feat: add api to simulate gasless bundle (#43)

core/types/bundle_gasless.go

@@ -0,0 +1,21 @@
+package types
+
+import (
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
+)
+
+type SimulateGaslessBundleArgs struct {
+	Txs []hexutil.Bytes `json:"txs"`
+}
+
+type GaslessTxSimResult struct {
+	Hash    common.Hash
+	GasUsed uint64
+	Valid   bool
+}
+
+type SimulateGaslessBundleResp struct {
+	Results          []GaslessTxSimResult
+	BasedBlockNumber int64
+}

eth/api_backend.go

@@ -304,6 +304,10 @@ func (b *EthAPIBackend) SendBundle(ctx context.Context, bundle *types.Bundle) er
 	return b.eth.txPool.AddBundle(bundle)
 }
 
+func (b *EthAPIBackend) SimulateGaslessBundle(bundle *types.Bundle) (*types.SimulateGaslessBundleResp, error) {
+	return b.Miner().SimulateGaslessBundle(bundle)
+}
+
 func (b *EthAPIBackend) BundlePrice() *big.Int {
 	bundles := b.eth.txPool.AllBundles()
 	gasFloor := big.NewInt(b.eth.config.Miner.MevGasPriceFloor)

ethclient/ethclient.go

@@ -779,6 +779,16 @@ func (ec *Client) BestBidGasFee(ctx context.Context, parentHash common.Hash) (*b
 	return fee, nil
 }
 
+// SimulateGaslessBundle simulates a gasless bundle
+func (ec *Client) SimulateGaslessBundle(ctx context.Context, args types.SimulateGaslessBundleArgs) (*types.SimulateGaslessBundleResp, error) {
+	var bundle types.SimulateGaslessBundleResp
+	err := ec.c.CallContext(ctx, &bundle, "eth_simulateGaslessBundle", args)
+	if err != nil {
+		return nil, err
+	}
+	return &bundle, nil
+}
+
 // SendBundle sends a bundle
 func (ec *Client) SendBundle(ctx context.Context, args types.SendBundleArgs) (common.Hash, error) {
 	var hash common.Hash

internal/ethapi/api_bundle.go

@@ -25,6 +25,29 @@ func (s *PrivateTxBundleAPI) BundlePrice(ctx context.Context) *big.Int {
 	return s.b.BundlePrice()
 }
 
+// SimulateGaslessBundle simulates the execution of a list of transactions with order
+func (s *PrivateTxBundleAPI) SimulateGaslessBundle(_ context.Context, args types.SimulateGaslessBundleArgs) (*types.SimulateGaslessBundleResp, error) {
+	if len(args.Txs) == 0 {
+		return nil, newBundleError(errors.New("bundle missing txs"))
+	}
+
+	var txs types.Transactions
+
+	for _, encodedTx := range args.Txs {
+		tx := new(types.Transaction)
+		if err := tx.UnmarshalBinary(encodedTx); err != nil {
+			return nil, err
+		}
+		txs = append(txs, tx)
+	}
+
+	bundle := &types.Bundle{
+		Txs: txs,
+	}
+
+	return s.b.SimulateGaslessBundle(bundle)
+}
+
 // SendBundle will add the signed transaction to the transaction pool.
 // The sender is responsible for signing the transaction and using the correct nonce and ensuring validity
 func (s *PrivateTxBundleAPI) SendBundle(ctx context.Context, args types.SendBundleArgs) (common.Hash, error) {

internal/ethapi/backend.go

@@ -79,6 +79,7 @@ type Backend interface {
 	// Transaction pool API
 	SendTx(ctx context.Context, signedTx *types.Transaction) error
 	SendBundle(ctx context.Context, bundle *types.Bundle) error
+	SimulateGaslessBundle(bundle *types.Bundle) (*types.SimulateGaslessBundleResp, error)
 	BundlePrice() *big.Int
 	GetTransaction(ctx context.Context, txHash common.Hash) (bool, *types.Transaction, common.Hash, uint64, uint64, error)
 	GetPoolTransactions() (types.Transactions, error)

