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 <linux/filter.h>
  30 #include <linux/if_packet.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         "retries\0"        Required_argument "t"
  50         "tryagain\0"       Required_argument "A"
  51         "syslog\0"         No_argument       "S"
  52         "request-option\0" Required_argument "O"
  53         "no-default-options\0" No_argument   "o"
  54         "foreground\0"     No_argument       "f"
  55         "background\0"     No_argument       "b"
  56         "broadcast\0"      No_argument       "B"
  57         IF_FEATURE_UDHCPC_ARPING("arping\0"     No_argument       "a")
  58         IF_FEATURE_UDHCP_PORT("client-port\0"   Required_argument "P")
  59         ;
  60 #endif
  61 /* Must match getopt32 option string order */
  62 enum {
  63         OPT_C = 1 << 0,
  64         OPT_V = 1 << 1,
  65         OPT_H = 1 << 2,
  66         OPT_h = 1 << 3,
  67         OPT_F = 1 << 4,
  68         OPT_i = 1 << 5,
  69         OPT_n = 1 << 6,
  70         OPT_p = 1 << 7,
  71         OPT_q = 1 << 8,
  72         OPT_R = 1 << 9,
  73         OPT_r = 1 << 10,
  74         OPT_s = 1 << 11,
  75         OPT_T = 1 << 12,
  76         OPT_t = 1 << 13,
  77         OPT_S = 1 << 14,
  78         OPT_A = 1 << 15,
  79         OPT_O = 1 << 16,
  80         OPT_o = 1 << 17,
  81         OPT_x = 1 << 18,
  82         OPT_f = 1 << 19,
  83         OPT_B = 1 << 20,
  84 /* The rest has variable bit positions, need to be clever */
  85         OPTBIT_B = 20,
  86         USE_FOR_MMU(             OPTBIT_b,)
  87         IF_FEATURE_UDHCPC_ARPING(OPTBIT_a,)
  88         IF_FEATURE_UDHCP_PORT(   OPTBIT_P,)
  89         USE_FOR_MMU(             OPT_b = 1 << OPTBIT_b,)
  90         IF_FEATURE_UDHCPC_ARPING(OPT_a = 1 << OPTBIT_a,)
  91         IF_FEATURE_UDHCP_PORT(   OPT_P = 1 << OPTBIT_P,)
  92 };
  93
  94
  95 /*** Script execution code ***/
  96
  97 /* get a rough idea of how long an option will be (rounding up...) */
  98 static const uint8_t len_of_option_as_string[] = {
  99         [OPTION_IP              ] = sizeof("255.255.255.255 "),
 100         [OPTION_IP_PAIR         ] = sizeof("255.255.255.255 ") * 2,
 101         [OPTION_STATIC_ROUTES   ] = sizeof("255.255.255.255/32 255.255.255.255 "),
 102         [OPTION_6RD             ] = sizeof("32 128 ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 255.255.255.255 "),
 103         [OPTION_STRING          ] = 1,
 104         [OPTION_STRING_HOST     ] = 1,
 105 #if ENABLE_FEATURE_UDHCP_RFC3397
 106         [OPTION_DNS_STRING      ] = 1, /* unused */
 107         /* Hmmm, this severely overestimates size if SIP_SERVERS option
 108          * is in domain name form: N-byte option in binary form
 109          * mallocs ~16*N bytes. But it is freed almost at once.
 110          */
 111         [OPTION_SIP_SERVERS     ] = sizeof("255.255.255.255 "),
 112 #endif
 113 //      [OPTION_BOOLEAN         ] = sizeof("yes "),
 114         [OPTION_U8              ] = sizeof("255 "),
 115         [OPTION_U16             ] = sizeof("65535 "),
 116 //      [OPTION_S16             ] = sizeof("-32768 "),
 117         [OPTION_U32             ] = sizeof("4294967295 "),
 118         [OPTION_S32             ] = sizeof("-2147483684 "),
 119 };
 120
 121 /* note: ip is a pointer to an IP in network order, possibly misaliged */
 122 static int sprint_nip(char *dest, const char *pre, const uint8_t *ip)
 123 {
 124         return sprintf(dest, "%s%u.%u.%u.%u", pre, ip[0], ip[1], ip[2], ip[3]);
 125 }
 126
 127 /* really simple implementation, just count the bits */
 128 static int mton(uint32_t mask)
 129 {
 130         int i = 0;
 131         mask = ntohl(mask); /* 111110000-like bit pattern */
 132         while (mask) {
 133                 i++;
 134                 mask <<= 1;
 135         }
 136         return i;
 137 }
 138
 139 /* Check if a given label represents a valid DNS label
 140  * Return pointer to the first character after the label upon success,
 141  * NULL otherwise.
 142  * See RFC1035, 2.3.1
 143  */
 144 /* We don't need to be particularly anal. For example, allowing _, hyphen
 145  * at the end, or leading and trailing dots would be ok, since it
 146  * can't be used for attacks. (Leading hyphen can be, if someone uses
 147  * cmd "$hostname"
 148  * in the script: then hostname may be treated as an option)
 149  */
 150 static const char *valid_domain_label(const char *label)
 151 {
 152         unsigned char ch;
 153         unsigned pos = 0;
 154
 155         for (;;) {
 156                 ch = *label;
 157                 if ((ch|0x20) < 'a' || (ch|0x20) > 'z') {
 158                         if (pos == 0) {
 159                                 /* label must begin with letter */
 160                                 return NULL;
 161                         }
 162                         if (ch < '0' || ch > '9') {
 163                                 if (ch == '\0' || ch == '.')
 164                                         return label;
 165                                 /* DNS allows only '-', but we are more permissive */
 166                                 if (ch != '-' && ch != '_')
 167                                         return NULL;
 168                         }
 169                 }
 170                 label++;
 171                 pos++;
 172                 //Do we want this?
 173                 //if (pos > 63) /* NS_MAXLABEL; labels must be 63 chars or less */
 174                 //      return NULL;
 175         }
 176 }
 177
 178 /* Check if a given name represents a valid DNS name */
 179 /* See RFC1035, 2.3.1 */
 180 static int good_hostname(const char *name)
 181 {
 182         //const char *start = name;
 183
 184         for (;;) {
 185                 name = valid_domain_label(name);
 186                 if (!name)
 187                         return 0;
 188                 if (!name[0])
 189                         return 1;
 190                         //Do we want this?
 191                         //return ((name - start) < 1025); /* NS_MAXDNAME */
 192                 name++;
 193         }
 194 }
 195
 196 /* Create "opt_name=opt_value" string */
 197 static NOINLINE char *xmalloc_optname_optval(uint8_t *option, const struct dhcp_optflag *optflag, const char *opt_name)
 198 {
 199         unsigned upper_length;
 200         int len, type, optlen;
 201         char *dest, *ret;
 202
 203         /* option points to OPT_DATA, need to go back to get OPT_LEN */
 204         len = option[-OPT_DATA + OPT_LEN];
 205
 206         type = optflag->flags & OPTION_TYPE_MASK;
 207         optlen = dhcp_option_lengths[type];
 208         upper_length = len_of_option_as_string[type]
 209                 * ((unsigned)(len + optlen - 1) / (unsigned)optlen);
 210
 211         dest = ret = xmalloc(upper_length + strlen(opt_name) + 2);
 212         dest += sprintf(ret, "%s=", opt_name);
 213
 214         while (len >= optlen) {
 215                 switch (type) {
 216                 case OPTION_IP:
 217                 case OPTION_IP_PAIR:
 218                         dest += sprint_nip(dest, "", option);
 219                         if (type == OPTION_IP)
 220                                 break;
 221                         dest += sprint_nip(dest, "/", option + 4);
 222                         break;
 223 //              case OPTION_BOOLEAN:
 224 //                      dest += sprintf(dest, *option ? "yes" : "no");
 225 //                      break;
 226                 case OPTION_U8:
 227                         dest += sprintf(dest, "%u", *option);
 228                         break;
 229 //              case OPTION_S16:
 230                 case OPTION_U16: {
 231                         uint16_t val_u16;
 232                         move_from_unaligned16(val_u16, option);
 233                         dest += sprintf(dest, "%u", ntohs(val_u16));
 234                         break;
 235                 }
 236                 case OPTION_S32:
 237                 case OPTION_U32: {
 238                         uint32_t val_u32;
 239                         move_from_unaligned32(val_u32, option);
 240                         dest += sprintf(dest, type == OPTION_U32 ? "%lu" : "%ld", (unsigned long) ntohl(val_u32));
 241                         break;
 242                 }
 243                 /* Note: options which use 'return' instead of 'break'
 244                  * (for example, OPTION_STRING) skip the code which handles
 245                  * the case of list of options.
