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 <netinet/if_ether.h>
  29 #include <netpacket/packet.h>
  30 #include <linux/filter.h>
  31
  32 /* struct client_config_t client_config is in bb_common_bufsiz1 */
  33
  34
  35 #if ENABLE_LONG_OPTS
  36 static const char udhcpc_longopts[] ALIGN1 =
  37         "clientid-none\0"  No_argument       "C"
  38         "vendorclass\0"    Required_argument "V"
  39         "hostname\0"       Required_argument "H"
  40         "fqdn\0"           Required_argument "F"
  41         "interface\0"      Required_argument "i"
  42         "now\0"            No_argument       "n"
  43         "pidfile\0"        Required_argument "p"
  44         "quit\0"           No_argument       "q"
  45         "release\0"        No_argument       "R"
  46         "request\0"        Required_argument "r"
  47         "script\0"         Required_argument "s"
  48         "timeout\0"        Required_argument "T"
  49         "version\0"        No_argument       "v"
  50         "retries\0"        Required_argument "t"
  51         "tryagain\0"       Required_argument "A"
  52         "syslog\0"         No_argument       "S"
  53         "request-option\0" Required_argument "O"
  54         "no-default-options\0" No_argument   "o"
  55         "foreground\0"     No_argument       "f"
  56         "background\0"     No_argument       "b"
  57         "broadcast\0"      No_argument       "B"
  58         IF_FEATURE_UDHCPC_ARPING("arping\0"     No_argument       "a")
  59         IF_FEATURE_UDHCP_PORT("client-port\0"   Required_argument "P")
  60         ;
  61 #endif
  62 /* Must match getopt32 option string order */
  63 enum {
  64         OPT_C = 1 << 0,
  65         OPT_V = 1 << 1,
  66         OPT_H = 1 << 2,
  67         OPT_h = 1 << 3,
  68         OPT_F = 1 << 4,
  69         OPT_i = 1 << 5,
  70         OPT_n = 1 << 6,
  71         OPT_p = 1 << 7,
  72         OPT_q = 1 << 8,
  73         OPT_R = 1 << 9,
  74         OPT_r = 1 << 10,
  75         OPT_s = 1 << 11,
  76         OPT_T = 1 << 12,
  77         OPT_t = 1 << 13,
  78         OPT_S = 1 << 14,
  79         OPT_A = 1 << 15,
  80         OPT_O = 1 << 16,
  81         OPT_o = 1 << 17,
  82         OPT_x = 1 << 18,
  83         OPT_f = 1 << 19,
  84         OPT_B = 1 << 20,
  85 /* The rest has variable bit positions, need to be clever */
  86         OPTBIT_B = 20,
  87         USE_FOR_MMU(             OPTBIT_b,)
  88         IF_FEATURE_UDHCPC_ARPING(OPTBIT_a,)
  89         IF_FEATURE_UDHCP_PORT(   OPTBIT_P,)
  90         USE_FOR_MMU(             OPT_b = 1 << OPTBIT_b,)
  91         IF_FEATURE_UDHCPC_ARPING(OPT_a = 1 << OPTBIT_a,)
  92         IF_FEATURE_UDHCP_PORT(   OPT_P = 1 << OPTBIT_P,)
  93 };
  94
  95
  96 /*** Script execution code ***/
  97
  98 /* get a rough idea of how long an option will be (rounding up...) */
  99 static const uint8_t len_of_option_as_string[] = {
 100         [OPTION_IP              ] = sizeof("255.255.255.255 "),
 101         [OPTION_IP_PAIR         ] = sizeof("255.255.255.255 ") * 2,
 102         [OPTION_STATIC_ROUTES   ] = sizeof("255.255.255.255/32 255.255.255.255 "),
 103         [OPTION_STRING          ] = 1,
 104 #if ENABLE_FEATURE_UDHCP_RFC3397
 105         [OPTION_DNS_STRING      ] = 1, /* unused */
 106         /* Hmmm, this severely overestimates size if SIP_SERVERS option
 107          * is in domain name form: N-byte option in binary form
 108          * mallocs ~16*N bytes. But it is freed almost at once.
 109          */
 110         [OPTION_SIP_SERVERS     ] = sizeof("255.255.255.255 "),
 111 #endif
 112 //      [OPTION_BOOLEAN         ] = sizeof("yes "),
 113         [OPTION_U8              ] = sizeof("255 "),
 114         [OPTION_U16             ] = sizeof("65535 "),
 115 //      [OPTION_S16             ] = sizeof("-32768 "),
 116         [OPTION_U32             ] = sizeof("4294967295 "),
 117         [OPTION_S32             ] = sizeof("-2147483684 "),
 118 };
 119
 120 /* note: ip is a pointer to an IP in network order, possibly misaliged */
 121 static int sprint_nip(char *dest, const char *pre, const uint8_t *ip)
 122 {
 123         return sprintf(dest, "%s%u.%u.%u.%u", pre, ip[0], ip[1], ip[2], ip[3]);
 124 }
 125
 126 /* really simple implementation, just count the bits */
 127 static int mton(uint32_t mask)
 128 {
 129         int i = 0;
 130         mask = ntohl(mask); /* 111110000-like bit pattern */
 131         while (mask) {
 132                 i++;
 133                 mask <<= 1;
 134         }
 135         return i;
 136 }
 137
 138 /* Create "opt_name=opt_value" string */
 139 static NOINLINE char *xmalloc_optname_optval(uint8_t *option, const struct dhcp_optflag *optflag, const char *opt_name)
 140 {
 141         unsigned upper_length;
 142         int len, type, optlen;
 143         char *dest, *ret;
 144
 145         /* option points to OPT_DATA, need to go back and get OPT_LEN */
 146         len = option[OPT_LEN - OPT_DATA];
 147
 148         type = optflag->flags & OPTION_TYPE_MASK;
 149         optlen = dhcp_option_lengths[type];
 150         upper_length = len_of_option_as_string[type] * ((unsigned)len / (unsigned)optlen);
 151
 152         dest = ret = xmalloc(upper_length + strlen(opt_name) + 2);
 153         dest += sprintf(ret, "%s=", opt_name);
 154
 155         while (len >= optlen) {
 156                 unsigned ip_ofs = 0;
 157
 158                 switch (type) {
 159                 case OPTION_IP_PAIR:
 160                         dest += sprint_nip(dest, "", option);
 161                         *dest++ = '/';
 162                         ip_ofs = 4;
 163                         /* fall through */
 164                 case OPTION_IP:
 165                         dest += sprint_nip(dest, "", option + ip_ofs);
 166                         break;
 167 //              case OPTION_BOOLEAN:
 168 //                      dest += sprintf(dest, *option ? "yes" : "no");
 169 //                      break;
 170                 case OPTION_U8:
 171                         dest += sprintf(dest, "%u", *option);
 172                         break;
 173 //              case OPTION_S16:
 174                 case OPTION_U16: {
 175                         uint16_t val_u16;
 176                         move_from_unaligned16(val_u16, option);
 177                         dest += sprintf(dest, "%u", ntohs(val_u16));
 178                         break;
 179                 }
 180                 case OPTION_S32:
 181                 case OPTION_U32: {
 182                         uint32_t val_u32;
 183                         move_from_unaligned32(val_u32, option);
 184                         dest += sprintf(dest, type == OPTION_U32 ? "%lu" : "%ld", (unsigned long) ntohl(val_u32));
 185                         break;
 186                 }
 187                 case OPTION_STRING:
 188                         memcpy(dest, option, len);
 189                         dest[len] = '\0';
 190                         return ret;      /* Short circuit this case */
 191                 case OPTION_STATIC_ROUTES: {
 192                         /* Option binary format:
 193                          * mask [one byte, 0..32]
 194                          * ip [big endian, 0..4 bytes depending on mask]
 195                          * router [big endian, 4 bytes]
 196                          * may be repeated
 197                          *
 198                          * We convert it to a string "IP/MASK ROUTER IP2/MASK2 ROUTER2"
 199                          */
 200                         const char *pfx = "";
 201
 202                         while (len >= 1 + 4) { /* mask + 0-byte ip + router */
 203                                 uint32_t nip;
 204                                 uint8_t *p;
 205                                 unsigned mask;
 206                                 int bytes;
 207
 208                                 mask = *option++;
 209                                 if (mask > 32)
 210                                         break;
 211                                 len--;
 212
 213                                 nip = 0;
 214                                 p = (void*) &nip;
 215                                 bytes = (mask + 7) / 8; /* 0 -> 0, 1..8 -> 1, 9..16 -> 2 etc */
 216                                 while (--bytes >= 0) {
 217                                         *p++ = *option++;
 218                                         len--;
 219                                 }
 220                                 if (len < 4)
 221                                         break;
 222
 223                                 /* print ip/mask */
 224                                 dest += sprint_nip(dest, pfx, (void*) &nip);
 225                                 pfx = " ";
 226                                 dest += sprintf(dest, "/%u ", mask);
 227                                 /* print router */
 228                                 dest += sprint_nip(dest, "", option);
 229                                 option += 4;
 230                                 len -= 4;
 231                         }
 232
 233                         return ret;
 234                 }
 235 #if ENABLE_FEATURE_UDHCP_RFC3397
 236                 case OPTION_DNS_STRING:
 237                         /* unpack option into dest; use ret for prefix (i.e., "optname=") */
 238                         dest = dname_dec(option, len, ret);
 239                         if (dest) {
 240                                 free(ret);
 241                                 return dest;
 242                         }
 243                         /* error. return "optname=" string */
 244                         return ret;
 245                 case OPTION_SIP_SERVERS:
 246                         /* Option binary format:
 247                          * type: byte
 248                          * type=0: domain names, dns-compressed
 249                          * type=1: IP addrs
 250                          */
 251                         option++;
 252                         len--;
 253                         if (option[-1] == 0) {
 254                                 dest = dname_dec(option, len, ret);
 255                                 if (dest) {
 256                                         free(ret);
 257                                         return dest;
 258                                 }
 259                         } else
 260                         if (option[-1] == 1) {
 261                                 const char *pfx = "";
 262                                 while (1) {
 263                                         len -= 4;
 264                                         if (len < 0)
 265                                                 break;
 266                                         dest += sprint_nip(dest, pfx, option);
 267                                         pfx = " ";
 268                                         option += 4;
 269                                 }
 270                         }
 271                         return ret;
 272 #endif
 273                 } /* switch */
 274                 option += optlen;
 275                 len -= optlen;
 276 // TODO: it can be a list only if (optflag->flags & OPTION_LIST).
