core: change ordering of txs of equal gas price from arrival time to hash

core/types/transaction.go

@@ -422,12 +422,38 @@ func (s *TxByPriceAndTime) Pop() interface{} {
 	return x
 }
 
+type TxByPriceAndHash Transactions
+
+func (s TxByPriceAndHash) Len() int { return len(s) }
+func (s TxByPriceAndHash) Less(i, j int) bool {
+	// If the prices are equal, use the transaction hash for
+	// deterministic sorting
+	cmp := s[i].ImmutableGasPrice().Cmp(s[j].ImmutableGasPrice())
+	if cmp == 0 {
+		return bytes.Compare(s[i].Hash().Bytes(), s[j].Hash().Bytes()) == -1
+	}
+	return cmp > 0
+}
+func (s TxByPriceAndHash) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
+
+func (s *TxByPriceAndHash) Push(x interface{}) {
+	*s = append(*s, x.(*Transaction))
+}
+
+func (s *TxByPriceAndHash) Pop() interface{} {
+	old := *s
+	n := len(old)
+	x := old[n-1]
+	*s = old[0 : n-1]
+	return x
+}
+
 // TransactionsByPriceAndNonce represents a set of transactions that can return
 // transactions in a profit-maximizing sorted order, while supporting removing
 // entire batches of transactions for non-executable accounts.
 type TransactionsByPriceAndNonce struct {
 	txs    map[common.Address]Transactions // Per account nonce-sorted list of transactions
-	heads  TxByPriceAndTime                // Next transaction for each unique account (price heap)
+	heads  TxByPriceAndHash                // Next transaction for each unique account (price heap)
 	signer Signer                          // Signer for the set of transactions
 }
 
@@ -437,8 +463,8 @@ type TransactionsByPriceAndNonce struct {
 // Note, the input map is reowned so the caller should not interact any more with
 // if after providing it to the constructor.
 func NewTransactionsByPriceAndNonce(signer Signer, txs map[common.Address]Transactions) *TransactionsByPriceAndNonce {
-	// Initialize a price and received time based heap with the head transactions
-	heads := make(TxByPriceAndTime, 0, len(txs))
+	// Initialize a price and transaction hash based heap with the head transactions
+	heads := make(TxByPriceAndHash, 0, len(txs))
 	for from, accTxs := range txs {
 		// Ensure the sender address is from the signer
 		if acc, _ := Sender(signer, accTxs[0]); acc != from {

core/types/transaction_test.go

@@ -310,11 +310,11 @@ func TestTransactionPriceNonceSort(t *testing.T) {
 	}
 }
 
-// Tests that if multiple transactions have the same price, the ones seen earlier
-// are prioritized to avoid network spam attacks aiming for a specific ordering.
-func TestTransactionTimeSort(t *testing.T) {
+// Tests if transactions with the same gas price are lexicographical sorted by hash
+// to prevent network spam attacks and to make the transaction sorting traceable
+func TestTransactionHashSort(t *testing.T) {
 	// Generate a batch of accounts to start with
-	keys := make([]*ecdsa.PrivateKey, 5)
+	keys := make([]*ecdsa.PrivateKey, 10)
 	for i := 0; i < len(keys); i++ {
 		keys[i], _ = crypto.GenerateKey()
 	}
@@ -350,9 +350,9 @@ func TestTransactionTimeSort(t *testing.T) {
 			if txi.GasPrice().Cmp(next.GasPrice()) < 0 {
 				t.Errorf("invalid gasprice ordering: tx #%d (A=%x P=%v) < tx #%d (A=%x P=%v)", i, fromi[:4], txi.GasPrice(), i+1, fromNext[:4], next.GasPrice())
 			}
-			// Make sure time order is ascending if the txs have the same gas price
-			if txi.GasPrice().Cmp(next.GasPrice()) == 0 && txi.time.After(next.time) {
-				t.Errorf("invalid received time ordering: tx #%d (A=%x T=%v) > tx #%d (A=%x T=%v)", i, fromi[:4], txi.time, i+1, fromNext[:4], next.time)
+			// Make sure hash order is lexicographical if the txs have the same gas price
+			if txi.GasPrice().Cmp(next.GasPrice()) == 0 && bytes.Compare(txi.Hash().Bytes(), next.Hash().Bytes()) > 0 {
+				t.Errorf("invalid hash ordering: tx #%d (H=%x) > tx #%d (H=%x)", i, txi.Hash().Bytes()[:4], i+1, next.Hash().Bytes()[:4])
 			}
 		}
 	}