 1;
1264                                         continue;
1265                                 }
1266                                 /* Timed out, enter init state */
1267                                 bb_info_msg("Lease lost, entering init state");
1268                                 udhcp_run_script(NULL, "deconfig");
1269                                 state = INIT_SELECTING;
1270                                 /*timeout = 0; - already is */
1271                                 packet_num = 0;
1272                                 continue;
1273                         /* case RELEASED: */
1274                         }
1275                         /* yah, I know, *you* say it would never happen */
1276                         timeout = INT_MAX;
1277                         continue; /* back to main loop */
1278                 } /* if select timed out */
1279
1280                 /* select() didn't timeout, something happened */
1281
1282                 /* Is it a signal? */
1283                 /* note: udhcp_sp_read checks FD_ISSET before reading */
1284                 switch (udhcp_sp_read(&rfds)) {
1285                 case SIGUSR1:
1286                         perform_renew();
1287                         if (state == RENEW_REQUESTED)
1288                                 goto case_RENEW_REQUESTED;
1289                         /* Start things over */
1290                         packet_num = 0;
1291                         /* Kill any timeouts, user wants this to hurry along */
1292                         timeout = 0;
1293                         continue;
1294                 case SIGUSR2:
1295                         perform_release(requested_ip, server_addr);
1296                         timeout = INT_MAX;
1297                         continue;
1298                 case SIGTERM:
1299                         bb_info_msg("Received SIGTERM");
1300                         if (opt & OPT_R) /* release on quit */
1301                                 perform_release(requested_ip, server_addr);
1302                         goto ret0;
1303                 }
1304
1305                 /* Is it a packet? */
1306                 if (listen_mode == LISTEN_NONE || !FD_ISSET(sockfd, &rfds))
1307                         continue; /* no */
1308
1309                 {
1310                         int len;
1311
1312                         /* A packet is ready, read it */
1313                         if (listen_mode == LISTEN_KERNEL)
1314                                 len = udhcp_recv_kernel_packet(&packet, sockfd);
1315                         else
1316                                 len = udhcp_recv_raw_packet(&packet, sockfd);
1317                         if (len == -1) {
1318                                 /* Error is severe, reopen socket */
1319                                 bb_info_msg("Read error: %s, reopening socket", strerror(errno));
1320                                 sleep(discover_timeout); /* 3 seconds by default */
1321                                 change_listen_mode(listen_mode); /* just close and reopen */
1322                         }
1323                         /* If this packet will turn out to be unrelated/bogus,
1324                          * we will go back and wait for next one.
1325                          * Be sure timeout is properly decreased. */
1326                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1327                         if (len < 0)
1328                                 continue;
1329                 }
1330
1331                 if (packet.xid != xid) {
1332                         log1("xid %x (our is %x), ignoring packet",
1333                                 (unsigned)packet.xid, (unsigned)xid);
1334                         continue;
1335                 }
1336
1337                 /* Ignore packets that aren't for us */
1338                 if (packet.hlen != 6
1339                  || memcmp(packet.chaddr, client_config.client_mac, 6) != 0
1340                 ) {
1341 //FIXME: need to also check that last 10 bytes are zero
1342                         log1("chaddr does not match, ignoring packet"); // log2?
1343                         continue;
1344                 }
1345
1346                 message = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
1347                 if (message == NULL) {
1348                         bb_error_msg("no message type option, ignoring packet");
1349                         continue;
1350                 }
1351
1352                 switch (state) {
1353                 case INIT_SELECTING:
1354                         /* Must be a DHCPOFFER to one of our xid's */
1355                         if (*message == DHCPOFFER) {
1356                 /* TODO: why we don't just fetch server's IP from IP header? */
1357                                 temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
1358                                 if (!temp) {
1359                                         bb_error_msg("no server ID in message");
1360                                         continue;
1361                                         /* still selecting - this server looks bad */
1362                                 }
1363                                 /* it IS unaligned sometimes, don't "optimize" */
1364                                 move_from_unaligned32(server_addr, temp);
1365                                 /*xid = packet.xid; - already is */
1366                                 requested_ip = packet.yiaddr;
1367
1368                                 /* enter requesting state */
1369                                 state = REQUESTING;
1370                                 timeout = 0;
1371                                 packet_num = 0;
1372                                 already_waited_sec = 0;
1373                         }
1374                         continue;
1375                 case REQUESTING:
1376                 case RENEWING:
1377                 case RENEW_REQUESTED:
1378                 case REBINDING:
1379                         if (*message == DHCPACK) {
1380                                 temp = udhcp_get_option(&packet, DHCP_LEASE_TIME);
1381                                 if (!temp) {
