[xcm] Small enhancements for NetworkExportTable and xcm-builder (#1848)

## Summary

This PR introduces several enhancements.

The current implementation of `NetworkExportTable` lacks remote location
filtering support beyond `NetworkId` lookup. To provide more control and
granularity, it's essential to allow configuration for bridging to
different consensus `NetworkId` while restricting access e.g. to
particular remote parachains.

Additionally, the `StartsWith` and `Equals` and
`StartsWithExplicitGlobalConsensus` helper functions, which are in
active use, are moved to the `xcm-builder` and `frame_support` modules
for better code organization.

Adds a new `LocationWithAssetFilters` filter to enable location-based
and asset-related filtering. This filter is useful for configuring the
`pallet_xcm` filter for
[XcmTeleportFilter](https://github.com/paritytech/polkadot-sdk/blob/master/polkadot/xcm/pallet-xcm/src/lib.rs#L212)
and
[XcmReserveTransferFilter](https://github.com/paritytech/polkadot-sdk/blob/master/polkadot/xcm/pallet-xcm/src/lib.rs#L216)
to restrict specific assets.

Furthermore, the `BridgeMessage` fields are not accessible outside of
`xcm-builder`, limiting the ability to create custom logic dependent on
it.

---------

Co-authored-by: Francisco Aguirre <franciscoaguirreperez@gmail.com>

bridges/modules/xcm-bridge-hub-router/src/mock.rs

@@ -27,7 +27,7 @@ use sp_runtime::{
 	BuildStorage,
 };
 use xcm::prelude::*;
-use xcm_builder::NetworkExportTable;
+use xcm_builder::{NetworkExportTable, NetworkExportTableItem};
 
 pub type AccountId = u64;
 type Block = frame_system::mocking::MockBlock<TestRuntime>;
@@ -53,8 +53,15 @@ parameter_types! {
 	pub UniversalLocation: InteriorMultiLocation = X2(GlobalConsensus(ThisNetworkId::get()), Parachain(1000));
 	pub SiblingBridgeHubLocation: MultiLocation = ParentThen(X1(Parachain(1002))).into();
 	pub BridgeFeeAsset: AssetId = MultiLocation::parent().into();
-	pub BridgeTable: Vec<(NetworkId, MultiLocation, Option<MultiAsset>)>
-		= vec![(BridgedNetworkId::get(), SiblingBridgeHubLocation::get(), Some((BridgeFeeAsset::get(), BASE_FEE).into()))];
+	pub BridgeTable: Vec<NetworkExportTableItem>
+		= vec![
+			NetworkExportTableItem::new(
+				BridgedNetworkId::get(),
+				None,
+				SiblingBridgeHubLocation::get(),
+				Some((BridgeFeeAsset::get(), BASE_FEE).into())
+			)
+		];
 }
 
 impl frame_system::Config for TestRuntime {

cumulus/parachains/runtimes/assets/asset-hub-kusama/src/xcm_config.rs

@@ -21,9 +21,7 @@ use super::{
 use crate::ForeignAssets;
 use assets_common::{
 	local_and_foreign_assets::MatchesLocalAndForeignAssetsMultiLocation,
-	matching::{
-		FromSiblingParachain, IsForeignConcreteAsset, StartsWith, StartsWithExplicitGlobalConsensus,
-	},
+	matching::{FromSiblingParachain, IsForeignConcreteAsset},
 };
 use frame_support::{
 	match_types, parameter_types,
@@ -45,8 +43,8 @@ use xcm_builder::{
 	EnsureXcmOrigin, FungiblesAdapter, HashedDescription, IsConcrete, LocalMint, NoChecking,
 	ParentAsSuperuser, ParentIsPreset, RelayChainAsNative, SiblingParachainAsNative,
 	SiblingParachainConvertsVia, SignedAccountId32AsNative, SignedToAccountId32,
-	SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId, UsingComponents,
-	WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	SovereignSignedViaLocation, StartsWith, StartsWithExplicitGlobalConsensus, TakeWeightCredit,
+	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 };
 use xcm_executor::{traits::WithOriginFilter, XcmExecutor};
 

