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                 /* Without MSG_DONTROUTE, the packet was seen routed over
 699                  * _other interface_ if server ID is bogus (example: 1.1.1.1).
 700                  */
 701                 return udhcp_send_kernel_packet(packet,
 702                         ciaddr, CLIENT_PORT,
 703                         server, SERVER_PORT,
 704                         /*send_flags: "to hosts only on directly connected networks" */ MSG_DONTROUTE
 705                 );
 706         }
 707         return raw_bcast_from_client_config_ifindex(packet, ciaddr);
 708 }
 709
 710 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
 711 /* NOINLINE: limit stack usage in caller */
 712 static NOINLINE int send_discover(uint32_t xid, uint32_t requested)
 713 {
 714         struct dhcp_packet packet;
 715
 716         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 717          * random xid field (we override it below),
 718          * client-id option (unless -C), message type option:
 719          */
 720         init_packet(&packet, DHCPDISCOVER);
 721
 722         packet.xid = xid;
 723         if (requested)
 724                 udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 725
 726         /* Add options: maxsize,
 727          * optionally: hostname, fqdn, vendorclass,
 728          * "param req" option according to -O, options specified with -x
 729          */
 730         add_client_options(&packet);
 731
 732         bb_error_msg("sending %s", "discover");
 733         return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
 734 }
 735
 736 /* Broadcast a DHCP request message */
 737 /* RFC 2131 3.1 paragraph 3:
 738  * "The client _broadcasts_ a DHCPREQUEST message..."
 739  */
 740 /* NOINLINE: limit stack usage in caller */
 741 static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requested)
 742 {
 743         struct dhcp_packet packet;
 744         struct in_addr temp_addr;
 745
 746 /*
 747  * RFC 2131 4.3.2 DHCPREQUEST message
 748  * ...
 749  * If the DHCPREQUEST message contains a 'server identifier'
 750  * option, the message is in response to a DHCPOFFER message.
 751  * Otherwise, the message is a request to verify or extend an
 752  * existing lease. If the client uses a 'client identifier'
 753  * in a DHCPREQUEST message, it MUST use that same 'client identifier'
 754  * in all subsequent messages. If the client included a list
 755  * of requested parameters in a DHCPDISCOVER message, it MUST
 756  * include that list in all subsequent messages.
 757  */
 758         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 759          * random xid field (we override it below),
 760          * client-id option (unless -C), message type option:
 761          */
 762         init_packet(&packet, DHCPREQUEST);
 763
 764         packet.xid = xid;
 765         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 766
 767         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 768
 769         /* Add options: maxsize,
 770          * optionally: hostname, fqdn, vendorclass,
 771          * "param req" option according to -O, and options specified with -x
 772          */
 773         add_client_options(&packet);
 774
 775         temp_addr.s_addr = requested;
 776         bb_error_msg("sending select for %s", inet_ntoa(temp_addr));
 777         return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
 778 }
 779
 780 /* Unicast or broadcast a DHCP renew message */
 781 /* NOINLINE: limit stack usage in caller */
 782 static NOINLINE int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
 783 {
 784         struct dhcp_packet packet;
 785         struct in_addr temp_addr;
 786
 787 /*
 788  * RFC 2131 4.3.2 DHCPREQUEST message
 789  * ...
 790  * DHCPREQUEST generated during RENEWING state:
 791  *
 792  * 'server identifier' MUST NOT be filled in, 'requested IP address'
 793  * option MUST NOT be filled in, 'ciaddr' MUST be filled in with
 794  * client's IP address. In this situation, the client is completely
 795  * configured, and is trying to extend its lease. This message will
 796  * be unicast, so no relay agents will be involved in its
 797  * transmission.  Because 'giaddr' is therefore not filled in, the
 798  * DHCP server will trust the value in 'ciaddr', and use it when
 799  * replying to the client.
 800  */
 801         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 802          * random xid field (we override it below),
 803          * client-id option (unless -C), message type option:
 804          */
 805         init_packet(&packet, DHCPREQUEST);
 806
 807         packet.xid = xid;
 808         packet.ciaddr = ciaddr;
 809
 810         /* Add options: maxsize,
 811          * optionally: hostname, fqdn, vendorclass,
 812          * "param req" option according to -O, and options specified with -x
 813          */
 814         add_client_options(&packet);
 815
 816         temp_addr.s_addr = server;
 817         bb_error_msg("sending renew to %s", inet_ntoa(temp_addr));
 818         return bcast_or_ucast(&packet, ciaddr, server);
 819 }
 820
 821 #if ENABLE_FEATURE_UDHCPC_ARPING
 822 /* Broadcast a DHCP decline message */
 823 /* NOINLINE: limit stack usage in caller */
 824 static NOINLINE int send_decline(/*uint32_t xid,*/ uint32_t server, uint32_t requested)
 825 {
 826         struct dhcp_packet packet;
 827
 828         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 829          * client-id option (unless -C), message type option:
 830          */
 831         init_packet(&packet, DHCPDECLINE);
 832
 833 #if 0
 834         /* RFC 2131 says DHCPDECLINE's xid is randomly selected by client,
 835          * but in case the server is buggy and wants DHCPDECLINE's xid
 836          * to match the xid which started entire handshake,
 837          * we use the same xid we used in initial DHCPDISCOVER:
 838          */
 839         packet.xid = xid;
 840 #endif
 841         /* DHCPDECLINE uses "requested ip", not ciaddr, to store offered IP */
 842         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 843
 844         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 845
 846         bb_error_msg("sending %s", "decline");
 847         return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
 848 }
 849 #endif
 850
 851 /* Unicast a DHCP release message */
 852 static int send_release(uint32_t server, uint32_t ciaddr)
 853 {
 854         struct dhcp_packet packet;
 855
 856         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 857          * client-id option (unless -C), message type option:
 858          */
 859         init_packet(&packet, DHCPRELEASE);
 860
 861         /* DHCPRELEASE uses ciaddr, not "requested ip", to store IP being released */
 862         packet.ciaddr = ciaddr;
 863
 864         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 865
 866         bb_error_msg("sending %s", "release");
 867         /* Note: normally we unicast here since "server" is not zero.