 277 // Should we bail out/warn if we see multi-ip option which is
 278 // not allowed to be such (for example, DHCP_BROADCAST)? -
 279                 if (len <= 0 /* || !(optflag->flags & OPTION_LIST) */)
 280                         break;
 281                 *dest++ = ' ';
 282                 *dest = '\0';
 283         }
 284         return ret;
 285 }
 286
 287 /* put all the parameters into the environment */
 288 static char **fill_envp(struct dhcp_packet *packet)
 289 {
 290         int envc;
 291         int i;
 292         char **envp, **curr;
 293         const char *opt_name;
 294         uint8_t *temp;
 295         uint8_t overload = 0;
 296
 297 #define BITMAP unsigned
 298 #define BBITS (sizeof(BITMAP) * 8)
 299 #define BMASK(i) (1 << (i & (sizeof(BITMAP) * 8 - 1)))
 300 #define FOUND_OPTS(i) (found_opts[(unsigned)i / BBITS])
 301         BITMAP found_opts[256 / BBITS];
 302
 303         memset(found_opts, 0, sizeof(found_opts));
 304
 305         /* We need 6 elements for:
 306          * "interface=IFACE"
 307          * "ip=N.N.N.N" from packet->yiaddr
 308          * "siaddr=IP" from packet->siaddr_nip (unless 0)
 309          * "boot_file=FILE" from packet->file (unless overloaded)
 310          * "sname=SERVER_HOSTNAME" from packet->sname (unless overloaded)
 311          * terminating NULL
 312          */
 313         envc = 6;
 314         /* +1 element for each option, +2 for subnet option: */
 315         if (packet) {
 316                 /* note: do not search for "pad" (0) and "end" (255) options */
 317                 for (i = 1; i < 255; i++) {
 318                         temp = udhcp_get_option(packet, i);
 319                         if (temp) {
 320                                 if (i == DHCP_OPTION_OVERLOAD)
 321                                         overload = *temp;
 322                                 else if (i == DHCP_SUBNET)
 323                                         envc++; /* for mton */
 324                                 envc++;
 325                                 /*if (i != DHCP_MESSAGE_TYPE)*/
 326                                 FOUND_OPTS(i) |= BMASK(i);
 327                         }
 328                 }
 329         }
 330         curr = envp = xzalloc(sizeof(envp[0]) * envc);
 331
 332         *curr = xasprintf("interface=%s", client_config.interface);
 333         putenv(*curr++);
 334
 335         if (!packet)
 336                 return envp;
 337
 338         *curr = xmalloc(sizeof("ip=255.255.255.255"));
 339         sprint_nip(*curr, "ip=", (uint8_t *) &packet->yiaddr);
 340         putenv(*curr++);
 341
 342         opt_name = dhcp_option_strings;
 343         i = 0;
 344         while (*opt_name) {
 345                 uint8_t code = dhcp_optflags[i].code;
 346                 BITMAP *found_ptr = &FOUND_OPTS(code);
 347                 BITMAP found_mask = BMASK(code);
 348                 if (!(*found_ptr & found_mask))
 349                         goto next;
 350                 *found_ptr &= ~found_mask; /* leave only unknown options */
 351                 temp = udhcp_get_option(packet, code);
 352                 *curr = xmalloc_optname_optval(temp, &dhcp_optflags[i], opt_name);
 353                 putenv(*curr++);
 354                 if (code == DHCP_SUBNET) {
 355                         /* Subnet option: make things like "$ip/$mask" possible */
 356                         uint32_t subnet;
 357                         move_from_unaligned32(subnet, temp);
 358                         *curr = xasprintf("mask=%d", mton(subnet));
 359                         putenv(*curr++);
 360                 }
 361  next:
 362                 opt_name += strlen(opt_name) + 1;
 363                 i++;
 364         }
 365         if (packet->siaddr_nip) {
 366                 *curr = xmalloc(sizeof("siaddr=255.255.255.255"));
 367                 sprint_nip(*curr, "siaddr=", (uint8_t *) &packet->siaddr_nip);
 368                 putenv(*curr++);
 369         }
 370         if (!(overload & FILE_FIELD) && packet->file[0]) {
 371                 /* watch out for invalid packets */
 372                 *curr = xasprintf("boot_file=%."DHCP_PKT_FILE_LEN_STR"s", packet->file);
 373                 putenv(*curr++);
 374         }
 375         if (!(overload & SNAME_FIELD) && packet->sname[0]) {
 376                 /* watch out for invalid packets */
 377                 *curr = xasprintf("sname=%."DHCP_PKT_SNAME_LEN_STR"s", packet->sname);
 378                 putenv(*curr++);
 379         }
 380         /* Handle unknown options */
 381         for (i = 0; i < 256;) {
 382                 BITMAP bitmap = FOUND_OPTS(i);
 383                 if (!bitmap) {
 384                         i += BBITS;
 385                         continue;
 386                 }
 387                 if (bitmap & BMASK(i)) {
 388                         unsigned len, ofs;
 389
 390                         temp = udhcp_get_option(packet, i);
 391                         /* udhcp_get_option returns ptr to data portion,
 392                          * need to go back to get len
 393                          */
 394                         len = temp[-OPT_DATA + OPT_LEN];
 395                         *curr = xmalloc(sizeof("optNNN=") + 1 + len*2);
 396                         ofs = sprintf(*curr, "opt%u=", i);
 397                         bin2hex(*curr + ofs, (void*) temp, len)[0] = '\0';
 398                         putenv(*curr++);
 399                 }
 400                 i++;
 401         }
 402         return envp;
 403 }
 404
 405 /* Call a script with a par file and env vars */
 406 static void udhcp_run_script(struct dhcp_packet *packet, const char *name)
 407 {
 408         char **envp, **curr;
 409         char *argv[3];
 410
 411         if (client_config.script == NULL)
 412                 return;
 413
 414         envp = fill_envp(packet);
 415
 416         /* call script */
 417         log1("Executing %s %s", client_config.script, name);
 418         argv[0] = (char*) client_config.script;
 419         argv[1] = (char*) name;
 420         argv[2] = NULL;
 421         spawn_and_wait(argv);
 422
 423         for (curr = envp; *curr; curr++) {
 424                 log2(" %s", *curr);
 425                 bb_unsetenv_and_free(*curr);
 426         }
 427         free(envp);
 428 }
 429
 430
 431 /*** Sending/receiving packets ***/
 432
 433 static ALWAYS_INLINE uint32_t random_xid(void)
 434 {
 435         return rand();
 436 }
 437
 438 /* Initialize the packet with the proper defaults */
 439 static void init_packet(struct dhcp_packet *packet, char type)
 440 {
 441         uint16_t secs;
 442
 443         /* Fill in: op, htype, hlen, cookie fields; message type option: */
 444         udhcp_init_header(packet, type);
 445
 446         packet->xid = random_xid();
 447
 448         client_config.last_secs = monotonic_sec();
 449         if (client_config.first_secs == 0)
 450                 client_config.first_secs = client_config.last_secs;
 451         secs = client_config.last_secs - client_config.first_secs;
 452         packet->secs = htons(secs);
 453
 454         memcpy(packet->chaddr, client_config.client_mac, 6);
 455         if (client_config.clientid)
 456                 udhcp_add_binary_option(packet, client_config.clientid);
 457 }
 458
 459 static void add_client_options(struct dhcp_packet *packet)
 460 {
 461         uint8_t c;
 462         int i, end, len;
 463
 464         udhcp_add_simple_option(packet, DHCP_MAX_SIZE, htons(IP_UDP_DHCP_SIZE));
 465
 466         /* Add a "param req" option with the list of options we'd like to have
 467          * from stubborn DHCP servers. Pull the data from the struct in common.c.
