network: move peer filtering to getPeers()

It doesn't change much, we can't magically get more valid peers and if some
die while we're iterating we'd detect that by an error returned from send().

pkg/network/server.go

@@ -288,7 +288,7 @@ func (s *Server) Shutdown() {
 	s.transport.Close()
 	s.discovery.Close()
 	s.consensus.Shutdown()
-	for _, p := range s.getPeers() {
+	for _, p := range s.getPeers(nil) {
 		p.Disconnect(errServerShutdown)
 	}
 	s.bQueue.discard()
@@ -431,7 +431,7 @@ func (s *Server) runProto() {
 		case <-pingTimer.C:
 			if s.chain.BlockHeight() == prevHeight {
 				// Get a copy of s.peers to avoid holding a lock while sending.
-				for _, peer := range s.getPeers() {
+				for _, peer := range s.getPeers(nil) {
 					_ = peer.SendPing(NewMessage(CMDPing, payload.NewPing(s.chain.BlockHeight(), s.id)))
 				}
 			}
@@ -489,14 +489,17 @@ func (s *Server) UnsubscribeFromNotaryRequests(ch chan<- mempoolevent.Event) {
 	s.notaryRequestPool.UnsubscribeFromTransactions(ch)
 }
 
-// getPeers returns current list of peers connected to
+// getPeers returns current list of peers connected to the server filtered by
-// the server.
+// isOK function if it's given.
-func (s *Server) getPeers() []Peer {
+func (s *Server) getPeers(isOK func(Peer) bool) []Peer {
 	s.lock.RLock()
 	defer s.lock.RUnlock()
 
 	peers := make([]Peer, 0, len(s.peers))
 	for k := range s.peers {
+		if isOK != nil && !isOK(k) {
+			continue
+		}
 		peers = append(peers, k)
 	}
 
@@ -1142,7 +1145,7 @@ func (s *Server) requestTx(hashes ...util.Uint256) {
 // peer is considered invalid if it returns false).
 func (s *Server) iteratePeersWithSendMsg(msg *Message, send func(Peer, bool, []byte) error, peerOK func(Peer) bool) {
 	// Get a copy of s.peers to avoid holding a lock while sending.
-	peers := s.getPeers()
+	peers := s.getPeers(peerOK)
 	if len(peers) == 0 {
 		return
 	}
@@ -1158,9 +1161,6 @@ func (s *Server) iteratePeersWithSendMsg(msg *Message, send func(Peer, bool, []b
 	okCount := 0
 	sentCount := 0
 	for i, peer := range peers {
-		if peerOK != nil && !peerOK(peer) {
-			continue
-		}
 		okCount++
 		if err := send(peer, false, pkt); err != nil {
 			continue
@@ -1179,7 +1179,7 @@ func (s *Server) iteratePeersWithSendMsg(msg *Message, send func(Peer, bool, []b
 
 	// Perform blocking send now.
 	for i, peer := range peers {
-		if success[i] || (peerOK != nil && !peerOK(peer)) {
+		if success[i] {
 			continue
 		}
 		if err := send(peer, true, pkt); err != nil {