miner/miner.go

@@ -309,6 +309,47 @@ func (miner *Miner) GasCeil() uint64 {
 
 func (miner *Miner) SimulateBundle(bundle *types.Bundle) (*big.Int, error) {
 	parent := miner.eth.BlockChain().CurrentBlock()
+
+	parentState, err := miner.eth.BlockChain().StateAt(parent.Root)
+	if err != nil {
+		return nil, err
+	}
+
+	env, err := miner.prepareSimulationEnv(parent, parentState)
+	if err != nil {
+		return nil, err
+	}
+
+	s, err := miner.worker.simulateBundle(env, bundle, parentState, env.gasPool, 0, true, true)
+	if err != nil {
+		return nil, err
+	}
+
+	return s.BundleGasPrice, nil
+}
+
+func (miner *Miner) SimulateGaslessBundle(bundle *types.Bundle) (*types.SimulateGaslessBundleResp, error) {
+	parent := miner.eth.BlockChain().CurrentBlock()
+
+	parentState, err := miner.eth.BlockChain().StateAt(parent.Root)
+	if err != nil {
+		return nil, err
+	}
+
+	env, err := miner.prepareSimulationEnv(parent, parentState)
+	if err != nil {
+		return nil, err
+	}
+
+	resp, err := miner.worker.simulateGaslessBundle(env, bundle)
+	if err != nil {
+		return nil, err
+	}
+
+	return resp, nil
+}
+
+func (miner *Miner) prepareSimulationEnv(parent *types.Header, state *state.StateDB) (*environment, error) {
 	timestamp := time.Now().Unix()
 	if parent.Time >= uint64(timestamp) {
 		timestamp = int64(parent.Time + 1)
@@ -351,28 +392,17 @@ func (miner *Miner) SimulateBundle(bundle *types.Bundle) (*big.Int, error) {
 		// }
 	}
 
-	state, err := miner.eth.BlockChain().StateAt(parent.Root)
-	if err != nil {
-		return nil, err
-	}
-
 	env := &environment{
-		header: header,
-		state:  state.Copy(),
-		signer: types.MakeSigner(miner.worker.chainConfig, header.Number, header.Time),
+		header:  header,
+		state:   state.Copy(),
+		signer:  types.MakeSigner(miner.worker.chainConfig, header.Number, header.Time),
+		gasPool: prepareGasPool(header.GasLimit),
 	}
 
 	if !miner.worker.chainConfig.IsFeynman(header.Number, header.Time) {
 		// Handle upgrade build-in system contract code
 		systemcontracts.UpgradeBuildInSystemContract(miner.worker.chainConfig, header.Number, parent.Time, header.Time, env.state)
 	}
 
-	gasPool := prepareGasPool(env.header.GasLimit)
-	s, err := miner.worker.simulateBundle(env, bundle, state, gasPool, 0, true, true)
-
-	if err != nil {
-		return nil, err
-	}
-
-	return s.BundleGasPrice, nil
+	return env, nil
 }

miner/worker_builder.go

@@ -495,6 +495,44 @@ func (w *worker) simulateBundle(
 	}, nil
 }
 
+func (w *worker) simulateGaslessBundle(env *environment, bundle *types.Bundle) (*types.SimulateGaslessBundleResp, error) {
+	result := make([]types.GaslessTxSimResult, 0)
+
+	txIdx := 0
+	for _, tx := range bundle.Txs {
+		env.state.SetTxContext(tx.Hash(), txIdx)
+
+		var (
+			snap  = env.state.Snapshot()
+			gp    = env.gasPool.Gas()
+			valid = true
+		)
+
+		receipt, err := core.ApplyTransaction(w.chainConfig, w.chain, &w.coinbase, env.gasPool, env.state, env.header, tx,
+			&env.header.GasUsed, *w.chain.GetVMConfig())
+		if err != nil {
+			env.state.RevertToSnapshot(snap)
+			env.gasPool.SetGas(gp)
+			valid = false
+			log.Warn("fail to simulate gasless bundle, skipped", "txHash", tx.Hash(), "err", err)
+		} else {
+			txIdx++
+		}
+
+		result = append(result, types.GaslessTxSimResult{
+			Hash:    tx.Hash(),
+			GasUsed: receipt.GasUsed,
+			Valid:   valid,
+		})
+	}
+
+	return &types.SimulateGaslessBundleResp{
+		Results:          result,
+		BasedBlockNumber: env.header.Number.Int64(),
+	}, nil
+
+}
+
 func containsHash(arr []common.Hash, match common.Hash) bool {
 	for _, elem := range arr {
 		if elem == match {