btcd/mempool.go
David Hill a1bb291b28 mempool: Have ProcessTransaction return accepted transactions. (#547)
It is not the responsibility of mempool to relay transactions, so
return a slice of transactions accepted to the mempool due to the
passed transaction to the caller.
2016-04-14 12:58:09 -05:00

1004 lines
34 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 main
import (
"container/list"
"crypto/rand"
"fmt"
"math"
"math/big"
"sync"
"sync/atomic"
"time"
"github.com/btcsuite/btcd/blockchain"
"github.com/btcsuite/btcd/blockchain/indexers"
"github.com/btcsuite/btcd/mining"
"github.com/btcsuite/btcd/txscript"
"github.com/btcsuite/btcd/wire"
"github.com/btcsuite/btcutil"
)
const (
// mempoolHeight is the height used for the "block" height field of the
// contextual transaction information provided in a transaction view.
mempoolHeight = 0x7fffffff
)
// mempoolTxDesc is a descriptor containing a transaction in the mempool along
// with additional metadata.
type mempoolTxDesc struct {
mining.TxDesc
// StartingPriority is the priority of the transaction when it was added
// to the pool.
StartingPriority float64
}
// mempoolConfig is a descriptor containing the memory pool configuration.
type mempoolConfig struct {
// Policy defines the various mempool configuration options related
// to policy.
Policy mempoolPolicy
// FetchUtxoView defines the function to use to fetch unspent
// transaction output information.
FetchUtxoView func(*btcutil.Tx) (*blockchain.UtxoViewpoint, error)
// Chain defines the concurrent safe block chain instance which houses
// the current best chain.
Chain *blockchain.BlockChain
// SigCache defines a signature cache to use.
SigCache *txscript.SigCache
// TimeSource defines the timesource to use.
TimeSource blockchain.MedianTimeSource
// AddrIndex defines the optional address index instance to use for
// indexing the unconfirmed transactions in the memory pool.
// This can be nil if the address index is not enabled.
AddrIndex *indexers.AddrIndex
}
// mempoolPolicy houses the policy (configuration parameters) which is used to
// control the mempool.
type mempoolPolicy struct {
// DisableRelayPriority defines whether to relay free or low-fee
// transactions that do not have enough priority to be relayed.
DisableRelayPriority bool
// FreeTxRelayLimit defines the given amount in thousands of bytes
// per minute that transactions with no fee are rate limited to.
FreeTxRelayLimit float64
// MaxOrphanTxs is the maximum number of orphan transactions
// that can be queued.
MaxOrphanTxs int
// MaxOrphanTxSize is the maximum size allowed for orphan transactions.
// This helps prevent memory exhaustion attacks from sending a lot of
// of big orphans.
MaxOrphanTxSize int
// MaxSigOpsPerTx is the maximum number of signature operations
// in a single transaction we will relay or mine. It is a fraction
// of the max signature operations for a block.
MaxSigOpsPerTx int
// MinRelayTxFee defines the minimum transaction fee in BTC/kB to be
// considered a non-zero fee.
MinRelayTxFee btcutil.Amount
}
// txMemPool is used as a source of transactions that need to be mined into
// blocks and relayed to other peers. It is safe for concurrent access from
// multiple peers.
type txMemPool struct {
// The following variables must only be used atomically.
lastUpdated int64 // last time pool was updated
sync.RWMutex
cfg mempoolConfig
pool map[wire.ShaHash]*mempoolTxDesc
orphans map[wire.ShaHash]*btcutil.Tx
orphansByPrev map[wire.ShaHash]map[wire.ShaHash]*btcutil.Tx
outpoints map[wire.OutPoint]*btcutil.Tx
pennyTotal float64 // exponentially decaying total for penny spends.
lastPennyUnix int64 // unix time of last ``penny spend''
}
// Ensure the txMemPool type implements the mining.TxSource interface.
var _ mining.TxSource = (*txMemPool)(nil)
// removeOrphan is the internal function which implements the public
// RemoveOrphan. See the comment for RemoveOrphan for more details.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *txMemPool) removeOrphan(txHash *wire.ShaHash) {
// Nothing to do if passed tx is not an orphan.
tx, exists := mp.orphans[*txHash]
if !exists {
return
}
// Remove the reference from the previous orphan index.
for _, txIn := range tx.MsgTx().TxIn {
originTxHash := txIn.PreviousOutPoint.Hash
if orphans, exists := mp.orphansByPrev[originTxHash]; exists {
delete(orphans, *tx.Sha())
// Remove the map entry altogether if there are no
// longer any orphans which depend on it.
if len(orphans) == 0 {
delete(mp.orphansByPrev, originTxHash)
}
}
}
// Remove the transaction from the orphan pool.
delete(mp.orphans, *txHash)
}
// RemoveOrphan removes the passed orphan transaction from the orphan pool and
// previous orphan index.
