networking/udhcp/dhcpc.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * udhcp client
   4  * Russ Dill <Russ.Dill@asu.edu> July 2001
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19  */
  20 //applet:IF_UDHCPC(APPLET(udhcpc, BB_DIR_SBIN, BB_SUID_DROP))
  21
  22 //kbuild:lib-$(CONFIG_UDHCPC) += common.o packet.o signalpipe.o socket.o
  23 //kbuild:lib-$(CONFIG_UDHCPC) += dhcpc.o
  24 //kbuild:lib-$(CONFIG_FEATURE_UDHCPC_ARPING) += arpping.o
  25 //kbuild:lib-$(CONFIG_FEATURE_UDHCP_RFC3397) += domain_codec.o
  26
  27 #include <syslog.h>
  28 /* Override ENABLE_FEATURE_PIDFILE - ifupdown needs our pidfile to always exist */
  29 #define WANT_PIDFILE 1
  30 #include "common.h"
  31 #include "dhcpd.h"
  32 #include "dhcpc.h"
  33
  34 #include <netinet/if_ether.h>
  35 #include <linux/filter.h>
  36 #include <linux/if_packet.h>
  37
  38 #ifndef PACKET_AUXDATA
  39 # define PACKET_AUXDATA 8
  40 struct tpacket_auxdata {
  41         uint32_t tp_status;
  42         uint32_t tp_len;
  43         uint32_t tp_snaplen;
  44         uint16_t tp_mac;
  45         uint16_t tp_net;
  46         uint16_t tp_vlan_tci;
  47         uint16_t tp_padding;
  48 };
  49 #endif
  50
  51
  52 /* "struct client_config_t client_config" is in bb_common_bufsiz1 */
  53
  54
  55 #if ENABLE_LONG_OPTS
  56 static const char udhcpc_longopts[] ALIGN1 =
  57         "clientid-none\0"  No_argument       "C"
  58         "vendorclass\0"    Required_argument "V"
  59         "hostname\0"       Required_argument "H"
  60         "fqdn\0"           Required_argument "F"
  61         "interface\0"      Required_argument "i"
  62         "now\0"            No_argument       "n"
  63         "pidfile\0"        Required_argument "p"
  64         "quit\0"           No_argument       "q"
  65         "release\0"        No_argument       "R"
  66         "request\0"        Required_argument "r"
  67         "script\0"         Required_argument "s"
  68         "timeout\0"        Required_argument "T"
  69         "retries\0"        Required_argument "t"
  70         "tryagain\0"       Required_argument "A"
  71         "syslog\0"         No_argument       "S"
  72         "request-option\0" Required_argument "O"
  73         "no-default-options\0" No_argument   "o"
  74         "foreground\0"     No_argument       "f"
  75         USE_FOR_MMU(
  76         "background\0"     No_argument       "b"
  77         )
  78         "broadcast\0"      No_argument       "B"
  79         IF_FEATURE_UDHCPC_ARPING("arping\0"     Optional_argument "a")
  80         IF_FEATURE_UDHCP_PORT("client-port\0"   Required_argument "P")
  81         ;
  82 #endif
  83 /* Must match getopt32 option string order */
  84 enum {
  85         OPT_C = 1 << 0,
  86         OPT_V = 1 << 1,
  87         OPT_H = 1 << 2,
  88         OPT_h = 1 << 3,
  89         OPT_F = 1 << 4,
  90         OPT_i = 1 << 5,
  91         OPT_n = 1 << 6,
  92         OPT_p = 1 << 7,
  93         OPT_q = 1 << 8,
  94         OPT_R = 1 << 9,
  95         OPT_r = 1 << 10,
  96         OPT_s = 1 << 11,
  97         OPT_T = 1 << 12,
  98         OPT_t = 1 << 13,
  99         OPT_S = 1 << 14,
 100         OPT_A = 1 << 15,
 101         OPT_O = 1 << 16,
 102         OPT_o = 1 << 17,
 103         OPT_x = 1 << 18,
 104         OPT_f = 1 << 19,
 105         OPT_B = 1 << 20,
 106 /* The rest has variable bit positions, need to be clever */
 107         OPTBIT_B = 20,
 108         USE_FOR_MMU(             OPTBIT_b,)
 109         IF_FEATURE_UDHCPC_ARPING(OPTBIT_a,)
 110         IF_FEATURE_UDHCP_PORT(   OPTBIT_P,)
 111         USE_FOR_MMU(             OPT_b = 1 << OPTBIT_b,)
 112         IF_FEATURE_UDHCPC_ARPING(OPT_a = 1 << OPTBIT_a,)
 113         IF_FEATURE_UDHCP_PORT(   OPT_P = 1 << OPTBIT_P,)
 114 };
 115
 116
 117 /*** Script execution code ***/
 118
 119 /* get a rough idea of how long an option will be (rounding up...) */
 120 static const uint8_t len_of_option_as_string[] ALIGN1 = {
 121         [OPTION_IP              ] = sizeof("255.255.255.255 "),
 122         [OPTION_IP_PAIR         ] = sizeof("255.255.255.255 ") * 2,
 123         [OPTION_STATIC_ROUTES   ] = sizeof("255.255.255.255/32 255.255.255.255 "),
 124         [OPTION_6RD             ] = sizeof("132 128 ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 255.255.255.255 "),
 125         [OPTION_STRING          ] = 1,
 126         [OPTION_STRING_HOST     ] = 1,
 127 #if ENABLE_FEATURE_UDHCP_RFC3397
 128         [OPTION_DNS_STRING      ] = 1, /* unused */
 129         /* Hmmm, this severely overestimates size if SIP_SERVERS option
 130          * is in domain name form: N-byte option in binary form
 131          * mallocs ~16*N bytes. But it is freed almost at once.
 132          */
 133         [OPTION_SIP_SERVERS     ] = sizeof("255.255.255.255 "),
 134 #endif
 135 //      [OPTION_BOOLEAN         ] = sizeof("yes "),
 136         [OPTION_U8              ] = sizeof("255 "),
 137         [OPTION_U16             ] = sizeof("65535 "),
 138 //      [OPTION_S16             ] = sizeof("-32768 "),
 139         [OPTION_U32             ] = sizeof("4294967295 "),
 140         [OPTION_S32             ] = sizeof("-2147483684 "),
 141 };
 142
 143 /* note: ip is a pointer to an IP in network order, possibly misaliged */
 144 static int sprint_nip(char *dest, const char *pre, const uint8_t *ip)
 145 {
 146         return sprintf(dest, "%s%u.%u.%u.%u", pre, ip[0], ip[1], ip[2], ip[3]);
 147 }
 148
 149 /* really simple implementation, just count the bits */
 150 static int mton(uint32_t mask)
 151 {
 152         int i = 0;
 153         mask = ntohl(mask); /* 111110000-like bit pattern */
 154         while (mask) {
 155                 i++;
 156                 mask <<= 1;
 157         }
 158         return i;
 159 }
 160
 161 #if ENABLE_FEATURE_UDHCPC_SANITIZEOPT
 162 /* Check if a given label represents a valid DNS label
 163  * Return pointer to the first character after the label upon success,
 164  * NULL otherwise.
 165  * See RFC1035, 2.3.1
 166  */
 167 /* We don't need to be particularly anal. For example, allowing _, hyphen
 168  * at the end, or leading and trailing dots would be ok, since it
 169  * can't be used for attacks. (Leading hyphen can be, if someone uses
 170  * cmd "$hostname"
 171  * in the script: then hostname may be treated as an option)
 172  */
 173 static const char *valid_domain_label(const char *label)
 174 {
 175         unsigned char ch;
 176         unsigned pos = 0;
 177
 178         for (;;) {
 179                 ch = *label;
 180                 if ((ch|0x20) < 'a' || (ch|0x20) > 'z') {
 181                         if (ch < '0' || ch > '9') {
 182                                 if (ch == '\0' || ch == '.')
 183                                         return label;
 184                                 /* DNS allows only '-', but we are more permissive */
 185                                 if (ch != '-' && ch != '_')
 186                                         return NULL;
 187                         }
 188                 }
 189                 label++;
 190                 pos++;
 191                 //Do we want this?
 192                 //if (pos > 63) /* NS_MAXLABEL; labels must be 63 chars or less */
 193                 //      return NULL;
 194         }
 195 }
 196
 197 /* Check if a given name represents a valid DNS name */
 198 /* See RFC1035, 2.3.1 */
 199 static int good_hostname(const char *name)
 200 {
 201         //const char *start = name;
 202
 203         for (;;) {
 204                 name = valid_domain_label(name);
 205                 if (!name)
 206                         return 0;
 207                 if (!name[0])
 208                         return 1;
 209                         //Do we want this?
