set the default value for the ack_delay_exponent, if it is not sent

internal/handshake/transport_parameter_test.go

@@ -108,6 +108,14 @@ var _ = Describe("Transport Parameters", func() {
 		Expect(b.Len()).To(Equal(defaultLen + 2 /* parameter ID */ + 2 /* length field */ + 1 /* value */))
 	})
 
+	It("sets the default value for the ack_delay_exponent, when no value was sent", func() {
+		b := &bytes.Buffer{}
+		(&TransportParameters{AckDelayExponent: protocol.DefaultAckDelayExponent}).marshal(b)
+		p := &TransportParameters{}
+		Expect(p.unmarshal(b.Bytes(), protocol.PerspectiveServer)).To(Succeed())
+		Expect(p.AckDelayExponent).To(BeEquivalentTo(protocol.DefaultAckDelayExponent))
+	})
+
 	It("errors when the varint value has the wrong length", func() {
 		b := &bytes.Buffer{}
 		utils.BigEndian.WriteUint16(b, uint16(initialMaxStreamDataBidiLocalParameterID))

internal/handshake/transport_parameters.go

@@ -54,6 +54,8 @@ func (p *TransportParameters) unmarshal(data []byte, sentBy protocol.Perspective
 	// needed to check that every parameter is only sent at most once
 	var parameterIDs []transportParameterID
 
+	var readAckDelayExponent bool
+
 	r := bytes.NewReader(data)
 	for r.Len() >= 4 {
 		paramIDInt, _ := utils.BigEndian.ReadUint16(r)
@@ -61,6 +63,9 @@ func (p *TransportParameters) unmarshal(data []byte, sentBy protocol.Perspective
 		paramLen, _ := utils.BigEndian.ReadUint16(r)
 		parameterIDs = append(parameterIDs, paramID)
 		switch paramID {
+		case ackDelayExponentParameterID:
+			readAckDelayExponent = true
+			fallthrough
 		case initialMaxStreamDataBidiLocalParameterID,
 			initialMaxStreamDataBidiRemoteParameterID,
 			initialMaxStreamDataUniParameterID,
@@ -68,8 +73,7 @@ func (p *TransportParameters) unmarshal(data []byte, sentBy protocol.Perspective
 			initialMaxStreamsBidiParameterID,
 			initialMaxStreamsUniParameterID,
 			idleTimeoutParameterID,
-			maxPacketSizeParameterID,
-			ackDelayExponentParameterID:
+			maxPacketSizeParameterID:
 			if err := p.readNumericTransportParameter(r, paramID, int(paramLen)); err != nil {
 				return err
 			}
@@ -104,6 +108,10 @@ func (p *TransportParameters) unmarshal(data []byte, sentBy protocol.Perspective
 		}
 	}
 
+	if !readAckDelayExponent {
+		p.AckDelayExponent = protocol.DefaultAckDelayExponent
+	}
+
 	// check that every transport parameter was sent at most once
 	sort.Slice(parameterIDs, func(i, j int) bool { return parameterIDs[i] < parameterIDs[j] })
 	for i := 0; i < len(parameterIDs)-1; i++ {