move ap4 block gas cost check to header

See https://github.com/ava-labs/coreth/pull/849

consensus/dummy/consensus.go

@@ -154,20 +154,14 @@ func verifyHeaderGasFields(config *params.ChainConfig, header *types.Header, par
 		return fmt.Errorf("expected base fee (%d), found (%d)", expectedBaseFee, header.BaseFee)
 	}
 
-	if !config.IsSubnetEVM(header.Time) {
-		if header.BlockGasCost != nil {
-			return fmt.Errorf("invalid blockGasCost before fork: have %d, want <nil>", header.BlockGasCost)
-		}
-		return nil
-	}
-
 	// Enforce BlockGasCost constraints
 	expectedBlockGasCost := customheader.BlockGasCost(
+		config,
 		feeConfig,
 		parent,
 		header.Time,
 	)
-	if !utils.BigEqualUint64(header.BlockGasCost, expectedBlockGasCost) {
+	if !utils.BigEqual(header.BlockGasCost, expectedBlockGasCost) {
 		return fmt.Errorf("invalid block gas cost: have %d, want %d", header.BlockGasCost, expectedBlockGasCost)
 	}
 	return nil
@@ -334,25 +328,24 @@ func (eng *DummyEngine) verifyBlockFee(
 func (eng *DummyEngine) Finalize(chain consensus.ChainHeaderReader, block *types.Block, parent *types.Header, state *state.StateDB, receipts []*types.Receipt) error {
 	config := chain.Config()
 	timestamp := block.Time()
+	// we use the parent to determine the fee config
+	// since the current block has not been finalized yet.
+	feeConfig, _, err := chain.GetFeeConfigAt(parent)
+	if err != nil {
+		return err
+	}
+	// Verify the BlockGasCost set in the header matches the expected value.
+	blockGasCost := block.BlockGasCost()
+	expectedBlockGasCost := customheader.BlockGasCost(
+		config,
+		feeConfig,
+		parent,
+		timestamp,
+	)
+	if !utils.BigEqual(blockGasCost, expectedBlockGasCost) {
+		return fmt.Errorf("invalid blockGasCost: have %d, want %d", blockGasCost, expectedBlockGasCost)
+	}
 	if config.IsSubnetEVM(timestamp) {
-		// we use the parent to determine the fee config
-		// since the current block has not been finalized yet.
-		feeConfig, _, err := chain.GetFeeConfigAt(parent)
-		if err != nil {
-			return err
-		}
-
-		// Verify the BlockGasCost set in the header matches the expected value.
-		blockGasCost := block.BlockGasCost()
-		expectedBlockGasCost := customheader.BlockGasCost(
-			feeConfig,
-			parent,
-			timestamp,
-		)
-		if !utils.BigEqualUint64(blockGasCost, expectedBlockGasCost) {
-			return fmt.Errorf("invalid blockGasCost: have %d, want %d", blockGasCost, expectedBlockGasCost)
-		}
-
 		// Verify the block fee was paid.
 		if err := eng.verifyBlockFee(
 			block.BaseFee(),
@@ -371,21 +364,20 @@ func (eng *DummyEngine) FinalizeAndAssemble(chain consensus.ChainHeaderReader, h
 	uncles []*types.Header, receipts []*types.Receipt,
 ) (*types.Block, error) {
 	config := chain.Config()
+	// we use the parent to determine the fee config
+	// since the current block has not been finalized yet.
+	feeConfig, _, err := chain.GetFeeConfigAt(parent)
+	if err != nil {
+		return nil, err
+	}
+	// Calculate the required block gas cost for this block.
+	header.BlockGasCost = customheader.BlockGasCost(
+		config,
+		feeConfig,
+		parent,
+		header.Time,
+	)
 	if config.IsSubnetEVM(header.Time) {
-		// we use the parent to determine the fee config
-		// since the current block has not been finalized yet.
-		feeConfig, _, err := chain.GetFeeConfigAt(parent)
-		if err != nil {
-			return nil, err
-		}
-		// Calculate the required block gas cost for this block.
-		blockGasCost := customheader.BlockGasCost(
-			feeConfig,
-			parent,
-			header.Time,
-		)
-		header.BlockGasCost = new(big.Int).SetUint64(blockGasCost)
-
 		// Verify that this block covers the block fee.
 		if err := eng.verifyBlockFee(
 			header.BaseFee,

