[pallet_xcm] Customizable/extendable remote_message estimation

runtime/kusama/src/xcm_config.rs

@@ -40,9 +40,10 @@ use xcm_builder::{
 	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, ChildParachainAsNative,
 	ChildParachainConvertsVia, ChildSystemParachainAsSuperuser,
 	CurrencyAdapter as XcmCurrencyAdapter, FixedWeightBounds, IsChildSystemParachain, IsConcrete,
-	MintLocation, OriginToPluralityVoice, SignedAccountId32AsNative, SignedToAccountId32,
-	SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId, UsingComponents,
-	WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	MintLocation, OriginToPluralityVoice, ProvideWeighableInstructions, SignedAccountId32AsNative,
+	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId,
+	UniversalWeigherAdapter, UsingComponents, WeightInfoBounds, WithComputedOrigin,
+	WithUniqueTopic,
 };
 use xcm_executor::traits::WithOriginFilter;
 
@@ -383,6 +384,20 @@ pub type LocalPalletOriginToLocation = (
 	FellowsToPlurality,
 );
 
+/// Helper for adding more instructions to the weight estimation on destination side.
+pub struct DestinationWeigherAddons;
+impl ProvideWeighableInstructions<()> for DestinationWeigherAddons {
+	fn provide_for(
+		_dest: impl Into<MultiLocation>,
+		_message: &Xcm<()>,
+	) -> sp_std::vec::Vec<Instruction<()>> {
+		sp_std::vec![
+			// runtime uses `WithUniqueTopic` which (possibly) adds `SetTopic` instruction
+			SetTopic([3; 32])
+		]
+	}
+}
+
 impl pallet_xcm::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	// We only allow the root, the council, fellows and the staking admin to send messages.
@@ -401,6 +416,11 @@ impl pallet_xcm::Config for Runtime {
 	// transfer.
 	type XcmReserveTransferFilter = Everything;
 	type Weigher = FixedWeightBounds<BaseXcmWeight, RuntimeCall, MaxInstructions>;
+	type DestinationWeigher = UniversalWeigherAdapter<
+		// use local weight for remote message and hope for the best.
+		FixedWeightBounds<BaseXcmWeight, (), MaxInstructions>,
+		DestinationWeigherAddons,
+	>;
 	type UniversalLocation = UniversalLocation;
 	type RuntimeOrigin = RuntimeOrigin;
 	type RuntimeCall = RuntimeCall;

runtime/polkadot/src/xcm_config.rs

@@ -43,8 +43,8 @@ use xcm_builder::{
 	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, BackingToPlurality,
 	ChildParachainAsNative, ChildParachainConvertsVia, CurrencyAdapter as XcmCurrencyAdapter,
 	FixedWeightBounds, IsConcrete, MintLocation, OriginToPluralityVoice, SignedAccountId32AsNative,
-	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, UsingComponents,
-	WithComputedOrigin,
+	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, UniversalWeigherAdapter,
+	UsingComponents, WithComputedOrigin,
 };
 use xcm_executor::traits::WithOriginFilter;
 
@@ -408,6 +408,11 @@ impl pallet_xcm::Config for Runtime {
 	type XcmTeleportFilter = Everything; // == Allow All
 	type XcmReserveTransferFilter = Everything; // == Allow All
 	type Weigher = FixedWeightBounds<BaseXcmWeight, RuntimeCall, MaxInstructions>;
+	type DestinationWeigher = UniversalWeigherAdapter<
+		// use local weight for remote message and hope for the best.
+		FixedWeightBounds<BaseXcmWeight, (), MaxInstructions>,
+		(),
+	>;
 	type UniversalLocation = UniversalLocation;
 	type RuntimeOrigin = RuntimeOrigin;
 	type RuntimeCall = RuntimeCall;

runtime/rococo/src/xcm_config.rs

@@ -39,9 +39,9 @@ use xcm_builder::{
 	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, BackingToPlurality,
 	ChildParachainAsNative, ChildParachainConvertsVia, ChildSystemParachainAsSuperuser,
 	CurrencyAdapter as XcmCurrencyAdapter, FixedWeightBounds, IsChildSystemParachain, IsConcrete,
-	MintLocation, SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation,
-	TakeWeightCredit, TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin,
-	WithUniqueTopic,
+	MintLocation, ProvideWeighableInstructions, SignedAccountId32AsNative, SignedToAccountId32,
+	SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId, UniversalWeigherAdapter,
+	UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 };
 use xcm_executor::{traits::WithOriginFilter, XcmExecutor};
 
