DatabaseMysqlBase visibility cleanups

[mediawiki.git] / includes / libs / IP.php

<?php
/**
 * Functions and constants to play with IP addresses and ranges
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 * @author Antoine Musso "<hashar at free dot fr>", Aaron Schulz
 */

use IPSet\IPSet;

// Some regex definition to "play" with IP address and IP address blocks

// An IPv4 address is made of 4 bytes from x00 to xFF which is d0 to d255
define( 'RE_IP_BYTE', '(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|0?[0-9]?[0-9])' );
define( 'RE_IP_ADD', RE_IP_BYTE . '\.' . RE_IP_BYTE . '\.' . RE_IP_BYTE . '\.' . RE_IP_BYTE );
// An IPv4 block is an IP address and a prefix (d1 to d32)
define( 'RE_IP_PREFIX', '(3[0-2]|[12]?\d)' );
define( 'RE_IP_BLOCK', RE_IP_ADD . '\/' . RE_IP_PREFIX );

// An IPv6 address is made up of 8 words (each x0000 to xFFFF).
// However, the "::" abbreviation can be used on consecutive x0000 words.
define( 'RE_IPV6_WORD', '([0-9A-Fa-f]{1,4})' );
define( 'RE_IPV6_PREFIX', '(12[0-8]|1[01][0-9]|[1-9]?\d)' );
define( 'RE_IPV6_ADD',
        '(?:' . // starts with "::" (including "::")
                ':(?::|(?::' . RE_IPV6_WORD . '){1,7})' .
        '|' . // ends with "::" (except "::")
                RE_IPV6_WORD . '(?::' . RE_IPV6_WORD . '){0,6}::' .
        '|' . // contains one "::" in the middle (the ^ makes the test fail if none found)
                RE_IPV6_WORD . '(?::((?(-1)|:))?' . RE_IPV6_WORD . '){1,6}(?(-2)|^)' .
        '|' . // contains no "::"
                RE_IPV6_WORD . '(?::' . RE_IPV6_WORD . '){7}' .
        ')'
);
// An IPv6 block is an IP address and a prefix (d1 to d128)
define( 'RE_IPV6_BLOCK', RE_IPV6_ADD . '\/' . RE_IPV6_PREFIX );
// For IPv6 canonicalization (NOT for strict validation; these are quite lax!)
define( 'RE_IPV6_GAP', ':(?:0+:)*(?::(?:0+:)*)?' );
define( 'RE_IPV6_V4_PREFIX', '0*' . RE_IPV6_GAP . '(?:ffff:)?' );

// This might be useful for regexps used elsewhere, matches any IPv4 or IPv6 address or network
define( 'IP_ADDRESS_STRING',
        '(?:' .
                RE_IP_ADD . '(?:\/' . RE_IP_PREFIX . ')?' . // IPv4
        '|' .
                RE_IPV6_ADD . '(?:\/' . RE_IPV6_PREFIX . ')?' . // IPv6
        ')'
);

/**
 * A collection of public static functions to play with IP address
 * and IP blocks.
 */
class IP {
        /** @var IPSet */
        private static $proxyIpSet = null;

        /**
         * Determine if a string is as valid IP address or network (CIDR prefix).
         * SIIT IPv4-translated addresses are rejected.
         * @note canonicalize() tries to convert translated addresses to IPv4.
         *
         * @param string $ip Possible IP address
         * @return bool
         */
        public static function isIPAddress( $ip ) {
                return (bool)preg_match( '/^' . IP_ADDRESS_STRING . '$/', $ip );
        }

        /**
         * Given a string, determine if it as valid IP in IPv6 only.
         * @note Unlike isValid(), this looks for networks too.
         *
         * @param string $ip Possible IP address
         * @return bool
         */
        public static function isIPv6( $ip ) {
                return (bool)preg_match( '/^' . RE_IPV6_ADD . '(?:\/' . RE_IPV6_PREFIX . ')?$/', $ip );
        }

