// 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, orphan transaction handling, and insertion into the memory pool.
func (mp *txMemPool) maybeAcceptTransaction(tx *btcwire.MsgTx, isOrphan *bool) error {
*isOrphan = false
txHash, err := tx.TxSha()
if err != nil {
return err
}
// 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. It is more expensive to
// detect a duplicate transaction in the main chain, so that is done
// later.
if mp.isTransactionInPool(&txHash) {
str := fmt.Sprintf("already have transaction %v", txHash)
return TxRuleError(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 = btcchain.CheckTransactionSanity(tx)
if err != nil {
if _, ok := err.(btcchain.RuleError); ok {
return TxRuleError(err.Error())
}
return err
}
// A standalone transaction must not be a coinbase transaction.
if btcchain.IsCoinBase(tx) {
str := fmt.Sprintf("transaction %v is an individual coinbase",
txHash)
return TxRuleError(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.LockTime > math.MaxInt32 {
str := fmt.Sprintf("transaction %v is has a lock time after "+
"2038 which is not accepted yet", txHash)
return TxRuleError(str)
}
// Get the current height of the main chain. A standalone transaction
// will be mined into the next block at best, so
_, curHeight, err := mp.server.db.NewestSha()
if err != nil {
return err
}
nextBlockHeight := curHeight + 1
// Don't allow non-standard transactions on the main network.
if activeNetParams.btcnet == btcwire.MainNet {
err := checkTransactionStandard(tx, nextBlockHeight)
if err != nil {
str := fmt.Sprintf("transaction %v is not a standard "+
"transaction: %v", txHash, err)
return TxRuleError(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 err
}
// Fetch all of the transactions 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.
txStore, err := mp.fetchInputTransactions(tx)
if err != nil {
return err
}
// Don't allow the transaction if it exists in the main chain and is not
// not already fully spent.
if txD, exists := txStore[txHash]; exists && txD.Err == nil {
for _, isOutputSpent := range txD.Spent {
if !isOutputSpent {
str := fmt.Sprintf("transaction already exists")
return TxRuleError(str)
}
}
}
delete(txStore, txHash)
// Transaction is an orphan if any of the inputs don't exist.
for _, txD := range txStore {
if txD.Err == btcdb.TxShaMissing {
*isOrphan = true
return 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 := btcchain.CheckTransactionInputs(tx, nextBlockHeight, txStore)
if err != nil {
return err
}
// Don't allow transactions with non-standard inputs on the main
// network.
if activeNetParams.btcnet == btcwire.MainNet {
err := checkInputsStandard(tx)
if err != nil {
str := fmt.Sprintf("transaction %v has a non-standard "+
"input: %v", txHash, err)
return TxRuleError(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.
// TODO(davec): Don't allow the transaction if the transation fee
// would be too low to get into an empty block.
_ = txFee
// Verify crypto signatures for each input and reject the transaction if
// any don't verify.
err = btcchain.ValidateTransactionScripts(tx, &txHash, time.Now(), txStore)
if err != nil {
return err
}
// TODO(davec): Rate-limit free transactions
// Add to transaction pool.
mp.addTransaction(tx, &txHash)
mp.lock.RLock()
log.Debugf("[TXMP] Accepted transaction %v (pool size: %v)", txHash,
len(mp.pool))
mp.lock.RUnlock()
// TODO(davec): Notifications
// Generate the inventory vector and relay it.
iv := btcwire.NewInvVect(btcwire.InvVect_Tx, &txHash)
mp.server.RelayInventory(iv)
return nil
}
// 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, isOrphan *bool, isNew, rateLimit bool) error {
if isOrphan != nil {
*isOrphan = false
}
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 TxRuleError(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 := btcchain.CheckTransactionSanity(tx)
if err != nil {
if _, ok := err.(btcchain.RuleError); ok {
return TxRuleError(err.Error())
}
return err
}
// A standalone transaction must not be a coinbase transaction.
if btcchain.IsCoinBase(tx) {
str := fmt.Sprintf("transaction %v is an individual coinbase",
txHash)
return TxRuleError(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 TxRuleError(str)
}
// Get the current height of the main chain. A standalone transaction
// will be mined into the next block at best, so it's height is at least
// one more than the current height.
