3 files changed, 45 insertions, 23 deletions
diff --git a/internal/ethapi/api.go b/internal/ethapi/api.go
index cf82cc866..6b11cbc97 100644
--- a/internal/ethapi/api.go
+++ b/internal/ethapi/api.go
@@ -48,6 +48,8 @@ import (
 
 const defaultGas = 90000
 
+var emptyHex = "0x"
+
 // PublicEthereumAPI provides an API to access Ethereum related information.
 // It offers only methods that operate on public data that is freely available to anyone.
 type PublicEthereumAPI struct {
@@ -574,12 +576,12 @@ type CallArgs struct {
 	Data     hexutil.Bytes   `json:"data"`
 }
 
-func (s *PublicBlockChainAPI) doCall(ctx context.Context, args CallArgs, blockNr rpc.BlockNumber) (string, *big.Int, error) {
+func (s *PublicBlockChainAPI) doCall(ctx context.Context, args CallArgs, blockNr rpc.BlockNumber, vmCfg vm.Config) ([]byte, *big.Int, error) {
 	defer func(start time.Time) { glog.V(logger.Debug).Infof("call took %v", time.Since(start)) }(time.Now())
 
 	state, header, err := s.b.StateAndHeaderByNumber(ctx, blockNr)
 	if state == nil || err != nil {
-		return "0x", common.Big0, err
+		return nil, common.Big0, err
 	}
 	// Set sender address or use a default if none specified
 	addr := args.From
@@ -589,40 +591,60 @@ func (s *PublicBlockChainAPI) doCall(ctx context.Context, args CallArgs, blockNr
 				addr = accounts[0].Address
 			}
 		}
-	} else {
-		addr = args.From
 	}
 	// Set default gas & gas price if none were set
 	gas, gasPrice := args.Gas.ToInt(), args.GasPrice.ToInt()
-	if gas.Cmp(common.Big0) == 0 {
+	if gas.BitLen() == 0 {
 		gas = big.NewInt(50000000)
 	}
-	if gasPrice.Cmp(common.Big0) == 0 {
+	if gasPrice.BitLen() == 0 {
 		gasPrice = new(big.Int).Mul(big.NewInt(50), common.Shannon)
 	}
+
+	// Create new call message
 	msg := types.NewMessage(addr, args.To, 0, args.Value.ToInt(), gas, gasPrice, args.Data, false)
 
-	// Execute the call and return
-	vmenv, vmError, err := s.b.GetVMEnv(ctx, msg, state, header)
-	if err != nil {
-		return "0x", common.Big0, err
+	// Setup context so it may be cancelled the call has completed
+	// or, in case of unmetered gas, setup a context with a timeout.
+	var cancel context.CancelFunc
+	if vmCfg.DisableGasMetering {
+		ctx, cancel = context.WithTimeout(ctx, time.Second*5)
+	} else {
+		ctx, cancel = context.WithCancel(ctx)
 	}
+	// Make sure the context is cancelled when the call has completed
+	// this makes sure resources are cleaned up.
+	defer func() { cancel() }()
+
+	// Get a new instance of the EVM.
+	evm, vmError, err := s.b.GetEVM(ctx, msg, state, header, vmCfg)
+	if err != nil {
+		return nil, common.Big0, err
+	}
+	// Wait for the context to be done and cancel the evm. Even if the
+	// EVM has finished, cancelling may be done (repeatedly)
+	go func() {
+		select {
+		case <-ctx.Done():
+			evm.Cancel()
+		}
+	}()
+
+	// Setup the gas pool (also for unmetered requests)
+	// and apply the message.
 	gp := new(core.GasPool).AddGas(common.MaxBig)
-	res, gas, err := core.ApplyMessage(vmenv, msg, gp)
+	res, gas, err := core.ApplyMessage(evm, msg, gp)
 	if err := vmError(); err != nil {
-		return "0x", common.Big0, err
-	}
-	if len(res) == 0 { // backwards compatibility
-		return "0x", gas, err
+		return nil, common.Big0, err
 	}
-	return common.ToHex(res), gas, err
+	return res, gas, err
 }
 
