[FAB-6207] Refactor gossip state demux direct msgs

Previously, while introduced CR for FAB-5084, new channel has been added
into state transfer to reflect replication of the private data across
peers. This commit, commit removes duplicated code by leveraging same
channel and demuxing direct messages based on the type. This also used
to increase testability of the state code.

Change-Id: Iab76d818da592f55bfcdbb83c7f948df66691e7c
Signed-off-by: Artem Barger <bartem@il.ibm.com>

gossip/state/state.go

@@ -136,8 +136,6 @@ type GossipStateProviderImpl struct {
 
 	commChan <-chan proto.ReceivedMessage
 
-	pvtDataChan <-chan proto.ReceivedMessage
-
 	// Queue of payloads which wasn't acquired yet
 	payloads PayloadsBuffer
 
@@ -177,13 +175,13 @@ func NewGossipStateProvider(chainID string, services *ServicesMediator, ledger l
 	remoteStateMsgFilter := func(message interface{}) bool {
 		receivedMsg := message.(proto.ReceivedMessage)
 		msg := receivedMsg.GetGossipMessage()
-		if !msg.IsRemoteStateMessage() {
+		if !(msg.IsRemoteStateMessage() || msg.GetPrivateData() != nil) {
 			return false
 		}
 		connInfo := receivedMsg.GetConnectionInfo()
 		authErr := services.VerifyByChannel(msg.Channel, connInfo.Identity, connInfo.Auth.Signature, connInfo.Auth.SignedData)
 		if authErr != nil {
-			logger.Warning("Got unauthorized nodeMetastate transfer request from", string(connInfo.Identity))
+			logger.Warning("Got unauthorized request from", string(connInfo.Identity))
 			return false
 		}
 		return true
@@ -192,23 +190,6 @@ func NewGossipStateProvider(chainID string, services *ServicesMediator, ledger l
 	// Filter message which are only relevant for nodeMetastate transfer
 	_, commChan := services.Accept(remoteStateMsgFilter, true)
 
-	// Filter private data messages
-	_, pvtDataChan := services.Accept(func(message interface{}) bool {
-		receivedMsg := message.(proto.ReceivedMessage)
-		msg := receivedMsg.GetGossipMessage()
-		if msg.GetPrivateData() == nil {
-			return false
-		}
-		connInfo := receivedMsg.GetConnectionInfo()
-		authErr := services.VerifyByChannel(msg.Channel, connInfo.Identity, connInfo.Auth.Signature, connInfo.Auth.SignedData)
-		if authErr != nil {
-			logger.Warning("Got unauthorized private data message from", string(connInfo.Identity))
-			return false
-		}
-		return true
-
-	}, true)
-
 	height, err := ledger.LedgerHeight()
 	if height == 0 {
 		// Panic here since this is an indication of invalid situation which should not happen in normal
@@ -236,9 +217,6 @@ func NewGossipStateProvider(chainID string, services *ServicesMediator, ledger l
 		// Channel to read direct messages from other peers
 		commChan: commChan,
 
-		// Channel for private data messages
-		pvtDataChan: pvtDataChan,
-
 		// Create a queue for payload received
 		payloads: NewPayloadsBuffer(height),
 
@@ -291,18 +269,28 @@ func (s *GossipStateProviderImpl) listen() {
 			logger.Debug("Received new message via gossip channel")
 			go s.queueNewMessage(msg)
 		case msg := <-s.commChan:
-			logger.Debug("Direct message ", msg)
-			go s.directMessage(msg)
-		case msg := <-s.pvtDataChan:
-			logger.Debug("Private data message ", msg)
-			go s.privateDataMessage(msg)
+			logger.Debug("Dispatching a message", msg)
+			go s.dispatch(msg)
 		case <-s.stopCh:
 			s.stopCh <- struct{}{}
 			logger.Debug("Stop listening for new messages")
 			return
 		}
 	}
 }
+func (s *GossipStateProviderImpl) dispatch(msg proto.ReceivedMessage) {
+	// Check type of the message
+	if msg.GetGossipMessage().IsRemoteStateMessage() {
+		logger.Debug("Handling direct state transfer message")
+		// Got state transfer request response
+		s.directMessage(msg)
+	} else if msg.GetGossipMessage().GetPrivateData() != nil {
+		logger.Debug("Handling private data collection message")
+		// Handling private data replication message
+		s.privateDataMessage(msg)
+	}
+
+}
 func (s *GossipStateProviderImpl) privateDataMessage(msg proto.ReceivedMessage) {
 	if !bytes.Equal(msg.GetGossipMessage().Channel, []byte(s.chainID)) {
 		logger.Warning("Received state transfer request for channel",