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"     Optional_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 #if ENABLE_FEATURE_UDHCPC_SANITIZEOPT
 140 /* Check if a given label represents a valid DNS label
 141  * Return pointer to the first character after the label upon success,
 142  * NULL otherwise.
 143  * See RFC1035, 2.3.1
 144  */
 145 /* We don't need to be particularly anal. For example, allowing _, hyphen
 146  * at the end, or leading and trailing dots would be ok, since it
 147  * can't be used for attacks. (Leading hyphen can be, if someone uses
 148  * cmd "$hostname"
 149  * in the script: then hostname may be treated as an option)
 150  */
 151 static const char *valid_domain_label(const char *label)
 152 {
 153         unsigned char ch;
 154         unsigned pos = 0;
 155
 156         for (;;) {
 157                 ch = *label;
 158                 if ((ch|0x20) < 'a' || (ch|0x20) > 'z') {
 159                         if (pos == 0) {
 160                                 /* label must begin with letter */
 161                                 return NULL;
 162                         }
 163                         if (ch < '0' || ch > '9') {
 164                                 if (ch == '\0' || ch == '.')
 165                                         return label;
 166                                 /* DNS allows only '-', but we are more permissive */
 167                                 if (ch != '-' && ch != '_')
 168                                         return NULL;
 169                         }
 170                 }
 171                 label++;
 172                 pos++;
 173                 //Do we want this?
 174                 //if (pos > 63) /* NS_MAXLABEL; labels must be 63 chars or less */
 175                 //      return NULL;
 176         }
 177 }
 178
 179 /* Check if a given name represents a valid DNS name */
 180 /* See RFC1035, 2.3.1 */
 181 static int good_hostname(const char *name)
 182 {
 183         //const char *start = name;
 184
 185         for (;;) {
 186                 name = valid_domain_label(name);
 187                 if (!name)
 188                         return 0;
 189                 if (!name[0])
 190                         return 1;
 191                         //Do we want this?
 192                         //return ((name - start) < 1025); /* NS_MAXDNAME */
 193                 name++;
 194         }
 195 }
 196 #else
 197 # define good_hostname(name) 1
 198 #endif
 199
 200 /* Create "opt_name=opt_value" string */
 201 static NOINLINE char *xmalloc_optname_optval(uint8_t *option, const struct dhcp_optflag *optflag, const char *opt_name)
 202 {
 203         unsigned upper_length;
 204         int len, type, optlen;
 205         char *dest, *ret;
 206
 207         /* option points to OPT_DATA, need to go back to get OPT_LEN */
 208         len = option[-OPT_DATA + OPT_LEN];
 209
 210         type = optflag->flags & OPTION_TYPE_MASK;
 211         optlen = dhcp_option_lengths[type];
 212         upper_length = len_of_option_as_string[type]
 213                 * ((unsigned)(len + optlen - 1) / (unsigned)optlen);
 214
 215         dest = ret = xmalloc(upper_length + strlen(opt_name) + 2);
 216         dest += sprintf(ret, "%s=", opt_name);
 217
 218         while (len >= optlen) {
 219                 switch (type) {
 220                 case OPTION_IP:
 221                 case OPTION_IP_PAIR:
 222                         dest += sprint_nip(dest, "", option);
 223                         if (type == OPTION_IP)
 224                                 break;
 225                         dest += sprint_nip(dest, "/", option + 4);
 226                         break;
 227 //              case OPTION_BOOLEAN:
 228 //                      dest += sprintf(dest, *option ? "yes" : "no");
 229 //                      break;
 230                 case OPTION_U8:
 231                         dest += sprintf(dest, "%u", *option);
 232                         break;
 233 //              case OPTION_S16:
 234                 case OPTION_U16: {
 235                         uint16_t val_u16;
 236                         move_from_unaligned16(val_u16, option);
 237                         dest += sprintf(dest, "%u", ntohs(val_u16));
 238                         break;
 239                 }
 240                 case OPTION_S32:
 241                 case OPTION_U32: {
 242                         uint32_t val_u32;
 243                         move_from_unaligned32(val_u32, option);
 244                         dest += sprintf(dest, type == OPTION_U32 ? "%lu" : "%ld", (unsigned long) ntohl(val_u32));
 245                         break;
 246                 }
 247                 /* Note: options which use 'return' instead of 'break'
 248                  * (for example, OPTION_STRING) skip the code which handles
 249                  * the case of list of options.
 250                  */
 251                 case OPTION_STRING:
 252                 case OPTION_STRING_HOST:
 253                         memcpy(dest, option, len);
 254                         dest[len] = '\0';
 255                         if (type == OPTION_STRING_HOST && !good_hostname(dest))
 256                                 safe_strncpy(dest, "bad", len);
 257                         return ret;
 258                 case OPTION_STATIC_ROUTES: {
 259                         /* Option binary format:
 260                          * mask [one byte, 0..32]
 261                          * ip [big endian, 0..4 bytes depending on mask]
 262                          * router [big endian, 4 bytes]
 263                          * may be repeated
 264                          *
 265                          * We convert it to a string "IP/MASK ROUTER IP2/MASK2 ROUTER2"
 266                          */
 267                         const char *pfx = "";
 268
 269                         while (len >= 1 + 4) { /* mask + 0-byte ip + router */
 270                                 uint32_t nip;
 271                                 uint8_t *p;
 272                                 unsigned mask;
 273                                 int bytes;
 274
 275                                 mask = *option++;
 276                                 if (mask > 32)
 277                                         break;
 278                                 len--;
 279
 280                                 nip = 0;
 281                                 p = (void*) &nip;
 282                                 bytes = (mask + 7) / 8; /* 0 -> 0, 1..8 -> 1, 9..16 -> 2 etc */
 283                                 while (--bytes >= 0) {
 284                                         *p++ = *option++;
 285                                         len--;
 286                                 }
 287                                 if (len < 4)
 288                                         break;
 289
 290                                 /* print ip/mask */
 291                                 dest += sprint_nip(dest, pfx, (void*) &nip);
 292                                 pfx = " ";
 293                                 dest += sprintf(dest, "/%u ", mask);
 294                                 /* print router */
 295                                 dest += sprint_nip(dest, "", option);
 296                                 option += 4;
 297                                 len -= 4;
 298                         }
 299
 300                         return ret;
 301                 }
 302                 case OPTION_6RD:
 303                         /* Option binary format (see RFC 5969):
 304                          *  0                   1                   2                   3
 305                          *  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
 306                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 307                          * |  OPTION_6RD   | option-length |  IPv4MaskLen  |  6rdPrefixLen |
 308                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 309                          * |                           6rdPrefix                           |
 310                          * ...                        (16 octets)                        ...
 311                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 312                          * ...                   6rdBRIPv4Address(es)                    ...
 313                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 314                          * We convert it to a string
 315                          * "IPv4MaskLen 6rdPrefixLen 6rdPrefix 6rdBRIPv4Address..."
 316                          *
 317                          * Sanity check: ensure that our length is at least 22 bytes, that
 318                          * IPv4MaskLen <= 32,
 319                          * 6rdPrefixLen <= 128,
 320                          * 6rdPrefixLen + (32 - IPv4MaskLen) <= 128
 321                          * (2nd condition need no check - it follows from 1st and 3rd).
 322                          * Else, return envvar with empty value ("optname=")
 323                          */
 324                         if (len >= (1 + 1 + 16 + 4)
 325                          && option[0] <= 32
 326                          && (option[1] + 32 - option[0]) <= 128
 327                         ) {
 328                                 /* IPv4MaskLen */
 329                                 dest += sprintf(dest, "%u ", *option++);
 330                                 /* 6rdPrefixLen */
 331                                 dest += sprintf(dest, "%u ", *option++);
 332                                 /* 6rdPrefix */
 333                                 dest += sprint_nip6(dest, /* "", */ option);
 334                                 option += 16;
 335                                 len -= 1 + 1 + 16 + 4;
 336                                 /* "+ 4" above corresponds to the length of IPv4 addr
 337                                  * we consume in the loop below */
 338                                 while (1) {
 339                                         /* 6rdBRIPv4Address(es) */
 340                                         dest += sprint_nip(dest, " ", option);
 341                                         option += 4;
 342                                         len -= 4; /* do we have yet another 4+ bytes? */
 343                                         if (len < 0)
 344                                                 break; /* no */
 345                                 }
 346                         }
 347
 348                         return ret;
 349 #if ENABLE_FEATURE_UDHCP_RFC3397
 350                 case OPTION_DNS_STRING:
 351                         /* unpack option into dest; use ret for prefix (i.e., "optname=") */
 352                         dest = dname_dec(option, len, ret);
 353                         if (dest) {
 354                                 free(ret);
 355                                 return dest;
 356                         }
 357                         /* error. return "optname=" string */
 358                         return ret;
 359                 case OPTION_SIP_SERVERS:
 360                         /* Option binary format:
 361                          * type: byte
 362                          * type=0: domain names, dns-compressed
 363                          * type=1: IP addrs
 364                          */
 365                         option++;
 366                         len--;
 367                         if (option[-1] == 0) {
 368                                 dest = dname_dec(option, len, ret);
 369                                 if (dest) {
 370                                         free(ret);
 371                                         return dest;
 372                                 }
 373                         } else
 374                         if (option[-1] == 1) {
 375                                 const char *pfx = "";
 376                                 while (1) {
 377                                         len -= 4;
 378                                         if (len < 0)
 379                                                 break;
 380                                         dest += sprint_nip(dest, pfx, option);
 381                                         pfx = " ";
 382                                         option += 4;
 383                                 }
 384                         }
 385                         return ret;
 386 #endif
 387                 } /* switch */
 388
 389                 /* If we are here, try to format any remaining data
 390                  * in the option as another, similarly-formatted option
 391                  */
 392                 option += optlen;
 393                 len -= optlen;
 394 // TODO: it can be a list only if (optflag->flags & OPTION_LIST).
