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         USE_FOR_MMU(
  77         "background\0"     No_argument       "b"
  78         )
  79         "broadcast\0"      No_argument       "B"
  80         IF_FEATURE_UDHCPC_ARPING("arping\0"     Optional_argument "a")
  81         IF_FEATURE_UDHCP_PORT("client-port\0"   Required_argument "P")
  82         ;
  83 #endif
  84 /* Must match getopt32 option string order */
  85 enum {
  86         OPT_C = 1 << 0,
  87         OPT_V = 1 << 1,
  88         OPT_H = 1 << 2,
  89         OPT_h = 1 << 3,
  90         OPT_F = 1 << 4,
  91         OPT_i = 1 << 5,
  92         OPT_n = 1 << 6,
  93         OPT_p = 1 << 7,
  94         OPT_q = 1 << 8,
  95         OPT_R = 1 << 9,
  96         OPT_r = 1 << 10,
  97         OPT_s = 1 << 11,
  98         OPT_T = 1 << 12,
  99         OPT_t = 1 << 13,
 100         OPT_S = 1 << 14,
 101         OPT_A = 1 << 15,
 102         OPT_O = 1 << 16,
 103         OPT_o = 1 << 17,
 104         OPT_x = 1 << 18,
 105         OPT_f = 1 << 19,
 106         OPT_B = 1 << 20,
 107 /* The rest has variable bit positions, need to be clever */
 108         OPTBIT_B = 20,
 109         USE_FOR_MMU(             OPTBIT_b,)
 110         IF_FEATURE_UDHCPC_ARPING(OPTBIT_a,)
 111         IF_FEATURE_UDHCP_PORT(   OPTBIT_P,)
 112         USE_FOR_MMU(             OPT_b = 1 << OPTBIT_b,)
 113         IF_FEATURE_UDHCPC_ARPING(OPT_a = 1 << OPTBIT_a,)
 114         IF_FEATURE_UDHCP_PORT(   OPT_P = 1 << OPTBIT_P,)
 115 };
 116
 117
 118 /*** Script execution code ***/
 119
 120 /* get a rough idea of how long an option will be (rounding up...) */
 121 static const uint8_t len_of_option_as_string[] ALIGN1 = {
 122         [OPTION_IP              ] = sizeof("255.255.255.255 "),
 123         [OPTION_IP_PAIR         ] = sizeof("255.255.255.255 ") * 2,
 124         [OPTION_STATIC_ROUTES   ] = sizeof("255.255.255.255/32 255.255.255.255 "),
 125         [OPTION_6RD             ] = sizeof("132 128 ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 255.255.255.255 "),
 126         [OPTION_STRING          ] = 1,
 127         [OPTION_STRING_HOST     ] = 1,
 128 #if ENABLE_FEATURE_UDHCP_RFC3397
 129         [OPTION_DNS_STRING      ] = 1, /* unused */
 130         /* Hmmm, this severely overestimates size if SIP_SERVERS option
 131          * is in domain name form: N-byte option in binary form
 132          * mallocs ~16*N bytes. But it is freed almost at once.
 133          */
 134         [OPTION_SIP_SERVERS     ] = sizeof("255.255.255.255 "),
 135 #endif
 136 //      [OPTION_BOOLEAN         ] = sizeof("yes "),
 137         [OPTION_U8              ] = sizeof("255 "),
 138         [OPTION_U16             ] = sizeof("65535 "),
 139 //      [OPTION_S16             ] = sizeof("-32768 "),
 140         [OPTION_U32             ] = sizeof("4294967295 "),
 141         [OPTION_S32             ] = sizeof("-2147483684 "),
 142 };
 143
 144 /* note: ip is a pointer to an IP in network order, possibly misaliged */
 145 static int sprint_nip(char *dest, const char *pre, const uint8_t *ip)
 146 {
 147         return sprintf(dest, "%s%u.%u.%u.%u", pre, ip[0], ip[1], ip[2], ip[3]);
 148 }
 149
 150 /* really simple implementation, just count the bits */
 151 static int mton(uint32_t mask)
 152 {
 153         int i = 0;
 154         mask = ntohl(mask); /* 111110000-like bit pattern */
 155         while (mask) {
 156                 i++;
 157                 mask <<= 1;
 158         }
 159         return i;
 160 }
 161
 162 #if ENABLE_FEATURE_UDHCPC_SANITIZEOPT
 163 /* Check if a given label represents a valid DNS label
 164  * Return pointer to the first character after the label upon success,
 165  * NULL otherwise.
 166  * See RFC1035, 2.3.1
 167  */
 168 /* We don't need to be particularly anal. For example, allowing _, hyphen
 169  * at the end, or leading and trailing dots would be ok, since it
 170  * can't be used for attacks. (Leading hyphen can be, if someone uses
 171  * cmd "$hostname"
 172  * in the script: then hostname may be treated as an option)
 173  */
 174 static const char *valid_domain_label(const char *label)
 175 {
 176         unsigned char ch;
 177         unsigned pos = 0;
 178
 179         for (;;) {
 180                 ch = *label;
 181                 if ((ch|0x20) < 'a' || (ch|0x20) > 'z') {
 182                         if (ch < '0' || ch > '9') {
 183                                 if (ch == '\0' || ch == '.')
 184                                         return label;
 185                                 /* DNS allows only '-', but we are more permissive */
 186                                 if (ch != '-' && ch != '_')
 187                                         return NULL;
 188                         }
 189                 }
 190                 label++;
 191                 pos++;
 192                 //Do we want this?
 193                 //if (pos > 63) /* NS_MAXLABEL; labels must be 63 chars or less */
 194                 //      return NULL;
 195         }
 196 }
 197
 198 /* Check if a given name represents a valid DNS name */
 199 /* See RFC1035, 2.3.1 */
 200 static int good_hostname(const char *name)
 201 {
 202         //const char *start = name;
 203
 204         for (;;) {
 205                 name = valid_domain_label(name);
 206                 if (!name)
 207                         return 0;
 208                 if (!name[0])
 209                         return 1;
 210                         //Do we want this?
 211                         //return ((name - start) < 1025); /* NS_MAXDNAME */
 212                 name++;
 213                 if (*name == '\0')
 214                         return 1; // We allow trailing dot too
 215         }
 216 }
 217 #else
 218 # define good_hostname(name) 1
 219 #endif
 220
 221 /* Create "opt_name=opt_value" string */
 222 static NOINLINE char *xmalloc_optname_optval(uint8_t *option, const struct dhcp_optflag *optflag, const char *opt_name)
 223 {
 224         unsigned upper_length;
 225         int len, type, optlen;
 226         char *dest, *ret;
 227
 228         /* option points to OPT_DATA, need to go back to get OPT_LEN */
 229         len = option[-OPT_DATA + OPT_LEN];
 230
 231         type = optflag->flags & OPTION_TYPE_MASK;
 232         optlen = dhcp_option_lengths[type];
 233         upper_length = len_of_option_as_string[type]
 234                 * ((unsigned)(len + optlen) / (unsigned)optlen);
 235
 236         dest = ret = xmalloc(upper_length + strlen(opt_name) + 2);
 237         dest += sprintf(ret, "%s=", opt_name);
 238
 239         while (len >= optlen) {
 240                 switch (type) {
 241                 case OPTION_IP:
 242                 case OPTION_IP_PAIR:
 243                         dest += sprint_nip(dest, "", option);
 244                         if (type == OPTION_IP)
 245                                 break;
 246                         dest += sprint_nip(dest, "/", option + 4);
 247                         break;
 248 //              case OPTION_BOOLEAN:
 249 //                      dest += sprintf(dest, *option ? "yes" : "no");
 250 //                      break;
 251                 case OPTION_U8:
 252                         dest += sprintf(dest, "%u", *option);
 253                         break;
 254 //              case OPTION_S16:
 255                 case OPTION_U16: {
 256                         uint16_t val_u16;
 257                         move_from_unaligned16(val_u16, option);
 258                         dest += sprintf(dest, "%u", ntohs(val_u16));
 259                         break;
 260                 }
 261                 case OPTION_S32:
 262                 case OPTION_U32: {
 263                         uint32_t val_u32;
 264                         move_from_unaligned32(val_u32, option);
 265                         dest += sprintf(dest, type == OPTION_U32 ? "%lu" : "%ld", (unsigned long) ntohl(val_u32));
 266                         break;
 267                 }
 268                 /* Note: options which use 'return' instead of 'break'
 269                  * (for example, OPTION_STRING) skip the code which handles
 270                  * the case of list of options.
