kubernetes/cmd/kubeadm/app/util/endpoint.go

// GetControlPlaneEndpoint returns a properly formatted endpoint for the control plane built according following rules:
// - If the controlPlaneEndpoint is defined, use it.
// - if the controlPlaneEndpoint is defined but without a port number, use the controlPlaneEndpoint + localEndpoint.BindPort is used.
// - Otherwise, in case the controlPlaneEndpoint is not defined, use the localEndpoint.AdvertiseAddress + the localEndpoint.BindPort.
func GetControlPlaneEndpoint(controlPlaneEndpoint string, localEndpoint *kubeadmapi.APIEndpoint) (string, error) { … }

// GetLocalAPIEndpoint parses an APIEndpoint and returns it as a string,
// or returns and error in case it cannot be parsed.
func GetLocalAPIEndpoint(localEndpoint *kubeadmapi.APIEndpoint) (string, error) { … }

// ParseHostPort parses a network address of the form "host:port", "ipv4:port", "[ipv6]:port" into host and port;
// ":port" can be eventually omitted.
// If the string is not a valid representation of network address, ParseHostPort returns an error.
func ParseHostPort(hostport string) (string, string, error) { … }

// ParsePort parses a string representing a TCP port.
// If the string is not a valid representation of a TCP port, ParsePort returns an error.
func ParsePort(port string) (int, error) { … }

// parseAPIEndpoint parses an APIEndpoint and returns the AdvertiseAddress as net.IP and the BindPort as string.
// If the BindPort or AdvertiseAddress are invalid it returns an error.
func parseAPIEndpoint(localEndpoint *kubeadmapi.APIEndpoint) (net.IP, string, error) { … }

// formatURL takes a host and a port string and creates a net.URL using https scheme
func formatURL(host, port string) *url.URL { … }