 395 // Should we bail out/warn if we see multi-ip option which is
 396 // not allowed to be such (for example, DHCP_BROADCAST)? -
 397                 if (len < optlen /* || !(optflag->flags & OPTION_LIST) */)
 398                         break;
 399                 *dest++ = ' ';
 400                 *dest = '\0';
 401         } /* while */
 402
 403         return ret;
 404 }
 405
 406 /* put all the parameters into the environment */
 407 static char **fill_envp(struct dhcp_packet *packet)
 408 {
 409         int envc;
 410         int i;
 411         char **envp, **curr;
 412         const char *opt_name;
 413         uint8_t *temp;
 414         uint8_t overload = 0;
 415
 416 #define BITMAP unsigned
 417 #define BBITS (sizeof(BITMAP) * 8)
 418 #define BMASK(i) (1 << (i & (sizeof(BITMAP) * 8 - 1)))
 419 #define FOUND_OPTS(i) (found_opts[(unsigned)i / BBITS])
 420         BITMAP found_opts[256 / BBITS];
 421
 422         memset(found_opts, 0, sizeof(found_opts));
 423
 424         /* We need 6 elements for:
 425          * "interface=IFACE"
 426          * "ip=N.N.N.N" from packet->yiaddr
 427          * "siaddr=IP" from packet->siaddr_nip (unless 0)
 428          * "boot_file=FILE" from packet->file (unless overloaded)
 429          * "sname=SERVER_HOSTNAME" from packet->sname (unless overloaded)
 430          * terminating NULL
 431          */
 432         envc = 6;
 433         /* +1 element for each option, +2 for subnet option: */
 434         if (packet) {
 435                 /* note: do not search for "pad" (0) and "end" (255) options */
 436 //TODO: change logic to scan packet _once_
 437                 for (i = 1; i < 255; i++) {
 438                         temp = udhcp_get_option(packet, i);
 439                         if (temp) {
 440                                 if (i == DHCP_OPTION_OVERLOAD)
 441                                         overload = *temp;
 442                                 else if (i == DHCP_SUBNET)
 443                                         envc++; /* for $mask */
 444                                 envc++;
 445                                 /*if (i != DHCP_MESSAGE_TYPE)*/
 446                                 FOUND_OPTS(i) |= BMASK(i);
 447                         }
 448                 }
 449         }
 450         curr = envp = xzalloc(sizeof(envp[0]) * envc);
 451
 452         *curr = xasprintf("interface=%s", client_config.interface);
 453         putenv(*curr++);
 454
 455         if (!packet)
 456                 return envp;
 457
 458         /* Export BOOTP fields. Fields we don't (yet?) export:
 459          * uint8_t op;      // always BOOTREPLY
 460          * uint8_t htype;   // hardware address type. 1 = 10mb ethernet
 461          * uint8_t hlen;    // hardware address length
 462          * uint8_t hops;    // used by relay agents only
 463          * uint32_t xid;
 464          * uint16_t secs;   // elapsed since client began acquisition/renewal
 465          * uint16_t flags;  // only one flag so far: bcast. Never set by server
 466          * uint32_t ciaddr; // client IP (usually == yiaddr. can it be different
 467          *                  // if during renew server wants to give us differn IP?)
 468          * uint32_t gateway_nip; // relay agent IP address
 469          * uint8_t chaddr[16]; // link-layer client hardware address (MAC)
 470          * TODO: export gateway_nip as $giaddr?
 471          */
 472         /* Most important one: yiaddr as $ip */
 473         *curr = xmalloc(sizeof("ip=255.255.255.255"));
 474         sprint_nip(*curr, "ip=", (uint8_t *) &packet->yiaddr);
 475         putenv(*curr++);
 476         if (packet->siaddr_nip) {
 477                 /* IP address of next server to use in bootstrap */
 478                 *curr = xmalloc(sizeof("siaddr=255.255.255.255"));
 479                 sprint_nip(*curr, "siaddr=", (uint8_t *) &packet->siaddr_nip);
 480                 putenv(*curr++);
 481         }
 482         if (!(overload & FILE_FIELD) && packet->file[0]) {
 483                 /* watch out for invalid packets */
 484                 *curr = xasprintf("boot_file=%."DHCP_PKT_FILE_LEN_STR"s", packet->file);
 485                 putenv(*curr++);
 486         }
 487         if (!(overload & SNAME_FIELD) && packet->sname[0]) {
 488                 /* watch out for invalid packets */
 489                 *curr = xasprintf("sname=%."DHCP_PKT_SNAME_LEN_STR"s", packet->sname);
 490                 putenv(*curr++);
 491         }
 492
 493         /* Export known DHCP options */
 494         opt_name = dhcp_option_strings;
 495         i = 0;
 496         while (*opt_name) {
 497                 uint8_t code = dhcp_optflags[i].code;
 498                 BITMAP *found_ptr = &FOUND_OPTS(code);
 499                 BITMAP found_mask = BMASK(code);
 500                 if (!(*found_ptr & found_mask))
 501                         goto next;
 502                 *found_ptr &= ~found_mask; /* leave only unknown options */
 503                 temp = udhcp_get_option(packet, code);
 504                 *curr = xmalloc_optname_optval(temp, &dhcp_optflags[i], opt_name);
 505                 putenv(*curr++);
 506                 if (code == DHCP_SUBNET) {
 507                         /* Subnet option: make things like "$ip/$mask" possible */
 508                         uint32_t subnet;
 509                         move_from_unaligned32(subnet, temp);
 510                         *curr = xasprintf("mask=%u", mton(subnet));
 511                         putenv(*curr++);
 512                 }
 513  next:
 514                 opt_name += strlen(opt_name) + 1;
 515                 i++;
 516         }
 517         /* Export unknown options */
 518         for (i = 0; i < 256;) {
 519                 BITMAP bitmap = FOUND_OPTS(i);
 520                 if (!bitmap) {
 521                         i += BBITS;
 522                         continue;
 523                 }
 524                 if (bitmap & BMASK(i)) {
 525                         unsigned len, ofs;
 526
 527                         temp = udhcp_get_option(packet, i);
 528                         /* udhcp_get_option returns ptr to data portion,
 529                          * need to go back to get len
 530                          */
 531                         len = temp[-OPT_DATA + OPT_LEN];
 532                         *curr = xmalloc(sizeof("optNNN=") + 1 + len*2);
 533                         ofs = sprintf(*curr, "opt%u=", i);
 534                         *bin2hex(*curr + ofs, (void*) temp, len) = '\0';
 535                         putenv(*curr++);
 536                 }
 537                 i++;
 538         }
 539
 540         return envp;
 541 }
 542
 543 /* Call a script with a par file and env vars */
 544 static void udhcp_run_script(struct dhcp_packet *packet, const char *name)
 545 {
 546         char **envp, **curr;
 547         char *argv[3];
 548
 549         envp = fill_envp(packet);
 550
 551         /* call script */
 552         log1("Executing %s %s", client_config.script, name);
 553         argv[0] = (char*) client_config.script;
 554         argv[1] = (char*) name;
 555         argv[2] = NULL;
 556         spawn_and_wait(argv);
 557
 558         for (curr = envp; *curr; curr++) {
 559                 log2(" %s", *curr);
 560                 bb_unsetenv_and_free(*curr);
 561         }
 562         free(envp);
 563 }
 564
 565
 566 /*** Sending/receiving packets ***/
 567
 568 static ALWAYS_INLINE uint32_t random_xid(void)
 569 {
 570         return rand();
 571 }
 572
 573 /* Initialize the packet with the proper defaults */
 574 static void init_packet(struct dhcp_packet *packet, char type)
 575 {
 576         uint16_t secs;
 577
 578         /* Fill in: op, htype, hlen, cookie fields; message type option: */
 579         udhcp_init_header(packet, type);
 580
 581         packet->xid = random_xid();
 582
 583         client_config.last_secs = monotonic_sec();
 584         if (client_config.first_secs == 0)
 585                 client_config.first_secs = client_config.last_secs;
 586         secs = client_config.last_secs - client_config.first_secs;
 587         packet->secs = htons(secs);
 588
 589         memcpy(packet->chaddr, client_config.client_mac, 6);
 590         if (client_config.clientid)
 591                 udhcp_add_binary_option(packet, client_config.clientid);
 592 }
 593
 594 static void add_client_options(struct dhcp_packet *packet)
 595 {
 596         int i, end, len;
 597
 598         udhcp_add_simple_option(packet, DHCP_MAX_SIZE, htons(IP_UDP_DHCP_SIZE));
 599
 600         /* Add a "param req" option with the list of options we'd like to have
 601          * from stubborn DHCP servers. Pull the data from the struct in common.c.