 271                  */
 272                 case OPTION_STRING:
 273                 case OPTION_STRING_HOST:
 274                         memcpy(dest, option, len);
 275                         dest[len] = '\0';
 276                         if (type == OPTION_STRING_HOST && !good_hostname(dest))
 277                                 safe_strncpy(dest, "bad", len);
 278                         return ret;
 279                 case OPTION_STATIC_ROUTES: {
 280                         /* Option binary format:
 281                          * mask [one byte, 0..32]
 282                          * ip [big endian, 0..4 bytes depending on mask]
 283                          * router [big endian, 4 bytes]
 284                          * may be repeated
 285                          *
 286                          * We convert it to a string "IP/MASK ROUTER IP2/MASK2 ROUTER2"
 287                          */
 288                         const char *pfx = "";
 289
 290                         while (len >= 1 + 4) { /* mask + 0-byte ip + router */
 291                                 uint32_t nip;
 292                                 uint8_t *p;
 293                                 unsigned mask;
 294                                 int bytes;
 295
 296                                 mask = *option++;
 297                                 if (mask > 32)
 298                                         break;
 299                                 len--;
 300
 301                                 nip = 0;
 302                                 p = (void*) &nip;
 303                                 bytes = (mask + 7) / 8; /* 0 -> 0, 1..8 -> 1, 9..16 -> 2 etc */
 304                                 while (--bytes >= 0) {
 305                                         *p++ = *option++;
 306                                         len--;
 307                                 }
 308                                 if (len < 4)
 309                                         break;
 310
 311                                 /* print ip/mask */
 312                                 dest += sprint_nip(dest, pfx, (void*) &nip);
 313                                 pfx = " ";
 314                                 dest += sprintf(dest, "/%u ", mask);
 315                                 /* print router */
 316                                 dest += sprint_nip(dest, "", option);
 317                                 option += 4;
 318                                 len -= 4;
 319                         }
 320
 321                         return ret;
 322                 }
 323                 case OPTION_6RD:
 324                         /* Option binary format (see RFC 5969):
 325                          *  0                   1                   2                   3
 326                          *  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
 327                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 328                          * |  OPTION_6RD   | option-length |  IPv4MaskLen  |  6rdPrefixLen |
 329                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 330                          * |                           6rdPrefix                           |
 331                          * ...                        (16 octets)                        ...
 332                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 333                          * ...                   6rdBRIPv4Address(es)                    ...
 334                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 335                          * We convert it to a string
 336                          * "IPv4MaskLen 6rdPrefixLen 6rdPrefix 6rdBRIPv4Address..."
 337                          *
 338                          * Sanity check: ensure that our length is at least 22 bytes, that
 339                          * IPv4MaskLen <= 32,
 340                          * 6rdPrefixLen <= 128,
 341                          * 6rdPrefixLen + (32 - IPv4MaskLen) <= 128
 342                          * (2nd condition need no check - it follows from 1st and 3rd).
 343                          * Else, return envvar with empty value ("optname=")
 344                          */
 345                         if (len >= (1 + 1 + 16 + 4)
 346                          && option[0] <= 32
 347                          && (option[1] + 32 - option[0]) <= 128
 348                         ) {
 349                                 /* IPv4MaskLen */
 350                                 dest += sprintf(dest, "%u ", *option++);
 351                                 /* 6rdPrefixLen */
 352                                 dest += sprintf(dest, "%u ", *option++);
 353                                 /* 6rdPrefix */
 354                                 dest += sprint_nip6(dest, /* "", */ option);
 355                                 option += 16;
 356                                 len -= 1 + 1 + 16 + 4;
 357                                 /* "+ 4" above corresponds to the length of IPv4 addr
 358                                  * we consume in the loop below */
 359                                 while (1) {
 360                                         /* 6rdBRIPv4Address(es) */
 361                                         dest += sprint_nip(dest, " ", option);
 362                                         option += 4;
 363                                         len -= 4; /* do we have yet another 4+ bytes? */
 364                                         if (len < 0)
 365                                                 break; /* no */
 366                                 }
 367                         }
 368
 369                         return ret;
 370 #if ENABLE_FEATURE_UDHCP_RFC3397
 371                 case OPTION_DNS_STRING:
 372                         /* unpack option into dest; use ret for prefix (i.e., "optname=") */
 373                         dest = dname_dec(option, len, ret);
 374                         if (dest) {
 375                                 free(ret);
 376                                 return dest;
 377                         }
 378                         /* error. return "optname=" string */
 379                         return ret;
 380                 case OPTION_SIP_SERVERS:
 381                         /* Option binary format:
 382                          * type: byte
 383                          * type=0: domain names, dns-compressed
 384                          * type=1: IP addrs
 385                          */
 386                         option++;
 387                         len--;
 388                         if (option[-1] == 0) {
 389                                 dest = dname_dec(option, len, ret);
 390                                 if (dest) {
 391                                         free(ret);
 392                                         return dest;
 393                                 }
 394                         } else
 395                         if (option[-1] == 1) {
 396                                 const char *pfx = "";
 397                                 while (1) {
 398                                         len -= 4;
 399                                         if (len < 0)
 400                                                 break;
 401                                         dest += sprint_nip(dest, pfx, option);
 402                                         pfx = " ";
 403                                         option += 4;
 404                                 }
 405                         }
 406                         return ret;
 407 #endif
 408                 } /* switch */
 409
 410                 /* If we are here, try to format any remaining data
 411                  * in the option as another, similarly-formatted option
 412                  */
 413                 option += optlen;
 414                 len -= optlen;
 415 // TODO: it can be a list only if (optflag->flags & OPTION_LIST).
 416 // Should we bail out/warn if we see multi-ip option which is
 417 // not allowed to be such (for example, DHCP_BROADCAST)? -
 418                 if (len < optlen /* || !(optflag->flags & OPTION_LIST) */)
 419                         break;
 420                 *dest++ = ' ';
 421                 *dest = '\0';
 422         } /* while */
 423
 424         return ret;
 425 }
 426
 427 /* put all the parameters into the environment */
 428 static char **fill_envp(struct dhcp_packet *packet)
 429 {
 430         int envc;
 431         int i;
 432         char **envp, **curr;
 433         const char *opt_name;
 434         uint8_t *temp;
 435         uint8_t overload = 0;
 436
 437 #define BITMAP unsigned
 438 #define BBITS (sizeof(BITMAP) * 8)
 439 #define BMASK(i) (1 << (i & (sizeof(BITMAP) * 8 - 1)))
 440 #define FOUND_OPTS(i) (found_opts[(unsigned)i / BBITS])
 441         BITMAP found_opts[256 / BBITS];
 442
 443         memset(found_opts, 0, sizeof(found_opts));
 444
 445         /* We need 6 elements for:
 446          * "interface=IFACE"
 447          * "ip=N.N.N.N" from packet->yiaddr
 448          * "siaddr=IP" from packet->siaddr_nip (unless 0)
 449          * "boot_file=FILE" from packet->file (unless overloaded)
 450          * "sname=SERVER_HOSTNAME" from packet->sname (unless overloaded)
 451          * terminating NULL
 452          */
 453         envc = 6;
 454         /* +1 element for each option, +2 for subnet option: */
 455         if (packet) {
 456                 /* note: do not search for "pad" (0) and "end" (255) options */
 457 //TODO: change logic to scan packet _once_
 458                 for (i = 1; i < 255; i++) {
 459                         temp = udhcp_get_option(packet, i);
 460                         if (temp) {
 461                                 if (i == DHCP_OPTION_OVERLOAD)
 462                                         overload |= *temp;
 463                                 else if (i == DHCP_SUBNET)
 464                                         envc++; /* for $mask */
 465                                 envc++;
 466                                 /*if (i != DHCP_MESSAGE_TYPE)*/
 467                                 FOUND_OPTS(i) |= BMASK(i);
 468                         }
 469                 }
 470         }
 471         curr = envp = xzalloc(sizeof(envp[0]) * envc);
 472
 473         *curr = xasprintf("interface=%s", client_config.interface);
 474         putenv(*curr++);
 475
 476         if (!packet)
 477                 return envp;
 478
 479         /* Export BOOTP fields. Fields we don't (yet?) export:
 480          * uint8_t op;      // always BOOTREPLY
 481          * uint8_t htype;   // hardware address type. 1 = 10mb ethernet
 482          * uint8_t hlen;    // hardware address length
 483          * uint8_t hops;    // used by relay agents only
 484          * uint32_t xid;
 485          * uint16_t secs;   // elapsed since client began acquisition/renewal
 486          * uint16_t flags;  // only one flag so far: bcast. Never set by server
 487          * uint32_t ciaddr; // client IP (usually == yiaddr. can it be different
 488          *                  // if during renew server wants to give us different IP?)
 489          * uint32_t gateway_nip; // relay agent IP address
 490          * uint8_t chaddr[16]; // link-layer client hardware address (MAC)
 491          * TODO: export gateway_nip as $giaddr?