 210                         //return ((name - start) < 1025); /* NS_MAXDNAME */
 211                 name++;
 212                 if (*name == '\0')
 213                         return 1; // We allow trailing dot too
 214         }
 215 }
 216 #else
 217 # define good_hostname(name) 1
 218 #endif
 219
 220 /* Create "opt_name=opt_value" string */
 221 static NOINLINE char *xmalloc_optname_optval(uint8_t *option, const struct dhcp_optflag *optflag, const char *opt_name)
 222 {
 223         unsigned upper_length;
 224         int len, type, optlen;
 225         char *dest, *ret;
 226
 227         /* option points to OPT_DATA, need to go back to get OPT_LEN */
 228         len = option[-OPT_DATA + OPT_LEN];
 229
 230         type = optflag->flags & OPTION_TYPE_MASK;
 231         optlen = dhcp_option_lengths[type];
 232         upper_length = len_of_option_as_string[type]
 233                 * ((unsigned)(len + optlen) / (unsigned)optlen);
 234
 235         dest = ret = xmalloc(upper_length + strlen(opt_name) + 2);
 236         dest += sprintf(ret, "%s=", opt_name);
 237
 238         while (len >= optlen) {
 239                 switch (type) {
 240                 case OPTION_IP:
 241                 case OPTION_IP_PAIR:
 242                         dest += sprint_nip(dest, "", option);
 243                         if (type == OPTION_IP)
 244                                 break;
 245                         dest += sprint_nip(dest, "/", option + 4);
 246                         break;
 247 //              case OPTION_BOOLEAN:
 248 //                      dest += sprintf(dest, *option ? "yes" : "no");
 249 //                      break;
 250                 case OPTION_U8:
 251                         dest += sprintf(dest, "%u", *option);
 252                         break;
 253 //              case OPTION_S16:
 254                 case OPTION_U16: {
 255                         uint16_t val_u16;
 256                         move_from_unaligned16(val_u16, option);
 257                         dest += sprintf(dest, "%u", ntohs(val_u16));
 258                         break;
 259                 }
 260                 case OPTION_S32:
 261                 case OPTION_U32: {
 262                         uint32_t val_u32;
 263                         move_from_unaligned32(val_u32, option);
 264                         dest += sprintf(dest, type == OPTION_U32 ? "%lu" : "%ld", (unsigned long) ntohl(val_u32));
 265                         break;
 266                 }
 267                 /* Note: options which use 'return' instead of 'break'
 268                  * (for example, OPTION_STRING) skip the code which handles
 269                  * the case of list of options.
 270                  */
 271                 case OPTION_STRING:
 272                 case OPTION_STRING_HOST:
 273                         memcpy(dest, option, len);
 274                         dest[len] = '\0';
 275                         if (type == OPTION_STRING_HOST && !good_hostname(dest))
 276                                 safe_strncpy(dest, "bad", len);
 277                         return ret;
 278                 case OPTION_STATIC_ROUTES: {
 279                         /* Option binary format:
 280                          * mask [one byte, 0..32]
 281                          * ip [big endian, 0..4 bytes depending on mask]
 282                          * router [big endian, 4 bytes]
 283                          * may be repeated
 284                          *
 285                          * We convert it to a string "IP/MASK ROUTER IP2/MASK2 ROUTER2"
 286                          */
 287                         const char *pfx = "";
 288
 289                         while (len >= 1 + 4) { /* mask + 0-byte ip + router */
 290                                 uint32_t nip;
 291                                 uint8_t *p;
 292                                 unsigned mask;
 293                                 int bytes;
 294
 295                                 mask = *option++;
 296                                 if (mask > 32)
 297                                         break;
 298                                 len--;
 299
 300                                 nip = 0;
 301                                 p = (void*) &nip;
 302                                 bytes = (mask + 7) / 8; /* 0 -> 0, 1..8 -> 1, 9..16 -> 2 etc */
 303                                 while (--bytes >= 0) {
 304                                         *p++ = *option++;
 305                                         len--;
 306                                 }
 307                                 if (len < 4)
 308                                         break;
 309
 310                                 /* print ip/mask */
 311                                 dest += sprint_nip(dest, pfx, (void*) &nip);
 312                                 pfx = " ";
 313                                 dest += sprintf(dest, "/%u ", mask);
 314                                 /* print router */
 315                                 dest += sprint_nip(dest, "", option);
 316                                 option += 4;
 317                                 len -= 4;
 318                         }
 319
 320                         return ret;
 321                 }
 322                 case OPTION_6RD:
 323                         /* Option binary format (see RFC 5969):
 324                          *  0                   1                   2                   3
 325                          *  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
 326                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 327                          * |  OPTION_6RD   | option-length |  IPv4MaskLen  |  6rdPrefixLen |
 328                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 329                          * |                           6rdPrefix                           |
 330                          * ...                        (16 octets)                        ...
 331                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 332                          * ...                   6rdBRIPv4Address(es)                    ...
 333                          * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 334                          * We convert it to a string
 335                          * "IPv4MaskLen 6rdPrefixLen 6rdPrefix 6rdBRIPv4Address..."
 336                          *
 337                          * Sanity check: ensure that our length is at least 22 bytes, that
 338                          * IPv4MaskLen <= 32,
 339                          * 6rdPrefixLen <= 128,
 340                          * 6rdPrefixLen + (32 - IPv4MaskLen) <= 128
 341                          * (2nd condition need no check - it follows from 1st and 3rd).
 342                          * Else, return envvar with empty value ("optname=")
 343                          */
 344                         if (len >= (1 + 1 + 16 + 4)
 345                          && option[0] <= 32
 346                          && (option[1] + 32 - option[0]) <= 128
 347                         ) {
 348                                 /* IPv4MaskLen */
 349                                 dest += sprintf(dest, "%u ", *option++);
 350                                 /* 6rdPrefixLen */
 351                                 dest += sprintf(dest, "%u ", *option++);
 352                                 /* 6rdPrefix */
 353                                 dest += sprint_nip6(dest, /* "", */ option);
 354                                 option += 16;
 355                                 len -= 1 + 1 + 16 + 4;
 356                                 /* "+ 4" above corresponds to the length of IPv4 addr
 357                                  * we consume in the loop below */
 358                                 while (1) {
 359                                         /* 6rdBRIPv4Address(es) */
 360                                         dest += sprint_nip(dest, " ", option);
 361                                         option += 4;
 362                                         len -= 4; /* do we have yet another 4+ bytes? */
 363                                         if (len < 0)
 364                                                 break; /* no */
 365                                 }
 366                         }
 367
 368                         return ret;
 369 #if ENABLE_FEATURE_UDHCP_RFC3397
 370                 case OPTION_DNS_STRING:
 371                         /* unpack option into dest; use ret for prefix (i.e., "optname=") */
 372                         dest = dname_dec(option, len, ret);
 373                         if (dest) {
 374                                 free(ret);
 375                                 return dest;
 376                         }
 377                         /* error. return "optname=" string */
 378                         return ret;
 379                 case OPTION_SIP_SERVERS:
 380                         /* Option binary format:
 381                          * type: byte
 382                          * type=0: domain names, dns-compressed
 383                          * type=1: IP addrs
 384                          */
 385                         option++;
 386                         len--;
 387                         if (option[-1] == 0) {
 388                                 dest = dname_dec(option, len, ret);
 389                                 if (dest) {
 390                                         free(ret);
 391                                         return dest;
 392                                 }
 393                         } else
 394                         if (option[-1] == 1) {
 395                                 const char *pfx = "";
 396                                 while (1) {
 397                                         len -= 4;
 398                                         if (len < 0)
 399                                                 break;
 400                                         dest += sprint_nip(dest, pfx, option);
 401                                         pfx = " ";
 402                                         option += 4;
 403                                 }
 404                         }
 405                         return ret;
 406 #endif
 407                 } /* switch */
 408
 409                 /* If we are here, try to format any remaining data
 410                  * in the option as another, similarly-formatted option
 411                  */
 412                 option += optlen;
 413                 len -= optlen;
 414 // TODO: it can be a list only if (optflag->flags & OPTION_LIST).
 415 // Should we bail out/warn if we see multi-ip option which is
 416 // not allowed to be such (for example, DHCP_BROADCAST)? -
 417                 if (len < optlen /* || !(optflag->flags & OPTION_LIST) */)
 418                         break;
 419                 *dest++ = ' ';
 420                 *dest = '\0';
 421         } /* while */
 422
 423         return ret;
 424 }
 425
 426 /* put all the parameters into the environment */
 427 static char **fill_envp(struct dhcp_packet *packet)
 428 {
 429         int envc;
 430         int i;
 431         char **envp, **curr;
 432         const char *opt_name;
 433         uint8_t *temp;
 434         uint8_t overload = 0;
 435
 436 #define BITMAP unsigned
 437 #define BBITS (sizeof(BITMAP) * 8)
 438 #define BMASK(i) (1 << (i & (sizeof(BITMAP) * 8 - 1)))
 439 #define FOUND_OPTS(i) (found_opts[(unsigned)i / BBITS])
 440         BITMAP found_opts[256 / BBITS];
 441
 442         memset(found_opts, 0, sizeof(found_opts));
 443
 444         /* We need 6 elements for:
 445          * "interface=IFACE"
 446          * "ip=N.N.N.N" from packet->yiaddr
 447          * "siaddr=IP" from packet->siaddr_nip (unless 0)
 448          * "boot_file=FILE" from packet->file (unless overloaded)
 449          * "sname=SERVER_HOSTNAME" from packet->sname (unless overloaded)
 450          * terminating NULL
 451          */
 452         envc = 6;
 453         /* +1 element for each option, +2 for subnet option: */
 454         if (packet) {
 455                 /* note: do not search for "pad" (0) and "end" (255) options */
 456 //TODO: change logic to scan packet _once_
 457                 for (i = 1; i < 255; i++) {
 458                         temp = udhcp_get_option(packet, i);
 459                         if (temp) {
 460                                 if (i == DHCP_OPTION_OVERLOAD)
 461                                         overload |= *temp;
 462                                 else if (i == DHCP_SUBNET)
 463                                         envc++; /* for $mask */
 464                                 envc++;
 465                                 /*if (i != DHCP_MESSAGE_TYPE)*/
 466                                 FOUND_OPTS(i) |= BMASK(i);
 467                         }
 468                 }
 469         }
 470         curr = envp = xzalloc(sizeof(envp[0]) * envc);
 471
 472         *curr = xasprintf("interface=%s", client_config.interface);
 473         putenv(*curr++);
 474
 475         if (!packet)
 476                 return envp;
 477
 478         /* Export BOOTP fields. Fields we don't (yet?) export:
 479          * uint8_t op;      // always BOOTREPLY
 480          * uint8_t htype;   // hardware address type. 1 = 10mb ethernet
 481          * uint8_t hlen;    // hardware address length
 482          * uint8_t hops;    // used by relay agents only
 483          * uint32_t xid;
 484          * uint16_t secs;   // elapsed since client began acquisition/renewal
 485          * uint16_t flags;  // only one flag so far: bcast. Never set by server
 486          * uint32_t ciaddr; // client IP (usually == yiaddr. can it be different
 487          *                  // if during renew server wants to give us different IP?)
