send a reserved version number in version negotiation packets

client_test.go

@@ -369,7 +369,7 @@ var _ = Describe("Client", func() {
 				Expect(firstSession.closeReason).To(Equal(errCloseSessionForNewVersion))
 				Consistently(func() bool { return secondSession.closed }).Should(BeFalse())
 				Expect(cl.connectionID).ToNot(BeEquivalentTo(0x1337))
-				Expect(negotiatedVersions).To(Equal([]protocol.VersionNumber{newVersion}))
+				Expect(negotiatedVersions).To(ContainElement(newVersion))
 				Expect(initialVersion).To(Equal(actualInitialVersion))
 
 				handshakeChan <- handshakeEvent{encLevel: protocol.EncryptionSecure}

internal/wire/header_test.go

@@ -129,7 +129,10 @@ var _ = Describe("Header", func() {
 			Expect(err).ToNot(HaveOccurred())
 			Expect(hdr.isPublicHeader).To(BeTrue())
 			Expect(hdr.ConnectionID).To(Equal(protocol.ConnectionID(0x42)))
-			Expect(hdr.SupportedVersions).To(Equal(versions))
+			// in addition to the versions, the supported versions might contain a reserved version number
+			for _, version := range versions {
+				Expect(hdr.SupportedVersions).To(ContainElement(version))
+			}
 		})
 
 		It("parses an IETF draft style Version Negotiation Packet", func() {
@@ -141,7 +144,11 @@ var _ = Describe("Header", func() {
 			Expect(hdr.IsVersionNegotiation).To(BeTrue())
 			Expect(hdr.ConnectionID).To(Equal(protocol.ConnectionID(0x42)))
 			Expect(hdr.PacketNumber).To(Equal(protocol.PacketNumber(0x77)))
-			Expect(hdr.SupportedVersions).To(Equal(versions))
+			Expect(hdr.Version).To(BeZero())
+			// in addition to the versions, the supported versions might contain a reserved version number
+			for _, version := range versions {
+				Expect(hdr.SupportedVersions).To(ContainElement(version))
+			}
 		})
 	})
 

internal/wire/ietf_header_test.go

@@ -28,7 +28,9 @@ var _ = Describe("IETF draft Header", func() {
 				Expect(h.Version).To(BeZero())
 				Expect(h.ConnectionID).To(Equal(protocol.ConnectionID(0x1234567890)))
 				Expect(h.PacketNumber).To(Equal(protocol.PacketNumber(0x1337)))
-				Expect(h.SupportedVersions).To(Equal(versions))
+				for _, v := range versions {
+					Expect(h.SupportedVersions).To(ContainElement(v))
+				}
 			})
 
 			It("errors if it contains versions of the wrong length", func() {
@@ -42,7 +44,8 @@ var _ = Describe("IETF draft Header", func() {
 			It("errors if the version list is emtpy", func() {
 				versions := []protocol.VersionNumber{0x22334455}
 				data := ComposeVersionNegotiation(0x1234567890, 0x1337, versions)
-				_, err := parseHeader(bytes.NewReader(data[:len(data)-4]), protocol.PerspectiveServer)
+				// remove 8 bytes (two versions), since ComposeVersionNegotiation also added a reserved version number
+				_, err := parseHeader(bytes.NewReader(data[:len(data)-8]), protocol.PerspectiveServer)
 				Expect(err).To(MatchError("InvalidVersionNegotiationPacket: empty version list"))
 			})
 		})

internal/wire/public_header_test.go

@@ -97,14 +97,18 @@ var _ = Describe("Public Header", func() {
 				return data
 			}
 
-			It("parses version negotiation packets sent by the server", func() {
+			It("parses", func() {
-				b := bytes.NewReader(ComposeGQUICVersionNegotiation(0x1337, protocol.SupportedVersions))
+				versions := []protocol.VersionNumber{0x13, 0x37}
+				b := bytes.NewReader(ComposeGQUICVersionNegotiation(0x1337, versions))
 				hdr, err := parsePublicHeader(b, protocol.PerspectiveServer)
 				Expect(err).ToNot(HaveOccurred())
 				Expect(hdr.VersionFlag).To(BeTrue())
 				Expect(hdr.Version).To(BeZero()) // unitialized
 				Expect(hdr.IsVersionNegotiation).To(BeTrue())
-				Expect(hdr.SupportedVersions).To(Equal(protocol.SupportedVersions))
+				// in addition to the versions, the supported versions might contain a reserved version number
+				for _, version := range versions {
+					Expect(hdr.SupportedVersions).To(ContainElement(version))
+				}
 				Expect(b.Len()).To(BeZero())
 			})
 

internal/wire/version_negotiation.go

@@ -21,9 +21,7 @@ func ComposeGQUICVersionNegotiation(connID protocol.ConnectionID, versions []pro
 		utils.Errorf("error composing version negotiation packet: %s", err.Error())
 		return nil
 	}
-	for _, v := range versions {
+	writeVersions(fullReply, versions)
-		utils.BigEndian.WriteUint32(fullReply, uint32(v))
-	}
 	return fullReply.Bytes()
 }
 
@@ -48,8 +46,14 @@ func ComposeVersionNegotiation(
 		utils.Errorf("error composing version negotiation packet: %s", err.Error())
 		return nil
 	}
-	for _, v := range versions {
+	writeVersions(fullReply, versions)
-		utils.BigEndian.WriteUint32(fullReply, uint32(v))
-	}
 	return fullReply.Bytes()
 }
+
+// writeVersions writes the versions for a Version Negotiation Packet.
+// It inserts one reserved version number at a random position.
+func writeVersions(buf *bytes.Buffer, supported []protocol.VersionNumber) {
+	for _, v := range protocol.GetGreasedVersions(supported) {
+		utils.BigEndian.WriteUint32(buf, uint32(v))
+	}
+}

internal/wire/version_negotiation_test.go

@@ -16,7 +16,11 @@ var _ = Describe("Version Negotiation Packets", func() {
 		Expect(err).ToNot(HaveOccurred())
 		Expect(hdr.VersionFlag).To(BeTrue())
 		Expect(hdr.ConnectionID).To(Equal(protocol.ConnectionID(0x1337)))
-		Expect(hdr.SupportedVersions).To(Equal(versions))
+		// the supported versions should include one reserved version number
+		Expect(hdr.SupportedVersions).To(HaveLen(len(versions) + 1))
+		for _, version := range versions {
+			Expect(hdr.SupportedVersions).To(ContainElement(version))
+		}
 	})
 
 	It("writes in IETF draft style", func() {
@@ -27,6 +31,11 @@ var _ = Describe("Version Negotiation Packets", func() {
 		Expect(hdr.IsVersionNegotiation).To(BeTrue())
 		Expect(hdr.ConnectionID).To(Equal(protocol.ConnectionID(0x1337)))
 		Expect(hdr.PacketNumber).To(Equal(protocol.PacketNumber(0x42)))
-		Expect(hdr.SupportedVersions).To(Equal(versions))
+		Expect(hdr.Version).To(BeZero())
+		// the supported versions should include one reserved version number
+		Expect(hdr.SupportedVersions).To(HaveLen(len(versions) + 1))
+		for _, version := range versions {
+			Expect(hdr.SupportedVersions).To(ContainElement(version))
+		}
 	})
 })