cumulus/parachains/runtimes/assets/asset-hub-polkadot/src/xcm_config.rs

@@ -18,9 +18,7 @@ use super::{
 	ParachainInfo, ParachainSystem, PolkadotXcm, Runtime, RuntimeCall, RuntimeEvent, RuntimeOrigin,
 	TrustBackedAssetsInstance, WeightToFee, XcmpQueue,
 };
-use assets_common::matching::{
-	FromSiblingParachain, IsForeignConcreteAsset, StartsWith, StartsWithExplicitGlobalConsensus,
-};
+use assets_common::matching::{FromSiblingParachain, IsForeignConcreteAsset};
 use frame_support::{
 	match_types, parameter_types,
 	traits::{ConstU32, Contains, Everything, Nothing, PalletInfoAccess},
@@ -41,8 +39,8 @@ use xcm_builder::{
 	EnsureXcmOrigin, FungiblesAdapter, HashedDescription, IsConcrete, LocalMint, NoChecking,
 	ParentAsSuperuser, ParentIsPreset, RelayChainAsNative, SiblingParachainAsNative,
 	SiblingParachainConvertsVia, SignedAccountId32AsNative, SignedToAccountId32,
-	SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId, UsingComponents,
-	WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	SovereignSignedViaLocation, StartsWith, StartsWithExplicitGlobalConsensus, TakeWeightCredit,
+	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 };
 use xcm_executor::{traits::WithOriginFilter, XcmExecutor};
 

cumulus/parachains/runtimes/assets/asset-hub-westend/src/xcm_config.rs

@@ -21,9 +21,7 @@ use super::{
 use crate::ForeignAssets;
 use assets_common::{
 	local_and_foreign_assets::MatchesLocalAndForeignAssetsMultiLocation,
-	matching::{
-		FromSiblingParachain, IsForeignConcreteAsset, StartsWith, StartsWithExplicitGlobalConsensus,
-	},
+	matching::{FromSiblingParachain, IsForeignConcreteAsset},
 };
 use frame_support::{
 	match_types, parameter_types,
@@ -45,8 +43,8 @@ use xcm_builder::{
 	EnsureXcmOrigin, FungiblesAdapter, HashedDescription, IsConcrete, LocalMint, NoChecking,
 	ParentAsSuperuser, ParentIsPreset, RelayChainAsNative, SiblingParachainAsNative,
 	SiblingParachainConvertsVia, SignedAccountId32AsNative, SignedToAccountId32,
-	SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId, UsingComponents,
-	WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	SovereignSignedViaLocation, StartsWith, StartsWithExplicitGlobalConsensus, TakeWeightCredit,
+	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 };
 use xcm_executor::{traits::WithOriginFilter, XcmExecutor};
 

cumulus/parachains/runtimes/assets/common/src/lib.rs

@@ -21,11 +21,11 @@ pub mod local_and_foreign_assets;
 pub mod matching;
 pub mod runtime_api;
 
-use crate::matching::{Equals, LocalMultiLocationPattern, ParentLocation, StartsWith};
-use frame_support::traits::EverythingBut;
+use crate::matching::{LocalMultiLocationPattern, ParentLocation};
+use frame_support::traits::{Equals, EverythingBut};
 use parachains_common::AssetIdForTrustBackedAssets;
 use xcm::prelude::MultiLocation;
-use xcm_builder::{AsPrefixedGeneralIndex, MatchedConvertedConcreteId};
+use xcm_builder::{AsPrefixedGeneralIndex, MatchedConvertedConcreteId, StartsWith};
 use xcm_executor::traits::{Identity, JustTry};
 
 /// `MultiLocation` vs `AssetIdForTrustBackedAssets` converter for `TrustBackedAssets`
@@ -96,9 +96,9 @@ pub type PoolAssetsConvertedConcreteId<PoolAssetsPalletLocation, Balance> =
 #[cfg(test)]
 mod tests {
 	use super::*;
-	use crate::matching::StartsWithExplicitGlobalConsensus;
 	use sp_runtime::traits::MaybeEquivalence;
 	use xcm::latest::prelude::*;
+	use xcm_builder::StartsWithExplicitGlobalConsensus;
 	use xcm_executor::traits::{Error as MatchError, MatchesFungibles};
 
 	#[test]

cumulus/parachains/runtimes/assets/common/src/local_and_foreign_assets.rs

@@ -407,13 +407,14 @@ where
 #[cfg(test)]
 mod tests {
 	use crate::{
-		local_and_foreign_assets::MultiLocationConverter, matching::StartsWith,
-		AssetIdForPoolAssetsConvert, AssetIdForTrustBackedAssetsConvert,
+		local_and_foreign_assets::MultiLocationConverter, AssetIdForPoolAssetsConvert,
+		AssetIdForTrustBackedAssetsConvert,
 	};
 	use frame_support::traits::EverythingBut;
 	use pallet_asset_conversion::{MultiAssetIdConversionResult, MultiAssetIdConverter};
 	use sp_runtime::traits::MaybeEquivalence;
 	use xcm::latest::prelude::*;
+	use xcm_builder::StartsWith;
 