        /**
         * Given a string, determine if it as valid IP in IPv4 only.
         * @note Unlike isValid(), this looks for networks too.
         *
         * @param string $ip Possible IP address
         * @return bool
         */
        public static function isIPv4( $ip ) {
                return (bool)preg_match( '/^' . RE_IP_ADD . '(?:\/' . RE_IP_PREFIX . ')?$/', $ip );
        }

        /**
         * Validate an IP address. Ranges are NOT considered valid.
         * SIIT IPv4-translated addresses are rejected.
         * @note canonicalize() tries to convert translated addresses to IPv4.
         *
         * @param string $ip
         * @return bool True if it is valid
         */
        public static function isValid( $ip ) {
                return ( preg_match( '/^' . RE_IP_ADD . '$/', $ip )
                        || preg_match( '/^' . RE_IPV6_ADD . '$/', $ip ) );
        }

        /**
         * Validate an IP Block (valid address WITH a valid prefix).
         * SIIT IPv4-translated addresses are rejected.
         * @note canonicalize() tries to convert translated addresses to IPv4.
         *
         * @param string $ipblock
         * @return bool True if it is valid
         */
        public static function isValidBlock( $ipblock ) {
                return ( preg_match( '/^' . RE_IPV6_BLOCK . '$/', $ipblock )
                        || preg_match( '/^' . RE_IP_BLOCK . '$/', $ipblock ) );
        }

        /**
         * Convert an IP into a verbose, uppercase, normalized form.
         * Both IPv4 and IPv6 addresses are trimmed. Additionally,
         * IPv6 addresses in octet notation are expanded to 8 words;
         * IPv4 addresses have leading zeros, in each octet, removed.
         *
         * @param string $ip IP address in quad or octet form (CIDR or not).
         * @return string
         */
        public static function sanitizeIP( $ip ) {
                $ip = trim( $ip );
                if ( $ip === '' ) {
                        return null;
                }
                /* If not an IP, just return trimmed value, since sanitizeIP() is called
                 * in a number of contexts where usernames are supplied as input.
                 */
                if ( !self::isIPAddress( $ip ) ) {
                        return $ip;
                }
                if ( self::isIPv4( $ip ) ) {
                        // Remove leading 0's from octet representation of IPv4 address
                        $ip = preg_replace( '/(?:^|(?<=\.))0+(?=[1-9]|0\.|0$)/', '', $ip );
                        return $ip;
                }
                // Remove any whitespaces, convert to upper case
                $ip = strtoupper( $ip );
                // Expand zero abbreviations
                $abbrevPos = strpos( $ip, '::' );
                if ( $abbrevPos !== false ) {
                        // We know this is valid IPv6. Find the last index of the
                        // address before any CIDR number (e.g. "a:b:c::/24").
                        $CIDRStart = strpos( $ip, "/" );
                        $addressEnd = ( $CIDRStart !== false )
                                ? $CIDRStart - 1
                                : strlen( $ip ) - 1;
                        // If the '::' is at the beginning...
                        if ( $abbrevPos == 0 ) {
                                $repeat = '0:';
                                $extra = ( $ip == '::' ) ? '0' : ''; // for the address '::'
                                $pad = 9; // 7+2 (due to '::')
                        // If the '::' is at the end...
                        } elseif ( $abbrevPos == ( $addressEnd - 1 ) ) {
                                $repeat = ':0';
                                $extra = '';
                                $pad = 9; // 7+2 (due to '::')
                        // If the '::' is in the middle...
                        } else {
                                $repeat = ':0';
                                $extra = ':';
                                $pad = 8; // 6+2 (due to '::')
                        }
                        $ip = str_replace( '::',
                                str_repeat( $repeat, $pad - substr_count( $ip, ':' ) ) . $extra,
                                $ip
                        );
                }
                // Remove leading zeros from each bloc as needed
                $ip = preg_replace( '/(^|:)0+(' . RE_IPV6_WORD . ')/', '$1$2', $ip );

