only skip packet numbers in the application data packet number space

internal/ackhandler/packet_number_generator.go

@@ -8,10 +8,35 @@ import (
 	"github.com/lucas-clemente/quic-go/internal/protocol"
 )
 
-// The packetNumberGenerator generates the packet number for the next packet
+type packetNumberGenerator interface {
+	Peek() protocol.PacketNumber
+	Pop() protocol.PacketNumber
+}
+
+type sequentialPacketNumberGenerator struct {
+	next protocol.PacketNumber
+}
+
+var _ packetNumberGenerator = &sequentialPacketNumberGenerator{}
+
+func newSequentialPacketNumberGenerator(initial protocol.PacketNumber) packetNumberGenerator {
+	return &sequentialPacketNumberGenerator{next: initial}
+}
+
+func (p *sequentialPacketNumberGenerator) Peek() protocol.PacketNumber {
+	return p.next
+}
+
+func (p *sequentialPacketNumberGenerator) Pop() protocol.PacketNumber {
+	next := p.next
+	p.next++
+	return next
+}
+
+// The skippingPacketNumberGenerator generates the packet number for the next packet
 // it randomly skips a packet number every averagePeriod packets (on average).
 // It is guaranteed to never skip two consecutive packet numbers.
-type packetNumberGenerator struct {
+type skippingPacketNumberGenerator struct {
 	rand          *mrand.Rand
 	averagePeriod protocol.PacketNumber
 
@@ -19,10 +44,12 @@ type packetNumberGenerator struct {
 	nextToSkip protocol.PacketNumber
 }
 
-func newPacketNumberGenerator(initial, averagePeriod protocol.PacketNumber) *packetNumberGenerator {
+var _ packetNumberGenerator = &skippingPacketNumberGenerator{}
+
+func newSkippingPacketNumberGenerator(initial, averagePeriod protocol.PacketNumber) packetNumberGenerator {
 	b := make([]byte, 8)
 	rand.Read(b) // it's not the end of the world if we don't get perfect random here
-	g := &packetNumberGenerator{
+	g := &skippingPacketNumberGenerator{
 		rand:          mrand.New(mrand.NewSource(int64(binary.LittleEndian.Uint64(b)))),
 		next:          initial,
 		averagePeriod: averagePeriod,
@@ -31,16 +58,13 @@ func newPacketNumberGenerator(initial, averagePeriod protocol.PacketNumber) *pac
 	return g
 }
 
-func (p *packetNumberGenerator) Peek() protocol.PacketNumber {
+func (p *skippingPacketNumberGenerator) Peek() protocol.PacketNumber {
 	return p.next
 }
 
-func (p *packetNumberGenerator) Pop() protocol.PacketNumber {
+func (p *skippingPacketNumberGenerator) Pop() protocol.PacketNumber {
 	next := p.next
-
+	p.next++ // generate a new packet number for the next packet
-	// generate a new packet number for the next packet
-	p.next++
-
 	if p.next == p.nextToSkip {
 		p.next++
 		p.generateNewSkip()
@@ -48,7 +72,7 @@ func (p *packetNumberGenerator) Pop() protocol.PacketNumber {
 	return next
 }
 
-func (p *packetNumberGenerator) generateNewSkip() {
+func (p *skippingPacketNumberGenerator) generateNewSkip() {
 	// make sure that there are never two consecutive packet numbers that are skipped
 	p.nextToSkip = p.next + 2 + protocol.PacketNumber(p.rand.Int31n(int32(2*p.averagePeriod)))
 }

internal/ackhandler/packet_number_generator_test.go

@@ -6,16 +6,29 @@ import (
 	. "github.com/onsi/gomega"
 )
 
-var _ = Describe("Packet Number Generator", func() {
+var _ = Describe("Sequential Packet Number Generator", func() {
-	var png *packetNumberGenerator
+	It("generates sequential packet numbers", func() {
+		const initialPN protocol.PacketNumber = 123
+		png := newSequentialPacketNumberGenerator(initialPN)
+
+		for i := initialPN; i < initialPN+1000; i++ {
+			Expect(png.Peek()).To(Equal(i))
+			Expect(png.Peek()).To(Equal(i))
+			Expect(png.Pop()).To(Equal(i))
+		}
+	})
+})
+
+var _ = Describe("Skipping Packet Number Generator", func() {
+	var png *skippingPacketNumberGenerator
 	const initialPN protocol.PacketNumber = 8
 
