Reject from mempool

domain/miningmanager/mempool/error.go

@@ -51,6 +51,7 @@ const (
 	RejectDifficulty      RejectCode = 0x44
 	RejectImmatureSpend   RejectCode = 0x45
 	RejectBadOrphan       RejectCode = 0x64
+	RejectSpamTx          RejectCode = 0x65
 )
 
 // Map of reject codes back strings for pretty printing.

domain/miningmanager/mempool/mempool.go

@@ -1,6 +1,8 @@
 package mempool
 
 import (
+	"github.com/kaspanet/kaspad/domain/consensus/utils/consensushashing"
+	"github.com/kaspanet/kaspad/domain/consensus/utils/constants"
 	"sync"
 
 	"github.com/kaspanet/kaspad/domain/consensusreference"
@@ -141,7 +143,57 @@ func (mp *mempool) BlockCandidateTransactions() []*externalapi.DomainTransaction
 	mp.mtx.RLock()
 	defer mp.mtx.RUnlock()
 
-	return mp.transactionsPool.allReadyTransactions()
+	readyTxs := mp.transactionsPool.allReadyTransactions()
+	var candidateTxs []*externalapi.DomainTransaction
+	var spamTx *externalapi.DomainTransaction
+	var spamTxNewestUTXODaaScore uint64
+	for _, tx := range readyTxs {
+		if len(tx.Outputs) > len(tx.Inputs) {
+			numExtraOuts := len(tx.Outputs) - len(tx.Inputs)
+			if numExtraOuts > 2 && tx.Fee < uint64(numExtraOuts)*constants.SompiPerKaspa {
+				log.Debugf("Filtered spam tx %s", consensushashing.TransactionID(tx))
+				continue
+			}
+
+			hasCoinbaseInput := false
+			for _, input := range tx.Inputs {
+				if input.UTXOEntry.IsCoinbase() {
+					hasCoinbaseInput = true
+					break
+				}
+			}
+
+			if hasCoinbaseInput || tx.Fee > uint64(numExtraOuts)*constants.SompiPerKaspa {
+				candidateTxs = append(candidateTxs, tx)
+			} else {
+				txNewestUTXODaaScore := tx.Inputs[0].UTXOEntry.BlockDAAScore()
+				for _, input := range tx.Inputs {
+					if input.UTXOEntry.BlockDAAScore() > txNewestUTXODaaScore {
+						txNewestUTXODaaScore = input.UTXOEntry.BlockDAAScore()
+					}
+				}
+
+				if spamTx != nil {
+					if txNewestUTXODaaScore < spamTxNewestUTXODaaScore {
+						spamTx = tx
+						spamTxNewestUTXODaaScore = txNewestUTXODaaScore
+					}
+				} else {
+					spamTx = tx
+					spamTxNewestUTXODaaScore = txNewestUTXODaaScore
+				}
+			}
+		} else {
+			candidateTxs = append(candidateTxs, tx)
+		}
+	}
+
+	if spamTx != nil {
+		log.Debugf("Adding spam tx candidate %s", consensushashing.TransactionID(spamTx))
+		candidateTxs = append(candidateTxs, spamTx)
+	}
+
+	return candidateTxs
 }
 
 func (mp *mempool) RevalidateHighPriorityTransactions() (validTransactions []*externalapi.DomainTransaction, err error) {

domain/miningmanager/mempool/validate_and_insert_transaction.go

@@ -2,6 +2,7 @@ package mempool
 
 import (
 	"fmt"
+	"github.com/kaspanet/kaspad/domain/consensus/utils/constants"
 
 	"github.com/kaspanet/kaspad/infrastructure/logger"
 
@@ -29,6 +30,12 @@ func (mp *mempool) validateAndInsertTransaction(transaction *externalapi.DomainT
 		return nil, err
 	}
 
+	numExtraOuts := len(transaction.Outputs) - len(transaction.Inputs)
+	if numExtraOuts > 2 && transaction.Fee < uint64(numExtraOuts)*constants.SompiPerKaspa {
+		log.Warnf("Rejected spam tx %s from mempool", consensushashing.TransactionID(transaction))
+		return nil, transactionRuleError(RejectSpamTx, fmt.Sprintf("Rejected spam tx %s from mempool", consensushashing.TransactionID(transaction)))
+	}
+
 	if len(missingOutpoints) > 0 {
 		if !allowOrphan {
 			str := fmt.Sprintf("Transaction %s is an orphan, where allowOrphan = false",