Guard mempool drop percentage config

lib/mempool.go

@@ -41,11 +41,7 @@ type MempoolTx struct {
 
 // NewMempool() creates a new FeeMempool instance of a Mempool
 func NewMempool(config MempoolConfig) Mempool {
-	// if the config drop percentage is set to 0
-	if config.DropPercentage == 0 {
-		// set the drop percentage to the default mempool config
-		config.DropPercentage = DefaultMempoolConfig().DropPercentage
-	}
+	config.DropPercentage = normalizeDropPercentage(config.DropPercentage)
 	// return the default mempool
 	return &FeeMempool{
 		pool:   MempoolTxs{},
@@ -281,6 +277,7 @@ func (t *MempoolTxs) delete(txs [][]byte) (deleted []MempoolTx, deletedBz int) {
 
 // drop() removes the bottom (the lowest fee) X percent of Transactions
 func (t *MempoolTxs) drop(percent int) (dropped []MempoolTx) {
+	percent = normalizeDropPercentage(percent)
 	// calculate the percent using integer division
 	numDrop := (len(t.s)*percent)/100 + 1
 	// avoid slicing out of bounds
@@ -300,6 +297,13 @@ func (t *MempoolTxs) drop(percent int) (dropped []MempoolTx) {
 	return
 }
 
+func normalizeDropPercentage(percent int) int {
+	if percent <= 0 {
+		return DefaultMempoolConfig().DropPercentage
+	}
+	return percent
+}
+
 // copy() returns a shallow copy of the MempoolTxs
 func (t *MempoolTxs) copy() *MempoolTxs {
 	// allocate a destination

lib/mempool_test.go

@@ -221,6 +221,39 @@ func TestAddTransaction(t *testing.T) {
 	}
 }
 
+func TestAddTransactionNormalizesNegativeDropPercentage(t *testing.T) {
+	sig := &Signature{
+		PublicKey: newTestPublicKeyBytes(t),
+		Signature: newTestPublicKeyBytes(t),
+	}
+	a, e := NewAny(sig)
+	require.NoError(t, e)
+
+	mempool := NewMempool(MempoolConfig{
+		MaxTotalBytes:       math.MaxUint64,
+		MaxTransactionCount: 4,
+		IndividualMaxTxSize: math.MaxUint32,
+		DropPercentage:      -35,
+	})
+
+	for i := uint64(1); i <= 4; i++ {
+		tx, err := Marshal(&Transaction{
+			MessageType:   testMessageName,
+			Msg:           a,
+			Signature:     sig,
+			CreatedHeight: 1,
+			Time:          uint64(time.Now().UnixMicro()),
+			Fee:           i,
+			NetworkId:     1,
+			ChainId:       i,
+		})
+		require.NoError(t, err)
+		require.NoError(t, mempool.AddTransactions(tx))
+	}
+
+	require.Equal(t, 2, mempool.TxCount())
+}
+
 func TestGetAndContainsTransaction(t *testing.T) {
 	// pre-define a test message
 	sig := &Signature{