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 #ifndef PACKET_AUXDATA
  33 # define PACKET_AUXDATA 8
  34 struct tpacket_auxdata {
  35         uint32_t tp_status;
  36         uint32_t tp_len;
  37         uint32_t tp_snaplen;
  38         uint16_t tp_mac;
  39         uint16_t tp_net;
  40         uint16_t tp_vlan_tci;
  41         uint16_t tp_padding;
  42 };
  43 #endif
  44
  45
  46 /* "struct client_config_t client_config" is in bb_common_bufsiz1 */
  47
  48
  49 #if ENABLE_LONG_OPTS
  50 static const char udhcpc_longopts[] ALIGN1 =
  51         "clientid-none\0"  No_argument       "C"
  52         "vendorclass\0"    Required_argument "V"
  53         "hostname\0"       Required_argument "H"
  54         "fqdn\0"           Required_argument "F"
  55         "interface\0"      Required_argument "i"
  56         "now\0"            No_argument       "n"
  57         "pidfile\0"        Required_argument "p"
  58         "quit\0"           No_argument       "q"
  59         "release\0"        No_argument       "R"
  60         "request\0"        Required_argument "r"
  61         "script\0"         Required_argument "s"
  62         "timeout\0"        Required_argument "T"
  63         "retries\0"        Required_argument "t"
  64         "tryagain\0"       Required_argument "A"
  65         "syslog\0"         No_argument       "S"
  66         "request-option\0" Required_argument "O"
  67         "no-default-options\0" No_argument   "o"
  68         "foreground\0"     No_argument       "f"
  69         "background\0"     No_argument       "b"
  70         "broadcast\0"      No_argument       "B"
  71         IF_FEATURE_UDHCPC_ARPING("arping\0"     Optional_argument "a")
  72         IF_FEATURE_UDHCP_PORT("client-port\0"   Required_argument "P")
  73         ;
  74 #endif
  75 /* Must match getopt32 option string order */
  76 enum {
  77         OPT_C = 1 << 0,
  78         OPT_V = 1 << 1,
  79         OPT_H = 1 << 2,
  80         OPT_h = 1 << 3,
  81         OPT_F = 1 << 4,
  82         OPT_i = 1 << 5,
  83         OPT_n = 1 << 6,
  84         OPT_p = 1 << 7,
  85         OPT_q = 1 << 8,
  86         OPT_R = 1 << 9,
  87         OPT_r = 1 << 10,
  88         OPT_s = 1 << 11,
  89         OPT_T = 1 << 12,
  90         OPT_t = 1 << 13,
  91         OPT_S = 1 << 14,
  92         OPT_A = 1 << 15,
  93         OPT_O = 1 << 16,
  94         OPT_o = 1 << 17,
  95         OPT_x = 1 << 18,
  96         OPT_f = 1 << 19,
  97         OPT_B = 1 << 20,
  98 /* The rest has variable bit positions, need to be clever */
  99         OPTBIT_B = 20,
 100         USE_FOR_MMU(             OPTBIT_b,)
 101         IF_FEATURE_UDHCPC_ARPING(OPTBIT_a,)
 102         IF_FEATURE_UDHCP_PORT(   OPTBIT_P,)
 103         USE_FOR_MMU(             OPT_b = 1 << OPTBIT_b,)
 104         IF_FEATURE_UDHCPC_ARPING(OPT_a = 1 << OPTBIT_a,)
 105         IF_FEATURE_UDHCP_PORT(   OPT_P = 1 << OPTBIT_P,)
 106 };
 107
 108
 109 /*** Script execution code ***/
 110
 111 /* get a rough idea of how long an option will be (rounding up...) */
 112 static const uint8_t len_of_option_as_string[] = {
 113         [OPTION_IP              ] = sizeof("255.255.255.255 "),
 114         [OPTION_IP_PAIR         ] = sizeof("255.255.255.255 ") * 2,
 115         [OPTION_STATIC_ROUTES   ] = sizeof("255.255.255.255/32 255.255.255.255 "),
 116         [OPTION_6RD             ] = sizeof("132 128 ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 255.255.255.255 "),
 117         [OPTION_STRING          ] = 1,
 118         [OPTION_STRING_HOST     ] = 1,
 119 #if ENABLE_FEATURE_UDHCP_RFC3397
 120         [OPTION_DNS_STRING      ] = 1, /* unused */
 121         /* Hmmm, this severely overestimates size if SIP_SERVERS option
 122          * is in domain name form: N-byte option in binary form
 123          * mallocs ~16*N bytes. But it is freed almost at once.
 124          */
 125         [OPTION_SIP_SERVERS     ] = sizeof("255.255.255.255 "),
 126 #endif
 127 //      [OPTION_BOOLEAN         ] = sizeof("yes "),
 128         [OPTION_U8              ] = sizeof("255 "),
 129         [OPTION_U16             ] = sizeof("65535 "),
 130 //      [OPTION_S16             ] = sizeof("-32768 "),
 131         [OPTION_U32             ] = sizeof("4294967295 "),
 132         [OPTION_S32             ] = sizeof("-2147483684 "),
 133 };
 134
 135 /* note: ip is a pointer to an IP in network order, possibly misaliged */
 136 static int sprint_nip(char *dest, const char *pre, const uint8_t *ip)
 137 {
 138         return sprintf(dest, "%s%u.%u.%u.%u", pre, ip[0], ip[1], ip[2], ip[3]);
 139 }
 140
 141 /* really simple implementation, just count the bits */
 142 static int mton(uint32_t mask)
 143 {
 144         int i = 0;
 145         mask = ntohl(mask); /* 111110000-like bit pattern */
 146         while (mask) {
 147                 i++;
 148                 mask <<= 1;
 149         }
 150         return i;
 151 }
 152
 153 #if ENABLE_FEATURE_UDHCPC_SANITIZEOPT
 154 /* Check if a given label represents a valid DNS label
 155  * Return pointer to the first character after the label upon success,
 156  * NULL otherwise.
 157  * See RFC1035, 2.3.1
 158  */
 159 /* We don't need to be particularly anal. For example, allowing _, hyphen
 160  * at the end, or leading and trailing dots would be ok, since it
 161  * can't be used for attacks. (Leading hyphen can be, if someone uses
 162  * cmd "$hostname"
 163  * in the script: then hostname may be treated as an option)
 164  */
 165 static const char *valid_domain_label(const char *label)
 166 {
 167         unsigned char ch;
 168         unsigned pos = 0;
 169
 170         for (;;) {
 171                 ch = *label;
 172                 if ((ch|0x20) < 'a' || (ch|0x20) > 'z') {
 173                         if (ch < '0' || ch > '9') {
 174                                 if (ch == '\0' || ch == '.')
 175                                         return label;
 176                                 /* DNS allows only '-', but we are more permissive */
 177                                 if (ch != '-' && ch != '_')
 178                                         return NULL;
 179                         }
 180                 }
 181                 label++;
 182                 pos++;
 183                 //Do we want this?
 184                 //if (pos > 63) /* NS_MAXLABEL; labels must be 63 chars or less */
 185                 //      return NULL;
 186         }
 187 }
 188
 189 /* Check if a given name represents a valid DNS name */
 190 /* See RFC1035, 2.3.1 */
 191 static int good_hostname(const char *name)
 192 {
 193         //const char *start = name;
 194
 195         for (;;) {
 196                 name = valid_domain_label(name);
 197                 if (!name)
 198                         return 0;
 199                 if (!name[0])
 200                         return 1;
 201                         //Do we want this?
 202                         //return ((name - start) < 1025); /* NS_MAXDNAME */
 203                 name++;
 204                 if (*name == '\0')
 205                         return 1; // We allow trailing dot too
 206         }
 207 }
 208 #else
 209 # define good_hostname(name) 1
 210 #endif
 211
 212 /* Create "opt_name=opt_value" string */
 213 static NOINLINE char *xmalloc_optname_optval(uint8_t *option, const struct dhcp_optflag *optflag, const char *opt_name)
 214 {
 215         unsigned upper_length;
 216         int len, type, optlen;
 217         char *dest, *ret;
 218
 219         /* option points to OPT_DATA, need to go back to get OPT_LEN */
 220         len = option[-OPT_DATA + OPT_LEN];
 221
 222         type = optflag->flags & OPTION_TYPE_MASK;
 223         optlen = dhcp_option_lengths[type];
 224         upper_length = len_of_option_as_string[type]
 225                 * ((unsigned)(len + optlen) / (unsigned)optlen);
 226
 227         dest = ret = xmalloc(upper_length + strlen(opt_name) + 2);
 228         dest += sprintf(ret, "%s=", opt_name);
 229
 230         while (len >= optlen) {
 231                 switch (type) {
 232                 case OPTION_IP:
 233                 case OPTION_IP_PAIR:
 234                         dest += sprint_nip(dest, "", option);
 235                         if (type == OPTION_IP)
 236                                 break;
 237                         dest += sprint_nip(dest, "/", option + 4);
 238                         break;
 239 //              case OPTION_BOOLEAN:
 240 //                      dest += sprintf(dest, *option ? "yes" : "no");
 241 //                      break;
 242                 case OPTION_U8:
 243                         dest += sprintf(dest, "%u", *option);
 244                         break;
 245 //              case OPTION_S16:
 246                 case OPTION_U16: {
 247                         uint16_t val_u16;
 248                         move_from_unaligned16(val_u16, option);
 249                         dest += sprintf(dest, "%u", ntohs(val_u16));
 250                         break;
 251                 }
 252                 case OPTION_S32:
 253                 case OPTION_U32: {
 254                         uint32_t val_u32;
 255                         move_from_unaligned32(val_u32, option);
 256                         dest += sprintf(dest, type == OPTION_U32 ? "%lu" : "%ld", (unsigned long) ntohl(val_u32));
 257                         break;
 258                 }
 259                 /* Note: options which use 'return' instead of 'break'
 260                  * (for example, OPTION_STRING) skip the code which handles
 261                  * the case of list of options.