@@ -351,6 +351,21 @@ pub type LocalOriginToLocation = (
 	// And a usual Signed origin to be used in XCM as a corresponding AccountId32
 	SignedToAccountId32<RuntimeOrigin, AccountId, ThisNetwork>,
 );
+
+/// Helper for adding more instructions to the weight estimation on destination side.
+pub struct DestinationWeigherAddons;
+impl ProvideWeighableInstructions<()> for DestinationWeigherAddons {
+	fn provide_for(
+		_dest: impl Into<MultiLocation>,
+		_message: &Xcm<()>,
+	) -> sp_std::vec::Vec<Instruction<()>> {
+		sp_std::vec![
+			// runtime uses `WithUniqueTopic` which (possibly) adds `SetTopic` instruction
+			SetTopic([3; 32])
+		]
+	}
+}
+
 impl pallet_xcm::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type SendXcmOrigin = xcm_builder::EnsureXcmOrigin<RuntimeOrigin, LocalOriginToLocation>;
@@ -364,6 +379,11 @@ impl pallet_xcm::Config for Runtime {
 	// transfer.
 	type XcmReserveTransferFilter = Everything;
 	type Weigher = FixedWeightBounds<BaseXcmWeight, RuntimeCall, MaxInstructions>;
+	type DestinationWeigher = UniversalWeigherAdapter<
+		// use local weight for remote message and hope for the best.
+		FixedWeightBounds<BaseXcmWeight, (), MaxInstructions>,
+		DestinationWeigherAddons,
+	>;
 	type UniversalLocation = UniversalLocation;
 	type RuntimeOrigin = RuntimeOrigin;
 	type RuntimeCall = RuntimeCall;

runtime/test-runtime/src/xcm_config.rs

@@ -23,7 +23,7 @@ use frame_system::EnsureRoot;
 use xcm::latest::prelude::*;
 use xcm_builder::{
 	AllowUnpaidExecutionFrom, EnsureXcmOrigin, FixedWeightBounds, SignedAccountId32AsNative,
-	SignedToAccountId32,
+	SignedToAccountId32, UniversalWeigherAdapter,
 };
 use xcm_executor::{
 	traits::{TransactAsset, WeightTrader},
@@ -127,21 +127,24 @@ impl pallet_xcm::Config for crate::Runtime {
 	// The config types here are entirely configurable, since the only one that is sorely needed
 	// is `XcmExecutor`, which will be used in unit tests located in xcm-executor.
 	type RuntimeEvent = crate::RuntimeEvent;
-	type ExecuteXcmOrigin = EnsureXcmOrigin<crate::RuntimeOrigin, LocalOriginToLocation>;
-	type UniversalLocation = UniversalLocation;
+	type Currency = crate::Balances;
+	type CurrencyMatcher = ();
 	type SendXcmOrigin = EnsureXcmOrigin<crate::RuntimeOrigin, LocalOriginToLocation>;
-	type Weigher = FixedWeightBounds<BaseXcmWeight, crate::RuntimeCall, MaxInstructions>;
 	type XcmRouter = DoNothingRouter;
+	type ExecuteXcmOrigin = EnsureXcmOrigin<crate::RuntimeOrigin, LocalOriginToLocation>;
 	type XcmExecuteFilter = Everything;
 	type XcmExecutor = xcm_executor::XcmExecutor<XcmConfig>;
 	type XcmTeleportFilter = Everything;
 	type XcmReserveTransferFilter = Everything;
+	type Weigher = FixedWeightBounds<BaseXcmWeight, crate::RuntimeCall, MaxInstructions>;
+	type DestinationWeigher =
+		UniversalWeigherAdapter<FixedWeightBounds<BaseXcmWeight, (), MaxInstructions>, ()>;
+	type UniversalLocation = UniversalLocation;
 	type RuntimeOrigin = crate::RuntimeOrigin;
 	type RuntimeCall = crate::RuntimeCall;
 	const VERSION_DISCOVERY_QUEUE_SIZE: u32 = 100;
 	type AdvertisedXcmVersion = pallet_xcm::CurrentXcmVersion;
-	type Currency = crate::Balances;
-	type CurrencyMatcher = ();
+	type AdminOrigin = EnsureRoot<crate::AccountId>;
 	type TrustedLockers = ();
 	type SovereignAccountOf = ();
 	type MaxLockers = frame_support::traits::ConstU32<8>;
@@ -150,5 +153,4 @@ impl pallet_xcm::Config for crate::Runtime {
 	type WeightInfo = pallet_xcm::TestWeightInfo;
 	#[cfg(feature = "runtime-benchmarks")]
 	type ReachableDest = ReachableDest;
-	type AdminOrigin = EnsureRoot<crate::AccountId>;
 }