                return $ip;
        }

        /**
         * Prettify an IP for display to end users.
         * This will make it more compact and lower-case.
         *
         * @param string $ip
         * @return string
         */
        public static function prettifyIP( $ip ) {
                $ip = self::sanitizeIP( $ip ); // normalize (removes '::')
                if ( self::isIPv6( $ip ) ) {
                        // Split IP into an address and a CIDR
                        if ( strpos( $ip, '/' ) !== false ) {
                                list( $ip, $cidr ) = explode( '/', $ip, 2 );
                        } else {
                                list( $ip, $cidr ) = [ $ip, '' ];
                        }
                        // Get the largest slice of words with multiple zeros
                        $offset = 0;
                        $longest = $longestPos = false;
                        while ( preg_match(
                                '!(?:^|:)0(?::0)+(?:$|:)!', $ip, $m, PREG_OFFSET_CAPTURE, $offset
                        ) ) {
                                list( $match, $pos ) = $m[0]; // full match
                                if ( strlen( $match ) > strlen( $longest ) ) {
                                        $longest = $match;
                                        $longestPos = $pos;
                                }
                                $offset = ( $pos + strlen( $match ) ); // advance
                        }
                        if ( $longest !== false ) {
                                // Replace this portion of the string with the '::' abbreviation
                                $ip = substr_replace( $ip, '::', $longestPos, strlen( $longest ) );
                        }
                        // Add any CIDR back on
                        if ( $cidr !== '' ) {
                                $ip = "{$ip}/{$cidr}";
                        }
                        // Convert to lower case to make it more readable
                        $ip = strtolower( $ip );
                }

                return $ip;
        }

        /**
         * Given a host/port string, like one might find in the host part of a URL
         * per RFC 2732, split the hostname part and the port part and return an
         * array with an element for each. If there is no port part, the array will
         * have false in place of the port. If the string was invalid in some way,
         * false is returned.
         *
         * This was easy with IPv4 and was generally done in an ad-hoc way, but
         * with IPv6 it's somewhat more complicated due to the need to parse the
         * square brackets and colons.
         *
         * A bare IPv6 address is accepted despite the lack of square brackets.
         *
         * @param string $both The string with the host and port
         * @return array|false Array normally, false on certain failures
         */
        public static function splitHostAndPort( $both ) {
                if ( substr( $both, 0, 1 ) === '[' ) {
                        if ( preg_match( '/^\[(' . RE_IPV6_ADD . ')\](?::(?P<port>\d+))?$/', $both, $m ) ) {
                                if ( isset( $m['port'] ) ) {
                                        return [ $m[1], intval( $m['port'] ) ];
                                } else {
                                        return [ $m[1], false ];
                                }
                        } else {
                                // Square bracket found but no IPv6
                                return false;
                        }
                }
                $numColons = substr_count( $both, ':' );
                if ( $numColons >= 2 ) {
                        // Is it a bare IPv6 address?
                        if ( preg_match( '/^' . RE_IPV6_ADD . '$/', $both ) ) {
                                return [ $both, false ];
                        } else {
                                // Not valid IPv6, but too many colons for anything else
                                return false;
                        }
                }
                if ( $numColons >= 1 ) {
                        // Host:port?
                        $bits = explode( ':', $both );
                        if ( preg_match( '/^\d+/', $bits[1] ) ) {
                                return [ $bits[0], intval( $bits[1] ) ];
                        } else {
                                // Not a valid port
                                return false;
                        }
                }

                // Plain hostname
                return [ $both, false ];
        }

        /**
         * Given a host name and a port, combine them into host/port string like
         * you might find in a URL. If the host contains a colon, wrap it in square
         * brackets like in RFC 2732. If the port matches the default port, omit
         * the port specification
         *
         * @param string $host
         * @param int $port
         * @param bool|int $defaultPort
         * @return string
         */
        public static function combineHostAndPort( $host, $port, $defaultPort = false ) {
                if ( strpos( $host, ':' ) !== false ) {
                        $host = "[$host]";
                }
                if ( $defaultPort !== false && $port == $defaultPort ) {
                        return $host;
                } else {
                        return "$host:$port";
                }
        }

