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>
  22  */
  23
  24 // Some regex definition to "play" with IP address and IP address blocks
  25
  26 // An IP 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 // For IPv6 canonicalization (NOT for strict validation; these are quite lax!)
  33 define( 'RE_IPV6_WORD', '([0-9A-Fa-f]{1,4})' );
  34 define( 'RE_IPV6_GAP', ':(?:0+:)*(?::(?:0+:)*)?' );
  35 define( 'RE_IPV6_V4_PREFIX', '0*' . RE_IPV6_GAP . '(?:ffff:)?' );
  36 // An IPv6 block is an IP address and a prefix (d1 to d128)
  37 define( 'RE_IPV6_PREFIX', '(12[0-8]|1[01][0-9]|[1-9]?\d)');
  38 // An IPv6 IP is made up of 8 octets. However abbreviations like "::" can be used.
  39 // This is lax! Number of octets/double colons validation not done.
  40 define( 'RE_IPV6_ADD',
  41         '(' .
  42                 ':(:' . RE_IPV6_WORD . '){1,7}' . // IPs that start with ":"
  43         '|' .
  44                 RE_IPV6_WORD . '(:{1,2}' . RE_IPV6_WORD . '|::$){1,7}' . // IPs that don't start with ":"
  45         ')'
  46 );
  47 define( 'RE_IPV6_BLOCK', RE_IPV6_ADD . '\/' . RE_IPV6_PREFIX );
  48 // This might be useful for regexps used elsewhere, matches any IPv6 or IPv6 address or network
  49 define( 'IP_ADDRESS_STRING',
  50         '(?:' .
  51                 RE_IP_ADD . '(\/' . RE_IP_PREFIX . '|)' . // IPv4
  52         '|' .
  53                 RE_IPV6_ADD . '(\/' . RE_IPV6_PREFIX . '|)' . // IPv6
  54         ')'
  55 );
  56
  57 /**
  58  * A collection of public static functions to play with IP address
  59  * and IP blocks.
  60  */
  61 class IP {
  62         /**
  63          * Given a string, determine if it as valid IP
  64          * Unlike isValid(), this looks for networks too
  65          * @param $ip IP address.
  66          * @return string
  67          */
  68         public static function isIPAddress( $ip ) {
  69                 if ( !$ip ) {
  70                         return false;
  71                 }
  72                 if ( is_array( $ip ) ) {
  73                   throw new MWException( 'invalid value passed to ' . __METHOD__ );
  74                 }
  75                 // IPv6 IPs with two "::" strings are ambiguous and thus invalid
  76                 return preg_match( '/^' . IP_ADDRESS_STRING . '$/', $ip ) && ( substr_count( $ip, '::' ) < 2 );
  77         }
  78
  79         public static function isIPv6( $ip ) {
  80                 if ( !$ip ) {
  81                         return false;
  82                 }
  83                 if( is_array( $ip ) ) {
  84                         throw new MWException( 'invalid value passed to ' . __METHOD__ );
  85                 }
  86                 $doubleColons = substr_count( $ip, '::' );
  87                 // IPv6 IPs with two "::" strings are ambiguous and thus invalid
  88                 return preg_match( '/^' . RE_IPV6_ADD . '(\/' . RE_IPV6_PREFIX . '|)$/', $ip )
  89                         && ( $doubleColons == 1 || substr_count( $ip, ':' ) == 7 );
  90         }
  91
  92         public static function isIPv4( $ip ) {
  93                 if ( !$ip ) {
  94                         return false;
  95                 }
  96                 return preg_match( '/^' . RE_IP_ADD . '(\/' . RE_IP_PREFIX . '|)$/', $ip);
  97         }
  98
  99         /**
 100          * Given an IP address in dotted-quad notation, returns an IPv6 octet.
 101          * See http://www.answers.com/topic/ipv4-compatible-address
 102          * IPs with the first 92 bits as zeros are reserved from IPv6
 103          * @param $ip quad-dotted IP address.
