blockchain: Use hash values in structs.

This modifies the blockNode and BestState structs in the blockchain
package to store hashes directly instead of pointers to them and updates
callers to deal with the API change in the exported BestState struct.

In general, the preferred approach for hashes moving forward is to store
hash values in complex data structures, particularly those that will be
used for cache entries, and accept pointers to hashes in arguments to
functions.

Some of the reasoning behind making this change is:

- It is generally preferred to avoid storing pointers to data in cache
  objects since doing so can easily lead to storing interior pointers
  into other structs that then can't be GC'd
- Keeping the hash values directly in the block node provides better
  cache locality

blockchain/blockindex.go

@@ -31,13 +31,13 @@ type blockNode struct {
 	children []*blockNode
 
 	// hash is the double sha 256 of the block.
-	hash *chainhash.Hash
+	hash chainhash.Hash
 
 	// parentHash is the double sha 256 of the parent block.  This is kept
 	// here over simply relying on parent.hash directly since block nodes
 	// are sparse and the parent node might not be in memory when its hash
 	// is needed.
-	parentHash *chainhash.Hash
+	parentHash chainhash.Hash
 
 	// height is the position in the block chain.
 	height int32
@@ -67,13 +67,9 @@ type blockNode struct {
 // for the passed block.  The work sum is updated accordingly when the node is
 // inserted into a chain.
 func newBlockNode(blockHeader *wire.BlockHeader, blockHash *chainhash.Hash, height int32) *blockNode {
-	// Make a copy of the hash so the node doesn't keep a reference to part
-	// of the full block/block header preventing it from being garbage
-	// collected.
-	prevHash := blockHeader.PrevBlock
 	node := blockNode{
-		hash:       blockHash,
+		hash:       *blockHash,
-		parentHash: &prevHash,
+		parentHash: blockHeader.PrevBlock,
 		workSum:    CalcWork(blockHeader.Bits),
 		height:     height,
 		version:    blockHeader.Version,
@@ -92,7 +88,7 @@ func (node *blockNode) Header() wire.BlockHeader {
 	// No lock is needed because all accessed fields are immutable.
 	return wire.BlockHeader{
 		Version:    node.version,
-		PrevBlock:  *node.parentHash,
+		PrevBlock:  node.parentHash,
 		MerkleRoot: node.merkleRoot,
 		Timestamp:  time.Unix(node.timestamp, 0),
 		Bits:       node.bits,
@@ -115,7 +111,7 @@ func removeChildNode(children []*blockNode, node *blockNode) []*blockNode {
 	// does not reevaluate the slice on each iteration nor does it adjust
 	// the index for the modified slice.
 	for i := 0; i < len(children); i++ {
-		if children[i].hash.IsEqual(node.hash) {
+		if children[i].hash.IsEqual(&node.hash) {
 			copy(children[i:], children[i+1:])
 			children[len(children)-1] = nil
 			return children[:len(children)-1]
@@ -286,7 +282,7 @@ func (bi *blockIndex) prevNodeFromNode(node *blockNode) (*blockNode, error) {
 	var prevBlockNode *blockNode
 	err := bi.db.View(func(dbTx database.Tx) error {
 		var err error
-		prevBlockNode, err = bi.loadBlockNode(dbTx, node.parentHash)
+		prevBlockNode, err = bi.loadBlockNode(dbTx, &node.parentHash)
 		return err
 	})
 	return prevBlockNode, err
@@ -339,7 +335,7 @@ func (bi *blockIndex) RelativeNode(anchor *blockNode, distance uint32) (*blockNo
 			// pulling it into the memory cache in the processes.
 			default:
 				iterNode, err = bi.loadBlockNode(dbTx,
-					iterNode.parentHash)
+					&iterNode.parentHash)
 				if err != nil {
 					return err
 				}
@@ -389,8 +385,8 @@ func (bi *blockIndex) AncestorNode(node *blockNode, height int32) (*blockNode, e
 // This function is safe for concurrent access.
 func (bi *blockIndex) AddNode(node *blockNode) {
 	bi.Lock()
-	bi.index[*node.hash] = node
+	bi.index[node.hash] = node
-	if prevHash := node.parentHash; prevHash != nil && *prevHash != *zeroHash {
+	if prevHash := &node.parentHash; *prevHash != *zeroHash {
 		bi.depNodes[*prevHash] = append(bi.depNodes[*prevHash], node)
 	}
 	bi.Unlock()