 262                  */
 263                 case OPTION_STRING:
 264                 case OPTION_STRING_HOST:
 265                         memcpy(dest, option, len);
 266                         dest[len] = '\0';
 267                         if (type == OPTION_STRING_HOST && !good_hostname(dest))
 268                                 safe_strncpy(dest, "bad", len);
 269                         return ret;
 270                 case OPTION_STATIC_ROUTES: {
 271                         /* Option binary format:
 272                          * mask [one byte, 0..32]
 273                          * ip [big endian, 0..4 bytes depending on mask]
 274                          * router [big endian, 4 bytes]
 275                          * may be repeated
 276                          *
 277                          * We convert it to a string "IP/MASK ROUTER IP2/MASK2 ROUTER2"
 278                          */
 279                         const char *pfx = "";
 280
 281                         while (len >= 1 + 4) { /* mask + 0-byte ip + router */
 282                                 uint32_t nip;
 283                                 uint8_t *p;
 284                                 unsigned mask;
 285                                 int bytes;
 286
 287                                 mask = *option++;
 288                                 if (mask > 32)
 289                                         break;
 290                                 len--;
 291
 292                                 nip = 0;
 293                                 p = (void*) &nip;
 294                                 bytes = (mask + 7) / 8; /* 0 -> 0, 1..8 -> 1, 9..16 -> 2 etc */
 295                                 while (--bytes >= 0) {
 296                                         *p++ = *option++;
 297                                         len--;
 298                                 }
 299                                 if (len < 4)
 300                                         break;
 301
 302                                 /* print ip/mask */
 303                                 dest += sprint_nip(dest, pfx, (void*) &nip);
 304                                 pfx = " ";
 305                                 dest += sprintf(dest, "/%u ", mask);
 306                                 /* print router */
 307                                 dest += sprint_nip(dest, "", option);
 308                                 option += 4;
 309                                 len -= 4;
 310                         }
 311
 312                         return ret;
 313                 }
 314                 case OPTION_6RD:
 315                         /* Option binary format (see RFC 5969):
 316                          *  0                   1                   2                   3
 317                          *  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
 318                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 319                          * |  OPTION_6RD   | option-length |  IPv4MaskLen  |  6rdPrefixLen |
 320                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 321                          * |                           6rdPrefix                           |
 322                          * ...                        (16 octets)                        ...
 323                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 324                          * ...                   6rdBRIPv4Address(es)                    ...
 325                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 326                          * We convert it to a string
 327                          * "IPv4MaskLen 6rdPrefixLen 6rdPrefix 6rdBRIPv4Address..."
 328                          *
 329                          * Sanity check: ensure that our length is at least 22 bytes, that
 330                          * IPv4MaskLen <= 32,
 331                          * 6rdPrefixLen <= 128,
 332                          * 6rdPrefixLen + (32 - IPv4MaskLen) <= 128
 333                          * (2nd condition need no check - it follows from 1st and 3rd).
 334                          * Else, return envvar with empty value ("optname=")
 335                          */
 336                         if (len >= (1 + 1 + 16 + 4)
 337                          && option[0] <= 32
 338                          && (option[1] + 32 - option[0]) <= 128
 339                         ) {
 340                                 /* IPv4MaskLen */
 341                                 dest += sprintf(dest, "%u ", *option++);
 342                                 /* 6rdPrefixLen */
 343                                 dest += sprintf(dest, "%u ", *option++);
 344                                 /* 6rdPrefix */
 345                                 dest += sprint_nip6(dest, /* "", */ option);
 346                                 option += 16;
 347                                 len -= 1 + 1 + 16 + 4;
 348                                 /* "+ 4" above corresponds to the length of IPv4 addr
 349                                  * we consume in the loop below */
 350                                 while (1) {
 351                                         /* 6rdBRIPv4Address(es) */
 352                                         dest += sprint_nip(dest, " ", option);
 353                                         option += 4;
 354                                         len -= 4; /* do we have yet another 4+ bytes? */
 355                                         if (len < 0)
 356                                                 break; /* no */
 357                                 }
 358                         }
 359
 360                         return ret;
 361 #if ENABLE_FEATURE_UDHCP_RFC3397
 362                 case OPTION_DNS_STRING:
 363                         /* unpack option into dest; use ret for prefix (i.e., "optname=") */
 364                         dest = dname_dec(option, len, ret);
 365                         if (dest) {
 366                                 free(ret);
 367                                 return dest;
 368                         }
 369                         /* error. return "optname=" string */
 370                         return ret;
 371                 case OPTION_SIP_SERVERS:
 372                         /* Option binary format:
 373                          * type: byte
 374                          * type=0: domain names, dns-compressed
 375                          * type=1: IP addrs
 376                          */
 377                         option++;
 378                         len--;
 379                         if (option[-1] == 0) {
 380                                 dest = dname_dec(option, len, ret);
 381                                 if (dest) {
 382                                         free(ret);
 383                                         return dest;
 384                                 }
 385                         } else
 386                         if (option[-1] == 1) {
 387                                 const char *pfx = "";
 388                                 while (1) {
 389                                         len -= 4;
 390                                         if (len < 0)
 391                                                 break;
 392                                         dest += sprint_nip(dest, pfx, option);
 393                                         pfx = " ";
 394                                         option += 4;
 395                                 }
 396                         }
 397                         return ret;
 398 #endif
 399                 } /* switch */
 400
 401                 /* If we are here, try to format any remaining data
 402                  * in the option as another, similarly-formatted option
 403                  */
 404                 option += optlen;
 405                 len -= optlen;
 406 // TODO: it can be a list only if (optflag->flags & OPTION_LIST).
 407 // Should we bail out/warn if we see multi-ip option which is
 408 // not allowed to be such (for example, DHCP_BROADCAST)? -
 409                 if (len < optlen /* || !(optflag->flags & OPTION_LIST) */)
 410                         break;
 411                 *dest++ = ' ';
 412                 *dest = '\0';
 413         } /* while */
 414
 415         return ret;
 416 }
 417
 418 /* put all the parameters into the environment */
 419 static char **fill_envp(struct dhcp_packet *packet)
 420 {
 421         int envc;
 422         int i;
 423         char **envp, **curr;
 424         const char *opt_name;
 425         uint8_t *temp;
 426         uint8_t overload = 0;
 427
 428 #define BITMAP unsigned
 429 #define BBITS (sizeof(BITMAP) * 8)
 430 #define BMASK(i) (1 << (i & (sizeof(BITMAP) * 8 - 1)))
 431 #define FOUND_OPTS(i) (found_opts[(unsigned)i / BBITS])
 432         BITMAP found_opts[256 / BBITS];
 433
 434         memset(found_opts, 0, sizeof(found_opts));
 435
 436         /* We need 6 elements for:
 437          * "interface=IFACE"
 438          * "ip=N.N.N.N" from packet->yiaddr
 439          * "siaddr=IP" from packet->siaddr_nip (unless 0)
 440          * "boot_file=FILE" from packet->file (unless overloaded)
 441          * "sname=SERVER_HOSTNAME" from packet->sname (unless overloaded)
 442          * terminating NULL
 443          */
 444         envc = 6;
 445         /* +1 element for each option, +2 for subnet option: */
 446         if (packet) {
 447                 /* note: do not search for "pad" (0) and "end" (255) options */
 448 //TODO: change logic to scan packet _once_
 449                 for (i = 1; i < 255; i++) {
 450                         temp = udhcp_get_option(packet, i);
 451                         if (temp) {
 452                                 if (i == DHCP_OPTION_OVERLOAD)
 453                                         overload = *temp;
 454                                 else if (i == DHCP_SUBNET)
 455                                         envc++; /* for $mask */
 456                                 envc++;
 457                                 /*if (i != DHCP_MESSAGE_TYPE)*/
 458                                 FOUND_OPTS(i) |= BMASK(i);
 459                         }
 460                 }
 461         }
 462         curr = envp = xzalloc(sizeof(envp[0]) * envc);
 463
 464         *curr = xasprintf("interface=%s", client_config.interface);
 465         putenv(*curr++);
 466
 467         if (!packet)
 468                 return envp;
 469
 470         /* Export BOOTP fields. Fields we don't (yet?) export:
 471          * uint8_t op;      // always BOOTREPLY
 472          * uint8_t htype;   // hardware address type. 1 = 10mb ethernet
 473          * uint8_t hlen;    // hardware address length
 474          * uint8_t hops;    // used by relay agents only
 475          * uint32_t xid;
 476          * uint16_t secs;   // elapsed since client began acquisition/renewal
 477          * uint16_t flags;  // only one flag so far: bcast. Never set by server
 478          * uint32_t ciaddr; // client IP (usually == yiaddr. can it be different
 479          *                  // if during renew server wants to give us differn IP?)
 480          * uint32_t gateway_nip; // relay agent IP address
 481          * uint8_t chaddr[16]; // link-layer client hardware address (MAC)
 482          * TODO: export gateway_nip as $giaddr?