 	#[test]
 	fn test_multi_location_converter_works() {

cumulus/parachains/runtimes/assets/common/src/matching.rs

@@ -14,38 +14,12 @@
 // limitations under the License.
 
 use cumulus_primitives_core::ParaId;
-use frame_support::{
-	pallet_prelude::Get,
-	traits::{Contains, ContainsPair},
-};
+use frame_support::{pallet_prelude::Get, traits::ContainsPair};
 use xcm::{
 	latest::prelude::{MultiAsset, MultiLocation},
 	prelude::*,
 };
 
-pub struct StartsWith<T>(sp_std::marker::PhantomData<T>);
-impl<Location: Get<MultiLocation>> Contains<MultiLocation> for StartsWith<Location> {
-	fn contains(t: &MultiLocation) -> bool {
-		t.starts_with(&Location::get())
-	}
-}
-
-pub struct Equals<T>(sp_std::marker::PhantomData<T>);
-impl<Location: Get<MultiLocation>> Contains<MultiLocation> for Equals<Location> {
-	fn contains(t: &MultiLocation) -> bool {
-		t == &Location::get()
-	}
-}
-
-pub struct StartsWithExplicitGlobalConsensus<T>(sp_std::marker::PhantomData<T>);
-impl<Network: Get<NetworkId>> Contains<MultiLocation>
-	for StartsWithExplicitGlobalConsensus<Network>
-{
-	fn contains(t: &MultiLocation) -> bool {
-		matches!(t.interior.global_consensus(), Ok(requested_network) if requested_network.eq(&Network::get()))
-	}
-}
-
 frame_support::parameter_types! {
 	pub LocalMultiLocationPattern: MultiLocation = MultiLocation::new(0, Here);
 	pub ParentLocation: MultiLocation = MultiLocation::parent();

polkadot/xcm/xcm-builder/src/filter_asset_location.rs

@@ -14,11 +14,12 @@
 // You should have received a copy of the GNU General Public License
 // along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
 
-//! Various implementations of `ContainsPair<MultiAsset, MultiLocation>`.
+//! Various implementations of `ContainsPair<MultiAsset, MultiLocation>` or
+//! `Contains<(MultiLocation, Vec<MultiAsset>)>`.
 
-use frame_support::traits::{ContainsPair, Get};
-use sp_std::marker::PhantomData;
-use xcm::latest::{AssetId::Concrete, MultiAsset, MultiAssetFilter, MultiLocation};
+use frame_support::traits::{Contains, ContainsPair, Get};
+use sp_std::{marker::PhantomData, vec::Vec};
+use xcm::latest::{AssetId::Concrete, MultiAsset, MultiAssetFilter, MultiLocation, WildMultiAsset};
 