runtime/westend/src/xcm_config.rs

@@ -38,8 +38,9 @@ use xcm_builder::{
 	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, ChildParachainAsNative,
 	ChildParachainConvertsVia, ChildSystemParachainAsSuperuser,
 	CurrencyAdapter as XcmCurrencyAdapter, IsChildSystemParachain, IsConcrete, MintLocation,
-	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
-	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	ProvideWeighableInstructions, SignedAccountId32AsNative, SignedToAccountId32,
+	SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId, UniversalWeigherAdapter,
+	UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 };
 use xcm_executor::{traits::WithOriginFilter, XcmExecutor};
 
@@ -278,6 +279,20 @@ pub type LocalOriginToLocation = (
 	SignedToAccountId32<RuntimeOrigin, AccountId, ThisNetwork>,
 );
 
+/// Helper for adding more instructions to the weight estimation on destination side.
+pub struct DestinationWeigherAddons;
+impl ProvideWeighableInstructions<()> for DestinationWeigherAddons {
+	fn provide_for(
+		_dest: impl Into<MultiLocation>,
+		_message: &Xcm<()>,
+	) -> sp_std::vec::Vec<Instruction<()>> {
+		sp_std::vec![
+			// runtime uses `WithUniqueTopic` which (possibly) adds `SetTopic` instruction
+			SetTopic([3; 32])
+		]
+	}
+}
+
 impl pallet_xcm::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type SendXcmOrigin = xcm_builder::EnsureXcmOrigin<RuntimeOrigin, LocalOriginToLocation>;
@@ -291,6 +306,11 @@ impl pallet_xcm::Config for Runtime {
 	type XcmReserveTransferFilter = Everything;
 	type Weigher =
 		WeightInfoBounds<weights::xcm::WestendXcmWeight<RuntimeCall>, RuntimeCall, MaxInstructions>;
+	type DestinationWeigher = UniversalWeigherAdapter<
+		// use local weight for remote message and hope for the best.
+		WeightInfoBounds<weights::xcm::WestendXcmWeight<()>, (), MaxInstructions>,
+		DestinationWeigherAddons,
+	>;
 	type UniversalLocation = UniversalLocation;
 	type RuntimeOrigin = RuntimeOrigin;
 	type RuntimeCall = RuntimeCall;

xcm/pallet-xcm/src/lib.rs

@@ -53,7 +53,7 @@ pub use pallet::*;
 use xcm_executor::{
 	traits::{
 		CheckSuspension, ClaimAssets, ConvertLocation, DropAssets, MatchesFungible, OnResponse,
-		QueryHandler, QueryResponseStatus, VersionChangeNotifier, WeightBounds,
+		QueryHandler, QueryResponseStatus, UniversalWeigher, VersionChangeNotifier, WeightBounds,
 	},
 	Assets,
 };
@@ -218,6 +218,9 @@ pub mod pallet {
 		/// Means of measuring the weight consumed by an XCM message locally.
 		type Weigher: WeightBounds<<Self as SysConfig>::RuntimeCall>;
 
+		/// Means of approximating the weight consumed by an XCM message on destination.
+		type DestinationWeigher: UniversalWeigher;
+
 		/// This chain's Universal Location.
 		type UniversalLocation: Get<InteriorMultiLocation>;
 