 483          */
 484         /* Most important one: yiaddr as $ip */
 485         *curr = xmalloc(sizeof("ip=255.255.255.255"));
 486         sprint_nip(*curr, "ip=", (uint8_t *) &packet->yiaddr);
 487         putenv(*curr++);
 488         if (packet->siaddr_nip) {
 489                 /* IP address of next server to use in bootstrap */
 490                 *curr = xmalloc(sizeof("siaddr=255.255.255.255"));
 491                 sprint_nip(*curr, "siaddr=", (uint8_t *) &packet->siaddr_nip);
 492                 putenv(*curr++);
 493         }
 494         if (!(overload & FILE_FIELD) && packet->file[0]) {
 495                 /* watch out for invalid packets */
 496                 *curr = xasprintf("boot_file=%."DHCP_PKT_FILE_LEN_STR"s", packet->file);
 497                 putenv(*curr++);
 498         }
 499         if (!(overload & SNAME_FIELD) && packet->sname[0]) {
 500                 /* watch out for invalid packets */
 501                 *curr = xasprintf("sname=%."DHCP_PKT_SNAME_LEN_STR"s", packet->sname);
 502                 putenv(*curr++);
 503         }
 504
 505         /* Export known DHCP options */
 506         opt_name = dhcp_option_strings;
 507         i = 0;
 508         while (*opt_name) {
 509                 uint8_t code = dhcp_optflags[i].code;
 510                 BITMAP *found_ptr = &FOUND_OPTS(code);
 511                 BITMAP found_mask = BMASK(code);
 512                 if (!(*found_ptr & found_mask))
 513                         goto next;
 514                 *found_ptr &= ~found_mask; /* leave only unknown options */
 515                 temp = udhcp_get_option(packet, code);
 516                 *curr = xmalloc_optname_optval(temp, &dhcp_optflags[i], opt_name);
 517                 putenv(*curr++);
 518                 if (code == DHCP_SUBNET) {
 519                         /* Subnet option: make things like "$ip/$mask" possible */
 520                         uint32_t subnet;
 521                         move_from_unaligned32(subnet, temp);
 522                         *curr = xasprintf("mask=%u", mton(subnet));
 523                         putenv(*curr++);
 524                 }
 525  next:
 526                 opt_name += strlen(opt_name) + 1;
 527                 i++;
 528         }
 529         /* Export unknown options */
 530         for (i = 0; i < 256;) {
 531                 BITMAP bitmap = FOUND_OPTS(i);
 532                 if (!bitmap) {
 533                         i += BBITS;
 534                         continue;
 535                 }
 536                 if (bitmap & BMASK(i)) {
 537                         unsigned len, ofs;
 538
 539                         temp = udhcp_get_option(packet, i);
 540                         /* udhcp_get_option returns ptr to data portion,
 541                          * need to go back to get len
 542                          */
 543                         len = temp[-OPT_DATA + OPT_LEN];
 544                         *curr = xmalloc(sizeof("optNNN=") + 1 + len*2);
 545                         ofs = sprintf(*curr, "opt%u=", i);
 546                         *bin2hex(*curr + ofs, (void*) temp, len) = '\0';
 547                         putenv(*curr++);
 548                 }
 549                 i++;
 550         }
 551
 552         return envp;
 553 }
 554
 555 /* Call a script with a par file and env vars */
 556 static void udhcp_run_script(struct dhcp_packet *packet, const char *name)
 557 {
 558         char **envp, **curr;
 559         char *argv[3];
 560
 561         envp = fill_envp(packet);
 562
 563         /* call script */
 564         log1("executing %s %s", client_config.script, name);
 565         argv[0] = (char*) client_config.script;
 566         argv[1] = (char*) name;
 567         argv[2] = NULL;
 568         spawn_and_wait(argv);
 569
 570         for (curr = envp; *curr; curr++) {
 571                 log2(" %s", *curr);
 572                 bb_unsetenv_and_free(*curr);
 573         }
 574         free(envp);
 575 }
 576
 577
 578 /*** Sending/receiving packets ***/
 579
 580 static ALWAYS_INLINE uint32_t random_xid(void)
 581 {
 582         return rand();
 583 }
 584
 585 /* Initialize the packet with the proper defaults */
 586 static void init_packet(struct dhcp_packet *packet, char type)
 587 {
 588         uint16_t secs;
 589
 590         /* Fill in: op, htype, hlen, cookie fields; message type option: */
 591         udhcp_init_header(packet, type);
 592
 593         packet->xid = random_xid();
 594
 595         client_config.last_secs = monotonic_sec();
 596         if (client_config.first_secs == 0)
 597                 client_config.first_secs = client_config.last_secs;
 598         secs = client_config.last_secs - client_config.first_secs;
 599         packet->secs = htons(secs);
 600
 601         memcpy(packet->chaddr, client_config.client_mac, 6);
 602         if (client_config.clientid)
 603                 udhcp_add_binary_option(packet, client_config.clientid);
 604 }
 605
 606 static void add_client_options(struct dhcp_packet *packet)
 607 {
 608         int i, end, len;
 609
 610         udhcp_add_simple_option(packet, DHCP_MAX_SIZE, htons(IP_UDP_DHCP_SIZE));
 611
 612         /* Add a "param req" option with the list of options we'd like to have
 613          * from stubborn DHCP servers. Pull the data from the struct in common.c.
 614          * No bounds checking because it goes towards the head of the packet. */
 615         end = udhcp_end_option(packet->options);
 616         len = 0;
 617         for (i = 1; i < DHCP_END; i++) {
 618                 if (client_config.opt_mask[i >> 3] & (1 << (i & 7))) {
 619                         packet->options[end + OPT_DATA + len] = i;
 620                         len++;
 621                 }
 622         }
 623         if (len) {
 624                 packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
 625                 packet->options[end + OPT_LEN] = len;
 626                 packet->options[end + OPT_DATA + len] = DHCP_END;
 627         }
 628
 629         if (client_config.vendorclass)
 630                 udhcp_add_binary_option(packet, client_config.vendorclass);
 631         if (client_config.hostname)
 632                 udhcp_add_binary_option(packet, client_config.hostname);
 633         if (client_config.fqdn)
 634                 udhcp_add_binary_option(packet, client_config.fqdn);
 635
 636         /* Request broadcast replies if we have no IP addr */
 637         if ((option_mask32 & OPT_B) && packet->ciaddr == 0)
 638                 packet->flags |= htons(BROADCAST_FLAG);
 639
 640         /* Add -x options if any */
 641         {
 642                 struct option_set *curr = client_config.options;
 643                 while (curr) {
 644                         udhcp_add_binary_option(packet, curr->data);
 645                         curr = curr->next;
 646                 }
 647 //              if (client_config.sname)
 648 //                      strncpy((char*)packet->sname, client_config.sname, sizeof(packet->sname) - 1);
 649 //              if (client_config.boot_file)
 650 //                      strncpy((char*)packet->file, client_config.boot_file, sizeof(packet->file) - 1);
 651         }
 652
 653         // This will be needed if we remove -V VENDOR_STR in favor of
 654         // -x vendor:VENDOR_STR
 655         //if (!udhcp_find_option(packet.options, DHCP_VENDOR))
 656         //      /* not set, set the default vendor ID */
 657         //      ...add (DHCP_VENDOR, "udhcp "BB_VER) opt...
 658 }
 659
 660 /* RFC 2131
 661  * 4.4.4 Use of broadcast and unicast
 662  *
 663  * The DHCP client broadcasts DHCPDISCOVER, DHCPREQUEST and DHCPINFORM
 664  * messages, unless the client knows the address of a DHCP server.
 665  * The client unicasts DHCPRELEASE messages to the server. Because
 666  * the client is declining the use of the IP address supplied by the server,
 667  * the client broadcasts DHCPDECLINE messages.
 668  *
 669  * When the DHCP client knows the address of a DHCP server, in either
 670  * INIT or REBOOTING state, the client may use that address
 671  * in the DHCPDISCOVER or DHCPREQUEST rather than the IP broadcast address.
 672  * The client may also use unicast to send DHCPINFORM messages
 673  * to a known DHCP server. If the client receives no response to DHCP
 674  * messages sent to the IP address of a known DHCP server, the DHCP
 675  * client reverts to using the IP broadcast address.
 676  */
 677
 678 static int raw_bcast_from_client_config_ifindex(struct dhcp_packet *packet, uint32_t src_nip)
 679 {
 680         return udhcp_send_raw_packet(packet,
 681                 /*src*/ src_nip, CLIENT_PORT,
 682                 /*dst*/ INADDR_BROADCAST, SERVER_PORT, MAC_BCAST_ADDR,
 683                 client_config.ifindex);
 684 }
 685
 686 static int bcast_or_ucast(struct dhcp_packet *packet, uint32_t ciaddr, uint32_t server)
 687 {
 688         if (server)
 689                 return udhcp_send_kernel_packet(packet,
 690                         ciaddr, CLIENT_PORT,
 691                         server, SERVER_PORT);
 692         return raw_bcast_from_client_config_ifindex(packet, ciaddr);
 693 }
 694
 695 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
 696 /* NOINLINE: limit stack usage in caller */
 697 static NOINLINE int send_discover(uint32_t xid, uint32_t requested)
 698 {
 699         struct dhcp_packet packet;
 700
 701         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 702          * random xid field (we override it below),
 703          * client-id option (unless -C), message type option:
 704          */
 705         init_packet(&packet, DHCPDISCOVER);
 706
 707         packet.xid = xid;
 708         if (requested)
 709                 udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 710
 711         /* Add options: maxsize,
 712          * optionally: hostname, fqdn, vendorclass,
 713          * "param req" option according to -O, options specified with -x
 714          */
 715         add_client_options(&packet);
 716
 717         bb_error_msg("sending %s", "discover");
 718         return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
 719 }
 720
 721 /* Broadcast a DHCP request message */
 722 /* RFC 2131 3.1 paragraph 3:
 723  * "The client _broadcasts_ a DHCPREQUEST message..."
 724  */
 725 /* NOINLINE: limit stack usage in caller */
 726 static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requested)
 727 {
 728         struct dhcp_packet packet;
 729         struct in_addr addr;
 730
 731 /*
 732  * RFC 2131 4.3.2 DHCPREQUEST message
 733  * ...