 /// Accepts an asset iff it is a native asset.
 pub struct NativeAsset;
@@ -40,3 +41,171 @@ impl<T: Get<(MultiAssetFilter, MultiLocation)>> ContainsPair<MultiAsset, MultiLo
 		a.matches(asset) && &o == origin
 	}
 }
+
+/// Accepts a tuple `(location, assets)` if the `location` is contained in the `Contains`
+/// implementation of the given `Location` and if every asset from `assets` matches at least one of
+/// the `MultiAssetFilter` instances provided by the `Get` implementation of `AssetFilters`.
+pub struct LocationWithAssetFilters<Location, AssetFilters>(
+	sp_std::marker::PhantomData<(Location, AssetFilters)>,
+);
+impl<Location: Contains<MultiLocation>, AssetFilters: Get<Vec<MultiAssetFilter>>>
+	Contains<(MultiLocation, Vec<MultiAsset>)> for LocationWithAssetFilters<Location, AssetFilters>
+{
+	fn contains((location, assets): &(MultiLocation, Vec<MultiAsset>)) -> bool {
+		log::trace!(target: "xcm::contains", "LocationWithAssetFilters location: {:?}, assets: {:?}", location, assets);
+
+		// `location` must match the `Location` filter.
+		if !Location::contains(location) {
+			return false
+		}
+
+		// All `assets` must match at least one of the `AssetFilters`.
+		let filters = AssetFilters::get();
+		assets.iter().all(|asset| {
+			for filter in &filters {
+				if filter.matches(asset) {
+					return true
+				}
+			}
+			false
+		})
+	}
+}
+
+/// Implementation of `Get<Vec<MultiAssetFilter>>` which accepts every asset.
+/// (For example, it can be used with `LocationWithAssetFilters`).
+pub struct AllAssets;
+impl Get<Vec<MultiAssetFilter>> for AllAssets {
+	fn get() -> Vec<MultiAssetFilter> {
+		sp_std::vec![MultiAssetFilter::Wild(WildMultiAsset::All)]
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+	use frame_support::traits::Equals;
+	use xcm::latest::prelude::*;
+
+	#[test]
+	fn location_with_asset_filters_works() {
+		frame_support::parameter_types! {
+			pub ParaA: MultiLocation = MultiLocation::new(1, X1(Parachain(1001)));
+			pub ParaB: MultiLocation = MultiLocation::new(1, X1(Parachain(1002)));
+			pub ParaC: MultiLocation = MultiLocation::new(1, X1(Parachain(1003)));
+
+			pub AssetXLocation: MultiLocation = MultiLocation::new(1, X1(GeneralIndex(1111)));
+			pub AssetYLocation: MultiLocation = MultiLocation::new(1, X1(GeneralIndex(2222)));
+			pub AssetZLocation: MultiLocation = MultiLocation::new(1, X1(GeneralIndex(3333)));
+
+			pub OnlyAssetXOrAssetY: sp_std::vec::Vec<MultiAssetFilter> = sp_std::vec![
+				Wild(AllOf { fun: WildFungible, id: Concrete(AssetXLocation::get()) }),
+				Wild(AllOf { fun: WildFungible, id: Concrete(AssetYLocation::get()) }),
+			];
+			pub OnlyAssetZ: sp_std::vec::Vec<MultiAssetFilter> = sp_std::vec![
+				Wild(AllOf { fun: WildFungible, id: Concrete(AssetZLocation::get()) })
+			];
+		}
+
+		let test_data: Vec<(MultiLocation, Vec<MultiAsset>, bool)> = vec![
+			(ParaA::get(), vec![(AssetXLocation::get(), 1).into()], true),
+			(ParaA::get(), vec![(AssetYLocation::get(), 1).into()], true),
+			(ParaA::get(), vec![(AssetZLocation::get(), 1).into()], false),
+			(
+				ParaA::get(),
+				vec![(AssetXLocation::get(), 1).into(), (AssetYLocation::get(), 1).into()],
+				true,
+			),
+			(
+				ParaA::get(),
+				vec![(AssetXLocation::get(), 1).into(), (AssetZLocation::get(), 1).into()],
+				false,
+			),
+			(
+				ParaA::get(),
+				vec![(AssetYLocation::get(), 1).into(), (AssetZLocation::get(), 1).into()],
+				false,
+			),
+			(
+				ParaA::get(),
+				vec![
+					(AssetXLocation::get(), 1).into(),
+					(AssetYLocation::get(), 1).into(),
+					(AssetZLocation::get(), 1).into(),
+				],
+				false,
+			),
+			(ParaB::get(), vec![(AssetXLocation::get(), 1).into()], false),
+			(ParaB::get(), vec![(AssetYLocation::get(), 1).into()], false),
+			(ParaB::get(), vec![(AssetZLocation::get(), 1).into()], true),
+			(
+				ParaB::get(),
+				vec![(AssetXLocation::get(), 1).into(), (AssetYLocation::get(), 1).into()],
+				false,
+			),
+			(
+				ParaB::get(),
+				vec![(AssetXLocation::get(), 1).into(), (AssetZLocation::get(), 1).into()],
+				false,
+			),
+			(
+				ParaB::get(),
+				vec![(AssetYLocation::get(), 1).into(), (AssetZLocation::get(), 1).into()],
+				false,
+			),
+			(
+				ParaB::get(),
+				vec![
+					(AssetXLocation::get(), 1).into(),
+					(AssetYLocation::get(), 1).into(),
+					(AssetZLocation::get(), 1).into(),
+				],
+				false,
+			),
+			(ParaC::get(), vec![(AssetXLocation::get(), 1).into()], true),
+			(ParaC::get(), vec![(AssetYLocation::get(), 1).into()], true),
+			(ParaC::get(), vec![(AssetZLocation::get(), 1).into()], true),
+			(
+				ParaC::get(),
+				vec![(AssetXLocation::get(), 1).into(), (AssetYLocation::get(), 1).into()],
+				true,
+			),
+			(
+				ParaC::get(),
+				vec![(AssetXLocation::get(), 1).into(), (AssetZLocation::get(), 1).into()],
+				true,
+			),
+			(
+				ParaC::get(),
+				vec![(AssetYLocation::get(), 1).into(), (AssetZLocation::get(), 1).into()],
+				true,
+			),
+			(
+				ParaC::get(),
+				vec![
+					(AssetXLocation::get(), 1).into(),
+					(AssetYLocation::get(), 1).into(),
+					(AssetZLocation::get(), 1).into(),
+				],
+				true,
+			),
+		];
+
+		type Filter = (
+			// For ParaA accept only asset X and Y.
+			LocationWithAssetFilters<Equals<ParaA>, OnlyAssetXOrAssetY>,
+			// For ParaB accept only asset Z.
+			LocationWithAssetFilters<Equals<ParaB>, OnlyAssetZ>,
+			// For ParaC accept all assets.
+			LocationWithAssetFilters<Equals<ParaC>, AllAssets>,
+		);
+
+		for (location, assets, expected_result) in test_data {
+			assert_eq!(
+				Filter::contains(&(location, assets.clone())),
+				expected_result,
+				"expected_result: {expected_result} not matched for (location, assets): ({:?}, {:?})!", location, assets,
+			)
+		}
+	}
+}

