networking/udhcp/dhcpc.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * udhcp client
   4  *
   5  * Russ Dill <Russ.Dill@asu.edu> July 2001
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20  */
  21 #include <syslog.h>
  22 /* Override ENABLE_FEATURE_PIDFILE - ifupdown needs our pidfile to always exist */
  23 #define WANT_PIDFILE 1
  24 #include "common.h"
  25 #include "dhcpd.h"
  26 #include "dhcpc.h"
  27
  28 #include <netinet/if_ether.h>
  29 #include <netpacket/packet.h>
  30 #include <linux/filter.h>
  31
  32 /* struct client_config_t client_config is in bb_common_bufsiz1 */
  33
  34
  35 #if ENABLE_LONG_OPTS
  36 static const char udhcpc_longopts[] ALIGN1 =
  37         "clientid-none\0"  No_argument       "C"
  38         "vendorclass\0"    Required_argument "V"
  39         "hostname\0"       Required_argument "H"
  40         "fqdn\0"           Required_argument "F"
  41         "interface\0"      Required_argument "i"
  42         "now\0"            No_argument       "n"
  43         "pidfile\0"        Required_argument "p"
  44         "quit\0"           No_argument       "q"
  45         "release\0"        No_argument       "R"
  46         "request\0"        Required_argument "r"
  47         "script\0"         Required_argument "s"
  48         "timeout\0"        Required_argument "T"
  49         "version\0"        No_argument       "v"
  50         "retries\0"        Required_argument "t"
  51         "tryagain\0"       Required_argument "A"
  52         "syslog\0"         No_argument       "S"
  53         "request-option\0" Required_argument "O"
  54         "no-default-options\0" No_argument   "o"
  55         "foreground\0"     No_argument       "f"
  56         "background\0"     No_argument       "b"
  57         "broadcast\0"      No_argument       "B"
  58         IF_FEATURE_UDHCPC_ARPING("arping\0"     No_argument       "a")
  59         IF_FEATURE_UDHCP_PORT("client-port\0"   Required_argument "P")
  60         ;
  61 #endif
  62 /* Must match getopt32 option string order */
  63 enum {
  64         OPT_C = 1 << 0,
  65         OPT_V = 1 << 1,
  66         OPT_H = 1 << 2,
  67         OPT_h = 1 << 3,
  68         OPT_F = 1 << 4,
  69         OPT_i = 1 << 5,
  70         OPT_n = 1 << 6,
  71         OPT_p = 1 << 7,
  72         OPT_q = 1 << 8,
  73         OPT_R = 1 << 9,
  74         OPT_r = 1 << 10,
  75         OPT_s = 1 << 11,
  76         OPT_T = 1 << 12,
  77         OPT_t = 1 << 13,
  78         OPT_S = 1 << 14,
  79         OPT_A = 1 << 15,
  80         OPT_O = 1 << 16,
  81         OPT_o = 1 << 17,
  82         OPT_x = 1 << 18,
  83         OPT_f = 1 << 19,
  84         OPT_B = 1 << 20,
  85 /* The rest has variable bit positions, need to be clever */
  86         OPTBIT_B = 20,
  87         USE_FOR_MMU(             OPTBIT_b,)
  88         IF_FEATURE_UDHCPC_ARPING(OPTBIT_a,)
  89         IF_FEATURE_UDHCP_PORT(   OPTBIT_P,)
  90         USE_FOR_MMU(             OPT_b = 1 << OPTBIT_b,)
  91         IF_FEATURE_UDHCPC_ARPING(OPT_a = 1 << OPTBIT_a,)
  92         IF_FEATURE_UDHCP_PORT(   OPT_P = 1 << OPTBIT_P,)
  93 };
  94
  95
  96 /*** Script execution code ***/
  97
  98 /* get a rough idea of how long an option will be (rounding up...) */
  99 static const uint8_t len_of_option_as_string[] = {
 100         [OPTION_IP              ] = sizeof("255.255.255.255 "),
 101         [OPTION_IP_PAIR         ] = sizeof("255.255.255.255 ") * 2,
 102         [OPTION_STATIC_ROUTES   ] = sizeof("255.255.255.255/32 255.255.255.255 "),
 103         [OPTION_6RD             ] = sizeof("32 128 ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 255.255.255.255 "),
 104         [OPTION_STRING          ] = 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 static int sprint_nip6(char *dest, /*const char *pre,*/ const uint8_t *ip)
 128 {
 129         char hexstrbuf[16 * 2];
 130         bin2hex(hexstrbuf, (void*)ip, 16);
 131         return sprintf(dest, /* "%s" */
 132                 "%.4s:%.4s:%.4s:%.4s:%.4s:%.4s:%.4s:%.4s",
 133                 /* pre, */
 134                 hexstrbuf + 0 * 4,
 135                 hexstrbuf + 1 * 4,
 136                 hexstrbuf + 2 * 4,
 137                 hexstrbuf + 3 * 4,
 138                 hexstrbuf + 4 * 4,
 139                 hexstrbuf + 5 * 4,
 140                 hexstrbuf + 6 * 4,
 141                 hexstrbuf + 7 * 4
 142         );
 143 }
 144
 145 /* really simple implementation, just count the bits */
 146 static int mton(uint32_t mask)
 147 {
 148         int i = 0;
 149         mask = ntohl(mask); /* 111110000-like bit pattern */
 150         while (mask) {
 151                 i++;
 152                 mask <<= 1;
 153         }
 154         return i;
 155 }
 156
 157 /* Create "opt_name=opt_value" string */
 158 static NOINLINE char *xmalloc_optname_optval(uint8_t *option, const struct dhcp_optflag *optflag, const char *opt_name)
 159 {
 160         unsigned upper_length;
 161         int len, type, optlen;
 162         char *dest, *ret;
 163
 164         /* option points to OPT_DATA, need to go back and get OPT_LEN */
 165         len = option[OPT_LEN - OPT_DATA];
 166
 167         type = optflag->flags & OPTION_TYPE_MASK;
 168         optlen = dhcp_option_lengths[type];
 169         upper_length = len_of_option_as_string[type]
 170                 * ((unsigned)(len + optlen - 1) / (unsigned)optlen);
 171
 172         dest = ret = xmalloc(upper_length + strlen(opt_name) + 2);
 173         dest += sprintf(ret, "%s=", opt_name);
 174
 175         while (len >= optlen) {
 176                 unsigned ip_ofs = 0;
 177
 178                 switch (type) {
 179                 case OPTION_IP_PAIR:
 180                         dest += sprint_nip(dest, "", option);
 181                         *dest++ = '/';
 182                         ip_ofs = 4;
 183                         /* fall through */
 184                 case OPTION_IP:
 185                         dest += sprint_nip(dest, "", option + ip_ofs);
 186                         break;
 187 //              case OPTION_BOOLEAN:
 188 //                      dest += sprintf(dest, *option ? "yes" : "no");
 189 //                      break;
 190                 case OPTION_U8:
 191                         dest += sprintf(dest, "%u", *option);
 192                         break;
 193 //              case OPTION_S16:
 194                 case OPTION_U16: {
 195                         uint16_t val_u16;
 196                         move_from_unaligned16(val_u16, option);
 197                         dest += sprintf(dest, "%u", ntohs(val_u16));
 198                         break;
 199                 }
 200                 case OPTION_S32:
 201                 case OPTION_U32: {
 202                         uint32_t val_u32;
 203                         move_from_unaligned32(val_u32, option);
 204                         dest += sprintf(dest, type == OPTION_U32 ? "%lu" : "%ld", (unsigned long) ntohl(val_u32));
 205                         break;
 206                 }
 207                 case OPTION_STRING:
 208                         memcpy(dest, option, len);
 209                         dest[len] = '\0';
 210                         return ret;      /* Short circuit this case */
 211                 case OPTION_STATIC_ROUTES: {
 212                         /* Option binary format:
 213                          * mask [one byte, 0..32]
 214                          * ip [big endian, 0..4 bytes depending on mask]
 215                          * router [big endian, 4 bytes]
 216                          * may be repeated
 217                          *
 218                          * We convert it to a string "IP/MASK ROUTER IP2/MASK2 ROUTER2"
 219                          */
 220                         const char *pfx = "";
 221
 222                         while (len >= 1 + 4) { /* mask + 0-byte ip + router */
 223                                 uint32_t nip;
 224                                 uint8_t *p;
 225                                 unsigned mask;
 226                                 int bytes;
 227
 228                                 mask = *option++;
 229                                 if (mask > 32)
 230                                         break;
 231                                 len--;
 232
 233                                 nip = 0;
 234                                 p = (void*) &nip;
 235                                 bytes = (mask + 7) / 8; /* 0 -> 0, 1..8 -> 1, 9..16 -> 2 etc */
 236                                 while (--bytes >= 0) {
 237                                         *p++ = *option++;
 238                                         len--;
 239                                 }
 240                                 if (len < 4)
 241                                         break;
 242
 243                                 /* print ip/mask */
 244                                 dest += sprint_nip(dest, pfx, (void*) &nip);
 245                                 pfx = " ";
 246                                 dest += sprintf(dest, "/%u ", mask);
 247                                 /* print router */
 248                                 dest += sprint_nip(dest, "", option);
 249                                 option += 4;
 250                                 len -= 4;
 251                         }
 252
 253                         return ret;
 254                 }
 255                 case OPTION_6RD: {
 256                         /* Option binary format (see RFC 5969):
 257                          * 0                   1                   2                   3
 258                          * 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
 259                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 260                          * |  OPTION_6RD   | option-length |  IPv4MaskLen  |  6rdPrefixLen |
 261                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 262                          * |                                                               |
 263                          * |                           6rdPrefix                           |
 264                          * |                          (16 octets)                          |
 265                          * |                                                               |
 266                          * |                                                               |
 267                          * |                                                               |
 268                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 269                          * |                     6rdBRIPv4Address(es)                      |
 270                          * .                                                               .
