networking/udhcp/dhcpc.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * udhcp client
   4  * Russ Dill <Russ.Dill@asu.edu> July 2001
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19  */
  20 //applet:IF_UDHCPC(APPLET(udhcpc, BB_DIR_SBIN, BB_SUID_DROP))
  21
  22 //kbuild:lib-$(CONFIG_UDHCPC) += common.o packet.o signalpipe.o socket.o
  23 //kbuild:lib-$(CONFIG_UDHCPC) += dhcpc.o
  24 //kbuild:lib-$(CONFIG_FEATURE_UDHCPC_ARPING) += arpping.o
  25 //kbuild:lib-$(CONFIG_FEATURE_UDHCP_RFC3397) += domain_codec.o
  26
  27 #include <syslog.h>
  28 /* Override ENABLE_FEATURE_PIDFILE - ifupdown needs our pidfile to always exist */
  29 #define WANT_PIDFILE 1
  30 #include "common.h"
  31 #include "dhcpd.h"
  32 #include "dhcpc.h"
  33
  34 #include <netinet/if_ether.h>
  35 #include <linux/filter.h>
  36 #include <linux/if_packet.h>
  37
  38 #ifndef PACKET_AUXDATA
  39 # define PACKET_AUXDATA 8
  40 struct tpacket_auxdata {
  41         uint32_t tp_status;
  42         uint32_t tp_len;
  43         uint32_t tp_snaplen;
  44         uint16_t tp_mac;
  45         uint16_t tp_net;
  46         uint16_t tp_vlan_tci;
  47         uint16_t tp_padding;
  48 };
  49 #endif
  50
  51
  52 /* "struct client_config_t client_config" is in bb_common_bufsiz1 */
  53
  54
  55 #if ENABLE_LONG_OPTS
  56 static const char udhcpc_longopts[] ALIGN1 =
  57         "clientid-none\0"  No_argument       "C"
  58         "vendorclass\0"    Required_argument "V"
  59         "hostname\0"       Required_argument "H"
  60         "fqdn\0"           Required_argument "F"
  61         "interface\0"      Required_argument "i"
  62         "now\0"            No_argument       "n"
  63         "pidfile\0"        Required_argument "p"
  64         "quit\0"           No_argument       "q"
  65         "release\0"        No_argument       "R"
  66         "request\0"        Required_argument "r"
  67         "script\0"         Required_argument "s"
  68         "timeout\0"        Required_argument "T"
  69         "retries\0"        Required_argument "t"
  70         "tryagain\0"       Required_argument "A"
  71         "syslog\0"         No_argument       "S"
  72         "request-option\0" Required_argument "O"
  73         "no-default-options\0" No_argument   "o"
  74         "foreground\0"     No_argument       "f"
  75         USE_FOR_MMU(
  76         "background\0"     No_argument       "b"
  77         )
  78         "broadcast\0"      No_argument       "B"
  79         IF_FEATURE_UDHCPC_ARPING("arping\0"     Optional_argument "a")
  80         IF_FEATURE_UDHCP_PORT("client-port\0"   Required_argument "P")
  81         ;
  82 #endif
  83 /* Must match getopt32 option string order */
  84 enum {
  85         OPT_C = 1 << 0,
  86         OPT_V = 1 << 1,
  87         OPT_H = 1 << 2,
  88         OPT_h = 1 << 3,
  89         OPT_F = 1 << 4,
  90         OPT_i = 1 << 5,
  91         OPT_n = 1 << 6,
  92         OPT_p = 1 << 7,
  93         OPT_q = 1 << 8,
  94         OPT_R = 1 << 9,
  95         OPT_r = 1 << 10,
  96         OPT_s = 1 << 11,
  97         OPT_T = 1 << 12,
  98         OPT_t = 1 << 13,
  99         OPT_S = 1 << 14,
 100         OPT_A = 1 << 15,
 101         OPT_O = 1 << 16,
 102         OPT_o = 1 << 17,
 103         OPT_x = 1 << 18,
 104         OPT_f = 1 << 19,
 105         OPT_B = 1 << 20,
 106 /* The rest has variable bit positions, need to be clever */
 107         OPTBIT_B = 20,
 108         USE_FOR_MMU(             OPTBIT_b,)
 109         IF_FEATURE_UDHCPC_ARPING(OPTBIT_a,)
 110         IF_FEATURE_UDHCP_PORT(   OPTBIT_P,)
 111         USE_FOR_MMU(             OPT_b = 1 << OPTBIT_b,)
 112         IF_FEATURE_UDHCPC_ARPING(OPT_a = 1 << OPTBIT_a,)
 113         IF_FEATURE_UDHCP_PORT(   OPT_P = 1 << OPTBIT_P,)
 114 };
 115
 116
 117 /*** Script execution code ***/
 118
 119 /* get a rough idea of how long an option will be (rounding up...) */
 120 static const uint8_t len_of_option_as_string[] ALIGN1 = {
 121         [OPTION_IP              ] = sizeof("255.255.255.255 "),
 122         [OPTION_IP_PAIR         ] = sizeof("255.255.255.255 ") * 2,
 123         [OPTION_STATIC_ROUTES   ] = sizeof("255.255.255.255/32 255.255.255.255 "),
 124         [OPTION_6RD             ] = sizeof("132 128 ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 255.255.255.255 "),
 125         [OPTION_STRING          ] = 1,
 126         [OPTION_STRING_HOST     ] = 1,
 127 #if ENABLE_FEATURE_UDHCP_RFC3397
 128         [OPTION_DNS_STRING      ] = 1, /* unused */
 129         /* Hmmm, this severely overestimates size if SIP_SERVERS option
 130          * is in domain name form: N-byte option in binary form
 131          * mallocs ~16*N bytes. But it is freed almost at once.
 132          */
 133         [OPTION_SIP_SERVERS     ] = sizeof("255.255.255.255 "),
 134 #endif
 135 //      [OPTION_BOOLEAN         ] = sizeof("yes "),
 136         [OPTION_U8              ] = sizeof("255 "),
 137         [OPTION_U16             ] = sizeof("65535 "),
 138 //      [OPTION_S16             ] = sizeof("-32768 "),
 139         [OPTION_U32             ] = sizeof("4294967295 "),
 140         [OPTION_S32             ] = sizeof("-2147483684 "),
 141 };
 142
 143 /* note: ip is a pointer to an IP in network order, possibly misaliged */
 144 static int sprint_nip(char *dest, const char *pre, const uint8_t *ip)
 145 {
 146         return sprintf(dest, "%s%u.%u.%u.%u", pre, ip[0], ip[1], ip[2], ip[3]);
 147 }
 148
 149 /* really simple implementation, just count the bits */
 150 static int mton(uint32_t mask)
 151 {
 152         int i = 0;
 153         mask = ntohl(mask); /* 111110000-like bit pattern */
 154         while (mask) {
 155                 i++;
 156                 mask <<= 1;
 157         }
 158         return i;
 159 }
 160
 161 #if ENABLE_FEATURE_UDHCPC_SANITIZEOPT
 162 /* Check if a given label represents a valid DNS label
 163  * Return pointer to the first character after the label
 164  * (NUL or dot) upon success, NULL otherwise.
 165  * See RFC1035, 2.3.1
 166  */
 167 /* We don't need to be particularly anal. For example, allowing _, hyphen
 168  * at the end, or leading and trailing dots would be ok, since it
 169  * can't be used for attacks. (Leading hyphen can be, if someone uses
 170  * cmd "$hostname"
 171  * in the script: then hostname may be treated as an option)
 172  */
 173 static const char *valid_domain_label(const char *label)
 174 {
 175         unsigned char ch;
 176         //unsigned pos = 0;
 177
 178         if (label[0] == '-')
 179                 return NULL;
 180         for (;;) {
 181                 ch = *label;
 182                 if ((ch|0x20) < 'a' || (ch|0x20) > 'z') {
 183                         if (ch < '0' || ch > '9') {
 184                                 if (ch == '\0' || ch == '.')
 185                                         return label;
 186                                 /* DNS allows only '-', but we are more permissive */
 187                                 if (ch != '-' && ch != '_')
 188                                         return NULL;
 189                         }
 190                 }
 191                 label++;
 192                 //pos++;
 193                 //Do we want this?
 194                 //if (pos > 63) /* NS_MAXLABEL; labels must be 63 chars or less */
 195                 //      return NULL;
 196         }
 197 }
 198
 199 /* Check if a given name represents a valid DNS name */
 200 /* See RFC1035, 2.3.1 */
 201 static int good_hostname(const char *name)
 202 {
 203         //const char *start = name;
 204
 205         for (;;) {
 206                 name = valid_domain_label(name);
 207                 if (!name)
 208                         return 0;
 209                 if (!name[0])
 210                         return 1;
 211                         //Do we want this?
