includes/IP.php

   1 <?php
   2 /**
   3  * Functions and constants to play with IP addresses and ranges
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @author Ashar Voultoiz <hashar at free dot fr>, Aaron Schulz
  22  */
  23
  24 // Some regex definition to "play" with IP address and IP address blocks
  25
  26 // An IPv4 address is made of 4 bytes from x00 to xFF which is d0 to d255
  27 define( 'RE_IP_BYTE', '(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|0?[0-9]?[0-9])' );
  28 define( 'RE_IP_ADD', RE_IP_BYTE . '\.' . RE_IP_BYTE . '\.' . RE_IP_BYTE . '\.' . RE_IP_BYTE );
  29 // An IPv4 block is an IP address and a prefix (d1 to d32)
  30 define( 'RE_IP_PREFIX', '(3[0-2]|[12]?\d)' );
  31 define( 'RE_IP_BLOCK', RE_IP_ADD . '\/' . RE_IP_PREFIX );
  32
  33 // An IPv6 address is made up of 8 words (each x0000 to xFFFF).
  34 // However, the "::" abbreviation can be used on consecutive x0000 words.
  35 define( 'RE_IPV6_WORD', '([0-9A-Fa-f]{1,4})' );
  36 define( 'RE_IPV6_PREFIX', '(12[0-8]|1[01][0-9]|[1-9]?\d)');
  37 define( 'RE_IPV6_ADD',
  38         '(?:' . // starts with "::" (includes the address "::")
  39                 '::|:(?::' . RE_IPV6_WORD . '){1,7}' .
  40         '|' . // ends with "::" (not including the address "::")
  41                 RE_IPV6_WORD . '(?::' . RE_IPV6_WORD . '){0,6}::' .
  42         '|' . // has no "::"
  43                 RE_IPV6_WORD . '(?::' . RE_IPV6_WORD . '){7}' .
  44         '|' . // contains one "::" in the middle (awkward regex for PCRE 4.0+ compatibility)
  45                 RE_IPV6_WORD . '(?::(?P<abn>(?!(?P=abn)):(?P<iabn>))?' . RE_IPV6_WORD . '){1,6}(?P=iabn)' .
  46                 // NOTE: (?!(?P=abn)) fails iff "::" used twice; (?P=iabn) passes iff a "::" was found.
  47
  48                 // Better regexp (PCRE 7.2+ only), allows intuitive regex concatenation
  49                 #RE_IPV6_WORD . '(?::((?(-1)|:))?' . RE_IPV6_WORD . '){1,6}(?(-2)|^)' .
  50         ')'
  51 );
  52 // An IPv6 block is an IP address and a prefix (d1 to d128)
  53 define( 'RE_IPV6_BLOCK', RE_IPV6_ADD . '\/' . RE_IPV6_PREFIX );
  54 // For IPv6 canonicalization (NOT for strict validation; these are quite lax!)
  55 define( 'RE_IPV6_GAP', ':(?:0+:)*(?::(?:0+:)*)?' );
  56 define( 'RE_IPV6_V4_PREFIX', '0*' . RE_IPV6_GAP . '(?:ffff:)?' );
  57
  58 // This might be useful for regexps used elsewhere, matches any IPv6 or IPv6 address or network
  59 define( 'IP_ADDRESS_STRING',
  60         '(?:' .
  61                 RE_IP_ADD . '(?:\/' . RE_IP_PREFIX . ')?' . // IPv4
  62         '|' .
  63                 RE_IPV6_ADD . '(?:\/' . RE_IPV6_PREFIX . ')?' . // IPv6
  64         ')'
  65 );
  66
  67 /**
  68  * A collection of public static functions to play with IP address
  69  * and IP blocks.
  70  */
  71 class IP {
  72         /**
  73          * Determine if a string is as valid IP address or network (CIDR prefix).
  74          * SIIT IPv4-translated addresses are rejected.
  75          * Note: canonicalize() tries to convert translated addresses to IPv4.
  76          *
  77          * @param $ip String: possible IP address
  78          * @return Boolean
  79          */
  80         public static function isIPAddress( $ip ) {
  81                 return (bool)preg_match( '/^' . IP_ADDRESS_STRING . '$/', $ip );
  82         }
  83
  84         /**
  85          * Given a string, determine if it as valid IP in IPv6 only.
  86          * Note: Unlike isValid(), this looks for networks too.