 271                          * .                                                               .
 272                          * .                                                               .
 273                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 274                          *
 275                          * We convert it to a string
 276                          * "IPv4MaskLen 6rdPrefixLen 6rdPrefix 6rdBRIPv4Address..."
 277                          */
 278
 279                         /* Sanity check: ensure that our length is at least 22 bytes, that
 280                          * IPv4MaskLen <= 32,
 281                          * 6rdPrefixLen <= 128,
 282                          * 6rdPrefixLen + (32 - IPv4MaskLen) <= 128
 283                          * (2nd condition need no check - it follows from 1st and 3rd).
 284                          * If any of these requirements is not fulfilled, return with empty
 285                          * value.
 286                          */
 287                         if (len >= 22
 288                          && option[0] <= 32
 289                          && (option[1] + 32 - option[0]) <= 128
 290                         ) {
 291                                 /* IPv4MaskLen */
 292                                 dest += sprintf(dest, "%u ", *option++);
 293                                 /* 6rdPrefixLen */
 294                                 dest += sprintf(dest, "%u ", *option++);
 295                                 /* 6rdPrefix */
 296                                 dest += sprint_nip6(dest, /* "", */ option);
 297                                 option += 16;
 298                                 len -= 1 + 1 + 16;
 299                                 /* 6rdBRIPv4Address(es) */
 300                                 while (1) {
 301                                         dest += sprint_nip(dest, " ", option);
 302                                         option += 4;
 303                                         len -= 4;
 304                                         if (len < 0)
 305                                                 break;
 306                                 }
 307                         }
 308
 309                         return ret;
 310                 }
 311 #if ENABLE_FEATURE_UDHCP_RFC3397
 312                 case OPTION_DNS_STRING:
 313                         /* unpack option into dest; use ret for prefix (i.e., "optname=") */
 314                         dest = dname_dec(option, len, ret);
 315                         if (dest) {
 316                                 free(ret);
 317                                 return dest;
 318                         }
 319                         /* error. return "optname=" string */
 320                         return ret;
 321                 case OPTION_SIP_SERVERS:
 322                         /* Option binary format:
 323                          * type: byte
 324                          * type=0: domain names, dns-compressed
 325                          * type=1: IP addrs
 326                          */
 327                         option++;
 328                         len--;
 329                         if (option[-1] == 0) {
 330                                 dest = dname_dec(option, len, ret);
 331                                 if (dest) {
 332                                         free(ret);
 333                                         return dest;
 334                                 }
 335                         } else
 336                         if (option[-1] == 1) {
 337                                 const char *pfx = "";
 338                                 while (1) {
 339                                         len -= 4;
 340                                         if (len < 0)
 341                                                 break;
 342                                         dest += sprint_nip(dest, pfx, option);
 343                                         pfx = " ";
 344                                         option += 4;
 345                                 }
 346                         }
 347                         return ret;
 348 #endif
 349                 } /* switch */
 350                 option += optlen;
 351                 len -= optlen;
 352 // TODO: it can be a list only if (optflag->flags & OPTION_LIST).
 353 // Should we bail out/warn if we see multi-ip option which is
 354 // not allowed to be such (for example, DHCP_BROADCAST)? -
 355                 if (len <= 0 /* || !(optflag->flags & OPTION_LIST) */)
 356                         break;
 357                 *dest++ = ' ';
 358                 *dest = '\0';
 359         }
 360         return ret;
 361 }
 362
 363 /* put all the parameters into the environment */
 364 static char **fill_envp(struct dhcp_packet *packet)
 365 {
 366         int envc;
 367         int i;
 368         char **envp, **curr;
 369         const char *opt_name;
 370         uint8_t *temp;
 371         uint8_t overload = 0;
 372
 373 #define BITMAP unsigned
 374 #define BBITS (sizeof(BITMAP) * 8)
 375 #define BMASK(i) (1 << (i & (sizeof(BITMAP) * 8 - 1)))
 376 #define FOUND_OPTS(i) (found_opts[(unsigned)i / BBITS])
 377         BITMAP found_opts[256 / BBITS];
 378
 379         memset(found_opts, 0, sizeof(found_opts));
 380
 381         /* We need 6 elements for:
 382          * "interface=IFACE"
 383          * "ip=N.N.N.N" from packet->yiaddr
 384          * "siaddr=IP" from packet->siaddr_nip (unless 0)
 385          * "boot_file=FILE" from packet->file (unless overloaded)
 386          * "sname=SERVER_HOSTNAME" from packet->sname (unless overloaded)
 387          * terminating NULL
 388          */
 389         envc = 6;
 390         /* +1 element for each option, +2 for subnet option: */
 391         if (packet) {
 392                 /* note: do not search for "pad" (0) and "end" (255) options */
 393                 for (i = 1; i < 255; i++) {
 394                         temp = udhcp_get_option(packet, i);
 395                         if (temp) {
 396                                 if (i == DHCP_OPTION_OVERLOAD)
 397                                         overload = *temp;
 398                                 else if (i == DHCP_SUBNET)
 399                                         envc++; /* for mton */
 400                                 envc++;
 401                                 /*if (i != DHCP_MESSAGE_TYPE)*/
 402                                 FOUND_OPTS(i) |= BMASK(i);
 403                         }
 404                 }
 405         }
 406         curr = envp = xzalloc(sizeof(envp[0]) * envc);
 407
 408         *curr = xasprintf("interface=%s", client_config.interface);
 409         putenv(*curr++);
 410
 411         if (!packet)
 412                 return envp;
 413
 414         *curr = xmalloc(sizeof("ip=255.255.255.255"));
 415         sprint_nip(*curr, "ip=", (uint8_t *) &packet->yiaddr);
 416         putenv(*curr++);
 417
 418         opt_name = dhcp_option_strings;
 419         i = 0;
 420         while (*opt_name) {
 421                 uint8_t code = dhcp_optflags[i].code;
 422                 BITMAP *found_ptr = &FOUND_OPTS(code);
 423                 BITMAP found_mask = BMASK(code);
 424                 if (!(*found_ptr & found_mask))
 425                         goto next;
 426                 *found_ptr &= ~found_mask; /* leave only unknown options */
 427                 temp = udhcp_get_option(packet, code);
 428                 *curr = xmalloc_optname_optval(temp, &dhcp_optflags[i], opt_name);
 429                 putenv(*curr++);
 430                 if (code == DHCP_SUBNET) {
 431                         /* Subnet option: make things like "$ip/$mask" possible */
 432                         uint32_t subnet;
 433                         move_from_unaligned32(subnet, temp);
 434                         *curr = xasprintf("mask=%d", mton(subnet));
 435                         putenv(*curr++);
 436                 }
 437  next:
 438                 opt_name += strlen(opt_name) + 1;
 439                 i++;
 440         }
 441         if (packet->siaddr_nip) {
 442                 *curr = xmalloc(sizeof("siaddr=255.255.255.255"));
 443                 sprint_nip(*curr, "siaddr=", (uint8_t *) &packet->siaddr_nip);
 444                 putenv(*curr++);
 445         }
 446         if (!(overload & FILE_FIELD) && packet->file[0]) {
 447                 /* watch out for invalid packets */
 448                 *curr = xasprintf("boot_file=%."DHCP_PKT_FILE_LEN_STR"s", packet->file);
 449                 putenv(*curr++);
 450         }
 451         if (!(overload & SNAME_FIELD) && packet->sname[0]) {