 246                  */
 247                 case OPTION_STRING:
 248                 case OPTION_STRING_HOST:
 249                         memcpy(dest, option, len);
 250                         dest[len] = '\0';
 251                         if (type == OPTION_STRING_HOST && !good_hostname(dest))
 252                                 safe_strncpy(dest, "bad", len);
 253                         return ret;
 254                 case OPTION_STATIC_ROUTES: {
 255                         /* Option binary format:
 256                          * mask [one byte, 0..32]
 257                          * ip [big endian, 0..4 bytes depending on mask]
 258                          * router [big endian, 4 bytes]
 259                          * may be repeated
 260                          *
 261                          * We convert it to a string "IP/MASK ROUTER IP2/MASK2 ROUTER2"
 262                          */
 263                         const char *pfx = "";
 264
 265                         while (len >= 1 + 4) { /* mask + 0-byte ip + router */
 266                                 uint32_t nip;
 267                                 uint8_t *p;
 268                                 unsigned mask;
 269                                 int bytes;
 270
 271                                 mask = *option++;
 272                                 if (mask > 32)
 273                                         break;
 274                                 len--;
 275
 276                                 nip = 0;
 277                                 p = (void*) &nip;
 278                                 bytes = (mask + 7) / 8; /* 0 -> 0, 1..8 -> 1, 9..16 -> 2 etc */
 279                                 while (--bytes >= 0) {
 280                                         *p++ = *option++;
 281                                         len--;
 282                                 }
 283                                 if (len < 4)
 284                                         break;
 285
 286                                 /* print ip/mask */
 287                                 dest += sprint_nip(dest, pfx, (void*) &nip);
 288                                 pfx = " ";
 289                                 dest += sprintf(dest, "/%u ", mask);
 290                                 /* print router */
 291                                 dest += sprint_nip(dest, "", option);
 292                                 option += 4;
 293                                 len -= 4;
 294                         }
 295
 296                         return ret;
 297                 }
 298                 case OPTION_6RD:
 299                         /* Option binary format (see RFC 5969):
 300                          *  0                   1                   2                   3
 301                          *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 302                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 303                          * |  OPTION_6RD   | option-length |  IPv4MaskLen  |  6rdPrefixLen |
 304                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 305                          * |                           6rdPrefix                           |
 306                          * ...                        (16 octets)                        ...
 307                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 308                          * ...                   6rdBRIPv4Address(es)                    ...
 309                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 310                          * We convert it to a string
 311                          * "IPv4MaskLen 6rdPrefixLen 6rdPrefix 6rdBRIPv4Address..."
 312                          *
 313                          * Sanity check: ensure that our length is at least 22 bytes, that
 314                          * IPv4MaskLen <= 32,
 315                          * 6rdPrefixLen <= 128,
 316                          * 6rdPrefixLen + (32 - IPv4MaskLen) <= 128
 317                          * (2nd condition need no check - it follows from 1st and 3rd).
 318                          * Else, return envvar with empty value ("optname=")
 319                          */
 320                         if (len >= (1 + 1 + 16 + 4)
 321                          && option[0] <= 32
 322                          && (option[1] + 32 - option[0]) <= 128
 323                         ) {
 324                                 /* IPv4MaskLen */
 325                                 dest += sprintf(dest, "%u ", *option++);
 326                                 /* 6rdPrefixLen */
 327                                 dest += sprintf(dest, "%u ", *option++);
 328                                 /* 6rdPrefix */
 329                                 dest += sprint_nip6(dest, /* "", */ option);
 330                                 option += 16;
 331                                 len -= 1 + 1 + 16 + 4;
 332                                 /* "+ 4" above corresponds to the length of IPv4 addr
 333                                  * we consume in the loop below */
 334                                 while (1) {
 335                                         /* 6rdBRIPv4Address(es) */
 336                                         dest += sprint_nip(dest, " ", option);
 337                                         option += 4;
 338                                         len -= 4; /* do we have yet another 4+ bytes? */
 339                                         if (len < 0)
 340                                                 break; /* no */
 341                                 }
 342                         }
 343
 344                         return ret;
 345 #if ENABLE_FEATURE_UDHCP_RFC3397
 346                 case OPTION_DNS_STRING:
 347                         /* unpack option into dest; use ret for prefix (i.e., "optname=") */
 348                         dest = dname_dec(option, len, ret);
 349                         if (dest) {
 350                                 free(ret);
 351                                 return dest;
 352                         }
 353                         /* error. return "optname=" string */
 354                         return ret;
 355                 case OPTION_SIP_SERVERS:
 356                         /* Option binary format:
 357                          * type: byte
 358                          * type=0: domain names, dns-compressed
 359                          * type=1: IP addrs
 360                          */
 361                         option++;
 362                         len--;
 363                         if (option[-1] == 0) {
 364                                 dest = dname_dec(option, len, ret);
 365                                 if (dest) {
 366                                         free(ret);
 367                                         return dest;
 368                                 }
 369                         } else
 370                         if (option[-1] == 1) {
 371                                 const char *pfx = "";
 372                                 while (1) {
 373                                         len -= 4;
 374                                         if (len < 0)
 375                                                 break;
 376                                         dest += sprint_nip(dest, pfx, option);
 377                                         pfx = " ";
 378                                         option += 4;
 379                                 }
 380                         }
 381                         return ret;
 382 #endif
 383                 } /* switch */
 384
 385                 /* If we are here, try to format any remaining data
 386                  * in the option as another, similarly-formatted option
 387                  */
 388                 option += optlen;
 389                 len -= optlen;
 390 // TODO: it can be a list only if (optflag->flags & OPTION_LIST).
 391 // Should we bail out/warn if we see multi-ip option which is
 392 // not allowed to be such (for example, DHCP_BROADCAST)? -
 393                 if (len < optlen /* || !(optflag->flags & OPTION_LIST) */)
 394                         break;
 395                 *dest++ = ' ';
 396                 *dest = '\0';
 397         } /* while */
 398
 399         return ret;
 400 }
 401
 402 /* put all the parameters into the environment */
 403 static char **fill_envp(struct dhcp_packet *packet)
 404 {
 405         int envc;
 406         int i;
 407         char **envp, **curr;
 408         const char *opt_name;
 409         uint8_t *temp;
 410         uint8_t overload = 0;
 411
 412 #define BITMAP unsigned
 413 #define BBITS (sizeof(BITMAP) * 8)
 414 #define BMASK(i) (1 << (i & (sizeof(BITMAP) * 8 - 1)))
 415 #define FOUND_OPTS(i) (found_opts[(unsigned)i / BBITS])
 416         BITMAP found_opts[256 / BBITS];
 417
 418         memset(found_opts, 0, sizeof(found_opts));
 419
 420         /* We need 6 elements for:
 421          * "interface=IFACE"
 422          * "ip=N.N.N.N" from packet->yiaddr
 423          * "siaddr=IP" from packet->siaddr_nip (unless 0)
 424          * "boot_file=FILE" from packet->file (unless overloaded)
 425          * "sname=SERVER_HOSTNAME" from packet->sname (unless overloaded)
 426          * terminating NULL
 427          */
 428         envc = 6;
 429         /* +1 element for each option, +2 for subnet option: */
 430         if (packet) {
 431                 /* note: do not search for "pad" (0) and "end" (255) options */
 432 //TODO: change logic to scan packet _once_
 433                 for (i = 1; i < 255; i++) {
 434                         temp = udhcp_get_option(packet, i);
 435                         if (temp) {
 436                                 if (i == DHCP_OPTION_OVERLOAD)
 437                                         overload = *temp;
 438                                 else if (i == DHCP_SUBNET)
 439                                         envc++; /* for $mask */
 440                                 envc++;
 441                                 /*if (i != DHCP_MESSAGE_TYPE)*/
 442                                 FOUND_OPTS(i) |= BMASK(i);
 443                         }
 444                 }
 445         }
 446         curr = envp = xzalloc(sizeof(envp[0]) * envc);
 447
 448         *curr = xasprintf("interface=%s", client_config.interface);
 449         putenv(*curr++);
 450
 451         if (!packet)
 452                 return envp;
 453
 454         /* Export BOOTP fields. Fields we don't (yet?) export:
 455          * uint8_t op;      // always BOOTREPLY
 456          * uint8_t htype;   // hardware address type. 1 = 10mb ethernet
 457          * uint8_t hlen;    // hardware address length
 458          * uint8_t hops;    // used by relay agents only
 459          * uint32_t xid;
 460          * uint16_t secs;   // elapsed since client began acquisition/renewal
 461          * uint16_t flags;  // only one flag so far: bcast. Never set by server
 462          * uint32_t ciaddr; // client IP (usually == yiaddr. can it be different
 463          *                  // if during renew server wants to give us differn IP?)
 464          * uint32_t gateway_nip; // relay agent IP address
 465          * uint8_t chaddr[16]; // link-layer client hardware address (MAC)
 466          * TODO: export gateway_nip as $giaddr?
