a5a4fa7032
This change makes use of uin256 to represent balance in state. It touches primarily upon statedb, stateobject and state processing, trying to avoid changes in transaction pools, core types, rpc and tracers.
236 lines
8.9 KiB
Go
236 lines
8.9 KiB
Go
// Copyright 2023 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum 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 go-ethereum 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 go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package gasestimator
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import (
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"context"
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"errors"
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"fmt"
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"math"
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"math/big"
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"github.com/ethereum/go-ethereum/common"
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"github.com/ethereum/go-ethereum/core"
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"github.com/ethereum/go-ethereum/core/state"
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"github.com/ethereum/go-ethereum/core/types"
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"github.com/ethereum/go-ethereum/core/vm"
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"github.com/ethereum/go-ethereum/log"
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"github.com/ethereum/go-ethereum/params"
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)
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// Options are the contextual parameters to execute the requested call.
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//
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// Whilst it would be possible to pass a blockchain object that aggregates all
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// these together, it would be excessively hard to test. Splitting the parts out
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// allows testing without needing a proper live chain.
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type Options struct {
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Config *params.ChainConfig // Chain configuration for hard fork selection
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Chain core.ChainContext // Chain context to access past block hashes
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Header *types.Header // Header defining the block context to execute in
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State *state.StateDB // Pre-state on top of which to estimate the gas
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ErrorRatio float64 // Allowed overestimation ratio for faster estimation termination
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}
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// Estimate returns the lowest possible gas limit that allows the transaction to
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// run successfully with the provided context options. It returns an error if the
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// transaction would always revert, or if there are unexpected failures.
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func Estimate(ctx context.Context, call *core.Message, opts *Options, gasCap uint64) (uint64, []byte, error) {
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// Binary search the gas limit, as it may need to be higher than the amount used
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var (
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lo uint64 // lowest-known gas limit where tx execution fails
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hi uint64 // lowest-known gas limit where tx execution succeeds
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)
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// Determine the highest gas limit can be used during the estimation.
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hi = opts.Header.GasLimit
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if call.GasLimit >= params.TxGas {
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hi = call.GasLimit
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}
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// Normalize the max fee per gas the call is willing to spend.
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var feeCap *big.Int
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if call.GasFeeCap != nil {
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feeCap = call.GasFeeCap
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} else if call.GasPrice != nil {
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feeCap = call.GasPrice
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} else {
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feeCap = common.Big0
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}
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// Recap the highest gas limit with account's available balance.
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if feeCap.BitLen() != 0 {
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balance := opts.State.GetBalance(call.From).ToBig()
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available := balance
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if call.Value != nil {
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if call.Value.Cmp(available) >= 0 {
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return 0, nil, core.ErrInsufficientFundsForTransfer
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}
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available.Sub(available, call.Value)
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}
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allowance := new(big.Int).Div(available, feeCap)
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// If the allowance is larger than maximum uint64, skip checking
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if allowance.IsUint64() && hi > allowance.Uint64() {
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transfer := call.Value
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if transfer == nil {
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transfer = new(big.Int)
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}
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log.Debug("Gas estimation capped by limited funds", "original", hi, "balance", balance,
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"sent", transfer, "maxFeePerGas", feeCap, "fundable", allowance)
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hi = allowance.Uint64()
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}
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}
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// Recap the highest gas allowance with specified gascap.
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if gasCap != 0 && hi > gasCap {
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log.Debug("Caller gas above allowance, capping", "requested", hi, "cap", gasCap)
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hi = gasCap
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}
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// If the transaction is a plain value transfer, short circuit estimation and
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// directly try 21000. Returning 21000 without any execution is dangerous as
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// some tx field combos might bump the price up even for plain transfers (e.g.
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// unused access list items). Ever so slightly wasteful, but safer overall.
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if len(call.Data) == 0 {
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if call.To != nil && opts.State.GetCodeSize(*call.To) == 0 {
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failed, _, err := execute(ctx, call, opts, params.TxGas)
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if !failed && err == nil {
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return params.TxGas, nil, nil
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}
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}
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}
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// We first execute the transaction at the highest allowable gas limit, since if this fails we
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// can return error immediately.