 868          * However, there _are_ people who run "address-less" DHCP servers,
 869          * and reportedly ISC dhcp client and Windows allow that.
 870          */
 871         return bcast_or_ucast(&packet, ciaddr, server);
 872 }
 873
 874 /* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */
 875 /* NOINLINE: limit stack usage in caller */
 876 static NOINLINE int udhcp_recv_raw_packet(struct dhcp_packet *dhcp_pkt, int fd)
 877 {
 878         int bytes;
 879         struct ip_udp_dhcp_packet packet;
 880         uint16_t check;
 881         unsigned char cmsgbuf[CMSG_LEN(sizeof(struct tpacket_auxdata))];
 882         struct iovec iov;
 883         struct msghdr msg;
 884         struct cmsghdr *cmsg;
 885
 886         /* used to use just safe_read(fd, &packet, sizeof(packet))
 887          * but we need to check for TP_STATUS_CSUMNOTREADY :(
 888          */
 889         iov.iov_base = &packet;
 890         iov.iov_len = sizeof(packet);
 891         memset(&msg, 0, sizeof(msg));
 892         msg.msg_iov = &iov;
 893         msg.msg_iovlen = 1;
 894         msg.msg_control = cmsgbuf;
 895         msg.msg_controllen = sizeof(cmsgbuf);
 896         for (;;) {
 897                 bytes = recvmsg(fd, &msg, 0);
 898                 if (bytes < 0) {
 899                         if (errno == EINTR)
 900                                 continue;
 901                         log1("packet read error, ignoring");
 902                         /* NB: possible down interface, etc. Caller should pause. */
 903                         return bytes; /* returns -1 */
 904                 }
 905                 break;
 906         }
 907
 908         if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) {
 909                 log1("packet is too short, ignoring");
 910                 return -2;
 911         }
 912
 913         if (bytes < ntohs(packet.ip.tot_len)) {
 914                 /* packet is bigger than sizeof(packet), we did partial read */
 915                 log1("oversized packet, ignoring");
 916                 return -2;
 917         }
 918
 919         /* ignore any extra garbage bytes */
 920         bytes = ntohs(packet.ip.tot_len);
 921
 922         /* make sure its the right packet for us, and that it passes sanity checks */
 923         if (packet.ip.protocol != IPPROTO_UDP
 924          || packet.ip.version != IPVERSION
 925          || packet.ip.ihl != (sizeof(packet.ip) >> 2)
 926          || packet.udp.dest != htons(CLIENT_PORT)
 927         /* || bytes > (int) sizeof(packet) - can't happen */
 928          || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
 929         ) {
 930                 log1("unrelated/bogus packet, ignoring");
 931                 return -2;
 932         }
 933
 934         /* verify IP checksum */
 935         check = packet.ip.check;
 936         packet.ip.check = 0;
 937         if (check != inet_cksum((uint16_t *)&packet.ip, sizeof(packet.ip))) {
 938                 log1("bad IP header checksum, ignoring");
 939                 return -2;
 940         }
 941
 942         for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
 943                 if (cmsg->cmsg_level == SOL_PACKET
 944                  && cmsg->cmsg_type == PACKET_AUXDATA
 945                 ) {
 946                         /* some VMs don't checksum UDP and TCP data
 947                          * they send to the same physical machine,
 948                          * here we detect this case:
 949                          */
 950                         struct tpacket_auxdata *aux = (void *)CMSG_DATA(cmsg);
 951                         if (aux->tp_status & TP_STATUS_CSUMNOTREADY)
 952                                 goto skip_udp_sum_check;
 953                 }
 954         }
 955
 956         /* verify UDP checksum. IP header has to be modified for this */
 957         memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
 958         /* ip.xx fields which are not memset: protocol, check, saddr, daddr */
 959         packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
 960         check = packet.udp.check;
 961         packet.udp.check = 0;
 962         if (check && check != inet_cksum((uint16_t *)&packet, bytes)) {
 963                 log1("packet with bad UDP checksum received, ignoring");
 964                 return -2;
 965         }
 966  skip_udp_sum_check:
 967
 968         if (packet.data.cookie != htonl(DHCP_MAGIC)) {
 969                 bb_error_msg("packet with bad magic, ignoring");
 970                 return -2;
 971         }
 972
 973         log1("received %s", "a packet");
 974         udhcp_dump_packet(&packet.data);
 975
 976         bytes -= sizeof(packet.ip) + sizeof(packet.udp);
 977         memcpy(dhcp_pkt, &packet.data, bytes);
 978         return bytes;
 979 }
 980
 981
 982 /*** Main ***/
 983
 984 static int sockfd = -1;
 985
 986 #define LISTEN_NONE   0
 987 #define LISTEN_KERNEL 1
 988 #define LISTEN_RAW    2
 989 static smallint listen_mode;
 990
 991 /* initial state: (re)start DHCP negotiation */
 992 #define INIT_SELECTING  0
 993 /* discover was sent, DHCPOFFER reply received */
 994 #define REQUESTING      1
 995 /* select/renew was sent, DHCPACK reply received */
 996 #define BOUND           2
 997 /* half of lease passed, want to renew it by sending unicast renew requests */
 998 #define RENEWING        3
 999 /* renew requests were not answered, lease is almost over, send broadcast renew */
1000 #define REBINDING       4
1001 /* manually requested renew (SIGUSR1) */
1002 #define RENEW_REQUESTED 5
1003 /* release, possibly manually requested (SIGUSR2) */
1004 #define RELEASED        6
1005 static smallint state;
1006
1007 static int udhcp_raw_socket(int ifindex)
1008 {
1009         int fd;
1010         struct sockaddr_ll sock;
1011
1012         log2("opening raw socket on ifindex %d", ifindex);
1013
1014         fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
1015         /* ^^^^^
1016          * SOCK_DGRAM: remove link-layer headers on input (SOCK_RAW keeps them)
1017          * ETH_P_IP: want to receive only packets with IPv4 eth type
1018          */
1019         log2("got raw socket fd");
1020
1021         memset(&sock, 0, sizeof(sock)); /* let's be deterministic */
1022         sock.sll_family = AF_PACKET;
1023         sock.sll_protocol = htons(ETH_P_IP);
1024         sock.sll_ifindex = ifindex;
1025         /*sock.sll_hatype = ARPHRD_???;*/
1026         /*sock.sll_pkttype = PACKET_???;*/
1027         /*sock.sll_halen = ???;*/
1028         /*sock.sll_addr[8] = ???;*/
1029         xbind(fd, (struct sockaddr *) &sock, sizeof(sock));
1030
1031 #if 0 /* Several users reported breakage when BPF filter is used */
1032         if (CLIENT_PORT == 68) {
1033                 /* Use only if standard port is in use */
1034                 /*
1035                  *      I've selected not to see LL header, so BPF doesn't see it, too.
