Blockchain tests support: Introduce difficulty calculation in t8n (#682)

- Add ommer block reward
- Difficulty calculation added
- Use it in t8n interface implementation

Author: rodiazet

test/state/CMakeLists.txt

@@ -12,6 +12,8 @@ target_sources(
     bloom_filter.hpp
     bloom_filter.cpp
     errors.hpp
+    ethash_difficulty.hpp
+    ethash_difficulty.cpp
     hash_utils.hpp
     hash_utils.cpp
     host.hpp

test/state/ethash_difficulty.cpp

@@ -0,0 +1,62 @@
+// evmone: Fast Ethereum Virtual Machine implementation
+// Copyright 2023 The evmone Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+#include "ethash_difficulty.hpp"
+#include <algorithm>
+#include <cassert>
+
+namespace evmone::state
+{
+namespace
+{
+int64_t get_bomb_delay(evmc_revision rev) noexcept
+{
+    switch (rev)
+    {
+    default:
+        return 0;
+    case EVMC_BYZANTIUM:
+        return 3'000'000;
+    case EVMC_CONSTANTINOPLE:
+    case EVMC_PETERSBURG:
+    case EVMC_ISTANBUL:
+        return 5'000'000;
+    case EVMC_BERLIN:
+        return 9'000'000;
+    case EVMC_LONDON:
+        return 9'700'000;
+    }
+}
+}  // namespace
+
+int64_t calculate_difficulty(int64_t parent_difficulty, bool parent_has_ommers,
+    int64_t parent_timestamp, int64_t current_timestamp, int64_t block_number,
+    evmc_revision rev) noexcept
+{
+    // The calculation follows Ethereum Yellow Paper section 4.3.4. "Block Header Validity".
+
+    if (rev >= EVMC_PARIS)
+        return 0;  // No difficulty after the Merge.
+
+    // TODO: Implement for older revisions
+    if (rev < EVMC_BYZANTIUM)
+        return 0x020000;
+
+    static constexpr auto min_difficulty = int64_t{1} << 17;
+
+    const auto delay = get_bomb_delay(rev);
+    const auto fake_block_number = std::max(int64_t{0}, block_number - delay);
+    const auto p = (fake_block_number / 100'000) - 2;
+    assert(p < 63);
+    const auto epsilon = p < 0 ? 0 : int64_t{1} << p;
+    const auto y = parent_has_ommers ? 2 : 1;
+
+    const auto timestamp_diff = current_timestamp - parent_timestamp;
+    assert(timestamp_diff > 0);
+    const auto sigma_2 = std::max(y - timestamp_diff / 9, int64_t{-99});
+    const auto x = parent_difficulty / 2048;
+    const auto difficulty = parent_difficulty + x * sigma_2 + epsilon;
+    return std::max(min_difficulty, difficulty);
+}
+}  // namespace evmone::state

test/state/ethash_difficulty.hpp

@@ -0,0 +1,13 @@
+// evmone: Fast Ethereum Virtual Machine implementation
+// Copyright 2023 The evmone Authors.
+// SPDX-License-Identifier: Apache-2.0
+#pragma once
+
+#include <evmc/evmc.h>
+
+namespace evmone::state
+{
+int64_t calculate_difficulty(int64_t parent_difficulty, bool parent_has_ommers,
+    int64_t parent_timestamp, int64_t current_timestamp, int64_t block_number,
+    evmc_revision rev) noexcept;
+}  // namespace evmone::state

test/state/hash_utils.hpp

@@ -22,6 +22,10 @@ using namespace evmc::literals;
 /// Better than ethash::hash256 because has some additional handy constructors.
 using hash256 = bytes32;
 
+/// The hash of the empty RLP list, i.e. keccak256({0xc0}).
+static constexpr auto EmptyListHash =
+    0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347_bytes32;
+
 /// Computes Keccak hash out of input bytes (wrapper of ethash::keccak256).
 inline hash256 keccak256(bytes_view data) noexcept
 {

test/state/state.cpp

@@ -136,11 +136,24 @@ std::variant<int64_t, std::error_code> validate_transaction(const Account& sende
 }
 