_, curHeight, err := mp.server.db.NewestSha()
if err != nil {
return err
}
nextBlockHeight := curHeight + 1
// Don't allow non-standard transactions if the network parameters
// forbid their relaying.
if !activeNetParams.RelayNonStdTxs {
err := checkTransactionStandard(tx, nextBlockHeight)
if err != nil {
str := fmt.Sprintf("transaction %v is not a standard "+
"transaction: %v", txHash, err)
return TxRuleError(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 err
}
// Fetch all of the transactions 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.
txStore, err := mp.fetchInputTransactions(tx)
if err != nil {
return err
}
// Don't allow the transaction if it exists in the main chain and is not
// not already fully spent.
if txD, exists := txStore[*txHash]; exists && txD.Err == nil {
for _, isOutputSpent := range txD.Spent {
if !isOutputSpent {
return TxRuleError("transaction already exists")
}
}
}
delete(txStore, *txHash)
// Transaction is an orphan if any of the inputs don't exist.
for _, txD := range txStore {
if txD.Err == btcdb.TxShaMissing {
if isOrphan != nil {
*isOrphan = true
}
return 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 := btcchain.CheckTransactionInputs(tx, nextBlockHeight, txStore)
if err != nil {
if _, ok := err.(btcchain.RuleError); ok {
return TxRuleError(err.Error())
}
return err
}
// Don't allow transactions with non-standard inputs if the network
// parameters forbid their relaying.
if !activeNetParams.RelayNonStdTxs {
err := checkInputsStandard(tx, txStore)
if err != nil {
str := fmt.Sprintf("transaction %v has a non-standard "+
"input: %v", txHash, err)
return TxRuleError(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 fees too low to get into a mined block.
minRequiredFee := calcMinRelayFee(tx)
if txFee < minRequiredFee {
str := fmt.Sprintf("transaction %v has %d fees which is under "+
"the required amount of %d", txHash, txFee,
minRequiredFee)
return TxRuleError(str)
}
// Free-to-relay transactions are rate limited here to prevent
// penny-flooding with tiny transactions as a form of attack.
if rateLimit && minRequiredFee == 0 {
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 >= cfg.FreeTxRelayLimit*10*1000 {
str := fmt.Sprintf("transaction %v has 0 fees and has "+
"been rejected by the rate limiter", txHash)
return TxRuleError(str)
}
oldTotal := mp.pennyTotal
mp.pennyTotal += float64(tx.MsgTx().SerializeSize())
txmpLog.Tracef("rate limit: curTotal %v, nextTotal: %v, "+
"limit %v", oldTotal, mp.pennyTotal,
cfg.FreeTxRelayLimit*10*1000)
}
// Verify crypto signatures for each input and reject the transaction if
// any don't verify.
err = btcchain.ValidateTransactionScripts(tx, txStore,
standardScriptVerifyFlags)
if err != nil {
return err
}
// Add to transaction pool.
mp.addTransaction(tx, curHeight, txFee)
txmpLog.Debugf("Accepted transaction %v (pool size: %v)", txHash,
len(mp.pool))
// Notify websocket clients about mempool transactions.
if mp.server.rpcServer != nil {
mp.server.rpcServer.ntfnMgr.NotifyMempoolTx(tx, isNew)
}
return nil
}
// 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, isOrphan *bool, isNew, rateLimit bool) error {
if isOrphan != nil {
*isOrphan = false
}
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 txRuleError(btcwire.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 := btcchain.CheckTransactionSanity(tx)
if err != nil {
if cerr, ok := err.(btcchain.RuleError); ok {
return chainRuleError(cerr)
}
return err
}
// A standalone transaction must not be a coinbase transaction.
if btcchain.IsCoinBase(tx) {
str := fmt.Sprintf("transaction %v is an individual coinbase",
txHash)
return txRuleError(btcwire.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 txRuleError(btcwire.RejectNonstandard, str)
}
// Get the current height of the main chain. A standalone transaction
// will be mined into the next block at best, so it's height is at least
// one more than the current height.