 	BeforeEach(func() {
-		png = newPacketNumberGenerator(initialPN, 100)
+		png = newSkippingPacketNumberGenerator(initialPN, 100).(*skippingPacketNumberGenerator)
 	})
 
 	It("can be initialized to return any first packet number", func() {
-		png = newPacketNumberGenerator(12345, 100)
+		png = newSkippingPacketNumberGenerator(12345, 100).(*skippingPacketNumberGenerator)
 		Expect(png.Pop()).To(Equal(protocol.PacketNumber(12345)))
 	})
 

internal/ackhandler/sent_packet_handler.go

@@ -25,7 +25,7 @@ const (
 
 type packetNumberSpace struct {
 	history *sentPacketHistory
-	pns     *packetNumberGenerator
+	pns     packetNumberGenerator
 
 	lossTime                   time.Time
 	lastAckElicitingPacketTime time.Time
@@ -34,10 +34,16 @@ type packetNumberSpace struct {
 	largestSent  protocol.PacketNumber
 }
 
-func newPacketNumberSpace(initialPN protocol.PacketNumber, rttStats *utils.RTTStats) *packetNumberSpace {
+func newPacketNumberSpace(initialPN protocol.PacketNumber, skipPNs bool, rttStats *utils.RTTStats) *packetNumberSpace {
+	var pns packetNumberGenerator
+	if skipPNs {
+		pns = newSkippingPacketNumberGenerator(initialPN, protocol.SkipPacketAveragePeriodLength)
+	} else {
+		pns = newSequentialPacketNumberGenerator(initialPN)
+	}
 	return &packetNumberSpace{
 		history:      newSentPacketHistory(rttStats),
-		pns:          newPacketNumberGenerator(initialPN, protocol.SkipPacketAveragePeriodLength),
+		pns:          pns,
 		largestSent:  protocol.InvalidPacketNumber,
 		largestAcked: protocol.InvalidPacketNumber,
 	}
@@ -94,7 +100,7 @@ var (
 )
 
 func newSentPacketHandler(
-	initialPacketNumber protocol.PacketNumber,
+	initialPN protocol.PacketNumber,
 	rttStats *utils.RTTStats,
 	pers protocol.Perspective,
 	tracer logging.ConnectionTracer,
@@ -110,9 +116,9 @@ func newSentPacketHandler(
 	return &sentPacketHandler{
 		peerCompletedAddressValidation: pers == protocol.PerspectiveServer,
 		peerAddressValidated:           pers == protocol.PerspectiveClient,
-		initialPackets:                 newPacketNumberSpace(initialPacketNumber, rttStats),
+		initialPackets:                 newPacketNumberSpace(initialPN, false, rttStats),
-		handshakePackets:               newPacketNumberSpace(0, rttStats),
+		handshakePackets:               newPacketNumberSpace(0, false, rttStats),
-		appDataPackets:                 newPacketNumberSpace(0, rttStats),
+		appDataPackets:                 newPacketNumberSpace(0, true, rttStats),
 		rttStats:                       rttStats,
 		congestion:                     congestion,
 		perspective:                    pers,
@@ -765,8 +771,8 @@ func (h *sentPacketHandler) ResetForRetry() error {
 			h.tracer.UpdatedMetrics(h.rttStats, h.congestion.GetCongestionWindow(), h.bytesInFlight, h.packetsInFlight())
 		}
 	}
-	h.initialPackets = newPacketNumberSpace(h.initialPackets.pns.Pop(), h.rttStats)
+	h.initialPackets = newPacketNumberSpace(h.initialPackets.pns.Pop(), false, h.rttStats)
-	h.appDataPackets = newPacketNumberSpace(h.appDataPackets.pns.Pop(), h.rttStats)
+	h.appDataPackets = newPacketNumberSpace(h.appDataPackets.pns.Pop(), true, h.rttStats)
 	oldAlarm := h.alarm
 	h.alarm = time.Time{}
 	if h.tracer != nil {