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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

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fanquake 2022-04-07 09:43:25 +01:00
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5 changed files with 362 additions and 21 deletions
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45
doc/policy/packages.md
View file

@ -72,3 +72,48 @@ test accepts):
a competing package or transaction with a mutated witness, even though the two
same-txid-different-witness transactions are conflicting and cannot replace each other, the
honest package should still be considered for acceptance.
### Package Fees and Feerate
*Package Feerate* is the total modified fees (base fees + any fee delta from
`prioritisetransaction`) divided by the total virtual size of all transactions in the package.
If any transactions in the package are already in the mempool, they are not submitted again
("deduplicated") and are thus excluded from this calculation.
To meet the two feerate requirements of a mempool, i.e., the pre-configured minimum relay feerate
(`minRelayTxFee`) and the dynamic mempool minimum feerate, the total package feerate is used instead
of the individual feerate. The individual transactions are allowed to be below the feerate
requirements if the package meets the feerate requirements. For example, the parent(s) in the
package can pay no fees but be paid for by the child.
*Rationale*: This can be thought of as "CPFP within a package," solving the issue of a parent not
meeting minimum fees on its own. This would allow contracting applications to adjust their fees at
broadcast time instead of overshooting or risking becoming stuck or pinned.
*Rationale*: It would be incorrect to use the fees of transactions that are already in the mempool, as
we do not want a transaction's fees to be double-counted.
Implementation Note: Transactions within a package are always validated individually first, and
package validation is used for the transactions that failed. Since package feerate is only
calculated using transactions that are not in the mempool, this implementation detail affects the
outcome of package validation.
*Rationale*: Packages are intended for incentive-compatible fee-bumping: transaction B is a
"legitimate" fee-bump for transaction A only if B is a descendant of A and has a *higher* feerate
than A. We want to prevent "parents pay for children" behavior; fees of parents should not help
their children, since the parents can be mined without the child. More generally, if transaction A
is not needed in order for transaction B to be mined, A's fees cannot help B. In a
child-with-parents package, simply excluding any parent transactions that meet feerate requirements
individually is sufficient to ensure this.
*Rationale*: We must not allow a low-feerate child to prevent its parent from being accepted; fees
of children should not negatively impact their parents, since they are not necessary for the parents
to be mined. More generally, if transaction B is not needed in order for transaction A to be mined,
B's fees cannot harm A. In a child-with-parents package, simply validating parents individually
first is sufficient to ensure this.
*Rationale*: As a principle, we want to avoid accidentally restricting policy in order to be
backward-compatible for users and applications that rely on p2p transaction relay. Concretely,
package validation should not prevent the acceptance of a transaction that would otherwise be
policy-valid on its own. By always accepting a transaction that passes individual validation before
trying package validation, we prevent any unintentional restriction of policy.

14
src/test/fuzz/tx_pool.cpp
View file

@ -234,14 +234,18 @@ FUZZ_TARGET_INIT(tx_pool_standard, initialize_tx_pool)
const bool bypass_limits = fuzzed_data_provider.ConsumeBool();
::fRequireStandard = fuzzed_data_provider.ConsumeBool();
// Make sure ProcessNewPackage on one transaction works and always fully validates the transaction.
// Make sure ProcessNewPackage on one transaction works.
// The result is not guaranteed to be the same as what is returned by ATMP.
const auto result_package = WITH_LOCK(::cs_main,
return ProcessNewPackage(chainstate, tx_pool, {tx}, true));
auto it = result_package.m_tx_results.find(tx->GetWitnessHash());
Assert(it != result_package.m_tx_results.end());
Assert(it->second.m_result_type == MempoolAcceptResult::ResultType::VALID ||
it->second.m_result_type == MempoolAcceptResult::ResultType::INVALID);
// If something went wrong due to a package-specific policy, it might not return a
// validation result for the transaction.
