add a function to distinguish between long and short header packets (#3498)

integrationtests/self/datagram_test.go

@@ -13,6 +13,7 @@ import (
 	"github.com/lucas-clemente/quic-go"
 	quicproxy "github.com/lucas-clemente/quic-go/integrationtests/tools/proxy"
 	"github.com/lucas-clemente/quic-go/internal/protocol"
+	"github.com/lucas-clemente/quic-go/internal/wire"
 
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
@@ -73,7 +74,7 @@ var _ = Describe("Datagram test", func() {
 							return false
 						}
 						// don't drop Long Header packets
-						if packet[0]&0x80 == 1 {
+						if wire.IsLongHeaderPacket(packet[0]) {
 							return false
 						}
 						drop := mrand.Int()%10 == 0

integrationtests/self/zero_rtt_test.go

@@ -732,7 +732,7 @@ var _ = Describe("0-RTT", func() {
 				proxy, err := quicproxy.NewQuicProxy("localhost:0", &quicproxy.Opts{
 					RemoteAddr: ln.Addr().String(),
 					DelayPacket: func(dir quicproxy.Direction, data []byte) time.Duration {
-						if dir == quicproxy.DirectionIncoming && data[0]&0x80 > 0 && data[0]&0x30>>4 == 0 { // Initial packet from client
+						if dir == quicproxy.DirectionIncoming && wire.IsLongHeaderPacket(data[0]) && data[0]&0x30>>4 == 0 { // Initial packet from client
 							return rtt/2 + rtt
 						}
 						return rtt / 2

internal/wire/header.go

@@ -19,8 +19,7 @@ func ParseConnectionID(data []byte, shortHeaderConnIDLen int) (protocol.Connecti
 	if len(data) == 0 {
 		return nil, io.EOF
 	}
-	isLongHeader := data[0]&0x80 > 0
+	if !IsLongHeaderPacket(data[0]) {
-	if !isLongHeader {
 		if len(data) < shortHeaderConnIDLen+1 {
 			return nil, io.EOF
 		}
@@ -36,12 +35,17 @@ func ParseConnectionID(data []byte, shortHeaderConnIDLen int) (protocol.Connecti
 	return protocol.ConnectionID(data[6 : 6+destConnIDLen]), nil
 }
 
+// IsLongHeaderPacket says if this is a Long Header packet
+func IsLongHeaderPacket(firstByte byte) bool {
+	return firstByte&0x80 > 0
+}
+
 // IsVersionNegotiationPacket says if this is a version negotiation packet
 func IsVersionNegotiationPacket(b []byte) bool {
 	if len(b) < 5 {
 		return false
 	}
-	return b[0]&0x80 > 0 && b[1] == 0 && b[2] == 0 && b[3] == 0 && b[4] == 0
+	return IsLongHeaderPacket(b[0]) && b[1] == 0 && b[2] == 0 && b[3] == 0 && b[4] == 0
 }
 
 // Is0RTTPacket says if this is a 0-RTT packet.
@@ -50,7 +54,7 @@ func Is0RTTPacket(b []byte) bool {
 	if len(b) < 5 {
 		return false
 	}
-	if b[0]&0x80 == 0 {
+	if !IsLongHeaderPacket(b[0]) {
 		return false
 	}
 	version := protocol.VersionNumber(binary.BigEndian.Uint32(b[1:5]))
@@ -129,7 +133,7 @@ func parseHeaderImpl(b *bytes.Reader, shortHeaderConnIDLen int) (*Header, error)
 
 	h := &Header{
 		typeByte:     typeByte,
-		IsLongHeader: typeByte&0x80 > 0,
+		IsLongHeader: IsLongHeaderPacket(typeByte),
 	}
 
 	if !h.IsLongHeader {

internal/wire/header_test.go

@@ -576,6 +576,11 @@ var _ = Describe("Header Parsing", func() {
 		})
 	})
 
+	It("distinguishes long and short header packets", func() {
+		Expect(IsLongHeaderPacket(0x40)).To(BeFalse())
+		Expect(IsLongHeaderPacket(0x80 ^ 0x40 ^ 0x12)).To(BeTrue())
+	})
+
 	It("tells its packet type for logging", func() {
 		Expect((&Header{IsLongHeader: true, Type: protocol.PacketTypeHandshake}).PacketType()).To(Equal("Handshake"))
 		Expect((&Header{}).PacketType()).To(Equal("1-RTT"))

internal/wire/version_negotiation_test.go

@@ -56,7 +56,7 @@ var _ = Describe("Version Negotiation Packets", func() {
 		destConnID := protocol.ConnectionID{1, 2, 3, 4, 5, 6, 7, 8}
 		versions := []protocol.VersionNumber{1001, 1003}
 		data := ComposeVersionNegotiation(destConnID, srcConnID, versions)
-		Expect(data[0] & 0x80).ToNot(BeZero())
+		Expect(IsLongHeaderPacket(data[0])).To(BeTrue())
 		hdr, supportedVersions, err := ParseVersionNegotiationPacket(bytes.NewReader(data))
 		Expect(err).ToNot(HaveOccurred())
 		Expect(hdr.DestConnectionID).To(Equal(destConnID))

packet_handler_map.go

@@ -390,7 +390,7 @@ func (h *packetHandlerMap) handlePacket(p *receivedPacket) {
 			return
 		}
 	}
-	if p.data[0]&0x80 == 0 {
+	if !wire.IsLongHeaderPacket(p.data[0]) {
 		go h.maybeSendStatelessReset(p, connID)
 		return
 	}
@@ -433,7 +433,7 @@ func (h *packetHandlerMap) handlePacket(p *receivedPacket) {
 
 func (h *packetHandlerMap) maybeHandleStatelessReset(data []byte) bool {
 	// stateless resets are always short header packets
-	if data[0]&0x80 != 0 {
+	if wire.IsLongHeaderPacket(data[0]) {
 		return false
 	}
 	if len(data) < 17 /* type byte + 16 bytes for the reset token */ {

packet_handler_map_test.go

@@ -453,7 +453,7 @@ var _ = Describe("Packet Handler Map", func() {
 					done := make(chan struct{})
 					conn.EXPECT().WriteTo(gomock.Any(), addr).Do(func(b []byte, _ net.Addr) {
 						defer close(done)
-						Expect(b[0] & 0x80).To(BeZero()) // short header packet
+						Expect(wire.IsLongHeaderPacket(b[0])).To(BeFalse()) // short header packet
 						Expect(b).To(HaveLen(protocol.MinStatelessResetSize))
 					})
 					handler.handlePacket(&receivedPacket{