//
// This function is safe for concurrent access.
func (mp *txMemPool) RemoveOrphan(txHash *wire.ShaHash) {
mp.Lock()
mp.removeOrphan(txHash)
mp.Unlock()
}
// limitNumOrphans limits the number of orphan transactions by evicting a random
// orphan if adding a new one would cause it to overflow the max allowed.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *txMemPool) limitNumOrphans() error {
if len(mp.orphans)+1 > mp.cfg.Policy.MaxOrphanTxs &&
mp.cfg.Policy.MaxOrphanTxs > 0 {
// Generate a cryptographically random hash.
randHashBytes := make([]byte, wire.HashSize)
_, err := rand.Read(randHashBytes)
if err != nil {
return err
}
randHashNum := new(big.Int).SetBytes(randHashBytes)
// Try to find the first entry that is greater than the random
// hash. Use the first entry (which is already pseudorandom due
// to Go's range statement over maps) as a fallback if none of
// the hashes in the orphan pool are larger than the random
// hash.
var foundHash *wire.ShaHash
for txHash := range mp.orphans {
if foundHash == nil {
foundHash = &txHash
}
txHashNum := blockchain.ShaHashToBig(&txHash)
if txHashNum.Cmp(randHashNum) > 0 {
foundHash = &txHash
break
}
}
mp.removeOrphan(foundHash)
}
return nil
}
// addOrphan adds an orphan transaction to the orphan pool.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *txMemPool) addOrphan(tx *btcutil.Tx) {
// Limit the number orphan transactions to prevent memory exhaustion. A
// random orphan is evicted to make room if needed.
mp.limitNumOrphans()
mp.orphans[*tx.Sha()] = tx
for _, txIn := range tx.MsgTx().TxIn {
originTxHash := txIn.PreviousOutPoint.Hash
if _, exists := mp.orphansByPrev[originTxHash]; !exists {
mp.orphansByPrev[originTxHash] =
make(map[wire.ShaHash]*btcutil.Tx)
}
mp.orphansByPrev[originTxHash][*tx.Sha()] = tx
}
txmpLog.Debugf("Stored orphan transaction %v (total: %d)", tx.Sha(),
len(mp.orphans))
}
// maybeAddOrphan potentially adds an orphan to the orphan pool.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *txMemPool) maybeAddOrphan(tx *btcutil.Tx) error {
// Ignore orphan transactions that are too large. This helps avoid
// a memory exhaustion attack based on sending a lot of really large
// orphans. In the case there is a valid transaction larger than this,
// it will ultimtely be rebroadcast after the parent transactions
// have been mined or otherwise received.
//
// Note that the number of orphan transactions in the orphan pool is
// also limited, so this equates to a maximum memory used of
// mp.cfg.Policy.MaxOrphanTxSize * mp.cfg.Policy.MaxOrphanTxs (which is ~5MB
// using the default values at the time this comment was written).
serializedLen := tx.MsgTx().SerializeSize()
if serializedLen > mp.cfg.Policy.MaxOrphanTxSize {
str := fmt.Sprintf("orphan transaction size of %d bytes is "+
"larger than max allowed size of %d bytes",
serializedLen, mp.cfg.Policy.MaxOrphanTxSize)
return txRuleError(wire.RejectNonstandard, str)
}
// Add the orphan if the none of the above disqualified it.
mp.addOrphan(tx)
return nil
}
// isTransactionInPool returns whether or not the passed transaction already
// exists in the main pool.
//
// This function MUST be called with the mempool lock held (for reads).
func (mp *txMemPool) isTransactionInPool(hash *wire.ShaHash) bool {
if _, exists := mp.pool[*hash]; exists {
return true
}
return false
}
// IsTransactionInPool returns whether or not the passed transaction already
// exists in the main pool.
