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_option *type_p, 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         type = type_p->flags & OPTION_TYPE_MASK;
  93         optlen = dhcp_option_lengths[type];
  94         upper_length = len_of_option_as_string[type] * ((unsigned)len / (unsigned)optlen);
  95
  96         dest = ret = xmalloc(upper_length + strlen(opt_name) + 2);
  97         dest += sprintf(ret, "%s=", opt_name);
  98
  99         while (len >= optlen) {
 100                 switch (type) {
 101                 case OPTION_IP_PAIR:
 102                         dest += sprint_nip(dest, "", option);
 103                         *dest++ = '/';
 104                         option += 4;
 105                         optlen = 4;
 106                 case OPTION_IP:
 107                         dest += sprint_nip(dest, "", option);
 108 // TODO: it can be a list only if (type_p->flags & OPTION_LIST).
 109 // Should we bail out/warn if we see multi-ip option which is
 110 // not allowed to be such? For example, DHCP_BROADCAST...
 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                 if (len <= 0)
 222                         break;
 223                 *dest++ = ' ';
 224                 *dest = '\0';
 225         }
 226         return ret;
 227 }
 228
 229 /* put all the parameters into the environment */
 230 static char **fill_envp(struct dhcp_packet *packet)
 231 {
 232         int num_options = 0;
 233         int i;
 234         char **envp, **curr;
 235         const char *opt_name;
 236         uint8_t *temp;
 237         uint8_t over = 0;
 238
 239         if (packet) {
 240                 for (i = 0; dhcp_options[i].code; i++) {
 241                         if (udhcp_get_option(packet, dhcp_options[i].code)) {
 242                                 num_options++;
 243                                 if (dhcp_options[i].code == DHCP_SUBNET)
 244                                         num_options++; /* for mton */
 245                         }
 246                 }
 247                 if (packet->siaddr_nip)
 248                         num_options++;
 249                 temp = udhcp_get_option(packet, DHCP_OPTION_OVERLOAD);
 250                 if (temp)
 251                         over = *temp;
 252                 if (!(over & FILE_FIELD) && packet->file[0])
 253                         num_options++;
 254                 if (!(over & SNAME_FIELD) && packet->sname[0])
 255                         num_options++;
 256         }
 257
 258         curr = envp = xzalloc(sizeof(char *) * (num_options + 3));
 259         *curr = xasprintf("interface=%s", client_config.interface);
 260         putenv(*curr++);
 261
 262         if (packet == NULL)
 263                 return envp;
 264
 265         *curr = xmalloc(sizeof("ip=255.255.255.255"));
 266         sprint_nip(*curr, "ip=", (uint8_t *) &packet->yiaddr);
 267         putenv(*curr++);
 268
 269         opt_name = dhcp_option_strings;
 270         i = 0;
 271         while (*opt_name) {
 272                 temp = udhcp_get_option(packet, dhcp_options[i].code);
 273                 if (!temp)
 274                         goto next;
 275                 *curr = xmalloc_optname_optval(temp, &dhcp_options[i], opt_name);
 276                 putenv(*curr++);
 277
 278                 /* Fill in a subnet bits option for things like /24 */
 279                 if (dhcp_options[i].code == DHCP_SUBNET) {
 280                         uint32_t subnet;
 281                         move_from_unaligned32(subnet, temp);
 282                         *curr = xasprintf("mask=%d", mton(subnet));
 283                         putenv(*curr++);
 284                 }
 285  next:
 286                 opt_name += strlen(opt_name) + 1;
 287                 i++;
 288         }
 289         if (packet->siaddr_nip) {
 290                 *curr = xmalloc(sizeof("siaddr=255.255.255.255"));
 291                 sprint_nip(*curr, "siaddr=", (uint8_t *) &packet->siaddr_nip);
 292                 putenv(*curr++);
 293         }
 294         if (!(over & FILE_FIELD) && packet->file[0]) {
 295                 /* watch out for invalid packets */
 296                 *curr = xasprintf("boot_file=%."DHCP_PKT_FILE_LEN_STR"s", packet->file);
 297                 putenv(*curr++);
 298         }
 299         if (!(over & SNAME_FIELD) && packet->sname[0]) {
 300                 /* watch out for invalid packets */
 301                 *curr = xasprintf("sname=%."DHCP_PKT_SNAME_LEN_STR"s", packet->sname);
 302                 putenv(*curr++);
 303         }
 304         return envp;
 305 }
 306
 307 /* Call a script with a par file and env vars */
 308 static void udhcp_run_script(struct dhcp_packet *packet, const char *name)
 309 {
 310         char **envp, **curr;
 311         char *argv[3];
 312
 313         if (client_config.script == NULL)
 314                 return;
 315
 316         envp = fill_envp(packet);
 317
 318         /* call script */
 319         log1("Executing %s %s", client_config.script, name);
 320         argv[0] = (char*) client_config.script;
 321         argv[1] = (char*) name;
 322         argv[2] = NULL;
 323         spawn_and_wait(argv);
 324
 325         for (curr = envp; *curr; curr++) {
 326                 log2(" %s", *curr);
 327                 bb_unsetenv(*curr);
 328                 free(*curr);
 329         }
 330         free(envp);
 331 }
 332
 333
 334 /*** Sending/receiving packets ***/
 335
 336 static ALWAYS_INLINE uint32_t random_xid(void)
 337 {
 338         return rand();
 339 }
 340
 341 /* Initialize the packet with the proper defaults */
 342 static void init_packet(struct dhcp_packet *packet, char type)
 343 {
 344         udhcp_init_header(packet, type);
 345         memcpy(packet->chaddr, client_config.client_mac, 6);
 346         if (client_config.clientid)
 347                 udhcp_add_binary_option(packet, client_config.clientid);
 348         if (client_config.hostname)
 349                 udhcp_add_binary_option(packet, client_config.hostname);
 350         if (client_config.fqdn)
 351                 udhcp_add_binary_option(packet, client_config.fqdn);
 352         if (type != DHCPDECLINE
 353          && type != DHCPRELEASE
 354          && client_config.vendorclass
 355         ) {
 356                 udhcp_add_binary_option(packet, client_config.vendorclass);
 357         }
 358 }
 359
 360 static void add_client_options(struct dhcp_packet *packet)
 361 {
 362         /* Add a "param req" option with the list of options we'd like to have
 363          * from stubborn DHCP servers. Pull the data from the struct in common.c.
