peer: Implement sendheaders support (BIP0130).

Upstream commit 8a58f8c.

Modified the supported protocol version passed to peer to
wire.BIP0111Version which is the version in Decred just before the new
protocol version for wire.SendHeadersVersion.

peer/peer.go

@@ -28,7 +28,7 @@ import (
 
 const (
 	// MaxProtocolVersion is the max protocol version the peer supports.
-	MaxProtocolVersion = 2
+	MaxProtocolVersion = wire.SendHeadersVersion
 
 	// outputBufferSize is the number of elements the output channels use.
 	outputBufferSize = 5000
@@ -183,6 +183,10 @@ type MessageListeners struct {
 	// OnReject is invoked when a peer receives a reject wire message.
 	OnReject func(p *Peer, msg *wire.MsgReject)
 
+	// OnSendHeaders is invoked when a peer receives a sendheaders wire
+	// message.
+	OnSendHeaders func(p *Peer, msg *wire.MsgSendHeaders)
+
 	// OnRead is invoked when a peer receives a wire message.  It consists
 	// of the number of bytes read, the message, and whether or not an error
 	// in the read occurred.  Typically, callers will opt to use the
@@ -408,15 +412,16 @@ type Peer struct {
 	cfg     Config
 	inbound bool
 
-	flagsMtx        sync.Mutex // protects the peer flags below
-	na              *wire.NetAddress
-	id              int32
-	userAgent       string
-	services        wire.ServiceFlag
-	versionKnown    bool
-	protocolVersion uint32
-	versionSent     bool
-	verAckReceived  bool
+	flagsMtx             sync.Mutex // protects the peer flags below
+	na                   *wire.NetAddress
+	id                   int32
+	userAgent            string
+	services             wire.ServiceFlag
+	versionKnown         bool
+	protocolVersion      uint32
+	sendHeadersPreferred bool // peer sent a sendheaders message
+	versionSent          bool
+	verAckReceived       bool
 
 	knownInventory     *mruInventoryMap
 	prevGetBlocksMtx   sync.Mutex
@@ -732,6 +737,17 @@ func (p *Peer) StartingHeight() int32 {
 	return p.startingHeight
 }
 
+// WantsHeaders returns if the peer wants header messages instead of
+// inventory vectors for blocks.
+//
+// This function is safe for concurrent access.
+func (p *Peer) WantsHeaders() bool {
+	p.flagsMtx.Lock()
+	defer p.flagsMtx.Unlock()
+
+	return p.sendHeadersPreferred
+}
+
 // pushVersionMsg sends a version message to the connected peer using the
 // current state.
 func (p *Peer) pushVersionMsg() error {
@@ -1603,6 +1619,15 @@ out:
 				p.cfg.Listeners.OnReject(p, msg)
 			}
 
+		case *wire.MsgSendHeaders:
+			p.flagsMtx.Lock()
+			p.sendHeadersPreferred = true
+			p.flagsMtx.Unlock()
+
+			if p.cfg.Listeners.OnSendHeaders != nil {
+				p.cfg.Listeners.OnSendHeaders(p, msg)
+			}
+
 		default:
 			log.Debugf("Received unhandled message of type %v:",
 				rmsg.Command())

peer/peer_test.go

@@ -381,6 +381,9 @@ func TestPeerListeners(t *testing.T) {
 			OnReject: func(p *peer.Peer, msg *wire.MsgReject) {
 				ok <- msg
 			},
+			OnSendHeaders: func(p *peer.Peer, msg *wire.MsgSendHeaders) {
+				ok <- msg
+			},
 		},
 		UserAgentName:    "peer",
 		UserAgentVersion: "1.0",
@@ -503,9 +506,13 @@ func TestPeerListeners(t *testing.T) {
 		// only one version message is allowed
 		// only one verack message is allowed
 		{
-			"OnMsgReject",
+			"OnReject",
 			wire.NewMsgReject("block", wire.RejectDuplicate, "dupe block"),
 		},
+		{
+			"OnSendHeaders",
+			wire.NewMsgSendHeaders(),
+		},
 	}
 	t.Logf("Running %d tests", len(tests))
 	for _, test := range tests {

server.go

@@ -1594,6 +1594,7 @@ func newPeerConfig(sp *serverPeer) *peer.Config {
 		ChainParams:      sp.server.chainParams,
 		Services:         sp.server.services,
 		DisableRelayTx:   false,
+		ProtocolVersion:  wire.BIP0111Version,
 	}
 }