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

12 files changed, 161 insertions, 13 deletions

diff --git a/core/governance.go b/core/governance.go
index 12124760e..9929867c9 100644
--- a/core/governance.go
+++ b/core/governance.go
@@ -134,3 +134,7 @@ func (g *Governance) IsDKGFinal(round uint64) bool {
 	count := headHelper.DKGFinalizedsCount(big.NewInt(int64(round))).Uint64()
 	return count >= threshold
 }
+
+func (g *Governance) MinGasPrice(round uint64) *big.Int {
+	return g.GetGovStateHelperAtRound(round).MinGasPrice()
+}
diff --git a/core/tx_pool.go b/core/tx_pool.go
index 871b50be1..0a1b3f132 100644
--- a/core/tx_pool.go
+++ b/core/tx_pool.go
@@ -24,10 +24,13 @@ import (
 	"sync"
 	"time"
 
+	dexCore "github.com/dexon-foundation/dexon-consensus/core"
+
 	"github.com/dexon-foundation/dexon/common"
 	"github.com/dexon-foundation/dexon/common/prque"
 	"github.com/dexon-foundation/dexon/core/state"
 	"github.com/dexon-foundation/dexon/core/types"
+	"github.com/dexon-foundation/dexon/core/vm"
 	"github.com/dexon-foundation/dexon/event"
 	"github.com/dexon-foundation/dexon/log"
 	"github.com/dexon-foundation/dexon/metrics"
@@ -115,6 +118,7 @@ const (
 type blockChain interface {
 	CurrentBlock() *types.Block
 	GetBlock(hash common.Hash, number uint64) *types.Block
+	GetBlockByNumber(number uint64) *types.Block
 	StateAt(root common.Hash) (*state.StateDB, error)
 
 	SubscribeChainHeadEvent(ch chan<- ChainHeadEvent) event.Subscription
@@ -206,6 +210,7 @@ type TxPool struct {
 	chainconfig  *params.ChainConfig
 	chain        blockChain
 	gasPrice     *big.Int
+	govGasPrice  *big.Int
 	txFeed       event.Feed
 	scope        event.SubscriptionScope
 	chainHeadCh  chan ChainHeadEvent
@@ -385,6 +390,28 @@ func (pool *TxPool) reset(oldHead, newHead *types.Header) {
 	pool.currentState = statedb
 	pool.pendingState = state.ManageState(statedb)
 	pool.currentMaxGas = newHead.GasLimit
+	if oldHead == nil || oldHead.Round != newHead.Round {
+		round := newHead.Round
+		if round < dexCore.ConfigRoundShift {
+			round = 0
+		} else {
+			round -= dexCore.ConfigRoundShift
+		}
+		state := &vm.GovernanceStateHelper{StateDB: statedb}
+		height := state.RoundHeight(new(big.Int).SetUint64((round))).Uint64()
+		block := pool.chain.GetBlockByNumber(height)
+		if block == nil {
+			log.Error("Failed to get block", "round", round, "height", height)
+			panic("cannot get config for new round's min gas price")
+		}
+		configState, err := pool.chain.StateAt(block.Header().Root)
+		if err != nil {
+			log.Error("Failed to get txpool state for min gas price", "err", err)
+			panic("cannot get state for new round's min gas price")
+		}
+		govState := &vm.GovernanceStateHelper{StateDB: configState}
+		pool.setGovPrice(govState.MinGasPrice())
+	}
 
 	// validate the pool of pending transactions, this will remove
 	// any transactions that have been included in the block or
@@ -438,10 +465,21 @@ func (pool *TxPool) SetGasPrice(price *big.Int) {
 	defer pool.mu.Unlock()
 
 	pool.gasPrice = price
+	pool.removeUnderpricedTx(price)
+	log.Info("Transaction pool price threshold updated", "price", price)
+}
+
+// setGovPrice updates the minimum price required by the transaction pool for a
+// new transaction, and drops all transactions below this threshold.
+func (pool *TxPool) setGovPrice(price *big.Int) {
+	pool.govGasPrice = price
+	pool.removeUnderpricedTx(price)
+}
+
+func (pool *TxPool) removeUnderpricedTx(price *big.Int) {
 	for _, tx := range pool.priced.Cap(price, pool.locals) {
 		pool.removeTx(tx.Hash(), false)
 	}
-	log.Info("Transaction pool price threshold updated", "price", price)
 }
 
