Introduce nodeList for quicker lookup based on node ID. It is mirrored from peerList.

This improves the speed of lookup in FindNode if the node is already connected.

Kademlia.go

@@ -181,6 +181,14 @@ func IsNodeContact(nodeID []byte) (node *dht.Node, peer *PeerInfo) {
 
 // FindNode finds a node via the DHT
 func FindNode(nodeID []byte, Timeout time.Duration) (node *dht.Node, peer *PeerInfo, err error) {
+	// first check if in mirrored node list
+	var nodeID2 [protocol.HashSize]byte
+	copy(nodeID2[:], nodeID)
+	if peer, ok := nodeList[nodeID2]; ok {
+		return nil, peer, nil
+	}
+
+	// Search the node via DHT.
 	node, err = nodesDHT.FindNode(nodeID)
 	if node == nil {
 		return nil, nil, err

Peer ID.go

@@ -28,6 +28,7 @@ var nodeID []byte
 
 func initPeerID() {
 	peerList = make(map[[btcec.PubKeyBytesLenCompressed]byte]*PeerInfo)
+	nodeList = make(map[[protocol.HashSize]byte]*PeerInfo)
 
 	// load existing key from config, if available
 	if len(config.PrivateKey) > 0 {
@@ -120,6 +121,9 @@ type peerAddress struct {
 var peerList map[[btcec.PubKeyBytesLenCompressed]byte]*PeerInfo
 var peerlistMutex sync.RWMutex
 
+// nodeList is a mirror of peerList but using the node ID
+var nodeList map[[protocol.HashSize]byte]*PeerInfo
+
 // PeerlistAdd adds a new peer to the peer list. It does not validate the peer info. If the peer is already added, it does nothing. Connections must be live.
 func PeerlistAdd(PublicKey *btcec.PublicKey, connections ...*Connection) (peer *PeerInfo, added bool) {
 	if len(connections) == 0 {
@@ -140,6 +144,11 @@ func PeerlistAdd(PublicKey *btcec.PublicKey, connections ...*Connection) (peer *
 
 	peerList[publicKeyCompressed] = peer
 
+	// also add to mirrored nodeList
+	var nodeID [protocol.HashSize]byte
+	copy(nodeID[:], peer.NodeID)
+	nodeList[nodeID] = peer
+
 	// add to Kademlia
 	nodesDHT.AddNode(&dht.Node{ID: peer.NodeID, Info: peer})
 
@@ -168,6 +177,11 @@ func PeerlistRemove(peer *PeerInfo) {
 	nodesDHT.RemoveNode(peer.NodeID)
 
 	delete(peerList, publicKey2Compressed(peer.PublicKey))
+
+	var nodeID [protocol.HashSize]byte
+	copy(nodeID[:], peer.NodeID)
+
+	delete(nodeList, nodeID)
 }
 
 // PeerlistGet returns the full peer list