 void finalize(State& state, evmc_revision rev, const address& coinbase,
-    std::optional<uint64_t> block_reward, std::span<Withdrawal> withdrawals)
+    std::optional<uint64_t> block_reward, std::span<Ommer> ommers,
+    std::span<Withdrawal> withdrawals)
 {
     // TODO: The block reward can be represented as a withdrawal.
     if (block_reward.has_value())
-        state.touch(coinbase).balance += *block_reward;
+    {
+        const auto reward = *block_reward;
+        assert(reward % 32 == 0);  // Assume block reward is divisible by 32.
+        const auto reward_by_32 = reward / 32;
+        const auto reward_by_8 = reward / 8;
+
+        state.touch(coinbase).balance += reward + reward_by_32 * ommers.size();
+        for (const auto& ommer : ommers)
+        {
+            assert(ommer.delta > 0 && ommer.delta < 8);
+            state.touch(ommer.beneficiary).balance += reward_by_8 * (8 - ommer.delta);
+        }
+    }
 
     for (const auto& withdrawal : withdrawals)
         state.touch(withdrawal.recipient).balance += withdrawal.get_amount();

test/state/state.hpp

@@ -66,6 +66,12 @@ class State
     [[nodiscard]] const auto& get_accounts() const noexcept { return m_accounts; }
 };
 
+struct Ommer
+{
+    address beneficiary;  ///< Ommer block beneficiary address.
+    uint32_t delta = 0;   ///< Difference between current and ommer block number.
+};
+
 struct Withdrawal
 {
     uint64_t index = 0;
@@ -84,10 +90,15 @@ struct BlockInfo
 {
     int64_t number = 0;
     int64_t timestamp = 0;
+    int64_t parent_timestamp = 0;
     int64_t gas_limit = 0;
     address coinbase;
+    int64_t difficulty = 0;
+    int64_t parent_difficulty = 0;
+    hash256 parent_ommers_hash = {};
     bytes32 prev_randao;
     uint64_t base_fee = 0;
+    std::vector<Ommer> ommers = {};
     std::vector<Withdrawal> withdrawals;
     std::unordered_map<int64_t, hash256> known_block_hashes = {};
 };
@@ -168,7 +179,8 @@ struct TransactionReceipt
 /// Applies block reward to coinbase, withdrawals (post Shanghai) and deletes empty touched accounts
 /// (post Spurious Dragon).
 void finalize(State& state, evmc_revision rev, const address& coinbase,
-    std::optional<uint64_t> block_reward, std::span<Withdrawal> withdrawals);
+    std::optional<uint64_t> block_reward, std::span<Ommer> ommers,
+    std::span<Withdrawal> withdrawals);
 
 [[nodiscard]] std::variant<TransactionReceipt, std::error_code> transition(State& state,
     const BlockInfo& block, const Transaction& tx, evmc_revision rev, evmc::VM& vm,

test/statetest/statetest.hpp

@@ -50,7 +50,7 @@ struct StateTransitionTest
         {
             TestMultiTransaction::Indexes indexes;
             hash256 state_hash;
-            hash256 logs_hash;
+            hash256 logs_hash = EmptyListHash;
             bool exception = false;
         };
 

test/statetest/statetest_loader.cpp

@@ -157,16 +157,30 @@ state::Withdrawal from_json<state::Withdrawal>(const json::json& j)
 template <>
 state::BlockInfo from_json<state::BlockInfo>(const json::json& j)
 {
-    evmc::bytes32 difficulty;
+    evmc::bytes32 prev_randao;
+    int64_t current_difficulty = 0;
+    int64_t parent_difficulty = 0;
     const auto prev_randao_it = j.find("currentRandom");
     const auto current_difficulty_it = j.find("currentDifficulty");
     const auto parent_difficulty_it = j.find("parentDifficulty");
+
+    if (current_difficulty_it != j.end())
+        current_difficulty = from_json<int64_t>(*current_difficulty_it);
+    if (parent_difficulty_it != j.end())
+        parent_difficulty = from_json<int64_t>(*parent_difficulty_it);
+
+    // When it's not defined init it with difficulty value.
     if (prev_randao_it != j.end())
-        difficulty = from_json<bytes32>(*prev_randao_it);
+        prev_randao = from_json<bytes32>(*prev_randao_it);
     else if (current_difficulty_it != j.end())
-        difficulty = from_json<bytes32>(*current_difficulty_it);
+        prev_randao = from_json<bytes32>(*current_difficulty_it);
     else if (parent_difficulty_it != j.end())
-        difficulty = from_json<bytes32>(*parent_difficulty_it);
+        prev_randao = from_json<bytes32>(*parent_difficulty_it);
+
+    hash256 parent_uncle_hash;
+    const auto parent_uncle_hash_it = j.find("parentUncleHash");
+    if (parent_uncle_hash_it != j.end())
+        parent_uncle_hash = from_json<hash256>(*parent_uncle_hash_it);
 
