github.com/palisadeinc/bor@v0.0.0-20230615125219-ab7196213d15/consensus/misc/eip1559.go

// 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/holiman/uint256"

	"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)
		baseFeeChangeDenominatorUint64 = params.BaseFeeChangeDenominator(config.Bor, parent.Number)
		baseFeeChangeDenominator       = new(big.Int).SetUint64(baseFeeChangeDenominatorUint64)
	)
	// 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,
		)
	}
}

// CalcBaseFee calculates the basefee of the header.
func CalcBaseFeeUint(config *params.ChainConfig, parent *types.Header) *uint256.Int {
	var (
		initialBaseFeeUint             = uint256.NewInt(params.InitialBaseFee)
		baseFeeChangeDenominatorUint64 = params.BaseFeeChangeDenominator(config.Bor, parent.Number)
		baseFeeChangeDenominatorUint   = uint256.NewInt(baseFeeChangeDenominatorUint64)
	)

	// If the current block is the first EIP-1559 block, return the InitialBaseFee.
	if !config.IsLondon(parent.Number) {
		return initialBaseFeeUint.Clone()
	}

	var (
		parentGasTarget    = parent.GasLimit / params.ElasticityMultiplier
		parentGasTargetBig = uint256.NewInt(parentGasTarget)
	)

	// If the parent gasUsed is the same as the target, the baseFee remains unchanged.
	if parent.GasUsed == parentGasTarget {
		return math.FromBig(parent.BaseFee)
	}

	if parent.GasUsed > parentGasTarget {
		// If the parent block used more gas than its target, the baseFee should increase.
		gasUsedDelta := uint256.NewInt(parent.GasUsed - parentGasTarget)

		parentBaseFee := math.FromBig(parent.BaseFee)
		x := gasUsedDelta.Mul(parentBaseFee, gasUsedDelta)
		y := x.Div(x, parentGasTargetBig)
		baseFeeDelta := math.BigMaxUint(
			x.Div(y, baseFeeChangeDenominatorUint),
			math.U1,
		)

		return x.Add(parentBaseFee, baseFeeDelta)
	}

	// Otherwise if the parent block used less gas than its target, the baseFee should decrease.
	gasUsedDelta := uint256.NewInt(parentGasTarget - parent.GasUsed)
	parentBaseFee := math.FromBig(parent.BaseFee)
	x := gasUsedDelta.Mul(parentBaseFee, gasUsedDelta)
	y := x.Div(x, parentGasTargetBig)
	baseFeeDelta := x.Div(y, baseFeeChangeDenominatorUint)

	return math.BigMaxUint(
		x.Sub(parentBaseFee, baseFeeDelta),
		math.U0.Clone(),
	)
}