Add the ability to suspend or resume XCM execution on the XCMP queue

pallets/xcmp-queue/src/lib.rs

@@ -81,6 +81,9 @@ pub mod pallet {
 
 		/// The origin that is allowed to execute overweight messages.
 		type ExecuteOverweightOrigin: EnsureOrigin<Self::Origin>;
+
+		/// The origin that is allowed to resume or suspend the XCMP queue.
+		type ControllerOrigin: EnsureOrigin<Self::Origin>;
 	}
 
 	#[pallet::hooks]
@@ -129,6 +132,32 @@ pub mod pallet {
 			Self::deposit_event(Event::OverweightServiced(index, used));
 			Ok(Some(used.saturating_add(1_000_000)).into())
 		}
+
+		/// Suspends all XCM executions for the XCMP queue, regardless of the sender's origin.
+		///
+		/// - `origin`: Must pass `ControllerOrigin`.
+		#[pallet::weight(T::DbWeight::get().writes(1))]
+		pub fn suspend_xcm_execution(origin: OriginFor<T>) -> DispatchResult {
+			T::ControllerOrigin::ensure_origin(origin)?;
+
+			QueueActive::<T>::put(false);
+
+			Ok(())
+		}
+
+		/// Resumes all XCM executions for the XCMP queue.
+		///
+		/// Note that this function doesn't change the status of the in/out bound channels.
+		///
+		/// - `origin`: Must pass `ControllerOrigin`.
+		#[pallet::weight(T::DbWeight::get().writes(1))]
+		pub fn resume_xcm_execution(origin: OriginFor<T>) -> DispatchResult {
+			T::ControllerOrigin::ensure_origin(origin)?;
+
+			QueueActive::<T>::put(true);
+
+			Ok(())
+		}
 	}
 
 	#[pallet::event]
@@ -220,6 +249,10 @@ pub mod pallet {
 	/// available free overweight index.
 	#[pallet::storage]
 	pub(super) type OverweightCount<T: Config> = StorageValue<_, OverweightIndex, ValueQuery>;
+
+	/// Whether or not the XCMP queue is active in executing incoming XCMs or not.
+	#[pallet::storage]
+	pub(super) type QueueActive<T: Config> = StorageValue<_, bool, ValueQuery>;
 }
 
 #[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Encode, Decode, RuntimeDebug, TypeInfo)]
@@ -619,6 +652,11 @@ impl<T: Config> Pallet<T> {
 	/// for the second &c. though empirical and or practical factors may give rise to adjusting it
 	/// further.
 	fn service_xcmp_queue(max_weight: Weight) -> Weight {
+		let active = QueueActive::<T>::get();
+		if !active {
+			return 0
+		}
+
 		let mut status = <InboundXcmpStatus<T>>::get(); // <- sorted.
 		if status.len() == 0 {
 			return 0

pallets/xcmp-queue/src/mock.rs

@@ -160,6 +160,7 @@ impl Config for Test {
 	type ChannelInfo = ParachainSystem;
 	type VersionWrapper = ();
 	type ExecuteOverweightOrigin = EnsureRoot<AccountId>;
+	type ControllerOrigin = EnsureRoot<AccountId>;
 }
 
 pub fn new_test_ext() -> sp_io::TestExternalities {

pallets/xcmp-queue/src/tests.rs

@@ -82,3 +82,21 @@ fn service_overweight_bad_xcm_format() {
 		assert_noop!(XcmpQueue::service_overweight(Origin::root(), 0, 1000), Error::<Test>::BadXcm);
 	});
 }
+
+#[test]
+fn suspend_xcm_execution_works() {
+	new_test_ext().execute_with(|| {
+		QueueActive::<Test>::put(false);
+
+		let xcm = Instruction::<()>::ClearOrigin.encode();
+		let mut message_format = XcmpMessageFormat::ConcatenatedVersionedXcm.encode();
+		message_format.extend(xcm.clone());
+		let messages = vec![(Default::default(), 1u32.into(), message_format.as_slice())];
+
+		// This shouldn't have executed the incoming XCM
+		XcmpQueue::handle_xcmp_messages(messages.into_iter(), Weight::max_value());
+
+		let queued_xcm = InboundXcmpMessages::<Test>::get(ParaId::default(), 1u32);
+		assert_eq!(queued_xcm, xcm);
+	});
+}

parachain-template/runtime/src/lib.rs

@@ -525,6 +525,7 @@ impl cumulus_pallet_xcmp_queue::Config for Runtime {
 	type ChannelInfo = ParachainSystem;
 	type VersionWrapper = ();
 	type ExecuteOverweightOrigin = EnsureRoot<AccountId>;
+	type ControllerOrigin = EnsureRoot<AccountId>;
 }
 
 impl cumulus_pallet_dmp_queue::Config for Runtime {

polkadot-parachains/rococo-parachain/src/lib.rs

@@ -454,6 +454,7 @@ impl cumulus_pallet_xcmp_queue::Config for Runtime {
 	type ChannelInfo = ParachainSystem;
 	type VersionWrapper = ();
 	type ExecuteOverweightOrigin = EnsureRoot<AccountId>;
+	type ControllerOrigin = EnsureRoot<AccountId>;
 }
 
 impl cumulus_pallet_dmp_queue::Config for Runtime {

polkadot-parachains/statemint/src/lib.rs

@@ -616,6 +616,7 @@ impl cumulus_pallet_xcmp_queue::Config for Runtime {
 	type ChannelInfo = ParachainSystem;
 	type VersionWrapper = PolkadotXcm;
 	type ExecuteOverweightOrigin = EnsureRoot<AccountId>;
+	type ControllerOrigin = EnsureRoot<AccountId>;
 }
 
 impl cumulus_pallet_dmp_queue::Config for Runtime {

polkadot-parachains/westmint/src/lib.rs

@@ -596,6 +596,7 @@ impl cumulus_pallet_xcmp_queue::Config for Runtime {
 	type ChannelInfo = ParachainSystem;
 	type VersionWrapper = PolkadotXcm;
 	type ExecuteOverweightOrigin = EnsureRoot<AccountId>;
+	type ControllerOrigin = EnsureRoot<AccountId>;
 }
 
 impl cumulus_pallet_dmp_queue::Config for Runtime {