 364          * No bounds checking because it goes towards the head of the packet. */
 365         uint8_t c;
 366         int end = udhcp_end_option(packet->options);
 367         int i, len = 0;
 368
 369         for (i = 0; (c = dhcp_options[i].code) != 0; i++) {
 370                 if ((   (dhcp_options[i].flags & OPTION_REQ)
 371                      && !client_config.no_default_options
 372                     )
 373                  || (client_config.opt_mask[c >> 3] & (1 << (c & 7)))
 374                 ) {
 375                         packet->options[end + OPT_DATA + len] = c;
 376                         len++;
 377                 }
 378         }
 379         if (len) {
 380                 packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
 381                 packet->options[end + OPT_LEN] = len;
 382                 packet->options[end + OPT_DATA + len] = DHCP_END;
 383         }
 384
 385         /* Add -x options if any */
 386         {
 387                 struct option_set *curr = client_config.options;
 388                 while (curr) {
 389                         udhcp_add_binary_option(packet, curr->data);
 390                         curr = curr->next;
 391                 }
 392 //              if (client_config.sname)
 393 //                      strncpy((char*)packet->sname, client_config.sname, sizeof(packet->sname) - 1);
 394 //              if (client_config.boot_file)
 395 //                      strncpy((char*)packet->file, client_config.boot_file, sizeof(packet->file) - 1);
 396         }
 397 }
 398
 399 /* RFC 2131
 400  * 4.4.4 Use of broadcast and unicast
 401  *
 402  * The DHCP client broadcasts DHCPDISCOVER, DHCPREQUEST and DHCPINFORM
 403  * messages, unless the client knows the address of a DHCP server.
 404  * The client unicasts DHCPRELEASE messages to the server. Because
 405  * the client is declining the use of the IP address supplied by the server,
 406  * the client broadcasts DHCPDECLINE messages.
 407  *
 408  * When the DHCP client knows the address of a DHCP server, in either
 409  * INIT or REBOOTING state, the client may use that address
 410  * in the DHCPDISCOVER or DHCPREQUEST rather than the IP broadcast address.
 411  * The client may also use unicast to send DHCPINFORM messages
 412  * to a known DHCP server. If the client receives no response to DHCP
 413  * messages sent to the IP address of a known DHCP server, the DHCP
 414  * client reverts to using the IP broadcast address.
 415  */
 416
 417 static int raw_bcast_from_client_config_ifindex(struct dhcp_packet *packet)
 418 {
 419         return udhcp_send_raw_packet(packet,
 420                 /*src*/ INADDR_ANY, CLIENT_PORT,
 421                 /*dst*/ INADDR_BROADCAST, SERVER_PORT, MAC_BCAST_ADDR,
 422                 client_config.ifindex);
 423 }
 424
 425 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
 426 static int send_discover(uint32_t xid, uint32_t requested)
 427 {
 428         struct dhcp_packet packet;
 429
 430         init_packet(&packet, DHCPDISCOVER);
 431         packet.xid = xid;
 432         if (requested)
 433                 udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 434         /* Explicitly saying that we want RFC-compliant packets helps
 435          * some buggy DHCP servers to NOT send bigger packets */
 436         udhcp_add_simple_option(&packet, DHCP_MAX_SIZE, htons(576));
 437         add_client_options(&packet);
 438
 439         bb_info_msg("Sending discover...");
 440         return raw_bcast_from_client_config_ifindex(&packet);
 441 }
 442
 443 /* Broadcast a DHCP request message */
 444 /* RFC 2131 3.1 paragraph 3:
 445  * "The client _broadcasts_ a DHCPREQUEST message..."