 104          * @return string
 105          */
 106         public static function IPv4toIPv6( $ip ) {
 107                 if ( !$ip ) {
 108                         return null;
 109                 }
 110                 // Convert only if needed
 111                 if ( self::isIPv6( $ip ) ) {
 112                         return $ip;
 113                 }
 114                 // IPv4 CIDRs
 115                 if ( strpos( $ip, '/' ) !== false ) {
 116                         $parts = explode( '/', $ip, 2 );
 117                         if ( count( $parts ) != 2 ) {
 118                                 return false;
 119                         }
 120                         $network = self::toUnsigned( $parts[0] );
 121                         if ( $network !== false && is_numeric( $parts[1] ) && $parts[1] >= 0 && $parts[1] <= 32 ) {
 122                                 $bits = $parts[1] + 96;
 123                                 return self::toOctet( $network ) . "/$bits";
 124                         } else {
 125                                 return false;
 126                         }
 127                 }
 128                 return self::toOctet( self::toUnsigned( $ip ) );
 129         }
 130
 131         /**
 132          * Given an IPv6 address in octet notation, returns an unsigned integer.
 133          * @param $ip octet ipv6 IP address.
 134          * @return string
 135          */
 136         public static function toUnsigned6( $ip ) {
 137                 if ( !$ip ) {
 138                         return null;
 139                 }
 140                 $ip = explode( ':', self::sanitizeIP( $ip ) );
 141                 $r_ip = '';
 142                 foreach ( $ip as $v ) {
 143                         $r_ip .= str_pad( $v, 4, 0, STR_PAD_LEFT );
 144                 }
 145                 $r_ip = wfBaseConvert( $r_ip, 16, 10 );
 146                 return $r_ip;
 147         }
 148
 149         /**
 150          * Given an IPv6 address in octet notation, returns the expanded octet.
 151          * IPv4 IPs will be trimmed, thats it...
 152          * @param $ip octet ipv6 IP address.
 153          * @return string
 154          */
 155         public static function sanitizeIP( $ip ) {
 156                 $ip = trim( $ip );
 157                 if ( $ip === '' ) {
 158                         return null;
 159                 }
 160                 // Trim and return IPv4 addresses
 161                 if ( self::isIPv4( $ip ) ) {
 162                         return $ip;
 163                 }
 164                 // Only IPv6 addresses can be expanded
 165                 if ( !self::isIPv6( $ip ) ) {
 166                         return $ip;
 167                 }
 168                 // Remove any whitespaces, convert to upper case
 169                 $ip = strtoupper( $ip );
 170                 // Expand zero abbreviations
 171                 $abbrevPos = strpos( $ip, '::' );
 172                 if ( $abbrevPos !== false ) {
 173                         // If the '::' is at the beginning...
 174                         if( $abbrevPos == 0 ) {
 175                                 $repeat = '0:';
 176                                 $extra = '';
 177                                 $pad = 9; // 7+2 (due to '::')
 178                         // If the '::' is at the end...
 179                         } elseif( $abbrevPos == ( strlen( $ip ) - 2 ) ) {
 180                                 $repeat = ':0';
 181                                 $extra = '';
 182                                 $pad = 9; // 7+2 (due to '::')
 183                         // If the '::' is at the end...
 184                         } else {
 185                                 $repeat = ':0';
 186                                 $extra = ':';
 187                                 $pad = 8; // 6+2 (due to '::')
 188                         }
 189                         $ip = str_replace( '::', str_repeat( $repeat, $pad - substr_count( $ip, ':' ) ) . $extra, $ip );
 190                 }
 191                 // Remove leading zereos from each bloc as needed
 192                 $ip = preg_replace( '/(^|:)0+' . RE_IPV6_WORD . '/', '$1$2', $ip );
 193                 return $ip;
 194         }
 195
 196         /**
 197          * Given an unsigned integer, returns an IPv6 address in octet notation
 198          * @param $ip_int integer IP address.