//
// This function is safe for concurrent access.
func (mp *txMemPool) IsTransactionInPool(hash *wire.ShaHash) bool {
// Protect concurrent access.
mp.RLock()
defer mp.RUnlock()
return mp.isTransactionInPool(hash)
}
// isOrphanInPool returns whether or not the passed transaction already exists
// in the orphan pool.
//
// This function MUST be called with the mempool lock held (for reads).
func (mp *txMemPool) isOrphanInPool(hash *wire.ShaHash) bool {
if _, exists := mp.orphans[*hash]; exists {
return true
}
return false
}
// IsOrphanInPool returns whether or not the passed transaction already exists
// in the orphan pool.
//
// This function is safe for concurrent access.
func (mp *txMemPool) IsOrphanInPool(hash *wire.ShaHash) bool {
// Protect concurrent access.
mp.RLock()
defer mp.RUnlock()
return mp.isOrphanInPool(hash)
}
// haveTransaction returns whether or not the passed transaction already exists
// in the main pool or in the orphan pool.
//
// This function MUST be called with the mempool lock held (for reads).
func (mp *txMemPool) haveTransaction(hash *wire.ShaHash) bool {
return mp.isTransactionInPool(hash) || mp.isOrphanInPool(hash)
}
// HaveTransaction returns whether or not the passed transaction already exists
// in the main pool or in the orphan pool.
//
// This function is safe for concurrent access.
func (mp *txMemPool) HaveTransaction(hash *wire.ShaHash) bool {
// Protect concurrent access.
mp.RLock()
defer mp.RUnlock()
return mp.haveTransaction(hash)
}
// removeTransaction is the internal function which implements the public
// RemoveTransaction. See the comment for RemoveTransaction for more details.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *txMemPool) removeTransaction(tx *btcutil.Tx, removeRedeemers bool) {
txHash := tx.Sha()
if removeRedeemers {
// Remove any transactions which rely on this one.
for i := uint32(0); i < uint32(len(tx.MsgTx().TxOut)); i++ {
outpoint := wire.NewOutPoint(txHash, i)
if txRedeemer, exists := mp.outpoints[*outpoint]; exists {
mp.removeTransaction(txRedeemer, true)
}
}
}
// Remove the transaction if needed.
if txDesc, exists := mp.pool[*txHash]; exists {
// Remove unconfirmed address index entries associated with the
// transaction if enabled.
if mp.cfg.AddrIndex != nil {
mp.cfg.AddrIndex.RemoveUnconfirmedTx(txHash)
}
// Mark the referenced outpoints as unspent by the pool.
for _, txIn := range txDesc.Tx.MsgTx().TxIn {
delete(mp.outpoints, txIn.PreviousOutPoint)
}
delete(mp.pool, *txHash)
atomic.StoreInt64(&mp.lastUpdated, time.Now().Unix())
}
}
// RemoveTransaction removes the passed transaction from the mempool. When the
// removeRedeemers flag is set, any transactions that redeem outputs from the
// removed transaction will also be removed recursively from the mempool, as
// they would otherwise become orphans.
//
// This function is safe for concurrent access.
func (mp *txMemPool) RemoveTransaction(tx *btcutil.Tx, removeRedeemers bool) {
// Protect concurrent access.
mp.Lock()
defer mp.Unlock()
mp.removeTransaction(tx, removeRedeemers)
}
// RemoveDoubleSpends removes all transactions which spend outputs spent by the
// passed transaction from the memory pool. Removing those transactions then
// leads to removing all transactions which rely on them, recursively. This is
// necessary when a block is connected to the main chain because the block may
// contain transactions which were previously unknown to the memory pool.
//
// This function is safe for concurrent access.
func (mp *txMemPool) RemoveDoubleSpends(tx *btcutil.Tx) {
// Protect concurrent access.
mp.Lock()
defer mp.Unlock()
for _, txIn := range tx.MsgTx().TxIn {
if txRedeemer, ok := mp.outpoints[txIn.PreviousOutPoint]; ok {
if !txRedeemer.Sha().IsEqual(tx.Sha()) {
mp.removeTransaction(txRedeemer, true)
}
}
}
}
// addTransaction adds the passed transaction to the memory pool. It should
// not be called directly as it doesn't perform any validation. This is a
// helper for maybeAcceptTransaction.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *txMemPool) addTransaction(utxoView *blockchain.UtxoViewpoint, tx *btcutil.Tx, height int32, fee int64) {
// Add the transaction to the pool and mark the referenced outpoints
// as spent by the pool.
