feat(protocol): apply a min value for gas excess

packages/protocol/contracts/L2/Lib1559Math.sol

@@ -17,6 +17,7 @@ library Lib1559Math {
     function calc1559BaseFee(
         uint32 _gasTargetPerL1Block,
         uint8 _adjustmentQuotient,
+        uint64 _gasExcessMinValue,
         uint64 _gasExcess,
         uint64 _gasIssuance,
         uint32 _parentGasUsed
@@ -29,7 +30,7 @@ library Lib1559Math {
         // value as this has already happened
         uint256 excess = uint256(_gasExcess) + _parentGasUsed;
         excess = excess > _gasIssuance ? excess - _gasIssuance : 1;
-        gasExcess_ = uint64(excess.min(type(uint64).max));
+        gasExcess_ = uint64(excess.min(type(uint64).max).max(_gasExcessMinValue));
 
         // The base fee per gas used by this block is the spot price at the
         // bonding curve, regardless the actual amount of gas used by this

packages/protocol/contracts/L2/LibL2Config.sol

@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.24;
+
+/// @title LibL2Config
+library LibL2Config {
+    struct Config {
+        uint32 gasTargetPerL1Block;
+        uint8 basefeeAdjustmentQuotient;
+        uint64 gasExcessMinValue;
+    }
+
+    /// @notice Returns EIP1559 related configurations.
+    /// @return config_ struct containing configuration parameters.
+    function get() internal pure returns (Config memory config_) {
+        // Assuming we sell 3x more blockspace than Ethereum: 15_000_000 * 4
+        // Note that Brecht's concern is that this value may be too large.
+        // We need to monitor L2 state growth and lower this value when necessary.
+        config_.gasTargetPerL1Block = 60_000_000;
+        config_.basefeeAdjustmentQuotient = 8;
+
+        // This value is picked to make the min base fee close to but slightly smaller than 0.1gwei
+        config_.gasExcessMinValue = 18_435_000_000;
+    }
+}

packages/protocol/contracts/L2/TaikoL2.sol

@@ -9,6 +9,7 @@ import "../libs/LibAddress.sol";
 import "../signal/ISignalService.sol";
 import "../signal/LibSignals.sol";
 import "./Lib1559Math.sol";
+import "./LibL2Config.sol";
 
 /// @title TaikoL2
 /// @notice Taiko L2 is a smart contract that handles cross-layer message
@@ -21,11 +22,6 @@ contract TaikoL2 is EssentialContract {
     using LibAddress for address;
     using SafeERC20 for IERC20;
 
-    struct Config {
-        uint32 gasTargetPerL1Block;
-        uint8 basefeeAdjustmentQuotient;
-    }
-
     /// @notice Golden touch address is the only address that can do the anchor transaction.
     address public constant GOLDEN_TOUCH_ADDRESS = 0x0000777735367b36bC9B61C50022d9D0700dB4Ec;
 
@@ -208,12 +204,13 @@ contract TaikoL2 is EssentialContract {
         view
         returns (uint256 basefee_, uint64 gasExcess_)
     {
-        Config memory config = getConfig();
+        LibL2Config.Config memory config = getConfig();
         uint64 gasIssuance = uint64(_l1BlockId - lastSyncedBlock) * config.gasTargetPerL1Block;
 
         (basefee_, gasExcess_) = Lib1559Math.calc1559BaseFee(
             config.gasTargetPerL1Block,
             config.basefeeAdjustmentQuotient,
+            config.gasExcessMinValue,
             gasExcess,
             gasIssuance,
             _parentGasUsed
@@ -232,12 +229,8 @@ contract TaikoL2 is EssentialContract {
 
     /// @notice Returns EIP1559 related configurations.
     /// @return config_ struct containing configuration parameters.
-    function getConfig() public view virtual returns (Config memory config_) {
-        // Assuming we sell 3x more blockspace than Ethereum: 15_000_000 * 4
-        // Note that Brecht's concern is that this value may be too large.
-        // We need to monitor L2 state growth and lower this value when necessary.
-        config_.gasTargetPerL1Block = 60_000_000;
-        config_.basefeeAdjustmentQuotient = 8;
+    function getConfig() public view virtual returns (LibL2Config.Config memory) {
+        return LibL2Config.get();
     }
 