_, curHeight, err := mp.server.db.NewestSha()
if err != nil {
// This is an unexpected error so don't turn it into a rule
// error.
return err
}
nextBlockHeight := curHeight + 1
// Don't allow non-standard transactions if the network parameters
// forbid their relaying.
if !activeNetParams.RelayNonStdTxs {
err := checkTransactionStandard(tx, nextBlockHeight)
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 = btcwire.RejectNonstandard
}
str := fmt.Sprintf("transaction %v is not standard: %v",
txHash, err)
return 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 err
}
// Fetch all of the transactions 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.
txStore, err := mp.fetchInputTransactions(tx)
if err != nil {
if cerr, ok := err.(btcchain.RuleError); ok {
return chainRuleError(cerr)
}
return err
}
// Don't allow the transaction if it exists in the main chain and is not
// not already fully spent.
if txD, exists := txStore[*txHash]; exists && txD.Err == nil {
for _, isOutputSpent := range txD.Spent {
if !isOutputSpent {
return txRuleError(btcwire.RejectDuplicate,
"transaction already exists")
}
}
}
delete(txStore, *txHash)
// Transaction is an orphan if any of the inputs don't exist.
for _, txD := range txStore {
if txD.Err == btcdb.ErrTxShaMissing {
if isOrphan != nil {
*isOrphan = true
}
return 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 := btcchain.CheckTransactionInputs(tx, nextBlockHeight, txStore)
if err != nil {
if cerr, ok := err.(btcchain.RuleError); ok {
return chainRuleError(cerr)
}
return err
}
// Don't allow transactions with non-standard inputs if the network
// parameters forbid their relaying.
if !activeNetParams.RelayNonStdTxs {
err := checkInputsStandard(tx, txStore)
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 = btcwire.RejectNonstandard
}
str := fmt.Sprintf("transaction %v has a non-standard "+
"input: %v", txHash, err)
return 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 := btcchain.CountP2SHSigOps(tx, false, txStore)
if err != nil {
if cerr, ok := err.(btcchain.RuleError); ok {
return chainRuleError(cerr)
}
return err
}
numSigOps += btcchain.CountSigOps(tx)
if numSigOps > maxSigOpsPerTx {
str := fmt.Sprintf("transaction %v has too many sigops: %d > %d",
txHash, numSigOps, maxSigOpsPerTx)
return txRuleError(btcwire.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)
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 txRuleError(btcwire.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 >= cfg.FreeTxRelayLimit*10*1000 {
str := fmt.Sprintf("transaction %v has been rejected "+
"by the rate limiter due to low fees", txHash)
return txRuleError(btcwire.RejectInsufficientFee, str)
}
oldTotal := mp.pennyTotal
mp.pennyTotal += float64(serializedSize)
txmpLog.Tracef("rate limit: curTotal %v, nextTotal: %v, "+
"limit %v", oldTotal, mp.pennyTotal,
cfg.FreeTxRelayLimit*10*1000)
}
// Verify crypto signatures for each input and reject the transaction if
// any don't verify.
err = btcchain.ValidateTransactionScripts(tx, txStore,
standardScriptVerifyFlags)
if err != nil {
if cerr, ok := err.(btcchain.RuleError); ok {
return chainRuleError(cerr)
}
return err
}
// Add to transaction pool.
mp.addTransaction(tx, curHeight, txFee)
txmpLog.Debugf("Accepted transaction %v (pool size: %v)", txHash,
len(mp.pool))
if mp.server.rpcServer != nil {
// Notify websocket clients about mempool transactions.
mp.server.rpcServer.ntfnMgr.NotifyMempoolTx(tx, isNew)
// Potentially notify any getblocktemplate long poll clients
// about stale block templates due to the new transaction.
mp.server.rpcServer.gbtWorkState.NotifyMempoolTx(mp.lastUpdated)
}
return nil
}