 602          * No bounds checking because it goes towards the head of the packet. */
 603         end = udhcp_end_option(packet->options);
 604         len = 0;
 605         for (i = 1; i < DHCP_END; i++) {
 606                 if (client_config.opt_mask[i >> 3] & (1 << (i & 7))) {
 607                         packet->options[end + OPT_DATA + len] = i;
 608                         len++;
 609                 }
 610         }
 611         if (len) {
 612                 packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
 613                 packet->options[end + OPT_LEN] = len;
 614                 packet->options[end + OPT_DATA + len] = DHCP_END;
 615         }
 616
 617         if (client_config.vendorclass)
 618                 udhcp_add_binary_option(packet, client_config.vendorclass);
 619         if (client_config.hostname)
 620                 udhcp_add_binary_option(packet, client_config.hostname);
 621         if (client_config.fqdn)
 622                 udhcp_add_binary_option(packet, client_config.fqdn);
 623
 624         /* Request broadcast replies if we have no IP addr */
 625         if ((option_mask32 & OPT_B) && packet->ciaddr == 0)
 626                 packet->flags |= htons(BROADCAST_FLAG);
 627
 628         /* Add -x options if any */
 629         {
 630                 struct option_set *curr = client_config.options;
 631                 while (curr) {
 632                         udhcp_add_binary_option(packet, curr->data);
 633                         curr = curr->next;
 634                 }
 635 //              if (client_config.sname)
 636 //                      strncpy((char*)packet->sname, client_config.sname, sizeof(packet->sname) - 1);
 637 //              if (client_config.boot_file)
 638 //                      strncpy((char*)packet->file, client_config.boot_file, sizeof(packet->file) - 1);
 639         }
 640
 641         // This will be needed if we remove -V VENDOR_STR in favor of
 642         // -x vendor:VENDOR_STR
 643         //if (!udhcp_find_option(packet.options, DHCP_VENDOR))
 644         //      /* not set, set the default vendor ID */
 645         //      ...add (DHCP_VENDOR, "udhcp "BB_VER) opt...
 646 }
 647
 648 /* RFC 2131
 649  * 4.4.4 Use of broadcast and unicast
 650  *
 651  * The DHCP client broadcasts DHCPDISCOVER, DHCPREQUEST and DHCPINFORM
 652  * messages, unless the client knows the address of a DHCP server.
 653  * The client unicasts DHCPRELEASE messages to the server. Because
 654  * the client is declining the use of the IP address supplied by the server,
 655  * the client broadcasts DHCPDECLINE messages.
 656  *
 657  * When the DHCP client knows the address of a DHCP server, in either
 658  * INIT or REBOOTING state, the client may use that address
 659  * in the DHCPDISCOVER or DHCPREQUEST rather than the IP broadcast address.
 660  * The client may also use unicast to send DHCPINFORM messages
 661  * to a known DHCP server. If the client receives no response to DHCP
 662  * messages sent to the IP address of a known DHCP server, the DHCP
 663  * client reverts to using the IP broadcast address.
 664  */
 665
 666 static int raw_bcast_from_client_config_ifindex(struct dhcp_packet *packet)
 667 {
 668         return udhcp_send_raw_packet(packet,
 669                 /*src*/ INADDR_ANY, CLIENT_PORT,
 670                 /*dst*/ INADDR_BROADCAST, SERVER_PORT, MAC_BCAST_ADDR,
 671                 client_config.ifindex);
 672 }
 673
 674 static int bcast_or_ucast(struct dhcp_packet *packet, uint32_t ciaddr, uint32_t server)
 675 {
 676         if (server)
 677                 return udhcp_send_kernel_packet(packet,
 678                         ciaddr, CLIENT_PORT,
 679                         server, SERVER_PORT);
 680         return raw_bcast_from_client_config_ifindex(packet);
 681 }
 682
 683 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
 684 /* NOINLINE: limit stack usage in caller */
 685 static NOINLINE int send_discover(uint32_t xid, uint32_t requested)
 686 {
 687         struct dhcp_packet packet;
 688
 689         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 690          * random xid field (we override it below),
 691          * client-id option (unless -C), message type option:
 692          */
 693         init_packet(&packet, DHCPDISCOVER);
 694
 695         packet.xid = xid;
 696         if (requested)
 697                 udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 698
 699         /* Add options: maxsize,
 700          * optionally: hostname, fqdn, vendorclass,
 701          * "param req" option according to -O, options specified with -x
 702          */
 703         add_client_options(&packet);
 704
 705         bb_info_msg("Sending discover...");
 706         return raw_bcast_from_client_config_ifindex(&packet);
 707 }
 708
 709 /* Broadcast a DHCP request message */
 710 /* RFC 2131 3.1 paragraph 3:
 711  * "The client _broadcasts_ a DHCPREQUEST message..."
 712  */
 713 /* NOINLINE: limit stack usage in caller */
 714 static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requested)
 715 {
 716         struct dhcp_packet packet;
 717         struct in_addr addr;
 718
 719 /*
 720  * RFC 2131 4.3.2 DHCPREQUEST message
 721  * ...
 722  * If the DHCPREQUEST message contains a 'server identifier'
 723  * option, the message is in response to a DHCPOFFER message.
 724  * Otherwise, the message is a request to verify or extend an
 725  * existing lease. If the client uses a 'client identifier'
 726  * in a DHCPREQUEST message, it MUST use that same 'client identifier'
 727  * in all subsequent messages. If the client included a list
 728  * of requested parameters in a DHCPDISCOVER message, it MUST
 729  * include that list in all subsequent messages.
 730  */
 731         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 732          * random xid field (we override it below),
 733          * client-id option (unless -C), message type option:
 734          */
 735         init_packet(&packet, DHCPREQUEST);
 736
 737         packet.xid = xid;
 738         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 739
 740         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 741
 742         /* Add options: maxsize,
 743          * optionally: hostname, fqdn, vendorclass,
 744          * "param req" option according to -O, and options specified with -x
 745          */
 746         add_client_options(&packet);
 747
 748         addr.s_addr = requested;
 749         bb_info_msg("Sending select for %s...", inet_ntoa(addr));
 750         return raw_bcast_from_client_config_ifindex(&packet);
 751 }
 752
 753 /* Unicast or broadcast a DHCP renew message */
 754 /* NOINLINE: limit stack usage in caller */
 755 static NOINLINE int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
 756 {
 757         struct dhcp_packet packet;
 758
 759 /*
 760  * RFC 2131 4.3.2 DHCPREQUEST message
 761  * ...
 762  * DHCPREQUEST generated during RENEWING state:
 763  *
 764  * 'server identifier' MUST NOT be filled in, 'requested IP address'
 765  * option MUST NOT be filled in, 'ciaddr' MUST be filled in with
 766  * client's IP address. In this situation, the client is completely
 767  * configured, and is trying to extend its lease. This message will
 768  * be unicast, so no relay agents will be involved in its
 769  * transmission.  Because 'giaddr' is therefore not filled in, the
 770  * DHCP server will trust the value in 'ciaddr', and use it when
 771  * replying to the client.
 772  */
 773         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 774          * random xid field (we override it below),
 775          * client-id option (unless -C), message type option:
 776          */
 777         init_packet(&packet, DHCPREQUEST);
 778
 779         packet.xid = xid;
 780         packet.ciaddr = ciaddr;
 781
 782         /* Add options: maxsize,
 783          * optionally: hostname, fqdn, vendorclass,
 784          * "param req" option according to -O, and options specified with -x
 785          */
 786         add_client_options(&packet);
 787
 788         bb_info_msg("Sending renew...");
 789         return bcast_or_ucast(&packet, ciaddr, server);
 790 }
 791
 792 #if ENABLE_FEATURE_UDHCPC_ARPING
 793 /* Broadcast a DHCP decline message */
 794 /* NOINLINE: limit stack usage in caller */
 795 static NOINLINE int send_decline(/*uint32_t xid,*/ uint32_t server, uint32_t requested)
 796 {
 797         struct dhcp_packet packet;
 798
 799         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 800          * client-id option (unless -C), message type option:
 801          */
 802         init_packet(&packet, DHCPDECLINE);
 803
 804 #if 0
 805         /* RFC 2131 says DHCPDECLINE's xid is randomly selected by client,
 806          * but in case the server is buggy and wants DHCPDECLINE's xid
 807          * to match the xid which started entire handshake,
 808          * we use the same xid we used in initial DHCPDISCOVER:
 809          */
 810         packet.xid = xid;
 811 #endif
 812         /* DHCPDECLINE uses "requested ip", not ciaddr, to store offered IP */
 813         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 814
 815         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 816
 817         bb_info_msg("Sending decline...");
 818         return raw_bcast_from_client_config_ifindex(&packet);
 819 }
 820 #endif
 821
 822 /* Unicast a DHCP release message */
 823 static int send_release(uint32_t server, uint32_t ciaddr)
 824 {
 825         struct dhcp_packet packet;
 826
 827         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 828          * client-id option (unless -C), message type option:
 829          */
 830         init_packet(&packet, DHCPRELEASE);
 831
 832         /* DHCPRELEASE uses ciaddr, not "requested ip", to store IP being released */
 833         packet.ciaddr = ciaddr;
 834
 835         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 836
 837         bb_info_msg("Sending release...");
 838         /* Note: normally we unicast here since "server" is not zero.