 468          * No bounds checking because it goes towards the head of the packet. */
 469         end = udhcp_end_option(packet->options);
 470         len = 0;
 471         for (i = 0; (c = dhcp_optflags[i].code) != 0; i++) {
 472                 if ((   (dhcp_optflags[i].flags & OPTION_REQ)
 473                      && !client_config.no_default_options
 474                     )
 475                  || (client_config.opt_mask[c >> 3] & (1 << (c & 7)))
 476                 ) {
 477                         packet->options[end + OPT_DATA + len] = c;
 478                         len++;
 479                 }
 480         }
 481         if (len) {
 482                 packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
 483                 packet->options[end + OPT_LEN] = len;
 484                 packet->options[end + OPT_DATA + len] = DHCP_END;
 485         }
 486
 487         if (client_config.vendorclass)
 488                 udhcp_add_binary_option(packet, client_config.vendorclass);
 489         if (client_config.hostname)
 490                 udhcp_add_binary_option(packet, client_config.hostname);
 491         if (client_config.fqdn)
 492                 udhcp_add_binary_option(packet, client_config.fqdn);
 493
 494         /* Request broadcast replies if we have no IP addr */
 495         if ((option_mask32 & OPT_B) && packet->ciaddr == 0)
 496                 packet->flags |= htons(BROADCAST_FLAG);
 497
 498         /* Add -x options if any */
 499         {
 500                 struct option_set *curr = client_config.options;
 501                 while (curr) {
 502                         udhcp_add_binary_option(packet, curr->data);
 503                         curr = curr->next;
 504                 }
 505 //              if (client_config.sname)
 506 //                      strncpy((char*)packet->sname, client_config.sname, sizeof(packet->sname) - 1);
 507 //              if (client_config.boot_file)
 508 //                      strncpy((char*)packet->file, client_config.boot_file, sizeof(packet->file) - 1);
 509         }
 510 }
 511
 512 /* RFC 2131
 513  * 4.4.4 Use of broadcast and unicast
 514  *
 515  * The DHCP client broadcasts DHCPDISCOVER, DHCPREQUEST and DHCPINFORM
 516  * messages, unless the client knows the address of a DHCP server.
 517  * The client unicasts DHCPRELEASE messages to the server. Because
 518  * the client is declining the use of the IP address supplied by the server,
 519  * the client broadcasts DHCPDECLINE messages.
 520  *
 521  * When the DHCP client knows the address of a DHCP server, in either
 522  * INIT or REBOOTING state, the client may use that address
 523  * in the DHCPDISCOVER or DHCPREQUEST rather than the IP broadcast address.
 524  * The client may also use unicast to send DHCPINFORM messages
 525  * to a known DHCP server. If the client receives no response to DHCP
 526  * messages sent to the IP address of a known DHCP server, the DHCP
 527  * client reverts to using the IP broadcast address.
 528  */
 529
 530 static int raw_bcast_from_client_config_ifindex(struct dhcp_packet *packet)
 531 {
 532         return udhcp_send_raw_packet(packet,
 533                 /*src*/ INADDR_ANY, CLIENT_PORT,
 534                 /*dst*/ INADDR_BROADCAST, SERVER_PORT, MAC_BCAST_ADDR,
 535                 client_config.ifindex);
 536 }
 537
 538 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
 539 /* NOINLINE: limit stack usage in caller */
 540 static NOINLINE int send_discover(uint32_t xid, uint32_t requested)
 541 {
 542         struct dhcp_packet packet;
 543
 544         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 545          * random xid field (we override it below),
 546          * client-id option (unless -C), message type option:
 547          */
 548         init_packet(&packet, DHCPDISCOVER);
 549
 550         packet.xid = xid;
 551         if (requested)
 552                 udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 553
 554         /* Add options: maxsize,
 555          * optionally: hostname, fqdn, vendorclass,
 556          * "param req" option according to -O, options specified with -x
 557          */
 558         add_client_options(&packet);
 559
 560         bb_info_msg("Sending discover...");
 561         return raw_bcast_from_client_config_ifindex(&packet);
 562 }
 563
 564 /* Broadcast a DHCP request message */
 565 /* RFC 2131 3.1 paragraph 3:
 566  * "The client _broadcasts_ a DHCPREQUEST message..."
 567  */
 568 /* NOINLINE: limit stack usage in caller */
 569 static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requested)
 570 {
 571         struct dhcp_packet packet;
 572         struct in_addr addr;
 573
 574 /*
 575  * RFC 2131 4.3.2 DHCPREQUEST message
 576  * ...
 577  * If the DHCPREQUEST message contains a 'server identifier'
 578  * option, the message is in response to a DHCPOFFER message.
 579  * Otherwise, the message is a request to verify or extend an
 580  * existing lease. If the client uses a 'client identifier'
 581  * in a DHCPREQUEST message, it MUST use that same 'client identifier'
 582  * in all subsequent messages. If the client included a list
 583  * of requested parameters in a DHCPDISCOVER message, it MUST
 584  * include that list in all subsequent messages.
 585  */
 586         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 587          * random xid field (we override it below),
 588          * client-id option (unless -C), message type option:
 589          */
 590         init_packet(&packet, DHCPREQUEST);
 591
 592         packet.xid = xid;
 593         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 594
 595         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 596
 597         /* Add options: maxsize,
 598          * optionally: hostname, fqdn, vendorclass,
 599          * "param req" option according to -O, and options specified with -x
 600          */
 601         add_client_options(&packet);
 602
 603         addr.s_addr = requested;
 604         bb_info_msg("Sending select for %s...", inet_ntoa(addr));
 605         return raw_bcast_from_client_config_ifindex(&packet);
 606 }
 607
 608 /* Unicast or broadcast a DHCP renew message */
 609 /* NOINLINE: limit stack usage in caller */
 610 static NOINLINE int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
 611 {
 612         struct dhcp_packet packet;
 613
 614 /*
 615  * RFC 2131 4.3.2 DHCPREQUEST message
 616  * ...
 617  * DHCPREQUEST generated during RENEWING state:
 618  *
 619  * 'server identifier' MUST NOT be filled in, 'requested IP address'
 620  * option MUST NOT be filled in, 'ciaddr' MUST be filled in with
 621  * client's IP address. In this situation, the client is completely
 622  * configured, and is trying to extend its lease. This message will
 623  * be unicast, so no relay agents will be involved in its
 624  * transmission.  Because 'giaddr' is therefore not filled in, the
 625  * DHCP server will trust the value in 'ciaddr', and use it when
 626  * replying to the client.