 492          */
 493         /* Most important one: yiaddr as $ip */
 494         *curr = xmalloc(sizeof("ip=255.255.255.255"));
 495         sprint_nip(*curr, "ip=", (uint8_t *) &packet->yiaddr);
 496         putenv(*curr++);
 497         if (packet->siaddr_nip) {
 498                 /* IP address of next server to use in bootstrap */
 499                 *curr = xmalloc(sizeof("siaddr=255.255.255.255"));
 500                 sprint_nip(*curr, "siaddr=", (uint8_t *) &packet->siaddr_nip);
 501                 putenv(*curr++);
 502         }
 503         if (!(overload & FILE_FIELD) && packet->file[0]) {
 504                 /* watch out for invalid packets */
 505                 *curr = xasprintf("boot_file=%."DHCP_PKT_FILE_LEN_STR"s", packet->file);
 506                 putenv(*curr++);
 507         }
 508         if (!(overload & SNAME_FIELD) && packet->sname[0]) {
 509                 /* watch out for invalid packets */
 510                 *curr = xasprintf("sname=%."DHCP_PKT_SNAME_LEN_STR"s", packet->sname);
 511                 putenv(*curr++);
 512         }
 513
 514         /* Export known DHCP options */
 515         opt_name = dhcp_option_strings;
 516         i = 0;
 517         while (*opt_name) {
 518                 uint8_t code = dhcp_optflags[i].code;
 519                 BITMAP *found_ptr = &FOUND_OPTS(code);
 520                 BITMAP found_mask = BMASK(code);
 521                 if (!(*found_ptr & found_mask))
 522                         goto next;
 523                 *found_ptr &= ~found_mask; /* leave only unknown options */
 524                 temp = udhcp_get_option(packet, code);
 525                 *curr = xmalloc_optname_optval(temp, &dhcp_optflags[i], opt_name);
 526                 putenv(*curr++);
 527                 if (code == DHCP_SUBNET) {
 528                         /* Subnet option: make things like "$ip/$mask" possible */
 529                         uint32_t subnet;
 530                         move_from_unaligned32(subnet, temp);
 531                         *curr = xasprintf("mask=%u", mton(subnet));
 532                         putenv(*curr++);
 533                 }
 534  next:
 535                 opt_name += strlen(opt_name) + 1;
 536                 i++;
 537         }
 538         /* Export unknown options */
 539         for (i = 0; i < 256;) {
 540                 BITMAP bitmap = FOUND_OPTS(i);
 541                 if (!bitmap) {
 542                         i += BBITS;
 543                         continue;
 544                 }
 545                 if (bitmap & BMASK(i)) {
 546                         unsigned len, ofs;
 547
 548                         temp = udhcp_get_option(packet, i);
 549                         /* udhcp_get_option returns ptr to data portion,
 550                          * need to go back to get len
 551                          */
 552                         len = temp[-OPT_DATA + OPT_LEN];
 553                         *curr = xmalloc(sizeof("optNNN=") + 1 + len*2);
 554                         ofs = sprintf(*curr, "opt%u=", i);
 555                         *bin2hex(*curr + ofs, (void*) temp, len) = '\0';
 556                         putenv(*curr++);
 557                 }
 558                 i++;
 559         }
 560
 561         return envp;
 562 }
 563
 564 /* Call a script with a par file and env vars */
 565 static void udhcp_run_script(struct dhcp_packet *packet, const char *name)
 566 {
 567         char **envp, **curr;
 568         char *argv[3];
 569
 570         envp = fill_envp(packet);
 571
 572         /* call script */
 573         log1("executing %s %s", client_config.script, name);
 574         argv[0] = (char*) client_config.script;
 575         argv[1] = (char*) name;
 576         argv[2] = NULL;
 577         spawn_and_wait(argv);
 578
 579         for (curr = envp; *curr; curr++) {
 580                 log2(" %s", *curr);
 581                 bb_unsetenv_and_free(*curr);
 582         }
 583         free(envp);
 584 }
 585
 586
 587 /*** Sending/receiving packets ***/
 588
 589 static ALWAYS_INLINE uint32_t random_xid(void)
 590 {
 591         return rand();
 592 }
 593
 594 /* Initialize the packet with the proper defaults */
 595 static void init_packet(struct dhcp_packet *packet, char type)
 596 {
 597         uint16_t secs;
 598
 599         /* Fill in: op, htype, hlen, cookie fields; message type option: */
 600         udhcp_init_header(packet, type);
 601
 602         packet->xid = random_xid();
 603
 604         client_config.last_secs = monotonic_sec();
 605         if (client_config.first_secs == 0)
 606                 client_config.first_secs = client_config.last_secs;
 607         secs = client_config.last_secs - client_config.first_secs;
 608         packet->secs = htons(secs);
 609
 610         memcpy(packet->chaddr, client_config.client_mac, 6);
 611         if (client_config.clientid)
 612                 udhcp_add_binary_option(packet, client_config.clientid);
 613 }
 614
 615 static void add_client_options(struct dhcp_packet *packet)
 616 {
 617         int i, end, len;
 618
 619         udhcp_add_simple_option(packet, DHCP_MAX_SIZE, htons(IP_UDP_DHCP_SIZE));
 620
 621         /* Add a "param req" option with the list of options we'd like to have
 622          * from stubborn DHCP servers. Pull the data from the struct in common.c.
 623          * No bounds checking because it goes towards the head of the packet. */
 624         end = udhcp_end_option(packet->options);
 625         len = 0;
 626         for (i = 1; i < DHCP_END; i++) {
 627                 if (client_config.opt_mask[i >> 3] & (1 << (i & 7))) {
 628                         packet->options[end + OPT_DATA + len] = i;
 629                         len++;
 630                 }
 631         }
 632         if (len) {
 633                 packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
 634                 packet->options[end + OPT_LEN] = len;
 635                 packet->options[end + OPT_DATA + len] = DHCP_END;
 636         }
 637
 638         if (client_config.vendorclass)
 639                 udhcp_add_binary_option(packet, client_config.vendorclass);
 640         if (client_config.hostname)
 641                 udhcp_add_binary_option(packet, client_config.hostname);
 642         if (client_config.fqdn)
 643                 udhcp_add_binary_option(packet, client_config.fqdn);
 644
 645         /* Request broadcast replies if we have no IP addr */
 646         if ((option_mask32 & OPT_B) && packet->ciaddr == 0)
 647                 packet->flags |= htons(BROADCAST_FLAG);
 648
 649         /* Add -x options if any */
 650         {
 651                 struct option_set *curr = client_config.options;
 652                 while (curr) {
 653                         udhcp_add_binary_option(packet, curr->data);
 654                         curr = curr->next;
 655                 }
 656 //              if (client_config.sname)
 657 //                      strncpy((char*)packet->sname, client_config.sname, sizeof(packet->sname) - 1);
 658 //              if (client_config.boot_file)
 659 //                      strncpy((char*)packet->file, client_config.boot_file, sizeof(packet->file) - 1);
 660         }
 661
 662         // This will be needed if we remove -V VENDOR_STR in favor of
 663         // -x vendor:VENDOR_STR
 664         //if (!udhcp_find_option(packet.options, DHCP_VENDOR))
 665         //      /* not set, set the default vendor ID */
 666         //      ...add (DHCP_VENDOR, "udhcp "BB_VER) opt...
 667 }
 668
 669 /* RFC 2131
 670  * 4.4.4 Use of broadcast and unicast
 671  *
 672  * The DHCP client broadcasts DHCPDISCOVER, DHCPREQUEST and DHCPINFORM
 673  * messages, unless the client knows the address of a DHCP server.
 674  * The client unicasts DHCPRELEASE messages to the server. Because
 675  * the client is declining the use of the IP address supplied by the server,
 676  * the client broadcasts DHCPDECLINE messages.
 677  *
 678  * When the DHCP client knows the address of a DHCP server, in either
 679  * INIT or REBOOTING state, the client may use that address
 680  * in the DHCPDISCOVER or DHCPREQUEST rather than the IP broadcast address.
 681  * The client may also use unicast to send DHCPINFORM messages
 682  * to a known DHCP server. If the client receives no response to DHCP
 683  * messages sent to the IP address of a known DHCP server, the DHCP
 684  * client reverts to using the IP broadcast address.
 685  */
 686
 687 static int raw_bcast_from_client_config_ifindex(struct dhcp_packet *packet, uint32_t src_nip)
 688 {
 689         return udhcp_send_raw_packet(packet,
 690                 /*src*/ src_nip, CLIENT_PORT,
 691                 /*dst*/ INADDR_BROADCAST, SERVER_PORT, MAC_BCAST_ADDR,
 692                 client_config.ifindex);
 693 }
 694
 695 static int bcast_or_ucast(struct dhcp_packet *packet, uint32_t ciaddr, uint32_t server)
 696 {
 697         if (server)
 698                 return udhcp_send_kernel_packet(packet,
 699                         ciaddr, CLIENT_PORT,
 700                         server, SERVER_PORT);
 701         return raw_bcast_from_client_config_ifindex(packet, ciaddr);
 702 }
 703
 704 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
 705 /* NOINLINE: limit stack usage in caller */
 706 static NOINLINE int send_discover(uint32_t xid, uint32_t requested)
 707 {
 708         struct dhcp_packet packet;
 709
 710         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 711          * random xid field (we override it below),
 712          * client-id option (unless -C), message type option:
 713          */
 714         init_packet(&packet, DHCPDISCOVER);
 715
 716         packet.xid = xid;
 717         if (requested)
 718                 udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 719
 720         /* Add options: maxsize,
 721          * optionally: hostname, fqdn, vendorclass,
 722          * "param req" option according to -O, options specified with -x
 723          */
 724         add_client_options(&packet);
 725
 726         bb_error_msg("sending %s", "discover");
 727         return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
 728 }
 729
 730 /* Broadcast a DHCP request message */
 731 /* RFC 2131 3.1 paragraph 3:
 732  * "The client _broadcasts_ a DHCPREQUEST message..."
 733  */
 734 /* NOINLINE: limit stack usage in caller */
 735 static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requested)
 736 {
 737         struct dhcp_packet packet;
 738         struct in_addr addr;
 739
 740 /*
 741  * RFC 2131 4.3.2 DHCPREQUEST message
 742  * ...
 743  * If the DHCPREQUEST message contains a 'server identifier'
 744  * option, the message is in response to a DHCPOFFER message.
 745  * Otherwise, the message is a request to verify or extend an
 746  * existing lease. If the client uses a 'client identifier'
 747  * in a DHCPREQUEST message, it MUST use that same 'client identifier'
 748  * in all subsequent messages. If the client included a list
 749  * of requested parameters in a DHCPDISCOVER message, it MUST
 750  * include that list in all subsequent messages.
 751  */
 752         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 753          * random xid field (we override it below),
 754          * client-id option (unless -C), message type option:
 755          */
 756         init_packet(&packet, DHCPREQUEST);
 757
 758         packet.xid = xid;
 759         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 760
 761         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 762
 763         /* Add options: maxsize,
 764          * optionally: hostname, fqdn, vendorclass,
 765          * "param req" option according to -O, and options specified with -x
 766          */
 767         add_client_options(&packet);
 768
 769         addr.s_addr = requested;
 770         bb_error_msg("sending select for %s", inet_ntoa(addr));
 771         return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
 772 }
 773
 774 /* Unicast or broadcast a DHCP renew message */
 775 /* NOINLINE: limit stack usage in caller */
 776 static NOINLINE int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
 777 {
 778         struct dhcp_packet packet;
 779
 780 /*
 781  * RFC 2131 4.3.2 DHCPREQUEST message
 782  * ...
