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mempool: Stake-related readability improvements.
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This does some minor cleanup of the code in the maybeAcceptTransaction
function to use some local bools with more easily readable names for
dealing with stake transactions.

It also improves the readability of the double spending exceptions
section and avoids some additional if statements.
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@davecgh
davecgh committed Sep 14, 2018
1 parent 2d6a3dd commit 06d0021
Showing 1 changed file with 50 additions and 52 deletions.
102 changes: 50 additions & 52 deletions mempool/mempool.go
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Original file line number Diff line number Diff line change
Expand Up @@ -44,9 +44,9 @@ const (
// DCR/kB, this results in a maximum allowed high fee of 1 DCR/kB.
maxRelayFeeMultiplier = 1e4

// maxSSGensDoubleSpends is the maximum number of SSGen double spends
// allowed in the pool.
maxSSGensDoubleSpends = 5
// maxVoteDoubleSpends is the maximum number of vote double spends allowed
// in the pool.
maxVoteDoubleSpends = 5

// heightDiffToPruneTicket is the number of blocks to pass by in terms
// of height before old tickets are pruned.
Expand Down Expand Up @@ -876,7 +876,10 @@ func (mp *TxPool) maybeAcceptTransaction(tx *dcrutil.Tx, isNew, rateLimit, allow

// If the transaction is a ticket, ensure that it meets the next
// stake difficulty.
if txType == stake.TxTypeSStx {
isVote := txType == stake.TxTypeSSGen
isRevocation := txType == stake.TxTypeSSRtx
isTicket := txType == stake.TxTypeSStx
if isTicket {
sDiff, err := mp.cfg.NextStakeDifficulty()
if err != nil {
// This is an unexpected error so don't turn it into a
Expand All @@ -892,60 +895,56 @@ func (mp *TxPool) maybeAcceptTransaction(tx *dcrutil.Tx, isNew, rateLimit, allow
}
}

// Handle stake transaction double spending exceptions.
if (txType == stake.TxTypeSSGen) || (txType == stake.TxTypeSSRtx) {
if txType == stake.TxTypeSSGen {
ssGenAlreadyFound := 0
for _, mpTx := range mp.pool {
if mpTx.Type == stake.TxTypeSSGen {
if mpTx.Tx.MsgTx().TxIn[1].PreviousOutPoint ==
msgTx.TxIn[1].PreviousOutPoint {
ssGenAlreadyFound++
}
}
if ssGenAlreadyFound > maxSSGensDoubleSpends {
str := fmt.Sprintf("transaction %v in the pool "+
"with more than %v ssgens",
msgTx.TxIn[1].PreviousOutPoint,
maxSSGensDoubleSpends)
return nil, txRuleError(wire.RejectDuplicate, str)
// Aside from a few exceptions for votes and revocations, 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.
if !isVote && !isRevocation {
err = mp.checkPoolDoubleSpend(tx, txType)
if err != nil {
return nil, err
}
} else if isVote {
voteAlreadyFound := 0
for _, mpTx := range mp.pool {
if mpTx.Type == stake.TxTypeSSGen {
if mpTx.Tx.MsgTx().TxIn[1].PreviousOutPoint ==
msgTx.TxIn[1].PreviousOutPoint {
voteAlreadyFound++
}
}
if voteAlreadyFound > maxVoteDoubleSpends {
str := fmt.Sprintf("transaction %v in the pool with more than "+
"%v votes", msgTx.TxIn[1].PreviousOutPoint,
maxVoteDoubleSpends)
return nil, txRuleError(wire.RejectDuplicate, str)
}
}

if txType == stake.TxTypeSSRtx {
for _, mpTx := range mp.pool {
if mpTx.Type == stake.TxTypeSSRtx {
if mpTx.Tx.MsgTx().TxIn[0].PreviousOutPoint ==
msgTx.TxIn[0].PreviousOutPoint {
str := fmt.Sprintf("transaction %v in the pool "+
" as a ssrtx. Only one ssrtx allowed.",
msgTx.TxIn[0].PreviousOutPoint)
return nil, txRuleError(wire.RejectDuplicate, str)
}
} else if isRevocation {
for _, mpTx := range mp.pool {
if mpTx.Type == stake.TxTypeSSRtx {
if mpTx.Tx.MsgTx().TxIn[0].PreviousOutPoint ==
msgTx.TxIn[0].PreviousOutPoint {
str := fmt.Sprintf("transaction %v in the pool as a "+
"revocation. Only one revocation is allowed.",
msgTx.TxIn[0].PreviousOutPoint)
return nil, txRuleError(wire.RejectDuplicate, str)
}
}
}
} else {
// 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, txType)
if err != nil {
return nil, err
}
}

// Votes that are on too old of blocks are rejected.
if txType == stake.TxTypeSSGen {
if isVote {
_, voteHeight := stake.SSGenBlockVotedOn(msgTx)
if (int64(voteHeight) < nextBlockHeight-maximumVoteAgeDelta) &&
!mp.cfg.Policy.AllowOldVotes {

str := fmt.Sprintf("transaction %v votes on old "+
"block height of %v which is before the "+
"current cutoff height of %v",
Expand Down Expand Up @@ -978,7 +977,7 @@ func (mp *TxPool) maybeAcceptTransaction(tx *dcrutil.Tx, isNew, rateLimit, allow
// Transaction is an orphan if any of the inputs don't exist.
var missingParents []*chainhash.Hash
for i, txIn := range msgTx.TxIn {
if i == 0 && txType == stake.TxTypeSSGen {
if i == 0 && isVote {
continue
}

Expand Down Expand Up @@ -1076,7 +1075,7 @@ func (mp *TxPool) maybeAcceptTransaction(tx *dcrutil.Tx, isNew, rateLimit, allow
return nil, err
}

numSigOps += blockchain.CountSigOps(tx, false, (txType == stake.TxTypeSSGen))
numSigOps += blockchain.CountSigOps(tx, false, isVote)
if numSigOps > mp.cfg.Policy.MaxSigOpsPerTx {
str := fmt.Sprintf("transaction %v has too many sigops: %d > %d",
txHash, numSigOps, mp.cfg.Policy.MaxSigOpsPerTx)
Expand Down Expand Up @@ -1157,7 +1156,7 @@ func (mp *TxPool) maybeAcceptTransaction(tx *dcrutil.Tx, isNew, rateLimit, allow
// also performed on regular transactions above, but fees lower than the
// miniumum may be allowed when there is sufficient priority, and these
// checks aren't desired for ticket purchases.
if txType == stake.TxTypeSStx {
if isTicket {
minTicketFee := calcMinRequiredTxRelayFee(serializedSize,
mp.cfg.Policy.MinRelayTxFee)
if txFee < minTicketFee {
Expand Down Expand Up @@ -1200,9 +1199,8 @@ func (mp *TxPool) maybeAcceptTransaction(tx *dcrutil.Tx, isNew, rateLimit, allow
// Add to transaction pool.
mp.addTransaction(utxoView, tx, txType, bestHeight, txFee)

// If it's an SSGen (vote), insert it into the list of
// votes.
if txType == stake.TxTypeSSGen {
// Keep track of vote separately.
if isVote {
mp.votesMtx.Lock()
err := mp.insertVote(tx)
mp.votesMtx.Unlock()
Expand Down

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