@@ -1218,14 +1221,14 @@ impl<T: Config> Pallet<T> {
 			Some(weight_limit) => weight_limit,
 			None => {
 				let fees = fees.clone();
-				let mut remote_message = Xcm(vec![
+				let remote_message = Xcm(vec![
 					ReserveAssetDeposited(assets.clone()),
 					ClearOrigin,
 					BuyExecution { fees, weight_limit: Limited(Weight::zero()) },
 					DepositAsset { assets: Wild(AllCounted(max_assets)), beneficiary },
 				]);
-				// use local weight for remote message and hope for the best.
-				let remote_weight = T::Weigher::weight(&mut remote_message)
+				// estimate remote_message weight
+				let remote_weight = T::DestinationWeigher::weigh(dest, remote_message)
 					.map_err(|()| Error::<T>::UnweighableMessage)?;
 				Limited(remote_weight)
 			},
@@ -1278,14 +1281,14 @@ impl<T: Config> Pallet<T> {
 			Some(weight_limit) => weight_limit,
 			None => {
 				let fees = fees.clone();
-				let mut remote_message = Xcm(vec![
+				let remote_message = Xcm(vec![
 					ReceiveTeleportedAsset(assets.clone()),
 					ClearOrigin,
 					BuyExecution { fees, weight_limit: Limited(Weight::zero()) },
 					DepositAsset { assets: Wild(AllCounted(max_assets)), beneficiary },
 				]);
-				// use local weight for remote message and hope for the best.
-				let remote_weight = T::Weigher::weight(&mut remote_message)
+				// estimate remote_message weight
+				let remote_weight = T::DestinationWeigher::weigh(dest, remote_message)
 					.map_err(|()| Error::<T>::UnweighableMessage)?;
 				Limited(remote_weight)
 			},

xcm/pallet-xcm/src/mock.rs

@@ -31,8 +31,8 @@ use xcm_builder::{
 	AccountId32Aliases, AllowKnownQueryResponses, AllowSubscriptionsFrom,
 	AllowTopLevelPaidExecutionFrom, Case, ChildParachainAsNative, ChildParachainConvertsVia,
 	ChildSystemParachainAsSuperuser, CurrencyAdapter as XcmCurrencyAdapter, FixedRateOfFungible,
-	FixedWeightBounds, IsConcrete, SignedAccountId32AsNative, SignedToAccountId32,
-	SovereignSignedViaLocation, TakeWeightCredit,
+	FixedWeightBounds, IsConcrete, ProvideWeighableInstructions, SignedAccountId32AsNative,
+	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, UniversalWeigherAdapter,
 };
 use xcm_executor::XcmExecutor;
 
@@ -324,6 +324,13 @@ parameter_types! {
 	pub ReachableDest: Option<MultiLocation> = Some(Parachain(1000).into());
 }
 
+pub struct AdditionalDestinationInstructions;
+impl ProvideWeighableInstructions<()> for AdditionalDestinationInstructions {
+	fn provide_for(_dest: impl Into<MultiLocation>, _message: &Xcm<()>) -> Vec<Instruction<()>> {
+		sp_std::vec![SetTopic([13; 32])]
+	}
+}
+
 impl pallet_xcm::Config for Test {
 	type RuntimeEvent = RuntimeEvent;
 	type SendXcmOrigin = xcm_builder::EnsureXcmOrigin<RuntimeOrigin, LocalOriginToLocation>;
@@ -334,6 +341,10 @@ impl pallet_xcm::Config for Test {
 	type XcmTeleportFilter = Everything;
 	type XcmReserveTransferFilter = Everything;
 	type Weigher = FixedWeightBounds<BaseXcmWeight, RuntimeCall, MaxInstructions>;
+	type DestinationWeigher = UniversalWeigherAdapter<
+		FixedWeightBounds<BaseXcmWeight, (), MaxInstructions>,
+		AdditionalDestinationInstructions,
+	>;
 	type UniversalLocation = UniversalLocation;
 	type RuntimeOrigin = RuntimeOrigin;
 	type RuntimeCall = RuntimeCall;