 446  */
 447 static int send_select(uint32_t xid, uint32_t server, uint32_t requested)
 448 {
 449         struct dhcp_packet packet;
 450         struct in_addr addr;
 451
 452         init_packet(&packet, DHCPREQUEST);
 453         packet.xid = xid;
 454         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 455         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 456         add_client_options(&packet);
 457
 458         addr.s_addr = requested;
 459         bb_info_msg("Sending select for %s...", inet_ntoa(addr));
 460         return raw_bcast_from_client_config_ifindex(&packet);
 461 }
 462
 463 /* Unicast or broadcast a DHCP renew message */
 464 static int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
 465 {
 466         struct dhcp_packet packet;
 467
 468         init_packet(&packet, DHCPREQUEST);
 469         packet.xid = xid;
 470         packet.ciaddr = ciaddr;
 471         add_client_options(&packet);
 472
 473         bb_info_msg("Sending renew...");
 474         if (server)
 475                 return udhcp_send_kernel_packet(&packet,
 476                         ciaddr, CLIENT_PORT,
 477                         server, SERVER_PORT);
 478         return raw_bcast_from_client_config_ifindex(&packet);
 479 }
 480
 481 #if ENABLE_FEATURE_UDHCPC_ARPING
 482 /* Broadcast a DHCP decline message */
 483 static int send_decline(uint32_t xid, uint32_t server, uint32_t requested)
 484 {
 485         struct dhcp_packet packet;
 486
 487         init_packet(&packet, DHCPDECLINE);
 488         packet.xid = xid;
 489         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 490         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 491
 492         bb_info_msg("Sending decline...");
 493         return raw_bcast_from_client_config_ifindex(&packet);
 494 }
 495 #endif
 496
 497 /* Unicast a DHCP release message */
 498 static int send_release(uint32_t server, uint32_t ciaddr)
 499 {
 500         struct dhcp_packet packet;
 501
 502         init_packet(&packet, DHCPRELEASE);
 503         packet.xid = random_xid();
 504         packet.ciaddr = ciaddr;
 505
 506         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 507
 508         bb_info_msg("Sending release...");
 509         return udhcp_send_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
 510 }
 511
 512 /* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */
 513 static NOINLINE int udhcp_recv_raw_packet(struct dhcp_packet *dhcp_pkt, int fd)
 514 {
 515         int bytes;
 516         struct ip_udp_dhcp_packet packet;
 517         uint16_t check;
 518
 519         memset(&packet, 0, sizeof(packet));
 520         bytes = safe_read(fd, &packet, sizeof(packet));
 521         if (bytes < 0) {
 522                 log1("Packet read error, ignoring");
 523                 /* NB: possible down interface, etc. Caller should pause. */
 524                 return bytes; /* returns -1 */
 525         }
 526
 527         if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) {
 528                 log1("Packet is too short, ignoring");
 529                 return -2;
 530         }
 531
 532         if (bytes < ntohs(packet.ip.tot_len)) {
 533                 /* packet is bigger than sizeof(packet), we did partial read */
 534                 log1("Oversized packet, ignoring");
 535                 return -2;
 536         }
 537
 538         /* ignore any extra garbage bytes */
 539         bytes = ntohs(packet.ip.tot_len);
 540
 541         /* make sure its the right packet for us, and that it passes sanity checks */
 542         if (packet.ip.protocol != IPPROTO_UDP || packet.ip.version != IPVERSION
 543          || packet.ip.ihl != (sizeof(packet.ip) >> 2)
 544          || packet.udp.dest != htons(CLIENT_PORT)
 545         /* || bytes > (int) sizeof(packet) - can't happen */
 546          || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
 547         ) {
 548                 log1("Unrelated/bogus packet, ignoring");
 549                 return -2;
 550         }
 551
 552         /* verify IP checksum */
 553         check = packet.ip.check;
 554         packet.ip.check = 0;
 555         if (check != udhcp_checksum(&packet.ip, sizeof(packet.ip))) {
 556                 log1("Bad IP header checksum, ignoring");
 557                 return -2;
 558         }
 559
 560         /* verify UDP checksum. IP header has to be modified for this */
 561         memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
 562         /* ip.xx fields which are not memset: protocol, check, saddr, daddr */
 563         packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
 564         check = packet.udp.check;
 565         packet.udp.check = 0;
 566         if (check && check != udhcp_checksum(&packet, bytes)) {
 567                 log1("Packet with bad UDP checksum received, ignoring");
 568                 return -2;
 569         }
 570
 571         memcpy(dhcp_pkt, &packet.data, bytes - (sizeof(packet.ip) + sizeof(packet.udp)));
 572
 573         if (dhcp_pkt->cookie != htonl(DHCP_MAGIC)) {
 574                 bb_info_msg("Packet with bad magic, ignoring");
 575                 return -2;
 576         }
 577         log1("Got valid DHCP packet");
 578         udhcp_dump_packet(dhcp_pkt);
 579         return bytes - (sizeof(packet.ip) + sizeof(packet.udp));
 580 }
 581
 582
 583 /*** Main ***/
 584
 585 static int sockfd = -1;
 586
 587 #define LISTEN_NONE   0
 588 #define LISTEN_KERNEL 1
 589 #define LISTEN_RAW    2
 590 static smallint listen_mode;
 591
 592 /* initial state: (re)start DHCP negotiation */
 593 #define INIT_SELECTING  0
 594 /* discover was sent, DHCPOFFER reply received */
 595 #define REQUESTING      1
 596 /* select/renew was sent, DHCPACK reply received */
 597 #define BOUND           2
 598 /* half of lease passed, want to renew it by sending unicast renew requests */
 599 #define RENEWING        3
 600 /* renew requests were not answered, lease is almost over, send broadcast renew */
 601 #define REBINDING       4
 602 /* manually requested renew (SIGUSR1) */
 603 #define RENEW_REQUESTED 5
 604 /* release, possibly manually requested (SIGUSR2) */
 605 #define RELEASED        6
 606 static smallint state;
 607
 608 static int udhcp_raw_socket(int ifindex)
 609 {
 610         int fd;
 611         struct sockaddr_ll sock;
 612
 613         /*
 614          * Comment:
 615          *
 616          *      I've selected not to see LL header, so BPF doesn't see it, too.
 617          *      The filter may also pass non-IP and non-ARP packets, but we do
 618          *      a more complete check when receiving the message in userspace.
 619          *
 620          * and filter shamelessly stolen from:
 621          *
 622          *      http://www.flamewarmaster.de/software/dhcpclient/
 623          *
 624          * There are a few other interesting ideas on that page (look under
 625          * "Motivation").  Use of netlink events is most interesting.  Think
 626          * of various network servers listening for events and reconfiguring.
 627          * That would obsolete sending HUP signals and/or make use of restarts.
 628          *
 629          * Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
 630          * License: GPL v2.
 631          *
 632          * TODO: make conditional?
