Send Announcement instead of ping in case blockchain info was not refreshed within a certain threshold. This helps to keep the global blockchain cache active, with no additional overhead. Close #78

Message Send.go

@@ -26,6 +26,26 @@ func (peer *PeerInfo) pingConnection(connection *Connection) {
 	}
 }
 
+// pingConnectionAnnouncement sends an empty announcement via a particular connection.
+// It has the same effect as ping, but returns the blockchain version and height of the other peer in the Response message, which may be useful for keeping the global blockchain cache up to date.
+func (peer *PeerInfo) pingConnectionAnnouncement(connection *Connection) {
+	_, blockchainHeight, blockchainVersion := UserBlockchain.Header()
+	packets := protocol.EncodeAnnouncement(false, false, nil, nil, nil, FeatureSupport(), blockchainHeight, blockchainVersion, userAgent)
+	if len(packets) != 1 {
+		return
+	}
+
+	raw := &protocol.PacketRaw{Command: protocol.CommandAnnouncement, Payload: packets[0], Sequence: networks.Sequences.NewSequence(peer.PublicKey, &peer.messageSequence, nil).SequenceNumber}
+	Filters.MessageOutAnnouncement(peer.PublicKey, peer, raw, false, nil, nil, nil)
+
+	err := peer.sendConnection(raw, connection)
+	connection.LastPingOut = time.Now()
+
+	if (connection.Status == ConnectionActive || connection.Status == ConnectionRedundant) && IsNetworkErrorFatal(err) {
+		peer.invalidateActiveConnection(connection)
+	}
+}
+
 // Ping sends a ping. This function exists only for debugging purposes, it should not be used normally.
 // This ping is not used for uptime detection and the LastPingOut time in connections is not set.
 func (peer *PeerInfo) Ping() {

Network.go

@@ -180,6 +180,7 @@ func (nets *Networks) packetWorker() {
 				isBlockchainUpdate := peer.BlockchainHeight != announce.BlockchainHeight || peer.BlockchainVersion != announce.BlockchainVersion
 				peer.BlockchainHeight = announce.BlockchainHeight
 				peer.BlockchainVersion = announce.BlockchainVersion
+				peer.blockchainLastRefresh = time.Now()
 
 				Filters.MessageIn(peer, raw, announce)
 
@@ -215,6 +216,7 @@ func (nets *Networks) packetWorker() {
 				isBlockchainUpdate := peer.BlockchainHeight != response.BlockchainHeight || peer.BlockchainVersion != response.BlockchainVersion
 				peer.BlockchainHeight = response.BlockchainHeight
 				peer.BlockchainVersion = response.BlockchainVersion
+				peer.blockchainLastRefresh = time.Now()
 
 				Filters.MessageIn(peer, raw, response)
 
@@ -235,6 +237,7 @@ func (nets *Networks) packetWorker() {
 				isBlockchainUpdate := peer.BlockchainHeight != announce.BlockchainHeight || peer.BlockchainVersion != announce.BlockchainVersion
 				peer.BlockchainHeight = announce.BlockchainHeight
 				peer.BlockchainVersion = announce.BlockchainVersion
+				peer.blockchainLastRefresh = time.Now()
 
 				Filters.MessageIn(peer, raw, announce)
 

Peer ID.go

@@ -13,6 +13,7 @@ import (
 	"net"
 	"os"
 	"sync"
+	"time"
 
 	"github.com/PeernetOfficial/core/btcec"
 	"github.com/PeernetOfficial/core/dht"
@@ -87,21 +88,22 @@ func SelfUserAgent() string {
 