blockchain/blocklocator.go

@@ -121,7 +121,7 @@ func (bi *blockIndex) blockLocatorFromHash(hash *chainhash.Hash) BlockLocator {
 					iterNode = iterNode.parent
 				}
 				if iterNode != nil && iterNode.height == blockHeight {
-					locator = append(locator, iterNode.hash)
+					locator = append(locator, &iterNode.hash)
 				}
 				continue
 			}
@@ -176,7 +176,7 @@ func (b *BlockChain) BlockLocatorFromHash(hash *chainhash.Hash) BlockLocator {
 func (b *BlockChain) LatestBlockLocator() (BlockLocator, error) {
 	b.chainLock.RLock()
 	b.index.RLock()
-	locator := b.index.blockLocatorFromHash(b.bestNode.hash)
+	locator := b.index.blockLocatorFromHash(&b.bestNode.hash)
 	b.index.RUnlock()
 	b.chainLock.RUnlock()
 	return locator, nil

blockchain/chain.go

@@ -42,13 +42,13 @@ type orphanBlock struct {
 // However, the returned snapshot must be treated as immutable since it is
 // shared by all callers.
 type BestState struct {
-	Hash       *chainhash.Hash // The hash of the block.
+	Hash       chainhash.Hash // The hash of the block.
-	Height     int32           // The height of the block.
+	Height     int32          // The height of the block.
-	Bits       uint32          // The difficulty bits of the block.
+	Bits       uint32         // The difficulty bits of the block.
-	BlockSize  uint64          // The size of the block.
+	BlockSize  uint64         // The size of the block.
-	NumTxns    uint64          // The number of txns in the block.
+	NumTxns    uint64         // The number of txns in the block.
-	TotalTxns  uint64          // The total number of txns in the chain.
+	TotalTxns  uint64         // The total number of txns in the chain.
-	MedianTime time.Time       // Median time as per CalcPastMedianTime.
+	MedianTime time.Time      // Median time as per CalcPastMedianTime.
 }
 
 // newBestState returns a new best stats instance for the given parameters.
@@ -522,7 +522,7 @@ func (b *BlockChain) getReorganizeNodes(node *blockNode) (*list.List, *list.List
 	// common ancestor adding each block to the list of nodes to detach from
 	// the main chain.
 	for n := b.bestNode; n != nil && n.parent != nil; n = n.parent {
-		if n.hash.IsEqual(ancestor.hash) {
+		if n.hash.IsEqual(&ancestor.hash) {
 			break
 		}
 		detachNodes.PushBack(n)
@@ -559,7 +559,7 @@ func dbMaybeStoreBlock(dbTx database.Tx, block *btcutil.Block) error {
 func (b *BlockChain) connectBlock(node *blockNode, block *btcutil.Block, view *UtxoViewpoint, stxos []spentTxOut) error {
 	// Make sure it's extending the end of the best chain.
 	prevHash := &block.MsgBlock().Header.PrevBlock
-	if !prevHash.IsEqual(b.bestNode.hash) {
+	if !prevHash.IsEqual(&b.bestNode.hash) {
 		return AssertError("connectBlock must be called with a block " +
 			"that extends the main chain")
 	}
@@ -689,7 +689,7 @@ func (b *BlockChain) connectBlock(node *blockNode, block *btcutil.Block, view *U
 // This function MUST be called with the chain state lock held (for writes).
 func (b *BlockChain) disconnectBlock(node *blockNode, block *btcutil.Block, view *UtxoViewpoint) error {
 	// Make sure the node being disconnected is the end of the best chain.
-	if !node.hash.IsEqual(b.bestNode.hash) {
+	if !node.hash.IsEqual(&b.bestNode.hash) {
 		return AssertError("disconnectBlock must be called with the " +
 			"block at the end of the main chain")
 	}
@@ -713,7 +713,7 @@ func (b *BlockChain) disconnectBlock(node *blockNode, block *btcutil.Block, view
 	var prevBlock *btcutil.Block
 	err = b.db.View(func(dbTx database.Tx) error {
 		var err error
-		prevBlock, err = dbFetchBlockByHash(dbTx, prevNode.hash)
+		prevBlock, err = dbFetchBlockByHash(dbTx, &prevNode.hash)
 		return err
 	})
 	if err != nil {
@@ -843,13 +843,13 @@ func (b *BlockChain) reorganizeChain(detachNodes, attachNodes *list.List, flags
 	// database and using that information to unspend all of the spent txos
 	// and remove the utxos created by the blocks.
 	view := NewUtxoViewpoint()
-	view.SetBestHash(b.bestNode.hash)
+	view.SetBestHash(&b.bestNode.hash)
 	for e := detachNodes.Front(); e != nil; e = e.Next() {
 		n := e.Value.(*blockNode)
 		var block *btcutil.Block
 		err := b.db.View(func(dbTx database.Tx) error {
 			var err error
-			block, err = dbFetchBlockByHash(dbTx, n.hash)
+			block, err = dbFetchBlockByHash(dbTx, &n.hash)
 			return err
 		})
 		if err != nil {
@@ -903,7 +903,7 @@ func (b *BlockChain) reorganizeChain(detachNodes, attachNodes *list.List, flags
 			// NOTE: This block is not in the main chain, so the
 			// block has to be loaded directly from the database
 			// instead of using the dbFetchBlockByHash function.
-			blockBytes, err := dbTx.FetchBlock(n.hash)
+			blockBytes, err := dbTx.FetchBlock(&n.hash)
 			if err != nil {
 				return err
 			}
@@ -944,7 +944,7 @@ func (b *BlockChain) reorganizeChain(detachNodes, attachNodes *list.List, flags
 	// view to be valid from the viewpoint of each block being connected or
 	// disconnected.
 	view = NewUtxoViewpoint()
-	view.SetBestHash(b.bestNode.hash)
+	view.SetBestHash(&b.bestNode.hash)
 