 467          */
 468         /* Most important one: yiaddr as $ip */
 469         *curr = xmalloc(sizeof("ip=255.255.255.255"));
 470         sprint_nip(*curr, "ip=", (uint8_t *) &packet->yiaddr);
 471         putenv(*curr++);
 472         if (packet->siaddr_nip) {
 473                 /* IP address of next server to use in bootstrap */
 474                 *curr = xmalloc(sizeof("siaddr=255.255.255.255"));
 475                 sprint_nip(*curr, "siaddr=", (uint8_t *) &packet->siaddr_nip);
 476                 putenv(*curr++);
 477         }
 478         if (!(overload & FILE_FIELD) && packet->file[0]) {
 479                 /* watch out for invalid packets */
 480                 *curr = xasprintf("boot_file=%."DHCP_PKT_FILE_LEN_STR"s", packet->file);
 481                 putenv(*curr++);
 482         }
 483         if (!(overload & SNAME_FIELD) && packet->sname[0]) {
 484                 /* watch out for invalid packets */
 485                 *curr = xasprintf("sname=%."DHCP_PKT_SNAME_LEN_STR"s", packet->sname);
 486                 putenv(*curr++);
 487         }
 488
 489         /* Export known DHCP options */
 490         opt_name = dhcp_option_strings;
 491         i = 0;
 492         while (*opt_name) {
 493                 uint8_t code = dhcp_optflags[i].code;
 494                 BITMAP *found_ptr = &FOUND_OPTS(code);
 495                 BITMAP found_mask = BMASK(code);
 496                 if (!(*found_ptr & found_mask))
 497                         goto next;
 498                 *found_ptr &= ~found_mask; /* leave only unknown options */
 499                 temp = udhcp_get_option(packet, code);
 500                 *curr = xmalloc_optname_optval(temp, &dhcp_optflags[i], opt_name);
 501                 putenv(*curr++);
 502                 if (code == DHCP_SUBNET) {
 503                         /* Subnet option: make things like "$ip/$mask" possible */
 504                         uint32_t subnet;
 505                         move_from_unaligned32(subnet, temp);
 506                         *curr = xasprintf("mask=%u", mton(subnet));
 507                         putenv(*curr++);
 508                 }
 509  next:
 510                 opt_name += strlen(opt_name) + 1;
 511                 i++;
 512         }
 513         /* Export unknown options */
 514         for (i = 0; i < 256;) {
 515                 BITMAP bitmap = FOUND_OPTS(i);
 516                 if (!bitmap) {
 517                         i += BBITS;
 518                         continue;
 519                 }
 520                 if (bitmap & BMASK(i)) {
 521                         unsigned len, ofs;
 522
 523                         temp = udhcp_get_option(packet, i);
 524                         /* udhcp_get_option returns ptr to data portion,
 525                          * need to go back to get len
 526                          */
 527                         len = temp[-OPT_DATA + OPT_LEN];
 528                         *curr = xmalloc(sizeof("optNNN=") + 1 + len*2);
 529                         ofs = sprintf(*curr, "opt%u=", i);
 530                         *bin2hex(*curr + ofs, (void*) temp, len) = '\0';
 531                         putenv(*curr++);
 532                 }
 533                 i++;
 534         }
 535
 536         return envp;
 537 }
 538
 539 /* Call a script with a par file and env vars */
 540 static void udhcp_run_script(struct dhcp_packet *packet, const char *name)
 541 {
 542         char **envp, **curr;
 543         char *argv[3];
 544
 545         envp = fill_envp(packet);
 546
 547         /* call script */
 548         log1("Executing %s %s", client_config.script, name);
 549         argv[0] = (char*) client_config.script;
 550         argv[1] = (char*) name;
 551         argv[2] = NULL;
 552         spawn_and_wait(argv);
 553
 554         for (curr = envp; *curr; curr++) {
 555                 log2(" %s", *curr);
 556                 bb_unsetenv_and_free(*curr);
 557         }
 558         free(envp);
 559 }
 560
 561
 562 /*** Sending/receiving packets ***/
 563
 564 static ALWAYS_INLINE uint32_t random_xid(void)
 565 {
 566         return rand();
 567 }
 568
 569 /* Initialize the packet with the proper defaults */
 570 static void init_packet(struct dhcp_packet *packet, char type)
 571 {
 572         uint16_t secs;
 573
 574         /* Fill in: op, htype, hlen, cookie fields; message type option: */
 575         udhcp_init_header(packet, type);
 576
 577         packet->xid = random_xid();
 578
 579         client_config.last_secs = monotonic_sec();
 580         if (client_config.first_secs == 0)
 581                 client_config.first_secs = client_config.last_secs;
 582         secs = client_config.last_secs - client_config.first_secs;
 583         packet->secs = htons(secs);
 584
 585         memcpy(packet->chaddr, client_config.client_mac, 6);
 586         if (client_config.clientid)
 587                 udhcp_add_binary_option(packet, client_config.clientid);
 588 }
 589
 590 static void add_client_options(struct dhcp_packet *packet)
 591 {
 592         int i, end, len;
 593
 594         udhcp_add_simple_option(packet, DHCP_MAX_SIZE, htons(IP_UDP_DHCP_SIZE));
 595
 596         /* Add a "param req" option with the list of options we'd like to have
 597          * from stubborn DHCP servers. Pull the data from the struct in common.c.
 598          * No bounds checking because it goes towards the head of the packet. */
 599         end = udhcp_end_option(packet->options);
 600         len = 0;
 601         for (i = 1; i < DHCP_END; i++) {
 602                 if (client_config.opt_mask[i >> 3] & (1 << (i & 7))) {
 603                         packet->options[end + OPT_DATA + len] = i;
 604                         len++;
 605                 }
 606         }
 607         if (len) {
 608                 packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
 609                 packet->options[end + OPT_LEN] = len;
 610                 packet->options[end + OPT_DATA + len] = DHCP_END;
 611         }
 612
 613         if (client_config.vendorclass)
 614                 udhcp_add_binary_option(packet, client_config.vendorclass);
 615         if (client_config.hostname)
 616                 udhcp_add_binary_option(packet, client_config.hostname);
 617         if (client_config.fqdn)
 618                 udhcp_add_binary_option(packet, client_config.fqdn);
 619
 620         /* Request broadcast replies if we have no IP addr */
 621         if ((option_mask32 & OPT_B) && packet->ciaddr == 0)
 622                 packet->flags |= htons(BROADCAST_FLAG);
 623
 624         /* Add -x options if any */
 625         {
 626                 struct option_set *curr = client_config.options;
 627                 while (curr) {
 628                         udhcp_add_binary_option(packet, curr->data);
 629                         curr = curr->next;
 630                 }
 631 //              if (client_config.sname)
 632 //                      strncpy((char*)packet->sname, client_config.sname, sizeof(packet->sname) - 1);
 633 //              if (client_config.boot_file)
 634 //                      strncpy((char*)packet->file, client_config.boot_file, sizeof(packet->file) - 1);
 635         }
 636
 637         // This will be needed if we remove -V VENDOR_STR in favor of
 638         // -x vendor:VENDOR_STR
 639         //if (!udhcp_find_option(packet.options, DHCP_VENDOR))
 640         //      /* not set, set the default vendor ID */
 641         //      ...add (DHCP_VENDOR, "udhcp "BB_VER) opt...
 642 }
 643
 644 /* RFC 2131
 645  * 4.4.4 Use of broadcast and unicast
 646  *
 647  * The DHCP client broadcasts DHCPDISCOVER, DHCPREQUEST and DHCPINFORM
 648  * messages, unless the client knows the address of a DHCP server.
 649  * The client unicasts DHCPRELEASE messages to the server. Because
 650  * the client is declining the use of the IP address supplied by the server,
 651  * the client broadcasts DHCPDECLINE messages.
 652  *
 653  * When the DHCP client knows the address of a DHCP server, in either
 654  * INIT or REBOOTING state, the client may use that address
 655  * in the DHCPDISCOVER or DHCPREQUEST rather than the IP broadcast address.
 656  * The client may also use unicast to send DHCPINFORM messages
 657  * to a known DHCP server. If the client receives no response to DHCP
 658  * messages sent to the IP address of a known DHCP server, the DHCP
 659  * client reverts to using the IP broadcast address.
 660  */
 661
 662 static int raw_bcast_from_client_config_ifindex(struct dhcp_packet *packet)
 663 {
 664         return udhcp_send_raw_packet(packet,
 665                 /*src*/ INADDR_ANY, CLIENT_PORT,
 666                 /*dst*/ INADDR_BROADCAST, SERVER_PORT, MAC_BCAST_ADDR,
 667                 client_config.ifindex);
 668 }
 669
 670 static int bcast_or_ucast(struct dhcp_packet *packet, uint32_t ciaddr, uint32_t server)
 671 {
 672         if (server)
 673                 return udhcp_send_kernel_packet(packet,
 674                         ciaddr, CLIENT_PORT,
 675                         server, SERVER_PORT);
 676         return raw_bcast_from_client_config_ifindex(packet);
 677 }
 678
 679 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
 680 /* NOINLINE: limit stack usage in caller */
 681 static NOINLINE int send_discover(uint32_t xid, uint32_t requested)
 682 {
 683         struct dhcp_packet packet;
 684
 685         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 686          * random xid field (we override it below),
 687          * client-id option (unless -C), message type option:
 688          */
 689         init_packet(&packet, DHCPDISCOVER);
 690
 691         packet.xid = xid;
 692         if (requested)
 693                 udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 694
 695         /* Add options: maxsize,
 696          * optionally: hostname, fqdn, vendorclass,
 697          * "param req" option according to -O, options specified with -x
 698          */
 699         add_client_options(&packet);
 700
 701         bb_info_msg("Sending discover...");
 702         return raw_bcast_from_client_config_ifindex(&packet);
 703 }
 704
 705 /* Broadcast a DHCP request message */
 706 /* RFC 2131 3.1 paragraph 3:
 707  * "The client _broadcasts_ a DHCPREQUEST message..."
 708  */
 709 /* NOINLINE: limit stack usage in caller */
 710 static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requested)
 711 {
 712         struct dhcp_packet packet;
 713         struct in_addr addr;
 714
 715 /*
 716  * RFC 2131 4.3.2 DHCPREQUEST message
 717  * ...
 718  * If the DHCPREQUEST message contains a 'server identifier'
 719  * option, the message is in response to a DHCPOFFER message.