        /**
         * Convert an IPv4 or IPv6 hexadecimal representation back to readable format
         *
         * @param string $hex Number, with "v6-" prefix if it is IPv6
         * @return string Quad-dotted (IPv4) or octet notation (IPv6)
         */
        public static function formatHex( $hex ) {
                if ( substr( $hex, 0, 3 ) == 'v6-' ) { // IPv6
                        return self::hexToOctet( substr( $hex, 3 ) );
                } else { // IPv4
                        return self::hexToQuad( $hex );
                }
        }

        /**
         * Converts a hexadecimal number to an IPv6 address in octet notation
         *
         * @param string $ip_hex Pure hex (no v6- prefix)
         * @return string (of format a:b:c:d:e:f:g:h)
         */
        public static function hexToOctet( $ip_hex ) {
                // Pad hex to 32 chars (128 bits)
                $ip_hex = str_pad( strtoupper( $ip_hex ), 32, '0', STR_PAD_LEFT );
                // Separate into 8 words
                $ip_oct = substr( $ip_hex, 0, 4 );
                for ( $n = 1; $n < 8; $n++ ) {
                        $ip_oct .= ':' . substr( $ip_hex, 4 * $n, 4 );
                }
                // NO leading zeroes
                $ip_oct = preg_replace( '/(^|:)0+(' . RE_IPV6_WORD . ')/', '$1$2', $ip_oct );

                return $ip_oct;
        }

        /**
         * Converts a hexadecimal number to an IPv4 address in quad-dotted notation
         *
         * @param string $ip_hex Pure hex
         * @return string (of format a.b.c.d)
         */
        public static function hexToQuad( $ip_hex ) {
                // Pad hex to 8 chars (32 bits)
                $ip_hex = str_pad( strtoupper( $ip_hex ), 8, '0', STR_PAD_LEFT );
                // Separate into four quads
                $s = '';
                for ( $i = 0; $i < 4; $i++ ) {
                        if ( $s !== '' ) {
                                $s .= '.';
                        }
                        $s .= base_convert( substr( $ip_hex, $i * 2, 2 ), 16, 10 );
                }

                return $s;
        }

        /**
         * Determine if an IP address really is an IP address, and if it is public,
         * i.e. not RFC 1918 or similar
         *
         * @param string $ip
         * @return bool
         */
        public static function isPublic( $ip ) {
                static $privateSet = null;
                if ( !$privateSet ) {
                        $privateSet = new IPSet( [
                                '10.0.0.0/8', # RFC 1918 (private)
                                '172.16.0.0/12', # RFC 1918 (private)
                                '192.168.0.0/16', # RFC 1918 (private)
                                '0.0.0.0/8', # this network
                                '127.0.0.0/8', # loopback
                                'fc00::/7', # RFC 4193 (local)
                                '0:0:0:0:0:0:0:1', # loopback
                                '169.254.0.0/16', # link-local
                                'fe80::/10', # link-local
                        ] );
                }
                return !$privateSet->match( $ip );
        }

