implement basic version negotiation

client.go

@@ -16,8 +16,9 @@ import (
 
 // A Client of QUIC
 type Client struct {
-	addr *net.UDPAddr
-	conn *net.UDPConn
+	addr     *net.UDPAddr
+	conn     *net.UDPConn
+	hostname string
 
 	connectionID protocol.ConnectionID
 	version      protocol.VersionNumber
@@ -27,6 +28,11 @@ type Client struct {
 
 var errHostname = errors.New("Invalid hostname")
 
+var (
+	errCloseSessionForNewVersion = errors.New("closing session in order to recreate it with a new version")
+	errInvalidVersionNegotiation = qerr.Error(qerr.InvalidVersionNegotiationPacket, "Server already supports client's version and should have accepted the connection.")
+)
+
 // NewClient makes a new client
 func NewClient(addr string) (*Client, error) {
 	hostname, err := utils.HostnameFromAddr(addr)
@@ -54,18 +60,17 @@ func NewClient(addr string) (*Client, error) {
 	rand.Seed(time.Now().UTC().UnixNano())
 	connectionID := protocol.ConnectionID(rand.Int63())
 
-	utils.Infof("Starting new connection to %s (%s), connectionID %x", host, udpAddr.String(), connectionID)
-
 	client := &Client{
 		addr:         udpAddr,
 		conn:         conn,
-		version:      protocol.Version36,
+		hostname:     hostname,
+		version:      protocol.SupportedVersions[len(protocol.SupportedVersions)-1], // use the highest supported version by default
 		connectionID: connectionID,
 	}
 
-	streamCallback := func(session *Session, stream utils.Stream) {}
+	utils.Infof("Starting new connection to %s (%s), connectionID %x, version %d", host, udpAddr.String(), connectionID, client.version)
 
-	client.session, err = newClientSession(conn, udpAddr, hostname, client.version, client.connectionID, streamCallback, client.closeCallback)
+	err = client.createNewSession()
 	if err != nil {
 		return nil, err
 	}
@@ -75,8 +80,6 @@ func NewClient(addr string) (*Client, error) {
 
 // Listen listens
 func (c *Client) Listen() error {
-	go c.session.run()
-
 	for {
 		data := getPacketBuffer()
 		data = data[:protocol.MaxPacketSize]
@@ -120,6 +123,32 @@ func (c *Client) handlePacket(packet []byte) error {
 	}
 	hdr.Raw = packet[:len(packet)-r.Len()]
 
+	// TODO: ignore delayed / duplicated version negotiation packets
+
+	if hdr.VersionFlag {
+		// check if the server sent the offered version in supported versions
+		for _, v := range hdr.SupportedVersions {
+			if v == c.version {
+				return errInvalidVersionNegotiation
+			}
+		}
+
+		ok, highestSupportedVersion := protocol.HighestSupportedVersion(hdr.SupportedVersions)
+		if !ok {
+			return qerr.VersionNegotiationMismatch
+		}
+
+		utils.Infof("Switching to QUIC version %d", highestSupportedVersion)
+		c.version = highestSupportedVersion
+		c.session.Close(errCloseSessionForNewVersion)
+		err = c.createNewSession()
+		if err != nil {
+			return err
+		}
+
+		return nil // version negotiation packets have no payload
+	}
+
 	c.session.handlePacket(&receivedPacket{
 		remoteAddr:   c.addr,
 		publicHeader: hdr,
@@ -129,6 +158,19 @@ func (c *Client) handlePacket(packet []byte) error {
 	return nil
 }
 
+func (c *Client) createNewSession() error {
+	var err error
+	c.session, err = newClientSession(c.conn, c.addr, c.hostname, c.version, c.connectionID, c.streamCallback, c.closeCallback)
+	if err != nil {
+		return err
+	}
+
+	go c.session.run()
+	return nil
+}
+
+func (c *Client) streamCallback(session *Session, stream utils.Stream) {}
+
 func (c *Client) closeCallback(id protocol.ConnectionID) {
 	utils.Infof("Connection %x closed.", id)
 }

client_test.go

@@ -2,6 +2,7 @@ package quic
 
 import (
 	"bytes"
+	"encoding/binary"
 	"net"
 
 	"github.com/lucas-clemente/quic-go/protocol"
@@ -17,10 +18,20 @@ var _ = Describe("Client", func() {
 
 	BeforeEach(func() {
 		client = &Client{}
-		session = &mockSession{}
+		session = &mockSession{connectionID: 0x1337}
+		client.connectionID = 0x1337
 		client.session = session
+		client.version = protocol.Version36
 	})
 
+	startUDPConn := func() {
+		var err error
+		client.addr, err = net.ResolveUDPAddr("udp", "127.0.0.1:0")
+		Expect(err).ToNot(HaveOccurred())
+		client.conn, err = net.ListenUDP("udp", client.addr)
+		Expect(err).NotTo(HaveOccurred())
+	}
+
 	It("errors on invalid public header", func() {
 		err := client.handlePacket(nil)
 		Expect(err.(*qerr.QuicError).ErrorCode).To(Equal(qerr.InvalidPacketHeader))
@@ -42,6 +53,17 @@ var _ = Describe("Client", func() {
 		Expect(session.closeReason).To(BeNil())
 	})
 