 452                 /* watch out for invalid packets */
 453                 *curr = xasprintf("sname=%."DHCP_PKT_SNAME_LEN_STR"s", packet->sname);
 454                 putenv(*curr++);
 455         }
 456         /* Handle unknown options */
 457         for (i = 0; i < 256;) {
 458                 BITMAP bitmap = FOUND_OPTS(i);
 459                 if (!bitmap) {
 460                         i += BBITS;
 461                         continue;
 462                 }
 463                 if (bitmap & BMASK(i)) {
 464                         unsigned len, ofs;
 465
 466                         temp = udhcp_get_option(packet, i);
 467                         /* udhcp_get_option returns ptr to data portion,
 468                          * need to go back to get len
 469                          */
 470                         len = temp[-OPT_DATA + OPT_LEN];
 471                         *curr = xmalloc(sizeof("optNNN=") + 1 + len*2);
 472                         ofs = sprintf(*curr, "opt%u=", i);
 473                         *bin2hex(*curr + ofs, (void*) temp, len) = '\0';
 474                         putenv(*curr++);
 475                 }
 476                 i++;
 477         }
 478         return envp;
 479 }
 480
 481 /* Call a script with a par file and env vars */
 482 static void udhcp_run_script(struct dhcp_packet *packet, const char *name)
 483 {
 484         char **envp, **curr;
 485         char *argv[3];
 486
 487         if (client_config.script == NULL)
 488                 return;
 489
 490         envp = fill_envp(packet);
 491
 492         /* call script */
 493         log1("Executing %s %s", client_config.script, name);
 494         argv[0] = (char*) client_config.script;
 495         argv[1] = (char*) name;
 496         argv[2] = NULL;
 497         spawn_and_wait(argv);
 498
 499         for (curr = envp; *curr; curr++) {
 500                 log2(" %s", *curr);
 501                 bb_unsetenv_and_free(*curr);
 502         }
 503         free(envp);
 504 }
 505
 506
 507 /*** Sending/receiving packets ***/
 508
 509 static ALWAYS_INLINE uint32_t random_xid(void)
 510 {
 511         return rand();
 512 }
 513
 514 /* Initialize the packet with the proper defaults */
 515 static void init_packet(struct dhcp_packet *packet, char type)
 516 {
 517         uint16_t secs;
 518
 519         /* Fill in: op, htype, hlen, cookie fields; message type option: */
 520         udhcp_init_header(packet, type);
 521
 522         packet->xid = random_xid();
 523
 524         client_config.last_secs = monotonic_sec();
 525         if (client_config.first_secs == 0)
 526                 client_config.first_secs = client_config.last_secs;
 527         secs = client_config.last_secs - client_config.first_secs;
 528         packet->secs = htons(secs);
 529
 530         memcpy(packet->chaddr, client_config.client_mac, 6);
 531         if (client_config.clientid)
 532                 udhcp_add_binary_option(packet, client_config.clientid);
 533 }
 534
 535 static void add_client_options(struct dhcp_packet *packet)
 536 {
 537         uint8_t c;
 538         int i, end, len;
 539
 540         udhcp_add_simple_option(packet, DHCP_MAX_SIZE, htons(IP_UDP_DHCP_SIZE));
 541
 542         /* Add a "param req" option with the list of options we'd like to have
 543          * from stubborn DHCP servers. Pull the data from the struct in common.c.
 544          * No bounds checking because it goes towards the head of the packet. */
 545         end = udhcp_end_option(packet->options);
 546         len = 0;
 547         for (i = 0; (c = dhcp_optflags[i].code) != 0; i++) {
 548                 if ((   (dhcp_optflags[i].flags & OPTION_REQ)
 549                      && !client_config.no_default_options
 550                     )
 551                  || (client_config.opt_mask[c >> 3] & (1 << (c & 7)))
 552                 ) {
 553                         packet->options[end + OPT_DATA + len] = c;
 554                         len++;
 555                 }
 556         }
 557         if (len) {
 558                 packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
 559                 packet->options[end + OPT_LEN] = len;
 560                 packet->options[end + OPT_DATA + len] = DHCP_END;
 561         }
 562
 563         if (client_config.vendorclass)
 564                 udhcp_add_binary_option(packet, client_config.vendorclass);
 565         if (client_config.hostname)
 566                 udhcp_add_binary_option(packet, client_config.hostname);
 567         if (client_config.fqdn)
 568                 udhcp_add_binary_option(packet, client_config.fqdn);
 569
 570         /* Request broadcast replies if we have no IP addr */
 571         if ((option_mask32 & OPT_B) && packet->ciaddr == 0)
 572                 packet->flags |= htons(BROADCAST_FLAG);
 573
 574         /* Add -x options if any */
 575         {
 576                 struct option_set *curr = client_config.options;
 577                 while (curr) {
 578                         udhcp_add_binary_option(packet, curr->data);
 579                         curr = curr->next;
 580                 }
 581 //              if (client_config.sname)
 582 //                      strncpy((char*)packet->sname, client_config.sname, sizeof(packet->sname) - 1);
 583 //              if (client_config.boot_file)
 584 //                      strncpy((char*)packet->file, client_config.boot_file, sizeof(packet->file) - 1);
 585         }
 586 }
 587
 588 /* RFC 2131
 589  * 4.4.4 Use of broadcast and unicast
 590  *
 591  * The DHCP client broadcasts DHCPDISCOVER, DHCPREQUEST and DHCPINFORM
 592  * messages, unless the client knows the address of a DHCP server.
 593  * The client unicasts DHCPRELEASE messages to the server. Because
 594  * the client is declining the use of the IP address supplied by the server,
 595  * the client broadcasts DHCPDECLINE messages.
 596  *
 597  * When the DHCP client knows the address of a DHCP server, in either
 598  * INIT or REBOOTING state, the client may use that address
 599  * in the DHCPDISCOVER or DHCPREQUEST rather than the IP broadcast address.
 600  * The client may also use unicast to send DHCPINFORM messages
 601  * to a known DHCP server. If the client receives no response to DHCP
 602  * messages sent to the IP address of a known DHCP server, the DHCP
 603  * client reverts to using the IP broadcast address.
 604  */
 605
 606 static int raw_bcast_from_client_config_ifindex(struct dhcp_packet *packet)
 607 {
 608         return udhcp_send_raw_packet(packet,
 609                 /*src*/ INADDR_ANY, CLIENT_PORT,
 610                 /*dst*/ INADDR_BROADCAST, SERVER_PORT, MAC_BCAST_ADDR,
 611                 client_config.ifindex);
 612 }
 613
 614 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
 615 /* NOINLINE: limit stack usage in caller */
 616 static NOINLINE int send_discover(uint32_t xid, uint32_t requested)
 617 {
 618         struct dhcp_packet packet;
 619
 620         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 621          * random xid field (we override it below),
 622          * client-id option (unless -C), message type option:
 623          */
 624         init_packet(&packet, DHCPDISCOVER);
 625
 626         packet.xid = xid;
 627         if (requested)
 628                 udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 629
 630         /* Add options: maxsize,
 631          * optionally: hostname, fqdn, vendorclass,
 632          * "param req" option according to -O, options specified with -x
 633          */
 634         add_client_options(&packet);
 635
 636         bb_info_msg("Sending discover...");
 637         return raw_bcast_from_client_config_ifindex(&packet);
 638 }
 639
 640 /* Broadcast a DHCP request message */
 641 /* RFC 2131 3.1 paragraph 3:
 642  * "The client _broadcasts_ a DHCPREQUEST message..."
 643  */
 644 /* NOINLINE: limit stack usage in caller */
 645 static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requested)
 646 {
 647         struct dhcp_packet packet;
 648         struct in_addr addr;
 649
 650 /*
 651  * RFC 2131 4.3.2 DHCPREQUEST message
 652  * ...
 653  * If the DHCPREQUEST message contains a 'server identifier'
 654  * option, the message is in response to a DHCPOFFER message.
 655  * Otherwise, the message is a request to verify or extend an
 656  * existing lease. If the client uses a 'client identifier'
 657  * in a DHCPREQUEST message, it MUST use that same 'client identifier'
 658  * in all subsequent messages. If the client included a list
 659  * of requested parameters in a DHCPDISCOVER message, it MUST
 660  * include that list in all subsequent messages.
