{suspend, resume} xcm execution when {enter, exit}ing maintenance-mode

pallets/maintenance-mode/src/lib.rs

@@ -58,19 +58,34 @@ pub mod pallet {
 	use cumulus_primitives_core::{
 		relay_chain::BlockNumber as RelayBlockNumber, DmpMessageHandler, ParaId, XcmpMessageHandler,
 	};
-	#[cfg(feature = "xcm-support")]
-	use sp_std::vec::Vec;
-
 	use frame_support::pallet_prelude::*;
 	use frame_support::traits::{
 		Contains, EnsureOrigin, OffchainWorker, OnFinalize, OnIdle, OnInitialize, OnRuntimeUpgrade,
 	};
 	use frame_system::pallet_prelude::*;
+	use sp_runtime::DispatchResult;
+	#[cfg(feature = "xcm-support")]
+	use sp_std::vec::Vec;
 	/// Pallet for migrations
 	#[pallet::pallet]
 	#[pallet::without_storage_info]
 	pub struct Pallet<T>(PhantomData<T>);
 
+	/// Pause and resume execution of XCM
+	pub trait PauseXcmExecution {
+		fn suspend_xcm_execution() -> DispatchResult;
+		fn resume_xcm_execution() -> DispatchResult;
+	}
+
+	impl PauseXcmExecution for () {
+		fn suspend_xcm_execution() -> DispatchResult {
+			Ok(())
+		}
+		fn resume_xcm_execution() -> DispatchResult {
+			Ok(())
+		}
+	}
+
 	/// Configuration trait of this pallet.
 	#[pallet::config]
 	pub trait Config: frame_system::Config {
@@ -88,6 +103,9 @@ pub mod pallet {
 		/// able to return to normal mode. For example, if your MaintenanceOrigin is a council, make
 		/// sure that your councilors can still cast votes.
 		type MaintenanceOrigin: EnsureOrigin<Self::Origin>;
+		/// Handler to suspend and resume XCM execution
+		#[cfg(feature = "xcm-support")]
+		type XcmExecutionManager: PauseXcmExecution;
 		/// The DMP handler to be used in normal operating mode
 		#[cfg(feature = "xcm-support")]
 		type NormalDmpHandler: DmpMessageHandler;
@@ -125,6 +143,10 @@ pub mod pallet {
 		EnteredMaintenanceMode,
 		/// The chain returned to its normal operating state
 		NormalOperationResumed,
+		/// The call to suspend on_idle XCM execution failed with inner error
+		FailedToSuspendIdleXcmExecution { error: DispatchError },
+		/// The call to resume on_idle XCM execution failed with inner error
+		FailedToResumeIdleXcmExecution { error: DispatchError },
 	}
 
 	/// An error that can occur while executing this pallet's extrinsics.
@@ -147,8 +169,8 @@ pub mod pallet {
 		///
 		/// Weight cost is:
 		/// * One DB read to ensure we're not already in maintenance mode
-		/// * Two DB writes - 1 for the mode and 1 for the event
-		#[pallet::weight(T::DbWeight::get().read + 2 * T::DbWeight::get().write)]
+		/// * Three DB writes - 1 for the mode, 1 for suspending xcm execution, 1 for the event
+		#[pallet::weight(T::DbWeight::get().read + 3 * T::DbWeight::get().write)]
 		pub fn enter_maintenance_mode(origin: OriginFor<T>) -> DispatchResultWithPostInfo {
 			// Ensure Origin
 			T::MaintenanceOrigin::ensure_origin(origin)?;
@@ -163,6 +185,10 @@ pub mod pallet {
 
 			// Write to storage
 			MaintenanceMode::<T>::put(true);
+			// Suspend XCM execution
+			if let Err(error) = T::XcmExecutionManager::suspend_xcm_execution() {
+				<Pallet<T>>::deposit_event(Event::FailedToSuspendIdleXcmExecution { error });
+			}
 
 			// Event
 			<Pallet<T>>::deposit_event(Event::EnteredMaintenanceMode);
@@ -174,8 +200,8 @@ pub mod pallet {
 		///
 		/// Weight cost is:
 		/// * One DB read to ensure we're in maintenance mode
-		/// * Two DB writes - 1 for the mode and 1 for the event
-		#[pallet::weight(T::DbWeight::get().read + 2 * T::DbWeight::get().write)]
+		/// * Three DB writes - 1 for the mode, 1 for resuming xcm execution, 1 for the event
+		#[pallet::weight(T::DbWeight::get().read + 3 * T::DbWeight::get().write)]
 		pub fn resume_normal_operation(origin: OriginFor<T>) -> DispatchResultWithPostInfo {
 			// Ensure Origin
 			T::MaintenanceOrigin::ensure_origin(origin)?;
@@ -190,6 +216,10 @@ pub mod pallet {
 