 627  */
 628         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 629          * random xid field (we override it below),
 630          * client-id option (unless -C), message type option:
 631          */
 632         init_packet(&packet, DHCPREQUEST);
 633
 634         packet.xid = xid;
 635         packet.ciaddr = ciaddr;
 636
 637         /* Add options: maxsize,
 638          * optionally: hostname, fqdn, vendorclass,
 639          * "param req" option according to -O, and options specified with -x
 640          */
 641         add_client_options(&packet);
 642
 643         bb_info_msg("Sending renew...");
 644         if (server)
 645                 return udhcp_send_kernel_packet(&packet,
 646                         ciaddr, CLIENT_PORT,
 647                         server, SERVER_PORT);
 648         return raw_bcast_from_client_config_ifindex(&packet);
 649 }
 650
 651 #if ENABLE_FEATURE_UDHCPC_ARPING
 652 /* Broadcast a DHCP decline message */
 653 /* NOINLINE: limit stack usage in caller */
 654 static NOINLINE int send_decline(uint32_t xid, uint32_t server, uint32_t requested)
 655 {
 656         struct dhcp_packet packet;
 657
 658         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 659          * client-id option (unless -C), message type option:
 660          */
 661         init_packet(&packet, DHCPDECLINE);
 662
 663         /* RFC 2131 says DHCPDECLINE's xid is randomly selected by client,
 664          * but in case the server is buggy and wants DHCPDECLINE's xid
 665          * to match the xid which started entire handshake,
 666          * we use the same xid we used in initial DHCPDISCOVER:
 667          */
 668         packet.xid = xid;
 669         /* DHCPDECLINE uses "requested ip", not ciaddr, to store offered IP */
 670         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 671
 672         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 673
 674         bb_info_msg("Sending decline...");
 675         return raw_bcast_from_client_config_ifindex(&packet);
 676 }
 677 #endif
 678
 679 /* Unicast a DHCP release message */
 680 static int send_release(uint32_t server, uint32_t ciaddr)
 681 {
 682         struct dhcp_packet packet;
 683
 684         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 685          * client-id option (unless -C), message type option:
 686          */
 687         init_packet(&packet, DHCPRELEASE);
 688
 689         /* DHCPRELEASE uses ciaddr, not "requested ip", to store IP being released */
 690         packet.ciaddr = ciaddr;
 691
 692         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 693
 694         bb_info_msg("Sending release...");
 695         return udhcp_send_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
 696 }
 697
 698 /* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */
 699 /* NOINLINE: limit stack usage in caller */
 700 static NOINLINE int udhcp_recv_raw_packet(struct dhcp_packet *dhcp_pkt, int fd)
 701 {
 702         int bytes;
 703         struct ip_udp_dhcp_packet packet;
 704         uint16_t check;
 705
 706         memset(&packet, 0, sizeof(packet));
 707         bytes = safe_read(fd, &packet, sizeof(packet));
 708         if (bytes < 0) {
 709                 log1("Packet read error, ignoring");
 710                 /* NB: possible down interface, etc. Caller should pause. */
 711                 return bytes; /* returns -1 */
 712         }
 713
 714         if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) {
 715                 log1("Packet is too short, ignoring");
 716                 return -2;
 717         }
 718
 719         if (bytes < ntohs(packet.ip.tot_len)) {
 720                 /* packet is bigger than sizeof(packet), we did partial read */
 721                 log1("Oversized packet, ignoring");
 722                 return -2;
 723         }
 724
 725         /* ignore any extra garbage bytes */
 726         bytes = ntohs(packet.ip.tot_len);
 727
 728         /* make sure its the right packet for us, and that it passes sanity checks */
 729         if (packet.ip.protocol != IPPROTO_UDP || packet.ip.version != IPVERSION
 730          || packet.ip.ihl != (sizeof(packet.ip) >> 2)
 731          || packet.udp.dest != htons(CLIENT_PORT)
 732         /* || bytes > (int) sizeof(packet) - can't happen */
 733          || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
 734         ) {
 735                 log1("Unrelated/bogus packet, ignoring");
 736                 return -2;
 737         }
 738
 739         /* verify IP checksum */
 740         check = packet.ip.check;
 741         packet.ip.check = 0;
 742         if (check != inet_cksum((uint16_t *)&packet.ip, sizeof(packet.ip))) {
 743                 log1("Bad IP header checksum, ignoring");
 744                 return -2;
 745         }
 746
 747         /* verify UDP checksum. IP header has to be modified for this */
 748         memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
 749         /* ip.xx fields which are not memset: protocol, check, saddr, daddr */
 750         packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
 751         check = packet.udp.check;
 752         packet.udp.check = 0;
 753         if (check && check != inet_cksum((uint16_t *)&packet, bytes)) {
 754                 log1("Packet with bad UDP checksum received, ignoring");
 755                 return -2;
 756         }
 757
 758         memcpy(dhcp_pkt, &packet.data, bytes - (sizeof(packet.ip) + sizeof(packet.udp)));
 759
 760         if (dhcp_pkt->cookie != htonl(DHCP_MAGIC)) {
 761                 bb_info_msg("Packet with bad magic, ignoring");
 762                 return -2;
 763         }
 764         log1("Got valid DHCP packet");
 765         udhcp_dump_packet(dhcp_pkt);
 766         return bytes - (sizeof(packet.ip) + sizeof(packet.udp));
 767 }
 768
 769
 770 /*** Main ***/
 771
 772 static int sockfd = -1;
 773
 774 #define LISTEN_NONE   0
 775 #define LISTEN_KERNEL 1
 776 #define LISTEN_RAW    2
 777 static smallint listen_mode;
 778
 779 /* initial state: (re)start DHCP negotiation */
 780 #define INIT_SELECTING  0
 781 /* discover was sent, DHCPOFFER reply received */
 782 #define REQUESTING      1
 783 /* select/renew was sent, DHCPACK reply received */
 784 #define BOUND           2
 785 /* half of lease passed, want to renew it by sending unicast renew requests */
 786 #define RENEWING        3
 787 /* renew requests were not answered, lease is almost over, send broadcast renew */
 788 #define REBINDING       4
 789 /* manually requested renew (SIGUSR1) */
 790 #define RENEW_REQUESTED 5
 791 /* release, possibly manually requested (SIGUSR2) */
 792 #define RELEASED        6
 793 static smallint state;
 794
 795 static int udhcp_raw_socket(int ifindex)
 796 {
 797         int fd;
 798         struct sockaddr_ll sock;
 799
 800         /*
 801          * Comment:
 802          *
 803          *      I've selected not to see LL header, so BPF doesn't see it, too.
 804          *      The filter may also pass non-IP and non-ARP packets, but we do
 805          *      a more complete check when receiving the message in userspace.
 806          *
 807          * and filter shamelessly stolen from:
 808          *
 809          *      http://www.flamewarmaster.de/software/dhcpclient/
 810          *
 811          * There are a few other interesting ideas on that page (look under
 812          * "Motivation").  Use of netlink events is most interesting.  Think
 813          * of various network servers listening for events and reconfiguring.
 814          * That would obsolete sending HUP signals and/or make use of restarts.
 815          *
 816          * Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
 817          * License: GPL v2.
 818          *
 819          * TODO: make conditional?
 820          */
 821         static const struct sock_filter filter_instr[] = {
 822                 /* load 9th byte (protocol) */
 823                 BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
 824                 /* jump to L1 if it is IPPROTO_UDP, else to L4 */
 825                 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 0, 6),
 826                 /* L1: load halfword from offset 6 (flags and frag offset) */
 827                 BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 6),
 828                 /* jump to L4 if any bits in frag offset field are set, else to L2 */
 829                 BPF_JUMP(BPF_JMP|BPF_JSET|BPF_K, 0x1fff, 4, 0),
 830                 /* L2: skip IP header (load index reg with header len) */
 831                 BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0),
 832                 /* load udp destination port from halfword[header_len + 2] */
 833                 BPF_STMT(BPF_LD|BPF_H|BPF_IND, 2),
 834                 /* jump to L3 if udp dport is CLIENT_PORT, else to L4 */
 835                 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 68, 0, 1),
 836                 /* L3: accept packet */
 837                 BPF_STMT(BPF_RET|BPF_K, 0xffffffff),
 838                 /* L4: discard packet */
 839                 BPF_STMT(BPF_RET|BPF_K, 0),
 840         };
 841         static const struct sock_fprog filter_prog = {
 842                 .len = sizeof(filter_instr) / sizeof(filter_instr[0]),
 843                 /* casting const away: */
 844                 .filter = (struct sock_filter *) filter_instr,
 845         };
 846
 847         log1("Opening raw socket on ifindex %d", ifindex); //log2?
