func retrieveListenerType(l *listener.Listener) string {
	nHTTP := 0
	nTCP := 0
	for _, filterChain := range getFilterChains(l) {
		for _, filter := range filterChain.GetFilters() {
			if filter.Name == HTTPListener {
				nHTTP++
			} else if filter.Name == TCPListener {
				if !strings.Contains(string(filter.GetTypedConfig().GetValue()), util.BlackHoleCluster) {
					nTCP++
				}
			}