 // PeerInfo stores information about a single remote peer
 type PeerInfo struct {
-	PublicKey          *btcec.PublicKey // Public key
-	NodeID             []byte           // Node ID in Kademlia network = blake3(Public Key).
-	connectionActive   []*Connection    // List of active established connections to the peer.
-	connectionInactive []*Connection    // List of former connections that are no longer valid. They may be removed after a while.
-	connectionLatest   *Connection      // Latest valid connection.
-	sync.RWMutex                        // Mutex for access to list of connections.
-	messageSequence    uint32           // Sequence number. Increased with every message.
-	IsRootPeer         bool             // Whether the peer is a trusted root peer.
-	UserAgent          string           // User Agent reported by remote peer. Empty if no Announcement/Response message was yet received.
-	Features           uint8            // Feature bit array. 0 = IPv4_LISTEN, 1 = IPv6_LISTEN, 1 = FIREWALL
-	isVirtual          bool             // Whether it is a virtual peer for establishing a connection.
-	targetAddresses    []*peerAddress   // Virtual peer: Addresses to send any replies.
-	traversePeer       *PeerInfo        // Virtual peer: Same field as in connection.
-	BlockchainHeight   uint64           // Blockchain height
-	BlockchainVersion  uint64           // Blockchain version
+	PublicKey             *btcec.PublicKey // Public key
+	NodeID                []byte           // Node ID in Kademlia network = blake3(Public Key).
+	connectionActive      []*Connection    // List of active established connections to the peer.
+	connectionInactive    []*Connection    // List of former connections that are no longer valid. They may be removed after a while.
+	connectionLatest      *Connection      // Latest valid connection.
+	sync.RWMutex                           // Mutex for access to list of connections.
+	messageSequence       uint32           // Sequence number. Increased with every message.
+	IsRootPeer            bool             // Whether the peer is a trusted root peer.
+	UserAgent             string           // User Agent reported by remote peer. Empty if no Announcement/Response message was yet received.
+	Features              uint8            // Feature bit array. 0 = IPv4_LISTEN, 1 = IPv6_LISTEN, 1 = FIREWALL
+	isVirtual             bool             // Whether it is a virtual peer for establishing a connection.
+	targetAddresses       []*peerAddress   // Virtual peer: Addresses to send any replies.
+	traversePeer          *PeerInfo        // Virtual peer: Same field as in connection.
+	BlockchainHeight      uint64           // Blockchain height
+	BlockchainVersion     uint64           // Blockchain version
+	blockchainLastRefresh time.Time        // Last refresh of the blockchain info.
 
 	// statistics
 	StatsPacketSent     uint64 // Count of packets sent

Ping.go

@@ -6,11 +6,17 @@ Author:     Peter Kleissner
 
 package core
 
-import "time"
+import (
+	"time"
+)
 
 // pingTime is the time in seconds to send out ping messages
 const pingTime = 10
 
+// thresholdBlockchainRefresh is the threshold to refresh the blockchain information by sending an Announcement (and expecting the Response message).
+// This helps for keeping the global blockchain cache up to date.
+const thresholdBlockchainRefresh = 60 * time.Second
+
 // connectionInvalidate is the threshold in seconds to invalidate formerly active connections that no longer receive incoming packets.
 const connectionInvalidate = 22
 
@@ -25,6 +31,7 @@ func autoPingAll() {
 		thresholdInvalidate2 := time.Now().Add(-connectionInvalidate * time.Second * 4)
 		thresholdPingOut1 := time.Now().Add(-pingTime * time.Second)
 		thresholdPingOut2 := time.Now().Add(-pingTime * time.Second * 4)
+		thresholdBlockchainRefresh := time.Now().Add(-thresholdBlockchainRefresh)
 
 		for _, peer := range PeerlistGet() {
 			// first handle active connections
@@ -43,7 +50,12 @@ func autoPingAll() {
 				}
 
 				if connection.LastPacketIn.Before(thresholdPing) && connection.LastPingOut.Before(thresholdPing) {
-					peer.pingConnection(connection)
+					if connection.Status == ConnectionActive && peer.blockchainLastRefresh.Before(thresholdBlockchainRefresh) {
+						peer.pingConnectionAnnouncement(connection)
+					} else {
+						// just a regular ping otherwise
+						peer.pingConnection(connection)
+					}
 					continue
 				}
 			}

protocol/Message Encoding Response.go

@@ -110,7 +110,8 @@ func DecodeResponse(msg *MessageRaw) (result *MessageResponse, err error) {
 	read += 6
 
 	if countPeerResponses == 0 && countEmbeddedFiles == 0 && countHashesNotFound == 0 {
-		return nil, errors.New("response: empty")
+		// Empty responses are allowed. They can be useful as quasi-pings to get the latest blockchain info of the peer.
+		return
 	}
 
 	data := msg.Payload[read:]