eth: fix data race accessing peer.recentHash

eth/peer.go

@@ -40,9 +40,11 @@ type peer struct {
 
 	protv, netid int
 
-	recentHash common.Hash
-	id         string
-	td         *big.Int
+	id string
+	td *big.Int
+
+	head     common.Hash
+	headLock sync.RWMutex
 
 	genesis, ourHash common.Hash
 	ourTd            *big.Int
@@ -51,14 +53,14 @@ type peer struct {
 	blockHashes *set.Set
 }
 
-func newPeer(protv, netid int, genesis, recentHash common.Hash, td *big.Int, p *p2p.Peer, rw p2p.MsgReadWriter) *peer {
+func newPeer(protv, netid int, genesis, head common.Hash, td *big.Int, p *p2p.Peer, rw p2p.MsgReadWriter) *peer {
 	id := p.ID()
 
 	return &peer{
 		Peer:        p,
 		rw:          rw,
 		genesis:     genesis,
-		ourHash:     recentHash,
+		ourHash:     head,
 		ourTd:       td,
 		protv:       protv,
 		netid:       netid,
@@ -68,6 +70,23 @@ func newPeer(protv, netid int, genesis, recentHash common.Hash, td *big.Int, p *
 	}
 }
 
+// Head retrieves a copy of the current head (most recent) hash of the peer.
+func (p *peer) Head() (hash common.Hash) {
+	p.headLock.RLock()
+	defer p.headLock.RUnlock()
+
+	copy(hash[:], p.head[:])
+	return hash
+}
+
+// SetHead updates the head (most recent) hash of the peer.
+func (p *peer) SetHead(hash common.Hash) {
+	p.headLock.Lock()
+	defer p.headLock.Unlock()
+
+	copy(p.head[:], hash[:])
+}
+
 // sendTransactions sends transactions to the peer and includes the hashes
 // in it's tx hash set for future reference. The tx hash will allow the
 // manager to check whether the peer has already received this particular
@@ -160,7 +179,7 @@ func (p *peer) handleStatus() error {
 	// Set the total difficulty of the peer
 	p.td = status.TD
 	// set the best hash of the peer
-	p.recentHash = status.CurrentBlock
+	p.head = status.CurrentBlock
 
 	return <-errc
 }