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 //applet:IF_UDHCPC(APPLET(udhcpc, BB_DIR_SBIN, BB_SUID_DROP))
  22
  23 //kbuild:lib-$(CONFIG_UDHCPC) += common.o packet.o signalpipe.o socket.o
  24 //kbuild:lib-$(CONFIG_UDHCPC) += dhcpc.o
  25 //kbuild:lib-$(CONFIG_FEATURE_UDHCPC_ARPING) += arpping.o
  26 //kbuild:lib-$(CONFIG_FEATURE_UDHCP_RFC3397) += domain_codec.o
  27
  28 #include <syslog.h>
  29 /* Override ENABLE_FEATURE_PIDFILE - ifupdown needs our pidfile to always exist */
  30 #define WANT_PIDFILE 1
  31 #include "common.h"
  32 #include "dhcpd.h"
  33 #include "dhcpc.h"
  34
  35 #include <netinet/if_ether.h>
  36 #include <linux/filter.h>
  37 #include <linux/if_packet.h>
  38
  39 #ifndef PACKET_AUXDATA
  40 # define PACKET_AUXDATA 8
  41 struct tpacket_auxdata {
  42         uint32_t tp_status;
  43         uint32_t tp_len;
  44         uint32_t tp_snaplen;
  45         uint16_t tp_mac;
  46         uint16_t tp_net;
  47         uint16_t tp_vlan_tci;
  48         uint16_t tp_padding;
  49 };
  50 #endif
  51
  52
  53 /* "struct client_config_t client_config" is in bb_common_bufsiz1 */
  54
  55
  56 #if ENABLE_LONG_OPTS
  57 static const char udhcpc_longopts[] ALIGN1 =
  58         "clientid-none\0"  No_argument       "C"
  59         "vendorclass\0"    Required_argument "V"
  60         "hostname\0"       Required_argument "H"
  61         "fqdn\0"           Required_argument "F"
  62         "interface\0"      Required_argument "i"
  63         "now\0"            No_argument       "n"
  64         "pidfile\0"        Required_argument "p"
  65         "quit\0"           No_argument       "q"
  66         "release\0"        No_argument       "R"
  67         "request\0"        Required_argument "r"
  68         "script\0"         Required_argument "s"
  69         "timeout\0"        Required_argument "T"
  70         "retries\0"        Required_argument "t"
  71         "tryagain\0"       Required_argument "A"
  72         "syslog\0"         No_argument       "S"
  73         "request-option\0" Required_argument "O"
  74         "no-default-options\0" No_argument   "o"
  75         "foreground\0"     No_argument       "f"
  76         "background\0"     No_argument       "b"
  77         "broadcast\0"      No_argument       "B"
  78         IF_FEATURE_UDHCPC_ARPING("arping\0"     Optional_argument "a")
  79         IF_FEATURE_UDHCP_PORT("client-port\0"   Required_argument "P")
  80         ;
  81 #endif
  82 /* Must match getopt32 option string order */
  83 enum {
  84         OPT_C = 1 << 0,
  85         OPT_V = 1 << 1,
  86         OPT_H = 1 << 2,
  87         OPT_h = 1 << 3,
  88         OPT_F = 1 << 4,
  89         OPT_i = 1 << 5,
  90         OPT_n = 1 << 6,
  91         OPT_p = 1 << 7,
  92         OPT_q = 1 << 8,
  93         OPT_R = 1 << 9,
  94         OPT_r = 1 << 10,
  95         OPT_s = 1 << 11,
  96         OPT_T = 1 << 12,
  97         OPT_t = 1 << 13,
  98         OPT_S = 1 << 14,
  99         OPT_A = 1 << 15,
 100         OPT_O = 1 << 16,
 101         OPT_o = 1 << 17,
 102         OPT_x = 1 << 18,
 103         OPT_f = 1 << 19,
 104         OPT_B = 1 << 20,
 105 /* The rest has variable bit positions, need to be clever */
 106         OPTBIT_B = 20,
 107         USE_FOR_MMU(             OPTBIT_b,)
 108         IF_FEATURE_UDHCPC_ARPING(OPTBIT_a,)
 109         IF_FEATURE_UDHCP_PORT(   OPTBIT_P,)
 110         USE_FOR_MMU(             OPT_b = 1 << OPTBIT_b,)
 111         IF_FEATURE_UDHCPC_ARPING(OPT_a = 1 << OPTBIT_a,)
 112         IF_FEATURE_UDHCP_PORT(   OPT_P = 1 << OPTBIT_P,)
 113 };
 114
 115
 116 /*** Script execution code ***/
 117
 118 /* get a rough idea of how long an option will be (rounding up...) */
 119 static const uint8_t len_of_option_as_string[] ALIGN1 = {
 120         [OPTION_IP              ] = sizeof("255.255.255.255 "),
 121         [OPTION_IP_PAIR         ] = sizeof("255.255.255.255 ") * 2,
 122         [OPTION_STATIC_ROUTES   ] = sizeof("255.255.255.255/32 255.255.255.255 "),
 123         [OPTION_6RD             ] = sizeof("132 128 ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 255.255.255.255 "),
 124         [OPTION_STRING          ] = 1,
 125         [OPTION_STRING_HOST     ] = 1,
 126 #if ENABLE_FEATURE_UDHCP_RFC3397
 127         [OPTION_DNS_STRING      ] = 1, /* unused */
 128         /* Hmmm, this severely overestimates size if SIP_SERVERS option
 129          * is in domain name form: N-byte option in binary form
 130          * mallocs ~16*N bytes. But it is freed almost at once.
 131          */
 132         [OPTION_SIP_SERVERS     ] = sizeof("255.255.255.255 "),
 133 #endif
 134 //      [OPTION_BOOLEAN         ] = sizeof("yes "),
 135         [OPTION_U8              ] = sizeof("255 "),
 136         [OPTION_U16             ] = sizeof("65535 "),
 137 //      [OPTION_S16             ] = sizeof("-32768 "),
 138         [OPTION_U32             ] = sizeof("4294967295 "),
 139         [OPTION_S32             ] = sizeof("-2147483684 "),
 140 };
 141
 142 /* note: ip is a pointer to an IP in network order, possibly misaliged */
 143 static int sprint_nip(char *dest, const char *pre, const uint8_t *ip)
 144 {
 145         return sprintf(dest, "%s%u.%u.%u.%u", pre, ip[0], ip[1], ip[2], ip[3]);
 146 }
 147
 148 /* really simple implementation, just count the bits */
 149 static int mton(uint32_t mask)
 150 {
 151         int i = 0;
 152         mask = ntohl(mask); /* 111110000-like bit pattern */
 153         while (mask) {
 154                 i++;
 155                 mask <<= 1;
 156         }
 157         return i;
 158 }
 159
 160 #if ENABLE_FEATURE_UDHCPC_SANITIZEOPT
 161 /* Check if a given label represents a valid DNS label
 162  * Return pointer to the first character after the label upon success,
 163  * NULL otherwise.
 164  * See RFC1035, 2.3.1
 165  */
 166 /* We don't need to be particularly anal. For example, allowing _, hyphen
 167  * at the end, or leading and trailing dots would be ok, since it
 168  * can't be used for attacks. (Leading hyphen can be, if someone uses
 169  * cmd "$hostname"
 170  * in the script: then hostname may be treated as an option)
 171  */
 172 static const char *valid_domain_label(const char *label)
 173 {
 174         unsigned char ch;
 175         unsigned pos = 0;
 176
 177         for (;;) {
 178                 ch = *label;
 179                 if ((ch|0x20) < 'a' || (ch|0x20) > 'z') {
 180                         if (ch < '0' || ch > '9') {
 181                                 if (ch == '\0' || ch == '.')
 182                                         return label;
 183                                 /* DNS allows only '-', but we are more permissive */
 184                                 if (ch != '-' && ch != '_')
 185                                         return NULL;
 186                         }
 187                 }
 188                 label++;
 189                 pos++;
 190                 //Do we want this?
 191                 //if (pos > 63) /* NS_MAXLABEL; labels must be 63 chars or less */
 192                 //      return NULL;
 193         }
 194 }
 195
 196 /* Check if a given name represents a valid DNS name */
 197 /* See RFC1035, 2.3.1 */
 198 static int good_hostname(const char *name)
 199 {
 200         //const char *start = name;
 201
 202         for (;;) {
 203                 name = valid_domain_label(name);
 204                 if (!name)
 205                         return 0;
 206                 if (!name[0])
 207                         return 1;
 208                         //Do we want this?
 209                         //return ((name - start) < 1025); /* NS_MAXDNAME */
 210                 name++;
 211                 if (*name == '\0')
 212                         return 1; // We allow trailing dot too
 213         }
 214 }
 215 #else
 216 # define good_hostname(name) 1
 217 #endif
 218
 219 /* Create "opt_name=opt_value" string */
 220 static NOINLINE char *xmalloc_optname_optval(uint8_t *option, const struct dhcp_optflag *optflag, const char *opt_name)
 221 {
 222         unsigned upper_length;
 223         int len, type, optlen;
 224         char *dest, *ret;
 225
 226         /* option points to OPT_DATA, need to go back to get OPT_LEN */
 227         len = option[-OPT_DATA + OPT_LEN];
 228
 229         type = optflag->flags & OPTION_TYPE_MASK;
 230         optlen = dhcp_option_lengths[type];
 231         upper_length = len_of_option_as_string[type]
 232                 * ((unsigned)(len + optlen) / (unsigned)optlen);
 233
 234         dest = ret = xmalloc(upper_length + strlen(opt_name) + 2);
 235         dest += sprintf(ret, "%s=", opt_name);
 236
 237         while (len >= optlen) {
 238                 switch (type) {
 239                 case OPTION_IP:
 240                 case OPTION_IP_PAIR:
 241                         dest += sprint_nip(dest, "", option);
 242                         if (type == OPTION_IP)
 243                                 break;
 244                         dest += sprint_nip(dest, "/", option + 4);
 245                         break;
 246 //              case OPTION_BOOLEAN:
 247 //                      dest += sprintf(dest, *option ? "yes" : "no");
 248 //                      break;
 249                 case OPTION_U8:
 250                         dest += sprintf(dest, "%u", *option);
 251                         break;
 252 //              case OPTION_S16:
 253                 case OPTION_U16: {
 254                         uint16_t val_u16;
 255                         move_from_unaligned16(val_u16, option);
 256                         dest += sprintf(dest, "%u", ntohs(val_u16));
 257                         break;
 258                 }
 259                 case OPTION_S32:
 260                 case OPTION_U32: {
 261                         uint32_t val_u32;
 262                         move_from_unaligned32(val_u32, option);
 263                         dest += sprintf(dest, type == OPTION_U32 ? "%lu" : "%ld", (unsigned long) ntohl(val_u32));
 264                         break;
 265                 }
 266                 /* Note: options which use 'return' instead of 'break'
 267                  * (for example, OPTION_STRING) skip the code which handles
 268                  * the case of list of options.