 661  */
 662         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 663          * random xid field (we override it below),
 664          * client-id option (unless -C), message type option:
 665          */
 666         init_packet(&packet, DHCPREQUEST);
 667
 668         packet.xid = xid;
 669         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 670
 671         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 672
 673         /* Add options: maxsize,
 674          * optionally: hostname, fqdn, vendorclass,
 675          * "param req" option according to -O, and options specified with -x
 676          */
 677         add_client_options(&packet);
 678
 679         addr.s_addr = requested;
 680         bb_info_msg("Sending select for %s...", inet_ntoa(addr));
 681         return raw_bcast_from_client_config_ifindex(&packet);
 682 }
 683
 684 /* Unicast or broadcast a DHCP renew message */
 685 /* NOINLINE: limit stack usage in caller */
 686 static NOINLINE int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
 687 {
 688         struct dhcp_packet packet;
 689
 690 /*
 691  * RFC 2131 4.3.2 DHCPREQUEST message
 692  * ...
 693  * DHCPREQUEST generated during RENEWING state:
 694  *
 695  * 'server identifier' MUST NOT be filled in, 'requested IP address'
 696  * option MUST NOT be filled in, 'ciaddr' MUST be filled in with
 697  * client's IP address. In this situation, the client is completely
 698  * configured, and is trying to extend its lease. This message will
 699  * be unicast, so no relay agents will be involved in its
 700  * transmission.  Because 'giaddr' is therefore not filled in, the
 701  * DHCP server will trust the value in 'ciaddr', and use it when
 702  * replying to the client.
 703  */
 704         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 705          * random xid field (we override it below),
 706          * client-id option (unless -C), message type option:
 707          */
 708         init_packet(&packet, DHCPREQUEST);
 709
 710         packet.xid = xid;
 711         packet.ciaddr = ciaddr;
 712
 713         /* Add options: maxsize,
 714          * optionally: hostname, fqdn, vendorclass,
 715          * "param req" option according to -O, and options specified with -x
 716          */
 717         add_client_options(&packet);
 718
 719         bb_info_msg("Sending renew...");
 720         if (server)
 721                 return udhcp_send_kernel_packet(&packet,
 722                         ciaddr, CLIENT_PORT,
 723                         server, SERVER_PORT);
 724         return raw_bcast_from_client_config_ifindex(&packet);
 725 }
 726
 727 #if ENABLE_FEATURE_UDHCPC_ARPING
 728 /* Broadcast a DHCP decline message */
 729 /* NOINLINE: limit stack usage in caller */
 730 static NOINLINE int send_decline(uint32_t xid, uint32_t server, uint32_t requested)
 731 {
 732         struct dhcp_packet packet;
 733
 734         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 735          * client-id option (unless -C), message type option:
 736          */
 737         init_packet(&packet, DHCPDECLINE);
 738
 739         /* RFC 2131 says DHCPDECLINE's xid is randomly selected by client,
 740          * but in case the server is buggy and wants DHCPDECLINE's xid
 741          * to match the xid which started entire handshake,
 742          * we use the same xid we used in initial DHCPDISCOVER:
 743          */
 744         packet.xid = xid;
 745         /* DHCPDECLINE uses "requested ip", not ciaddr, to store offered IP */
 746         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 747
 748         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 749
 750         bb_info_msg("Sending decline...");
 751         return raw_bcast_from_client_config_ifindex(&packet);
 752 }
 753 #endif
 754
 755 /* Unicast a DHCP release message */
 756 static int send_release(uint32_t server, uint32_t ciaddr)
 757 {
 758         struct dhcp_packet packet;
 759
 760         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 761          * client-id option (unless -C), message type option:
 762          */
 763         init_packet(&packet, DHCPRELEASE);
 764
 765         /* DHCPRELEASE uses ciaddr, not "requested ip", to store IP being released */
 766         packet.ciaddr = ciaddr;
 767
 768         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 769
 770         bb_info_msg("Sending release...");
 771         return udhcp_send_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
 772 }
 773
 774 /* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */
 775 /* NOINLINE: limit stack usage in caller */
 776 static NOINLINE int udhcp_recv_raw_packet(struct dhcp_packet *dhcp_pkt, int fd)
 777 {
 778         int bytes;
 779         struct ip_udp_dhcp_packet packet;
 780         uint16_t check;
 781
 782         memset(&packet, 0, sizeof(packet));
 783         bytes = safe_read(fd, &packet, sizeof(packet));
 784         if (bytes < 0) {
 785                 log1("Packet read error, ignoring");
 786                 /* NB: possible down interface, etc. Caller should pause. */
 787                 return bytes; /* returns -1 */
 788         }
 789
 790         if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) {
 791                 log1("Packet is too short, ignoring");
 792                 return -2;
 793         }
 794
 795         if (bytes < ntohs(packet.ip.tot_len)) {
 796                 /* packet is bigger than sizeof(packet), we did partial read */
 797                 log1("Oversized packet, ignoring");
 798                 return -2;
 799         }
 800
 801         /* ignore any extra garbage bytes */
 802         bytes = ntohs(packet.ip.tot_len);
 803
 804         /* make sure its the right packet for us, and that it passes sanity checks */
 805         if (packet.ip.protocol != IPPROTO_UDP
 806          || packet.ip.version != IPVERSION
 807          || packet.ip.ihl != (sizeof(packet.ip) >> 2)
 808          || packet.udp.dest != htons(CLIENT_PORT)
 809         /* || bytes > (int) sizeof(packet) - can't happen */
 810          || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
 811         ) {
 812                 log1("Unrelated/bogus packet, ignoring");
 813                 return -2;
 814         }
 815
 816         /* verify IP checksum */
 817         check = packet.ip.check;
 818         packet.ip.check = 0;
 819         if (check != inet_cksum((uint16_t *)&packet.ip, sizeof(packet.ip))) {
 820                 log1("Bad IP header checksum, ignoring");
 821                 return -2;
 822         }
 823
 824         /* verify UDP checksum. IP header has to be modified for this */
 825         memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
 826         /* ip.xx fields which are not memset: protocol, check, saddr, daddr */
 827         packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
 828         check = packet.udp.check;
 829         packet.udp.check = 0;
 830         if (check && check != inet_cksum((uint16_t *)&packet, bytes)) {
 831                 log1("Packet with bad UDP checksum received, ignoring");
 832                 return -2;
 833         }
 834
 835         if (packet.data.cookie != htonl(DHCP_MAGIC)) {
 836                 bb_info_msg("Packet with bad magic, ignoring");
 837                 return -2;
 838         }
 839
 840         log1("Got valid DHCP packet");
 841         udhcp_dump_packet(&packet.data);
 842
 843         bytes -= sizeof(packet.ip) + sizeof(packet.udp);
 844         memcpy(dhcp_pkt, &packet.data, bytes);
 845         return bytes;
 846 }
 847
 848
 849 /*** Main ***/
 850
 851 static int sockfd = -1;
 852
 853 #define LISTEN_NONE   0
 854 #define LISTEN_KERNEL 1
 855 #define LISTEN_RAW    2
 856 static smallint listen_mode;
 857
 858 /* initial state: (re)start DHCP negotiation */
 859 #define INIT_SELECTING  0
 860 /* discover was sent, DHCPOFFER reply received */
 861 #define REQUESTING      1
 862 /* select/renew was sent, DHCPACK reply received */
 863 #define BOUND           2
 864 /* half of lease passed, want to renew it by sending unicast renew requests */
 865 #define RENEWING        3
 866 /* renew requests were not answered, lease is almost over, send broadcast renew */
 867 #define REBINDING       4
 868 /* manually requested renew (SIGUSR1) */
 869 #define RENEW_REQUESTED 5
 870 /* release, possibly manually requested (SIGUSR2) */
 871 #define RELEASED        6
 872 static smallint state;
 873
 874 static int udhcp_raw_socket(int ifindex)
 875 {
 876         int fd;
 877         struct sockaddr_ll sock;
 878
 879         /*
 880          * Comment:
 881          *
 882          *      I've selected not to see LL header, so BPF doesn't see it, too.
 883          *      The filter may also pass non-IP and non-ARP packets, but we do
 884          *      a more complete check when receiving the message in userspace.
 885          *
 886          * and filter shamelessly stolen from:
 887          *
 888          *      http://www.flamewarmaster.de/software/dhcpclient/
 889          *
 890          * There are a few other interesting ideas on that page (look under
 891          * "Motivation").  Use of netlink events is most interesting.  Think
 892          * of various network servers listening for events and reconfiguring.