1036                  *      The filter may also pass non-IP and non-ARP packets, but we do
1037                  *      a more complete check when receiving the message in userspace.
1038                  *
1039                  * and filter shamelessly stolen from:
1040                  *
1041                  *      http://www.flamewarmaster.de/software/dhcpclient/
1042                  *
1043                  * There are a few other interesting ideas on that page (look under
1044                  * "Motivation").  Use of netlink events is most interesting.  Think
1045                  * of various network servers listening for events and reconfiguring.
1046                  * That would obsolete sending HUP signals and/or make use of restarts.
1047                  *
1048                  * Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
1049                  * License: GPL v2.
1050                  */
1051                 static const struct sock_filter filter_instr[] = {
1052                         /* load 9th byte (protocol) */
1053                         BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
1054                         /* jump to L1 if it is IPPROTO_UDP, else to L4 */
1055                         BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 0, 6),
1056                         /* L1: load halfword from offset 6 (flags and frag offset) */
1057                         BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 6),
1058                         /* jump to L4 if any bits in frag offset field are set, else to L2 */
1059                         BPF_JUMP(BPF_JMP|BPF_JSET|BPF_K, 0x1fff, 4, 0),
1060                         /* L2: skip IP header (load index reg with header len) */
1061                         BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0),
1062                         /* load udp destination port from halfword[header_len + 2] */
1063                         BPF_STMT(BPF_LD|BPF_H|BPF_IND, 2),
1064                         /* jump to L3 if udp dport is CLIENT_PORT, else to L4 */
1065                         BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 68, 0, 1),
1066                         /* L3: accept packet ("accept 0x7fffffff bytes") */
1067                         /* Accepting 0xffffffff works too but kernel 2.6.19 is buggy */
1068                         BPF_STMT(BPF_RET|BPF_K, 0x7fffffff),
1069                         /* L4: discard packet ("accept zero bytes") */
1070                         BPF_STMT(BPF_RET|BPF_K, 0),
1071                 };
1072                 static const struct sock_fprog filter_prog = {
1073                         .len = sizeof(filter_instr) / sizeof(filter_instr[0]),
1074                         /* casting const away: */
1075                         .filter = (struct sock_filter *) filter_instr,
1076                 };
1077                 /* Ignoring error (kernel may lack support for this) */
1078                 if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
1079                                 sizeof(filter_prog)) >= 0)
1080                         log1("attached filter to raw socket fd"); // log?
1081         }
1082 #endif
1083
1084         if (setsockopt_1(fd, SOL_PACKET, PACKET_AUXDATA) != 0) {
1085                 if (errno != ENOPROTOOPT)
1086                         log1("can't set PACKET_AUXDATA on raw socket");
1087         }
1088
1089         log1("created raw socket");
1090
1091         return fd;
1092 }
1093
1094 static void change_listen_mode(int new_mode)
1095 {
1096         log1("entering listen mode: %s",
1097                 new_mode != LISTEN_NONE
1098                         ? (new_mode == LISTEN_KERNEL ? "kernel" : "raw")
1099                         : "none"
1100         );
1101
1102         listen_mode = new_mode;
1103         if (sockfd >= 0) {
1104                 close(sockfd);
1105                 sockfd = -1;
1106         }
1107         if (new_mode == LISTEN_KERNEL)
1108                 sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
1109         else if (new_mode != LISTEN_NONE)
1110                 sockfd = udhcp_raw_socket(client_config.ifindex);
1111         /* else LISTEN_NONE: sockfd stays closed */
1112 }
1113
1114 /* Called only on SIGUSR1 */
1115 static void perform_renew(void)
1116 {
1117         bb_error_msg("performing DHCP renew");
1118         switch (state) {
1119         case BOUND:
1120                 change_listen_mode(LISTEN_KERNEL);
1121         case RENEWING:
1122         case REBINDING:
1123                 state = RENEW_REQUESTED;
1124                 break;
1125         case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
1126                 udhcp_run_script(NULL, "deconfig");
1127         case REQUESTING:
1128         case RELEASED:
1129                 change_listen_mode(LISTEN_RAW);
1130                 state = INIT_SELECTING;
1131                 break;
1132         case INIT_SELECTING:
1133                 break;
1134         }
1135 }
1136
1137 static void perform_release(uint32_t server_addr, uint32_t requested_ip)
1138 {
1139         char buffer[sizeof("255.255.255.255")];
1140         struct in_addr temp_addr;
1141
1142         /* send release packet */
1143         if (state == BOUND
1144          || state == RENEWING
1145          || state == REBINDING
1146          || state == RENEW_REQUESTED
1147         ) {
1148                 temp_addr.s_addr = server_addr;
1149                 strcpy(buffer, inet_ntoa(temp_addr));
1150                 temp_addr.s_addr = requested_ip;
1151                 bb_error_msg("unicasting a release of %s to %s",
1152                                 inet_ntoa(temp_addr), buffer);
1153                 send_release(server_addr, requested_ip); /* unicast */
1154         }
1155         bb_error_msg("entering released state");
1156 /*
1157  * We can be here on: SIGUSR2,
1158  * or on exit (SIGTERM) and -R "release on quit" is specified.
1159  * Users requested to be notified in all cases, even if not in one
1160  * of the states above.