 734  * If the DHCPREQUEST message contains a 'server identifier'
 735  * option, the message is in response to a DHCPOFFER message.
 736  * Otherwise, the message is a request to verify or extend an
 737  * existing lease. If the client uses a 'client identifier'
 738  * in a DHCPREQUEST message, it MUST use that same 'client identifier'
 739  * in all subsequent messages. If the client included a list
 740  * of requested parameters in a DHCPDISCOVER message, it MUST
 741  * include that list in all subsequent messages.
 742  */
 743         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 744          * random xid field (we override it below),
 745          * client-id option (unless -C), message type option:
 746          */
 747         init_packet(&packet, DHCPREQUEST);
 748
 749         packet.xid = xid;
 750         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 751
 752         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 753
 754         /* Add options: maxsize,
 755          * optionally: hostname, fqdn, vendorclass,
 756          * "param req" option according to -O, and options specified with -x
 757          */
 758         add_client_options(&packet);
 759
 760         addr.s_addr = requested;
 761         bb_error_msg("sending select for %s", inet_ntoa(addr));
 762         return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
 763 }
 764
 765 /* Unicast or broadcast a DHCP renew message */
 766 /* NOINLINE: limit stack usage in caller */
 767 static NOINLINE int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
 768 {
 769         struct dhcp_packet packet;
 770
 771 /*
 772  * RFC 2131 4.3.2 DHCPREQUEST message
 773  * ...
 774  * DHCPREQUEST generated during RENEWING state:
 775  *
 776  * 'server identifier' MUST NOT be filled in, 'requested IP address'
 777  * option MUST NOT be filled in, 'ciaddr' MUST be filled in with
 778  * client's IP address. In this situation, the client is completely
 779  * configured, and is trying to extend its lease. This message will
 780  * be unicast, so no relay agents will be involved in its
 781  * transmission.  Because 'giaddr' is therefore not filled in, the
 782  * DHCP server will trust the value in 'ciaddr', and use it when
 783  * replying to the client.
 784  */
 785         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 786          * random xid field (we override it below),
 787          * client-id option (unless -C), message type option:
 788          */
 789         init_packet(&packet, DHCPREQUEST);
 790
 791         packet.xid = xid;
 792         packet.ciaddr = ciaddr;
 793
 794         /* Add options: maxsize,
 795          * optionally: hostname, fqdn, vendorclass,
 796          * "param req" option according to -O, and options specified with -x
 797          */
 798         add_client_options(&packet);
 799
 800         bb_error_msg("sending %s", "renew");
 801         return bcast_or_ucast(&packet, ciaddr, server);
 802 }
 803
 804 #if ENABLE_FEATURE_UDHCPC_ARPING
 805 /* Broadcast a DHCP decline message */
 806 /* NOINLINE: limit stack usage in caller */
 807 static NOINLINE int send_decline(/*uint32_t xid,*/ uint32_t server, uint32_t requested)
 808 {
 809         struct dhcp_packet packet;
 810
 811         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 812          * client-id option (unless -C), message type option:
 813          */
 814         init_packet(&packet, DHCPDECLINE);
 815
 816 #if 0
 817         /* RFC 2131 says DHCPDECLINE's xid is randomly selected by client,
 818          * but in case the server is buggy and wants DHCPDECLINE's xid
 819          * to match the xid which started entire handshake,
 820          * we use the same xid we used in initial DHCPDISCOVER:
 821          */
 822         packet.xid = xid;
 823 #endif
 824         /* DHCPDECLINE uses "requested ip", not ciaddr, to store offered IP */
 825         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 826
 827         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 828
 829         bb_error_msg("sending %s", "decline");
 830         return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
 831 }
 832 #endif
 833
 834 /* Unicast a DHCP release message */
 835 static int send_release(uint32_t server, uint32_t ciaddr)
 836 {
 837         struct dhcp_packet packet;
 838
 839         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 840          * client-id option (unless -C), message type option:
 841          */
 842         init_packet(&packet, DHCPRELEASE);
 843
 844         /* DHCPRELEASE uses ciaddr, not "requested ip", to store IP being released */
 845         packet.ciaddr = ciaddr;
 846
 847         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 848
 849         bb_error_msg("sending %s", "release");
 850         /* Note: normally we unicast here since "server" is not zero.
 851          * However, there _are_ people who run "address-less" DHCP servers,
 852          * and reportedly ISC dhcp client and Windows allow that.
 853          */
 854         return bcast_or_ucast(&packet, ciaddr, server);
 855 }
 856
 857 /* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */
 858 /* NOINLINE: limit stack usage in caller */
 859 static NOINLINE int udhcp_recv_raw_packet(struct dhcp_packet *dhcp_pkt, int fd)
 860 {
 861         int bytes;
 862         struct ip_udp_dhcp_packet packet;
 863         uint16_t check;
 864         unsigned char cmsgbuf[CMSG_LEN(sizeof(struct tpacket_auxdata))];
 865         struct iovec iov;
 866         struct msghdr msg;
 867         struct cmsghdr *cmsg;
 868
 869         /* used to use just safe_read(fd, &packet, sizeof(packet))
 870          * but we need to check for TP_STATUS_CSUMNOTREADY :(
 871          */
 872         iov.iov_base = &packet;
 873         iov.iov_len = sizeof(packet);
 874         memset(&msg, 0, sizeof(msg));
 875         msg.msg_iov = &iov;
 876         msg.msg_iovlen = 1;
 877         msg.msg_control = cmsgbuf;
 878         msg.msg_controllen = sizeof(cmsgbuf);
 879         for (;;) {
 880                 bytes = recvmsg(fd, &msg, 0);
 881                 if (bytes < 0) {
 882                         if (errno == EINTR)
 883                                 continue;
 884                         log1("packet read error, ignoring");
 885                         /* NB: possible down interface, etc. Caller should pause. */
 886                         return bytes; /* returns -1 */
 887                 }
 888                 break;
 889         }
 890
 891         if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) {
 892                 log1("packet is too short, ignoring");
 893                 return -2;
 894         }
 895
 896         if (bytes < ntohs(packet.ip.tot_len)) {
 897                 /* packet is bigger than sizeof(packet), we did partial read */
 898                 log1("oversized packet, ignoring");
 899                 return -2;
 900         }
 901
 902         /* ignore any extra garbage bytes */
 903         bytes = ntohs(packet.ip.tot_len);
 904
 905         /* make sure its the right packet for us, and that it passes sanity checks */
 906         if (packet.ip.protocol != IPPROTO_UDP
 907          || packet.ip.version != IPVERSION
 908          || packet.ip.ihl != (sizeof(packet.ip) >> 2)
 909          || packet.udp.dest != htons(CLIENT_PORT)
 910         /* || bytes > (int) sizeof(packet) - can't happen */
 911          || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
 912         ) {
 913                 log1("unrelated/bogus packet, ignoring");
 914                 return -2;
 915         }
 916
 917         /* verify IP checksum */
 918         check = packet.ip.check;
 919         packet.ip.check = 0;
 920         if (check != inet_cksum((uint16_t *)&packet.ip, sizeof(packet.ip))) {
 921                 log1("bad IP header checksum, ignoring");
 922                 return -2;
 923         }
 924
 925         for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
 926                 if (cmsg->cmsg_level == SOL_PACKET
 927                  && cmsg->cmsg_type == PACKET_AUXDATA
 928                 ) {
 929                         /* some VMs don't checksum UDP and TCP data
 930                          * they send to the same physical machine,
 931                          * here we detect this case:
 932                          */
 933                         struct tpacket_auxdata *aux = (void *)CMSG_DATA(cmsg);
 934                         if (aux->tp_status & TP_STATUS_CSUMNOTREADY)
 935                                 goto skip_udp_sum_check;
 936                 }
 937         }
 938
 939         /* verify UDP checksum. IP header has to be modified for this */
 940         memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
 941         /* ip.xx fields which are not memset: protocol, check, saddr, daddr */
 942         packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
 943         check = packet.udp.check;
 944         packet.udp.check = 0;
 945         if (check && check != inet_cksum((uint16_t *)&packet, bytes)) {
 946                 log1("packet with bad UDP checksum received, ignoring");
 947                 return -2;
 948         }
 949  skip_udp_sum_check:
 950
 951         if (packet.data.cookie != htonl(DHCP_MAGIC)) {
 952                 bb_error_msg("packet with bad magic, ignoring");
 953                 return -2;
 954         }
 955
 956         log1("received %s", "a packet");
 957         udhcp_dump_packet(&packet.data);
 958
 959         bytes -= sizeof(packet.ip) + sizeof(packet.udp);
 960         memcpy(dhcp_pkt, &packet.data, bytes);
 961         return bytes;
 962 }
 963
 964
 965 /*** Main ***/
 966
 967 static int sockfd = -1;
 968
 969 #define LISTEN_NONE   0
 970 #define LISTEN_KERNEL 1
 971 #define LISTEN_RAW    2
 972 static smallint listen_mode;
 973
 974 /* initial state: (re)start DHCP negotiation */
 975 #define INIT_SELECTING  0
 976 /* discover was sent, DHCPOFFER reply received */
 977 #define REQUESTING      1
 978 /* select/renew was sent, DHCPACK reply received */
 979 #define BOUND           2
 980 /* half of lease passed, want to renew it by sending unicast renew requests */
 981 #define RENEWING        3
 982 /* renew requests were not answered, lease is almost over, send broadcast renew */
 983 #define REBINDING       4
 984 /* manually requested renew (SIGUSR1) */
 985 #define RENEW_REQUESTED 5
 986 /* release, possibly manually requested (SIGUSR2) */
 987 #define RELEASED        6
 988 static smallint state;
 989
 990 static int udhcp_raw_socket(int ifindex)
 991 {
 992         int fd;
 993         struct sockaddr_ll sock;
 994
 995         log1("opening raw socket on ifindex %d", ifindex); //log2?