 839          * However, there _are_ people who run "address-less" DHCP servers,
 840          * and reportedly ISC dhcp client and Windows allow that.
 841          */
 842         return bcast_or_ucast(&packet, ciaddr, server);
 843 }
 844
 845 /* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */
 846 /* NOINLINE: limit stack usage in caller */
 847 static NOINLINE int udhcp_recv_raw_packet(struct dhcp_packet *dhcp_pkt, int fd)
 848 {
 849         int bytes;
 850         struct ip_udp_dhcp_packet packet;
 851         uint16_t check;
 852         unsigned char cmsgbuf[CMSG_LEN(sizeof(struct tpacket_auxdata))];
 853         struct iovec iov;
 854         struct msghdr msg;
 855         struct cmsghdr *cmsg;
 856
 857         /* used to use just safe_read(fd, &packet, sizeof(packet))
 858          * but we need to check for TP_STATUS_CSUMNOTREADY :(
 859          */
 860         iov.iov_base = &packet;
 861         iov.iov_len = sizeof(packet);
 862         memset(&msg, 0, sizeof(msg));
 863         msg.msg_iov = &iov;
 864         msg.msg_iovlen = 1;
 865         msg.msg_control = cmsgbuf;
 866         msg.msg_controllen = sizeof(cmsgbuf);
 867         for (;;) {
 868                 bytes = recvmsg(fd, &msg, 0);
 869                 if (bytes < 0) {
 870                         if (errno == EINTR)
 871                                 continue;
 872                         log1("Packet read error, ignoring");
 873                         /* NB: possible down interface, etc. Caller should pause. */
 874                         return bytes; /* returns -1 */
 875                 }
 876                 break;
 877         }
 878
 879         if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) {
 880                 log1("Packet is too short, ignoring");
 881                 return -2;
 882         }
 883
 884         if (bytes < ntohs(packet.ip.tot_len)) {
 885                 /* packet is bigger than sizeof(packet), we did partial read */
 886                 log1("Oversized packet, ignoring");
 887                 return -2;
 888         }
 889
 890         /* ignore any extra garbage bytes */
 891         bytes = ntohs(packet.ip.tot_len);
 892
 893         /* make sure its the right packet for us, and that it passes sanity checks */
 894         if (packet.ip.protocol != IPPROTO_UDP
 895          || packet.ip.version != IPVERSION
 896          || packet.ip.ihl != (sizeof(packet.ip) >> 2)
 897          || packet.udp.dest != htons(CLIENT_PORT)
 898         /* || bytes > (int) sizeof(packet) - can't happen */
 899          || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
 900         ) {
 901                 log1("Unrelated/bogus packet, ignoring");
 902                 return -2;
 903         }
 904
 905         /* verify IP checksum */
 906         check = packet.ip.check;
 907         packet.ip.check = 0;
 908         if (check != inet_cksum((uint16_t *)&packet.ip, sizeof(packet.ip))) {
 909                 log1("Bad IP header checksum, ignoring");
 910                 return -2;
 911         }
 912
 913         for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
 914                 if (cmsg->cmsg_level == SOL_PACKET
 915                  && cmsg->cmsg_type == PACKET_AUXDATA
 916                 ) {
 917                         /* some VMs don't checksum UDP and TCP data
 918                          * they send to the same physical machine,
 919                          * here we detect this case:
 920                          */
 921                         struct tpacket_auxdata *aux = (void *)CMSG_DATA(cmsg);
 922                         if (aux->tp_status & TP_STATUS_CSUMNOTREADY)
 923                                 goto skip_udp_sum_check;
 924                 }
 925         }
 926
 927         /* verify UDP checksum. IP header has to be modified for this */
 928         memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
 929         /* ip.xx fields which are not memset: protocol, check, saddr, daddr */
 930         packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
 931         check = packet.udp.check;
 932         packet.udp.check = 0;
 933         if (check && check != inet_cksum((uint16_t *)&packet, bytes)) {
 934                 log1("Packet with bad UDP checksum received, ignoring");
 935                 return -2;
 936         }
 937  skip_udp_sum_check:
 938
 939         if (packet.data.cookie != htonl(DHCP_MAGIC)) {
 940                 bb_info_msg("Packet with bad magic, ignoring");
 941                 return -2;
 942         }
 943
 944         log1("Received a packet");
 945         udhcp_dump_packet(&packet.data);
 946
 947         bytes -= sizeof(packet.ip) + sizeof(packet.udp);
 948         memcpy(dhcp_pkt, &packet.data, bytes);
 949         return bytes;
 950 }
 951
 952
 953 /*** Main ***/
 954
 955 static int sockfd = -1;
 956
 957 #define LISTEN_NONE   0
 958 #define LISTEN_KERNEL 1
 959 #define LISTEN_RAW    2
 960 static smallint listen_mode;
 961
 962 /* initial state: (re)start DHCP negotiation */
 963 #define INIT_SELECTING  0
 964 /* discover was sent, DHCPOFFER reply received */
 965 #define REQUESTING      1
 966 /* select/renew was sent, DHCPACK reply received */
 967 #define BOUND           2
 968 /* half of lease passed, want to renew it by sending unicast renew requests */
 969 #define RENEWING        3
 970 /* renew requests were not answered, lease is almost over, send broadcast renew */
 971 #define REBINDING       4
 972 /* manually requested renew (SIGUSR1) */
 973 #define RENEW_REQUESTED 5
 974 /* release, possibly manually requested (SIGUSR2) */
 975 #define RELEASED        6
 976 static smallint state;
 977
 978 static int udhcp_raw_socket(int ifindex)
 979 {
 980         int fd;
 981         struct sockaddr_ll sock;
 982
 983         log1("Opening raw socket on ifindex %d", ifindex); //log2?
 984
 985         fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
 986         /* ^^^^^
 987          * SOCK_DGRAM: remove link-layer headers on input (SOCK_RAW keeps them)
 988          * ETH_P_IP: want to receive only packets with IPv4 eth type
 989          */
 990         log1("Got raw socket fd"); //log2?
 991
 992         sock.sll_family = AF_PACKET;
 993         sock.sll_protocol = htons(ETH_P_IP);
 994         sock.sll_ifindex = ifindex;
 995         xbind(fd, (struct sockaddr *) &sock, sizeof(sock));
 996
 997 #if 0 /* Several users reported breakage when BPF filter is used */
 998         if (CLIENT_PORT == 68) {
 999                 /* Use only if standard port is in use */
1000                 /*
1001                  *      I've selected not to see LL header, so BPF doesn't see it, too.
1002                  *      The filter may also pass non-IP and non-ARP packets, but we do
1003                  *      a more complete check when receiving the message in userspace.
1004                  *
1005                  * and filter shamelessly stolen from:
1006                  *
1007                  *      http://www.flamewarmaster.de/software/dhcpclient/
1008                  *
1009                  * There are a few other interesting ideas on that page (look under
1010                  * "Motivation").  Use of netlink events is most interesting.  Think
1011                  * of various network servers listening for events and reconfiguring.
1012                  * That would obsolete sending HUP signals and/or make use of restarts.
1013                  *
1014                  * Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
1015                  * License: GPL v2.
1016                  */
1017                 static const struct sock_filter filter_instr[] = {
1018                         /* load 9th byte (protocol) */
1019                         BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
1020                         /* jump to L1 if it is IPPROTO_UDP, else to L4 */
1021                         BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 0, 6),
1022                         /* L1: load halfword from offset 6 (flags and frag offset) */
1023                         BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 6),
1024                         /* jump to L4 if any bits in frag offset field are set, else to L2 */
1025                         BPF_JUMP(BPF_JMP|BPF_JSET|BPF_K, 0x1fff, 4, 0),
1026                         /* L2: skip IP header (load index reg with header len) */
1027                         BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0),
1028                         /* load udp destination port from halfword[header_len + 2] */
1029                         BPF_STMT(BPF_LD|BPF_H|BPF_IND, 2),
1030                         /* jump to L3 if udp dport is CLIENT_PORT, else to L4 */
1031                         BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 68, 0, 1),
1032                         /* L3: accept packet ("accept 0x7fffffff bytes") */
1033                         /* Accepting 0xffffffff works too but kernel 2.6.19 is buggy */
1034                         BPF_STMT(BPF_RET|BPF_K, 0x7fffffff),
1035                         /* L4: discard packet ("accept zero bytes") */
1036                         BPF_STMT(BPF_RET|BPF_K, 0),
1037                 };
1038                 static const struct sock_fprog filter_prog = {
1039                         .len = sizeof(filter_instr) / sizeof(filter_instr[0]),
1040                         /* casting const away: */
1041                         .filter = (struct sock_filter *) filter_instr,
1042                 };
1043                 /* Ignoring error (kernel may lack support for this) */
1044                 if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
1045                                 sizeof(filter_prog)) >= 0)
1046                         log1("Attached filter to raw socket fd"); // log?
