internal/ethapi: use same state for each invocation within EstimateGa…

…s (#27505)

EstimateGas repeatedly executes a transaction, performing a binary search with multiple gas prices to determine proper pricing. Each call retrieves a new copy of the state (https://github.com/ethereum/go-ethereum/blob/master/internal/ethapi/api.go#L1017) . Because the pending/latest state can change during the execution of EstimateGas, this can potentially cause strange behavior (as noted here: ethereum/go-ethereum#27502 (comment)).

This PR modifies EstimateGas to retrieve the state once and use a copy of it for every call invocation it does.

internal/ethapi/api.go

@@ -1011,13 +1011,7 @@ func (context *ChainContext) GetHeader(hash common.Hash, number uint64) *types.H
 	return header
 }
 
-func DoCall(ctx context.Context, b Backend, args TransactionArgs, blockNrOrHash rpc.BlockNumberOrHash, overrides *StateOverride, blockOverrides *BlockOverrides, timeout time.Duration, globalGasCap uint64) (*core.ExecutionResult, error) {
-	defer func(start time.Time) { log.Debug("Executing EVM call finished", "runtime", time.Since(start)) }(time.Now())
-
-	state, header, err := b.StateAndHeaderByNumberOrHash(ctx, blockNrOrHash)
-	if state == nil || err != nil {
-		return nil, err
-	}
+func doCall(ctx context.Context, b Backend, args TransactionArgs, state *state.StateDB, header *types.Header, overrides *StateOverride, blockOverrides *BlockOverrides, timeout time.Duration, globalGasCap uint64) (*core.ExecutionResult, error) {
 	if err := overrides.Apply(state); err != nil {
 		return nil, err
 	}
@@ -1068,6 +1062,17 @@ func DoCall(ctx context.Context, b Backend, args TransactionArgs, blockNrOrHash
 	return result, nil
 }
 
+func DoCall(ctx context.Context, b Backend, args TransactionArgs, blockNrOrHash rpc.BlockNumberOrHash, overrides *StateOverride, blockOverrides *BlockOverrides, timeout time.Duration, globalGasCap uint64) (*core.ExecutionResult, error) {
+	defer func(start time.Time) { log.Debug("Executing EVM call finished", "runtime", time.Since(start)) }(time.Now())
+
+	state, header, err := b.StateAndHeaderByNumberOrHash(ctx, blockNrOrHash)
+	if state == nil || err != nil {
+		return nil, err
+	}
+
+	return doCall(ctx, b, args, state, header, overrides, blockOverrides, timeout, globalGasCap)
+}
+
 func newRevertError(result *core.ExecutionResult) *revertError {
 	reason, errUnpack := abi.UnpackRevert(result.Revert())
 	err := errors.New("execution reverted")
@@ -1187,10 +1192,10 @@ func DoEstimateGas(ctx context.Context, b Backend, args TransactionArgs, blockNr
 	cap = hi
 
 	// Create a helper to check if a gas allowance results in an executable transaction
-	executable := func(gas uint64) (bool, *core.ExecutionResult, error) {
+	executable := func(gas uint64, state *state.StateDB, header *types.Header) (bool, *core.ExecutionResult, error) {
 		args.Gas = (*hexutil.Uint64)(&gas)
 
-		result, err := DoCall(ctx, b, args, blockNrOrHash, nil, nil, 0, gasCap)
+		result, err := doCall(ctx, b, args, state, header, nil, nil, 0, gasCap)
 		if err != nil {
 			if errors.Is(err, core.ErrIntrinsicGas) {
 				return true, nil, nil // Special case, raise gas limit
@@ -1199,10 +1204,15 @@ func DoEstimateGas(ctx context.Context, b Backend, args TransactionArgs, blockNr
 		}
 		return result.Failed(), result, nil
 	}
+	state, header, err := b.StateAndHeaderByNumberOrHash(ctx, blockNrOrHash)
+	if state == nil || err != nil {
+		return 0, err
+	}
 	// Execute the binary search and hone in on an executable gas limit
 	for lo+1 < hi {
+		s := state.Copy()
 		mid := (hi + lo) / 2
-		failed, _, err := executable(mid)
+		failed, _, err := executable(mid, s, header)
 
 		// If the error is not nil(consensus error), it means the provided message
 		// call or transaction will never be accepted no matter how much gas it is
@@ -1218,7 +1228,7 @@ func DoEstimateGas(ctx context.Context, b Backend, args TransactionArgs, blockNr
 	}
 	// Reject the transaction as invalid if it still fails at the highest allowance
 	if hi == cap {
-		failed, result, err := executable(hi)
+		failed, result, err := executable(hi, state, header)
 		if err != nil {
 			return 0, err
 		}