Requests::match_domain( $host, $reference )

Source

File: wp-includes/class-requests.php

public static function match_domain($host, $reference) {
		// Check for a direct match
		if ($host === $reference) {
			return true;
		}

		// Calculate the valid wildcard match if the host is not an IP address
		// Also validates that the host has 3 parts or more, as per Firefox's
		// ruleset.
		$parts = explode('.', $host);
		if (ip2long($host) === false && count($parts) >= 3) {
			$parts[0] = '*';
			$wildcard = implode('.', $parts);
			if ($wildcard === $reference) {
				return true;
			}
		}

		return false;
	}