 212                         //return ((name - start) < 1025); /* NS_MAXDNAME */
 213                 name++;
 214                 if (*name == '\0')
 215                         return 1; // We allow trailing dot too
 216         }
 217 }
 218 #else
 219 # define good_hostname(name) 1
 220 #endif
 221
 222 /* Create "opt_name=opt_value" string */
 223 static NOINLINE char *xmalloc_optname_optval(uint8_t *option, const struct dhcp_optflag *optflag, const char *opt_name)
 224 {
 225         unsigned upper_length;
 226         int len, type, optlen;
 227         char *dest, *ret;
 228
 229         /* option points to OPT_DATA, need to go back to get OPT_LEN */
 230         len = option[-OPT_DATA + OPT_LEN];
 231
 232         type = optflag->flags & OPTION_TYPE_MASK;
 233         optlen = dhcp_option_lengths[type];
 234         upper_length = len_of_option_as_string[type]
 235                 * ((unsigned)(len + optlen) / (unsigned)optlen);
 236
 237         dest = ret = xmalloc(upper_length + strlen(opt_name) + 2);
 238         dest += sprintf(ret, "%s=", opt_name);
 239
 240         while (len >= optlen) {
 241                 switch (type) {
 242                 case OPTION_IP:
 243                 case OPTION_IP_PAIR:
 244                         dest += sprint_nip(dest, "", option);
 245                         if (type == OPTION_IP)
 246                                 break;
 247                         dest += sprint_nip(dest, "/", option + 4);
 248                         break;
 249 //              case OPTION_BOOLEAN:
 250 //                      dest += sprintf(dest, *option ? "yes" : "no");
 251 //                      break;
 252                 case OPTION_U8:
 253                         dest += sprintf(dest, "%u", *option);
 254                         break;
 255 //              case OPTION_S16:
 256                 case OPTION_U16: {
 257                         uint16_t val_u16;
 258                         move_from_unaligned16(val_u16, option);
 259                         dest += sprintf(dest, "%u", ntohs(val_u16));
 260                         break;
 261                 }
 262                 case OPTION_S32:
 263                 case OPTION_U32: {
 264                         uint32_t val_u32;
 265                         move_from_unaligned32(val_u32, option);
 266                         dest += sprintf(dest, type == OPTION_U32 ? "%lu" : "%ld", (unsigned long) ntohl(val_u32));
 267                         break;
 268                 }
 269                 /* Note: options which use 'return' instead of 'break'
 270                  * (for example, OPTION_STRING) skip the code which handles
 271                  * the case of list of options.
 272                  */
 273                 case OPTION_STRING:
 274                 case OPTION_STRING_HOST:
 275                         memcpy(dest, option, len);
 276                         dest[len] = '\0';
 277 //TODO: it appears option 15 DHCP_DOMAIN_NAME is often abused
 278 //by DHCP admins to contain a space-separated list of domains,
 279 //not one domain name (presumably, to work as list of search domains,
 280 //instead of using proper option 119 DHCP_DOMAIN_SEARCH).
 281 //Currently, good_hostname() balks on strings containing spaces.
 282 //Do we need to allow it? Only for DHCP_DOMAIN_NAME option?
 283                         if (type == OPTION_STRING_HOST && !good_hostname(dest))
 284                                 safe_strncpy(dest, "bad", len);
 285                         return ret;
 286                 case OPTION_STATIC_ROUTES: {
 287                         /* Option binary format:
 288                          * mask [one byte, 0..32]
 289                          * ip [big endian, 0..4 bytes depending on mask]
 290                          * router [big endian, 4 bytes]
 291                          * may be repeated
 292                          *
 293                          * We convert it to a string "IP/MASK ROUTER IP2/MASK2 ROUTER2"
 294                          */
 295                         const char *pfx = "";
 296
 297                         while (len >= 1 + 4) { /* mask + 0-byte ip + router */
 298                                 uint32_t nip;
 299                                 uint8_t *p;
 300                                 unsigned mask;
 301                                 int bytes;
 302
 303                                 mask = *option++;
 304                                 if (mask > 32)
 305                                         break;
 306                                 len--;
 307
 308                                 nip = 0;
 309                                 p = (void*) &nip;
 310                                 bytes = (mask + 7) / 8; /* 0 -> 0, 1..8 -> 1, 9..16 -> 2 etc */
 311                                 while (--bytes >= 0) {
 312                                         *p++ = *option++;
 313                                         len--;
 314                                 }
 315                                 if (len < 4)
 316                                         break;
 317
 318                                 /* print ip/mask */
 319                                 dest += sprint_nip(dest, pfx, (void*) &nip);
 320                                 pfx = " ";
 321                                 dest += sprintf(dest, "/%u ", mask);
 322                                 /* print router */
 323                                 dest += sprint_nip(dest, "", option);
 324                                 option += 4;
 325                                 len -= 4;
 326                         }
 327
 328                         return ret;
 329                 }
 330                 case OPTION_6RD:
 331                         /* Option binary format (see RFC 5969):
 332                          *  0                   1                   2                   3
 333                          *  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
 334                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 335                          * |  OPTION_6RD   | option-length |  IPv4MaskLen  |  6rdPrefixLen |
 336                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 337                          * |                           6rdPrefix                           |
 338                          * ...                        (16 octets)                        ...
 339                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 340                          * ...                   6rdBRIPv4Address(es)                    ...
 341                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 342                          * We convert it to a string
 343                          * "IPv4MaskLen 6rdPrefixLen 6rdPrefix 6rdBRIPv4Address..."
 344                          *
 345                          * Sanity check: ensure that our length is at least 22 bytes, that
 346                          * IPv4MaskLen <= 32,
 347                          * 6rdPrefixLen <= 128,
 348                          * 6rdPrefixLen + (32 - IPv4MaskLen) <= 128
 349                          * (2nd condition need no check - it follows from 1st and 3rd).
 350                          * Else, return envvar with empty value ("optname=")
 351                          */
 352                         if (len >= (1 + 1 + 16 + 4)
 353                          && option[0] <= 32
 354                          && (option[1] + 32 - option[0]) <= 128
 355                         ) {
 356                                 /* IPv4MaskLen */
 357                                 dest += sprintf(dest, "%u ", *option++);
 358                                 /* 6rdPrefixLen */
 359                                 dest += sprintf(dest, "%u ", *option++);
 360                                 /* 6rdPrefix */
 361                                 dest += sprint_nip6(dest, /* "", */ option);
 362                                 option += 16;
 363                                 len -= 1 + 1 + 16 + 4;
 364                                 /* "+ 4" above corresponds to the length of IPv4 addr
 365                                  * we consume in the loop below */
 366                                 while (1) {
 367                                         /* 6rdBRIPv4Address(es) */
 368                                         dest += sprint_nip(dest, " ", option);
 369                                         option += 4;
 370                                         len -= 4; /* do we have yet another 4+ bytes? */
 371                                         if (len < 0)
 372                                                 break; /* no */
 373                                 }
 374                         }
 375
 376                         return ret;
 377 #if ENABLE_FEATURE_UDHCP_RFC3397
 378                 case OPTION_DNS_STRING:
 379                         /* unpack option into dest; use ret for prefix (i.e., "optname=") */
 380                         dest = dname_dec(option, len, ret);
 381                         if (dest) {
 382                                 free(ret);
 383                                 return dest;
 384                         }
 385                         /* error. return "optname=" string */
 386                         return ret;
 387                 case OPTION_SIP_SERVERS:
 388                         /* Option binary format:
 389                          * type: byte
 390                          * type=0: domain names, dns-compressed
 391                          * type=1: IP addrs
 392                          */
 393                         option++;
 394                         len--;
 395                         if (option[-1] == 0) {
 396                                 dest = dname_dec(option, len, ret);
 397                                 if (dest) {
 398                                         free(ret);
 399                                         return dest;
 400                                 }
 401                         } else
 402                         if (option[-1] == 1) {
 403                                 const char *pfx = "";
 404                                 while (1) {
 405                                         len -= 4;
 406                                         if (len < 0)
 407                                                 break;
 408                                         dest += sprint_nip(dest, pfx, option);
 409                                         pfx = " ";
 410                                         option += 4;
 411                                 }
 412                         }
 413                         return ret;
 414 #endif
 415                 } /* switch */
 416
 417                 /* If we are here, try to format any remaining data
 418                  * in the option as another, similarly-formatted option
 419                  */
 420                 option += optlen;
 421                 len -= optlen;
 422 // TODO: it can be a list only if (optflag->flags & OPTION_LIST).
 423 // Should we bail out/warn if we see multi-ip option which is
 424 // not allowed to be such (for example, DHCP_BROADCAST)? -
 425                 if (len < optlen /* || !(optflag->flags & OPTION_LIST) */)
 426                         break;
 427                 *dest++ = ' ';
 428                 *dest = '\0';
 429         } /* while */
 430
 431         return ret;
 432 }
 433
 434 /* put all the parameters into the environment */
 435 static char **fill_envp(struct dhcp_packet *packet)
 436 {
 437         int envc;
 438         int i;
 439         char **envp, **curr;
 440         const char *opt_name;
 441         uint8_t *temp;
 442         uint8_t overload = 0;
 443
 444 #define BITMAP unsigned
 445 #define BBITS (sizeof(BITMAP) * 8)
 446 #define BMASK(i) (1 << (i & (sizeof(BITMAP) * 8 - 1)))
 447 #define FOUND_OPTS(i) (found_opts[(unsigned)i / BBITS])
 448         BITMAP found_opts[256 / BBITS];
 449
 450         memset(found_opts, 0, sizeof(found_opts));
 451
 452         /* We need 6 elements for:
 453          * "interface=IFACE"
 454          * "ip=N.N.N.N" from packet->yiaddr
 455          * "siaddr=IP" from packet->siaddr_nip (unless 0)
 456          * "boot_file=FILE" from packet->file (unless overloaded)
 457          * "sname=SERVER_HOSTNAME" from packet->sname (unless overloaded)
 458          * terminating NULL
 459          */
 460         envc = 6;
 461         /* +1 element for each option, +2 for subnet option: */
 462         if (packet) {
 463                 /* note: do not search for "pad" (0) and "end" (255) options */
 464 //TODO: change logic to scan packet _once_
 465                 for (i = 1; i < 255; i++) {
 466                         temp = udhcp_get_option(packet, i);
 467                         if (temp) {
 468                                 if (i == DHCP_OPTION_OVERLOAD)
 469                                         overload |= *temp;
 470                                 else if (i == DHCP_SUBNET)
 471                                         envc++; /* for $mask */
 472                                 envc++;
 473                                 /*if (i != DHCP_MESSAGE_TYPE)*/
 474                                 FOUND_OPTS(i) |= BMASK(i);
 475                         }
 476                 }
 477         }
 478         curr = envp = xzalloc(sizeof(envp[0]) * envc);
 479
 480         *curr = xasprintf("interface=%s", client_config.interface);
 481         putenv(*curr++);
 482
 483         if (!packet)
 484                 return envp;
 485
 486         /* Export BOOTP fields. Fields we don't (yet?) export:
 487          * uint8_t op;      // always BOOTREPLY
 488          * uint8_t htype;   // hardware address type. 1 = 10mb ethernet
 489          * uint8_t hlen;    // hardware address length
 490          * uint8_t hops;    // used by relay agents only
 491          * uint32_t xid;
 492          * uint16_t secs;   // elapsed since client began acquisition/renewal
 493          * uint16_t flags;  // only one flag so far: bcast. Never set by server
 494          * uint32_t ciaddr; // client IP (usually == yiaddr. can it be different
 495          *                  // if during renew server wants to give us different IP?)