 // Call executes the given transaction on the state for the given block number.
 // It doesn't make and changes in the state/blockchain and is useful to execute and retrieve values.
-func (s *PublicBlockChainAPI) Call(ctx context.Context, args CallArgs, blockNr rpc.BlockNumber) (string, error) {
-	result, _, err := s.doCall(ctx, args, blockNr)
-	return result, err
+func (s *PublicBlockChainAPI) Call(ctx context.Context, args CallArgs, blockNr rpc.BlockNumber) (hexutil.Bytes, error) {
+	result, _, err := s.doCall(ctx, args, blockNr, vm.Config{DisableGasMetering: true})
+	return (hexutil.Bytes)(result), err
 }
 
 // EstimateGas returns an estimate of the amount of gas needed to execute the given transaction.
@@ -644,7 +666,7 @@ func (s *PublicBlockChainAPI) EstimateGas(ctx context.Context, args CallArgs) (*
 		mid := (hi + lo) / 2
 		(*big.Int)(&args.Gas).SetUint64(mid)
 
-		_, gas, err := s.doCall(ctx, args, rpc.PendingBlockNumber)
+		_, gas, err := s.doCall(ctx, args, rpc.PendingBlockNumber, vm.Config{})
 
 		// If the transaction became invalid or used all the gas (failed), raise the gas limit
 		if err != nil || gas.Cmp((*big.Int)(&args.Gas)) == 0 {
diff --git a/internal/ethapi/backend.go b/internal/ethapi/backend.go
index ebb14a5b5..214214f51 100644
--- a/internal/ethapi/backend.go
+++ b/internal/ethapi/backend.go
@@ -51,7 +51,7 @@ type Backend interface {
 	GetBlock(ctx context.Context, blockHash common.Hash) (*types.Block, error)
 	GetReceipts(ctx context.Context, blockHash common.Hash) (types.Receipts, error)
 	GetTd(blockHash common.Hash) *big.Int
-	GetVMEnv(ctx context.Context, msg core.Message, state State, header *types.Header) (*vm.EVM, func() error, error)
+	GetEVM(ctx context.Context, msg core.Message, state State, header *types.Header, vmCfg vm.Config) (*vm.EVM, func() error, error)
 	// TxPool API
 	SendTx(ctx context.Context, signedTx *types.Transaction) error
 	RemoveTx(txHash common.Hash)
diff --git a/internal/ethapi/tracer_test.go b/internal/ethapi/tracer_test.go
index 65a23f55e..693afe802 100644
--- a/internal/ethapi/tracer_test.go
+++ b/internal/ethapi/tracer_test.go
@@ -45,7 +45,7 @@ func (account) ForEachStorage(cb func(key, value common.Hash) bool) {}
 func runTrace(tracer *JavascriptTracer) (interface{}, error) {
 	env := vm.NewEVM(vm.Context{}, nil, params.TestChainConfig, vm.Config{Debug: true, Tracer: tracer})
 
-	contract := vm.NewContract(account{}, account{}, big.NewInt(0), big.NewInt(10000))
+	contract := vm.NewContract(account{}, account{}, big.NewInt(0), 10000)
 	contract.Code = []byte{byte(vm.PUSH1), 0x1, byte(vm.PUSH1), 0x1, 0x0}
 
 	_, err := env.Interpreter().Run(contract, []byte{})
@@ -134,7 +134,7 @@ func TestHaltBetweenSteps(t *testing.T) {
 	}
 
 	env := vm.NewEVM(vm.Context{}, nil, params.TestChainConfig, vm.Config{Debug: true, Tracer: tracer})
-	contract := vm.NewContract(&account{}, &account{}, big.NewInt(0), big.NewInt(0))
+	contract := vm.NewContract(&account{}, &account{}, big.NewInt(0), 0)
 
 	tracer.CaptureState(env, 0, 0, big.NewInt(0), big.NewInt(0), nil, nil, contract, 0, nil)
 	timeout := errors.New("stahp")