peer: add an idle timer to the readHandler

In this commit, we add an idle timer to the readHandler itself. This
will serve to slowly prune away inactive TCP connections as a result of
remote peer being blocked either upon reading or writing to the socket.
Our ping timer interval is 1 minute, so an idle timer interval of 5
minutes seem reasonable.

peer.go

@@ -37,6 +37,9 @@ const (
 	// pingInterval is the interval at which ping messages are sent.
 	pingInterval = 1 * time.Minute
 
+	// idleTimeout is the duration of inactivity before we time out a peer.
+	idleTimeout = 5 * time.Minute
+
 	// outgoingQueueLen is the buffer size of the channel which houses
 	// messages to be sent across the wire, requested by objects outside
 	// this struct.
@@ -597,10 +600,19 @@ func (c *chanMsgStream) AddMsg(msg lnwire.Message) {
 // NOTE: This method MUST be run as a goroutine.
 func (p *peer) readHandler() {
 
+	// We'll stop the timer after a new messages is received, and also
+	// reset it after we process the next message.
+	idleTimer := time.AfterFunc(idleTimeout, func() {
+		err := fmt.Errorf("Peer %s no answer for %s -- disconnecting",
+			p, idleTimeout)
+		p.Disconnect(err)
+	})
+
 	chanMsgStreams := make(map[lnwire.ChannelID]*chanMsgStream)
 out:
 	for atomic.LoadInt32(&p.disconnect) == 0 {
 		nextMsg, err := p.readNextMessage()
+		idleTimer.Stop()
 		if err != nil {
 			peerLog.Infof("unable to read message from %v: %v",
 				p, err)
@@ -611,6 +623,7 @@ out:
 			// us to introduce new messages in a forwards
 			// compatible manner.
 			case *lnwire.UnknownMessage:
+				idleTimer.Reset(idleTimeout)
 				continue
 
 			// If the error we encountered wasn't just a message we
@@ -717,6 +730,8 @@ out:
 			// stream so we can continue processing message.
 			chanStream.AddMsg(nextMsg)
 		}
+
+		idleTimer.Reset(idleTimeout)
 	}
 
 	p.wg.Done()