plugin/evm/header/block_gas_cost.go

@@ -22,11 +22,16 @@ var (
 
 // BlockGasCost calculates the required block gas cost based on the parent
 // header and the timestamp of the new block.
+// Prior to Subnet-EVM, the returned block gas cost will be nil.
 func BlockGasCost(
+	config *params.ChainConfig,
 	feeConfig commontype.FeeConfig,
 	parent *types.Header,
 	timestamp uint64,
-) uint64 {
+) *big.Int {
+	if !config.IsSubnetEVM(timestamp) {
+		return nil
+	}
 	step := feeConfig.BlockGasCostStep.Uint64()
 	// Treat an invalid parent/current time combination as 0 elapsed time.
 	//
@@ -36,12 +41,12 @@ func BlockGasCost(
 	if parent.Time <= timestamp {
 		timeElapsed = timestamp - parent.Time
 	}
-	return BlockGasCostWithStep(
+	return new(big.Int).SetUint64(BlockGasCostWithStep(
 		feeConfig,
 		parent.BlockGasCost,
 		step,
 		timeElapsed,
-	)
+	))
 }
 
 // BlockGasCostWithStep calculates the required block gas cost based on the

plugin/evm/header/block_gas_cost_test.go

@@ -57,35 +57,50 @@ func BlockGasCostTest(t *testing.T, feeConfig commontype.FeeConfig) {
 
 	tests := []struct {
 		name       string
+		upgrades   params.NetworkUpgrades
 		parentTime uint64
 		parentCost *big.Int
 		timestamp  uint64
-		expected   uint64
+		expected   *big.Int
 	}{
+		{
+			name:       "before_subnet_evm",
+			parentTime: 10,
+			upgrades:   params.TestPreSubnetEVMChainConfig.NetworkUpgrades,
+			parentCost: maxBlockGasCostBig,
+			timestamp:  10 + targetBlockRate + 1,
+			expected:   nil,
+		},
 		{
 			name:       "normal",
+			upgrades:   params.TestChainConfig.NetworkUpgrades,
 			parentTime: 10,
 			parentCost: maxBlockGasCostBig,
 			timestamp:  10 + targetBlockRate + 1,
-			expected:   maxBlockGasCost - blockGasCostStep,
+			expected:   new(big.Int).SetUint64(maxBlockGasCost - blockGasCostStep),
 		},
 		{
 			name:       "negative_time_elapsed",
+			upgrades:   params.TestChainConfig.NetworkUpgrades,
 			parentTime: 10,
 			parentCost: feeConfig.MinBlockGasCost,
 			timestamp:  9,
-			expected:   minBlockGasCost + blockGasCostStep*targetBlockRate,
+			expected:   new(big.Int).SetUint64(minBlockGasCost + blockGasCostStep*targetBlockRate),
 		},
 	}
 
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
+			config := &params.ChainConfig{
+				NetworkUpgrades: test.upgrades,
+			}
 			parent := &types.Header{
 				Time:         test.parentTime,
 				BlockGasCost: test.parentCost,
 			}
 
 			assert.Equal(t, test.expected, BlockGasCost(
+				config,
 				feeConfig,
 				parent,
 				test.timestamp,

plugin/evm/header/gas_limit_test.go

@@ -147,10 +147,10 @@ func VerifyGasLimitTest(t *testing.T, feeConfig commontype.FeeConfig) {
 
 func TestGasCapacity(t *testing.T) {
 	t.Run("normal", func(t *testing.T) {
-		GasLimitTest(t, testFeeConfig)
+		GasCapacityTest(t, testFeeConfig)
 	})
 	t.Run("double", func(t *testing.T) {
-		GasLimitTest(t, testFeeConfigDouble)
+		GasCapacityTest(t, testFeeConfigDouble)
 	})
 }