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         type = optflag->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 (optflag->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 envc;
 233         int i;
 234         char **envp, **curr;
 235         const char *opt_name;
 236         uint8_t *temp;
 237         uint8_t overload = 0;
 238
 239         /* We need 6 elements for:
 240          * "interface=IFACE"
 241          * "ip=N.N.N.N" from packet->yiaddr
 242          * "siaddr=IP" from packet->siaddr_nip (unless 0)
 243          * "boot_file=FILE" from packet->file (unless overloaded)
 244          * "sname=SERVER_HOSTNAME" from packet->sname (unless overloaded)
 245          * terminating NULL
 246          */
 247         envc = 6;
 248         /* +1 element for each option, +2 for subnet option: */
 249         if (packet) {
 250                 for (i = 0; dhcp_optflags[i].code; i++) {
 251                         if (udhcp_get_option(packet, dhcp_optflags[i].code)) {
 252                                 if (dhcp_optflags[i].code == DHCP_SUBNET)
 253                                         envc++; /* for mton */
 254                                 envc++;
 255                         }
 256                 }
 257                 temp = udhcp_get_option(packet, DHCP_OPTION_OVERLOAD);
 258                 if (temp)
 259                         overload = *temp;
 260         }
 261         curr = envp = xzalloc(sizeof(char *) * envc);
 262
 263         *curr = xasprintf("interface=%s", client_config.interface);
 264         putenv(*curr++);
 265
 266         if (!packet)
 267                 return envp;
 268
 269         *curr = xmalloc(sizeof("ip=255.255.255.255"));
 270         sprint_nip(*curr, "ip=", (uint8_t *) &packet->yiaddr);
 271         putenv(*curr++);
 272
 273         opt_name = dhcp_option_strings;
 274         i = 0;
 275         while (*opt_name) {
 276                 temp = udhcp_get_option(packet, dhcp_optflags[i].code);
 277                 if (!temp)
 278                         goto next;
 279                 *curr = xmalloc_optname_optval(temp, &dhcp_optflags[i], opt_name);
 280                 putenv(*curr++);
 281                 if (dhcp_optflags[i].code == DHCP_SUBNET) {
 282                         /* Subnet option: make things like "$ip/$mask" possible */
 283                         uint32_t subnet;
 284                         move_from_unaligned32(subnet, temp);
 285                         *curr = xasprintf("mask=%d", mton(subnet));
 286                         putenv(*curr++);
 287                 }
 288  next:
 289                 opt_name += strlen(opt_name) + 1;
 290                 i++;
 291         }
 292         if (packet->siaddr_nip) {
 293                 *curr = xmalloc(sizeof("siaddr=255.255.255.255"));
 294                 sprint_nip(*curr, "siaddr=", (uint8_t *) &packet->siaddr_nip);
 295                 putenv(*curr++);
 296         }
 297         if (!(overload & FILE_FIELD) && packet->file[0]) {
 298                 /* watch out for invalid packets */
 299                 *curr = xasprintf("boot_file=%."DHCP_PKT_FILE_LEN_STR"s", packet->file);
 300                 putenv(*curr++);
 301         }
 302         if (!(overload & SNAME_FIELD) && packet->sname[0]) {
 303                 /* watch out for invalid packets */
 304                 *curr = xasprintf("sname=%."DHCP_PKT_SNAME_LEN_STR"s", packet->sname);
 305                 putenv(*curr++);
 306         }
 307         return envp;
 308 }
 309
 310 /* Call a script with a par file and env vars */
 311 static void udhcp_run_script(struct dhcp_packet *packet, const char *name)
 312 {
 313         char **envp, **curr;
 314         char *argv[3];
 315
 316         if (client_config.script == NULL)
 317                 return;
 318
 319         envp = fill_envp(packet);
 320
 321         /* call script */
 322         log1("Executing %s %s", client_config.script, name);
 323         argv[0] = (char*) client_config.script;
 324         argv[1] = (char*) name;
 325         argv[2] = NULL;
 326         spawn_and_wait(argv);
 327
 328         for (curr = envp; *curr; curr++) {
 329                 log2(" %s", *curr);
 330                 bb_unsetenv_and_free(*curr);
 331         }
 332         free(envp);
 333 }
 334
 335
 336 /*** Sending/receiving packets ***/
 337
 338 static ALWAYS_INLINE uint32_t random_xid(void)
 339 {
 340         return rand();
 341 }
 342
 343 /* Initialize the packet with the proper defaults */
 344 static void init_packet(struct dhcp_packet *packet, char type)
 345 {
 346         udhcp_init_header(packet, type);
 347         memcpy(packet->chaddr, client_config.client_mac, 6);
 348         if (client_config.clientid)
 349                 udhcp_add_binary_option(packet, client_config.clientid);
 350         if (client_config.hostname)
 351                 udhcp_add_binary_option(packet, client_config.hostname);
 352         if (client_config.fqdn)
 353                 udhcp_add_binary_option(packet, client_config.fqdn);
 354         if (type != DHCPDECLINE
 355          && type != DHCPRELEASE
 356          && client_config.vendorclass
 357         ) {
 358                 udhcp_add_binary_option(packet, client_config.vendorclass);
 359         }
 360 }
 361
 362 static void add_client_options(struct dhcp_packet *packet)
 363 {
 364         /* Add a "param req" option with the list of options we'd like to have
 365          * from stubborn DHCP servers. Pull the data from the struct in common.c.
