make it possible to configure the QUIC versions for the client

client.go

@@ -47,12 +47,13 @@ func Dial(pconn net.PacketConn, remoteAddr net.Addr, host string, config *Config
 		return nil, err
 	}
 
+	clientConfig := populateClientConfig(config)
 	c := &client{
 		conn:         &conn{pconn: pconn, currentAddr: remoteAddr},
 		connectionID: connID,
 		hostname:     hostname,
-		config:       config,
-		version:      protocol.SupportedVersions[len(protocol.SupportedVersions)-1], // use the highest supported version by default
+		config:       clientConfig,
+		version:      clientConfig.Versions[0],
 	}
 
 	c.connStateChangeOrErrCond.L = &c.mutex
@@ -67,6 +68,19 @@ func Dial(pconn net.PacketConn, remoteAddr net.Addr, host string, config *Config
 	return c.establishConnection()
 }
 
+func populateClientConfig(config *Config) *Config {
+	versions := config.Versions
+	if len(versions) == 0 {
+		versions = protocol.SupportedVersions
+	}
+
+	return &Config{
+		TLSConfig: config.TLSConfig,
+		ConnState: config.ConnState,
+		Versions:  versions,
+	}
+}
+
 // DialAddr establishes a new QUIC connection to a server.
 // The hostname for SNI is taken from the given address.
 func DialAddr(addr string, config *Config) (Session, error) {
@@ -191,7 +205,7 @@ func (c *client) handlePacketWithVersionFlag(hdr *PublicHeader) error {
 		}
 	}
 
-	ok, highestSupportedVersion := protocol.HighestSupportedVersion(hdr.SupportedVersions)
+	ok, highestSupportedVersion := protocol.HighestSupportedVersion(c.config.Versions, hdr.SupportedVersions)
 	if !ok {
 		return qerr.InvalidVersion
 	}

client_test.go

@@ -34,6 +34,7 @@ var _ = Describe("Client", func() {
 					versionNegotiateConnStateCalled = true
 				}
 			},
+			Versions: []protocol.VersionNumber{protocol.SupportedVersions[0], 77, 78},
 		}
 		addr = &net.UDPAddr{IP: net.IPv4(192, 168, 100, 200), Port: 1337}
 		sess = &mockSession{connectionID: 0x1337}
@@ -41,7 +42,7 @@ var _ = Describe("Client", func() {
 			config:       config,
 			connectionID: 0x1337,
 			session:      sess,
-			version:      protocol.Version36,
+			version:      protocol.SupportedVersions[0],
 			conn:         &conn{pconn: packetConn, currentAddr: addr},
 		}
 	})
@@ -56,7 +57,6 @@ var _ = Describe("Client", func() {
 	Context("Dialing", func() {
 		It("creates a new client", func() {
 			packetConn.dataToRead = []byte{0x0, 0x1, 0x0}
-			var err error
 			sess, err := Dial(packetConn, addr, "quic.clemente.io:1337", config)
 			Expect(err).ToNot(HaveOccurred())
 			Expect(*(*[]protocol.VersionNumber)(unsafe.Pointer(reflect.ValueOf(sess.(*session).cryptoSetup).Elem().FieldByName("negotiatedVersions").UnsafeAddr()))).To(BeNil())
@@ -64,6 +64,11 @@ var _ = Describe("Client", func() {
 			sess.Close(nil)
 		})
 
+		It("uses all supported versions, if none are specified in the quic.Config", func() {
+			c := populateClientConfig(&Config{})
+			Expect(c.Versions).To(Equal(protocol.SupportedVersions))
+		})
+
 		It("errors when receiving an invalid first packet from the server", func() {
 			packetConn.dataToRead = []byte{0xff}
 			sess, err := Dial(packetConn, addr, "quic.clemente.io:1337", config)
@@ -213,11 +218,13 @@ var _ = Describe("Client", func() {
 		})
 