  87          *
  88          * @param $ip String: possible IP address
  89          * @return Boolean
  90          */
  91         public static function isIPv6( $ip ) {
  92                 return (bool)preg_match( '/^' . RE_IPV6_ADD . '(?:\/' . RE_IPV6_PREFIX . ')?$/', $ip );
  93         }
  94
  95         /**
  96          * Given a string, determine if it as valid IP in IPv4 only.
  97          * Note: Unlike isValid(), this looks for networks too.
  98          *
  99          * @param $ip String: possible IP address
 100          * @return Boolean
 101          */
 102         public static function isIPv4( $ip ) {
 103                 return (bool)preg_match( '/^' . RE_IP_ADD . '(?:\/' . RE_IP_PREFIX . ')?$/', $ip );
 104         }
 105
 106         /**
 107          * Validate an IP address. Ranges are NOT considered valid.
 108          * SIIT IPv4-translated addresses are rejected.
 109          * Note: canonicalize() tries to convert translated addresses to IPv4.
 110          *
 111          * @param $ip String
 112          * @return Boolean: True if it is valid.
 113          */
 114         public static function isValid( $ip ) {
 115                 return ( preg_match( '/^' . RE_IP_ADD . '$/', $ip )
 116                         || preg_match( '/^' . RE_IPV6_ADD . '$/', $ip ) );
 117         }
 118
 119         /**
 120          * Validate an IP Block (valid address WITH a valid prefix).
 121          * SIIT IPv4-translated addresses are rejected.
 122          * Note: canonicalize() tries to convert translated addresses to IPv4.
 123          *
 124          * @param $ipblock String
 125          * @return Boolean: True if it is valid.
 126          */
 127         public static function isValidBlock( $ipblock ) {
 128                 return ( preg_match( '/^' . RE_IPV6_BLOCK . '$/', $ipblock )
 129                         || preg_match( '/^' . RE_IP_BLOCK . '$/', $ipblock ) );
 130         }
 131
 132         /**
 133          * Convert an IP into a nice standard form.
 134          * IPv6 addresses in octet notation are expanded to 8 words.
 135          * IPv4 addresses are just trimmed.
 136          *
 137          * @param $ip String: IP address in quad or octet form (CIDR or not).
 138          * @return String
 139          */
 140         public static function sanitizeIP( $ip ) {
 141                 $ip = trim( $ip );
 142                 if ( $ip === '' ) {
 143                         return null;
 144                 }
 145                 if ( self::isIPv4( $ip ) || !self::isIPv6( $ip ) ) {
 146                         return $ip; // nothing else to do for IPv4 addresses or invalid ones
 147                 }
 148                 // Remove any whitespaces, convert to upper case
 149                 $ip = strtoupper( $ip );
 150                 // Expand zero abbreviations
 151                 $abbrevPos = strpos( $ip, '::' );
 152                 if ( $abbrevPos !== false ) {
 153                         // We know this is valid IPv6. Find the last index of the
 154                         // address before any CIDR number (e.g. "a:b:c::/24").
 155                         $CIDRStart = strpos( $ip, "/" );
 156                         $addressEnd = ( $CIDRStart !== false )
 157                                 ? $CIDRStart - 1
 158                                 : strlen( $ip ) - 1;
 159                         // If the '::' is at the beginning...
 160                         if ( $abbrevPos == 0 ) {
 161                                 $repeat = '0:';
 162                                 $extra = ( $ip == '::' ) ? '0' : ''; // for the address '::'
 163                                 $pad = 9; // 7+2 (due to '::')
 164                         // If the '::' is at the end...
 165                         } elseif ( $abbrevPos == ( $addressEnd - 1 ) ) {
 166                                 $repeat = ':0';
 167                                 $extra = '';
 168                                 $pad = 9; // 7+2 (due to '::')
 169                         // If the '::' is in the middle...
 170                         } else {
 171                                 $repeat = ':0';
 172                                 $extra = ':';
 173                                 $pad = 8; // 6+2 (due to '::')
 174                         }
 175                         $ip = str_replace( '::',
 176                                 str_repeat( $repeat, $pad - substr_count( $ip, ':' ) ) . $extra,
 177                                 $ip
 178                         );
 179                 }
 180                 // Remove leading zereos from each bloc as needed
 181                 $ip = preg_replace( '/(^|:)0+(' . RE_IPV6_WORD . ')/', '$1$2', $ip );
 182                 return $ip;
 183         }
 184
 185         /**
 186          * Given an unsigned integer, returns an IPv6 address in octet notation
 187          *
 188          * @param $ip_int String: IP address.
