public static function is_trusted_client($ip)
 {
     if (!defined('TRUSTED_CLIENTS')) {
         return false;
     }
     // pack string in array
     $trusted = explode(',', TRUSTED_CLIENTS);
     foreach ($trusted as $mask) {
         if (MpUtils::check_netmask(trim($mask), $ip)) {
             return true;
         }
     }
     return false;
 }