 366          * No bounds checking because it goes towards the head of the packet. */
 367         uint8_t c;
 368         int end = udhcp_end_option(packet->options);
 369         int i, len = 0;
 370
 371         for (i = 0; (c = dhcp_optflags[i].code) != 0; i++) {
 372                 if ((   (dhcp_optflags[i].flags & OPTION_REQ)
 373                      && !client_config.no_default_options
 374                     )
 375                  || (client_config.opt_mask[c >> 3] & (1 << (c & 7)))
 376                 ) {
 377                         packet->options[end + OPT_DATA + len] = c;
 378                         len++;
 379                 }
 380         }
 381         if (len) {
 382                 packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
 383                 packet->options[end + OPT_LEN] = len;
 384                 packet->options[end + OPT_DATA + len] = DHCP_END;
 385         }
 386
 387         /* Add -x options if any */
 388         {
 389                 struct option_set *curr = client_config.options;
 390                 while (curr) {
 391                         udhcp_add_binary_option(packet, curr->data);
 392                         curr = curr->next;
 393                 }
 394 //              if (client_config.sname)
 395 //                      strncpy((char*)packet->sname, client_config.sname, sizeof(packet->sname) - 1);
 396 //              if (client_config.boot_file)
 397 //                      strncpy((char*)packet->file, client_config.boot_file, sizeof(packet->file) - 1);
 398         }
 399 }
 400
 401 /* RFC 2131
 402  * 4.4.4 Use of broadcast and unicast
 403  *
 404  * The DHCP client broadcasts DHCPDISCOVER, DHCPREQUEST and DHCPINFORM
 405  * messages, unless the client knows the address of a DHCP server.
 406  * The client unicasts DHCPRELEASE messages to the server. Because
 407  * the client is declining the use of the IP address supplied by the server,
 408  * the client broadcasts DHCPDECLINE messages.
 409  *
 410  * When the DHCP client knows the address of a DHCP server, in either
 411  * INIT or REBOOTING state, the client may use that address
 412  * in the DHCPDISCOVER or DHCPREQUEST rather than the IP broadcast address.
 413  * The client may also use unicast to send DHCPINFORM messages
 414  * to a known DHCP server. If the client receives no response to DHCP
 415  * messages sent to the IP address of a known DHCP server, the DHCP
 416  * client reverts to using the IP broadcast address.
 417  */
 418
 419 static int raw_bcast_from_client_config_ifindex(struct dhcp_packet *packet)
 420 {
 421         return udhcp_send_raw_packet(packet,
 422                 /*src*/ INADDR_ANY, CLIENT_PORT,
 423                 /*dst*/ INADDR_BROADCAST, SERVER_PORT, MAC_BCAST_ADDR,
 424                 client_config.ifindex);
 425 }
 426
 427 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
 428 static int send_discover(uint32_t xid, uint32_t requested)
 429 {
 430         struct dhcp_packet packet;
 431
 432         init_packet(&packet, DHCPDISCOVER);
 433         packet.xid = xid;
 434         if (requested)
 435                 udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 436         /* Explicitly saying that we want RFC-compliant packets helps
 437          * some buggy DHCP servers to NOT send bigger packets */
 438         udhcp_add_simple_option(&packet, DHCP_MAX_SIZE, htons(576));
 439         add_client_options(&packet);
 440
 441         bb_info_msg("Sending discover...");
 442         return raw_bcast_from_client_config_ifindex(&packet);
 443 }
 444
 445 /* Broadcast a DHCP request message */
 446 /* RFC 2131 3.1 paragraph 3:
 447  * "The client _broadcasts_ a DHCPREQUEST message..."
 448  */
 449 static int send_select(uint32_t xid, uint32_t server, uint32_t requested)
 450 {
 451         struct dhcp_packet packet;
 452         struct in_addr addr;
 453
 454         init_packet(&packet, DHCPREQUEST);
 455         packet.xid = xid;
 456         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 457         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 458         add_client_options(&packet);
 459
 460         addr.s_addr = requested;
 461         bb_info_msg("Sending select for %s...", inet_ntoa(addr));
 462         return raw_bcast_from_client_config_ifindex(&packet);
 463 }
 464
 465 /* Unicast or broadcast a DHCP renew message */
 466 static int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
 467 {
 468         struct dhcp_packet packet;
 469
 470         init_packet(&packet, DHCPREQUEST);
 471         packet.xid = xid;
 472         packet.ciaddr = ciaddr;
 473         add_client_options(&packet);
 474
 475         bb_info_msg("Sending renew...");
 476         if (server)
 477                 return udhcp_send_kernel_packet(&packet,
 478                         ciaddr, CLIENT_PORT,
 479                         server, SERVER_PORT);
 480         return raw_bcast_from_client_config_ifindex(&packet);
 481 }
 482
 483 #if ENABLE_FEATURE_UDHCPC_ARPING
 484 /* Broadcast a DHCP decline message */
 485 static int send_decline(uint32_t xid, uint32_t server, uint32_t requested)
 486 {
 487         struct dhcp_packet packet;
 488
 489         init_packet(&packet, DHCPDECLINE);
 490         packet.xid = xid;
 491         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 492         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 493
 494         bb_info_msg("Sending decline...");
 495         return raw_bcast_from_client_config_ifindex(&packet);
 496 }
 497 #endif
 498
 499 /* Unicast a DHCP release message */
 500 static int send_release(uint32_t server, uint32_t ciaddr)
 501 {
 502         struct dhcp_packet packet;
 503
 504         init_packet(&packet, DHCPRELEASE);
 505         packet.xid = random_xid();
 506         packet.ciaddr = ciaddr;
 507
 508         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 509
 510         bb_info_msg("Sending release...");
 511         return udhcp_send_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
 512 }
 513
 514 /* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */
 515 static NOINLINE int udhcp_recv_raw_packet(struct dhcp_packet *dhcp_pkt, int fd)
 516 {
 517         int bytes;
 518         struct ip_udp_dhcp_packet packet;
 519         uint16_t check;
 520