 633          */
 634 #define SERVER_AND_CLIENT_PORTS  ((67 << 16) + 68)
 635         static const struct sock_filter filter_instr[] = {
 636                 /* check for udp */
 637                 BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
 638                 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 2, 0),     /* L5, L1, is UDP? */
 639                 /* ugly check for arp on ethernet-like and IPv4 */
 640                 BPF_STMT(BPF_LD|BPF_W|BPF_ABS, 2),                      /* L1: */
 641                 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 0x08000604, 3, 4),      /* L3, L4 */
 642                 /* skip IP header */
 643                 BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0),                     /* L5: */
 644                 /* check udp source and destination ports */
 645                 BPF_STMT(BPF_LD|BPF_W|BPF_IND, 0),
 646                 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, SERVER_AND_CLIENT_PORTS, 0, 1), /* L3, L4 */
 647                 /* returns */
 648                 BPF_STMT(BPF_RET|BPF_K, 0x0fffffff ),                   /* L3: pass */
 649                 BPF_STMT(BPF_RET|BPF_K, 0),                             /* L4: reject */
 650         };
 651         static const struct sock_fprog filter_prog = {
 652                 .len = sizeof(filter_instr) / sizeof(filter_instr[0]),
 653                 /* casting const away: */
 654                 .filter = (struct sock_filter *) filter_instr,
 655         };
 656
 657         log1("Opening raw socket on ifindex %d", ifindex); //log2?
 658
 659         fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
 660         log1("Got raw socket fd %d", fd); //log2?
 661
 662         if (SERVER_PORT == 67 && CLIENT_PORT == 68) {
 663                 /* Use only if standard ports are in use */
 664                 /* Ignoring error (kernel may lack support for this) */
 665                 if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
 666                                 sizeof(filter_prog)) >= 0)
 667                         log1("Attached filter to raw socket fd %d", fd); // log?
 668         }
 669
 670         sock.sll_family = AF_PACKET;
 671         sock.sll_protocol = htons(ETH_P_IP);
 672         sock.sll_ifindex = ifindex;
 673         xbind(fd, (struct sockaddr *) &sock, sizeof(sock));
 674         log1("Created raw socket");
 675
 676         return fd;
 677 }
 678
 679 static void change_listen_mode(int new_mode)
 680 {
 681         log1("Entering listen mode: %s",
 682                 new_mode != LISTEN_NONE
 683                         ? (new_mode == LISTEN_KERNEL ? "kernel" : "raw")
 684                         : "none"
 685         );
 686
 687         listen_mode = new_mode;
 688         if (sockfd >= 0) {
 689                 close(sockfd);
 690                 sockfd = -1;
 691         }
 692         if (new_mode == LISTEN_KERNEL)
 693                 sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
 694         else if (new_mode != LISTEN_NONE)
 695                 sockfd = udhcp_raw_socket(client_config.ifindex);
 696         /* else LISTEN_NONE: sockfd stays closed */
 697 }
 698
 699 static void perform_renew(void)
 700 {
 701         bb_info_msg("Performing a DHCP renew");
 702         switch (state) {
 703         case BOUND:
 704                 change_listen_mode(LISTEN_KERNEL);
 705         case RENEWING:
 706         case REBINDING:
 707                 state = RENEW_REQUESTED;
 708                 break;
 709         case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
 710                 udhcp_run_script(NULL, "deconfig");
 711         case REQUESTING:
 712         case RELEASED:
 713                 change_listen_mode(LISTEN_RAW);
 714                 state = INIT_SELECTING;
 715                 break;
 716         case INIT_SELECTING:
 717                 break;
 718         }
 719 }
 720
 721 static void perform_release(uint32_t requested_ip, uint32_t server_addr)
 722 {
 723         char buffer[sizeof("255.255.255.255")];
 724         struct in_addr temp_addr;
 725
 726         /* send release packet */
 727         if (state == BOUND || state == RENEWING || state == REBINDING) {
 728                 temp_addr.s_addr = server_addr;
 729                 strcpy(buffer, inet_ntoa(temp_addr));
 730                 temp_addr.s_addr = requested_ip;
 731                 bb_info_msg("Unicasting a release of %s to %s",
 732                                 inet_ntoa(temp_addr), buffer);
 733                 send_release(server_addr, requested_ip); /* unicast */
 734                 udhcp_run_script(NULL, "deconfig");
 735         }
 736         bb_info_msg("Entering released state");
 737
 738         change_listen_mode(LISTEN_NONE);
 739         state = RELEASED;
 740 }
 741
 742 static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
 743 {
 744         uint8_t *storage;
 745         int len = strnlen(str, 255);
 746         storage = xzalloc(len + extra + OPT_DATA);
 747         storage[OPT_CODE] = code;
 748         storage[OPT_LEN] = len + extra;
 749         memcpy(storage + extra + OPT_DATA, str, len);
 750         return storage;
 751 }
 752
 753 #if BB_MMU
 754 static void client_background(void)
 755 {
 756         bb_daemonize(0);
 757         logmode &= ~LOGMODE_STDIO;
 758         /* rewrite pidfile, as our pid is different now */
 759         write_pidfile(client_config.pidfile);
 760 }
 761 #endif
 762
 763 int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 764 int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 765 {
 766         uint8_t *temp, *message;
 767         const char *str_c, *str_V, *str_h, *str_F, *str_r;
 768         IF_FEATURE_UDHCP_PORT(char *str_P;)
 769         llist_t *list_O = NULL;
 770         llist_t *list_x = NULL;