polkadot/xcm/xcm-builder/src/lib.rs

@@ -83,6 +83,9 @@ pub use weight::{
 	FixedRateOfFungible, FixedWeightBounds, TakeRevenue, UsingComponents, WeightInfoBounds,
 };
 
+mod matches_location;
+pub use matches_location::{StartsWith, StartsWithExplicitGlobalConsensus};
+
 mod matches_token;
 pub use matches_token::{IsAbstract, IsConcrete};
 
@@ -90,7 +93,7 @@ mod matcher;
 pub use matcher::{CreateMatcher, MatchXcm, Matcher};
 
 mod filter_asset_location;
-pub use filter_asset_location::{Case, NativeAsset};
+pub use filter_asset_location::{AllAssets, Case, LocationWithAssetFilters, NativeAsset};
 
 mod routing;
 pub use routing::{WithTopicSource, WithUniqueTopic};
@@ -99,7 +102,7 @@ mod universal_exports;
 pub use universal_exports::{
 	ensure_is_remote, BridgeBlobDispatcher, BridgeMessage, DispatchBlob, DispatchBlobError,
 	ExporterFor, HaulBlob, HaulBlobError, HaulBlobExporter, NetworkExportTable,
-	SovereignPaidRemoteExporter, UnpaidLocalExporter, UnpaidRemoteExporter,
+	NetworkExportTableItem, SovereignPaidRemoteExporter, UnpaidLocalExporter, UnpaidRemoteExporter,
 };
 
 mod origin_aliases;

polkadot/xcm/xcm-builder/src/matches_location.rs

@@ -0,0 +1,50 @@
+// Copyright (C) Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Various implementations and utilities for matching and filtering `MultiLocation` and
+//! `InteriorMultiLocation` types.
+
+use frame_support::traits::{Contains, Get};
+use xcm::latest::{InteriorMultiLocation, MultiLocation, NetworkId};
+
+/// An implementation of `Contains` that checks for `MultiLocation` or
+/// `InteriorMultiLocation` if starts with the provided type `T`.
+pub struct StartsWith<T>(sp_std::marker::PhantomData<T>);
+impl<T: Get<MultiLocation>> Contains<MultiLocation> for StartsWith<T> {
+	fn contains(t: &MultiLocation) -> bool {
+		t.starts_with(&T::get())
+	}
+}
+impl<T: Get<InteriorMultiLocation>> Contains<InteriorMultiLocation> for StartsWith<T> {
+	fn contains(t: &InteriorMultiLocation) -> bool {
+		t.starts_with(&T::get())
+	}
+}
+
+/// An implementation of `Contains` that checks for `MultiLocation` or
+/// `InteriorMultiLocation` if starts with expected `GlobalConsensus(NetworkId)` provided as type
+/// `T`.
+pub struct StartsWithExplicitGlobalConsensus<T>(sp_std::marker::PhantomData<T>);
+impl<T: Get<NetworkId>> Contains<MultiLocation> for StartsWithExplicitGlobalConsensus<T> {
+	fn contains(location: &MultiLocation) -> bool {
+		matches!(location.interior.global_consensus(), Ok(requested_network) if requested_network.eq(&T::get()))
+	}
+}
+impl<T: Get<NetworkId>> Contains<InteriorMultiLocation> for StartsWithExplicitGlobalConsensus<T> {
+	fn contains(location: &InteriorMultiLocation) -> bool {
+		matches!(location.global_consensus(), Ok(requested_network) if requested_network.eq(&T::get()))
+	}
+}