 521         memset(&packet, 0, sizeof(packet));
 522         bytes = safe_read(fd, &packet, sizeof(packet));
 523         if (bytes < 0) {
 524                 log1("Packet read error, ignoring");
 525                 /* NB: possible down interface, etc. Caller should pause. */
 526                 return bytes; /* returns -1 */
 527         }
 528
 529         if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) {
 530                 log1("Packet is too short, ignoring");
 531                 return -2;
 532         }
 533
 534         if (bytes < ntohs(packet.ip.tot_len)) {
 535                 /* packet is bigger than sizeof(packet), we did partial read */
 536                 log1("Oversized packet, ignoring");
 537                 return -2;
 538         }
 539
 540         /* ignore any extra garbage bytes */
 541         bytes = ntohs(packet.ip.tot_len);
 542
 543         /* make sure its the right packet for us, and that it passes sanity checks */
 544         if (packet.ip.protocol != IPPROTO_UDP || packet.ip.version != IPVERSION
 545          || packet.ip.ihl != (sizeof(packet.ip) >> 2)
 546          || packet.udp.dest != htons(CLIENT_PORT)
 547         /* || bytes > (int) sizeof(packet) - can't happen */
 548          || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
 549         ) {
 550                 log1("Unrelated/bogus packet, ignoring");
 551                 return -2;
 552         }
 553
 554         /* verify IP checksum */
 555         check = packet.ip.check;
 556         packet.ip.check = 0;
 557         if (check != udhcp_checksum(&packet.ip, sizeof(packet.ip))) {
 558                 log1("Bad IP header checksum, ignoring");
 559                 return -2;
 560         }
 561
 562         /* verify UDP checksum. IP header has to be modified for this */
 563         memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
 564         /* ip.xx fields which are not memset: protocol, check, saddr, daddr */
 565         packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
 566         check = packet.udp.check;
 567         packet.udp.check = 0;
 568         if (check && check != udhcp_checksum(&packet, bytes)) {
 569                 log1("Packet with bad UDP checksum received, ignoring");
 570                 return -2;
 571         }
 572
 573         memcpy(dhcp_pkt, &packet.data, bytes - (sizeof(packet.ip) + sizeof(packet.udp)));
 574
 575         if (dhcp_pkt->cookie != htonl(DHCP_MAGIC)) {
 576                 bb_info_msg("Packet with bad magic, ignoring");
 577                 return -2;
 578         }
 579         log1("Got valid DHCP packet");
 580         udhcp_dump_packet(dhcp_pkt);
 581         return bytes - (sizeof(packet.ip) + sizeof(packet.udp));
 582 }
 583
 584
 585 /*** Main ***/
 586
 587 static int sockfd = -1;
 588
 589 #define LISTEN_NONE   0
 590 #define LISTEN_KERNEL 1
 591 #define LISTEN_RAW    2
 592 static smallint listen_mode;
 593
 594 /* initial state: (re)start DHCP negotiation */
 595 #define INIT_SELECTING  0
 596 /* discover was sent, DHCPOFFER reply received */
 597 #define REQUESTING      1
 598 /* select/renew was sent, DHCPACK reply received */
 599 #define BOUND           2
 600 /* half of lease passed, want to renew it by sending unicast renew requests */
 601 #define RENEWING        3
 602 /* renew requests were not answered, lease is almost over, send broadcast renew */
 603 #define REBINDING       4
 604 /* manually requested renew (SIGUSR1) */
 605 #define RENEW_REQUESTED 5
 606 /* release, possibly manually requested (SIGUSR2) */
 607 #define RELEASED        6
 608 static smallint state;
 609
 610 static int udhcp_raw_socket(int ifindex)
 611 {
 612         int fd;
 613         struct sockaddr_ll sock;
 614
 615         /*
 616          * Comment:
 617          *
 618          *      I've selected not to see LL header, so BPF doesn't see it, too.
 619          *      The filter may also pass non-IP and non-ARP packets, but we do
 620          *      a more complete check when receiving the message in userspace.
 621          *
 622          * and filter shamelessly stolen from:
 623          *
 624          *      http://www.flamewarmaster.de/software/dhcpclient/
 625          *
 626          * There are a few other interesting ideas on that page (look under
 627          * "Motivation").  Use of netlink events is most interesting.  Think
 628          * of various network servers listening for events and reconfiguring.
 629          * That would obsolete sending HUP signals and/or make use of restarts.
 630          *
 631          * Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
 632          * License: GPL v2.
 633          *
 634          * TODO: make conditional?
 635          */
 636 #define SERVER_AND_CLIENT_PORTS  ((67 << 16) + 68)
 637         static const struct sock_filter filter_instr[] = {
 638                 /* check for udp */
 639                 BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
 640                 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 2, 0),     /* L5, L1, is UDP? */
 641                 /* ugly check for arp on ethernet-like and IPv4 */
 642                 BPF_STMT(BPF_LD|BPF_W|BPF_ABS, 2),                      /* L1: */
 643                 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 0x08000604, 3, 4),      /* L3, L4 */
 644                 /* skip IP header */
 645                 BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0),                     /* L5: */
 646                 /* check udp source and destination ports */
 647                 BPF_STMT(BPF_LD|BPF_W|BPF_IND, 0),
 648                 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, SERVER_AND_CLIENT_PORTS, 0, 1), /* L3, L4 */
 649                 /* returns */
 650                 BPF_STMT(BPF_RET|BPF_K, 0x0fffffff ),                   /* L3: pass */
 651                 BPF_STMT(BPF_RET|BPF_K, 0),                             /* L4: reject */
 652         };
 653         static const struct sock_fprog filter_prog = {
 654                 .len = sizeof(filter_instr) / sizeof(filter_instr[0]),
 655                 /* casting const away: */
 656                 .filter = (struct sock_filter *) filter_instr,
 657         };
 658
 659         log1("Opening raw socket on ifindex %d", ifindex); //log2?