 720  * Otherwise, the message is a request to verify or extend an
 721  * existing lease. If the client uses a 'client identifier'
 722  * in a DHCPREQUEST message, it MUST use that same 'client identifier'
 723  * in all subsequent messages. If the client included a list
 724  * of requested parameters in a DHCPDISCOVER message, it MUST
 725  * include that list in all subsequent messages.
 726  */
 727         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 728          * random xid field (we override it below),
 729          * client-id option (unless -C), message type option:
 730          */
 731         init_packet(&packet, DHCPREQUEST);
 732
 733         packet.xid = xid;
 734         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 735
 736         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 737
 738         /* Add options: maxsize,
 739          * optionally: hostname, fqdn, vendorclass,
 740          * "param req" option according to -O, and options specified with -x
 741          */
 742         add_client_options(&packet);
 743
 744         addr.s_addr = requested;
 745         bb_info_msg("Sending select for %s...", inet_ntoa(addr));
 746         return raw_bcast_from_client_config_ifindex(&packet);
 747 }
 748
 749 /* Unicast or broadcast a DHCP renew message */
 750 /* NOINLINE: limit stack usage in caller */
 751 static NOINLINE int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
 752 {
 753         struct dhcp_packet packet;
 754
 755 /*
 756  * RFC 2131 4.3.2 DHCPREQUEST message
 757  * ...
 758  * DHCPREQUEST generated during RENEWING state:
 759  *
 760  * 'server identifier' MUST NOT be filled in, 'requested IP address'
 761  * option MUST NOT be filled in, 'ciaddr' MUST be filled in with
 762  * client's IP address. In this situation, the client is completely
 763  * configured, and is trying to extend its lease. This message will
 764  * be unicast, so no relay agents will be involved in its
 765  * transmission.  Because 'giaddr' is therefore not filled in, the
 766  * DHCP server will trust the value in 'ciaddr', and use it when
 767  * replying to the client.
 768  */
 769         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 770          * random xid field (we override it below),
 771          * client-id option (unless -C), message type option:
 772          */
 773         init_packet(&packet, DHCPREQUEST);
 774
 775         packet.xid = xid;
 776         packet.ciaddr = ciaddr;
 777
 778         /* Add options: maxsize,
 779          * optionally: hostname, fqdn, vendorclass,
 780          * "param req" option according to -O, and options specified with -x
 781          */
 782         add_client_options(&packet);
 783
 784         bb_info_msg("Sending renew...");
 785         return bcast_or_ucast(&packet, ciaddr, server);
 786 }
 787
 788 #if ENABLE_FEATURE_UDHCPC_ARPING
 789 /* Broadcast a DHCP decline message */
 790 /* NOINLINE: limit stack usage in caller */
 791 static NOINLINE int send_decline(/*uint32_t xid,*/ uint32_t server, uint32_t requested)
 792 {
 793         struct dhcp_packet packet;
 794
 795         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 796          * client-id option (unless -C), message type option:
 797          */
 798         init_packet(&packet, DHCPDECLINE);
 799
 800 #if 0
 801         /* RFC 2131 says DHCPDECLINE's xid is randomly selected by client,
 802          * but in case the server is buggy and wants DHCPDECLINE's xid
 803          * to match the xid which started entire handshake,
 804          * we use the same xid we used in initial DHCPDISCOVER:
 805          */
 806         packet.xid = xid;
 807 #endif
 808         /* DHCPDECLINE uses "requested ip", not ciaddr, to store offered IP */
 809         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 810
 811         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 812
 813         bb_info_msg("Sending decline...");
 814         return raw_bcast_from_client_config_ifindex(&packet);
 815 }
 816 #endif
 817
 818 /* Unicast a DHCP release message */
 819 static int send_release(uint32_t server, uint32_t ciaddr)
 820 {
 821         struct dhcp_packet packet;
 822
 823         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 824          * client-id option (unless -C), message type option:
 825          */
 826         init_packet(&packet, DHCPRELEASE);
 827
 828         /* DHCPRELEASE uses ciaddr, not "requested ip", to store IP being released */
 829         packet.ciaddr = ciaddr;
 830
 831         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 832
 833         bb_info_msg("Sending release...");
 834         /* Note: normally we unicast here since "server" is not zero.
 835          * However, there _are_ people who run "address-less" DHCP servers,
 836          * and reportedly ISC dhcp client and Windows allow that.
 837          */
 838         return bcast_or_ucast(&packet, ciaddr, server);
 839 }
 840
 841 /* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */
 842 /* NOINLINE: limit stack usage in caller */
 843 static NOINLINE int udhcp_recv_raw_packet(struct dhcp_packet *dhcp_pkt, int fd)
 844 {
 845         int bytes;
 846         struct ip_udp_dhcp_packet packet;
 847         uint16_t check;
 848         unsigned char cmsgbuf[CMSG_LEN(sizeof(struct tpacket_auxdata))];
 849         struct iovec iov;
 850         struct msghdr msg;
 851         struct cmsghdr *cmsg;
 852
 853         /* used to use just safe_read(fd, &packet, sizeof(packet))
 854          * but we need to check for TP_STATUS_CSUMNOTREADY :(
 855          */
 856         iov.iov_base = &packet;
 857         iov.iov_len = sizeof(packet);
 858         memset(&msg, 0, sizeof(msg));
 859         msg.msg_iov = &iov;
 860         msg.msg_iovlen = 1;
 861         msg.msg_control = cmsgbuf;
 862         msg.msg_controllen = sizeof(cmsgbuf);
 863         for (;;) {
 864                 bytes = recvmsg(fd, &msg, 0);
 865                 if (bytes < 0) {
 866                         if (errno == EINTR)
 867                                 continue;
 868                         log1("Packet read error, ignoring");
 869                         /* NB: possible down interface, etc. Caller should pause. */
 870                         return bytes; /* returns -1 */
 871                 }
 872                 break;
 873         }
 874
 875         if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) {
 876                 log1("Packet is too short, ignoring");
 877                 return -2;
 878         }
 879
 880         if (bytes < ntohs(packet.ip.tot_len)) {
 881                 /* packet is bigger than sizeof(packet), we did partial read */
 882                 log1("Oversized packet, ignoring");
 883                 return -2;
 884         }
 885
 886         /* ignore any extra garbage bytes */
 887         bytes = ntohs(packet.ip.tot_len);
 888
 889         /* make sure its the right packet for us, and that it passes sanity checks */
 890         if (packet.ip.protocol != IPPROTO_UDP
 891          || packet.ip.version != IPVERSION
 892          || packet.ip.ihl != (sizeof(packet.ip) >> 2)
 893          || packet.udp.dest != htons(CLIENT_PORT)
 894         /* || bytes > (int) sizeof(packet) - can't happen */
 895          || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
 896         ) {
 897                 log1("Unrelated/bogus packet, ignoring");
 898                 return -2;
 899         }
 900
 901         /* verify IP checksum */
 902         check = packet.ip.check;
 903         packet.ip.check = 0;
 904         if (check != inet_cksum((uint16_t *)&packet.ip, sizeof(packet.ip))) {
 905                 log1("Bad IP header checksum, ignoring");
 906                 return -2;
 907         }
 908
 909         for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
 910                 if (cmsg->cmsg_level == SOL_PACKET
 911                  && cmsg->cmsg_type == PACKET_AUXDATA
 912                 ) {
 913                         /* some VMs don't checksum UDP and TCP data
 914                          * they send to the same physical machine,
 915                          * here we detect this case:
 916                          */
 917                         struct tpacket_auxdata *aux = (void *)CMSG_DATA(cmsg);
 918                         if (aux->tp_status & TP_STATUS_CSUMNOTREADY)
 919                                 goto skip_udp_sum_check;
 920                 }
 921         }
 922
 923         /* verify UDP checksum. IP header has to be modified for this */
 924         memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
 925         /* ip.xx fields which are not memset: protocol, check, saddr, daddr */
 926         packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
 927         check = packet.udp.check;
 928         packet.udp.check = 0;
 929         if (check && check != inet_cksum((uint16_t *)&packet, bytes)) {
 930                 log1("Packet with bad UDP checksum received, ignoring");
 931                 return -2;
 932         }
 933  skip_udp_sum_check:
 934
 935         if (packet.data.cookie != htonl(DHCP_MAGIC)) {
 936                 bb_info_msg("Packet with bad magic, ignoring");
 937                 return -2;
 938         }
 939
 940         log1("Received a packet");
 941         udhcp_dump_packet(&packet.data);
 942
 943         bytes -= sizeof(packet.ip) + sizeof(packet.udp);
 944         memcpy(dhcp_pkt, &packet.data, bytes);
 945         return bytes;
 946 }
 947
 948
 949 /*** Main ***/
 950
 951 static int sockfd = -1;
 952
 953 #define LISTEN_NONE   0
 954 #define LISTEN_KERNEL 1
 955 #define LISTEN_RAW    2
 956 static smallint listen_mode;
 957
 958 /* initial state: (re)start DHCP negotiation */
 959 #define INIT_SELECTING  0
 960 /* discover was sent, DHCPOFFER reply received */
 961 #define REQUESTING      1
 962 /* select/renew was sent, DHCPACK reply received */
 963 #define BOUND           2
 964 /* half of lease passed, want to renew it by sending unicast renew requests */
 965 #define RENEWING        3
 966 /* renew requests were not answered, lease is almost over, send broadcast renew */
 967 #define REBINDING       4
 968 /* manually requested renew (SIGUSR1) */
 969 #define RENEW_REQUESTED 5
 970 /* release, possibly manually requested (SIGUSR2) */
 971 #define RELEASED        6
 972 static smallint state;
 973
 974 static int udhcp_raw_socket(int ifindex)
 975 {
 976         int fd;
 977         struct sockaddr_ll sock;
 978
 979         log1("Opening raw socket on ifindex %d", ifindex); //log2?