 496          * uint32_t gateway_nip; // relay agent IP address
 497          * uint8_t chaddr[16]; // link-layer client hardware address (MAC)
 498          * TODO: export gateway_nip as $giaddr?
 499          */
 500         /* Most important one: yiaddr as $ip */
 501         *curr = xmalloc(sizeof("ip=255.255.255.255"));
 502         sprint_nip(*curr, "ip=", (uint8_t *) &packet->yiaddr);
 503         putenv(*curr++);
 504         if (packet->siaddr_nip) {
 505                 /* IP address of next server to use in bootstrap */
 506                 *curr = xmalloc(sizeof("siaddr=255.255.255.255"));
 507                 sprint_nip(*curr, "siaddr=", (uint8_t *) &packet->siaddr_nip);
 508                 putenv(*curr++);
 509         }
 510         if (!(overload & FILE_FIELD) && packet->file[0]) {
 511                 /* watch out for invalid packets */
 512                 *curr = xasprintf("boot_file=%."DHCP_PKT_FILE_LEN_STR"s", packet->file);
 513                 putenv(*curr++);
 514         }
 515         if (!(overload & SNAME_FIELD) && packet->sname[0]) {
 516                 /* watch out for invalid packets */
 517                 *curr = xasprintf("sname=%."DHCP_PKT_SNAME_LEN_STR"s", packet->sname);
 518                 putenv(*curr++);
 519         }
 520
 521         /* Export known DHCP options */
 522         opt_name = dhcp_option_strings;
 523         i = 0;
 524         while (*opt_name) {
 525                 uint8_t code = dhcp_optflags[i].code;
 526                 BITMAP *found_ptr = &FOUND_OPTS(code);
 527                 BITMAP found_mask = BMASK(code);
 528                 if (!(*found_ptr & found_mask))
 529                         goto next;
 530                 *found_ptr &= ~found_mask; /* leave only unknown options */
 531                 temp = udhcp_get_option(packet, code);
 532                 *curr = xmalloc_optname_optval(temp, &dhcp_optflags[i], opt_name);
 533                 putenv(*curr++);
 534                 if (code == DHCP_SUBNET && temp[-OPT_DATA + OPT_LEN] == 4) {
 535                         /* Subnet option: make things like "$ip/$mask" possible */
 536                         uint32_t subnet;
 537                         move_from_unaligned32(subnet, temp);
 538                         *curr = xasprintf("mask=%u", mton(subnet));
 539                         putenv(*curr++);
 540                 }
 541  next:
 542                 opt_name += strlen(opt_name) + 1;
 543                 i++;
 544         }
 545         /* Export unknown options */
 546         for (i = 0; i < 256;) {
 547                 BITMAP bitmap = FOUND_OPTS(i);
 548                 if (!bitmap) {
 549                         i += BBITS;
 550                         continue;
 551                 }
 552                 if (bitmap & BMASK(i)) {
 553                         unsigned len, ofs;
 554
 555                         temp = udhcp_get_option(packet, i);
 556                         /* udhcp_get_option returns ptr to data portion,
 557                          * need to go back to get len
 558                          */
 559                         len = temp[-OPT_DATA + OPT_LEN];
 560                         *curr = xmalloc(sizeof("optNNN=") + 1 + len*2);
 561                         ofs = sprintf(*curr, "opt%u=", i);
 562                         *bin2hex(*curr + ofs, (void*) temp, len) = '\0';
 563                         putenv(*curr++);
 564                 }
 565                 i++;
 566         }
 567
 568         return envp;
 569 }
 570
 571 /* Call a script with a par file and env vars */
 572 static void udhcp_run_script(struct dhcp_packet *packet, const char *name)
 573 {
 574         char **envp, **curr;
 575         char *argv[3];
 576
 577         envp = fill_envp(packet);
 578
 579         /* call script */
 580         log1("executing %s %s", client_config.script, name);
 581         argv[0] = (char*) client_config.script;
 582         argv[1] = (char*) name;
 583         argv[2] = NULL;
 584         spawn_and_wait(argv);
 585
 586         for (curr = envp; *curr; curr++) {
 587                 log2(" %s", *curr);
 588                 bb_unsetenv_and_free(*curr);
 589         }
 590         free(envp);
 591 }
 592
 593
 594 /*** Sending/receiving packets ***/
 595
 596 static ALWAYS_INLINE uint32_t random_xid(void)
 597 {
 598         return rand();
 599 }
 600
 601 /* Initialize the packet with the proper defaults */
 602 static void init_packet(struct dhcp_packet *packet, char type)
 603 {
 604         uint16_t secs;
 605
 606         /* Fill in: op, htype, hlen, cookie fields; message type option: */
 607         udhcp_init_header(packet, type);
 608
 609         packet->xid = random_xid();
 610
 611         client_config.last_secs = monotonic_sec();
 612         if (client_config.first_secs == 0)
 613                 client_config.first_secs = client_config.last_secs;
 614         secs = client_config.last_secs - client_config.first_secs;
 615         packet->secs = htons(secs);
 616
 617         memcpy(packet->chaddr, client_config.client_mac, 6);
 618         if (client_config.clientid)
 619                 udhcp_add_binary_option(packet, client_config.clientid);
 620 }
 621
 622 static void add_client_options(struct dhcp_packet *packet)
 623 {
 624         int i, end, len;
 625
 626         udhcp_add_simple_option(packet, DHCP_MAX_SIZE, htons(IP_UDP_DHCP_SIZE));
 627
 628         /* Add a "param req" option with the list of options we'd like to have
 629          * from stubborn DHCP servers. Pull the data from the struct in common.c.
 630          * No bounds checking because it goes towards the head of the packet. */
 631         end = udhcp_end_option(packet->options);
 632         len = 0;
 633         for (i = 1; i < DHCP_END; i++) {
 634                 if (client_config.opt_mask[i >> 3] & (1 << (i & 7))) {
 635                         packet->options[end + OPT_DATA + len] = i;
 636                         len++;
 637                 }
 638         }
 639         if (len) {
 640                 packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
 641                 packet->options[end + OPT_LEN] = len;
 642                 packet->options[end + OPT_DATA + len] = DHCP_END;
 643         }
 644
 645         if (client_config.vendorclass)
 646                 udhcp_add_binary_option(packet, client_config.vendorclass);
 647         if (client_config.hostname)
 648                 udhcp_add_binary_option(packet, client_config.hostname);
 649         if (client_config.fqdn)
 650                 udhcp_add_binary_option(packet, client_config.fqdn);
 651
 652         /* Request broadcast replies if we have no IP addr */
 653         if ((option_mask32 & OPT_B) && packet->ciaddr == 0)
 654                 packet->flags |= htons(BROADCAST_FLAG);
 655
 656         /* Add -x options if any */
 657         {
 658                 struct option_set *curr = client_config.options;
 659                 while (curr) {
 660                         udhcp_add_binary_option(packet, curr->data);
 661                         curr = curr->next;
 662                 }
 663 //              if (client_config.sname)
 664 //                      strncpy((char*)packet->sname, client_config.sname, sizeof(packet->sname) - 1);
 665 //              if (client_config.boot_file)
 666 //                      strncpy((char*)packet->file, client_config.boot_file, sizeof(packet->file) - 1);
 667         }
 668
 669         // This will be needed if we remove -V VENDOR_STR in favor of
 670         // -x vendor:VENDOR_STR
 671         //if (!udhcp_find_option(packet.options, DHCP_VENDOR))
 672         //      /* not set, set the default vendor ID */
 673         //      ...add (DHCP_VENDOR, "udhcp "BB_VER) opt...
 674 }
 675
 676 /* RFC 2131
 677  * 4.4.4 Use of broadcast and unicast
 678  *
 679  * The DHCP client broadcasts DHCPDISCOVER, DHCPREQUEST and DHCPINFORM
 680  * messages, unless the client knows the address of a DHCP server.
 681  * The client unicasts DHCPRELEASE messages to the server. Because
 682  * the client is declining the use of the IP address supplied by the server,
 683  * the client broadcasts DHCPDECLINE messages.
 684  *
 685  * When the DHCP client knows the address of a DHCP server, in either
 686  * INIT or REBOOTING state, the client may use that address
 687  * in the DHCPDISCOVER or DHCPREQUEST rather than the IP broadcast address.
 688  * The client may also use unicast to send DHCPINFORM messages
 689  * to a known DHCP server. If the client receives no response to DHCP
 690  * messages sent to the IP address of a known DHCP server, the DHCP
 691  * client reverts to using the IP broadcast address.