 // State returns the virtual managed state of the transaction pool.
@@ -551,6 +589,10 @@ func (pool *TxPool) validateTx(tx *types.Transaction, local bool) error {
 	if err != nil {
 		return ErrInvalidSender
 	}
+	// Drop all transactions under governance minimum gas price.
+	if pool.govGasPrice.Cmp(tx.GasPrice()) > 0 {
+		return ErrUnderpriced
+	}
 	// Drop non-local transactions under our own minimal accepted gas price
 	local = local || pool.locals.contains(from) // account may be local even if the transaction arrived from the network
 	if !local && pool.gasPrice.Cmp(tx.GasPrice()) > 0 {
diff --git a/core/tx_pool_test.go b/core/tx_pool_test.go
index 96151850d..70d4a351a 100644
--- a/core/tx_pool_test.go
+++ b/core/tx_pool_test.go
@@ -61,6 +61,10 @@ func (bc *testBlockChain) GetBlock(hash common.Hash, number uint64) *types.Block
 	return bc.CurrentBlock()
 }
 
+func (bc *testBlockChain) GetBlockByNumber(uint64) *types.Block {
+	return bc.CurrentBlock()
+}
+
 func (bc *testBlockChain) StateAt(common.Hash) (*state.StateDB, error) {
 	return bc.statedb, nil
 }
diff --git a/core/vm/oracle_contract_abi.go b/core/vm/oracle_contract_abi.go
index fde973203..ff4a94b29 100644
--- a/core/vm/oracle_contract_abi.go
+++ b/core/vm/oracle_contract_abi.go
@@ -566,6 +566,20 @@ const GovernanceABIJSON = `
   {
     "constant": true,
     "inputs": [],
+    "name": "minGasPrice",
+    "outputs": [
+      {
+        "name": "",
+        "type": "uint256"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "view",
+    "type": "function"
+  },
+  {
+    "constant": true,
+    "inputs": [],
     "name": "lockupPeriod",
     "outputs": [
       {
@@ -855,6 +869,10 @@ const GovernanceABIJSON = `
       {
         "name": "FineValues",
         "type": "uint256[]"
+      },
+      {
+        "name": "MinGasPrice",
+        "type": "uint256"
       }
     ],
     "name": "updateConfiguration",
diff --git a/core/vm/oracle_contracts.go b/core/vm/oracle_contracts.go
index 1eeb57a5a..826e0396c 100644
--- a/core/vm/oracle_contracts.go
+++ b/core/vm/oracle_contracts.go
@@ -83,6 +83,7 @@ const (
 	fineValuesLoc
 	finedRecordsLoc
 	dkgResetCountLoc
+	minGasPriceLoc
 )
 
 func publicKeyToNodeID(pkBytes []byte) (Bytes32, error) {
@@ -894,6 +895,11 @@ func (s *GovernanceStateHelper) IncDKGResetCount(round *big.Int) {
 	s.setStateBigInt(loc, new(big.Int).Add(count, big.NewInt(1)))
 }
 
+// uint256 public minGasPrice;
+func (s *GovernanceStateHelper) MinGasPrice() *big.Int {
+	return s.getStateBigInt(big.NewInt(minGasPriceLoc))
+}
+
 // Stake is a helper function for creating genesis state.
 func (s *GovernanceStateHelper) Stake(
 	addr common.Address, publicKey []byte, staked *big.Int,
@@ -948,6 +954,7 @@ func (s *GovernanceStateHelper) Configuration() *params.DexconConfig {
 		RoundLength:       s.getStateBigInt(big.NewInt(roundLengthLoc)).Uint64(),
 		MinBlockInterval:  s.getStateBigInt(big.NewInt(minBlockIntervalLoc)).Uint64(),
 		FineValues:        s.FineValues(),
+		MinGasPrice:       s.getStateBigInt(big.NewInt(minGasPriceLoc)),
 	}
 }
 
@@ -966,6 +973,7 @@ func (s *GovernanceStateHelper) UpdateConfiguration(cfg *params.DexconConfig) {
 	s.setStateBigInt(big.NewInt(roundLengthLoc), big.NewInt(int64(cfg.RoundLength)))
 	s.setStateBigInt(big.NewInt(minBlockIntervalLoc), big.NewInt(int64(cfg.MinBlockInterval)))
 	s.SetFineValues(cfg.FineValues)
+	s.setStateBigInt(big.NewInt(minGasPriceLoc), cfg.MinGasPrice)
 }
 
 type rawConfigStruct struct {
@@ -979,6 +987,7 @@ type rawConfigStruct struct {
 	RoundLength      *big.Int
 	MinBlockInterval *big.Int
 	FineValues       []*big.Int
+	MinGasPrice      *big.Int
 }
 