if (result_package.m_state.GetResult() != PackageValidationResult::PCKG_POLICY) {
auto it = result_package.m_tx_results.find(tx->GetWitnessHash());
Assert(it != result_package.m_tx_results.end());
Assert(it->second.m_result_type == MempoolAcceptResult::ResultType::VALID ||
it->second.m_result_type == MempoolAcceptResult::ResultType::INVALID);
}
const auto res = WITH_LOCK(::cs_main, return AcceptToMemoryPool(chainstate, tx, GetTime(), bypass_limits, /*test_accept=*/false));
const bool accepted = res.m_result_type == MempoolAcceptResult::ResultType::VALID;

227
src/test/txpackage_tests.cpp
View file

@ -98,7 +98,9 @@ BOOST_FIXTURE_TEST_CASE(package_validation_tests, TestChain100Setup)
BOOST_CHECK(it_child != result_parent_child.m_tx_results.end());
BOOST_CHECK_MESSAGE(it_child->second.m_state.IsValid(),
"Package validation unexpectedly failed: " << it_child->second.m_state.GetRejectReason());
BOOST_CHECK(result_parent_child.m_package_feerate.has_value());
BOOST_CHECK(result_parent_child.m_package_feerate.value() ==
CFeeRate(2 * COIN, GetVirtualTransactionSize(*tx_parent) + GetVirtualTransactionSize(*tx_child)));
// A single, giant transaction submitted through ProcessNewPackage fails on single tx policy.
CTransactionRef giant_ptx = create_placeholder_tx(999, 999);
@ -110,6 +112,7 @@ BOOST_FIXTURE_TEST_CASE(package_validation_tests, TestChain100Setup)
auto it_giant_tx = result_single_large.m_tx_results.find(giant_ptx->GetWitnessHash());
BOOST_CHECK(it_giant_tx != result_single_large.m_tx_results.end());
BOOST_CHECK_EQUAL(it_giant_tx->second.m_state.GetRejectReason(), "tx-size");
BOOST_CHECK(result_single_large.m_package_feerate == std::nullopt);
// Check that mempool size hasn't changed.
BOOST_CHECK_EQUAL(m_node.mempool->size(), initialPoolSize);
@ -230,6 +233,7 @@ BOOST_FIXTURE_TEST_CASE(package_submission_tests, TestChain100Setup)
BOOST_CHECK_EQUAL(result_unrelated_submit.m_state.GetResult(), PackageValidationResult::PCKG_POLICY);
BOOST_CHECK_EQUAL(result_unrelated_submit.m_state.GetRejectReason(), "package-not-child-with-parents");
BOOST_CHECK_EQUAL(m_node.mempool->size(), expected_pool_size);
BOOST_CHECK(result_unrelated_submit.m_package_feerate == std::nullopt);
// Parent and Child (and Grandchild) Package
Package package_parent_child;
@ -271,6 +275,7 @@ BOOST_FIXTURE_TEST_CASE(package_submission_tests, TestChain100Setup)
BOOST_CHECK_EQUAL(result_3gen_submit.m_state.GetResult(), PackageValidationResult::PCKG_POLICY);
BOOST_CHECK_EQUAL(result_3gen_submit.m_state.GetRejectReason(), "package-not-child-with-parents");
BOOST_CHECK_EQUAL(m_node.mempool->size(), expected_pool_size);
BOOST_CHECK(result_3gen_submit.m_package_feerate == std::nullopt);
}
// Child with missing parent.
@ -286,6 +291,7 @@ BOOST_FIXTURE_TEST_CASE(package_submission_tests, TestChain100Setup)
BOOST_CHECK_EQUAL(result_missing_parent.m_state.GetRejectReason(), "package-not-child-with-unconfirmed-parents");
BOOST_CHECK_EQUAL(m_node.mempool->size(), expected_pool_size);
BOOST_CHECK(result_missing_parent.m_package_feerate == std::nullopt);
}
// Submit package with parent + child.
@ -305,6 +311,10 @@ BOOST_FIXTURE_TEST_CASE(package_submission_tests, TestChain100Setup)
BOOST_CHECK_EQUAL(m_node.mempool->size(), expected_pool_size);
BOOST_CHECK(m_node.mempool->exists(GenTxid::Txid(tx_parent->GetHash())));
BOOST_CHECK(m_node.mempool->exists(GenTxid::Txid(tx_child->GetHash())));
// Since both transactions have high feerates, they each passed validation individually.
