Merge bitcoin/bitcoin#28984: Cluster size 2 package rbf

94ed4fbf8e Add release note for size 2 package rbf (Greg Sanders)
afd52d8e63 doc: update package RBF comment (Greg Sanders)
6e3c4394cf mempool: Improve logging of replaced transactions (Greg Sanders)
d3466e4cc5 CheckPackageMempoolAcceptResult: Check package rbf invariants (Greg Sanders)
316d7b63c9 Fuzz: pass mempool to CheckPackageMempoolAcceptResult (Greg Sanders)
4d15bcf448 [test] package rbf (glozow)
dc21f61c72 [policy] package rbf (Suhas Daftuar)
5da3967815 PackageV3Checks: Relax assumptions (Greg Sanders)

Pull request description:

  Allows any 2 transaction package with no in-mempool ancestors to do package RBF when directly conflicting with other mempool clusters of size two or less.

  Proposed validation steps:
  1) If the transaction package is of size 1, legacy rbf rules apply.
  2) Otherwise the transaction package consists of a (parent, child) pair with no other in-mempool ancestors (or descendants, obviously), so it is also going to create a cluster of size 2. If larger, fail.
  3) The package rbf may not evict more than 100 transactions from the mempool(bip125 rule 5)
  4) The package is a single chunk
  5) Every directly conflicted mempool transaction is connected to at most 1 other in-mempool transaction (ie the cluster size of the conflict is at most 2).
  6) Diagram check: We ensure that the replacement is strictly superior, improving the mempool
  7) The total fee of the package, minus the total fee of what is being evicted, is at least the minrelayfee * size of the package (equivalent to bip125 rule 3 and 4)

  Post-cluster mempool this will likely be expanded to general package rbf, but this is what we can safely support today.

ACKs for top commit:
  achow101:
    ACK 94ed4fbf8e
  glozow:
    reACK 94ed4fbf8e via range-diff
  ismaelsadeeq:
    re-ACK 94ed4fbf8e
  theStack:
    Code-review ACK 94ed4fbf8e
  murchandamus:
    utACK 94ed4fbf8e

Tree-SHA512: 9bd383e695964f362f147482bbf73b1e77c4d792bda2e91d7f30d74b3540a09146a5528baf86854a113005581e8c75f04737302517b7d5124296bd7a151e3992

src/test/fuzz/package_eval.cpp

@@ -314,7 +314,7 @@ FUZZ_TARGET(tx_package_eval, .init = initialize_tx_pool)
             // just use result_package.m_state here. This makes the expect_valid check meaningless, but
             // we can still verify that the contents of m_tx_results are consistent with m_state.
             const bool expect_valid{result_package.m_state.IsValid()};
-            Assert(!CheckPackageMempoolAcceptResult(txs, result_package, expect_valid, nullptr));
+            Assert(!CheckPackageMempoolAcceptResult(txs, result_package, expect_valid, &tx_pool));
         } else {
             // This is empty if it fails early checks, or "full" if transactions are looked at deeper
             Assert(result_package.m_tx_results.size() == txs.size() || result_package.m_tx_results.empty());

