accept multiple Retries

client.go

@@ -29,8 +29,7 @@ type client struct {
 
 	packetHandlers packetHandlerManager
 
-	token         []byte
-	receivedRetry bool
+	token []byte
 
 	versionNegotiated                bool // has the server accepted our version
 	receivedVersionNegotiationPacket bool
@@ -486,15 +485,16 @@ func (c *client) handleVersionNegotiationPacket(hdr *wire.Header) error {
 func (c *client) handleRetryPacket(hdr *wire.Header) {
 	c.logger.Debugf("<- Received Retry")
 	hdr.Log(c.logger)
-	if c.receivedRetry { // only accept a single Retry
-		c.logger.Debugf("Received more than one Retry. Ignoring.")
+	// A server that performs multiple retries must use a source connection ID of at least 8 bytes.
+	// Only a server that won't send additional Retries can use shorter connection IDs.
+	if hdr.OrigDestConnectionID.Len() < protocol.MinConnectionIDLenInitial {
+		c.logger.Debugf("Received a Retry with a too short Original Destination Connection ID: %d bytes, must have at least %d bytes.", hdr.OrigDestConnectionID.Len(), protocol.MinConnectionIDLenInitial)
 		return
 	}
 	if !hdr.OrigDestConnectionID.Equal(c.destConnID) {
 		c.logger.Debugf("Received spoofed Retry. Original Destination Connection ID: %s, expected: %s", hdr.OrigDestConnectionID, c.destConnID)
 		return
 	}
-	c.receivedRetry = true
 	c.destConnID = hdr.SrcConnectionID
 	c.token = hdr.Token
 	c.session.destroy(errCloseSessionForRetry)