 692  */
 693
 694 static int raw_bcast_from_client_config_ifindex(struct dhcp_packet *packet, uint32_t src_nip)
 695 {
 696         return udhcp_send_raw_packet(packet,
 697                 /*src*/ src_nip, CLIENT_PORT,
 698                 /*dst*/ INADDR_BROADCAST, SERVER_PORT, MAC_BCAST_ADDR,
 699                 client_config.ifindex);
 700 }
 701
 702 static int bcast_or_ucast(struct dhcp_packet *packet, uint32_t ciaddr, uint32_t server)
 703 {
 704         if (server)
 705                 return udhcp_send_kernel_packet(packet,
 706                         ciaddr, CLIENT_PORT,
 707                         server, SERVER_PORT);
 708         return raw_bcast_from_client_config_ifindex(packet, ciaddr);
 709 }
 710
 711 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
 712 /* NOINLINE: limit stack usage in caller */
 713 static NOINLINE int send_discover(uint32_t xid, uint32_t requested)
 714 {
 715         struct dhcp_packet packet;
 716
 717         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 718          * random xid field (we override it below),
 719          * client-id option (unless -C), message type option:
 720          */
 721         init_packet(&packet, DHCPDISCOVER);
 722
 723         packet.xid = xid;
 724         if (requested)
 725                 udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 726
 727         /* Add options: maxsize,
 728          * optionally: hostname, fqdn, vendorclass,
 729          * "param req" option according to -O, options specified with -x
 730          */
 731         add_client_options(&packet);
 732
 733         bb_error_msg("sending %s", "discover");
 734         return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
 735 }
 736
 737 /* Broadcast a DHCP request message */
 738 /* RFC 2131 3.1 paragraph 3:
 739  * "The client _broadcasts_ a DHCPREQUEST message..."
 740  */
 741 /* NOINLINE: limit stack usage in caller */
 742 static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requested)
 743 {
 744         struct dhcp_packet packet;
 745         struct in_addr temp_addr;
 746
 747 /*
 748  * RFC 2131 4.3.2 DHCPREQUEST message
 749  * ...
 750  * If the DHCPREQUEST message contains a 'server identifier'
 751  * option, the message is in response to a DHCPOFFER message.
 752  * Otherwise, the message is a request to verify or extend an
 753  * existing lease. If the client uses a 'client identifier'
 754  * in a DHCPREQUEST message, it MUST use that same 'client identifier'
 755  * in all subsequent messages. If the client included a list
 756  * of requested parameters in a DHCPDISCOVER message, it MUST
 757  * include that list in all subsequent messages.
 758  */
 759         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 760          * random xid field (we override it below),
 761          * client-id option (unless -C), message type option:
 762          */
 763         init_packet(&packet, DHCPREQUEST);
 764
 765         packet.xid = xid;
 766         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 767
 768         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 769
 770         /* Add options: maxsize,
 771          * optionally: hostname, fqdn, vendorclass,
 772          * "param req" option according to -O, and options specified with -x
 773          */
 774         add_client_options(&packet);
 775
 776         temp_addr.s_addr = requested;
 777         bb_error_msg("sending select for %s", inet_ntoa(temp_addr));
 778         return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
 779 }
 780
 781 /* Unicast or broadcast a DHCP renew message */
 782 /* NOINLINE: limit stack usage in caller */
 783 static NOINLINE int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
 784 {
 785         struct dhcp_packet packet;
 786         struct in_addr temp_addr;
 787
 788 /*
 789  * RFC 2131 4.3.2 DHCPREQUEST message
 790  * ...
 791  * DHCPREQUEST generated during RENEWING state:
 792  *
 793  * 'server identifier' MUST NOT be filled in, 'requested IP address'
 794  * option MUST NOT be filled in, 'ciaddr' MUST be filled in with
 795  * client's IP address. In this situation, the client is completely
 796  * configured, and is trying to extend its lease. This message will
 797  * be unicast, so no relay agents will be involved in its
 798  * transmission.  Because 'giaddr' is therefore not filled in, the
 799  * DHCP server will trust the value in 'ciaddr', and use it when
 800  * replying to the client.
 801  */
 802         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 803          * random xid field (we override it below),
 804          * client-id option (unless -C), message type option:
 805          */
 806         init_packet(&packet, DHCPREQUEST);
 807
 808         packet.xid = xid;
 809         packet.ciaddr = ciaddr;
 810
 811         /* Add options: maxsize,
 812          * optionally: hostname, fqdn, vendorclass,
 813          * "param req" option according to -O, and options specified with -x
 814          */
 815         add_client_options(&packet);
 816
 817         temp_addr.s_addr = server;
 818         bb_error_msg("sending renew to %s", inet_ntoa(temp_addr));
 819         return bcast_or_ucast(&packet, ciaddr, server);
 820 }
 821
 822 #if ENABLE_FEATURE_UDHCPC_ARPING
 823 /* Broadcast a DHCP decline message */
 824 /* NOINLINE: limit stack usage in caller */
 825 static NOINLINE int send_decline(/*uint32_t xid,*/ uint32_t server, uint32_t requested)
 826 {
 827         struct dhcp_packet packet;
 828
 829         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 830          * client-id option (unless -C), message type option:
 831          */
 832         init_packet(&packet, DHCPDECLINE);
 833
 834 #if 0
 835         /* RFC 2131 says DHCPDECLINE's xid is randomly selected by client,
 836          * but in case the server is buggy and wants DHCPDECLINE's xid
 837          * to match the xid which started entire handshake,
 838          * we use the same xid we used in initial DHCPDISCOVER:
 839          */
 840         packet.xid = xid;
 841 #endif
 842         /* DHCPDECLINE uses "requested ip", not ciaddr, to store offered IP */
 843         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 844
 845         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 846
 847         bb_error_msg("sending %s", "decline");
 848         return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
 849 }
 850 #endif
 851
 852 /* Unicast a DHCP release message */
 853 static
 854 ALWAYS_INLINE /* one caller, help compiler to use this fact */
 855 int send_release(uint32_t server, uint32_t ciaddr)
 856 {
 857         struct dhcp_packet packet;
 858
 859         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 860          * client-id option (unless -C), message type option:
 861          */
 862         init_packet(&packet, DHCPRELEASE);
 863
 864         /* DHCPRELEASE uses ciaddr, not "requested ip", to store IP being released */
 865         packet.ciaddr = ciaddr;
 866
 867         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 868
 869         bb_error_msg("sending %s", "release");
 870         /* Note: normally we unicast here since "server" is not zero.
 871          * However, there _are_ people who run "address-less" DHCP servers,
 872          * and reportedly ISC dhcp client and Windows allow that.
 873          */
 874         return bcast_or_ucast(&packet, ciaddr, server);
 875 }
 876
 877 /* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */
 878 /* NOINLINE: limit stack usage in caller */
 879 static NOINLINE int udhcp_recv_raw_packet(struct dhcp_packet *dhcp_pkt, int fd)
 880 {
 881         int bytes;
 882         struct ip_udp_dhcp_packet packet;
 883         uint16_t check;
 884         unsigned char cmsgbuf[CMSG_LEN(sizeof(struct tpacket_auxdata))];
 885         struct iovec iov;
 886         struct msghdr msg;
 887         struct cmsghdr *cmsg;
 888
 889         /* used to use just safe_read(fd, &packet, sizeof(packet))
 890          * but we need to check for TP_STATUS_CSUMNOTREADY :(
 891          */
 892         iov.iov_base = &packet;
 893         iov.iov_len = sizeof(packet);
 894         memset(&msg, 0, sizeof(msg));
 895         msg.msg_iov = &iov;
 896         msg.msg_iovlen = 1;
 897         msg.msg_control = cmsgbuf;
 898         msg.msg_controllen = sizeof(cmsgbuf);
 899         for (;;) {
 900                 bytes = recvmsg(fd, &msg, 0);
 901                 if (bytes < 0) {
 902                         if (errno == EINTR)
 903                                 continue;
 904                         log1("packet read error, ignoring");
 905                         /* NB: possible down interface, etc. Caller should pause. */
 906                         return bytes; /* returns -1 */
 907                 }
 908                 break;
 909         }
 910
 911         if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) {
 912                 log1("packet is too short, ignoring");
 913                 return -2;
 914         }
 915
 916         if (bytes < ntohs(packet.ip.tot_len)) {
 917                 /* packet is bigger than sizeof(packet), we did partial read */
 918                 log1("oversized packet, ignoring");
 919                 return -2;
 920         }
 921
 922         /* ignore any extra garbage bytes */
 923         bytes = ntohs(packet.ip.tot_len);
 924
 925         /* make sure its the right packet for us, and that it passes sanity checks */
 926         if (packet.ip.protocol != IPPROTO_UDP
 927          || packet.ip.version != IPVERSION
 928          || packet.ip.ihl != (sizeof(packet.ip) >> 2)
 929          || packet.udp.dest != htons(CLIENT_PORT)
 930         /* || bytes > (int) sizeof(packet) - can't happen */
 931          || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
 932         ) {
 933                 log1("unrelated/bogus packet, ignoring");
 934                 return -2;
 935         }
 936
 937         /* verify IP checksum */
 938         check = packet.ip.check;
 939         packet.ip.check = 0;
 940         if (check != inet_cksum((uint16_t *)&packet.ip, sizeof(packet.ip))) {
 941                 log1("bad IP header checksum, ignoring");
 942                 return -2;
 943         }
 944
 945         for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
 946                 if (cmsg->cmsg_level == SOL_PACKET
 947                  && cmsg->cmsg_type == PACKET_AUXDATA
 948                 ) {
 949                         /* some VMs don't checksum UDP and TCP data
 950                          * they send to the same physical machine,
 951                          * here we detect this case:
 952                          */
 953                         struct tpacket_auxdata *aux = (void *)CMSG_DATA(cmsg);