 488          * uint32_t gateway_nip; // relay agent IP address
 489          * uint8_t chaddr[16]; // link-layer client hardware address (MAC)
 490          * TODO: export gateway_nip as $giaddr?
 491          */
 492         /* Most important one: yiaddr as $ip */
 493         *curr = xmalloc(sizeof("ip=255.255.255.255"));
 494         sprint_nip(*curr, "ip=", (uint8_t *) &packet->yiaddr);
 495         putenv(*curr++);
 496         if (packet->siaddr_nip) {
 497                 /* IP address of next server to use in bootstrap */
 498                 *curr = xmalloc(sizeof("siaddr=255.255.255.255"));
 499                 sprint_nip(*curr, "siaddr=", (uint8_t *) &packet->siaddr_nip);
 500                 putenv(*curr++);
 501         }
 502         if (!(overload & FILE_FIELD) && packet->file[0]) {
 503                 /* watch out for invalid packets */
 504                 *curr = xasprintf("boot_file=%."DHCP_PKT_FILE_LEN_STR"s", packet->file);
 505                 putenv(*curr++);
 506         }
 507         if (!(overload & SNAME_FIELD) && packet->sname[0]) {
 508                 /* watch out for invalid packets */
 509                 *curr = xasprintf("sname=%."DHCP_PKT_SNAME_LEN_STR"s", packet->sname);
 510                 putenv(*curr++);
 511         }
 512
 513         /* Export known DHCP options */
 514         opt_name = dhcp_option_strings;
 515         i = 0;
 516         while (*opt_name) {
 517                 uint8_t code = dhcp_optflags[i].code;
 518                 BITMAP *found_ptr = &FOUND_OPTS(code);
 519                 BITMAP found_mask = BMASK(code);
 520                 if (!(*found_ptr & found_mask))
 521                         goto next;
 522                 *found_ptr &= ~found_mask; /* leave only unknown options */
 523                 temp = udhcp_get_option(packet, code);
 524                 *curr = xmalloc_optname_optval(temp, &dhcp_optflags[i], opt_name);
 525                 putenv(*curr++);
 526                 if (code == DHCP_SUBNET) {
 527                         /* Subnet option: make things like "$ip/$mask" possible */
 528                         uint32_t subnet;
 529                         move_from_unaligned32(subnet, temp);
 530                         *curr = xasprintf("mask=%u", mton(subnet));
 531                         putenv(*curr++);
 532                 }
 533  next:
 534                 opt_name += strlen(opt_name) + 1;
 535                 i++;
 536         }
 537         /* Export unknown options */
 538         for (i = 0; i < 256;) {
 539                 BITMAP bitmap = FOUND_OPTS(i);
 540                 if (!bitmap) {
 541                         i += BBITS;
 542                         continue;
 543                 }
 544                 if (bitmap & BMASK(i)) {
 545                         unsigned len, ofs;
 546
 547                         temp = udhcp_get_option(packet, i);
 548                         /* udhcp_get_option returns ptr to data portion,
 549                          * need to go back to get len
 550                          */
 551                         len = temp[-OPT_DATA + OPT_LEN];
 552                         *curr = xmalloc(sizeof("optNNN=") + 1 + len*2);
 553                         ofs = sprintf(*curr, "opt%u=", i);
 554                         *bin2hex(*curr + ofs, (void*) temp, len) = '\0';
 555                         putenv(*curr++);
 556                 }
 557                 i++;
 558         }
 559
 560         return envp;
 561 }
 562
 563 /* Call a script with a par file and env vars */
 564 static void udhcp_run_script(struct dhcp_packet *packet, const char *name)
 565 {
 566         char **envp, **curr;
 567         char *argv[3];
 568
 569         envp = fill_envp(packet);
 570
 571         /* call script */
 572         log1("executing %s %s", client_config.script, name);
 573         argv[0] = (char*) client_config.script;
 574         argv[1] = (char*) name;
 575         argv[2] = NULL;
 576         spawn_and_wait(argv);
 577
 578         for (curr = envp; *curr; curr++) {
 579                 log2(" %s", *curr);
 580                 bb_unsetenv_and_free(*curr);
 581         }
 582         free(envp);
 583 }
 584
 585
 586 /*** Sending/receiving packets ***/
 587
 588 static ALWAYS_INLINE uint32_t random_xid(void)
 589 {
 590         return rand();
 591 }
 592
 593 /* Initialize the packet with the proper defaults */
 594 static void init_packet(struct dhcp_packet *packet, char type)
 595 {
 596         uint16_t secs;
 597
 598         /* Fill in: op, htype, hlen, cookie fields; message type option: */
 599         udhcp_init_header(packet, type);
 600
 601         packet->xid = random_xid();
 602
 603         client_config.last_secs = monotonic_sec();
 604         if (client_config.first_secs == 0)
 605                 client_config.first_secs = client_config.last_secs;
 606         secs = client_config.last_secs - client_config.first_secs;
 607         packet->secs = htons(secs);
 608
 609         memcpy(packet->chaddr, client_config.client_mac, 6);
 610         if (client_config.clientid)
 611                 udhcp_add_binary_option(packet, client_config.clientid);
 612 }
 613
 614 static void add_client_options(struct dhcp_packet *packet)
 615 {
 616         int i, end, len;
 617
 618         udhcp_add_simple_option(packet, DHCP_MAX_SIZE, htons(IP_UDP_DHCP_SIZE));
 619
 620         /* Add a "param req" option with the list of options we'd like to have
 621          * from stubborn DHCP servers. Pull the data from the struct in common.c.
 622          * No bounds checking because it goes towards the head of the packet. */
 623         end = udhcp_end_option(packet->options);
 624         len = 0;
 625         for (i = 1; i < DHCP_END; i++) {
 626                 if (client_config.opt_mask[i >> 3] & (1 << (i & 7))) {
 627                         packet->options[end + OPT_DATA + len] = i;
 628                         len++;
 629                 }
 630         }
 631         if (len) {
 632                 packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
 633                 packet->options[end + OPT_LEN] = len;
 634                 packet->options[end + OPT_DATA + len] = DHCP_END;
 635         }
 636
 637         if (client_config.vendorclass)
 638                 udhcp_add_binary_option(packet, client_config.vendorclass);
 639         if (client_config.hostname)
 640                 udhcp_add_binary_option(packet, client_config.hostname);
 641         if (client_config.fqdn)
 642                 udhcp_add_binary_option(packet, client_config.fqdn);
 643
 644         /* Request broadcast replies if we have no IP addr */
 645         if ((option_mask32 & OPT_B) && packet->ciaddr == 0)
 646                 packet->flags |= htons(BROADCAST_FLAG);
 647
 648         /* Add -x options if any */
 649         {
 650                 struct option_set *curr = client_config.options;
 651                 while (curr) {
 652                         udhcp_add_binary_option(packet, curr->data);
 653                         curr = curr->next;
 654                 }
 655 //              if (client_config.sname)
 656 //                      strncpy((char*)packet->sname, client_config.sname, sizeof(packet->sname) - 1);
 657 //              if (client_config.boot_file)
 658 //                      strncpy((char*)packet->file, client_config.boot_file, sizeof(packet->file) - 1);
 659         }
 660
 661         // This will be needed if we remove -V VENDOR_STR in favor of
 662         // -x vendor:VENDOR_STR
 663         //if (!udhcp_find_option(packet.options, DHCP_VENDOR))
 664         //      /* not set, set the default vendor ID */
 665         //      ...add (DHCP_VENDOR, "udhcp "BB_VER) opt...
 666 }
 667
 668 /* RFC 2131
 669  * 4.4.4 Use of broadcast and unicast
 670  *
 671  * The DHCP client broadcasts DHCPDISCOVER, DHCPREQUEST and DHCPINFORM
 672  * messages, unless the client knows the address of a DHCP server.
 673  * The client unicasts DHCPRELEASE messages to the server. Because
 674  * the client is declining the use of the IP address supplied by the server,
 675  * the client broadcasts DHCPDECLINE messages.
 676  *
 677  * When the DHCP client knows the address of a DHCP server, in either
 678  * INIT or REBOOTING state, the client may use that address
 679  * in the DHCPDISCOVER or DHCPREQUEST rather than the IP broadcast address.
 680  * The client may also use unicast to send DHCPINFORM messages
 681  * to a known DHCP server. If the client receives no response to DHCP
 682  * messages sent to the IP address of a known DHCP server, the DHCP
 683  * client reverts to using the IP broadcast address.
 684  */
 685
 686 static int raw_bcast_from_client_config_ifindex(struct dhcp_packet *packet, uint32_t src_nip)
 687 {
 688         return udhcp_send_raw_packet(packet,
 689                 /*src*/ src_nip, CLIENT_PORT,
 690                 /*dst*/ INADDR_BROADCAST, SERVER_PORT, MAC_BCAST_ADDR,
 691                 client_config.ifindex);
 692 }
 693
 694 static int bcast_or_ucast(struct dhcp_packet *packet, uint32_t ciaddr, uint32_t server)
 695 {
 696         if (server) {
 697                 /* Without MSG_DONTROUTE, the packet was seen routed over
 698                  * _other interface_ if server ID is bogus (example: 1.1.1.1).
