RPC gas capping (#391)

* Fix rpc gas capping

* Add test for gas capping when creating tx message

Author: jenikd

ethapi/transaction_args.go

@@ -174,18 +174,22 @@ func (args *TransactionArgs) ToMessage(globalGasCap uint64, baseFee *big.Int) (*
 	// Set sender address or use zero address if none specified.
 	addr := args.from()
 
-	// Set default gas & gas price if none were set
-	gas := globalGasCap
-	if gas == 0 {
-		gas = uint64(math.MaxUint64 / 2)
+	// Tosca uses int64 for gas so it needs to be limited by MaxInt64
+	if globalGasCap == 0 || globalGasCap > math.MaxInt64 {
+		globalGasCap = math.MaxInt64
 	}
+
+	gas := globalGasCap
+
 	if args.Gas != nil {
-		gas = uint64(*args.Gas)
-	}
-	if globalGasCap != 0 && globalGasCap < gas {
-		log.Warn("Caller gas above allowance, capping", "requested", gas, "cap", globalGasCap)
-		gas = globalGasCap
+		argsGas := uint64(*args.Gas)
+		if argsGas > gas {
+			log.Warn("Caller gas above allowance, capping", "requested", argsGas, "cap", gas)
+		} else {
+			gas = argsGas
+		}
 	}
+
 	var (
 		gasPrice  *big.Int
 		gasFeeCap *big.Int

ethapi/transaction_args_test.go

@@ -0,0 +1,75 @@
+package ethapi
+
+import (
+	"math"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/stretchr/testify/require"
+)
+
+func TestGasCap(t *testing.T) {
+
+	var (
+		gas10M       = hexutil.Uint64(10_000_000)
+		gasMaxUint64 = hexutil.Uint64(math.MaxUint64)
+	)
+
+	tests := []struct {
+		name         string
+		argGas       *hexutil.Uint64
+		globalGasCap uint64
+		expectedGas  uint64
+	}{
+		{
+			name:         "gas cap 0 and arg gas nil",
+			globalGasCap: 0,
+			argGas:       nil,
+			expectedGas:  math.MaxInt64,
+		}, {
+			name:         "gas cap 0 and arg gas 10M",
+			globalGasCap: 0,
+			argGas:       &gas10M,
+			expectedGas:  10_000_000,
+		}, {
+			name:         "gas cap 0 and arg gas maxUint64",
+			globalGasCap: 0,
+			argGas:       &gasMaxUint64,
+			expectedGas:  math.MaxInt64,
+		}, {
+			name:         "gas cap 50M and arg gas nil",
+			globalGasCap: 50_000_000,
+			argGas:       nil,
+			expectedGas:  50_000_000,
+		}, {
+			name:         "gas cap 50M and arg gas 10M",
+			globalGasCap: 50_000_000,
+			argGas:       &gas10M,
+			expectedGas:  10_000_000,
+		}, {
+			name:         "gas cap 50M and arg gas maxUint64",
+			globalGasCap: 50_000_000,
+			argGas:       &gasMaxUint64,
+			expectedGas:  50_000_000,
+		}, {
+			name:         "gas cap maxUint64 and arg gas 10M",
+			globalGasCap: math.MaxUint64,
+			argGas:       &gas10M,
+			expectedGas:  10_000_000,
+		}, {
+			name:         "gas cap maxUint64 and arg gas maxUint64",
+			globalGasCap: math.MaxUint64,
+			argGas:       &gasMaxUint64,
+			expectedGas:  math.MaxInt64,
+		},
+	}
+
+	for _, test := range tests {
+		args := TransactionArgs{Gas: test.argGas}
+
+		msg, err := args.ToMessage(test.globalGasCap, nil)
+
+		require.Nil(t, err)
+		require.Equal(t, test.expectedGas, msg.GasLimit, test.name)
+	}
+}