 783  * DHCPREQUEST generated during RENEWING state:
 784  *
 785  * 'server identifier' MUST NOT be filled in, 'requested IP address'
 786  * option MUST NOT be filled in, 'ciaddr' MUST be filled in with
 787  * client's IP address. In this situation, the client is completely
 788  * configured, and is trying to extend its lease. This message will
 789  * be unicast, so no relay agents will be involved in its
 790  * transmission.  Because 'giaddr' is therefore not filled in, the
 791  * DHCP server will trust the value in 'ciaddr', and use it when
 792  * replying to the client.
 793  */
 794         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 795          * random xid field (we override it below),
 796          * client-id option (unless -C), message type option:
 797          */
 798         init_packet(&packet, DHCPREQUEST);
 799
 800         packet.xid = xid;
 801         packet.ciaddr = ciaddr;
 802
 803         /* Add options: maxsize,
 804          * optionally: hostname, fqdn, vendorclass,
 805          * "param req" option according to -O, and options specified with -x
 806          */
 807         add_client_options(&packet);
 808
 809         bb_error_msg("sending %s", "renew");
 810         return bcast_or_ucast(&packet, ciaddr, server);
 811 }
 812
 813 #if ENABLE_FEATURE_UDHCPC_ARPING
 814 /* Broadcast a DHCP decline message */
 815 /* NOINLINE: limit stack usage in caller */
 816 static NOINLINE int send_decline(/*uint32_t xid,*/ uint32_t server, uint32_t requested)
 817 {
 818         struct dhcp_packet packet;
 819
 820         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 821          * client-id option (unless -C), message type option:
 822          */
 823         init_packet(&packet, DHCPDECLINE);
 824
 825 #if 0
 826         /* RFC 2131 says DHCPDECLINE's xid is randomly selected by client,
 827          * but in case the server is buggy and wants DHCPDECLINE's xid
 828          * to match the xid which started entire handshake,
 829          * we use the same xid we used in initial DHCPDISCOVER:
 830          */
 831         packet.xid = xid;
 832 #endif
 833         /* DHCPDECLINE uses "requested ip", not ciaddr, to store offered IP */
 834         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 835
 836         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 837
 838         bb_error_msg("sending %s", "decline");
 839         return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
 840 }
 841 #endif
 842
 843 /* Unicast a DHCP release message */
 844 static int send_release(uint32_t server, uint32_t ciaddr)
 845 {
 846         struct dhcp_packet packet;
 847
 848         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 849          * client-id option (unless -C), message type option:
 850          */
 851         init_packet(&packet, DHCPRELEASE);
 852
 853         /* DHCPRELEASE uses ciaddr, not "requested ip", to store IP being released */
 854         packet.ciaddr = ciaddr;
 855
 856         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 857
 858         bb_error_msg("sending %s", "release");
 859         /* Note: normally we unicast here since "server" is not zero.
 860          * However, there _are_ people who run "address-less" DHCP servers,
 861          * and reportedly ISC dhcp client and Windows allow that.
 862          */
 863         return bcast_or_ucast(&packet, ciaddr, server);
 864 }
 865
 866 /* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */
 867 /* NOINLINE: limit stack usage in caller */
 868 static NOINLINE int udhcp_recv_raw_packet(struct dhcp_packet *dhcp_pkt, int fd)
 869 {
 870         int bytes;
 871         struct ip_udp_dhcp_packet packet;
 872         uint16_t check;
 873         unsigned char cmsgbuf[CMSG_LEN(sizeof(struct tpacket_auxdata))];
 874         struct iovec iov;
 875         struct msghdr msg;
 876         struct cmsghdr *cmsg;
 877
 878         /* used to use just safe_read(fd, &packet, sizeof(packet))
 879          * but we need to check for TP_STATUS_CSUMNOTREADY :(
 880          */
 881         iov.iov_base = &packet;
 882         iov.iov_len = sizeof(packet);
 883         memset(&msg, 0, sizeof(msg));
 884         msg.msg_iov = &iov;
 885         msg.msg_iovlen = 1;
 886         msg.msg_control = cmsgbuf;
 887         msg.msg_controllen = sizeof(cmsgbuf);
 888         for (;;) {
 889                 bytes = recvmsg(fd, &msg, 0);
 890                 if (bytes < 0) {
 891                         if (errno == EINTR)
 892                                 continue;
 893                         log1("packet read error, ignoring");
 894                         /* NB: possible down interface, etc. Caller should pause. */
 895                         return bytes; /* returns -1 */
 896                 }
 897                 break;
 898         }
 899
 900         if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) {
 901                 log1("packet is too short, ignoring");
 902                 return -2;
 903         }
 904
 905         if (bytes < ntohs(packet.ip.tot_len)) {
 906                 /* packet is bigger than sizeof(packet), we did partial read */
 907                 log1("oversized packet, ignoring");
 908                 return -2;
 909         }
 910
 911         /* ignore any extra garbage bytes */
 912         bytes = ntohs(packet.ip.tot_len);
 913
 914         /* make sure its the right packet for us, and that it passes sanity checks */
 915         if (packet.ip.protocol != IPPROTO_UDP
 916          || packet.ip.version != IPVERSION
 917          || packet.ip.ihl != (sizeof(packet.ip) >> 2)
 918          || packet.udp.dest != htons(CLIENT_PORT)
 919         /* || bytes > (int) sizeof(packet) - can't happen */
 920          || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
 921         ) {
 922                 log1("unrelated/bogus packet, ignoring");
 923                 return -2;
 924         }
 925
 926         /* verify IP checksum */
 927         check = packet.ip.check;
 928         packet.ip.check = 0;
 929         if (check != inet_cksum((uint16_t *)&packet.ip, sizeof(packet.ip))) {
 930                 log1("bad IP header checksum, ignoring");
 931                 return -2;
 932         }
 933
 934         for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
 935                 if (cmsg->cmsg_level == SOL_PACKET
 936                  && cmsg->cmsg_type == PACKET_AUXDATA
 937                 ) {
 938                         /* some VMs don't checksum UDP and TCP data
 939                          * they send to the same physical machine,
 940                          * here we detect this case:
 941                          */
 942                         struct tpacket_auxdata *aux = (void *)CMSG_DATA(cmsg);
 943                         if (aux->tp_status & TP_STATUS_CSUMNOTREADY)
 944                                 goto skip_udp_sum_check;
 945                 }
 946         }
 947
 948         /* verify UDP checksum. IP header has to be modified for this */
 949         memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
 950         /* ip.xx fields which are not memset: protocol, check, saddr, daddr */
 951         packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
 952         check = packet.udp.check;
 953         packet.udp.check = 0;
 954         if (check && check != inet_cksum((uint16_t *)&packet, bytes)) {
 955                 log1("packet with bad UDP checksum received, ignoring");
 956                 return -2;
 957         }
 958  skip_udp_sum_check:
 959
 960         if (packet.data.cookie != htonl(DHCP_MAGIC)) {
 961                 bb_error_msg("packet with bad magic, ignoring");
 962                 return -2;
 963         }
 964
 965         log1("received %s", "a packet");
 966         udhcp_dump_packet(&packet.data);
 967
 968         bytes -= sizeof(packet.ip) + sizeof(packet.udp);
 969         memcpy(dhcp_pkt, &packet.data, bytes);
 970         return bytes;
 971 }
 972
 973
 974 /*** Main ***/
 975
 976 static int sockfd = -1;
 977
 978 #define LISTEN_NONE   0
 979 #define LISTEN_KERNEL 1
 980 #define LISTEN_RAW    2
 981 static smallint listen_mode;
 982
 983 /* initial state: (re)start DHCP negotiation */
 984 #define INIT_SELECTING  0
 985 /* discover was sent, DHCPOFFER reply received */
 986 #define REQUESTING      1
 987 /* select/renew was sent, DHCPACK reply received */
 988 #define BOUND           2
 989 /* half of lease passed, want to renew it by sending unicast renew requests */
 990 #define RENEWING        3
 991 /* renew requests were not answered, lease is almost over, send broadcast renew */
 992 #define REBINDING       4
 993 /* manually requested renew (SIGUSR1) */
 994 #define RENEW_REQUESTED 5
 995 /* release, possibly manually requested (SIGUSR2) */
 996 #define RELEASED        6
 997 static smallint state;
 998
 999 static int udhcp_raw_socket(int ifindex)
1000 {
1001         int fd;
1002         struct sockaddr_ll sock;
1003
1004         log1("opening raw socket on ifindex %d", ifindex); //log2?
1005
1006         fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
1007         /* ^^^^^
1008          * SOCK_DGRAM: remove link-layer headers on input (SOCK_RAW keeps them)
1009          * ETH_P_IP: want to receive only packets with IPv4 eth type
1010          */
1011         log1("got raw socket fd"); //log2?
1012
1013         sock.sll_family = AF_PACKET;
1014         sock.sll_protocol = htons(ETH_P_IP);
1015         sock.sll_ifindex = ifindex;
1016         xbind(fd, (struct sockaddr *) &sock, sizeof(sock));
1017
1018 #if 0 /* Several users reported breakage when BPF filter is used */
1019         if (CLIENT_PORT == 68) {
1020                 /* Use only if standard port is in use */
1021                 /*
1022                  *      I've selected not to see LL header, so BPF doesn't see it, too.
