only use the conn ID backwards compatibility mode with draft-29

conn_id_generator.go

@@ -22,6 +22,8 @@ type connIDGenerator struct {
 	retireConnectionID     func(protocol.ConnectionID)
 	replaceWithClosed      func(protocol.ConnectionID, packetHandler)
 	queueControlFrame      func(wire.Frame)
+
+	version protocol.VersionNumber
 }
 
 func newConnIDGenerator(
@@ -33,6 +35,7 @@ func newConnIDGenerator(
 	retireConnectionID func(protocol.ConnectionID),
 	replaceWithClosed func(protocol.ConnectionID, packetHandler),
 	queueControlFrame func(wire.Frame),
+	version protocol.VersionNumber,
 ) *connIDGenerator {
 	m := &connIDGenerator{
 		connIDLen:              initialConnectionID.Len(),
@@ -43,6 +46,7 @@ func newConnIDGenerator(
 		retireConnectionID:     retireConnectionID,
 		replaceWithClosed:      replaceWithClosed,
 		queueControlFrame:      queueControlFrame,
+		version:                version,
 	}
 	m.activeSrcConnIDs[0] = initialConnectionID
 	m.initialClientDestConnID = initialClientDestConnID
@@ -76,7 +80,7 @@ func (m *connIDGenerator) Retire(seq uint64, sentWithDestConnID protocol.Connect
 	if !ok {
 		return nil
 	}
-	if connID.Equal(sentWithDestConnID) && !RetireBugBackwardsCompatibilityMode {
+	if connID.Equal(sentWithDestConnID) && !protocol.UseRetireBugBackwardsCompatibilityMode(RetireBugBackwardsCompatibilityMode, m.version) {
 		return qerr.NewError(qerr.ProtocolViolation, fmt.Sprintf("tried to retire connection ID %d (%s), which was used as the Destination Connection ID on this packet", seq, connID))
 	}
 	m.retireConnectionID(connID)
@@ -89,7 +93,7 @@ func (m *connIDGenerator) Retire(seq uint64, sentWithDestConnID protocol.Connect
 }
 
 func (m *connIDGenerator) issueNewConnID() error {
-	if RetireBugBackwardsCompatibilityMode {
+	if protocol.UseRetireBugBackwardsCompatibilityMode(RetireBugBackwardsCompatibilityMode, m.version) {
 		return nil
 	}
 	connID, err := protocol.GenerateConnectionID(m.connIDLen)

conn_id_generator_test.go

@@ -41,6 +41,7 @@ var _ = Describe("Connection ID Generator", func() {
 			func(c protocol.ConnectionID) { retiredConnIDs = append(retiredConnIDs, c) },
 			func(c protocol.ConnectionID, h packetHandler) { replacedWithClosed[string(c)] = h },
 			func(f wire.Frame) { queuedFrames = append(queuedFrames, f) },
+			protocol.VersionDraft29,
 		)
 	})
 

internal/protocol/version.go

@@ -62,6 +62,12 @@ func (vn VersionNumber) toGQUICVersion() int {
 	return int(10*(vn-gquicVersion0)/0x100) + int(vn%0x10)
 }
 
+// UseRetireBugBackwardsCompatibilityMode says if it is necessary to use the backwards compatilibity mode.
+// This is only the case if it 1. is enabled and 2. draft-29 is used.
+func UseRetireBugBackwardsCompatibilityMode(enabled bool, v VersionNumber) bool {
+	return enabled && v == VersionDraft29
+}
+
 // IsSupportedVersion returns true if the server supports this version
 func IsSupportedVersion(supported []VersionNumber, v VersionNumber) bool {
 	for _, t := range supported {

internal/protocol/version_test.go

@@ -49,6 +49,13 @@ var _ = Describe("Version", func() {
 		}
 	})
 
+	It("says if backwards compatibility mode should be used", func() {
+		Expect(UseRetireBugBackwardsCompatibilityMode(true, VersionDraft29)).To(BeTrue())
+		Expect(UseRetireBugBackwardsCompatibilityMode(true, VersionDraft32)).To(BeFalse())
+		Expect(UseRetireBugBackwardsCompatibilityMode(false, VersionDraft29)).To(BeFalse())
+		Expect(UseRetireBugBackwardsCompatibilityMode(false, VersionDraft32)).To(BeFalse())
+	})
+
 	Context("highest supported version", func() {
 		It("finds the supported version", func() {
 			supportedVersions := []VersionNumber{1, 2, 3}

session.go

@@ -268,6 +268,7 @@ var newSession = func(
 		runner.Retire,
 		runner.ReplaceWithClosed,
 		s.queueControlFrame,
+		s.version,
 	)
 	s.preSetup()
 	s.sentPacketHandler, s.receivedPacketHandler = ackhandler.NewAckHandler(
@@ -390,6 +391,7 @@ var newClientSession = func(
 		runner.Retire,
 		runner.ReplaceWithClosed,
 		s.queueControlFrame,
+		s.version,
 	)
 	s.preSetup()
 	s.sentPacketHandler, s.receivedPacketHandler = ackhandler.NewAckHandler(