ipv6_hack.php

<?php
/* IPv6 to IPv4, a dirty hack
 *
 * This will create fake IPv4 for IPv6 users based on the 64 first bits of their IP.
 * As most currently existing IPv6 providers are assigning /64 classes to their customers,
 * banning the generated IPv4 effectively bans the whole IPv6.
 *
 * Also this script generates a 32bits IPv4 from 64bits of IPv6 using XOR.
 * While this means people using IPv6 might share the same generated IPv4 (quite unlikely),
 * it is usually impossible for someone to obtain a different generated IPv4 without access
 * to more than a /64 (I believe only system administrators have this kind of thing).
 *
 * Author: NewEraCracker
 * License: Public Domain
 */

//@link: http://php.net/manual/en/function.inet-pton.php
if ( !function_exists('inet_pton'))
{
	function inet_pton($ip)
	{
		if(strpos($ip, '.') !== FALSE)
		{
			// Pack ipv4
			$ip = trim($ip,':f');
			$ip = pack('N',ip2long($ip));
		}
		elseif(strpos($ip, ':') !== FALSE)
		{
			// Expand ipv6
			$_count = count(explode(':', $ip));
			while($_count<=8)
			{
				$ip = str_replace('::',':0::',$ip);
				$_count++;
			}
			unset($_count);
			$ip = str_replace('::',':',$ip);

			// Pack ipv6
			$ip = explode(':', $ip);
			$res = str_pad('', (4*(8-count($ip))), '0000', STR_PAD_LEFT);
			foreach ($ip as $seg)
			{
				$res .= str_pad($seg, 4, '0', STR_PAD_LEFT);
			}
			$ip = pack('H'.strlen($res), $res);
		}
		else
		{
			return false;
		}
		
		if(strlen($ip)==4 || strlen($ip)==16)
		{
			return $ip;
		}
		else
		{
			return false;
		}
		
	}
}

//@link: http://php.net/manual/en/function.inet-ntop.php
if ( !function_exists('inet_ntop'))
{
	function inet_ntop($ip){
		if(strlen($ip)==4)
		{
			// Unpack ipv4
			list(,$ip)=unpack('N',$ip);
			$ip=long2ip($ip);
		}
		elseif(strlen($ip)==16)
		{
			// Unpack ipv6
			$ip=bin2hex($ip);
			$ip=substr(chunk_split($ip,4,':'),0,-1);
			$ip=explode(':',$ip);
			$res='';
			foreach($ip as $seg)
			{
				while($seg{0}=='0') $seg=substr($seg,1);
				if($seg!='')
				{
					$res.=($res==''?'':':').$seg;
				}
				else
				{
					if (strpos($res,'::')===false) {
							if (substr($res,-1)==':') continue;
							$res.=':';
							continue;
					}
					$res.=($res==''?'':':').'0';
				}
			}
			$ip=$res;
		}
		else
		{
			return false;
		}

		return $ip;
	}
}

//@link: http://blog.magicaltux.net/2010/02/18/invision-power-board-and-ipv6-a-dirty-hack/
$encoded_ip = inet_pton($_SERVER['REMOTE_ADDR']);
if (strlen($encoded_ip) == 16) {
    $ipv4 = '';
    for($i = 0; $i < 8; $i += 2) $ipv4 .= chr(ord($encoded_ip[$i]) ^ ord($encoded_ip[$i+1]));
    $_SERVER['REMOTE_ADDR'] = inet_ntop($ipv4);
}

?>