use the connection ID manager to save the destination connection ID

conn_id_manager.go

@@ -11,28 +11,34 @@ import (
 type connIDManager struct {
 	queue utils.NewConnectionIDList
 
+	activeSequenceNumber uint64
+	activeConnectionID   protocol.ConnectionID
+
 	queueControlFrame func(wire.Frame)
 }
 
-func newConnIDManager(queueControlFrame func(wire.Frame)) *connIDManager {
+func newConnIDManager(
-	return &connIDManager{queueControlFrame: queueControlFrame}
+	initialDestConnID protocol.ConnectionID,
+	queueControlFrame func(wire.Frame),
+) *connIDManager {
+	h := &connIDManager{queueControlFrame: queueControlFrame}
+	h.activeConnectionID = initialDestConnID
+	return h
 }
 
 func (h *connIDManager) Add(f *wire.NewConnectionIDFrame) error {
 	if err := h.add(f); err != nil {
 		return err
 	}
-	if h.queue.Len() > protocol.MaxActiveConnectionIDs {
+	if h.queue.Len() >= protocol.MaxActiveConnectionIDs {
-		// delete the first connection ID in the queue
+		h.updateConnectionID()
-		val := h.queue.Remove(h.queue.Front())
-		h.queueControlFrame(&wire.RetireConnectionIDFrame{
-			SequenceNumber: val.SequenceNumber,
-		})
 	}
 	return nil
 }
 
 func (h *connIDManager) add(f *wire.NewConnectionIDFrame) error {
+	// Retire elements in the queue.
+	// Doesn't retire the active connection ID.
 	var next *utils.NewConnectionIDElement
 	for el := h.queue.Front(); el != nil; el = next {
 		if el.Value.SequenceNumber >= f.RetirePriorTo {
@@ -52,27 +58,55 @@ func (h *connIDManager) add(f *wire.NewConnectionIDFrame) error {
 			ConnectionID:        f.ConnectionID,
 			StatelessResetToken: &f.StatelessResetToken,
 		})
-		return nil
+	} else {
-	}
+		// insert a new element somewhere in the middle
-	// insert a new element somewhere in the middle
+		for el := h.queue.Front(); el != nil; el = el.Next() {
-	for el := h.queue.Front(); el != nil; el = el.Next() {
+			if el.Value.SequenceNumber == f.SequenceNumber {
-		if el.Value.SequenceNumber == f.SequenceNumber {
+				if !el.Value.ConnectionID.Equal(f.ConnectionID) {
-			if !el.Value.ConnectionID.Equal(f.ConnectionID) {
+					return fmt.Errorf("received conflicting connection IDs for sequence number %d", f.SequenceNumber)
-				return fmt.Errorf("received conflicting connection IDs for sequence number %d", f.SequenceNumber)
+				}
+				if *el.Value.StatelessResetToken != f.StatelessResetToken {
+					return fmt.Errorf("received conflicting stateless reset tokens for sequence number %d", f.SequenceNumber)
+				}
+				break
 			}
-			if *el.Value.StatelessResetToken != f.StatelessResetToken {
+			if el.Value.SequenceNumber > f.SequenceNumber {
-				return fmt.Errorf("received conflicting stateless reset tokens for sequence number %d", f.SequenceNumber)
+				h.queue.InsertBefore(utils.NewConnectionID{
+					SequenceNumber:      f.SequenceNumber,
+					ConnectionID:        f.ConnectionID,
+					StatelessResetToken: &f.StatelessResetToken,
+				}, el)
+				break
 			}
-			return nil
-		}
-		if el.Value.SequenceNumber > f.SequenceNumber {
-			h.queue.InsertBefore(utils.NewConnectionID{
-				SequenceNumber:      f.SequenceNumber,
-				ConnectionID:        f.ConnectionID,
-				StatelessResetToken: &f.StatelessResetToken,
-			}, el)
-			return nil
 		}
 	}
-	panic("should have processed NEW_CONNECTION_ID frame")
+
+	// Retire the active connection ID, if necessary.
+	if h.activeSequenceNumber < f.RetirePriorTo {
+		// The queue is guaranteed to have at least one element at this point.
+		h.updateConnectionID()
+	}
+	return nil
+}
+
+func (h *connIDManager) updateConnectionID() {
+	h.queueControlFrame(&wire.RetireConnectionIDFrame{
+		SequenceNumber: h.activeSequenceNumber,
+	})
+	front := h.queue.Remove(h.queue.Front())
+	h.activeSequenceNumber = front.SequenceNumber
+	h.activeConnectionID = front.ConnectionID
+}
+
+// is called when the server performs a Retry
+// and when the server changes the connection ID in the first Initial sent
+func (h *connIDManager) ChangeInitialConnID(newConnID protocol.ConnectionID) {
+	if h.activeSequenceNumber != 0 {
+		panic("expected first connection ID to have sequence number 0")
+	}
+	h.activeConnectionID = newConnID
+}
+
+func (h *connIDManager) Get() protocol.ConnectionID {
+	return h.activeConnectionID
 }