 848
 849         fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
 850         log1("Got raw socket fd %d", fd); //log2?
 851
 852         sock.sll_family = AF_PACKET;
 853         sock.sll_protocol = htons(ETH_P_IP);
 854         sock.sll_ifindex = ifindex;
 855         xbind(fd, (struct sockaddr *) &sock, sizeof(sock));
 856
 857         if (CLIENT_PORT == 68) {
 858                 /* Use only if standard port is in use */
 859                 /* Ignoring error (kernel may lack support for this) */
 860                 if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
 861                                 sizeof(filter_prog)) >= 0)
 862                         log1("Attached filter to raw socket fd %d", fd); // log?
 863         }
 864
 865         log1("Created raw socket");
 866
 867         return fd;
 868 }
 869
 870 static void change_listen_mode(int new_mode)
 871 {
 872         log1("Entering listen mode: %s",
 873                 new_mode != LISTEN_NONE
 874                         ? (new_mode == LISTEN_KERNEL ? "kernel" : "raw")
 875                         : "none"
 876         );
 877
 878         listen_mode = new_mode;
 879         if (sockfd >= 0) {
 880                 close(sockfd);
 881                 sockfd = -1;
 882         }
 883         if (new_mode == LISTEN_KERNEL)
 884                 sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
 885         else if (new_mode != LISTEN_NONE)
 886                 sockfd = udhcp_raw_socket(client_config.ifindex);
 887         /* else LISTEN_NONE: sockfd stays closed */
 888 }
 889
 890 /* Called only on SIGUSR1 */
 891 static void perform_renew(void)
 892 {
 893         bb_info_msg("Performing a DHCP renew");
 894         switch (state) {
 895         case BOUND:
 896                 change_listen_mode(LISTEN_KERNEL);
 897         case RENEWING:
 898         case REBINDING:
 899                 state = RENEW_REQUESTED;
 900                 break;
 901         case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
 902                 udhcp_run_script(NULL, "deconfig");
 903         case REQUESTING:
 904         case RELEASED:
 905                 change_listen_mode(LISTEN_RAW);
 906                 state = INIT_SELECTING;
 907                 break;
 908         case INIT_SELECTING:
 909                 break;
 910         }
 911 }
 912
 913 static void perform_release(uint32_t requested_ip, uint32_t server_addr)
 914 {
 915         char buffer[sizeof("255.255.255.255")];
 916         struct in_addr temp_addr;
 917
 918         /* send release packet */
 919         if (state == BOUND || state == RENEWING || state == REBINDING) {
 920                 temp_addr.s_addr = server_addr;
 921                 strcpy(buffer, inet_ntoa(temp_addr));
 922                 temp_addr.s_addr = requested_ip;
 923                 bb_info_msg("Unicasting a release of %s to %s",
 924                                 inet_ntoa(temp_addr), buffer);
 925                 send_release(server_addr, requested_ip); /* unicast */
 926                 udhcp_run_script(NULL, "deconfig");
 927         }
 928         bb_info_msg("Entering released state");
 929
 930         change_listen_mode(LISTEN_NONE);
 931         state = RELEASED;
 932 }
 933
 934 static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
 935 {
 936         uint8_t *storage;
 937         int len = strnlen(str, 255);
 938         storage = xzalloc(len + extra + OPT_DATA);
 939         storage[OPT_CODE] = code;
 940         storage[OPT_LEN] = len + extra;
 941         memcpy(storage + extra + OPT_DATA, str, len);
 942         return storage;
 943 }
 944
 945 #if BB_MMU
 946 static void client_background(void)
 947 {
 948         bb_daemonize(0);
 949         logmode &= ~LOGMODE_STDIO;
 950         /* rewrite pidfile, as our pid is different now */
 951         write_pidfile(client_config.pidfile);
 952 }
 953 #endif
 954
 955 //usage:#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
 956 //usage:# define IF_UDHCP_VERBOSE(...) __VA_ARGS__
 957 //usage:#else
 958 //usage:# define IF_UDHCP_VERBOSE(...)
 959 //usage:#endif
 960 //usage:#define udhcpc_trivial_usage
 961 //usage:       "[-fbnq"IF_UDHCP_VERBOSE("v")"oCRB] [-i IFACE] [-r IP] [-s PROG] [-p PIDFILE]\n"
 962 //usage:       "        [-H HOSTNAME] [-V VENDOR] [-x OPT:VAL]... [-O OPT]..." IF_FEATURE_UDHCP_PORT(" [-P N]")
 963 //usage:#define udhcpc_full_usage "\n"
 964 //usage:        IF_LONG_OPTS(
 965 //usage:     "\n        -i,--interface IFACE    Interface to use (default eth0)"
 966 //usage:     "\n        -p,--pidfile FILE       Create pidfile"
 967 //usage:     "\n        -s,--script PROG        Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
 968 //usage:     "\n        -B,--broadcast          Request broadcast replies"
 969 //usage:     "\n        -t,--retries N          Send up to N discover packets"
 970 //usage:     "\n        -T,--timeout N          Pause between packets (default 3 seconds)"
 971 //usage:     "\n        -A,--tryagain N         Wait N seconds after failure (default 20)"
 972 //usage:     "\n        -f,--foreground         Run in foreground"
 973 //usage:        USE_FOR_MMU(
 974 //usage:     "\n        -b,--background         Background if lease is not obtained"
 975 //usage:        )
 976 //usage:     "\n        -n,--now                Exit if lease is not obtained"
 977 //usage:     "\n        -q,--quit               Exit after obtaining lease"
 978 //usage:     "\n        -R,--release            Release IP on exit"
 979 //usage:     "\n        -S,--syslog             Log to syslog too"
 980 //usage:        IF_FEATURE_UDHCP_PORT(
 981 //usage:     "\n        -P,--client-port N      Use port N (default 68)"
 982 //usage:        )
 983 //usage:        IF_FEATURE_UDHCPC_ARPING(
 984 //usage:     "\n        -a,--arping             Use arping to validate offered address"
 985 //usage:        )
 986 //usage:     "\n        -O,--request-option OPT Request option OPT from server (cumulative)"
 987 //usage:     "\n        -o,--no-default-options Don't request any options (unless -O is given)"
 988 //usage:     "\n        -r,--request IP         Request this IP address"
 989 //usage:     "\n        -x OPT:VAL              Include option OPT in sent packets (cumulative)"
 990 //usage:     "\n                                Examples of string, numeric, and hex byte opts:"
 991 //usage:     "\n                                -x hostname:bbox - option 12"
 992 //usage:     "\n                                -x lease:3600 - option 51 (lease time)"
 993 //usage:     "\n                                -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
 994 //usage:     "\n        -F,--fqdn NAME          Ask server to update DNS mapping for NAME"
 995 //usage:     "\n        -H,-h,--hostname NAME   Send NAME as client hostname (default none)"
 996 //usage:     "\n        -V,--vendorclass VENDOR Vendor identifier (default 'udhcp VERSION')"
 997 //usage:     "\n        -C,--clientid-none      Don't send MAC as client identifier"
 998 //usage:        IF_UDHCP_VERBOSE(
 999 //usage:     "\n        -v                      Verbose"
1000 //usage:        )
1001 //usage:        )
1002 //usage:        IF_NOT_LONG_OPTS(
1003 //usage:     "\n        -i IFACE        Interface to use (default eth0)"
1004 //usage:     "\n        -p FILE         Create pidfile"
1005 //usage:     "\n        -s PROG         Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
1006 //usage:     "\n        -B              Request broadcast replies"
1007 //usage:     "\n        -t N            Send up to N discover packets"
1008 //usage:     "\n        -T N            Pause between packets (default 3 seconds)"
1009 //usage:     "\n        -A N            Wait N seconds (default 20) after failure"
1010 //usage:     "\n        -f              Run in foreground"
1011 //usage:        USE_FOR_MMU(
1012 //usage:     "\n        -b              Background if lease is not obtained"
1013 //usage:        )
1014 //usage:     "\n        -n              Exit if lease is not obtained"
1015 //usage:     "\n        -q              Exit after obtaining lease"
1016 //usage:     "\n        -R              Release IP on exit"
1017 //usage:     "\n        -S              Log to syslog too"
1018 //usage:        IF_FEATURE_UDHCP_PORT(
1019 //usage:     "\n        -P N            Use port N (default 68)"