xcm/pallet-xcm/src/tests.rs

@@ -378,7 +378,11 @@ fn teleport_assets_works() {
 				Xcm(vec![
 					ReceiveTeleportedAsset((Here, SEND_AMOUNT).into()),
 					ClearOrigin,
-					buy_limited_execution((Here, SEND_AMOUNT), Weight::from_parts(4000, 4000)),
+					buy_limited_execution(
+						(Here, SEND_AMOUNT),
+						// 4 instruction + AdditionalDestinationInstructions adds 1 instruction
+						Weight::from_parts(5000, 5000)
+					),
 					DepositAsset { assets: AllCounted(1).into(), beneficiary: dest },
 				]),
 			)]
@@ -511,7 +515,11 @@ fn reserve_transfer_assets_works() {
 				Xcm(vec![
 					ReserveAssetDeposited((Parent, SEND_AMOUNT).into()),
 					ClearOrigin,
-					buy_limited_execution((Parent, SEND_AMOUNT), Weight::from_parts(4000, 4000)),
+					buy_limited_execution(
+						(Parent, SEND_AMOUNT),
+						// 4 instruction + AdditionalDestinationInstructions adds 1 instruction
+						Weight::from_parts(5000, 5000)
+					),
 					DepositAsset { assets: AllCounted(1).into(), beneficiary: dest },
 				]),
 			)]

xcm/xcm-builder/src/lib.rs

@@ -79,7 +79,8 @@ pub use nonfungibles_adapter::{
 
 mod weight;
 pub use weight::{
-	FixedRateOfFungible, FixedWeightBounds, TakeRevenue, UsingComponents, WeightInfoBounds,
+	FixedRateOfFungible, FixedWeightBounds, ProvideWeighableInstructions, TakeRevenue,
+	UniversalWeigherAdapter, UsingComponents, WeightInfoBounds,
 };
 
 mod matches_token;

xcm/xcm-builder/src/weight.rs

@@ -24,10 +24,10 @@ use frame_support::{
 };
 use parity_scale_codec::Decode;
 use sp_runtime::traits::{SaturatedConversion, Saturating, Zero};
-use sp_std::{marker::PhantomData, result::Result};
+use sp_std::{marker::PhantomData, result::Result, vec::Vec};
 use xcm::latest::{prelude::*, Weight};
 use xcm_executor::{
-	traits::{WeightBounds, WeightTrader},
+	traits::{UniversalWeigher, WeightBounds, WeightTrader},
 	Assets,
 };
 
@@ -114,6 +114,37 @@ where
 	}
 }
 
+/// Adapter for `UniversalWeigher` which can estimate weights for XCM message,
+/// that is executed on destination with possibility to add additional instructions on the way (e.g. SetTopic, UniversalOrigin, ...).
+pub struct UniversalWeigherAdapter<Weigher, AdditionalInstructions>(
+	PhantomData<(Weigher, AdditionalInstructions)>,
+);
+impl<Weigher: WeightBounds<()>, AdditionalInstructions: ProvideWeighableInstructions<()>>
+	UniversalWeigher for UniversalWeigherAdapter<Weigher, AdditionalInstructions>
+{
+	fn weigh(dest: impl Into<MultiLocation>, mut message: Xcm<()>) -> Result<Weight, ()> {
+		message.0.extend(AdditionalInstructions::provide_for(dest, &message));
+		Weigher::weight(&mut message)
+	}
+}
+
+/// Function trait for generating instruction for (dest, message).
+pub trait ProvideWeighableInstructions<RuntimeCall> {
+	fn provide_for(
+		dest: impl Into<MultiLocation>,
+		message: &Xcm<RuntimeCall>,
+	) -> Vec<Instruction<RuntimeCall>>;
+}
+
+impl<RuntimeCall> ProvideWeighableInstructions<RuntimeCall> for () {
+	fn provide_for(
+		_dest: impl Into<MultiLocation>,
+		_message: &Xcm<RuntimeCall>,
+	) -> Vec<Instruction<RuntimeCall>> {
+		Vec::new()
+	}
+}
+
 /// Function trait for handling some revenue. Similar to a negative imbalance (credit) handler, but for a
 /// `MultiAsset`. Sensible implementations will deposit the asset in some known treasury or block-author account.
 pub trait TakeRevenue {