1047         }
1048 #endif
1049
1050         if (setsockopt(fd, SOL_PACKET, PACKET_AUXDATA,
1051                         &const_int_1, sizeof(int)) < 0
1052         ) {
1053                 if (errno != ENOPROTOOPT)
1054                         log1("Can't set PACKET_AUXDATA on raw socket");
1055         }
1056
1057         log1("Created raw socket");
1058
1059         return fd;
1060 }
1061
1062 static void change_listen_mode(int new_mode)
1063 {
1064         log1("Entering listen mode: %s",
1065                 new_mode != LISTEN_NONE
1066                         ? (new_mode == LISTEN_KERNEL ? "kernel" : "raw")
1067                         : "none"
1068         );
1069
1070         listen_mode = new_mode;
1071         if (sockfd >= 0) {
1072                 close(sockfd);
1073                 sockfd = -1;
1074         }
1075         if (new_mode == LISTEN_KERNEL)
1076                 sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
1077         else if (new_mode != LISTEN_NONE)
1078                 sockfd = udhcp_raw_socket(client_config.ifindex);
1079         /* else LISTEN_NONE: sockfd stays closed */
1080 }
1081
1082 /* Called only on SIGUSR1 */
1083 static void perform_renew(void)
1084 {
1085         bb_info_msg("Performing a DHCP renew");
1086         switch (state) {
1087         case BOUND:
1088                 change_listen_mode(LISTEN_KERNEL);
1089         case RENEWING:
1090         case REBINDING:
1091                 state = RENEW_REQUESTED;
1092                 break;
1093         case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
1094                 udhcp_run_script(NULL, "deconfig");
1095         case REQUESTING:
1096         case RELEASED:
1097                 change_listen_mode(LISTEN_RAW);
1098                 state = INIT_SELECTING;
1099                 break;
1100         case INIT_SELECTING:
1101                 break;
1102         }
1103 }
1104
1105 static void perform_release(uint32_t server_addr, uint32_t requested_ip)
1106 {
1107         char buffer[sizeof("255.255.255.255")];
1108         struct in_addr temp_addr;
1109
1110         /* send release packet */
1111         if (state == BOUND || state == RENEWING || state == REBINDING) {
1112                 temp_addr.s_addr = server_addr;
1113                 strcpy(buffer, inet_ntoa(temp_addr));
1114                 temp_addr.s_addr = requested_ip;
1115                 bb_info_msg("Unicasting a release of %s to %s",
1116                                 inet_ntoa(temp_addr), buffer);
1117                 send_release(server_addr, requested_ip); /* unicast */
1118                 udhcp_run_script(NULL, "deconfig");
1119         }
1120         bb_info_msg("Entering released state");
1121
1122         change_listen_mode(LISTEN_NONE);
1123         state = RELEASED;
1124 }
1125
1126 static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
1127 {
1128         uint8_t *storage;
1129         int len = strnlen(str, 255);
1130         storage = xzalloc(len + extra + OPT_DATA);
1131         storage[OPT_CODE] = code;
1132         storage[OPT_LEN] = len + extra;
1133         memcpy(storage + extra + OPT_DATA, str, len);
1134         return storage;
1135 }
1136
1137 #if BB_MMU
1138 static void client_background(void)
1139 {
1140         bb_daemonize(0);
1141         logmode &= ~LOGMODE_STDIO;
1142         /* rewrite pidfile, as our pid is different now */
1143         write_pidfile(client_config.pidfile);
1144 }
1145 #endif
1146
1147 //usage:#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
1148 //usage:# define IF_UDHCP_VERBOSE(...) __VA_ARGS__
1149 //usage:#else
1150 //usage:# define IF_UDHCP_VERBOSE(...)
1151 //usage:#endif
1152 //usage:#define udhcpc_trivial_usage
1153 //usage:       "[-fbq"IF_UDHCP_VERBOSE("v")"RB]"IF_FEATURE_UDHCPC_ARPING(" [-a[MSEC]]")" [-t N] [-T SEC] [-A SEC/-n]\n"
1154 //usage:       "        [-i IFACE]"IF_FEATURE_UDHCP_PORT(" [-P PORT]")" [-s PROG] [-p PIDFILE]\n"
1155 //usage:       "        [-oC] [-r IP] [-V VENDOR] [-F NAME] [-x OPT:VAL]... [-O OPT]..."
1156 //usage:#define udhcpc_full_usage "\n"
1157 //usage:        IF_LONG_OPTS(
1158 //usage:     "\n        -i,--interface IFACE    Interface to use (default eth0)"
1159 //usage:        IF_FEATURE_UDHCP_PORT(
1160 //usage:     "\n        -P,--client-port PORT   Use PORT (default 68)"
1161 //usage:        )
1162 //usage:     "\n        -s,--script PROG        Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
1163 //usage:     "\n        -p,--pidfile FILE       Create pidfile"
1164 //usage:     "\n        -B,--broadcast          Request broadcast replies"
1165 //usage:     "\n        -t,--retries N          Send up to N discover packets (default 3)"
1166 //usage:     "\n        -T,--timeout SEC        Pause between packets (default 3)"
1167 //usage:     "\n        -A,--tryagain SEC       Wait if lease is not obtained (default 20)"
1168 //usage:     "\n        -n,--now                Exit if lease is not obtained"
1169 //usage:     "\n        -q,--quit               Exit after obtaining lease"
1170 //usage:     "\n        -R,--release            Release IP on exit"
1171 //usage:     "\n        -f,--foreground         Run in foreground"
1172 //usage:        USE_FOR_MMU(
1173 //usage:     "\n        -b,--background         Background if lease is not obtained"
1174 //usage:        )
1175 //usage:     "\n        -S,--syslog             Log to syslog too"
1176 //usage:        IF_FEATURE_UDHCPC_ARPING(
1177 //usage:     "\n        -a[MSEC],--arping[=MSEC] Validate offered address with ARP ping"
1178 //usage:        )
1179 //usage:     "\n        -r,--request IP         Request this IP address"
1180 //usage:     "\n        -o,--no-default-options Don't request any options (unless -O is given)"
1181 //usage:     "\n        -O,--request-option OPT Request option OPT from server (cumulative)"
1182 //usage:     "\n        -x OPT:VAL              Include option OPT in sent packets (cumulative)"
1183 //usage:     "\n                                Examples of string, numeric, and hex byte opts:"
1184 //usage:     "\n                                -x hostname:bbox - option 12"
1185 //usage:     "\n                                -x lease:3600 - option 51 (lease time)"
1186 //usage:     "\n                                -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
1187 //usage:     "\n        -F,--fqdn NAME          Ask server to update DNS mapping for NAME"
1188 //usage:     "\n        -V,--vendorclass VENDOR Vendor identifier (default 'udhcp VERSION')"
1189 //usage:     "\n        -C,--clientid-none      Don't send MAC as client identifier"
1190 //usage:        IF_UDHCP_VERBOSE(
1191 //usage:     "\n        -v                      Verbose"
1192 //usage:        )
1193 //usage:        )
1194 //usage:        IF_NOT_LONG_OPTS(
1195 //usage:     "\n        -i IFACE        Interface to use (default eth0)"
1196 //usage:        IF_FEATURE_UDHCP_PORT(
1197 //usage:     "\n        -P PORT         Use PORT (default 68)"
1198 //usage:        )
1199 //usage:     "\n        -s PROG         Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
1200 //usage:     "\n        -p FILE         Create pidfile"
1201 //usage:     "\n        -B              Request broadcast replies"
1202 //usage:     "\n        -t N            Send up to N discover packets (default 3)"
1203 //usage:     "\n        -T SEC          Pause between packets (default 3)"
1204 //usage:     "\n        -A SEC          Wait if lease is not obtained (default 20)"
1205 //usage:     "\n        -n              Exit if lease is not obtained"
1206 //usage:     "\n        -q              Exit after obtaining lease"
1207 //usage:     "\n        -R              Release IP on exit"
1208 //usage:     "\n        -f              Run in foreground"
1209 //usage:        USE_FOR_MMU(
1210 //usage:     "\n        -b              Background if lease is not obtained"
1211 //usage:        )
1212 //usage:     "\n        -S              Log to syslog too"
1213 //usage:        IF_FEATURE_UDHCPC_ARPING(
1214 //usage:     "\n        -a[MSEC]        Validate offered address with ARP ping"
1215 //usage:        )
1216 //usage:     "\n        -r IP           Request this IP address"
1217 //usage:     "\n        -o              Don't request any options (unless -O is given)"
1218 //usage:     "\n        -O OPT          Request option OPT from server (cumulative)"
1219 //usage:     "\n        -x OPT:VAL      Include option OPT in sent packets (cumulative)"
1220 //usage:     "\n                        Examples of string, numeric, and hex byte opts:"
1221 //usage:     "\n                        -x hostname:bbox - option 12"