1161  */
1162         udhcp_run_script(NULL, "deconfig");
1163
1164         change_listen_mode(LISTEN_NONE);
1165         state = RELEASED;
1166 }
1167
1168 static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
1169 {
1170         uint8_t *storage;
1171         int len = strnlen(str, 255);
1172         storage = xzalloc(len + extra + OPT_DATA);
1173         storage[OPT_CODE] = code;
1174         storage[OPT_LEN] = len + extra;
1175         memcpy(storage + extra + OPT_DATA, str, len);
1176         return storage;
1177 }
1178
1179 #if BB_MMU
1180 static void client_background(void)
1181 {
1182         bb_daemonize(0);
1183         logmode &= ~LOGMODE_STDIO;
1184         /* rewrite pidfile, as our pid is different now */
1185         write_pidfile(client_config.pidfile);
1186 }
1187 #endif
1188
1189 //usage:#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
1190 //usage:# define IF_UDHCP_VERBOSE(...) __VA_ARGS__
1191 //usage:#else
1192 //usage:# define IF_UDHCP_VERBOSE(...)
1193 //usage:#endif
1194 //usage:#define udhcpc_trivial_usage
1195 //usage:       "[-fbq"IF_UDHCP_VERBOSE("v")"RB]"IF_FEATURE_UDHCPC_ARPING(" [-a[MSEC]]")" [-t N] [-T SEC] [-A SEC/-n]\n"
1196 //usage:       "        [-i IFACE]"IF_FEATURE_UDHCP_PORT(" [-P PORT]")" [-s PROG] [-p PIDFILE]\n"
1197 //usage:       "        [-oC] [-r IP] [-V VENDOR] [-F NAME] [-x OPT:VAL]... [-O OPT]..."
1198 //usage:#define udhcpc_full_usage "\n"
1199 //usage:     "\n        -i IFACE        Interface to use (default eth0)"
1200 //usage:        IF_FEATURE_UDHCP_PORT(
1201 //usage:     "\n        -P PORT         Use PORT (default 68)"
1202 //usage:        )
1203 //usage:     "\n        -s PROG         Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
1204 //usage:     "\n        -p FILE         Create pidfile"
1205 //usage:     "\n        -B              Request broadcast replies"
1206 //usage:     "\n        -t N            Send up to N discover packets (default 3)"
1207 //usage:     "\n        -T SEC          Pause between packets (default 3)"
1208 //usage:     "\n        -A SEC          Wait if lease is not obtained (default 20)"
1209 //usage:     "\n        -n              Exit if lease is not obtained"
1210 //usage:     "\n        -q              Exit after obtaining lease"
1211 //usage:     "\n        -R              Release IP on exit"
1212 //usage:     "\n        -f              Run in foreground"
1213 //usage:        USE_FOR_MMU(
1214 //usage:     "\n        -b              Background if lease is not obtained"
1215 //usage:        )
1216 //usage:     "\n        -S              Log to syslog too"
1217 //usage:        IF_FEATURE_UDHCPC_ARPING(
1218 //usage:     "\n        -a[MSEC]        Validate offered address with ARP ping"
1219 //usage:        )
1220 //usage:     "\n        -r IP           Request this IP address"
1221 //usage:     "\n        -o              Don't request any options (unless -O is given)"
1222 //usage:     "\n        -O OPT          Request option OPT from server (cumulative)"
1223 //usage:     "\n        -x OPT:VAL      Include option OPT in sent packets (cumulative)"
1224 //usage:     "\n                        Examples of string, numeric, and hex byte opts:"
1225 //usage:     "\n                        -x hostname:bbox - option 12"
1226 //usage:     "\n                        -x lease:3600 - option 51 (lease time)"
1227 //usage:     "\n                        -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
1228 //usage:     "\n        -F NAME         Ask server to update DNS mapping for NAME"
1229 //usage:     "\n        -V VENDOR       Vendor identifier (default 'udhcp VERSION')"
1230 //usage:     "\n        -C              Don't send MAC as client identifier"
1231 //usage:        IF_UDHCP_VERBOSE(
1232 //usage:     "\n        -v              Verbose"
1233 //usage:        )
1234 //usage:     "\nSignals:"
1235 //usage:     "\n        USR1    Renew lease"
1236 //usage:     "\n        USR2    Release lease"
1237
1238
1239 int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
1240 int udhcpc_main(int argc UNUSED_PARAM, char **argv)
1241 {
1242         uint8_t *message;
1243         const char *str_V, *str_h, *str_F, *str_r;
1244         IF_FEATURE_UDHCPC_ARPING(const char *str_a = "2000";)
1245         IF_FEATURE_UDHCP_PORT(char *str_P;)
1246         void *clientid_mac_ptr;
1247         llist_t *list_O = NULL;
1248         llist_t *list_x = NULL;
1249         int tryagain_timeout = 20;
1250         int discover_timeout = 3;
1251         int discover_retries = 3;
1252         uint32_t server_addr = server_addr; /* for compiler */
1253         uint32_t requested_ip = 0;
1254         uint32_t xid = xid; /* for compiler */
1255         int packet_num;
1256         int timeout; /* must be signed */
1257         unsigned already_waited_sec;
1258         unsigned opt;
1259         IF_FEATURE_UDHCPC_ARPING(unsigned arpping_ms;)
1260         int retval;
1261
1262         setup_common_bufsiz();
1263
1264         /* Default options */
1265         IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;)
1266         IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
1267         client_config.interface = "eth0";
1268         client_config.script = CONFIG_UDHCPC_DEFAULT_SCRIPT;
1269         str_V = "udhcp "BB_VER;
1270
1271         /* Parse command line */
1272         opt = getopt32long(argv, "^"
1273                 /* O,x: list; -T,-t,-A take numeric param */
1274                 "CV:H:h:F:i:np:qRr:s:T:+t:+SA:+O:*ox:*fB"
1275                 USE_FOR_MMU("b")
1276                 IF_FEATURE_UDHCPC_ARPING("a::")
1277                 IF_FEATURE_UDHCP_PORT("P:")
1278                 "v"
1279                 "\0" IF_UDHCP_VERBOSE("vv") /* -v is a counter */
1280                 , udhcpc_longopts
1281                 , &str_V, &str_h, &str_h, &str_F
1282                 , &client_config.interface, &client_config.pidfile /* i,p */
1283                 , &str_r /* r */
1284                 , &client_config.script /* s */
1285                 , &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */
1286                 , &list_O
1287                 , &list_x
1288                 IF_FEATURE_UDHCPC_ARPING(, &str_a)
1289                 IF_FEATURE_UDHCP_PORT(, &str_P)
1290                 IF_UDHCP_VERBOSE(, &dhcp_verbose)
1291         );
1292         if (opt & (OPT_h|OPT_H)) {
1293                 //msg added 2011-11
1294                 bb_error_msg("option -h NAME is deprecated, use -x hostname:NAME");
1295                 client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
1296         }
1297         if (opt & OPT_F) {
1298                 /* FQDN option format: [0x51][len][flags][0][0]<fqdn> */
1299                 client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
1300                 /* Flag bits: 0000NEOS
1301                  * S: 1 = Client requests server to update A RR in DNS as well as PTR
1302                  * O: 1 = Server indicates to client that DNS has been updated regardless
1303                  * E: 1 = Name is in DNS format, i.e. <4>host<6>domain<3>com<0>,
1304                  *    not "host.domain.com". Format 0 is obsolete.