 699                  */
 700                 return udhcp_send_kernel_packet(packet,
 701                         ciaddr, CLIENT_PORT,
 702                         server, SERVER_PORT,
 703                         /*send_flags: "to hosts only on directly connected networks" */ MSG_DONTROUTE
 704                 );
 705         }
 706         return raw_bcast_from_client_config_ifindex(packet, ciaddr);
 707 }
 708
 709 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
 710 /* NOINLINE: limit stack usage in caller */
 711 static NOINLINE int send_discover(uint32_t xid, uint32_t requested)
 712 {
 713         struct dhcp_packet packet;
 714
 715         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 716          * random xid field (we override it below),
 717          * client-id option (unless -C), message type option:
 718          */
 719         init_packet(&packet, DHCPDISCOVER);
 720
 721         packet.xid = xid;
 722         if (requested)
 723                 udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 724
 725         /* Add options: maxsize,
 726          * optionally: hostname, fqdn, vendorclass,
 727          * "param req" option according to -O, options specified with -x
 728          */
 729         add_client_options(&packet);
 730
 731         bb_error_msg("sending %s", "discover");
 732         return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
 733 }
 734
 735 /* Broadcast a DHCP request message */
 736 /* RFC 2131 3.1 paragraph 3:
 737  * "The client _broadcasts_ a DHCPREQUEST message..."
 738  */
 739 /* NOINLINE: limit stack usage in caller */
 740 static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requested)
 741 {
 742         struct dhcp_packet packet;
 743         struct in_addr temp_addr;
 744
 745 /*
 746  * RFC 2131 4.3.2 DHCPREQUEST message
 747  * ...
 748  * If the DHCPREQUEST message contains a 'server identifier'
 749  * option, the message is in response to a DHCPOFFER message.
 750  * Otherwise, the message is a request to verify or extend an
 751  * existing lease. If the client uses a 'client identifier'
 752  * in a DHCPREQUEST message, it MUST use that same 'client identifier'
 753  * in all subsequent messages. If the client included a list
 754  * of requested parameters in a DHCPDISCOVER message, it MUST
 755  * include that list in all subsequent messages.
 756  */
 757         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 758          * random xid field (we override it below),
 759          * client-id option (unless -C), message type option:
 760          */
 761         init_packet(&packet, DHCPREQUEST);
 762
 763         packet.xid = xid;
 764         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 765
 766         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 767
 768         /* Add options: maxsize,
 769          * optionally: hostname, fqdn, vendorclass,
 770          * "param req" option according to -O, and options specified with -x
 771          */
 772         add_client_options(&packet);
 773
 774         temp_addr.s_addr = requested;
 775         bb_error_msg("sending select for %s", inet_ntoa(temp_addr));
 776         return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
 777 }
 778
 779 /* Unicast or broadcast a DHCP renew message */
 780 /* NOINLINE: limit stack usage in caller */
 781 static NOINLINE int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
 782 {
 783         struct dhcp_packet packet;
 784         struct in_addr temp_addr;
 785
 786 /*
 787  * RFC 2131 4.3.2 DHCPREQUEST message
 788  * ...
 789  * DHCPREQUEST generated during RENEWING state:
 790  *
 791  * 'server identifier' MUST NOT be filled in, 'requested IP address'
 792  * option MUST NOT be filled in, 'ciaddr' MUST be filled in with
 793  * client's IP address. In this situation, the client is completely
 794  * configured, and is trying to extend its lease. This message will
 795  * be unicast, so no relay agents will be involved in its
 796  * transmission.  Because 'giaddr' is therefore not filled in, the
 797  * DHCP server will trust the value in 'ciaddr', and use it when
 798  * replying to the client.
 799  */
 800         /* Fill in: op, htype, hlen, cookie, chaddr fields,
 801          * random xid field (we override it below),
 802          * client-id option (unless -C), message type option:
 803          */
 804         init_packet(&packet, DHCPREQUEST);
 805
 806         packet.xid = xid;
 807         packet.ciaddr = ciaddr;
 808
 809         /* Add options: maxsize,
 810          * optionally: hostname, fqdn, vendorclass,
 811          * "param req" option according to -O, and options specified with -x
 812          */
 813         add_client_options(&packet);
 814
 815         temp_addr.s_addr = server;
 816         bb_error_msg("sending renew to %s", inet_ntoa(temp_addr));
 817         return bcast_or_ucast(&packet, ciaddr, server);
 818 }
 819
 820 #if ENABLE_FEATURE_UDHCPC_ARPING
 821 /* Broadcast a DHCP decline message */
 822 /* NOINLINE: limit stack usage in caller */
 823 static NOINLINE int send_decline(/*uint32_t xid,*/ uint32_t server, uint32_t requested)
 824 {
 825         struct dhcp_packet packet;
 826
 827         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 828          * client-id option (unless -C), message type option:
 829          */
 830         init_packet(&packet, DHCPDECLINE);
 831
 832 #if 0
 833         /* RFC 2131 says DHCPDECLINE's xid is randomly selected by client,
 834          * but in case the server is buggy and wants DHCPDECLINE's xid
 835          * to match the xid which started entire handshake,
 836          * we use the same xid we used in initial DHCPDISCOVER:
 837          */
 838         packet.xid = xid;
 839 #endif
 840         /* DHCPDECLINE uses "requested ip", not ciaddr, to store offered IP */
 841         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 842
 843         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 844
 845         bb_error_msg("sending %s", "decline");
 846         return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
 847 }
 848 #endif
 849
 850 /* Unicast a DHCP release message */
 851 static int send_release(uint32_t server, uint32_t ciaddr)
 852 {
 853         struct dhcp_packet packet;
 854
 855         /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
 856          * client-id option (unless -C), message type option:
 857          */
 858         init_packet(&packet, DHCPRELEASE);
 859
 860         /* DHCPRELEASE uses ciaddr, not "requested ip", to store IP being released */
 861         packet.ciaddr = ciaddr;
 862
 863         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
 864
 865         bb_error_msg("sending %s", "release");
 866         /* Note: normally we unicast here since "server" is not zero.
 867          * However, there _are_ people who run "address-less" DHCP servers,
 868          * and reportedly ISC dhcp client and Windows allow that.
 869          */
 870         return bcast_or_ucast(&packet, ciaddr, server);
 871 }
 872
 873 /* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */
 874 /* NOINLINE: limit stack usage in caller */
 875 static NOINLINE int udhcp_recv_raw_packet(struct dhcp_packet *dhcp_pkt, int fd)
 876 {
 877         int bytes;
 878         struct ip_udp_dhcp_packet packet;
 879         uint16_t check;
 880         unsigned char cmsgbuf[CMSG_LEN(sizeof(struct tpacket_auxdata))];
 881         struct iovec iov;
 882         struct msghdr msg;
 883         struct cmsghdr *cmsg;
 884
 885         /* used to use just safe_read(fd, &packet, sizeof(packet))
 886          * but we need to check for TP_STATUS_CSUMNOTREADY :(
 887          */
 888         iov.iov_base = &packet;
 889         iov.iov_len = sizeof(packet);
 890         memset(&msg, 0, sizeof(msg));
 891         msg.msg_iov = &iov;
 892         msg.msg_iovlen = 1;
 893         msg.msg_control = cmsgbuf;
 894         msg.msg_controllen = sizeof(cmsgbuf);
 895         for (;;) {
 896                 bytes = recvmsg(fd, &msg, 0);
 897                 if (bytes < 0) {
 898                         if (errno == EINTR)
 899                                 continue;
 900                         log1("packet read error, ignoring");
 901                         /* NB: possible down interface, etc. Caller should pause. */
 902                         return bytes; /* returns -1 */
 903                 }
 904                 break;
 905         }
 906
 907         if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) {
 908                 log1("packet is too short, ignoring");
 909                 return -2;
 910         }
 911
 912         if (bytes < ntohs(packet.ip.tot_len)) {
 913                 /* packet is bigger than sizeof(packet), we did partial read */
 914                 log1("oversized packet, ignoring");
 915                 return -2;
 916         }
 917
 918         /* ignore any extra garbage bytes */
 919         bytes = ntohs(packet.ip.tot_len);
 920
 921         /* make sure its the right packet for us, and that it passes sanity checks */
 922         if (packet.ip.protocol != IPPROTO_UDP
 923          || packet.ip.version != IPVERSION
 924          || packet.ip.ihl != (sizeof(packet.ip) >> 2)
 925          || packet.udp.dest != htons(CLIENT_PORT)
 926         /* || bytes > (int) sizeof(packet) - can't happen */
 927          || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
 928         ) {
 929                 log1("unrelated/bogus packet, ignoring");
 930                 return -2;
 931         }
 932
 933         /* verify IP checksum */
 934         check = packet.ip.check;
 935         packet.ip.check = 0;
 936         if (check != inet_cksum((uint16_t *)&packet.ip, sizeof(packet.ip))) {
 937                 log1("bad IP header checksum, ignoring");
 938                 return -2;
 939         }
 940
 941         for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
 942                 if (cmsg->cmsg_level == SOL_PACKET
 943                  && cmsg->cmsg_type == PACKET_AUXDATA
 944                 ) {
 945                         /* some VMs don't checksum UDP and TCP data
 946                          * they send to the same physical machine,
 947                          * here we detect this case:
 948                          */
 949                         struct tpacket_auxdata *aux = (void *)CMSG_DATA(cmsg);
 950                         if (aux->tp_status & TP_STATUS_CSUMNOTREADY)
 951                                 goto skip_udp_sum_check;
 952                 }