1222 //usage:     "\n                        -x lease:3600 - option 51 (lease time)"
1223 //usage:     "\n                        -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
1224 //usage:     "\n        -F NAME         Ask server to update DNS mapping for NAME"
1225 //usage:     "\n        -V VENDOR       Vendor identifier (default 'udhcp VERSION')"
1226 //usage:     "\n        -C              Don't send MAC as client identifier"
1227 //usage:        IF_UDHCP_VERBOSE(
1228 //usage:     "\n        -v              Verbose"
1229 //usage:        )
1230 //usage:        )
1231 //usage:     "\nSignals:"
1232 //usage:     "\n        USR1    Renew lease"
1233 //usage:     "\n        USR2    Release lease"
1234
1235
1236 int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
1237 int udhcpc_main(int argc UNUSED_PARAM, char **argv)
1238 {
1239         uint8_t *message;
1240         const char *str_V, *str_h, *str_F, *str_r;
1241         IF_FEATURE_UDHCPC_ARPING(const char *str_a = "2000";)
1242         IF_FEATURE_UDHCP_PORT(char *str_P;)
1243         void *clientid_mac_ptr;
1244         llist_t *list_O = NULL;
1245         llist_t *list_x = NULL;
1246         int tryagain_timeout = 20;
1247         int discover_timeout = 3;
1248         int discover_retries = 3;
1249         uint32_t server_addr = server_addr; /* for compiler */
1250         uint32_t requested_ip = 0;
1251         uint32_t xid = xid; /* for compiler */
1252         int packet_num;
1253         int timeout; /* must be signed */
1254         unsigned already_waited_sec;
1255         unsigned opt;
1256         IF_FEATURE_UDHCPC_ARPING(unsigned arpping_ms;)
1257         int max_fd;
1258         int retval;
1259         fd_set rfds;
1260
1261         /* Default options */
1262         IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;)
1263         IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
1264         client_config.interface = "eth0";
1265         client_config.script = CONFIG_UDHCPC_DEFAULT_SCRIPT;
1266         str_V = "udhcp "BB_VER;
1267
1268         /* Parse command line */
1269         /* O,x: list; -T,-t,-A take numeric param */
1270         opt_complementary = "O::x::T+:t+:A+" IF_UDHCP_VERBOSE(":vv") ;
1271         IF_LONG_OPTS(applet_long_options = udhcpc_longopts;)
1272         opt = getopt32(argv, "CV:H:h:F:i:np:qRr:s:T:t:SA:O:ox:fB"
1273                 USE_FOR_MMU("b")
1274                 IF_FEATURE_UDHCPC_ARPING("a::")
1275                 IF_FEATURE_UDHCP_PORT("P:")
1276                 "v"
1277                 , &str_V, &str_h, &str_h, &str_F
1278                 , &client_config.interface, &client_config.pidfile, &str_r /* i,p */
1279                 , &client_config.script /* s */
1280                 , &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */
1281                 , &list_O
1282                 , &list_x
1283                 IF_FEATURE_UDHCPC_ARPING(, &str_a)
1284                 IF_FEATURE_UDHCP_PORT(, &str_P)
1285                 IF_UDHCP_VERBOSE(, &dhcp_verbose)
1286         );
1287         if (opt & (OPT_h|OPT_H)) {
1288                 //msg added 2011-11
1289                 bb_error_msg("option -h NAME is deprecated, use -x hostname:NAME");
1290                 client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
1291         }
1292         if (opt & OPT_F) {
1293                 /* FQDN option format: [0x51][len][flags][0][0]<fqdn> */
1294                 client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
1295                 /* Flag bits: 0000NEOS
1296                  * S: 1 = Client requests server to update A RR in DNS as well as PTR
1297                  * O: 1 = Server indicates to client that DNS has been updated regardless
1298                  * E: 1 = Name is in DNS format, i.e. <4>host<6>domain<3>com<0>,
1299                  *    not "host.domain.com". Format 0 is obsolete.
1300                  * N: 1 = Client requests server to not update DNS (S must be 0 then)
1301                  * Two [0] bytes which follow are deprecated and must be 0.
1302                  */
1303                 client_config.fqdn[OPT_DATA + 0] = 0x1;
1304                 /*client_config.fqdn[OPT_DATA + 1] = 0; - xzalloc did it */
1305                 /*client_config.fqdn[OPT_DATA + 2] = 0; */
1306         }
1307         if (opt & OPT_r)
1308                 requested_ip = inet_addr(str_r);
1309 #if ENABLE_FEATURE_UDHCP_PORT
1310         if (opt & OPT_P) {
1311                 CLIENT_PORT = xatou16(str_P);
1312                 SERVER_PORT = CLIENT_PORT - 1;
1313         }
1314 #endif
1315         IF_FEATURE_UDHCPC_ARPING(arpping_ms = xatou(str_a);)
1316         while (list_O) {
1317                 char *optstr = llist_pop(&list_O);
1318                 unsigned n = bb_strtou(optstr, NULL, 0);
1319                 if (errno || n > 254) {
1320                         n = udhcp_option_idx(optstr);
1321                         n = dhcp_optflags[n].code;
1322                 }
1323                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
1324         }
1325         if (!(opt & OPT_o)) {
1326                 unsigned i, n;
1327                 for (i = 0; (n = dhcp_optflags[i].code) != 0; i++) {
1328                         if (dhcp_optflags[i].flags & OPTION_REQ) {
1329                                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
1330                         }
1331                 }
1332         }
1333         while (list_x) {
1334                 char *optstr = llist_pop(&list_x);
1335                 char *colon = strchr(optstr, ':');
1336                 if (colon)
1337                         *colon = ' ';
1338                 /* now it looks similar to udhcpd's config file line:
1339                  * "optname optval", using the common routine: */
1340                 udhcp_str2optset(optstr, &client_config.options);
1341         }
1342
1343         if (udhcp_read_interface(client_config.interface,
1344                         &client_config.ifindex,
1345                         NULL,
1346                         client_config.client_mac)
1347         ) {
1348                 return 1;
1349         }
1350
1351         clientid_mac_ptr = NULL;
1352         if (!(opt & OPT_C) && !udhcp_find_option(client_config.options, DHCP_CLIENT_ID)) {
1353                 /* not suppressed and not set, set the default client ID */
1354                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
1355                 client_config.clientid[OPT_DATA] = 1; /* type: ethernet */
1356                 clientid_mac_ptr = client_config.clientid + OPT_DATA+1;
1357                 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1358         }
1359         if (str_V[0] != '\0') {
1360                 // can drop -V, str_V, client_config.vendorclass,
1361                 // but need to add "vendor" to the list of recognized
1362                 // string opts for this to work;
1363                 // and need to tweak add_client_options() too...
1364                 // ...so the question is, should we?
1365                 //bb_error_msg("option -V VENDOR is deprecated, use -x vendor:VENDOR");
1366                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
1367         }
1368
1369 #if !BB_MMU
1370         /* on NOMMU reexec (i.e., background) early */
1371         if (!(opt & OPT_f)) {
1372                 bb_daemonize_or_rexec(0 /* flags */, argv);
1373                 logmode = LOGMODE_NONE;
1374         }
1375 #endif
1376         if (opt & OPT_S) {
1377                 openlog(applet_name, LOG_PID, LOG_DAEMON);
1378                 logmode |= LOGMODE_SYSLOG;
1379         }
1380
1381         /* Make sure fd 0,1,2 are open */
1382         bb_sanitize_stdio();
1383         /* Equivalent of doing a fflush after every \n */
1384         setlinebuf(stdout);
1385         /* Create pidfile */
1386         write_pidfile(client_config.pidfile);
1387         /* Goes to stdout (unless NOMMU) and possibly syslog */
1388         bb_info_msg("%s (v"BB_VER") started", applet_name);
1389         /* Set up the signal pipe */
1390         udhcp_sp_setup();
1391         /* We want random_xid to be random... */
1392         srand(monotonic_us());
1393
1394         state = INIT_SELECTING;
1395         udhcp_run_script(NULL, "deconfig");
1396         change_listen_mode(LISTEN_RAW);
1397         packet_num = 0;
1398         timeout = 0;
1399         already_waited_sec = 0;
1400
1401         /* Main event loop. select() waits on signal pipe and possibly
1402          * on sockfd.
1403          * "continue" statements in code below jump to the top of the loop.