polkadot/xcm/xcm-builder/src/tests/bridging/paid_remote_relay_relay.rs

@@ -27,8 +27,14 @@ parameter_types! {
 	pub UniversalLocation: Junctions = X2(GlobalConsensus(Local::get()), Parachain(100));
 	pub RelayUniversalLocation: Junctions = X1(GlobalConsensus(Local::get()));
 	pub RemoteUniversalLocation: Junctions = X1(GlobalConsensus(Remote::get()));
-	pub BridgeTable: Vec<(NetworkId, MultiLocation, Option<MultiAsset>)>
-		= vec![(Remote::get(), MultiLocation::parent(), Some((Parent, 200u128 + if UsingTopic::get() { 20 } else { 0 }).into()))];
+	pub BridgeTable: Vec<NetworkExportTableItem> = vec![
+		NetworkExportTableItem::new(
+			Remote::get(),
+			None,
+			MultiLocation::parent(),
+			Some((Parent, 200u128 + if UsingTopic::get() { 20 } else { 0 }).into())
+		)
+	];
 	// ^^^ 100 to use the bridge (export) and 100 for the remote execution weight (5 instructions
 	//     x (10 + 10) weight each).
 }

polkadot/xcm/xcm-builder/src/tests/bridging/remote_para_para.rs

@@ -24,8 +24,14 @@ parameter_types! {
 	pub UniversalLocation: Junctions = X2(GlobalConsensus(Local::get()), Parachain(1000));
 	pub ParaBridgeUniversalLocation: Junctions = X2(GlobalConsensus(Local::get()), Parachain(1));
 	pub RemoteParaBridgeUniversalLocation: Junctions = X2(GlobalConsensus(Remote::get()), Parachain(1));
-	pub BridgeTable: Vec<(NetworkId, MultiLocation, Option<MultiAsset>)>
-		= vec![(Remote::get(), (Parent, Parachain(1)).into(), None)];
+	pub BridgeTable: Vec<NetworkExportTableItem> = vec![
+		NetworkExportTableItem::new(
+			Remote::get(),
+			None,
+			(Parent, Parachain(1)).into(),
+			None
+		)
+	];
 }
 type TheBridge = TestBridge<
 	BridgeBlobDispatcher<TestRemoteIncomingRouter, RemoteParaBridgeUniversalLocation, ()>,

polkadot/xcm/xcm-builder/src/tests/bridging/remote_para_para_via_relay.rs

@@ -24,8 +24,14 @@ parameter_types! {
 	pub UniversalLocation: Junctions = X1(GlobalConsensus(Local::get()));
 	pub ParaBridgeUniversalLocation: Junctions = X2(GlobalConsensus(Local::get()), Parachain(1));
 	pub RemoteParaBridgeUniversalLocation: Junctions = X2(GlobalConsensus(Remote::get()), Parachain(1));
-	pub BridgeTable: Vec<(NetworkId, MultiLocation, Option<MultiAsset>)>
-		= vec![(Remote::get(), Parachain(1).into(), None)];
+	pub BridgeTable: Vec<NetworkExportTableItem> = vec![
+		NetworkExportTableItem::new(
+			Remote::get(),
+			None,
+			Parachain(1).into(),
+			None
+		)
+	];
 }
 type TheBridge = TestBridge<
 	BridgeBlobDispatcher<TestRemoteIncomingRouter, RemoteParaBridgeUniversalLocation, ()>,