 953         }
 954
 955         /* verify UDP checksum. IP header has to be modified for this */
 956         memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
 957         /* ip.xx fields which are not memset: protocol, check, saddr, daddr */
 958         packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
 959         check = packet.udp.check;
 960         packet.udp.check = 0;
 961         if (check && check != inet_cksum((uint16_t *)&packet, bytes)) {
 962                 log1("packet with bad UDP checksum received, ignoring");
 963                 return -2;
 964         }
 965  skip_udp_sum_check:
 966
 967         if (packet.data.cookie != htonl(DHCP_MAGIC)) {
 968                 bb_error_msg("packet with bad magic, ignoring");
 969                 return -2;
 970         }
 971
 972         log1("received %s", "a packet");
 973         udhcp_dump_packet(&packet.data);
 974
 975         bytes -= sizeof(packet.ip) + sizeof(packet.udp);
 976         memcpy(dhcp_pkt, &packet.data, bytes);
 977         return bytes;
 978 }
 979
 980
 981 /*** Main ***/
 982
 983 static int sockfd = -1;
 984
 985 #define LISTEN_NONE   0
 986 #define LISTEN_KERNEL 1
 987 #define LISTEN_RAW    2
 988 static smallint listen_mode;
 989
 990 /* initial state: (re)start DHCP negotiation */
 991 #define INIT_SELECTING  0
 992 /* discover was sent, DHCPOFFER reply received */
 993 #define REQUESTING      1
 994 /* select/renew was sent, DHCPACK reply received */
 995 #define BOUND           2
 996 /* half of lease passed, want to renew it by sending unicast renew requests */
 997 #define RENEWING        3
 998 /* renew requests were not answered, lease is almost over, send broadcast renew */
 999 #define REBINDING       4
1000 /* manually requested renew (SIGUSR1) */
1001 #define RENEW_REQUESTED 5
1002 /* release, possibly manually requested (SIGUSR2) */
1003 #define RELEASED        6
1004 static smallint state;
1005
1006 static int udhcp_raw_socket(int ifindex)
1007 {
1008         int fd;
1009         struct sockaddr_ll sock;
1010
1011         log2("opening raw socket on ifindex %d", ifindex);
1012
1013         fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
1014         /* ^^^^^
1015          * SOCK_DGRAM: remove link-layer headers on input (SOCK_RAW keeps them)
1016          * ETH_P_IP: want to receive only packets with IPv4 eth type
1017          */
1018         log2("got raw socket fd");
1019
1020         memset(&sock, 0, sizeof(sock)); /* let's be deterministic */
1021         sock.sll_family = AF_PACKET;
1022         sock.sll_protocol = htons(ETH_P_IP);
1023         sock.sll_ifindex = ifindex;
1024         /*sock.sll_hatype = ARPHRD_???;*/
1025         /*sock.sll_pkttype = PACKET_???;*/
1026         /*sock.sll_halen = ???;*/
1027         /*sock.sll_addr[8] = ???;*/
1028         xbind(fd, (struct sockaddr *) &sock, sizeof(sock));
1029
1030 #if 0 /* Several users reported breakage when BPF filter is used */
1031         if (CLIENT_PORT == 68) {
1032                 /* Use only if standard port is in use */
1033                 /*
1034                  *      I've selected not to see LL header, so BPF doesn't see it, too.
1035                  *      The filter may also pass non-IP and non-ARP packets, but we do
1036                  *      a more complete check when receiving the message in userspace.
1037                  *
1038                  * and filter shamelessly stolen from:
1039                  *
1040                  *      http://www.flamewarmaster.de/software/dhcpclient/
1041                  *
1042                  * There are a few other interesting ideas on that page (look under
1043                  * "Motivation").  Use of netlink events is most interesting.  Think
1044                  * of various network servers listening for events and reconfiguring.
1045                  * That would obsolete sending HUP signals and/or make use of restarts.
1046                  *
1047                  * Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
1048                  * License: GPL v2.
1049                  */
1050                 static const struct sock_filter filter_instr[] = {
1051                         /* load 9th byte (protocol) */
1052                         BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
1053                         /* jump to L1 if it is IPPROTO_UDP, else to L4 */
1054                         BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 0, 6),
1055                         /* L1: load halfword from offset 6 (flags and frag offset) */
1056                         BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 6),
1057                         /* jump to L4 if any bits in frag offset field are set, else to L2 */
1058                         BPF_JUMP(BPF_JMP|BPF_JSET|BPF_K, 0x1fff, 4, 0),
1059                         /* L2: skip IP header (load index reg with header len) */
1060                         BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0),
1061                         /* load udp destination port from halfword[header_len + 2] */
1062                         BPF_STMT(BPF_LD|BPF_H|BPF_IND, 2),
1063                         /* jump to L3 if udp dport is CLIENT_PORT, else to L4 */
1064                         BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 68, 0, 1),
1065                         /* L3: accept packet ("accept 0x7fffffff bytes") */
1066                         /* Accepting 0xffffffff works too but kernel 2.6.19 is buggy */
1067                         BPF_STMT(BPF_RET|BPF_K, 0x7fffffff),
1068                         /* L4: discard packet ("accept zero bytes") */
1069                         BPF_STMT(BPF_RET|BPF_K, 0),
1070                 };
1071                 static const struct sock_fprog filter_prog = {
1072                         .len = sizeof(filter_instr) / sizeof(filter_instr[0]),
1073                         /* casting const away: */
1074                         .filter = (struct sock_filter *) filter_instr,
1075                 };
1076                 /* Ignoring error (kernel may lack support for this) */
1077                 if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
1078                                 sizeof(filter_prog)) >= 0)
1079                         log1("attached filter to raw socket fd"); // log?
1080         }
1081 #endif
1082
1083         if (setsockopt_1(fd, SOL_PACKET, PACKET_AUXDATA) != 0) {
1084                 if (errno != ENOPROTOOPT)
1085                         log1("can't set PACKET_AUXDATA on raw socket");
1086         }
1087
1088         log1("created raw socket");
1089
1090         return fd;
1091 }
1092
1093 static void change_listen_mode(int new_mode)
1094 {
1095         log1("entering listen mode: %s",
1096                 new_mode != LISTEN_NONE
1097                         ? (new_mode == LISTEN_KERNEL ? "kernel" : "raw")
1098                         : "none"
1099         );
1100
1101         listen_mode = new_mode;
1102         if (sockfd >= 0) {
1103                 close(sockfd);
1104                 sockfd = -1;
1105         }
1106         if (new_mode == LISTEN_KERNEL)
1107                 sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
1108         else if (new_mode != LISTEN_NONE)
1109                 sockfd = udhcp_raw_socket(client_config.ifindex);
1110         /* else LISTEN_NONE: sockfd stays closed */
1111 }
1112
1113 /* Called only on SIGUSR1 */
1114 static void perform_renew(void)
1115 {
1116         bb_error_msg("performing DHCP renew");
1117         switch (state) {
1118         case BOUND:
1119                 change_listen_mode(LISTEN_KERNEL);
1120         case RENEWING:
1121         case REBINDING:
1122                 state = RENEW_REQUESTED;
1123                 break;
1124         case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
1125                 udhcp_run_script(NULL, "deconfig");
1126         case REQUESTING:
1127         case RELEASED:
1128                 change_listen_mode(LISTEN_RAW);
1129                 state = INIT_SELECTING;
1130                 break;
1131         case INIT_SELECTING:
1132                 break;
1133         }
1134 }
1135
1136 static void perform_release(uint32_t server_addr, uint32_t requested_ip)
1137 {
1138         char buffer[sizeof("255.255.255.255")];
1139         struct in_addr temp_addr;
1140
1141         /* send release packet */
1142         if (state == BOUND
1143          || state == RENEWING
1144          || state == REBINDING
1145          || state == RENEW_REQUESTED
1146         ) {
1147                 temp_addr.s_addr = server_addr;
1148                 strcpy(buffer, inet_ntoa(temp_addr));
1149                 temp_addr.s_addr = requested_ip;
1150                 bb_error_msg("unicasting a release of %s to %s",
1151                                 inet_ntoa(temp_addr), buffer);
1152                 send_release(server_addr, requested_ip); /* unicast */
1153         }
1154         bb_error_msg("entering released state");
1155 /*
1156  * We can be here on: SIGUSR2,
1157  * or on exit (SIGTERM) and -R "release on quit" is specified.
1158  * Users requested to be notified in all cases, even if not in one
1159  * of the states above.
1160  */
1161         udhcp_run_script(NULL, "deconfig");
1162
1163         change_listen_mode(LISTEN_NONE);
1164         state = RELEASED;
1165 }
1166
1167 static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
1168 {
1169         uint8_t *storage;
1170         int len = strnlen(str, 255);
1171         storage = xzalloc(len + extra + OPT_DATA);
1172         storage[OPT_CODE] = code;
1173         storage[OPT_LEN] = len + extra;
1174         memcpy(storage + extra + OPT_DATA, str, len);
1175         return storage;
1176 }
1177
1178 #if BB_MMU
1179 static void client_background(void)
1180 {
1181         bb_daemonize(0);
1182         logmode &= ~LOGMODE_STDIO;
1183         /* rewrite pidfile, as our pid is different now */
1184         write_pidfile(client_config.pidfile);
1185 }
1186 #endif
1187
1188 //usage:#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
1189 //usage:# define IF_UDHCP_VERBOSE(...) __VA_ARGS__
1190 //usage:#else
1191 //usage:# define IF_UDHCP_VERBOSE(...)
1192 //usage:#endif
1193 //usage:#define udhcpc_trivial_usage
1194 //usage:       "[-fbq"IF_UDHCP_VERBOSE("v")"RB]"IF_FEATURE_UDHCPC_ARPING(" [-a[MSEC]]")" [-t N] [-T SEC] [-A SEC/-n]\n"
1195 //usage:       "        [-i IFACE]"IF_FEATURE_UDHCP_PORT(" [-P PORT]")" [-s PROG] [-p PIDFILE]\n"
1196 //usage:       "        [-oC] [-r IP] [-V VENDOR] [-F NAME] [-x OPT:VAL]... [-O OPT]..."
