core: Fixed gas price (#205)

* core/vm: update abi
* core/vm: add MinGasPrice to gov
* params: Add MinGasPrice to Config
* dex: SuggestPrice from Governance
* test: add minGasPrice to genesis.json
* core: check underpriced tx
* dex: verify with gas price

3 files changed, 48 insertions, 7 deletions

diff --git a/dex/api_backend.go b/dex/api_backend.go
index 719625946..d423b41f7 100644
--- a/dex/api_backend.go
+++ b/dex/api_backend.go
@@ -195,7 +195,7 @@ func (b *DexAPIBackend) ProtocolVersion() int {
 }
 
 func (b *DexAPIBackend) SuggestPrice(ctx context.Context) (*big.Int, error) {
-	return b.gpo.SuggestPrice(ctx)
+	return b.dex.governance.MinGasPrice(b.dex.blockchain.CurrentBlock().Round()), nil
 }
 
 func (b *DexAPIBackend) ChainDb() ethdb.Database {
diff --git a/dex/app.go b/dex/app.go
index d2bd02f0c..ab4e80058 100644
--- a/dex/app.go
+++ b/dex/app.go
@@ -124,6 +124,18 @@ func (d *DexconApp) validateNonce(txs types.Transactions) (map[common.Address]ui
 	return addressFirstNonce, nil
 }
 
+// validateGasPrice checks if no gas price is lower than minGasPrice defined in
+// governance contract.
+func (d *DexconApp) validateGasPrice(txs types.Transactions, round uint64) bool {
+	minGasPrice := d.gov.MinGasPrice(round)
+	for _, tx := range txs {
+		if minGasPrice.Cmp(tx.GasPrice()) > 0 {
+			return false
+		}
+	}
+	return true
+}
+
 // PreparePayload is called when consensus core is preparing payload for block.
 func (d *DexconApp) PreparePayload(position coreTypes.Position) (payload []byte, err error) {
 	// softLimit limits the runtime of inner call to preparePayload.
@@ -410,6 +422,10 @@ func (d *DexconApp) VerifyBlock(block *coreTypes.Block) coreTypes.BlockVerifySta
 		log.Error("Validate nonce failed", "error", err)
 		return coreTypes.VerifyInvalidBlock
 	}
+	if !d.validateGasPrice(transactions, block.Position.Round) {
+		log.Error("Validate gas price failed")
+		return coreTypes.VerifyInvalidBlock
+	}
 
 	// Check if nonce is strictly increasing for every address.
 	chainID := big.NewInt(int64(block.Position.ChainID))
diff --git a/dex/app_test.go b/dex/app_test.go
index 09c61c11c..73d952f31 100644
--- a/dex/app_test.go
+++ b/dex/app_test.go
@@ -234,7 +234,7 @@ func TestVerifyBlock(t *testing.T) {
 		common.BytesToAddress([]byte{9}),
 		big.NewInt(50000000000000001),
 		params.TxGas,
-		big.NewInt(1),
+		big.NewInt(10),
 		nil)
 	tx, err = types.SignTx(tx, signer, key)
 	if err != nil {
@@ -269,7 +269,7 @@ func TestVerifyBlock(t *testing.T) {
 		common.BytesToAddress([]byte{9}),
 		big.NewInt(1),
 		params.TxGas,
-		big.NewInt(1),
+		big.NewInt(10),
 		make([]byte, 1))
 	tx, err = types.SignTx(tx, signer, key)
 	if err != nil {
@@ -304,7 +304,7 @@ func TestVerifyBlock(t *testing.T) {
 		common.BytesToAddress([]byte{9}),
 		big.NewInt(1),
 		params.TxGas,
-		big.NewInt(1),
+		big.NewInt(10),
 		make([]byte, 1))
 	tx1, err = types.SignTx(tx, signer, key)
 	if err != nil {
@@ -317,7 +317,7 @@ func TestVerifyBlock(t *testing.T) {
 		common.BytesToAddress([]byte{9}),
 		big.NewInt(1),
 		params.TxGas,
-		big.NewInt(1),
+		big.NewInt(10),
 		make([]byte, 1))
 	tx2, err = types.SignTx(tx, signer, key)
 	if err != nil {
@@ -334,6 +334,30 @@ func TestVerifyBlock(t *testing.T) {
 	if status != coreTypes.VerifyInvalidBlock {
 		t.Fatalf("verify fail expect invalid block but get %v", status)
 	}
+
+	// Invalid gas price.
+	tx = types.NewTransaction(
+		0,
+		common.BytesToAddress([]byte{9}),
+		big.NewInt(1),
+		params.TxGas,
+		big.NewInt(5),
+		make([]byte, 1))
+	tx, err = types.SignTx(tx, signer, key)
+	if err != nil {
+		return
+	}
+	block.Payload, err = rlp.EncodeToBytes(types.Transactions{tx})
+	if err != nil {
+		return
+	}
+
+	// Expect invalid block.
+	status = dex.app.VerifyBlock(block)
+	if status != coreTypes.VerifyInvalidBlock {
+		t.Fatalf("verify fail expect invalid block but get %v", status)
+	}
+
 }
 
 func TestBlockConfirmed(t *testing.T) {
@@ -489,6 +513,7 @@ func newTestDexonWithGenesis(allocKey *ecdsa.PrivateKey) (*Dexon, error) {
 			PublicKey: crypto.FromECDSAPub(&key.PublicKey),
 		},
 	}
+	genesis.Config.Dexcon.MinGasPrice = big.NewInt(10)
 	chainConfig, _, err := core.SetupGenesisBlock(db, genesis)
 	if err != nil {
 		return nil, err
@@ -530,7 +555,7 @@ func addTx(dex *Dexon, nonce int, signer types.Signer, key *ecdsa.PrivateKey) (
 		common.BytesToAddress([]byte{9}),
 		big.NewInt(int64(nonce*1)),
 		params.TxGas,
-		big.NewInt(1),
+		big.NewInt(10),
 		nil)
 	tx, err := types.SignTx(tx, signer, key)
 	if err != nil {
@@ -638,7 +663,7 @@ func prepareDataWithoutTxPool(dex *Dexon, key *ecdsa.PrivateKey, startNonce, txN
 			common.BytesToAddress([]byte{9}),
 			big.NewInt(int64(n*1)),
 			params.TxGas,
-			big.NewInt(1),
+			big.NewInt(10),
 			nil)
 		tx, err = types.SignTx(tx, signer, key)
 		if err != nil {