func GetDestinationCluster(destination *networking.Destination, service *model.Service, listenerPort int) string {
	if len(destination.GetHost()) == 0 {
		// only happens when the gateway-api BackendRef is invalid
		return "UnknownService"
	}
	h := host.Name(destination.Host)
	// If this is an Alias, point to the concrete service
	// TODO: this will not work if we have Alias -> Alias -> Concrete service.