mp.pool[*tx.Sha()] = &mempoolTxDesc{
TxDesc: mining.TxDesc{
Tx: tx,
Added: time.Now(),
Height: height,
Fee: fee,
},
StartingPriority: calcPriority(tx.MsgTx(), utxoView, height),
}
for _, txIn := range tx.MsgTx().TxIn {
mp.outpoints[txIn.PreviousOutPoint] = tx
}
atomic.StoreInt64(&mp.lastUpdated, time.Now().Unix())
// Add unconfirmed address index entries associated with the transaction
// if enabled.
if mp.cfg.AddrIndex != nil {
mp.cfg.AddrIndex.AddUnconfirmedTx(tx, utxoView)
}
}
// checkPoolDoubleSpend checks whether or not the passed transaction is
// attempting to spend coins already spent by other transactions in the pool.
// Note it does not check for double spends against transactions already in the
// main chain.
//
// This function MUST be called with the mempool lock held (for reads).
func (mp *txMemPool) checkPoolDoubleSpend(tx *btcutil.Tx) error {
for _, txIn := range tx.MsgTx().TxIn {
if txR, exists := mp.outpoints[txIn.PreviousOutPoint]; exists {
str := fmt.Sprintf("output %v already spent by "+
"transaction %v in the memory pool",
txIn.PreviousOutPoint, txR.Sha())
return txRuleError(wire.RejectDuplicate, str)
}
}
return nil
}
// fetchInputUtxos loads utxo details about the input transactions referenced by
// the passed transaction. First, it loads the details form the viewpoint of
// the main chain, then it adjusts them based upon the contents of the
// transaction pool.
//
// This function MUST be called with the mempool lock held (for reads).
func (mp *txMemPool) fetchInputUtxos(tx *btcutil.Tx) (*blockchain.UtxoViewpoint, error) {
utxoView, err := mp.cfg.FetchUtxoView(tx)
if err != nil {
return nil, err
}
// Attempt to populate any missing inputs from the transaction pool.
for originHash, entry := range utxoView.Entries() {
if entry != nil && !entry.IsFullySpent() {
continue
}
if poolTxDesc, exists := mp.pool[originHash]; exists {
utxoView.AddTxOuts(poolTxDesc.Tx, mempoolHeight)
}
}
return utxoView, nil
}
// FetchTransaction returns the requested transaction from the transaction pool.
// This only fetches from the main transaction pool and does not include
// orphans.
//
// This function is safe for concurrent access.
func (mp *txMemPool) FetchTransaction(txHash *wire.ShaHash) (*btcutil.Tx, error) {
// Protect concurrent access.
mp.RLock()
defer mp.RUnlock()
if txDesc, exists := mp.pool[*txHash]; exists {
return txDesc.Tx, nil
}
return nil, fmt.Errorf("transaction is not in the pool")
}
// maybeAcceptTransaction is the internal function which implements the public
// MaybeAcceptTransaction. See the comment for MaybeAcceptTransaction for
// more details.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *txMemPool) maybeAcceptTransaction(tx *btcutil.Tx, isNew, rateLimit bool) ([]*wire.ShaHash, error) {
txHash := tx.Sha()
// Don't accept the transaction if it already exists in the pool. This
// applies to orphan transactions as well. This check is intended to
// be a quick check to weed out duplicates.
if mp.haveTransaction(txHash) {
str := fmt.Sprintf("already have transaction %v", txHash)
return nil, txRuleError(wire.RejectDuplicate, str)
}
// Perform preliminary sanity checks on the transaction. This makes
// use of btcchain which contains the invariant rules for what
// transactions are allowed into blocks.
err := blockchain.CheckTransactionSanity(tx)
if err != nil {
if cerr, ok := err.(blockchain.RuleError); ok {
return nil, chainRuleError(cerr)
}
return nil, err
}
// A standalone transaction must not be a coinbase transaction.
if blockchain.IsCoinBase(tx) {
str := fmt.Sprintf("transaction %v is an individual coinbase",
txHash)
return nil, txRuleError(wire.RejectInvalid, str)
}
// Don't accept transactions with a lock time after the maximum int32
// value for now. This is an artifact of older bitcoind clients which
// treated this field as an int32 and would treat anything larger
// incorrectly (as negative).
