Implements eth_call (#127)

* Fixed tx receipt error on failed transaction

* Add returnData to failed transaction for logs bloom

* Added simulate call option, without returning evm data

* Added encoding and decoding of data from EVM execution for usability

* Remove unused context parameter

* Fix function comment and remove unnecessary logging on eth_call

rpc/eth_api.go

@@ -3,12 +3,14 @@ package rpc
 import (
 	"bytes"
 	"fmt"
+	"log"
 	"math/big"
 	"strconv"
 
 	emintcrypto "github.com/cosmos/ethermint/crypto"
 	emintkeys "github.com/cosmos/ethermint/keys"
 	"github.com/cosmos/ethermint/rpc/args"
+	emint "github.com/cosmos/ethermint/types"
 	"github.com/cosmos/ethermint/utils"
 	"github.com/cosmos/ethermint/version"
 	"github.com/cosmos/ethermint/x/evm"
@@ -21,12 +23,15 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	ethtypes "github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/rlp"
+	"github.com/ethereum/go-ethereum/rpc"
 
 	"github.com/cosmos/cosmos-sdk/client/context"
 	"github.com/cosmos/cosmos-sdk/client/flags"
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	authutils "github.com/cosmos/cosmos-sdk/x/auth/client/utils"
+	authtypes "github.com/cosmos/cosmos-sdk/x/auth/types"
 
 	"github.com/spf13/viper"
 )
@@ -324,19 +329,115 @@ func (e *PublicEthAPI) SendRawTransaction(data hexutil.Bytes) (common.Hash, erro
 	return common.HexToHash(res.TxHash), nil
 }
 
-// CallArgs represents arguments to a smart contract call as provided by RPC clients.
+// CallArgs represents the arguments for a call.
 type CallArgs struct {
-	From     common.Address `json:"from"`
-	To       common.Address `json:"to"`
-	Gas      hexutil.Uint64 `json:"gas"`
-	GasPrice hexutil.Big    `json:"gasPrice"`
-	Value    hexutil.Big    `json:"value"`
-	Data     hexutil.Bytes  `json:"data"`
+	From     *common.Address `json:"from"`
+	To       *common.Address `json:"to"`
+	Gas      *hexutil.Uint64 `json:"gas"`
+	GasPrice *hexutil.Big    `json:"gasPrice"`
+	Value    *hexutil.Big    `json:"value"`
+	Data     *hexutil.Bytes  `json:"data"`
 }
 