 893          * That would obsolete sending HUP signals and/or make use of restarts.
 894          *
 895          * Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
 896          * License: GPL v2.
 897          *
 898          * TODO: make conditional?
 899          */
 900         static const struct sock_filter filter_instr[] = {
 901                 /* load 9th byte (protocol) */
 902                 BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
 903                 /* jump to L1 if it is IPPROTO_UDP, else to L4 */
 904                 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 0, 6),
 905                 /* L1: load halfword from offset 6 (flags and frag offset) */
 906                 BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 6),
 907                 /* jump to L4 if any bits in frag offset field are set, else to L2 */
 908                 BPF_JUMP(BPF_JMP|BPF_JSET|BPF_K, 0x1fff, 4, 0),
 909                 /* L2: skip IP header (load index reg with header len) */
 910                 BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0),
 911                 /* load udp destination port from halfword[header_len + 2] */
 912                 BPF_STMT(BPF_LD|BPF_H|BPF_IND, 2),
 913                 /* jump to L3 if udp dport is CLIENT_PORT, else to L4 */
 914                 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 68, 0, 1),
 915                 /* L3: accept packet */
 916                 BPF_STMT(BPF_RET|BPF_K, 0xffffffff),
 917                 /* L4: discard packet */
 918                 BPF_STMT(BPF_RET|BPF_K, 0),
 919         };
 920         static const struct sock_fprog filter_prog = {
 921                 .len = sizeof(filter_instr) / sizeof(filter_instr[0]),
 922                 /* casting const away: */
 923                 .filter = (struct sock_filter *) filter_instr,
 924         };
 925
 926         log1("Opening raw socket on ifindex %d", ifindex); //log2?
 927
 928         fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
 929         log1("Got raw socket fd %d", fd); //log2?
 930
 931         sock.sll_family = AF_PACKET;
 932         sock.sll_protocol = htons(ETH_P_IP);
 933         sock.sll_ifindex = ifindex;
 934         xbind(fd, (struct sockaddr *) &sock, sizeof(sock));
 935
 936         if (CLIENT_PORT == 68) {
 937                 /* Use only if standard port is in use */
 938                 /* Ignoring error (kernel may lack support for this) */
 939                 if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
 940                                 sizeof(filter_prog)) >= 0)
 941                         log1("Attached filter to raw socket fd %d", fd); // log?
 942         }
 943
 944         log1("Created raw socket");
 945
 946         return fd;
 947 }
 948
 949 static void change_listen_mode(int new_mode)
 950 {
 951         log1("Entering listen mode: %s",
 952                 new_mode != LISTEN_NONE
 953                         ? (new_mode == LISTEN_KERNEL ? "kernel" : "raw")
 954                         : "none"
 955         );
 956
 957         listen_mode = new_mode;
 958         if (sockfd >= 0) {
 959                 close(sockfd);
 960                 sockfd = -1;
 961         }
 962         if (new_mode == LISTEN_KERNEL)
 963                 sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
 964         else if (new_mode != LISTEN_NONE)
 965                 sockfd = udhcp_raw_socket(client_config.ifindex);
 966         /* else LISTEN_NONE: sockfd stays closed */
 967 }
 968
 969 /* Called only on SIGUSR1 */
 970 static void perform_renew(void)
 971 {
 972         bb_info_msg("Performing a DHCP renew");
 973         switch (state) {
 974         case BOUND:
 975                 change_listen_mode(LISTEN_KERNEL);
 976         case RENEWING:
 977         case REBINDING:
 978                 state = RENEW_REQUESTED;
 979                 break;
 980         case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
 981                 udhcp_run_script(NULL, "deconfig");
 982         case REQUESTING:
 983         case RELEASED:
 984                 change_listen_mode(LISTEN_RAW);
 985                 state = INIT_SELECTING;
 986                 break;
 987         case INIT_SELECTING:
 988                 break;
 989         }
 990 }
 991
 992 static void perform_release(uint32_t requested_ip, uint32_t server_addr)
 993 {
 994         char buffer[sizeof("255.255.255.255")];
 995         struct in_addr temp_addr;
 996
 997         /* send release packet */
 998         if (state == BOUND || state == RENEWING || state == REBINDING) {
 999                 temp_addr.s_addr = server_addr;
1000                 strcpy(buffer, inet_ntoa(temp_addr));
1001                 temp_addr.s_addr = requested_ip;
1002                 bb_info_msg("Unicasting a release of %s to %s",
1003                                 inet_ntoa(temp_addr), buffer);
1004                 send_release(server_addr, requested_ip); /* unicast */
1005                 udhcp_run_script(NULL, "deconfig");
1006         }
1007         bb_info_msg("Entering released state");
1008
1009         change_listen_mode(LISTEN_NONE);
1010         state = RELEASED;
1011 }
1012
1013 static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
1014 {
1015         uint8_t *storage;
1016         int len = strnlen(str, 255);
1017         storage = xzalloc(len + extra + OPT_DATA);
1018         storage[OPT_CODE] = code;
1019         storage[OPT_LEN] = len + extra;
1020         memcpy(storage + extra + OPT_DATA, str, len);
1021         return storage;
1022 }
1023
1024 #if BB_MMU
1025 static void client_background(void)
1026 {
1027         bb_daemonize(0);
1028         logmode &= ~LOGMODE_STDIO;
1029         /* rewrite pidfile, as our pid is different now */
1030         write_pidfile(client_config.pidfile);
1031 }
1032 #endif
1033
1034 //usage:#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
1035 //usage:# define IF_UDHCP_VERBOSE(...) __VA_ARGS__
1036 //usage:#else
1037 //usage:# define IF_UDHCP_VERBOSE(...)
1038 //usage:#endif
1039 //usage:#define udhcpc_trivial_usage
1040 //usage:       "[-fbnq"IF_UDHCP_VERBOSE("v")"oCRB] [-i IFACE] [-r IP] [-s PROG] [-p PIDFILE]\n"
1041 //usage:       "        [-H HOSTNAME] [-V VENDOR] [-x OPT:VAL]... [-O OPT]..." IF_FEATURE_UDHCP_PORT(" [-P N]")
1042 //usage:#define udhcpc_full_usage "\n"
1043 //usage:        IF_LONG_OPTS(
1044 //usage:     "\n        -i,--interface IFACE    Interface to use (default eth0)"
1045 //usage:     "\n        -p,--pidfile FILE       Create pidfile"
1046 //usage:     "\n        -s,--script PROG        Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
1047 //usage:     "\n        -B,--broadcast          Request broadcast replies"
1048 //usage:     "\n        -t,--retries N          Send up to N discover packets"
1049 //usage:     "\n        -T,--timeout N          Pause between packets (default 3 seconds)"
1050 //usage:     "\n        -A,--tryagain N         Wait N seconds after failure (default 20)"
1051 //usage:     "\n        -f,--foreground         Run in foreground"
1052 //usage:        USE_FOR_MMU(
1053 //usage:     "\n        -b,--background         Background if lease is not obtained"
1054 //usage:        )
1055 //usage:     "\n        -n,--now                Exit if lease is not obtained"
1056 //usage:     "\n        -q,--quit               Exit after obtaining lease"
1057 //usage:     "\n        -R,--release            Release IP on exit"
1058 //usage:     "\n        -S,--syslog             Log to syslog too"
1059 //usage:        IF_FEATURE_UDHCP_PORT(
1060 //usage:     "\n        -P,--client-port N      Use port N (default 68)"
1061 //usage:        )
1062 //usage:        IF_FEATURE_UDHCPC_ARPING(
1063 //usage:     "\n        -a,--arping             Use arping to validate offered address"
1064 //usage:        )
1065 //usage:     "\n        -O,--request-option OPT Request option OPT from server (cumulative)"
1066 //usage:     "\n        -o,--no-default-options Don't request any options (unless -O is given)"
1067 //usage:     "\n        -r,--request IP         Request this IP address"
1068 //usage:     "\n        -x OPT:VAL              Include option OPT in sent packets (cumulative)"
1069 //usage:     "\n                                Examples of string, numeric, and hex byte opts:"
1070 //usage:     "\n                                -x hostname:bbox - option 12"
1071 //usage:     "\n                                -x lease:3600 - option 51 (lease time)"
1072 //usage:     "\n                                -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
1073 //usage:     "\n        -F,--fqdn NAME          Ask server to update DNS mapping for NAME"
1074 //usage:     "\n        -H,-h,--hostname NAME   Send NAME as client hostname (default none)"
1075 //usage:     "\n        -V,--vendorclass VENDOR Vendor identifier (default 'udhcp VERSION')"
1076 //usage:     "\n        -C,--clientid-none      Don't send MAC as client identifier"
1077 //usage:        IF_UDHCP_VERBOSE(
1078 //usage:     "\n        -v                      Verbose"
1079 //usage:        )
1080 //usage:        )
1081 //usage:        IF_NOT_LONG_OPTS(
1082 //usage:     "\n        -i IFACE        Interface to use (default eth0)"
1083 //usage:     "\n        -p FILE         Create pidfile"