        /**
         * Return a zero-padded upper case hexadecimal representation of an IP address.
         *
         * Hexadecimal addresses are used because they can easily be extended to
         * IPv6 support. To separate the ranges, the return value from this
         * function for an IPv6 address will be prefixed with "v6-", a non-
         * hexadecimal string which sorts after the IPv4 addresses.
         *
         * @param string $ip Quad dotted/octet IP address.
         * @return string|bool False on failure
         */
        public static function toHex( $ip ) {
                if ( self::isIPv6( $ip ) ) {
                        $n = 'v6-' . self::IPv6ToRawHex( $ip );
                } elseif ( self::isIPv4( $ip ) ) {
                        // T62035/T97897: An IP with leading 0's fails in ip2long sometimes (e.g. *.08),
                        // also double/triple 0 needs to be changed to just a single 0 for ip2long.
                        $ip = self::sanitizeIP( $ip );
                        $n = ip2long( $ip );
                        if ( $n < 0 ) {
                                $n += pow( 2, 32 );
                                # On 32-bit platforms (and on Windows), 2^32 does not fit into an int,
                                # so $n becomes a float. We convert it to string instead.
                                if ( is_float( $n ) ) {
                                        $n = (string)$n;
                                }
                        }
                        if ( $n !== false ) {
                                # Floating points can handle the conversion; faster than Wikimedia\base_convert()
                                $n = strtoupper( str_pad( base_convert( $n, 10, 16 ), 8, '0', STR_PAD_LEFT ) );
                        }
                } else {
                        $n = false;
                }

                return $n;
        }

        /**
         * Given an IPv6 address in octet notation, returns a pure hex string.
         *
         * @param string $ip Octet ipv6 IP address.
         * @return string|bool Pure hex (uppercase); false on failure
         */
        private static function IPv6ToRawHex( $ip ) {
                $ip = self::sanitizeIP( $ip );
                if ( !$ip ) {
                        return false;
                }
                $r_ip = '';
                foreach ( explode( ':', $ip ) as $v ) {
                        $r_ip .= str_pad( $v, 4, 0, STR_PAD_LEFT );
                }

                return $r_ip;
        }

        /**
         * Convert a network specification in CIDR notation
         * to an integer network and a number of bits
         *
         * @param string $range IP with CIDR prefix
         * @return array(int or string, int)
         */
        public static function parseCIDR( $range ) {
                if ( self::isIPv6( $range ) ) {
                        return self::parseCIDR6( $range );
                }
                $parts = explode( '/', $range, 2 );
                if ( count( $parts ) != 2 ) {
                        return [ false, false ];
                }
                list( $network, $bits ) = $parts;
                $network = ip2long( $network );
                if ( $network !== false && is_numeric( $bits ) && $bits >= 0 && $bits <= 32 ) {
                        if ( $bits == 0 ) {
                                $network = 0;
                        } else {
                                $network &= ~( ( 1 << ( 32 - $bits ) ) - 1 );
                        }
                        # Convert to unsigned
                        if ( $network < 0 ) {
                                $network += pow( 2, 32 );
                        }
                } else {
                        $network = false;
                        $bits = false;
                }

                return [ $network, $bits ];
        }

        /**
         * Given a string range in a number of formats,
         * return the start and end of the range in hexadecimal.
         *
         * Formats are:
         *     1.2.3.4/24          CIDR
         *     1.2.3.4 - 1.2.3.5   Explicit range
         *     1.2.3.4             Single IP
         *
         *     2001:0db8:85a3::7344/96                       CIDR
         *     2001:0db8:85a3::7344 - 2001:0db8:85a3::7344   Explicit range
         *     2001:0db8:85a3::7344                          Single IP
         * @param string $range IP range
         * @return array(string, string)
         */
        public static function parseRange( $range ) {
                // CIDR notation
                if ( strpos( $range, '/' ) !== false ) {
                        if ( self::isIPv6( $range ) ) {
                                return self::parseRange6( $range );
                        }
                        list( $network, $bits ) = self::parseCIDR( $range );
                        if ( $network === false ) {
                                $start = $end = false;
                        } else {
                                $start = sprintf( '%08X', $network );
                                $end = sprintf( '%08X', $network + pow( 2, ( 32 - $bits ) ) - 1 );
                        }
                // Explicit range
                } elseif ( strpos( $range, '-' ) !== false ) {
                        list( $start, $end ) = array_map( 'trim', explode( '-', $range, 2 ) );
                        if ( self::isIPv6( $start ) && self::isIPv6( $end ) ) {
                                return self::parseRange6( $range );
                        }
                        if ( self::isIPv4( $start ) && self::isIPv4( $end ) ) {
                                $start = self::toHex( $start );
                                $end = self::toHex( $end );
                                if ( $start > $end ) {
                                        $start = $end = false;
                                }
                        } else {
                                $start = $end = false;
                        }
                } else {
                        # Single IP
                        $start = $end = self::toHex( $range );
                }
                if ( $start === false || $end === false ) {
                        return [ false, false ];
                } else {
                        return [ $start, $end ];
                }
        }