 269                  */
 270                 case OPTION_STRING:
 271                 case OPTION_STRING_HOST:
 272                         memcpy(dest, option, len);
 273                         dest[len] = '\0';
 274                         if (type == OPTION_STRING_HOST && !good_hostname(dest))
 275                                 safe_strncpy(dest, "bad", len);
 276                         return ret;
 277                 case OPTION_STATIC_ROUTES: {
 278                         /* Option binary format:
 279                          * mask [one byte, 0..32]
 280                          * ip [big endian, 0..4 bytes depending on mask]
 281                          * router [big endian, 4 bytes]
 282                          * may be repeated
 283                          *
 284                          * We convert it to a string "IP/MASK ROUTER IP2/MASK2 ROUTER2"
 285                          */
 286                         const char *pfx = "";
 287
 288                         while (len >= 1 + 4) { /* mask + 0-byte ip + router */
 289                                 uint32_t nip;
 290                                 uint8_t *p;
 291                                 unsigned mask;
 292                                 int bytes;
 293
 294                                 mask = *option++;
 295                                 if (mask > 32)
 296                                         break;
 297                                 len--;
 298
 299                                 nip = 0;
 300                                 p = (void*) &nip;
 301                                 bytes = (mask + 7) / 8; /* 0 -> 0, 1..8 -> 1, 9..16 -> 2 etc */
 302                                 while (--bytes >= 0) {
 303                                         *p++ = *option++;
 304                                         len--;
 305                                 }
 306                                 if (len < 4)
 307                                         break;
 308
 309                                 /* print ip/mask */
 310                                 dest += sprint_nip(dest, pfx, (void*) &nip);
 311                                 pfx = " ";
 312                                 dest += sprintf(dest, "/%u ", mask);
 313                                 /* print router */
 314                                 dest += sprint_nip(dest, "", option);
 315                                 option += 4;
 316                                 len -= 4;
 317                         }
 318
 319                         return ret;
 320                 }
 321                 case OPTION_6RD:
 322                         /* Option binary format (see RFC 5969):
 323                          *  0                   1                   2                   3
 324                          *  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
 325                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 326                          * |  OPTION_6RD   | option-length |  IPv4MaskLen  |  6rdPrefixLen |
 327                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 328                          * |                           6rdPrefix                           |
 329                          * ...                        (16 octets)                        ...
 330                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 331                          * ...                   6rdBRIPv4Address(es)                    ...
 332                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 333                          * We convert it to a string
 334                          * "IPv4MaskLen 6rdPrefixLen 6rdPrefix 6rdBRIPv4Address..."
 335                          *
 336                          * Sanity check: ensure that our length is at least 22 bytes, that
 337                          * IPv4MaskLen <= 32,
 338                          * 6rdPrefixLen <= 128,
 339                          * 6rdPrefixLen + (32 - IPv4MaskLen) <= 128
 340                          * (2nd condition need no check - it follows from 1st and 3rd).
 341                          * Else, return envvar with empty value ("optname=")
 342                          */
 343                         if (len >= (1 + 1 + 16 + 4)
 344                          && option[0] <= 32
 345                          && (option[1] + 32 - option[0]) <= 128
 346                         ) {
 347                                 /* IPv4MaskLen */
 348                                 dest += sprintf(dest, "%u ", *option++);
 349                                 /* 6rdPrefixLen */
 350                                 dest += sprintf(dest, "%u ", *option++);
 351                                 /* 6rdPrefix */
 352                                 dest += sprint_nip6(dest, /* "", */ option);
 353                                 option += 16;
 354                                 len -= 1 + 1 + 16 + 4;
 355                                 /* "+ 4" above corresponds to the length of IPv4 addr
 356                                  * we consume in the loop below */
 357                                 while (1) {
 358                                         /* 6rdBRIPv4Address(es) */
 359                                         dest += sprint_nip(dest, " ", option);
 360                                         option += 4;
 361                                         len -= 4; /* do we have yet another 4+ bytes? */
 362                                         if (len < 0)
 363                                                 break; /* no */
 364                                 }
 365                         }
 366
 367                         return ret;
 368 #if ENABLE_FEATURE_UDHCP_RFC3397
 369                 case OPTION_DNS_STRING:
 370                         /* unpack option into dest; use ret for prefix (i.e., "optname=") */
 371                         dest = dname_dec(option, len, ret);
 372                         if (dest) {
 373                                 free(ret);
 374                                 return dest;
 375                         }
 376                         /* error. return "optname=" string */
 377                         return ret;
 378                 case OPTION_SIP_SERVERS:
 379                         /* Option binary format:
 380                          * type: byte
 381                          * type=0: domain names, dns-compressed
 382                          * type=1: IP addrs
 383                          */
 384                         option++;
 385                         len--;
 386                         if (option[-1] == 0) {
 387                                 dest = dname_dec(option, len, ret);
 388                                 if (dest) {
 389                                         free(ret);
 390                                         return dest;
 391                                 }
 392                         } else
 393                         if (option[-1] == 1) {
 394                                 const char *pfx = "";
 395                                 while (1) {
 396                                         len -= 4;
 397                                         if (len < 0)
 398                                                 break;
 399                                         dest += sprint_nip(dest, pfx, option);
 400                                         pfx = " ";
 401                                         option += 4;
 402                                 }
 403                         }
 404                         return ret;
 405 #endif
 406                 } /* switch */
 407
 408                 /* If we are here, try to format any remaining data
 409                  * in the option as another, similarly-formatted option
 410                  */
 411                 option += optlen;
 412                 len -= optlen;
 413 // TODO: it can be a list only if (optflag->flags & OPTION_LIST).
 414 // Should we bail out/warn if we see multi-ip option which is
 415 // not allowed to be such (for example, DHCP_BROADCAST)? -
 416                 if (len < optlen /* || !(optflag->flags & OPTION_LIST) */)
 417                         break;
 418                 *dest++ = ' ';
 419                 *dest = '\0';
 420         } /* while */
 421
 422         return ret;
 423 }
 424
 425 /* put all the parameters into the environment */
 426 static char **fill_envp(struct dhcp_packet *packet)
 427 {
 428         int envc;
 429         int i;
 430         char **envp, **curr;
 431         const char *opt_name;
 432         uint8_t *temp;
 433         uint8_t overload = 0;
 434
 435 #define BITMAP unsigned
 436 #define BBITS (sizeof(BITMAP) * 8)
 437 #define BMASK(i) (1 << (i & (sizeof(BITMAP) * 8 - 1)))
 438 #define FOUND_OPTS(i) (found_opts[(unsigned)i / BBITS])
 439         BITMAP found_opts[256 / BBITS];
 440
 441         memset(found_opts, 0, sizeof(found_opts));
 442
 443         /* We need 6 elements for:
 444          * "interface=IFACE"
 445          * "ip=N.N.N.N" from packet->yiaddr
 446          * "siaddr=IP" from packet->siaddr_nip (unless 0)
 447          * "boot_file=FILE" from packet->file (unless overloaded)
 448          * "sname=SERVER_HOSTNAME" from packet->sname (unless overloaded)
 449          * terminating NULL
 450          */
 451         envc = 6;
 452         /* +1 element for each option, +2 for subnet option: */
 453         if (packet) {
 454                 /* note: do not search for "pad" (0) and "end" (255) options */
 455 //TODO: change logic to scan packet _once_
 456                 for (i = 1; i < 255; i++) {
 457                         temp = udhcp_get_option(packet, i);
 458                         if (temp) {
 459                                 if (i == DHCP_OPTION_OVERLOAD)
 460                                         overload |= *temp;
 461                                 else if (i == DHCP_SUBNET)
 462                                         envc++; /* for $mask */
 463                                 envc++;
 464                                 /*if (i != DHCP_MESSAGE_TYPE)*/
 465                                 FOUND_OPTS(i) |= BMASK(i);
 466                         }
 467                 }
 468         }
 469         curr = envp = xzalloc(sizeof(envp[0]) * envc);
 470
 471         *curr = xasprintf("interface=%s", client_config.interface);
 472         putenv(*curr++);
 473
 474         if (!packet)
 475                 return envp;
 476
 477         /* Export BOOTP fields. Fields we don't (yet?) export:
 478          * uint8_t op;      // always BOOTREPLY
 479          * uint8_t htype;   // hardware address type. 1 = 10mb ethernet
 480          * uint8_t hlen;    // hardware address length
 481          * uint8_t hops;    // used by relay agents only
 482          * uint32_t xid;
 483          * uint16_t secs;   // elapsed since client began acquisition/renewal
 484          * uint16_t flags;  // only one flag so far: bcast. Never set by server
 485          * uint32_t ciaddr; // client IP (usually == yiaddr. can it be different
 486          *                  // if during renew server wants to give us different IP?)
