implement sending of datagrams

interface.go

@@ -187,6 +187,10 @@ type Session interface {
 	// It blocks until the handshake completes.
 	// Warning: This API should not be considered stable and might change soon.
 	ConnectionState() ConnectionState
+
+	// SendMessage sends a message as a datagram.
+	// See https://datatracker.ietf.org/doc/draft-pauly-quic-datagram/.
+	SendMessage([]byte) error
 }
 
 // An EarlySession is a session that is handshaking.

internal/mocks/quic/early_session.go

@@ -210,3 +210,17 @@ func (mr *MockEarlySessionMockRecorder) RemoteAddr() *gomock.Call {
 	mr.mock.ctrl.T.Helper()
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "RemoteAddr", reflect.TypeOf((*MockEarlySession)(nil).RemoteAddr))
 }
+
+// SendMessage mocks base method
+func (m *MockEarlySession) SendMessage(arg0 []byte) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "SendMessage", arg0)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// SendMessage indicates an expected call of SendMessage
+func (mr *MockEarlySessionMockRecorder) SendMessage(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "SendMessage", reflect.TypeOf((*MockEarlySession)(nil).SendMessage), arg0)
+}

mock_quic_session_test.go

@@ -224,6 +224,20 @@ func (mr *MockQuicSessionMockRecorder) RemoteAddr() *gomock.Call {
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "RemoteAddr", reflect.TypeOf((*MockQuicSession)(nil).RemoteAddr))
 }
 
+// SendMessage mocks base method
+func (m *MockQuicSession) SendMessage(arg0 []byte) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "SendMessage", arg0)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// SendMessage indicates an expected call of SendMessage
+func (mr *MockQuicSessionMockRecorder) SendMessage(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "SendMessage", reflect.TypeOf((*MockQuicSession)(nil).SendMessage), arg0)
+}
+
 // destroy mocks base method
 func (m *MockQuicSession) destroy(arg0 error) {
 	m.ctrl.T.Helper()

session.go

@@ -512,6 +512,9 @@ func (s *session) preSetup() {
 	s.sessionCreationTime = now
 
 	s.windowUpdateQueue = newWindowUpdateQueue(s.streamsMap, s.connFlowController, s.framer.QueueControlFrame)
+	if s.config.EnableDatagrams {
+		s.datagramQueue = newDatagramQueue(s.scheduleSending)
+	}
 }
 
 // run the session main loop
@@ -1115,6 +1118,8 @@ func (s *session) handleFrame(f wire.Frame, encLevel protocol.EncryptionLevel, d
 		err = s.handleRetireConnectionIDFrame(frame, destConnID)
 	case *wire.HandshakeDoneFrame:
 		err = s.handleHandshakeDoneFrame()
+	case *wire.DatagramFrame:
+		// TODO: handle DATRAGRAM frames
 	default:
 		err = fmt.Errorf("unexpected frame type: %s", reflect.ValueOf(&frame).Elem().Type().Name())
 	}
@@ -1739,6 +1744,17 @@ func (s *session) onStreamCompleted(id protocol.StreamID) {
 	}
 }
 
+func (s *session) SendMessage(p []byte) error {
+	f := &wire.DatagramFrame{DataLenPresent: true}
+	if protocol.ByteCount(len(p)) > f.MaxDataLen(s.peerParams.MaxDatagramFrameSize, s.version) {
+		return errors.New("message too large")
+	}
+	f.Data = make([]byte, len(p))
+	copy(f.Data, p)
+	s.datagramQueue.AddAndWait(f)
+	return nil
+}
+
 func (s *session) LocalAddr() net.Addr {
 	return s.conn.LocalAddr()
 }