 		It("changes the version after receiving a version negotiation packet", func() {
-			newVersion := protocol.Version35
+			newVersion := protocol.VersionNumber(77)
+			Expect(config.Versions).To(ContainElement(newVersion))
 			Expect(newVersion).ToNot(Equal(cl.version))
 			Expect(sess.packetCount).To(BeZero())
 			cl.connectionID = 0x1337
 			err := cl.handlePacket(nil, composeVersionNegotiation(0x1337, []protocol.VersionNumber{newVersion}))
+			Expect(err).ToNot(HaveOccurred())
 			Expect(cl.version).To(Equal(newVersion))
 			Expect(cl.connState).To(Equal(ConnStateVersionNegotiated))
 			Eventually(func() bool { return versionNegotiateConnStateCalled }).Should(BeTrue())
@@ -229,7 +236,7 @@ var _ = Describe("Client", func() {
 			Expect(sess.packetCount).To(BeZero())
 			// if the version negotiation packet was passed to the new session, it would end up as an undecryptable packet there
 			Expect(cl.session.(*session).undecryptablePackets).To(BeEmpty())
-			Expect(*(*[]protocol.VersionNumber)(unsafe.Pointer(reflect.ValueOf(cl.session.(*session).cryptoSetup).Elem().FieldByName("negotiatedVersions").UnsafeAddr()))).To(Equal([]protocol.VersionNumber{35}))
+			Expect(*(*[]protocol.VersionNumber)(unsafe.Pointer(reflect.ValueOf(cl.session.(*session).cryptoSetup).Elem().FieldByName("negotiatedVersions").UnsafeAddr()))).To(Equal([]protocol.VersionNumber{newVersion}))
 		})
 
 		It("errors if no matching version is found", func() {
@@ -237,6 +244,20 @@ var _ = Describe("Client", func() {
 			Expect(err).To(MatchError(qerr.InvalidVersion))
 		})
 
+		It("errors if the version is supported by quic-go, but disabled by the quic.Config", func() {
+			v := protocol.SupportedVersions[1]
+			Expect(v).ToNot(Equal(cl.version))
+			Expect(config.Versions).ToNot(ContainElement(v))
+			err := cl.handlePacket(nil, composeVersionNegotiation(0x1337, []protocol.VersionNumber{v}))
+			Expect(err).To(MatchError(qerr.InvalidVersion))
+		})
+
+		It("changes to the version preferred by the quic.Config", func() {
+			err := cl.handlePacket(nil, composeVersionNegotiation(0x1337, []protocol.VersionNumber{config.Versions[2], config.Versions[1]}))
+			Expect(err).ToNot(HaveOccurred())
+			Expect(cl.version).To(Equal(config.Versions[1]))
+		})
+
 		It("ignores delayed version negotiation packets", func() {
 			// if the version was not yet negotiated, handlePacket would return a VersionNegotiationMismatch error, see above test
 			cl.connState = ConnStateVersionNegotiated

protocol/version.go

@@ -8,8 +8,8 @@ const (
 	Version35 VersionNumber = 35 + iota
 	Version36
 	Version37
-	VersionWhatever    = 0 // for when the version doesn't matter
-	VersionUnsupported = -1
+	VersionWhatever    VersionNumber = 0 // for when the version doesn't matter
+	VersionUnsupported VersionNumber = -1
 )
 
 // SupportedVersions lists the versions that the server supports
@@ -40,16 +40,14 @@ func IsSupportedVersion(supported []VersionNumber, v VersionNumber) bool {
 }
 