 199          * @return string
 200          */
 201         public static function toOctet( $ip_int ) {
 202                 // Convert to padded uppercase hex
 203                 $ip_hex = wfBaseConvert( $ip_int, 10, 16, 32, false );
 204                 // Separate into 8 octets
 205                 $ip_oct = substr( $ip_hex, 0, 4 );
 206                 for ( $n = 1; $n < 8; $n++ ) {
 207                         $ip_oct .= ':' . substr( $ip_hex, 4 * $n, 4 );
 208                 }
 209                 // NO leading zeroes
 210                 $ip_oct = preg_replace( '/(^|:)0+' . RE_IPV6_WORD . '/', '$1$2', $ip_oct );
 211                 return $ip_oct;
 212         }
 213
 214         /**
 215          * Convert an IPv4 or IPv6 hexadecimal representation back to readable format
 216          */
 217         public static function formatHex( $hex ) {
 218                 if ( substr( $hex, 0, 3 ) == 'v6-' ) {
 219                         return self::hexToOctet( $hex );
 220                 } else {
 221                         return self::hexToQuad( $hex );
 222                 }
 223         }
 224
 225         /**
 226          * Given a hexadecimal number, returns to an IPv6 address in octet notation
 227          * @param $ip_hex string hex IP
 228          * @return string
 229          */
 230         public static function hextoOctet( $ip_hex ) {
 231                 // Convert to padded uppercase hex
 232                 $ip_hex = str_pad( strtoupper( $ip_hex ), 32, '0' );
 233                 // Separate into 8 octets
 234                 $ip_oct = substr( $ip_hex, 0, 4 );
 235                 for ( $n = 1; $n < 8; $n++ ) {
 236                         $ip_oct .= ':' . substr( $ip_hex, 4 * $n, 4 );
 237                 }
 238                 // NO leading zeroes
 239                 $ip_oct = preg_replace( '/(^|:)0+' . RE_IPV6_WORD . '/', '$1$2', $ip_oct );
 240                 return $ip_oct;
 241         }
 242
 243         /**
 244          * Converts a hexadecimal number to an IPv4 address in octet notation
 245          * @param $ip string Hex IP
 246          * @return string
 247          */
 248         public static function hexToQuad( $ip ) {
 249                 // Converts a hexadecimal IP to nnn.nnn.nnn.nnn format
 250                 $s = '';
 251                 for ( $i = 0; $i < 4; $i++ ) {
 252                         if ( $s !== '' ) {
 253                                 $s .= '.';
 254                         }
 255                         $s .= base_convert( substr( $ip, $i * 2, 2 ), 16, 10 );
 256                 }
 257                 return $s;
 258         }
 259
 260         /**
 261          * Convert a network specification in IPv6 CIDR notation to an integer network and a number of bits
 262          * @return array(string, int)
 263          */
 264         public static function parseCIDR6( $range ) {
 265                 # Expand any IPv6 IP
 266                 $parts = explode( '/', IP::sanitizeIP( $range ), 2 );
 267                 if ( count( $parts ) != 2 ) {
 268                         return array( false, false );
 269                 }
 270                 $network = self::toUnsigned6( $parts[0] );
 271                 if ( $network !== false && is_numeric( $parts[1] ) && $parts[1] >= 0 && $parts[1] <= 128 ) {
 272                         $bits = $parts[1];
 273                         if ( $bits == 0 ) {
 274                                 $network = 0;
 275                         } else {
 276                         # Native 32 bit functions WONT work here!!!
 277                         # Convert to a padded binary number
 278                                 $network = wfBaseConvert( $network, 10, 2, 128 );
 279                         # Truncate the last (128-$bits) bits and replace them with zeros
 280                                 $network = str_pad( substr( $network, 0, $bits ), 128, 0, STR_PAD_RIGHT );
 281                         # Convert back to an integer
 282                                 $network = wfBaseConvert( $network, 2, 10 );
 283                         }
 284                 } else {
 285                         $network = false;
 286                         $bits = false;
 287                 }
 288                 return array( $network, $bits );
 289         }
 290
 291         /**
 292          * Given a string range in a number of formats, return the start and end of
 293          * the range in hexadecimal. For IPv6.