 996
 997         fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
 998         /* ^^^^^
 999          * SOCK_DGRAM: remove link-layer headers on input (SOCK_RAW keeps them)
1000          * ETH_P_IP: want to receive only packets with IPv4 eth type
1001          */
1002         log1("got raw socket fd"); //log2?
1003
1004         sock.sll_family = AF_PACKET;
1005         sock.sll_protocol = htons(ETH_P_IP);
1006         sock.sll_ifindex = ifindex;
1007         xbind(fd, (struct sockaddr *) &sock, sizeof(sock));
1008
1009 #if 0 /* Several users reported breakage when BPF filter is used */
1010         if (CLIENT_PORT == 68) {
1011                 /* Use only if standard port is in use */
1012                 /*
1013                  *      I've selected not to see LL header, so BPF doesn't see it, too.
1014                  *      The filter may also pass non-IP and non-ARP packets, but we do
1015                  *      a more complete check when receiving the message in userspace.
1016                  *
1017                  * and filter shamelessly stolen from:
1018                  *
1019                  *      http://www.flamewarmaster.de/software/dhcpclient/
1020                  *
1021                  * There are a few other interesting ideas on that page (look under
1022                  * "Motivation").  Use of netlink events is most interesting.  Think
1023                  * of various network servers listening for events and reconfiguring.
1024                  * That would obsolete sending HUP signals and/or make use of restarts.
1025                  *
1026                  * Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
1027                  * License: GPL v2.
1028                  */
1029                 static const struct sock_filter filter_instr[] = {
1030                         /* load 9th byte (protocol) */
1031                         BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
1032                         /* jump to L1 if it is IPPROTO_UDP, else to L4 */
1033                         BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 0, 6),
1034                         /* L1: load halfword from offset 6 (flags and frag offset) */
1035                         BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 6),
1036                         /* jump to L4 if any bits in frag offset field are set, else to L2 */
1037                         BPF_JUMP(BPF_JMP|BPF_JSET|BPF_K, 0x1fff, 4, 0),
1038                         /* L2: skip IP header (load index reg with header len) */
1039                         BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0),
1040                         /* load udp destination port from halfword[header_len + 2] */
1041                         BPF_STMT(BPF_LD|BPF_H|BPF_IND, 2),
1042                         /* jump to L3 if udp dport is CLIENT_PORT, else to L4 */
1043                         BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 68, 0, 1),
1044                         /* L3: accept packet ("accept 0x7fffffff bytes") */
1045                         /* Accepting 0xffffffff works too but kernel 2.6.19 is buggy */
1046                         BPF_STMT(BPF_RET|BPF_K, 0x7fffffff),
1047                         /* L4: discard packet ("accept zero bytes") */
1048                         BPF_STMT(BPF_RET|BPF_K, 0),
1049                 };
1050                 static const struct sock_fprog filter_prog = {
1051                         .len = sizeof(filter_instr) / sizeof(filter_instr[0]),
1052                         /* casting const away: */
1053                         .filter = (struct sock_filter *) filter_instr,
1054                 };
1055                 /* Ignoring error (kernel may lack support for this) */
1056                 if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
1057                                 sizeof(filter_prog)) >= 0)
1058                         log1("attached filter to raw socket fd"); // log?
1059         }
1060 #endif
1061
1062         if (setsockopt_1(fd, SOL_PACKET, PACKET_AUXDATA) != 0) {
1063                 if (errno != ENOPROTOOPT)
1064                         log1("can't set PACKET_AUXDATA on raw socket");
1065         }
1066
1067         log1("created raw socket");
1068
1069         return fd;
1070 }
1071
1072 static void change_listen_mode(int new_mode)
1073 {
1074         log1("entering listen mode: %s",
1075                 new_mode != LISTEN_NONE
1076                         ? (new_mode == LISTEN_KERNEL ? "kernel" : "raw")
1077                         : "none"
1078         );
1079
1080         listen_mode = new_mode;
1081         if (sockfd >= 0) {
1082                 close(sockfd);
1083                 sockfd = -1;
1084         }
1085         if (new_mode == LISTEN_KERNEL)
1086                 sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
1087         else if (new_mode != LISTEN_NONE)
1088                 sockfd = udhcp_raw_socket(client_config.ifindex);
1089         /* else LISTEN_NONE: sockfd stays closed */
1090 }
1091
1092 /* Called only on SIGUSR1 */
1093 static void perform_renew(void)
1094 {
1095         bb_error_msg("performing DHCP renew");
1096         switch (state) {
1097         case BOUND:
1098                 change_listen_mode(LISTEN_KERNEL);
1099         case RENEWING:
1100         case REBINDING:
1101                 state = RENEW_REQUESTED;
1102                 break;
1103         case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
1104                 udhcp_run_script(NULL, "deconfig");
1105         case REQUESTING:
1106         case RELEASED:
1107                 change_listen_mode(LISTEN_RAW);
1108                 state = INIT_SELECTING;
1109                 break;
1110         case INIT_SELECTING:
1111                 break;
1112         }
1113 }
1114
1115 static void perform_release(uint32_t server_addr, uint32_t requested_ip)
1116 {
1117         char buffer[sizeof("255.255.255.255")];
1118         struct in_addr temp_addr;
1119
1120         /* send release packet */
1121         if (state == BOUND || state == RENEWING || state == REBINDING) {
1122                 temp_addr.s_addr = server_addr;
1123                 strcpy(buffer, inet_ntoa(temp_addr));
1124                 temp_addr.s_addr = requested_ip;
1125                 bb_error_msg("unicasting a release of %s to %s",
1126                                 inet_ntoa(temp_addr), buffer);
1127                 send_release(server_addr, requested_ip); /* unicast */
1128                 udhcp_run_script(NULL, "deconfig");
1129         }
1130         bb_error_msg("entering released state");
1131
1132         change_listen_mode(LISTEN_NONE);
1133         state = RELEASED;
1134 }
1135
1136 static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
1137 {
1138         uint8_t *storage;
1139         int len = strnlen(str, 255);
1140         storage = xzalloc(len + extra + OPT_DATA);
1141         storage[OPT_CODE] = code;
1142         storage[OPT_LEN] = len + extra;
1143         memcpy(storage + extra + OPT_DATA, str, len);
1144         return storage;
1145 }
1146
1147 #if BB_MMU
1148 static void client_background(void)
1149 {
1150         bb_daemonize(0);
1151         logmode &= ~LOGMODE_STDIO;
1152         /* rewrite pidfile, as our pid is different now */
1153         write_pidfile(client_config.pidfile);
1154 }
1155 #endif
1156
1157 //usage:#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
1158 //usage:# define IF_UDHCP_VERBOSE(...) __VA_ARGS__
1159 //usage:#else
1160 //usage:# define IF_UDHCP_VERBOSE(...)
1161 //usage:#endif
1162 //usage:#define udhcpc_trivial_usage
1163 //usage:       "[-fbq"IF_UDHCP_VERBOSE("v")"RB]"IF_FEATURE_UDHCPC_ARPING(" [-a[MSEC]]")" [-t N] [-T SEC] [-A SEC/-n]\n"
1164 //usage:       "        [-i IFACE]"IF_FEATURE_UDHCP_PORT(" [-P PORT]")" [-s PROG] [-p PIDFILE]\n"
1165 //usage:       "        [-oC] [-r IP] [-V VENDOR] [-F NAME] [-x OPT:VAL]... [-O OPT]..."