 	// Disconnect blocks from the main chain.
 	for i, e := 0, detachNodes.Front(); e != nil; i, e = i+1, e.Next() {
@@ -1040,12 +1040,12 @@ func (b *BlockChain) connectBestChain(node *blockNode, block *btcutil.Block, fla
 
 	// We are extending the main (best) chain with a new block.  This is the
 	// most common case.
-	if node.parentHash.IsEqual(b.bestNode.hash) {
+	if node.parentHash.IsEqual(&b.bestNode.hash) {
 		// Perform several checks to verify the block can be connected
 		// to the main chain without violating any rules and without
 		// actually connecting the block.
 		view := NewUtxoViewpoint()
-		view.SetBestHash(node.parentHash)
+		view.SetBestHash(&node.parentHash)
 		stxos := make([]spentTxOut, 0, countSpentOutputs(block))
 		if !fastAdd {
 			err := b.checkConnectBlock(node, block, view, &stxos)
@@ -1096,7 +1096,7 @@ func (b *BlockChain) connectBestChain(node *blockNode, block *btcutil.Block, fla
 	// become the main chain, but in either case the entry is needed in the
 	// index for future processing.
 	b.index.Lock()
-	b.index.index[*node.hash] = node
+	b.index.index[node.hash] = node
 	b.index.Unlock()
 
 	// Connect the parent node to this node.
@@ -1112,7 +1112,7 @@ func (b *BlockChain) connectBestChain(node *blockNode, block *btcutil.Block, fla
 			node.parent.children = children
 
 			b.index.Lock()
-			delete(b.index.index, *node.hash)
+			delete(b.index.index, node.hash)
 			b.index.Unlock()
 		}()
 	}
@@ -1134,7 +1134,7 @@ func (b *BlockChain) connectBestChain(node *blockNode, block *btcutil.Block, fla
 		}
 
 		// Log information about how the block is forking the chain.
-		if fork.hash.IsEqual(node.parent.hash) {
+		if fork.hash.IsEqual(&node.parent.hash) {
 			log.Infof("FORK: Block %v forks the chain at height %d"+
 				"/block %v, but does not cause a reorganize",
 				node.hash, fork.height, fork.hash)

blockchain/chainio.go

@@ -1064,7 +1064,7 @@ func deserializeBestChainState(serializedData []byte) (bestChainState, error) {
 func dbPutBestState(dbTx database.Tx, snapshot *BestState, workSum *big.Int) error {
 	// Serialize the current best chain state.
 	serializedData := serializeBestChainState(bestChainState{
-		hash:      *snapshot.Hash,
+		hash:      snapshot.Hash,
 		height:    uint32(snapshot.Height),
 		totalTxns: snapshot.TotalTxns,
 		workSum:   workSum,
@@ -1129,7 +1129,7 @@ func (b *BlockChain) createChainState() error {
 