1084 //usage:     "\n        -s PROG         Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
1085 //usage:     "\n        -B              Request broadcast replies"
1086 //usage:     "\n        -t N            Send up to N discover packets"
1087 //usage:     "\n        -T N            Pause between packets (default 3 seconds)"
1088 //usage:     "\n        -A N            Wait N seconds (default 20) after failure"
1089 //usage:     "\n        -f              Run in foreground"
1090 //usage:        USE_FOR_MMU(
1091 //usage:     "\n        -b              Background if lease is not obtained"
1092 //usage:        )
1093 //usage:     "\n        -n              Exit if lease is not obtained"
1094 //usage:     "\n        -q              Exit after obtaining lease"
1095 //usage:     "\n        -R              Release IP on exit"
1096 //usage:     "\n        -S              Log to syslog too"
1097 //usage:        IF_FEATURE_UDHCP_PORT(
1098 //usage:     "\n        -P N            Use port N (default 68)"
1099 //usage:        )
1100 //usage:        IF_FEATURE_UDHCPC_ARPING(
1101 //usage:     "\n        -a              Use arping to validate offered address"
1102 //usage:        )
1103 //usage:     "\n        -O OPT          Request option OPT from server (cumulative)"
1104 //usage:     "\n        -o              Don't request any options (unless -O is given)"
1105 //usage:     "\n        -r IP           Request this IP address"
1106 //usage:     "\n        -x OPT:VAL      Include option OPT in sent packets (cumulative)"
1107 //usage:     "\n                        Examples of string, numeric, and hex byte opts:"
1108 //usage:     "\n                        -x hostname:bbox - option 12"
1109 //usage:     "\n                        -x lease:3600 - option 51 (lease time)"
1110 //usage:     "\n                        -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
1111 //usage:     "\n        -F NAME         Ask server to update DNS mapping for NAME"
1112 //usage:     "\n        -H,-h NAME      Send NAME as client hostname (default none)"
1113 //usage:     "\n        -V VENDOR       Vendor identifier (default 'udhcp VERSION')"
1114 //usage:     "\n        -C              Don't send MAC as client identifier"
1115 //usage:        IF_UDHCP_VERBOSE(
1116 //usage:     "\n        -v              Verbose"
1117 //usage:        )
1118 //usage:        )
1119 //usage:     "\nSignals:"
1120 //usage:     "\n        USR1    Renew current lease"
1121 //usage:     "\n        USR2    Release current lease"
1122
1123
1124 int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
1125 int udhcpc_main(int argc UNUSED_PARAM, char **argv)
1126 {
1127         uint8_t *temp, *message;
1128         const char *str_V, *str_h, *str_F, *str_r;
1129         IF_FEATURE_UDHCP_PORT(char *str_P;)
1130         void *clientid_mac_ptr;
1131         llist_t *list_O = NULL;
1132         llist_t *list_x = NULL;
1133         int tryagain_timeout = 20;
1134         int discover_timeout = 3;
1135         int discover_retries = 3;
1136         uint32_t server_addr = server_addr; /* for compiler */
1137         uint32_t requested_ip = 0;
1138         uint32_t xid = 0;
1139         uint32_t lease_seconds = 0; /* can be given as 32-bit quantity */
1140         int packet_num;
1141         int timeout; /* must be signed */
1142         unsigned already_waited_sec;
1143         unsigned opt;
1144         int max_fd;
1145         int retval;
1146         struct timeval tv;
1147         struct dhcp_packet packet;
1148         fd_set rfds;
1149
1150         /* Default options */
1151         IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;)
1152         IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
1153         client_config.interface = "eth0";
1154         client_config.script = CONFIG_UDHCPC_DEFAULT_SCRIPT;
1155         str_V = "udhcp "BB_VER;
1156
1157         /* Parse command line */
1158         /* O,x: list; -T,-t,-A take numeric param */
1159         opt_complementary = "O::x::T+:t+:A+" IF_UDHCP_VERBOSE(":vv") ;
1160         IF_LONG_OPTS(applet_long_options = udhcpc_longopts;)
1161         opt = getopt32(argv, "CV:H:h:F:i:np:qRr:s:T:t:SA:O:ox:fB"
1162                 USE_FOR_MMU("b")
1163                 IF_FEATURE_UDHCPC_ARPING("a")
1164                 IF_FEATURE_UDHCP_PORT("P:")
1165                 "v"
1166                 , &str_V, &str_h, &str_h, &str_F
1167                 , &client_config.interface, &client_config.pidfile, &str_r /* i,p */
1168                 , &client_config.script /* s */
1169                 , &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */
1170                 , &list_O
1171                 , &list_x
1172                 IF_FEATURE_UDHCP_PORT(, &str_P)
1173                 IF_UDHCP_VERBOSE(, &dhcp_verbose)
1174                 );
1175         if (opt & (OPT_h|OPT_H))
1176                 client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
1177         if (opt & OPT_F) {
1178                 /* FQDN option format: [0x51][len][flags][0][0]<fqdn> */
1179                 client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
1180                 /* Flag bits: 0000NEOS
1181                  * S: 1 = Client requests server to update A RR in DNS as well as PTR
1182                  * O: 1 = Server indicates to client that DNS has been updated regardless
1183                  * E: 1 = Name is in DNS format, i.e. <4>host<6>domain<3>com<0>,
1184                  *    not "host.domain.com". Format 0 is obsolete.
1185                  * N: 1 = Client requests server to not update DNS (S must be 0 then)
1186                  * Two [0] bytes which follow are deprecated and must be 0.
1187                  */
1188                 client_config.fqdn[OPT_DATA + 0] = 0x1;
1189                 /*client_config.fqdn[OPT_DATA + 1] = 0; - xzalloc did it */
1190                 /*client_config.fqdn[OPT_DATA + 2] = 0; */
1191         }
1192         if (opt & OPT_r)
1193                 requested_ip = inet_addr(str_r);
1194 #if ENABLE_FEATURE_UDHCP_PORT
1195         if (opt & OPT_P) {
1196                 CLIENT_PORT = xatou16(str_P);
1197                 SERVER_PORT = CLIENT_PORT - 1;
1198         }
1199 #endif
1200         if (opt & OPT_o)
1201                 client_config.no_default_options = 1;
1202         while (list_O) {
1203                 char *optstr = llist_pop(&list_O);
1204                 unsigned n = bb_strtou(optstr, NULL, 0);
1205                 if (errno || n > 254) {
1206                         n = udhcp_option_idx(optstr);
1207                         n = dhcp_optflags[n].code;
1208                 }
1209                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
1210         }
1211         while (list_x) {
1212                 char *optstr = llist_pop(&list_x);
1213                 char *colon = strchr(optstr, ':');
1214                 if (colon)
1215                         *colon = ' ';
1216                 /* now it looks similar to udhcpd's config file line:
1217                  * "optname optval", using the common routine: */
1218                 udhcp_str2optset(optstr, &client_config.options);
1219         }
1220
1221         if (udhcp_read_interface(client_config.interface,
1222                         &client_config.ifindex,
1223                         NULL,
1224                         client_config.client_mac)
1225         ) {
1226                 return 1;
1227         }
1228
1229         clientid_mac_ptr = NULL;
1230         if (!(opt & OPT_C) && !udhcp_find_option(client_config.options, DHCP_CLIENT_ID)) {
1231                 /* not suppressed and not set, set the default client ID */
1232                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
1233                 client_config.clientid[OPT_DATA] = 1; /* type: ethernet */
1234                 clientid_mac_ptr = client_config.clientid + OPT_DATA+1;
1235                 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1236         }
1237         if (str_V[0] != '\0')
1238                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
1239 #if !BB_MMU
1240         /* on NOMMU reexec (i.e., background) early */
1241         if (!(opt & OPT_f)) {
1242                 bb_daemonize_or_rexec(0 /* flags */, argv);
1243                 logmode = LOGMODE_NONE;
1244         }
1245 #endif
1246         if (opt & OPT_S) {
1247                 openlog(applet_name, LOG_PID, LOG_DAEMON);
1248                 logmode |= LOGMODE_SYSLOG;
1249         }
1250
1251         /* Make sure fd 0,1,2 are open */
1252         bb_sanitize_stdio();
1253         /* Equivalent of doing a fflush after every \n */
1254         setlinebuf(stdout);
1255         /* Create pidfile */
1256         write_pidfile(client_config.pidfile);
1257         /* Goes to stdout (unless NOMMU) and possibly syslog */
1258         bb_info_msg("%s (v"BB_VER") started", applet_name);
1259         /* Set up the signal pipe */
1260         udhcp_sp_setup();
1261         /* We want random_xid to be random... */
1262         srand(monotonic_us());
1263
1264         state = INIT_SELECTING;
1265         udhcp_run_script(NULL, "deconfig");
1266         change_listen_mode(LISTEN_RAW);
1267         packet_num = 0;
1268         timeout = 0;
1269         already_waited_sec = 0;
1270
1271         /* Main event loop. select() waits on signal pipe and possibly
1272          * on sockfd.