     uint64_t base_fee = 0;
     if (j.contains("currentBaseFee"))
@@ -192,10 +206,26 @@ state::BlockInfo from_json<state::BlockInfo>(const json::json& j)
             block_hashes[from_json<int64_t>(j_num)] = from_json<hash256>(j_hash);
     }
 
+    std::vector<state::Ommer> ommers;
+    if (const auto ommers_it = j.find("ommers"); ommers_it != j.end())
+    {
+        for (const auto& ommer : *ommers_it)
+        {
+            ommers.push_back(
+                {from_json<evmc::address>(ommer.at("address")), ommer.at("delta").get<uint32_t>()});
+        }
+    }
+
+    int64_t parent_timestamp = 0;
+    auto parent_timestamp_it = j.find("parentTimestamp");
+    if (parent_timestamp_it != j.end())
+        parent_timestamp = from_json<int64_t>(*parent_timestamp_it);
+
     return {from_json<int64_t>(j.at("currentNumber")), from_json<int64_t>(j.at("currentTimestamp")),
-        from_json<int64_t>(j.at("currentGasLimit")),
-        from_json<evmc::address>(j.at("currentCoinbase")), difficulty, base_fee,
-        std::move(withdrawals), std::move(block_hashes)};
+        parent_timestamp, from_json<int64_t>(j.at("currentGasLimit")),
+        from_json<evmc::address>(j.at("currentCoinbase")), current_difficulty, parent_difficulty,
+        parent_uncle_hash, prev_randao, base_fee, std::move(ommers), std::move(withdrawals),
+        std::move(block_hashes)};
 }
 
 template <>

test/statetest/statetest_runner.cpp

@@ -31,7 +31,7 @@ void run_state_test(const StateTransitionTest& test, evmc::VM& vm)
                 state::transition(state, test.block, tx, rev, vm, test.block.gas_limit);
 
             // Finalize block with reward 0.
-            state::finalize(state, rev, test.block.coinbase, 0, {});
+            state::finalize(state, rev, test.block.coinbase, 0, {}, {});
 
             if (holds_alternative<state::TransactionReceipt>(res))
                 EXPECT_EQ(logs_hash(get<state::TransactionReceipt>(res).logs), expected.logs_hash);

test/t8n/t8n.cpp

@@ -3,6 +3,7 @@
 // SPDX-License-Identifier: Apache-2.0
 
 #include "../state/errors.hpp"
+#include "../state/ethash_difficulty.hpp"
 #include "../state/mpt_hash.hpp"
 #include "../state/rlp.hpp"
 #include "../statetest/statetest.hpp"
@@ -84,8 +85,24 @@ int main(int argc, const char* argv[])
         }
 
         json::json j_result;
-        // FIXME: Calculate difficulty properly
-        j_result["currentDifficulty"] = "0x20000";
+
+        // Difficulty was received from upstream. No need to calc
+        // TODO: Check if it's needed by the blockchain test. If not remove if statement true branch
+        if (block.difficulty != 0)
+            j_result["currentDifficulty"] = hex0x(block.difficulty);
+        else
+        {
+            const auto current_difficulty = state::calculate_difficulty(block.parent_difficulty,
+                block.parent_ommers_hash != EmptyListHash, block.parent_timestamp, block.timestamp,
+                block.number, rev);
+
+            j_result["currentDifficulty"] = hex0x(current_difficulty);
+            block.difficulty = current_difficulty;
+
+            if (rev < EVMC_PARIS)  // Override prev_randao with difficulty pre-Merge
+                block.prev_randao = intx::be::store<bytes32>(intx::uint256{current_difficulty});
+        }
+
         j_result["currentBaseFee"] = hex0x(block.base_fee);
 
         int64_t cumulative_gas_used = 0;
@@ -193,7 +210,8 @@ int main(int argc, const char* argv[])
                 }
             }
 