 487          * uint32_t gateway_nip; // relay agent IP address
 488          * uint8_t chaddr[16]; // link-layer client hardware address (MAC)
 489          * TODO: export gateway_nip as $giaddr?
 490          */
 491         /* Most important one: yiaddr as $ip */
 492         *curr = xmalloc(sizeof("ip=255.255.255.255"));
 493         sprint_nip(*curr, "ip=", (uint8_t *) &packet->yiaddr);
 494         putenv(*curr++);
 495         if (packet->siaddr_nip) {
 496                 /* IP address of next server to use in bootstrap */
 497                 *curr = xmalloc(sizeof("siaddr=255.255.255.255"));
 498                 sprint_nip(*curr, "siaddr=", (uint8_t *) &packet->siaddr_nip);
 499                 putenv(*curr++);
 500         }
 501         if (!(overload & FILE_FIELD) && packet->file[0]) {
 502                 /* watch out for invalid packets */
 503                 *curr = xasprintf("boot_file=%."DHCP_PKT_FILE_LEN_STR"s", packet->file);
 504                 putenv(*curr++);
 505         }
 506         if (!(overload & SNAME_FIELD) && packet->sname[0]) {
 507                 /* watch out for invalid packets */
 508                 *curr = xasprintf("sname=%."DHCP_PKT_SNAME_LEN_STR"s", packet->sname);
 509                 putenv(*curr++);
 510         }
 511
 512         /* Export known DHCP options */
 513         opt_name = dhcp_option_strings;
 514         i = 0;
 515         while (*opt_name) {
 516                 uint8_t code = dhcp_optflags[i].code;
 517                 BITMAP *found_ptr = &FOUND_OPTS(code);
 518                 BITMAP found_mask = BMASK(code);
 519                 if (!(*found_ptr & found_mask))
 520                         goto next;
 521                 *found_ptr &= ~found_mask; /* leave only unknown options */
 522                 temp = udhcp_get_option(packet, code);
 523                 *curr = xmalloc_optname_optval(temp, &dhcp_optflags[i], opt_name);
 524                 putenv(*curr++);
 525                 if (code == DHCP_SUBNET) {
 526                         /* Subnet option: make things like "$ip/$mask" possible */
 527                         uint32_t subnet;
 528                         move_from_unaligned32(subnet, temp);
 529                         *curr = xasprintf("mask=%u", mton(subnet));
 530                         putenv(*curr++);
 531                 }
 532  next:
 533                 opt_name += strlen(opt_name) + 1;
 534                 i++;
 535         }
 536         /* Export unknown options */
 537         for (i = 0; i < 256;) {
 538                 BITMAP bitmap = FOUND_OPTS(i);
 539                 if (!bitmap) {
 540                         i += BBITS;
 541                         continue;
 542                 }
 543                 if (bitmap & BMASK(i)) {
 544                         unsigned len, ofs;
 545
 546                         temp = udhcp_get_option(packet, i);
 547                         /* udhcp_get_option returns ptr to data portion,
 548                          * need to go back to get len
 549                          */
 550                         len = temp[-OPT_DATA + OPT_LEN];
 551                         *curr = xmalloc(sizeof("optNNN=") + 1 + len*2);
 552                         ofs = sprintf(*curr, "opt%u=", i);
 553                         *bin2hex(*curr + ofs, (void*) temp, len) = '\0';
 554                         putenv(*curr++);
 555                 }
 556                 i++;
 557         }
 558
 559         return envp;
 560 }
 561
 562 /* Call a script with a par file and env vars */
 563 static void udhcp_run_script(struct dhcp_packet *packet, const char *name)
 564 {
 565         char **envp, **curr;
 566         char *argv[3];
 567
 568         envp = fill_envp(packet);
 569
 570         /* call script */
 571         log1("executing %s %s", client_config.script, name);
 572         argv[0] = (char*) client_config.script;
 573         argv[1] = (char*) name;
 574         argv[2] = NULL;
 575         spawn_and_wait(argv);
 576
 577         for (curr = envp; *curr; curr++) {
 578                 log2(" %s", *curr);
 579                 bb_unsetenv_and_free(*curr);
 580         }
 581         free(envp);
 582 }
 583
 584
 585 /*** Sending/receiving packets ***/
 586
 587 static ALWAYS_INLINE uint32_t random_xid(void)
 588 {
 589         return rand();
 590 }
 591
 592 /* Initialize the packet with the proper defaults */
 593 static void init_packet(struct dhcp_packet *packet, char type)
 594 {
 595         uint16_t secs;
 596
 597         /* Fill in: op, htype, hlen, cookie fields; message type option: */
 598         udhcp_init_header(packet, type);
 599
 600         packet->xid = random_xid();
 601
 602         client_config.last_secs = monotonic_sec();
 603         if (client_config.first_secs == 0)
 604                 client_config.first_secs = client_config.last_secs;
 605         secs = client_config.last_secs - client_config.first_secs;
 606         packet->secs = htons(secs);
 607
 608         memcpy(packet->chaddr, client_config.client_mac, 6);
 609         if (client_config.clientid)
 610                 udhcp_add_binary_option(packet, client_config.clientid);
 611 }
 612
 613 static void add_client_options(struct dhcp_packet *packet)
 614 {
 615         int i, end, len;
 616
 617         udhcp_add_simple_option(packet, DHCP_MAX_SIZE, htons(IP_UDP_DHCP_SIZE));
 618
 619         /* Add a "param req" option with the list of options we'd like to have
 620          * from stubborn DHCP servers. Pull the data from the struct in common.c.
 621          * No bounds checking because it goes towards the head of the packet. */
 622         end = udhcp_end_option(packet->options);
 623         len = 0;
 624         for (i = 1; i < DHCP_END; i++) {
 625                 if (client_config.opt_mask[i >> 3] & (1 << (i & 7))) {
 626                         packet->options[end + OPT_DATA + len] = i;
 627                         len++;
 628                 }
 629         }
 630         if (len) {
 631                 packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
 632                 packet->options[end + OPT_LEN] = len;
 633                 packet->options[end + OPT_DATA + len] = DHCP_END;
 634         }
 635
 636         if (client_config.vendorclass)
 637                 udhcp_add_binary_option(packet, client_config.vendorclass);
 638         if (client_config.hostname)
 639                 udhcp_add_binary_option(packet, client_config.hostname);
 640         if (client_config.fqdn)
 641                 udhcp_add_binary_option(packet, client_config.fqdn);
 642
 643         /* Request broadcast replies if we have no IP addr */
 644         if ((option_mask32 & OPT_B) && packet->ciaddr == 0)
 645                 packet->flags |= htons(BROADCAST_FLAG);
 646
 647         /* Add -x options if any */
 648         {
 649                 struct option_set *curr = client_config.options;
 650                 while (curr) {
 651                         udhcp_add_binary_option(packet, curr->data);
 652                         curr = curr->next;
 653                 }
 654 //              if (client_config.sname)
 655 //                      strncpy((char*)packet->sname, client_config.sname, sizeof(packet->sname) - 1);
 656 //              if (client_config.boot_file)
 657 //                      strncpy((char*)packet->file, client_config.boot_file, sizeof(packet->file) - 1);
 658         }
 659
 660         // This will be needed if we remove -V VENDOR_STR in favor of
 661         // -x vendor:VENDOR_STR
 662         //if (!udhcp_find_option(packet.options, DHCP_VENDOR))
 663         //      /* not set, set the default vendor ID */
 664         //      ...add (DHCP_VENDOR, "udhcp "BB_VER) opt...
 665 }
 666
 667 /* RFC 2131
 668  * 4.4.4 Use of broadcast and unicast
 669  *
 670  * The DHCP client broadcasts DHCPDISCOVER, DHCPREQUEST and DHCPINFORM
 671  * messages, unless the client knows the address of a DHCP server.
 672  * The client unicasts DHCPRELEASE messages to the server. Because
 673  * the client is declining the use of the IP address supplied by the server,
 674  * the client broadcasts DHCPDECLINE messages.
 675  *
 676  * When the DHCP client knows the address of a DHCP server, in either
 677  * INIT or REBOOTING state, the client may use that address
 678  * in the DHCPDISCOVER or DHCPREQUEST rather than the IP broadcast address.
 679  * The client may also use unicast to send DHCPINFORM messages
 680  * to a known DHCP server. If the client receives no response to DHCP
 681  * messages sent to the IP address of a known DHCP server, the DHCP
 682  * client reverts to using the IP broadcast address.
 683  */
 684
 685 static int raw_bcast_from_client_config_ifindex(struct dhcp_packet *packet, uint32_t src_nip)
 686 {
 687         return udhcp_send_raw_packet(packet,
 688                 /*src*/ src_nip, CLIENT_PORT,
 689                 /*dst*/ INADDR_BROADCAST, SERVER_PORT, MAC_BCAST_ADDR,
 690                 client_config.ifindex);
 691 }
 692
 693 static int bcast_or_ucast(struct dhcp_packet *packet, uint32_t ciaddr, uint32_t server)
 694 {
 695         if (server)
 696                 return udhcp_send_kernel_packet(packet,
 697                         ciaddr, CLIENT_PORT,
 698                         server, SERVER_PORT);
 699         return raw_bcast_from_client_config_ifindex(packet, ciaddr);
 700 }
 701
 702 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
 703 /* NOINLINE: limit stack usage in caller */
 704 static NOINLINE int send_discover(uint32_t xid, uint32_t requested)
 705 {
 706         struct dhcp_packet packet;
 707
 708         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 709          * random xid field (we override it below),
 710          * client-id option (unless -C), message type option:
 711          */
 712         init_packet(&packet, DHCPDISCOVER);
 713
 714         packet.xid = xid;
 715         if (requested)
 716                 udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 717
 718         /* Add options: maxsize,
 719          * optionally: hostname, fqdn, vendorclass,
 720          * "param req" option according to -O, options specified with -x
 721          */
 722         add_client_options(&packet);
 723
 724         bb_error_msg("sending %s", "discover");
 725         return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
 726 }
 727
 728 /* Broadcast a DHCP request message */
 729 /* RFC 2131 3.1 paragraph 3:
 730  * "The client _broadcasts_ a DHCPREQUEST message..."
