// connectBlock handles connecting the passed node/block to the end of the main
// (best) chain.
func (b *BlockChain) connectBlock(node *blockNode, block *btcutil.Block) error {
// Make sure it's extending the end of the best chain.
prevHash := &block.MsgBlock().Header.PrevBlock
if b.bestChain != nil && !prevHash.IsEqual(b.bestChain.hash) {
return fmt.Errorf("connectBlock must be called with a block " +
"that extends the main chain")
}
// Insert the block into the database which houses the main chain.
_, err := b.db.InsertBlock(block)
if err != nil {
return err
}
// Add the new node to the memory main chain indices for faster
// lookups.
node.inMainChain = true
b.index[*node.hash] = node
b.depNodes[*prevHash] = append(b.depNodes[*prevHash], node)
// This node is now the end of the best chain.
b.bestChain = node
// Notify the caller that the block was connected to the main chain.
// The caller would typically want to react with actions such as
// updating wallets.
b.sendNotification(NTBlockConnected, block)
return nil
}
// checkProofOfWork ensures the block header bits which indicate the target
// difficulty is in min/max range and that the block hash is less than the
// target difficulty as claimed.
//
//
// The flags modify the behavior of this function as follows:
// - BFNoPoWCheck: The check to ensure the block hash is less than the target
// difficulty is not performed.
func checkProofOfWork(block *btcutil.Block, powLimit *big.Int, flags BehaviorFlags) error {
// The target difficulty must be larger than zero.
target := CompactToBig(block.MsgBlock().Header.Bits)
if target.Sign() <= 0 {
str := fmt.Sprintf("block target difficulty of %064x is too low",
target)
return ruleError(ErrUnexpectedDifficulty, str)
}
// The target difficulty must be less than the maximum allowed.
if target.Cmp(powLimit) > 0 {
str := fmt.Sprintf("block target difficulty of %064x is "+
"higher than max of %064x", target, powLimit)
return ruleError(ErrUnexpectedDifficulty, str)
}
// The block hash must be less than the claimed target unless the flag
// to avoid proof of work checks is set.
if flags&BFNoPoWCheck != BFNoPoWCheck {
// The block hash must be less than the claimed target.
blockHash, err := block.Sha()
if err != nil {
return err
}
hashNum := ShaHashToBig(blockHash)
if hashNum.Cmp(target) > 0 {
str := fmt.Sprintf("block hash of %064x is higher than "+
"expected max of %064x", hashNum, target)
return ruleError(ErrHighHash, str)
}
}
return nil
}
// CheckConnectBlock performs several checks to confirm connecting the passed
// block to the main chain does not violate any rules. An example of some of
// the checks performed are ensuring connecting the block would not cause any
// duplicate transaction hashes for old transactions that aren't already fully
// spent, double spends, exceeding the maximum allowed signature operations
// per block, invalid values in relation to the expected block subsidy, or fail
// transaction script validation.
//
// This function is NOT safe for concurrent access.
func (b *BlockChain) CheckConnectBlock(block *btcutil.Block) error {
prevNode := b.bestChain
blockSha, _ := block.Sha()
newNode := newBlockNode(&block.MsgBlock().Header, blockSha, block.Height())
if prevNode != nil {
newNode.parent = prevNode
newNode.workSum.Add(prevNode.workSum, newNode.workSum)
}
return b.checkConnectBlock(newNode, block)
}
// DropAfterBlockBySha will remove any blocks from the database after
// the given block.
func (db *LevelDb) DropAfterBlockBySha(sha *btcwire.ShaHash) (rerr error) {
db.dbLock.Lock()
defer db.dbLock.Unlock()
defer func() {
if rerr == nil {
rerr = db.processBatches()
} else {
db.lBatch().Reset()
}
}()
startheight := db.nextBlock - 1
keepidx, err := db.getBlkLoc(sha)
if err != nil {
// should the error here be normalized ?
log.Tracef("block loc failed %v ", sha)
return err
}
for height := startheight; height > keepidx; height = height - 1 {
var blk *btcutil.Block
blksha, buf, err := db.getBlkByHeight(height)
if err != nil {
return err
}
blk, err = btcutil.NewBlockFromBytes(buf)
if err != nil {
return err
}
for _, tx := range blk.MsgBlock().Transactions {
err = db.unSpend(tx)
if err != nil {
return err
}
}
// rather than iterate the list of tx backward, do it twice.