1020 //usage:        )
1021 //usage:        IF_FEATURE_UDHCPC_ARPING(
1022 //usage:     "\n        -a              Use arping to validate offered address"
1023 //usage:        )
1024 //usage:     "\n        -O OPT          Request option OPT from server (cumulative)"
1025 //usage:     "\n        -o              Don't request any options (unless -O is given)"
1026 //usage:     "\n        -r IP           Request this IP address"
1027 //usage:     "\n        -x OPT:VAL      Include option OPT in sent packets (cumulative)"
1028 //usage:     "\n                        Examples of string, numeric, and hex byte opts:"
1029 //usage:     "\n                        -x hostname:bbox - option 12"
1030 //usage:     "\n                        -x lease:3600 - option 51 (lease time)"
1031 //usage:     "\n                        -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
1032 //usage:     "\n        -F NAME         Ask server to update DNS mapping for NAME"
1033 //usage:     "\n        -H,-h NAME      Send NAME as client hostname (default none)"
1034 //usage:     "\n        -V VENDOR       Vendor identifier (default 'udhcp VERSION')"
1035 //usage:     "\n        -C              Don't send MAC as client identifier"
1036 //usage:        IF_UDHCP_VERBOSE(
1037 //usage:     "\n        -v              Verbose"
1038 //usage:        )
1039 //usage:        )
1040 //usage:     "\nSignals:"
1041 //usage:     "\n        USR1    Renew current lease"
1042 //usage:     "\n        USR2    Release current lease"
1043
1044
1045 int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
1046 int udhcpc_main(int argc UNUSED_PARAM, char **argv)
1047 {
1048         uint8_t *temp, *message;
1049         const char *str_V, *str_h, *str_F, *str_r;
1050         IF_FEATURE_UDHCP_PORT(char *str_P;)
1051         void *clientid_mac_ptr;
1052         llist_t *list_O = NULL;
1053         llist_t *list_x = NULL;
1054         int tryagain_timeout = 20;
1055         int discover_timeout = 3;
1056         int discover_retries = 3;
1057         uint32_t server_addr = server_addr; /* for compiler */
1058         uint32_t requested_ip = 0;
1059         uint32_t xid = 0;
1060         uint32_t lease_seconds = 0; /* can be given as 32-bit quantity */
1061         int packet_num;
1062         int timeout; /* must be signed */
1063         unsigned already_waited_sec;
1064         unsigned opt;
1065         int max_fd;
1066         int retval;
1067         struct timeval tv;
1068         struct dhcp_packet packet;
1069         fd_set rfds;
1070
1071         /* Default options */
1072         IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;)
1073         IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
1074         client_config.interface = "eth0";
1075         client_config.script = CONFIG_UDHCPC_DEFAULT_SCRIPT;
1076         str_V = "udhcp "BB_VER;
1077
1078         /* Parse command line */
1079         /* O,x: list; -T,-t,-A take numeric param */
1080         opt_complementary = "O::x::T+:t+:A+" IF_UDHCP_VERBOSE(":vv") ;
1081         IF_LONG_OPTS(applet_long_options = udhcpc_longopts;)
1082         opt = getopt32(argv, "CV:H:h:F:i:np:qRr:s:T:t:SA:O:ox:fB"
1083                 USE_FOR_MMU("b")
1084                 IF_FEATURE_UDHCPC_ARPING("a")
1085                 IF_FEATURE_UDHCP_PORT("P:")
1086                 "v"
1087                 , &str_V, &str_h, &str_h, &str_F
1088                 , &client_config.interface, &client_config.pidfile, &str_r /* i,p */
1089                 , &client_config.script /* s */
1090                 , &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */
1091                 , &list_O
1092                 , &list_x
1093                 IF_FEATURE_UDHCP_PORT(, &str_P)
1094                 IF_UDHCP_VERBOSE(, &dhcp_verbose)
1095                 );
1096         if (opt & (OPT_h|OPT_H))
1097                 client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
1098         if (opt & OPT_F) {
1099                 /* FQDN option format: [0x51][len][flags][0][0]<fqdn> */
1100                 client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
1101                 /* Flag bits: 0000NEOS
1102                  * S: 1 = Client requests server to update A RR in DNS as well as PTR
1103                  * O: 1 = Server indicates to client that DNS has been updated regardless
1104                  * E: 1 = Name is in DNS format, i.e. <4>host<6>domain<3>com<0>,
1105                  *    not "host.domain.com". Format 0 is obsolete.
1106                  * N: 1 = Client requests server to not update DNS (S must be 0 then)
1107                  * Two [0] bytes which follow are deprecated and must be 0.
1108                  */
1109                 client_config.fqdn[OPT_DATA + 0] = 0x1;
1110                 /*client_config.fqdn[OPT_DATA + 1] = 0; - xzalloc did it */
1111                 /*client_config.fqdn[OPT_DATA + 2] = 0; */
1112         }
1113         if (opt & OPT_r)
1114                 requested_ip = inet_addr(str_r);
1115 #if ENABLE_FEATURE_UDHCP_PORT
1116         if (opt & OPT_P) {
1117                 CLIENT_PORT = xatou16(str_P);
1118                 SERVER_PORT = CLIENT_PORT - 1;
1119         }
1120 #endif
1121         if (opt & OPT_o)
1122                 client_config.no_default_options = 1;
1123         while (list_O) {
1124                 char *optstr = llist_pop(&list_O);
1125                 unsigned n = bb_strtou(optstr, NULL, 0);
1126                 if (errno || n > 254) {
1127                         n = udhcp_option_idx(optstr);
1128                         n = dhcp_optflags[n].code;
1129                 }
1130                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
1131         }
1132         while (list_x) {
1133                 char *optstr = llist_pop(&list_x);
1134                 char *colon = strchr(optstr, ':');
1135                 if (colon)
1136                         *colon = ' ';
1137                 /* now it looks similar to udhcpd's config file line:
1138                  * "optname optval", using the common routine: */
1139                 udhcp_str2optset(optstr, &client_config.options);
1140         }
1141
1142         if (udhcp_read_interface(client_config.interface,
1143                         &client_config.ifindex,
1144                         NULL,
1145                         client_config.client_mac)
1146         ) {
1147                 return 1;
1148         }
1149
1150         clientid_mac_ptr = NULL;
1151         if (!(opt & OPT_C) && !udhcp_find_option(client_config.options, DHCP_CLIENT_ID)) {
1152                 /* not suppressed and not set, set the default client ID */
1153                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
1154                 client_config.clientid[OPT_DATA] = 1; /* type: ethernet */
1155                 clientid_mac_ptr = client_config.clientid + OPT_DATA+1;
1156                 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1157         }
1158         if (str_V[0] != '\0')
1159                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
1160 #if !BB_MMU
1161         /* on NOMMU reexec (i.e., background) early */
1162         if (!(opt & OPT_f)) {
1163                 bb_daemonize_or_rexec(0 /* flags */, argv);
1164                 logmode = LOGMODE_NONE;
1165         }
1166 #endif
1167         if (opt & OPT_S) {
1168                 openlog(applet_name, LOG_PID, LOG_DAEMON);
1169                 logmode |= LOGMODE_SYSLOG;
1170         }
1171
1172         /* Make sure fd 0,1,2 are open */
1173         bb_sanitize_stdio();
1174         /* Equivalent of doing a fflush after every \n */
1175         setlinebuf(stdout);
1176         /* Create pidfile */
1177         write_pidfile(client_config.pidfile);
1178         /* Goes to stdout (unless NOMMU) and possibly syslog */
1179         bb_info_msg("%s (v"BB_VER") started", applet_name);
1180         /* Set up the signal pipe */
1181         udhcp_sp_setup();
1182         /* We want random_xid to be random... */
1183         srand(monotonic_us());
1184
1185         state = INIT_SELECTING;
1186         udhcp_run_script(NULL, "deconfig");
1187         change_listen_mode(LISTEN_RAW);
1188         packet_num = 0;
1189         timeout = 0;
1190         already_waited_sec = 0;
1191
1192         /* Main event loop. select() waits on signal pipe and possibly
1193          * on sockfd.