1197 //usage:#define udhcpc_full_usage "\n"
1198 //usage:     "\n        -i IFACE        Interface to use (default eth0)"
1199 //usage:        IF_FEATURE_UDHCP_PORT(
1200 //usage:     "\n        -P PORT         Use PORT (default 68)"
1201 //usage:        )
1202 //usage:     "\n        -s PROG         Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
1203 //usage:     "\n        -p FILE         Create pidfile"
1204 //usage:     "\n        -B              Request broadcast replies"
1205 //usage:     "\n        -t N            Send up to N discover packets (default 3)"
1206 //usage:     "\n        -T SEC          Pause between packets (default 3)"
1207 //usage:     "\n        -A SEC          Wait if lease is not obtained (default 20)"
1208 //usage:     "\n        -n              Exit if lease is not obtained"
1209 //usage:     "\n        -q              Exit after obtaining lease"
1210 //usage:     "\n        -R              Release IP on exit"
1211 //usage:     "\n        -f              Run in foreground"
1212 //usage:        USE_FOR_MMU(
1213 //usage:     "\n        -b              Background if lease is not obtained"
1214 //usage:        )
1215 //usage:     "\n        -S              Log to syslog too"
1216 //usage:        IF_FEATURE_UDHCPC_ARPING(
1217 //usage:     "\n        -a[MSEC]        Validate offered address with ARP ping"
1218 //usage:        )
1219 //usage:     "\n        -r IP           Request this IP address"
1220 //usage:     "\n        -o              Don't request any options (unless -O is given)"
1221 //usage:     "\n        -O OPT          Request option OPT from server (cumulative)"
1222 //usage:     "\n        -x OPT:VAL      Include option OPT in sent packets (cumulative)"
1223 //usage:     "\n                        Examples of string, numeric, and hex byte opts:"
1224 //usage:     "\n                        -x hostname:bbox - option 12"
1225 //usage:     "\n                        -x lease:3600 - option 51 (lease time)"
1226 //usage:     "\n                        -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
1227 //usage:     "\n        -F NAME         Ask server to update DNS mapping for NAME"
1228 //usage:     "\n        -V VENDOR       Vendor identifier (default 'udhcp VERSION')"
1229 //usage:     "\n        -C              Don't send MAC as client identifier"
1230 //usage:        IF_UDHCP_VERBOSE(
1231 //usage:     "\n        -v              Verbose"
1232 //usage:        )
1233 //usage:     "\nSignals:"
1234 //usage:     "\n        USR1    Renew lease"
1235 //usage:     "\n        USR2    Release lease"
1236
1237
1238 int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
1239 int udhcpc_main(int argc UNUSED_PARAM, char **argv)
1240 {
1241         uint8_t *message;
1242         const char *str_V, *str_h, *str_F, *str_r;
1243         IF_FEATURE_UDHCPC_ARPING(const char *str_a = "2000";)
1244         IF_FEATURE_UDHCP_PORT(char *str_P;)
1245         void *clientid_mac_ptr;
1246         llist_t *list_O = NULL;
1247         llist_t *list_x = NULL;
1248         int tryagain_timeout = 20;
1249         int discover_timeout = 3;
1250         int discover_retries = 3;
1251         uint32_t server_addr = server_addr; /* for compiler */
1252         uint32_t requested_ip = 0;
1253         uint32_t xid = xid; /* for compiler */
1254         int packet_num;
1255         int timeout; /* must be signed */
1256         unsigned already_waited_sec;
1257         unsigned opt;
1258         IF_FEATURE_UDHCPC_ARPING(unsigned arpping_ms;)
1259         int retval;
1260
1261         setup_common_bufsiz();
1262
1263         /* Default options */
1264         IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;)
1265         IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
1266         client_config.interface = "eth0";
1267         client_config.script = CONFIG_UDHCPC_DEFAULT_SCRIPT;
1268         str_V = "udhcp "BB_VER;
1269
1270         /* Parse command line */
1271         opt = getopt32long(argv, "^"
1272                 /* O,x: list; -T,-t,-A take numeric param */
1273                 "CV:H:h:F:i:np:qRr:s:T:+t:+SA:+O:*ox:*fB"
1274                 USE_FOR_MMU("b")
1275                 IF_FEATURE_UDHCPC_ARPING("a::")
1276                 IF_FEATURE_UDHCP_PORT("P:")
1277                 "v"
1278                 "\0" IF_UDHCP_VERBOSE("vv") /* -v is a counter */
1279                 , udhcpc_longopts
1280                 , &str_V, &str_h, &str_h, &str_F
1281                 , &client_config.interface, &client_config.pidfile /* i,p */
1282                 , &str_r /* r */
1283                 , &client_config.script /* s */
1284                 , &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */
1285                 , &list_O
1286                 , &list_x
1287                 IF_FEATURE_UDHCPC_ARPING(, &str_a)
1288                 IF_FEATURE_UDHCP_PORT(, &str_P)
1289                 IF_UDHCP_VERBOSE(, &dhcp_verbose)
1290         );
1291         if (opt & (OPT_h|OPT_H)) {
1292                 //msg added 2011-11
1293                 bb_error_msg("option -h NAME is deprecated, use -x hostname:NAME");
1294                 client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
1295         }
1296         if (opt & OPT_F) {
1297                 /* FQDN option format: [0x51][len][flags][0][0]<fqdn> */
1298                 client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
1299                 /* Flag bits: 0000NEOS
1300                  * S: 1 = Client requests server to update A RR in DNS as well as PTR
1301                  * O: 1 = Server indicates to client that DNS has been updated regardless
1302                  * E: 1 = Name is in DNS format, i.e. <4>host<6>domain<3>com<0>,
1303                  *    not "host.domain.com". Format 0 is obsolete.
1304                  * N: 1 = Client requests server to not update DNS (S must be 0 then)
1305                  * Two [0] bytes which follow are deprecated and must be 0.
1306                  */
1307                 client_config.fqdn[OPT_DATA + 0] = 0x1;
1308                 /*client_config.fqdn[OPT_DATA + 1] = 0; - xzalloc did it */
1309                 /*client_config.fqdn[OPT_DATA + 2] = 0; */
1310         }
1311         if (opt & OPT_r)
1312                 requested_ip = inet_addr(str_r);
1313 #if ENABLE_FEATURE_UDHCP_PORT
1314         if (opt & OPT_P) {
1315                 CLIENT_PORT = xatou16(str_P);
1316                 SERVER_PORT = CLIENT_PORT - 1;
1317         }
1318 #endif
1319         IF_FEATURE_UDHCPC_ARPING(arpping_ms = xatou(str_a);)
1320         while (list_O) {
1321                 char *optstr = llist_pop(&list_O);
1322                 unsigned n = bb_strtou(optstr, NULL, 0);
1323                 if (errno || n > 254) {
1324                         n = udhcp_option_idx(optstr, dhcp_option_strings);
1325                         n = dhcp_optflags[n].code;
1326                 }
1327                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
1328         }
1329         if (!(opt & OPT_o)) {
1330                 unsigned i, n;
1331                 for (i = 0; (n = dhcp_optflags[i].code) != 0; i++) {
1332                         if (dhcp_optflags[i].flags & OPTION_REQ) {
1333                                 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
1334                         }
1335                 }
1336         }
1337         while (list_x) {
1338                 char *optstr = llist_pop(&list_x);
1339                 char *colon = strchr(optstr, ':');
1340                 if (colon)
1341                         *colon = ' ';
1342                 /* now it looks similar to udhcpd's config file line:
1343                  * "optname optval", using the common routine: */
1344                 udhcp_str2optset(optstr, &client_config.options, dhcp_optflags, dhcp_option_strings);
1345                 if (colon)
1346                         *colon = ':'; /* restore it for NOMMU reexec */
1347         }
1348
1349         if (udhcp_read_interface(client_config.interface,
1350                         &client_config.ifindex,
1351                         NULL,
1352                         client_config.client_mac)
1353         ) {
1354                 return 1;
1355         }
1356
1357         clientid_mac_ptr = NULL;
1358         if (!(opt & OPT_C) && !udhcp_find_option(client_config.options, DHCP_CLIENT_ID)) {
1359                 /* not suppressed and not set, set the default client ID */
1360                 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
1361                 client_config.clientid[OPT_DATA] = 1; /* type: ethernet */
1362                 clientid_mac_ptr = client_config.clientid + OPT_DATA+1;
1363                 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1364         }
1365         if (str_V[0] != '\0') {
1366                 // can drop -V, str_V, client_config.vendorclass,
1367                 // but need to add "vendor" to the list of recognized
1368                 // string opts for this to work;
1369                 // and need to tweak add_client_options() too...
1370                 // ...so the question is, should we?
1371                 //bb_error_msg("option -V VENDOR is deprecated, use -x vendor:VENDOR");
1372                 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
1373         }
1374
1375 #if !BB_MMU
1376         /* on NOMMU reexec (i.e., background) early */
1377         if (!(opt & OPT_f)) {
1378                 bb_daemonize_or_rexec(0 /* flags */, argv);
1379                 logmode = LOGMODE_NONE;
1380         }
1381 #endif
1382         if (opt & OPT_S) {
1383                 openlog(applet_name, LOG_PID, LOG_DAEMON);
1384                 logmode |= LOGMODE_SYSLOG;
1385         }
1386
1387         /* Make sure fd 0,1,2 are open */
1388         bb_sanitize_stdio();
1389         /* Create pidfile */
1390         write_pidfile(client_config.pidfile);
1391         /* Goes to stdout (unless NOMMU) and possibly syslog */
1392         bb_error_msg("started, v"BB_VER);
1393         /* Set up the signal pipe */
1394         udhcp_sp_setup();
1395         /* We want random_xid to be random... */
1396         srand(monotonic_us());
1397
1398         state = INIT_SELECTING;
1399         udhcp_run_script(NULL, "deconfig");
1400         change_listen_mode(LISTEN_RAW);
1401         packet_num = 0;
1402         timeout = 0;
1403         already_waited_sec = 0;
1404
1405         /* Main event loop. select() waits on signal pipe and possibly
1406          * on sockfd.