 // Call performs a raw contract call.
-func (e *PublicEthAPI) Call(args CallArgs, blockNum BlockNumber) hexutil.Bytes {
-	return nil
+func (e *PublicEthAPI) Call(args CallArgs, blockNr rpc.BlockNumber, overrides *map[common.Address]account) (hexutil.Bytes, error) {
+	result, err := e.doCall(args, blockNr, vm.Config{}, big.NewInt(emint.DefaultRPCGasLimit))
+	return (hexutil.Bytes)(result), err
+}
+
+// account indicates the overriding fields of account during the execution of
+// a message call.
+// Note, state and stateDiff can't be specified at the same time. If state is
+// set, message execution will only use the data in the given state. Otherwise
+// if statDiff is set, all diff will be applied first and then execute the call
+// message.
+type account struct {
+	Nonce     *hexutil.Uint64              `json:"nonce"`
+	Code      *hexutil.Bytes               `json:"code"`
+	Balance   **hexutil.Big                `json:"balance"`
+	State     *map[common.Hash]common.Hash `json:"state"`
+	StateDiff *map[common.Hash]common.Hash `json:"stateDiff"`
+}
+
+// DoCall performs a simulated call operation through the evm
+func (e *PublicEthAPI) doCall(args CallArgs, blockNr rpc.BlockNumber, vmCfg vm.Config, globalGasCap *big.Int) ([]byte, error) {
+	// Set height for historical queries
+	ctx := e.cliCtx.WithHeight(blockNr.Int64())
+
+	// Set sender address or use a default if none specified
+	var addr common.Address
+	if args.From == nil {
+		if e.key != nil {
+			addr = common.BytesToAddress(e.key.PubKey().Address().Bytes())
+		}
+		// No error handled here intentionally to match geth behaviour
+	} else {
+		addr = *args.From
+	}
+
+	// Set default gas & gas price if none were set
+	// Change this to uint64(math.MaxUint64 / 2) if gas cap can be configured
+	gas := uint64(emint.DefaultRPCGasLimit)
+	if args.Gas != nil {
+		gas = uint64(*args.Gas)
+	}
+	if globalGasCap != nil && globalGasCap.Uint64() < gas {
+		log.Println("Caller gas above allowance, capping", "requested", gas, "cap", globalGasCap)
+		gas = globalGasCap.Uint64()
+	}
+
+	// Set gas price using default or parameter if passed in
+	gasPrice := new(big.Int).SetUint64(emint.DefaultGasPrice)
+	if args.GasPrice != nil {
+		gasPrice = args.GasPrice.ToInt()
+	}
+
+	// Set value for transaction
+	value := new(big.Int)
+	if args.Value != nil {
+		value = args.Value.ToInt()
+	}
+
+	// Set Data if provided
+	var data []byte
+	if args.Data != nil {
+		data = []byte(*args.Data)
+	}
+
+	// Set destination address for call
+	var toAddr sdk.AccAddress
+	if args.To != nil {
+		toAddr = sdk.AccAddress(args.To.Bytes())
+	}
+
+	// Create new call message
+	msg := types.NewEmintMsg(0, &toAddr, sdk.NewIntFromBigInt(value), gas,
+		sdk.NewIntFromBigInt(gasPrice), data, sdk.AccAddress(addr.Bytes()))
+
+	// Generate tx to be used to simulate (signature isn't needed)
+	tx := authtypes.NewStdTx([]sdk.Msg{msg}, authtypes.StdFee{}, []authtypes.StdSignature{authtypes.StdSignature{}}, "")
+
+	// Encode transaction by default Tx encoder
+	txEncoder := authutils.GetTxEncoder(ctx.Codec)
+	txBytes, err := txEncoder(tx)
+	if err != nil {
+		return []byte{}, err
+	}
+
+	// Transaction simulation through query
+	res, _, err := ctx.QueryWithData("app/simulate", txBytes)
+	if err != nil {
+		return []byte{}, err
+	}
+
+	var simResult sdk.Result
+	if err = ctx.Codec.UnmarshalBinaryLengthPrefixed(res, &simResult); err != nil {
+		return nil, err
+	}
+
+	_, _, ret, err := types.DecodeReturnData(simResult.Data)
+
+	return ret, err
 }
 
 // EstimateGas estimates gas usage for the given smart contract call.
@@ -606,13 +707,7 @@ func (e *PublicEthAPI) GetTransactionReceipt(hash common.Hash) (map[string]inter
 	e.cliCtx.Codec.MustUnmarshalJSON(res, &logs)
 
 	txData := tx.TxResult.GetData()
-	var bloomFilter ethtypes.Bloom
-	var contractAddress common.Address
-	if len(txData) >= 20 {
-		// TODO: change hard coded indexing of bytes
-		bloomFilter = ethtypes.BytesToBloom(txData[20:])
-		contractAddress = common.BytesToAddress(txData[:20])
-	}
+	contractAddress, bloomFilter, _, _ := types.DecodeReturnData(txData)
 
 	fields := map[string]interface{}{
 		"blockHash":         blockHash,
@@ -630,7 +725,6 @@ func (e *PublicEthAPI) GetTransactionReceipt(hash common.Hash) (map[string]inter
 	}
 
 	if contractAddress != (common.Address{}) {
-		// TODO: change hard coded indexing of first 20 bytes
 		fields["contractAddress"] = contractAddress
 	}
 