if tx.MsgTx().LockTime > math.MaxInt32 {
str := fmt.Sprintf("transaction %v has a lock time after "+
"2038 which is not accepted yet", txHash)
return nil, txRuleError(wire.RejectNonstandard, str)
}
// Get the current height of the main chain. A standalone transaction
// will be mined into the next block at best, so its height is at least
// one more than the current height.
best := mp.cfg.Chain.BestSnapshot()
nextBlockHeight := best.Height + 1
// Don't allow non-standard transactions if the network parameters
// forbid their relaying.
if !activeNetParams.RelayNonStdTxs {
err := checkTransactionStandard(tx, nextBlockHeight,
mp.cfg.TimeSource, mp.cfg.Policy.MinRelayTxFee)
if err != nil {
// Attempt to extract a reject code from the error so
// it can be retained. When not possible, fall back to
// a non standard error.
rejectCode, found := extractRejectCode(err)
if !found {
rejectCode = wire.RejectNonstandard
}
str := fmt.Sprintf("transaction %v is not standard: %v",
txHash, err)
return nil, txRuleError(rejectCode, str)
}
}
// The transaction may not use any of the same outputs as other
// transactions already in the pool as that would ultimately result in a
// double spend. This check is intended to be quick and therefore only
// detects double spends within the transaction pool itself. The
// transaction could still be double spending coins from the main chain
// at this point. There is a more in-depth check that happens later
// after fetching the referenced transaction inputs from the main chain
// which examines the actual spend data and prevents double spends.
err = mp.checkPoolDoubleSpend(tx)
if err != nil {
return nil, err
}
// Fetch all of the unspent transaction outputs referenced by the inputs
// to this transaction. This function also attempts to fetch the
// transaction itself to be used for detecting a duplicate transaction
// without needing to do a separate lookup.
utxoView, err := mp.fetchInputUtxos(tx)
if err != nil {
if cerr, ok := err.(blockchain.RuleError); ok {
return nil, chainRuleError(cerr)
}
return nil, err
}
// Don't allow the transaction if it exists in the main chain and is not
// not already fully spent.
txEntry := utxoView.LookupEntry(txHash)
if txEntry != nil && !txEntry.IsFullySpent() {
return nil, txRuleError(wire.RejectDuplicate,
"transaction already exists")
}
delete(utxoView.Entries(), *txHash)
// Transaction is an orphan if any of the referenced input transactions
// don't exist. Adding orphans to the orphan pool is not handled by
// this function, and the caller should use maybeAddOrphan if this
// behavior is desired.
var missingParents []*wire.ShaHash
for originHash, entry := range utxoView.Entries() {
if entry == nil || entry.IsFullySpent() {
// Must make a copy of the hash here since the iterator
// is replaced and taking its address directly would
// result in all of the entries pointing to the same
// memory location and thus all be the final hash.
hashCopy := originHash
missingParents = append(missingParents, &hashCopy)
}
}
if len(missingParents) > 0 {
return missingParents, nil
}
// Perform several checks on the transaction inputs using the invariant
// rules in btcchain for what transactions are allowed into blocks.
// Also returns the fees associated with the transaction which will be
// used later.
txFee, err := blockchain.CheckTransactionInputs(tx, nextBlockHeight,
utxoView)
if err != nil {
if cerr, ok := err.(blockchain.RuleError); ok {
return nil, chainRuleError(cerr)
}
return nil, err
}
// Don't allow transactions with non-standard inputs if the network
// parameters forbid their relaying.
if !activeNetParams.RelayNonStdTxs {
err := checkInputsStandard(tx, utxoView)
if err != nil {
// Attempt to extract a reject code from the error so
// it can be retained. When not possible, fall back to
// a non standard error.
rejectCode, found := extractRejectCode(err)
if !found {
rejectCode = wire.RejectNonstandard
}
str := fmt.Sprintf("transaction %v has a non-standard "+
"input: %v", txHash, err)
return nil, txRuleError(rejectCode, str)
}
}
// NOTE: if you modify this code to accept non-standard transactions,
// you should add code here to check that the transaction does a
// reasonable number of ECDSA signature verifications.