     /// @notice Tells if we need to validate basefee (for simulation).

packages/protocol/test/L2/Lib1559Math.t.sol

@@ -7,28 +7,33 @@ contract TestLib1559Math is TaikoTest {
     using LibMath for uint256;
 
     function test_eip1559_math() external {
-        uint256 gasTarget = 60_000_000;
-        uint256 adjustmentQuotient = 8;
-        uint256 adjustmentFactor = gasTarget * adjustmentQuotient;
+        LibL2Config.Config memory config = LibL2Config.get();
+        uint256 adjustmentFactor = config.gasTargetPerL1Block * config.basefeeAdjustmentQuotient;
 
         uint256 baseFee;
         uint256 i;
+
+        baseFee = Lib1559Math.basefee(config.gasExcessMinValue, adjustmentFactor);
+        assertEq(baseFee, 99_627_953); // slightly smaller than 0.1gwei
+        console2.log("gasExcessMinValue:", config.gasExcessMinValue);
+        console2.log("min base fee:", baseFee);
+
         for (; baseFee < 1 gwei; ++i) {
-            baseFee = Lib1559Math.basefee(gasTarget * i, adjustmentFactor);
-            console2.log("baseFee:", i, baseFee);
+            baseFee = Lib1559Math.basefee(config.gasTargetPerL1Block * i, adjustmentFactor);
+            console2.log("base fee:", i, baseFee);
         }
 
-        // basefee will reach 1 gwei if gasExcess > 19620000000
-        console2.log("basefee will reach 1 gwei if gasExcess >", gasTarget * i);
+        // base fee will reach 1 gwei if gasExcess > 19620000000
+        console2.log("base fee will reach 1 gwei if gasExcess >", config.gasTargetPerL1Block * i);
         assertEq(i, 327);
 
         for (; baseFee < 10 gwei; ++i) {
-            baseFee = Lib1559Math.basefee(gasTarget * i, adjustmentFactor);
-            console2.log("baseFee:", i, baseFee);
+            baseFee = Lib1559Math.basefee(config.gasTargetPerL1Block * i, adjustmentFactor);
+            console2.log("base fee:", i, baseFee);
         }
 
-        // basefee will reach 10 gwei if gasExcess > 20760000000
-        console2.log("basefee will reach 10 gwei if gasExcess >", gasTarget * i);
+        // base fee will reach 10 gwei if gasExcess > 20760000000
+        console2.log("base fee will reach 10 gwei if gasExcess >", config.gasTargetPerL1Block * i);
         assertEq(i, 346);
     }
 }

packages/protocol/test/L2/TaikoL2.t.sol

@@ -55,7 +55,9 @@ contract TestTaikoL2 is TaikoTest {
             )
         );
 
-        L2.setConfigAndExcess(TaikoL2.Config(gasTarget, quotient), gasExcess);
+        L2.setConfigAndExcess(
+            LibL2Config.Config(gasTarget, quotient, uint64(gasTarget) * 300), gasExcess
+        );
 
         ss.authorize(address(L2), true);
 
@@ -67,46 +69,9 @@ contract TestTaikoL2 is TaikoTest {
         vm.deal(address(L2), 100 ether);
     }
 
-    function test_L2_AnchorTx_with_constant_block_time() external {
-        for (uint256 i; i < 100; ++i) {
-            vm.fee(1);
-
-            vm.prank(L2.GOLDEN_TOUCH_ADDRESS());
-            _anchor(BLOCK_GAS_LIMIT);
-
-            vm.roll(block.number + 1);
-            vm.warp(block.timestamp + 30);
-        }
-    }
-
-    function test_L2_AnchorTx_with_decreasing_block_time() external {
-        for (uint256 i; i < 32; ++i) {
-            vm.fee(1);
-
-            vm.prank(L2.GOLDEN_TOUCH_ADDRESS());
-            _anchor(BLOCK_GAS_LIMIT);
-
-            vm.roll(block.number + 1);
-            vm.warp(block.timestamp + 30 - i);
-        }
-    }
-
-    function test_L2_AnchorTx_with_increasing_block_time() external {
-        for (uint256 i; i < 30; ++i) {
-            vm.fee(1);
-
-            vm.prank(L2.GOLDEN_TOUCH_ADDRESS());
-            _anchor(BLOCK_GAS_LIMIT);
-
-            vm.roll(block.number + 1);
-
-            vm.warp(block.timestamp + 30 + i);
-        }
-    }
-
     // calling anchor in the same block more than once should fail
     function test_L2_AnchorTx_revert_in_same_block() external {
-        vm.fee(1);
+        vm.fee(40_253_331);
 