+	It("creates new sessions with the right parameters", func() {
+		startUDPConn()
+		client.session = nil
+		client.hostname = "hostname"
+		err := client.createNewSession()
+		Expect(err).ToNot(HaveOccurred())
+		Expect(client.session).ToNot(BeNil())
+		Expect(client.session.(*Session).connectionID).To(Equal(client.connectionID))
+		Expect(client.session.(*Session).version).To(Equal(client.version))
+	})
+
 	Context("handling packets", func() {
 		It("errors on too large packets", func() {
 			err := client.handlePacket(bytes.Repeat([]byte{'f'}, int(protocol.MaxPacketSize+1)))
@@ -49,11 +71,7 @@ var _ = Describe("Client", func() {
 		})
 
 		It("handles packets", func(done Done) {
-			var err error
-			client.addr, err = net.ResolveUDPAddr("udp", "127.0.0.1:0")
-			Expect(err).ToNot(HaveOccurred())
-			client.conn, err = net.ListenUDP("udp", client.addr)
-			Expect(err).NotTo(HaveOccurred())
+			startUDPConn()
 			serverConn, err := net.DialUDP("udp", nil, client.conn.LocalAddr().(*net.UDPAddr))
 			Expect(err).NotTo(HaveOccurred())
 
@@ -84,11 +102,7 @@ var _ = Describe("Client", func() {
 		})
 
 		It("closes the session when encountering an error while handling a packet", func(done Done) {
-			var err error
-			client.addr, err = net.ResolveUDPAddr("udp", "127.0.0.1:0")
-			Expect(err).ToNot(HaveOccurred())
-			client.conn, err = net.ListenUDP("udp", client.addr)
-			Expect(err).NotTo(HaveOccurred())
+			startUDPConn()
 			serverConn, err := net.DialUDP("udp", nil, client.conn.LocalAddr().(*net.UDPAddr))
 			Expect(err).NotTo(HaveOccurred())
 
@@ -111,4 +125,49 @@ var _ = Describe("Client", func() {
 			Expect(err).ToNot(HaveOccurred())
 		})
 	})
+
+	Context("version negotiation", func() {
+		getVersionNegotiation := func(versions []protocol.VersionNumber) []byte {
+			oldVersionNegotiationPacket := composeVersionNegotiation(0x1337)
+			oldSupportVersionTags := protocol.SupportedVersionsAsTags
+			var b bytes.Buffer
+			for _, v := range versions {
+				s := make([]byte, 4)
+				binary.LittleEndian.PutUint32(s, protocol.VersionNumberToTag(v))
+				b.Write(s)
+			}
+			protocol.SupportedVersionsAsTags = b.Bytes()
+			packet := composeVersionNegotiation(client.connectionID)
+			protocol.SupportedVersionsAsTags = oldSupportVersionTags
+			Expect(composeVersionNegotiation(0x1337)).To(Equal(oldVersionNegotiationPacket))
+			return packet
+		}
+
+		It("changes the version after receiving a version negotiation packet", func() {
+			startUDPConn()
+			newVersion := protocol.Version35
+			Expect(newVersion).ToNot(Equal(client.version))
+			Expect(session.packetCount).To(BeZero())
+			err := client.handlePacket(getVersionNegotiation([]protocol.VersionNumber{newVersion}))
+			Expect(client.version).To(Equal(newVersion))
+			// it swapped the sessions
+			Expect(client.session).ToNot(Equal(session))
+			Expect(err).ToNot(HaveOccurred())
+			// it didn't pass the version negoation packet to the session (since it has no payload)
+			Expect(session.packetCount).To(BeZero())
+
+			err = client.Close()
+			Expect(err).ToNot(HaveOccurred())
+		})
+
+		It("errors if no matching version is found", func() {
+			err := client.handlePacket(getVersionNegotiation([]protocol.VersionNumber{1}))
+			Expect(err).To(MatchError(qerr.VersionNegotiationMismatch))
+		})
+
+		It("errors if the server should have accepted the offered version", func() {
+			err := client.handlePacket(getVersionNegotiation([]protocol.VersionNumber{client.version}))
+			Expect(err).To(MatchError(errInvalidVersionNegotiation))
+		})
+	})
 })

session.go

@@ -480,6 +480,15 @@ func (s *Session) closeImpl(e error, remoteClose bool) error {
 		return errSessionAlreadyClosed
 	}
 
+	if e == errCloseSessionForNewVersion {
+		s.closeStreamsWithError(e)
+		// when the run loop exits, it will call the closeCallback
+		// replace it with an noop function to make sure this doesn't have any effect
+		s.closeCallback = func(protocol.ConnectionID) {}
+		s.closeChan <- nil
+		return nil
+	}
+
 	if e == nil {
 		e = qerr.PeerGoingAway
 	}

session_test.go

@@ -590,6 +590,14 @@ var _ = Describe("Session", func() {
 			Expect(err.Error()).To(ContainSubstring(testErr.Error()))
 			Expect(session.runClosed).ToNot(Receive()) // channel should be drained by Close()
 		})
+
+		It("closes the session in order to replace it with another QUIC version", func() {
+			session.Close(errCloseSessionForNewVersion)
+			Expect(closeCallbackCalled).To(BeFalse())
+			Eventually(func() int { return runtime.NumGoroutine() }).Should(Equal(nGoRoutinesBefore))
+			Expect(atomic.LoadUint32(&session.closed) != 0).To(BeTrue())
+			Expect(conn.written).To(BeEmpty()) // no CONNECTION_CLOSE or PUBLIC_RESET sent
+		})
 	})
 
 	Context("receiving packets", func() {