 731  */
 732 /* NOINLINE: limit stack usage in caller */
 733 static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requested)
 734 {
 735         struct dhcp_packet packet;
 736         struct in_addr addr;
 737
 738 /*
 739  * RFC 2131 4.3.2 DHCPREQUEST message
 740  * ...
 741  * If the DHCPREQUEST message contains a 'server identifier'
 742  * option, the message is in response to a DHCPOFFER message.
 743  * Otherwise, the message is a request to verify or extend an
 744  * existing lease. If the client uses a 'client identifier'
 745  * in a DHCPREQUEST message, it MUST use that same 'client identifier'
 746  * in all subsequent messages. If the client included a list
 747  * of requested parameters in a DHCPDISCOVER message, it MUST
 748  * include that list in all subsequent messages.
 749  */
 750         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 751          * random xid field (we override it below),
 752          * client-id option (unless -C), message type option:
 753          */
 754         init_packet(&packet, DHCPREQUEST);
 755
 756         packet.xid = xid;
 757         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 758
 759         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 760
 761         /* Add options: maxsize,
 762          * optionally: hostname, fqdn, vendorclass,
 763          * "param req" option according to -O, and options specified with -x
 764          */
 765         add_client_options(&packet);
 766
 767         addr.s_addr = requested;
 768         bb_error_msg("sending select for %s", inet_ntoa(addr));
 769         return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
 770 }
 771
 772 /* Unicast or broadcast a DHCP renew message */
 773 /* NOINLINE: limit stack usage in caller */
 774 static NOINLINE int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
 775 {
 776         struct dhcp_packet packet;
 777
 778 /*
 779  * RFC 2131 4.3.2 DHCPREQUEST message
 780  * ...
 781  * DHCPREQUEST generated during RENEWING state:
 782  *
 783  * 'server identifier' MUST NOT be filled in, 'requested IP address'
 784  * option MUST NOT be filled in, 'ciaddr' MUST be filled in with
 785  * client's IP address. In this situation, the client is completely
 786  * configured, and is trying to extend its lease. This message will
 787  * be unicast, so no relay agents will be involved in its
 788  * transmission.  Because 'giaddr' is therefore not filled in, the
 789  * DHCP server will trust the value in 'ciaddr', and use it when
 790  * replying to the client.
 791  */
 792         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 793          * random xid field (we override it below),
 794          * client-id option (unless -C), message type option:
 795          */
 796         init_packet(&packet, DHCPREQUEST);
 797
 798         packet.xid = xid;
 799         packet.ciaddr = ciaddr;
 800
 801         /* Add options: maxsize,
 802          * optionally: hostname, fqdn, vendorclass,
 803          * "param req" option according to -O, and options specified with -x
 804          */
 805         add_client_options(&packet);
 806
 807         bb_error_msg("sending %s", "renew");
 808         return bcast_or_ucast(&packet, ciaddr, server);
 809 }
 810
 811 #if ENABLE_FEATURE_UDHCPC_ARPING
 812 /* Broadcast a DHCP decline message */
 813 /* NOINLINE: limit stack usage in caller */
 814 static NOINLINE int send_decline(/*uint32_t xid,*/ uint32_t server, uint32_t requested)
 815 {
 816         struct dhcp_packet packet;
 817
 818         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 819          * client-id option (unless -C), message type option:
 820          */
 821         init_packet(&packet, DHCPDECLINE);
 822
 823 #if 0
 824         /* RFC 2131 says DHCPDECLINE's xid is randomly selected by client,
 825          * but in case the server is buggy and wants DHCPDECLINE's xid
 826          * to match the xid which started entire handshake,
 827          * we use the same xid we used in initial DHCPDISCOVER:
 828          */
 829         packet.xid = xid;
 830 #endif
 831         /* DHCPDECLINE uses "requested ip", not ciaddr, to store offered IP */
 832         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 833
 834         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 835
 836         bb_error_msg("sending %s", "decline");
 837         return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
 838 }
 839 #endif
 840
 841 /* Unicast a DHCP release message */
 842 static int send_release(uint32_t server, uint32_t ciaddr)
 843 {
 844         struct dhcp_packet packet;
 845
 846         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 847          * client-id option (unless -C), message type option:
 848          */
 849         init_packet(&packet, DHCPRELEASE);
 850
 851         /* DHCPRELEASE uses ciaddr, not "requested ip", to store IP being released */
 852         packet.ciaddr = ciaddr;
 853
 854         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 855
 856         bb_error_msg("sending %s", "release");
 857         /* Note: normally we unicast here since "server" is not zero.
 858          * However, there _are_ people who run "address-less" DHCP servers,
 859          * and reportedly ISC dhcp client and Windows allow that.
 860          */
 861         return bcast_or_ucast(&packet, ciaddr, server);
 862 }
 863
 864 /* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */
 865 /* NOINLINE: limit stack usage in caller */
 866 static NOINLINE int udhcp_recv_raw_packet(struct dhcp_packet *dhcp_pkt, int fd)
 867 {
 868         int bytes;
 869         struct ip_udp_dhcp_packet packet;
 870         uint16_t check;
 871         unsigned char cmsgbuf[CMSG_LEN(sizeof(struct tpacket_auxdata))];
 872         struct iovec iov;
 873         struct msghdr msg;
 874         struct cmsghdr *cmsg;
 875
 876         /* used to use just safe_read(fd, &packet, sizeof(packet))
 877          * but we need to check for TP_STATUS_CSUMNOTREADY :(
 878          */
 879         iov.iov_base = &packet;
 880         iov.iov_len = sizeof(packet);
 881         memset(&msg, 0, sizeof(msg));
 882         msg.msg_iov = &iov;
 883         msg.msg_iovlen = 1;
 884         msg.msg_control = cmsgbuf;
 885         msg.msg_controllen = sizeof(cmsgbuf);
 886         for (;;) {
 887                 bytes = recvmsg(fd, &msg, 0);
 888                 if (bytes < 0) {
 889                         if (errno == EINTR)
 890                                 continue;
 891                         log1("packet read error, ignoring");
 892                         /* NB: possible down interface, etc. Caller should pause. */
 893                         return bytes; /* returns -1 */
 894                 }
 895                 break;
 896         }
 897
 898         if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) {
 899                 log1("packet is too short, ignoring");
 900                 return -2;
 901         }
 902
 903         if (bytes < ntohs(packet.ip.tot_len)) {
 904                 /* packet is bigger than sizeof(packet), we did partial read */
 905                 log1("oversized packet, ignoring");
 906                 return -2;
 907         }
 908
 909         /* ignore any extra garbage bytes */
 910         bytes = ntohs(packet.ip.tot_len);
 911
 912         /* make sure its the right packet for us, and that it passes sanity checks */
 913         if (packet.ip.protocol != IPPROTO_UDP
 914          || packet.ip.version != IPVERSION
 915          || packet.ip.ihl != (sizeof(packet.ip) >> 2)
 916          || packet.udp.dest != htons(CLIENT_PORT)
 917         /* || bytes > (int) sizeof(packet) - can't happen */
 918          || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
 919         ) {
 920                 log1("unrelated/bogus packet, ignoring");
 921                 return -2;
 922         }
 923
 924         /* verify IP checksum */
 925         check = packet.ip.check;
 926         packet.ip.check = 0;
 927         if (check != inet_cksum((uint16_t *)&packet.ip, sizeof(packet.ip))) {
 928                 log1("bad IP header checksum, ignoring");
 929                 return -2;
 930         }
 931
 932         for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
 933                 if (cmsg->cmsg_level == SOL_PACKET
 934                  && cmsg->cmsg_type == PACKET_AUXDATA
 935                 ) {
 936                         /* some VMs don't checksum UDP and TCP data
 937                          * they send to the same physical machine,
 938                          * here we detect this case:
 939                          */
 940                         struct tpacket_auxdata *aux = (void *)CMSG_DATA(cmsg);
 941                         if (aux->tp_status & TP_STATUS_CSUMNOTREADY)
 942                                 goto skip_udp_sum_check;
 943                 }
 944         }
 945
 946         /* verify UDP checksum. IP header has to be modified for this */
 947         memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
 948         /* ip.xx fields which are not memset: protocol, check, saddr, daddr */
 949         packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
 950         check = packet.udp.check;
 951         packet.udp.check = 0;
 952         if (check && check != inet_cksum((uint16_t *)&packet, bytes)) {
 953                 log1("packet with bad UDP checksum received, ignoring");
 954                 return -2;
 955         }
 956  skip_udp_sum_check:
 957
 958         if (packet.data.cookie != htonl(DHCP_MAGIC)) {
 959                 bb_error_msg("packet with bad magic, ignoring");
 960                 return -2;
 961         }
 962
 963         log1("received %s", "a packet");
 964         udhcp_dump_packet(&packet.data);
 965
 966         bytes -= sizeof(packet.ip) + sizeof(packet.udp);
 967         memcpy(dhcp_pkt, &packet.data, bytes);
 968         return bytes;
 969 }
 970
 971
 972 /*** Main ***/
 973
 974 static int sockfd = -1;
 975
 976 #define LISTEN_NONE   0
 977 #define LISTEN_KERNEL 1
 978 #define LISTEN_RAW    2
 979 static smallint listen_mode;
 980
 981 /* initial state: (re)start DHCP negotiation */
 982 #define INIT_SELECTING  0
 983 /* discover was sent, DHCPOFFER reply received */
 984 #define REQUESTING      1
 985 /* select/renew was sent, DHCPACK reply received */
 986 #define BOUND           2
 987 /* half of lease passed, want to renew it by sending unicast renew requests */
 988 #define RENEWING        3
 989 /* renew requests were not answered, lease is almost over, send broadcast renew */
 990 #define REBINDING       4
 991 /* manually requested renew (SIGUSR1) */
 992 #define RENEW_REQUESTED 5
 993 /* release, possibly manually requested (SIGUSR2) */
 994 #define RELEASED        6
 995 static smallint state;
 996
 997 static int udhcp_raw_socket(int ifindex)
 998 {
 999         int fd;
1000         struct sockaddr_ll sock;
1001
1002         log1("opening raw socket on ifindex %d", ifindex); //log2?
