108 lines
4.0 KiB
Go
108 lines
4.0 KiB
Go
// Copyright 2021 Evmos Foundation
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// This file is part of Evmos' Ethermint library.
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//
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// The Ethermint library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The Ethermint library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the Ethermint library. If not, see https://github.com/evmos/ethermint/blob/main/LICENSE
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package keeper
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import (
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"math/big"
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sdk "github.com/cosmos/cosmos-sdk/types"
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"github.com/ethereum/go-ethereum/common"
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"github.com/ethereum/go-ethereum/common/math"
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)
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// CalculateBaseFee calculates the base fee for the current block. This is only calculated once per
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// block during BeginBlock. If the NoBaseFee parameter is enabled or below activation height, this function returns nil.
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// NOTE: This code is inspired from the go-ethereum EIP1559 implementation and adapted to Cosmos SDK-based
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// chains. For the canonical code refer to: https://github.com/ethereum/go-ethereum/blob/master/consensus/misc/eip1559.go
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func (k Keeper) CalculateBaseFee(ctx sdk.Context) *big.Int {
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params := k.GetParams(ctx)
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// Ignore the calculation if not enabled
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if !params.IsBaseFeeEnabled(ctx.BlockHeight()) {
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return nil
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}
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consParams := ctx.ConsensusParams()
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// If the current block is the first EIP-1559 block, return the base fee
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// defined in the parameters (DefaultBaseFee if it hasn't been changed by
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// governance).
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if ctx.BlockHeight() == params.EnableHeight {
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return params.BaseFee.BigInt()
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}
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// get the block gas used and the base fee values for the parent block.
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// NOTE: this is not the parent's base fee but the current block's base fee,
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// as it is retrieved from the transient store, which is committed to the
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// persistent KVStore after EndBlock (ABCI Commit).
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parentBaseFee := params.BaseFee.BigInt()
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if parentBaseFee == nil {
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return nil
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}
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parentGasUsed := k.GetBlockGasWanted(ctx)
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gasLimit := new(big.Int).SetUint64(math.MaxUint64)
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// NOTE: a MaxGas equal to -1 means that block gas is unlimited
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if consParams != nil && consParams.Block.MaxGas > -1 {
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gasLimit = big.NewInt(consParams.Block.MaxGas)
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}
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// CONTRACT: ElasticityMultiplier cannot be 0 as it's checked in the params
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// validation
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parentGasTargetBig := new(big.Int).Div(gasLimit, new(big.Int).SetUint64(uint64(params.ElasticityMultiplier)))
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if !parentGasTargetBig.IsUint64() {
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return nil
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}
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parentGasTarget := parentGasTargetBig.Uint64()
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baseFeeChangeDenominator := new(big.Int).SetUint64(uint64(params.BaseFeeChangeDenominator))
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// If the parent gasUsed is the same as the target, the baseFee remains
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// unchanged.
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if parentGasUsed == parentGasTarget {
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return new(big.Int).Set(parentBaseFee)
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}
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if parentGasUsed > parentGasTarget {
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// If the parent block used more gas than its target, the baseFee should
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// increase.
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gasUsedDelta := new(big.Int).SetUint64(parentGasUsed - parentGasTarget)
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x := new(big.Int).Mul(parentBaseFee, gasUsedDelta)
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y := x.Div(x, parentGasTargetBig)
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baseFeeDelta := math.BigMax(
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x.Div(y, baseFeeChangeDenominator),
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common.Big1,
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)
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return x.Add(parentBaseFee, baseFeeDelta)
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}
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// Otherwise if the parent block used less gas than its target, the baseFee
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// should decrease.
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gasUsedDelta := new(big.Int).SetUint64(parentGasTarget - parentGasUsed)
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x := new(big.Int).Mul(parentBaseFee, gasUsedDelta)
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y := x.Div(x, parentGasTargetBig)
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baseFeeDelta := x.Div(y, baseFeeChangeDenominator)
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// Set global min gas price as lower bound of the base fee, transactions below
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// the min gas price don't even reach the mempool.
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minGasPrice := params.MinGasPrice.TruncateInt().BigInt()
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return math.BigMax(x.Sub(parentBaseFee, baseFeeDelta), minGasPrice)
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}
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