1166 //usage:#define udhcpc_full_usage "\n"
1167 //usage:        IF_LONG_OPTS(
1168 //usage:     "\n        -i,--interface IFACE    Interface to use (default eth0)"
1169 //usage:        IF_FEATURE_UDHCP_PORT(
1170 //usage:     "\n        -P,--client-port PORT   Use PORT (default 68)"
1171 //usage:        )
1172 //usage:     "\n        -s,--script PROG        Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
1173 //usage:     "\n        -p,--pidfile FILE       Create pidfile"
1174 //usage:     "\n        -B,--broadcast          Request broadcast replies"
1175 //usage:     "\n        -t,--retries N          Send up to N discover packets (default 3)"
1176 //usage:     "\n        -T,--timeout SEC        Pause between packets (default 3)"
1177 //usage:     "\n        -A,--tryagain SEC       Wait if lease is not obtained (default 20)"
1178 //usage:     "\n        -n,--now                Exit if lease is not obtained"
1179 //usage:     "\n        -q,--quit               Exit after obtaining lease"
1180 //usage:     "\n        -R,--release            Release IP on exit"
1181 //usage:     "\n        -f,--foreground         Run in foreground"
1182 //usage:        USE_FOR_MMU(
1183 //usage:     "\n        -b,--background         Background if lease is not obtained"
1184 //usage:        )
1185 //usage:     "\n        -S,--syslog             Log to syslog too"
1186 //usage:        IF_FEATURE_UDHCPC_ARPING(
1187 //usage:     "\n        -a[MSEC],--arping[=MSEC] Validate offered address with ARP ping"
1188 //usage:        )
1189 //usage:     "\n        -r,--request IP         Request this IP address"
1190 //usage:     "\n        -o,--no-default-options Don't request any options (unless -O is given)"
1191 //usage:     "\n        -O,--request-option OPT Request option OPT from server (cumulative)"
1192 //usage:     "\n        -x OPT:VAL              Include option OPT in sent packets (cumulative)"
1193 //usage:     "\n                                Examples of string, numeric, and hex byte opts:"
1194 //usage:     "\n                                -x hostname:bbox - option 12"
1195 //usage:     "\n                                -x lease:3600 - option 51 (lease time)"
1196 //usage:     "\n                                -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
1197 //usage:     "\n        -F,--fqdn NAME          Ask server to update DNS mapping for NAME"
1198 //usage:     "\n        -V,--vendorclass VENDOR Vendor identifier (default 'udhcp VERSION')"
1199 //usage:     "\n        -C,--clientid-none      Don't send MAC as client identifier"
1200 //usage:        IF_UDHCP_VERBOSE(
1201 //usage:     "\n        -v                      Verbose"
1202 //usage:        )
1203 //usage:        )
1204 //usage:        IF_NOT_LONG_OPTS(
1205 //usage:     "\n        -i IFACE        Interface to use (default eth0)"
1206 //usage:        IF_FEATURE_UDHCP_PORT(
1207 //usage:     "\n        -P PORT         Use PORT (default 68)"
1208 //usage:        )
1209 //usage:     "\n        -s PROG         Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
1210 //usage:     "\n        -p FILE         Create pidfile"
1211 //usage:     "\n        -B              Request broadcast replies"
1212 //usage:     "\n        -t N            Send up to N discover packets (default 3)"
1213 //usage:     "\n        -T SEC          Pause between packets (default 3)"
1214 //usage:     "\n        -A SEC          Wait if lease is not obtained (default 20)"
1215 //usage:     "\n        -n              Exit if lease is not obtained"
1216 //usage:     "\n        -q              Exit after obtaining lease"
1217 //usage:     "\n        -R              Release IP on exit"
1218 //usage:     "\n        -f              Run in foreground"
1219 //usage:        USE_FOR_MMU(
1220 //usage:     "\n        -b              Background if lease is not obtained"
1221 //usage:        )
1222 //usage:     "\n        -S              Log to syslog too"
1223 //usage:        IF_FEATURE_UDHCPC_ARPING(
1224 //usage:     "\n        -a[MSEC]        Validate offered address with ARP ping"
1225 //usage:        )
1226 //usage:     "\n        -r IP           Request this IP address"
1227 //usage:     "\n        -o              Don't request any options (unless -O is given)"
1228 //usage:     "\n        -O OPT          Request option OPT from server (cumulative)"
1229 //usage:     "\n        -x OPT:VAL      Include option OPT in sent packets (cumulative)"
1230 //usage:     "\n                        Examples of string, numeric, and hex byte opts:"
1231 //usage:     "\n                        -x hostname:bbox - option 12"
1232 //usage:     "\n                        -x lease:3600 - option 51 (lease time)"
1233 //usage:     "\n                        -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
1234 //usage:     "\n        -F NAME         Ask server to update DNS mapping for NAME"
1235 //usage:     "\n        -V VENDOR       Vendor identifier (default 'udhcp VERSION')"
1236 //usage:     "\n        -C              Don't send MAC as client identifier"
1237 //usage:        IF_UDHCP_VERBOSE(
1238 //usage:     "\n        -v              Verbose"
1239 //usage:        )
1240 //usage:        )
1241 //usage:     "\nSignals:"
1242 //usage:     "\n        USR1    Renew lease"
1243 //usage:     "\n        USR2    Release lease"
1244
1245
1246 int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
1247 int udhcpc_main(int argc UNUSED_PARAM, char **argv)
1248 {
1249         uint8_t *message;
1250         const char *str_V, *str_h, *str_F, *str_r;
1251         IF_FEATURE_UDHCPC_ARPING(const char *str_a = "2000";)
1252         IF_FEATURE_UDHCP_PORT(char *str_P;)
1253         void *clientid_mac_ptr;
1254         llist_t *list_O = NULL;
1255         llist_t *list_x = NULL;
1256         int tryagain_timeout = 20;
1257         int discover_timeout = 3;
1258         int discover_retries = 3;
1259         uint32_t server_addr = server_addr; /* for compiler */
1260         uint32_t requested_ip = 0;
1261         uint32_t xid = xid; /* for compiler */
1262         int packet_num;
1263         int timeout; /* must be signed */
1264         unsigned already_waited_sec;
1265         unsigned opt;
1266         IF_FEATURE_UDHCPC_ARPING(unsigned arpping_ms;)
1267         int max_fd;
1268         int retval;
1269         fd_set rfds;
1270
1271         /* Default options */
1272         IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;)
1273         IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
1274         client_config.interface = "eth0";
1275         client_config.script = CONFIG_UDHCPC_DEFAULT_SCRIPT;
1276         str_V = "udhcp "BB_VER;
1277
1278         /* Parse command line */
1279         /* O,x: list; -T,-t,-A take numeric param */
1280         opt_complementary = "O::x::T+:t+:A+" IF_UDHCP_VERBOSE(":vv") ;
1281         IF_LONG_OPTS(applet_long_options = udhcpc_longopts;)
1282         opt = getopt32(argv, "CV:H:h:F:i:np:qRr:s:T:t:SA:O:ox:fB"
1283                 USE_FOR_MMU("b")
1284                 IF_FEATURE_UDHCPC_ARPING("a::")
1285                 IF_FEATURE_UDHCP_PORT("P:")
1286                 "v"
1287                 , &str_V, &str_h, &str_h, &str_F
1288                 , &client_config.interface, &client_config.pidfile, &str_r /* i,p */
1289                 , &client_config.script /* s */
1290                 , &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */
1291                 , &list_O
1292                 , &list_x
1293                 IF_FEATURE_UDHCPC_ARPING(, &str_a)
1294                 IF_FEATURE_UDHCP_PORT(, &str_P)
1295                 IF_UDHCP_VERBOSE(, &dhcp_verbose)
1296         );
1297         if (opt & (OPT_h|OPT_H)) {
1298                 //msg added 2011-11
1299                 bb_error_msg("option -h NAME is deprecated, use -x hostname:NAME");
1300                 client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
1301         }
1302         if (opt & OPT_F) {
1303                 /* FQDN option format: [0x51][len][flags][0][0]<fqdn> */
1304                 client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
1305                 /* Flag bits: 0000NEOS
1306                  * S: 1 = Client requests server to update A RR in DNS as well as PTR
1307                  * O: 1 = Server indicates to client that DNS has been updated regardless
1308                  * E: 1 = Name is in DNS format, i.e. <4>host<6>domain<3>com<0>,
1309                  *    not "host.domain.com". Format 0 is obsolete.
1310                  * N: 1 = Client requests server to not update DNS (S must be 0 then)
1311                  * Two [0] bytes which follow are deprecated and must be 0.
1312                  */
1313                 client_config.fqdn[OPT_DATA + 0] = 0x1;
1314                 /*client_config.fqdn[OPT_DATA + 1] = 0; - xzalloc did it */
1315                 /*client_config.fqdn[OPT_DATA + 2] = 0; */
1316         }
1317         if (opt & OPT_r)
1318                 requested_ip = inet_addr(str_r);
1319 #if ENABLE_FEATURE_UDHCP_PORT
1320         if (opt & OPT_P) {
1321                 CLIENT_PORT = xatou16(str_P);
1322                 SERVER_PORT = CLIENT_PORT - 1;
1323         }
1324 #endif
1325         IF_FEATURE_UDHCPC_ARPING(arpping_ms = xatou(str_a);)
1326         while (list_O) {
1327                 char *optstr = llist_pop(&list_O);
1328                 unsigned n = bb_strtou(optstr, NULL, 0);
1329                 if (errno || n > 254) {
1330                         n = udhcp_option_idx(optstr);
1331                         n = dhcp_optflags[n].code;
1332                 }
1333                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
1334         }
1335         if (!(opt & OPT_o)) {
1336                 unsigned i, n;
1337                 for (i = 0; (n = dhcp_optflags[i].code) != 0; i++) {
1338                         if (dhcp_optflags[i].flags & OPTION_REQ) {
1339                                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
1340                         }
1341                 }
1342         }
1343         while (list_x) {
1344                 char *optstr = llist_pop(&list_x);
1345                 char *colon = strchr(optstr, ':');
1346                 if (colon)
1347                         *colon = ' ';
1348                 /* now it looks similar to udhcpd's config file line:
1349                  * "optname optval", using the common routine: */
1350                 udhcp_str2optset(optstr, &client_config.options);
1351         }
1352
1353         if (udhcp_read_interface(client_config.interface,
1354                         &client_config.ifindex,
1355                         NULL,
1356                         client_config.client_mac)
1357         ) {
1358                 return 1;
1359         }
1360
1361         clientid_mac_ptr = NULL;
1362         if (!(opt & OPT_C) && !udhcp_find_option(client_config.options, DHCP_CLIENT_ID)) {
1363                 /* not suppressed and not set, set the default client ID */
1364                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
1365                 client_config.clientid[OPT_DATA] = 1; /* type: ethernet */
1366                 clientid_mac_ptr = client_config.clientid + OPT_DATA+1;
1367                 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1368         }
1369         if (str_V[0] != '\0') {
1370                 // can drop -V, str_V, client_config.vendorclass,
1371                 // but need to add "vendor" to the list of recognized
1372                 // string opts for this to work;
1373                 // and need to tweak add_client_options() too...
1374                 // ...so the question is, should we?