1407          * "continue" statements in code below jump to the top of the loop.
1408          */
1409         for (;;) {
1410                 int tv;
1411                 struct pollfd pfds[2];
1412                 struct dhcp_packet packet;
1413                 /* silence "uninitialized!" warning */
1414                 unsigned timestamp_before_wait = timestamp_before_wait;
1415
1416                 //bb_error_msg("sockfd:%d, listen_mode:%d", sockfd, listen_mode);
1417
1418                 /* Was opening raw or udp socket here
1419                  * if (listen_mode != LISTEN_NONE && sockfd < 0),
1420                  * but on fast network renew responses return faster
1421                  * than we open sockets. Thus this code is moved
1422                  * to change_listen_mode(). Thus we open listen socket
1423                  * BEFORE we send renew request (see "case BOUND:"). */
1424
1425                 udhcp_sp_fd_set(pfds, sockfd);
1426
1427                 tv = timeout - already_waited_sec;
1428                 retval = 0;
1429                 /* If we already timed out, fall through with retval = 0, else... */
1430                 if (tv > 0) {
1431                         log1("waiting %u seconds", tv);
1432                         timestamp_before_wait = (unsigned)monotonic_sec();
1433                         retval = poll(pfds, 2, tv < INT_MAX/1000 ? tv * 1000 : INT_MAX);
1434                         if (retval < 0) {
1435                                 /* EINTR? A signal was caught, don't panic */
1436                                 if (errno == EINTR) {
1437                                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1438                                         continue;
1439                                 }
1440                                 /* Else: an error occurred, panic! */
1441                                 bb_perror_msg_and_die("poll");
1442                         }
1443                 }
1444
1445                 /* If timeout dropped to zero, time to become active:
1446                  * resend discover/renew/whatever
1447                  */
1448                 if (retval == 0) {
1449                         /* When running on a bridge, the ifindex may have changed
1450                          * (e.g. if member interfaces were added/removed
1451                          * or if the status of the bridge changed).
1452                          * Refresh ifindex and client_mac:
1453                          */
1454                         if (udhcp_read_interface(client_config.interface,
1455                                         &client_config.ifindex,
1456                                         NULL,
1457                                         client_config.client_mac)
1458                         ) {
1459                                 goto ret0; /* iface is gone? */
1460                         }
1461                         if (clientid_mac_ptr)
1462                                 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1463
1464                         /* We will restart the wait in any case */
1465                         already_waited_sec = 0;
1466
1467                         switch (state) {
1468                         case INIT_SELECTING:
1469                                 if (!discover_retries || packet_num < discover_retries) {
1470                                         if (packet_num == 0)
1471                                                 xid = random_xid();
1472                                         /* broadcast */
1473                                         send_discover(xid, requested_ip);
1474                                         timeout = discover_timeout;
1475                                         packet_num++;
1476                                         continue;
1477                                 }
1478  leasefail:
1479                                 udhcp_run_script(NULL, "leasefail");
1480 #if BB_MMU /* -b is not supported on NOMMU */
1481                                 if (opt & OPT_b) { /* background if no lease */
1482                                         bb_error_msg("no lease, forking to background");
1483                                         client_background();
1484                                         /* do not background again! */
1485                                         opt = ((opt & ~OPT_b) | OPT_f);
1486                                 } else
1487 #endif
1488                                 if (opt & OPT_n) { /* abort if no lease */
1489                                         bb_error_msg("no lease, failing");
1490                                         retval = 1;
1491                                         goto ret;
1492                                 }
1493                                 /* wait before trying again */
1494                                 timeout = tryagain_timeout;
1495                                 packet_num = 0;
1496                                 continue;
1497                         case REQUESTING:
1498                                 if (packet_num < 3) {
1499                                         /* send broadcast select packet */
1500                                         send_select(xid, server_addr, requested_ip);
1501                                         timeout = discover_timeout;
1502                                         packet_num++;
1503                                         continue;
1504                                 }
1505                                 /* Timed out, go back to init state.
1506                                  * "discover...select...discover..." loops
1507                                  * were seen in the wild. Treat them similarly
1508                                  * to "no response to discover" case */
1509                                 change_listen_mode(LISTEN_RAW);
1510                                 state = INIT_SELECTING;
1511                                 goto leasefail;
1512                         case BOUND:
1513                                 /* 1/2 lease passed, enter renewing state */
1514                                 state = RENEWING;
1515                                 client_config.first_secs = 0; /* make secs field count from 0 */
1516                                 change_listen_mode(LISTEN_KERNEL);
1517                                 log1("entering renew state");
1518                                 /* fall right through */
1519                         case RENEW_REQUESTED: /* manual (SIGUSR1) renew */
1520                         case_RENEW_REQUESTED:
1521                         case RENEWING:
1522                                 if (timeout > 60) {
1523                                         /* send an unicast renew request */
1524                         /* Sometimes observed to fail (EADDRNOTAVAIL) to bind
1525                          * a new UDP socket for sending inside send_renew.
1526                          * I hazard to guess existing listening socket
1527                          * is somehow conflicting with it, but why is it
1528                          * not deterministic then?! Strange.
1529                          * Anyway, it does recover by eventually failing through
1530                          * into INIT_SELECTING state.
1531                          */
1532                                         if (send_renew(xid, server_addr, requested_ip) >= 0) {
1533                                                 timeout >>= 1;
1534 //TODO: the timeout to receive an answer for our renew should not be selected
1535 //with "timeout = lease_seconds / 2; ...; timeout = timeout / 2": it is often huge.
1536 //Waiting e.g. 4*3600 seconds for a reply does not make sense
1537 //(if reply isn't coming, we keep an open socket for hours),
1538 //it should be something like 10 seconds.
1539 //Also, it's probably best to try sending renew in kernel mode a few (3-5) times
1540 //and fall back to raw mode if it does not work.
1541                                                 continue;
1542                                         }
1543                                         /* else: error sending.
1544                                          * example: ENETUNREACH seen with server
1545                                          * which gave us bogus server ID 1.1.1.1
1546                                          * which wasn't reachable (and probably did not exist).
1547                                          */
1548                                 }
1549                                 /* Timed out or error, enter rebinding state */
1550                                 log1("entering rebinding state");
1551                                 state = REBINDING;
1552                                 /* fall right through */
1553                         case REBINDING:
1554                                 /* Switch to bcast receive */
1555                                 change_listen_mode(LISTEN_RAW);
1556                                 /* Lease is *really* about to run out,
1557                                  * try to find DHCP server using broadcast */
1558                                 if (timeout > 0) {
1559                                         /* send a broadcast renew request */
1560                                         send_renew(xid, 0 /*INADDR_ANY*/, requested_ip);
1561                                         timeout >>= 1;
1562                                         continue;
1563                                 }
1564                                 /* Timed out, enter init state */
1565                                 bb_error_msg("lease lost, entering init state");
1566                                 udhcp_run_script(NULL, "deconfig");
1567                                 state = INIT_SELECTING;
1568                                 client_config.first_secs = 0; /* make secs field count from 0 */
1569                                 /*timeout = 0; - already is */
1570                                 packet_num = 0;
1571                                 continue;
1572                         /* case RELEASED: */
1573                         }
1574                         /* yah, I know, *you* say it would never happen */
1575                         timeout = INT_MAX;
1576                         continue; /* back to main loop */
1577                 } /* if poll timed out */
1578
1579                 /* poll() didn't timeout, something happened */
1580
1581                 /* Is it a signal? */
1582                 switch (udhcp_sp_read()) {
1583                 case SIGUSR1:
1584                         client_config.first_secs = 0; /* make secs field count from 0 */
1585                         already_waited_sec = 0;
1586                         perform_renew();
1587                         if (state == RENEW_REQUESTED) {
1588                                 /* We might be either on the same network
1589                                  * (in which case renew might work),
1590                                  * or we might be on a completely different one
1591                                  * (in which case renew won't ever succeed).
1592                                  * For the second case, must make sure timeout
1593                                  * is not too big, or else we can send
1594                                  * futile renew requests for hours.
1595                                  * (Ab)use -A TIMEOUT value (usually 20 sec)
1596                                  * as a cap on the timeout.
1597                                  */
1598                                 if (timeout > tryagain_timeout)
1599                                         timeout = tryagain_timeout;
1600                                 goto case_RENEW_REQUESTED;
1601                         }
1602                         /* Start things over */
1603                         packet_num = 0;
1604                         /* Kill any timeouts, user wants this to hurry along */
1605                         timeout = 0;
1606                         continue;
1607                 case SIGUSR2:
1608                         perform_release(server_addr, requested_ip);
1609                         timeout = INT_MAX;
1610                         continue;
1611                 case SIGTERM:
1612                         bb_error_msg("received %s", "SIGTERM");
1613                         goto ret0;
1614                 }
1615
1616                 /* Is it a packet? */
1617                 if (!pfds[1].revents)
1618                         continue; /* no */
1619
1620                 {
1621                         int len;
1622
1623                         /* A packet is ready, read it */
1624                         if (listen_mode == LISTEN_KERNEL)
1625                                 len = udhcp_recv_kernel_packet(&packet, sockfd);
1626                         else
1627                                 len = udhcp_recv_raw_packet(&packet, sockfd);
1628                         if (len == -1) {
1629                                 /* Error is severe, reopen socket */
1630                                 bb_error_msg("read error: "STRERROR_FMT", reopening socket" STRERROR_ERRNO);
1631                                 sleep(discover_timeout); /* 3 seconds by default */
1632                                 change_listen_mode(listen_mode); /* just close and reopen */
1633                         }
1634                         /* If this packet will turn out to be unrelated/bogus,
1635                          * we will go back and wait for next one.