1003
1004         fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
1005         /* ^^^^^
1006          * SOCK_DGRAM: remove link-layer headers on input (SOCK_RAW keeps them)
1007          * ETH_P_IP: want to receive only packets with IPv4 eth type
1008          */
1009         log1("got raw socket fd"); //log2?
1010
1011         sock.sll_family = AF_PACKET;
1012         sock.sll_protocol = htons(ETH_P_IP);
1013         sock.sll_ifindex = ifindex;
1014         xbind(fd, (struct sockaddr *) &sock, sizeof(sock));
1015
1016 #if 0 /* Several users reported breakage when BPF filter is used */
1017         if (CLIENT_PORT == 68) {
1018                 /* Use only if standard port is in use */
1019                 /*
1020                  *      I've selected not to see LL header, so BPF doesn't see it, too.
1021                  *      The filter may also pass non-IP and non-ARP packets, but we do
1022                  *      a more complete check when receiving the message in userspace.
1023                  *
1024                  * and filter shamelessly stolen from:
1025                  *
1026                  *      http://www.flamewarmaster.de/software/dhcpclient/
1027                  *
1028                  * There are a few other interesting ideas on that page (look under
1029                  * "Motivation").  Use of netlink events is most interesting.  Think
1030                  * of various network servers listening for events and reconfiguring.
1031                  * That would obsolete sending HUP signals and/or make use of restarts.
1032                  *
1033                  * Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
1034                  * License: GPL v2.
1035                  */
1036                 static const struct sock_filter filter_instr[] = {
1037                         /* load 9th byte (protocol) */
1038                         BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
1039                         /* jump to L1 if it is IPPROTO_UDP, else to L4 */
1040                         BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 0, 6),
1041                         /* L1: load halfword from offset 6 (flags and frag offset) */
1042                         BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 6),
1043                         /* jump to L4 if any bits in frag offset field are set, else to L2 */
1044                         BPF_JUMP(BPF_JMP|BPF_JSET|BPF_K, 0x1fff, 4, 0),
1045                         /* L2: skip IP header (load index reg with header len) */
1046                         BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0),
1047                         /* load udp destination port from halfword[header_len + 2] */
1048                         BPF_STMT(BPF_LD|BPF_H|BPF_IND, 2),
1049                         /* jump to L3 if udp dport is CLIENT_PORT, else to L4 */
1050                         BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 68, 0, 1),
1051                         /* L3: accept packet ("accept 0x7fffffff bytes") */
1052                         /* Accepting 0xffffffff works too but kernel 2.6.19 is buggy */
1053                         BPF_STMT(BPF_RET|BPF_K, 0x7fffffff),
1054                         /* L4: discard packet ("accept zero bytes") */
1055                         BPF_STMT(BPF_RET|BPF_K, 0),
1056                 };
1057                 static const struct sock_fprog filter_prog = {
1058                         .len = sizeof(filter_instr) / sizeof(filter_instr[0]),
1059                         /* casting const away: */
1060                         .filter = (struct sock_filter *) filter_instr,
1061                 };
1062                 /* Ignoring error (kernel may lack support for this) */
1063                 if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
1064                                 sizeof(filter_prog)) >= 0)
1065                         log1("attached filter to raw socket fd"); // log?
1066         }
1067 #endif
1068
1069         if (setsockopt_1(fd, SOL_PACKET, PACKET_AUXDATA) != 0) {
1070                 if (errno != ENOPROTOOPT)
1071                         log1("can't set PACKET_AUXDATA on raw socket");
1072         }
1073
1074         log1("created raw socket");
1075
1076         return fd;
1077 }
1078
1079 static void change_listen_mode(int new_mode)
1080 {
1081         log1("entering listen mode: %s",
1082                 new_mode != LISTEN_NONE
1083                         ? (new_mode == LISTEN_KERNEL ? "kernel" : "raw")
1084                         : "none"
1085         );
1086
1087         listen_mode = new_mode;
1088         if (sockfd >= 0) {
1089                 close(sockfd);
1090                 sockfd = -1;
1091         }
1092         if (new_mode == LISTEN_KERNEL)
1093                 sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
1094         else if (new_mode != LISTEN_NONE)
1095                 sockfd = udhcp_raw_socket(client_config.ifindex);
1096         /* else LISTEN_NONE: sockfd stays closed */
1097 }
1098
1099 /* Called only on SIGUSR1 */
1100 static void perform_renew(void)
1101 {
1102         bb_error_msg("performing DHCP renew");
1103         switch (state) {
1104         case BOUND:
1105                 change_listen_mode(LISTEN_KERNEL);
1106         case RENEWING:
1107         case REBINDING:
1108                 state = RENEW_REQUESTED;
1109                 break;
1110         case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
1111                 udhcp_run_script(NULL, "deconfig");
1112         case REQUESTING:
1113         case RELEASED:
1114                 change_listen_mode(LISTEN_RAW);
1115                 state = INIT_SELECTING;
1116                 break;
1117         case INIT_SELECTING:
1118                 break;
1119         }
1120 }
1121
1122 static void perform_release(uint32_t server_addr, uint32_t requested_ip)
1123 {
1124         char buffer[sizeof("255.255.255.255")];
1125         struct in_addr temp_addr;
1126
1127         /* send release packet */
1128         if (state == BOUND
1129          || state == RENEWING
1130          || state == REBINDING
1131          || state == RENEW_REQUESTED
1132         ) {
1133                 temp_addr.s_addr = server_addr;
1134                 strcpy(buffer, inet_ntoa(temp_addr));
1135                 temp_addr.s_addr = requested_ip;
1136                 bb_error_msg("unicasting a release of %s to %s",
1137                                 inet_ntoa(temp_addr), buffer);
1138                 send_release(server_addr, requested_ip); /* unicast */
1139         }
1140         bb_error_msg("entering released state");
1141 /*
1142  * We can be here on: SIGUSR2,
1143  * or on exit (SIGTERM) and -R "release on quit" is specified.
1144  * Users requested to be notified in all cases, even if not in one
1145  * of the states above.
1146  */
1147         udhcp_run_script(NULL, "deconfig");
1148
1149         change_listen_mode(LISTEN_NONE);
1150         state = RELEASED;
1151 }
1152
1153 static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
1154 {
1155         uint8_t *storage;
1156         int len = strnlen(str, 255);
1157         storage = xzalloc(len + extra + OPT_DATA);
1158         storage[OPT_CODE] = code;
1159         storage[OPT_LEN] = len + extra;
1160         memcpy(storage + extra + OPT_DATA, str, len);
1161         return storage;
1162 }
1163
1164 #if BB_MMU
1165 static void client_background(void)
1166 {
1167         bb_daemonize(0);
1168         logmode &= ~LOGMODE_STDIO;
1169         /* rewrite pidfile, as our pid is different now */
1170         write_pidfile(client_config.pidfile);
1171 }
1172 #endif
1173
1174 //usage:#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
1175 //usage:# define IF_UDHCP_VERBOSE(...) __VA_ARGS__
1176 //usage:#else
1177 //usage:# define IF_UDHCP_VERBOSE(...)
1178 //usage:#endif
1179 //usage:#define udhcpc_trivial_usage
1180 //usage:       "[-fbq"IF_UDHCP_VERBOSE("v")"RB]"IF_FEATURE_UDHCPC_ARPING(" [-a[MSEC]]")" [-t N] [-T SEC] [-A SEC/-n]\n"
1181 //usage:       "        [-i IFACE]"IF_FEATURE_UDHCP_PORT(" [-P PORT]")" [-s PROG] [-p PIDFILE]\n"
1182 //usage:       "        [-oC] [-r IP] [-V VENDOR] [-F NAME] [-x OPT:VAL]... [-O OPT]..."