1375                 //bb_error_msg("option -V VENDOR is deprecated, use -x vendor:VENDOR");
1376                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
1377         }
1378
1379 #if !BB_MMU
1380         /* on NOMMU reexec (i.e., background) early */
1381         if (!(opt & OPT_f)) {
1382                 bb_daemonize_or_rexec(0 /* flags */, argv);
1383                 logmode = LOGMODE_NONE;
1384         }
1385 #endif
1386         if (opt & OPT_S) {
1387                 openlog(applet_name, LOG_PID, LOG_DAEMON);
1388                 logmode |= LOGMODE_SYSLOG;
1389         }
1390
1391         /* Make sure fd 0,1,2 are open */
1392         bb_sanitize_stdio();
1393         /* Equivalent of doing a fflush after every \n */
1394         setlinebuf(stdout);
1395         /* Create pidfile */
1396         write_pidfile(client_config.pidfile);
1397         /* Goes to stdout (unless NOMMU) and possibly syslog */
1398         bb_error_msg("started, v"BB_VER);
1399         /* Set up the signal pipe */
1400         udhcp_sp_setup();
1401         /* We want random_xid to be random... */
1402         srand(monotonic_us());
1403
1404         state = INIT_SELECTING;
1405         udhcp_run_script(NULL, "deconfig");
1406         change_listen_mode(LISTEN_RAW);
1407         packet_num = 0;
1408         timeout = 0;
1409         already_waited_sec = 0;
1410
1411         /* Main event loop. select() waits on signal pipe and possibly
1412          * on sockfd.
1413          * "continue" statements in code below jump to the top of the loop.
1414          */
1415         for (;;) {
1416                 struct timeval tv;
1417                 struct dhcp_packet packet;
1418                 /* silence "uninitialized!" warning */
1419                 unsigned timestamp_before_wait = timestamp_before_wait;
1420
1421                 //bb_error_msg("sockfd:%d, listen_mode:%d", sockfd, listen_mode);
1422
1423                 /* Was opening raw or udp socket here
1424                  * if (listen_mode != LISTEN_NONE && sockfd < 0),
1425                  * but on fast network renew responses return faster
1426                  * than we open sockets. Thus this code is moved
1427                  * to change_listen_mode(). Thus we open listen socket
1428                  * BEFORE we send renew request (see "case BOUND:"). */
1429
1430                 max_fd = udhcp_sp_fd_set(&rfds, sockfd);
1431
1432                 tv.tv_sec = timeout - already_waited_sec;
1433                 tv.tv_usec = 0;
1434                 retval = 0;
1435                 /* If we already timed out, fall through with retval = 0, else... */
1436                 if ((int)tv.tv_sec > 0) {
1437                         log1("waiting on select %u seconds", (int)tv.tv_sec);
1438                         timestamp_before_wait = (unsigned)monotonic_sec();
1439                         retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
1440                         if (retval < 0) {
1441                                 /* EINTR? A signal was caught, don't panic */
1442                                 if (errno == EINTR) {
1443                                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1444                                         continue;
1445                                 }
1446                                 /* Else: an error occured, panic! */
1447                                 bb_perror_msg_and_die("select");
1448                         }
1449                 }
1450
1451                 /* If timeout dropped to zero, time to become active:
1452                  * resend discover/renew/whatever
1453                  */
1454                 if (retval == 0) {
1455                         /* When running on a bridge, the ifindex may have changed
1456                          * (e.g. if member interfaces were added/removed
1457                          * or if the status of the bridge changed).
1458                          * Refresh ifindex and client_mac:
1459                          */
1460                         if (udhcp_read_interface(client_config.interface,
1461                                         &client_config.ifindex,
1462                                         NULL,
1463                                         client_config.client_mac)
1464                         ) {
1465                                 goto ret0; /* iface is gone? */
1466                         }
1467                         if (clientid_mac_ptr)
1468                                 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1469
1470                         /* We will restart the wait in any case */
1471                         already_waited_sec = 0;
1472
1473                         switch (state) {
1474                         case INIT_SELECTING:
1475                                 if (!discover_retries || packet_num < discover_retries) {
1476                                         if (packet_num == 0)
1477                                                 xid = random_xid();
1478                                         /* broadcast */
1479                                         send_discover(xid, requested_ip);
1480                                         timeout = discover_timeout;
1481                                         packet_num++;
1482                                         continue;
1483                                 }
1484  leasefail:
1485                                 udhcp_run_script(NULL, "leasefail");
1486 #if BB_MMU /* -b is not supported on NOMMU */
1487                                 if (opt & OPT_b) { /* background if no lease */
1488                                         bb_error_msg("no lease, forking to background");
1489                                         client_background();
1490                                         /* do not background again! */
1491                                         opt = ((opt & ~OPT_b) | OPT_f);
1492                                 } else
1493 #endif
1494                                 if (opt & OPT_n) { /* abort if no lease */
1495                                         bb_error_msg("no lease, failing");
1496                                         retval = 1;
1497                                         goto ret;
1498                                 }
1499                                 /* wait before trying again */
1500                                 timeout = tryagain_timeout;
1501                                 packet_num = 0;
1502                                 continue;
1503                         case REQUESTING:
1504                                 if (packet_num < 3) {
1505                                         /* send broadcast select packet */
1506                                         send_select(xid, server_addr, requested_ip);
1507                                         timeout = discover_timeout;
1508                                         packet_num++;
1509                                         continue;
1510                                 }
1511                                 /* Timed out, go back to init state.
1512                                  * "discover...select...discover..." loops
1513                                  * were seen in the wild. Treat them similarly
1514                                  * to "no response to discover" case */
1515                                 change_listen_mode(LISTEN_RAW);
1516                                 state = INIT_SELECTING;
1517                                 goto leasefail;
1518                         case BOUND:
1519                                 /* 1/2 lease passed, enter renewing state */
1520                                 state = RENEWING;
1521                                 client_config.first_secs = 0; /* make secs field count from 0 */
1522                                 change_listen_mode(LISTEN_KERNEL);
1523                                 log1("entering renew state");
1524                                 /* fall right through */
1525                         case RENEW_REQUESTED: /* manual (SIGUSR1) renew */
1526                         case_RENEW_REQUESTED:
1527                         case RENEWING:
1528                                 if (timeout > 60) {
1529                                         /* send an unicast renew request */
1530                         /* Sometimes observed to fail (EADDRNOTAVAIL) to bind
1531                          * a new UDP socket for sending inside send_renew.
1532                          * I hazard to guess existing listening socket
1533                          * is somehow conflicting with it, but why is it
1534                          * not deterministic then?! Strange.
1535                          * Anyway, it does recover by eventually failing through
1536                          * into INIT_SELECTING state.
1537                          */
1538                                         send_renew(xid, server_addr, requested_ip);
1539                                         timeout >>= 1;
1540                                         continue;
1541                                 }
1542                                 /* Timed out, enter rebinding state */
1543                                 log1("entering rebinding state");
1544                                 state = REBINDING;
1545                                 /* fall right through */
1546                         case REBINDING:
1547                                 /* Switch to bcast receive */
1548                                 change_listen_mode(LISTEN_RAW);
1549                                 /* Lease is *really* about to run out,
1550                                  * try to find DHCP server using broadcast */
1551                                 if (timeout > 0) {
1552                                         /* send a broadcast renew request */
1553                                         send_renew(xid, 0 /*INADDR_ANY*/, requested_ip);
1554                                         timeout >>= 1;
1555                                         continue;
1556                                 }
1557                                 /* Timed out, enter init state */
1558                                 bb_error_msg("lease lost, entering init state");
1559                                 udhcp_run_script(NULL, "deconfig");
1560                                 state = INIT_SELECTING;
1561                                 client_config.first_secs = 0; /* make secs field count from 0 */
1562                                 /*timeout = 0; - already is */
1563                                 packet_num = 0;
1564                                 continue;
1565                         /* case RELEASED: */
1566                         }
1567                         /* yah, I know, *you* say it would never happen */
1568                         timeout = INT_MAX;
1569                         continue; /* back to main loop */
1570                 } /* if select timed out */
1571
1572                 /* select() didn't timeout, something happened */
1573
1574                 /* Is it a signal? */
1575                 /* note: udhcp_sp_read checks FD_ISSET before reading */
1576                 switch (udhcp_sp_read(&rfds)) {
1577                 case SIGUSR1:
1578                         client_config.first_secs = 0; /* make secs field count from 0 */
1579                         already_waited_sec = 0;
1580                         perform_renew();
1581                         if (state == RENEW_REQUESTED) {
1582                                 /* We might be either on the same network
1583                                  * (in which case renew might work),
1584                                  * or we might be on a completely different one
1585                                  * (in which case renew won't ever succeed).
1586                                  * For the second case, must make sure timeout
1587                                  * is not too big, or else we can send
1588                                  * futile renew requests for hours.
1589                                  * (Ab)use -A TIMEOUT value (usually 20 sec)
1590                                  * as a cap on the timeout.
1591                                  */
1592                                 if (timeout > tryagain_timeout)
1593                                         timeout = tryagain_timeout;
1594                                 goto case_RENEW_REQUESTED;
1595                         }
1596                         /* Start things over */
1597                         packet_num = 0;
1598                         /* Kill any timeouts, user wants this to hurry along */
1599                         timeout = 0;
1600                         continue;
1601                 case SIGUSR2:
1602                         perform_release(server_addr, requested_ip);
1603                         timeout = INT_MAX;
1604                         continue;
1605                 case SIGTERM:
1606                         bb_error_msg("received %s", "SIGTERM");
1607                         goto ret0;
1608                 }
1609
1610                 /* Is it a packet? */
1611                 if (listen_mode == LISTEN_NONE || !FD_ISSET(sockfd, &rfds))
1612                         continue; /* no */
1613
1614                 {
1615                         int len;
1616
1617                         /* A packet is ready, read it */
1618                         if (listen_mode == LISTEN_KERNEL)
1619                                 len = udhcp_recv_kernel_packet(&packet, sockfd);
1620                         else
1621                                 len = udhcp_recv_raw_packet(&packet, sockfd);
1622                         if (len == -1) {
1623                                 /* Error is severe, reopen socket */
1624                                 bb_error_msg("read error: %s, reopening socket", strerror(errno));
1625                                 sleep(discover_timeout); /* 3 seconds by default */
1626                                 change_listen_mode(listen_mode); /* just close and reopen */
1627                         }
1628                         /* If this packet will turn out to be unrelated/bogus,
1629                          * we will go back and wait for next one.
