use the new packet number format

internal/protocol/packet_number.go

@@ -1,5 +1,21 @@
 package protocol
 
+// PacketNumberLen is the length of the packet number in bytes
+type PacketNumberLen uint8
+
+const (
+	// PacketNumberLenInvalid is the default value and not a valid length for a packet number
+	PacketNumberLenInvalid PacketNumberLen = 0
+	// PacketNumberLen1 is a packet number length of 1 byte
+	PacketNumberLen1 PacketNumberLen = 1
+	// PacketNumberLen2 is a packet number length of 2 bytes
+	PacketNumberLen2 PacketNumberLen = 2
+	// PacketNumberLen3 is a packet number length of 3 bytes
+	PacketNumberLen3 PacketNumberLen = 3
+	// PacketNumberLen4 is a packet number length of 4 bytes
+	PacketNumberLen4 PacketNumberLen = 4
+)
+
 // InferPacketNumber calculates the packet number based on the received packet number, its length and the last seen packet number
 func InferPacketNumber(
 	packetNumberLength PacketNumberLen,
@@ -9,11 +25,13 @@ func InferPacketNumber(
 	var epochDelta PacketNumber
 	switch packetNumberLength {
 	case PacketNumberLen1:
-		epochDelta = PacketNumber(1) << 7
+		epochDelta = PacketNumber(1) << 8
 	case PacketNumberLen2:
-		epochDelta = PacketNumber(1) << 14
+		epochDelta = PacketNumber(1) << 16
+	case PacketNumberLen3:
+		epochDelta = PacketNumber(1) << 24
 	case PacketNumberLen4:
-		epochDelta = PacketNumber(1) << 30
+		epochDelta = PacketNumber(1) << 32
 	}
 	epoch := lastPacketNumber & ^(epochDelta - 1)
 	prevEpochBegin := epoch - epochDelta
@@ -43,9 +61,12 @@ func delta(a, b PacketNumber) PacketNumber {
 // it never chooses a PacketNumberLen of 1 byte, since this is too short under certain circumstances
 func GetPacketNumberLengthForHeader(packetNumber, leastUnacked PacketNumber) PacketNumberLen {
 	diff := uint64(packetNumber - leastUnacked)
-	if diff < (1 << (14 - 1)) {
+	if diff < (1 << (16 - 1)) {
 		return PacketNumberLen2
 	}
+	if diff < (1 << (24 - 1)) {
+		return PacketNumberLen3
+	}
 	return PacketNumberLen4
 }
 
@@ -57,5 +78,8 @@ func GetPacketNumberLength(packetNumber PacketNumber) PacketNumberLen {
 	if packetNumber < (1 << (uint8(PacketNumberLen2) * 8)) {
 		return PacketNumberLen2
 	}
+	if packetNumber < (1 << (uint8(PacketNumberLen3) * 8)) {
+		return PacketNumberLen3
+	}
 	return PacketNumberLen4
 }

internal/protocol/packet_number_test.go

@@ -12,18 +12,12 @@ import (
 var _ = Describe("packet number calculation", func() {
 	Context("infering a packet number", func() {
 		getEpoch := func(len PacketNumberLen) uint64 {
-			switch len {
-			case PacketNumberLen1:
-				return uint64(1) << 7
-			case PacketNumberLen2:
-				return uint64(1) << 14
-			case PacketNumberLen4:
-				return uint64(1) << 30
-			default:
+			if len > 4 {
 				Fail("invalid packet number len")
 			}
 			return uint64(1) << (len * 8)
 		}
+
 		check := func(length PacketNumberLen, expected, last uint64) {
 			epoch := getEpoch(length)
 			epochMask := epoch - 1
@@ -151,8 +145,13 @@ var _ = Describe("packet number calculation", func() {
 							Expect(length).To(Equal(PacketNumberLen2))
 						})
 
-						It("sends out higher packet numbers as 4 bytes, if a lot of ACKs are missing", func() {
+						It("sends out higher packet numbers as 3 bytes, if a lot of ACKs are missing", func() {
 							length := GetPacketNumberLengthForHeader(40000, 2)
+							Expect(length).To(Equal(PacketNumberLen3))
+						})
+
+						It("sends out higher packet numbers as 4 bytes, if a lot of ACKs are missing", func() {
+							length := GetPacketNumberLengthForHeader(40000000, 2)
 							Expect(length).To(Equal(PacketNumberLen4))
 						})
 					})
@@ -225,6 +224,10 @@ var _ = Describe("packet number calculation", func() {
 			Expect(GetPacketNumberLength(0xFFFF)).To(Equal(PacketNumberLen2))
 		})
 
+		It("3 byte", func() {
+			Expect(GetPacketNumberLength(0xFFFFFF)).To(Equal(PacketNumberLen3))
+		})
+
 		It("4 byte", func() {
 			Expect(GetPacketNumberLength(0xFFFFFFFF)).To(Equal(PacketNumberLen4))
 		})

internal/protocol/protocol.go

@@ -7,20 +7,6 @@ import (
 // A PacketNumber in QUIC
 type PacketNumber uint64
 
-// PacketNumberLen is the length of the packet number in bytes
-type PacketNumberLen uint8
-
-const (
-	// PacketNumberLenInvalid is the default value and not a valid length for a packet number
-	PacketNumberLenInvalid PacketNumberLen = 0
-	// PacketNumberLen1 is a packet number length of 1 byte
-	PacketNumberLen1 PacketNumberLen = 1
-	// PacketNumberLen2 is a packet number length of 2 bytes
-	PacketNumberLen2 PacketNumberLen = 2
-	// PacketNumberLen4 is a packet number length of 4 bytes
-	PacketNumberLen4 PacketNumberLen = 4
-)
-
 // The PacketType is the Long Header Type
 type PacketType uint8