conn_id_manager_test.go

@@ -12,10 +12,11 @@ var _ = Describe("Connection ID Manager", func() {
 		m          *connIDManager
 		frameQueue []wire.Frame
 	)
+	initialConnID := protocol.ConnectionID{1, 1, 1, 1}
 
 	BeforeEach(func() {
 		frameQueue = nil
-		m = newConnIDManager(func(f wire.Frame) {
+		m = newConnIDManager(initialConnID, func(f wire.Frame) {
 			frameQueue = append(frameQueue, f)
 		})
 	})
@@ -28,10 +29,13 @@ var _ = Describe("Connection ID Manager", func() {
 		return val.ConnectionID, val.StatelessResetToken
 	}
 
-	It("returns nil if empty", func() {
+	It("returns the initial connection ID", func() {
-		c, rt := get()
+		Expect(m.Get()).To(Equal(initialConnID))
-		Expect(c).To(BeNil())
+	})
-		Expect(rt).To(BeNil())
+
+	It("changes the initial connection ID", func() {
+		m.ChangeInitialConnID(protocol.ConnectionID{1, 2, 3, 4, 5})
+		Expect(m.Get()).To(Equal(protocol.ConnectionID{1, 2, 3, 4, 5}))
 	})
 
 	It("adds and gets connection IDs", func() {
@@ -111,26 +115,28 @@ var _ = Describe("Connection ID Manager", func() {
 			SequenceNumber: 17,
 			ConnectionID:   protocol.ConnectionID{3, 4, 5, 6},
 		})).To(Succeed())
-		Expect(frameQueue).To(HaveLen(2))
+		Expect(frameQueue).To(HaveLen(3))
 		Expect(frameQueue[0].(*wire.RetireConnectionIDFrame).SequenceNumber).To(BeEquivalentTo(10))
 		Expect(frameQueue[1].(*wire.RetireConnectionIDFrame).SequenceNumber).To(BeEquivalentTo(13))
-		c, _ := get()
+		Expect(frameQueue[2].(*wire.RetireConnectionIDFrame).SequenceNumber).To(BeZero())
-		Expect(c).To(Equal(protocol.ConnectionID{3, 4, 5, 6}))
+		Expect(m.Get()).To(Equal(protocol.ConnectionID{3, 4, 5, 6}))
 	})
 
 	It("retires old connection IDs when the peer sends too many new ones", func() {
-		for i := uint8(0); i < protocol.MaxActiveConnectionIDs; i++ {
+		for i := uint8(1); i <= protocol.MaxActiveConnectionIDs; i++ {
 			Expect(m.Add(&wire.NewConnectionIDFrame{
 				SequenceNumber: uint64(i),
 				ConnectionID:   protocol.ConnectionID{i, i, i, i},
 			})).To(Succeed())
 		}
-		Expect(frameQueue).To(BeEmpty())
+		Expect(frameQueue).To(HaveLen(1))
+		Expect(frameQueue[0].(*wire.RetireConnectionIDFrame).SequenceNumber).To(BeZero())
+		frameQueue = nil
 		Expect(m.Add(&wire.NewConnectionIDFrame{
-			SequenceNumber: protocol.MaxActiveConnectionIDs,
+			SequenceNumber: protocol.MaxActiveConnectionIDs + 1,
 			ConnectionID:   protocol.ConnectionID{1, 2, 3, 4},
 		})).To(Succeed())
 		Expect(frameQueue).To(HaveLen(1))
-		Expect(frameQueue[0].(*wire.RetireConnectionIDFrame).SequenceNumber).To(BeEquivalentTo(0))
+		Expect(frameQueue[0].(*wire.RetireConnectionIDFrame).SequenceNumber).To(BeEquivalentTo(1))
 	})
 })

mock_packer_test.go

@@ -9,7 +9,6 @@ import (
 
 	gomock "github.com/golang/mock/gomock"
 	handshake "github.com/lucas-clemente/quic-go/internal/handshake"
-	protocol "github.com/lucas-clemente/quic-go/internal/protocol"
 	wire "github.com/lucas-clemente/quic-go/internal/wire"
 )
 
