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Implement economic adjustments for Conflicts attribute
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Transaction that conflicts with mempooled transactions have to pay
larger network fee than the sum of all conflicting transactions in
the pool that have the same sender as the newcomer.

Port the nspcc-dev/neo-go#3031.
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@AnnaShaleva
AnnaShaleva committed Jun 1, 2023
1 parent 1dbf965 commit dab46a8
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Showing 2 changed files with 49 additions and 10 deletions.
10 changes: 8 additions & 2 deletions src/Neo/Ledger/MemoryPool.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -352,13 +352,15 @@ internal VerifyResult TryAdd(Transaction tx, DataCache snapshot)
private bool CheckConflicts(Transaction tx, out List<PoolItem> conflictsList)
{
conflictsList = new();
long conflictsFeeSum = 0;
// Step 1: check if `tx` was in Conflicts attributes of unsorted transactions.
if (_conflicts.TryGetValue(tx.Hash, out var conflicting))
{
foreach (var hash in conflicting)
{
var unsortedTx = _unsortedTransactions[hash];
if (unsortedTx.Tx.Signers.Select(s => s.Account).Contains(tx.Sender) && unsortedTx.Tx.NetworkFee > tx.NetworkFee) return false;
if (unsortedTx.Tx.Signers.Select(s => s.Account).Contains(tx.Sender))
conflictsFeeSum += unsortedTx.Tx.NetworkFee;
conflictsList.Add(unsortedTx);
}
}
Expand All @@ -368,10 +370,14 @@ private bool CheckConflicts(Transaction tx, out List<PoolItem> conflictsList)
if (_unsortedTransactions.TryGetValue(hash, out PoolItem unsortedTx))
{
if (!tx.Signers.Select(p => p.Account).Contains(unsortedTx.Tx.Sender)) return false;
if (unsortedTx.Tx.NetworkFee >= tx.NetworkFee) return false;
conflictsFeeSum += unsortedTx.Tx.NetworkFee;
conflictsList.Add(unsortedTx);
}
}
// Network fee of tx have to be larger than the sum of conflicting txs network fees.
if (conflictsFeeSum != 0 && conflictsFeeSum >= tx.NetworkFee)
return false;

// Step 3: take into account sender's conflicting transactions while balance check,
// this will be done in VerifyStateDependant.

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49 changes: 41 additions & 8 deletions tests/Neo.UnitTests/Ledger/UT_MemoryPool.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -306,12 +306,14 @@ public async Task TryAdd_AddRangeOfConflictingTransactions()
{
// Arrange: prepare mempooled txs that have conflicts.
long txFee = 1;
var maliciousSender = new UInt160(Crypto.Hash160(new byte[] { 1, 2, 3 }));
var snapshot = GetSnapshot();
BigInteger balance = NativeContract.GAS.BalanceOf(snapshot, senderAccount);
ApplicationEngine engine = ApplicationEngine.Create(TriggerType.Application, null, snapshot, settings: TestBlockchain.TheNeoSystem.Settings, gas: long.MaxValue);
engine.LoadScript(Array.Empty<byte>());
await NativeContract.GAS.Burn(engine, UInt160.Zero, balance);
_ = NativeContract.GAS.Mint(engine, UInt160.Zero, 100, true); // balance enough for all mempooled txs
_ = NativeContract.GAS.Mint(engine, maliciousSender, 100, true); // balance enough for all mempooled txs

var mp1 = CreateTransactionWithFeeAndBalanceVerify(txFee); // mp1 doesn't conflict with anyone and not in the pool yet

Expand All @@ -336,6 +338,18 @@ public async Task TryAdd_AddRangeOfConflictingTransactions()
var mp5 = CreateTransactionWithFeeAndBalanceVerify(2 * txFee); // mp5 conflicts with mp4 and has smaller network fee
mp5.Attributes = new TransactionAttribute[] { new Conflicts() { Hash = mp4.Hash } };

var mp6 = CreateTransactionWithFeeAndBalanceVerify(mp2_1.NetworkFee + mp2_2.NetworkFee + 1); // mp6 conflicts with mp2_1 and mp2_2 and has larger network fee.
mp6.Attributes = new TransactionAttribute[] { new Conflicts() { Hash = mp2_1.Hash }, new Conflicts() { Hash = mp2_2.Hash } };

var mp7 = CreateTransactionWithFeeAndBalanceVerify(txFee * 2 + 1); // mp7 doesn't conflicts with anyone, but mp8, mp9 and mp10malicious has smaller sum network fee and conflict with mp7.
var mp8 = CreateTransactionWithFeeAndBalanceVerify(txFee);
mp8.Attributes = new TransactionAttribute[] { new Conflicts() { Hash = mp7.Hash } };
var mp9 = CreateTransactionWithFeeAndBalanceVerify(txFee);
mp9.Attributes = new TransactionAttribute[] { new Conflicts() { Hash = mp7.Hash } };
var mp10malicious = CreateTransactionWithFeeAndBalanceVerify(txFee);
mp10malicious.Attributes = new TransactionAttribute[] { new Conflicts() { Hash = mp7.Hash } };
mp10malicious.Signers = new Signer[] { new Signer() { Account = maliciousSender, Scopes = WitnessScope.None } };