 980
 981         fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
 982         /* ^^^^^
 983          * SOCK_DGRAM: remove link-layer headers on input (SOCK_RAW keeps them)
 984          * ETH_P_IP: want to receive only packets with IPv4 eth type
 985          */
 986         log1("Got raw socket fd"); //log2?
 987
 988         sock.sll_family = AF_PACKET;
 989         sock.sll_protocol = htons(ETH_P_IP);
 990         sock.sll_ifindex = ifindex;
 991         xbind(fd, (struct sockaddr *) &sock, sizeof(sock));
 992
 993 #if 0 /* Several users reported breakage when BPF filter is used */
 994         if (CLIENT_PORT == 68) {
 995                 /* Use only if standard port is in use */
 996                 /*
 997                  *      I've selected not to see LL header, so BPF doesn't see it, too.
 998                  *      The filter may also pass non-IP and non-ARP packets, but we do
 999                  *      a more complete check when receiving the message in userspace.
1000                  *
1001                  * and filter shamelessly stolen from:
1002                  *
1003                  *      http://www.flamewarmaster.de/software/dhcpclient/
1004                  *
1005                  * There are a few other interesting ideas on that page (look under
1006                  * "Motivation").  Use of netlink events is most interesting.  Think
1007                  * of various network servers listening for events and reconfiguring.
1008                  * That would obsolete sending HUP signals and/or make use of restarts.
1009                  *
1010                  * Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
1011                  * License: GPL v2.
1012                  */
1013                 static const struct sock_filter filter_instr[] = {
1014                         /* load 9th byte (protocol) */
1015                         BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
1016                         /* jump to L1 if it is IPPROTO_UDP, else to L4 */
1017                         BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 0, 6),
1018                         /* L1: load halfword from offset 6 (flags and frag offset) */
1019                         BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 6),
1020                         /* jump to L4 if any bits in frag offset field are set, else to L2 */
1021                         BPF_JUMP(BPF_JMP|BPF_JSET|BPF_K, 0x1fff, 4, 0),
1022                         /* L2: skip IP header (load index reg with header len) */
1023                         BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0),
1024                         /* load udp destination port from halfword[header_len + 2] */
1025                         BPF_STMT(BPF_LD|BPF_H|BPF_IND, 2),
1026                         /* jump to L3 if udp dport is CLIENT_PORT, else to L4 */
1027                         BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 68, 0, 1),
1028                         /* L3: accept packet */
1029                         BPF_STMT(BPF_RET|BPF_K, 0xffffffff),
1030                         /* L4: discard packet */
1031                         BPF_STMT(BPF_RET|BPF_K, 0),
1032                 };
1033                 static const struct sock_fprog filter_prog = {
1034                         .len = sizeof(filter_instr) / sizeof(filter_instr[0]),
1035                         /* casting const away: */
1036                         .filter = (struct sock_filter *) filter_instr,
1037                 };
1038                 /* Ignoring error (kernel may lack support for this) */
1039                 if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
1040                                 sizeof(filter_prog)) >= 0)
1041                         log1("Attached filter to raw socket fd"); // log?
1042         }
1043 #endif
1044
1045         if (setsockopt(fd, SOL_PACKET, PACKET_AUXDATA,
1046                         &const_int_1, sizeof(int)) < 0
1047         ) {
1048                 if (errno != ENOPROTOOPT)
1049                         log1("Can't set PACKET_AUXDATA on raw socket");
1050         }
1051
1052         log1("Created raw socket");
1053
1054         return fd;
1055 }
1056
1057 static void change_listen_mode(int new_mode)
1058 {
1059         log1("Entering listen mode: %s",
1060                 new_mode != LISTEN_NONE
1061                         ? (new_mode == LISTEN_KERNEL ? "kernel" : "raw")
1062                         : "none"
1063         );
1064
1065         listen_mode = new_mode;
1066         if (sockfd >= 0) {
1067                 close(sockfd);
1068                 sockfd = -1;
1069         }
1070         if (new_mode == LISTEN_KERNEL)
1071                 sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
1072         else if (new_mode != LISTEN_NONE)
1073                 sockfd = udhcp_raw_socket(client_config.ifindex);
1074         /* else LISTEN_NONE: sockfd stays closed */
1075 }
1076
1077 /* Called only on SIGUSR1 */
1078 static void perform_renew(void)
1079 {
1080         bb_info_msg("Performing a DHCP renew");
1081         switch (state) {
1082         case BOUND:
1083                 change_listen_mode(LISTEN_KERNEL);
1084         case RENEWING:
1085         case REBINDING:
1086                 state = RENEW_REQUESTED;
1087                 break;
1088         case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
1089                 udhcp_run_script(NULL, "deconfig");
1090         case REQUESTING:
1091         case RELEASED:
1092                 change_listen_mode(LISTEN_RAW);
1093                 state = INIT_SELECTING;
1094                 break;
1095         case INIT_SELECTING:
1096                 break;
1097         }
1098 }
1099
1100 static void perform_release(uint32_t server_addr, uint32_t requested_ip)
1101 {
1102         char buffer[sizeof("255.255.255.255")];
1103         struct in_addr temp_addr;
1104
1105         /* send release packet */
1106         if (state == BOUND || state == RENEWING || state == REBINDING) {
1107                 temp_addr.s_addr = server_addr;
1108                 strcpy(buffer, inet_ntoa(temp_addr));
1109                 temp_addr.s_addr = requested_ip;
1110                 bb_info_msg("Unicasting a release of %s to %s",
1111                                 inet_ntoa(temp_addr), buffer);
1112                 send_release(server_addr, requested_ip); /* unicast */
1113                 udhcp_run_script(NULL, "deconfig");
1114         }
1115         bb_info_msg("Entering released state");
1116
1117         change_listen_mode(LISTEN_NONE);
1118         state = RELEASED;
1119 }
1120
1121 static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
1122 {
1123         uint8_t *storage;
1124         int len = strnlen(str, 255);
1125         storage = xzalloc(len + extra + OPT_DATA);
1126         storage[OPT_CODE] = code;
1127         storage[OPT_LEN] = len + extra;
1128         memcpy(storage + extra + OPT_DATA, str, len);
1129         return storage;
1130 }
1131
1132 #if BB_MMU
1133 static void client_background(void)
1134 {
1135         bb_daemonize(0);
1136         logmode &= ~LOGMODE_STDIO;
1137         /* rewrite pidfile, as our pid is different now */
1138         write_pidfile(client_config.pidfile);
1139 }
1140 #endif
1141
1142 //usage:#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
1143 //usage:# define IF_UDHCP_VERBOSE(...) __VA_ARGS__
1144 //usage:#else
1145 //usage:# define IF_UDHCP_VERBOSE(...)
1146 //usage:#endif
1147 //usage:#define udhcpc_trivial_usage
1148 //usage:       "[-fbq"IF_UDHCP_VERBOSE("v")IF_FEATURE_UDHCPC_ARPING("a")"RB] [-t N] [-T SEC] [-A SEC/-n]\n"
1149 //usage:       "        [-i IFACE]"IF_FEATURE_UDHCP_PORT(" [-P PORT]")" [-s PROG] [-p PIDFILE]\n"
1150 //usage:       "        [-oC] [-r IP] [-V VENDOR] [-F NAME] [-x OPT:VAL]... [-O OPT]..."