@@ -36,18 +35,6 @@ func (m *MockPacker) EXPECT() *MockPackerMockRecorder {
 	return m.recorder
 }
 
-// ChangeDestConnectionID mocks base method
-func (m *MockPacker) ChangeDestConnectionID(arg0 protocol.ConnectionID) {
-	m.ctrl.T.Helper()
-	m.ctrl.Call(m, "ChangeDestConnectionID", arg0)
-}
-
-// ChangeDestConnectionID indicates an expected call of ChangeDestConnectionID
-func (mr *MockPackerMockRecorder) ChangeDestConnectionID(arg0 interface{}) *gomock.Call {
-	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "ChangeDestConnectionID", reflect.TypeOf((*MockPacker)(nil).ChangeDestConnectionID), arg0)
-}
-
 // HandleTransportParameters mocks base method
 func (m *MockPacker) HandleTransportParameters(arg0 *handshake.TransportParameters) {
 	m.ctrl.T.Helper()

packet_packer.go

@@ -21,7 +21,6 @@ type packer interface {
 
 	HandleTransportParameters(*handshake.TransportParameters)
 	SetToken([]byte)
-	ChangeDestConnectionID(protocol.ConnectionID)
 }
 
 type sealer interface {
@@ -128,8 +127,8 @@ type ackFrameSource interface {
 }
 
 type packetPacker struct {
-	destConnID protocol.ConnectionID
+	srcConnID     protocol.ConnectionID
-	srcConnID  protocol.ConnectionID
+	getDestConnID func() protocol.ConnectionID
 
 	perspective protocol.Perspective
 	version     protocol.VersionNumber
@@ -155,8 +154,8 @@ type packetPacker struct {
 var _ packer = &packetPacker{}
 
 func newPacketPacker(
-	destConnID protocol.ConnectionID,
 	srcConnID protocol.ConnectionID,
+	getDestConnID func() protocol.ConnectionID,
 	initialStream cryptoStream,
 	handshakeStream cryptoStream,
 	packetNumberManager packetNumberManager,
@@ -170,7 +169,7 @@ func newPacketPacker(
 ) *packetPacker {
 	return &packetPacker{
 		cryptoSetup:         cryptoSetup,
-		destConnID:          destConnID,
+		getDestConnID:       getDestConnID,
 		srcConnID:           srcConnID,
 		initialStream:       initialStream,
 		handshakeStream:     handshakeStream,
@@ -432,7 +431,7 @@ func (p *packetPacker) getShortHeader(kp protocol.KeyPhaseBit) *wire.ExtendedHea
 	hdr := &wire.ExtendedHeader{}
 	hdr.PacketNumber = pn
 	hdr.PacketNumberLen = pnLen
-	hdr.DestConnectionID = p.destConnID
+	hdr.DestConnectionID = p.getDestConnID()
 	hdr.KeyPhase = kp
 	return hdr
 }
@@ -442,7 +441,7 @@ func (p *packetPacker) getLongHeader(encLevel protocol.EncryptionLevel) *wire.Ex
 	hdr := &wire.ExtendedHeader{}
 	hdr.PacketNumber = pn
 	hdr.PacketNumberLen = pnLen
-	hdr.DestConnectionID = p.destConnID
+	hdr.DestConnectionID = p.getDestConnID()
 
 	switch encLevel {
 	case protocol.EncryptionInitial:
@@ -550,10 +549,6 @@ func (p *packetPacker) writeAndSealPacketWithPadding(
 	}, nil
 }
 
