config: add minimum network fee setting

Follow neo-project/neo#1901.

config/protocol.mainnet.yml

@@ -36,6 +36,7 @@ ProtocolConfiguration:
   MaxTransactionsPerBlock: 500
   MaxFreeTransactionsPerBlock: 20
   MaxFreeTransactionSize: 1024
+  MinimumNetworkFee: 0
   FeePerExtraByte: 0.00001
 
 ApplicationConfiguration:

config/protocol.testnet.yml

@@ -36,6 +36,7 @@ ProtocolConfiguration:
   MaxTransactionsPerBlock: 500
   MaxFreeTransactionsPerBlock: 20
   MaxFreeTransactionSize: 1024
+  MinimumNetworkFee: 0
   FeePerExtraByte: 0.00001
 
 ApplicationConfiguration:

pkg/config/protocol_config.go

@@ -36,7 +36,9 @@ type (
 		MaxFreeTransactionSize int `yaml:"MaxFreeTransactionSize"`
 		// Maximum number of low priority transactions accepted into block.
 		MaxFreeTransactionsPerBlock int `yaml:"MaxFreeTransactionsPerBlock"`
-		MemPoolSize                 int `yaml:"MemPoolSize"`
+		// MinimumNetworkFee sets the minimum required network fee for transaction to pass validation.
+		MinimumNetworkFee util.Fixed8 `yaml:"MinimumNetworkFee"`
+		MemPoolSize       int         `yaml:"MemPoolSize"`
 		// SaveStorageBatch enables storage batch saving before every persist.
 		SaveStorageBatch  bool     `yaml:"SaveStorageBatch"`
 		SecondsPerBlock   int      `yaml:"SecondsPerBlock"`

pkg/core/blockchain.go

@@ -168,6 +168,10 @@ func NewBlockchain(s storage.Store, cfg config.ProtocolConfiguration, log *zap.L
 		cfg.MaxFreeTransactionSize = 0
 		log.Info("MaxFreeTransactionSize is not set or wrong, setting default value (unlimited)", zap.Int("MaxFreeTransactionSize", cfg.MaxFreeTransactionSize))
 	}
+	if cfg.MinimumNetworkFee < 0 {
+		cfg.MinimumNetworkFee = 0
+		log.Info("MinimumNetworkFee is not set or wrong, setting default value (0)", zap.String("MinimumNetworkFee", cfg.MinimumNetworkFee.String()))
+	}
 	if cfg.FeePerExtraByte <= 0 {
 		cfg.FeePerExtraByte = 0
 		log.Info("FeePerExtraByte is not set or wrong, setting default value", zap.Float64("FeePerExtraByte", cfg.FeePerExtraByte))
@@ -1996,13 +2000,16 @@ func (bc *Blockchain) PoolTx(t *transaction.Transaction) error {
 	if t.Type != transaction.ClaimType {
 		txSize := io.GetVarSize(t)
 		maxFree := bc.config.MaxFreeTransactionSize
+		netFee := bc.NetworkFee(t)
 		if maxFree != 0 && txSize > maxFree {
-			netFee := bc.NetworkFee(t)
 			if bc.IsLowPriority(netFee) ||
 				netFee < util.Fixed8FromFloat(bc.config.FeePerExtraByte)*util.Fixed8(txSize-maxFree) {
 				return ErrPolicy
 			}
 		}
+		if t.Type == transaction.InvocationType && netFee < bc.config.MinimumNetworkFee {
+			return ErrPolicy
+		}
 	}
 	if err := bc.memPool.Add(t, bc); err != nil {
 		switch err {

pkg/rpc/server/server.go

@@ -89,6 +89,7 @@ var rpcHandlers = map[string]func(*Server, request.Params) (interface{}, *respon
 	"getclaimable":         (*Server).getClaimable,
 	"getconnectioncount":   (*Server).getConnectionCount,
 	"getcontractstate":     (*Server).getContractState,
+	"getminimumnetworkfee": (*Server).getMinimumNetworkFee,
 	"getnep5balances":      (*Server).getNEP5Balances,
 	"getnep5transfers":     (*Server).getNEP5Transfers,
 	"getpeers":             (*Server).getPeers,
@@ -798,6 +799,10 @@ func (s *Server) getNEP5Transfers(ps request.Params) (interface{}, *response.Err
 	return bs, nil
 }
 
+func (s *Server) getMinimumNetworkFee(ps request.Params) (interface{}, *response.Error) {
+	return s.chain.GetConfig().MinimumNetworkFee, nil
+}
+
 func (s *Server) getProof(ps request.Params) (interface{}, *response.Error) {
 	root, err := ps.Value(0).GetUint256()
 	if err != nil {