1273          * "continue" statements in code below jump to the top of the loop.
1274          */
1275         for (;;) {
1276                 /* silence "uninitialized!" warning */
1277                 unsigned timestamp_before_wait = timestamp_before_wait;
1278
1279                 //bb_error_msg("sockfd:%d, listen_mode:%d", sockfd, listen_mode);
1280
1281                 /* Was opening raw or udp socket here
1282                  * if (listen_mode != LISTEN_NONE && sockfd < 0),
1283                  * but on fast network renew responses return faster
1284                  * than we open sockets. Thus this code is moved
1285                  * to change_listen_mode(). Thus we open listen socket
1286                  * BEFORE we send renew request (see "case BOUND:"). */
1287
1288                 max_fd = udhcp_sp_fd_set(&rfds, sockfd);
1289
1290                 tv.tv_sec = timeout - already_waited_sec;
1291                 tv.tv_usec = 0;
1292                 retval = 0;
1293                 /* If we already timed out, fall through with retval = 0, else... */
1294                 if ((int)tv.tv_sec > 0) {
1295                         timestamp_before_wait = (unsigned)monotonic_sec();
1296                         log1("Waiting on select...");
1297                         retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
1298                         if (retval < 0) {
1299                                 /* EINTR? A signal was caught, don't panic */
1300                                 if (errno == EINTR) {
1301                                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1302                                         continue;
1303                                 }
1304                                 /* Else: an error occured, panic! */
1305                                 bb_perror_msg_and_die("select");
1306                         }
1307                 }
1308
1309                 /* If timeout dropped to zero, time to become active:
1310                  * resend discover/renew/whatever
1311                  */
1312                 if (retval == 0) {
1313                         /* When running on a bridge, the ifindex may have changed
1314                          * (e.g. if member interfaces were added/removed
1315                          * or if the status of the bridge changed).
1316                          * Refresh ifindex and client_mac:
1317                          */
1318                         if (udhcp_read_interface(client_config.interface,
1319                                         &client_config.ifindex,
1320                                         NULL,
1321                                         client_config.client_mac)
1322                         ) {
1323                                 return 1; /* iface is gone? */
1324                         }
1325                         if (clientid_mac_ptr)
1326                                 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1327
1328                         /* We will restart the wait in any case */
1329                         already_waited_sec = 0;
1330
1331                         switch (state) {
1332                         case INIT_SELECTING:
1333                                 if (packet_num < discover_retries) {
1334                                         if (packet_num == 0)
1335                                                 xid = random_xid();
1336                                         /* broadcast */
1337                                         send_discover(xid, requested_ip);
1338                                         timeout = discover_timeout;
1339                                         packet_num++;
1340                                         continue;
1341                                 }
1342  leasefail:
1343                                 udhcp_run_script(NULL, "leasefail");
1344 #if BB_MMU /* -b is not supported on NOMMU */
1345                                 if (opt & OPT_b) { /* background if no lease */
1346                                         bb_info_msg("No lease, forking to background");
1347                                         client_background();
1348                                         /* do not background again! */
1349                                         opt = ((opt & ~OPT_b) | OPT_f);
1350                                 } else
1351 #endif
1352                                 if (opt & OPT_n) { /* abort if no lease */
1353                                         bb_info_msg("No lease, failing");
1354                                         retval = 1;
1355                                         goto ret;
1356                                 }
1357                                 /* wait before trying again */
1358                                 timeout = tryagain_timeout;
1359                                 packet_num = 0;
1360                                 continue;
1361                         case REQUESTING:
1362                                 if (packet_num < discover_retries) {
1363                                         /* send broadcast select packet */
1364                                         send_select(xid, server_addr, requested_ip);
1365                                         timeout = discover_timeout;
1366                                         packet_num++;
1367                                         continue;
1368                                 }
1369                                 /* Timed out, go back to init state.
1370                                  * "discover...select...discover..." loops
1371                                  * were seen in the wild. Treat them similarly
1372                                  * to "no response to discover" case */
1373                                 change_listen_mode(LISTEN_RAW);
1374                                 state = INIT_SELECTING;
1375                                 goto leasefail;
1376                         case BOUND:
1377                                 /* 1/2 lease passed, enter renewing state */
1378                                 state = RENEWING;
1379                                 client_config.first_secs = 0; /* make secs field count from 0 */
1380                                 change_listen_mode(LISTEN_KERNEL);
1381                                 log1("Entering renew state");
1382                                 /* fall right through */
1383                         case RENEW_REQUESTED: /* manual (SIGUSR1) renew */
1384                         case_RENEW_REQUESTED:
1385                         case RENEWING:
1386                                 if (timeout > 60) {
1387                                         /* send an unicast renew request */
1388                         /* Sometimes observed to fail (EADDRNOTAVAIL) to bind
1389                          * a new UDP socket for sending inside send_renew.
1390                          * I hazard to guess existing listening socket
1391                          * is somehow conflicting with it, but why is it
1392                          * not deterministic then?! Strange.
1393                          * Anyway, it does recover by eventually failing through
1394                          * into INIT_SELECTING state.
1395                          */
1396                                         send_renew(xid, server_addr, requested_ip);
1397                                         timeout >>= 1;
1398                                         continue;
1399                                 }
1400                                 /* Timed out, enter rebinding state */
1401                                 log1("Entering rebinding state");
1402                                 state = REBINDING;
1403                                 /* fall right through */
1404                         case REBINDING:
1405                                 /* Switch to bcast receive */
1406                                 change_listen_mode(LISTEN_RAW);
1407                                 /* Lease is *really* about to run out,
1408                                  * try to find DHCP server using broadcast */
1409                                 if (timeout > 0) {
1410                                         /* send a broadcast renew request */
1411                                         send_renew(xid, 0 /*INADDR_ANY*/, requested_ip);
1412                                         timeout >>= 1;
1413                                         continue;
1414                                 }
1415                                 /* Timed out, enter init state */
1416                                 bb_info_msg("Lease lost, entering init state");
1417                                 udhcp_run_script(NULL, "deconfig");
1418                                 state = INIT_SELECTING;
1419                                 client_config.first_secs = 0; /* make secs field count from 0 */
1420                                 /*timeout = 0; - already is */
1421                                 packet_num = 0;
1422                                 continue;
1423                         /* case RELEASED: */
1424                         }
1425                         /* yah, I know, *you* say it would never happen */
1426                         timeout = INT_MAX;
1427                         continue; /* back to main loop */
1428                 } /* if select timed out */
1429
1430                 /* select() didn't timeout, something happened */
1431
1432                 /* Is it a signal? */
1433                 /* note: udhcp_sp_read checks FD_ISSET before reading */
1434                 switch (udhcp_sp_read(&rfds)) {
1435                 case SIGUSR1:
1436                         client_config.first_secs = 0; /* make secs field count from 0 */
1437                         already_waited_sec = 0;
1438                         perform_renew();
1439                         if (state == RENEW_REQUESTED) {
1440                                 /* We might be either on the same network
1441                                  * (in which case renew might work),
1442                                  * or we might be on a completely different one
1443                                  * (in which case renew won't ever succeed).
1444                                  * For the second case, must make sure timeout
1445                                  * is not too big, or else we can send
1446                                  * futile renew requests for hours.