1636                          * Be sure timeout is properly decreased. */
1637                         already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1638                         if (len < 0)
1639                                 continue;
1640                 }
1641
1642                 if (packet.xid != xid) {
1643                         log1("xid %x (our is %x), ignoring packet",
1644                                 (unsigned)packet.xid, (unsigned)xid);
1645                         continue;
1646                 }
1647
1648                 /* Ignore packets that aren't for us */
1649                 if (packet.hlen != 6
1650                  || memcmp(packet.chaddr, client_config.client_mac, 6) != 0
1651                 ) {
1652 //FIXME: need to also check that last 10 bytes are zero
1653                         log1("chaddr does not match, ignoring packet"); // log2?
1654                         continue;
1655                 }
1656
1657                 message = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
1658                 if (message == NULL) {
1659                         bb_error_msg("no message type option, ignoring packet");
1660                         continue;
1661                 }
1662
1663                 switch (state) {
1664                 case INIT_SELECTING:
1665                         /* Must be a DHCPOFFER */
1666                         if (*message == DHCPOFFER) {
1667                                 uint8_t *temp;
1668
1669 /* What exactly is server's IP? There are several values.
1670  * Example DHCP offer captured with tchdump:
1671  *
1672  * 10.34.25.254:67 > 10.34.25.202:68 // IP header's src
1673  * BOOTP fields:
1674  * Your-IP 10.34.25.202
1675  * Server-IP 10.34.32.125   // "next server" IP
1676  * Gateway-IP 10.34.25.254  // relay's address (if DHCP relays are in use)
1677  * DHCP options:
1678  * DHCP-Message Option 53, length 1: Offer
1679  * Server-ID Option 54, length 4: 10.34.255.7       // "server ID"
1680  * Default-Gateway Option 3, length 4: 10.34.25.254 // router
1681  *
1682  * We think that real server IP (one to use in renew/release)
1683  * is one in Server-ID option. But I am not 100% sure.
1684  * IP header's src and Gateway-IP (same in this example)
1685  * might work too.
1686  * "Next server" and router are definitely wrong ones to use, though...
1687  */
1688 /* We used to ignore pcakets without DHCP_SERVER_ID.
1689  * I've got user reports from people who run "address-less" servers.
1690  * They either supply DHCP_SERVER_ID of 0.0.0.0 or don't supply it at all.
1691  * They say ISC DHCP client supports this case.
1692  */
1693                                 server_addr = 0;
1694                                 temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
1695                                 if (!temp) {
1696                                         bb_error_msg("no server ID, using 0.0.0.0");
1697                                 } else {
1698                                         /* it IS unaligned sometimes, don't "optimize" */
1699                                         move_from_unaligned32(server_addr, temp);
1700                                 }
1701                                 /*xid = packet.xid; - already is */
1702                                 requested_ip = packet.yiaddr;
1703
1704                                 /* enter requesting state */
1705                                 state = REQUESTING;
1706                                 timeout = 0;
1707                                 packet_num = 0;
1708                                 already_waited_sec = 0;
1709                         }
1710                         continue;
1711                 case REQUESTING:
1712                 case RENEWING:
1713                 case RENEW_REQUESTED:
1714                 case REBINDING:
1715                         if (*message == DHCPACK) {
1716                                 unsigned start;
1717                                 uint32_t lease_seconds;
1718                                 struct in_addr temp_addr;
1719                                 uint8_t *temp;
1720
1721                                 temp = udhcp_get_option(&packet, DHCP_LEASE_TIME);
1722                                 if (!temp) {
1723                                         bb_error_msg("no lease time with ACK, using 1 hour lease");
1724                                         lease_seconds = 60 * 60;
1725                                 } else {
1726                                         /* it IS unaligned sometimes, don't "optimize" */
1727                                         move_from_unaligned32(lease_seconds, temp);
1728                                         lease_seconds = ntohl(lease_seconds);
1729                                         /* paranoia: must not be too small and not prone to overflows */
1730                                         if (lease_seconds < 0x10)
1731                                                 lease_seconds = 0x10;
1732                                         //if (lease_seconds > 0x7fffffff)
1733                                         //      lease_seconds = 0x7fffffff;
1734                                         //^^^not necessary since "timeout = lease_seconds / 2"
1735                                         //does not overflow even for 0xffffffff.
1736                                 }
1737 #if ENABLE_FEATURE_UDHCPC_ARPING
1738                                 if (opt & OPT_a) {
1739 /* RFC 2131 3.1 paragraph 5:
1740  * "The client receives the DHCPACK message with configuration
1741  * parameters. The client SHOULD perform a final check on the
1742  * parameters (e.g., ARP for allocated network address), and notes
1743  * the duration of the lease specified in the DHCPACK message. At this
1744  * point, the client is configured. If the client detects that the
1745  * address is already in use (e.g., through the use of ARP),
1746  * the client MUST send a DHCPDECLINE message to the server and restarts
1747  * the configuration process..." */
1748                                         if (!arpping(packet.yiaddr,
1749                                                         NULL,
1750                                                         (uint32_t) 0,
1751                                                         client_config.client_mac,
1752                                                         client_config.interface,
1753                                                         arpping_ms)
1754                                         ) {
1755                                                 bb_error_msg("offered address is in use "
1756                                                         "(got ARP reply), declining");
1757                                                 send_decline(/*xid,*/ server_addr, packet.yiaddr);
1758
1759                                                 if (state != REQUESTING)
1760                                                         udhcp_run_script(NULL, "deconfig");
1761                                                 change_listen_mode(LISTEN_RAW);
1762                                                 state = INIT_SELECTING;
1763                                                 client_config.first_secs = 0; /* make secs field count from 0 */
1764                                                 requested_ip = 0;
1765                                                 timeout = tryagain_timeout;
1766                                                 packet_num = 0;
1767                                                 already_waited_sec = 0;
1768                                                 continue; /* back to main loop */
1769                                         }
1770                                 }
1771 #endif
1772                                 /* enter bound state */
1773                                 temp_addr.s_addr = packet.yiaddr;
1774                                 bb_error_msg("lease of %s obtained, lease time %u",
1775                                         inet_ntoa(temp_addr), (unsigned)lease_seconds);
1776                                 requested_ip = packet.yiaddr;
1777
1778                                 start = monotonic_sec();
1779                                 udhcp_run_script(&packet, state == REQUESTING ? "bound" : "renew");
1780                                 already_waited_sec = (unsigned)monotonic_sec() - start;
1781                                 timeout = lease_seconds / 2;
1782                                 if ((unsigned)timeout < already_waited_sec) {
1783                                         /* Something went wrong. Back to discover state */
1784                                         timeout = already_waited_sec = 0;
1785                                 }
1786
1787                                 state = BOUND;
1788                                 change_listen_mode(LISTEN_NONE);
1789                                 if (opt & OPT_q) { /* quit after lease */
1790                                         goto ret0;
1791                                 }
1792                                 /* future renew failures should not exit (JM) */
1793                                 opt &= ~OPT_n;
1794 #if BB_MMU /* NOMMU case backgrounded earlier */
1795                                 if (!(opt & OPT_f)) {
1796                                         client_background();
1797                                         /* do not background again! */
1798                                         opt = ((opt & ~OPT_b) | OPT_f);
1799                                 }
1800 #endif
1801                                 /* make future renew packets use different xid */
1802                                 /* xid = random_xid(); ...but why bother? */
1803
1804                                 continue; /* back to main loop */
1805                         }
1806                         if (*message == DHCPNAK) {
1807                                 /* If network has more than one DHCP server,
1808                                  * "wrong" server can reply first, with a NAK.
1809                                  * Do not interpret it as a NAK from "our" server.
1810                                  */
1811                                 if (server_addr != 0) {
1812                                         uint32_t svid;
1813                                         uint8_t *temp;
1814
1815                                         temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
1816                                         if (!temp) {
1817  non_matching_svid:
1818                                                 log1("received DHCP NAK with wrong"
1819                                                         " server ID, ignoring packet");
1820                                                 continue;
1821                                         }
1822                                         move_from_unaligned32(svid, temp);
1823                                         if (svid != server_addr)
1824                                                 goto non_matching_svid;
1825                                 }
1826                                 /* return to init state */
1827                                 bb_error_msg("received %s", "DHCP NAK");
1828                                 udhcp_run_script(&packet, "nak");
1829                                 if (state != REQUESTING)
1830                                         udhcp_run_script(NULL, "deconfig");
1831                                 change_listen_mode(LISTEN_RAW);
1832                                 sleep(3); /* avoid excessive network traffic */
1833                                 state = INIT_SELECTING;
1834                                 client_config.first_secs = 0; /* make secs field count from 0 */
1835                                 requested_ip = 0;
1836                                 timeout = 0;
1837                                 packet_num = 0;
1838                                 already_waited_sec = 0;
1839                         }
1840                         continue;
1841                 /* case BOUND: - ignore all packets */
1842                 /* case RELEASED: - ignore all packets */
1843                 }
1844                 /* back to main loop */
1845         } /* for (;;) - main loop ends */
1846
1847  ret0:
1848         if (opt & OPT_R) /* release on quit */
1849                 perform_release(server_addr, requested_ip);
1850         retval = 0;
1851  ret:
1852         /*if (client_config.pidfile) - remove_pidfile has its own check */
1853                 remove_pidfile(client_config.pidfile);
1854         return retval;
1855 }