 954                         if (aux->tp_status & TP_STATUS_CSUMNOTREADY)
 955                                 goto skip_udp_sum_check;
 956                 }
 957         }
 958
 959         /* verify UDP checksum. IP header has to be modified for this */
 960         memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
 961         /* ip.xx fields which are not memset: protocol, check, saddr, daddr */
 962         packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
 963         check = packet.udp.check;
 964         packet.udp.check = 0;
 965         if (check && check != inet_cksum((uint16_t *)&packet, bytes)) {
 966                 log1("packet with bad UDP checksum received, ignoring");
 967                 return -2;
 968         }
 969  skip_udp_sum_check:
 970
 971         if (packet.data.cookie != htonl(DHCP_MAGIC)) {
 972                 bb_error_msg("packet with bad magic, ignoring");
 973                 return -2;
 974         }
 975
 976         log1("received %s", "a packet");
 977         udhcp_dump_packet(&packet.data);
 978
 979         bytes -= sizeof(packet.ip) + sizeof(packet.udp);
 980         memcpy(dhcp_pkt, &packet.data, bytes);
 981         return bytes;
 982 }
 983
 984
 985 /*** Main ***/
 986
 987 static int sockfd = -1;
 988
 989 #define LISTEN_NONE   0
 990 #define LISTEN_KERNEL 1
 991 #define LISTEN_RAW    2
 992 static smallint listen_mode;
 993
 994 /* initial state: (re)start DHCP negotiation */
 995 #define INIT_SELECTING  0
 996 /* discover was sent, DHCPOFFER reply received */
 997 #define REQUESTING      1
 998 /* select/renew was sent, DHCPACK reply received */
 999 #define BOUND           2
1000 /* half of lease passed, want to renew it by sending unicast renew requests */
1001 #define RENEWING        3
1002 /* renew requests were not answered, lease is almost over, send broadcast renew */
1003 #define REBINDING       4
1004 /* manually requested renew (SIGUSR1) */
1005 #define RENEW_REQUESTED 5
1006 /* release, possibly manually requested (SIGUSR2) */
1007 #define RELEASED        6
1008 static smallint state;
1009
1010 static int udhcp_raw_socket(int ifindex)
1011 {
1012         int fd;
1013         struct sockaddr_ll sock;
1014
1015         log2("opening raw socket on ifindex %d", ifindex);
1016
1017         fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
1018         /* ^^^^^
1019          * SOCK_DGRAM: remove link-layer headers on input (SOCK_RAW keeps them)
1020          * ETH_P_IP: want to receive only packets with IPv4 eth type
1021          */
1022         log2("got raw socket fd");
1023
1024         memset(&sock, 0, sizeof(sock)); /* let's be deterministic */
1025         sock.sll_family = AF_PACKET;
1026         sock.sll_protocol = htons(ETH_P_IP);
1027         sock.sll_ifindex = ifindex;
1028         /*sock.sll_hatype = ARPHRD_???;*/
1029         /*sock.sll_pkttype = PACKET_???;*/
1030         /*sock.sll_halen = ???;*/
1031         /*sock.sll_addr[8] = ???;*/
1032         xbind(fd, (struct sockaddr *) &sock, sizeof(sock));
1033
1034 #if 0 /* Several users reported breakage when BPF filter is used */
1035         if (CLIENT_PORT == 68) {
1036                 /* Use only if standard port is in use */
1037                 /*
1038                  *      I've selected not to see LL header, so BPF doesn't see it, too.
1039                  *      The filter may also pass non-IP and non-ARP packets, but we do
1040                  *      a more complete check when receiving the message in userspace.
1041                  *
1042                  * and filter shamelessly stolen from:
1043                  *
1044                  *      http://www.flamewarmaster.de/software/dhcpclient/
1045                  *
1046                  * There are a few other interesting ideas on that page (look under
1047                  * "Motivation").  Use of netlink events is most interesting.  Think
1048                  * of various network servers listening for events and reconfiguring.
1049                  * That would obsolete sending HUP signals and/or make use of restarts.
1050                  *
1051                  * Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
1052                  * License: GPL v2.
1053                  */
1054                 static const struct sock_filter filter_instr[] = {
1055                         /* load 9th byte (protocol) */
1056                         BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
1057                         /* jump to L1 if it is IPPROTO_UDP, else to L4 */
1058                         BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 0, 6),
1059                         /* L1: load halfword from offset 6 (flags and frag offset) */
1060                         BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 6),
1061                         /* jump to L4 if any bits in frag offset field are set, else to L2 */
1062                         BPF_JUMP(BPF_JMP|BPF_JSET|BPF_K, 0x1fff, 4, 0),
1063                         /* L2: skip IP header (load index reg with header len) */
1064                         BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0),
1065                         /* load udp destination port from halfword[header_len + 2] */
1066                         BPF_STMT(BPF_LD|BPF_H|BPF_IND, 2),
1067                         /* jump to L3 if udp dport is CLIENT_PORT, else to L4 */
1068                         BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 68, 0, 1),
1069                         /* L3: accept packet ("accept 0x7fffffff bytes") */
1070                         /* Accepting 0xffffffff works too but kernel 2.6.19 is buggy */
1071                         BPF_STMT(BPF_RET|BPF_K, 0x7fffffff),
1072                         /* L4: discard packet ("accept zero bytes") */
1073                         BPF_STMT(BPF_RET|BPF_K, 0),
1074                 };
1075                 static const struct sock_fprog filter_prog = {
1076                         .len = sizeof(filter_instr) / sizeof(filter_instr[0]),
1077                         /* casting const away: */
1078                         .filter = (struct sock_filter *) filter_instr,
1079                 };
1080                 /* Ignoring error (kernel may lack support for this) */
1081                 if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
1082                                 sizeof(filter_prog)) >= 0)
1083                         log1("attached filter to raw socket fd"); // log?
1084         }
1085 #endif
1086
1087         if (setsockopt_1(fd, SOL_PACKET, PACKET_AUXDATA) != 0) {
1088                 if (errno != ENOPROTOOPT)
1089                         log1("can't set PACKET_AUXDATA on raw socket");
1090         }
1091
1092         log1("created raw socket");
1093
1094         return fd;
1095 }
1096
1097 static void change_listen_mode(int new_mode)
1098 {
1099         log1("entering listen mode: %s",
1100                 new_mode != LISTEN_NONE
1101                         ? (new_mode == LISTEN_KERNEL ? "kernel" : "raw")
1102                         : "none"
1103         );
1104
1105         listen_mode = new_mode;
1106         if (sockfd >= 0) {
1107                 close(sockfd);
1108                 sockfd = -1;
1109         }
1110         if (new_mode == LISTEN_KERNEL)
1111                 sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
1112         else if (new_mode != LISTEN_NONE)
1113                 sockfd = udhcp_raw_socket(client_config.ifindex);
1114         /* else LISTEN_NONE: sockfd stays closed */
1115 }
1116
1117 /* Called only on SIGUSR1 */
1118 static void perform_renew(void)
1119 {
1120         bb_error_msg("performing DHCP renew");
1121         switch (state) {
1122         case BOUND:
1123                 change_listen_mode(LISTEN_KERNEL);
1124         case RENEWING:
1125         case REBINDING:
1126                 state = RENEW_REQUESTED;
1127                 break;
1128         case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
1129                 udhcp_run_script(NULL, "deconfig");
1130         case REQUESTING:
1131         case RELEASED:
1132                 change_listen_mode(LISTEN_RAW);
1133                 state = INIT_SELECTING;
1134                 break;
1135         case INIT_SELECTING:
1136                 break;
1137         }
1138 }
1139
1140 static void perform_release(uint32_t server_addr, uint32_t requested_ip)
1141 {
1142         char buffer[sizeof("255.255.255.255")];
1143         struct in_addr temp_addr;
1144
1145         /* send release packet */
1146         if (state == BOUND
1147          || state == RENEWING
1148          || state == REBINDING
1149          || state == RENEW_REQUESTED
1150         ) {
1151                 temp_addr.s_addr = server_addr;
1152                 strcpy(buffer, inet_ntoa(temp_addr));
1153                 temp_addr.s_addr = requested_ip;
1154                 bb_error_msg("unicasting a release of %s to %s",
1155                                 inet_ntoa(temp_addr), buffer);
1156                 send_release(server_addr, requested_ip); /* unicast */
1157         }
1158         bb_error_msg("entering released state");
1159 /*
1160  * We can be here on: SIGUSR2,
1161  * or on exit (SIGTERM) and -R "release on quit" is specified.
1162  * Users requested to be notified in all cases, even if not in one
1163  * of the states above.
1164  */
1165         udhcp_run_script(NULL, "deconfig");
1166
1167         change_listen_mode(LISTEN_NONE);
1168         state = RELEASED;
1169 }
1170
1171 static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
1172 {
1173         uint8_t *storage;
1174         int len = strnlen(str, 255);
1175         storage = xzalloc(len + extra + OPT_DATA);
1176         storage[OPT_CODE] = code;
1177         storage[OPT_LEN] = len + extra;
1178         memcpy(storage + extra + OPT_DATA, str, len);
1179         return storage;
1180 }
1181
1182 #if BB_MMU
1183 static void client_background(void)
1184 {
1185         bb_daemonize(0);
1186         logmode &= ~LOGMODE_STDIO;
1187         /* rewrite pidfile, as our pid is different now */
1188         write_pidfile(client_config.pidfile);
1189 }
1190 #endif
1191
1192 //usage:#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
1193 //usage:# define IF_UDHCP_VERBOSE(...) __VA_ARGS__
1194 //usage:#else
1195 //usage:# define IF_UDHCP_VERBOSE(...)
1196 //usage:#endif
1197 //usage:#define udhcpc_trivial_usage
1198 //usage:       "[-fbq"IF_UDHCP_VERBOSE("v")"RB]"IF_FEATURE_UDHCPC_ARPING(" [-a[MSEC]]")" [-t N] [-T SEC] [-A SEC/-n]\n"
1199 //usage:       "        [-i IFACE]"IF_FEATURE_UDHCP_PORT(" [-P PORT]")" [-s PROG] [-p PIDFILE]\n"
1200 //usage:       "        [-oC] [-r IP] [-V VENDOR] [-F NAME] [-x OPT:VAL]... [-O OPT]..."