// Don't allow transactions with an excessive number of signature
// operations which would result in making it impossible to mine. Since
// the coinbase address itself can contain signature operations, the
// maximum allowed signature operations per transaction is less than
// the maximum allowed signature operations per block.
numSigOps, err := blockchain.CountP2SHSigOps(tx, false, utxoView)
if err != nil {
if cerr, ok := err.(blockchain.RuleError); ok {
return nil, chainRuleError(cerr)
}
return nil, err
}
numSigOps += blockchain.CountSigOps(tx)
if numSigOps > mp.cfg.Policy.MaxSigOpsPerTx {
str := fmt.Sprintf("transaction %v has too many sigops: %d > %d",
txHash, numSigOps, mp.cfg.Policy.MaxSigOpsPerTx)
return nil, txRuleError(wire.RejectNonstandard, str)
}
// Don't allow transactions with fees too low to get into a mined block.
//
// Most miners allow a free transaction area in blocks they mine to go
// alongside the area used for high-priority transactions as well as
// transactions with fees. A transaction size of up to 1000 bytes is
// considered safe to go into this section. Further, the minimum fee
// calculated below on its own would encourage several small
// transactions to avoid fees rather than one single larger transaction
// which is more desirable. Therefore, as long as the size of the
// transaction does not exceeed 1000 less than the reserved space for
// high-priority transactions, don't require a fee for it.
serializedSize := int64(tx.MsgTx().SerializeSize())
minFee := calcMinRequiredTxRelayFee(serializedSize,
mp.cfg.Policy.MinRelayTxFee)
if serializedSize >= (defaultBlockPrioritySize-1000) && txFee < minFee {
str := fmt.Sprintf("transaction %v has %d fees which is under "+
"the required amount of %d", txHash, txFee,
minFee)
return nil, txRuleError(wire.RejectInsufficientFee, str)
}
// Require that free transactions have sufficient priority to be mined
// in the next block. Transactions which are being added back to the
// memory pool from blocks that have been disconnected during a reorg
// are exempted.
if isNew && !mp.cfg.Policy.DisableRelayPriority && txFee < minFee {
currentPriority := calcPriority(tx.MsgTx(), utxoView,
nextBlockHeight)
if currentPriority <= minHighPriority {
str := fmt.Sprintf("transaction %v has insufficient "+
"priority (%g <= %g)", txHash,
currentPriority, minHighPriority)
return nil, txRuleError(wire.RejectInsufficientFee, str)
}
}
// Free-to-relay transactions are rate limited here to prevent
// penny-flooding with tiny transactions as a form of attack.
if rateLimit && txFee < minFee {
nowUnix := time.Now().Unix()
// we decay passed data with an exponentially decaying ~10
// minutes window - matches bitcoind handling.
mp.pennyTotal *= math.Pow(1.0-1.0/600.0,
float64(nowUnix-mp.lastPennyUnix))
mp.lastPennyUnix = nowUnix
// Are we still over the limit?
if mp.pennyTotal >= mp.cfg.Policy.FreeTxRelayLimit*10*1000 {
str := fmt.Sprintf("transaction %v has been rejected "+
"by the rate limiter due to low fees", txHash)
return nil, txRuleError(wire.RejectInsufficientFee, str)
}
oldTotal := mp.pennyTotal
mp.pennyTotal += float64(serializedSize)
txmpLog.Tracef("rate limit: curTotal %v, nextTotal: %v, "+
"limit %v", oldTotal, mp.pennyTotal,
mp.cfg.Policy.FreeTxRelayLimit*10*1000)
}
// Verify crypto signatures for each input and reject the transaction if
// any don't verify.
err = blockchain.ValidateTransactionScripts(tx, utxoView,
txscript.StandardVerifyFlags, mp.cfg.SigCache)
if err != nil {
if cerr, ok := err.(blockchain.RuleError); ok {
return nil, chainRuleError(cerr)
}
return nil, err
}
// Add to transaction pool.
mp.addTransaction(utxoView, tx, best.Height, txFee)
txmpLog.Debugf("Accepted transaction %v (pool size: %v)", txHash,
len(mp.pool))
return nil, nil
}
// MaybeAcceptTransaction is the main workhorse for handling insertion of new
// free-standing transactions into a memory pool. It includes functionality
// such as rejecting duplicate transactions, ensuring transactions follow all
// rules, detecting orphan transactions, and insertion into the memory pool.