1183 //usage:#define udhcpc_full_usage "\n"
1184 //usage:        IF_LONG_OPTS(
1185 //usage:     "\n        -i,--interface IFACE    Interface to use (default eth0)"
1186 //usage:        IF_FEATURE_UDHCP_PORT(
1187 //usage:     "\n        -P,--client-port PORT   Use PORT (default 68)"
1188 //usage:        )
1189 //usage:     "\n        -s,--script PROG        Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
1190 //usage:     "\n        -p,--pidfile FILE       Create pidfile"
1191 //usage:     "\n        -B,--broadcast          Request broadcast replies"
1192 //usage:     "\n        -t,--retries N          Send up to N discover packets (default 3)"
1193 //usage:     "\n        -T,--timeout SEC        Pause between packets (default 3)"
1194 //usage:     "\n        -A,--tryagain SEC       Wait if lease is not obtained (default 20)"
1195 //usage:     "\n        -n,--now                Exit if lease is not obtained"
1196 //usage:     "\n        -q,--quit               Exit after obtaining lease"
1197 //usage:     "\n        -R,--release            Release IP on exit"
1198 //usage:     "\n        -f,--foreground         Run in foreground"
1199 //usage:        USE_FOR_MMU(
1200 //usage:     "\n        -b,--background         Background if lease is not obtained"
1201 //usage:        )
1202 //usage:     "\n        -S,--syslog             Log to syslog too"
1203 //usage:        IF_FEATURE_UDHCPC_ARPING(
1204 //usage:     "\n        -a[MSEC],--arping[=MSEC] Validate offered address with ARP ping"
1205 //usage:        )
1206 //usage:     "\n        -r,--request IP         Request this IP address"
1207 //usage:     "\n        -o,--no-default-options Don't request any options (unless -O is given)"
1208 //usage:     "\n        -O,--request-option OPT Request option OPT from server (cumulative)"
1209 //usage:     "\n        -x OPT:VAL              Include option OPT in sent packets (cumulative)"
1210 //usage:     "\n                                Examples of string, numeric, and hex byte opts:"
1211 //usage:     "\n                                -x hostname:bbox - option 12"
1212 //usage:     "\n                                -x lease:3600 - option 51 (lease time)"
1213 //usage:     "\n                                -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
1214 //usage:     "\n        -F,--fqdn NAME          Ask server to update DNS mapping for NAME"
1215 //usage:     "\n        -V,--vendorclass VENDOR Vendor identifier (default 'udhcp VERSION')"
1216 //usage:     "\n        -C,--clientid-none      Don't send MAC as client identifier"
1217 //usage:        IF_UDHCP_VERBOSE(
1218 //usage:     "\n        -v                      Verbose"
1219 //usage:        )
1220 //usage:        )
1221 //usage:        IF_NOT_LONG_OPTS(
1222 //usage:     "\n        -i IFACE        Interface to use (default eth0)"
1223 //usage:        IF_FEATURE_UDHCP_PORT(
1224 //usage:     "\n        -P PORT         Use PORT (default 68)"
1225 //usage:        )
1226 //usage:     "\n        -s PROG         Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
1227 //usage:     "\n        -p FILE         Create pidfile"
1228 //usage:     "\n        -B              Request broadcast replies"
1229 //usage:     "\n        -t N            Send up to N discover packets (default 3)"
1230 //usage:     "\n        -T SEC          Pause between packets (default 3)"
1231 //usage:     "\n        -A SEC          Wait if lease is not obtained (default 20)"
1232 //usage:     "\n        -n              Exit if lease is not obtained"
1233 //usage:     "\n        -q              Exit after obtaining lease"
1234 //usage:     "\n        -R              Release IP on exit"
1235 //usage:     "\n        -f              Run in foreground"
1236 //usage:        USE_FOR_MMU(
1237 //usage:     "\n        -b              Background if lease is not obtained"
1238 //usage:        )
1239 //usage:     "\n        -S              Log to syslog too"
1240 //usage:        IF_FEATURE_UDHCPC_ARPING(
1241 //usage:     "\n        -a[MSEC]        Validate offered address with ARP ping"
1242 //usage:        )
1243 //usage:     "\n        -r IP           Request this IP address"
1244 //usage:     "\n        -o              Don't request any options (unless -O is given)"
1245 //usage:     "\n        -O OPT          Request option OPT from server (cumulative)"
1246 //usage:     "\n        -x OPT:VAL      Include option OPT in sent packets (cumulative)"
1247 //usage:     "\n                        Examples of string, numeric, and hex byte opts:"
1248 //usage:     "\n                        -x hostname:bbox - option 12"
1249 //usage:     "\n                        -x lease:3600 - option 51 (lease time)"
1250 //usage:     "\n                        -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
1251 //usage:     "\n        -F NAME         Ask server to update DNS mapping for NAME"
1252 //usage:     "\n        -V VENDOR       Vendor identifier (default 'udhcp VERSION')"
1253 //usage:     "\n        -C              Don't send MAC as client identifier"
1254 //usage:        IF_UDHCP_VERBOSE(
1255 //usage:     "\n        -v              Verbose"
1256 //usage:        )
1257 //usage:        )
1258 //usage:     "\nSignals:"
1259 //usage:     "\n        USR1    Renew lease"
1260 //usage:     "\n        USR2    Release lease"
1261
1262
1263 int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
1264 int udhcpc_main(int argc UNUSED_PARAM, char **argv)
1265 {
1266         uint8_t *message;
1267         const char *str_V, *str_h, *str_F, *str_r;
1268         IF_FEATURE_UDHCPC_ARPING(const char *str_a = "2000";)
1269         IF_FEATURE_UDHCP_PORT(char *str_P;)
1270         void *clientid_mac_ptr;
1271         llist_t *list_O = NULL;
1272         llist_t *list_x = NULL;
1273         int tryagain_timeout = 20;
1274         int discover_timeout = 3;
1275         int discover_retries = 3;
1276         uint32_t server_addr = server_addr; /* for compiler */
1277         uint32_t requested_ip = 0;
1278         uint32_t xid = xid; /* for compiler */
1279         int packet_num;
1280         int timeout; /* must be signed */
1281         unsigned already_waited_sec;
1282         unsigned opt;
1283         IF_FEATURE_UDHCPC_ARPING(unsigned arpping_ms;)
1284         int retval;
1285
1286         setup_common_bufsiz();
1287
1288         /* Default options */
1289         IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;)
1290         IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
1291         client_config.interface = "eth0";
1292         client_config.script = CONFIG_UDHCPC_DEFAULT_SCRIPT;
1293         str_V = "udhcp "BB_VER;
1294
1295         /* Parse command line */
1296         /* O,x: list; -T,-t,-A take numeric param */
1297         IF_UDHCP_VERBOSE(opt_complementary = "vv";)
1298         IF_LONG_OPTS(applet_long_options = udhcpc_longopts;)
1299         opt = getopt32(argv, "CV:H:h:F:i:np:qRr:s:T:+t:+SA:+O:*ox:*fB"
1300                 USE_FOR_MMU("b")
1301                 IF_FEATURE_UDHCPC_ARPING("a::")
1302                 IF_FEATURE_UDHCP_PORT("P:")
1303                 "v"
1304                 , &str_V, &str_h, &str_h, &str_F
1305                 , &client_config.interface, &client_config.pidfile, &str_r /* i,p */
1306                 , &client_config.script /* s */
1307                 , &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */
1308                 , &list_O
1309                 , &list_x
1310                 IF_FEATURE_UDHCPC_ARPING(, &str_a)
1311                 IF_FEATURE_UDHCP_PORT(, &str_P)
1312                 IF_UDHCP_VERBOSE(, &dhcp_verbose)
1313         );
1314         if (opt & (OPT_h|OPT_H)) {
1315                 //msg added 2011-11
1316                 bb_error_msg("option -h NAME is deprecated, use -x hostname:NAME");
1317                 client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
1318         }
1319         if (opt & OPT_F) {
1320                 /* FQDN option format: [0x51][len][flags][0][0]<fqdn> */
1321                 client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
1322                 /* Flag bits: 0000NEOS
1323                  * S: 1 = Client requests server to update A RR in DNS as well as PTR
1324                  * O: 1 = Server indicates to client that DNS has been updated regardless
1325                  * E: 1 = Name is in DNS format, i.e. <4>host<6>domain<3>com<0>,
1326                  *    not "host.domain.com". Format 0 is obsolete.
1327                  * N: 1 = Client requests server to not update DNS (S must be 0 then)
1328                  * Two [0] bytes which follow are deprecated and must be 0.
1329                  */
1330                 client_config.fqdn[OPT_DATA + 0] = 0x1;
1331                 /*client_config.fqdn[OPT_DATA + 1] = 0; - xzalloc did it */
1332                 /*client_config.fqdn[OPT_DATA + 2] = 0; */
1333         }
1334         if (opt & OPT_r)
1335                 requested_ip = inet_addr(str_r);
1336 #if ENABLE_FEATURE_UDHCP_PORT
1337         if (opt & OPT_P) {
1338                 CLIENT_PORT = xatou16(str_P);
1339                 SERVER_PORT = CLIENT_PORT - 1;
1340         }
1341 #endif
1342         IF_FEATURE_UDHCPC_ARPING(arpping_ms = xatou(str_a);)
1343         while (list_O) {
1344                 char *optstr = llist_pop(&list_O);
1345                 unsigned n = bb_strtou(optstr, NULL, 0);
1346                 if (errno || n > 254) {
1347                         n = udhcp_option_idx(optstr);
1348                         n = dhcp_optflags[n].code;
1349                 }
1350                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
1351         }
1352         if (!(opt & OPT_o)) {
1353                 unsigned i, n;
1354                 for (i = 0; (n = dhcp_optflags[i].code) != 0; i++) {
1355                         if (dhcp_optflags[i].flags & OPTION_REQ) {
1356                                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
1357                         }
1358                 }
1359         }
1360         while (list_x) {
1361                 char *optstr = llist_pop(&list_x);
1362                 char *colon = strchr(optstr, ':');
1363                 if (colon)
1364                         *colon = ' ';
1365                 /* now it looks similar to udhcpd's config file line:
1366                  * "optname optval", using the common routine: */
1367                 udhcp_str2optset(optstr, &client_config.options);
1368         }
1369
1370         if (udhcp_read_interface(client_config.interface,
1371                         &client_config.ifindex,
1372                         NULL,
1373                         client_config.client_mac)
1374         ) {
1375                 return 1;
1376         }
1377
1378         clientid_mac_ptr = NULL;
1379         if (!(opt & OPT_C) && !udhcp_find_option(client_config.options, DHCP_CLIENT_ID)) {
1380                 /* not suppressed and not set, set the default client ID */
1381                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
1382                 client_config.clientid[OPT_DATA] = 1; /* type: ethernet */
1383                 clientid_mac_ptr = client_config.clientid + OPT_DATA+1;
1384                 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1385         }
1386         if (str_V[0] != '\0') {
1387                 // can drop -V, str_V, client_config.vendorclass,
1388                 // but need to add "vendor" to the list of recognized
1389                 // string opts for this to work;
1390                 // and need to tweak add_client_options() too...
1391                 // ...so the question is, should we?