 189          * @return String
 190          */
 191         public static function toOctet( $ip_int ) {
 192                 return self::hexToOctet( wfBaseConvert( $ip_int, 10, 16, 32, false ) );
 193         }
 194
 195         /**
 196          * Convert an IPv4 or IPv6 hexadecimal representation back to readable format
 197          *
 198          * @param $hex String: number, with "v6-" prefix if it is IPv6
 199          * @return String: quad-dotted (IPv4) or octet notation (IPv6)
 200          */
 201         public static function formatHex( $hex ) {
 202                 if ( substr( $hex, 0, 3 ) == 'v6-' ) { // IPv6
 203                         return self::hexToOctet( substr( $hex, 3 ) );
 204                 } else { // IPv4
 205                         return self::hexToQuad( $hex );
 206                 }
 207         }
 208
 209         /**
 210          * Converts a hexadecimal number to an IPv6 address in octet notation
 211          *
 212          * @param $ip_hex String: pure hex (no v6- prefix)
 213          * @return String (of format a:b:c:d:e:f:g:h)
 214          */
 215         public static function hexToOctet( $ip_hex ) {
 216                 // Pad hex to 32 chars (128 bits)
 217                 $ip_hex = str_pad( strtoupper( $ip_hex ), 32, '0', STR_PAD_LEFT );
 218                 // Separate into 8 words
 219                 $ip_oct = substr( $ip_hex, 0, 4 );
 220                 for ( $n = 1; $n < 8; $n++ ) {
 221                         $ip_oct .= ':' . substr( $ip_hex, 4 * $n, 4 );
 222                 }
 223                 // NO leading zeroes
 224                 $ip_oct = preg_replace( '/(^|:)0+(' . RE_IPV6_WORD . ')/', '$1$2', $ip_oct );
 225                 return $ip_oct;
 226         }
 227
 228         /**
 229          * Converts a hexadecimal number to an IPv4 address in quad-dotted notation
 230          *
 231          * @param $ip_hex String: pure hex
 232          * @return String (of format a.b.c.d)
 233          */
 234         public static function hexToQuad( $ip_hex ) {
 235                 // Pad hex to 8 chars (32 bits)
 236                 $ip_hex = str_pad( strtoupper( $ip_hex ), 8, '0', STR_PAD_LEFT );
 237                 // Separate into four quads
 238                 $s = '';
 239                 for ( $i = 0; $i < 4; $i++ ) {
 240                         if ( $s !== '' ) {
 241                                 $s .= '.';
 242                         }
 243                         $s .= base_convert( substr( $ip_hex, $i * 2, 2 ), 16, 10 );
 244                 }
 245                 return $s;
 246         }
 247
 248         /**
 249          * Determine if an IP address really is an IP address, and if it is public,
 250          * i.e. not RFC 1918 or similar
 251          * Comes from ProxyTools.php
 252          *
 253          * @param $ip String
 254          * @return Boolean
 255          */
 256         public static function isPublic( $ip ) {
 257                 if ( self::isIPv6( $ip ) ) {
 258                         return self::isPublic6( $ip );
 259                 }
 260                 $n = self::toUnsigned( $ip );
 261                 if ( !$n ) {
 262                         return false;
 263                 }
 264
 265                 // ip2long accepts incomplete addresses, as well as some addresses
 266                 // followed by garbage characters. Check that it's really valid.
 267                 if ( $ip != long2ip( $n ) ) {
 268                         return false;
 269                 }
 270
 271                 static $privateRanges = false;
 272                 if ( !$privateRanges ) {
 273                         $privateRanges = array(
 274                                 array( '10.0.0.0',    '10.255.255.255' ),   # RFC 1918 (private)
 275                                 array( '172.16.0.0',  '172.31.255.255' ),   #     "
 276                                 array( '192.168.0.0', '192.168.255.255' ),  #     "
 277                                 array( '0.0.0.0',     '0.255.255.255' ),    # this network
 278                                 array( '127.0.0.0',   '127.255.255.255' ),  # loopback
 279                         );
 280                 }
 281
 282                 foreach ( $privateRanges as $r ) {
 283                         $start = self::toUnsigned( $r[0] );
 284                         $end = self::toUnsigned( $r[1] );
 285                         if ( $n >= $start && $n <= $end ) {
 286                                 return false;
 287                         }
 288                 }
 289                 return true;
 290         }
 291
 292         /**
 293          * Determine if an IPv6 address really is an IP address, and if it is public,
 294          * i.e. not RFC 4193 or similar
 295          *
 296          * @param $ip String
 297          * @return Boolean
 298          */
 299         private static function isPublic6( $ip ) {
 300                 static $privateRanges = false;
 301                 if ( !$privateRanges ) {
 302                         $privateRanges = array(
 303                                 array( 'fc::', 'fdff:ffff:ffff:ffff:ffff:ffff:ffff:ffff' ), # RFC 4193 (local)
 304                                 array( '0:0:0:0:0:0:0:1', '0:0:0:0:0:0:0:1' ), # loopback
 305                         );
 306                 }
 307                 $n = self::toHex( $ip );
 308                 foreach ( $privateRanges as $r ) {
 309                         $start = self::toHex( $r[0] );
 310                         $end = self::toHex( $r[1] );
 311                         if ( $n >= $start && $n <= $end ) {
 312                                 return false;
 313                         }
 314                 }
 315                 return true;
 316         }
 317
 318         /**
 319          * Return a zero-padded upper case hexadecimal representation of an IP address.