1630                          * Be sure timeout is properly decreased. */
1631                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1632                         if (len < 0)
1633                                 continue;
1634                 }
1635
1636                 if (packet.xid != xid) {
1637                         log1("xid %x (our is %x), ignoring packet",
1638                                 (unsigned)packet.xid, (unsigned)xid);
1639                         continue;
1640                 }
1641
1642                 /* Ignore packets that aren't for us */
1643                 if (packet.hlen != 6
1644                  || memcmp(packet.chaddr, client_config.client_mac, 6) != 0
1645                 ) {
1646 //FIXME: need to also check that last 10 bytes are zero
1647                         log1("chaddr does not match, ignoring packet"); // log2?
1648                         continue;
1649                 }
1650
1651                 message = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
1652                 if (message == NULL) {
1653                         bb_error_msg("no message type option, ignoring packet");
1654                         continue;
1655                 }
1656
1657                 switch (state) {
1658                 case INIT_SELECTING:
1659                         /* Must be a DHCPOFFER */
1660                         if (*message == DHCPOFFER) {
1661                                 uint8_t *temp;
1662
1663 /* What exactly is server's IP? There are several values.
1664  * Example DHCP offer captured with tchdump:
1665  *
1666  * 10.34.25.254:67 > 10.34.25.202:68 // IP header's src
1667  * BOOTP fields:
1668  * Your-IP 10.34.25.202
1669  * Server-IP 10.34.32.125   // "next server" IP
1670  * Gateway-IP 10.34.25.254  // relay's address (if DHCP relays are in use)
1671  * DHCP options:
1672  * DHCP-Message Option 53, length 1: Offer
1673  * Server-ID Option 54, length 4: 10.34.255.7       // "server ID"
1674  * Default-Gateway Option 3, length 4: 10.34.25.254 // router
1675  *
1676  * We think that real server IP (one to use in renew/release)
1677  * is one in Server-ID option. But I am not 100% sure.
1678  * IP header's src and Gateway-IP (same in this example)
1679  * might work too.
1680  * "Next server" and router are definitely wrong ones to use, though...
1681  */
1682 /* We used to ignore pcakets without DHCP_SERVER_ID.
1683  * I've got user reports from people who run "address-less" servers.
1684  * They either supply DHCP_SERVER_ID of 0.0.0.0 or don't supply it at all.
1685  * They say ISC DHCP client supports this case.
1686  */
1687                                 server_addr = 0;
1688                                 temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
1689                                 if (!temp) {
1690                                         bb_error_msg("no server ID, using 0.0.0.0");
1691                                 } else {
1692                                         /* it IS unaligned sometimes, don't "optimize" */
1693                                         move_from_unaligned32(server_addr, temp);
1694                                 }
1695                                 /*xid = packet.xid; - already is */
1696                                 requested_ip = packet.yiaddr;
1697
1698                                 /* enter requesting state */
1699                                 state = REQUESTING;
1700                                 timeout = 0;
1701                                 packet_num = 0;
1702                                 already_waited_sec = 0;
1703                         }
1704                         continue;
1705                 case REQUESTING:
1706                 case RENEWING:
1707                 case RENEW_REQUESTED:
1708                 case REBINDING:
1709                         if (*message == DHCPACK) {
1710                                 unsigned start;
1711                                 uint32_t lease_seconds;
1712                                 struct in_addr temp_addr;
1713                                 uint8_t *temp;
1714
1715                                 temp = udhcp_get_option(&packet, DHCP_LEASE_TIME);
1716                                 if (!temp) {
1717                                         bb_error_msg("no lease time with ACK, using 1 hour lease");
1718                                         lease_seconds = 60 * 60;
1719                                 } else {
1720                                         /* it IS unaligned sometimes, don't "optimize" */
1721                                         move_from_unaligned32(lease_seconds, temp);
1722                                         lease_seconds = ntohl(lease_seconds);
1723                                         /* paranoia: must not be too small and not prone to overflows */
1724                                         if (lease_seconds < 0x10)
1725                                                 lease_seconds = 0x10;
1726                                         if (lease_seconds >= 0x10000000)
1727                                                 lease_seconds = 0x0fffffff;
1728                                 }
1729 #if ENABLE_FEATURE_UDHCPC_ARPING
1730                                 if (opt & OPT_a) {
1731 /* RFC 2131 3.1 paragraph 5:
1732  * "The client receives the DHCPACK message with configuration
1733  * parameters. The client SHOULD perform a final check on the
1734  * parameters (e.g., ARP for allocated network address), and notes
1735  * the duration of the lease specified in the DHCPACK message. At this
1736  * point, the client is configured. If the client detects that the
1737  * address is already in use (e.g., through the use of ARP),
1738  * the client MUST send a DHCPDECLINE message to the server and restarts
1739  * the configuration process..." */
1740                                         if (!arpping(packet.yiaddr,
1741                                                         NULL,
1742                                                         (uint32_t) 0,
1743                                                         client_config.client_mac,
1744                                                         client_config.interface,
1745                                                         arpping_ms)
1746                                         ) {
1747                                                 bb_error_msg("offered address is in use "
1748                                                         "(got ARP reply), declining");
1749                                                 send_decline(/*xid,*/ server_addr, packet.yiaddr);
1750
1751                                                 if (state != REQUESTING)
1752                                                         udhcp_run_script(NULL, "deconfig");
1753                                                 change_listen_mode(LISTEN_RAW);
1754                                                 state = INIT_SELECTING;
1755                                                 client_config.first_secs = 0; /* make secs field count from 0 */
1756                                                 requested_ip = 0;
1757                                                 timeout = tryagain_timeout;
1758                                                 packet_num = 0;
1759                                                 already_waited_sec = 0;
1760                                                 continue; /* back to main loop */
1761                                         }
1762                                 }
1763 #endif
1764                                 /* enter bound state */
1765                                 temp_addr.s_addr = packet.yiaddr;
1766                                 bb_error_msg("lease of %s obtained, lease time %u",
1767                                         inet_ntoa(temp_addr), (unsigned)lease_seconds);
1768                                 requested_ip = packet.yiaddr;
1769
1770                                 start = monotonic_sec();
1771                                 udhcp_run_script(&packet, state == REQUESTING ? "bound" : "renew");
1772                                 already_waited_sec = (unsigned)monotonic_sec() - start;
1773                                 timeout = lease_seconds / 2;
1774                                 if ((unsigned)timeout < already_waited_sec) {
1775                                         /* Something went wrong. Back to discover state */
1776                                         timeout = already_waited_sec = 0;
1777                                 }
1778
1779                                 state = BOUND;
1780                                 change_listen_mode(LISTEN_NONE);
1781                                 if (opt & OPT_q) { /* quit after lease */
1782                                         goto ret0;
1783                                 }
1784                                 /* future renew failures should not exit (JM) */
1785                                 opt &= ~OPT_n;
1786 #if BB_MMU /* NOMMU case backgrounded earlier */
1787                                 if (!(opt & OPT_f)) {
1788                                         client_background();
1789                                         /* do not background again! */
1790                                         opt = ((opt & ~OPT_b) | OPT_f);
1791                                 }
1792 #endif
1793                                 /* make future renew packets use different xid */
1794                                 /* xid = random_xid(); ...but why bother? */
1795
1796                                 continue; /* back to main loop */
1797                         }
1798                         if (*message == DHCPNAK) {
1799                                 /* If network has more than one DHCP server,
1800                                  * "wrong" server can reply first, with a NAK.
1801                                  * Do not interpret it as a NAK from "our" server.
1802                                  */
1803                                 if (server_addr != 0) {
1804                                         uint32_t svid;
1805                                         uint8_t *temp;
1806
1807                                         temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
1808                                         if (!temp) {
1809  non_matching_svid:
1810                                                 log1("%s with wrong server ID, ignoring packet",
1811                                                         "Received DHCP NAK"
1812                                                 );
1813                                                 continue;
1814                                         }
1815                                         move_from_unaligned32(svid, temp);
1816                                         if (svid != server_addr)
1817                                                 goto non_matching_svid;
1818                                 }
1819                                 /* return to init state */
1820                                 bb_error_msg("received %s", "DHCP NAK");
1821                                 udhcp_run_script(&packet, "nak");
1822                                 if (state != REQUESTING)
1823                                         udhcp_run_script(NULL, "deconfig");
1824                                 change_listen_mode(LISTEN_RAW);
1825                                 sleep(3); /* avoid excessive network traffic */
1826                                 state = INIT_SELECTING;
1827                                 client_config.first_secs = 0; /* make secs field count from 0 */
1828                                 requested_ip = 0;
1829                                 timeout = 0;
1830                                 packet_num = 0;
1831                                 already_waited_sec = 0;
1832                         }
1833                         continue;
1834                 /* case BOUND: - ignore all packets */
1835                 /* case RELEASED: - ignore all packets */
1836                 }
1837                 /* back to main loop */
1838         } /* for (;;) - main loop ends */
1839
1840  ret0:
1841         if (opt & OPT_R) /* release on quit */
1842                 perform_release(server_addr, requested_ip);
1843         retval = 0;
1844  ret:
1845         /*if (client_config.pidfile) - remove_pidfile has its own check */
1846                 remove_pidfile(client_config.pidfile);
1847         return retval;
1848 }