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failed, result, err := execute(ctx, call, opts, hi)
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if err != nil {
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return 0, nil, err
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}
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if failed {
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if result != nil && !errors.Is(result.Err, vm.ErrOutOfGas) {
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return 0, result.Revert(), result.Err
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}
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return 0, nil, fmt.Errorf("gas required exceeds allowance (%d)", hi)
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}
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// For almost any transaction, the gas consumed by the unconstrained execution
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// above lower-bounds the gas limit required for it to succeed. One exception
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// is those that explicitly check gas remaining in order to execute within a
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// given limit, but we probably don't want to return the lowest possible gas
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// limit for these cases anyway.
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lo = result.UsedGas - 1
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// There's a fairly high chance for the transaction to execute successfully
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// with gasLimit set to the first execution's usedGas + gasRefund. Explicitly
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// check that gas amount and use as a limit for the binary search.
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optimisticGasLimit := (result.UsedGas + result.RefundedGas + params.CallStipend) * 64 / 63
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if optimisticGasLimit < hi {
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failed, _, err = execute(ctx, call, opts, optimisticGasLimit)
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if err != nil {
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// This should not happen under normal conditions since if we make it this far the
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// transaction had run without error at least once before.
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log.Error("Execution error in estimate gas", "err", err)
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return 0, nil, err
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}
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if failed {
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lo = optimisticGasLimit
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} else {
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hi = optimisticGasLimit
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}
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}
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// Binary search for the smallest gas limit that allows the tx to execute successfully.
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for lo+1 < hi {
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if opts.ErrorRatio > 0 {
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// It is a bit pointless to return a perfect estimation, as changing
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// network conditions require the caller to bump it up anyway. Since
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// wallets tend to use 20-25% bump, allowing a small approximation
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// error is fine (as long as it's upwards).
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if float64(hi-lo)/float64(hi) < opts.ErrorRatio {
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break
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}
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}
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mid := (hi + lo) / 2
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if mid > lo*2 {
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// Most txs don't need much higher gas limit than their gas used, and most txs don't
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// require near the full block limit of gas, so the selection of where to bisect the
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// range here is skewed to favor the low side.
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mid = lo * 2
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}
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failed, _, err = execute(ctx, call, opts, mid)
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if err != nil {
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// This should not happen under normal conditions since if we make it this far the
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// transaction had run without error at least once before.
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log.Error("Execution error in estimate gas", "err", err)
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return 0, nil, err
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}
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if failed {
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lo = mid
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} else {
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hi = mid
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}
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}
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return hi, nil, nil
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}
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// execute is a helper that executes the transaction under a given gas limit and
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// returns true if the transaction fails for a reason that might be related to
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// not enough gas. A non-nil error means execution failed due to reasons unrelated
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// to the gas limit.
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func execute(ctx context.Context, call *core.Message, opts *Options, gasLimit uint64) (bool, *core.ExecutionResult, error) {
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// Configure the call for this specific execution (and revert the change after)
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defer func(gas uint64) { call.GasLimit = gas }(call.GasLimit)
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call.GasLimit = gasLimit
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// Execute the call and separate execution faults caused by a lack of gas or
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// other non-fixable conditions
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result, err := run(ctx, call, opts)
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if err != nil {
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if errors.Is(err, core.ErrIntrinsicGas) {
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return true, nil, nil // Special case, raise gas limit
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}
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return true, nil, err // Bail out
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}
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return result.Failed(), result, nil
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}
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// run assembles the EVM as defined by the consensus rules and runs the requested
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// call invocation.
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func run(ctx context.Context, call *core.Message, opts *Options) (*core.ExecutionResult, error) {
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// Assemble the call and the call context
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var (
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msgContext = core.NewEVMTxContext(call)
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evmContext = core.NewEVMBlockContext(opts.Header, opts.Chain, nil)
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dirtyState = opts.State.Copy()
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evm = vm.NewEVM(evmContext, msgContext, dirtyState, opts.Config, vm.Config{NoBaseFee: true})
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)
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// Monitor the outer context and interrupt the EVM upon cancellation. To avoid
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// a dangling goroutine until the outer estimation finishes, create an internal
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// context for the lifetime of this method call.
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ctx, cancel := context.WithCancel(ctx)
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defer cancel()
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go func() {
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<-ctx.Done()
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evm.Cancel()
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}()
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// Execute the call, returning a wrapped error or the result
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result, err := core.ApplyMessage(evm, call, new(core.GasPool).AddGas(math.MaxUint64))
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if vmerr := dirtyState.Error(); vmerr != nil {
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return nil, vmerr
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}
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if err != nil {
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return result, fmt.Errorf("failed with %d gas: %w", call.GasLimit, err)
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}
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return result, nil
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}
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