 660
 661         fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
 662         log1("Got raw socket fd %d", fd); //log2?
 663
 664         if (SERVER_PORT == 67 && CLIENT_PORT == 68) {
 665                 /* Use only if standard ports are in use */
 666                 /* Ignoring error (kernel may lack support for this) */
 667                 if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
 668                                 sizeof(filter_prog)) >= 0)
 669                         log1("Attached filter to raw socket fd %d", fd); // log?
 670         }
 671
 672         sock.sll_family = AF_PACKET;
 673         sock.sll_protocol = htons(ETH_P_IP);
 674         sock.sll_ifindex = ifindex;
 675         xbind(fd, (struct sockaddr *) &sock, sizeof(sock));
 676         log1("Created raw socket");
 677
 678         return fd;
 679 }
 680
 681 static void change_listen_mode(int new_mode)
 682 {
 683         log1("Entering listen mode: %s",
 684                 new_mode != LISTEN_NONE
 685                         ? (new_mode == LISTEN_KERNEL ? "kernel" : "raw")
 686                         : "none"
 687         );
 688
 689         listen_mode = new_mode;
 690         if (sockfd >= 0) {
 691                 close(sockfd);
 692                 sockfd = -1;
 693         }
 694         if (new_mode == LISTEN_KERNEL)
 695                 sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
 696         else if (new_mode != LISTEN_NONE)
 697                 sockfd = udhcp_raw_socket(client_config.ifindex);
 698         /* else LISTEN_NONE: sockfd stays closed */
 699 }
 700
 701 static void perform_renew(void)
 702 {
 703         bb_info_msg("Performing a DHCP renew");
 704         switch (state) {
 705         case BOUND:
 706                 change_listen_mode(LISTEN_KERNEL);
 707         case RENEWING:
 708         case REBINDING:
 709                 state = RENEW_REQUESTED;
 710                 break;
 711         case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
 712                 udhcp_run_script(NULL, "deconfig");
 713         case REQUESTING:
 714         case RELEASED:
 715                 change_listen_mode(LISTEN_RAW);
 716                 state = INIT_SELECTING;
 717                 break;
 718         case INIT_SELECTING:
 719                 break;
 720         }
 721 }
 722
 723 static void perform_release(uint32_t requested_ip, uint32_t server_addr)
 724 {
 725         char buffer[sizeof("255.255.255.255")];
 726         struct in_addr temp_addr;
 727
 728         /* send release packet */
 729         if (state == BOUND || state == RENEWING || state == REBINDING) {
 730                 temp_addr.s_addr = server_addr;
 731                 strcpy(buffer, inet_ntoa(temp_addr));
 732                 temp_addr.s_addr = requested_ip;
 733                 bb_info_msg("Unicasting a release of %s to %s",
 734                                 inet_ntoa(temp_addr), buffer);
 735                 send_release(server_addr, requested_ip); /* unicast */
 736                 udhcp_run_script(NULL, "deconfig");
 737         }
 738         bb_info_msg("Entering released state");
 739
 740         change_listen_mode(LISTEN_NONE);
 741         state = RELEASED;
 742 }
 743
 744 static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
 745 {
 746         uint8_t *storage;
 747         int len = strnlen(str, 255);
 748         storage = xzalloc(len + extra + OPT_DATA);
 749         storage[OPT_CODE] = code;
 750         storage[OPT_LEN] = len + extra;
 751         memcpy(storage + extra + OPT_DATA, str, len);
 752         return storage;
 753 }
 754
 755 #if BB_MMU
 756 static void client_background(void)
 757 {
 758         bb_daemonize(0);
 759         logmode &= ~LOGMODE_STDIO;
 760         /* rewrite pidfile, as our pid is different now */
 761         write_pidfile(client_config.pidfile);
 762 }
 763 #endif
 764
 765 int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 766 int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 767 {
 768         uint8_t *temp, *message;
 769         const char *str_c, *str_V, *str_h, *str_F, *str_r;
 770         IF_FEATURE_UDHCP_PORT(char *str_P;)
 771         llist_t *list_O = NULL;
 772         llist_t *list_x = NULL;
 773         int tryagain_timeout = 20;
 774         int discover_timeout = 3;
 775         int discover_retries = 3;
 776         uint32_t server_addr = server_addr; /* for compiler */
 777         uint32_t requested_ip = 0;
 778         uint32_t xid = 0;
 779         uint32_t lease_seconds = 0; /* can be given as 32-bit quantity */
 780         int packet_num;
 781         int timeout; /* must be signed */
 782         unsigned already_waited_sec;
 783         unsigned opt;
 784         int max_fd;
 785         int retval;
 786         struct timeval tv;
 787         struct dhcp_packet packet;
 788         fd_set rfds;
 789
 790 #if ENABLE_LONG_OPTS
 791         static const char udhcpc_longopts[] ALIGN1 =
 792                 "clientid\0"       Required_argument "c"