1447                                  * (Ab)use -A TIMEOUT value (usually 20 sec)
1448                                  * as a cap on the timeout.
1449                                  */
1450                                 if (timeout > tryagain_timeout)
1451                                         timeout = tryagain_timeout;
1452                                 goto case_RENEW_REQUESTED;
1453                         }
1454                         /* Start things over */
1455                         packet_num = 0;
1456                         /* Kill any timeouts, user wants this to hurry along */
1457                         timeout = 0;
1458                         continue;
1459                 case SIGUSR2:
1460                         perform_release(requested_ip, server_addr);
1461                         timeout = INT_MAX;
1462                         continue;
1463                 case SIGTERM:
1464                         bb_info_msg("Received SIGTERM");
1465                         if (opt & OPT_R) /* release on quit */
1466                                 perform_release(requested_ip, server_addr);
1467                         goto ret0;
1468                 }
1469
1470                 /* Is it a packet? */
1471                 if (listen_mode == LISTEN_NONE || !FD_ISSET(sockfd, &rfds))
1472                         continue; /* no */
1473
1474                 {
1475                         int len;
1476
1477                         /* A packet is ready, read it */
1478                         if (listen_mode == LISTEN_KERNEL)
1479                                 len = udhcp_recv_kernel_packet(&packet, sockfd);
1480                         else
1481                                 len = udhcp_recv_raw_packet(&packet, sockfd);
1482                         if (len == -1) {
1483                                 /* Error is severe, reopen socket */
1484                                 bb_info_msg("Read error: %s, reopening socket", strerror(errno));
1485                                 sleep(discover_timeout); /* 3 seconds by default */
1486                                 change_listen_mode(listen_mode); /* just close and reopen */
1487                         }
1488                         /* If this packet will turn out to be unrelated/bogus,
1489                          * we will go back and wait for next one.
1490                          * Be sure timeout is properly decreased. */
1491                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1492                         if (len < 0)
1493                                 continue;
1494                 }
1495
1496                 if (packet.xid != xid) {
1497                         log1("xid %x (our is %x), ignoring packet",
1498                                 (unsigned)packet.xid, (unsigned)xid);
1499                         continue;
1500                 }
1501
1502                 /* Ignore packets that aren't for us */
1503                 if (packet.hlen != 6
1504                  || memcmp(packet.chaddr, client_config.client_mac, 6) != 0
1505                 ) {
1506 //FIXME: need to also check that last 10 bytes are zero
1507                         log1("chaddr does not match, ignoring packet"); // log2?
1508                         continue;
1509                 }
1510
1511                 message = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
1512                 if (message == NULL) {
1513                         bb_error_msg("no message type option, ignoring packet");
1514                         continue;
1515                 }
1516
1517                 switch (state) {
1518                 case INIT_SELECTING:
1519                         /* Must be a DHCPOFFER to one of our xid's */
1520                         if (*message == DHCPOFFER) {
1521                 /* TODO: why we don't just fetch server's IP from IP header? */
1522                                 temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
1523                                 if (!temp) {
1524                                         bb_error_msg("no server ID, ignoring packet");
1525                                         continue;
1526                                         /* still selecting - this server looks bad */
1527                                 }
1528                                 /* it IS unaligned sometimes, don't "optimize" */
1529                                 move_from_unaligned32(server_addr, temp);
1530                                 /*xid = packet.xid; - already is */
1531                                 requested_ip = packet.yiaddr;
1532
1533                                 /* enter requesting state */
1534                                 state = REQUESTING;
1535                                 timeout = 0;
1536                                 packet_num = 0;
1537                                 already_waited_sec = 0;
1538                         }
1539                         continue;
1540                 case REQUESTING:
1541                 case RENEWING:
1542                 case RENEW_REQUESTED:
1543                 case REBINDING:
1544                         if (*message == DHCPACK) {
1545                                 temp = udhcp_get_option(&packet, DHCP_LEASE_TIME);
1546                                 if (!temp) {
1547                                         bb_error_msg("no lease time with ACK, using 1 hour lease");
1548                                         lease_seconds = 60 * 60;
1549                                 } else {
1550                                         /* it IS unaligned sometimes, don't "optimize" */
1551                                         move_from_unaligned32(lease_seconds, temp);
1552                                         lease_seconds = ntohl(lease_seconds);
1553                                         lease_seconds &= 0x0fffffff; /* paranoia: must not be prone to overflows */
1554                                         if (lease_seconds < 10) /* and not too small */
1555                                                 lease_seconds = 10;
1556                                 }
1557 #if ENABLE_FEATURE_UDHCPC_ARPING
1558                                 if (opt & OPT_a) {
1559 /* RFC 2131 3.1 paragraph 5:
1560  * "The client receives the DHCPACK message with configuration
1561  * parameters. The client SHOULD perform a final check on the
1562  * parameters (e.g., ARP for allocated network address), and notes
1563  * the duration of the lease specified in the DHCPACK message. At this
1564  * point, the client is configured. If the client detects that the
1565  * address is already in use (e.g., through the use of ARP),
1566  * the client MUST send a DHCPDECLINE message to the server and restarts
1567  * the configuration process..." */
1568                                         if (!arpping(packet.yiaddr,
1569                                                         NULL,
1570                                                         (uint32_t) 0,
1571                                                         client_config.client_mac,
1572                                                         client_config.interface)
1573                                         ) {
1574                                                 bb_info_msg("Offered address is in use "
1575                                                         "(got ARP reply), declining");
1576                                                 send_decline(xid, server_addr, packet.yiaddr);
1577
1578                                                 if (state != REQUESTING)
1579                                                         udhcp_run_script(NULL, "deconfig");
1580                                                 change_listen_mode(LISTEN_RAW);
1581                                                 state = INIT_SELECTING;
1582                                                 client_config.first_secs = 0; /* make secs field count from 0 */
1583                                                 requested_ip = 0;
1584                                                 timeout = tryagain_timeout;
1585                                                 packet_num = 0;
1586                                                 already_waited_sec = 0;
1587                                                 continue; /* back to main loop */
1588                                         }
1589                                 }
1590 #endif
1591                                 /* enter bound state */
1592                                 timeout = lease_seconds / 2;
1593                                 {
1594                                         struct in_addr temp_addr;
1595                                         temp_addr.s_addr = packet.yiaddr;
1596                                         bb_info_msg("Lease of %s obtained, lease time %u",
1597                                                 inet_ntoa(temp_addr), (unsigned)lease_seconds);
1598                                 }
1599                                 requested_ip = packet.yiaddr;
1600                                 udhcp_run_script(&packet, state == REQUESTING ? "bound" : "renew");
1601
1602                                 state = BOUND;
1603                                 change_listen_mode(LISTEN_NONE);
1604                                 if (opt & OPT_q) { /* quit after lease */
1605                                         if (opt & OPT_R) /* release on quit */
1606                                                 perform_release(requested_ip, server_addr);
1607                                         goto ret0;
1608                                 }
1609                                 /* future renew failures should not exit (JM) */
1610                                 opt &= ~OPT_n;
1611 #if BB_MMU /* NOMMU case backgrounded earlier */
1612                                 if (!(opt & OPT_f)) {
1613                                         client_background();
1614                                         /* do not background again! */
1615                                         opt = ((opt & ~OPT_b) | OPT_f);
1616                                 }
1617 #endif
1618                                 already_waited_sec = 0;
1619                                 continue; /* back to main loop */
1620                         }
1621                         if (*message == DHCPNAK) {
1622                                 /* return to init state */
1623                                 bb_info_msg("Received DHCP NAK");
1624                                 udhcp_run_script(&packet, "nak");
1625                                 if (state != REQUESTING)
1626                                         udhcp_run_script(NULL, "deconfig");
1627                                 change_listen_mode(LISTEN_RAW);
1628                                 sleep(3); /* avoid excessive network traffic */
1629                                 state = INIT_SELECTING;
1630                                 client_config.first_secs = 0; /* make secs field count from 0 */
1631                                 requested_ip = 0;
1632                                 timeout = 0;
1633                                 packet_num = 0;
1634                                 already_waited_sec = 0;
1635                         }
1636                         continue;
1637                 /* case BOUND: - ignore all packets */
1638                 /* case RELEASED: - ignore all packets */
1639                 }
1640                 /* back to main loop */
1641         } /* for (;;) - main loop ends */
1642
1643  ret0:
1644         retval = 0;
1645  ret:
1646         /*if (client_config.pidfile) - remove_pidfile has its own check */
1647                 remove_pidfile(client_config.pidfile);
1648         return retval;
1649 }