-func (p *packetPacker) ChangeDestConnectionID(connID protocol.ConnectionID) {
-	p.destConnID = connID
-}
-
 func (p *packetPacker) SetToken(token []byte) {
 	p.token = token
 }

packet_packer_test.go

@@ -77,7 +77,7 @@ var _ = Describe("Packet packer", func() {
 
 		packer = newPacketPacker(
 			protocol.ConnectionID{1, 2, 3, 4, 5, 6, 7, 8},
-			protocol.ConnectionID{1, 2, 3, 4, 5, 6, 7, 8},
+			func() protocol.ConnectionID { return protocol.ConnectionID{1, 2, 3, 4, 5, 6, 7, 8} },
 			initialStream,
 			handshakeStream,
 			pnManager,
@@ -126,28 +126,12 @@ var _ = Describe("Packet packer", func() {
 			srcConnID := protocol.ConnectionID{1, 2, 3, 4, 5, 6, 7, 8}
 			destConnID := protocol.ConnectionID{8, 7, 6, 5, 4, 3, 2, 1}
 			packer.srcConnID = srcConnID
-			packer.destConnID = destConnID
+			packer.getDestConnID = func() protocol.ConnectionID { return destConnID }
 			h := packer.getLongHeader(protocol.EncryptionHandshake)
 			Expect(h.SrcConnectionID).To(Equal(srcConnID))
 			Expect(h.DestConnectionID).To(Equal(destConnID))
 		})
 
-		It("changes the destination connection ID", func() {
-			pnManager.EXPECT().PeekPacketNumber(protocol.EncryptionInitial).Return(protocol.PacketNumber(0x42), protocol.PacketNumberLen2).Times(2)
-			srcConnID := protocol.ConnectionID{1, 1, 1, 1, 1, 1, 1, 1}
-			packer.srcConnID = srcConnID
-			dest1 := protocol.ConnectionID{1, 2, 3, 4, 5, 6, 7, 8}
-			dest2 := protocol.ConnectionID{8, 7, 6, 5, 4, 3, 2, 1}
-			packer.ChangeDestConnectionID(dest1)
-			h := packer.getLongHeader(protocol.EncryptionInitial)
-			Expect(h.SrcConnectionID).To(Equal(srcConnID))
-			Expect(h.DestConnectionID).To(Equal(dest1))
-			packer.ChangeDestConnectionID(dest2)
-			h = packer.getLongHeader(protocol.EncryptionInitial)
-			Expect(h.SrcConnectionID).To(Equal(srcConnID))
-			Expect(h.DestConnectionID).To(Equal(dest2))
-		})
-
 		It("gets a short header", func() {
 			pnManager.EXPECT().PeekPacketNumber(protocol.Encryption1RTT).Return(protocol.PacketNumber(0x1337), protocol.PacketNumberLen4)
 			h := packer.getShortHeader(protocol.KeyPhaseOne)
@@ -397,7 +381,7 @@ var _ = Describe("Packet packer", func() {
 				Expect(err).ToNot(HaveOccurred())
 				// cut off the tag that the mock sealer added
 				packet.raw = packet.raw[:len(packet.raw)-sealer.Overhead()]
-				hdr, _, _, err := wire.ParsePacket(packet.raw, len(packer.destConnID))
+				hdr, _, _, err := wire.ParsePacket(packet.raw, len(packer.getDestConnID()))
 				Expect(err).ToNot(HaveOccurred())
 				r := bytes.NewReader(packet.raw)
 				extHdr, err := hdr.ParseExtended(r, packer.version)

session.go

@@ -104,7 +104,6 @@ var errCloseForRecreating = errors.New("closing session in order to recreate it"
 type session struct {
 	sessionRunner sessionRunner
 
-	destConnID     protocol.ConnectionID
 	origDestConnID protocol.ConnectionID // if the server sends a Retry, this is the connection ID we used initially
 	srcConnID      protocol.ConnectionID
 