for _, tx := range blk.Transactions() {
var txUo txUpdateObj
txUo.delete = true
db.txUpdateMap[*tx.Sha()] = &txUo
}
db.lBatch().Delete(shaBlkToKey(blksha))
db.lBatch().Delete(int64ToKey(height))
}
db.nextBlock = keepidx + 1
return nil
}
// addOrphanBlock adds the passed block (which is already determined to be
// an orphan prior calling this function) to the orphan pool. It lazily cleans
// up any expired blocks so a separate cleanup poller doesn't need to be run.
// It also imposes a maximum limit on the number of outstanding orphan
// blocks and will remove the oldest received orphan block if the limit is
// exceeded.
func (b *BlockChain) addOrphanBlock(block *btcutil.Block) {
// Remove expired orphan blocks.
for _, oBlock := range b.orphans {
if time.Now().After(oBlock.expiration) {
b.removeOrphanBlock(oBlock)
continue
}
// Update the oldest orphan block pointer so it can be discarded
// in case the orphan pool fills up.
if b.oldestOrphan == nil || oBlock.expiration.Before(b.oldestOrphan.expiration) {
b.oldestOrphan = oBlock
}
}
// Limit orphan blocks to prevent memory exhaustion.
if len(b.orphans)+1 > maxOrphanBlocks {
// Remove the oldest orphan to make room for the new one.
b.removeOrphanBlock(b.oldestOrphan)
b.oldestOrphan = nil
}
// Get the block sha. It is safe to ignore the error here since any
// errors would've been caught prior to calling this function.
blockSha, _ := block.Sha()
// Protect concurrent access. This is intentionally done here instead
// of near the top since removeOrphanBlock does its own locking and
// the range iterator is not invalidated by removing map entries.
b.orphanLock.Lock()
defer b.orphanLock.Unlock()
// Insert the block into the orphan map with an expiration time
// 1 hour from now.
expiration := time.Now().Add(time.Hour)
oBlock := &orphanBlock{
block: block,
expiration: expiration,
}
b.orphans[*blockSha] = oBlock
// Add to previous hash lookup index for faster dependency lookups.
prevHash := &block.MsgBlock().Header.PrevBlock
b.prevOrphans[*prevHash] = append(b.prevOrphans[*prevHash], oBlock)
return
}
// getPrevNodeFromBlock returns a block node for the block previous to the
// passed block (the passed block's parent). When it is already in the memory
// block chain, it simply returns it. Otherwise, it loads the previous block
// from the block database, creates a new block node from it, and returns it.
// The returned node will be nil if the genesis block is passed.
func (b *BlockChain) getPrevNodeFromBlock(block *btcutil.Block) (*blockNode, error) {
// Genesis block.
prevHash := &block.MsgBlock().Header.PrevBlock
if prevHash.IsEqual(zeroHash) {
return nil, nil
}
// Return the existing previous block node if it's already there.
if bn, ok := b.index[*prevHash]; ok {
return bn, nil
}
// Dynamically load the previous block from the block database, create
// a new block node for it, and update the memory chain accordingly.
prevBlockNode, err := b.loadBlockNode(prevHash)
if err != nil {
return nil, err
}
return prevBlockNode, nil
}
// checkBlockScripts executes and validates the scripts for all transactions in
// the passed block.
func checkBlockScripts(block *btcutil.Block, txStore TxStore) error {
// Setup the script validation flags. Blocks created after the BIP0016
// activation time need to have the pay-to-script-hash checks enabled.
var flags txscript.ScriptFlags
if block.MsgBlock().Header.Timestamp.After(txscript.Bip16Activation) {
flags |= txscript.ScriptBip16
}
// Collect all of the transaction inputs and required information for
// validation for all transactions in the block into a single slice.
numInputs := 0
for _, tx := range block.Transactions() {
numInputs += len(tx.MsgTx().TxIn)
}
txValItems := make([]*txValidateItem, 0, numInputs)
for _, tx := range block.Transactions() {
for txInIdx, txIn := range tx.MsgTx().TxIn {
// Skip coinbases.
if txIn.PreviousOutPoint.Index == math.MaxUint32 {
continue
}
txVI := &txValidateItem{
txInIndex: txInIdx,
txIn: txIn,
tx: tx,
}
txValItems = append(txValItems, txVI)
}
}
// Validate all of the inputs.
validator := newTxValidator(txStore, flags)
if err := validator.Validate(txValItems); err != nil {
return err
}
return nil
}
// ProcessBlock is the main workhorse for handling insertion of new blocks into
// the block chain. It includes functionality such as rejecting duplicate
// blocks, ensuring blocks follow all rules, orphan handling, and insertion into
// the block chain along with best chain selection and reorganization.