 		// Add the genesis block hash to height and height to hash
 		// mappings to the index.
-		err = dbPutBlockIndex(dbTx, b.bestNode.hash, b.bestNode.height)
+		err = dbPutBlockIndex(dbTx, &b.bestNode.hash, b.bestNode.height)
 		if err != nil {
 			return err
 		}

blockchain/fullblocks_test.go

@@ -165,7 +165,7 @@ func TestFullBlocks(t *testing.T) {
 
 		// Ensure hash and height match.
 		best := chain.BestSnapshot()
-		if *best.Hash != item.Block.BlockHash() ||
+		if best.Hash != item.Block.BlockHash() ||
 			best.Height != blockHeight {
 
 			t.Fatalf("block %q (hash %s, height %d) should be "+

blockchain/thresholdstate.go

@@ -103,20 +103,20 @@ type thresholdStateCache struct {
 
 // Lookup returns the threshold state associated with the given hash along with
 // a boolean that indicates whether or not it is valid.
-func (c *thresholdStateCache) Lookup(hash chainhash.Hash) (ThresholdState, bool) {
+func (c *thresholdStateCache) Lookup(hash *chainhash.Hash) (ThresholdState, bool) {
-	state, ok := c.entries[hash]
+	state, ok := c.entries[*hash]
 	return state, ok
 }
 
 // Update updates the cache to contain the provided hash to threshold state
 // mapping while properly tracking needed updates flush changes to the database.
-func (c *thresholdStateCache) Update(hash chainhash.Hash, state ThresholdState) {
+func (c *thresholdStateCache) Update(hash *chainhash.Hash, state ThresholdState) {
-	if existing, ok := c.entries[hash]; ok && existing == state {
+	if existing, ok := c.entries[*hash]; ok && existing == state {
 		return
 	}
 
-	c.dbUpdates[hash] = state
+	c.dbUpdates[*hash] = state
-	c.entries[hash] = state
+	c.entries[*hash] = state
 }
 
 // MarkFlushed marks all of the current udpates as flushed to the database.
@@ -170,7 +170,7 @@ func (b *BlockChain) thresholdState(prevNode *blockNode, checker thresholdCondit
 	for prevNode != nil {
 		// Nothing more to do if the state of the block is already
 		// cached.
-		if _, ok := cache.Lookup(*prevNode.hash); ok {
+		if _, ok := cache.Lookup(&prevNode.hash); ok {
 			break
 		}
 
@@ -184,7 +184,7 @@ func (b *BlockChain) thresholdState(prevNode *blockNode, checker thresholdCondit
 		// The state is simply defined if the start time hasn't been
 		// been reached yet.
 		if uint64(medianTime.Unix()) < checker.BeginTime() {
-			cache.Update(*prevNode.hash, ThresholdDefined)
+			cache.Update(&prevNode.hash, ThresholdDefined)
 			break
 		}
 
@@ -206,7 +206,7 @@ func (b *BlockChain) thresholdState(prevNode *blockNode, checker thresholdCondit
 	state := ThresholdDefined
 	if prevNode != nil {
 		var ok bool
-		state, ok = cache.Lookup(*prevNode.hash)
+		state, ok = cache.Lookup(&prevNode.hash)
 		if !ok {
 			return ThresholdFailed, AssertError(fmt.Sprintf(
 				"thresholdState: cache lookup failed for %v",
@@ -298,7 +298,7 @@ func (b *BlockChain) thresholdState(prevNode *blockNode, checker thresholdCondit
 
 		// Update the cache to avoid recalculating the state in the
 		// future.
-		cache.Update(*prevNode.hash, state)
+		cache.Update(&prevNode.hash, state)
 	}
 
 	return state, nil

blockchain/thresholdstate_test.go

@@ -69,7 +69,7 @@ nextTest:
 			hash[0] = uint8(i + 1)
 
 			// Ensure the hash isn't available in the cache already.
-			_, ok := cache.Lookup(hash)
+			_, ok := cache.Lookup(&hash)
 			if ok {
 				t.Errorf("Lookup (%s): has entry for hash %v",
 					test.name, hash)
@@ -78,8 +78,8 @@ nextTest:
 
 			// Ensure hash that was added to the cache reports it's
 			// available and the state is the expected value.
-			cache.Update(hash, test.state)
+			cache.Update(&hash, test.state)
-			state, ok := cache.Lookup(hash)
+			state, ok := cache.Lookup(&hash)
 			if !ok {
 				t.Errorf("Lookup (%s): missing entry for hash "+
 					"%v", test.name, hash)
@@ -118,7 +118,7 @@ nextTest:
 