 771         int tryagain_timeout = 20;
 772         int discover_timeout = 3;
 773         int discover_retries = 3;
 774         uint32_t server_addr = server_addr; /* for compiler */
 775         uint32_t requested_ip = 0;
 776         uint32_t xid = 0;
 777         uint32_t lease_seconds = 0; /* can be given as 32-bit quantity */
 778         int packet_num;
 779         int timeout; /* must be signed */
 780         unsigned already_waited_sec;
 781         unsigned opt;
 782         int max_fd;
 783         int retval;
 784         struct timeval tv;
 785         struct dhcp_packet packet;
 786         fd_set rfds;
 787
 788 #if ENABLE_LONG_OPTS
 789         static const char udhcpc_longopts[] ALIGN1 =
 790                 "clientid\0"       Required_argument "c"
 791                 "clientid-none\0"  No_argument       "C"
 792                 "vendorclass\0"    Required_argument "V"
 793                 "hostname\0"       Required_argument "H"
 794                 "fqdn\0"           Required_argument "F"
 795                 "interface\0"      Required_argument "i"
 796                 "now\0"            No_argument       "n"
 797                 "pidfile\0"        Required_argument "p"
 798                 "quit\0"           No_argument       "q"
 799                 "release\0"        No_argument       "R"
 800                 "request\0"        Required_argument "r"
 801                 "script\0"         Required_argument "s"
 802                 "timeout\0"        Required_argument "T"
 803                 "version\0"        No_argument       "v"
 804                 "retries\0"        Required_argument "t"
 805                 "tryagain\0"       Required_argument "A"
 806                 "syslog\0"         No_argument       "S"
 807                 "request-option\0" Required_argument "O"
 808                 "no-default-options\0" No_argument   "o"
 809                 "foreground\0"     No_argument       "f"
 810                 "background\0"     No_argument       "b"
 811                 IF_FEATURE_UDHCPC_ARPING("arping\0"     No_argument       "a")
 812                 IF_FEATURE_UDHCP_PORT("client-port\0"   Required_argument "P")
 813                 ;
 814 #endif
 815         enum {
 816                 OPT_c = 1 << 0,
 817                 OPT_C = 1 << 1,
 818                 OPT_V = 1 << 2,
 819                 OPT_H = 1 << 3,
 820                 OPT_h = 1 << 4,
 821                 OPT_F = 1 << 5,
 822                 OPT_i = 1 << 6,
 823                 OPT_n = 1 << 7,
 824                 OPT_p = 1 << 8,
 825                 OPT_q = 1 << 9,
 826                 OPT_R = 1 << 10,
 827                 OPT_r = 1 << 11,
 828                 OPT_s = 1 << 12,
 829                 OPT_T = 1 << 13,
 830                 OPT_t = 1 << 14,
 831                 OPT_S = 1 << 15,
 832                 OPT_A = 1 << 16,
 833                 OPT_O = 1 << 17,
 834                 OPT_o = 1 << 18,
 835                 OPT_x = 1 << 19,
 836                 OPT_f = 1 << 20,
 837 /* The rest has variable bit positions, need to be clever */
 838                 OPTBIT_f = 20,
 839                 USE_FOR_MMU(             OPTBIT_b,)
 840                 IF_FEATURE_UDHCPC_ARPING(OPTBIT_a,)
 841                 IF_FEATURE_UDHCP_PORT(   OPTBIT_P,)
 842                 USE_FOR_MMU(             OPT_b = 1 << OPTBIT_b,)
 843                 IF_FEATURE_UDHCPC_ARPING(OPT_a = 1 << OPTBIT_a,)
 844                 IF_FEATURE_UDHCP_PORT(   OPT_P = 1 << OPTBIT_P,)
 845         };
 846
 847         /* Default options. */
 848         IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;)
 849         IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
 850         client_config.interface = "eth0";
 851         client_config.script = CONFIG_UDHCPC_DEFAULT_SCRIPT;
 852         str_V = "udhcp "BB_VER;
 853
 854         /* Parse command line */
 855         /* Cc: mutually exclusive; O,x: list; -T,-t,-A take numeric param */
 856         opt_complementary = "c--C:C--c:O::x::T+:t+:A+"
 857 #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
 858                 ":vv"
 859 #endif
 860                 ;
 861         IF_LONG_OPTS(applet_long_options = udhcpc_longopts;)
 862         opt = getopt32(argv, "c:CV:H:h:F:i:np:qRr:s:T:t:SA:O:ox:f"
 863                 USE_FOR_MMU("b")
 864                 IF_FEATURE_UDHCPC_ARPING("a")
 865                 IF_FEATURE_UDHCP_PORT("P:")
 866                 "v"
 867                 , &str_c, &str_V, &str_h, &str_h, &str_F
 868                 , &client_config.interface, &client_config.pidfile, &str_r /* i,p */
 869                 , &client_config.script /* s */
 870                 , &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */
 871                 , &list_O
 872                 , &list_x
 873                 IF_FEATURE_UDHCP_PORT(, &str_P)
 874 #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
 875                 , &dhcp_verbose
 876 #endif
 877                 );
 878         if (opt & (OPT_h|OPT_H))
 879                 client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
 880         if (opt & OPT_F) {
 881                 /* FQDN option format: [0x51][len][flags][0][0]<fqdn> */
 882                 client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
 883                 /* Flag bits: 0000NEOS
 884                  * S: 1 = Client requests server to update A RR in DNS as well as PTR
 885                  * O: 1 = Server indicates to client that DNS has been updated regardless
 886                  * E: 1 = Name is in DNS format, i.e. <4>host<6>domain<3>com<0>,
 887                  *    not "host.domain.com". Format 0 is obsolete.
 888                  * N: 1 = Client requests server to not update DNS (S must be 0 then)
 889                  * Two [0] bytes which follow are deprecated and must be 0.
