enforce 1559 total gas limit; don't allow BaseFee to drop to 0

Author: i-norden

consensus/ethash/consensus.go

@@ -270,9 +270,18 @@ func (ethash *Ethash) verifyHeader(chain consensus.ChainReader, header, parent *
 	if header.GasLimit > max {
 		return fmt.Errorf("invalid gasLimit: have %v, max %v", header.GasLimit, max)
 	}
-	// Verify that the gasUsed is <= gasLimit
-	if header.GasUsed > header.GasLimit {
-		return fmt.Errorf("invalid gasUsed: have %d, gasLimit %d", header.GasUsed, header.GasLimit)
+
+	// Verify that total gas usage is below the gas limit
+	// Before EIP1559 activation, the "gasLimit" field in the header directly represents the gas limit
+	// After EIP1559 activation, the "gasLimit" field in the header represents the total gas target
+	// After EIP1559 activation, the *total* gas limit is equal to total gas target * slack coefficient
+	// The individual limits on legacy and EIP1559 gas usage during the transition period are enforced in the core/block_validator.go
+	var slackCoefficient uint64 = 1
+	if chain.Config().IsEIP1559(header.Number) {
+		slackCoefficient = chain.Config().EIP1559.EIP1559SlackCoefficient
+	}
+	if header.GasUsed > header.GasLimit*slackCoefficient {
+		return fmt.Errorf("invalid gasUsed: have %d, gasLimit %d, slack coefficient %d", header.GasUsed, header.GasLimit, chain.Config().EIP1559.EIP1559SlackCoefficient)
 	}
 
 	// Verify that the gas limit remains within allowed bounds

consensus/misc/basefee.go

@@ -18,7 +18,6 @@ package misc
 
 import (
 	"errors"
-	"fmt"
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -30,7 +29,7 @@ var (
 	errInvalidBaseFee       = errors.New("invalid BaseFee")
 	errMissingParentBaseFee = errors.New("parent header is missing BaseFee")
 	errMissingBaseFee       = errors.New("current header is missing BaseFee")
-	errHaveBaseFee          = fmt.Errorf("BaseFee should not be set before block %d", params.EIP1559ForkBlockNumber)
+	errHaveBaseFee          = errors.New("BaseFee should not be set before EIP1559 activation %d")
 )
 
 // VerifyEIP1559BaseFee verifies that the EIP1559 BaseFee field is valid for the current block height
@@ -79,7 +78,6 @@ func CalcBaseFee(config *params.ChainConfig, parent *types.Header) *big.Int {
 	mul := new(big.Int).Mul(parent.BaseFee, delta)
 	div := new(big.Int).Div(mul, parentGasTarget)
 	div2 := new(big.Int).Div(div, new(big.Int).SetUint64(config.EIP1559.EIP1559BaseFeeMaxChangeDenominator))
-
 	baseFee := new(big.Int).Add(parent.BaseFee, div2)
 
 	// A valid BASEFEE is one such that abs(BASEFEE - PARENT_BASEFEE) <= max(1, PARENT_BASEFEE // BASEFEE_MAX_CHANGE_DENOMINATOR)
@@ -100,6 +98,10 @@ func CalcBaseFee(config *params.ChainConfig, parent *types.Header) *big.Int {
 		}
 		baseFee.Set(new(big.Int).Add(parent.BaseFee, max))
 	}
+	// Prevent BaseFee from dropping to zero
+	if baseFee.Cmp(common.Big0) == 0 {
+		baseFee.Set(common.Big1)
+	}
 	return baseFee
 }
 

core/gaspool.go

@@ -37,9 +37,9 @@ func NewLegacyGasPool(chainConfig *params.ChainConfig, height, gasLimit *big.Int
 
 // NewEIP1559GasPool returns a GasPool filled to the EIP1559 gas limit
 func NewEIP1559GasPool(chainConfig *params.ChainConfig, height, gasLimit *big.Int) *GasPool {
-	// EIP1559 gas limit is 2x the EIP1559GasTarget
+	// EIP1559 gas limit is slack coefficient * EIP1559GasTarget
 	eip1559GasTarget := misc.CalcEIP1559GasTarget(chainConfig, height, gasLimit)
-	return new(GasPool).AddGas(2 * eip1559GasTarget.Uint64())
+	return new(GasPool).AddGas(chainConfig.EIP1559.EIP1559SlackCoefficient * eip1559GasTarget.Uint64())
 }
 
 // AddGas makes gas available for execution.