@@ -201,13 +200,13 @@ var newSession = func(
 		sessionRunner:         runner,
 		config:                conf,
 		srcConnID:             srcConnID,
-		destConnID:            destConnID,
 		tokenGenerator:        tokenGenerator,
 		perspective:           protocol.PerspectiveServer,
 		handshakeCompleteChan: make(chan struct{}),
 		logger:                logger,
 		version:               v,
 	}
+	s.connIDManager = newConnIDManager(destConnID, s.queueControlFrame)
 	s.preSetup()
 	s.sentPacketHandler = ackhandler.NewSentPacketHandler(0, s.rttStats, s.traceCallback, s.logger)
 	initialStream := newCryptoStream()
@@ -231,9 +230,10 @@ var newSession = func(
 		logger,
 	)
 	s.cryptoStreamHandler = cs
+	s.connIDManager = newConnIDManager(destConnID, s.queueControlFrame)
 	s.packer = newPacketPacker(
-		s.destConnID,
 		s.srcConnID,
+		s.connIDManager.Get,
 		initialStream,
 		handshakeStream,
 		s.sentPacketHandler,
@@ -269,13 +269,13 @@ var newClientSession = func(
 		sessionRunner:         runner,
 		config:                conf,
 		srcConnID:             srcConnID,
-		destConnID:            destConnID,
 		perspective:           protocol.PerspectiveClient,
 		handshakeCompleteChan: make(chan struct{}),
 		logger:                logger,
 		initialVersion:        initialVersion,
 		version:               v,
 	}
+	s.connIDManager = newConnIDManager(destConnID, s.queueControlFrame)
 	s.preSetup()
 	s.sentPacketHandler = ackhandler.NewSentPacketHandler(initialPacketNumber, s.rttStats, s.traceCallback, s.logger)
 	initialStream := newCryptoStream()
@@ -285,7 +285,7 @@ var newClientSession = func(
 		initialStream,
 		handshakeStream,
 		oneRTTStream,
-		s.destConnID,
+		destConnID,
 		conn.RemoteAddr(),
 		params,
 		&handshakeRunner{
@@ -303,8 +303,8 @@ var newClientSession = func(
 	s.cryptoStreamManager = newCryptoStreamManager(cs, initialStream, handshakeStream, oneRTTStream)
 	s.unpacker = newPacketUnpacker(cs, s.version)
 	s.packer = newPacketPacker(
-		s.destConnID,
 		s.srcConnID,
+		s.connIDManager.Get,
 		initialStream,
 		handshakeStream,
 		s.sentPacketHandler,
@@ -333,7 +333,6 @@ func (s *session) preSetup() {
 	s.sendQueue = newSendQueue(s.conn)
 	s.retransmissionQueue = newRetransmissionQueue(s.version)
 	s.frameParser = wire.NewFrameParser(s.version)
-	s.connIDManager = newConnIDManager(s.queueControlFrame)
 	s.rttStats = &congestion.RTTStats{}
 	s.receivedPacketHandler = ackhandler.NewReceivedPacketHandler(s.rttStats, s.logger, s.version)
 	s.connFlowController = flowcontrol.NewConnectionFlowController(
@@ -601,8 +600,9 @@ func (s *session) handleSinglePacket(p *receivedPacket, hdr *wire.Header) bool /
 
 	// The server can change the source connection ID with the first Handshake packet.
 	// After this, all packets with a different source connection have to be ignored.
-	if s.receivedFirstPacket && hdr.IsLongHeader && !hdr.SrcConnectionID.Equal(s.destConnID) {
+	destConnID := s.connIDManager.Get()
-		s.logger.Debugf("Dropping packet with unexpected source connection ID: %s (expected %s)", hdr.SrcConnectionID, s.destConnID)
+	if s.receivedFirstPacket && hdr.IsLongHeader && !hdr.SrcConnectionID.Equal(destConnID) {
+		s.logger.Debugf("Dropping packet with unexpected source connection ID: %s (expected %s)", hdr.SrcConnectionID, destConnID)
 		return false
 	}
 	// drop 0-RTT packets
@@ -652,11 +652,12 @@ func (s *session) handleRetryPacket(hdr *wire.Header) bool /* was this a valid R
 		return false
 	}
 	(&wire.ExtendedHeader{Header: *hdr}).Log(s.logger)
-	if !hdr.OrigDestConnectionID.Equal(s.destConnID) {
+	destConnID := s.connIDManager.Get()
-		s.logger.Debugf("Ignoring spoofed Retry. Original Destination Connection ID: %s, expected: %s", hdr.OrigDestConnectionID, s.destConnID)
+	if !hdr.OrigDestConnectionID.Equal(destConnID) {
+		s.logger.Debugf("Ignoring spoofed Retry. Original Destination Connection ID: %s, expected: %s", hdr.OrigDestConnectionID, destConnID)
 		return false
 	}
-	if hdr.SrcConnectionID.Equal(s.destConnID) {
+	if hdr.SrcConnectionID.Equal(destConnID) {
 		s.logger.Debugf("Ignoring Retry, since the server didn't change the Source Connection ID.")
 		return false
 	}
@@ -668,16 +669,16 @@ func (s *session) handleRetryPacket(hdr *wire.Header) bool /* was this a valid R
 	}
 	s.logger.Debugf("<- Received Retry")
 	s.logger.Debugf("Switching destination connection ID to: %s", hdr.SrcConnectionID)
-	s.origDestConnID = s.destConnID
+	s.origDestConnID = destConnID
-	s.destConnID = hdr.SrcConnectionID
+	newDestConnID := hdr.SrcConnectionID
 	s.receivedRetry = true
 	if err := s.sentPacketHandler.ResetForRetry(); err != nil {
 		s.closeLocal(err)
 		return false
 	}
-	s.cryptoStreamHandler.ChangeConnectionID(s.destConnID)
+	s.cryptoStreamHandler.ChangeConnectionID(newDestConnID)
 	s.packer.SetToken(hdr.Token)
-	s.packer.ChangeDestConnectionID(s.destConnID)
+	s.connIDManager.ChangeInitialConnID(newDestConnID)
 	s.scheduleSending()
 	return true
 }
@@ -688,10 +689,9 @@ func (s *session) handleUnpackedPacket(packet *unpackedPacket, rcvTime time.Time
 	}
 