polkadot/xcm/xcm-builder/src/tests/bridging/remote_relay_relay.rs

@@ -24,8 +24,14 @@ parameter_types! {
 	pub UniversalLocation: Junctions = X2(GlobalConsensus(Local::get()), Parachain(1000));
 	pub RelayUniversalLocation: Junctions = X1(GlobalConsensus(Local::get()));
 	pub RemoteUniversalLocation: Junctions = X1(GlobalConsensus(Remote::get()));
-	pub BridgeTable: Vec<(NetworkId, MultiLocation, Option<MultiAsset>)>
-		= vec![(Remote::get(), MultiLocation::parent(), None)];
+	pub BridgeTable: Vec<NetworkExportTableItem> = vec![
+		NetworkExportTableItem::new(
+			Remote::get(),
+			None,
+			MultiLocation::parent(),
+			None
+		)
+	];
 }
 type TheBridge =
 	TestBridge<BridgeBlobDispatcher<TestRemoteIncomingRouter, RemoteUniversalLocation, ()>>;

polkadot/xcm/xcm-builder/src/universal_exports.rs

@@ -117,16 +117,54 @@ impl ExporterFor for Tuple {
 	}
 }
 
+/// Configuration item representing a single exporter in the `NetworkExportTable`.
+pub struct NetworkExportTableItem {
+	/// Supported remote network.
+	pub remote_network: NetworkId,
+	/// Remote location filter.
+	/// If `Some`, the requested remote location must be equal to one of the items in the vector.
+	/// These are locations in the remote network.
+	/// If `None`, then the check is skipped.
+	pub remote_location_filter: Option<Vec<InteriorMultiLocation>>,
+	/// Locally-routable bridge with bridging capabilities to the `remote_network` and
+	/// `remote_location`. See [`ExporterFor`] for more details.
+	pub bridge: MultiLocation,
+	/// The local payment.
+	/// See [`ExporterFor`] for more details.
+	pub payment: Option<MultiAsset>,
+}
+
+impl NetworkExportTableItem {
+	pub fn new(
+		remote_network: NetworkId,
+		remote_location_filter: Option<Vec<InteriorMultiLocation>>,
+		bridge: MultiLocation,
+		payment: Option<MultiAsset>,
+	) -> Self {
+		Self { remote_network, remote_location_filter, bridge, payment }
+	}
+}
+
+/// An adapter for the implementation of `ExporterFor`, which attempts to find the
+/// `(bridge_location, payment)` for the requested `network` and `remote_location` in the provided
+/// `T` table containing various exporters.
 pub struct NetworkExportTable<T>(sp_std::marker::PhantomData<T>);
-impl<T: Get<Vec<(NetworkId, MultiLocation, Option<MultiAsset>)>>> ExporterFor
-	for NetworkExportTable<T>
-{
+impl<T: Get<Vec<NetworkExportTableItem>>> ExporterFor for NetworkExportTable<T> {
 	fn exporter_for(
 		network: &NetworkId,
-		_: &InteriorMultiLocation,
+		remote_location: &InteriorMultiLocation,
 		_: &Xcm<()>,
 	) -> Option<(MultiLocation, Option<MultiAsset>)> {
-		T::get().into_iter().find(|(ref j, ..)| j == network).map(|(_, l, p)| (l, p))
+		T::get()
+			.into_iter()
+			.find(|item| {
+				&item.remote_network == network &&
+					item.remote_location_filter
+						.as_ref()
+						.map(|filters| filters.iter().any(|filter| filter == remote_location))
+						.unwrap_or(true)
+			})
+			.map(|item| (item.bridge, item.payment))
 	}
 }
 
@@ -329,8 +367,8 @@ pub struct BridgeMessage {
 	/// The message destination as a *Universal Location*. This means it begins with a
 	/// `GlobalConsensus` junction describing the network under which global consensus happens.
 	/// If this does not match our global consensus then it's a fatal error.
-	universal_dest: VersionedInteriorMultiLocation,
-	message: VersionedXcm<()>,
+	pub universal_dest: VersionedInteriorMultiLocation,
+	pub message: VersionedXcm<()>,
 }
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
@@ -504,7 +542,7 @@ mod tests {
 			pub UniversalLocation: InteriorMultiLocation = X2(GlobalConsensus(Local::get()), Parachain(1234));
 			pub DifferentRemote: NetworkId = ByGenesis([22; 32]);
 			// no routers
-			pub BridgeTable: Vec<(NetworkId, MultiLocation, Option<MultiAsset>)> = vec![];
+			pub BridgeTable: Vec<NetworkExportTableItem> = vec![];
 		}
 
