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Merge bitcoin/bitcoin#24152: policy / validation: CPFP fee bumping within packages

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9bebf35e26 [validation] don't package validate if not policy or missing inputs (glozow)
51edcffa0e [unit test] package feerate and package cpfp (glozow)
1b93748c93 [validation] try individual validation before package validation (glozow)
17a8ffd802 [packages/policy] use package feerate in package validation (glozow)
09f32cffa6 [docs] package feerate (glozow)

Pull request description:

  Part of #22290, aka [Package Mempool Accept](https://gist.github.com/glozow/dc4e9d5c5b14ade7cdfac40f43adb18a).

  This enables CPFP fee bumping in child-with-unconfirmed-parents packages by introducing [package feerate](https://gist.github.com/glozow/dc4e9d5c5b14ade7cdfac40f43adb18a#fee-related-checks-use-package-feerate) (total modified fees divided by total virtual size) and using it in place of individual feerate. We also always [validate individual transactions first](https://gist.github.com/glozow/dc4e9d5c5b14ade7cdfac40f43adb18a#always-try-individual-submission-first) to avoid incentive-incompatible policies like "parents pay for children" or "siblings pay for siblings" behavior.

ACKs for top commit:
  instagibbs:
    reACK 9bebf35e26
  mzumsande:
    Code review ACK 9bebf35e26
  t-bast:
    ACK 9bebf35e26