1305                  * N: 1 = Client requests server to not update DNS (S must be 0 then)
1306                  * Two [0] bytes which follow are deprecated and must be 0.
1307                  */
1308                 client_config.fqdn[OPT_DATA + 0] = 0x1;
1309                 /*client_config.fqdn[OPT_DATA + 1] = 0; - xzalloc did it */
1310                 /*client_config.fqdn[OPT_DATA + 2] = 0; */
1311         }
1312         if (opt & OPT_r)
1313                 requested_ip = inet_addr(str_r);
1314 #if ENABLE_FEATURE_UDHCP_PORT
1315         if (opt & OPT_P) {
1316                 CLIENT_PORT = xatou16(str_P);
1317                 SERVER_PORT = CLIENT_PORT - 1;
1318         }
1319 #endif
1320         IF_FEATURE_UDHCPC_ARPING(arpping_ms = xatou(str_a);)
1321         while (list_O) {
1322                 char *optstr = llist_pop(&list_O);
1323                 unsigned n = bb_strtou(optstr, NULL, 0);
1324                 if (errno || n > 254) {
1325                         n = udhcp_option_idx(optstr, dhcp_option_strings);
1326                         n = dhcp_optflags[n].code;
1327                 }
1328                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
1329         }
1330         if (!(opt & OPT_o)) {
1331                 unsigned i, n;
1332                 for (i = 0; (n = dhcp_optflags[i].code) != 0; i++) {
1333                         if (dhcp_optflags[i].flags & OPTION_REQ) {
1334                                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
1335                         }
1336                 }
1337         }
1338         while (list_x) {
1339                 char *optstr = llist_pop(&list_x);
1340                 char *colon = strchr(optstr, ':');
1341                 if (colon)
1342                         *colon = ' ';
1343                 /* now it looks similar to udhcpd's config file line:
1344                  * "optname optval", using the common routine: */
1345                 udhcp_str2optset(optstr, &client_config.options, dhcp_optflags, dhcp_option_strings);
1346                 if (colon)
1347                         *colon = ':'; /* restore it for NOMMU reexec */
1348         }
1349
1350         if (udhcp_read_interface(client_config.interface,
1351                         &client_config.ifindex,
1352                         NULL,
1353                         client_config.client_mac)
1354         ) {
1355                 return 1;
1356         }
1357
1358         clientid_mac_ptr = NULL;
1359         if (!(opt & OPT_C) && !udhcp_find_option(client_config.options, DHCP_CLIENT_ID)) {
1360                 /* not suppressed and not set, set the default client ID */
1361                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
1362                 client_config.clientid[OPT_DATA] = 1; /* type: ethernet */
1363                 clientid_mac_ptr = client_config.clientid + OPT_DATA+1;
1364                 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1365         }
1366         if (str_V[0] != '\0') {
1367                 // can drop -V, str_V, client_config.vendorclass,
1368                 // but need to add "vendor" to the list of recognized
1369                 // string opts for this to work;
1370                 // and need to tweak add_client_options() too...
1371                 // ...so the question is, should we?
1372                 //bb_error_msg("option -V VENDOR is deprecated, use -x vendor:VENDOR");
1373                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
1374         }
1375
1376 #if !BB_MMU
1377         /* on NOMMU reexec (i.e., background) early */
1378         if (!(opt & OPT_f)) {
1379                 bb_daemonize_or_rexec(0 /* flags */, argv);
1380                 logmode = LOGMODE_NONE;
1381         }
1382 #endif
1383         if (opt & OPT_S) {
1384                 openlog(applet_name, LOG_PID, LOG_DAEMON);
1385                 logmode |= LOGMODE_SYSLOG;
1386         }
1387
1388         /* Make sure fd 0,1,2 are open */
1389         bb_sanitize_stdio();
1390         /* Equivalent of doing a fflush after every \n */
1391         setlinebuf(stdout);
1392         /* Create pidfile */
1393         write_pidfile(client_config.pidfile);
1394         /* Goes to stdout (unless NOMMU) and possibly syslog */
1395         bb_error_msg("started, v"BB_VER);
1396         /* Set up the signal pipe */
1397         udhcp_sp_setup();
1398         /* We want random_xid to be random... */
1399         srand(monotonic_us());
1400
1401         state = INIT_SELECTING;
1402         udhcp_run_script(NULL, "deconfig");
1403         change_listen_mode(LISTEN_RAW);
1404         packet_num = 0;
1405         timeout = 0;
1406         already_waited_sec = 0;
1407
1408         /* Main event loop. select() waits on signal pipe and possibly
1409          * on sockfd.
1410          * "continue" statements in code below jump to the top of the loop.