1151 //usage:#define udhcpc_full_usage "\n"
1152 //usage:        IF_LONG_OPTS(
1153 //usage:     "\n        -i,--interface IFACE    Interface to use (default eth0)"
1154 //usage:        IF_FEATURE_UDHCP_PORT(
1155 //usage:     "\n        -P,--client-port PORT   Use PORT (default 68)"
1156 //usage:        )
1157 //usage:     "\n        -s,--script PROG        Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
1158 //usage:     "\n        -p,--pidfile FILE       Create pidfile"
1159 //usage:     "\n        -B,--broadcast          Request broadcast replies"
1160 //usage:     "\n        -t,--retries N          Send up to N discover packets (default 3)"
1161 //usage:     "\n        -T,--timeout SEC        Pause between packets (default 3)"
1162 //usage:     "\n        -A,--tryagain SEC       Wait if lease is not obtained (default 20)"
1163 //usage:     "\n        -n,--now                Exit if lease is not obtained"
1164 //usage:     "\n        -q,--quit               Exit after obtaining lease"
1165 //usage:     "\n        -R,--release            Release IP on exit"
1166 //usage:     "\n        -f,--foreground         Run in foreground"
1167 //usage:        USE_FOR_MMU(
1168 //usage:     "\n        -b,--background         Background if lease is not obtained"
1169 //usage:        )
1170 //usage:     "\n        -S,--syslog             Log to syslog too"
1171 //usage:        IF_FEATURE_UDHCPC_ARPING(
1172 //usage:     "\n        -a,--arping             Use arping to validate offered address"
1173 //usage:        )
1174 //usage:     "\n        -r,--request IP         Request this IP address"
1175 //usage:     "\n        -o,--no-default-options Don't request any options (unless -O is given)"
1176 //usage:     "\n        -O,--request-option OPT Request option OPT from server (cumulative)"
1177 //usage:     "\n        -x OPT:VAL              Include option OPT in sent packets (cumulative)"
1178 //usage:     "\n                                Examples of string, numeric, and hex byte opts:"
1179 //usage:     "\n                                -x hostname:bbox - option 12"
1180 //usage:     "\n                                -x lease:3600 - option 51 (lease time)"
1181 //usage:     "\n                                -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
1182 //usage:     "\n        -F,--fqdn NAME          Ask server to update DNS mapping for NAME"
1183 //usage:     "\n        -V,--vendorclass VENDOR Vendor identifier (default 'udhcp VERSION')"
1184 //usage:     "\n        -C,--clientid-none      Don't send MAC as client identifier"
1185 //usage:        IF_UDHCP_VERBOSE(
1186 //usage:     "\n        -v                      Verbose"
1187 //usage:        )
1188 //usage:        )
1189 //usage:        IF_NOT_LONG_OPTS(
1190 //usage:     "\n        -i IFACE        Interface to use (default eth0)"
1191 //usage:        IF_FEATURE_UDHCP_PORT(
1192 //usage:     "\n        -P PORT         Use PORT (default 68)"
1193 //usage:        )
1194 //usage:     "\n        -s PROG         Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
1195 //usage:     "\n        -p FILE         Create pidfile"
1196 //usage:     "\n        -B              Request broadcast replies"
1197 //usage:     "\n        -t N            Send up to N discover packets (default 3)"
1198 //usage:     "\n        -T SEC          Pause between packets (default 3)"
1199 //usage:     "\n        -A SEC          Wait if lease is not obtained (default 20)"
1200 //usage:     "\n        -n              Exit if lease is not obtained"
1201 //usage:     "\n        -q              Exit after obtaining lease"
1202 //usage:     "\n        -R              Release IP on exit"
1203 //usage:     "\n        -f              Run in foreground"
1204 //usage:        USE_FOR_MMU(
1205 //usage:     "\n        -b              Background if lease is not obtained"
1206 //usage:        )
1207 //usage:     "\n        -S              Log to syslog too"
1208 //usage:        IF_FEATURE_UDHCPC_ARPING(
1209 //usage:     "\n        -a              Use arping to validate offered address"
1210 //usage:        )
1211 //usage:     "\n        -r IP           Request this IP address"
1212 //usage:     "\n        -o              Don't request any options (unless -O is given)"
1213 //usage:     "\n        -O OPT          Request option OPT from server (cumulative)"
1214 //usage:     "\n        -x OPT:VAL      Include option OPT in sent packets (cumulative)"
1215 //usage:     "\n                        Examples of string, numeric, and hex byte opts:"
1216 //usage:     "\n                        -x hostname:bbox - option 12"
1217 //usage:     "\n                        -x lease:3600 - option 51 (lease time)"
1218 //usage:     "\n                        -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
1219 //usage:     "\n        -F NAME         Ask server to update DNS mapping for NAME"
1220 //usage:     "\n        -V VENDOR       Vendor identifier (default 'udhcp VERSION')"
1221 //usage:     "\n        -C              Don't send MAC as client identifier"
1222 //usage:        IF_UDHCP_VERBOSE(
1223 //usage:     "\n        -v              Verbose"
1224 //usage:        )
1225 //usage:        )
1226 //usage:     "\nSignals:"
1227 //usage:     "\n        USR1    Renew lease"
1228 //usage:     "\n        USR2    Release lease"
1229
1230
1231 int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
1232 int udhcpc_main(int argc UNUSED_PARAM, char **argv)
1233 {
1234         uint8_t *temp, *message;
1235         const char *str_V, *str_h, *str_F, *str_r;
1236         IF_FEATURE_UDHCP_PORT(char *str_P;)
1237         void *clientid_mac_ptr;
1238         llist_t *list_O = NULL;
1239         llist_t *list_x = NULL;
1240         int tryagain_timeout = 20;
1241         int discover_timeout = 3;
1242         int discover_retries = 3;
1243         uint32_t server_addr = server_addr; /* for compiler */
1244         uint32_t requested_ip = 0;
1245         uint32_t xid = xid; /* for compiler */
1246         int packet_num;
1247         int timeout; /* must be signed */
1248         unsigned already_waited_sec;
1249         unsigned opt;
1250         int max_fd;
1251         int retval;
1252         fd_set rfds;
1253
1254         /* Default options */
1255         IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;)
1256         IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
1257         client_config.interface = "eth0";
1258         client_config.script = CONFIG_UDHCPC_DEFAULT_SCRIPT;
1259         str_V = "udhcp "BB_VER;
1260
1261         /* Parse command line */
1262         /* O,x: list; -T,-t,-A take numeric param */
1263         opt_complementary = "O::x::T+:t+:A+" IF_UDHCP_VERBOSE(":vv") ;
1264         IF_LONG_OPTS(applet_long_options = udhcpc_longopts;)
1265         opt = getopt32(argv, "CV:H:h:F:i:np:qRr:s:T:t:SA:O:ox:fB"
1266                 USE_FOR_MMU("b")
1267                 IF_FEATURE_UDHCPC_ARPING("a")
1268                 IF_FEATURE_UDHCP_PORT("P:")
1269                 "v"
1270                 , &str_V, &str_h, &str_h, &str_F
1271                 , &client_config.interface, &client_config.pidfile, &str_r /* i,p */
1272                 , &client_config.script /* s */
1273                 , &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */
1274                 , &list_O
1275                 , &list_x
1276                 IF_FEATURE_UDHCP_PORT(, &str_P)
1277                 IF_UDHCP_VERBOSE(, &dhcp_verbose)
1278         );
1279         if (opt & (OPT_h|OPT_H)) {
1280                 //msg added 2011-11
1281                 bb_error_msg("option -h NAME is deprecated, use -x hostname:NAME");
1282                 client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
1283         }
1284         if (opt & OPT_F) {
1285                 /* FQDN option format: [0x51][len][flags][0][0]<fqdn> */
1286                 client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
1287                 /* Flag bits: 0000NEOS
1288                  * S: 1 = Client requests server to update A RR in DNS as well as PTR
1289                  * O: 1 = Server indicates to client that DNS has been updated regardless
1290                  * E: 1 = Name is in DNS format, i.e. <4>host<6>domain<3>com<0>,
1291                  *    not "host.domain.com". Format 0 is obsolete.
1292                  * N: 1 = Client requests server to not update DNS (S must be 0 then)
1293                  * Two [0] bytes which follow are deprecated and must be 0.
1294                  */
1295                 client_config.fqdn[OPT_DATA + 0] = 0x1;
1296                 /*client_config.fqdn[OPT_DATA + 1] = 0; - xzalloc did it */
1297                 /*client_config.fqdn[OPT_DATA + 2] = 0; */
1298         }
1299         if (opt & OPT_r)
1300                 requested_ip = inet_addr(str_r);
1301 #if ENABLE_FEATURE_UDHCP_PORT
1302         if (opt & OPT_P) {
1303                 CLIENT_PORT = xatou16(str_P);
1304                 SERVER_PORT = CLIENT_PORT - 1;
1305         }
1306 #endif
1307         while (list_O) {
1308                 char *optstr = llist_pop(&list_O);
1309                 unsigned n = bb_strtou(optstr, NULL, 0);
1310                 if (errno || n > 254) {
1311                         n = udhcp_option_idx(optstr);
1312                         n = dhcp_optflags[n].code;
1313                 }
1314                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
1315         }
1316         if (!(opt & OPT_o)) {
1317                 unsigned i, n;
1318                 for (i = 0; (n = dhcp_optflags[i].code) != 0; i++) {
1319                         if (dhcp_optflags[i].flags & OPTION_REQ) {
1320                                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
1321                         }
1322                 }
1323         }
1324         while (list_x) {
1325                 char *optstr = llist_pop(&list_x);
1326                 char *colon = strchr(optstr, ':');
1327                 if (colon)
1328                         *colon = ' ';
1329                 /* now it looks similar to udhcpd's config file line:
1330                  * "optname optval", using the common routine: */
1331                 udhcp_str2optset(optstr, &client_config.options);
1332         }
1333
1334         if (udhcp_read_interface(client_config.interface,
1335                         &client_config.ifindex,
1336                         NULL,
1337                         client_config.client_mac)
1338         ) {
1339                 return 1;
1340         }
1341
1342         clientid_mac_ptr = NULL;
1343         if (!(opt & OPT_C) && !udhcp_find_option(client_config.options, DHCP_CLIENT_ID)) {
1344                 /* not suppressed and not set, set the default client ID */
1345                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
1346                 client_config.clientid[OPT_DATA] = 1; /* type: ethernet */
1347                 clientid_mac_ptr = client_config.clientid + OPT_DATA+1;
1348                 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1349         }
1350         if (str_V[0] != '\0') {
1351                 // can drop -V, str_V, client_config.vendorclass,
1352                 // but need to add "vendor" to the list of recognized
1353                 // string opts for this to work;
1354                 // and need to tweak add_client_options() too...
1355                 // ...so the question is, should we?