 890                  */
 891                 client_config.fqdn[OPT_DATA + 0] = 0x1;
 892                 /*client_config.fqdn[OPT_DATA + 1] = 0; - xzalloc did it */
 893                 /*client_config.fqdn[OPT_DATA + 2] = 0; */
 894         }
 895         if (opt & OPT_r)
 896                 requested_ip = inet_addr(str_r);
 897 #if ENABLE_FEATURE_UDHCP_PORT
 898         if (opt & OPT_P) {
 899                 CLIENT_PORT = xatou16(str_P);
 900                 SERVER_PORT = CLIENT_PORT - 1;
 901         }
 902 #endif
 903         if (opt & OPT_o)
 904                 client_config.no_default_options = 1;
 905         while (list_O) {
 906                 char *optstr = llist_pop(&list_O);
 907                 unsigned n = udhcp_option_idx(optstr);
 908                 n = dhcp_options[n].code;
 909                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
 910         }
 911         while (list_x) {
 912                 char *optstr = llist_pop(&list_x);
 913                 char *colon = strchr(optstr, ':');
 914                 if (colon)
 915                         *colon = ' ';
 916                 /* now it looks similar to udhcpd's config file line:
 917                  * "optname optval", using the common routine: */
 918                 udhcp_str2optset(optstr, &client_config.options);
 919         }
 920
 921         if (udhcp_read_interface(client_config.interface,
 922                         &client_config.ifindex,
 923                         NULL,
 924                         client_config.client_mac)
 925         ) {
 926                 return 1;
 927         }
 928
 929         if (opt & OPT_c) {
 930                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, str_c, 0);
 931         } else if (!(opt & OPT_C)) {
 932                 /* not set and not suppressed, set the default client ID */
 933                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
 934                 client_config.clientid[OPT_DATA] = 1; /* type: ethernet */
 935                 memcpy(client_config.clientid + OPT_DATA+1, client_config.client_mac, 6);
 936         }
 937         if (str_V[0] != '\0')
 938                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
 939 #if !BB_MMU
 940         /* on NOMMU reexec (i.e., background) early */
 941         if (!(opt & OPT_f)) {
 942                 bb_daemonize_or_rexec(0 /* flags */, argv);
 943                 logmode = LOGMODE_NONE;
 944         }
 945 #endif
 946         if (opt & OPT_S) {
 947                 openlog(applet_name, LOG_PID, LOG_DAEMON);
 948                 logmode |= LOGMODE_SYSLOG;
 949         }
 950
 951         /* Make sure fd 0,1,2 are open */
 952         bb_sanitize_stdio();
 953         /* Equivalent of doing a fflush after every \n */
 954         setlinebuf(stdout);
 955         /* Create pidfile */
 956         write_pidfile(client_config.pidfile);
 957         /* Goes to stdout (unless NOMMU) and possibly syslog */
 958         bb_info_msg("%s (v"BB_VER") started", applet_name);
 959         /* Set up the signal pipe */
 960         udhcp_sp_setup();
 961         /* We want random_xid to be random... */
 962         srand(monotonic_us());
 963
 964         state = INIT_SELECTING;
 965         udhcp_run_script(NULL, "deconfig");
 966         change_listen_mode(LISTEN_RAW);
 967         packet_num = 0;
 968         timeout = 0;
 969         already_waited_sec = 0;
 970
 971         /* Main event loop. select() waits on signal pipe and possibly
 972          * on sockfd.
 973          * "continue" statements in code below jump to the top of the loop.
 974          */
 975         for (;;) {
 976                 /* silence "uninitialized!" warning */
 977                 unsigned timestamp_before_wait = timestamp_before_wait;
 978
 979                 //bb_error_msg("sockfd:%d, listen_mode:%d", sockfd, listen_mode);
 980
 981                 /* Was opening raw or udp socket here
 982                  * if (listen_mode != LISTEN_NONE && sockfd < 0),
 983                  * but on fast network renew responses return faster
 984                  * than we open sockets. Thus this code is moved
 985                  * to change_listen_mode(). Thus we open listen socket
 986                  * BEFORE we send renew request (see "case BOUND:"). */
 987
 988                 max_fd = udhcp_sp_fd_set(&rfds, sockfd);
 989
 990                 tv.tv_sec = timeout - already_waited_sec;
 991                 tv.tv_usec = 0;
 992                 retval = 0;
 993                 /* If we already timed out, fall through with retval = 0, else... */
 994                 if ((int)tv.tv_sec > 0) {
 995                         timestamp_before_wait = (unsigned)monotonic_sec();
 996                         log1("Waiting on select...");
 997                         retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
 998                         if (retval < 0) {
 999                                 /* EINTR? A signal was caught, don't panic */
1000                                 if (errno == EINTR) {
1001                                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1002                                         continue;
1003                                 }
1004                                 /* Else: an error occured, panic! */
1005                                 bb_perror_msg_and_die("select");
1006                         }
1007                 }
1008
1009                 /* If timeout dropped to zero, time to become active:
1010                  * resend discover/renew/whatever
1011                  */
1012                 if (retval == 0) {
1013                         /* We will restart the wait in any case */
1014                         already_waited_sec = 0;
1015
1016                         switch (state) {
1017                         case INIT_SELECTING:
1018                                 if (packet_num < discover_retries) {
1019                                         if (packet_num == 0)
1020                                                 xid = random_xid();
1021                                         /* broadcast */
1022                                         send_discover(xid, requested_ip);
1023                                         timeout = discover_timeout;
1024                                         packet_num++;
1025                                         continue;
1026                                 }
1027  leasefail:
1028                                 udhcp_run_script(NULL, "leasefail");
1029 #if BB_MMU /* -b is not supported on NOMMU */
1030                                 if (opt & OPT_b) { /* background if no lease */
1031                                         bb_info_msg("No lease, forking to background");
1032                                         client_background();
1033                                         /* do not background again! */
1034                                         opt = ((opt & ~OPT_b) | OPT_f);
1035                                 } else
1036 #endif
1037                                 if (opt & OPT_n) { /* abort if no lease */
1038                                         bb_info_msg("No lease, failing");
1039                                         retval = 1;
1040                                         goto ret;
1041                                 }
1042                                 /* wait before trying again */
1043                                 timeout = tryagain_timeout;
1044                                 packet_num = 0;
1045                                 continue;
1046                         case REQUESTING:
1047                                 if (packet_num < discover_retries) {
1048                                         /* send broadcast select packet */
1049                                         send_select(xid, server_addr, requested_ip);
1050                                         timeout = discover_timeout;
1051                                         packet_num++;
1052                                         continue;
1053                                 }
1054                                 /* Timed out, go back to init state.