types/params.go

@@ -0,0 +1,8 @@
+package types
+
+const (
+	// DefaultGasPrice is default gas price for evm transactions
+	DefaultGasPrice = 20
+	// DefaultRPCGasLimit is default gas limit for RPC call operations
+	DefaultRPCGasLimit = 10000000
+)

x/evm/handler.go

@@ -20,8 +20,8 @@ func NewHandler(keeper Keeper) sdk.Handler {
 		switch msg := msg.(type) {
 		case types.EthereumTxMsg:
 			return handleETHTxMsg(ctx, keeper, msg)
-		case types.EmintMsg:
-			return handleEmintMsg(ctx, keeper, msg)
+		case *types.EmintMsg:
+			return handleEmintMsg(ctx, keeper, *msg)
 		default:
 			errMsg := fmt.Sprintf("Unrecognized ethermint Msg type: %v", msg.Type())
 			return sdk.ErrUnknownRequest(errMsg).Result()
@@ -67,6 +67,7 @@ func handleETHTxMsg(ctx sdk.Context, keeper Keeper, msg types.EthereumTxMsg) sdk
 		Csdb:         keeper.csdb.WithContext(ctx),
 		ChainID:      intChainID,
 		THash:        &ethHash,
+		Simulate:     ctx.IsCheckTx(),
 	}
 	// Prepare db for logs
 	keeper.csdb.Prepare(ethHash, common.Hash{}, keeper.txCount.get())
@@ -97,6 +98,7 @@ func handleEmintMsg(ctx sdk.Context, keeper Keeper, msg types.EmintMsg) sdk.Resu
 		Payload:      msg.Payload,
 		Csdb:         keeper.csdb.WithContext(ctx),
 		ChainID:      intChainID,
+		Simulate:     ctx.IsCheckTx(),
 	}
 
 	if msg.Recipient != nil {

x/evm/types/msg.go

@@ -391,7 +391,7 @@ func GenerateFromArgs(args args.SendTxArgs, ctx context.CLIContext) (msg *Ethere
 	if args.GasPrice == nil {
 		// Set default gas price
 		// TODO: Change to min gas price from context once available through server/daemon
-		gasPrice = big.NewInt(20)
+		gasPrice = big.NewInt(types.DefaultGasPrice)
 	}
 
 	if args.Nonce == nil {

x/evm/types/state_transition.go

@@ -25,6 +25,7 @@ type StateTransition struct {
 	Csdb         *CommitStateDB
 	ChainID      *big.Int
 	THash        *common.Hash
+	Simulate     bool
 }
 
 // TransitionCSDB performs an evm state transition from a transaction
@@ -60,6 +61,7 @@ func (st StateTransition) TransitionCSDB(ctx sdk.Context) (sdk.Result, *big.Int)
 	)
 
 	var (
+		ret         []byte
 		leftOverGas uint64
 		addr        common.Address
 		vmerr       error
@@ -67,11 +69,11 @@ func (st StateTransition) TransitionCSDB(ctx sdk.Context) (sdk.Result, *big.Int)
 	)
 
 	if contractCreation {
-		_, addr, leftOverGas, vmerr = vmenv.Create(senderRef, st.Payload, gasLimit, st.Amount)
+		ret, addr, leftOverGas, vmerr = vmenv.Create(senderRef, st.Payload, gasLimit, st.Amount)
 	} else {
 		// Increment the nonce for the next transaction
 		st.Csdb.SetNonce(st.Sender, st.Csdb.GetNonce(st.Sender)+1)
-		_, leftOverGas, vmerr = vmenv.Call(senderRef, *st.Recipient, st.Payload, gasLimit, st.Amount)
+		ret, leftOverGas, vmerr = vmenv.Call(senderRef, *st.Recipient, st.Payload, gasLimit, st.Amount)
 	}
 
 	// Generate bloom filter to be saved in tx receipt data
@@ -83,8 +85,8 @@ func (st StateTransition) TransitionCSDB(ctx sdk.Context) (sdk.Result, *big.Int)
 		bloomFilter = ethtypes.BytesToBloom(bloomInt.Bytes())
 	}
 