-            state::finalize(state, rev, block.coinbase, block_reward, block.withdrawals);
+            state::finalize(
+                state, rev, block.coinbase, block_reward, block.ommers, block.withdrawals);
 
             j_result["logsHash"] = hex0x(logs_hash(txs_logs));
             j_result["stateRoot"] = hex0x(state::mpt_hash(state.get_accounts()));

test/unittests/CMakeLists.txt

@@ -34,6 +34,7 @@ target_sources(
     execution_state_test.cpp
     instructions_test.cpp
     state_bloom_filter_test.cpp
+    state_difficulty_test.cpp
     state_mpt_hash_test.cpp
     state_mpt_test.cpp
     state_new_account_address_test.cpp

test/unittests/state_difficulty_test.cpp

@@ -0,0 +1,75 @@
+// evmone: Fast Ethereum Virtual Machine implementation
+// Copyright 2023 The evmone Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+#include <gmock/gmock.h>
+#include <test/state/ethash_difficulty.hpp>
+
+using namespace evmone::state;
+
+struct DifficultyTest  // NOLINT(clang-analyzer-optin.performance.Padding)
+{
+    evmc_revision rev;
+    const char* name;
+    int64_t block_number;
+    int64_t difficulty;
+    int64_t timestamp;
+    int64_t parent_difficulty;
+    int64_t parent_timestamp;
+    bool parent_has_ommers;
+};
+
+/// Example difficulty tests from
+/// https://github.com/ethereum/tests/blob/develop/DifficultyTests.
+static constexpr DifficultyTest tests[] = {
+    {
+        EVMC_BYZANTIUM,
+        "DifficultyTest1",
+        0x0186a0,
+        0x69702c7f2c9fad14,
+        0x28d214819,
+        0x6963001f28ba95c2,
+        0x28d214818,
+        false,
+    },
+    {
+        EVMC_BYZANTIUM,
+        "DifficultyTest1038",
+        0x0dbba0,
+        0x79f2cbb8c97579b0,
+        0x72e440371,
+        0x79f2cbb8c97579b0,
+        0x72e44035d,
+        true,
+    },
+    {
+        EVMC_BERLIN,
+        "DifficultyTest1",
+        0x186a0,
+        0x56c67d1e106966c3,
+        0x63ed689e9,
+        0x56bba5a95b3dff04,
+        0x63ed689e8,
+        false,
+    },
+    {
+        EVMC_BERLIN,
+        "DifficultyTest1040",
+        0x10c8e0,
+        0x68f7512123928555,
+        0x617ec9fcc,
+        0x68f7512123928555,
+        0x617ec9fb8,
+        true,
+    },
+};
+
+TEST(state_difficulty, tests)
+{
+    for (const auto& t : tests)
+    {
+        const auto difficulty = calculate_difficulty(t.parent_difficulty, t.parent_has_ommers,
+            t.parent_timestamp, t.timestamp, t.block_number, t.rev);
+        EXPECT_EQ(difficulty, t.difficulty) << t.rev << "/" << t.name;
+    }
+}

test/unittests/state_rlp_test.cpp

@@ -25,6 +25,12 @@ TEST(state_rlp, empty_bytes_hash)
     EXPECT_EQ(keccak256({}), emptyBytesHash);
 }
 
+TEST(state_rlp, empty_list_hash)
+{
+    EXPECT_EQ(keccak256(bytes{0xc0}), EmptyListHash);  // Hash of empty RLP list: 0xc0.
+    EXPECT_EQ(keccak256(rlp::encode(std::vector<uint64_t>{})), EmptyListHash);
+}
+
 TEST(state_rlp, empty_mpt_hash)
 {
     const auto rlp_null = rlp::encode(0);

test/unittests/state_transition.cpp

@@ -41,7 +41,8 @@ void state_transition::TearDown()
     ASSERT_TRUE(holds_alternative<TransactionReceipt>(res))
         << std::get<std::error_code>(res).message();
     const auto& receipt = std::get<TransactionReceipt>(res);
-    evmone::state::finalize(state, rev, block.coinbase, 0, block.withdrawals);
+    evmone::state::finalize(
+        state, rev, block.coinbase, block_reward, block.ommers, block.withdrawals);
 
     EXPECT_EQ(receipt.status, expect.status);
     if (expect.gas_used.has_value())