// Package validation was unnecessary, so there is no package feerate.
BOOST_CHECK(submit_parent_child.m_package_feerate == std::nullopt);
}
// Already-in-mempool transactions should be detected and de-duplicated.
@ -325,6 +335,8 @@ BOOST_FIXTURE_TEST_CASE(package_submission_tests, TestChain100Setup)
BOOST_CHECK_EQUAL(m_node.mempool->size(), expected_pool_size);
BOOST_CHECK(m_node.mempool->exists(GenTxid::Txid(tx_parent->GetHash())));
BOOST_CHECK(m_node.mempool->exists(GenTxid::Txid(tx_child->GetHash())));
BOOST_CHECK(submit_deduped.m_package_feerate == std::nullopt);
}
}
@ -399,8 +411,12 @@ BOOST_FIXTURE_TEST_CASE(package_witness_swap_tests, TestChain100Setup)
BOOST_CHECK(m_node.mempool->exists(GenTxid::Txid(ptx_parent->GetHash())));
BOOST_CHECK(m_node.mempool->exists(GenTxid::Txid(ptx_child1->GetHash())));
// Child2 would have been validated individually.
BOOST_CHECK(submit_witness1.m_package_feerate == std::nullopt);
const auto submit_witness2 = ProcessNewPackage(m_node.chainman->ActiveChainstate(), *m_node.mempool,
{ptx_parent, ptx_child2}, /*test_accept=*/false);
BOOST_CHECK(submit_witness2.m_package_feerate == std::nullopt);
BOOST_CHECK_MESSAGE(submit_witness2.m_state.IsValid(),
"Package validation unexpectedly failed: " << submit_witness2.m_state.GetRejectReason());
auto it_parent2_deduped = submit_witness2.m_tx_results.find(ptx_parent->GetWitnessHash());
@ -424,6 +440,7 @@ BOOST_FIXTURE_TEST_CASE(package_witness_swap_tests, TestChain100Setup)
auto it_child_dup = submit_segwit_dedup.m_tx_results.find(ptx_child1->GetWitnessHash());
BOOST_CHECK(it_parent_dup->second.m_result_type == MempoolAcceptResult::ResultType::MEMPOOL_ENTRY);
BOOST_CHECK(it_child_dup->second.m_result_type == MempoolAcceptResult::ResultType::MEMPOOL_ENTRY);
BOOST_CHECK(submit_witness2.m_package_feerate == std::nullopt);
}
// Try submitting Package1{child2, grandchild} where child2 is same-txid-different-witness as
@ -458,6 +475,9 @@ BOOST_FIXTURE_TEST_CASE(package_witness_swap_tests, TestChain100Setup)
BOOST_CHECK(m_node.mempool->exists(GenTxid::Txid(ptx_child2->GetHash())));
BOOST_CHECK(!m_node.mempool->exists(GenTxid::Wtxid(ptx_child2->GetWitnessHash())));
BOOST_CHECK(m_node.mempool->exists(GenTxid::Wtxid(ptx_grandchild->GetWitnessHash())));
// Since child2 is ignored, grandchild would be validated individually.
BOOST_CHECK(submit_spend_ignored.m_package_feerate == std::nullopt);
}
// A package Package{parent1, parent2, parent3, child} where the parents are a mixture of
@ -516,11 +536,11 @@ BOOST_FIXTURE_TEST_CASE(package_witness_swap_tests, TestChain100Setup)
BOOST_CHECK(parent2_v2_result.m_result_type == MempoolAcceptResult::ResultType::VALID);
package_mixed.push_back(ptx_parent2_v1);
// parent3 will be a new transaction
// parent3 will be a new transaction. Put 0 fees on it to make it invalid on its own.