 		// check with local destination (should be remote)
@@ -539,4 +577,74 @@ mod tests {
 			>,
 		>(remote_dest, |result| assert_eq!(Err(NotApplicable), result));
 	}
+
+	#[test]
+	fn network_export_table_works() {
+		frame_support::parameter_types! {
+			pub NetworkA: NetworkId = ByGenesis([0; 32]);
+			pub Parachain1000InNetworkA: InteriorMultiLocation = X1(Parachain(1000));
+			pub Parachain2000InNetworkA: InteriorMultiLocation = X1(Parachain(2000));
+
+			pub NetworkB: NetworkId = ByGenesis([1; 32]);
+
+			pub BridgeToALocation: MultiLocation = MultiLocation::new(1, X1(Parachain(1234)));
+			pub BridgeToBLocation: MultiLocation = MultiLocation::new(1, X1(Parachain(4321)));
+
+			pub PaymentForNetworkAAndParachain2000: MultiAsset = (MultiLocation::parent(), 150).into();
+
+			pub BridgeTable: sp_std::vec::Vec<NetworkExportTableItem> = sp_std::vec![
+				// NetworkA allows `Parachain(1000)` as remote location WITHOUT payment.
+				NetworkExportTableItem::new(
+					NetworkA::get(),
+					Some(vec![Parachain1000InNetworkA::get()]),
+					BridgeToALocation::get(),
+					None
+				),
+				// NetworkA allows `Parachain(2000)` as remote location WITH payment.
+				NetworkExportTableItem::new(
+					NetworkA::get(),
+					Some(vec![Parachain2000InNetworkA::get()]),
+					BridgeToALocation::get(),
+					Some(PaymentForNetworkAAndParachain2000::get())
+				),
+				// NetworkB allows all remote location.
+				NetworkExportTableItem::new(
+					NetworkB::get(),
+					None,
+					BridgeToBLocation::get(),
+					None
+				)
+			];
+		}
+
+		let test_data = vec![
+			(NetworkA::get(), X1(Parachain(1000)), Some((BridgeToALocation::get(), None))),
+			(NetworkA::get(), X2(Parachain(1000), GeneralIndex(1)), None),
+			(
+				NetworkA::get(),
+				X1(Parachain(2000)),
+				Some((BridgeToALocation::get(), Some(PaymentForNetworkAAndParachain2000::get()))),
+			),
+			(NetworkA::get(), X2(Parachain(2000), GeneralIndex(1)), None),
+			(NetworkA::get(), X1(Parachain(3000)), None),
+			(NetworkB::get(), X1(Parachain(1000)), Some((BridgeToBLocation::get(), None))),
+			(NetworkB::get(), X1(Parachain(2000)), Some((BridgeToBLocation::get(), None))),
+			(NetworkB::get(), X1(Parachain(3000)), Some((BridgeToBLocation::get(), None))),
+		];
+
+		for (network, remote_location, expected_result) in test_data {
+			assert_eq!(
+				NetworkExportTable::<BridgeTable>::exporter_for(
+					&network,
+					&remote_location,
+					&Xcm::default()
+				),
+				expected_result,
+				"expected_result: {:?} not matched for network: {:?} and remote_location: {:?}",
+				expected_result,
+				network,
+				remote_location,
+			)
+		}
+	}
 }

substrate/frame/support/src/traits.rs

@@ -34,7 +34,7 @@ mod members;
 #[allow(deprecated)]
 pub use members::{AllowAll, DenyAll, Filter};
 pub use members::{
-	AsContains, ChangeMembers, Contains, ContainsLengthBound, ContainsPair, Everything,
+	AsContains, ChangeMembers, Contains, ContainsLengthBound, ContainsPair, Equals, Everything,
 	EverythingBut, FromContainsPair, InitializeMembers, InsideBoth, IsInVec, Nothing,
 	RankedMembers, SortedMembers, TheseExcept,
 };

substrate/frame/support/src/traits/members.rs

@@ -137,6 +137,14 @@ impl<A, B, These: ContainsPair<A, B>, Those: ContainsPair<A, B>> ContainsPair<A,
 	}
 }
 
+/// An implementation of [`Contains`] which contains only equal members to `T`.
+pub struct Equals<T>(PhantomData<T>);
+impl<X: PartialEq, T: super::Get<X>> Contains<X> for Equals<T> {
+	fn contains(t: &X) -> bool {
+		t == &T::get()
+	}
+}
+
 /// Create a type which implements the `Contains` trait for a particular type with syntax similar
 /// to `matches!`.
 #[macro_export]