_unit.SortedTxCount.Should().Be(3);
_unit.UnverifiedSortedTxCount.Should().Be(0);

Expand All @@ -352,21 +366,40 @@ public async Task TryAdd_AddRangeOfConflictingTransactions()
_unit.SortedTxCount.Should().Be(3);
_unit.GetVerifiedTransactions().Should().Contain(new List<Transaction>() { mp2_1, mp2_2, mp4 });

_unit.TryAdd(mp1, engine.Snapshot).Should().Be(VerifyResult.Succeed); // mp1 conflicts with mp2_1 and mp2_2 and has same network fee, mp2_1 and mp2_2 have Conflicts attribute => mp2_1 and mp2_2 should be removed from pool
_unit.SortedTxCount.Should().Be(2);
_unit.GetVerifiedTransactions().Should().Contain(new List<Transaction>() { mp1, mp4 });
_unit.TryAdd(mp1, engine.Snapshot).Should().Be(VerifyResult.HasConflicts); // mp1 conflicts with mp2_1 and mp2_2 and has same network fee => mp2_1 and mp2_2 should be left in pool.
_unit.SortedTxCount.Should().Be(3);
_unit.GetVerifiedTransactions().Should().Contain(new List<Transaction>() { mp2_1, mp2_2, mp4 });

_unit.TryAdd(mp2_1, engine.Snapshot).Should().Be(VerifyResult.HasConflicts); // mp2_1 conflicts with mp1 and has same network fee, mp2_1 has Conflicts attribute => mp2_1 shoouldn't be added to the pool
_unit.TryAdd(mp6, engine.Snapshot).Should().Be(VerifyResult.Succeed); // mp6 conflicts with mp2_1 and mp2_2 and has larger network fee than the sum of mp2_1 and mp2_2 fees => mp6 should be added.
_unit.SortedTxCount.Should().Be(2);
_unit.GetVerifiedTransactions().Should().Contain(new List<Transaction>() { mp1, mp4 });
_unit.GetVerifiedTransactions().Should().Contain(new List<Transaction>() { mp6, mp4 });

_unit.TryAdd(mp5, engine.Snapshot).Should().Be(VerifyResult.HasConflicts); // mp5 conflicts with mp4 and has smaller network fee => mp5 fails to be added
_unit.SortedTxCount.Should().Be(2);
_unit.GetVerifiedTransactions().Should().Contain(new List<Transaction>() { mp1, mp4 });
_unit.TryAdd(mp1, engine.Snapshot).Should().Be(VerifyResult.Succeed); // mp1 conflicts with mp2_1 and mp2_2, but they are not in the pool now => mp1 should be added.
_unit.SortedTxCount.Should().Be(3);
_unit.GetVerifiedTransactions().Should().Contain(new List<Transaction>() { mp1, mp6, mp4 });

_unit.TryAdd(mp2_1, engine.Snapshot).Should().Be(VerifyResult.HasConflicts); // mp2_1 conflicts with mp1 and has same network fee => mp2_1 shouldn't be added to the pool.
_unit.SortedTxCount.Should().Be(3);
_unit.GetVerifiedTransactions().Should().Contain(new List<Transaction>() { mp1, mp6, mp4 });

_unit.TryAdd(mp5, engine.Snapshot).Should().Be(VerifyResult.HasConflicts); // mp5 conflicts with mp4 and has smaller network fee => mp5 fails to be added.
_unit.SortedTxCount.Should().Be(3);
_unit.GetVerifiedTransactions().Should().Contain(new List<Transaction>() { mp1, mp6, mp4 });

_unit.TryAdd(mp8, engine.Snapshot).Should().Be(VerifyResult.Succeed); // mp8, mp9 and mp10malicious conflict with mp7, but mo7 is not in the pool yet.
_unit.TryAdd(mp9, engine.Snapshot).Should().Be(VerifyResult.Succeed);
_unit.TryAdd(mp10malicious, engine.Snapshot).Should().Be(VerifyResult.Succeed);
_unit.SortedTxCount.Should().Be(6);
_unit.GetVerifiedTransactions().Should().Contain(new List<Transaction>() { mp1, mp6, mp4, mp8, mp9, mp10malicious });
_unit.TryAdd(mp7, engine.Snapshot).Should().Be(VerifyResult.Succeed); // mp7 has larger network fee than the sum of mp8 and mp9 fees => should be added to the pool.
_unit.SortedTxCount.Should().Be(4);
_unit.GetVerifiedTransactions().Should().Contain(new List<Transaction>() { mp1, mp6, mp4, mp7 });

// Cleanup: revert the balance.
await NativeContract.GAS.Burn(engine, UInt160.Zero, 100);
_ = NativeContract.GAS.Mint(engine, UInt160.Zero, balance, true);
await NativeContract.GAS.Burn(engine, maliciousSender, 100);
_ = NativeContract.GAS.Mint(engine, maliciousSender, balance, true);
}

[TestMethod]
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