auto mtx_parent3 = CreateValidMempoolTransaction(/*input_transaction=*/m_coinbase_txns[3], /*input_vout=*/0,
/*input_height=*/0, /*input_signing_key=*/coinbaseKey,
/*output_destination=*/acs_spk,
/*output_amount=*/CAmount(49 * COIN), /*submit=*/false);
/*output_amount=*/CAmount(50 * COIN), /*submit=*/false);
CTransactionRef ptx_parent3 = MakeTransactionRef(mtx_parent3);
package_mixed.push_back(ptx_parent3);
@ -536,7 +556,7 @@ BOOST_FIXTURE_TEST_CASE(package_witness_swap_tests, TestChain100Setup)
mtx_mixed_child.vin[0].scriptWitness = acs_witness;
mtx_mixed_child.vin[1].scriptWitness = acs_witness;
mtx_mixed_child.vin[2].scriptWitness = acs_witness;
mtx_mixed_child.vout.push_back(CTxOut(145 * COIN, mixed_child_spk));
mtx_mixed_child.vout.push_back(CTxOut((48 + 49 + 50 - 1) * COIN, mixed_child_spk));
CTransactionRef ptx_mixed_child = MakeTransactionRef(mtx_mixed_child);
package_mixed.push_back(ptx_mixed_child);
@ -568,6 +588,205 @@ BOOST_FIXTURE_TEST_CASE(package_witness_swap_tests, TestChain100Setup)
BOOST_CHECK(!m_node.mempool->exists(GenTxid::Wtxid(ptx_parent2_v1->GetWitnessHash())));
BOOST_CHECK(m_node.mempool->exists(GenTxid::Txid(ptx_parent3->GetHash())));
BOOST_CHECK(m_node.mempool->exists(GenTxid::Txid(ptx_mixed_child->GetHash())));
// package feerate should include parent3 and child. It should not include parent1 or parent2_v1.
BOOST_CHECK(mixed_result.m_package_feerate.has_value());
const CFeeRate expected_feerate(1 * COIN, GetVirtualTransactionSize(*ptx_parent3) + GetVirtualTransactionSize(*ptx_mixed_child));
BOOST_CHECK_MESSAGE(mixed_result.m_package_feerate.value() == expected_feerate,
strprintf("Expected package feerate %s, got %s", expected_feerate.ToString(),
mixed_result.m_package_feerate.value().ToString()));
}
}
BOOST_FIXTURE_TEST_CASE(package_cpfp_tests, TestChain100Setup)
{
mineBlocks(5);
LOCK(::cs_main);
size_t expected_pool_size = m_node.mempool->size();
CKey child_key;
child_key.MakeNewKey(true);
CScript parent_spk = GetScriptForDestination(WitnessV0KeyHash(child_key.GetPubKey()));
CKey grandchild_key;
grandchild_key.MakeNewKey(true);
CScript child_spk = GetScriptForDestination(WitnessV0KeyHash(grandchild_key.GetPubKey()));
// zero-fee parent and high-fee child package
const CAmount coinbase_value{50 * COIN};
const CAmount parent_value{coinbase_value - 0};
const CAmount child_value{parent_value - COIN};
Package package_cpfp;
auto mtx_parent = CreateValidMempoolTransaction(/*input_transaction=*/ m_coinbase_txns[0], /*vout=*/ 0,
/*input_height=*/ 0, /*input_signing_key=*/ coinbaseKey,
/*output_destination=*/ parent_spk,
/*output_amount=*/ parent_value, /*submit=*/ false);
CTransactionRef tx_parent = MakeTransactionRef(mtx_parent);
package_cpfp.push_back(tx_parent);
auto mtx_child = CreateValidMempoolTransaction(/*input_transaction=*/ tx_parent, /*vout=*/ 0,
/*input_height=*/ 101, /*input_signing_key=*/ child_key,
/*output_destination=*/ child_spk,
/*output_amount=*/ child_value, /*submit=*/ false);
CTransactionRef tx_child = MakeTransactionRef(mtx_child);
package_cpfp.push_back(tx_child);
// Package feerate is calculated using modified fees, and prioritisetransaction accepts negative
// fee deltas. This should be taken into account. De-prioritise the parent transaction by -1BTC,
// bringing the package feerate to 0.