 320          *
 321          * Hexadecimal addresses are used because they can easily be extended to
 322          * IPv6 support. To separate the ranges, the return value from this
 323          * function for an IPv6 address will be prefixed with "v6-", a non-
 324          * hexadecimal string which sorts after the IPv4 addresses.
 325          *
 326          * @param $ip String: quad dotted/octet IP address.
 327          * @return String
 328          */
 329         public static function toHex( $ip ) {
 330                 if ( self::isIPv6( $ip ) ) {
 331                         $n = 'v6-' . self::IPv6ToRawHex( $ip );
 332                 } else {
 333                         $n = self::toUnsigned( $ip );
 334                         if ( $n !== false ) {
 335                                 $n = wfBaseConvert( $n, 10, 16, 8, false );
 336                         }
 337                 }
 338                 return $n;
 339         }
 340
 341         /**
 342          * Given an IPv6 address in octet notation, returns a pure hex string.
 343          *
 344          * @param $ip String: octet ipv6 IP address.
 345          * @return String: pure hex (uppercase)
 346          */
 347         private static function IPv6ToRawHex( $ip ) {
 348                 $ip = self::sanitizeIP( $ip );
 349                 if ( !$ip ) {
 350                         return null;
 351                 }
 352                 $r_ip = '';
 353                 foreach ( explode( ':', $ip ) as $v ) {
 354                         $r_ip .= str_pad( $v, 4, 0, STR_PAD_LEFT );
 355                 }
 356                 return $r_ip;
 357         }
 358
 359         /**
 360          * Given an IP address in dotted-quad/octet notation, returns an unsigned integer.
 361          * Like ip2long() except that it actually works and has a consistent error return value.
 362          * Comes from ProxyTools.php
 363          *
 364          * @param $ip String: quad dotted IP address.
 365          * @return Mixed: string/int/false
 366          */
 367         public static function toUnsigned( $ip ) {
 368                 if ( self::isIPv6( $ip ) ) {
 369                         $n = self::toUnsigned6( $ip );
 370                 } else {
 371                         $n = ip2long( $ip );
 372                         if ( $n < 0 ) {
 373                                 $n += pow( 2, 32 );
 374                         }
 375                 }
 376                 return $n;
 377         }
 378
 379         private static function toUnsigned6( $ip ) {
 380                 return wfBaseConvert( self::IPv6ToRawHex( $ip ), 16, 10 );
 381         }
 382
 383         /**
 384          * Convert a network specification in CIDR notation
 385          * to an integer network and a number of bits
 386          *
 387          * @param $range String: IP with CIDR prefix
 388          * @return array(int or string, int)
 389          */
 390         public static function parseCIDR( $range ) {
 391                 if ( self::isIPv6( $range ) ) {
 392                         return self::parseCIDR6( $range );
 393                 }
 394                 $parts = explode( '/', $range, 2 );
 395                 if ( count( $parts ) != 2 ) {
 396                         return array( false, false );
 397                 }
 398                 list( $network, $bits ) = $parts;
 399                 $network = ip2long( $network );
 400                 if ( $network !== false && is_numeric( $bits ) && $bits >= 0 && $bits <= 32 ) {
 401                         if ( $bits == 0 ) {
 402                                 $network = 0;
 403                         } else {
 404                                 $network &= ~( ( 1 << ( 32 - $bits ) ) - 1);
 405                         }
 406                         # Convert to unsigned
 407                         if ( $network < 0 ) {
 408                                 $network += pow( 2, 32 );
 409                         }
 410                 } else {
 411                         $network = false;
 412                         $bits = false;
 413                 }
 414                 return array( $network, $bits );
 415         }
 416
 417         /**
 418          * Given a string range in a number of formats,
 419          * return the start and end of the range in hexadecimal.