 294          *
 295          * Formats are:
 296          *     2001:0db8:85a3::7344/96                                   CIDR
 297          *     2001:0db8:85a3::7344 - 2001:0db8:85a3::7344   Explicit range
 298          *     2001:0db8:85a3::7344/96                                   Single IP
 299          * @return array(string, int)
 300          */
 301         public static function parseRange6( $range ) {
 302                 # Expand any IPv6 IP
 303                 $range = IP::sanitizeIP( $range );
 304                 if ( strpos( $range, '/' ) !== false ) {
 305                         # CIDR
 306                         list( $network, $bits ) = self::parseCIDR6( $range );
 307                         if ( $network === false ) {
 308                                 $start = $end = false;
 309                         } else {
 310                                 $start = wfBaseConvert( $network, 10, 16, 32, false );
 311                                 # Turn network to binary (again)
 312                                 $end = wfBaseConvert( $network, 10, 2, 128 );
 313                                 # Truncate the last (128-$bits) bits and replace them with ones
 314                                 $end = str_pad( substr( $end, 0, $bits ), 128, 1, STR_PAD_RIGHT );
 315                                 # Convert to hex
 316                                 $end = wfBaseConvert( $end, 2, 16, 32, false );
 317                                 # see toHex() comment
 318                                 $start = "v6-$start";
 319                                 $end = "v6-$end";
 320                         }
 321                 } elseif ( strpos( $range, '-' ) !== false ) {
 322                         # Explicit range
 323                         list( $start, $end ) = array_map( 'trim', explode( '-', $range, 2 ) );
 324                         $start = self::toUnsigned6( $start );
 325                         $end = self::toUnsigned6( $end );
 326                         if ( $start > $end ) {
 327                                 $start = $end = false;
 328                         } else {
 329                                 $start = wfBaseConvert( $start, 10, 16, 32, false );
 330                                 $end = wfBaseConvert( $end, 10, 16, 32, false );
 331                         }
 332                         # see toHex() comment
 333                         $start = "v6-$start";
 334                         $end = "v6-$end";
 335                 } else {
 336                         # Single IP
 337                         $start = $end = self::toHex( $range );
 338                 }
 339                 if ( $start === false || $end === false ) {
 340                         return array( false, false );
 341                 } else {
 342                         return array( $start, $end );
 343                 }
 344         }
 345
 346         /**
 347          * Validate an IP address.
 348          * @return boolean True if it is valid.
 349          */
 350         public static function isValid( $ip ) {
 351                 return ( preg_match( '/^' . RE_IP_ADD . '$/', $ip ) || preg_match( '/^' . RE_IPV6_ADD . '$/', $ip ) );
 352         }
 353
 354         /**
 355          * Validate an IP Block.
 356          * @return boolean True if it is valid.
 357          */
 358         public static function isValidBlock( $ipblock ) {
 359                 return ( count( self::toArray( $ipblock ) ) == 1 + 5 );
 360         }
 361
 362         /**
 363          * Determine if an IP address really is an IP address, and if it is public,
 364          * i.e. not RFC 1918 or similar
 365          * Comes from ProxyTools.php
 366          */
 367         public static function isPublic( $ip ) {
 368                 $n = self::toUnsigned( $ip );
 369                 if ( !$n ) {
 370                         return false;
 371                 }
 372
 373                 // ip2long accepts incomplete addresses, as well as some addresses
 374                 // followed by garbage characters. Check that it's really valid.
 375                 if( $ip != long2ip( $n ) ) {
 376                         return false;
 377                 }
 378
 379                 static $privateRanges = false;
 380                 if ( !$privateRanges ) {
 381                         $privateRanges = array(
 382                                 array( '10.0.0.0',    '10.255.255.255' ),   # RFC 1918 (private)
 383                                 array( '172.16.0.0',  '172.31.255.255' ),   #     "
 384                                 array( '192.168.0.0', '192.168.255.255' ),  #     "
 385                                 array( '0.0.0.0',     '0.255.255.255' ),    # this network
 386                                 array( '127.0.0.0',   '127.255.255.255' ),  # loopback
 387                         );
 388                 }
 389
 390                 foreach ( $privateRanges as $r ) {
 391                         $start = self::toUnsigned( $r[0] );
 392                         $end = self::toUnsigned( $r[1] );
 393                         if ( $n >= $start && $n <= $end ) {
 394                                 return false;
 395                         }
 396                 }
 397                 return true;
 398         }
 399
 400         /**
 401          * Split out an IP block as an array of 4 bytes and a mask,
 402          * return false if it can't be determined
 403          *
 404          * @param $ipblock string A quad dotted/octet IP address
 405          * @return array
 406          */
 407         public static function toArray( $ipblock ) {
 408                 $matches = array();
 409                 if( preg_match( '/^' . RE_IP_ADD . '(?:\/(?:' . RE_IP_PREFIX . '))?' . '$/', $ipblock, $matches ) ) {
 410                         return $matches;
 411                 } elseif ( preg_match( '/^' . RE_IPV6_ADD . '(?:\/(?:' . RE_IPV6_PREFIX . '))?' . '$/', $ipblock, $matches ) ) {
 412                         return $matches;
 413                 } else {
 414                         return false;
 415                 }
 416         }
 417
 418         /**
 419          * Return a zero-padded hexadecimal representation of an IP address.