m_node.mempool->PrioritiseTransaction(tx_parent->GetHash(), -1 * COIN);
{
BOOST_CHECK_EQUAL(m_node.mempool->size(), expected_pool_size);
const auto submit_cpfp_deprio = ProcessNewPackage(m_node.chainman->ActiveChainstate(), *m_node.mempool,
package_cpfp, /*test_accept=*/ false);
BOOST_CHECK_MESSAGE(submit_cpfp_deprio.m_state.IsInvalid(),
"Package validation unexpectedly succeeded: " << submit_cpfp_deprio.m_state.GetRejectReason());
BOOST_CHECK(submit_cpfp_deprio.m_tx_results.empty());
BOOST_CHECK_EQUAL(m_node.mempool->size(), expected_pool_size);
const CFeeRate expected_feerate(0, GetVirtualTransactionSize(*tx_parent) + GetVirtualTransactionSize(*tx_child));
BOOST_CHECK(submit_cpfp_deprio.m_package_feerate.has_value());
BOOST_CHECK(submit_cpfp_deprio.m_package_feerate.value() == CFeeRate{0});
BOOST_CHECK_MESSAGE(submit_cpfp_deprio.m_package_feerate.value() == expected_feerate,
strprintf("Expected package feerate %s, got %s", expected_feerate.ToString(),
submit_cpfp_deprio.m_package_feerate.value().ToString()));
}
// Clear the prioritisation of the parent transaction.
WITH_LOCK(m_node.mempool->cs, m_node.mempool->ClearPrioritisation(tx_parent->GetHash()));
// Package CPFP: Even though the parent pays 0 absolute fees, the child pays 1 BTC which is
// enough for the package feerate to meet the threshold.
{
BOOST_CHECK_EQUAL(m_node.mempool->size(), expected_pool_size);
const auto submit_cpfp = ProcessNewPackage(m_node.chainman->ActiveChainstate(), *m_node.mempool,
package_cpfp, /*test_accept=*/ false);
expected_pool_size += 2;
BOOST_CHECK_MESSAGE(submit_cpfp.m_state.IsValid(),
"Package validation unexpectedly failed: " << submit_cpfp.m_state.GetRejectReason());
auto it_parent = submit_cpfp.m_tx_results.find(tx_parent->GetWitnessHash());
auto it_child = submit_cpfp.m_tx_results.find(tx_child->GetWitnessHash());
BOOST_CHECK(it_parent != submit_cpfp.m_tx_results.end());
BOOST_CHECK(it_parent->second.m_result_type == MempoolAcceptResult::ResultType::VALID);
BOOST_CHECK(it_parent->second.m_base_fees.value() == 0);
BOOST_CHECK(it_child != submit_cpfp.m_tx_results.end());
BOOST_CHECK(it_child->second.m_result_type == MempoolAcceptResult::ResultType::VALID);
BOOST_CHECK(it_child->second.m_base_fees.value() == COIN);
BOOST_CHECK_EQUAL(m_node.mempool->size(), expected_pool_size);
BOOST_CHECK(m_node.mempool->exists(GenTxid::Txid(tx_parent->GetHash())));
BOOST_CHECK(m_node.mempool->exists(GenTxid::Txid(tx_child->GetHash())));
const CFeeRate expected_feerate(coinbase_value - child_value,
GetVirtualTransactionSize(*tx_parent) + GetVirtualTransactionSize(*tx_child));
BOOST_CHECK(expected_feerate.GetFeePerK() > 1000);
BOOST_CHECK(submit_cpfp.m_package_feerate.has_value());
BOOST_CHECK_MESSAGE(submit_cpfp.m_package_feerate.value() == expected_feerate,
strprintf("Expected package feerate %s, got %s", expected_feerate.ToString(),
submit_cpfp.m_package_feerate.value().ToString()));
}
// Just because we allow low-fee parents doesn't mean we allow low-feerate packages.
// This package just pays 200 satoshis total. This would be enough to pay for the child alone,
// but isn't enough for the entire package to meet the 1sat/vbyte minimum.