 420          *
 421          * Formats are:
 422          *     1.2.3.4/24          CIDR
 423          *     1.2.3.4 - 1.2.3.5   Explicit range
 424          *     1.2.3.4             Single IP
 425          *
 426          *     2001:0db8:85a3::7344/96                                   CIDR
 427          *     2001:0db8:85a3::7344 - 2001:0db8:85a3::7344   Explicit range
 428          *     2001:0db8:85a3::7344                                      Single IP
 429          * @param $range String: IP range
 430          * @return array(string, string)
 431          */
 432         public static function parseRange( $range ) {
 433                 // CIDR notation
 434                 if ( strpos( $range, '/' ) !== false ) {
 435                         if ( self::isIPv6( $range ) ) {
 436                                 return self::parseRange6( $range );
 437                         }
 438                         list( $network, $bits ) = self::parseCIDR( $range );
 439                         if ( $network === false ) {
 440                                 $start = $end = false;
 441                         } else {
 442                                 $start = sprintf( '%08X', $network );
 443                                 $end = sprintf( '%08X', $network + pow( 2, ( 32 - $bits ) ) - 1 );
 444                         }
 445                 // Explicit range
 446                 } elseif ( strpos( $range, '-' ) !== false ) {
 447                         list( $start, $end ) = array_map( 'trim', explode( '-', $range, 2 ) );
 448                         if ( self::isIPv6( $start ) && self::isIPv6( $end ) ) {
 449                                 return self::parseRange6( $range );
 450                         }
 451                         if ( self::isIPv4( $start ) && self::isIPv4( $end ) ) {
 452                                 $start = self::toUnsigned( $start );
 453                                 $end = self::toUnsigned( $end );
 454                                 if ( $start > $end ) {
 455                                         $start = $end = false;
 456                                 } else {
 457                                         $start = sprintf( '%08X', $start );
 458                                         $end = sprintf( '%08X', $end );
 459                                 }
 460                         } else {
 461                                 $start = $end = false;
 462                         }
 463                 } else {
 464                         # Single IP
 465                         $start = $end = self::toHex( $range );
 466                 }
 467                 if ( $start === false || $end === false ) {
 468                         return array( false, false );
 469                 } else {
 470                         return array( $start, $end );
 471                 }
 472         }
 473
 474         /**
 475          * Convert a network specification in IPv6 CIDR notation to an
 476          * integer network and a number of bits
 477          *
 478          * @return array(string, int)
 479          */
 480         private static function parseCIDR6( $range ) {
 481                 # Explode into <expanded IP,range>
 482                 $parts = explode( '/', IP::sanitizeIP( $range ), 2 );
 483                 if ( count( $parts ) != 2 ) {
 484                         return array( false, false );
 485                 }
 486                 list( $network, $bits ) = $parts;
 487                 $network = self::IPv6ToRawHex( $network );
 488                 if ( $network !== false && is_numeric( $bits ) && $bits >= 0 && $bits <= 128 ) {
 489                         if ( $bits == 0 ) {
 490                                 $network = "0";
 491                         } else {
 492                                 # Native 32 bit functions WONT work here!!!
 493                                 # Convert to a padded binary number
 494                                 $network = wfBaseConvert( $network, 16, 2, 128 );
 495                                 # Truncate the last (128-$bits) bits and replace them with zeros
 496                                 $network = str_pad( substr( $network, 0, $bits ), 128, 0, STR_PAD_RIGHT );
 497                                 # Convert back to an integer
 498                                 $network = wfBaseConvert( $network, 2, 10 );
 499                         }
 500                 } else {
 501                         $network = false;
 502                         $bits = false;
 503                 }
 504                 return array( $network, (int)$bits );
 505         }
 506
 507         /**
 508          * Given a string range in a number of formats, return the
 509          * start and end of the range in hexadecimal. For IPv6.
 510          *
 511          * Formats are:
 512          *     2001:0db8:85a3::7344/96                                   CIDR
 513          *     2001:0db8:85a3::7344 - 2001:0db8:85a3::7344   Explicit range
 514          *     2001:0db8:85a3::7344/96                                   Single IP
 515          * @return array(string, string)
 516          */
 517         private static function parseRange6( $range ) {
 518                 # Expand any IPv6 IP
 519                 $range = IP::sanitizeIP( $range );
 520                 // CIDR notation...
