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blockchain: Add InvalidateBlock() method to BlockChain
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InvalidateBlock() invalidates a given block and marks all its
descendents as invalid as well. The active chain tip changes if the
invalidated block is part of the best chain.
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kcalvinalvin committed Apr 30, 2024
1 parent ea39fe0 commit 635ae68
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138 changes: 138 additions & 0 deletions blockchain/chain.go
Original file line number Diff line number Diff line change
Expand Up @@ -1798,6 +1798,144 @@ func (b *BlockChain) LocateHeaders(locator BlockLocator, hashStop *chainhash.Has
return headers
}

// InvalidateBlock invalidates the requested block and all its descedents. If a block
// in the best chain is invalidated, the active chain tip will be the parent of the
// invalidated block.
//
// This function is safe for concurrent access.
func (b *BlockChain) InvalidateBlock(hash *chainhash.Hash) error {
b.chainLock.Lock()
defer b.chainLock.Unlock()

node := b.index.LookupNode(hash)
if node == nil {
// Return an error if the block doesn't exist.
return fmt.Errorf("Requested block hash of %s is not found "+
"and thus cannot be invalidated.", hash)
}
if node.height == 0 {
return fmt.Errorf("Requested block hash of %s is a at height 0 "+
"and is thus a genesis block and cannot be invalidated.",
node.hash)
}

// Nothing to do if the given block is already invalid.
if node.status.KnownInvalid() {
return nil
}

// Set the status of the block being invalidated.
b.index.SetStatusFlags(node, statusValidateFailed)
b.index.UnsetStatusFlags(node, statusValid)

// If the block we're invalidating is not on the best chain, we simply
// mark the block and all its descendants as invalid and return.
if !b.bestChain.Contains(node) {
// Grab all the tips excluding the active tip.
tips := b.index.InactiveTips(b.bestChain)
for _, tip := range tips {
// Continue if the given inactive tip is not a descendant of the block
// being invalidated.
if !tip.IsAncestor(node) {
continue
}

// Keep going back until we get to the block being invalidated.
// For each of the parent, we'll unset valid status and set invalid
// ancestor status.
for n := tip; n != nil && n != node; n = n.parent {
// Continue if it's already invalid.
if n.status.KnownInvalid() {
continue
}
b.index.SetStatusFlags(n, statusInvalidAncestor)
b.index.UnsetStatusFlags(n, statusValid)
}
}

if writeErr := b.index.flushToDB(); writeErr != nil {
return fmt.Errorf("Error flushing block index "+
"changes to disk: %v", writeErr)
}

// Return since the block being invalidated is on a side branch.
// Nothing else left to do.
return nil
}

// If we're here, it means a block from the active chain tip is getting
// invalidated.
//
// Grab all the nodes to detach from the active chain.
detachNodes := list.New()
for n := b.bestChain.Tip(); n != nil && n != node; n = n.parent {
// Continue if it's already invalid.
if n.status.KnownInvalid() {
continue
}

// Change the status of the block node.
b.index.SetStatusFlags(n, statusInvalidAncestor)
b.index.UnsetStatusFlags(n, statusValid)
detachNodes.PushBack(n)
}

// Push back the block node being invalidated.
detachNodes.PushBack(node)

// Reorg back to the parent of the block being invalidated.
// Nothing to attach so just pass an empty list.
err := b.reorganizeChain(detachNodes, list.New())
if err != nil {
return err
}

if writeErr := b.index.flushToDB(); writeErr != nil {
log.Warnf("Error flushing block index changes to disk: %v", writeErr)
}

// Grab all the tips.
tips := b.index.InactiveTips(b.bestChain)
tips = append(tips, b.bestChain.Tip())

// Here we'll check if the invalidation of the block in the active tip
// changes the status of the chain tips. If a side branch now has more
// worksum, it becomes the active chain tip.
var bestTip *blockNode
for _, tip := range tips {
// Skip invalid tips as they cannot become the active tip.
if tip.status.KnownInvalid() {
continue
}

// If we have no best tips, then set this tip as the best tip.
if bestTip == nil {
bestTip = tip
} else {
// If there is an existing best tip, then compare it
// against the current tip.
if tip.workSum.Cmp(bestTip.workSum) == 1 {
bestTip = tip
}
}
}

// Return if the best tip is the current tip.
if bestTip == b.bestChain.Tip() {
return nil
}

// Reorganize to the best tip if a side branch is now the most work tip.
detachNodes, attachNodes := b.getReorganizeNodes(bestTip)
err = b.reorganizeChain(detachNodes, attachNodes)

if writeErr := b.index.flushToDB(); writeErr != nil {
log.Warnf("Error flushing block index changes to disk: %v", writeErr)
}

return err
}

// IndexManager provides a generic interface that the is called when blocks are
// connected and disconnected to and from the tip of the main chain for the
// purpose of supporting optional indexes.
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