Enforce ClusterConfiguration at start, then no ordering

protocol.go

@@ -31,8 +31,7 @@ const (
 
 const (
 	stateInitial = iota
-	stateCCRcvd
-	stateIdxRcvd
+	stateReady
 )
 
 // FileInfo flags
@@ -103,7 +102,6 @@ type rawConnection struct {
 	id       DeviceID
 	name     string
 	receiver Model
-	state    int
 
 	cr *countingReader
 	cw *countingWriter
@@ -155,7 +153,6 @@ func NewConnection(deviceID DeviceID, reader io.Reader, writer io.Writer, receiv
 		id:          deviceID,
 		name:        name,
 		receiver:    nativeModel{receiver},
-		state:       stateInitial,
 		cr:          cr,
 		cw:          cw,
 		outbox:      make(chan hdrMsg),
@@ -285,6 +282,7 @@ func (c *rawConnection) readerLoop() (err error) {
 		c.close(err)
 	}()
 
+	state := stateInitial
 	for {
 		select {
 		case <-c.closed:
@@ -298,47 +296,54 @@ func (c *rawConnection) readerLoop() (err error) {
 		}
 
 		switch msg := msg.(type) {
+		case ClusterConfigMessage:
+			if state != stateInitial {
+				return fmt.Errorf("protocol error: cluster config message in state %d", state)
+			}
+			go c.receiver.ClusterConfig(c.id, msg)
+			state = stateReady
+
 		case IndexMessage:
 			switch hdr.msgType {
 			case messageTypeIndex:
-				if c.state < stateCCRcvd {
-					return fmt.Errorf("protocol error: index message in state %d", c.state)
+				if state != stateReady {
+					return fmt.Errorf("protocol error: index message in state %d", state)
 				}
 				c.handleIndex(msg)
-				c.state = stateIdxRcvd
+				state = stateReady
 
 			case messageTypeIndexUpdate:
-				if c.state < stateIdxRcvd {
-					return fmt.Errorf("protocol error: index update message in state %d", c.state)
+				if state != stateReady {
+					return fmt.Errorf("protocol error: index update message in state %d", state)
 				}
 				c.handleIndexUpdate(msg)
+				state = stateReady
 			}
 
 		case RequestMessage:
-			if c.state < stateIdxRcvd {
-				return fmt.Errorf("protocol error: request message in state %d", c.state)
+			if state != stateReady {
+				return fmt.Errorf("protocol error: request message in state %d", state)
 			}
 			// Requests are handled asynchronously
 			go c.handleRequest(hdr.msgID, msg)
 
 		case ResponseMessage:
-			if c.state < stateIdxRcvd {
-				return fmt.Errorf("protocol error: response message in state %d", c.state)
+			if state != stateReady {
+				return fmt.Errorf("protocol error: response message in state %d", state)
 			}
 			c.handleResponse(hdr.msgID, msg)
 
 		case pingMessage:
+			if state != stateReady {
+				return fmt.Errorf("protocol error: ping message in state %d", state)
+			}
 			c.send(hdr.msgID, messageTypePong, pongMessage{})
 
 		case pongMessage:
-			c.handlePong(hdr.msgID)
-
-		case ClusterConfigMessage:
-			if c.state != stateInitial {
-				return fmt.Errorf("protocol error: cluster config message in state %d", c.state)
+			if state != stateReady {
+				return fmt.Errorf("protocol error: pong message in state %d", state)
 			}
-			go c.receiver.ClusterConfig(c.id, msg)
-			c.state = stateCCRcvd
+			c.handlePong(hdr.msgID)
 
 		case CloseMessage:
 			return errors.New(msg.Reason)