core/txpool/legacypool: reject gapped tx from delegated account

core/txpool/legacypool/legacypool.go

@@ -66,6 +66,10 @@ var (
 	// transactions is reached for specific accounts.
 	ErrInflightTxLimitReached = errors.New("in-flight transaction limit reached for delegated accounts")
 
+	// ErrOutOfOrderTxFromDelegated is returned when the transaction with gapped
+	// nonce received from the accounts with delegation or pending delegation.
+	ErrOutOfOrderTxFromDelegated = errors.New("gapped-nonce tx from delegated accounts")
+
 	// ErrAuthorityReserved is returned if a transaction has an authorization
 	// signed by an address which already has in-flight transactions known to the
 	// pool.
@@ -605,33 +609,39 @@ func (pool *LegacyPool) validateTx(tx *types.Transaction) error {
 	return pool.validateAuth(tx)
 }
 
+// checkDelegationLimit determines if the tx sender is delegated or has a
+// pending delegation, and if so, ensures they have at most one in-flight
+// **executable** transaction, e.g. disallow stacked and gapped transactions
+// from the account.
+func (pool *LegacyPool) checkDelegationLimit(tx *types.Transaction) error {
+	from, _ := types.Sender(pool.signer, tx) // validated
+
+	// Short circuit if the sender has neither delegation nor pending delegation.
+	if pool.currentState.GetCodeHash(from) == types.EmptyCodeHash && len(pool.all.auths[from]) == 0 {
+		return nil
+	}
+	pending := pool.pending[from]
+	if pending == nil {
+		// Transaction with gapped nonce is not supported for delegated accounts
+		if pool.pendingNonces.get(from) != tx.Nonce() {
+			return ErrOutOfOrderTxFromDelegated
+		}
+		return nil
+	}
+	// Transaction replacement is supported
+	if pending.Contains(tx.Nonce()) {
+		return nil
+	}
+	return ErrInflightTxLimitReached
+}
+
 // validateAuth verifies that the transaction complies with code authorization
 // restrictions brought by SetCode transaction type.
 func (pool *LegacyPool) validateAuth(tx *types.Transaction) error {
-	from, _ := types.Sender(pool.signer, tx) // validated
-
 	// Allow at most one in-flight tx for delegated accounts or those with a
 	// pending authorization.
-	if pool.currentState.GetCodeHash(from) != types.EmptyCodeHash || len(pool.all.auths[from]) != 0 {
-		var (
-			count  int
-			exists bool
-		)
-		pending := pool.pending[from]
-		if pending != nil {
-			count += pending.Len()
-			exists = pending.Contains(tx.Nonce())
-		}
-		queue := pool.queue[from]
-		if queue != nil {
-			count += queue.Len()
-			exists = exists || queue.Contains(tx.Nonce())
-		}
-		// Replace the existing in-flight transaction for delegated accounts
-		// are still supported
-		if count >= 1 && !exists {
-			return ErrInflightTxLimitReached
-		}
+	if err := pool.checkDelegationLimit(tx); err != nil {
+		return err
 	}
 	// Authorities cannot conflict with any pending or queued transactions.
 	if auths := tx.SetCodeAuthorities(); len(auths) > 0 {

core/txpool/legacypool/legacypool_test.go

@@ -2262,14 +2262,19 @@ func TestSetCodeTransactions(t *testing.T) {
 				aa := common.Address{0xaa, 0xaa}
 				statedb.SetCode(addrA, append(types.DelegationPrefix, aa.Bytes()...))
 				statedb.SetCode(aa, []byte{byte(vm.ADDRESS), byte(vm.PUSH0), byte(vm.SSTORE)})
+
+				// Send gapped transaction, it should be rejected.
+				if err := pool.addRemoteSync(pricedTransaction(2, 100000, big.NewInt(1), keyA)); !errors.Is(err, ErrOutOfOrderTxFromDelegated) {
+					t.Fatalf("%s: error mismatch: want %v, have %v", name, ErrOutOfOrderTxFromDelegated, err)
+				}
 				// Send transactions. First is accepted, second is rejected.
 				if err := pool.addRemoteSync(pricedTransaction(0, 100000, big.NewInt(1), keyA)); err != nil {
 					t.Fatalf("%s: failed to add remote transaction: %v", name, err)
 				}
 				if err := pool.addRemoteSync(pricedTransaction(1, 100000, big.NewInt(1), keyA)); !errors.Is(err, ErrInflightTxLimitReached) {
 					t.Fatalf("%s: error mismatch: want %v, have %v", name, ErrInflightTxLimitReached, err)
 				}
-				// Also check gapped transaction.
+				// Check gapped transaction again.
 				if err := pool.addRemoteSync(pricedTransaction(2, 100000, big.NewInt(1), keyA)); !errors.Is(err, ErrInflightTxLimitReached) {
 					t.Fatalf("%s: error mismatch: want %v, have %v", name, ErrInflightTxLimitReached, err)
 				}