bug(feemarket): set lower bound of base fee to min gas price param

CHANGELOG.md

@@ -50,6 +50,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 ### Improvements
 
 * (feemarket) [tharsis#1120](https://github.com/evmos/ethermint/pull/1120) Make `min-gas-multiplier` parameter accept zero value
+* (feemarket) [tharsis#1135](https://github.com/evmos/ethermint/pull/1135) Set lower bound of base fee to min gas price param
 
 ### Bug Fixes
 

app/ante/fees.go

@@ -1,6 +1,7 @@
 package ante
 
 import (
+	"fmt"
 	"math/big"
 
 	sdk "github.com/cosmos/cosmos-sdk/types"
@@ -125,14 +126,19 @@ func (empd EthMinGasPriceDecorator) AnteHandle(ctx sdk.Context, tx sdk.Tx, simul
 		}
 
 		gasLimit := sdk.NewDecFromBigInt(new(big.Int).SetUint64(ethMsg.GetGas()))
+
 		requiredFee := minGasPrice.Mul(gasLimit)
 		fee := sdk.NewDecFromBigInt(feeAmt)
 
 		if fee.LT(requiredFee) {
+			// effectiveFee = min(basFee+tip, gasFeeCap) * gasLimit
+			fmt.Printf("\nfee: %d = min(baseFee %s + gasTipCap %s), gasFeeCap %s) * gasLimit %d", fee.TruncateInt().Int64(), baseFee, txData.GetGasTipCap(), txData.GetGasFeeCap(), gasLimit.TruncateInt().Int64())
+			fmt.Printf("\nrequiredFee %d = minGasPrice %d * gasLimit %d", requiredFee.TruncateInt().Int64(), minGasPrice.TruncateInt().Int64(), gasLimit.TruncateInt().Int64())
+
 			return ctx, sdkerrors.Wrapf(
 				sdkerrors.ErrInsufficientFee,
-				"provided fee < minimum global fee (%s < %s). Please increase the priority tip (for EIP-1559 txs) or the gas prices (for access list or legacy txs)",
-				fee, requiredFee,
+				"provided fee < minimum global fee (%d < %d). Please increase the priority tip (for EIP-1559 txs) or the gas prices (for access list or legacy txs)",
+				fee.TruncateInt().Int64(), requiredFee.TruncateInt().Int64(),
 			)
 		}
 	}

x/feemarket/keeper/eip1559.go

@@ -58,13 +58,15 @@ func (k Keeper) CalculateBaseFee(ctx sdk.Context) *big.Int {
 	parentGasTarget := parentGasTargetBig.Uint64()
 	baseFeeChangeDenominator := new(big.Int).SetUint64(uint64(params.BaseFeeChangeDenominator))
 
-	// If the parent gasUsed is the same as the target, the baseFee remains unchanged.
+	// If the parent gasUsed is the same as the target, the baseFee remains
+	// unchanged.
 	if parentGasUsed == parentGasTarget {
 		return new(big.Int).Set(parentBaseFee)
 	}
 
 	if parentGasUsed > parentGasTarget {
-		// If the parent block used more gas than its target, the baseFee should increase.
+		// If the parent block used more gas than its target, the baseFee should
+		// increase.
 		gasUsedDelta := new(big.Int).SetUint64(parentGasUsed - parentGasTarget)
 		x := new(big.Int).Mul(parentBaseFee, gasUsedDelta)
 		y := x.Div(x, parentGasTargetBig)
@@ -76,14 +78,15 @@ func (k Keeper) CalculateBaseFee(ctx sdk.Context) *big.Int {
 		return x.Add(parentBaseFee, baseFeeDelta)
 	}
 
-	// Otherwise if the parent block used less gas than its target, the baseFee should decrease.
+	// Otherwise if the parent block used less gas than its target, the baseFee
+	// should decrease.
 	gasUsedDelta := new(big.Int).SetUint64(parentGasTarget - parentGasUsed)
 	x := new(big.Int).Mul(parentBaseFee, gasUsedDelta)
 	y := x.Div(x, parentGasTargetBig)
 	baseFeeDelta := x.Div(y, baseFeeChangeDenominator)
 
-	return math.BigMax(
-		x.Sub(parentBaseFee, baseFeeDelta),
-		common.Big0,
-	)
+	// Set global min gas price as lower bound of the base fee, transactions below
+	// the min gas price don't even reach the mempool.
+	minGasPrice := params.MinGasPrice.TruncateInt().BigInt()
+	return math.BigMax(x.Sub(parentBaseFee, baseFeeDelta), minGasPrice)
 }

x/feemarket/keeper/eip1559_test.go

@@ -2,107 +2,109 @@ package keeper_test
 
 import (
 	"fmt"
-	abci "github.com/tendermint/tendermint/abci/types"
 	"math/big"
+
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	abci "github.com/tendermint/tendermint/abci/types"
 )
 