1194          * "continue" statements in code below jump to the top of the loop.
1195          */
1196         for (;;) {
1197                 /* silence "uninitialized!" warning */
1198                 unsigned timestamp_before_wait = timestamp_before_wait;
1199
1200                 //bb_error_msg("sockfd:%d, listen_mode:%d", sockfd, listen_mode);
1201
1202                 /* Was opening raw or udp socket here
1203                  * if (listen_mode != LISTEN_NONE && sockfd < 0),
1204                  * but on fast network renew responses return faster
1205                  * than we open sockets. Thus this code is moved
1206                  * to change_listen_mode(). Thus we open listen socket
1207                  * BEFORE we send renew request (see "case BOUND:"). */
1208
1209                 max_fd = udhcp_sp_fd_set(&rfds, sockfd);
1210
1211                 tv.tv_sec = timeout - already_waited_sec;
1212                 tv.tv_usec = 0;
1213                 retval = 0;
1214                 /* If we already timed out, fall through with retval = 0, else... */
1215                 if ((int)tv.tv_sec > 0) {
1216                         timestamp_before_wait = (unsigned)monotonic_sec();
1217                         log1("Waiting on select...");
1218                         retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
1219                         if (retval < 0) {
1220                                 /* EINTR? A signal was caught, don't panic */
1221                                 if (errno == EINTR) {
1222                                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1223                                         continue;
1224                                 }
1225                                 /* Else: an error occured, panic! */
1226                                 bb_perror_msg_and_die("select");
1227                         }
1228                 }
1229
1230                 /* If timeout dropped to zero, time to become active:
1231                  * resend discover/renew/whatever
1232                  */
1233                 if (retval == 0) {
1234                         /* When running on a bridge, the ifindex may have changed
1235                          * (e.g. if member interfaces were added/removed
1236                          * or if the status of the bridge changed).
1237                          * Refresh ifindex and client_mac:
1238                          */
1239                         if (udhcp_read_interface(client_config.interface,
1240                                         &client_config.ifindex,
1241                                         NULL,
1242                                         client_config.client_mac)
1243                         ) {
1244                                 return 1; /* iface is gone? */
1245                         }
1246                         if (clientid_mac_ptr)
1247                                 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1248
1249                         /* We will restart the wait in any case */
1250                         already_waited_sec = 0;
1251
1252                         switch (state) {
1253                         case INIT_SELECTING:
1254                                 if (packet_num < discover_retries) {
1255                                         if (packet_num == 0)
1256                                                 xid = random_xid();
1257                                         /* broadcast */
1258                                         send_discover(xid, requested_ip);
1259                                         timeout = discover_timeout;
1260                                         packet_num++;
1261                                         continue;
1262                                 }
1263  leasefail:
1264                                 udhcp_run_script(NULL, "leasefail");
1265 #if BB_MMU /* -b is not supported on NOMMU */
1266                                 if (opt & OPT_b) { /* background if no lease */
1267                                         bb_info_msg("No lease, forking to background");
1268                                         client_background();
1269                                         /* do not background again! */
1270                                         opt = ((opt & ~OPT_b) | OPT_f);
1271                                 } else
1272 #endif
1273                                 if (opt & OPT_n) { /* abort if no lease */
1274                                         bb_info_msg("No lease, failing");
1275                                         retval = 1;
1276                                         goto ret;
1277                                 }
1278                                 /* wait before trying again */
1279                                 timeout = tryagain_timeout;
1280                                 packet_num = 0;
1281                                 continue;
1282                         case REQUESTING:
1283                                 if (packet_num < discover_retries) {
1284                                         /* send broadcast select packet */
1285                                         send_select(xid, server_addr, requested_ip);
1286                                         timeout = discover_timeout;
1287                                         packet_num++;
1288                                         continue;
1289                                 }
1290                                 /* Timed out, go back to init state.
1291                                  * "discover...select...discover..." loops
1292                                  * were seen in the wild. Treat them similarly
1293                                  * to "no response to discover" case */
1294                                 change_listen_mode(LISTEN_RAW);
1295                                 state = INIT_SELECTING;
1296                                 goto leasefail;
1297                         case BOUND:
1298                                 /* 1/2 lease passed, enter renewing state */
1299                                 state = RENEWING;
1300                                 client_config.first_secs = 0; /* make secs field count from 0 */
1301                                 change_listen_mode(LISTEN_KERNEL);
1302                                 log1("Entering renew state");
1303                                 /* fall right through */
1304                         case RENEW_REQUESTED: /* manual (SIGUSR1) renew */
1305                         case_RENEW_REQUESTED:
1306                         case RENEWING:
1307                                 if (timeout > 60) {
1308                                         /* send an unicast renew request */
1309                         /* Sometimes observed to fail (EADDRNOTAVAIL) to bind
1310                          * a new UDP socket for sending inside send_renew.
1311                          * I hazard to guess existing listening socket
1312                          * is somehow conflicting with it, but why is it
1313                          * not deterministic then?! Strange.
1314                          * Anyway, it does recover by eventually failing through
1315                          * into INIT_SELECTING state.
1316                          */
1317                                         send_renew(xid, server_addr, requested_ip);
1318                                         timeout >>= 1;
1319                                         continue;
1320                                 }
1321                                 /* Timed out, enter rebinding state */
1322                                 log1("Entering rebinding state");
1323                                 state = REBINDING;
1324                                 /* fall right through */
1325                         case REBINDING:
1326                                 /* Switch to bcast receive */
1327                                 change_listen_mode(LISTEN_RAW);
1328                                 /* Lease is *really* about to run out,
1329                                  * try to find DHCP server using broadcast */
1330                                 if (timeout > 0) {
1331                                         /* send a broadcast renew request */
1332                                         send_renew(xid, 0 /*INADDR_ANY*/, requested_ip);
1333                                         timeout >>= 1;
1334                                         continue;
1335                                 }
1336                                 /* Timed out, enter init state */
1337                                 bb_info_msg("Lease lost, entering init state");
1338                                 udhcp_run_script(NULL, "deconfig");
1339                                 state = INIT_SELECTING;
1340                                 client_config.first_secs = 0; /* make secs field count from 0 */
1341                                 /*timeout = 0; - already is */
1342                                 packet_num = 0;
1343                                 continue;
1344                         /* case RELEASED: */
1345                         }
1346                         /* yah, I know, *you* say it would never happen */
1347                         timeout = INT_MAX;
1348                         continue; /* back to main loop */
1349                 } /* if select timed out */
1350
1351                 /* select() didn't timeout, something happened */
1352
1353                 /* Is it a signal? */
1354                 /* note: udhcp_sp_read checks FD_ISSET before reading */
1355                 switch (udhcp_sp_read(&rfds)) {
1356                 case SIGUSR1:
1357                         client_config.first_secs = 0; /* make secs field count from 0 */
1358                         already_waited_sec = 0;
1359                         perform_renew();
1360                         if (state == RENEW_REQUESTED) {
1361                                 /* We might be either on the same network
1362                                  * (in which case renew might work),
1363                                  * or we might be on a completely different one
1364                                  * (in which case renew won't ever succeed).
1365                                  * For the second case, must make sure timeout
1366                                  * is not too big, or else we can send
1367                                  * futile renew requests for hours.
1368                                  * (Ab)use -A TIMEOUT value (usually 20 sec)
1369                                  * as a cap on the timeout.
