move tracking of skipped packets to the packet number generator

internal/ackhandler/packet_number_generator.go

@@ -5,6 +5,7 @@ import (
 	"math"
 
 	"github.com/lucas-clemente/quic-go/internal/protocol"
+	"github.com/lucas-clemente/quic-go/internal/wire"
 )
 
 // The packetNumberGenerator generates the packet number for the next packet
@@ -15,6 +16,8 @@ type packetNumberGenerator struct {
 
 	next       protocol.PacketNumber
 	nextToSkip protocol.PacketNumber
+
+	history []protocol.PacketNumber
 }
 
 func newPacketNumberGenerator(initial, averagePeriod protocol.PacketNumber) *packetNumberGenerator {
@@ -37,6 +40,10 @@ func (p *packetNumberGenerator) Pop() protocol.PacketNumber {
 	p.next++
 
 	if p.next == p.nextToSkip {
+		if len(p.history)+1 > protocol.MaxTrackedSkippedPackets {
+			p.history = p.history[1:]
+		}
+		p.history = append(p.history, p.next)
 		p.next++
 		p.generateNewSkip()
 	}
@@ -60,3 +67,12 @@ func (p *packetNumberGenerator) getRandomNumber() uint16 {
 	num := uint16(b[0])<<8 + uint16(b[1])
 	return num
 }
+
+func (p *packetNumberGenerator) Validate(ack *wire.AckFrame) bool {
+	for _, pn := range p.history {
+		if ack.AcksPacket(pn) {
+			return false
+		}
+	}
+	return true
+}