1055                                  * "discover...select...discover..." loops
1056                                  * were seen in the wild. Treat them similarly
1057                                  * to "no response to discover" case */
1058                                 change_listen_mode(LISTEN_RAW);
1059                                 state = INIT_SELECTING;
1060                                 goto leasefail;
1061                         case BOUND:
1062                                 /* 1/2 lease passed, enter renewing state */
1063                                 state = RENEWING;
1064                                 change_listen_mode(LISTEN_KERNEL);
1065                                 log1("Entering renew state");
1066                                 /* fall right through */
1067                         case RENEW_REQUESTED: /* manual (SIGUSR1) renew */
1068                         case_RENEW_REQUESTED:
1069                         case RENEWING:
1070                                 if (timeout > 60) {
1071                                         /* send an unicast renew request */
1072                         /* Sometimes observed to fail (EADDRNOTAVAIL) to bind
1073                          * a new UDP socket for sending inside send_renew.
1074                          * I hazard to guess existing listening socket
1075                          * is somehow conflicting with it, but why is it
1076                          * not deterministic then?! Strange.
1077                          * Anyway, it does recover by eventually failing through
1078                          * into INIT_SELECTING state.
1079                          */
1080                                         send_renew(xid, server_addr, requested_ip);
1081                                         timeout >>= 1;
1082                                         continue;
1083                                 }
1084                                 /* Timed out, enter rebinding state */
1085                                 log1("Entering rebinding state");
1086                                 state = REBINDING;
1087                                 /* fall right through */
1088                         case REBINDING:
1089                                 /* Switch to bcast receive */
1090                                 change_listen_mode(LISTEN_RAW);
1091                                 /* Lease is *really* about to run out,
1092                                  * try to find DHCP server using broadcast */
1093                                 if (timeout > 0) {
1094                                         /* send a broadcast renew request */
1095                                         send_renew(xid, 0 /*INADDR_ANY*/, requested_ip);
1096                                         timeout >>= 1;
1097                                         continue;
1098                                 }
1099                                 /* Timed out, enter init state */
1100                                 bb_info_msg("Lease lost, entering init state");
1101                                 udhcp_run_script(NULL, "deconfig");
1102                                 state = INIT_SELECTING;
1103                                 /*timeout = 0; - already is */
1104                                 packet_num = 0;
1105                                 continue;
1106                         /* case RELEASED: */
1107                         }
1108                         /* yah, I know, *you* say it would never happen */
1109                         timeout = INT_MAX;
1110                         continue; /* back to main loop */
1111                 } /* if select timed out */
1112
1113                 /* select() didn't timeout, something happened */
1114
1115                 /* Is it a signal? */
1116                 /* note: udhcp_sp_read checks FD_ISSET before reading */
1117                 switch (udhcp_sp_read(&rfds)) {
1118                 case SIGUSR1:
1119                         perform_renew();
1120                         if (state == RENEW_REQUESTED)
1121                                 goto case_RENEW_REQUESTED;
1122                         /* Start things over */
1123                         packet_num = 0;
1124                         /* Kill any timeouts, user wants this to hurry along */
1125                         timeout = 0;
1126                         continue;
1127                 case SIGUSR2:
1128                         perform_release(requested_ip, server_addr);
1129                         timeout = INT_MAX;
1130                         continue;
1131                 case SIGTERM:
1132                         bb_info_msg("Received SIGTERM");
1133                         if (opt & OPT_R) /* release on quit */
1134                                 perform_release(requested_ip, server_addr);
1135                         goto ret0;
1136                 }
1137
1138                 /* Is it a packet? */
1139                 if (listen_mode == LISTEN_NONE || !FD_ISSET(sockfd, &rfds))
1140                         continue; /* no */
1141
1142                 {
1143                         int len;
1144
1145                         /* A packet is ready, read it */
1146                         if (listen_mode == LISTEN_KERNEL)
1147                                 len = udhcp_recv_kernel_packet(&packet, sockfd);
1148                         else
1149                                 len = udhcp_recv_raw_packet(&packet, sockfd);
1150                         if (len == -1) {
1151                                 /* Error is severe, reopen socket */
1152                                 bb_info_msg("Read error: %s, reopening socket", strerror(errno));
1153                                 sleep(discover_timeout); /* 3 seconds by default */
1154                                 change_listen_mode(listen_mode); /* just close and reopen */
1155                         }
1156                         /* If this packet will turn out to be unrelated/bogus,
1157                          * we will go back and wait for next one.
1158                          * Be sure timeout is properly decreased. */
1159                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1160                         if (len < 0)
1161                                 continue;
1162                 }
1163
1164                 if (packet.xid != xid) {
1165                         log1("xid %x (our is %x), ignoring packet",
1166                                 (unsigned)packet.xid, (unsigned)xid);
1167                         continue;
1168                 }
1169
1170                 /* Ignore packets that aren't for us */
1171                 if (packet.hlen != 6
1172                  || memcmp(packet.chaddr, client_config.client_mac, 6)
1173                 ) {
1174 //FIXME: need to also check that last 10 bytes are zero
1175                         log1("chaddr does not match, ignoring packet"); // log2?