1370                                  */
1371                                 if (timeout > tryagain_timeout)
1372                                         timeout = tryagain_timeout;
1373                                 goto case_RENEW_REQUESTED;
1374                         }
1375                         /* Start things over */
1376                         packet_num = 0;
1377                         /* Kill any timeouts, user wants this to hurry along */
1378                         timeout = 0;
1379                         continue;
1380                 case SIGUSR2:
1381                         perform_release(requested_ip, server_addr);
1382                         timeout = INT_MAX;
1383                         continue;
1384                 case SIGTERM:
1385                         bb_info_msg("Received SIGTERM");
1386                         if (opt & OPT_R) /* release on quit */
1387                                 perform_release(requested_ip, server_addr);
1388                         goto ret0;
1389                 }
1390
1391                 /* Is it a packet? */
1392                 if (listen_mode == LISTEN_NONE || !FD_ISSET(sockfd, &rfds))
1393                         continue; /* no */
1394
1395                 {
1396                         int len;
1397
1398                         /* A packet is ready, read it */
1399                         if (listen_mode == LISTEN_KERNEL)
1400                                 len = udhcp_recv_kernel_packet(&packet, sockfd);
1401                         else
1402                                 len = udhcp_recv_raw_packet(&packet, sockfd);
1403                         if (len == -1) {
1404                                 /* Error is severe, reopen socket */
1405                                 bb_info_msg("Read error: %s, reopening socket", strerror(errno));
1406                                 sleep(discover_timeout); /* 3 seconds by default */
1407                                 change_listen_mode(listen_mode); /* just close and reopen */
1408                         }
1409                         /* If this packet will turn out to be unrelated/bogus,
1410                          * we will go back and wait for next one.
1411                          * Be sure timeout is properly decreased. */
1412                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1413                         if (len < 0)
1414                                 continue;
1415                 }
1416
1417                 if (packet.xid != xid) {
1418                         log1("xid %x (our is %x), ignoring packet",
1419                                 (unsigned)packet.xid, (unsigned)xid);
1420                         continue;
1421                 }
1422
1423                 /* Ignore packets that aren't for us */
1424                 if (packet.hlen != 6
1425                  || memcmp(packet.chaddr, client_config.client_mac, 6) != 0
1426                 ) {
1427 //FIXME: need to also check that last 10 bytes are zero
1428                         log1("chaddr does not match, ignoring packet"); // log2?
1429                         continue;
1430                 }
1431
1432                 message = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
1433                 if (message == NULL) {
1434                         bb_error_msg("no message type option, ignoring packet");
1435                         continue;
1436                 }
1437
1438                 switch (state) {
1439                 case INIT_SELECTING:
1440                         /* Must be a DHCPOFFER to one of our xid's */
1441                         if (*message == DHCPOFFER) {
1442                 /* TODO: why we don't just fetch server's IP from IP header? */
1443                                 temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
1444                                 if (!temp) {
1445                                         bb_error_msg("no server ID, ignoring packet");
1446                                         continue;
1447                                         /* still selecting - this server looks bad */
1448                                 }
1449                                 /* it IS unaligned sometimes, don't "optimize" */
1450                                 move_from_unaligned32(server_addr, temp);
1451                                 /*xid = packet.xid; - already is */
1452                                 requested_ip = packet.yiaddr;
1453
1454                                 /* enter requesting state */
1455                                 state = REQUESTING;
1456                                 timeout = 0;
1457                                 packet_num = 0;
1458                                 already_waited_sec = 0;
1459                         }
1460                         continue;
1461                 case REQUESTING:
1462                 case RENEWING:
1463                 case RENEW_REQUESTED:
1464                 case REBINDING:
1465                         if (*message == DHCPACK) {
1466                                 temp = udhcp_get_option(&packet, DHCP_LEASE_TIME);
1467                                 if (!temp) {
1468                                         bb_error_msg("no lease time with ACK, using 1 hour lease");
1469                                         lease_seconds = 60 * 60;
1470                                 } else {
1471                                         /* it IS unaligned sometimes, don't "optimize" */
1472                                         move_from_unaligned32(lease_seconds, temp);
1473                                         lease_seconds = ntohl(lease_seconds);
1474                                         lease_seconds &= 0x0fffffff; /* paranoia: must not be prone to overflows */
1475                                         if (lease_seconds < 10) /* and not too small */
1476                                                 lease_seconds = 10;
1477                                 }
1478 #if ENABLE_FEATURE_UDHCPC_ARPING
1479                                 if (opt & OPT_a) {
1480 /* RFC 2131 3.1 paragraph 5:
1481  * "The client receives the DHCPACK message with configuration
1482  * parameters. The client SHOULD perform a final check on the
1483  * parameters (e.g., ARP for allocated network address), and notes
1484  * the duration of the lease specified in the DHCPACK message. At this
1485  * point, the client is configured. If the client detects that the
1486  * address is already in use (e.g., through the use of ARP),
1487  * the client MUST send a DHCPDECLINE message to the server and restarts
1488  * the configuration process..." */
1489                                         if (!arpping(packet.yiaddr,
1490                                                         NULL,
1491                                                         (uint32_t) 0,
1492                                                         client_config.client_mac,
1493                                                         client_config.interface)
1494                                         ) {
1495                                                 bb_info_msg("Offered address is in use "
1496                                                         "(got ARP reply), declining");
1497                                                 send_decline(xid, server_addr, packet.yiaddr);
1498
1499                                                 if (state != REQUESTING)
1500                                                         udhcp_run_script(NULL, "deconfig");
1501                                                 change_listen_mode(LISTEN_RAW);
1502                                                 state = INIT_SELECTING;
1503                                                 client_config.first_secs = 0; /* make secs field count from 0 */
1504                                                 requested_ip = 0;
1505                                                 timeout = tryagain_timeout;
1506                                                 packet_num = 0;
1507                                                 already_waited_sec = 0;
1508                                                 continue; /* back to main loop */
1509                                         }
1510                                 }
1511 #endif
1512                                 /* enter bound state */
1513                                 timeout = lease_seconds / 2;
1514                                 {
1515                                         struct in_addr temp_addr;
1516                                         temp_addr.s_addr = packet.yiaddr;
1517                                         bb_info_msg("Lease of %s obtained, lease time %u",
1518                                                 inet_ntoa(temp_addr), (unsigned)lease_seconds);
1519                                 }
1520                                 requested_ip = packet.yiaddr;
1521                                 udhcp_run_script(&packet, state == REQUESTING ? "bound" : "renew");
1522
1523                                 state = BOUND;
1524                                 change_listen_mode(LISTEN_NONE);
1525                                 if (opt & OPT_q) { /* quit after lease */
1526                                         if (opt & OPT_R) /* release on quit */
1527                                                 perform_release(requested_ip, server_addr);
1528                                         goto ret0;
1529                                 }
1530                                 /* future renew failures should not exit (JM) */
1531                                 opt &= ~OPT_n;
1532 #if BB_MMU /* NOMMU case backgrounded earlier */
1533                                 if (!(opt & OPT_f)) {
1534                                         client_background();
1535                                         /* do not background again! */
1536                                         opt = ((opt & ~OPT_b) | OPT_f);
1537                                 }
1538 #endif
1539                                 already_waited_sec = 0;
1540                                 continue; /* back to main loop */
1541                         }
1542                         if (*message == DHCPNAK) {
1543                                 /* return to init state */
1544                                 bb_info_msg("Received DHCP NAK");
1545                                 udhcp_run_script(&packet, "nak");
1546                                 if (state != REQUESTING)
1547                                         udhcp_run_script(NULL, "deconfig");
1548                                 change_listen_mode(LISTEN_RAW);
1549                                 sleep(3); /* avoid excessive network traffic */
1550                                 state = INIT_SELECTING;
1551                                 client_config.first_secs = 0; /* make secs field count from 0 */
1552                                 requested_ip = 0;
1553                                 timeout = 0;
1554                                 packet_num = 0;
1555                                 already_waited_sec = 0;
1556                         }
1557                         continue;
1558                 /* case BOUND: - ignore all packets */
1559                 /* case RELEASED: - ignore all packets */
1560                 }
1561                 /* back to main loop */
1562         } /* for (;;) - main loop ends */
1563
1564  ret0:
1565         retval = 0;
1566  ret:
1567         /*if (client_config.pidfile) - remove_pidfile has its own check */
1568                 remove_pidfile(client_config.pidfile);
1569         return retval;
1570 }