 			// Write to storage
 			MaintenanceMode::<T>::put(false);
+			// Resume XCM execution
+			if let Err(error) = T::XcmExecutionManager::resume_xcm_execution() {
+				<Pallet<T>>::deposit_event(Event::FailedToResumeIdleXcmExecution { error });
+			}
 
 			// Event
 			<Pallet<T>>::deposit_event(Event::NormalOperationResumed);

pallets/maintenance-mode/src/mock.rs

@@ -284,6 +284,8 @@ impl Config for Test {
 	type MaintenanceCallFilter = MaintenanceCallFilter;
 	type MaintenanceOrigin = EnsureRoot<AccountId>;
 	#[cfg(feature = "xcm-support")]
+	type XcmExecutionManager = ();
+	#[cfg(feature = "xcm-support")]
 	type NormalDmpHandler = NormalDmpHandler;
 	#[cfg(feature = "xcm-support")]
 	type MaintenanceDmpHandler = MaintenanceDmpHandler;

runtime/moonbase/src/lib.rs

@@ -1139,6 +1139,17 @@ impl Contains<Call> for NormalFilter {
 use cumulus_primitives_core::{
 	relay_chain::BlockNumber as RelayBlockNumber, DmpMessageHandler, ParaId, XcmpMessageHandler,
 };
+
+pub struct XcmExecutionManager;
+impl pallet_maintenance_mode::PauseXcmExecution for XcmExecutionManager {
+	fn suspend_xcm_execution() -> DispatchResult {
+		XcmpQueue::suspend_xcm_execution(Origin::root())
+	}
+	fn resume_xcm_execution() -> DispatchResult {
+		XcmpQueue::resume_xcm_execution(Origin::root())
+	}
+}
+
 pub struct MaintenanceDmpHandler;
 impl DmpMessageHandler for MaintenanceDmpHandler {
 	// This implementation makes messages be queued
@@ -1217,6 +1228,7 @@ impl pallet_maintenance_mode::Config for Runtime {
 	type MaintenanceCallFilter = MaintenanceFilter;
 	type MaintenanceOrigin =
 		pallet_collective::EnsureProportionAtLeast<_2, _3, AccountId, TechCommitteeInstance>;
+	type XcmExecutionManager = XcmExecutionManager;
 	type NormalDmpHandler = DmpQueue;
 	type MaintenanceDmpHandler = MaintenanceDmpHandler;
 	type NormalXcmpHandler = XcmpQueue;

runtime/moonbase/tests/integration_test.rs

@@ -25,7 +25,7 @@ use fp_evm::{Context, ExitSucceed, PrecompileOutput};
 use frame_support::{
 	assert_noop, assert_ok,
 	dispatch::Dispatchable,
-	traits::{fungible::Inspect, PalletInfo, StorageInfo, StorageInfoTrait},
+	traits::{fungible::Inspect, EnsureOrigin, PalletInfo, StorageInfo, StorageInfoTrait},
 	weights::{DispatchClass, Weight},
 	StorageHasher, Twox128,
 };
@@ -53,6 +53,16 @@ use sp_runtime::{
 };
 use xcm::latest::prelude::*;
 
+#[test]
+fn xcmp_queue_controller_origin_is_root() {
+	// important for the XcmExecutionManager impl of PauseExecution which uses root origin
+	// to suspend/resume XCM execution in xcmp_queue::on_idle
+	assert_ok!(
+		<moonbase_runtime::Runtime as cumulus_pallet_xcmp_queue::Config
+		>::ControllerOrigin::ensure_origin(root_origin())
+	);
+}
+
 #[test]
 fn fast_track_available() {
 	assert!(<moonbase_runtime::Runtime as pallet_democracy::Config>::InstantAllowed::get());

runtime/moonbeam/src/lib.rs

@@ -1086,6 +1086,16 @@ impl Contains<Call> for NormalFilter {
 	}
 }
 
+pub struct XcmExecutionManager;
+impl pallet_maintenance_mode::PauseXcmExecution for XcmExecutionManager {
+	fn suspend_xcm_execution() -> DispatchResult {
+		XcmpQueue::suspend_xcm_execution(Origin::root())
+	}
+	fn resume_xcm_execution() -> DispatchResult {
+		XcmpQueue::resume_xcm_execution(Origin::root())
+	}
+}
+
 pub struct MaintenanceDmpHandler;
 impl DmpMessageHandler for MaintenanceDmpHandler {
 	// This implementation makes messages be queued
@@ -1164,6 +1174,7 @@ impl pallet_maintenance_mode::Config for Runtime {
 	type MaintenanceCallFilter = MaintenanceFilter;
 	type MaintenanceOrigin =
 		pallet_collective::EnsureProportionAtLeast<_2, _3, AccountId, TechCommitteeInstance>;
+	type XcmExecutionManager = XcmExecutionManager;
 	type NormalDmpHandler = DmpQueue;
 	type MaintenanceDmpHandler = MaintenanceDmpHandler;
 	type NormalXcmpHandler = XcmpQueue;