1201 //usage:#define udhcpc_full_usage "\n"
1202 //usage:     "\n        -i IFACE        Interface to use (default eth0)"
1203 //usage:        IF_FEATURE_UDHCP_PORT(
1204 //usage:     "\n        -P PORT         Use PORT (default 68)"
1205 //usage:        )
1206 //usage:     "\n        -s PROG         Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
1207 //usage:     "\n        -p FILE         Create pidfile"
1208 //usage:     "\n        -B              Request broadcast replies"
1209 //usage:     "\n        -t N            Send up to N discover packets (default 3)"
1210 //usage:     "\n        -T SEC          Pause between packets (default 3)"
1211 //usage:     "\n        -A SEC          Wait if lease is not obtained (default 20)"
1212 //usage:        USE_FOR_MMU(
1213 //usage:     "\n        -b              Background if lease is not obtained"
1214 //usage:        )
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:     "\n        -S              Log to syslog too"
1220 //usage:        IF_FEATURE_UDHCPC_ARPING(
1221 //usage:     "\n        -a[MSEC]        Validate offered address with ARP ping"
1222 //usage:        )
1223 //usage:     "\n        -r IP           Request this IP address"
1224 //usage:     "\n        -o              Don't request any options (unless -O is given)"
1225 //usage:     "\n        -O OPT          Request option OPT from server (cumulative)"
1226 //usage:     "\n        -x OPT:VAL      Include option OPT in sent packets (cumulative)"
1227 //usage:     "\n                        Examples of string, numeric, and hex byte opts:"
1228 //usage:     "\n                        -x hostname:bbox - option 12"
1229 //usage:     "\n                        -x lease:3600 - option 51 (lease time)"
1230 //usage:     "\n                        -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
1231 //usage:     "\n                        -x 14:'\"dumpfile\"' - option 14 (shell-quoted)"
1232 //usage:     "\n        -F NAME         Ask server to update DNS mapping for NAME"
1233 //usage:     "\n        -V VENDOR       Vendor identifier (default 'udhcp VERSION')"
1234 //usage:     "\n        -C              Don't send MAC as client identifier"
1235 //usage:        IF_UDHCP_VERBOSE(
1236 //usage:     "\n        -v              Verbose"
1237 //usage:        )
1238 //usage:     "\nSignals:"
1239 //usage:     "\n        USR1    Renew lease"
1240 //usage:     "\n        USR2    Release lease"
1241
1242
1243 int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
1244 int udhcpc_main(int argc UNUSED_PARAM, char **argv)
1245 {
1246         uint8_t *message;
1247         const char *str_V, *str_h, *str_F, *str_r;
1248         IF_FEATURE_UDHCPC_ARPING(const char *str_a = "2000";)
1249         IF_FEATURE_UDHCP_PORT(char *str_P;)
1250         void *clientid_mac_ptr;
1251         llist_t *list_O = NULL;
1252         llist_t *list_x = NULL;
1253         int tryagain_timeout = 20;
1254         int discover_timeout = 3;
1255         int discover_retries = 3;
1256         uint32_t server_addr = server_addr; /* for compiler */
1257         uint32_t requested_ip = 0;
1258         uint32_t xid = xid; /* for compiler */
1259         int packet_num;
1260         int timeout; /* must be signed */
1261         unsigned already_waited_sec;
1262         unsigned opt;
1263         IF_FEATURE_UDHCPC_ARPING(unsigned arpping_ms;)
1264         int retval;
1265
1266         setup_common_bufsiz();
1267
1268         /* Default options */
1269         IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;)
1270         IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
1271         client_config.interface = "eth0";
1272         client_config.script = CONFIG_UDHCPC_DEFAULT_SCRIPT;
1273         str_V = "udhcp "BB_VER;
1274
1275         /* Parse command line */
1276         opt = getopt32long(argv, "^"
1277                 /* O,x: list; -T,-t,-A take numeric param */
1278                 "CV:H:h:F:i:np:qRr:s:T:+t:+SA:+O:*ox:*fB"
1279                 USE_FOR_MMU("b")
1280                 IF_FEATURE_UDHCPC_ARPING("a::")
1281                 IF_FEATURE_UDHCP_PORT("P:")
1282                 "v"
1283                 "\0" IF_UDHCP_VERBOSE("vv") /* -v is a counter */
1284                 , udhcpc_longopts
1285                 , &str_V, &str_h, &str_h, &str_F
1286                 , &client_config.interface, &client_config.pidfile /* i,p */
1287                 , &str_r /* r */
1288                 , &client_config.script /* s */
1289                 , &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */
1290                 , &list_O
1291                 , &list_x
1292                 IF_FEATURE_UDHCPC_ARPING(, &str_a)
1293                 IF_FEATURE_UDHCP_PORT(, &str_P)
1294                 IF_UDHCP_VERBOSE(, &dhcp_verbose)
1295         );
1296         if (opt & (OPT_h|OPT_H)) {
1297                 //msg added 2011-11
1298                 bb_error_msg("option -h NAME is deprecated, use -x hostname:NAME");
1299                 client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
1300         }
1301         if (opt & OPT_F) {
1302                 /* FQDN option format: [0x51][len][flags][0][0]<fqdn> */
1303                 client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
1304                 /* Flag bits: 0000NEOS
1305                  * S: 1 = Client requests server to update A RR in DNS as well as PTR
1306                  * O: 1 = Server indicates to client that DNS has been updated regardless
1307                  * E: 1 = Name is in DNS format, i.e. <4>host<6>domain<3>com<0>,
1308                  *    not "host.domain.com". Format 0 is obsolete.
1309                  * N: 1 = Client requests server to not update DNS (S must be 0 then)
1310                  * Two [0] bytes which follow are deprecated and must be 0.
1311                  */
1312                 client_config.fqdn[OPT_DATA + 0] = 0x1;
1313                 /*client_config.fqdn[OPT_DATA + 1] = 0; - xzalloc did it */
1314                 /*client_config.fqdn[OPT_DATA + 2] = 0; */
1315         }
1316         if (opt & OPT_r)
1317                 requested_ip = inet_addr(str_r);
1318 #if ENABLE_FEATURE_UDHCP_PORT
1319         if (opt & OPT_P) {
1320                 CLIENT_PORT = xatou16(str_P);
1321                 SERVER_PORT = CLIENT_PORT - 1;
1322         }
1323 #endif
1324         IF_FEATURE_UDHCPC_ARPING(arpping_ms = xatou(str_a);)
1325         while (list_O) {
1326                 char *optstr = llist_pop(&list_O);
1327                 unsigned n = bb_strtou(optstr, NULL, 0);
1328                 if (errno || n > 254) {
1329                         n = udhcp_option_idx(optstr, dhcp_option_strings);
1330                         n = dhcp_optflags[n].code;
1331                 }
1332                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
1333         }
1334         if (!(opt & OPT_o)) {
1335                 unsigned i, n;
1336                 for (i = 0; (n = dhcp_optflags[i].code) != 0; i++) {
1337                         if (dhcp_optflags[i].flags & OPTION_REQ) {
1338                                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
1339                         }
1340                 }
1341         }
1342         while (list_x) {
1343                 char *optstr = xstrdup(llist_pop(&list_x));
1344                 udhcp_str2optset(optstr, &client_config.options,
1345                                 dhcp_optflags, dhcp_option_strings,
1346                                 /*dhcpv6:*/ 0
1347                 );
1348                 free(optstr);
1349         }
1350
1351         if (udhcp_read_interface(client_config.interface,
1352                         &client_config.ifindex,
1353                         NULL,
1354                         client_config.client_mac)
1355         ) {
1356                 return 1;
1357         }
1358
1359         clientid_mac_ptr = NULL;
1360         if (!(opt & OPT_C) && !udhcp_find_option(client_config.options, DHCP_CLIENT_ID)) {
1361                 /* not suppressed and not set, set the default client ID */
1362                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
1363                 client_config.clientid[OPT_DATA] = 1; /* type: ethernet */
1364                 clientid_mac_ptr = client_config.clientid + OPT_DATA+1;
1365                 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1366         }
1367         if (str_V[0] != '\0') {
1368                 // can drop -V, str_V, client_config.vendorclass,
1369                 // but need to add "vendor" to the list of recognized
1370                 // string opts for this to work;
1371                 // and need to tweak add_client_options() too...
1372                 // ...so the question is, should we?
1373                 //bb_error_msg("option -V VENDOR is deprecated, use -x vendor:VENDOR");
1374                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
1375         }
1376
1377 #if !BB_MMU
1378         /* on NOMMU reexec (i.e., background) early */
1379         if (!(opt & OPT_f)) {
1380                 bb_daemonize_or_rexec(0 /* flags */, argv);
1381                 logmode = LOGMODE_NONE;
1382         }
1383 #endif
1384         if (opt & OPT_S) {
1385                 openlog(applet_name, LOG_PID, LOG_DAEMON);
1386                 logmode |= LOGMODE_SYSLOG;
1387         }
1388
1389         /* Make sure fd 0,1,2 are open */
1390         bb_sanitize_stdio();
1391         /* Create pidfile */
1392         write_pidfile(client_config.pidfile);
1393         /* Goes to stdout (unless NOMMU) and possibly syslog */
1394         bb_error_msg("started, v"BB_VER);
1395         /* Set up the signal pipe */
1396         udhcp_sp_setup();
1397         /* We want random_xid to be random... */
1398         srand(monotonic_us());
1399
1400         state = INIT_SELECTING;
1401         udhcp_run_script(NULL, "deconfig");
1402         change_listen_mode(LISTEN_RAW);
1403         packet_num = 0;
1404         timeout = 0;
1405         already_waited_sec = 0;
1406
1407         /* Main event loop. select() waits on signal pipe and possibly
1408          * on sockfd.
