lbcd/blockchain/checkpoints.go
Dave Collins 20910511e9
blockchain: Refactor to use new chain view.
- Remove inMainChain from block nodes since that can now be efficiently
  determined by using the chain view
- Track the best chain via a chain view instead of a single block node
  - Use the tip of the best chain view everywhere bestNode was used
  - Update chain view tip instead of updating best node
- Change reorg logic to use more efficient chain view fork finding logic
- Change block locator code over to use more efficient chain view logic
  - Remove now unused block-index-based block locator code
  - Move BlockLocator definition to chain.go
  - Move BlockLocatorFromHash and LatestBlockLocator to chain.go
    - Update both to use more efficient chain view logic
- Rework IsCheckpointCandidate to use block index and chain view
- Optimize MainChainHasBlock to use chain view instead of hitting db
  - Move to chain.go since it no longer involves database I/O
  - Removed error return since it can no longer fail
- Optimize BlockHeightByHash to use chain view instead of hitting db
  - Move to chain.go since it no longer involves database I/O
  - Removed error return since it can no longer fail
- Optimize BlockHashByHeight to use chain view instead of hitting db
  - Move to chain.go since it no longer involves database I/O
  - Removed error return since it can no longer fail
- Optimize HeightRange to use chain view instead of hitting db
  - Move to chain.go since it no longer involves database I/O
- Optimize BlockByHeight to use chain view for main chain check
- Optimize BlockByHash to use chain view for main chain check
2017-08-23 23:43:37 -05:00

261 lines
8.8 KiB
Go

// Copyright (c) 2013-2016 The btcsuite developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
package blockchain
import (
"fmt"
"time"
"github.com/btcsuite/btcd/chaincfg"
"github.com/btcsuite/btcd/chaincfg/chainhash"
"github.com/btcsuite/btcd/txscript"
"github.com/btcsuite/btcutil"
)
// CheckpointConfirmations is the number of blocks before the end of the current
// best block chain that a good checkpoint candidate must be.
const CheckpointConfirmations = 2016
// newHashFromStr converts the passed big-endian hex string into a
// chainhash.Hash. It only differs from the one available in chainhash in that
// it ignores the error since it will only (and must only) be called with
// hard-coded, and therefore known good, hashes.
func newHashFromStr(hexStr string) *chainhash.Hash {
hash, _ := chainhash.NewHashFromStr(hexStr)
return hash
}
// Checkpoints returns a slice of checkpoints (regardless of whether they are
// already known). When there are no checkpoints for the chain, it will return
// nil.
//
// This function is safe for concurrent access.
func (b *BlockChain) Checkpoints() []chaincfg.Checkpoint {
return b.checkpoints
}
// HasCheckpoints returns whether this BlockChain has checkpoints defined.
//
// This function is safe for concurrent access.
func (b *BlockChain) HasCheckpoints() bool {
return len(b.checkpoints) > 0
}
// LatestCheckpoint returns the most recent checkpoint (regardless of whether it
// is already known). When there are no defined checkpoints for the active chain
// instance, it will return nil.
//
// This function is safe for concurrent access.
func (b *BlockChain) LatestCheckpoint() *chaincfg.Checkpoint {
if !b.HasCheckpoints() {
return nil
}
return &b.checkpoints[len(b.checkpoints)-1]
}
// verifyCheckpoint returns whether the passed block height and hash combination
// match the checkpoint data. It also returns true if there is no checkpoint
// data for the passed block height.
func (b *BlockChain) verifyCheckpoint(height int32, hash *chainhash.Hash) bool {
if !b.HasCheckpoints() {
return true
}
// Nothing to check if there is no checkpoint data for the block height.
checkpoint, exists := b.checkpointsByHeight[height]
if !exists {
return true
}
if !checkpoint.Hash.IsEqual(hash) {
return false
}
log.Infof("Verified checkpoint at height %d/block %s", checkpoint.Height,
checkpoint.Hash)
return true
}
// findPreviousCheckpoint finds the most recent checkpoint that is already
// available in the downloaded portion of the block chain and returns the
// associated block node. It returns nil if a checkpoint can't be found (this
// should really only happen for blocks before the first checkpoint).
//
// This function MUST be called with the chain lock held (for reads).
func (b *BlockChain) findPreviousCheckpoint() (*blockNode, error) {
if !b.HasCheckpoints() {
return nil, nil
}
// Perform the initial search to find and cache the latest known
// checkpoint if the best chain is not known yet or we haven't already
// previously searched.
checkpoints := b.checkpoints
numCheckpoints := len(checkpoints)
if b.checkpointNode == nil && b.nextCheckpoint == nil {
// Loop backwards through the available checkpoints to find one
// that is already available.
for i := numCheckpoints - 1; i >= 0; i-- {
node := b.index.LookupNode(checkpoints[i].Hash)
if node == nil || !b.bestChain.Contains(node) {
continue
}
// Checkpoint found. Cache it for future lookups and
// set the next expected checkpoint accordingly.