//
// If the transaction is an orphan (missing parent transactions), the
// transaction is NOT added to the orphan pool, but each unknown referenced
// parent is returned. Use ProcessTransaction instead if new orphans should
// be added to the orphan pool.
//
// This function is safe for concurrent access.
func (mp *txMemPool) MaybeAcceptTransaction(tx *btcutil.Tx, isNew, rateLimit bool) ([]*wire.ShaHash, error) {
// Protect concurrent access.
mp.Lock()
defer mp.Unlock()
return mp.maybeAcceptTransaction(tx, isNew, rateLimit)
}
// processOrphans is the internal function which implements the public
// ProcessOrphans. See the comment for ProcessOrphans for more details.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *txMemPool) processOrphans(hash *wire.ShaHash) []*btcutil.Tx {
var acceptedTxns []*btcutil.Tx
// Start with processing at least the passed hash.
processHashes := list.New()
processHashes.PushBack(hash)
for processHashes.Len() > 0 {
// Pop the first hash to process.
firstElement := processHashes.Remove(processHashes.Front())
processHash := firstElement.(*wire.ShaHash)
// Look up all orphans that are referenced by the transaction we
// just accepted. This will typically only be one, but it could
// be multiple if the referenced transaction contains multiple
// outputs. Skip to the next item on the list of hashes to
// process if there are none.
orphans, exists := mp.orphansByPrev[*processHash]
if !exists || orphans == nil {
continue
}
for _, tx := range orphans {
// Remove the orphan from the orphan pool. Current
// behavior requires that all saved orphans with
// a newly accepted parent are removed from the orphan
// pool and potentially added to the memory pool, but
// transactions which cannot be added to memory pool
// (including due to still being orphans) are expunged
// from the orphan pool.
//
// TODO(jrick): The above described behavior sounds
// like a bug, and I think we should investigate
// potentially moving orphans to the memory pool, but
// leaving them in the orphan pool if not all parent
// transactions are known yet.
orphanHash := tx.Sha()
mp.removeOrphan(orphanHash)
// Potentially accept the transaction into the
// transaction pool.
missingParents, err := mp.maybeAcceptTransaction(tx,
true, true)
if err != nil {
// TODO: Remove orphans that depend on this
// failed transaction.
txmpLog.Debugf("Unable to move "+
"orphan transaction %v to mempool: %v",
tx.Sha(), err)
continue
}
if len(missingParents) > 0 {
// Transaction is still an orphan, so add it
// back.
mp.addOrphan(tx)
continue
}
// Add this transaction to the list of transactions
// that are no longer orphans.
acceptedTxns = append(acceptedTxns, tx)
// Add this transaction to the list of transactions to
// process so any orphans that depend on this one are
// handled too.
//
// TODO(jrick): In the case that this is still an orphan,
// we know that any other transactions in the orphan
// pool with this orphan as their parent are still
// orphans as well, and should be removed. While
// recursively calling removeOrphan and
// maybeAcceptTransaction on these transactions is not
// wrong per se, it is overkill if all we care about is
// recursively removing child transactions of this
// orphan.
processHashes.PushBack(orphanHash)
}
}
return acceptedTxns
}
// ProcessOrphans determines if there are any orphans which depend on the passed
// transaction hash (it is possible that they are no longer orphans) and
// potentially accepts them to the memory pool. It repeats the process for the
// newly accepted transactions (to detect further orphans which may no longer be
// orphans) until there are no more.
//
// It returns a slice of transactions added to the mempool. A nil slice means
// no transactions were moved from the orphan pool to the mempool.
//
// This function is safe for concurrent access.
func (mp *txMemPool) ProcessOrphans(hash *wire.ShaHash) []*btcutil.Tx {
mp.Lock()
acceptedTxns := mp.processOrphans(hash)
mp.Unlock()
return acceptedTxns
}
// ProcessTransaction is the main workhorse for handling insertion of new
// free-standing transactions into the memory pool. It includes functionality
// such as rejecting duplicate transactions, ensuring transactions follow all
// rules, orphan transaction handling, and insertion into the memory pool.
//
// It returns a slice of transactions added to the mempool. When the
// error is nil, the list will include the passed transaction itself along
// with any additional orphan transaactions that were added as a result of
// the passed one being accepted.