1409          * "continue" statements in code below jump to the top of the loop.
1410          */
1411         for (;;) {
1412                 int tv;
1413                 struct pollfd pfds[2];
1414                 struct dhcp_packet packet;
1415                 /* silence "uninitialized!" warning */
1416                 unsigned timestamp_before_wait = timestamp_before_wait;
1417
1418                 //bb_error_msg("sockfd:%d, listen_mode:%d", sockfd, listen_mode);
1419
1420                 /* Was opening raw or udp socket here
1421                  * if (listen_mode != LISTEN_NONE && sockfd < 0),
1422                  * but on fast network renew responses return faster
1423                  * than we open sockets. Thus this code is moved
1424                  * to change_listen_mode(). Thus we open listen socket
1425                  * BEFORE we send renew request (see "case BOUND:"). */
1426
1427                 udhcp_sp_fd_set(pfds, sockfd);
1428
1429                 tv = timeout - already_waited_sec;
1430                 retval = 0;
1431                 /* If we already timed out, fall through with retval = 0, else... */
1432                 if (tv > 0) {
1433                         log1("waiting %u seconds", tv);
1434                         timestamp_before_wait = (unsigned)monotonic_sec();
1435                         retval = poll(pfds, 2, tv < INT_MAX/1000 ? tv * 1000 : INT_MAX);
1436                         if (retval < 0) {
1437                                 /* EINTR? A signal was caught, don't panic */
1438                                 if (errno == EINTR) {
1439                                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1440                                         continue;
1441                                 }
1442                                 /* Else: an error occurred, panic! */
1443                                 bb_perror_msg_and_die("poll");
1444                         }
1445                 }
1446
1447                 /* If timeout dropped to zero, time to become active:
1448                  * resend discover/renew/whatever
1449                  */
1450                 if (retval == 0) {
1451                         /* When running on a bridge, the ifindex may have changed
1452                          * (e.g. if member interfaces were added/removed
1453                          * or if the status of the bridge changed).
1454                          * Refresh ifindex and client_mac:
1455                          */
1456                         if (udhcp_read_interface(client_config.interface,
1457                                         &client_config.ifindex,
1458                                         NULL,
1459                                         client_config.client_mac)
1460                         ) {
1461                                 goto ret0; /* iface is gone? */
1462                         }
1463                         if (clientid_mac_ptr)
1464                                 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1465
1466                         /* We will restart the wait in any case */
1467                         already_waited_sec = 0;
1468
1469                         switch (state) {
1470                         case INIT_SELECTING:
1471                                 if (!discover_retries || packet_num < discover_retries) {
1472                                         if (packet_num == 0)
1473                                                 xid = random_xid();
1474                                         /* broadcast */
1475                                         send_discover(xid, requested_ip);
1476                                         timeout = discover_timeout;
1477                                         packet_num++;
1478                                         continue;
1479                                 }
1480  leasefail:
1481                                 udhcp_run_script(NULL, "leasefail");
1482 #if BB_MMU /* -b is not supported on NOMMU */
1483                                 if (opt & OPT_b) { /* background if no lease */
1484                                         bb_error_msg("no lease, forking to background");
1485                                         client_background();
1486                                         /* do not background again! */
1487                                         opt = ((opt & ~(OPT_b|OPT_n)) | OPT_f);
1488                                         /* ^^^ also disables -n (-b takes priority over -n):
1489                                          * ifup's default udhcpc options are -R -n,
1490                                          * and users want to be able to add -b
1491                                          * (in a config file) to make it background
1492                                          * _and not exit_.
1493                                          */
1494                                 } else
1495 #endif
1496                                 if (opt & OPT_n) { /* abort if no lease */
1497                                         bb_error_msg("no lease, failing");
1498                                         retval = 1;
1499                                         goto ret;
1500                                 }
1501                                 /* wait before trying again */
1502                                 timeout = tryagain_timeout;
1503                                 packet_num = 0;
1504                                 continue;
1505                         case REQUESTING:
1506                                 if (packet_num < 3) {
1507                                         /* send broadcast select packet */
1508                                         send_select(xid, server_addr, requested_ip);
1509                                         timeout = discover_timeout;
1510                                         packet_num++;
1511                                         continue;
1512                                 }
1513                                 /* Timed out, go back to init state.
1514                                  * "discover...select...discover..." loops
1515                                  * were seen in the wild. Treat them similarly
1516                                  * to "no response to discover" case */
1517                                 change_listen_mode(LISTEN_RAW);
1518                                 state = INIT_SELECTING;
1519                                 goto leasefail;
1520                         case BOUND:
1521                                 /* 1/2 lease passed, enter renewing state */
1522                                 state = RENEWING;
1523                                 client_config.first_secs = 0; /* make secs field count from 0 */
1524                                 change_listen_mode(LISTEN_KERNEL);
1525                                 log1("entering renew state");
1526                                 /* fall right through */
1527                         case RENEW_REQUESTED: /* manual (SIGUSR1) renew */
1528                         case_RENEW_REQUESTED:
1529                         case RENEWING:
1530                                 if (timeout >= 60) {
1531                                         /* send an unicast renew request */
1532                         /* Sometimes observed to fail (EADDRNOTAVAIL) to bind
1533                          * a new UDP socket for sending inside send_renew.
1534                          * I hazard to guess existing listening socket
1535                          * is somehow conflicting with it, but why is it
1536                          * not deterministic then?! Strange.
1537                          * Anyway, it does recover by eventually failing through
1538                          * into INIT_SELECTING state.
1539                          */
1540                                         if (send_renew(xid, server_addr, requested_ip) >= 0) {
1541                                                 timeout >>= 1;
1542 //TODO: the timeout to receive an answer for our renew should not be selected
1543 //with "timeout = lease_seconds / 2; ...; timeout = timeout / 2": it is often huge.
1544 //Waiting e.g. 4*3600 seconds for a reply does not make sense
1545 //(if reply isn't coming, we keep an open socket for hours),
1546 //it should be something like 10 seconds.
1547 //Also, it's probably best to try sending renew in kernel mode a few (3-5) times
1548 //and fall back to raw mode if it does not work.
1549                                                 continue;
1550                                         }
1551                                         /* else: error sending.
1552                                          * example: ENETUNREACH seen with server
1553                                          * which gave us bogus server ID 1.1.1.1
1554                                          * which wasn't reachable (and probably did not exist).
1555                                          */
1556                                 }
1557                                 /* Timed out or error, enter rebinding state */
1558                                 log1("entering rebinding state");
1559                                 state = REBINDING;
1560                                 /* fall right through */
1561                         case REBINDING:
1562                                 /* Switch to bcast receive */
1563                                 change_listen_mode(LISTEN_RAW);
1564                                 /* Lease is *really* about to run out,
1565                                  * try to find DHCP server using broadcast */
1566                                 if (timeout > 0) {
1567                                         /* send a broadcast renew request */
1568                                         send_renew(xid, 0 /*INADDR_ANY*/, requested_ip);
1569                                         timeout >>= 1;
1570                                         continue;
1571                                 }
1572                                 /* Timed out, enter init state */
1573                                 bb_error_msg("lease lost, entering init state");
1574                                 udhcp_run_script(NULL, "deconfig");
1575                                 state = INIT_SELECTING;
1576                                 client_config.first_secs = 0; /* make secs field count from 0 */
1577                                 /*timeout = 0; - already is */
1578                                 packet_num = 0;
1579                                 continue;
1580                         /* case RELEASED: */
1581                         }
1582                         /* yah, I know, *you* say it would never happen */
1583                         timeout = INT_MAX;
1584                         continue; /* back to main loop */
1585                 } /* if poll timed out */
1586
1587                 /* poll() didn't timeout, something happened */
1588
1589                 /* Is it a signal? */
1590                 switch (udhcp_sp_read()) {
1591                 case SIGUSR1:
1592                         client_config.first_secs = 0; /* make secs field count from 0 */
1593                         already_waited_sec = 0;
1594                         perform_renew();
1595                         if (state == RENEW_REQUESTED) {
1596                                 /* We might be either on the same network
1597                                  * (in which case renew might work),
1598                                  * or we might be on a completely different one
1599                                  * (in which case renew won't ever succeed).
1600                                  * For the second case, must make sure timeout
1601                                  * is not too big, or else we can send
1602                                  * futile renew requests for hours.
1603                                  */
1604                                 if (timeout > 60)
1605                                         timeout = 60;
1606                                 goto case_RENEW_REQUESTED;
1607                         }
1608                         /* Start things over */
1609                         packet_num = 0;
1610                         /* Kill any timeouts, user wants this to hurry along */
1611                         timeout = 0;
1612                         continue;
1613                 case SIGUSR2:
1614                         perform_release(server_addr, requested_ip);
1615                         timeout = INT_MAX;
1616                         continue;
1617                 case SIGTERM:
1618                         bb_error_msg("received %s", "SIGTERM");
1619                         goto ret0;
1620                 }
1621
1622                 /* Is it a packet? */
1623                 if (!pfds[1].revents)
1624                         continue; /* no */
1625
1626                 {
1627                         int len;
1628
1629                         /* A packet is ready, read it */
1630                         if (listen_mode == LISTEN_KERNEL)
1631                                 len = udhcp_recv_kernel_packet(&packet, sockfd);
1632                         else
1633                                 len = udhcp_recv_raw_packet(&packet, sockfd);
1634                         if (len == -1) {
1635                                 /* Error is severe, reopen socket */
1636                                 bb_error_msg("read error: "STRERROR_FMT", reopening socket" STRERROR_ERRNO);
1637                                 sleep(discover_timeout); /* 3 seconds by default */
1638                                 change_listen_mode(listen_mode); /* just close and reopen */
1639                         }
1640                         /* If this packet will turn out to be unrelated/bogus,
1641                          * we will go back and wait for next one.