 	// The server can change the source connection ID with the first Handshake packet.
-	if s.perspective == protocol.PerspectiveClient && !s.receivedFirstPacket && packet.hdr.IsLongHeader && !packet.hdr.SrcConnectionID.Equal(s.destConnID) {
+	if s.perspective == protocol.PerspectiveClient && !s.receivedFirstPacket && packet.hdr.IsLongHeader && !packet.hdr.SrcConnectionID.Equal(s.connIDManager.Get()) {
 		s.logger.Debugf("Received first packet. Switching destination connection ID to: %s", packet.hdr.SrcConnectionID)
-		s.destConnID = packet.hdr.SrcConnectionID
+		s.connIDManager.ChangeInitialConnID(packet.hdr.SrcConnectionID)
-		s.packer.ChangeDestConnectionID(s.destConnID)
 	}
 
 	s.receivedFirstPacket = true
@@ -927,9 +927,9 @@ func (s *session) destroy(e error) {
 func (s *session) destroyImpl(e error) {
 	s.closeOnce.Do(func() {
 		if nerr, ok := e.(net.Error); ok && nerr.Timeout() {
-			s.logger.Errorf("Destroying session %s: %s", s.destConnID, e)
+			s.logger.Errorf("Destroying session %s: %s", s.connIDManager.Get(), e)
 		} else {
-			s.logger.Errorf("Destroying session %s with error: %s", s.destConnID, e)
+			s.logger.Errorf("Destroying session %s with error: %s", s.connIDManager.Get(), e)
 		}
 		s.sessionRunner.Remove(s.srcConnID)
 		s.closeChan <- closeError{err: e, sendClose: false, remote: false}

session_test.go

@@ -79,6 +79,7 @@ var _ = Describe("Session", func() {
 		packer        *MockPacker
 		cryptoSetup   *mocks.MockCryptoSetup
 	)
+	destConnID := protocol.ConnectionID{8, 7, 6, 5, 4, 3, 2, 1}
 
 	getPacket := func(pn protocol.PacketNumber) *packedPacket {
 		buffer := getPacketBuffer()
@@ -110,7 +111,7 @@ var _ = Describe("Session", func() {
 			mconn,
 			sessionRunner,
 			protocol.ConnectionID{1, 2, 3, 4, 5, 6, 7, 8, 9, 10},
-			protocol.ConnectionID{8, 7, 6, 5, 4, 3, 2, 1},
+			destConnID,
 			protocol.ConnectionID{1, 2, 3, 4, 5, 6, 7, 8},
 			populateServerConfig(&Config{}),
 			nil, // tls.Config
@@ -307,7 +308,7 @@ var _ = Describe("Session", func() {
 				SequenceNumber: 10,
 				ConnectionID:   protocol.ConnectionID{1, 2, 3, 4},
 			}, 1, protocol.Encryption1RTT)).To(Succeed())
-			Expect(sess.connIDManager.queue.Front().Value.ConnectionID).To(Equal(protocol.ConnectionID{1, 2, 3, 4}))
+			Expect(sess.connIDManager.queue.Back().Value.ConnectionID).To(Equal(protocol.ConnectionID{1, 2, 3, 4}))
 		})
 