 521                 if ( strpos( $range, '/' ) !== false ) {
 522                         list( $network, $bits ) = self::parseCIDR6( $range );
 523                         if ( $network === false ) {
 524                                 $start = $end = false;
 525                         } else {
 526                                 $start = wfBaseConvert( $network, 10, 16, 32, false );
 527                                 # Turn network to binary (again)
 528                                 $end = wfBaseConvert( $network, 10, 2, 128 );
 529                                 # Truncate the last (128-$bits) bits and replace them with ones
 530                                 $end = str_pad( substr( $end, 0, $bits ), 128, 1, STR_PAD_RIGHT );
 531                                 # Convert to hex
 532                                 $end = wfBaseConvert( $end, 2, 16, 32, false );
 533                                 # see toHex() comment
 534                                 $start = "v6-$start";
 535                                 $end = "v6-$end";
 536                         }
 537                 // Explicit range notation...
 538                 } elseif ( strpos( $range, '-' ) !== false ) {
 539                         list( $start, $end ) = array_map( 'trim', explode( '-', $range, 2 ) );
 540                         $start = self::toUnsigned6( $start );
 541                         $end = self::toUnsigned6( $end );
 542                         if ( $start > $end ) {
 543                                 $start = $end = false;
 544                         } else {
 545                                 $start = wfBaseConvert( $start, 10, 16, 32, false );
 546                                 $end = wfBaseConvert( $end, 10, 16, 32, false );
 547                         }
 548                         # see toHex() comment
 549                         $start = "v6-$start";
 550                         $end = "v6-$end";
 551                 } else {
 552                         # Single IP
 553                         $start = $end = self::toHex( $range );
 554                 }
 555                 if ( $start === false || $end === false ) {
 556                         return array( false, false );
 557                 } else {
 558                         return array( $start, $end );
 559                 }
 560         }
 561
 562         /**
 563          * Determine if a given IPv4/IPv6 address is in a given CIDR network
 564          *
 565          * @param $addr String: the address to check against the given range.
 566          * @param $range String: the range to check the given address against.
 567          * @return Boolean: whether or not the given address is in the given range.
 568          */
 569         public static function isInRange( $addr, $range ) {
 570                 $hexIP = self::toHex( $addr );
 571                 list( $start, $end ) = self::parseRange( $range );
 572                 return ( strcmp( $hexIP, $start ) >= 0 &&
 573                         strcmp( $hexIP, $end ) <= 0 );
 574         }
 575
 576         /**
 577          * Convert some unusual representations of IPv4 addresses to their
 578          * canonical dotted quad representation.
 579          *
 580          * This currently only checks a few IPV4-to-IPv6 related cases.  More
 581          * unusual representations may be added later.
 582          *
 583          * @param $addr String: something that might be an IP address
 584          * @return String: valid dotted quad IPv4 address or null
 585          */
 586         public static function canonicalize( $addr ) {
 587                 if ( self::isValid( $addr ) ) {
 588                         return $addr;
 589                 }
 590                 // Turn mapped addresses from ::ce:ffff:1.2.3.4 to 1.2.3.4
 591                 if ( strpos( $addr, ':' ) !== false && strpos( $addr, '.' ) !== false ) {
 592                         $addr = substr( $addr, strrpos( $addr, ':' ) + 1 );
 593                         if ( self::isIPv4( $addr ) ) {
 594                                 return $addr;
 595                         }
 596                 }
 597                 // IPv6 loopback address
 598                 $m = array();
 599                 if ( preg_match( '/^0*' . RE_IPV6_GAP . '1$/', $addr, $m ) ) {
 600                         return '127.0.0.1';
 601                 }
 602                 // IPv4-mapped and IPv4-compatible IPv6 addresses
 603                 if ( preg_match( '/^' . RE_IPV6_V4_PREFIX . '(' . RE_IP_ADD . ')$/i', $addr, $m ) ) {
 604                         return $m[1];
 605                 }
 606                 if ( preg_match( '/^' . RE_IPV6_V4_PREFIX . RE_IPV6_WORD .
 607                         ':' . RE_IPV6_WORD . '$/i', $addr, $m ) )
 608                 {
 609                         return long2ip( ( hexdec( $m[1] ) << 16 ) + hexdec( $m[2] ) );
 610                 }
 611
 612                 return null;  // give up
 613         }
 614 }