1411          */
1412         for (;;) {
1413                 int tv;
1414                 struct pollfd pfds[2];
1415                 struct dhcp_packet packet;
1416                 /* silence "uninitialized!" warning */
1417                 unsigned timestamp_before_wait = timestamp_before_wait;
1418
1419                 //bb_error_msg("sockfd:%d, listen_mode:%d", sockfd, listen_mode);
1420
1421                 /* Was opening raw or udp socket here
1422                  * if (listen_mode != LISTEN_NONE && sockfd < 0),
1423                  * but on fast network renew responses return faster
1424                  * than we open sockets. Thus this code is moved
1425                  * to change_listen_mode(). Thus we open listen socket
1426                  * BEFORE we send renew request (see "case BOUND:"). */
1427
1428                 udhcp_sp_fd_set(pfds, sockfd);
1429
1430                 tv = timeout - already_waited_sec;
1431                 retval = 0;
1432                 /* If we already timed out, fall through with retval = 0, else... */
1433                 if (tv > 0) {
1434                         log1("waiting %u seconds", tv);
1435                         timestamp_before_wait = (unsigned)monotonic_sec();
1436                         retval = poll(pfds, 2, tv < INT_MAX/1000 ? tv * 1000 : INT_MAX);
1437                         if (retval < 0) {
1438                                 /* EINTR? A signal was caught, don't panic */
1439                                 if (errno == EINTR) {
1440                                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1441                                         continue;
1442                                 }
1443                                 /* Else: an error occurred, panic! */
1444                                 bb_perror_msg_and_die("poll");
1445                         }
1446                 }
1447
1448                 /* If timeout dropped to zero, time to become active:
1449                  * resend discover/renew/whatever
1450                  */
1451                 if (retval == 0) {
1452                         /* When running on a bridge, the ifindex may have changed
1453                          * (e.g. if member interfaces were added/removed
1454                          * or if the status of the bridge changed).
1455                          * Refresh ifindex and client_mac:
1456                          */
1457                         if (udhcp_read_interface(client_config.interface,
1458                                         &client_config.ifindex,
1459                                         NULL,
1460                                         client_config.client_mac)
1461                         ) {
1462                                 goto ret0; /* iface is gone? */
1463                         }
1464                         if (clientid_mac_ptr)
1465                                 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1466
1467                         /* We will restart the wait in any case */
1468                         already_waited_sec = 0;
1469
1470                         switch (state) {
1471                         case INIT_SELECTING:
1472                                 if (!discover_retries || packet_num < discover_retries) {
1473                                         if (packet_num == 0)
1474                                                 xid = random_xid();
1475                                         /* broadcast */
1476                                         send_discover(xid, requested_ip);
1477                                         timeout = discover_timeout;
1478                                         packet_num++;
1479                                         continue;
1480                                 }
1481  leasefail:
1482                                 udhcp_run_script(NULL, "leasefail");
1483 #if BB_MMU /* -b is not supported on NOMMU */
1484                                 if (opt & OPT_b) { /* background if no lease */
1485                                         bb_error_msg("no lease, forking to background");
1486                                         client_background();
1487                                         /* do not background again! */
1488                                         opt = ((opt & ~OPT_b) | OPT_f);
1489                                 } else
1490 #endif
1491                                 if (opt & OPT_n) { /* abort if no lease */
1492                                         bb_error_msg("no lease, failing");
1493                                         retval = 1;
1494                                         goto ret;
1495                                 }
1496                                 /* wait before trying again */
1497                                 timeout = tryagain_timeout;
1498                                 packet_num = 0;
1499                                 continue;
1500                         case REQUESTING:
1501                                 if (packet_num < 3) {
1502                                         /* send broadcast select packet */
1503                                         send_select(xid, server_addr, requested_ip);
1504                                         timeout = discover_timeout;
1505                                         packet_num++;
1506                                         continue;
1507                                 }
1508                                 /* Timed out, go back to init state.
1509                                  * "discover...select...discover..." loops
1510                                  * were seen in the wild. Treat them similarly
1511                                  * to "no response to discover" case */
1512                                 change_listen_mode(LISTEN_RAW);
1513                                 state = INIT_SELECTING;
1514                                 goto leasefail;
1515                         case BOUND:
1516                                 /* 1/2 lease passed, enter renewing state */
1517                                 state = RENEWING;
1518                                 client_config.first_secs = 0; /* make secs field count from 0 */
1519                                 change_listen_mode(LISTEN_KERNEL);
1520                                 log1("entering renew state");
1521                                 /* fall right through */
1522                         case RENEW_REQUESTED: /* manual (SIGUSR1) renew */
1523                         case_RENEW_REQUESTED:
1524                         case RENEWING:
1525                                 if (timeout > 60) {
1526                                         /* send an unicast renew request */
1527                         /* Sometimes observed to fail (EADDRNOTAVAIL) to bind
1528                          * a new UDP socket for sending inside send_renew.
1529                          * I hazard to guess existing listening socket
1530                          * is somehow conflicting with it, but why is it
1531                          * not deterministic then?! Strange.
1532                          * Anyway, it does recover by eventually failing through
1533                          * into INIT_SELECTING state.
1534                          */
1535                                         if (send_renew(xid, server_addr, requested_ip) >= 0) {
1536                                                 timeout >>= 1;
1537 //TODO: the timeout to receive an answer for our renew should not be selected
1538 //with "timeout = lease_seconds / 2; ...; timeout = timeout / 2": it is often huge.
1539 //Waiting e.g. 4*3600 seconds for a reply does not make sense
1540 //(if reply isn't coming, we keep an open socket for hours),
1541 //it should be something like 10 seconds.
1542 //Also, it's probably best to try sending renew in kernel mode a few (3-5) times
1543 //and fall back to raw mode if it does not work.
1544                                                 continue;
1545                                         }
1546                                         /* else: error sending.
1547                                          * example: ENETUNREACH seen with server
1548                                          * which gave us bogus server ID 1.1.1.1
1549                                          * which wasn't reachable (and probably did not exist).