 // UpdateConfigurationRaw updates system configuration.
@@ -993,6 +1002,7 @@ func (s *GovernanceStateHelper) UpdateConfigurationRaw(cfg *rawConfigStruct) {
 	s.setStateBigInt(big.NewInt(roundLengthLoc), cfg.RoundLength)
 	s.setStateBigInt(big.NewInt(minBlockIntervalLoc), cfg.MinBlockInterval)
 	s.SetFineValues(cfg.FineValues)
+	s.setStateBigInt(big.NewInt(minGasPriceLoc), cfg.MinGasPrice)
 }
 
 // event ConfigurationChanged();
@@ -2227,6 +2237,12 @@ func (g *GovernanceContract) Run(evm *EVM, input []byte, contract *Contract) (re
 			return nil, errExecutionReverted
 		}
 		return res, nil
+	case "minGasPrice":
+		res, err := method.Outputs.Pack(g.state.MinGasPrice())
+		if err != nil {
+			return nil, errExecutionReverted
+		}
+		return res, nil
 	case "miningVelocity":
 		res, err := method.Outputs.Pack(g.state.MiningVelocity())
 		if err != nil {
diff --git a/core/vm/oracle_contracts_test.go b/core/vm/oracle_contracts_test.go
index dd17dddea..4980d4b77 100644
--- a/core/vm/oracle_contracts_test.go
+++ b/core/vm/oracle_contracts_test.go
@@ -654,7 +654,8 @@ func (g *OracleContractsTestSuite) TestUpdateConfiguration() {
 		big.NewInt(4),
 		big.NewInt(600),
 		big.NewInt(900),
-		[]*big.Int{big.NewInt(1), big.NewInt(1), big.NewInt(1)})
+		[]*big.Int{big.NewInt(1), big.NewInt(1), big.NewInt(1)},
+		big.NewInt(2e9))
 	g.Require().NoError(err)
 
 	// Call with non-owner.
@@ -770,6 +771,15 @@ func (g *OracleContractsTestSuite) TestConfigurationReading() {
 	err = GovernanceABI.ABI.Unpack(&value, "minBlockInterval", res)
 	g.Require().NoError(err)
 	g.Require().Equal(g.config.MinBlockInterval, value.Uint64())
+
+	// MinGasPrice.
+	input, err = GovernanceABI.ABI.Pack("minGasPrice")
+	g.Require().NoError(err)
+	res, err = g.call(GovernanceContractAddress, addr, input, big.NewInt(0))
+	g.Require().NoError(err)
+	err = GovernanceABI.ABI.Unpack(&value, "minGasPrice", res)
+	g.Require().NoError(err)
+	g.Require().Equal(g.config.MinGasPrice, value)
 }
 
 func (g *OracleContractsTestSuite) TestReportForkVote() {
diff --git a/dex/api_backend.go b/dex/api_backend.go
index 957f4d886..60a874701 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 {
diff --git a/params/config.go b/params/config.go
index 937234c84..c9a648bd8 100644
--- a/params/config.go
+++ b/params/config.go
@@ -26,8 +26,8 @@ import (
 
 // Genesis hashes to enforce below configs on.
 var (
-	MainnetGenesisHash = common.HexToHash("0x6c59132f64eae33054c0390e4d8f8ea5f0df1642b3a084c94388c44fe5eff70d")
-	TestnetGenesisHash = common.HexToHash("0x31847855ec3c1ba9a03ac3311f283775a70d7b0422b525c335aa094e5b81c902")
+	MainnetGenesisHash = common.HexToHash("0xf80aae99a7c44bc54d7b0cc8a16645fa3ea65c01b180339f17b31a698b031271")
+	TestnetGenesisHash = common.HexToHash("0x7f704c8d0a773d0fcca231d40bf39495553886bf8800b4a06920786a802103e1")
 )
 
 // TrustedCheckpoints associates each known checkpoint with the genesis hash of
@@ -72,6 +72,7 @@ var (
 				new(big.Int).Mul(big.NewInt(1e18), big.NewInt(1e4)),
 				new(big.Int).Mul(big.NewInt(1e18), big.NewInt(1e5)),
 			},
+			MinGasPrice: new(big.Int).Mul(big.NewInt(1e9), big.NewInt(1)),
 		},
 	}
 
@@ -117,6 +118,7 @@ var (
 				new(big.Int).Mul(big.NewInt(1e18), big.NewInt(1e4)),
 				new(big.Int).Mul(big.NewInt(1e18), big.NewInt(1e5)),
 			},
+			MinGasPrice: new(big.Int).Mul(big.NewInt(1e9), big.NewInt(1)),
 		},
 	}
 
