[fuzz] Add MiniMiner target + diff fuzz against BlockAssembler

Co-authored-by: dergoegge <n.goeggi@gmail.com>
Co-authored-by: mzumsande <mzumsande@gmail.com>
Co-authored-by: Murch <murch@murch.one>

2 files changed, 193 insertions, 0 deletions

diff --git a/src/Makefile.test.include b/src/Makefile.test.include
index 3e9d6ad9e3..26fd628770 100644
--- a/src/Makefile.test.include
+++ b/src/Makefile.test.include
@@ -283,6 +283,7 @@ test_fuzz_fuzz_SOURCES = \
  test/fuzz/message.cpp \
  test/fuzz/miniscript.cpp \
  test/fuzz/minisketch.cpp \
+ test/fuzz/mini_miner.cpp \
  test/fuzz/muhash.cpp \
  test/fuzz/multiplication_overflow.cpp \
  test/fuzz/net.cpp \
diff --git a/src/test/fuzz/mini_miner.cpp b/src/test/fuzz/mini_miner.cpp
new file mode 100644
index 0000000000..f49d940393
--- /dev/null
+++ b/src/test/fuzz/mini_miner.cpp
@@ -0,0 +1,192 @@
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+#include <test/fuzz/util/mempool.h>
+#include <test/util/script.h>
+#include <test/util/setup_common.h>
+#include <test/util/txmempool.h>
+#include <test/util/mining.h>
+
+#include <node/mini_miner.h>
+#include <node/miner.h>
+#include <primitives/transaction.h>
+#include <random.h>
+#include <txmempool.h>
+
+#include <deque>
+#include <vector>
+
+namespace {
+
+const TestingSetup* g_setup;
+std::deque<COutPoint> g_available_coins;
+void initialize_miner()
+{
+    static const auto testing_setup = MakeNoLogFileContext<const TestingSetup>();
+    g_setup = testing_setup.get();
+    for (uint32_t i = 0; i < uint32_t{100}; ++i) {
+        g_available_coins.push_back(COutPoint{uint256::ZERO, i});
+    }
+}
+
+// Test that the MiniMiner can run with various outpoints and feerates.
+FUZZ_TARGET_INIT(mini_miner, initialize_miner)
+{
+    FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
+    CTxMemPool pool{CTxMemPool::Options{}};
+    std::vector<COutPoint> outpoints;
+    std::deque<COutPoint> available_coins = g_available_coins;
+    LOCK2(::cs_main, pool.cs);
+    // Cluster size cannot exceed 500
+    LIMITED_WHILE(!available_coins.empty(), 500)
+    {
+        CMutableTransaction mtx = CMutableTransaction();
+        const size_t num_inputs = fuzzed_data_provider.ConsumeIntegralInRange<size_t>(1, available_coins.size());
+        const size_t num_outputs = fuzzed_data_provider.ConsumeIntegralInRange<size_t>(1, 50);
+        for (size_t n{0}; n < num_inputs; ++n) {
+            auto prevout = available_coins.front();
+            mtx.vin.push_back(CTxIn(prevout, CScript()));
+            available_coins.pop_front();
+        }
+        for (uint32_t n{0}; n < num_outputs; ++n) {
+            mtx.vout.push_back(CTxOut(100, P2WSH_OP_TRUE));
+        }
+        CTransactionRef tx = MakeTransactionRef(mtx);
+        TestMemPoolEntryHelper entry;
+        const CAmount fee{ConsumeMoney(fuzzed_data_provider, /*max=*/MAX_MONEY/100000)};
+        assert(MoneyRange(fee));
+        pool.addUnchecked(entry.Fee(fee).FromTx(tx));
+
+        // All outputs are available to spend
+        for (uint32_t n{0}; n < num_outputs; ++n) {
+            if (fuzzed_data_provider.ConsumeBool()) {
+                available_coins.push_back(COutPoint{tx->GetHash(), n});
+            }
+        }
+
+        if (fuzzed_data_provider.ConsumeBool() && !tx->vout.empty()) {
+            // Add outpoint from this tx (may or not be spent by a later tx)
+            outpoints.push_back(COutPoint{tx->GetHash(),
+                                          (uint32_t)fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, tx->vout.size())});
+        } else {
+            // Add some random outpoint (will be interpreted as confirmed or not yet submitted
+            // to mempool).
+            auto outpoint = ConsumeDeserializable<COutPoint>(fuzzed_data_provider);
+            if (outpoint.has_value() && std::find(outpoints.begin(), outpoints.end(), *outpoint) == outpoints.end()) {
+                outpoints.push_back(*outpoint);
+            }
+        }
+
+    }
+
+    const CFeeRate target_feerate{CFeeRate{ConsumeMoney(fuzzed_data_provider, /*max=*/MAX_MONEY/1000)}};
+    std::optional<CAmount> total_bumpfee;
+    CAmount sum_fees = 0;
+    {
+        node::MiniMiner mini_miner{pool, outpoints};
+        assert(mini_miner.IsReadyToCalculate());
+        const auto bump_fees = mini_miner.CalculateBumpFees(target_feerate);
+        for (const auto& outpoint : outpoints) {
+            auto it = bump_fees.find(outpoint);
+            assert(it != bump_fees.end());
+            assert(it->second >= 0);
+            sum_fees += it->second;
+        }
+        assert(!mini_miner.IsReadyToCalculate());
+    }
+    {
