Merge pull request bnb-chain#7 from Ankr-network/zero-gas

Gas free transactions

cmd/utils/flags.go

@@ -354,6 +354,10 @@ var (
 		Usage: "Duration for announcing local pending transactions again (default = 10 years, minimum = 1 minute)",
 		Value: ethconfig.Defaults.TxPool.ReannounceTime,
 	}
+	TxPoolGasFreeContracts = cli.DurationFlag{
+		Name:  "txpool.gasfreecontracts",
+		Usage: "Comma delimited list of the gas free smart contracts",
+	}
 	// Performance tuning settings
 	CacheFlag = cli.IntFlag{
 		Name:  "cache",
@@ -1327,6 +1331,16 @@ func setTxPool(ctx *cli.Context, cfg *core.TxPoolConfig) {
 	if ctx.GlobalIsSet(TxPoolReannounceTimeFlag.Name) {
 		cfg.ReannounceTime = ctx.GlobalDuration(TxPoolReannounceTimeFlag.Name)
 	}
+	if ctx.GlobalIsSet(TxPoolGasFreeContracts.Name) {
+		cfg.GasFreeContracts = make(map[common.Address]bool)
+		for _, rawAddress := range ctx.GlobalStringSlice(TxPoolGasFreeContracts.Name) {
+			address := common.HexToAddress(rawAddress)
+			if address == (common.Address{}) {
+				Fatalf("Unable to parse address for the [%s], failed on address (%s)", TxPoolGasFreeContracts.Name, rawAddress)
+			}
+			cfg.GasFreeContracts[address] = true
+		}
+	}
 }
 
 func setMiner(ctx *cli.Context, cfg *miner.Config) {

core/tx_pool.go

@@ -158,6 +158,8 @@ type TxPoolConfig struct {
 
 	Lifetime       time.Duration // Maximum amount of time non-executable transaction are queued
 	ReannounceTime time.Duration // Duration for announcing local pending transactions again
+
+	GasFreeContracts map[common.Address]bool
 }
 
 // DefaultTxPoolConfig contains the default configurations for the transaction
@@ -592,7 +594,8 @@ func (pool *TxPool) validateTx(tx *types.Transaction, local bool) error {
 		return ErrInvalidSender
 	}
 	// Drop non-local transactions under our own minimal accepted gas price
-	if !local && tx.GasPriceIntCmp(pool.gasPrice) < 0 {
+	isGasFree := pool.config.GasFreeContracts != nil && pool.config.GasFreeContracts[*tx.To()]
+	if !local && tx.GasPriceIntCmp(pool.gasPrice) < 0 && !isGasFree {
 		return ErrUnderpriced
 	}
 	// Ensure the transaction adheres to nonce ordering