1550                                          */
1551                                 }
1552                                 /* Timed out or error, enter rebinding state */
1553                                 log1("entering rebinding state");
1554                                 state = REBINDING;
1555                                 /* fall right through */
1556                         case REBINDING:
1557                                 /* Switch to bcast receive */
1558                                 change_listen_mode(LISTEN_RAW);
1559                                 /* Lease is *really* about to run out,
1560                                  * try to find DHCP server using broadcast */
1561                                 if (timeout > 0) {
1562                                         /* send a broadcast renew request */
1563                                         send_renew(xid, 0 /*INADDR_ANY*/, requested_ip);
1564                                         timeout >>= 1;
1565                                         continue;
1566                                 }
1567                                 /* Timed out, enter init state */
1568                                 bb_error_msg("lease lost, entering init state");
1569                                 udhcp_run_script(NULL, "deconfig");
1570                                 state = INIT_SELECTING;
1571                                 client_config.first_secs = 0; /* make secs field count from 0 */
1572                                 /*timeout = 0; - already is */
1573                                 packet_num = 0;
1574                                 continue;
1575                         /* case RELEASED: */
1576                         }
1577                         /* yah, I know, *you* say it would never happen */
1578                         timeout = INT_MAX;
1579                         continue; /* back to main loop */
1580                 } /* if select timed out */
1581
1582                 /* select() didn't timeout, something happened */
1583
1584                 /* Is it a signal? */
1585                 /* note: udhcp_sp_read checks poll result before reading */
1586                 switch (udhcp_sp_read(pfds)) {
1587                 case SIGUSR1:
1588                         client_config.first_secs = 0; /* make secs field count from 0 */
1589                         already_waited_sec = 0;
1590                         perform_renew();
1591                         if (state == RENEW_REQUESTED) {
1592                                 /* We might be either on the same network
1593                                  * (in which case renew might work),
1594                                  * or we might be on a completely different one
1595                                  * (in which case renew won't ever succeed).
1596                                  * For the second case, must make sure timeout
1597                                  * is not too big, or else we can send
1598                                  * futile renew requests for hours.
1599                                  * (Ab)use -A TIMEOUT value (usually 20 sec)
1600                                  * as a cap on the timeout.
1601                                  */
1602                                 if (timeout > tryagain_timeout)
1603                                         timeout = tryagain_timeout;
1604                                 goto case_RENEW_REQUESTED;
1605                         }
1606                         /* Start things over */
1607                         packet_num = 0;
1608                         /* Kill any timeouts, user wants this to hurry along */
1609                         timeout = 0;
1610                         continue;
1611                 case SIGUSR2:
1612                         perform_release(server_addr, requested_ip);
1613                         timeout = INT_MAX;
1614                         continue;
1615                 case SIGTERM:
1616                         bb_error_msg("received %s", "SIGTERM");
1617                         goto ret0;
1618                 }
1619
1620                 /* Is it a packet? */
1621                 if (listen_mode == LISTEN_NONE || !pfds[1].revents)
1622                         continue; /* no */
1623
1624                 {
1625                         int len;
1626
1627                         /* A packet is ready, read it */
1628                         if (listen_mode == LISTEN_KERNEL)
1629                                 len = udhcp_recv_kernel_packet(&packet, sockfd);
1630                         else
1631                                 len = udhcp_recv_raw_packet(&packet, sockfd);
1632                         if (len == -1) {
1633                                 /* Error is severe, reopen socket */
1634                                 bb_error_msg("read error: "STRERROR_FMT", reopening socket" STRERROR_ERRNO);
1635                                 sleep(discover_timeout); /* 3 seconds by default */
1636                                 change_listen_mode(listen_mode); /* just close and reopen */
1637                         }
1638                         /* If this packet will turn out to be unrelated/bogus,
1639                          * we will go back and wait for next one.
1640                          * Be sure timeout is properly decreased. */
1641                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1642                         if (len < 0)
1643                                 continue;
1644                 }
1645
1646                 if (packet.xid != xid) {
1647                         log1("xid %x (our is %x), ignoring packet",
1648                                 (unsigned)packet.xid, (unsigned)xid);
1649                         continue;
1650                 }
1651
1652                 /* Ignore packets that aren't for us */
1653                 if (packet.hlen != 6
1654                  || memcmp(packet.chaddr, client_config.client_mac, 6) != 0
1655                 ) {
1656 //FIXME: need to also check that last 10 bytes are zero
1657                         log1("chaddr does not match, ignoring packet"); // log2?
1658                         continue;
1659                 }
1660
1661                 message = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
1662                 if (message == NULL) {
1663                         bb_error_msg("no message type option, ignoring packet");
1664                         continue;
1665                 }
1666
1667                 switch (state) {
1668                 case INIT_SELECTING:
1669                         /* Must be a DHCPOFFER */
1670                         if (*message == DHCPOFFER) {
1671                                 uint8_t *temp;
1672
1673 /* What exactly is server's IP? There are several values.
1674  * Example DHCP offer captured with tchdump:
1675  *
1676  * 10.34.25.254:67 > 10.34.25.202:68 // IP header's src
1677  * BOOTP fields:
1678  * Your-IP 10.34.25.202
1679  * Server-IP 10.34.32.125   // "next server" IP
1680  * Gateway-IP 10.34.25.254  // relay's address (if DHCP relays are in use)
1681  * DHCP options:
1682  * DHCP-Message Option 53, length 1: Offer
1683  * Server-ID Option 54, length 4: 10.34.255.7       // "server ID"
1684  * Default-Gateway Option 3, length 4: 10.34.25.254 // router
1685  *
1686  * We think that real server IP (one to use in renew/release)
1687  * is one in Server-ID option. But I am not 100% sure.
1688  * IP header's src and Gateway-IP (same in this example)
1689  * might work too.
1690  * "Next server" and router are definitely wrong ones to use, though...
1691  */
1692 /* We used to ignore pcakets without DHCP_SERVER_ID.
1693  * I've got user reports from people who run "address-less" servers.
1694  * They either supply DHCP_SERVER_ID of 0.0.0.0 or don't supply it at all.
1695  * They say ISC DHCP client supports this case.