//
// This function is safe for concurrent access.
func (mp *txMemPool) ProcessTransaction(tx *btcutil.Tx, allowOrphan, rateLimit bool) ([]*btcutil.Tx, error) {
// Protect concurrent access.
mp.Lock()
defer mp.Unlock()
txmpLog.Tracef("Processing transaction %v", tx.Sha())
// Potentially accept the transaction to the memory pool.
missingParents, err := mp.maybeAcceptTransaction(tx, true, rateLimit)
if err != nil {
return nil, err
}
if len(missingParents) == 0 {
// Accept any orphan transactions that depend on this
// transaction (they may no longer be orphans if all inputs
// are now available) and repeat for those accepted
// transactions until there are no more.
newTxs := mp.processOrphans(tx.Sha())
acceptedTxs := make([]*btcutil.Tx, len(newTxs)+1)
// Add the parent transaction first so remote nodes
// do not add orphans.
acceptedTxs[0] = tx
copy(acceptedTxs[1:], newTxs)
return acceptedTxs, nil
}
// The transaction is an orphan (has inputs missing). Reject
// it if the flag to allow orphans is not set.
if !allowOrphan {
// Only use the first missing parent transaction in
// the error message.
//
// NOTE: RejectDuplicate is really not an accurate
// reject code here, but it matches the reference
// implementation and there isn't a better choice due
// to the limited number of reject codes. Missing
// inputs is assumed to mean they are already spent
// which is not really always the case.
str := fmt.Sprintf("orphan transaction %v references "+
"outputs of unknown or fully-spent "+
"transaction %v", tx.Sha(), missingParents[0])
return nil, txRuleError(wire.RejectDuplicate, str)
}
// Potentially add the orphan transaction to the orphan pool.
err = mp.maybeAddOrphan(tx)
if err != nil {
return nil, err
}
return nil, nil
}
// Count returns the number of transactions in the main pool. It does not
// include the orphan pool.
//
// This function is safe for concurrent access.
func (mp *txMemPool) Count() int {
mp.RLock()
defer mp.RUnlock()
return len(mp.pool)
}
// TxShas returns a slice of hashes for all of the transactions in the memory
// pool.
//
// This function is safe for concurrent access.
func (mp *txMemPool) TxShas() []*wire.ShaHash {
mp.RLock()
defer mp.RUnlock()
hashes := make([]*wire.ShaHash, len(mp.pool))
i := 0
for hash := range mp.pool {
hashCopy := hash
hashes[i] = &hashCopy
i++
}
return hashes
}
// TxDescs returns a slice of descriptors for all the transactions in the pool.
// The descriptors are to be treated as read only.
//
// This function is safe for concurrent access.
func (mp *txMemPool) TxDescs() []*mempoolTxDesc {
mp.RLock()
defer mp.RUnlock()
descs := make([]*mempoolTxDesc, len(mp.pool))
i := 0
for _, desc := range mp.pool {
descs[i] = desc
i++
}
return descs
}
// MiningDescs returns a slice of mining descriptors for all the transactions
// in the pool.
//
// This is part of the mining.TxSource interface implementation and is safe for
// concurrent access as required by the interface contract.
func (mp *txMemPool) MiningDescs() []*mining.TxDesc {
mp.RLock()
defer mp.RUnlock()
descs := make([]*mining.TxDesc, len(mp.pool))
i := 0
for _, desc := range mp.pool {
descs[i] = &desc.TxDesc
i++
}
return descs
}
// LastUpdated returns the last time a transaction was added to or removed from
// the main pool. It does not include the orphan pool.
//
// This function is safe for concurrent access.
func (mp *txMemPool) LastUpdated() time.Time {
return time.Unix(atomic.LoadInt64(&mp.lastUpdated), 0)
}
// newTxMemPool returns a new memory pool for validating and storing standalone
// transactions until they are mined into a block.
func newTxMemPool(cfg *mempoolConfig) *txMemPool {
memPool := &txMemPool{
cfg: *cfg,
pool: make(map[wire.ShaHash]*mempoolTxDesc),
orphans: make(map[wire.ShaHash]*btcutil.Tx),
orphansByPrev: make(map[wire.ShaHash]map[wire.ShaHash]*btcutil.Tx),
outpoints: make(map[wire.OutPoint]*btcutil.Tx),
}
return memPool
}