src/test/txpackage_tests.cpp

@@ -6,6 +6,7 @@
 #include <key_io.h>
 #include <policy/packages.h>
 #include <policy/policy.h>
+#include <policy/rbf.h>
 #include <primitives/transaction.h>
 #include <script/script.h>
 #include <serialize.h>
@@ -938,4 +939,147 @@ BOOST_FIXTURE_TEST_CASE(package_cpfp_tests, TestChain100Setup)
         BOOST_CHECK_EQUAL(m_node.mempool->size(), expected_pool_size);
     }
 }
+
+BOOST_FIXTURE_TEST_CASE(package_rbf_tests, TestChain100Setup)
+{
+    mineBlocks(5);
+    LOCK(::cs_main);
+    size_t expected_pool_size = m_node.mempool->size();
+    CKey child_key{GenerateRandomKey()};
+    CScript parent_spk = GetScriptForDestination(WitnessV0KeyHash(child_key.GetPubKey()));
+    CKey grandchild_key{GenerateRandomKey()};
+    CScript child_spk = GetScriptForDestination(WitnessV0KeyHash(grandchild_key.GetPubKey()));
+
+    const CAmount coinbase_value{50 * COIN};
+    // Test that de-duplication works. This is not actually package rbf.
+    {
+        // 1 parent paying 200sat, 1 child paying 300sat
+        Package package1;
+        // 1 parent paying 200sat, 1 child paying 500sat
+        Package package2;
+        // Package1 and package2 have the same parent. The children conflict.
+        auto mtx_parent = CreateValidMempoolTransaction(/*input_transaction=*/m_coinbase_txns[0], /*input_vout=*/0,
+                                                        /*input_height=*/0, /*input_signing_key=*/coinbaseKey,
+                                                        /*output_destination=*/parent_spk,
+                                                        /*output_amount=*/coinbase_value - low_fee_amt, /*submit=*/false);
+        CTransactionRef tx_parent = MakeTransactionRef(mtx_parent);
+        package1.push_back(tx_parent);
+        package2.push_back(tx_parent);
+
+        CTransactionRef tx_child_1 = MakeTransactionRef(CreateValidMempoolTransaction(tx_parent, 0, 101, child_key, child_spk, coinbase_value - low_fee_amt - 300, false));
+        package1.push_back(tx_child_1);
+        CTransactionRef tx_child_2 = MakeTransactionRef(CreateValidMempoolTransaction(tx_parent, 0, 101, child_key, child_spk, coinbase_value - low_fee_amt - 500, false));
+        package2.push_back(tx_child_2);
+
+        LOCK(m_node.mempool->cs);
+        const auto submit1 = ProcessNewPackage(m_node.chainman->ActiveChainstate(), *m_node.mempool, package1, /*test_accept=*/false, std::nullopt);
+        if (auto err_1{CheckPackageMempoolAcceptResult(package1, submit1, /*expect_valid=*/true, m_node.mempool.get())}) {
+            BOOST_ERROR(err_1.value());
+        }
+
+        // Check precise ResultTypes and mempool size. We know it_parent_1 and it_child_1 exist from above call
+        auto it_parent_1 = submit1.m_tx_results.find(tx_parent->GetWitnessHash());
+        auto it_child_1 = submit1.m_tx_results.find(tx_child_1->GetWitnessHash());
+        BOOST_CHECK_EQUAL(it_parent_1->second.m_result_type, MempoolAcceptResult::ResultType::VALID);
+        BOOST_CHECK_EQUAL(it_child_1->second.m_result_type, MempoolAcceptResult::ResultType::VALID);
+        expected_pool_size += 2;
+        BOOST_CHECK_EQUAL(m_node.mempool->size(), expected_pool_size);
+
+        const auto submit2 = ProcessNewPackage(m_node.chainman->ActiveChainstate(), *m_node.mempool, package2, /*test_accept=*/false, std::nullopt);
+        if (auto err_2{CheckPackageMempoolAcceptResult(package2, submit2, /*expect_valid=*/true, m_node.mempool.get())}) {
+            BOOST_ERROR(err_2.value());
+        }
+
+        // Check precise ResultTypes and mempool size. We know it_parent_2 and it_child_2 exist from above call
+        auto it_parent_2 = submit2.m_tx_results.find(tx_parent->GetWitnessHash());
+        auto it_child_2 = submit2.m_tx_results.find(tx_child_2->GetWitnessHash());
+        BOOST_CHECK_EQUAL(it_parent_2->second.m_result_type, MempoolAcceptResult::ResultType::MEMPOOL_ENTRY);
+        BOOST_CHECK_EQUAL(it_child_2->second.m_result_type, MempoolAcceptResult::ResultType::VALID);
+        BOOST_CHECK_EQUAL(m_node.mempool->size(), expected_pool_size);
+
+        // child1 has been replaced
+        BOOST_CHECK(!m_node.mempool->exists(GenTxid::Txid(tx_child_1->GetHash())));
+    }
+
+    // Test package rbf.
+    {
+        CTransactionRef tx_parent_1 = MakeTransactionRef(CreateValidMempoolTransaction(
+            m_coinbase_txns[1], /*input_vout=*/0, /*input_height=*/0,
+            coinbaseKey, parent_spk, coinbase_value - 200, /*submit=*/false));
+        CTransactionRef tx_child_1 = MakeTransactionRef(CreateValidMempoolTransaction(
+            tx_parent_1, /*input_vout=*/0, /*input_height=*/101,
+            child_key, child_spk, coinbase_value - 400, /*submit=*/false));
+
+        CTransactionRef tx_parent_2 = MakeTransactionRef(CreateValidMempoolTransaction(
+            m_coinbase_txns[1], /*input_vout=*/0, /*input_height=*/0,