Tree-SHA512: 5117cfcc3ce55c00384d9e8003a0589ceac1e6f738b1c299007d9cd9cdd2d7c530d31cfd23658b041a6604d39073bcc6e81f0639a300082a92097682a6ea8c8f
This commit is contained in:
fanquake
2022-04-07 09:43:25 +01:00
parent 41720a1f54 9bebf35e26
commit d844b5e799
5 changed files with 362 additions and 21 deletions
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89
src/validation.cpp
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@@ -460,6 +460,10 @@ public:
* partially submitted.
*/
const bool m_package_submission;
/** When true, use package feerates instead of individual transaction feerates for fee-based
* policies such as mempool min fee and min relay fee.
*/
const bool m_package_feerates;
/** Parameters for single transaction mempool validation. */
static ATMPArgs SingleAccept(const CChainParams& chainparams, int64_t accept_time,
@@ -472,6 +476,7 @@ public:
/* m_test_accept */ test_accept,
/* m_allow_bip125_replacement */ true,
/* m_package_submission */ false,
/* m_package_feerates */ false,
};
}
@@ -485,6 +490,7 @@ public:
/* m_test_accept */ true,
/* m_allow_bip125_replacement */ false,
/* m_package_submission */ false, // not submitting to mempool
/* m_package_feerates */ false,
};
}
@@ -498,6 +504,20 @@ public:
/* m_test_accept */ false,
/* m_allow_bip125_replacement */ false,
/* m_package_submission */ true,
/* m_package_feerates */ true,
};
}
/** Parameters for a single transaction within a package. */
static ATMPArgs SingleInPackageAccept(const ATMPArgs& package_args) {
return ATMPArgs{/* m_chainparams */ package_args.m_chainparams,
/* m_accept_time */ package_args.m_accept_time,
/* m_bypass_limits */ false,
/* m_coins_to_uncache */ package_args.m_coins_to_uncache,
/* m_test_accept */ package_args.m_test_accept,
/* m_allow_bip125_replacement */ true,
/* m_package_submission */ false,
/* m_package_feerates */ false, // only 1 transaction
};
}
@@ -510,14 +530,16 @@ public:
std::vector<COutPoint>& coins_to_uncache,
bool test_accept,
bool allow_bip125_replacement,
bool package_submission)
bool package_submission,
bool package_feerates)
: m_chainparams{chainparams},
m_accept_time{accept_time},
m_bypass_limits{bypass_limits},
m_coins_to_uncache{coins_to_uncache},
m_test_accept{test_accept},
m_allow_bip125_replacement{allow_bip125_replacement},
m_package_submission{package_submission}
m_package_submission{package_submission},
m_package_feerates{package_feerates}
{
}
};
@@ -819,9 +841,10 @@ bool MemPoolAccept::PreChecks(ATMPArgs& args, Workspace& ws)
return state.Invalid(TxValidationResult::TX_NOT_STANDARD, "bad-txns-too-many-sigops",
strprintf("%d", nSigOpsCost));
// No transactions are allowed below minRelayTxFee except from disconnected
// blocks
if (!bypass_limits && !CheckFeeRate(ws.m_vsize, ws.m_modified_fees, state)) return false;
// No individual transactions are allowed below minRelayTxFee and mempool min fee except from
// disconnected blocks and transactions in a package. Package transactions will be checked using
// package feerate later.
if (!bypass_limits && !args.m_package_feerates && !CheckFeeRate(ws.m_vsize, ws.m_modified_fees, state)) return false;
ws.m_iters_conflicting = m_pool.GetIterSet(ws.m_conflicts);
// Calculate in-mempool ancestors, up to a limit.
@@ -1205,12 +1228,27 @@ PackageMempoolAcceptResult MemPoolAccept::AcceptMultipleTransactions(const std::
m_viewmempool.PackageAddTransaction(ws.m_ptx);
}
// Transactions must meet two minimum feerates: the mempool minimum fee and min relay fee.
// For transactions consisting of exactly one child and its parents, it suffices to use the
// package feerate (total modified fees / total virtual size) to check this requirement.
const auto m_total_vsize = std::accumulate(workspaces.cbegin(), workspaces.cend(), int64_t{0},
[](int64_t sum, auto& ws) { return sum + ws.m_vsize; });
const auto m_total_modified_fees = std::accumulate(workspaces.cbegin(), workspaces.cend(), CAmount{0},
[](CAmount sum, auto& ws) { return sum + ws.m_modified_fees; });
const CFeeRate package_feerate(m_total_modified_fees, m_total_vsize);
TxValidationState placeholder_state;
if (args.m_package_feerates &&
!CheckFeeRate(m_total_vsize, m_total_modified_fees, placeholder_state)) {
package_state.Invalid(PackageValidationResult::PCKG_POLICY, "package-fee-too-low");
return PackageMempoolAcceptResult(package_state, package_feerate, {});
}
// Apply package mempool ancestor/descendant limits. Skip if there is only one transaction,
// because it's unnecessary. Also, CPFP carve out can increase the limit for individual
// transactions, but this exemption is not extended to packages in CheckPackageLimits().
std::string err_string;
if (txns.size() > 1 && !PackageMempoolChecks(txns, package_state)) {
return PackageMempoolAcceptResult(package_state, std::move(results));
return PackageMempoolAcceptResult(package_state, package_feerate, std::move(results));
}
for (Workspace& ws : workspaces) {
@@ -1218,7 +1256,7 @@ PackageMempoolAcceptResult MemPoolAccept::AcceptMultipleTransactions(const std::
// Exit early to avoid doing pointless work. Update the failed tx result; the rest are unfinished.
package_state.Invalid(PackageValidationResult::PCKG_TX, "transaction failed");
results.emplace(ws.m_ptx->GetWitnessHash(), MempoolAcceptResult::Failure(ws.m_state));
return PackageMempoolAcceptResult(package_state, std::move(results));
return PackageMempoolAcceptResult(package_state, package_feerate, std::move(results));
}
if (args.m_test_accept) {
// When test_accept=true, transactions that pass PolicyScriptChecks are valid because there are
@@ -1229,14 +1267,14 @@ PackageMempoolAcceptResult MemPoolAccept::AcceptMultipleTransactions(const std::
}
}
if (args.m_test_accept) return PackageMempoolAcceptResult(package_state, std::move(results));
if (args.m_test_accept) return PackageMempoolAcceptResult(package_state, package_feerate, std::move(results));
if (!SubmitPackage(args, workspaces, package_state, results)) {
// PackageValidationState filled in by SubmitPackage().
return PackageMempoolAcceptResult(package_state, std::move(results));
return PackageMempoolAcceptResult(package_state, package_feerate, std::move(results));
}
return PackageMempoolAcceptResult(package_state, std::move(results));
return PackageMempoolAcceptResult(package_state, package_feerate, std::move(results));
}
PackageMempoolAcceptResult MemPoolAccept::AcceptPackage(const Package& package, ATMPArgs& args)
@@ -1303,6 +1341,8 @@ PackageMempoolAcceptResult MemPoolAccept::AcceptPackage(const Package& package,
// transactions that are already in the mempool, and only call AcceptMultipleTransactions() with
// the new transactions. This ensures we don't double-count transaction counts and sizes when
// checking ancestor/descendant limits, or double-count transaction fees for fee-related policy.
ATMPArgs single_args = ATMPArgs::SingleInPackageAccept(args);
bool quit_early{false};
std::vector<CTransactionRef> txns_new;
for (const auto& tx : package) {
const auto& wtxid = tx->GetWitnessHash();
@@ -1329,18 +1369,43 @@ PackageMempoolAcceptResult MemPoolAccept::AcceptPackage(const Package& package,
results.emplace(wtxid, MempoolAcceptResult::MempoolTxDifferentWitness(iter.value()->GetTx().GetWitnessHash()));
} else {
// Transaction does not already exist in the mempool.
txns_new.push_back(tx);
// Try submitting the transaction on its own.
const auto single_res = AcceptSingleTransaction(tx, single_args);
if (single_res.m_result_type == MempoolAcceptResult::ResultType::VALID) {
// The transaction succeeded on its own and is now in the mempool. Don't include it
// in package validation, because its fees should only be "used" once.
assert(m_pool.exists(GenTxid::Wtxid(wtxid)));
results.emplace(wtxid, single_res);
} else if (single_res.m_state.GetResult() != TxValidationResult::TX_MEMPOOL_POLICY &&
single_res.m_state.GetResult() != TxValidationResult::TX_MISSING_INPUTS) {
// Package validation policy only differs from individual policy in its evaluation
// of feerate. For example, if a transaction fails here due to violation of a
// consensus rule, the result will not change when it is submitted as part of a
// package. To minimize the amount of repeated work, unless the transaction fails
// due to feerate or missing inputs (its parent is a previous transaction in the
// package that failed due to feerate), don't run package validation. Note that this
// decision might not make sense if different types of packages are allowed in the
// future. Continue individually validating the rest of the transactions, because
// some of them may still be valid.
quit_early = true;
} else {
txns_new.push_back(tx);
}
}
}
// Nothing to do if the entire package has already been submitted.
if (txns_new.empty()) return PackageMempoolAcceptResult(package_state, std::move(results));
if (quit_early || txns_new.empty()) {
// No package feerate when no package validation was done.
return PackageMempoolAcceptResult(package_state, std::move(results));
}
// Validate the (deduplicated) transactions as a package.
auto submission_result = AcceptMultipleTransactions(txns_new, args);
// Include already-in-mempool transaction results in the final result.
for (const auto& [wtxid, mempoolaccept_res] : results) {
submission_result.m_tx_results.emplace(wtxid, mempoolaccept_res);
}
if (submission_result.m_state.IsValid()) assert(submission_result.m_package_feerate.has_value());
return submission_result;
}