errs = appendErrors(errs, errors.New("HTTP route cannot contain both mirror and mirrors"))
	}

	return errs
}

// isInternalHeader returns true if a header refers to an internal value that cannot be modified by Envoy
func isInternalHeader(headerKey string) bool {
	return strings.HasPrefix(headerKey, ":") || strings.EqualFold(headerKey, "host")
}