1023                  *      The filter may also pass non-IP and non-ARP packets, but we do
1024                  *      a more complete check when receiving the message in userspace.
1025                  *
1026                  * and filter shamelessly stolen from:
1027                  *
1028                  *      http://www.flamewarmaster.de/software/dhcpclient/
1029                  *
1030                  * There are a few other interesting ideas on that page (look under
1031                  * "Motivation").  Use of netlink events is most interesting.  Think
1032                  * of various network servers listening for events and reconfiguring.
1033                  * That would obsolete sending HUP signals and/or make use of restarts.
1034                  *
1035                  * Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
1036                  * License: GPL v2.
1037                  */
1038                 static const struct sock_filter filter_instr[] = {
1039                         /* load 9th byte (protocol) */
1040                         BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
1041                         /* jump to L1 if it is IPPROTO_UDP, else to L4 */
1042                         BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 0, 6),
1043                         /* L1: load halfword from offset 6 (flags and frag offset) */
1044                         BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 6),
1045                         /* jump to L4 if any bits in frag offset field are set, else to L2 */
1046                         BPF_JUMP(BPF_JMP|BPF_JSET|BPF_K, 0x1fff, 4, 0),
1047                         /* L2: skip IP header (load index reg with header len) */
1048                         BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0),
1049                         /* load udp destination port from halfword[header_len + 2] */
1050                         BPF_STMT(BPF_LD|BPF_H|BPF_IND, 2),
1051                         /* jump to L3 if udp dport is CLIENT_PORT, else to L4 */
1052                         BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 68, 0, 1),
1053                         /* L3: accept packet ("accept 0x7fffffff bytes") */
1054                         /* Accepting 0xffffffff works too but kernel 2.6.19 is buggy */
1055                         BPF_STMT(BPF_RET|BPF_K, 0x7fffffff),
1056                         /* L4: discard packet ("accept zero bytes") */
1057                         BPF_STMT(BPF_RET|BPF_K, 0),
1058                 };
1059                 static const struct sock_fprog filter_prog = {
1060                         .len = sizeof(filter_instr) / sizeof(filter_instr[0]),
1061                         /* casting const away: */
1062                         .filter = (struct sock_filter *) filter_instr,
1063                 };
1064                 /* Ignoring error (kernel may lack support for this) */
1065                 if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
1066                                 sizeof(filter_prog)) >= 0)
1067                         log1("attached filter to raw socket fd"); // log?
1068         }
1069 #endif
1070
1071         if (setsockopt_1(fd, SOL_PACKET, PACKET_AUXDATA) != 0) {
1072                 if (errno != ENOPROTOOPT)
1073                         log1("can't set PACKET_AUXDATA on raw socket");
1074         }
1075
1076         log1("created raw socket");
1077
1078         return fd;
1079 }
1080
1081 static void change_listen_mode(int new_mode)
1082 {
1083         log1("entering listen mode: %s",
1084                 new_mode != LISTEN_NONE
1085                         ? (new_mode == LISTEN_KERNEL ? "kernel" : "raw")
1086                         : "none"
1087         );
1088
1089         listen_mode = new_mode;
1090         if (sockfd >= 0) {
1091                 close(sockfd);
1092                 sockfd = -1;
1093         }
1094         if (new_mode == LISTEN_KERNEL)
1095                 sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
1096         else if (new_mode != LISTEN_NONE)
1097                 sockfd = udhcp_raw_socket(client_config.ifindex);
1098         /* else LISTEN_NONE: sockfd stays closed */
1099 }
1100
1101 /* Called only on SIGUSR1 */
1102 static void perform_renew(void)
1103 {
1104         bb_error_msg("performing DHCP renew");
1105         switch (state) {
1106         case BOUND:
1107                 change_listen_mode(LISTEN_KERNEL);
1108         case RENEWING:
1109         case REBINDING:
1110                 state = RENEW_REQUESTED;
1111                 break;
1112         case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
1113                 udhcp_run_script(NULL, "deconfig");
1114         case REQUESTING:
1115         case RELEASED:
1116                 change_listen_mode(LISTEN_RAW);
1117                 state = INIT_SELECTING;
1118                 break;
1119         case INIT_SELECTING:
1120                 break;
1121         }
1122 }
1123
1124 static void perform_release(uint32_t server_addr, uint32_t requested_ip)
1125 {
1126         char buffer[sizeof("255.255.255.255")];
1127         struct in_addr temp_addr;
1128
1129         /* send release packet */
1130         if (state == BOUND
1131          || state == RENEWING
1132          || state == REBINDING
1133          || state == RENEW_REQUESTED
1134         ) {
1135                 temp_addr.s_addr = server_addr;
1136                 strcpy(buffer, inet_ntoa(temp_addr));
1137                 temp_addr.s_addr = requested_ip;
1138                 bb_error_msg("unicasting a release of %s to %s",
1139                                 inet_ntoa(temp_addr), buffer);
1140                 send_release(server_addr, requested_ip); /* unicast */
1141         }
1142         bb_error_msg("entering released state");
1143 /*
1144  * We can be here on: SIGUSR2,
1145  * or on exit (SIGTERM) and -R "release on quit" is specified.
1146  * Users requested to be notified in all cases, even if not in one
1147  * of the states above.
1148  */
1149         udhcp_run_script(NULL, "deconfig");
1150
1151         change_listen_mode(LISTEN_NONE);
1152         state = RELEASED;
1153 }
1154
1155 static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
1156 {
1157         uint8_t *storage;
1158         int len = strnlen(str, 255);
1159         storage = xzalloc(len + extra + OPT_DATA);
1160         storage[OPT_CODE] = code;
1161         storage[OPT_LEN] = len + extra;
1162         memcpy(storage + extra + OPT_DATA, str, len);
1163         return storage;
1164 }
1165
1166 #if BB_MMU
1167 static void client_background(void)
1168 {
1169         bb_daemonize(0);
1170         logmode &= ~LOGMODE_STDIO;
1171         /* rewrite pidfile, as our pid is different now */
1172         write_pidfile(client_config.pidfile);
1173 }
1174 #endif
1175
1176 //usage:#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
1177 //usage:# define IF_UDHCP_VERBOSE(...) __VA_ARGS__
1178 //usage:#else
1179 //usage:# define IF_UDHCP_VERBOSE(...)
1180 //usage:#endif
1181 //usage:#define udhcpc_trivial_usage
1182 //usage:       "[-fbq"IF_UDHCP_VERBOSE("v")"RB]"IF_FEATURE_UDHCPC_ARPING(" [-a[MSEC]]")" [-t N] [-T SEC] [-A SEC/-n]\n"
1183 //usage:       "        [-i IFACE]"IF_FEATURE_UDHCP_PORT(" [-P PORT]")" [-s PROG] [-p PIDFILE]\n"
1184 //usage:       "        [-oC] [-r IP] [-V VENDOR] [-F NAME] [-x OPT:VAL]... [-O OPT]..."