//
// It returns a bool which indicates whether or not the block is an orphan and
// any errors that occurred during processing. The returned bool is only valid
// when the error is nil.
func (b *BlockChain) ProcessBlock(block *btcutil.Block, timeSource MedianTimeSource, flags BehaviorFlags) (bool, error) {
fastAdd := flags&BFFastAdd == BFFastAdd
dryRun := flags&BFDryRun == BFDryRun
blockHash, err := block.Sha()
if err != nil {
return false, err
}
log.Tracef("Processing block %v", blockHash)
// The block must not already exist in the main chain or side chains.
exists, err := b.blockExists(blockHash)
if err != nil {
return false, err
}
if exists {
str := fmt.Sprintf("already have block %v", blockHash)
return false, ruleError(ErrDuplicateBlock, str)
}
// The block must not already exist as an orphan.
if _, exists := b.orphans[*blockHash]; exists {
str := fmt.Sprintf("already have block (orphan) %v", blockHash)
return false, ruleError(ErrDuplicateBlock, str)
}
// Perform preliminary sanity checks on the block and its transactions.
err = checkBlockSanity(block, b.netParams.PowLimit, timeSource, flags)
if err != nil {
return false, err
}
// Find the previous checkpoint and perform some additional checks based
// on the checkpoint. This provides a few nice properties such as
// preventing old side chain blocks before the last checkpoint,
// rejecting easy to mine, but otherwise bogus, blocks that could be
// used to eat memory, and ensuring expected (versus claimed) proof of
// work requirements since the previous checkpoint are met.
blockHeader := &block.MsgBlock().Header
checkpointBlock, err := b.findPreviousCheckpoint()
if err != nil {
return false, err
}
if checkpointBlock != nil {
// Ensure the block timestamp is after the checkpoint timestamp.
checkpointHeader := &checkpointBlock.MsgBlock().Header
checkpointTime := checkpointHeader.Timestamp
if blockHeader.Timestamp.Before(checkpointTime) {
str := fmt.Sprintf("block %v has timestamp %v before "+
"last checkpoint timestamp %v", blockHash,
blockHeader.Timestamp, checkpointTime)
return false, ruleError(ErrCheckpointTimeTooOld, str)
}
if !fastAdd {
// Even though the checks prior to now have already ensured the
// proof of work exceeds the claimed amount, the claimed amount
// is a field in the block header which could be forged. This
// check ensures the proof of work is at least the minimum
// expected based on elapsed time since the last checkpoint and
// maximum adjustment allowed by the retarget rules.
duration := blockHeader.Timestamp.Sub(checkpointTime)
requiredTarget := CompactToBig(b.calcEasiestDifficulty(
checkpointHeader.Bits, duration))
currentTarget := CompactToBig(blockHeader.Bits)
if currentTarget.Cmp(requiredTarget) > 0 {
str := fmt.Sprintf("block target difficulty of %064x "+
"is too low when compared to the previous "+
"checkpoint", currentTarget)
return false, ruleError(ErrDifficultyTooLow, str)
}
}
}
// Handle orphan blocks.
prevHash := &blockHeader.PrevBlock
if !prevHash.IsEqual(zeroHash) {
prevHashExists, err := b.blockExists(prevHash)
if err != nil {
return false, err
}
if !prevHashExists {
if !dryRun {
log.Infof("Adding orphan block %v with parent %v",
blockHash, prevHash)
b.addOrphanBlock(block)
}
return true, nil
}
}
// The block has passed all context independent checks and appears sane
// enough to potentially accept it into the block chain.
err = b.maybeAcceptBlock(block, flags)
if err != nil {
return false, err
}
// Don't process any orphans or log when the dry run flag is set.