@@ -153,6 +155,7 @@ var (
 				new(big.Int).Mul(big.NewInt(1e18), big.NewInt(1e4)),
 				new(big.Int).Mul(big.NewInt(1e18), big.NewInt(1e5)),
 			},
+			MinGasPrice: new(big.Int).Mul(big.NewInt(1e9), big.NewInt(1)),
 		},
 	}
 
@@ -299,6 +302,7 @@ type DexconConfig struct {
 	RoundLength       uint64         `json:"roundLength"`
 	MinBlockInterval  uint64         `json:"minBlockInterval"`
 	FineValues        []*big.Int     `json:"fineValues"`
+	MinGasPrice       *big.Int       `json:"minGasPrice"`
 }
 
 type dexconConfigSpecMarshaling struct {
@@ -306,11 +310,12 @@ type dexconConfigSpecMarshaling struct {
 	NextHalvingSupply *math.HexOrDecimal256
 	LastHalvedAmount  *math.HexOrDecimal256
 	FineValues        []*math.HexOrDecimal256
+	MinGasPrice       *math.HexOrDecimal256
 }
 
 // String implements the stringer interface, returning the consensus engine details.
 func (d *DexconConfig) String() string {
-	return fmt.Sprintf("{GenesisCRSText: %v Owner: %v MinStake: %v LockupPeriod: %v MiningVelocity: %v NextHalvingSupply: %v LastHalvedAmount: %v BlockGasLimit: %v LambdaBA: %v LambdaDKG: %v NotarySetSize: %v DKGSetSize: %v RoundLength: %v MinBlockInterval: %v FineValues: %v}",
+	return fmt.Sprintf("{GenesisCRSText: %v Owner: %v MinStake: %v LockupPeriod: %v MiningVelocity: %v NextHalvingSupply: %v LastHalvedAmount: %v BlockGasLimit: %v LambdaBA: %v LambdaDKG: %v NotarySetSize: %v DKGSetSize: %v RoundLength: %v MinBlockInterval: %v FineValues: %v MinGasPrice: %v}",
 		d.GenesisCRSText,
 		d.Owner,
 		d.MinStake,
@@ -326,6 +331,7 @@ func (d *DexconConfig) String() string {
 		d.RoundLength,
 		d.MinBlockInterval,
 		d.FineValues,
+		d.MinGasPrice,
 	)
 }
 
diff --git a/params/gen_dexcon_config.go b/params/gen_dexcon_config.go
index 566ed9fcd..1afe11f56 100644
--- a/params/gen_dexcon_config.go
+++ b/params/gen_dexcon_config.go
@@ -30,6 +30,7 @@ func (d DexconConfig) MarshalJSON() ([]byte, error) {
 		RoundLength       uint64                  `json:"roundLength"`
 		MinBlockInterval  uint64                  `json:"minBlockInterval"`
 		FineValues        []*math.HexOrDecimal256 `json:"fineValues"`
+		MinGasPrice       *math.HexOrDecimal256   `json:"minGasPrice"`
 	}
 	var enc DexconConfig
 	enc.GenesisCRSText = d.GenesisCRSText
@@ -52,6 +53,7 @@ func (d DexconConfig) MarshalJSON() ([]byte, error) {
 			enc.FineValues[k] = (*math.HexOrDecimal256)(v)
 		}
 	}
+	enc.MinGasPrice = (*math.HexOrDecimal256)(d.MinGasPrice)
 	return json.Marshal(&enc)
 }
 
@@ -73,6 +75,7 @@ func (d *DexconConfig) UnmarshalJSON(input []byte) error {
 		RoundLength       *uint64                 `json:"roundLength"`
 		MinBlockInterval  *uint64                 `json:"minBlockInterval"`
 		FineValues        []*math.HexOrDecimal256 `json:"fineValues"`
+		MinGasPrice       *math.HexOrDecimal256   `json:"minGasPrice"`
 	}
 	var dec DexconConfig
 	if err := json.Unmarshal(input, &dec); err != nil {
@@ -126,5 +129,8 @@ func (d *DexconConfig) UnmarshalJSON(input []byte) error {
 			d.FineValues[k] = (*big.Int)(v)
 		}
 	}
+	if dec.MinGasPrice != nil {
+		d.MinGasPrice = (*big.Int)(dec.MinGasPrice)
+	}
 	return nil
 }
diff --git a/test/genesis.json b/test/genesis.json
index 96ad4924c..9bbb97de3 100644
--- a/test/genesis.json
+++ b/test/genesis.json
@@ -30,7 +30,8 @@
         "0x21e19e0c9bab2400000",
         "0x21e19e0c9bab2400000",
         "0x152d02c7e14af6800000"
-      ]
+      ],
+      "minGasPrice": "0x3b9aca00"
     }
   },
   "nonce": "0x42",