1185 //usage:#define udhcpc_full_usage "\n"
1186 //usage:        IF_LONG_OPTS(
1187 //usage:     "\n        -i,--interface IFACE    Interface to use (default eth0)"
1188 //usage:        IF_FEATURE_UDHCP_PORT(
1189 //usage:     "\n        -P,--client-port PORT   Use PORT (default 68)"
1190 //usage:        )
1191 //usage:     "\n        -s,--script PROG        Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
1192 //usage:     "\n        -p,--pidfile FILE       Create pidfile"
1193 //usage:     "\n        -B,--broadcast          Request broadcast replies"
1194 //usage:     "\n        -t,--retries N          Send up to N discover packets (default 3)"
1195 //usage:     "\n        -T,--timeout SEC        Pause between packets (default 3)"
1196 //usage:     "\n        -A,--tryagain SEC       Wait if lease is not obtained (default 20)"
1197 //usage:     "\n        -n,--now                Exit if lease is not obtained"
1198 //usage:     "\n        -q,--quit               Exit after obtaining lease"
1199 //usage:     "\n        -R,--release            Release IP on exit"
1200 //usage:     "\n        -f,--foreground         Run in foreground"
1201 //usage:        USE_FOR_MMU(
1202 //usage:     "\n        -b,--background         Background if lease is not obtained"
1203 //usage:        )
1204 //usage:     "\n        -S,--syslog             Log to syslog too"
1205 //usage:        IF_FEATURE_UDHCPC_ARPING(
1206 //usage:     "\n        -a[MSEC],--arping[=MSEC] Validate offered address with ARP ping"
1207 //usage:        )
1208 //usage:     "\n        -r,--request IP         Request this IP address"
1209 //usage:     "\n        -o,--no-default-options Don't request any options (unless -O is given)"
1210 //usage:     "\n        -O,--request-option OPT Request option OPT from server (cumulative)"
1211 //usage:     "\n        -x OPT:VAL              Include option OPT in sent packets (cumulative)"
1212 //usage:     "\n                                Examples of string, numeric, and hex byte opts:"
1213 //usage:     "\n                                -x hostname:bbox - option 12"
1214 //usage:     "\n                                -x lease:3600 - option 51 (lease time)"
1215 //usage:     "\n                                -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
1216 //usage:     "\n        -F,--fqdn NAME          Ask server to update DNS mapping for NAME"
1217 //usage:     "\n        -V,--vendorclass VENDOR Vendor identifier (default 'udhcp VERSION')"
1218 //usage:     "\n        -C,--clientid-none      Don't send MAC as client identifier"
1219 //usage:        IF_UDHCP_VERBOSE(
1220 //usage:     "\n        -v                      Verbose"
1221 //usage:        )
1222 //usage:        )
1223 //usage:        IF_NOT_LONG_OPTS(
1224 //usage:     "\n        -i IFACE        Interface to use (default eth0)"
1225 //usage:        IF_FEATURE_UDHCP_PORT(
1226 //usage:     "\n        -P PORT         Use PORT (default 68)"
1227 //usage:        )
1228 //usage:     "\n        -s PROG         Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
1229 //usage:     "\n        -p FILE         Create pidfile"
1230 //usage:     "\n        -B              Request broadcast replies"
1231 //usage:     "\n        -t N            Send up to N discover packets (default 3)"
1232 //usage:     "\n        -T SEC          Pause between packets (default 3)"
1233 //usage:     "\n        -A SEC          Wait if lease is not obtained (default 20)"
1234 //usage:     "\n        -n              Exit if lease is not obtained"
1235 //usage:     "\n        -q              Exit after obtaining lease"
1236 //usage:     "\n        -R              Release IP on exit"
1237 //usage:     "\n        -f              Run in foreground"
1238 //usage:        USE_FOR_MMU(
1239 //usage:     "\n        -b              Background if lease is not obtained"
1240 //usage:        )
1241 //usage:     "\n        -S              Log to syslog too"
1242 //usage:        IF_FEATURE_UDHCPC_ARPING(
1243 //usage:     "\n        -a[MSEC]        Validate offered address with ARP ping"
1244 //usage:        )
1245 //usage:     "\n        -r IP           Request this IP address"
1246 //usage:     "\n        -o              Don't request any options (unless -O is given)"
1247 //usage:     "\n        -O OPT          Request option OPT from server (cumulative)"
1248 //usage:     "\n        -x OPT:VAL      Include option OPT in sent packets (cumulative)"
1249 //usage:     "\n                        Examples of string, numeric, and hex byte opts:"
1250 //usage:     "\n                        -x hostname:bbox - option 12"
1251 //usage:     "\n                        -x lease:3600 - option 51 (lease time)"
1252 //usage:     "\n                        -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
1253 //usage:     "\n        -F NAME         Ask server to update DNS mapping for NAME"
1254 //usage:     "\n        -V VENDOR       Vendor identifier (default 'udhcp VERSION')"
1255 //usage:     "\n        -C              Don't send MAC as client identifier"
1256 //usage:        IF_UDHCP_VERBOSE(
1257 //usage:     "\n        -v              Verbose"
1258 //usage:        )
1259 //usage:        )
1260 //usage:     "\nSignals:"
1261 //usage:     "\n        USR1    Renew lease"
1262 //usage:     "\n        USR2    Release lease"
1263
1264
1265 int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
1266 int udhcpc_main(int argc UNUSED_PARAM, char **argv)
1267 {
1268         uint8_t *message;
1269         const char *str_V, *str_h, *str_F, *str_r;
1270         IF_FEATURE_UDHCPC_ARPING(const char *str_a = "2000";)
1271         IF_FEATURE_UDHCP_PORT(char *str_P;)
1272         void *clientid_mac_ptr;
1273         llist_t *list_O = NULL;
1274         llist_t *list_x = NULL;
1275         int tryagain_timeout = 20;
1276         int discover_timeout = 3;
1277         int discover_retries = 3;
1278         uint32_t server_addr = server_addr; /* for compiler */
1279         uint32_t requested_ip = 0;
1280         uint32_t xid = xid; /* for compiler */
1281         int packet_num;
1282         int timeout; /* must be signed */
1283         unsigned already_waited_sec;
1284         unsigned opt;
1285         IF_FEATURE_UDHCPC_ARPING(unsigned arpping_ms;)
1286         int retval;
1287
1288         setup_common_bufsiz();
1289
1290         /* Default options */
1291         IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;)
1292         IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
1293         client_config.interface = "eth0";
1294         client_config.script = CONFIG_UDHCPC_DEFAULT_SCRIPT;
1295         str_V = "udhcp "BB_VER;
1296
1297         /* Parse command line */
1298         /* O,x: list; -T,-t,-A take numeric param */
1299         IF_UDHCP_VERBOSE(opt_complementary = "vv";)
1300         IF_LONG_OPTS(applet_long_options = udhcpc_longopts;)
1301         opt = getopt32(argv, "CV:H:h:F:i:np:qRr:s:T:+t:+SA:+O:*ox:*fB"
1302                 USE_FOR_MMU("b")
1303                 IF_FEATURE_UDHCPC_ARPING("a::")
1304                 IF_FEATURE_UDHCP_PORT("P:")
1305                 "v"
1306                 , &str_V, &str_h, &str_h, &str_F
1307                 , &client_config.interface, &client_config.pidfile, &str_r /* i,p */
1308                 , &client_config.script /* s */
1309                 , &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */
1310                 , &list_O
1311                 , &list_x
1312                 IF_FEATURE_UDHCPC_ARPING(, &str_a)
1313                 IF_FEATURE_UDHCP_PORT(, &str_P)
1314                 IF_UDHCP_VERBOSE(, &dhcp_verbose)
1315         );
1316         if (opt & (OPT_h|OPT_H)) {
1317                 //msg added 2011-11
1318                 bb_error_msg("option -h NAME is deprecated, use -x hostname:NAME");
1319                 client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
1320         }
1321         if (opt & OPT_F) {
1322                 /* FQDN option format: [0x51][len][flags][0][0]<fqdn> */
1323                 client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
1324                 /* Flag bits: 0000NEOS
1325                  * S: 1 = Client requests server to update A RR in DNS as well as PTR
1326                  * O: 1 = Server indicates to client that DNS has been updated regardless
1327                  * E: 1 = Name is in DNS format, i.e. <4>host<6>domain<3>com<0>,
1328                  *    not "host.domain.com". Format 0 is obsolete.
1329                  * N: 1 = Client requests server to not update DNS (S must be 0 then)
1330                  * Two [0] bytes which follow are deprecated and must be 0.
1331                  */
1332                 client_config.fqdn[OPT_DATA + 0] = 0x1;
1333                 /*client_config.fqdn[OPT_DATA + 1] = 0; - xzalloc did it */
1334                 /*client_config.fqdn[OPT_DATA + 2] = 0; */
1335         }
1336         if (opt & OPT_r)
1337                 requested_ip = inet_addr(str_r);
1338 #if ENABLE_FEATURE_UDHCP_PORT
1339         if (opt & OPT_P) {
1340                 CLIENT_PORT = xatou16(str_P);
1341                 SERVER_PORT = CLIENT_PORT - 1;
1342         }
1343 #endif
1344         IF_FEATURE_UDHCPC_ARPING(arpping_ms = xatou(str_a);)
1345         while (list_O) {
1346                 char *optstr = llist_pop(&list_O);
1347                 unsigned n = bb_strtou(optstr, NULL, 0);
1348                 if (errno || n > 254) {
1349                         n = udhcp_option_idx(optstr, dhcp_option_strings);
1350                         n = dhcp_optflags[n].code;
1351                 }
1352                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
1353         }
1354         if (!(opt & OPT_o)) {
1355                 unsigned i, n;
1356                 for (i = 0; (n = dhcp_optflags[i].code) != 0; i++) {
1357                         if (dhcp_optflags[i].flags & OPTION_REQ) {
1358                                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
1359                         }
1360                 }
1361         }
1362         while (list_x) {
1363                 char *optstr = llist_pop(&list_x);
1364                 char *colon = strchr(optstr, ':');
1365                 if (colon)
1366                         *colon = ' ';
1367                 /* now it looks similar to udhcpd's config file line:
1368                  * "optname optval", using the common routine: */
1369                 udhcp_str2optset(optstr, &client_config.options, dhcp_optflags, dhcp_option_strings);
1370                 if (colon)
1371                         *colon = ':'; /* restore it for NOMMU reexec */
1372         }
1373
1374         if (udhcp_read_interface(client_config.interface,
1375                         &client_config.ifindex,
1376                         NULL,
1377                         client_config.client_mac)
1378         ) {
1379                 return 1;
1380         }
1381
1382         clientid_mac_ptr = NULL;
1383         if (!(opt & OPT_C) && !udhcp_find_option(client_config.options, DHCP_CLIENT_ID)) {
1384                 /* not suppressed and not set, set the default client ID */
1385                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
1386                 client_config.clientid[OPT_DATA] = 1; /* type: ethernet */
1387                 clientid_mac_ptr = client_config.clientid + OPT_DATA+1;
1388                 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1389         }
1390         if (str_V[0] != '\0') {
1391                 // can drop -V, str_V, client_config.vendorclass,
1392                 // but need to add "vendor" to the list of recognized
1393                 // string opts for this to work;
1394                 // and need to tweak add_client_options() too...
1395                 // ...so the question is, should we?