1392                 //bb_error_msg("option -V VENDOR is deprecated, use -x vendor:VENDOR");
1393                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
1394         }
1395
1396 #if !BB_MMU
1397         /* on NOMMU reexec (i.e., background) early */
1398         if (!(opt & OPT_f)) {
1399                 bb_daemonize_or_rexec(0 /* flags */, argv);
1400                 logmode = LOGMODE_NONE;
1401         }
1402 #endif
1403         if (opt & OPT_S) {
1404                 openlog(applet_name, LOG_PID, LOG_DAEMON);
1405                 logmode |= LOGMODE_SYSLOG;
1406         }
1407
1408         /* Make sure fd 0,1,2 are open */
1409         bb_sanitize_stdio();
1410         /* Equivalent of doing a fflush after every \n */
1411         setlinebuf(stdout);
1412         /* Create pidfile */
1413         write_pidfile(client_config.pidfile);
1414         /* Goes to stdout (unless NOMMU) and possibly syslog */
1415         bb_error_msg("started, v"BB_VER);
1416         /* Set up the signal pipe */
1417         udhcp_sp_setup();
1418         /* We want random_xid to be random... */
1419         srand(monotonic_us());
1420
1421         state = INIT_SELECTING;
1422         udhcp_run_script(NULL, "deconfig");
1423         change_listen_mode(LISTEN_RAW);
1424         packet_num = 0;
1425         timeout = 0;
1426         already_waited_sec = 0;
1427
1428         /* Main event loop. select() waits on signal pipe and possibly
1429          * on sockfd.
1430          * "continue" statements in code below jump to the top of the loop.
1431          */
1432         for (;;) {
1433                 int tv;
1434                 struct pollfd pfds[2];
1435                 struct dhcp_packet packet;
1436                 /* silence "uninitialized!" warning */
1437                 unsigned timestamp_before_wait = timestamp_before_wait;
1438
1439                 //bb_error_msg("sockfd:%d, listen_mode:%d", sockfd, listen_mode);
1440
1441                 /* Was opening raw or udp socket here
1442                  * if (listen_mode != LISTEN_NONE && sockfd < 0),
1443                  * but on fast network renew responses return faster
1444                  * than we open sockets. Thus this code is moved
1445                  * to change_listen_mode(). Thus we open listen socket
1446                  * BEFORE we send renew request (see "case BOUND:"). */
1447
1448                 udhcp_sp_fd_set(pfds, sockfd);
1449
1450                 tv = timeout - already_waited_sec;
1451                 retval = 0;
1452                 /* If we already timed out, fall through with retval = 0, else... */
1453                 if (tv > 0) {
1454                         log1("waiting on select %u seconds", tv);
1455                         timestamp_before_wait = (unsigned)monotonic_sec();
1456                         retval = poll(pfds, 2, tv < INT_MAX/1000 ? tv * 1000 : INT_MAX);
1457                         if (retval < 0) {
1458                                 /* EINTR? A signal was caught, don't panic */
1459                                 if (errno == EINTR) {
1460                                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1461                                         continue;
1462                                 }
1463                                 /* Else: an error occurred, panic! */
1464                                 bb_perror_msg_and_die("select");
1465                         }
1466                 }
1467
1468                 /* If timeout dropped to zero, time to become active:
1469                  * resend discover/renew/whatever
1470                  */
1471                 if (retval == 0) {
1472                         /* When running on a bridge, the ifindex may have changed
1473                          * (e.g. if member interfaces were added/removed
1474                          * or if the status of the bridge changed).
1475                          * Refresh ifindex and client_mac:
1476                          */
1477                         if (udhcp_read_interface(client_config.interface,
1478                                         &client_config.ifindex,
1479                                         NULL,
1480                                         client_config.client_mac)
1481                         ) {
1482                                 goto ret0; /* iface is gone? */
1483                         }
1484                         if (clientid_mac_ptr)
1485                                 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1486
1487                         /* We will restart the wait in any case */
1488                         already_waited_sec = 0;
1489
1490                         switch (state) {
1491                         case INIT_SELECTING:
1492                                 if (!discover_retries || packet_num < discover_retries) {
1493                                         if (packet_num == 0)
1494                                                 xid = random_xid();
1495                                         /* broadcast */
1496                                         send_discover(xid, requested_ip);
1497                                         timeout = discover_timeout;
1498                                         packet_num++;
1499                                         continue;
1500                                 }
1501  leasefail:
1502                                 udhcp_run_script(NULL, "leasefail");
1503 #if BB_MMU /* -b is not supported on NOMMU */
1504                                 if (opt & OPT_b) { /* background if no lease */
1505                                         bb_error_msg("no lease, forking to background");
1506                                         client_background();
1507                                         /* do not background again! */
1508                                         opt = ((opt & ~OPT_b) | OPT_f);
1509                                 } else
1510 #endif
1511                                 if (opt & OPT_n) { /* abort if no lease */
1512                                         bb_error_msg("no lease, failing");
1513                                         retval = 1;
1514                                         goto ret;
1515                                 }
1516                                 /* wait before trying again */
1517                                 timeout = tryagain_timeout;
1518                                 packet_num = 0;
1519                                 continue;
1520                         case REQUESTING:
1521                                 if (packet_num < 3) {
1522                                         /* send broadcast select packet */
1523                                         send_select(xid, server_addr, requested_ip);
1524                                         timeout = discover_timeout;
1525                                         packet_num++;
1526                                         continue;
1527                                 }
1528                                 /* Timed out, go back to init state.
1529                                  * "discover...select...discover..." loops
1530                                  * were seen in the wild. Treat them similarly
1531                                  * to "no response to discover" case */
1532                                 change_listen_mode(LISTEN_RAW);
1533                                 state = INIT_SELECTING;
1534                                 goto leasefail;
1535                         case BOUND:
1536                                 /* 1/2 lease passed, enter renewing state */
1537                                 state = RENEWING;
1538                                 client_config.first_secs = 0; /* make secs field count from 0 */
1539                                 change_listen_mode(LISTEN_KERNEL);
1540                                 log1("entering renew state");
1541                                 /* fall right through */
1542                         case RENEW_REQUESTED: /* manual (SIGUSR1) renew */
1543                         case_RENEW_REQUESTED:
1544                         case RENEWING:
1545                                 if (timeout > 60) {
1546                                         /* send an unicast renew request */
1547                         /* Sometimes observed to fail (EADDRNOTAVAIL) to bind
1548                          * a new UDP socket for sending inside send_renew.
1549                          * I hazard to guess existing listening socket
1550                          * is somehow conflicting with it, but why is it
1551                          * not deterministic then?! Strange.
1552                          * Anyway, it does recover by eventually failing through
1553                          * into INIT_SELECTING state.
1554                          */
1555                                         send_renew(xid, server_addr, requested_ip);
1556                                         timeout >>= 1;
1557                                         continue;
1558                                 }
1559                                 /* Timed out, enter rebinding state */
1560                                 log1("entering rebinding state");
1561                                 state = REBINDING;
1562                                 /* fall right through */
1563                         case REBINDING:
1564                                 /* Switch to bcast receive */
1565                                 change_listen_mode(LISTEN_RAW);
1566                                 /* Lease is *really* about to run out,
1567                                  * try to find DHCP server using broadcast */
1568                                 if (timeout > 0) {
1569                                         /* send a broadcast renew request */
1570                                         send_renew(xid, 0 /*INADDR_ANY*/, requested_ip);
1571                                         timeout >>= 1;
1572                                         continue;
1573                                 }
1574                                 /* Timed out, enter init state */
1575                                 bb_error_msg("lease lost, entering init state");
1576                                 udhcp_run_script(NULL, "deconfig");
1577                                 state = INIT_SELECTING;
1578                                 client_config.first_secs = 0; /* make secs field count from 0 */
1579                                 /*timeout = 0; - already is */
1580                                 packet_num = 0;
1581                                 continue;
1582                         /* case RELEASED: */
1583                         }
1584                         /* yah, I know, *you* say it would never happen */
1585                         timeout = INT_MAX;
1586                         continue; /* back to main loop */
1587                 } /* if select timed out */
1588
1589                 /* select() didn't timeout, something happened */
1590
1591                 /* Is it a signal? */
1592                 /* note: udhcp_sp_read checks poll result before reading */
1593                 switch (udhcp_sp_read(pfds)) {
1594                 case SIGUSR1:
1595                         client_config.first_secs = 0; /* make secs field count from 0 */
1596                         already_waited_sec = 0;
1597                         perform_renew();
1598                         if (state == RENEW_REQUESTED) {
1599                                 /* We might be either on the same network
1600                                  * (in which case renew might work),
1601                                  * or we might be on a completely different one
1602                                  * (in which case renew won't ever succeed).
1603                                  * For the second case, must make sure timeout
1604                                  * is not too big, or else we can send
1605                                  * futile renew requests for hours.
1606                                  * (Ab)use -A TIMEOUT value (usually 20 sec)
1607                                  * as a cap on the timeout.
1608                                  */
1609                                 if (timeout > tryagain_timeout)
1610                                         timeout = tryagain_timeout;
1611                                 goto case_RENEW_REQUESTED;
1612                         }
1613                         /* Start things over */
1614                         packet_num = 0;
1615                         /* Kill any timeouts, user wants this to hurry along */
1616                         timeout = 0;
1617                         continue;
1618                 case SIGUSR2:
1619                         perform_release(server_addr, requested_ip);
1620                         timeout = INT_MAX;
1621                         continue;
1622                 case SIGTERM:
1623                         bb_error_msg("received %s", "SIGTERM");
1624                         goto ret0;
1625                 }
1626
1627                 /* Is it a packet? */
1628                 if (listen_mode == LISTEN_NONE || !pfds[1].revents)
1629                         continue; /* no */
1630
1631                 {
1632                         int len;
1633
1634                         /* A packet is ready, read it */
1635                         if (listen_mode == LISTEN_KERNEL)
1636                                 len = udhcp_recv_kernel_packet(&packet, sockfd);
1637                         else
1638                                 len = udhcp_recv_raw_packet(&packet, sockfd);
1639                         if (len == -1) {
1640                                 /* Error is severe, reopen socket */
1641                                 bb_error_msg("read error: %s, reopening socket", strerror(errno));
1642                                 sleep(discover_timeout); /* 3 seconds by default */
1643                                 change_listen_mode(listen_mode); /* just close and reopen */
1644                         }
1645                         /* If this packet will turn out to be unrelated/bogus,
1646                          * we will go back and wait for next one.
