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[doc] improve RBF documentation

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Document a few non-obvious things and delete no-longer-relevant comments
(e.g. about taking a lock that we're already holding).
No change in behavior.
This commit is contained in:
glozow
2021-08-16 10:40:46 +01:00
parent c78eb8651b
commit 3cf46f6055
4 changed files with 38 additions and 32 deletions
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22
src/validation.cpp
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@@ -771,34 +771,38 @@ bool MemPoolAccept::PreChecks(ATMPArgs& args, Workspace& ws)
// pathological case by making sure setConflicts and setAncestors don't
// intersect.
if (const auto err_string{EntriesAndTxidsDisjoint(setAncestors, setConflicts, hash)}) {
// We classify this as a consensus error because a transaction depending on something it
// conflicts with would be inconsistent.
return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-spends-conflicting-tx", *err_string);
}
// If we don't hold the lock allConflicting might be incomplete; the
// subsequent RemoveStaged() and addUnchecked() calls don't guarantee
// mempool consistency for us.
fReplacementTransaction = setConflicts.size();
if (fReplacementTransaction)
{
if (fReplacementTransaction) {
CFeeRate newFeeRate(nModifiedFees, nSize);
// It's possible that the replacement pays more fees than its direct conflicts but not more
// than all conflicts (i.e. the direct conflicts have high-fee descendants). However, if the
// replacement doesn't pay more fees than its direct conflicts, then we can be sure it's not
// more economically rational to mine. Before we go digging through the mempool for all
// transactions that would need to be removed (direct conflicts and all descendants), check
// that the replacement transaction pays more than its direct conflicts.
if (const auto err_string{PaysMoreThanConflicts(setIterConflicting, newFeeRate, hash)}) {
return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "insufficient fee", *err_string);
}
// Calculate all conflicting entries and enforce Rule #5.
// Calculate all conflicting entries and enforce BIP125 Rule #5.
if (const auto err_string{GetEntriesForConflicts(tx, m_pool, setIterConflicting, allConflicting)}) {
return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY,
"too many potential replacements", *err_string);
}
// Enforce Rule #2.
// Enforce BIP125 Rule #2.
if (const auto err_string{HasNoNewUnconfirmed(tx, m_pool, setIterConflicting)}) {
return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY,
"replacement-adds-unconfirmed", *err_string);
}
// Check if it's economically rational to mine this transaction rather
// than the ones it replaces. Enforce Rules #3 and #4.
// Check if it's economically rational to mine this transaction rather than the ones it
// replaces and pays for its own relay fees. Enforce BIP125 Rules #3 and #4.
for (CTxMemPool::txiter it : allConflicting) {
nConflictingFees += it->GetModifiedFee();
nConflictingSize += it->GetTxSize();