 420          *
 421          * Hexadecimal addresses are used because they can easily be extended to
 422          * IPv6 support. To separate the ranges, the return value from this
 423          * function for an IPv6 address will be prefixed with "v6-", a non-
 424          * hexadecimal string which sorts after the IPv4 addresses.
 425          *
 426          * @param $ip Quad dotted/octet IP address.
 427          * @return hexidecimal
 428          */
 429         public static function toHex( $ip ) {
 430                 $n = self::toUnsigned( $ip );
 431                 if ( $n !== false ) {
 432                         $n = self::isIPv6( $ip ) ? 'v6-' . wfBaseConvert( $n, 10, 16, 32, false ) : wfBaseConvert( $n, 10, 16, 8, false );
 433                 }
 434                 return $n;
 435         }
 436
 437         /**
 438          * Given an IP address in dotted-quad/octet notation, returns an unsigned integer.
 439          * Like ip2long() except that it actually works and has a consistent error return value.
 440          * Comes from ProxyTools.php
 441          * @param $ip Quad dotted IP address.
 442          * @return integer
 443          */
 444         public static function toUnsigned( $ip ) {
 445                 // Use IPv6 functions if needed
 446                 if ( self::isIPv6( $ip ) ) {
 447                         return self::toUnsigned6( $ip );
 448                 }
 449                 if ( $ip == '255.255.255.255' ) {
 450                         $n = -1;
 451                 } else {
 452                         $n = ip2long( $ip );
 453                         if ( $n == -1 || $n === false ) { # Return value on error depends on PHP version
 454                                 $n = false;
 455                         }
 456                 }
 457                 if ( $n < 0 ) {
 458                         $n += pow( 2, 32 );
 459                 }
 460                 return $n;
 461         }
 462
 463         /**
 464          * Convert a dotted-quad IP to a signed integer
 465          * Returns false on failure
 466          */
 467         public static function toSigned( $ip ) {
 468                 if ( $ip == '255.255.255.255' ) {
 469                         $n = -1;
 470                 } else {
 471                         $n = ip2long( $ip );
 472                         if ( $n == -1 ) {
 473                                 $n = false;
 474                         }
 475                 }
 476                 return $n;
 477         }
 478
 479         /**
 480          * Convert a network specification in CIDR notation to an integer network and a number of bits
 481          * @return array(string, int)
 482          */
 483         public static function parseCIDR( $range ) {
 484                 $parts = explode( '/', $range, 2 );
 485                 if ( count( $parts ) != 2 ) {
 486                         return array( false, false );
 487                 }
 488                 $network = self::toSigned( $parts[0] );
 489                 if ( $network !== false && is_numeric( $parts[1] ) && $parts[1] >= 0 && $parts[1] <= 32 ) {
 490                         $bits = $parts[1];
 491                         if ( $bits == 0 ) {
 492                                 $network = 0;
 493                         } else {
 494                                 $network &= ~( ( 1 << ( 32 - $bits ) ) - 1);
 495                         }
 496                         # Convert to unsigned
 497                         if ( $network < 0 ) {
 498                                 $network += pow( 2, 32 );
 499                         }
 500                 } else {
 501                         $network = false;
 502                         $bits = false;
 503                 }
 504                 return array( $network, $bits );
 505         }
 506
 507         /**
 508          * Given a string range in a number of formats, return the start and end of
 509          * the range in hexadecimal.