 			// Ensure hash is still available in the cache and the
 			// state is the expected value.
-			state, ok = cache.Lookup(hash)
+			state, ok = cache.Lookup(&hash)
 			if !ok {
 				t.Errorf("Lookup (%s): missing entry after "+
 					"flush for hash %v", test.name, hash)
@@ -134,8 +134,8 @@ nextTest:
 			// Ensure adding an existing hash with the same state
 			// doesn't break the existing entry and it is NOT added
 			// to the database updates map.
-			cache.Update(hash, test.state)
+			cache.Update(&hash, test.state)
-			state, ok = cache.Lookup(hash)
+			state, ok = cache.Lookup(&hash)
 			if !ok {
 				t.Errorf("Lookup (%s): missing entry after "+
 					"second add for hash %v", test.name,
@@ -160,8 +160,8 @@ nextTest:
 			if newState == test.state {
 				newState = ThresholdStarted
 			}
-			cache.Update(hash, newState)
+			cache.Update(&hash, newState)
-			state, ok = cache.Lookup(hash)
+			state, ok = cache.Lookup(&hash)
 			if !ok {
 				t.Errorf("Lookup (%s): missing entry after "+
 					"state change for hash %v", test.name,

blockchain/validate.go

@@ -968,7 +968,7 @@ func (b *BlockChain) checkConnectBlock(node *blockNode, block *btcutil.Block, vi
 	}
 
 	// Ensure the view is for the node being checked.
-	if !view.BestHash().IsEqual(node.parentHash) {
+	if !view.BestHash().IsEqual(&node.parentHash) {
 		return AssertError(fmt.Sprintf("inconsistent view when "+
 			"checking block connection: best hash is %v instead "+
 			"of expected %v", view.BestHash(), node.hash))
@@ -1146,7 +1146,7 @@ func (b *BlockChain) checkConnectBlock(node *blockNode, block *btcutil.Block, vi
 
 	// Update the best hash for view to include this block since all of its
 	// transactions have been connected.
-	view.SetBestHash(node.hash)
+	view.SetBestHash(&node.hash)
 
 	return nil
 }
@@ -1173,6 +1173,6 @@ func (b *BlockChain) CheckConnectBlock(block *btcutil.Block) error {
 	// Leave the spent txouts entry nil in the state since the information
 	// is not needed and thus extra work can be avoided.
 	view := NewUtxoViewpoint()
-	view.SetBestHash(prevNode.hash)
+	view.SetBestHash(&prevNode.hash)
 	return b.checkConnectBlock(newNode, block, view, nil)
 }

blockmanager.go

@@ -378,7 +378,7 @@ func (b *blockManager) handleDonePeerMsg(peers *list.List, sp *serverPeer) {
 		b.syncPeer = nil
 		if b.headersFirstMode {
 			best := b.chain.BestSnapshot()
-			b.resetHeaderState(best.Hash, best.Height)
+			b.resetHeaderState(&best.Hash, best.Height)
 		}
 		b.startSync(peers)
 	}
@@ -595,7 +595,7 @@ func (b *blockManager) handleBlockMsg(bmsg *blockMsg) {
 		// potential sync node candidacy.
 		best := b.chain.BestSnapshot()
 		heightUpdate = best.Height
-		blkHashUpdate = best.Hash
+		blkHashUpdate = &best.Hash
 
 		// Clear the rejected transactions.
 		b.rejectedTxns = make(map[chainhash.Hash]struct{})
@@ -1417,7 +1417,7 @@ func newBlockManager(s *server, indexManager blockchain.IndexManager) (*blockMan
 		// Initialize the next checkpoint based on the current height.
 		bm.nextCheckpoint = bm.findNextHeaderCheckpoint(best.Height)
 		if bm.nextCheckpoint != nil {
-			bm.resetHeaderState(best.Hash, best.Height)
+			bm.resetHeaderState(&best.Hash, best.Height)
 		}
 	} else {
 		bmgrLog.Info("Checkpoints are disabled")

cmd/findcheckpoint/findcheckpoint.go

@@ -166,7 +166,7 @@ func main() {
 	fmt.Printf("Block database loaded with block height %d\n", best.Height)
 