 793                 "clientid-none\0"  No_argument       "C"
 794                 "vendorclass\0"    Required_argument "V"
 795                 "hostname\0"       Required_argument "H"
 796                 "fqdn\0"           Required_argument "F"
 797                 "interface\0"      Required_argument "i"
 798                 "now\0"            No_argument       "n"
 799                 "pidfile\0"        Required_argument "p"
 800                 "quit\0"           No_argument       "q"
 801                 "release\0"        No_argument       "R"
 802                 "request\0"        Required_argument "r"
 803                 "script\0"         Required_argument "s"
 804                 "timeout\0"        Required_argument "T"
 805                 "version\0"        No_argument       "v"
 806                 "retries\0"        Required_argument "t"
 807                 "tryagain\0"       Required_argument "A"
 808                 "syslog\0"         No_argument       "S"
 809                 "request-option\0" Required_argument "O"
 810                 "no-default-options\0" No_argument   "o"
 811                 "foreground\0"     No_argument       "f"
 812                 "background\0"     No_argument       "b"
 813                 IF_FEATURE_UDHCPC_ARPING("arping\0"     No_argument       "a")
 814                 IF_FEATURE_UDHCP_PORT("client-port\0"   Required_argument "P")
 815                 ;
 816 #endif
 817         enum {
 818                 OPT_c = 1 << 0,
 819                 OPT_C = 1 << 1,
 820                 OPT_V = 1 << 2,
 821                 OPT_H = 1 << 3,
 822                 OPT_h = 1 << 4,
 823                 OPT_F = 1 << 5,
 824                 OPT_i = 1 << 6,
 825                 OPT_n = 1 << 7,
 826                 OPT_p = 1 << 8,
 827                 OPT_q = 1 << 9,
 828                 OPT_R = 1 << 10,
 829                 OPT_r = 1 << 11,
 830                 OPT_s = 1 << 12,
 831                 OPT_T = 1 << 13,
 832                 OPT_t = 1 << 14,
 833                 OPT_S = 1 << 15,
 834                 OPT_A = 1 << 16,
 835                 OPT_O = 1 << 17,
 836                 OPT_o = 1 << 18,
 837                 OPT_x = 1 << 19,
 838                 OPT_f = 1 << 20,
 839 /* The rest has variable bit positions, need to be clever */
 840                 OPTBIT_f = 20,
 841                 USE_FOR_MMU(             OPTBIT_b,)
 842                 IF_FEATURE_UDHCPC_ARPING(OPTBIT_a,)
 843                 IF_FEATURE_UDHCP_PORT(   OPTBIT_P,)
 844                 USE_FOR_MMU(             OPT_b = 1 << OPTBIT_b,)
 845                 IF_FEATURE_UDHCPC_ARPING(OPT_a = 1 << OPTBIT_a,)
 846                 IF_FEATURE_UDHCP_PORT(   OPT_P = 1 << OPTBIT_P,)
 847         };
 848
 849         /* Default options. */
 850         IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;)
 851         IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
 852         client_config.interface = "eth0";
 853         client_config.script = CONFIG_UDHCPC_DEFAULT_SCRIPT;
 854         str_V = "udhcp "BB_VER;
 855
 856         /* Parse command line */
 857         /* Cc: mutually exclusive; O,x: list; -T,-t,-A take numeric param */
 858         opt_complementary = "c--C:C--c:O::x::T+:t+:A+"
 859 #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
 860                 ":vv"
 861 #endif
 862                 ;
 863         IF_LONG_OPTS(applet_long_options = udhcpc_longopts;)
 864         opt = getopt32(argv, "c:CV:H:h:F:i:np:qRr:s:T:t:SA:O:ox:f"
 865                 USE_FOR_MMU("b")
 866                 IF_FEATURE_UDHCPC_ARPING("a")
 867                 IF_FEATURE_UDHCP_PORT("P:")
 868                 "v"
 869                 , &str_c, &str_V, &str_h, &str_h, &str_F
 870                 , &client_config.interface, &client_config.pidfile, &str_r /* i,p */
 871                 , &client_config.script /* s */
 872                 , &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */
 873                 , &list_O
 874                 , &list_x
 875                 IF_FEATURE_UDHCP_PORT(, &str_P)
 876 #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
 877                 , &dhcp_verbose
 878 #endif
 879                 );
 880         if (opt & (OPT_h|OPT_H))
 881                 client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
 882         if (opt & OPT_F) {
 883                 /* FQDN option format: [0x51][len][flags][0][0]<fqdn> */
 884                 client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
 885                 /* Flag bits: 0000NEOS
 886                  * S: 1 = Client requests server to update A RR in DNS as well as PTR
 887                  * O: 1 = Server indicates to client that DNS has been updated regardless
 888                  * E: 1 = Name is in DNS format, i.e. <4>host<6>domain<3>com<0>,
 889                  *    not "host.domain.com". Format 0 is obsolete.
 890                  * N: 1 = Client requests server to not update DNS (S must be 0 then)
 891                  * Two [0] bytes which follow are deprecated and must be 0.