 510          *
 511          * Formats are:
 512          *     1.2.3.4/24          CIDR
 513          *     1.2.3.4 - 1.2.3.5   Explicit range
 514          *     1.2.3.4             Single IP
 515          *
 516          *     2001:0db8:85a3::7344/96                                   CIDR
 517          *     2001:0db8:85a3::7344 - 2001:0db8:85a3::7344   Explicit range
 518          *     2001:0db8:85a3::7344                                      Single IP
 519          * @return array(string, int)
 520          */
 521         public static function parseRange( $range ) {
 522                 // Use IPv6 functions if needed
 523                 if ( self::isIPv6( $range ) ) {
 524                         return self::parseRange6( $range );
 525                 }
 526                 if ( strpos( $range, '/' ) !== false ) {
 527                         # CIDR
 528                         list( $network, $bits ) = self::parseCIDR( $range );
 529                         if ( $network === false ) {
 530                                 $start = $end = false;
 531                         } else {
 532                                 $start = sprintf( '%08X', $network );
 533                                 $end = sprintf( '%08X', $network + pow( 2, ( 32 - $bits ) ) - 1 );
 534                         }
 535                 } elseif ( strpos( $range, '-' ) !== false ) {
 536                         # Explicit range
 537                         list( $start, $end ) = array_map( 'trim', explode( '-', $range, 2 ) );
 538                         if( self::isIPAddress( $start ) && self::isIPAddress( $end ) ) {
 539                                 $start = self::toUnsigned( $start );
 540                                 $end = self::toUnsigned( $end );
 541                                 if ( $start > $end ) {
 542                                         $start = $end = false;
 543                                 } else {
 544                                         $start = sprintf( '%08X', $start );
 545                                         $end = sprintf( '%08X', $end );
 546                                 }
 547                         } else {
 548                                 $start = $end = false;
 549                         }
 550                 } else {
 551                         # Single IP
 552                         $start = $end = self::toHex( $range );
 553                 }
 554                 if ( $start === false || $end === false ) {
 555                         return array( false, false );
 556                 } else {
 557                         return array( $start, $end );
 558                 }
 559         }
 560
 561         /**
 562          * Determine if a given IPv4/IPv6 address is in a given CIDR network
 563          * @param $addr The address to check against the given range.
 564          * @param $range The range to check the given address against.
 565          * @return bool Whether or not the given address is in the given range.
 566          */
 567         public static function isInRange( $addr, $range ) {
 568                 // Convert to IPv6 if needed
 569                 $hexIP = self::toHex( $addr );
 570                 list( $start, $end ) = self::parseRange( $range );
 571                 return ( strcmp( $hexIP, $start ) >= 0 &&
 572                         strcmp( $hexIP, $end ) <= 0 );
 573         }
 574
 575         /**
 576          * Convert some unusual representations of IPv4 addresses to their
 577          * canonical dotted quad representation.
 578          *
 579          * This currently only checks a few IPV4-to-IPv6 related cases.  More
 580          * unusual representations may be added later.
 581          *
 582          * @param $addr something that might be an IP address
 583          * @return valid dotted quad IPv4 address or null
 584          */
 585         public static function canonicalize( $addr ) {
 586                 if ( self::isValid( $addr ) ) {
 587                         return $addr;
 588                 }
 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
 598                 // IPv6 loopback address
 599                 $m = array();
 600                 if ( preg_match( '/^0*' . RE_IPV6_GAP . '1$/', $addr, $m ) ) {
 601                         return '127.0.0.1';
 602                 }
 603
 604                 // IPv4-mapped and IPv4-compatible IPv6 addresses
 605                 if ( preg_match( '/^' . RE_IPV6_V4_PREFIX . '(' . RE_IP_ADD . ')$/i', $addr, $m ) ) {
 606                         return $m[1];
 607                 }
 608                 if ( preg_match( '/^' . RE_IPV6_V4_PREFIX . RE_IPV6_WORD . ':' . RE_IPV6_WORD . '$/i', $addr, $m ) ) {
 609                         return long2ip( ( hexdec( $m[1] ) << 16 ) + hexdec( $m[2] ) );
 610                 }
 611
 612                 return null;  // give up
 613         }
 614 }