kubernetes/staging/src/k8s.io/kubectl/pkg/util/service_port.go

// LookupContainerPortNumberByServicePort implements
// the handling of resolving container named port, as well as ignoring targetPort when clusterIP=None
// It returns an error when a named port can't find a match (with -1 returned), or when the service does not
// declare such port (with the input port number returned).
func LookupContainerPortNumberByServicePort(svc v1.Service, pod v1.Pod, port int32) (int32, error) { … }

// LookupServicePortNumberByName find service port number by its named port name
func LookupServicePortNumberByName(svc v1.Service, name string) (int32, error) { … }