1647                          * Be sure timeout is properly decreased. */
1648                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1649                         if (len < 0)
1650                                 continue;
1651                 }
1652
1653                 if (packet.xid != xid) {
1654                         log1("xid %x (our is %x), ignoring packet",
1655                                 (unsigned)packet.xid, (unsigned)xid);
1656                         continue;
1657                 }
1658
1659                 /* Ignore packets that aren't for us */
1660                 if (packet.hlen != 6
1661                  || memcmp(packet.chaddr, client_config.client_mac, 6) != 0
1662                 ) {
1663 //FIXME: need to also check that last 10 bytes are zero
1664                         log1("chaddr does not match, ignoring packet"); // log2?
1665                         continue;
1666                 }
1667
1668                 message = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
1669                 if (message == NULL) {
1670                         bb_error_msg("no message type option, ignoring packet");
1671                         continue;
1672                 }
1673
1674                 switch (state) {
1675                 case INIT_SELECTING:
1676                         /* Must be a DHCPOFFER */
1677                         if (*message == DHCPOFFER) {
1678                                 uint8_t *temp;
1679
1680 /* What exactly is server's IP? There are several values.
1681  * Example DHCP offer captured with tchdump:
1682  *
1683  * 10.34.25.254:67 > 10.34.25.202:68 // IP header's src
1684  * BOOTP fields:
1685  * Your-IP 10.34.25.202
1686  * Server-IP 10.34.32.125   // "next server" IP
1687  * Gateway-IP 10.34.25.254  // relay's address (if DHCP relays are in use)
1688  * DHCP options:
1689  * DHCP-Message Option 53, length 1: Offer
1690  * Server-ID Option 54, length 4: 10.34.255.7       // "server ID"
1691  * Default-Gateway Option 3, length 4: 10.34.25.254 // router
1692  *
1693  * We think that real server IP (one to use in renew/release)
1694  * is one in Server-ID option. But I am not 100% sure.
1695  * IP header's src and Gateway-IP (same in this example)
1696  * might work too.
1697  * "Next server" and router are definitely wrong ones to use, though...
1698  */
1699 /* We used to ignore pcakets without DHCP_SERVER_ID.
1700  * I've got user reports from people who run "address-less" servers.
1701  * They either supply DHCP_SERVER_ID of 0.0.0.0 or don't supply it at all.
1702  * They say ISC DHCP client supports this case.
1703  */
1704                                 server_addr = 0;
1705                                 temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
1706                                 if (!temp) {
1707                                         bb_error_msg("no server ID, using 0.0.0.0");
1708                                 } else {
1709                                         /* it IS unaligned sometimes, don't "optimize" */
1710                                         move_from_unaligned32(server_addr, temp);
1711                                 }
1712                                 /*xid = packet.xid; - already is */
1713                                 requested_ip = packet.yiaddr;
1714
1715                                 /* enter requesting state */
1716                                 state = REQUESTING;
1717                                 timeout = 0;
1718                                 packet_num = 0;
1719                                 already_waited_sec = 0;
1720                         }
1721                         continue;
1722                 case REQUESTING:
1723                 case RENEWING:
1724                 case RENEW_REQUESTED:
1725                 case REBINDING:
1726                         if (*message == DHCPACK) {
1727                                 unsigned start;
1728                                 uint32_t lease_seconds;
1729                                 struct in_addr temp_addr;
1730                                 uint8_t *temp;
1731
1732                                 temp = udhcp_get_option(&packet, DHCP_LEASE_TIME);
1733                                 if (!temp) {
1734                                         bb_error_msg("no lease time with ACK, using 1 hour lease");
1735                                         lease_seconds = 60 * 60;
1736                                 } else {
1737                                         /* it IS unaligned sometimes, don't "optimize" */
1738                                         move_from_unaligned32(lease_seconds, temp);
1739                                         lease_seconds = ntohl(lease_seconds);
1740                                         /* paranoia: must not be too small and not prone to overflows */
1741                                         if (lease_seconds < 0x10)
1742                                                 lease_seconds = 0x10;
1743                                         if (lease_seconds > 0x7fffffff / 1000)
1744                                                 lease_seconds = 0x7fffffff / 1000;
1745                                 }
1746 #if ENABLE_FEATURE_UDHCPC_ARPING
1747                                 if (opt & OPT_a) {
1748 /* RFC 2131 3.1 paragraph 5:
1749  * "The client receives the DHCPACK message with configuration
1750  * parameters. The client SHOULD perform a final check on the
1751  * parameters (e.g., ARP for allocated network address), and notes
1752  * the duration of the lease specified in the DHCPACK message. At this
1753  * point, the client is configured. If the client detects that the
1754  * address is already in use (e.g., through the use of ARP),
1755  * the client MUST send a DHCPDECLINE message to the server and restarts
1756  * the configuration process..." */
1757                                         if (!arpping(packet.yiaddr,
1758                                                         NULL,
1759                                                         (uint32_t) 0,
1760                                                         client_config.client_mac,
1761                                                         client_config.interface,
1762                                                         arpping_ms)
1763                                         ) {
1764                                                 bb_error_msg("offered address is in use "
1765                                                         "(got ARP reply), declining");
1766                                                 send_decline(/*xid,*/ server_addr, packet.yiaddr);
1767
1768                                                 if (state != REQUESTING)
1769                                                         udhcp_run_script(NULL, "deconfig");
1770                                                 change_listen_mode(LISTEN_RAW);
1771                                                 state = INIT_SELECTING;
1772                                                 client_config.first_secs = 0; /* make secs field count from 0 */
1773                                                 requested_ip = 0;
1774                                                 timeout = tryagain_timeout;
1775                                                 packet_num = 0;
1776                                                 already_waited_sec = 0;
1777                                                 continue; /* back to main loop */
1778                                         }
1779                                 }
1780 #endif
1781                                 /* enter bound state */
1782                                 temp_addr.s_addr = packet.yiaddr;
1783                                 bb_error_msg("lease of %s obtained, lease time %u",
1784                                         inet_ntoa(temp_addr), (unsigned)lease_seconds);
1785                                 requested_ip = packet.yiaddr;
1786
1787                                 start = monotonic_sec();
1788                                 udhcp_run_script(&packet, state == REQUESTING ? "bound" : "renew");
1789                                 already_waited_sec = (unsigned)monotonic_sec() - start;
1790                                 timeout = lease_seconds / 2;
1791                                 if ((unsigned)timeout < already_waited_sec) {
1792                                         /* Something went wrong. Back to discover state */
1793                                         timeout = already_waited_sec = 0;
1794                                 }
1795
1796                                 state = BOUND;
1797                                 change_listen_mode(LISTEN_NONE);
1798                                 if (opt & OPT_q) { /* quit after lease */
1799                                         goto ret0;
1800                                 }
1801                                 /* future renew failures should not exit (JM) */
1802                                 opt &= ~OPT_n;
1803 #if BB_MMU /* NOMMU case backgrounded earlier */
1804                                 if (!(opt & OPT_f)) {
1805                                         client_background();
1806                                         /* do not background again! */
1807                                         opt = ((opt & ~OPT_b) | OPT_f);
1808                                 }
1809 #endif
1810                                 /* make future renew packets use different xid */
1811                                 /* xid = random_xid(); ...but why bother? */
1812
1813                                 continue; /* back to main loop */
1814                         }
1815                         if (*message == DHCPNAK) {
1816                                 /* If network has more than one DHCP server,
1817                                  * "wrong" server can reply first, with a NAK.
1818                                  * Do not interpret it as a NAK from "our" server.
1819                                  */
1820                                 if (server_addr != 0) {
1821                                         uint32_t svid;
1822                                         uint8_t *temp;
1823
1824                                         temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
1825                                         if (!temp) {
1826  non_matching_svid:
1827                                                 log1("received DHCP NAK with wrong"
1828                                                         " server ID, ignoring packet");
1829                                                 continue;
1830                                         }
1831                                         move_from_unaligned32(svid, temp);
1832                                         if (svid != server_addr)
1833                                                 goto non_matching_svid;
1834                                 }
1835                                 /* return to init state */
1836                                 bb_error_msg("received %s", "DHCP NAK");
1837                                 udhcp_run_script(&packet, "nak");
1838                                 if (state != REQUESTING)
1839                                         udhcp_run_script(NULL, "deconfig");
1840                                 change_listen_mode(LISTEN_RAW);
1841                                 sleep(3); /* avoid excessive network traffic */
1842                                 state = INIT_SELECTING;
1843                                 client_config.first_secs = 0; /* make secs field count from 0 */
1844                                 requested_ip = 0;
1845                                 timeout = 0;
1846                                 packet_num = 0;
1847                                 already_waited_sec = 0;
1848                         }
1849                         continue;
1850                 /* case BOUND: - ignore all packets */
1851                 /* case RELEASED: - ignore all packets */
1852                 }
1853                 /* back to main loop */
1854         } /* for (;;) - main loop ends */
1855
1856  ret0:
1857         if (opt & OPT_R) /* release on quit */
1858                 perform_release(server_addr, requested_ip);
1859         retval = 0;
1860  ret:
1861         /*if (client_config.pidfile) - remove_pidfile has its own check */
1862                 remove_pidfile(client_config.pidfile);
1863         return retval;
1864 }