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