 // HighestSupportedVersion finds the highest version number that is both present in other and in SupportedVersions
-// the versions in other do not need to be ordered
 // it returns true and the version number, if there is one, otherwise false
-func HighestSupportedVersion(other []VersionNumber) (bool, VersionNumber) {
-	for _, v := range SupportedVersions {
-		for _, ver := range other {
-			if ver == v {
-				return true, ver
+func HighestSupportedVersion(ours, theirs []VersionNumber) (bool, VersionNumber) {
+	for _, ourVer := range ours {
+		for _, theirVer := range theirs {
+			if ourVer == theirVer {
+				return true, ourVer
 			}
 		}
 	}
-
-	return false, 0
+	return false, VersionUnsupported
 }

protocol/version_test.go

@@ -27,39 +27,33 @@ var _ = Describe("Version", func() {
 	})
 
 	Context("highest supported version", func() {
-		var initialSupportedVersions []VersionNumber
-
-		BeforeEach(func() {
-			initialSupportedVersions = make([]VersionNumber, len(SupportedVersions))
-			copy(initialSupportedVersions, SupportedVersions)
-		})
-
-		AfterEach(func() {
-			SupportedVersions = initialSupportedVersions
-		})
-
 		It("finds the supported version", func() {
-			SupportedVersions = []VersionNumber{3, 2, 1}
-			other := []VersionNumber{3, 4, 5, 6}
-			found, ver := HighestSupportedVersion(other)
+			supportedVersions := []VersionNumber{1, 2, 3}
+			other := []VersionNumber{6, 5, 4, 3}
+			found, ver := HighestSupportedVersion(supportedVersions, other)
 			Expect(found).To(BeTrue())
 			Expect(ver).To(Equal(VersionNumber(3)))
 		})
 
-		It("picks the highest supported version", func() {
-			SupportedVersions = []VersionNumber{7, 6, 3, 2, 1}
+		It("picks the preferred version", func() {
+			supportedVersions := []VersionNumber{2, 1, 3}
 			other := []VersionNumber{3, 6, 1, 8, 2, 10}
-			found, ver := HighestSupportedVersion(other)
+			found, ver := HighestSupportedVersion(supportedVersions, other)
 			Expect(found).To(BeTrue())
-			Expect(ver).To(Equal(VersionNumber(6)))
+			Expect(ver).To(Equal(VersionNumber(2)))
 		})
 
 		It("handles empty inputs", func() {
-			SupportedVersions = []VersionNumber{102, 101}
-			Expect(HighestSupportedVersion([]VersionNumber{})).To(BeFalse())
-			SupportedVersions = []VersionNumber{}
-			Expect(HighestSupportedVersion([]VersionNumber{1, 2})).To(BeFalse())
-			Expect(HighestSupportedVersion([]VersionNumber{})).To(BeFalse())
+			supportedVersions := []VersionNumber{102, 101}
+			found, _ := HighestSupportedVersion(supportedVersions, nil)
+			Expect(found).To(BeFalse())
+			found, _ = HighestSupportedVersion(supportedVersions, []VersionNumber{})
+			Expect(found).To(BeFalse())
+			supportedVersions = []VersionNumber{}
+			found, _ = HighestSupportedVersion(supportedVersions, []VersionNumber{1, 2})
+			Expect(found).To(BeFalse())
+			found, _ = HighestSupportedVersion(supportedVersions, []VersionNumber{})
+			Expect(found).To(BeFalse())
 		})
 	})
 })

server.go

@@ -68,7 +68,7 @@ func Listen(conn net.PacketConn, config *Config) (Listener, error) {
 
 	return &server{
 		conn:                      conn,
-		config:                    populateConfig(config),
+		config:                    populateServerConfig(config),
 		certChain:                 certChain,
 		scfg:                      scfg,
 		sessions:                  map[protocol.ConnectionID]packetHandler{},
@@ -77,7 +77,7 @@ func Listen(conn net.PacketConn, config *Config) (Listener, error) {
 	}, nil
 }
 
-func populateConfig(config *Config) *Config {
+func populateServerConfig(config *Config) *Config {
 	versions := config.Versions
 	if len(versions) == 0 {
 		versions = protocol.SupportedVersions