1404          */
1405         for (;;) {
1406                 struct timeval tv;
1407                 struct dhcp_packet packet;
1408                 /* silence "uninitialized!" warning */
1409                 unsigned timestamp_before_wait = timestamp_before_wait;
1410
1411                 //bb_error_msg("sockfd:%d, listen_mode:%d", sockfd, listen_mode);
1412
1413                 /* Was opening raw or udp socket here
1414                  * if (listen_mode != LISTEN_NONE && sockfd < 0),
1415                  * but on fast network renew responses return faster
1416                  * than we open sockets. Thus this code is moved
1417                  * to change_listen_mode(). Thus we open listen socket
1418                  * BEFORE we send renew request (see "case BOUND:"). */
1419
1420                 max_fd = udhcp_sp_fd_set(&rfds, sockfd);
1421
1422                 tv.tv_sec = timeout - already_waited_sec;
1423                 tv.tv_usec = 0;
1424                 retval = 0;
1425                 /* If we already timed out, fall through with retval = 0, else... */
1426                 if ((int)tv.tv_sec > 0) {
1427                         log1("Waiting on select %u seconds", (int)tv.tv_sec);
1428                         timestamp_before_wait = (unsigned)monotonic_sec();
1429                         retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
1430                         if (retval < 0) {
1431                                 /* EINTR? A signal was caught, don't panic */
1432                                 if (errno == EINTR) {
1433                                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1434                                         continue;
1435                                 }
1436                                 /* Else: an error occured, panic! */
1437                                 bb_perror_msg_and_die("select");
1438                         }
1439                 }
1440
1441                 /* If timeout dropped to zero, time to become active:
1442                  * resend discover/renew/whatever
1443                  */
1444                 if (retval == 0) {
1445                         /* When running on a bridge, the ifindex may have changed
1446                          * (e.g. if member interfaces were added/removed
1447                          * or if the status of the bridge changed).
1448                          * Refresh ifindex and client_mac:
1449                          */
1450                         if (udhcp_read_interface(client_config.interface,
1451                                         &client_config.ifindex,
1452                                         NULL,
1453                                         client_config.client_mac)
1454                         ) {
1455                                 goto ret0; /* iface is gone? */
1456                         }
1457                         if (clientid_mac_ptr)
1458                                 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1459
1460                         /* We will restart the wait in any case */
1461                         already_waited_sec = 0;
1462
1463                         switch (state) {
1464                         case INIT_SELECTING:
1465                                 if (!discover_retries || packet_num < discover_retries) {
1466                                         if (packet_num == 0)
1467                                                 xid = random_xid();
1468                                         /* broadcast */
1469                                         send_discover(xid, requested_ip);
1470                                         timeout = discover_timeout;
1471                                         packet_num++;
1472                                         continue;
1473                                 }
1474  leasefail:
1475                                 udhcp_run_script(NULL, "leasefail");
1476 #if BB_MMU /* -b is not supported on NOMMU */
1477                                 if (opt & OPT_b) { /* background if no lease */
1478                                         bb_info_msg("No lease, forking to background");
1479                                         client_background();
1480                                         /* do not background again! */
1481                                         opt = ((opt & ~OPT_b) | OPT_f);
1482                                 } else
1483 #endif
1484                                 if (opt & OPT_n) { /* abort if no lease */
1485                                         bb_info_msg("No lease, failing");
1486                                         retval = 1;
1487                                         goto ret;
1488                                 }
1489                                 /* wait before trying again */
1490                                 timeout = tryagain_timeout;
1491                                 packet_num = 0;
1492                                 continue;
1493                         case REQUESTING:
1494                                 if (!discover_retries || packet_num < discover_retries) {
1495                                         /* send broadcast select packet */
1496                                         send_select(xid, server_addr, requested_ip);
1497                                         timeout = discover_timeout;
1498                                         packet_num++;
1499                                         continue;
1500                                 }
1501                                 /* Timed out, go back to init state.
1502                                  * "discover...select...discover..." loops
1503                                  * were seen in the wild. Treat them similarly
1504                                  * to "no response to discover" case */
1505                                 change_listen_mode(LISTEN_RAW);
1506                                 state = INIT_SELECTING;
1507                                 goto leasefail;
1508                         case BOUND:
1509                                 /* 1/2 lease passed, enter renewing state */
1510                                 state = RENEWING;
1511                                 client_config.first_secs = 0; /* make secs field count from 0 */
1512                                 change_listen_mode(LISTEN_KERNEL);
1513                                 log1("Entering renew state");
1514                                 /* fall right through */
1515                         case RENEW_REQUESTED: /* manual (SIGUSR1) renew */
1516                         case_RENEW_REQUESTED:
1517                         case RENEWING:
1518                                 if (timeout > 60) {
1519                                         /* send an unicast renew request */
1520                         /* Sometimes observed to fail (EADDRNOTAVAIL) to bind
1521                          * a new UDP socket for sending inside send_renew.
1522                          * I hazard to guess existing listening socket
1523                          * is somehow conflicting with it, but why is it
1524                          * not deterministic then?! Strange.
1525                          * Anyway, it does recover by eventually failing through
1526                          * into INIT_SELECTING state.
1527                          */
1528                                         send_renew(xid, server_addr, requested_ip);
1529                                         timeout >>= 1;
1530                                         continue;
1531                                 }
1532                                 /* Timed out, enter rebinding state */
1533                                 log1("Entering rebinding state");
1534                                 state = REBINDING;
1535                                 /* fall right through */
1536                         case REBINDING:
1537                                 /* Switch to bcast receive */
1538                                 change_listen_mode(LISTEN_RAW);
1539                                 /* Lease is *really* about to run out,
1540                                  * try to find DHCP server using broadcast */
1541                                 if (timeout > 0) {
1542                                         /* send a broadcast renew request */
1543                                         send_renew(xid, 0 /*INADDR_ANY*/, requested_ip);
1544                                         timeout >>= 1;
1545                                         continue;
1546                                 }
1547                                 /* Timed out, enter init state */
1548                                 bb_info_msg("Lease lost, entering init state");
1549                                 udhcp_run_script(NULL, "deconfig");
1550                                 state = INIT_SELECTING;
1551                                 client_config.first_secs = 0; /* make secs field count from 0 */
1552                                 /*timeout = 0; - already is */
1553                                 packet_num = 0;
1554                                 continue;
1555                         /* case RELEASED: */
1556                         }
1557                         /* yah, I know, *you* say it would never happen */
1558                         timeout = INT_MAX;
1559                         continue; /* back to main loop */
1560                 } /* if select timed out */
1561
1562                 /* select() didn't timeout, something happened */
1563
1564                 /* Is it a signal? */
1565                 /* note: udhcp_sp_read checks FD_ISSET before reading */
1566                 switch (udhcp_sp_read(&rfds)) {
1567                 case SIGUSR1:
1568                         client_config.first_secs = 0; /* make secs field count from 0 */
1569                         already_waited_sec = 0;
1570                         perform_renew();
1571                         if (state == RENEW_REQUESTED) {
1572                                 /* We might be either on the same network
1573                                  * (in which case renew might work),
1574                                  * or we might be on a completely different one
1575                                  * (in which case renew won't ever succeed).
1576                                  * For the second case, must make sure timeout
1577                                  * is not too big, or else we can send
1578                                  * futile renew requests for hours.
1579                                  * (Ab)use -A TIMEOUT value (usually 20 sec)
1580                                  * as a cap on the timeout.
1581                                  */
1582                                 if (timeout > tryagain_timeout)
1583                                         timeout = tryagain_timeout;
1584                                 goto case_RENEW_REQUESTED;
1585                         }
1586                         /* Start things over */
1587                         packet_num = 0;
1588                         /* Kill any timeouts, user wants this to hurry along */
1589                         timeout = 0;
1590                         continue;
1591                 case SIGUSR2:
1592                         perform_release(server_addr, requested_ip);
1593                         timeout = INT_MAX;
1594                         continue;
1595                 case SIGTERM:
1596                         bb_info_msg("Received SIGTERM");
1597                         goto ret0;
1598                 }
1599
1600                 /* Is it a packet? */
1601                 if (listen_mode == LISTEN_NONE || !FD_ISSET(sockfd, &rfds))
1602                         continue; /* no */
1603
1604                 {
1605                         int len;
1606
1607                         /* A packet is ready, read it */
1608                         if (listen_mode == LISTEN_KERNEL)
1609                                 len = udhcp_recv_kernel_packet(&packet, sockfd);
1610                         else
1611                                 len = udhcp_recv_raw_packet(&packet, sockfd);
1612                         if (len == -1) {
1613                                 /* Error is severe, reopen socket */
1614                                 bb_info_msg("Read error: %s, reopening socket", strerror(errno));
1615                                 sleep(discover_timeout); /* 3 seconds by default */
1616                                 change_listen_mode(listen_mode); /* just close and reopen */
1617                         }
1618                         /* If this packet will turn out to be unrelated/bogus,
1619                          * we will go back and wait for next one.