         vm.prank(L2.GOLDEN_TOUCH_ADDRESS());
         _anchor(BLOCK_GAS_LIMIT);

packages/protocol/contracts/L2/TaikoL2EIP1559Configurable.sol → packages/protocol/test/L2/TaikoL2EIP1559Configurable.sol

@@ -1,29 +1,29 @@
 // SPDX-License-Identifier: MIT
 pragma solidity 0.8.24;
 
-import "./TaikoL2.sol";
+import "../../contracts/L2/TaikoL2.sol";
 
 /// @title TaikoL2EIP1559Configurable
 /// @notice TaikoL2 with a setter to change EIP-1559 configurations and states.
 /// @custom:security-contact [email protected]
 contract TaikoL2EIP1559Configurable is TaikoL2 {
     /// @notice EIP-1559 configuration.
-    Config public customConfig;
+    LibL2Config.Config public customConfig;
 
     uint256[49] private __gap;
 
     /// @notice Emits when the EIP-1559 configuration and gas excess are changed.
     /// @param config The new EIP-1559 config.
     /// @param gasExcess The new gas excess.
-    event ConfigAndExcessChanged(Config config, uint64 gasExcess);
+    event ConfigAndExcessChanged(LibL2Config.Config config, uint64 gasExcess);
 
     error L2_INVALID_CONFIG();
 
     /// @notice Sets EIP1559 configuration and gas excess.
     /// @param _newConfig The new EIP1559 config.
     /// @param _newGasExcess The new gas excess
     function setConfigAndExcess(
-        Config memory _newConfig,
+        LibL2Config.Config memory _newConfig,
         uint64 _newGasExcess
     )
         external
@@ -40,7 +40,7 @@ contract TaikoL2EIP1559Configurable is TaikoL2 {
     }
 
     /// @inheritdoc TaikoL2
-    function getConfig() public view override returns (Config memory) {
+    function getConfig() public view override returns (LibL2Config.Config memory) {
         return customConfig;
     }
 }

packages/protocol/test/L2/TaikoL2NoFeeCheck.t.sol

@@ -55,7 +55,9 @@ contract TestTaikoL2NoFeeCheck is TaikoTest {
             )
         );
 
-        L2.setConfigAndExcess(TaikoL2.Config(gasTarget, quotient), gasExcess);
+        L2.setConfigAndExcess(
+            LibL2Config.Config(gasTarget, quotient, uint64(gasTarget) * 300), gasExcess
+        );
 
         ss.authorize(address(L2), true);
 

packages/protocol/test/TaikoTest.sol

@@ -31,7 +31,6 @@ import "../contracts/L1/hooks/AssignmentHook.sol";
 import "../contracts/L1/provers/GuardianProver.sol";
 
 import "../contracts/L2/Lib1559Math.sol";
-import "../contracts/L2/TaikoL2EIP1559Configurable.sol";
 import "../contracts/L2/TaikoL2.sol";
 import "../contracts/L2/DelegateOwner.sol";
 
@@ -41,6 +40,7 @@ import "../contracts/team/airdrop/ERC20Airdrop2.sol";
 import "../contracts/team/airdrop/ERC721Airdrop.sol";
 
 import "../test/common/erc20/FreeMintERC20.sol";
+import "../test/L2/TaikoL2EIP1559Configurable.sol";
 
 import "./DeployCapability.sol";
 import "./HelperContracts.sol";