 func (suite *KeeperTestSuite) TestCalculateBaseFee() {
 	testCases := []struct {
-		name      string
-		NoBaseFee bool
-		malleate  func()
-		expFee    *big.Int
+		name                 string
+		NoBaseFee            bool
+		blockHeight          int64
+		parentBlockGasWanted uint64
+		minGasPrice          sdk.Dec
+		expFee               *big.Int
 	}{
 		{
 			"without BaseFee",
 			true,
-			func() {},
+			0,
+			0,
+			sdk.ZeroDec(),
 			nil,
 		},
 		{
 			"with BaseFee - initial EIP-1559 block",
 			false,
-			func() {
-				suite.ctx = suite.ctx.WithBlockHeight(0)
-			},
+			0,
+			0,
+			sdk.ZeroDec(),
 			suite.app.FeeMarketKeeper.GetParams(suite.ctx).BaseFee.BigInt(),
 		},
 		{
 			"with BaseFee - parent block wanted the same gas as its target",
 			false,
-			func() {
-				// non initial block
-				suite.ctx = suite.ctx.WithBlockHeight(1)
-
-				// Set gas used
-				suite.app.FeeMarketKeeper.SetBlockGasWanted(suite.ctx, 100)
-
-				// Set target/gasLimit through Consensus Param MaxGas
-				blockParams := abci.BlockParams{
-					MaxGas:   100,
-					MaxBytes: 10,
-				}
-				consParams := abci.ConsensusParams{Block: &blockParams}
-				suite.ctx = suite.ctx.WithConsensusParams(&consParams)
-
-				// set ElasticityMultiplier
-				params := suite.app.FeeMarketKeeper.GetParams(suite.ctx)
-				params.ElasticityMultiplier = 1
-				suite.app.FeeMarketKeeper.SetParams(suite.ctx, params)
-			},
+			1,
+			100,
+			sdk.ZeroDec(),
+			suite.app.FeeMarketKeeper.GetParams(suite.ctx).BaseFee.BigInt(),
+		},
+		{
+			"with BaseFee - parent block wanted the same gas as its target, with higher min gas price",
+			false,
+			1,
+			100,
+			sdk.NewDec(1500000000),
 			suite.app.FeeMarketKeeper.GetParams(suite.ctx).BaseFee.BigInt(),
 		},
 		{
 			"with BaseFee - parent block wanted more gas than its target",
 			false,
-			func() {
-				suite.ctx = suite.ctx.WithBlockHeight(1)
-
-				suite.app.FeeMarketKeeper.SetBlockGasWanted(suite.ctx, 200)
-
-				blockParams := abci.BlockParams{
-					MaxGas:   100,
-					MaxBytes: 10,
-				}
-				consParams := abci.ConsensusParams{Block: &blockParams}
-				suite.ctx = suite.ctx.WithConsensusParams(&consParams)
-
-				params := suite.app.FeeMarketKeeper.GetParams(suite.ctx)
-				params.ElasticityMultiplier = 1
-				suite.app.FeeMarketKeeper.SetParams(suite.ctx, params)
-			},
+			1,
+			200,
+			sdk.ZeroDec(),
+			big.NewInt(1125000000),
+		},
+		{
+			"with BaseFee - parent block wanted more gas than its target, with higher min gas price",
+			false,
+			1,
+			200,
+			sdk.NewDec(1500000000),
 			big.NewInt(1125000000),
 		},
 		{
 			"with BaseFee - Parent gas wanted smaller than parent gas target",
 			false,
-			func() {
-				suite.ctx = suite.ctx.WithBlockHeight(1)
-
-				suite.app.FeeMarketKeeper.SetBlockGasWanted(suite.ctx, 50)
-
-				blockParams := abci.BlockParams{
-					MaxGas:   100,
-					MaxBytes: 10,
-				}
-				consParams := abci.ConsensusParams{Block: &blockParams}
-				suite.ctx = suite.ctx.WithConsensusParams(&consParams)
-
-				params := suite.app.FeeMarketKeeper.GetParams(suite.ctx)
-				params.ElasticityMultiplier = 1
-				suite.app.FeeMarketKeeper.SetParams(suite.ctx, params)
-			},
+			1,
+			50,
+			sdk.ZeroDec(),
 			big.NewInt(937500000),
 		},
+		{
+			"with BaseFee - Parent gas wanted smaller than parent gas target, with higher min gas price",
+			false,
+			1,
+			50,
+			sdk.NewDec(1500000000),
+			big.NewInt(1500000000),
+		},
 	}
 	for _, tc := range testCases {
 		suite.Run(fmt.Sprintf("Case %s", tc.name), func() {
 			suite.SetupTest() // reset
+
 			params := suite.app.FeeMarketKeeper.GetParams(suite.ctx)
 			params.NoBaseFee = tc.NoBaseFee
+			params.MinGasPrice = tc.minGasPrice
+			params.ElasticityMultiplier = 1
 			suite.app.FeeMarketKeeper.SetParams(suite.ctx, params)
 
-			tc.malleate()
+			// Set block height
+			suite.ctx = suite.ctx.WithBlockHeight(tc.blockHeight)
+
+			// Set parent block gas
+			suite.app.FeeMarketKeeper.SetBlockGasWanted(suite.ctx, tc.parentBlockGasWanted)
+
+			// Set next block target/gasLimit through Consensus Param MaxGas
+			blockParams := abci.BlockParams{
+				MaxGas:   100,
+				MaxBytes: 10,
+			}
+			consParams := abci.ConsensusParams{Block: &blockParams}
+			suite.ctx = suite.ctx.WithConsensusParams(&consParams)
 
 			fee := suite.app.FeeMarketKeeper.CalculateBaseFee(suite.ctx)
 			if tc.NoBaseFee {