peer: Move IsWitnessEnabled() from serverPeer to Peer.

serverPeer is a problematic struct because it is local to the main
package.

peer/peer.go

@@ -416,6 +416,7 @@ type Peer struct {
 	protocolVersion      uint32 // negotiated protocol version
 	sendHeadersPreferred bool   // peer sent a sendheaders message
 	verAckReceived       bool
+	witnessEnabled       bool
 
 	wireEncoding wire.MessageEncoding
 
@@ -765,6 +766,18 @@ func (p *Peer) WantsHeaders() bool {
 	return sendHeadersPreferred
 }
 
+// IsWitnessEnabled returns true if the peer has signalled that it supports
+// segregated witness.
+//
+// This function is safe for concurrent access.
+func (p *Peer) IsWitnessEnabled() bool {
+	p.flagsMtx.Lock()
+	witnessEnabled := p.witnessEnabled
+	p.flagsMtx.Unlock()
+
+	return witnessEnabled
+}
+
 // localVersionMsg creates a version message that can be used to send to the
 // remote peer.
 func (p *Peer) localVersionMsg() (*wire.MsgVersion, error) {
@@ -1051,6 +1064,12 @@ func (p *Peer) handleRemoteVersionMsg(msg *wire.MsgVersion) error {
 
 	// Set the remote peer's user agent.
 	p.userAgent = msg.UserAgent
+
+	// Determine if the peer would like to receive witness data with
+	// transactions, or not.
+	if p.services&wire.SFNodeWitness == wire.SFNodeWitness {
+		p.witnessEnabled = true
+	}
 	p.flagsMtx.Unlock()
 
 	// Once the version message has been exchanged, we're able to determine

server.go

@@ -214,8 +214,6 @@ type serverPeer struct {
 
 	connReq         *connmgr.ConnReq
 	server          *server
-	witnessMtx      sync.Mutex
-	witnessEnabled  bool
 	persistent      bool
 	continueHash    *chainhash.Hash
 	relayMtx        sync.Mutex
@@ -249,17 +247,6 @@ func newServerPeer(s *server, isPersistent bool) *serverPeer {
 	}
 }
 
-// IsWitnessEnabled returns true if the target serverPeer has signalled that it
-// supports segregated witness.
-//
-// This function is safe for concurrent access.
-func (sp *serverPeer) IsWitnessEnabled() bool {
-	sp.witnessMtx.Lock()
-	enabled := sp.witnessEnabled
-	sp.witnessMtx.Unlock()
-	return enabled
-}
-
 // newestBlock returns the current best block hash and height using the format
 // required by the configuration for the peer package.
 func (sp *serverPeer) newestBlock() (*chainhash.Hash, int32, error) {
@@ -368,14 +355,6 @@ func (sp *serverPeer) OnVersion(_ *peer.Peer, msg *wire.MsgVersion) {
 	// is received.
 	sp.setDisableRelayTx(msg.DisableRelayTx)
 
-	// Determine if the peer would like to receive witness data with
-	// transactions, or not.
-	if sp.Services()&wire.SFNodeWitness == wire.SFNodeWitness {
-		sp.witnessMtx.Lock()
-		sp.witnessEnabled = true
-		sp.witnessMtx.Unlock()
-	}
-
 	// Update the address manager and request known addresses from the
 	// remote peer for outbound connections.  This is skipped when running
 	// on the simulation test network since it is only intended to connect