modifu getUserIP function

How can I override the default getUserIP() function so it uses the ip address if it is behind the load balancer

current

public function getUserIP()

{


    return isset($_SERVER['REMOTE_ADDR']) ? $_SERVER['REMOTE_ADDR'] : null;


}

to

public function getUserIP()

{


    return (isset($_SERVER['HTTP_X_FORWARDED_FOR']) && $_SERVER['HTTP_X_FORWARDED_FOR']) ? $_SERVER['HTTP_X_FORWARDED_FOR'] : null;


}

I dont want to modify the core default file otherwise i need to maintain my own changelog and each time I update the yii framework i have to re patch the code.