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Fix the mempool rate limiter.

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Before, btcd was rate limiting all transactions that had a minimum
fee of zero.  Now, btcd only rate limits transactions that contain
a fee less than the calculated fee based on size.

Closes #163
This commit is contained in:
David Hill 2014-08-18 11:57:02 -04:00
parent e720e398a1
commit 61a53adccd
1 changed files with 29 additions and 23 deletions
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52
mempool.go
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@ -370,9 +370,29 @@ func checkInputsStandard(tx *btcutil.Tx, txStore btcchain.TxStore) error {
return nil
}
// calcTxFee returns the minimum transaction fee required for the passed
// transaction.
func calcTxFee(size int) int64 {
// Calculate the minimum fee for a transaction to be allowed into the
// mempool and relayed by scaling the base fee (which is the minimum
// free transaction relay fee). minTxRelayFee is in Satoshi/KB, so
// divide the transaction size by 1000 to convert to kilobytes. Also,
// integer division is used so fees only increase on full kilobyte
// boundaries.
minFee := (1 + size/1000) * minTxRelayFee
// Set the minimum fee to the maximum possible value if the calculated
// fee is not in the valid range for monetary amounts.
if minFee < 0 || minFee > btcutil.MaxSatoshi {
minFee = btcutil.MaxSatoshi
}
return int64(minFee)
}
// calcMinRelayFee retuns the minimum transaction fee required for the passed
// transaction to be accepted into the memory pool and relayed.
func calcMinRelayFee(tx *btcutil.Tx) int64 {
func calcMinTxRelayFee(size int) int64 {
// 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
@ -382,26 +402,11 @@ func calcMinRelayFee(tx *btcutil.Tx) int64 {
// 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.
serializedLen := int64(tx.MsgTx().SerializeSize())
if serializedLen < (defaultBlockPrioritySize - 1000) {
if size < (defaultBlockPrioritySize - 1000) {
return 0
}
// Calculate the minimum fee for a transaction to be allowed into the
// mempool and relayed by scaling the base fee (which is the minimum
// free transaction relay fee). minTxRelayFee is in Satoshi/KB, so
// divide the transaction size by 1000 to convert to kilobytes. Also,
// integer division is used so fees only increase on full kilobyte
// boundaries.
minFee := (1 + serializedLen/1000) * minTxRelayFee
// Set the minimum fee to the maximum possible value if the calculated
// fee is not in the valid range for monetary amounts.
if minFee < 0 || minFee > btcutil.MaxSatoshi {
minFee = btcutil.MaxSatoshi
}
return minFee
return calcTxFee(size)
}
// removeOrphan removes the passed orphan transaction from the orphan pool and
@ -890,7 +895,8 @@ func (mp *txMemPool) maybeAcceptTransaction(tx *btcutil.Tx, isOrphan *bool, isNe
// reasonable number of ECDSA signature verifications.
// Don't allow transactions with fees too low to get into a mined block.
minRequiredFee := calcMinRelayFee(tx)
serializedSize := tx.MsgTx().SerializeSize()
minRequiredFee := calcMinTxRelayFee(serializedSize)
if txFee < minRequiredFee {
str := fmt.Sprintf("transaction %v has %d fees which is under "+
"the required amount of %d", txHash, txFee,
@ -900,7 +906,7 @@ func (mp *txMemPool) maybeAcceptTransaction(tx *btcutil.Tx, isOrphan *bool, isNe
// Free-to-relay transactions are rate limited here to prevent
// penny-flooding with tiny transactions as a form of attack.
if rateLimit && minRequiredFee == 0 {
if rateLimit && txFee < calcTxFee(serializedSize) {
nowUnix := time.Now().Unix()
// we decay passed data with an exponentially decaying ~10
// minutes window - matches bitcoind handling.
@ -910,13 +916,13 @@ func (mp *txMemPool) maybeAcceptTransaction(tx *btcutil.Tx, isOrphan *bool, isNe
// 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)
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(tx.MsgTx().SerializeSize())
mp.pennyTotal += float64(serializedSize)
txmpLog.Tracef("rate limit: curTotal %v, nextTotal: %v, "+
"limit %v", oldTotal, mp.pennyTotal,
cfg.FreeTxRelayLimit*10*1000)