if !dryRun {
// Accept any orphan blocks that depend on this block (they are
// no longer orphans) and repeat for those accepted blocks until
// there are no more.
err := b.processOrphans(blockHash, flags)
if err != nil {
return false, err
}
log.Debugf("Accepted block %v", blockHash)
}
return false, nil
}
// 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.
func (b *BlockChain) IsCheckpointCandidate(block *btcutil.Block) (bool, error) {
// Checkpoints must be enabled.
if b.noCheckpoints {
return false, fmt.Errorf("checkpoints are disabled")
}
blockHash, err := block.Sha()
if err != nil {
return false, err
}
// A checkpoint must be in the main chain.
exists, err := b.db.ExistsSha(blockHash)
if err != nil {
return false, err
}
if !exists {
return false, nil
}
// A checkpoint must be at least CheckpointConfirmations blocks before
// the end of the main chain.
blockHeight := block.Height()
_, mainChainHeight, err := b.db.NewestSha()
if err != nil {
return false, err
}
if blockHeight > (mainChainHeight - CheckpointConfirmations) {
return false, nil
}
// Get the previous block.
prevHash := &block.MsgBlock().Header.PrevBlock
prevBlock, err := b.db.FetchBlockBySha(prevHash)
if err != nil {
return false, err
}
// Get the next block.
nextHash, err := b.db.FetchBlockShaByHeight(blockHeight + 1)
if err != nil {
return false, err
}
nextBlock, err := b.db.FetchBlockBySha(nextHash)
if err != nil {
return false, err
}
// 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 := prevBlock.MsgBlock().Header.Timestamp
curTime := block.MsgBlock().Header.Timestamp
nextTime := nextBlock.MsgBlock().Header.Timestamp
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
}
}
return true, nil
}
// checkBlockSanity performs some preliminary checks on a block to ensure it is
// sane before continuing with block processing. These checks are context free.
//
// The flags do not modify the behavior of this function directly, however they
// are needed to pass along to checkProofOfWork.
func checkBlockSanity(block *btcutil.Block, powLimit *big.Int, timeSource MedianTimeSource, flags BehaviorFlags) error {
// A block must have at least one transaction.
msgBlock := block.MsgBlock()
numTx := len(msgBlock.Transactions)
if numTx == 0 {
return ruleError(ErrNoTransactions, "block does not contain "+
"any transactions")
}
// A block must not have more transactions than the max block payload.
if numTx > btcwire.MaxBlockPayload {
str := fmt.Sprintf("block contains too many transactions - "+
"got %d, max %d", numTx, btcwire.MaxBlockPayload)
return ruleError(ErrTooManyTransactions, str)
}
// A block must not exceed the maximum allowed block payload when
// serialized.
serializedSize := msgBlock.SerializeSize()
if serializedSize > btcwire.MaxBlockPayload {
str := fmt.Sprintf("serialized block is too big - got %d, "+
"max %d", serializedSize, btcwire.MaxBlockPayload)
return ruleError(ErrBlockTooBig, str)
}
// Ensure the proof of work bits in the block header is in min/max range
// and the block hash is less than the target value described by the
// bits.
err := checkProofOfWork(block, powLimit, flags)
if err != nil {
return err
}
// A block timestamp must not have a greater precision than one second.
// This check is necessary because Go time.Time values support
// nanosecond precision whereas the consensus rules only apply to
// seconds and it's much nicer to deal with standard Go time values
// instead of converting to seconds everywhere.
header := &block.MsgBlock().Header
if !header.Timestamp.Equal(time.Unix(header.Timestamp.Unix(), 0)) {
str := fmt.Sprintf("block timestamp of %v has a higher "+
"precision than one second", header.Timestamp)
return ruleError(ErrInvalidTime, str)
}
// Ensure the block time is not too far in the future.
maxTimestamp := timeSource.AdjustedTime().Add(time.Second *
MaxTimeOffsetSeconds)
if header.Timestamp.After(maxTimestamp) {
str := fmt.Sprintf("block timestamp of %v is too far in the "+
"future", header.Timestamp)
return ruleError(ErrTimeTooNew, str)
}
// The first transaction in a block must be a coinbase.
