peer: enforce strict timeout on opening handshake

This commit modifies the logic around the opening p2p handshake to
enforce a strict timeout around the receipt of the responding init
message. Before this commit, it was possible for the daemon and certain
RPC calls to deadlock as if a peer connected, but didn’t respond with
an init msg, then we’d be sitting there waiting for them to respond.
With this commit, we’ll now time out, kill the connection and then
possible attempt to re-connect if the connection was persistent.

peer.go

@@ -296,11 +296,31 @@ func (p *peer) Start() error {
 	// Before we launch any of the helper goroutines off the peer struct,
 	// we'll first ensure proper adherance to the p2p protocl. The init
 	// message MUST be sent before any other message.
-	msg, _, err := p.readNextMessage()
+	readErr := make(chan error, 1)
-	if err != nil {
+	msgChan := make(chan lnwire.Message, 1)
-		return err
+	go func() {
+		msg, _, err := p.readNextMessage()
+		if err != nil {
+			readErr <- err
+			msgChan <- nil
+		}
+		readErr <- nil
+		msgChan <- msg
+	}()
+
+	select {
+	// In order to avoid blocking indefinately, we'll give the other peer
+	// an upper timeout of 5 seconds to respond before we bail out early.
+	case <-time.After(time.Second * 5):
+		return fmt.Errorf("peer did not complete handshake within 5 " +
+			"seconds")
+	case err := <-readErr:
+		if err != nil {
+			return err
+		}
 	}
 
+	msg := <-msgChan
 	if msg, ok := msg.(*lnwire.Init); ok {
 		if err := p.handleInitMsg(msg); err != nil {
 			return err

server.go

@@ -550,9 +550,6 @@ func (s *server) peerConnected(conn net.Conn, connReq *connmgr.ConnReq, inbound
 
 	if err := p.Start(); err != nil {
 		srvrLog.Errorf("unable to start peer: %v", err)
-		if p.connReq != nil {
-			s.connMgr.Remove(p.connReq.ID())
-		}
 		p.Disconnect()
 		return
 	}