Package package_still_too_low;
auto mtx_parent_cheap = CreateValidMempoolTransaction(/*input_transaction=*/ m_coinbase_txns[1], /*vout=*/ 0,
/*input_height=*/ 0, /*input_signing_key=*/ coinbaseKey,
/*output_destination=*/ parent_spk,
/*output_amount=*/ coinbase_value, /*submit=*/ false);
CTransactionRef tx_parent_cheap = MakeTransactionRef(mtx_parent_cheap);
package_still_too_low.push_back(tx_parent_cheap);
auto mtx_child_cheap = CreateValidMempoolTransaction(/*input_transaction=*/ tx_parent_cheap, /*vout=*/ 0,
/*input_height=*/ 101, /* input_signing_key */ child_key,
/*output_destination=*/ child_spk,
/*output_amount=*/ coinbase_value - 200, /*submit=*/ false);
CTransactionRef tx_child_cheap = MakeTransactionRef(mtx_child_cheap);
package_still_too_low.push_back(tx_child_cheap);
// Cheap package should fail with package-fee-too-low.
{
BOOST_CHECK_EQUAL(m_node.mempool->size(), expected_pool_size);
const auto submit_package_too_low = ProcessNewPackage(m_node.chainman->ActiveChainstate(), *m_node.mempool,
package_still_too_low, /* test_accept */ false);
BOOST_CHECK_MESSAGE(submit_package_too_low.m_state.IsInvalid(), "Package validation unexpectedly succeeded");
BOOST_CHECK_EQUAL(submit_package_too_low.m_state.GetResult(), PackageValidationResult::PCKG_POLICY);
BOOST_CHECK_EQUAL(submit_package_too_low.m_state.GetRejectReason(), "package-fee-too-low");
BOOST_CHECK_EQUAL(m_node.mempool->size(), expected_pool_size);
const CFeeRate child_feerate(200, GetVirtualTransactionSize(*tx_child_cheap));
BOOST_CHECK(child_feerate.GetFeePerK() > 1000);
const CFeeRate expected_feerate(200,
GetVirtualTransactionSize(*tx_parent_cheap) + GetVirtualTransactionSize(*tx_child_cheap));
BOOST_CHECK(expected_feerate.GetFeePerK() < 1000);
BOOST_CHECK(submit_package_too_low.m_package_feerate.has_value());
BOOST_CHECK_MESSAGE(submit_package_too_low.m_package_feerate.value() == expected_feerate,
strprintf("Expected package feerate %s, got %s", expected_feerate.ToString(),
submit_package_too_low.m_package_feerate.value().ToString()));
}
// Package feerate includes the modified fees of the transactions.
// This means a child with its fee delta from prioritisetransaction can pay for a parent.
m_node.mempool->PrioritiseTransaction(tx_child_cheap->GetHash(), 1 * COIN);
// Now that the child's fees have "increased" by 1 BTC, the cheap package should succeed.
{
const auto submit_prioritised_package = ProcessNewPackage(m_node.chainman->ActiveChainstate(), *m_node.mempool,
package_still_too_low, /*test_accept=*/ false);
expected_pool_size += 2;
BOOST_CHECK_MESSAGE(submit_prioritised_package.m_state.IsValid(),
"Package validation unexpectedly failed" << submit_prioritised_package.m_state.GetRejectReason());
const CFeeRate expected_feerate(1 * COIN + 200,
GetVirtualTransactionSize(*tx_parent_cheap) + GetVirtualTransactionSize(*tx_child_cheap));
BOOST_CHECK(submit_prioritised_package.m_package_feerate.has_value());
BOOST_CHECK_MESSAGE(submit_prioritised_package.m_package_feerate.value() == expected_feerate,
strprintf("Expected package feerate %s, got %s", expected_feerate.ToString(),
submit_prioritised_package.m_package_feerate.value().ToString()));
}
// Package feerate is calculated without topology in mind; it's just aggregating fees and sizes.
// However, this should not allow parents to pay for children. Each transaction should be
// validated individually first, eliminating sufficient-feerate parents before they are unfairly
// included in the package feerate. It's also important that the low-fee child doesn't prevent
// the parent from being accepted.
