don't lock the client mutex when handling regular packets

client.go

@@ -27,7 +27,7 @@ type client struct {
 
 	token []byte
 
-	versionNegotiated                bool // has the server accepted our version
+	versionNegotiated                utils.AtomicBool // has the server accepted our version
 	receivedVersionNegotiationPacket bool
 	negotiatedVersions               []protocol.VersionNumber // the list of versions from the version negotiation packet
 
@@ -295,28 +295,29 @@ func (c *client) handlePacket(p *receivedPacket) {
 }
 
 func (c *client) handlePacketImpl(p *receivedPacket) error {
-	c.mutex.Lock()
-	defer c.mutex.Unlock()
-
 	// handle Version Negotiation Packets
 	if p.hdr.IsVersionNegotiation() {
+		c.mutex.Lock()
 		err := c.handleVersionNegotiationPacket(p.hdr)
 		if err != nil {
 			c.session.destroy(err)
 		}
+		c.mutex.Unlock()
 		// version negotiation packets have no payload
 		return err
 	}
 
 	if p.hdr.Type == protocol.PacketTypeRetry {
+		c.mutex.Lock()
 		c.handleRetryPacket(p.hdr)
+		c.mutex.Unlock()
 		return nil
 	}
 
 	// this is the first packet we are receiving
 	// since it is not a Version Negotiation Packet, this means the server supports the suggested version
-	if !c.versionNegotiated {
+	if !c.versionNegotiated.Get() {
-		c.versionNegotiated = true
+		c.versionNegotiated.Set(true)
 	}
 
 	c.session.handlePacket(p)
@@ -325,7 +326,7 @@ func (c *client) handlePacketImpl(p *receivedPacket) error {
 
 func (c *client) handleVersionNegotiationPacket(hdr *wire.Header) error {
 	// ignore delayed / duplicated version negotiation packets
-	if c.receivedVersionNegotiationPacket || c.versionNegotiated {
+	if c.receivedVersionNegotiationPacket || c.versionNegotiated.Get() {
 		c.logger.Debugf("Received a delayed Version Negotiation Packet.")
 		return nil
 	}

client_test.go

@@ -687,7 +687,7 @@ var _ = Describe("Client", func() {
 					},
 				})
 				Expect(err).ToNot(HaveOccurred())
-				Expect(cl.versionNegotiated).To(BeTrue())
+				Expect(cl.versionNegotiated.Get()).To(BeTrue())
 			})
 
 			It("errors if no matching version is found", func() {