        /**
         * Convert a network specification in IPv6 CIDR notation to an
         * integer network and a number of bits
         *
         * @param string $range
         *
         * @return array(string, int)
         */
        private static function parseCIDR6( $range ) {
                # Explode into <expanded IP,range>
                $parts = explode( '/', IP::sanitizeIP( $range ), 2 );
                if ( count( $parts ) != 2 ) {
                        return [ false, false ];
                }
                list( $network, $bits ) = $parts;
                $network = self::IPv6ToRawHex( $network );
                if ( $network !== false && is_numeric( $bits ) && $bits >= 0 && $bits <= 128 ) {
                        if ( $bits == 0 ) {
                                $network = "0";
                        } else {
                                # Native 32 bit functions WONT work here!!!
                                # Convert to a padded binary number
                                $network = Wikimedia\base_convert( $network, 16, 2, 128 );
                                # Truncate the last (128-$bits) bits and replace them with zeros
                                $network = str_pad( substr( $network, 0, $bits ), 128, 0, STR_PAD_RIGHT );
                                # Convert back to an integer
                                $network = Wikimedia\base_convert( $network, 2, 10 );
                        }
                } else {
                        $network = false;
                        $bits = false;
                }

                return [ $network, (int)$bits ];
        }

        /**
         * Given a string range in a number of formats, return the
         * start and end of the range in hexadecimal. For IPv6.
         *
         * Formats are:
         *     2001:0db8:85a3::7344/96                       CIDR
         *     2001:0db8:85a3::7344 - 2001:0db8:85a3::7344   Explicit range
         *     2001:0db8:85a3::7344/96                       Single IP
         *
         * @param string $range
         *
         * @return array(string, string)
         */
        private static function parseRange6( $range ) {
                # Expand any IPv6 IP
                $range = IP::sanitizeIP( $range );
                // CIDR notation...
                if ( strpos( $range, '/' ) !== false ) {
                        list( $network, $bits ) = self::parseCIDR6( $range );
                        if ( $network === false ) {
                                $start = $end = false;
                        } else {
                                $start = Wikimedia\base_convert( $network, 10, 16, 32, false );
                                # Turn network to binary (again)
                                $end = Wikimedia\base_convert( $network, 10, 2, 128 );
                                # Truncate the last (128-$bits) bits and replace them with ones
                                $end = str_pad( substr( $end, 0, $bits ), 128, 1, STR_PAD_RIGHT );
                                # Convert to hex
                                $end = Wikimedia\base_convert( $end, 2, 16, 32, false );
                                # see toHex() comment
                                $start = "v6-$start";
                                $end = "v6-$end";
                        }
                // Explicit range notation...
                } elseif ( strpos( $range, '-' ) !== false ) {
                        list( $start, $end ) = array_map( 'trim', explode( '-', $range, 2 ) );
                        $start = self::toHex( $start );
                        $end = self::toHex( $end );
                        if ( $start > $end ) {
                                $start = $end = false;
                        }
                } else {
                        # Single IP
                        $start = $end = self::toHex( $range );
                }
                if ( $start === false || $end === false ) {
                        return [ false, false ];
                } else {
                        return [ $start, $end ];
                }
        }