1356                 //bb_error_msg("option -V VENDOR is deprecated, use -x vendor:VENDOR");
1357                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
1358         }
1359
1360 #if !BB_MMU
1361         /* on NOMMU reexec (i.e., background) early */
1362         if (!(opt & OPT_f)) {
1363                 bb_daemonize_or_rexec(0 /* flags */, argv);
1364                 logmode = LOGMODE_NONE;
1365         }
1366 #endif
1367         if (opt & OPT_S) {
1368                 openlog(applet_name, LOG_PID, LOG_DAEMON);
1369                 logmode |= LOGMODE_SYSLOG;
1370         }
1371
1372         /* Make sure fd 0,1,2 are open */
1373         bb_sanitize_stdio();
1374         /* Equivalent of doing a fflush after every \n */
1375         setlinebuf(stdout);
1376         /* Create pidfile */
1377         write_pidfile(client_config.pidfile);
1378         /* Goes to stdout (unless NOMMU) and possibly syslog */
1379         bb_info_msg("%s (v"BB_VER") started", applet_name);
1380         /* Set up the signal pipe */
1381         udhcp_sp_setup();
1382         /* We want random_xid to be random... */
1383         srand(monotonic_us());
1384
1385         state = INIT_SELECTING;
1386         udhcp_run_script(NULL, "deconfig");
1387         change_listen_mode(LISTEN_RAW);
1388         packet_num = 0;
1389         timeout = 0;
1390         already_waited_sec = 0;
1391
1392         /* Main event loop. select() waits on signal pipe and possibly
1393          * on sockfd.
1394          * "continue" statements in code below jump to the top of the loop.
1395          */
1396         for (;;) {
1397                 struct timeval tv;
1398                 struct dhcp_packet packet;
1399                 /* silence "uninitialized!" warning */
1400                 unsigned timestamp_before_wait = timestamp_before_wait;
1401
1402                 //bb_error_msg("sockfd:%d, listen_mode:%d", sockfd, listen_mode);
1403
1404                 /* Was opening raw or udp socket here
1405                  * if (listen_mode != LISTEN_NONE && sockfd < 0),
1406                  * but on fast network renew responses return faster
1407                  * than we open sockets. Thus this code is moved
1408                  * to change_listen_mode(). Thus we open listen socket
1409                  * BEFORE we send renew request (see "case BOUND:"). */
1410
1411                 max_fd = udhcp_sp_fd_set(&rfds, sockfd);
1412
1413                 tv.tv_sec = timeout - already_waited_sec;
1414                 tv.tv_usec = 0;
1415                 retval = 0;
1416                 /* If we already timed out, fall through with retval = 0, else... */
1417                 if ((int)tv.tv_sec > 0) {
1418                         log1("Waiting on select %u seconds", (int)tv.tv_sec);
1419                         timestamp_before_wait = (unsigned)monotonic_sec();
1420                         retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
1421                         if (retval < 0) {
1422                                 /* EINTR? A signal was caught, don't panic */
1423                                 if (errno == EINTR) {
1424                                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1425                                         continue;
1426                                 }
1427                                 /* Else: an error occured, panic! */
1428                                 bb_perror_msg_and_die("select");
1429                         }
1430                 }
1431
1432                 /* If timeout dropped to zero, time to become active:
1433                  * resend discover/renew/whatever
1434                  */
1435                 if (retval == 0) {
1436                         /* When running on a bridge, the ifindex may have changed
1437                          * (e.g. if member interfaces were added/removed
1438                          * or if the status of the bridge changed).
1439                          * Refresh ifindex and client_mac:
1440                          */
1441                         if (udhcp_read_interface(client_config.interface,
1442                                         &client_config.ifindex,
1443                                         NULL,
1444                                         client_config.client_mac)
1445                         ) {
1446                                 goto ret0; /* iface is gone? */
1447                         }
1448                         if (clientid_mac_ptr)
1449                                 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1450
1451                         /* We will restart the wait in any case */
1452                         already_waited_sec = 0;
1453
1454                         switch (state) {
1455                         case INIT_SELECTING:
1456                                 if (!discover_retries || packet_num < discover_retries) {
1457                                         if (packet_num == 0)
1458                                                 xid = random_xid();
1459                                         /* broadcast */
1460                                         send_discover(xid, requested_ip);
1461                                         timeout = discover_timeout;
1462                                         packet_num++;
1463                                         continue;
1464                                 }
1465  leasefail:
1466                                 udhcp_run_script(NULL, "leasefail");
1467 #if BB_MMU /* -b is not supported on NOMMU */
1468                                 if (opt & OPT_b) { /* background if no lease */
1469                                         bb_info_msg("No lease, forking to background");
1470                                         client_background();
1471                                         /* do not background again! */
1472                                         opt = ((opt & ~OPT_b) | OPT_f);
1473                                 } else
1474 #endif
1475                                 if (opt & OPT_n) { /* abort if no lease */
1476                                         bb_info_msg("No lease, failing");
1477                                         retval = 1;
1478                                         goto ret;
1479                                 }
1480                                 /* wait before trying again */
1481                                 timeout = tryagain_timeout;
1482                                 packet_num = 0;
1483                                 continue;
1484                         case REQUESTING:
1485                                 if (!discover_retries || packet_num < discover_retries) {
1486                                         /* send broadcast select packet */
1487                                         send_select(xid, server_addr, requested_ip);
1488                                         timeout = discover_timeout;
1489                                         packet_num++;
1490                                         continue;
1491                                 }
1492                                 /* Timed out, go back to init state.
1493                                  * "discover...select...discover..." loops
1494                                  * were seen in the wild. Treat them similarly
1495                                  * to "no response to discover" case */
1496                                 change_listen_mode(LISTEN_RAW);
1497                                 state = INIT_SELECTING;
1498                                 goto leasefail;
1499                         case BOUND:
1500                                 /* 1/2 lease passed, enter renewing state */
1501                                 state = RENEWING;
1502                                 client_config.first_secs = 0; /* make secs field count from 0 */
1503                                 change_listen_mode(LISTEN_KERNEL);
1504                                 log1("Entering renew state");
1505                                 /* fall right through */
1506                         case RENEW_REQUESTED: /* manual (SIGUSR1) renew */
1507                         case_RENEW_REQUESTED:
1508                         case RENEWING:
1509                                 if (timeout > 60) {
1510                                         /* send an unicast renew request */
1511                         /* Sometimes observed to fail (EADDRNOTAVAIL) to bind
1512                          * a new UDP socket for sending inside send_renew.
1513                          * I hazard to guess existing listening socket
1514                          * is somehow conflicting with it, but why is it
1515                          * not deterministic then?! Strange.
1516                          * Anyway, it does recover by eventually failing through
1517                          * into INIT_SELECTING state.
1518                          */
1519                                         send_renew(xid, server_addr, requested_ip);
1520                                         timeout >>= 1;
1521                                         continue;
1522                                 }
1523                                 /* Timed out, enter rebinding state */
1524                                 log1("Entering rebinding state");
1525                                 state = REBINDING;
1526                                 /* fall right through */
1527                         case REBINDING:
1528                                 /* Switch to bcast receive */
1529                                 change_listen_mode(LISTEN_RAW);
1530                                 /* Lease is *really* about to run out,
1531                                  * try to find DHCP server using broadcast */
1532                                 if (timeout > 0) {
1533                                         /* send a broadcast renew request */
1534                                         send_renew(xid, 0 /*INADDR_ANY*/, requested_ip);
1535                                         timeout >>= 1;
1536                                         continue;
1537                                 }
1538                                 /* Timed out, enter init state */
1539                                 bb_info_msg("Lease lost, entering init state");
1540                                 udhcp_run_script(NULL, "deconfig");
1541                                 state = INIT_SELECTING;
1542                                 client_config.first_secs = 0; /* make secs field count from 0 */
1543                                 /*timeout = 0; - already is */
1544                                 packet_num = 0;
1545                                 continue;
1546                         /* case RELEASED: */
1547                         }
1548                         /* yah, I know, *you* say it would never happen */
1549                         timeout = INT_MAX;
1550                         continue; /* back to main loop */
1551                 } /* if select timed out */
1552
1553                 /* select() didn't timeout, something happened */
1554
1555                 /* Is it a signal? */
1556                 /* note: udhcp_sp_read checks FD_ISSET before reading */
1557                 switch (udhcp_sp_read(&rfds)) {
1558                 case SIGUSR1:
1559                         client_config.first_secs = 0; /* make secs field count from 0 */
1560                         already_waited_sec = 0;
1561                         perform_renew();
1562                         if (state == RENEW_REQUESTED) {
1563                                 /* We might be either on the same network
1564                                  * (in which case renew might work),
1565                                  * or we might be on a completely different one
1566                                  * (in which case renew won't ever succeed).
1567                                  * For the second case, must make sure timeout
1568                                  * is not too big, or else we can send
1569                                  * futile renew requests for hours.
1570                                  * (Ab)use -A TIMEOUT value (usually 20 sec)
1571                                  * as a cap on the timeout.