1176                         continue;
1177                 }
1178
1179                 message = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
1180                 if (message == NULL) {
1181                         bb_error_msg("no message type option, ignoring packet");
1182                         continue;
1183                 }
1184
1185                 switch (state) {
1186                 case INIT_SELECTING:
1187                         /* Must be a DHCPOFFER to one of our xid's */
1188                         if (*message == DHCPOFFER) {
1189                 /* TODO: why we don't just fetch server's IP from IP header? */
1190                                 temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
1191                                 if (!temp) {
1192                                         bb_error_msg("no server ID in message");
1193                                         continue;
1194                                         /* still selecting - this server looks bad */
1195                                 }
1196                                 /* it IS unaligned sometimes, don't "optimize" */
1197                                 move_from_unaligned32(server_addr, temp);
1198                                 xid = packet.xid;
1199                                 requested_ip = packet.yiaddr;
1200
1201                                 /* enter requesting state */
1202                                 state = REQUESTING;
1203                                 timeout = 0;
1204                                 packet_num = 0;
1205                                 already_waited_sec = 0;
1206                         }
1207                         continue;
1208                 case REQUESTING:
1209                 case RENEWING:
1210                 case RENEW_REQUESTED:
1211                 case REBINDING:
1212                         if (*message == DHCPACK) {
1213                                 temp = udhcp_get_option(&packet, DHCP_LEASE_TIME);
1214                                 if (!temp) {
1215                                         bb_error_msg("no lease time with ACK, using 1 hour lease");
1216                                         lease_seconds = 60 * 60;
1217                                 } else {
1218                                         /* it IS unaligned sometimes, don't "optimize" */
1219                                         move_from_unaligned32(lease_seconds, temp);
1220                                         lease_seconds = ntohl(lease_seconds);
1221                                         lease_seconds &= 0x0fffffff; /* paranoia: must not be prone to overflows */
1222                                         if (lease_seconds < 10) /* and not too small */
1223                                                 lease_seconds = 10;
1224                                 }
1225 #if ENABLE_FEATURE_UDHCPC_ARPING
1226                                 if (opt & OPT_a) {
1227 /* RFC 2131 3.1 paragraph 5:
1228  * "The client receives the DHCPACK message with configuration
1229  * parameters. The client SHOULD perform a final check on the
1230  * parameters (e.g., ARP for allocated network address), and notes
1231  * the duration of the lease specified in the DHCPACK message. At this
1232  * point, the client is configured. If the client detects that the
1233  * address is already in use (e.g., through the use of ARP),
1234  * the client MUST send a DHCPDECLINE message to the server and restarts
1235  * the configuration process..." */
1236                                         if (!arpping(packet.yiaddr,
1237                                                         NULL,
1238                                                         (uint32_t) 0,
1239                                                         client_config.client_mac,
1240                                                         client_config.interface)
1241                                         ) {
1242                                                 bb_info_msg("Offered address is in use "
1243                                                         "(got ARP reply), declining");
1244                                                 send_decline(xid, server_addr, packet.yiaddr);
1245
1246                                                 if (state != REQUESTING)
1247                                                         udhcp_run_script(NULL, "deconfig");
1248                                                 change_listen_mode(LISTEN_RAW);
1249                                                 state = INIT_SELECTING;
1250                                                 requested_ip = 0;
1251                                                 timeout = tryagain_timeout;
1252                                                 packet_num = 0;
1253                                                 already_waited_sec = 0;
1254                                                 continue; /* back to main loop */
1255                                         }
1256                                 }
1257 #endif
1258                                 /* enter bound state */
1259                                 timeout = lease_seconds / 2;
1260                                 {
1261                                         struct in_addr temp_addr;
1262                                         temp_addr.s_addr = packet.yiaddr;
1263                                         bb_info_msg("Lease of %s obtained, lease time %u",
1264                                                 inet_ntoa(temp_addr), (unsigned)lease_seconds);
1265                                 }
1266                                 requested_ip = packet.yiaddr;
1267                                 udhcp_run_script(&packet, state == REQUESTING ? "bound" : "renew");
1268
1269                                 state = BOUND;
1270                                 change_listen_mode(LISTEN_NONE);
1271                                 if (opt & OPT_q) { /* quit after lease */
1272                                         if (opt & OPT_R) /* release on quit */
1273                                                 perform_release(requested_ip, server_addr);
1274                                         goto ret0;
1275                                 }
1276                                 /* future renew failures should not exit (JM) */
1277                                 opt &= ~OPT_n;
1278 #if BB_MMU /* NOMMU case backgrounded earlier */
1279                                 if (!(opt & OPT_f)) {
1280                                         client_background();
1281                                         /* do not background again! */
1282                                         opt = ((opt & ~OPT_b) | OPT_f);
1283                                 }
1284 #endif
1285                                 already_waited_sec = 0;
1286                                 continue; /* back to main loop */
1287                         }
1288                         if (*message == DHCPNAK) {
1289                                 /* return to init state */
1290                                 bb_info_msg("Received DHCP NAK");
1291                                 udhcp_run_script(&packet, "nak");
1292                                 if (state != REQUESTING)
1293                                         udhcp_run_script(NULL, "deconfig");
1294                                 change_listen_mode(LISTEN_RAW);
1295                                 sleep(3); /* avoid excessive network traffic */
1296                                 state = INIT_SELECTING;
1297                                 requested_ip = 0;
1298                                 timeout = 0;
1299                                 packet_num = 0;
1300                                 already_waited_sec = 0;
1301                         }
1302                         continue;
1303                 /* case BOUND: - ignore all packets */
1304                 /* case RELEASED: - ignore all packets */
1305                 }
1306                 /* back to main loop */
1307         } /* for (;;) - main loop ends */
1308
1309  ret0:
1310         retval = 0;
1311  ret:
1312         /*if (client_config.pidfile) - remove_pidfile has its own check */
1313                 remove_pidfile(client_config.pidfile);
1314         return retval;
1315 }