transactions := block.Transactions()
if !IsCoinBase(transactions[0]) {
return ruleError(ErrFirstTxNotCoinbase, "first transaction in "+
"block is not a coinbase")
}
// A block must not have more than one coinbase.
for i, tx := range transactions[1:] {
if IsCoinBase(tx) {
str := fmt.Sprintf("block contains second coinbase at "+
"index %d", i)
return ruleError(ErrMultipleCoinbases, str)
}
}
// Do some preliminary checks on each transaction to ensure they are
// sane before continuing.
for _, tx := range transactions {
err := CheckTransactionSanity(tx)
if err != nil {
return err
}
}
// Build merkle tree and ensure the calculated merkle root matches the
// entry in the block header. This also has the effect of caching all
// of the transaction hashes in the block to speed up future hash
// checks. Bitcoind builds the tree here and checks the merkle root
// after the following checks, but there is no reason not to check the
// merkle root matches here.
merkles := BuildMerkleTreeStore(block.Transactions())
calculatedMerkleRoot := merkles[len(merkles)-1]
if !header.MerkleRoot.IsEqual(calculatedMerkleRoot) {
str := fmt.Sprintf("block merkle root is invalid - block "+
"header indicates %v, but calculated value is %v",
header.MerkleRoot, calculatedMerkleRoot)
return ruleError(ErrBadMerkleRoot, str)
}
// Check for duplicate transactions. This check will be fairly quick
// since the transaction hashes are already cached due to building the
// merkle tree above.
existingTxHashes := make(map[btcwire.ShaHash]struct{})
for _, tx := range transactions {
hash := tx.Sha()
if _, exists := existingTxHashes[*hash]; exists {
str := fmt.Sprintf("block contains duplicate "+
"transaction %v", hash)
return ruleError(ErrDuplicateTx, str)
}
existingTxHashes[*hash] = struct{}{}
}
// The number of signature operations must be less than the maximum
// allowed per block.
totalSigOps := 0
for _, tx := range transactions {
// We could potentially overflow the accumulator so check for
// overflow.
lastSigOps := totalSigOps
totalSigOps += CountSigOps(tx)
if totalSigOps < lastSigOps || totalSigOps > MaxSigOpsPerBlock {
str := fmt.Sprintf("block contains too many signature "+
"operations - got %v, max %v", totalSigOps,
MaxSigOpsPerBlock)
return ruleError(ErrTooManySigOps, str)
}
}
return nil
}
// InsertBlock inserts raw block and transaction data from a block into the
// database. The first block inserted into the database will be treated as the
// genesis block. Every subsequent block insert requires the referenced parent
// block to already exist.
func (db *LevelDb) InsertBlock(block *btcutil.Block) (height int64, rerr error) {
db.dbLock.Lock()
defer db.dbLock.Unlock()
defer func() {
if rerr == nil {
rerr = db.processBatches()
} else {
db.lBatch().Reset()
}
}()
blocksha, err := block.Sha()
if err != nil {
log.Warnf("Failed to compute block sha %v", blocksha)
return 0, err
}
mblock := block.MsgBlock()
rawMsg, err := block.Bytes()
if err != nil {
log.Warnf("Failed to obtain raw block sha %v", blocksha)
return 0, err
}
txloc, err := block.TxLoc()
if err != nil {
log.Warnf("Failed to obtain raw block sha %v", blocksha)
return 0, err
}
// Insert block into database
newheight, err := db.insertBlockData(blocksha, &mblock.Header.PrevBlock,
rawMsg)
if err != nil {
log.Warnf("Failed to insert block %v %v %v", blocksha,
&mblock.Header.PrevBlock, err)
return 0, err
}
// At least two blocks in the long past were generated by faulty
// miners, the sha of the transaction exists in a previous block,
// detect this condition and 'accept' the block.
for txidx, tx := range mblock.Transactions {
txsha, err := block.TxSha(txidx)
if err != nil {
log.Warnf("failed to compute tx name block %v idx %v err %v", blocksha, txidx, err)
return 0, err
}
spentbuflen := (len(tx.TxOut) + 7) / 8
spentbuf := make([]byte, spentbuflen, spentbuflen)
if len(tx.TxOut)%8 != 0 {
for i := uint(len(tx.TxOut) % 8); i < 8; i++ {
spentbuf[spentbuflen-1] |= (byte(1) << i)
}
}
err = db.insertTx(txsha, newheight, txloc[txidx].TxStart, txloc[txidx].TxLen, spentbuf)
if err != nil {
log.Warnf("block %v idx %v failed to insert tx %v %v err %v", blocksha, newheight, &txsha, txidx, err)
return 0, err
}
// Some old blocks contain duplicate transactions
// Attempt to cleanly bypass this problem by marking the
// first as fully spent.