1572                                  */
1573                                 if (timeout > tryagain_timeout)
1574                                         timeout = tryagain_timeout;
1575                                 goto case_RENEW_REQUESTED;
1576                         }
1577                         /* Start things over */
1578                         packet_num = 0;
1579                         /* Kill any timeouts, user wants this to hurry along */
1580                         timeout = 0;
1581                         continue;
1582                 case SIGUSR2:
1583                         perform_release(server_addr, requested_ip);
1584                         timeout = INT_MAX;
1585                         continue;
1586                 case SIGTERM:
1587                         bb_info_msg("Received SIGTERM");
1588                         goto ret0;
1589                 }
1590
1591                 /* Is it a packet? */
1592                 if (listen_mode == LISTEN_NONE || !FD_ISSET(sockfd, &rfds))
1593                         continue; /* no */
1594
1595                 {
1596                         int len;
1597
1598                         /* A packet is ready, read it */
1599                         if (listen_mode == LISTEN_KERNEL)
1600                                 len = udhcp_recv_kernel_packet(&packet, sockfd);
1601                         else
1602                                 len = udhcp_recv_raw_packet(&packet, sockfd);
1603                         if (len == -1) {
1604                                 /* Error is severe, reopen socket */
1605                                 bb_info_msg("Read error: %s, reopening socket", strerror(errno));
1606                                 sleep(discover_timeout); /* 3 seconds by default */
1607                                 change_listen_mode(listen_mode); /* just close and reopen */
1608                         }
1609                         /* If this packet will turn out to be unrelated/bogus,
1610                          * we will go back and wait for next one.
1611                          * Be sure timeout is properly decreased. */
1612                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1613                         if (len < 0)
1614                                 continue;
1615                 }
1616
1617                 if (packet.xid != xid) {
1618                         log1("xid %x (our is %x), ignoring packet",
1619                                 (unsigned)packet.xid, (unsigned)xid);
1620                         continue;
1621                 }
1622
1623                 /* Ignore packets that aren't for us */
1624                 if (packet.hlen != 6
1625                  || memcmp(packet.chaddr, client_config.client_mac, 6) != 0
1626                 ) {
1627 //FIXME: need to also check that last 10 bytes are zero
1628                         log1("chaddr does not match, ignoring packet"); // log2?
1629                         continue;
1630                 }
1631
1632                 message = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
1633                 if (message == NULL) {
1634                         bb_error_msg("no message type option, ignoring packet");
1635                         continue;
1636                 }
1637
1638                 switch (state) {
1639                 case INIT_SELECTING:
1640                         /* Must be a DHCPOFFER */
1641                         if (*message == DHCPOFFER) {
1642 /* What exactly is server's IP? There are several values.
1643  * Example DHCP offer captured with tchdump:
1644  *
1645  * 10.34.25.254:67 > 10.34.25.202:68 // IP header's src
1646  * BOOTP fields:
1647  * Your-IP 10.34.25.202
1648  * Server-IP 10.34.32.125   // "next server" IP
1649  * Gateway-IP 10.34.25.254  // relay's address (if DHCP relays are in use)
1650  * DHCP options:
1651  * DHCP-Message Option 53, length 1: Offer
1652  * Server-ID Option 54, length 4: 10.34.255.7       // "server ID"
1653  * Default-Gateway Option 3, length 4: 10.34.25.254 // router
1654  *
1655  * We think that real server IP (one to use in renew/release)
1656  * is one in Server-ID option. But I am not 100% sure.
1657  * IP header's src and Gateway-IP (same in this example)
1658  * might work too.
1659  * "Next server" and router are definitely wrong ones to use, though...
1660  */
1661 /* We used to ignore pcakets without DHCP_SERVER_ID.
1662  * I've got user reports from people who run "address-less" servers.
1663  * They either supply DHCP_SERVER_ID of 0.0.0.0 or don't supply it at all.
1664  * They say ISC DHCP client supports this case.
1665  */
1666                                 server_addr = 0;
1667                                 temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
1668                                 if (!temp) {
1669                                         bb_error_msg("no server ID, using 0.0.0.0");
1670                                 } else {
1671                                         /* it IS unaligned sometimes, don't "optimize" */
1672                                         move_from_unaligned32(server_addr, temp);
1673                                 }
1674                                 /*xid = packet.xid; - already is */
1675                                 requested_ip = packet.yiaddr;
1676
1677                                 /* enter requesting state */
1678                                 state = REQUESTING;
1679                                 timeout = 0;
1680                                 packet_num = 0;
1681                                 already_waited_sec = 0;
1682                         }
1683                         continue;
1684                 case REQUESTING:
1685                 case RENEWING:
1686                 case RENEW_REQUESTED:
1687                 case REBINDING:
1688                         if (*message == DHCPACK) {
1689                                 uint32_t lease_seconds;
1690                                 struct in_addr temp_addr;
1691
1692                                 temp = udhcp_get_option(&packet, DHCP_LEASE_TIME);
1693                                 if (!temp) {
1694                                         bb_error_msg("no lease time with ACK, using 1 hour lease");
1695                                         lease_seconds = 60 * 60;
1696                                 } else {
1697                                         /* it IS unaligned sometimes, don't "optimize" */
1698                                         move_from_unaligned32(lease_seconds, temp);
1699                                         lease_seconds = ntohl(lease_seconds);
1700                                         /* paranoia: must not be too small and not prone to overflows */
1701                                         if (lease_seconds < 0x10)
1702                                                 lease_seconds = 0x10;
1703                                         if (lease_seconds >= 0x10000000)
1704                                                 lease_seconds = 0x0fffffff;
1705                                 }
1706 #if ENABLE_FEATURE_UDHCPC_ARPING
1707                                 if (opt & OPT_a) {
1708 /* RFC 2131 3.1 paragraph 5:
1709  * "The client receives the DHCPACK message with configuration
1710  * parameters. The client SHOULD perform a final check on the
1711  * parameters (e.g., ARP for allocated network address), and notes
1712  * the duration of the lease specified in the DHCPACK message. At this
1713  * point, the client is configured. If the client detects that the
1714  * address is already in use (e.g., through the use of ARP),
1715  * the client MUST send a DHCPDECLINE message to the server and restarts
1716  * the configuration process..." */
1717                                         if (!arpping(packet.yiaddr,
1718                                                         NULL,
1719                                                         (uint32_t) 0,
1720                                                         client_config.client_mac,
1721                                                         client_config.interface)
1722                                         ) {
1723                                                 bb_info_msg("Offered address is in use "
1724                                                         "(got ARP reply), declining");
1725                                                 send_decline(/*xid,*/ server_addr, packet.yiaddr);
1726
1727                                                 if (state != REQUESTING)
1728                                                         udhcp_run_script(NULL, "deconfig");
1729                                                 change_listen_mode(LISTEN_RAW);
1730                                                 state = INIT_SELECTING;
1731                                                 client_config.first_secs = 0; /* make secs field count from 0 */
1732                                                 requested_ip = 0;
1733                                                 timeout = tryagain_timeout;
1734                                                 packet_num = 0;
1735                                                 already_waited_sec = 0;
1736                                                 continue; /* back to main loop */
1737                                         }
1738                                 }
1739 #endif
1740                                 /* enter bound state */
1741                                 timeout = lease_seconds / 2;
1742                                 temp_addr.s_addr = packet.yiaddr;
1743                                 bb_info_msg("Lease of %s obtained, lease time %u",
1744                                         inet_ntoa(temp_addr), (unsigned)lease_seconds);
1745                                 requested_ip = packet.yiaddr;
1746                                 udhcp_run_script(&packet, state == REQUESTING ? "bound" : "renew");
1747
1748                                 state = BOUND;
1749                                 change_listen_mode(LISTEN_NONE);
1750                                 if (opt & OPT_q) { /* quit after lease */
1751                                         goto ret0;
1752                                 }
1753                                 /* future renew failures should not exit (JM) */
1754                                 opt &= ~OPT_n;
1755 #if BB_MMU /* NOMMU case backgrounded earlier */
1756                                 if (!(opt & OPT_f)) {
1757                                         client_background();
1758                                         /* do not background again! */
1759                                         opt = ((opt & ~OPT_b) | OPT_f);
1760                                 }
1761 #endif
1762                                 /* make future renew packets use different xid */
1763                                 /* xid = random_xid(); ...but why bother? */
1764                                 already_waited_sec = 0;
1765                                 continue; /* back to main loop */
1766                         }
1767                         if (*message == DHCPNAK) {
1768                                 /* return to init state */
1769                                 bb_info_msg("Received DHCP NAK");
1770                                 udhcp_run_script(&packet, "nak");
1771                                 if (state != REQUESTING)
1772                                         udhcp_run_script(NULL, "deconfig");
1773                                 change_listen_mode(LISTEN_RAW);
1774                                 sleep(3); /* avoid excessive network traffic */
1775                                 state = INIT_SELECTING;
1776                                 client_config.first_secs = 0; /* make secs field count from 0 */
1777                                 requested_ip = 0;
1778                                 timeout = 0;
1779                                 packet_num = 0;
1780                                 already_waited_sec = 0;
1781                         }
1782                         continue;
1783                 /* case BOUND: - ignore all packets */
1784                 /* case RELEASED: - ignore all packets */
1785                 }
1786                 /* back to main loop */
1787         } /* for (;;) - main loop ends */
1788
1789  ret0:
1790         if (opt & OPT_R) /* release on quit */
1791                 perform_release(server_addr, requested_ip);
1792         retval = 0;
1793  ret:
1794         /*if (client_config.pidfile) - remove_pidfile has its own check */
1795                 remove_pidfile(client_config.pidfile);
1796         return retval;
1797 }