Package package_rich_parent;
const CAmount high_parent_fee{1 * COIN};
auto mtx_parent_rich = CreateValidMempoolTransaction(/*input_transaction=*/ m_coinbase_txns[2], /*vout=*/ 0,
/*input_height=*/ 0, /*input_signing_key=*/ coinbaseKey,
/*output_destination=*/ parent_spk,
/*output_amount=*/ coinbase_value - high_parent_fee, /*submit=*/ false);
CTransactionRef tx_parent_rich = MakeTransactionRef(mtx_parent_rich);
package_rich_parent.push_back(tx_parent_rich);
auto mtx_child_poor = CreateValidMempoolTransaction(/*input_transaction=*/ tx_parent_rich, /*vout=*/ 0,
/*input_height=*/ 101, /*input_signing_key=*/ child_key,
/*output_destination=*/ child_spk,
/*output_amount=*/ coinbase_value - high_parent_fee, /*submit=*/ false);
CTransactionRef tx_child_poor = MakeTransactionRef(mtx_child_poor);
package_rich_parent.push_back(tx_child_poor);
// Parent pays 1 BTC and child pays none. The parent should be accepted without the child.
{
BOOST_CHECK_EQUAL(m_node.mempool->size(), expected_pool_size);
const auto submit_rich_parent = ProcessNewPackage(m_node.chainman->ActiveChainstate(), *m_node.mempool,
package_rich_parent, /* test_accept */ false);
expected_pool_size += 1;
BOOST_CHECK_MESSAGE(submit_rich_parent.m_state.IsInvalid(), "Package validation unexpectedly succeeded");
// The child would have been validated on its own and failed, then submitted as a "package" of 1.
// The package feerate is just the child's feerate, which is 0sat/vb.
BOOST_CHECK(submit_rich_parent.m_package_feerate.has_value());
BOOST_CHECK_MESSAGE(submit_rich_parent.m_package_feerate.value() == CFeeRate(),
"expected 0, got " << submit_rich_parent.m_package_feerate.value().ToString());
BOOST_CHECK_EQUAL(submit_rich_parent.m_state.GetResult(), PackageValidationResult::PCKG_POLICY);
BOOST_CHECK_EQUAL(submit_rich_parent.m_state.GetRejectReason(), "package-fee-too-low");
auto it_parent = submit_rich_parent.m_tx_results.find(tx_parent_rich->GetWitnessHash());
BOOST_CHECK(it_parent != submit_rich_parent.m_tx_results.end());
BOOST_CHECK(it_parent->second.m_result_type == MempoolAcceptResult::ResultType::VALID);
BOOST_CHECK(it_parent->second.m_state.GetRejectReason() == "");
BOOST_CHECK_MESSAGE(it_parent->second.m_base_fees.value() == high_parent_fee,
strprintf("rich parent: expected fee %s, got %s", high_parent_fee, it_parent->second.m_base_fees.value()));
BOOST_CHECK_EQUAL(m_node.mempool->size(), expected_pool_size);
BOOST_CHECK(m_node.mempool->exists(GenTxid::Txid(tx_parent_rich->GetHash())));
BOOST_CHECK(!m_node.mempool->exists(GenTxid::Txid(tx_child_poor->GetHash())));
}
}
BOOST_AUTO_TEST_SUITE_END()

89
src/validation.cpp
View file

@ -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;
}

8
src/validation.h
View file

@ -234,11 +234,19 @@ struct PackageMempoolAcceptResult
* was a package-wide error (see result in m_state), m_tx_results will be empty.
*/
std::map<const uint256, const MempoolAcceptResult> m_tx_results;
/** Package feerate, defined as the aggregated modified fees divided by the total virtual size
* of all transactions in the package. May be unavailable if some inputs were not available or
* a transaction failure caused validation to terminate early. */
std::optional<CFeeRate> m_package_feerate;
explicit PackageMempoolAcceptResult(PackageValidationState state,
std::map<const uint256, const MempoolAcceptResult>&& results)
: m_state{state}, m_tx_results(std::move(results)) {}
explicit PackageMempoolAcceptResult(PackageValidationState state, CFeeRate feerate,
std::map<const uint256, const MempoolAcceptResult>&& results)
: m_state{state}, m_tx_results(std::move(results)), m_package_feerate{feerate} {}
/** Constructor to create a PackageMempoolAcceptResult from a single MempoolAcceptResult */
explicit PackageMempoolAcceptResult(const uint256& wtxid, const MempoolAcceptResult& result)
: m_tx_results{ {wtxid, result} } {}