fix: use EffectiveGasPrice in ante handler for dynamic fee tx (#817)

* Use effectiveGasPrice in ante handler for dynamic fee tx

Closes: #814

Solution:
- use effectiveGasPrice when check minimal-gas-prices, and deduct fee in ante handler
- implement an EthMempoolFeeDecorator

* add effectiveGasPrice to tx receipt

* changelog

* fix unit test

* fix comments

* add comments

* Apply suggestions from code review

Co-authored-by: Thomas Nguy <81727899+thomas-nguy@users.noreply.github.com>

* review suggestions

Co-authored-by: Thomas Nguy <81727899+thomas-nguy@users.noreply.github.com>
Co-authored-by: Federico Kunze Küllmer <31522760+fedekunze@users.noreply.github.com>

app/ante/ante.go

@@ -53,8 +53,8 @@ func NewAnteHandler(
 					// handle as *evmtypes.MsgEthereumTx
 
 					anteHandler = sdk.ChainAnteDecorators(
-						NewEthSetUpContextDecorator(), // outermost AnteDecorator. SetUpContext must be called first
-						authante.NewMempoolFeeDecorator(),
+						NewEthSetUpContextDecorator(),                         // outermost AnteDecorator. SetUpContext must be called first
+						NewEthMempoolFeeDecorator(evmKeeper, feeMarketKeeper), // Check eth effective gas price against minimal-gas-prices
 						authante.NewTxTimeoutHeightDecorator(),
 						authante.NewValidateMemoDecorator(ak),
 						NewEthValidateBasicDecorator(evmKeeper),

app/ante/ante_test.go

@@ -193,7 +193,7 @@ func (suite AnteTestSuite) TestAnteHandler() {
 				// bigger than MaxGasWanted
 				txBuilder.SetGasLimit(uint64(1 << 63))
 				return txBuilder.GetTx()
-			}, false, true, false,
+			}, true, false, false,
 		},
 		{
 			"fail - CheckTx (memo too long)",
@@ -286,7 +286,7 @@ func (suite AnteTestSuite) TestAnteHandler() {
 
 	for _, tc := range testCases {
 		suite.Run(tc.name, func() {
-			suite.ctx = suite.ctx.WithIsCheckTx(tc.reCheckTx).WithIsReCheckTx(tc.reCheckTx)
+			suite.ctx = suite.ctx.WithIsCheckTx(tc.checkTx).WithIsReCheckTx(tc.reCheckTx)
 
 			// expConsumed := params.TxGasContractCreation + params.TxGas
 			_, err := suite.anteHandler(suite.ctx, tc.txFn(), false)
@@ -314,8 +314,6 @@ func (suite AnteTestSuite) TestAnteHandlerWithDynamicTxFee() {
 	suite.Require().NoError(acc.SetSequence(1))
 	suite.app.AccountKeeper.SetAccount(suite.ctx, acc)
 
-	suite.app.EvmKeeper.AddBalance(addr, big.NewInt((ethparams.InitialBaseFee+10)*100000))
-
 	testCases := []struct {
 		name      string
 		txFn      func() sdk.Tx
@@ -501,7 +499,7 @@ func (suite AnteTestSuite) TestAnteHandlerWithDynamicTxFee() {
 				// bigger than MaxGasWanted
 				txBuilder.SetGasLimit(uint64(1 << 63))
 				return txBuilder.GetTx()
-			}, false, true, false,
+			}, true, false, false,
 		},
 		{
 			"fail - CheckTx (memo too long)",
@@ -530,7 +528,8 @@ func (suite AnteTestSuite) TestAnteHandlerWithDynamicTxFee() {
 
 	for _, tc := range testCases {
 		suite.Run(tc.name, func() {
-			suite.ctx = suite.ctx.WithIsCheckTx(tc.reCheckTx).WithIsReCheckTx(tc.reCheckTx)
+			suite.ctx = suite.ctx.WithIsCheckTx(tc.checkTx).WithIsReCheckTx(tc.reCheckTx)
+			suite.app.EvmKeeper.AddBalance(addr, big.NewInt((ethparams.InitialBaseFee+10)*100000))
 			_, err := suite.anteHandler(suite.ctx, tc.txFn(), false)
 			if tc.expPass {
 				suite.Require().NoError(err)

app/ante/eth.go

@@ -543,3 +543,58 @@ func (esc EthSetupContextDecorator) AnteHandle(ctx sdk.Context, tx sdk.Tx, simul
 	newCtx = ctx.WithGasMeter(sdk.NewInfiniteGasMeter())
 	return next(newCtx, tx, simulate)
 }
+
+// EthMempoolFeeDecorator will check if the transaction's effective fee is at least as large
+// as the local validator's minimum gasFee (defined in validator config).
+// If fee is too low, decorator returns error and tx is rejected from mempool.
+// Note this only applies when ctx.CheckTx = true
+// If fee is high enough or not CheckTx, then call next AnteHandler
+// CONTRACT: Tx must implement FeeTx to use MempoolFeeDecorator
+type EthMempoolFeeDecorator struct {
+	feemarketKeeper evmtypes.FeeMarketKeeper
+	evmKeeper       EVMKeeper
+}
+
+func NewEthMempoolFeeDecorator(ek EVMKeeper, fmk evmtypes.FeeMarketKeeper) EthMempoolFeeDecorator {
+	return EthMempoolFeeDecorator{
+		feemarketKeeper: fmk,
+		evmKeeper:       ek,
+	}
+}
+
+// AnteHandle ensures that the provided fees meet a minimum threshold for the validator,
+// if this is a CheckTx. This is only for local mempool purposes, and thus
+// is only ran on check tx.
+func (mfd EthMempoolFeeDecorator) AnteHandle(ctx sdk.Context, tx sdk.Tx, simulate bool, next sdk.AnteHandler) (newCtx sdk.Context, err error) {
+	if ctx.IsCheckTx() && !simulate {
+		if len(tx.GetMsgs()) != 1 {
+			return ctx, sdkerrors.Wrap(sdkerrors.ErrInvalidRequest, "only 1 ethereum msg supported per tx")
+		}
+		msg, ok := tx.GetMsgs()[0].(*evmtypes.MsgEthereumTx)
+		if !ok {
+			return ctx, sdkerrors.Wrapf(sdkerrors.ErrUnknownRequest, "invalid transaction type %T, expected %T", tx, (*evmtypes.MsgEthereumTx)(nil))
+		}
+
+		var feeAmt *big.Int
+
+		feeMktParams := mfd.feemarketKeeper.GetParams(ctx)
+		params := mfd.evmKeeper.GetParams(ctx)
+		chainID := mfd.evmKeeper.ChainID()
+		ethCfg := params.ChainConfig.EthereumConfig(chainID)
+		evmDenom := params.EvmDenom
+		if evmtypes.IsLondon(ethCfg, ctx.BlockHeight()) && !feeMktParams.NoBaseFee {
+			baseFee := mfd.feemarketKeeper.GetBaseFee(ctx)
+			feeAmt = msg.GetEffectiveFee(baseFee)
+		} else {
+			feeAmt = msg.GetFee()
+		}
+
+		glDec := sdk.NewDec(int64(msg.GetGas()))
+		requiredFee := ctx.MinGasPrices().AmountOf(evmDenom).Mul(glDec)
+		if sdk.NewDecFromBigInt(feeAmt).LT(requiredFee) {
+			return ctx, sdkerrors.Wrapf(sdkerrors.ErrInsufficientFee, "insufficient fees; got: %s required: %s", feeAmt, requiredFee)
+		}
+	}
+
+	return next(ctx, tx, simulate)
+}