Merge pull request #1215 from davecgh/blockchain_generalize_reorganizechain

blockchain: Generalize chain reorg.

blockchain/chain.go

@@ -1,4 +1,5 @@
-// Copyright (c) 2013-2017 The btcsuite developers
+// Copyright (c) 2013-2018 The btcsuite developers
+// Copyright (c) 2015-2018 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
@@ -819,6 +820,38 @@ func countSpentOutputs(block *btcutil.Block) int {
 //
 // This function MUST be called with the chain state lock held (for writes).
 func (b *BlockChain) reorganizeChain(detachNodes, attachNodes *list.List) error {
+	// Nothing to do if no reorganize nodes were provided.
+	if detachNodes.Len() == 0 && attachNodes.Len() == 0 {
+		return nil
+	}
+
+	// Ensure the provided nodes match the current best chain.
+	tip := b.bestChain.Tip()
+	if detachNodes.Len() != 0 {
+		firstDetachNode := detachNodes.Front().Value.(*blockNode)
+		if firstDetachNode.hash != tip.hash {
+			return AssertError(fmt.Sprintf("reorganize nodes to detach are "+
+				"not for the current best chain -- first detach node %v, "+
+				"current chain %v", &firstDetachNode.hash, &tip.hash))
+		}
+	}
+
+	// Ensure the provided nodes are for the same fork point.
+	if attachNodes.Len() != 0 && detachNodes.Len() != 0 {
+		firstAttachNode := attachNodes.Front().Value.(*blockNode)
+		lastDetachNode := detachNodes.Back().Value.(*blockNode)
+		if firstAttachNode.parent.hash != lastDetachNode.parent.hash {
+			return AssertError(fmt.Sprintf("reorganize nodes do not have the "+
+				"same fork point -- first attach parent %v, last detach "+
+				"parent %v", &firstAttachNode.parent.hash,
+				&lastDetachNode.parent.hash))
+		}
+	}
+
+	// Track the old and new best chains heads.
+	oldBest := tip
+	newBest := tip
+
 	// All of the blocks to detach and related spend journal entries needed
 	// to unspend transaction outputs in the blocks being disconnected must
 	// be loaded from the database during the reorg check phase below and
@@ -833,7 +866,7 @@ func (b *BlockChain) reorganizeChain(detachNodes, attachNodes *list.List) error
 	// 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.bestChain.Tip().hash)
+	view.SetBestHash(&oldBest.hash)
 	for e := detachNodes.Front(); e != nil; e = e.Next() {
 		n := e.Value.(*blockNode)
 		var block *btcutil.Block
@@ -845,6 +878,11 @@ func (b *BlockChain) reorganizeChain(detachNodes, attachNodes *list.List) error
 		if err != nil {
 			return err
 		}
+		if n.hash != *block.Hash() {
+			return AssertError(fmt.Sprintf("detach block node hash %v (height "+
+				"%v) does not match previous parent block hash %v", &n.hash,
+				n.height, block.Hash()))
+		}
 
 		// Load all of the utxos referenced by the block that aren't
 		// already in the view.
@@ -872,6 +910,15 @@ func (b *BlockChain) reorganizeChain(detachNodes, attachNodes *list.List) error
 		if err != nil {
 			return err
 		}
+
+		newBest = n.parent
+	}
+
+	// Set the fork point only if there are nodes to attach since otherwise
+	// blocks are only being disconnected and thus there is no fork point.
+	var forkNode *blockNode
+	if attachNodes.Len() > 0 {
+		forkNode = newBest
 	}
 
 	// Perform several checks to verify each block that needs to be attached
@@ -886,17 +933,9 @@ func (b *BlockChain) reorganizeChain(detachNodes, attachNodes *list.List) error
 	// at least a couple of ways accomplish that rollback, but both involve
 	// tweaking the chain and/or database.  This approach catches these
 	// issues before ever modifying the chain.
-	var validationError error
 	for e := attachNodes.Front(); e != nil; e = e.Next() {
 		n := e.Value.(*blockNode)
 
-		// If any previous nodes in attachNodes failed validation,
-		// mark this one as having an invalid ancestor.
-		if validationError != nil {
-			b.index.SetStatusFlags(n, statusInvalidAncestor)
-			continue
-		}
-
 		var block *btcutil.Block
 		err := b.db.View(func(dbTx database.Tx) error {
 			var err error
@@ -922,6 +961,8 @@ func (b *BlockChain) reorganizeChain(detachNodes, attachNodes *list.List) error
 			if err != nil {
 				return err
 			}
+
+			newBest = n
 			continue
 		}
 
@@ -929,23 +970,24 @@ func (b *BlockChain) reorganizeChain(detachNodes, attachNodes *list.List) error
 		// thus will not be generated.  This is done because the state
 		// is not being immediately written to the database, so it is
 		// not needed.
+		//
+		// In the case the block is determined to be invalid due to a
+		// rule violation, mark it as invalid and mark all of its
+		// descendants as having an invalid ancestor.
 		err = b.checkConnectBlock(n, block, view, nil)
 		if err != nil {
-			// If the block failed validation mark it as invalid, then
-			// continue to loop through remaining nodes, marking them as
-			// having an invalid ancestor.
 			if _, ok := err.(RuleError); ok {
 				b.index.SetStatusFlags(n, statusValidateFailed)
-				validationError = err
-				continue
+				for de := e.Next(); de != nil; de = de.Next() {
+					dn := de.Value.(*blockNode)
+					b.index.SetStatusFlags(dn, statusInvalidAncestor)
+				}
 			}
 			return err
 		}
 		b.index.SetStatusFlags(n, statusValid)
-	}
 
-	if validationError != nil {
-		return validationError
+		newBest = n
 	}
 
 	// Reset the view for the actual connection code below.  This is
@@ -1014,12 +1056,14 @@ func (b *BlockChain) reorganizeChain(detachNodes, attachNodes *list.List) error
 
 	// Log the point where the chain forked and old and new best chain
 	// heads.
-	firstAttachNode := attachNodes.Front().Value.(*blockNode)
-	firstDetachNode := detachNodes.Front().Value.(*blockNode)
-	lastAttachNode := attachNodes.Back().Value.(*blockNode)
-	log.Infof("REORGANIZE: Chain forks at %v", firstAttachNode.parent.hash)
-	log.Infof("REORGANIZE: Old best chain head was %v", firstDetachNode.hash)
-	log.Infof("REORGANIZE: New best chain head is %v", lastAttachNode.hash)
+	if forkNode != nil {
+		log.Infof("REORGANIZE: Chain forks at %v (height %v)", forkNode.hash,
+			forkNode.height)
+	}
+	log.Infof("REORGANIZE: Old best chain head was %v (height %v)",
+		&oldBest.hash, oldBest.height)
+	log.Infof("REORGANIZE: New best chain head is %v (height %v)",
+		newBest.hash, newBest.height)
 
 	return nil
 }