 892                  */
 893                 client_config.fqdn[OPT_DATA + 0] = 0x1;
 894                 /*client_config.fqdn[OPT_DATA + 1] = 0; - xzalloc did it */
 895                 /*client_config.fqdn[OPT_DATA + 2] = 0; */
 896         }
 897         if (opt & OPT_r)
 898                 requested_ip = inet_addr(str_r);
 899 #if ENABLE_FEATURE_UDHCP_PORT
 900         if (opt & OPT_P) {
 901                 CLIENT_PORT = xatou16(str_P);
 902                 SERVER_PORT = CLIENT_PORT - 1;
 903         }
 904 #endif
 905         if (opt & OPT_o)
 906                 client_config.no_default_options = 1;
 907         while (list_O) {
 908                 char *optstr = llist_pop(&list_O);
 909                 unsigned n = udhcp_option_idx(optstr);
 910                 n = dhcp_optflags[n].code;
 911                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
 912         }
 913         while (list_x) {
 914                 char *optstr = llist_pop(&list_x);
 915                 char *colon = strchr(optstr, ':');
 916                 if (colon)
 917                         *colon = ' ';
 918                 /* now it looks similar to udhcpd's config file line:
 919                  * "optname optval", using the common routine: */
 920                 udhcp_str2optset(optstr, &client_config.options);
 921         }
 922
 923         if (udhcp_read_interface(client_config.interface,
 924                         &client_config.ifindex,
 925                         NULL,
 926                         client_config.client_mac)
 927         ) {
 928                 return 1;
 929         }
 930
 931         if (opt & OPT_c) {
 932                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, str_c, 0);
 933         } else if (!(opt & OPT_C)) {
 934                 /* not set and not suppressed, set the default client ID */
 935                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
 936                 client_config.clientid[OPT_DATA] = 1; /* type: ethernet */
 937                 memcpy(client_config.clientid + OPT_DATA+1, client_config.client_mac, 6);
 938         }
 939         if (str_V[0] != '\0')
 940                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
 941 #if !BB_MMU
 942         /* on NOMMU reexec (i.e., background) early */
 943         if (!(opt & OPT_f)) {
 944                 bb_daemonize_or_rexec(0 /* flags */, argv);
 945                 logmode = LOGMODE_NONE;
 946         }
 947 #endif
 948         if (opt & OPT_S) {
 949                 openlog(applet_name, LOG_PID, LOG_DAEMON);
 950                 logmode |= LOGMODE_SYSLOG;
 951         }
 952
 953         /* Make sure fd 0,1,2 are open */
 954         bb_sanitize_stdio();
 955         /* Equivalent of doing a fflush after every \n */
 956         setlinebuf(stdout);
 957         /* Create pidfile */
 958         write_pidfile(client_config.pidfile);
 959         /* Goes to stdout (unless NOMMU) and possibly syslog */
 960         bb_info_msg("%s (v"BB_VER") started", applet_name);
 961         /* Set up the signal pipe */
 962         udhcp_sp_setup();
 963         /* We want random_xid to be random... */
 964         srand(monotonic_us());
 965
 966         state = INIT_SELECTING;
 967         udhcp_run_script(NULL, "deconfig");
 968         change_listen_mode(LISTEN_RAW);
 969         packet_num = 0;
 970         timeout = 0;
 971         already_waited_sec = 0;
 972
 973         /* Main event loop. select() waits on signal pipe and possibly
 974          * on sockfd.
 975          * "continue" statements in code below jump to the top of the loop.
 976          */
 977         for (;;) {
 978                 /* silence "uninitialized!" warning */
 979                 unsigned timestamp_before_wait = timestamp_before_wait;
 980
 981                 //bb_error_msg("sockfd:%d, listen_mode:%d", sockfd, listen_mode);
 982
 983                 /* Was opening raw or udp socket here
 984                  * if (listen_mode != LISTEN_NONE && sockfd < 0),
 985                  * but on fast network renew responses return faster
 986                  * than we open sockets. Thus this code is moved
 987                  * to change_listen_mode(). Thus we open listen socket
 988                  * BEFORE we send renew request (see "case BOUND:"). */
 989
 990                 max_fd = udhcp_sp_fd_set(&rfds, sockfd);
 991
 992                 tv.tv_sec = timeout - already_waited_sec;
 993                 tv.tv_usec = 0;
 994                 retval = 0;
 995                 /* If we already timed out, fall through with retval = 0, else... */
 996                 if ((int)tv.tv_sec > 0) {
 997                         timestamp_before_wait = (unsigned)monotonic_sec();
 998                         log1("Waiting on select...");
 999                         retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
1000                         if (retval < 0) {
1001                                 /* EINTR? A signal was caught, don't panic */
1002                                 if (errno == EINTR) {
1003                                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1004                                         continue;
1005                                 }
1006                                 /* Else: an error occured, panic! */
1007                                 bb_perror_msg_and_die("select");
1008                         }
1009                 }
1010
1011                 /* If timeout dropped to zero, time to become active:
1012                  * resend discover/renew/whatever
1013                  */
1014                 if (retval == 0) {
1015                         /* We will restart the wait in any case */
1016                         already_waited_sec = 0;
1017
1018                         switch (state) {
1019                         case INIT_SELECTING:
1020                                 if (packet_num < discover_retries) {
1021                                         if (packet_num == 0)
1022                                                 xid = random_xid();
1023                                         /* broadcast */
1024                                         send_discover(xid, requested_ip);
1025                                         timeout = discover_timeout;
1026                                         packet_num++;
1027                                         continue;
1028                                 }
1029  leasefail:
1030                                 udhcp_run_script(NULL, "leasefail");
1031 #if BB_MMU /* -b is not supported on NOMMU */
1032                                 if (opt & OPT_b) { /* background if no lease */
1033                                         bb_info_msg("No lease, forking to background");
1034                                         client_background();
1035                                         /* do not background again! */
1036                                         opt = ((opt & ~OPT_b) | OPT_f);
1037                                 } else
1038 #endif
1039                                 if (opt & OPT_n) { /* abort if no lease */
1040                                         bb_info_msg("No lease, failing");
1041                                         retval = 1;
1042                                         goto ret;
1043                                 }
1044                                 /* wait before trying again */
1045                                 timeout = tryagain_timeout;
1046                                 packet_num = 0;
1047                                 continue;
1048                         case REQUESTING:
1049                                 if (packet_num < discover_retries) {
1050                                         /* send broadcast select packet */
1051                                         send_select(xid, server_addr, requested_ip);
1052                                         timeout = discover_timeout;
1053                                         packet_num++;
1054                                         continue;
1055                                 }
1056                                 /* Timed out, go back to init state.
