kubernetes/vendor/go.etcd.io/etcd/client/pkg/v3/transport/keepalive_listener.go

// NewKeepAliveListener returns a listener that listens on the given address.
// Be careful when wrap around KeepAliveListener with another Listener if TLSInfo is not nil.
// Some pkgs (like go/http) might expect Listener to return TLSConn type to start TLS handshake.
// http://tldp.org/HOWTO/TCP-Keepalive-HOWTO/overview.html
//
// Note(ahrtr):
// only `net.TCPConn` supports `SetKeepAlive` and `SetKeepAlivePeriod`
// by default, so if you want to wrap multiple layers of net.Listener,
// the `keepaliveListener` should be the one which is closest to the
// original `net.Listener` implementation, namely `TCPListener`.
func NewKeepAliveListener(l net.Listener, scheme string, tlscfg *tls.Config) (net.Listener, error) { … }

type keepaliveListener …

func (kln *keepaliveListener) Accept() (net.Conn, error) { … }

func createKeepaliveConn(c net.Conn) (*keepAliveConn, error) { … }

type keepAliveConn …

// SetKeepAlive sets keepalive
func (l *keepAliveConn) SetKeepAlive(doKeepAlive bool) error { … }

type tlsKeepaliveListener …

// Accept waits for and returns the next incoming TLS connection.
// The returned connection c is a *tls.Conn.
func (l *tlsKeepaliveListener) Accept() (c net.Conn, err error) { … }

// NewListener creates a Listener which accepts connections from an inner
// Listener and wraps each connection with Server.
// The configuration config must be non-nil and must have
// at least one certificate.
func newTLSKeepaliveListener(inner net.Listener, config *tls.Config) net.Listener { … }