ante: fix fee check (#597)

* ante: fix fee check

* changelog

* comment

CHANGELOG.md

@@ -53,6 +53,7 @@ corresponding Ethereum API namespace:
 
 ### Bug Fixes
 
+* (ante) [\#597](https://github.com/cosmos/ethermint/pull/597) Fix incorrect fee check on `AnteHandler`.
 * (evm) [\#583](https://github.com/cosmos/ethermint/pull/583) Fixes incorrect resetting of tx count and block bloom during `BeginBlock`, as well as gas consumption.
 * (crypto) [\#577](https://github.com/cosmos/ethermint/pull/577) Fix `BIP44HDPath` that did not prepend `m/` to the path. This now uses the `DefaultBaseDerivationPath` variable from go-ethereum to ensure addresses are consistent.
 

app/ante/eth.go

@@ -100,20 +100,21 @@ func (emfd EthMempoolFeeDecorator) AnteHandle(ctx sdk.Context, tx sdk.Tx, simula
 
 	evmDenom := emfd.evmKeeper.GetParams(ctx).EvmDenom
 
-	// fee = GP * GL
+	// fee = gas price * gas limit
 	fee := sdk.NewInt64DecCoin(evmDenom, msgEthTx.Fee().Int64())
 
 	minGasPrices := ctx.MinGasPrices()
+	minFees := minGasPrices.AmountOf(evmDenom).MulInt64(int64(msgEthTx.Data.GasLimit))
 
-	// check that fee provided is greater than the minimum
-	// NOTE: we only check if aphotons are present in min gas prices. It is up to the
+	// check that fee provided is greater than the minimum defined by the validator node
+	// NOTE: we only check if the evm denom tokens are present in min gas prices. It is up to the
 	// sender if they want to send additional fees in other denominations.
 	var hasEnoughFees bool
-	if fee.Amount.GTE(minGasPrices.AmountOf(evmDenom)) {
+	if fee.Amount.GTE(minFees) {
 		hasEnoughFees = true
 	}
 
-	// reject transaction if minimum gas price is positive and the transaction does not
+	// reject transaction if minimum gas price is not zero and the transaction does not
 	// meet the minimum fee
 	if !ctx.MinGasPrices().IsZero() && !hasEnoughFees {
 		return ctx, sdkerrors.Wrap(