runtime/moonbeam/tests/integration_test.rs

@@ -25,7 +25,7 @@ use fp_evm::{Context, ExitSucceed, PrecompileOutput};
 use frame_support::{
 	assert_noop, assert_ok,
 	dispatch::Dispatchable,
-	traits::{fungible::Inspect, PalletInfo, StorageInfo, StorageInfoTrait},
+	traits::{fungible::Inspect, EnsureOrigin, PalletInfo, StorageInfo, StorageInfoTrait},
 	weights::{DispatchClass, Weight},
 	StorageHasher, Twox128,
 };
@@ -52,6 +52,16 @@ use xcm::latest::prelude::*;
 use xcm::{VersionedMultiAsset, VersionedMultiAssets, VersionedMultiLocation};
 use xtokens_precompiles::Action as XtokensAction;
 
+#[test]
+fn xcmp_queue_controller_origin_is_root() {
+	// important for the XcmExecutionManager impl of PauseExecution which uses root origin
+	// to suspend/resume XCM execution in xcmp_queue::on_idle
+	assert_ok!(
+		<moonbeam_runtime::Runtime as cumulus_pallet_xcmp_queue::Config
+		>::ControllerOrigin::ensure_origin(root_origin())
+	);
+}
+
 #[test]
 fn fast_track_available() {
 	assert!(<moonbeam_runtime::Runtime as pallet_democracy::Config>::InstantAllowed::get());

runtime/moonriver/src/lib.rs

@@ -1116,6 +1116,16 @@ impl Contains<Call> for NormalFilter {
 	}
 }
 
+pub struct XcmExecutionManager;
+impl pallet_maintenance_mode::PauseXcmExecution for XcmExecutionManager {
+	fn suspend_xcm_execution() -> DispatchResult {
+		XcmpQueue::suspend_xcm_execution(Origin::root())
+	}
+	fn resume_xcm_execution() -> DispatchResult {
+		XcmpQueue::resume_xcm_execution(Origin::root())
+	}
+}
+
 pub struct MaintenanceDmpHandler;
 impl DmpMessageHandler for MaintenanceDmpHandler {
 	// This implementation makes messages be queued
@@ -1194,6 +1204,7 @@ impl pallet_maintenance_mode::Config for Runtime {
 	type MaintenanceCallFilter = MaintenanceFilter;
 	type MaintenanceOrigin =
 		pallet_collective::EnsureProportionAtLeast<_2, _3, AccountId, TechCommitteeInstance>;
+	type XcmExecutionManager = XcmExecutionManager;
 	type NormalDmpHandler = DmpQueue;
 	type MaintenanceDmpHandler = MaintenanceDmpHandler;
 	type NormalXcmpHandler = XcmpQueue;

runtime/moonriver/tests/integration_test.rs

@@ -25,7 +25,7 @@ use fp_evm::{Context, ExitSucceed, PrecompileOutput};
 use frame_support::{
 	assert_noop, assert_ok,
 	dispatch::Dispatchable,
-	traits::{fungible::Inspect, PalletInfo, StorageInfo, StorageInfoTrait},
+	traits::{fungible::Inspect, EnsureOrigin, PalletInfo, StorageInfo, StorageInfoTrait},
 	weights::{DispatchClass, Weight},
 	StorageHasher, Twox128,
 };
@@ -50,6 +50,16 @@ use xcm::latest::prelude::*;
 use xcm::{VersionedMultiAssets, VersionedMultiLocation};
 use xtokens_precompiles::Action as XtokensAction;
 
+#[test]
+fn xcmp_queue_controller_origin_is_root() {
+	// important for the XcmExecutionManager impl of PauseExecution which uses root origin
+	// to suspend/resume XCM execution in xcmp_queue::on_idle
+	assert_ok!(
+		<moonriver_runtime::Runtime as cumulus_pallet_xcmp_queue::Config
+		>::ControllerOrigin::ensure_origin(root_origin())
+	);
+}
+
 #[test]
 fn fast_track_available() {
 	assert!(<moonriver_runtime::Runtime as pallet_democracy::Config>::InstantAllowed::get());