1396                 //bb_error_msg("option -V VENDOR is deprecated, use -x vendor:VENDOR");
1397                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
1398         }
1399
1400 #if !BB_MMU
1401         /* on NOMMU reexec (i.e., background) early */
1402         if (!(opt & OPT_f)) {
1403                 bb_daemonize_or_rexec(0 /* flags */, argv);
1404                 logmode = LOGMODE_NONE;
1405         }
1406 #endif
1407         if (opt & OPT_S) {
1408                 openlog(applet_name, LOG_PID, LOG_DAEMON);
1409                 logmode |= LOGMODE_SYSLOG;
1410         }
1411
1412         /* Make sure fd 0,1,2 are open */
1413         bb_sanitize_stdio();
1414         /* Equivalent of doing a fflush after every \n */
1415         setlinebuf(stdout);
1416         /* Create pidfile */
1417         write_pidfile(client_config.pidfile);
1418         /* Goes to stdout (unless NOMMU) and possibly syslog */
1419         bb_error_msg("started, v"BB_VER);
1420         /* Set up the signal pipe */
1421         udhcp_sp_setup();
1422         /* We want random_xid to be random... */
1423         srand(monotonic_us());
1424
1425         state = INIT_SELECTING;
1426         udhcp_run_script(NULL, "deconfig");
1427         change_listen_mode(LISTEN_RAW);
1428         packet_num = 0;
1429         timeout = 0;
1430         already_waited_sec = 0;
1431
1432         /* Main event loop. select() waits on signal pipe and possibly
1433          * on sockfd.
1434          * "continue" statements in code below jump to the top of the loop.
1435          */
1436         for (;;) {
1437                 int tv;
1438                 struct pollfd pfds[2];
1439                 struct dhcp_packet packet;
1440                 /* silence "uninitialized!" warning */
1441                 unsigned timestamp_before_wait = timestamp_before_wait;
1442
1443                 //bb_error_msg("sockfd:%d, listen_mode:%d", sockfd, listen_mode);
1444
1445                 /* Was opening raw or udp socket here
1446                  * if (listen_mode != LISTEN_NONE && sockfd < 0),
1447                  * but on fast network renew responses return faster
1448                  * than we open sockets. Thus this code is moved
1449                  * to change_listen_mode(). Thus we open listen socket
1450                  * BEFORE we send renew request (see "case BOUND:"). */
1451
1452                 udhcp_sp_fd_set(pfds, sockfd);
1453
1454                 tv = timeout - already_waited_sec;
1455                 retval = 0;
1456                 /* If we already timed out, fall through with retval = 0, else... */
1457                 if (tv > 0) {
1458                         log1("waiting on select %u seconds", tv);
1459                         timestamp_before_wait = (unsigned)monotonic_sec();
1460                         retval = poll(pfds, 2, tv < INT_MAX/1000 ? tv * 1000 : INT_MAX);
1461                         if (retval < 0) {
1462                                 /* EINTR? A signal was caught, don't panic */
1463                                 if (errno == EINTR) {
1464                                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1465                                         continue;
1466                                 }
1467                                 /* Else: an error occurred, panic! */
1468                                 bb_perror_msg_and_die("select");
1469                         }
1470                 }
1471
1472                 /* If timeout dropped to zero, time to become active:
1473                  * resend discover/renew/whatever
1474                  */
1475                 if (retval == 0) {
1476                         /* When running on a bridge, the ifindex may have changed
1477                          * (e.g. if member interfaces were added/removed
1478                          * or if the status of the bridge changed).
1479                          * Refresh ifindex and client_mac:
1480                          */
1481                         if (udhcp_read_interface(client_config.interface,
1482                                         &client_config.ifindex,
1483                                         NULL,
1484                                         client_config.client_mac)
1485                         ) {
1486                                 goto ret0; /* iface is gone? */
1487                         }
1488                         if (clientid_mac_ptr)
1489                                 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1490
1491                         /* We will restart the wait in any case */
1492                         already_waited_sec = 0;
1493
1494                         switch (state) {
1495                         case INIT_SELECTING:
1496                                 if (!discover_retries || packet_num < discover_retries) {
1497                                         if (packet_num == 0)
1498                                                 xid = random_xid();
1499                                         /* broadcast */
1500                                         send_discover(xid, requested_ip);
1501                                         timeout = discover_timeout;
1502                                         packet_num++;
1503                                         continue;
1504                                 }
1505  leasefail:
1506                                 udhcp_run_script(NULL, "leasefail");
1507 #if BB_MMU /* -b is not supported on NOMMU */
1508                                 if (opt & OPT_b) { /* background if no lease */
1509                                         bb_error_msg("no lease, forking to background");
1510                                         client_background();
1511                                         /* do not background again! */
1512                                         opt = ((opt & ~OPT_b) | OPT_f);
1513                                 } else
1514 #endif
1515                                 if (opt & OPT_n) { /* abort if no lease */
1516                                         bb_error_msg("no lease, failing");
1517                                         retval = 1;
1518                                         goto ret;
1519                                 }
1520                                 /* wait before trying again */
1521                                 timeout = tryagain_timeout;
1522                                 packet_num = 0;
1523                                 continue;
1524                         case REQUESTING:
1525                                 if (packet_num < 3) {
1526                                         /* send broadcast select packet */
1527                                         send_select(xid, server_addr, requested_ip);
1528                                         timeout = discover_timeout;
1529                                         packet_num++;
1530                                         continue;
1531                                 }
1532                                 /* Timed out, go back to init state.
1533                                  * "discover...select...discover..." loops
1534                                  * were seen in the wild. Treat them similarly
1535                                  * to "no response to discover" case */
1536                                 change_listen_mode(LISTEN_RAW);
1537                                 state = INIT_SELECTING;
1538                                 goto leasefail;
1539                         case BOUND:
1540                                 /* 1/2 lease passed, enter renewing state */
1541                                 state = RENEWING;
1542                                 client_config.first_secs = 0; /* make secs field count from 0 */
1543                                 change_listen_mode(LISTEN_KERNEL);
1544                                 log1("entering renew state");
1545                                 /* fall right through */
1546                         case RENEW_REQUESTED: /* manual (SIGUSR1) renew */
1547                         case_RENEW_REQUESTED:
1548                         case RENEWING:
1549                                 if (timeout > 60) {
1550                                         /* send an unicast renew request */
1551                         /* Sometimes observed to fail (EADDRNOTAVAIL) to bind
1552                          * a new UDP socket for sending inside send_renew.
1553                          * I hazard to guess existing listening socket
1554                          * is somehow conflicting with it, but why is it
1555                          * not deterministic then?! Strange.
1556                          * Anyway, it does recover by eventually failing through
1557                          * into INIT_SELECTING state.
1558                          */
1559                                         send_renew(xid, server_addr, requested_ip);
1560                                         timeout >>= 1;
1561                                         continue;
1562                                 }
1563                                 /* Timed out, enter rebinding state */
1564                                 log1("entering rebinding state");
1565                                 state = REBINDING;
1566                                 /* fall right through */
1567                         case REBINDING:
1568                                 /* Switch to bcast receive */
1569                                 change_listen_mode(LISTEN_RAW);
1570                                 /* Lease is *really* about to run out,
1571                                  * try to find DHCP server using broadcast */
1572                                 if (timeout > 0) {
1573                                         /* send a broadcast renew request */
1574                                         send_renew(xid, 0 /*INADDR_ANY*/, requested_ip);
1575                                         timeout >>= 1;
1576                                         continue;
1577                                 }
1578                                 /* Timed out, enter init state */
1579                                 bb_error_msg("lease lost, entering init state");
1580                                 udhcp_run_script(NULL, "deconfig");
1581                                 state = INIT_SELECTING;
1582                                 client_config.first_secs = 0; /* make secs field count from 0 */
1583                                 /*timeout = 0; - already is */
1584                                 packet_num = 0;
1585                                 continue;
1586                         /* case RELEASED: */
1587                         }
1588                         /* yah, I know, *you* say it would never happen */
1589                         timeout = INT_MAX;
1590                         continue; /* back to main loop */
1591                 } /* if select timed out */
1592
1593                 /* select() didn't timeout, something happened */
1594
1595                 /* Is it a signal? */
1596                 /* note: udhcp_sp_read checks poll result before reading */
1597                 switch (udhcp_sp_read(pfds)) {
1598                 case SIGUSR1:
1599                         client_config.first_secs = 0; /* make secs field count from 0 */
1600                         already_waited_sec = 0;
1601                         perform_renew();
1602                         if (state == RENEW_REQUESTED) {
1603                                 /* We might be either on the same network
1604                                  * (in which case renew might work),
1605                                  * or we might be on a completely different one
1606                                  * (in which case renew won't ever succeed).
1607                                  * For the second case, must make sure timeout
1608                                  * is not too big, or else we can send
1609                                  * futile renew requests for hours.
1610                                  * (Ab)use -A TIMEOUT value (usually 20 sec)
1611                                  * as a cap on the timeout.
1612                                  */
1613                                 if (timeout > tryagain_timeout)
1614                                         timeout = tryagain_timeout;
1615                                 goto case_RENEW_REQUESTED;
1616                         }
1617                         /* Start things over */
1618                         packet_num = 0;
1619                         /* Kill any timeouts, user wants this to hurry along */
1620                         timeout = 0;
1621                         continue;
1622                 case SIGUSR2:
1623                         perform_release(server_addr, requested_ip);
1624                         timeout = INT_MAX;
1625                         continue;
1626                 case SIGTERM:
1627                         bb_error_msg("received %s", "SIGTERM");
1628                         goto ret0;
1629                 }
1630
1631                 /* Is it a packet? */
1632                 if (listen_mode == LISTEN_NONE || !pfds[1].revents)
1633                         continue; /* no */
1634
1635                 {
1636                         int len;
1637
1638                         /* A packet is ready, read it */
1639                         if (listen_mode == LISTEN_KERNEL)
1640                                 len = udhcp_recv_kernel_packet(&packet, sockfd);
1641                         else
1642                                 len = udhcp_recv_raw_packet(&packet, sockfd);
1643                         if (len == -1) {
1644                                 /* Error is severe, reopen socket */
1645                                 bb_error_msg("read error: %s, reopening socket", strerror(errno));
1646                                 sleep(discover_timeout); /* 3 seconds by default */
1647                                 change_listen_mode(listen_mode); /* just close and reopen */
1648                         }
1649                         /* If this packet will turn out to be unrelated/bogus,
1650                          * we will go back and wait for next one.