+            coinbaseKey, parent_spk, coinbase_value - 800, /*submit=*/false));
+        CTransactionRef tx_child_2 = MakeTransactionRef(CreateValidMempoolTransaction(
+            tx_parent_2, /*input_vout=*/0, /*input_height=*/101,
+            child_key, child_spk, coinbase_value - 800 - 200, /*submit=*/false));
+
+        CTransactionRef tx_parent_3 = MakeTransactionRef(CreateValidMempoolTransaction(
+            m_coinbase_txns[1], /*input_vout=*/0, /*input_height=*/0,
+            coinbaseKey, parent_spk, coinbase_value - 199, /*submit=*/false));
+        CTransactionRef tx_child_3 = MakeTransactionRef(CreateValidMempoolTransaction(
+            tx_parent_3, /*input_vout=*/0, /*input_height=*/101,
+            child_key, child_spk, coinbase_value - 199 - 1300, /*submit=*/false));
+
+        // In all packages, the parents conflict with each other
+        BOOST_CHECK(tx_parent_1->GetHash() != tx_parent_2->GetHash() && tx_parent_2->GetHash() != tx_parent_3->GetHash());
+
+        // 1 parent paying 200sat, 1 child paying 200sat.
+        Package package1{tx_parent_1, tx_child_1};
+        // 1 parent paying 800sat, 1 child paying 200sat.
+        Package package2{tx_parent_2, tx_child_2};
+        // 1 parent paying 199sat, 1 child paying 1300sat.
+        Package package3{tx_parent_3, tx_child_3};
+
+        const auto submit1 = ProcessNewPackage(m_node.chainman->ActiveChainstate(), *m_node.mempool, package1, false, std::nullopt);
+        if (auto err_1{CheckPackageMempoolAcceptResult(package1, submit1, /*expect_valid=*/true, m_node.mempool.get())}) {
+            BOOST_ERROR(err_1.value());
+        }
+        auto it_parent_1 = submit1.m_tx_results.find(tx_parent_1->GetWitnessHash());
+        auto it_child_1 = submit1.m_tx_results.find(tx_child_1->GetWitnessHash());
+        BOOST_CHECK_EQUAL(it_parent_1->second.m_result_type, MempoolAcceptResult::ResultType::VALID);
+        BOOST_CHECK_EQUAL(it_child_1->second.m_result_type, MempoolAcceptResult::ResultType::VALID);
+        expected_pool_size += 2;
+        BOOST_CHECK_EQUAL(m_node.mempool->size(), expected_pool_size);
+
+        // This replacement is actually not package rbf; the parent carries enough fees
+        // to replace the entire package on its own.
+        const auto submit2 = ProcessNewPackage(m_node.chainman->ActiveChainstate(), *m_node.mempool, package2, false, std::nullopt);
+        if (auto err_2{CheckPackageMempoolAcceptResult(package2, submit2, /*expect_valid=*/true, m_node.mempool.get())}) {
+            BOOST_ERROR(err_2.value());
+        }
+        auto it_parent_2 = submit2.m_tx_results.find(tx_parent_2->GetWitnessHash());
+        auto it_child_2 = submit2.m_tx_results.find(tx_child_2->GetWitnessHash());
+        BOOST_CHECK_EQUAL(it_parent_2->second.m_result_type, MempoolAcceptResult::ResultType::VALID);
+        BOOST_CHECK_EQUAL(it_child_2->second.m_result_type, MempoolAcceptResult::ResultType::VALID);
+        BOOST_CHECK_EQUAL(m_node.mempool->size(), expected_pool_size);
+
+        // Package RBF, in which the replacement transaction's child sponsors the fees to meet RBF feerate rules
+        const auto submit3 = ProcessNewPackage(m_node.chainman->ActiveChainstate(), *m_node.mempool, package3, false, std::nullopt);
+        if (auto err_3{CheckPackageMempoolAcceptResult(package3, submit3, /*expect_valid=*/true, m_node.mempool.get())}) {
+            BOOST_ERROR(err_3.value());
+        }
+        auto it_parent_3 = submit3.m_tx_results.find(tx_parent_3->GetWitnessHash());
+        auto it_child_3 = submit3.m_tx_results.find(tx_child_3->GetWitnessHash());
+        BOOST_CHECK_EQUAL(it_parent_3->second.m_result_type, MempoolAcceptResult::ResultType::VALID);
+        BOOST_CHECK_EQUAL(it_child_3->second.m_result_type, MempoolAcceptResult::ResultType::VALID);
+
+        // package3 was considered as a package to replace both package2 transactions
+        BOOST_CHECK(it_parent_3->second.m_replaced_transactions.size() == 2);
+        BOOST_CHECK(it_child_3->second.m_replaced_transactions.empty());
+
+        std::vector<Wtxid> expected_package3_wtxids({tx_parent_3->GetWitnessHash(), tx_child_3->GetWitnessHash()});
+        const auto package3_total_vsize{GetVirtualTransactionSize(*tx_parent_3) + GetVirtualTransactionSize(*tx_child_3)};
+        BOOST_CHECK(it_parent_3->second.m_wtxids_fee_calculations.value() == expected_package3_wtxids);
+        BOOST_CHECK(it_child_3->second.m_wtxids_fee_calculations.value() == expected_package3_wtxids);
+        BOOST_CHECK_EQUAL(it_parent_3->second.m_effective_feerate.value().GetFee(package3_total_vsize), 199 + 1300);
+        BOOST_CHECK_EQUAL(it_child_3->second.m_effective_feerate.value().GetFee(package3_total_vsize), 199 + 1300);
+
+        BOOST_CHECK_EQUAL(m_node.mempool->size(), expected_pool_size);
+    }
+
+}
 BOOST_AUTO_TEST_SUITE_END()