1057                                  * "discover...select...discover..." loops
1058                                  * were seen in the wild. Treat them similarly
1059                                  * to "no response to discover" case */
1060                                 change_listen_mode(LISTEN_RAW);
1061                                 state = INIT_SELECTING;
1062                                 goto leasefail;
1063                         case BOUND:
1064                                 /* 1/2 lease passed, enter renewing state */
1065                                 state = RENEWING;
1066                                 change_listen_mode(LISTEN_KERNEL);
1067                                 log1("Entering renew state");
1068                                 /* fall right through */
1069                         case RENEW_REQUESTED: /* manual (SIGUSR1) renew */
1070                         case_RENEW_REQUESTED:
1071                         case RENEWING:
1072                                 if (timeout > 60) {
1073                                         /* send an unicast renew request */
1074                         /* Sometimes observed to fail (EADDRNOTAVAIL) to bind
1075                          * a new UDP socket for sending inside send_renew.
1076                          * I hazard to guess existing listening socket
1077                          * is somehow conflicting with it, but why is it
1078                          * not deterministic then?! Strange.
1079                          * Anyway, it does recover by eventually failing through
1080                          * into INIT_SELECTING state.
1081                          */
1082                                         send_renew(xid, server_addr, requested_ip);
1083                                         timeout >>= 1;
1084                                         continue;
1085                                 }
1086                                 /* Timed out, enter rebinding state */
1087                                 log1("Entering rebinding state");
1088                                 state = REBINDING;
1089                                 /* fall right through */
1090                         case REBINDING:
1091                                 /* Switch to bcast receive */
1092                                 change_listen_mode(LISTEN_RAW);
1093                                 /* Lease is *really* about to run out,
1094                                  * try to find DHCP server using broadcast */
1095                                 if (timeout > 0) {
1096                                         /* send a broadcast renew request */
1097                                         send_renew(xid, 0 /*INADDR_ANY*/, requested_ip);
1098                                         timeout >>= 1;
1099                                         continue;
1100                                 }
1101                                 /* Timed out, enter init state */
1102                                 bb_info_msg("Lease lost, entering init state");
1103                                 udhcp_run_script(NULL, "deconfig");
1104                                 state = INIT_SELECTING;
1105                                 /*timeout = 0; - already is */
1106                                 packet_num = 0;
1107                                 continue;
1108                         /* case RELEASED: */
1109                         }
1110                         /* yah, I know, *you* say it would never happen */
1111                         timeout = INT_MAX;
1112                         continue; /* back to main loop */
1113                 } /* if select timed out */
1114
1115                 /* select() didn't timeout, something happened */
1116
1117                 /* Is it a signal? */
1118                 /* note: udhcp_sp_read checks FD_ISSET before reading */
1119                 switch (udhcp_sp_read(&rfds)) {
1120                 case SIGUSR1:
1121                         perform_renew();
1122                         if (state == RENEW_REQUESTED)
1123                                 goto case_RENEW_REQUESTED;
1124                         /* Start things over */
1125                         packet_num = 0;
1126                         /* Kill any timeouts, user wants this to hurry along */
1127                         timeout = 0;
1128                         continue;
1129                 case SIGUSR2:
1130                         perform_release(requested_ip, server_addr);
1131                         timeout = INT_MAX;
1132                         continue;
1133                 case SIGTERM:
1134                         bb_info_msg("Received SIGTERM");
1135                         if (opt & OPT_R) /* release on quit */
1136                                 perform_release(requested_ip, server_addr);
1137                         goto ret0;
1138                 }
1139
1140                 /* Is it a packet? */
1141                 if (listen_mode == LISTEN_NONE || !FD_ISSET(sockfd, &rfds))
1142                         continue; /* no */
1143
1144                 {
1145                         int len;
1146
1147                         /* A packet is ready, read it */
1148                         if (listen_mode == LISTEN_KERNEL)
1149                                 len = udhcp_recv_kernel_packet(&packet, sockfd);
1150                         else
1151                                 len = udhcp_recv_raw_packet(&packet, sockfd);
1152                         if (len == -1) {
1153                                 /* Error is severe, reopen socket */
1154                                 bb_info_msg("Read error: %s, reopening socket", strerror(errno));
1155                                 sleep(discover_timeout); /* 3 seconds by default */
1156                                 change_listen_mode(listen_mode); /* just close and reopen */
1157                         }
1158                         /* If this packet will turn out to be unrelated/bogus,
1159                          * we will go back and wait for next one.
1160                          * Be sure timeout is properly decreased. */
1161                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1162                         if (len < 0)
1163                                 continue;
1164                 }
1165
1166                 if (packet.xid != xid) {
1167                         log1("xid %x (our is %x), ignoring packet",
1168                                 (unsigned)packet.xid, (unsigned)xid);
1169                         continue;
1170                 }
1171
1172                 /* Ignore packets that aren't for us */
1173                 if (packet.hlen != 6
1174                  || memcmp(packet.chaddr, client_config.client_mac, 6)
1175                 ) {
1176 //FIXME: need to also check that last 10 bytes are zero
1177                         log1("chaddr does not match, ignoring packet"); // log2?