1382                                         bb_error_msg("no lease time with ACK, using 1 hour lease");
1383                                         lease_seconds = 60 * 60;
1384                                 } else {
1385                                         /* it IS unaligned sometimes, don't "optimize" */
1386                                         move_from_unaligned32(lease_seconds, temp);
1387                                         lease_seconds = ntohl(lease_seconds);
1388                                         lease_seconds &= 0x0fffffff; /* paranoia: must not be prone to overflows */
1389                                         if (lease_seconds < 10) /* and not too small */
1390                                                 lease_seconds = 10;
1391                                 }
1392 #if ENABLE_FEATURE_UDHCPC_ARPING
1393                                 if (opt & OPT_a) {
1394 /* RFC 2131 3.1 paragraph 5:
1395  * "The client receives the DHCPACK message with configuration
1396  * parameters. The client SHOULD perform a final check on the
1397  * parameters (e.g., ARP for allocated network address), and notes
1398  * the duration of the lease specified in the DHCPACK message. At this
1399  * point, the client is configured. If the client detects that the
1400  * address is already in use (e.g., through the use of ARP),
1401  * the client MUST send a DHCPDECLINE message to the server and restarts
1402  * the configuration process..." */
1403                                         if (!arpping(packet.yiaddr,
1404                                                         NULL,
1405                                                         (uint32_t) 0,
1406                                                         client_config.client_mac,
1407                                                         client_config.interface)
1408                                         ) {
1409                                                 bb_info_msg("Offered address is in use "
1410                                                         "(got ARP reply), declining");
1411                                                 send_decline(xid, server_addr, packet.yiaddr);
1412
1413                                                 if (state != REQUESTING)
1414                                                         udhcp_run_script(NULL, "deconfig");
1415                                                 change_listen_mode(LISTEN_RAW);
1416                                                 state = INIT_SELECTING;
1417                                                 requested_ip = 0;
1418                                                 timeout = tryagain_timeout;
1419                                                 packet_num = 0;
1420                                                 already_waited_sec = 0;
1421                                                 continue; /* back to main loop */
1422                                         }
1423                                 }
1424 #endif
1425                                 /* enter bound state */
1426                                 timeout = lease_seconds / 2;
1427                                 {
1428                                         struct in_addr temp_addr;
1429                                         temp_addr.s_addr = packet.yiaddr;
1430                                         bb_info_msg("Lease of %s obtained, lease time %u",
1431                                                 inet_ntoa(temp_addr), (unsigned)lease_seconds);
1432                                 }
1433                                 requested_ip = packet.yiaddr;
1434                                 udhcp_run_script(&packet, state == REQUESTING ? "bound" : "renew");
1435
1436                                 state = BOUND;
1437                                 change_listen_mode(LISTEN_NONE);
1438                                 if (opt & OPT_q) { /* quit after lease */
1439                                         if (opt & OPT_R) /* release on quit */
1440                                                 perform_release(requested_ip, server_addr);
1441                                         goto ret0;
1442                                 }
1443                                 /* future renew failures should not exit (JM) */
1444                                 opt &= ~OPT_n;
1445 #if BB_MMU /* NOMMU case backgrounded earlier */
1446                                 if (!(opt & OPT_f)) {
1447                                         client_background();
1448                                         /* do not background again! */
1449                                         opt = ((opt & ~OPT_b) | OPT_f);
1450                                 }
1451 #endif
1452                                 already_waited_sec = 0;
1453                                 continue; /* back to main loop */
1454                         }
1455                         if (*message == DHCPNAK) {
1456                                 /* return to init state */
1457                                 bb_info_msg("Received DHCP NAK");
1458                                 udhcp_run_script(&packet, "nak");
1459                                 if (state != REQUESTING)
1460                                         udhcp_run_script(NULL, "deconfig");
1461                                 change_listen_mode(LISTEN_RAW);
1462                                 sleep(3); /* avoid excessive network traffic */
1463                                 state = INIT_SELECTING;
1464                                 requested_ip = 0;
1465                                 timeout = 0;
1466                                 packet_num = 0;
1467                                 already_waited_sec = 0;
1468                         }
1469                         continue;
1470                 /* case BOUND: - ignore all packets */
1471                 /* case RELEASED: - ignore all packets */
1472                 }
1473                 /* back to main loop */
1474         } /* for (;;) - main loop ends */
1475
1476  ret0:
1477         retval = 0;
1478  ret:
1479         /*if (client_config.pidfile) - remove_pidfile has its own check */
1480                 remove_pidfile(client_config.pidfile);
1481         return retval;
1482 }