        /**
         * Determine if a given IPv4/IPv6 address is in a given CIDR network
         *
         * @param string $addr The address to check against the given range.
         * @param string $range The range to check the given address against.
         * @return bool Whether or not the given address is in the given range.
         *
         * @note This can return unexpected results for invalid arguments!
         *       Make sure you pass a valid IP address and IP range.
         */
        public static function isInRange( $addr, $range ) {
                $hexIP = self::toHex( $addr );
                list( $start, $end ) = self::parseRange( $range );

                return ( strcmp( $hexIP, $start ) >= 0 &&
                        strcmp( $hexIP, $end ) <= 0 );
        }

        /**
         * Determines if an IP address is a list of CIDR a.b.c.d/n ranges.
         *
         * @since 1.25
         *
         * @param string $ip the IP to check
         * @param array $ranges the IP ranges, each element a range
         *
         * @return bool true if the specified adress belongs to the specified range; otherwise, false.
         */
        public static function isInRanges( $ip, $ranges ) {
                foreach ( $ranges as $range ) {
                        if ( self::isInRange( $ip, $range ) ) {
                                return true;
                        }
                }
                return false;
        }

        /**
         * Convert some unusual representations of IPv4 addresses to their
         * canonical dotted quad representation.
         *
         * This currently only checks a few IPV4-to-IPv6 related cases.  More
         * unusual representations may be added later.
         *
         * @param string $addr Something that might be an IP address
         * @return string|null Valid dotted quad IPv4 address or null
         */
        public static function canonicalize( $addr ) {
                // remove zone info (bug 35738)
                $addr = preg_replace( '/\%.*/', '', $addr );

                if ( self::isValid( $addr ) ) {
                        return $addr;
                }
                // Turn mapped addresses from ::ce:ffff:1.2.3.4 to 1.2.3.4
                if ( strpos( $addr, ':' ) !== false && strpos( $addr, '.' ) !== false ) {
                        $addr = substr( $addr, strrpos( $addr, ':' ) + 1 );
                        if ( self::isIPv4( $addr ) ) {
                                return $addr;
                        }
                }
                // IPv6 loopback address
                $m = [];
                if ( preg_match( '/^0*' . RE_IPV6_GAP . '1$/', $addr, $m ) ) {
                        return '127.0.0.1';
                }
                // IPv4-mapped and IPv4-compatible IPv6 addresses
                if ( preg_match( '/^' . RE_IPV6_V4_PREFIX . '(' . RE_IP_ADD . ')$/i', $addr, $m ) ) {
                        return $m[1];
                }
                if ( preg_match( '/^' . RE_IPV6_V4_PREFIX . RE_IPV6_WORD .
                        ':' . RE_IPV6_WORD . '$/i', $addr, $m )
                ) {
                        return long2ip( ( hexdec( $m[1] ) << 16 ) + hexdec( $m[2] ) );
                }

                return null; // give up
        }

        /**
         * Gets rid of unneeded numbers in quad-dotted/octet IP strings
         * For example, 127.111.113.151/24 -> 127.111.113.0/24
         * @param string $range IP address to normalize
         * @return string
         */
        public static function sanitizeRange( $range ) {
                list( /*...*/, $bits ) = self::parseCIDR( $range );
                list( $start, /*...*/ ) = self::parseRange( $range );
                $start = self::formatHex( $start );
                if ( $bits === false ) {
                        return $start; // wasn't actually a range
                }

                return "$start/$bits";
        }

        /**
         * Returns the subnet of a given IP
         *
         * @param string $ip
         * @return string|false
         */
        public static function getSubnet( $ip ) {
                $matches = [];
                $subnet = false;
                if ( IP::isIPv6( $ip ) ) {
                        $parts = IP::parseRange( "$ip/64" );
                        $subnet = $parts[0];
                } elseif ( preg_match( '/^(\d+\.\d+\.\d+)\.\d+$/', $ip, $matches ) ) {
                        // IPv4
                        $subnet = $matches[1];
                }
                return $subnet;
        }
}