1642                          * Be sure timeout is properly decreased. */
1643                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1644                         if (len < 0)
1645                                 continue;
1646                 }
1647
1648                 if (packet.xid != xid) {
1649                         log1("xid %x (our is %x), ignoring packet",
1650                                 (unsigned)packet.xid, (unsigned)xid);
1651                         continue;
1652                 }
1653
1654                 /* Ignore packets that aren't for us */
1655                 if (packet.hlen != 6
1656                  || memcmp(packet.chaddr, client_config.client_mac, 6) != 0
1657                 ) {
1658 //FIXME: need to also check that last 10 bytes are zero
1659                         log1("chaddr does not match, ignoring packet"); // log2?
1660                         continue;
1661                 }
1662
1663                 message = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
1664                 if (message == NULL) {
1665                         bb_error_msg("no message type option, ignoring packet");
1666                         continue;
1667                 }
1668
1669                 switch (state) {
1670                 case INIT_SELECTING:
1671                         /* Must be a DHCPOFFER */
1672                         if (*message == DHCPOFFER) {
1673                                 uint8_t *temp;
1674
1675 /* What exactly is server's IP? There are several values.
1676  * Example DHCP offer captured with tchdump:
1677  *
1678  * 10.34.25.254:67 > 10.34.25.202:68 // IP header's src
1679  * BOOTP fields:
1680  * Your-IP 10.34.25.202
1681  * Server-IP 10.34.32.125   // "next server" IP
1682  * Gateway-IP 10.34.25.254  // relay's address (if DHCP relays are in use)
1683  * DHCP options:
1684  * DHCP-Message Option 53, length 1: Offer
1685  * Server-ID Option 54, length 4: 10.34.255.7       // "server ID"
1686  * Default-Gateway Option 3, length 4: 10.34.25.254 // router
1687  *
1688  * We think that real server IP (one to use in renew/release)
1689  * is one in Server-ID option. But I am not 100% sure.
1690  * IP header's src and Gateway-IP (same in this example)
1691  * might work too.
1692  * "Next server" and router are definitely wrong ones to use, though...
1693  */
1694 /* We used to ignore pcakets without DHCP_SERVER_ID.
1695  * I've got user reports from people who run "address-less" servers.
1696  * They either supply DHCP_SERVER_ID of 0.0.0.0 or don't supply it at all.
1697  * They say ISC DHCP client supports this case.
1698  */
1699                                 server_addr = 0;
1700                                 temp = udhcp_get_option32(&packet, DHCP_SERVER_ID);
1701                                 if (!temp) {
1702                                         bb_error_msg("no server ID, using 0.0.0.0");
1703                                 } else {
1704                                         /* it IS unaligned sometimes, don't "optimize" */
1705                                         move_from_unaligned32(server_addr, temp);
1706                                 }
1707                                 /*xid = packet.xid; - already is */
1708                                 requested_ip = packet.yiaddr;
1709
1710                                 /* enter requesting state */
1711                                 state = REQUESTING;
1712                                 timeout = 0;
1713                                 packet_num = 0;
1714                                 already_waited_sec = 0;
1715                         }
1716                         continue;
1717                 case REQUESTING:
1718                 case RENEWING:
1719                 case RENEW_REQUESTED:
1720                 case REBINDING:
1721                         if (*message == DHCPACK) {
1722                                 unsigned start;
1723                                 uint32_t lease_seconds;
1724                                 struct in_addr temp_addr;
1725                                 uint8_t *temp;
1726
1727                                 temp = udhcp_get_option32(&packet, DHCP_LEASE_TIME);
1728                                 if (!temp) {
1729                                         bb_error_msg("no lease time with ACK, using 1 hour lease");
1730                                         lease_seconds = 60 * 60;
1731                                 } else {
1732                                         /* it IS unaligned sometimes, don't "optimize" */
1733                                         move_from_unaligned32(lease_seconds, temp);
1734                                         lease_seconds = ntohl(lease_seconds);
1735                                         /* paranoia: must not be too small and not prone to overflows */
1736                                         /* timeout > 60 - ensures at least one unicast renew attempt */
1737                                         if (lease_seconds < 2 * 61)
1738                                                 lease_seconds = 2 * 61;
1739                                         //if (lease_seconds > 0x7fffffff)
1740                                         //      lease_seconds = 0x7fffffff;
1741                                         //^^^not necessary since "timeout = lease_seconds / 2"
1742                                         //does not overflow even for 0xffffffff.
1743                                 }
1744 #if ENABLE_FEATURE_UDHCPC_ARPING
1745                                 if (opt & OPT_a) {
1746 /* RFC 2131 3.1 paragraph 5:
1747  * "The client receives the DHCPACK message with configuration
1748  * parameters. The client SHOULD perform a final check on the
1749  * parameters (e.g., ARP for allocated network address), and notes
1750  * the duration of the lease specified in the DHCPACK message. At this
1751  * point, the client is configured. If the client detects that the
1752  * address is already in use (e.g., through the use of ARP),
1753  * the client MUST send a DHCPDECLINE message to the server and restarts
1754  * the configuration process..." */
1755                                         if (!arpping(packet.yiaddr,
1756                                                         NULL,
1757                                                         (uint32_t) 0,
1758                                                         client_config.client_mac,
1759                                                         client_config.interface,
1760                                                         arpping_ms)
1761                                         ) {
1762                                                 bb_error_msg("offered address is in use "
1763                                                         "(got ARP reply), declining");
1764                                                 send_decline(/*xid,*/ server_addr, packet.yiaddr);
1765
1766                                                 if (state != REQUESTING)
1767                                                         udhcp_run_script(NULL, "deconfig");
1768                                                 change_listen_mode(LISTEN_RAW);
1769                                                 state = INIT_SELECTING;
1770                                                 client_config.first_secs = 0; /* make secs field count from 0 */
1771                                                 requested_ip = 0;
1772                                                 timeout = tryagain_timeout;
1773                                                 packet_num = 0;
1774                                                 already_waited_sec = 0;
1775                                                 continue; /* back to main loop */
1776                                         }
1777                                 }
1778 #endif
1779                                 /* enter bound state */
1780                                 temp_addr.s_addr = packet.yiaddr;
1781                                 bb_error_msg("lease of %s obtained, lease time %u",
1782                                         inet_ntoa(temp_addr), (unsigned)lease_seconds);
1783                                 requested_ip = packet.yiaddr;
1784
1785                                 start = monotonic_sec();
1786                                 udhcp_run_script(&packet, state == REQUESTING ? "bound" : "renew");
1787                                 already_waited_sec = (unsigned)monotonic_sec() - start;
1788                                 timeout = lease_seconds / 2;
1789                                 if ((unsigned)timeout < already_waited_sec) {
1790                                         /* Something went wrong. Back to discover state */
1791                                         timeout = already_waited_sec = 0;
1792                                 }
1793
1794                                 state = BOUND;
1795                                 change_listen_mode(LISTEN_NONE);
1796                                 if (opt & OPT_q) { /* quit after lease */
1797                                         goto ret0;
1798                                 }
1799                                 /* future renew failures should not exit (JM) */
1800                                 opt &= ~OPT_n;
1801 #if BB_MMU /* NOMMU case backgrounded earlier */
1802                                 if (!(opt & OPT_f)) {
1803                                         client_background();
1804                                         /* do not background again! */
1805                                         opt = ((opt & ~OPT_b) | OPT_f);
1806                                 }
1807 #endif
1808                                 /* make future renew packets use different xid */
1809                                 /* xid = random_xid(); ...but why bother? */
1810
1811                                 continue; /* back to main loop */
1812                         }
1813                         if (*message == DHCPNAK) {
1814                                 /* If network has more than one DHCP server,
1815                                  * "wrong" server can reply first, with a NAK.
1816                                  * Do not interpret it as a NAK from "our" server.
1817                                  */
1818                                 if (server_addr != 0) {
1819                                         uint32_t svid;
1820                                         uint8_t *temp;
1821
1822                                         temp = udhcp_get_option32(&packet, DHCP_SERVER_ID);
1823                                         if (!temp) {
1824  non_matching_svid:
1825                                                 log1("received DHCP NAK with wrong"
1826                                                         " server ID, ignoring packet");
1827                                                 continue;
1828                                         }
1829                                         move_from_unaligned32(svid, temp);
1830                                         if (svid != server_addr)
1831                                                 goto non_matching_svid;
1832                                 }
1833                                 /* return to init state */
1834                                 bb_error_msg("received %s", "DHCP NAK");
1835                                 udhcp_run_script(&packet, "nak");
1836                                 if (state != REQUESTING)
1837                                         udhcp_run_script(NULL, "deconfig");
1838                                 change_listen_mode(LISTEN_RAW);
1839                                 sleep(3); /* avoid excessive network traffic */
1840                                 state = INIT_SELECTING;
1841                                 client_config.first_secs = 0; /* make secs field count from 0 */
1842                                 requested_ip = 0;
1843                                 timeout = 0;
1844                                 packet_num = 0;
1845                                 already_waited_sec = 0;
1846                         }
1847                         continue;
1848                 /* case BOUND: - ignore all packets */
1849                 /* case RELEASED: - ignore all packets */
1850                 }
1851                 /* back to main loop */
1852         } /* for (;;) - main loop ends */
1853
1854  ret0:
1855         if (opt & OPT_R) /* release on quit */
1856                 perform_release(server_addr, requested_ip);
1857         retval = 0;
1858  ret:
1859         /*if (client_config.pidfile) - remove_pidfile has its own check */
1860                 remove_pidfile(client_config.pidfile);
1861         return retval;
1862 }