Symfony\Component\HttpFoundation\Request::normalizeAndFilterClientIps PHP Method

    private function normalizeAndFilterClientIps(array $clientIps, $ip)
    {
        $clientIps[] = $ip; // Complete the IP chain with the IP the request actually came from
        $firstTrustedIp = null;

        foreach ($clientIps as $key => $clientIp) {
            // Remove port (unfortunately, it does happen)
            if (preg_match('{((?:\d+\.){3}\d+)\:\d+}', $clientIp, $match)) {
                $clientIps[$key] = $clientIp = $match[1];
            }

            if (!filter_var($clientIp, FILTER_VALIDATE_IP)) {
                unset($clientIps[$key]);

                continue;
            }

            if (IpUtils::checkIp($clientIp, self::$trustedProxies)) {
                unset($clientIps[$key]);

                // Fallback to this when the client IP falls into the range of trusted proxies
                if (null === $firstTrustedIp) {
                    $firstTrustedIp = $clientIp;
                }
            }
        }

        // Now the IP chain contains only untrusted proxies and the client IP
        return $clientIps ? array_reverse($clientIps) : array($firstTrustedIp);
    }