implement a function that blocks until an early session can be used

session.go

@@ -143,6 +143,7 @@ type session struct {
 	undecryptablePackets []*receivedPacket
 
 	clientHelloWritten    <-chan struct{}
+	earlySessionReadyChan chan struct{}
 	handshakeCompleteChan chan struct{} // is closed when the handshake completes
 	handshakeComplete     bool
 
@@ -345,6 +346,7 @@ func (s *session) preSetup() {
 		s.rttStats,
 		s.logger,
 	)
+	s.earlySessionReadyChan = make(chan struct{})
 	if s.config.QuicTracer != nil {
 		s.traceCallback = func(ev quictrace.Event) {
 			s.config.QuicTracer.Trace(s.origDestConnID, ev)
@@ -468,6 +470,11 @@ runLoop:
 	return closeErr.err
 }
 
+// blocks until the early session can be used
+func (s *session) earlySessionReady() <-chan struct{} {
+	return s.earlySessionReadyChan
+}
+
 func (s *session) HandshakeComplete() context.Context {
 	return s.handshakeCtx
 }
@@ -1013,6 +1020,9 @@ func (s *session) processTransportParameters(data []byte) {
 	if params.StatelessResetToken != nil {
 		s.sessionRunner.AddResetToken(*params.StatelessResetToken, s)
 	}
+	// On the server side, the early session is ready as soon as we processed
+	// the client's transport parameters.
+	close(s.earlySessionReadyChan)
 }
 
 func (s *session) processTransportParametersForClient(data []byte) (*handshake.TransportParameters, error) {

session_test.go

@@ -1286,7 +1286,10 @@ var _ = Describe("Session", func() {
 			}
 			streamManager.EXPECT().UpdateLimits(params)
 			packer.EXPECT().HandleTransportParameters(params)
+			Expect(sess.earlySessionReady()).ToNot(BeClosed())
 			sess.processTransportParameters(params.Marshal())
+			Expect(sess.earlySessionReady()).To(BeClosed())
+
 			// make the go routine return
 			streamManager.EXPECT().CloseWithError(gomock.Any())
 			sessionRunner.EXPECT().Retire(gomock.Any())