 		It("handles PING frames", func() {
@@ -673,7 +674,7 @@ var _ = Describe("Session", func() {
 				Header: wire.Header{
 					IsLongHeader:     true,
 					Type:             protocol.PacketTypeHandshake,
-					DestConnectionID: sess.destConnID,
+					DestConnectionID: destConnID,
 					SrcConnectionID:  sess.srcConnID,
 					Length:           1,
 					Version:          sess.version,
@@ -685,7 +686,7 @@ var _ = Describe("Session", func() {
 				Header: wire.Header{
 					IsLongHeader:     true,
 					Type:             protocol.PacketTypeHandshake,
-					DestConnectionID: sess.destConnID,
+					DestConnectionID: destConnID,
 					SrcConnectionID:  protocol.ConnectionID{0xde, 0xad, 0xbe, 0xef},
 					Length:           1,
 					Version:          sess.version,
@@ -711,7 +712,7 @@ var _ = Describe("Session", func() {
 				Header: wire.Header{
 					IsLongHeader:     true,
 					Type:             protocol.PacketTypeHandshake,
-					DestConnectionID: sess.destConnID,
+					DestConnectionID: destConnID,
 					SrcConnectionID:  sess.srcConnID,
 					Length:           1,
 					Version:          sess.version,
@@ -752,7 +753,7 @@ var _ = Describe("Session", func() {
 						IsLongHeader:     true,
 						Type:             protocol.PacketTypeHandshake,
 						DestConnectionID: connID,
-						SrcConnectionID:  sess.destConnID,
+						SrcConnectionID:  destConnID,
 						Version:          protocol.VersionTLS,
 						Length:           length,
 					},
@@ -1507,6 +1508,7 @@ var _ = Describe("Client Session", func() {
 		tlsConf       *tls.Config
 		quicConf      *Config
 	)
+	destConnID := protocol.ConnectionID{8, 7, 6, 5, 4, 3, 2, 1}
 
 	getPacket := func(hdr *wire.ExtendedHeader, data []byte) *receivedPacket {
 		buf := &bytes.Buffer{}
@@ -1539,7 +1541,7 @@ var _ = Describe("Client Session", func() {
 		sess = newClientSession(
 			mconn,
 			sessionRunner,
-			protocol.ConnectionID{8, 7, 6, 5, 4, 3, 2, 1},
+			destConnID,
 			protocol.ConnectionID{1, 2, 3, 4, 5, 6, 7, 8},
 			quicConf,
 			tlsConf,
@@ -1571,7 +1573,6 @@ var _ = Describe("Client Session", func() {
 			sess.run()
 		}()
 		newConnID := protocol.ConnectionID{1, 3, 3, 7, 1, 3, 3, 7}
-		packer.EXPECT().ChangeDestConnectionID(newConnID)
 		Expect(sess.handlePacketImpl(getPacket(&wire.ExtendedHeader{
 			Header: wire.Header{
 				IsLongHeader:     true,
@@ -1627,7 +1628,6 @@ var _ = Describe("Client Session", func() {
 		It("handles Retry packets", func() {
 			cryptoSetup.EXPECT().ChangeConnectionID(protocol.ConnectionID{0xde, 0xad, 0xbe, 0xef})
 			packer.EXPECT().SetToken([]byte("foobar"))
-			packer.EXPECT().ChangeDestConnectionID(protocol.ConnectionID{0xde, 0xad, 0xbe, 0xef})
 			Expect(sess.handlePacketImpl(getPacket(validRetryHdr, nil))).To(BeTrue())
 		})
 
@@ -1637,7 +1637,7 @@ var _ = Describe("Client Session", func() {
 		})
 
 		It("ignores Retry packets if the server didn't change the connection ID", func() {
-			validRetryHdr.SrcConnectionID = sess.destConnID
+			validRetryHdr.SrcConnectionID = destConnID
 			Expect(sess.handlePacketImpl(getPacket(validRetryHdr, nil))).To(BeFalse())
 		})
 