1651                          * Be sure timeout is properly decreased. */
1652                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1653                         if (len < 0)
1654                                 continue;
1655                 }
1656
1657                 if (packet.xid != xid) {
1658                         log1("xid %x (our is %x), ignoring packet",
1659                                 (unsigned)packet.xid, (unsigned)xid);
1660                         continue;
1661                 }
1662
1663                 /* Ignore packets that aren't for us */
1664                 if (packet.hlen != 6
1665                  || memcmp(packet.chaddr, client_config.client_mac, 6) != 0
1666                 ) {
1667 //FIXME: need to also check that last 10 bytes are zero
1668                         log1("chaddr does not match, ignoring packet"); // log2?
1669                         continue;
1670                 }
1671
1672                 message = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
1673                 if (message == NULL) {
1674                         bb_error_msg("no message type option, ignoring packet");
1675                         continue;
1676                 }
1677
1678                 switch (state) {
1679                 case INIT_SELECTING:
1680                         /* Must be a DHCPOFFER */
1681                         if (*message == DHCPOFFER) {
1682                                 uint8_t *temp;
1683
1684 /* What exactly is server's IP? There are several values.
1685  * Example DHCP offer captured with tchdump:
1686  *
1687  * 10.34.25.254:67 > 10.34.25.202:68 // IP header's src
1688  * BOOTP fields:
1689  * Your-IP 10.34.25.202
1690  * Server-IP 10.34.32.125   // "next server" IP
1691  * Gateway-IP 10.34.25.254  // relay's address (if DHCP relays are in use)
1692  * DHCP options:
1693  * DHCP-Message Option 53, length 1: Offer
1694  * Server-ID Option 54, length 4: 10.34.255.7       // "server ID"
1695  * Default-Gateway Option 3, length 4: 10.34.25.254 // router
1696  *
1697  * We think that real server IP (one to use in renew/release)
1698  * is one in Server-ID option. But I am not 100% sure.
1699  * IP header's src and Gateway-IP (same in this example)
1700  * might work too.
1701  * "Next server" and router are definitely wrong ones to use, though...
1702  */
1703 /* We used to ignore pcakets without DHCP_SERVER_ID.
1704  * I've got user reports from people who run "address-less" servers.
1705  * They either supply DHCP_SERVER_ID of 0.0.0.0 or don't supply it at all.
1706  * They say ISC DHCP client supports this case.
1707  */
1708                                 server_addr = 0;
1709                                 temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
1710                                 if (!temp) {
1711                                         bb_error_msg("no server ID, using 0.0.0.0");
1712                                 } else {
1713                                         /* it IS unaligned sometimes, don't "optimize" */
1714                                         move_from_unaligned32(server_addr, temp);
1715                                 }
1716                                 /*xid = packet.xid; - already is */
1717                                 requested_ip = packet.yiaddr;
1718
1719                                 /* enter requesting state */
1720                                 state = REQUESTING;
1721                                 timeout = 0;
1722                                 packet_num = 0;
1723                                 already_waited_sec = 0;
1724                         }
1725                         continue;
1726                 case REQUESTING:
1727                 case RENEWING:
1728                 case RENEW_REQUESTED:
1729                 case REBINDING:
1730                         if (*message == DHCPACK) {
1731                                 unsigned start;
1732                                 uint32_t lease_seconds;
1733                                 struct in_addr temp_addr;
1734                                 uint8_t *temp;
1735
1736                                 temp = udhcp_get_option(&packet, DHCP_LEASE_TIME);
1737                                 if (!temp) {
1738                                         bb_error_msg("no lease time with ACK, using 1 hour lease");
1739                                         lease_seconds = 60 * 60;
1740                                 } else {
1741                                         /* it IS unaligned sometimes, don't "optimize" */
1742                                         move_from_unaligned32(lease_seconds, temp);
1743                                         lease_seconds = ntohl(lease_seconds);
1744                                         /* paranoia: must not be too small and not prone to overflows */
1745                                         if (lease_seconds < 0x10)
1746                                                 lease_seconds = 0x10;
1747                                         if (lease_seconds > 0x7fffffff / 1000)
1748                                                 lease_seconds = 0x7fffffff / 1000;
1749                                 }
1750 #if ENABLE_FEATURE_UDHCPC_ARPING
1751                                 if (opt & OPT_a) {
1752 /* RFC 2131 3.1 paragraph 5:
1753  * "The client receives the DHCPACK message with configuration
1754  * parameters. The client SHOULD perform a final check on the
1755  * parameters (e.g., ARP for allocated network address), and notes
1756  * the duration of the lease specified in the DHCPACK message. At this
1757  * point, the client is configured. If the client detects that the
1758  * address is already in use (e.g., through the use of ARP),
1759  * the client MUST send a DHCPDECLINE message to the server and restarts
1760  * the configuration process..." */
1761                                         if (!arpping(packet.yiaddr,
1762                                                         NULL,
1763                                                         (uint32_t) 0,
1764                                                         client_config.client_mac,
1765                                                         client_config.interface,
1766                                                         arpping_ms)
1767                                         ) {
1768                                                 bb_error_msg("offered address is in use "
1769                                                         "(got ARP reply), declining");
1770                                                 send_decline(/*xid,*/ server_addr, packet.yiaddr);
1771
1772                                                 if (state != REQUESTING)
1773                                                         udhcp_run_script(NULL, "deconfig");
1774                                                 change_listen_mode(LISTEN_RAW);
1775                                                 state = INIT_SELECTING;
1776                                                 client_config.first_secs = 0; /* make secs field count from 0 */
1777                                                 requested_ip = 0;
1778                                                 timeout = tryagain_timeout;
1779                                                 packet_num = 0;
1780                                                 already_waited_sec = 0;
1781                                                 continue; /* back to main loop */
1782                                         }
1783                                 }
1784 #endif
1785                                 /* enter bound state */
1786                                 temp_addr.s_addr = packet.yiaddr;
1787                                 bb_error_msg("lease of %s obtained, lease time %u",
1788                                         inet_ntoa(temp_addr), (unsigned)lease_seconds);
1789                                 requested_ip = packet.yiaddr;
1790
1791                                 start = monotonic_sec();
1792                                 udhcp_run_script(&packet, state == REQUESTING ? "bound" : "renew");
1793                                 already_waited_sec = (unsigned)monotonic_sec() - start;
1794                                 timeout = lease_seconds / 2;
1795                                 if ((unsigned)timeout < already_waited_sec) {
1796                                         /* Something went wrong. Back to discover state */
1797                                         timeout = already_waited_sec = 0;
1798                                 }
1799
1800                                 state = BOUND;
1801                                 change_listen_mode(LISTEN_NONE);
1802                                 if (opt & OPT_q) { /* quit after lease */
1803                                         goto ret0;
1804                                 }
1805                                 /* future renew failures should not exit (JM) */
1806                                 opt &= ~OPT_n;
1807 #if BB_MMU /* NOMMU case backgrounded earlier */
1808                                 if (!(opt & OPT_f)) {
1809                                         client_background();
1810                                         /* do not background again! */
1811                                         opt = ((opt & ~OPT_b) | OPT_f);
1812                                 }
1813 #endif
1814                                 /* make future renew packets use different xid */
1815                                 /* xid = random_xid(); ...but why bother? */
1816
1817                                 continue; /* back to main loop */
1818                         }
1819                         if (*message == DHCPNAK) {
1820                                 /* If network has more than one DHCP server,
1821                                  * "wrong" server can reply first, with a NAK.
1822                                  * Do not interpret it as a NAK from "our" server.
1823                                  */
1824                                 if (server_addr != 0) {
1825                                         uint32_t svid;
1826                                         uint8_t *temp;
1827
1828                                         temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
1829                                         if (!temp) {
1830  non_matching_svid:
1831                                                 log1("received DHCP NAK with wrong"
1832                                                         " server ID, ignoring packet");
1833                                                 continue;
1834                                         }
1835                                         move_from_unaligned32(svid, temp);
1836                                         if (svid != server_addr)
1837                                                 goto non_matching_svid;
1838                                 }
1839                                 /* return to init state */
1840                                 bb_error_msg("received %s", "DHCP NAK");
1841                                 udhcp_run_script(&packet, "nak");
1842                                 if (state != REQUESTING)
1843                                         udhcp_run_script(NULL, "deconfig");
1844                                 change_listen_mode(LISTEN_RAW);
1845                                 sleep(3); /* avoid excessive network traffic */
1846                                 state = INIT_SELECTING;
1847                                 client_config.first_secs = 0; /* make secs field count from 0 */
1848                                 requested_ip = 0;
1849                                 timeout = 0;
1850                                 packet_num = 0;
1851                                 already_waited_sec = 0;
1852                         }
1853                         continue;
1854                 /* case BOUND: - ignore all packets */
1855                 /* case RELEASED: - ignore all packets */
1856                 }
1857                 /* back to main loop */
1858         } /* for (;;) - main loop ends */
1859
1860  ret0:
1861         if (opt & OPT_R) /* release on quit */
1862                 perform_release(server_addr, requested_ip);
1863         retval = 0;
1864  ret:
1865         /*if (client_config.pidfile) - remove_pidfile has its own check */
1866                 remove_pidfile(client_config.pidfile);
1867         return retval;
1868 }