discuz的xplus投票怎么修改下，可以有效防止刷票？

研究了一下xplus的函数。

function _get_client_ip() {
		$clientip = '';
		if(getenv('HTTP_CLIENT_IP') && strcasecmp(getenv('HTTP_CLIENT_IP'), 'unknown')) {
			$clientip = getenv('HTTP_CLIENT_IP');
		} elseif(getenv('HTTP_X_FORWARDED_FOR') && strcasecmp(getenv('HTTP_X_FORWARDED_FOR'), 'unknown')) {
			$clientip = getenv('HTTP_X_FORWARDED_FOR');
		} elseif(getenv('REMOTE_ADDR') && strcasecmp(getenv('REMOTE_ADDR'), 'unknown')) {
			$clientip = getenv('REMOTE_ADDR');
		} elseif(isset($_SERVER['REMOTE_ADDR']) && $_SERVER['REMOTE_ADDR'] && strcasecmp($_SERVER['REMOTE_ADDR'], 'unknown')) {
			$clientip = $_SERVER['REMOTE_ADDR'];
		}

		preg_match("/[\d\.]{7,15}/", $clientip, $clientipmatches);
		$clientip = $clientipmatches[0] ? $clientipmatches[0] : 'unknown';
		return $clientip;
	}

这个函数是获取ip的 容易被仿造ip怎么修改一下更好？