src/test/util/txmempool.cpp

@@ -7,6 +7,7 @@
 #include <chainparams.h>
 #include <node/context.h>
 #include <node/mempool_args.h>
+#include <policy/rbf.h>
 #include <policy/v3_policy.h>
 #include <txmempool.h>
 #include <util/check.h>
@@ -68,6 +69,28 @@ std::optional<std::string> CheckPackageMempoolAcceptResult(const Package& txns,
             return strprintf("tx %s unexpectedly failed: %s", wtxid.ToString(), atmp_result.m_state.ToString());
         }
 
+        // Each subpackage is allowed MAX_REPLACEMENT_CANDIDATES replacements (only checking individually here)
+        if (atmp_result.m_replaced_transactions.size() > MAX_REPLACEMENT_CANDIDATES) {
+            return strprintf("tx %s result replaced too many transactions",
+                                wtxid.ToString());
+        }
+
+        // Replacements can't happen for subpackages larger than 2
+        if (!atmp_result.m_replaced_transactions.empty() &&
+            atmp_result.m_wtxids_fee_calculations.has_value() && atmp_result.m_wtxids_fee_calculations.value().size() > 2) {
+             return strprintf("tx %s was part of a too-large package RBF subpackage",
+                                wtxid.ToString());
+        }
+
+        if (!atmp_result.m_replaced_transactions.empty() && mempool) {
+            LOCK(mempool->cs);
+            // If replacements occurred and it used 2 transactions, this is a package RBF and should result in a cluster of size 2
+            if (atmp_result.m_wtxids_fee_calculations.has_value() && atmp_result.m_wtxids_fee_calculations.value().size() == 2) {
+                const auto cluster = mempool->GatherClusters({tx->GetHash()});
+                if (cluster.size() != 2) return strprintf("tx %s has too many ancestors or descendants for a package rbf", wtxid.ToString());
+            }
+        }
+
         // m_vsize and m_base_fees should exist iff the result was VALID or MEMPOOL_ENTRY
         const bool mempool_entry{atmp_result.m_result_type == MempoolAcceptResult::ResultType::MEMPOOL_ENTRY};
         if (atmp_result.m_base_fees.has_value() != (valid || mempool_entry)) {
@@ -108,6 +131,11 @@ std::optional<std::string> CheckPackageMempoolAcceptResult(const Package& txns,
                     return strprintf("wtxid %s should not be in mempool", wtxid.ToString());
                 }
             }
+            for (const auto& tx_ref : atmp_result.m_replaced_transactions) {
+                if (mempool->exists(GenTxid::Txid(tx_ref->GetHash()))) {
+                    return strprintf("tx %s should not be in mempool as it was replaced", tx_ref->GetWitnessHash().ToString());
+                }
+            }
         }
     }
     return std::nullopt;