eth, les: defer starting LES service until ETH initial sync is finished

les/server.go

@@ -42,6 +42,9 @@ type LesServer struct {
 	fcManager       *flowcontrol.ClientManager // nil if our node is client only
 	fcCostStats     *requestCostStats
 	defParams       *flowcontrol.ServerParams
+	srvr            *p2p.Server
+	synced, stopped bool
+	lock            sync.Mutex
 }
 
 func NewLesServer(eth *eth.Ethereum, config *eth.Config) (*LesServer, error) {
@@ -67,12 +70,35 @@ func (s *LesServer) Protocols() []p2p.Protocol {
 	return s.protocolManager.SubProtocols
 }
 
+// Start only starts the actual service if the ETH protocol has already been synced,
+// otherwise it will be started by Synced()
 func (s *LesServer) Start(srvr *p2p.Server) {
-	s.protocolManager.Start(srvr)
+	s.lock.Lock()
+	defer s.lock.Unlock()
 
+	s.srvr = srvr
+	if s.synced {
+		s.protocolManager.Start(s.srvr)
+	}
 }
 
+// Synced notifies the server that the ETH protocol has been synced and LES service can be started
+func (s *LesServer) Synced() {
+	s.lock.Lock()
+	defer s.lock.Unlock()
+
+	s.synced = true
+	if s.srvr != nil && !s.stopped {
+		s.protocolManager.Start(s.srvr)
+	}
+}
+
+// Stop stops the LES service
 func (s *LesServer) Stop() {
+	s.lock.Lock()
+	defer s.lock.Unlock()
+
+	s.stopped = true
 	s.fcCostStats.store()
 	s.fcManager.Stop()
 	go func() {