// http://blockexplorer.com/b/91812 dup in 91842
// http://blockexplorer.com/b/91722 dup in 91880
if newheight == 91812 {
dupsha, err := btcwire.NewShaHashFromStr("d5d27987d2a3dfc724e359870c6644b40e497bdc0589a033220fe15429d88599")
if err != nil {
panic("invalid sha string in source")
}
if txsha.IsEqual(dupsha) {
// marking TxOut[0] as spent
po := btcwire.NewOutPoint(dupsha, 0)
txI := btcwire.NewTxIn(po, []byte("garbage"))
var spendtx btcwire.MsgTx
spendtx.AddTxIn(txI)
err = db.doSpend(&spendtx)
if err != nil {
log.Warnf("block %v idx %v failed to spend tx %v %v err %v", blocksha, newheight, &txsha, txidx, err)
}
}
}
if newheight == 91722 {
dupsha, err := btcwire.NewShaHashFromStr("e3bf3d07d4b0375638d5f1db5255fe07ba2c4cb067cd81b84ee974b6585fb468")
if err != nil {
panic("invalid sha string in source")
}
if txsha.IsEqual(dupsha) {
// marking TxOut[0] as spent
po := btcwire.NewOutPoint(dupsha, 0)
txI := btcwire.NewTxIn(po, []byte("garbage"))
var spendtx btcwire.MsgTx
spendtx.AddTxIn(txI)
err = db.doSpend(&spendtx)
if err != nil {
log.Warnf("block %v idx %v failed to spend tx %v %v err %v", blocksha, newheight, &txsha, txidx, err)
}
}
}
err = db.doSpend(tx)
if err != nil {
log.Warnf("block %v idx %v failed to spend tx %v %v err %v", blocksha, newheight, txsha, txidx, err)
return 0, err
}
}
return newheight, nil
}
// InsertBlock inserts raw block and transaction data from a block into the
// database. The first block inserted into the database will be treated as the
// genesis block. Every subsequent block insert requires the referenced parent
// block to already exist. This is part of the database.Db interface
// implementation.
func (db *MemDb) InsertBlock(block *btcutil.Block) (int64, error) {
db.Lock()
defer db.Unlock()
if db.closed {
return 0, ErrDbClosed
}
blockHash, err := block.Sha()
if err != nil {
return 0, err
}
// Reject the insert if the previously reference block does not exist
// except in the case there are no blocks inserted yet where the first
// inserted block is assumed to be a genesis block.
msgBlock := block.MsgBlock()
if _, exists := db.blocksBySha[msgBlock.Header.PrevBlock]; !exists {
if len(db.blocks) > 0 {
return 0, database.ErrPrevShaMissing
}
}
// Build a map of in-flight transactions because some of the inputs in
// this block could be referencing other transactions earlier in this
// block which are not yet in the chain.
txInFlight := map[btcwire.ShaHash]int{}
transactions := block.Transactions()
for i, tx := range transactions {
txInFlight[*tx.Sha()] = i
}
// Loop through all transactions and inputs to ensure there are no error
// conditions that would prevent them from be inserted into the db.
// Although these checks could could be done in the loop below, checking
// for error conditions up front means the code below doesn't have to
// deal with rollback on errors.
newHeight := int64(len(db.blocks))
for i, tx := range transactions {
// Two old blocks contain duplicate transactions due to being
// mined by faulty miners and accepted by the origin Satoshi
// client. Rules have since been added to the ensure this
// problem can no longer happen, but the two duplicate
// transactions which were originally accepted are forever in
// the block chain history and must be dealth with specially.