+        node::MiniMiner mini_miner{pool, outpoints};
+        assert(mini_miner.IsReadyToCalculate());
+        total_bumpfee = mini_miner.CalculateTotalBumpFees(target_feerate);
+        assert(total_bumpfee.has_value());
+        assert(!mini_miner.IsReadyToCalculate());
+    }
+    // Overlapping ancestry across multiple outpoints can only reduce the total bump fee.
+    assert (sum_fees >= *total_bumpfee);
+}
+
+// Test that MiniMiner and BlockAssembler build the same block given the same transactions and constraints.
+FUZZ_TARGET_INIT(mini_miner_selection, initialize_miner)
+{
+    FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
+    CTxMemPool pool{CTxMemPool::Options{}};
+    // Make a copy to preserve determinism.
+    std::deque<COutPoint> available_coins = g_available_coins;
+    std::vector<CTransactionRef> transactions;
+
+    LOCK2(::cs_main, pool.cs);
+    LIMITED_WHILE(fuzzed_data_provider.ConsumeBool(), 100)
+    {
+        CMutableTransaction mtx = CMutableTransaction();
+        const size_t num_inputs = 2;
+        const size_t num_outputs = fuzzed_data_provider.ConsumeIntegralInRange<size_t>(2, 5);
+        for (size_t n{0}; n < num_inputs; ++n) {
+            auto prevout = available_coins.front();
+            mtx.vin.push_back(CTxIn(prevout, CScript()));
+            available_coins.pop_front();
+        }
+        for (uint32_t n{0}; n < num_outputs; ++n) {
+            mtx.vout.push_back(CTxOut(100, P2WSH_OP_TRUE));
+        }
+        CTransactionRef tx = MakeTransactionRef(mtx);
+
+        // First 2 outputs are available to spend. The rest are added to outpoints to calculate bumpfees.
+        // There is no overlap between spendable coins and outpoints passed to MiniMiner because the
+        // MiniMiner interprets spent coins as to-be-replaced and excludes them.
+        for (uint32_t n{0}; n < num_outputs - 1; ++n) {
+            if (fuzzed_data_provider.ConsumeBool()) {
+                available_coins.push_front(COutPoint{tx->GetHash(), n});
+            } else {
+                available_coins.push_back(COutPoint{tx->GetHash(), n});
+            }
+        }
+
+        // Stop if pool reaches DEFAULT_BLOCK_MAX_WEIGHT because BlockAssembler will stop when the
+        // block template reaches that, but the MiniMiner will keep going.
+        if (pool.GetTotalTxSize() + GetVirtualTransactionSize(*tx) >= DEFAULT_BLOCK_MAX_WEIGHT) break;
+        TestMemPoolEntryHelper entry;
+        const CAmount fee{ConsumeMoney(fuzzed_data_provider, /*max=*/MAX_MONEY/100000)};
+        assert(MoneyRange(fee));
+        pool.addUnchecked(entry.Fee(fee).FromTx(tx));
+        transactions.push_back(tx);
+    }
+    std::vector<COutPoint> outpoints;
+    for (const auto& coin : g_available_coins) {
+        if (!pool.GetConflictTx(coin)) outpoints.push_back(coin);
+    }
+    for (const auto& tx : transactions) {
+        assert(pool.exists(GenTxid::Txid(tx->GetHash())));
+        for (uint32_t n{0}; n < tx->vout.size(); ++n) {
+            COutPoint coin{tx->GetHash(), n};
+            if (!pool.GetConflictTx(coin)) outpoints.push_back(coin);
+        }
+    }
+    const CFeeRate target_feerate{ConsumeMoney(fuzzed_data_provider, /*max=*/MAX_MONEY/100000)};
+
+    node::BlockAssembler::Options miner_options;
+    miner_options.blockMinFeeRate = target_feerate;
+    miner_options.nBlockMaxWeight = DEFAULT_BLOCK_MAX_WEIGHT;
+    miner_options.test_block_validity = false;
+
+    node::BlockAssembler miner{g_setup->m_node.chainman->ActiveChainstate(), &pool, miner_options};
+    node::MiniMiner mini_miner{pool, outpoints};
+    assert(mini_miner.IsReadyToCalculate());
+
+    CScript spk_placeholder = CScript() << OP_0;
+    // Use BlockAssembler as oracle. BlockAssembler and MiniMiner should select the same
+    // transactions, stopping once packages do not meet target_feerate.
+    const auto blocktemplate{miner.CreateNewBlock(spk_placeholder)};
+    mini_miner.BuildMockTemplate(target_feerate);
+    assert(!mini_miner.IsReadyToCalculate());
+    auto mock_template_txids = mini_miner.GetMockTemplateTxids();
+    // MiniMiner doesn't add a coinbase tx.
+    assert(mock_template_txids.count(blocktemplate->block.vtx[0]->GetHash()) == 0);
+    mock_template_txids.emplace(blocktemplate->block.vtx[0]->GetHash());
+    assert(mock_template_txids.size() <= blocktemplate->block.vtx.size());
+    assert(mock_template_txids.size() >= blocktemplate->block.vtx.size());
+    assert(mock_template_txids.size() == blocktemplate->block.vtx.size());
+    for (const auto& tx : blocktemplate->block.vtx) {
+        assert(mock_template_txids.count(tx->GetHash()));
+    }
+}
+} // namespace