 	// Find checkpoint candidates.
-	candidates, err := findCandidates(chain, best.Hash)
+	candidates, err := findCandidates(chain, &best.Hash)
 	if err != nil {
 		fmt.Fprintln(os.Stderr, "Unable to identify candidates:", err)
 		return

mining/cpuminer/cpuminer.go

@@ -162,7 +162,7 @@ func (m *CPUMiner) submitBlock(block *btcutil.Block) bool {
 	// a new block, but the check only happens periodically, so it is
 	// possible a block was found and submitted in between.
 	msgBlock := block.MsgBlock()
-	if !msgBlock.Header.PrevBlock.IsEqual(m.g.BestSnapshot().Hash) {
+	if !msgBlock.Header.PrevBlock.IsEqual(&m.g.BestSnapshot().Hash) {
 		log.Debugf("Block submitted via CPU miner with previous "+
 			"block %s is stale", msgBlock.Header.PrevBlock)
 		return false
@@ -249,7 +249,7 @@ func (m *CPUMiner) solveBlock(msgBlock *wire.MsgBlock, blockHeight int32,
 				// The current block is stale if the best block
 				// has changed.
 				best := m.g.BestSnapshot()
-				if !header.PrevBlock.IsEqual(best.Hash) {
+				if !header.PrevBlock.IsEqual(&best.Hash) {
 					return false
 				}
 

mining/mining.go

@@ -435,7 +435,7 @@ func NewBlkTmplGenerator(policy *Policy, params *chaincfg.Params,
 func (g *BlkTmplGenerator) NewBlockTemplate(payToAddress btcutil.Address) (*BlockTemplate, error) {
 	// Extend the most recently known best block.
 	best := g.chain.BestSnapshot()
-	prevHash := best.Hash
+	prevHash := &best.Hash
 	nextBlockHeight := best.Height + 1
 
 	// Create a standard coinbase transaction paying to the provided

rpcserver.go

@@ -1470,7 +1470,7 @@ func (state *gbtWorkState) updateBlockTemplate(s *rpcServer, useCoinbaseValue bo
 	// generated.
 	var msgBlock *wire.MsgBlock
 	var targetDifficulty string
-	latestHash := s.server.blockManager.chain.BestSnapshot().Hash
+	latestHash := &s.server.blockManager.chain.BestSnapshot().Hash
 	template := state.template
 	if template == nil || state.prevHash == nil ||
 		!state.prevHash.IsEqual(latestHash) ||
@@ -2026,9 +2026,9 @@ func handleGetBlockTemplateProposal(s *rpcServer, request *btcjson.TemplateReque
 	block := btcutil.NewBlock(&msgBlock)
 
 	// Ensure the block is building from the expected previous block.
-	expectedPrevHash := s.server.blockManager.chain.BestSnapshot().Hash
+	expectedPrevHash := &s.server.blockManager.chain.BestSnapshot().Hash
 	prevHash := &block.MsgBlock().Header.PrevBlock
-	if expectedPrevHash == nil || !expectedPrevHash.IsEqual(prevHash) {
+	if !expectedPrevHash.IsEqual(prevHash) {
 		return "bad-prevblk", nil
 	}
 

rpcwebsocket.go

@@ -2471,7 +2471,7 @@ fetchRange:
 			blockManager := wsc.server.server.blockManager
 			pauseGuard := blockManager.Pause()
 			best := blockManager.chain.BestSnapshot()
-			curHash := best.Hash
+			curHash := &best.Hash
 			again := true
 			if lastBlockHash == nil || *lastBlockHash == *curHash {
 				again = false

server.go

@@ -246,7 +246,7 @@ func newServerPeer(s *server, isPersistent bool) *serverPeer {
 // required by the configuration for the peer package.
 func (sp *serverPeer) newestBlock() (*chainhash.Hash, int32, error) {
 	best := sp.server.blockManager.chain.BestSnapshot()
-	return best.Hash, best.Height, nil
+	return &best.Hash, best.Height, nil
 }
 
 // addKnownAddresses adds the given addresses to the set of known addresses to
@@ -1130,7 +1130,7 @@ func (s *server) pushBlockMsg(sp *serverPeer, hash *chainhash.Hash, doneChan cha
 	if sendInv {
 		best := sp.server.blockManager.chain.BestSnapshot()
 		invMsg := wire.NewMsgInvSizeHint(1)
-		iv := wire.NewInvVect(wire.InvTypeBlock, best.Hash)
+		iv := wire.NewInvVect(wire.InvTypeBlock, &best.Hash)
 		invMsg.AddInvVect(iv)
 		sp.QueueMessage(invMsg, doneChan)
 		sp.continueHash = nil