내부IP 주소 검사


## check private networks
##
function is_localnet($ipaddr)
{
  static $localnet =
array('10.0.0.0'=>'255.0.0.0','172.16.0.0'=>'255.240.0.0','192.168.0.0'=>'255.255.0.
0');

  if(!preg_match('/^(10|172|192\.168)\./',$ipaddr)) return; // is public ipaddr

  $ubit = sprintf('%032b',ip2long($ipaddr)); // inet_atob()

  foreach($localnet AS $pnet=>$pmask)
  {
        $pbit = sprintf('%032b',ip2long($pmask));
        $unet = ($ubit & $pbit);
        $unet = long2ip(bindec("$unet")); // inet_btoa()
        if($pnet == $unet)
        {
                $r = TRUE;
                break;
        }
  }

  return $r;
}