// http://blockexplorer.com/b/91842
// http://blockexplorer.com/b/91880
if newHeight == 91842 && tx.Sha().IsEqual(dupTxHash91842) {
continue
}
if newHeight == 91880 && tx.Sha().IsEqual(dupTxHash91880) {
continue
}
for _, txIn := range tx.MsgTx().TxIn {
if isCoinbaseInput(txIn) {
continue
}
// It is acceptable for a transaction input to reference
// the output of another transaction in this block only
// if the referenced transaction comes before the
// current one in this block.
prevOut := &txIn.PreviousOutPoint
if inFlightIndex, ok := txInFlight[prevOut.Hash]; ok {
if i <= inFlightIndex {
log.Warnf("InsertBlock: requested hash "+
" of %s does not exist in-flight",
tx.Sha())
return 0, database.ErrTxShaMissing
}
} else {
originTxns, exists := db.txns[prevOut.Hash]
if !exists {
log.Warnf("InsertBlock: requested hash "+
"of %s by %s does not exist",
prevOut.Hash, tx.Sha())
return 0, database.ErrTxShaMissing
}
originTxD := originTxns[len(originTxns)-1]
if prevOut.Index > uint32(len(originTxD.spentBuf)) {
log.Warnf("InsertBlock: requested hash "+
"of %s with index %d does not "+
"exist", tx.Sha(), prevOut.Index)
return 0, database.ErrTxShaMissing
}
}
}
// Prevent duplicate transactions in the same block.
if inFlightIndex, exists := txInFlight[*tx.Sha()]; exists &&
inFlightIndex < i {
log.Warnf("Block contains duplicate transaction %s",
tx.Sha())
return 0, database.ErrDuplicateSha
}
// Prevent duplicate transactions unless the old one is fully
// spent.
if txns, exists := db.txns[*tx.Sha()]; exists {
txD := txns[len(txns)-1]
if !isFullySpent(txD) {
log.Warnf("Attempt to insert duplicate "+
"transaction %s", tx.Sha())
return 0, database.ErrDuplicateSha
}
}
}
db.blocks = append(db.blocks, msgBlock)
db.blocksBySha[*blockHash] = newHeight
// Insert information about eacj transaction and spend all of the
// outputs referenced by the inputs to the transactions.
for i, tx := range block.Transactions() {
// Insert the transaction data.
txD := tTxInsertData{
blockHeight: newHeight,
offset: i,
spentBuf: make([]bool, len(tx.MsgTx().TxOut)),
}
db.txns[*tx.Sha()] = append(db.txns[*tx.Sha()], &txD)
// Spend all of the inputs.
for _, txIn := range tx.MsgTx().TxIn {
// Coinbase transaction has no inputs.
if isCoinbaseInput(txIn) {
continue
}
// Already checked for existing and valid ranges above.
prevOut := &txIn.PreviousOutPoint
originTxns := db.txns[prevOut.Hash]
originTxD := originTxns[len(originTxns)-1]
originTxD.spentBuf[prevOut.Index] = true
}
}
return newHeight, nil
}
// maybeAcceptBlock potentially accepts a block into the memory block chain.
// It performs several validation checks which depend on its position within
// the block chain before adding it. The block is expected to have already gone
// through ProcessBlock before calling this function with it.
//
// The flags modify the behavior of this function as follows:
// - BFFastAdd: The somewhat expensive BIP0034 validation is not performed.
// - BFDryRun: The memory chain index will not be pruned and no accept
// notification will be sent since the block is not being accepted.
func (b *BlockChain) maybeAcceptBlock(block *btcutil.Block, flags BehaviorFlags) error {
fastAdd := flags&BFFastAdd == BFFastAdd
dryRun := flags&BFDryRun == BFDryRun
// Get a block node for the block previous to this one. Will be nil
// if this is the genesis block.
prevNode, err := b.getPrevNodeFromBlock(block)
if err != nil {
log.Errorf("getPrevNodeFromBlock: %v", err)
return err
}
// The height of this block is one more than the referenced previous
// block.
blockHeight := int64(0)
if prevNode != nil {
blockHeight = prevNode.height + 1
}
block.SetHeight(blockHeight)
blockHeader := &block.MsgBlock().Header
if !fastAdd {
// Ensure the difficulty specified in the block header matches
// the calculated difficulty based on the previous block and
// difficulty retarget rules.
