p2p: limit ping requests from a single peer (#8113)

see:
ethereum/go-ethereum#27887

p2p/peer.go

@@ -114,6 +114,7 @@ type Peer struct {
 	wg       sync.WaitGroup
 	protoErr chan *PeerError
 	closed   chan struct{}
+	pingRecv chan struct{}
 	disc     chan *PeerError
 
 	// events receives message send / receive events if set
@@ -219,6 +220,7 @@ func newPeer(logger log.Logger, conn *conn, protocols []Protocol, pubkey [64]byt
 		disc:           make(chan *PeerError),
 		protoErr:       make(chan *PeerError, len(protomap)+1), // protocols + pingLoop
 		closed:         make(chan struct{}),
+		pingRecv:       make(chan struct{}, 16),
 		log:            logger.New("id", conn.node.ID(), "conn", conn.flags),
 		pubkey:         pubkey,
 		metricsEnabled: metricsEnabled,
@@ -287,6 +289,11 @@ func (p *Peer) pingLoop() {
 				return
 			}
 			ping.Reset(pingInterval)
+		case <-p.pingRecv:
+			if err := SendItems(p.rw, pongMsg); err != nil {
+				p.protoErr <- NewPeerError(PeerErrorPongFailure, DiscNetworkError, err, "Failed to send pongMsg")
+				return
+			}
 		case <-p.closed:
 			return
 		}
@@ -314,7 +321,10 @@ func (p *Peer) handle(msg Msg) error {
 	switch {
 	case msg.Code == pingMsg:
 		msg.Discard()
-		go SendItems(p.rw, pongMsg)
+		select {
+		case p.pingRecv <- struct{}{}:
+		case <-p.closed:
+		}
 	case msg.Code == discMsg:
 		// This is the last message.
 		// We don't need to discard because the connection will be closed after it.

p2p/peer_error.go

@@ -26,6 +26,7 @@ const (
 	PeerErrorInvalidMessageCode PeerErrorCode = iota
 	PeerErrorInvalidMessage
 	PeerErrorPingFailure
+	PeerErrorPongFailure
 	PeerErrorDiscReason
 	PeerErrorDiscReasonRemote
 	PeerErrorMessageReceive
@@ -47,6 +48,7 @@ var peerErrorCodeToString = map[PeerErrorCode]string{
 	PeerErrorInvalidMessageCode:     "invalid message code",
 	PeerErrorInvalidMessage:         "invalid message",
 	PeerErrorPingFailure:            "ping failure",
+	PeerErrorPongFailure:            "pong failure",
 	PeerErrorDiscReason:             "disconnect reason",
 	PeerErrorDiscReasonRemote:       "remote disconnect reason",
 	PeerErrorMessageReceive:         "failed to receive a message",