-	// TODO: coniditionally add either/ both of these to return data
-	returnData := append(addr.Bytes(), bloomFilter.Bytes()...)
+	// Encode all necessary data into slice of bytes to return in sdk result
+	returnData := EncodeReturnData(addr, bloomFilter, ret)
 
 	// handle errors
 	if vmerr != nil {
@@ -105,6 +107,8 @@ func (st StateTransition) TransitionCSDB(ctx sdk.Context) (sdk.Result, *big.Int)
 }
 
 func (st *StateTransition) checkNonce() sdk.Result {
+	// If simulated transaction, don't verify nonce
+	if !st.Simulate {
 		// Make sure this transaction's nonce is correct.
 		nonce := st.Csdb.GetNonce(st.Sender)
 		if nonce < st.AccountNonce {
@@ -112,6 +116,7 @@ func (st *StateTransition) checkNonce() sdk.Result {
 		} else if nonce > st.AccountNonce {
 			return emint.ErrInvalidNonce("nonce too low").Result()
 		}
+	}
 
 	return sdk.Result{}
 }

x/evm/types/utils.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/cosmos/ethermint/crypto"
 	ethcmn "github.com/ethereum/go-ethereum/common"
+	ethtypes "github.com/ethereum/go-ethereum/core/types"
 	ethcrypto "github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/rlp"
 
@@ -12,6 +13,11 @@ import (
 	"golang.org/x/crypto/sha3"
 )
 
+const (
+	bloomIdx  = ethcmn.AddressLength
+	returnIdx = bloomIdx + ethtypes.BloomByteLength
+)
+
 // GenerateEthAddress generates an Ethereum address.
 func GenerateEthAddress() ethcmn.Address {
 	priv, err := crypto.GenerateKey()
@@ -46,3 +52,24 @@ func rlpHash(x interface{}) (hash ethcmn.Hash) {
 
 	return hash
 }
+
+// EncodeReturnData takes all of the necessary data from the EVM execution
+// and returns the data as a byte slice
+func EncodeReturnData(addr ethcmn.Address, bloom ethtypes.Bloom, evmRet []byte) []byte {
+	// Append address, bloom, evm return bytes in that order
+	returnData := append(addr.Bytes(), bloom.Bytes()...)
+	return append(returnData, evmRet...)
+}
+
+// DecodeReturnData decodes the byte slice of values to their respective types
+func DecodeReturnData(bytes []byte) (addr ethcmn.Address, bloom ethtypes.Bloom, ret []byte, err error) {
+	if len(bytes) >= returnIdx {
+		addr = ethcmn.BytesToAddress(bytes[:bloomIdx])
+		bloom = ethtypes.BytesToBloom(bytes[bloomIdx:returnIdx])
+		ret = bytes[returnIdx:]
+	} else {
+		err = fmt.Errorf("Invalid format for encoded data, message must be an EVM state transition")
+	}
+
+	return
+}

x/evm/types/utils_test.go

@@ -0,0 +1,24 @@
+package types
+
+import (
+	"testing"
+
+	ethcmn "github.com/ethereum/go-ethereum/common"
+	ethtypes "github.com/ethereum/go-ethereum/core/types"
+	"github.com/stretchr/testify/require"
+)
+
+func TestEvmDataEncoding(t *testing.T) {
+	addr := ethcmn.HexToAddress("0x12345")
+	bloom := ethtypes.BytesToBloom([]byte{0x1, 0x3})
+	ret := []byte{0x5, 0x8}
+
+	encoded := EncodeReturnData(addr, bloom, ret)
+
+	decAddr, decBloom, decRet, err := DecodeReturnData(encoded)
+
+	require.NoError(t, err)
+	require.Equal(t, addr, decAddr)
+	require.Equal(t, bloom, decBloom)
+	require.Equal(t, ret, decRet)
+}