Policy: introduce fee for Conflicts attribute

This commit implements Conflicts attribute policy described in
neo-project#2907 (comment).

Signed-off-by: Anna Shaleva <shaleva.ann@nspcc.ru>

src/Neo/Network/P2P/Payloads/Transaction.cs

@@ -368,7 +368,9 @@ public virtual VerifyResult VerifyStateDependent(ProtocolSettings settings, Data
             foreach (TransactionAttribute attribute in Attributes)
                 if (!attribute.Verify(snapshot, this))
                     return VerifyResult.InvalidAttribute;
-            long net_fee = NetworkFee - Size * NativeContract.Policy.GetFeePerByte(snapshot);
+
+            long conflictsFee = GetAttributes<Conflicts>().Count() * Signers.Count() * NativeContract.Policy.GetConflictsFee(snapshot);
+            long net_fee = NetworkFee - Size * NativeContract.Policy.GetFeePerByte(snapshot) - conflictsFee;
             if (net_fee < 0) return VerifyResult.InsufficientFunds;
 
             if (net_fee > MaxVerificationGas) net_fee = MaxVerificationGas;

src/Neo/SmartContract/Native/PolicyContract.cs

@@ -31,6 +31,11 @@ public sealed class PolicyContract : NativeContract
         /// </summary>
         public const uint DefaultStoragePrice = 100000;
 
+        /// <summary>
+        /// The default fee for Conflicts attribute per signer.
+        /// </summary>
+        public const uint DefaultConflictsFee = 0;
+
         /// <summary>
         /// The default network fee per byte of transactions.
         /// </summary>
@@ -46,10 +51,16 @@ public sealed class PolicyContract : NativeContract
         /// </summary>
         public const uint MaxStoragePrice = 10000000;
 
+        /// <summary>
+        /// The maximum fee for Conflicts attribute per signer that the committee can set.
+        /// </summary>
+        public const uint MaxConflictsFee = 10_0000_0000;
+
         private const byte Prefix_BlockedAccount = 15;
         private const byte Prefix_FeePerByte = 10;
         private const byte Prefix_ExecFeeFactor = 18;
         private const byte Prefix_StoragePrice = 19;
+        private const byte Prefix_ConflictsFee = 20;
 
         internal PolicyContract()
         {
@@ -60,6 +71,7 @@ internal override ContractTask Initialize(ApplicationEngine engine)
             engine.Snapshot.Add(CreateStorageKey(Prefix_FeePerByte), new StorageItem(DefaultFeePerByte));
             engine.Snapshot.Add(CreateStorageKey(Prefix_ExecFeeFactor), new StorageItem(DefaultExecFeeFactor));
             engine.Snapshot.Add(CreateStorageKey(Prefix_StoragePrice), new StorageItem(DefaultStoragePrice));
+            engine.Snapshot.Add(CreateStorageKey(Prefix_ConflictsFee), new StorageItem(DefaultConflictsFee));
             return ContractTask.CompletedTask;
         }
 
@@ -96,6 +108,17 @@ public uint GetStoragePrice(DataCache snapshot)
             return (uint)(BigInteger)snapshot[CreateStorageKey(Prefix_StoragePrice)];
         }
 
+        /// <summary>
+        /// Gets the fee for Conflicts attribute per signer.
+        /// </summary>
+        /// <param name="snapshot">The snapshot used to read data.</param>
+        /// <returns>The fee for Conflicts attribute per signer.</returns>
+        [ContractMethod(CpuFee = 1 << 15, RequiredCallFlags = CallFlags.ReadStates)]
+        public uint GetConflictsFee(DataCache snapshot)
+        {
+            return (uint)(BigInteger)snapshot[CreateStorageKey(Prefix_ConflictsFee)];
+        }
+
         /// <summary>
         /// Determines whether the specified account is blocked.
         /// </summary>
@@ -132,6 +155,14 @@ private void SetStoragePrice(ApplicationEngine engine, uint value)
             engine.Snapshot.GetAndChange(CreateStorageKey(Prefix_StoragePrice)).Set(value);
         }
 
