Base Fee Floor (Fixed amount) (#235)

* Base Fee Floor

* Improve config description

consensus/misc/eip1559/eip1559.go

@@ -57,7 +57,15 @@ func VerifyEIP1559Header(config *params.ChainConfig, parent, header *types.Heade
 
 // CalcBaseFee calculates the basefee of the header.
 // The time belongs to the new block to check if Canyon is activted or not
-func CalcBaseFee(config *params.ChainConfig, parent *types.Header, time uint64) *big.Int {
+// **Notice** that the return value is catched by the deferred function which can change the return value
+func CalcBaseFee(config *params.ChainConfig, parent *types.Header, time uint64) (response *big.Int) {
+	defer func() {
+		// If the base fee response is below the floor, intercept the return and return the floor instead.
+		if config.Celo != nil {
+			response = math.BigMax(response, new(big.Int).SetUint64(config.Celo.EIP1559BaseFeeFloor))
+		}
+	}()
+
 	// If this is the cel2 transition block and the parent block has a base fee
 	// then use that.
 	if config.Cel2Time != nil && *config.Cel2Time == time && parent.BaseFee != nil {

consensus/misc/eip1559/eip1559_test.go

@@ -69,6 +69,15 @@ func opConfig() *params.ChainConfig {
 	return config
 }
 
+func celoConfig() *params.ChainConfig {
+	config := copyConfig(params.TestChainConfig)
+	ct := uint64(10)
+	config.Cel2Time = &ct
+	config.Celo = &params.CeloConfig{EIP1559BaseFeeFloor: params.InitialBaseFee}
+
+	return config
+}
+
 // TestBlockGasLimits tests the gasLimit checks for blocks both across
 // the EIP-1559 boundary and post-1559 blocks
 func TestBlockGasLimits(t *testing.T) {
@@ -176,3 +185,47 @@ func TestCalcBaseFeeOptimism(t *testing.T) {
 		}
 	}
 }
+
+// TestCalcBaseFeeCeloFloor assumes all blocks are 1559-blocks
+func TestCalcBaseFeeCeloFloor(t *testing.T) {
+	config := celoConfig()
+	tests := []struct {
+		parentBaseFee   int64
+		parentGasLimit  uint64
+		parentGasUsed   uint64
+		expectedBaseFee int64
+	}{
+		{params.InitialBaseFee, 20000000, 10000000, params.InitialBaseFee}, // usage == target
+		{params.InitialBaseFee, 20000000, 7000000, params.InitialBaseFee},  // usage below target
+		{params.InitialBaseFee, 20000000, 11000000, 1012500000},            // usage above target
+	}
+	for i, test := range tests {
+		parent := &types.Header{
+			Number:   common.Big32,
+			GasLimit: test.parentGasLimit,
+			GasUsed:  test.parentGasUsed,
+			BaseFee:  big.NewInt(test.parentBaseFee),
+			Time:     *config.Cel2Time,
+		}
+		if have, want := CalcBaseFee(config, parent, parent.Time+2), big.NewInt(test.expectedBaseFee); have.Cmp(want) != 0 {
+			t.Errorf("test %d: have %d  want %d, ", i, have, want)
+		}
+	}
+}
+
+// TestCalcBaseFeeCeloBlockActivation tests the base fee calculation for the celo block activation, mantaining the same base fee as the parent block
+func TestCalcBaseFeeCeloBlockActivation(t *testing.T) {
+	config := celoConfig()
+	// Before activation
+	// usage above target
+	parent := &types.Header{
+		Number:   common.Big32,
+		GasLimit: 20000000,
+		GasUsed:  15000000,
+		BaseFee:  big.NewInt(params.InitialBaseFee * 3),
+		Time:     *config.Cel2Time - 2,
+	}
+	if have, want := CalcBaseFee(config, parent, parent.Time+2), big.NewInt(params.InitialBaseFee*3); have.Cmp(want) != 0 {
+		t.Errorf("have %d  want %d, ", have, want)
+	}
+}

params/config.go

@@ -458,6 +458,8 @@ type ChainConfig struct {
 
 	// Optimism config, nil if not active
 	Optimism *OptimismConfig `json:"optimism,omitempty"`
+	// Celo config, nil if not active
+	Celo *CeloConfig `json:"celo,omitempty"`
 }
 
 // EthashConfig is the consensus engine configs for proof-of-work based sealing.
@@ -488,7 +490,21 @@ type OptimismConfig struct {
 
 // String implements the stringer interface, returning the optimism fee config details.
 func (o *OptimismConfig) String() string {
-	return "optimism"
+	denominatorCanyonStr := "nil"
+	if o.EIP1559DenominatorCanyon != nil {
+		denominatorCanyonStr = fmt.Sprintf("%d", *o.EIP1559DenominatorCanyon)
+	}
+	return fmt.Sprintf("optimism(eip1559Elasticity: %d, eip1559Denominator: %d, eip1559DenominatorCanyon: %s)",
+		o.EIP1559Elasticity, o.EIP1559Denominator, denominatorCanyonStr)
+}
+
+type CeloConfig struct {
+	EIP1559BaseFeeFloor uint64 `json:"eip1559BaseFeeFloor"`
+}
+
+// String implements the stringer interface, returning the celo config details.
+func (o *CeloConfig) String() string {
+	return fmt.Sprintf("celo(eip1559BaseFeeFloor: %d)", o.EIP1559BaseFeeFloor)
 }
 
 // Description returns a human-readable description of ChainConfig.
@@ -504,6 +520,8 @@ func (c *ChainConfig) Description() string {
 	switch {
 	case c.Optimism != nil:
 		banner += "Consensus: Optimism\n"
+		banner += fmt.Sprintf(" - %s\n", c.Optimism)
+		banner += fmt.Sprintf(" - %s\n", c.Celo)
 	case c.Ethash != nil:
 		if c.TerminalTotalDifficulty == nil {
 			banner += "Consensus: Ethash (proof-of-work)\n"