1620                          * Be sure timeout is properly decreased. */
1621                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1622                         if (len < 0)
1623                                 continue;
1624                 }
1625
1626                 if (packet.xid != xid) {
1627                         log1("xid %x (our is %x), ignoring packet",
1628                                 (unsigned)packet.xid, (unsigned)xid);
1629                         continue;
1630                 }
1631
1632                 /* Ignore packets that aren't for us */
1633                 if (packet.hlen != 6
1634                  || memcmp(packet.chaddr, client_config.client_mac, 6) != 0
1635                 ) {
1636 //FIXME: need to also check that last 10 bytes are zero
1637                         log1("chaddr does not match, ignoring packet"); // log2?
1638                         continue;
1639                 }
1640
1641                 message = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
1642                 if (message == NULL) {
1643                         bb_error_msg("no message type option, ignoring packet");
1644                         continue;
1645                 }
1646
1647                 switch (state) {
1648                 case INIT_SELECTING:
1649                         /* Must be a DHCPOFFER */
1650                         if (*message == DHCPOFFER) {
1651                                 uint8_t *temp;
1652
1653 /* What exactly is server's IP? There are several values.
1654  * Example DHCP offer captured with tchdump:
1655  *
1656  * 10.34.25.254:67 > 10.34.25.202:68 // IP header's src
1657  * BOOTP fields:
1658  * Your-IP 10.34.25.202
1659  * Server-IP 10.34.32.125   // "next server" IP
1660  * Gateway-IP 10.34.25.254  // relay's address (if DHCP relays are in use)
1661  * DHCP options:
1662  * DHCP-Message Option 53, length 1: Offer
1663  * Server-ID Option 54, length 4: 10.34.255.7       // "server ID"
1664  * Default-Gateway Option 3, length 4: 10.34.25.254 // router
1665  *
1666  * We think that real server IP (one to use in renew/release)
1667  * is one in Server-ID option. But I am not 100% sure.
1668  * IP header's src and Gateway-IP (same in this example)
1669  * might work too.
1670  * "Next server" and router are definitely wrong ones to use, though...
1671  */
1672 /* We used to ignore pcakets without DHCP_SERVER_ID.
1673  * I've got user reports from people who run "address-less" servers.
1674  * They either supply DHCP_SERVER_ID of 0.0.0.0 or don't supply it at all.
1675  * They say ISC DHCP client supports this case.
1676  */
1677                                 server_addr = 0;
1678                                 temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
1679                                 if (!temp) {
1680                                         bb_error_msg("no server ID, using 0.0.0.0");
1681                                 } else {
1682                                         /* it IS unaligned sometimes, don't "optimize" */
1683                                         move_from_unaligned32(server_addr, temp);
1684                                 }
1685                                 /*xid = packet.xid; - already is */
1686                                 requested_ip = packet.yiaddr;
1687
1688                                 /* enter requesting state */
1689                                 state = REQUESTING;
1690                                 timeout = 0;
1691                                 packet_num = 0;
1692                                 already_waited_sec = 0;
1693                         }
1694                         continue;
1695                 case REQUESTING:
1696                 case RENEWING:
1697                 case RENEW_REQUESTED:
1698                 case REBINDING:
1699                         if (*message == DHCPACK) {
1700                                 unsigned start;
1701                                 uint32_t lease_seconds;
1702                                 struct in_addr temp_addr;
1703                                 uint8_t *temp;
1704
1705                                 temp = udhcp_get_option(&packet, DHCP_LEASE_TIME);
1706                                 if (!temp) {
1707                                         bb_error_msg("no lease time with ACK, using 1 hour lease");
1708                                         lease_seconds = 60 * 60;
1709                                 } else {
1710                                         /* it IS unaligned sometimes, don't "optimize" */
1711                                         move_from_unaligned32(lease_seconds, temp);
1712                                         lease_seconds = ntohl(lease_seconds);
1713                                         /* paranoia: must not be too small and not prone to overflows */
1714                                         if (lease_seconds < 0x10)
1715                                                 lease_seconds = 0x10;
1716                                         if (lease_seconds >= 0x10000000)
1717                                                 lease_seconds = 0x0fffffff;
1718                                 }
1719 #if ENABLE_FEATURE_UDHCPC_ARPING
1720                                 if (opt & OPT_a) {
1721 /* RFC 2131 3.1 paragraph 5:
1722  * "The client receives the DHCPACK message with configuration
1723  * parameters. The client SHOULD perform a final check on the
1724  * parameters (e.g., ARP for allocated network address), and notes
1725  * the duration of the lease specified in the DHCPACK message. At this
1726  * point, the client is configured. If the client detects that the
1727  * address is already in use (e.g., through the use of ARP),
1728  * the client MUST send a DHCPDECLINE message to the server and restarts
1729  * the configuration process..." */
1730                                         if (!arpping(packet.yiaddr,
1731                                                         NULL,
1732                                                         (uint32_t) 0,
1733                                                         client_config.client_mac,
1734                                                         client_config.interface,
1735                                                         arpping_ms)
1736                                         ) {
1737                                                 bb_info_msg("Offered address is in use "
1738                                                         "(got ARP reply), declining");
1739                                                 send_decline(/*xid,*/ server_addr, packet.yiaddr);
1740
1741                                                 if (state != REQUESTING)
1742                                                         udhcp_run_script(NULL, "deconfig");
1743                                                 change_listen_mode(LISTEN_RAW);
1744                                                 state = INIT_SELECTING;
1745                                                 client_config.first_secs = 0; /* make secs field count from 0 */
1746                                                 requested_ip = 0;
1747                                                 timeout = tryagain_timeout;
1748                                                 packet_num = 0;
1749                                                 already_waited_sec = 0;
1750                                                 continue; /* back to main loop */
1751                                         }
1752                                 }
1753 #endif
1754                                 /* enter bound state */
1755                                 temp_addr.s_addr = packet.yiaddr;
1756                                 bb_info_msg("Lease of %s obtained, lease time %u",
1757                                         inet_ntoa(temp_addr), (unsigned)lease_seconds);
1758                                 requested_ip = packet.yiaddr;
1759
1760                                 start = monotonic_sec();
1761                                 udhcp_run_script(&packet, state == REQUESTING ? "bound" : "renew");
1762                                 already_waited_sec = (unsigned)monotonic_sec() - start;
1763                                 timeout = lease_seconds / 2;
1764                                 if ((unsigned)timeout < already_waited_sec) {
1765                                         /* Something went wrong. Back to discover state */
1766                                         timeout = already_waited_sec = 0;
1767                                 }
1768
1769                                 state = BOUND;
1770                                 change_listen_mode(LISTEN_NONE);
1771                                 if (opt & OPT_q) { /* quit after lease */
1772                                         goto ret0;
1773                                 }
1774                                 /* future renew failures should not exit (JM) */
1775                                 opt &= ~OPT_n;
1776 #if BB_MMU /* NOMMU case backgrounded earlier */
1777                                 if (!(opt & OPT_f)) {
1778                                         client_background();
1779                                         /* do not background again! */
1780                                         opt = ((opt & ~OPT_b) | OPT_f);
1781                                 }
1782 #endif
1783                                 /* make future renew packets use different xid */
1784                                 /* xid = random_xid(); ...but why bother? */
1785
1786                                 continue; /* back to main loop */
1787                         }
1788                         if (*message == DHCPNAK) {
1789                                 /* If network has more than one DHCP server,
1790                                  * "wrong" server can reply first, with a NAK.
1791                                  * Do not interpret it as a NAK from "our" server.
1792                                  */
1793                                 if (server_addr != 0) {
1794                                         uint32_t svid;
1795                                         uint8_t *temp;
1796
1797                                         temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
1798                                         if (!temp) {
1799  non_matching_svid:
1800                                                 log1("%s with wrong server ID, ignoring packet",
1801                                                         "Received DHCP NAK"
1802                                                 );
1803                                                 continue;
1804                                         }
1805                                         move_from_unaligned32(svid, temp);
1806                                         if (svid != server_addr)
1807                                                 goto non_matching_svid;
1808                                 }
1809                                 /* return to init state */
1810                                 bb_info_msg("Received DHCP NAK");
1811                                 udhcp_run_script(&packet, "nak");
1812                                 if (state != REQUESTING)
1813                                         udhcp_run_script(NULL, "deconfig");
1814                                 change_listen_mode(LISTEN_RAW);
1815                                 sleep(3); /* avoid excessive network traffic */
1816                                 state = INIT_SELECTING;
1817                                 client_config.first_secs = 0; /* make secs field count from 0 */
1818                                 requested_ip = 0;
1819                                 timeout = 0;
1820                                 packet_num = 0;
1821                                 already_waited_sec = 0;
1822                         }
1823                         continue;
1824                 /* case BOUND: - ignore all packets */
1825                 /* case RELEASED: - ignore all packets */
1826                 }
1827                 /* back to main loop */
1828         } /* for (;;) - main loop ends */
1829
1830  ret0:
1831         if (opt & OPT_R) /* release on quit */
1832                 perform_release(server_addr, requested_ip);
1833         retval = 0;
1834  ret:
1835         /*if (client_config.pidfile) - remove_pidfile has its own check */
1836                 remove_pidfile(client_config.pidfile);
1837         return retval;
1838 }