+        [ContractMethod(CpuFee = 1 << 15, RequiredCallFlags = CallFlags.States)]
+        private void SetConflictsFee(ApplicationEngine engine, uint value)
+        {
+            if (value > MaxConflictsFee) throw new ArgumentOutOfRangeException(nameof(value));
+            if (!CheckCommittee(engine)) throw new InvalidOperationException();
+            engine.Snapshot.GetAndChange(CreateStorageKey(Prefix_ConflictsFee)).Set(value);
+        }
+
         [ContractMethod(CpuFee = 1 << 15, RequiredCallFlags = CallFlags.States)]
         private bool BlockAccount(ApplicationEngine engine, UInt160 account)
         {

src/Neo/Wallets/Wallet.cs

@@ -661,6 +661,7 @@ public long CalculateNetworkFee(DataCache snapshot, Transaction tx)
                 }
             }
             networkFee += size * NativeContract.Policy.GetFeePerByte(snapshot);
+            networkFee += tx.GetAttributes<Conflicts>().Count() * tx.Signers.Count() * NativeContract.Policy.GetConflictsFee(snapshot);
             return networkFee;
         }
 

tests/Neo.UnitTests/SmartContract/Native/UT_PolicyContract.cs

@@ -33,6 +33,10 @@ public void Check_Default()
             var ret = NativeContract.Policy.Call(snapshot, "getFeePerByte");
             ret.Should().BeOfType<VM.Types.Integer>();
             ret.GetInteger().Should().Be(1000);
+
+            ret = NativeContract.Policy.Call(snapshot, "getConflictsFee");
+            ret.Should().BeOfType<VM.Types.Integer>();
+            ret.GetInteger().Should().Be(0);
         }
 
         [TestMethod]
@@ -174,6 +178,65 @@ public void Check_SetStoragePrice()
             ret.GetInteger().Should().Be(300300);
         }
 
+        [TestMethod]
+        public void Check_SetConflictsFee()
+        {
+            var snapshot = _snapshot.CreateSnapshot();
+
+            // Fake blockchain
+
+            Block block = new()
+            {
+                Header = new Header
+                {
+                    Index = 1000,
+                    PrevHash = UInt256.Zero
+                }
+            };
+
+            // Without signature
+
+            Assert.ThrowsException<InvalidOperationException>(() =>
+            {
+                NativeContract.Policy.Call(snapshot, new Nep17NativeContractExtensions.ManualWitness(), block,
+                "setConflictsFee", new ContractParameter(ContractParameterType.Integer) { Value = 100500 });
+            });
+
+            var ret = NativeContract.Policy.Call(snapshot, "getConflictsFee");
+            ret.Should().BeOfType<VM.Types.Integer>();
+            ret.GetInteger().Should().Be(0);
+
+            // With signature, wrong value
+            UInt160 committeeMultiSigAddr = NativeContract.NEO.GetCommitteeAddress(snapshot);
+            Assert.ThrowsException<ArgumentOutOfRangeException>(() =>
+            {
+                NativeContract.Policy.Call(snapshot, new Nep17NativeContractExtensions.ManualWitness(committeeMultiSigAddr), block,
+                    "setConflictsFee", new ContractParameter(ContractParameterType.Integer) { Value = 11_0000_0000 });
+            });
+
+            ret = NativeContract.Policy.Call(snapshot, "getConflictsFee");
+            ret.Should().BeOfType<VM.Types.Integer>();
+            ret.GetInteger().Should().Be(0);
+
+            // Proper set
+            ret = NativeContract.Policy.Call(snapshot, new Nep17NativeContractExtensions.ManualWitness(committeeMultiSigAddr), block,
+                "setConflictsFee", new ContractParameter(ContractParameterType.Integer) { Value = 300300 });
+            ret.IsNull.Should().BeTrue();
+
+            ret = NativeContract.Policy.Call(snapshot, "getConflictsFee");
+            ret.Should().BeOfType<VM.Types.Integer>();
+            ret.GetInteger().Should().Be(300300);
+
+            // Set to zero
+            ret = NativeContract.Policy.Call(snapshot, new Nep17NativeContractExtensions.ManualWitness(committeeMultiSigAddr), block,
+                "setConflictsFee", new ContractParameter(ContractParameterType.Integer) { Value = 0 });
+            ret.IsNull.Should().BeTrue();
+
+            ret = NativeContract.Policy.Call(snapshot, "getConflictsFee");
+            ret.Should().BeOfType<VM.Types.Integer>();
+            ret.GetInteger().Should().Be(0);
+        }
+
         [TestMethod]
         public void Check_BlockAccount()
         {