1696  */
1697                                 server_addr = 0;
1698                                 temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
1699                                 if (!temp) {
1700                                         bb_error_msg("no server ID, using 0.0.0.0");
1701                                 } else {
1702                                         /* it IS unaligned sometimes, don't "optimize" */
1703                                         move_from_unaligned32(server_addr, temp);
1704                                 }
1705                                 /*xid = packet.xid; - already is */
1706                                 requested_ip = packet.yiaddr;
1707
1708                                 /* enter requesting state */
1709                                 state = REQUESTING;
1710                                 timeout = 0;
1711                                 packet_num = 0;
1712                                 already_waited_sec = 0;
1713                         }
1714                         continue;
1715                 case REQUESTING:
1716                 case RENEWING:
1717                 case RENEW_REQUESTED:
1718                 case REBINDING:
1719                         if (*message == DHCPACK) {
1720                                 unsigned start;
1721                                 uint32_t lease_seconds;
1722                                 struct in_addr temp_addr;
1723                                 uint8_t *temp;
1724
1725                                 temp = udhcp_get_option(&packet, DHCP_LEASE_TIME);
1726                                 if (!temp) {
1727                                         bb_error_msg("no lease time with ACK, using 1 hour lease");
1728                                         lease_seconds = 60 * 60;
1729                                 } else {
1730                                         /* it IS unaligned sometimes, don't "optimize" */
1731                                         move_from_unaligned32(lease_seconds, temp);
1732                                         lease_seconds = ntohl(lease_seconds);
1733                                         /* paranoia: must not be too small and not prone to overflows */
1734                                         if (lease_seconds < 0x10)
1735                                                 lease_seconds = 0x10;
1736                                         if (lease_seconds > 0x7fffffff / 1000)
1737                                                 lease_seconds = 0x7fffffff / 1000;
1738                                 }
1739 #if ENABLE_FEATURE_UDHCPC_ARPING
1740                                 if (opt & OPT_a) {
1741 /* RFC 2131 3.1 paragraph 5:
1742  * "The client receives the DHCPACK message with configuration
1743  * parameters. The client SHOULD perform a final check on the
1744  * parameters (e.g., ARP for allocated network address), and notes
1745  * the duration of the lease specified in the DHCPACK message. At this
1746  * point, the client is configured. If the client detects that the
1747  * address is already in use (e.g., through the use of ARP),
1748  * the client MUST send a DHCPDECLINE message to the server and restarts
1749  * the configuration process..." */
1750                                         if (!arpping(packet.yiaddr,
1751                                                         NULL,
1752                                                         (uint32_t) 0,
1753                                                         client_config.client_mac,
1754                                                         client_config.interface,
1755                                                         arpping_ms)
1756                                         ) {
1757                                                 bb_error_msg("offered address is in use "
1758                                                         "(got ARP reply), declining");
1759                                                 send_decline(/*xid,*/ server_addr, packet.yiaddr);
1760
1761                                                 if (state != REQUESTING)
1762                                                         udhcp_run_script(NULL, "deconfig");
1763                                                 change_listen_mode(LISTEN_RAW);
1764                                                 state = INIT_SELECTING;
1765                                                 client_config.first_secs = 0; /* make secs field count from 0 */
1766                                                 requested_ip = 0;
1767                                                 timeout = tryagain_timeout;
1768                                                 packet_num = 0;
1769                                                 already_waited_sec = 0;
1770                                                 continue; /* back to main loop */
1771                                         }
1772                                 }
1773 #endif
1774                                 /* enter bound state */
1775                                 temp_addr.s_addr = packet.yiaddr;
1776                                 bb_error_msg("lease of %s obtained, lease time %u",
1777                                         inet_ntoa(temp_addr), (unsigned)lease_seconds);
1778                                 requested_ip = packet.yiaddr;
1779
1780                                 start = monotonic_sec();
1781                                 udhcp_run_script(&packet, state == REQUESTING ? "bound" : "renew");
1782                                 already_waited_sec = (unsigned)monotonic_sec() - start;
1783                                 timeout = lease_seconds / 2;
1784                                 if ((unsigned)timeout < already_waited_sec) {
1785                                         /* Something went wrong. Back to discover state */
1786                                         timeout = already_waited_sec = 0;
1787                                 }
1788
1789                                 state = BOUND;
1790                                 change_listen_mode(LISTEN_NONE);
1791                                 if (opt & OPT_q) { /* quit after lease */
1792                                         goto ret0;
1793                                 }
1794                                 /* future renew failures should not exit (JM) */
1795                                 opt &= ~OPT_n;
1796 #if BB_MMU /* NOMMU case backgrounded earlier */
1797                                 if (!(opt & OPT_f)) {
1798                                         client_background();
1799                                         /* do not background again! */
1800                                         opt = ((opt & ~OPT_b) | OPT_f);
1801                                 }
1802 #endif
1803                                 /* make future renew packets use different xid */
1804                                 /* xid = random_xid(); ...but why bother? */
1805
1806                                 continue; /* back to main loop */
1807                         }
1808                         if (*message == DHCPNAK) {
1809                                 /* If network has more than one DHCP server,
1810                                  * "wrong" server can reply first, with a NAK.
1811                                  * Do not interpret it as a NAK from "our" server.
1812                                  */
1813                                 if (server_addr != 0) {
1814                                         uint32_t svid;
1815                                         uint8_t *temp;
1816
1817                                         temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
1818                                         if (!temp) {
1819  non_matching_svid:
1820                                                 log1("received DHCP NAK with wrong"
1821                                                         " server ID, ignoring packet");
1822                                                 continue;
1823                                         }
1824                                         move_from_unaligned32(svid, temp);
1825                                         if (svid != server_addr)
1826                                                 goto non_matching_svid;
1827                                 }
1828                                 /* return to init state */
1829                                 bb_error_msg("received %s", "DHCP NAK");
1830                                 udhcp_run_script(&packet, "nak");
1831                                 if (state != REQUESTING)
1832                                         udhcp_run_script(NULL, "deconfig");
1833                                 change_listen_mode(LISTEN_RAW);
1834                                 sleep(3); /* avoid excessive network traffic */
1835                                 state = INIT_SELECTING;
1836                                 client_config.first_secs = 0; /* make secs field count from 0 */
1837                                 requested_ip = 0;
1838                                 timeout = 0;
1839                                 packet_num = 0;
1840                                 already_waited_sec = 0;
1841                         }
1842                         continue;
1843                 /* case BOUND: - ignore all packets */
1844                 /* case RELEASED: - ignore all packets */
1845                 }
1846                 /* back to main loop */
1847         } /* for (;;) - main loop ends */
1848
1849  ret0:
1850         if (opt & OPT_R) /* release on quit */
1851                 perform_release(server_addr, requested_ip);
1852         retval = 0;
1853  ret:
1854         /*if (client_config.pidfile) - remove_pidfile has its own check */
1855                 remove_pidfile(client_config.pidfile);
1856         return retval;
1857 }