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eip1559.go
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eip1559.go
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// Copyright 2021 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package misc
import (
"fmt"
"math/big"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/common/math"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/params"
)
// VerifyEip1559Header verifies some header attributes which were changed in EIP-1559,
// - gas limit check
// - basefee check
func VerifyEip1559Header(config *params.ChainConfig, parent, header *types.Header) error {
// Verify that the gas limit remains within allowed bounds
parentGasLimit := parent.GasLimit
if !config.IsLondon(parent.Number) {
parentGasLimit = parent.GasLimit * params.ElasticityMultiplier
}
if err := VerifyGaslimit(parentGasLimit, header.GasLimit); err != nil {
return err
}
// Verify the header is not malformed
if header.BaseFee == nil {
return fmt.Errorf("header is missing baseFee")
}
// Verify the baseFee is correct based on the parent header.
expectedBaseFee := CalcBaseFee(config, parent)
if header.BaseFee.Cmp(expectedBaseFee) != 0 {
return fmt.Errorf("invalid baseFee: have %s, want %s, parentBaseFee %s, parentGasUsed %d",
expectedBaseFee, header.BaseFee, parent.BaseFee, parent.GasUsed)
}
return nil
}
// CalcBaseFee calculates the basefee of the header.
func CalcBaseFee(config *params.ChainConfig, parent *types.Header) *big.Int {
// If the current block is the first EIP-1559 block, return the InitialBaseFee.
if !config.IsLondon(parent.Number) {
return new(big.Int).SetUint64(params.InitialBaseFee)
}
var (
parentGasTarget = parent.GasLimit / params.ElasticityMultiplier
parentGasTargetBig = new(big.Int).SetUint64(parentGasTarget)
baseFeeChangeDenominator = new(big.Int).SetUint64(params.BaseFeeChangeDenominator)
)
// If the parent gasUsed is the same as the target, the baseFee remains unchanged.
if parent.GasUsed == parentGasTarget {
return new(big.Int).Set(parent.BaseFee)
}
if parent.GasUsed > parentGasTarget {
// If the parent block used more gas than its target, the baseFee should increase.
gasUsedDelta := new(big.Int).SetUint64(parent.GasUsed - parentGasTarget)
x := new(big.Int).Mul(parent.BaseFee, gasUsedDelta)
y := x.Div(x, parentGasTargetBig)
baseFeeDelta := math.BigMax(
x.Div(y, baseFeeChangeDenominator),
common.Big1,
)
return x.Add(parent.BaseFee, baseFeeDelta)
} else {
// Otherwise if the parent block used less gas than its target, the baseFee should decrease.
gasUsedDelta := new(big.Int).SetUint64(parentGasTarget - parent.GasUsed)
x := new(big.Int).Mul(parent.BaseFee, gasUsedDelta)
y := x.Div(x, parentGasTargetBig)
baseFeeDelta := x.Div(y, baseFeeChangeDenominator)
return math.BigMax(
x.Sub(parent.BaseFee, baseFeeDelta),
common.Big0,
)
}
}