expectedDifficulty, err := b.calcNextRequiredDifficulty(prevNode,
block.MsgBlock().Header.Timestamp)
if err != nil {
return err
}
blockDifficulty := blockHeader.Bits
if blockDifficulty != expectedDifficulty {
str := "block difficulty of %d is not the expected value of %d"
str = fmt.Sprintf(str, blockDifficulty, expectedDifficulty)
return ruleError(ErrUnexpectedDifficulty, str)
}
// Ensure the timestamp for the block header is after the
// median time of the last several blocks (medianTimeBlocks).
medianTime, err := b.calcPastMedianTime(prevNode)
if err != nil {
log.Errorf("calcPastMedianTime: %v", err)
return err
}
if !blockHeader.Timestamp.After(medianTime) {
str := "block timestamp of %v is not after expected %v"
str = fmt.Sprintf(str, blockHeader.Timestamp,
medianTime)
return ruleError(ErrTimeTooOld, str)
}
// Ensure all transactions in the block are finalized.
for _, tx := range block.Transactions() {
if !IsFinalizedTransaction(tx, blockHeight,
blockHeader.Timestamp) {
str := fmt.Sprintf("block contains "+
"unfinalized transaction %v", tx.Sha())
return ruleError(ErrUnfinalizedTx, str)
}
}
}
// Ensure chain matches up to predetermined checkpoints.
// It's safe to ignore the error on Sha since it's already cached.
blockHash, _ := block.Sha()
if !b.verifyCheckpoint(blockHeight, blockHash) {
str := fmt.Sprintf("block at height %d does not match "+
"checkpoint hash", blockHeight)
return ruleError(ErrBadCheckpoint, str)
}
// Find the previous checkpoint and prevent blocks which fork the main
// chain before it. This prevents storage of new, otherwise valid,
// blocks which build off of old blocks that are likely at a much easier
// difficulty and therefore could be used to waste cache and disk space.
checkpointBlock, err := b.findPreviousCheckpoint()
if err != nil {
return err
}
if checkpointBlock != nil && blockHeight < checkpointBlock.Height() {
str := fmt.Sprintf("block at height %d forks the main chain "+
"before the previous checkpoint at height %d",
blockHeight, checkpointBlock.Height())
return ruleError(ErrForkTooOld, str)
}
if !fastAdd {
// Reject version 1 blocks once a majority of the network has
// upgraded. This is part of BIP0034.
if blockHeader.Version < 2 {
if b.isMajorityVersion(2, prevNode,
b.netParams.BlockV1RejectNumRequired,
b.netParams.BlockV1RejectNumToCheck) {
str := "new blocks with version %d are no " +
"longer valid"
str = fmt.Sprintf(str, blockHeader.Version)
return ruleError(ErrBlockVersionTooOld, str)
}
}
// Ensure coinbase starts with serialized block heights for
// blocks whose version is the serializedHeightVersion or
// newer once a majority of the network has upgraded. This is
// part of BIP0034.
if blockHeader.Version >= serializedHeightVersion {
if b.isMajorityVersion(serializedHeightVersion,
prevNode,
b.netParams.CoinbaseBlockHeightNumRequired,
b.netParams.CoinbaseBlockHeightNumToCheck) {
expectedHeight := int64(0)
if prevNode != nil {
expectedHeight = prevNode.height + 1
}
coinbaseTx := block.Transactions()[0]
err := checkSerializedHeight(coinbaseTx,
expectedHeight)
if err != nil {
return err
}
}
}
}
// Prune block nodes which are no longer needed before creating
// a new node.
if !dryRun {
err = b.pruneBlockNodes()
if err != nil {
return err
}
}
// Create a new block node for the block and add it to the in-memory
// block chain (could be either a side chain or the main chain).
newNode := newBlockNode(blockHeader, blockHash, blockHeight)
if prevNode != nil {
newNode.parent = prevNode
newNode.height = blockHeight
newNode.workSum.Add(prevNode.workSum, newNode.workSum)
}
// Connect the passed block to the chain while respecting proper chain
// selection according to the chain with the most proof of work. This
// also handles validation of the transaction scripts.
err = b.connectBestChain(newNode, block, flags)
if err != nil {
return err
}
// Notify the caller that the new block was accepted into the block
// chain. The caller would typically want to react by relaying the
// inventory to other peers.
if !dryRun {
b.sendNotification(NTBlockAccepted, block)
}
return nil
}