mv non-core components to extended repo

pkg/internal/util/tcp.go

@@ -0,0 +1,32 @@
+package util
+
+import (
+	"net"
+	"time"
+)
+
+const (
+	defaultKeepAlivePeriod = 180 * time.Second
+)
+
+// TCPKeepAliveListener is a TCP listener with keep alive enabled.
+type TCPKeepAliveListener struct {
+	KeepAlivePeriod time.Duration
+	*net.TCPListener
+}
+
+func (l *TCPKeepAliveListener) Accept() (c net.Conn, err error) {
+	tc, err := l.AcceptTCP()
+	if err != nil {
+		return
+	}
+
+	tc.SetKeepAlive(true)
+	period := l.KeepAlivePeriod
+	if period <= 0 {
+		period = defaultKeepAlivePeriod
+	}
+	tc.SetKeepAlivePeriod(period)
+
+	return tc, nil
+}