1178                         continue;
1179                 }
1180
1181                 message = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
1182                 if (message == NULL) {
1183                         bb_error_msg("no message type option, ignoring packet");
1184                         continue;
1185                 }
1186
1187                 switch (state) {
1188                 case INIT_SELECTING:
1189                         /* Must be a DHCPOFFER to one of our xid's */
1190                         if (*message == DHCPOFFER) {
1191                 /* TODO: why we don't just fetch server's IP from IP header? */
1192                                 temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
1193                                 if (!temp) {
1194                                         bb_error_msg("no server ID in message");
1195                                         continue;
1196                                         /* still selecting - this server looks bad */
1197                                 }
1198                                 /* it IS unaligned sometimes, don't "optimize" */
1199                                 move_from_unaligned32(server_addr, temp);
1200                                 xid = packet.xid;
1201                                 requested_ip = packet.yiaddr;
1202
1203                                 /* enter requesting state */
1204                                 state = REQUESTING;
1205                                 timeout = 0;
1206                                 packet_num = 0;
1207                                 already_waited_sec = 0;
1208                         }
1209                         continue;
1210                 case REQUESTING:
1211                 case RENEWING:
1212                 case RENEW_REQUESTED:
1213                 case REBINDING:
1214                         if (*message == DHCPACK) {
1215                                 temp = udhcp_get_option(&packet, DHCP_LEASE_TIME);
1216                                 if (!temp) {
1217                                         bb_error_msg("no lease time with ACK, using 1 hour lease");
1218                                         lease_seconds = 60 * 60;
1219                                 } else {
1220                                         /* it IS unaligned sometimes, don't "optimize" */
1221                                         move_from_unaligned32(lease_seconds, temp);
1222                                         lease_seconds = ntohl(lease_seconds);
1223                                         lease_seconds &= 0x0fffffff; /* paranoia: must not be prone to overflows */
1224                                         if (lease_seconds < 10) /* and not too small */
1225                                                 lease_seconds = 10;
1226                                 }
1227 #if ENABLE_FEATURE_UDHCPC_ARPING
1228                                 if (opt & OPT_a) {
1229 /* RFC 2131 3.1 paragraph 5:
1230  * "The client receives the DHCPACK message with configuration
1231  * parameters. The client SHOULD perform a final check on the
1232  * parameters (e.g., ARP for allocated network address), and notes
1233  * the duration of the lease specified in the DHCPACK message. At this
1234  * point, the client is configured. If the client detects that the
1235  * address is already in use (e.g., through the use of ARP),
1236  * the client MUST send a DHCPDECLINE message to the server and restarts
1237  * the configuration process..." */
1238                                         if (!arpping(packet.yiaddr,
1239                                                         NULL,
1240                                                         (uint32_t) 0,
1241                                                         client_config.client_mac,
1242                                                         client_config.interface)
1243                                         ) {
1244                                                 bb_info_msg("Offered address is in use "
1245                                                         "(got ARP reply), declining");
1246                                                 send_decline(xid, server_addr, packet.yiaddr);
1247
1248                                                 if (state != REQUESTING)
1249                                                         udhcp_run_script(NULL, "deconfig");
1250                                                 change_listen_mode(LISTEN_RAW);
1251                                                 state = INIT_SELECTING;
1252                                                 requested_ip = 0;
1253                                                 timeout = tryagain_timeout;
1254                                                 packet_num = 0;
1255                                                 already_waited_sec = 0;
1256                                                 continue; /* back to main loop */
1257                                         }
1258                                 }
1259 #endif
1260                                 /* enter bound state */
1261                                 timeout = lease_seconds / 2;
1262                                 {
1263                                         struct in_addr temp_addr;
1264                                         temp_addr.s_addr = packet.yiaddr;
1265                                         bb_info_msg("Lease of %s obtained, lease time %u",
1266                                                 inet_ntoa(temp_addr), (unsigned)lease_seconds);
1267                                 }
1268                                 requested_ip = packet.yiaddr;
1269                                 udhcp_run_script(&packet, state == REQUESTING ? "bound" : "renew");
1270
1271                                 state = BOUND;
1272                                 change_listen_mode(LISTEN_NONE);
1273                                 if (opt & OPT_q) { /* quit after lease */
1274                                         if (opt & OPT_R) /* release on quit */
1275                                                 perform_release(requested_ip, server_addr);
1276                                         goto ret0;
1277                                 }
1278                                 /* future renew failures should not exit (JM) */
1279                                 opt &= ~OPT_n;
1280 #if BB_MMU /* NOMMU case backgrounded earlier */
1281                                 if (!(opt & OPT_f)) {
1282                                         client_background();
1283                                         /* do not background again! */
1284                                         opt = ((opt & ~OPT_b) | OPT_f);
1285                                 }
1286 #endif
1287                                 already_waited_sec = 0;
1288                                 continue; /* back to main loop */
1289                         }
1290                         if (*message == DHCPNAK) {
1291                                 /* return to init state */
1292                                 bb_info_msg("Received DHCP NAK");
1293                                 udhcp_run_script(&packet, "nak");
1294                                 if (state != REQUESTING)
1295                                         udhcp_run_script(NULL, "deconfig");
1296                                 change_listen_mode(LISTEN_RAW);
1297                                 sleep(3); /* avoid excessive network traffic */
1298                                 state = INIT_SELECTING;
1299                                 requested_ip = 0;
1300                                 timeout = 0;
1301                                 packet_num = 0;
1302                                 already_waited_sec = 0;
1303                         }
1304                         continue;
1305                 /* case BOUND: - ignore all packets */
1306                 /* case RELEASED: - ignore all packets */
1307                 }
1308                 /* back to main loop */
1309         } /* for (;;) - main loop ends */
1310
1311  ret0:
1312         retval = 0;
1313  ret:
1314         /*if (client_config.pidfile) - remove_pidfile has its own check */
1315                 remove_pidfile(client_config.pidfile);
1316         return retval;
1317 }