b.checkpointNode = node
if i < numCheckpoints-1 {
b.nextCheckpoint = &checkpoints[i+1]
}
return b.checkpointNode, nil
}
// No known latest checkpoint. This will only happen on blocks
// before the first known checkpoint. So, set the next expected
// checkpoint to the first checkpoint and return the fact there
// is no latest known checkpoint block.
b.nextCheckpoint = &checkpoints[0]
return nil, nil
}
// At this point we've already searched for the latest known checkpoint,
// so when there is no next checkpoint, the current checkpoint lockin
// will always be the latest known checkpoint.
if b.nextCheckpoint == nil {
return b.checkpointNode, nil
}
// When there is a next checkpoint and the height of the current best
// chain does not exceed it, the current checkpoint lockin is still
// the latest known checkpoint.
if b.bestChain.Tip().height < b.nextCheckpoint.Height {
return b.checkpointNode, nil
}
// We've reached or exceeded the next checkpoint height. Note that
// once a checkpoint lockin has been reached, forks are prevented from
// any blocks before the checkpoint, so we don't have to worry about the
// checkpoint going away out from under us due to a chain reorganize.
// Cache the latest known checkpoint for future lookups. Note that if
// this lookup fails something is very wrong since the chain has already
// passed the checkpoint which was verified as accurate before inserting
// it.
checkpointNode := b.index.LookupNode(b.nextCheckpoint.Hash)
if checkpointNode == nil {
return nil, AssertError(fmt.Sprintf("findPreviousCheckpoint "+
"failed lookup of known good block node %s",
b.nextCheckpoint.Hash))
}
b.checkpointNode = checkpointNode
// Set the next expected checkpoint.
checkpointIndex := -1
for i := numCheckpoints - 1; i >= 0; i-- {
if checkpoints[i].Hash.IsEqual(b.nextCheckpoint.Hash) {
checkpointIndex = i
break
}
}
b.nextCheckpoint = nil
if checkpointIndex != -1 && checkpointIndex < numCheckpoints-1 {
b.nextCheckpoint = &checkpoints[checkpointIndex+1]
}
return b.checkpointNode, nil
}
// isNonstandardTransaction determines whether a transaction contains any
// scripts which are not one of the standard types.
func isNonstandardTransaction(tx *btcutil.Tx) bool {
// Check all of the output public key scripts for non-standard scripts.
for _, txOut := range tx.MsgTx().TxOut {
scriptClass := txscript.GetScriptClass(txOut.PkScript)
if scriptClass == txscript.NonStandardTy {
return true
}
}
return false
}
// IsCheckpointCandidate returns whether or not the passed block is a good
// checkpoint candidate.
//
// The factors used to determine a good checkpoint are:
// - The block must be in the main chain
// - The block must be at least 'CheckpointConfirmations' blocks prior to the
// current end of the main chain
// - The timestamps for the blocks before and after the checkpoint must have
// timestamps which are also before and after the checkpoint, respectively
// (due to the median time allowance this is not always the case)
// - The block must not contain any strange transaction such as those with
// nonstandard scripts
//
// The intent is that candidates are reviewed by a developer to make the final
// decision and then manually added to the list of checkpoints for a network.
//
// This function is safe for concurrent access.
func (b *BlockChain) IsCheckpointCandidate(block *btcutil.Block) (bool, error) {
b.chainLock.RLock()
defer b.chainLock.RUnlock()
// A checkpoint must be in the main chain.
node := b.index.LookupNode(block.Hash())
if node == nil || !b.bestChain.Contains(node) {
return false, nil
}
// Ensure the height of the passed block and the entry for the block in
// the main chain match. This should always be the case unless the
// caller provided an invalid block.
if node.height != block.Height() {
return false, fmt.Errorf("passed block height of %d does not "+
"match the main chain height of %d", block.Height(),
node.height)
}
// A checkpoint must be at least CheckpointConfirmations blocks
// before the end of the main chain.
mainChainHeight := b.bestChain.Tip().height
if node.height > (mainChainHeight - CheckpointConfirmations) {
return false, nil
}
// A checkpoint must be have at least one block after it.
//
// This should always succeed since the check above already made sure it
// is CheckpointConfirmations back, but be safe in case the constant
// changes.
nextNode := b.bestChain.Next(node)
if nextNode == nil {
return false, nil
}
// A checkpoint must be have at least one block before it.
if node.parent == nil {
return false, nil
}
// A checkpoint must have timestamps for the block and the blocks on
// either side of it in order (due to the median time allowance this is
// not always the case).
prevTime := time.Unix(node.parent.timestamp, 0)
curTime := block.MsgBlock().Header.Timestamp
nextTime := time.Unix(nextNode.timestamp, 0)
if prevTime.After(curTime) || nextTime.Before(curTime) {
return false, nil
}
// A checkpoint must have transactions that only contain standard
// scripts.
for _, tx := range block.Transactions() {
if isNonstandardTransaction(tx) {
return false, nil
}
}
// All of the checks passed, so the block is a candidate.
return true, nil
}