tcpproxy: Why is the in and out connection closed repeatedly

[SimFG]

Doubt at the end of the serve method.

etcd/server/proxy/tcpproxy/userspace.go

Lines 175 to 213 in 33ba538

	func (tp *TCPProxy) serve(in net.Conn) {
	var (
	err error
	out net.Conn
	)
	for {
	tp.mu.Lock()
	remote := tp.pick()
	tp.mu.Unlock()
	if remote == nil {
	break
	}
	// TODO: add timeout
	out, err = net.Dial("tcp", remote.addr)
	if err == nil {
	break
	}
	remote.inactivate()
	if tp.Logger != nil {
	tp.Logger.Warn("deactivated endpoint", zap.String("address", remote.addr), zap.Duration("interval", tp.MonitorInterval), zap.Error(err))
	}
	}
	if out == nil {
	in.Close()
	return
	}
	go func() {
	io.Copy(in, out)
	in.Close()
	out.Close()
	}()
	io.Copy(out, in)
	out.Close()
	in.Close()
	}