@@ -1724,7 +1724,7 @@ var _ = Describe("Client Session", func() {
 				Header: wire.Header{
 					IsLongHeader:     true,
 					Type:             protocol.PacketTypeInitial,
-					DestConnectionID: sess.destConnID,
+					DestConnectionID: destConnID,
 					SrcConnectionID:  sess.srcConnID,
 					Length:           1,
 					Version:          sess.version,
@@ -1736,7 +1736,7 @@ var _ = Describe("Client Session", func() {
 				Header: wire.Header{
 					IsLongHeader:     true,
 					Type:             protocol.PacketTypeInitial,
-					DestConnectionID: sess.destConnID,
+					DestConnectionID: destConnID,
 					SrcConnectionID:  protocol.ConnectionID{0xde, 0xad, 0xbe, 0xef},
 					Length:           1,
 					Version:          sess.version,
@@ -1746,7 +1746,6 @@ var _ = Describe("Client Session", func() {
 			}
 			Expect(sess.srcConnID).ToNot(Equal(hdr2.SrcConnectionID))
 			// Send one packet, which might change the connection ID.
-			packer.EXPECT().ChangeDestConnectionID(sess.srcConnID).MaxTimes(1)
 			// only EXPECT one call to the unpacker
 			unpacker.EXPECT().Unpack(gomock.Any(), gomock.Any(), gomock.Any()).Return(&unpackedPacket{
 				encryptionLevel: protocol.EncryptionInitial,
@@ -1762,7 +1761,7 @@ var _ = Describe("Client Session", func() {
 		// the connection to immediately break down
 		It("fails on Initial-level ACK for unsent packet", func() {
 			ackFrame := testutils.ComposeAckFrame(0, 0)
-			initialPacket := testutils.ComposeInitialPacket(sess.destConnID, sess.srcConnID, sess.version, sess.destConnID, []wire.Frame{ackFrame})
+			initialPacket := testutils.ComposeInitialPacket(destConnID, sess.srcConnID, sess.version, destConnID, []wire.Frame{ackFrame})
 			Expect(sess.handlePacketImpl(wrapPacket(initialPacket))).To(BeFalse())
 		})
 
@@ -1771,7 +1770,7 @@ var _ = Describe("Client Session", func() {
 		It("fails on Initial-level CONNECTION_CLOSE frame", func() {
 			sessionRunner.EXPECT().ReplaceWithClosed(gomock.Any(), gomock.Any())
 			connCloseFrame := testutils.ComposeConnCloseFrame()
-			initialPacket := testutils.ComposeInitialPacket(sess.destConnID, sess.srcConnID, sess.version, sess.destConnID, []wire.Frame{connCloseFrame})
+			initialPacket := testutils.ComposeInitialPacket(destConnID, sess.srcConnID, sess.version, destConnID, []wire.Frame{connCloseFrame})
 			Expect(sess.handlePacketImpl(wrapPacket(initialPacket))).To(BeTrue())
 		})
 
@@ -1781,10 +1780,9 @@ var _ = Describe("Client Session", func() {
 			newSrcConnID := protocol.ConnectionID{0xde, 0xad, 0xbe, 0xef}
 			cryptoSetup.EXPECT().ChangeConnectionID(newSrcConnID)
 			packer.EXPECT().SetToken([]byte("foobar"))
-			packer.EXPECT().ChangeDestConnectionID(newSrcConnID)
 
-			sess.handlePacketImpl(wrapPacket(testutils.ComposeRetryPacket(newSrcConnID, sess.destConnID, sess.destConnID, []byte("foobar"), sess.version)))
+			sess.handlePacketImpl(wrapPacket(testutils.ComposeRetryPacket(newSrcConnID, destConnID, destConnID, []byte("foobar"), sess.version)))
-			initialPacket := testutils.ComposeInitialPacket(sess.destConnID, sess.srcConnID, sess.version, sess.destConnID, nil)
+			initialPacket := testutils.ComposeInitialPacket(sess.connIDManager.Get(), sess.srcConnID, sess.version, sess.connIDManager.Get(), nil)
 			Expect(sess.handlePacketImpl(wrapPacket(initialPacket))).To(BeFalse())
 		})