Introduce XcmFeesToAccount fee manager (#1234)

Combination of paritytech/polkadot#7005, its addon PR
paritytech/polkadot#7585 and its companion paritytech/cumulus#2433.

This PR introduces a new XcmFeesToAccount struct which implements the
`FeeManager` trait, and assigns this struct as the `FeeManager` in the
XCM config for all runtimes.

The struct simply deposits all fees handled by the XCM executor to a
specified account. In all runtimes, the specified account is configured
as the treasury account.

XCM __delivery__ fees are now being introduced (unless the root origin
is sending a message to a system parachain on behalf of the originating
chain).

# Note for reviewers

Most file changes are tests that had to be modified to account for the
new fees.
Main changes are in:
- cumulus/pallets/xcmp-queue/src/lib.rs <- To make it track the delivery
fees exponential factor
- polkadot/xcm/xcm-builder/src/fee_handling.rs <- Added. Has the
FeeManager implementation
- All runtime xcm_config files <- To add the FeeManager to the XCM
configuration

# Important note

After this change, instructions that create and send a new XCM (Query*,
Report*, ExportMessage, InitiateReserveWithdraw, InitiateTeleport,
DepositReserveAsset, TransferReserveAsset, LockAsset and RequestUnlock)
will require the corresponding origin account in the origin register to
pay for transport delivery fees, and the onward message will fail to be
sent if the origin account does not have the required amount. This
delivery fee is on top of what we already collect as tx fees in
pallet-xcm and XCM BuyExecution fees!

Wallet UIs that want to expose the new delivery fee can do so using the
formula:

```
delivery_fee_factor * (base_fee + encoded_msg_len * per_byte_fee)
```

where the delivery fee factor can be obtained from the corresponding
pallet based on which transport you are using (UMP, HRMP or bridges),
the base fee is a constant, the encoded message length from the message
itself and the per byte fee is the same as the configured per byte fee
for txs (i.e. `TransactionByteFee`).

---------

Co-authored-by: Branislav Kontur <bkontur@gmail.com>
Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com>
Co-authored-by: Giles Cope <gilescope@gmail.com>
Co-authored-by: command-bot <>
Co-authored-by: Francisco Aguirre <franciscoaguirreperez@gmail.com>
Co-authored-by: Liam Aharon <liam.aharon@hotmail.com>
Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

cumulus/parachains/runtimes/assets/asset-hub-rococo/src/lib.rs

@@ -93,7 +93,7 @@ pub use sp_runtime::BuildStorage;
 // Polkadot imports
 use pallet_xcm::{EnsureXcm, IsVoiceOfBody};
 use polkadot_runtime_common::{BlockHashCount, SlowAdjustingFeeUpdate};
-use xcm::latest::BodyId;
+use xcm::latest::prelude::*;
 use xcm_executor::XcmExecutor;
 
 use crate::xcm_config::{
@@ -636,6 +636,20 @@ impl parachain_info::Config for Runtime {}
 
 impl cumulus_pallet_aura_ext::Config for Runtime {}
 
+parameter_types! {
+	/// The asset ID for the asset that we use to pay for message delivery fees.
+	pub FeeAssetId: AssetId = Concrete(xcm_config::TokenLocation::get());
+	/// The base fee for the message delivery fees.
+	pub const BaseDeliveryFee: u128 = CENTS.saturating_mul(3);
+}
+
+pub type PriceForSiblingParachainDelivery = polkadot_runtime_common::xcm_sender::ExponentialPrice<
+	FeeAssetId,
+	BaseDeliveryFee,
+	TransactionByteFee,
+	XcmpQueue,
+>;
+
 impl cumulus_pallet_xcmp_queue::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type XcmExecutor = XcmExecutor<XcmConfig>;
@@ -645,7 +659,7 @@ impl cumulus_pallet_xcmp_queue::Config for Runtime {
 	type ControllerOrigin = EnsureRoot<AccountId>;
 	type ControllerOriginConverter = xcm_config::XcmOriginToTransactDispatchOrigin;
 	type WeightInfo = weights::cumulus_pallet_xcmp_queue::WeightInfo<Runtime>;
-	type PriceForSiblingDelivery = ();
+	type PriceForSiblingDelivery = PriceForSiblingParachainDelivery;
 }
 
 impl cumulus_pallet_dmp_queue::Config for Runtime {
@@ -1315,9 +1329,21 @@ impl_runtime_apis! {
 			use xcm_config::{TokenLocation, MaxAssetsIntoHolding};
 			use pallet_xcm_benchmarks::asset_instance_from;
 
+			parameter_types! {
+				pub ExistentialDepositMultiAsset: Option<MultiAsset> = Some((
+					TokenLocation::get(),
+					ExistentialDeposit::get()
+				).into());
+			}
+
 			impl pallet_xcm_benchmarks::Config for Runtime {
 				type XcmConfig = xcm_config::XcmConfig;
 				type AccountIdConverter = xcm_config::LocationToAccountId;
+				type DeliveryHelper = cumulus_primitives_utility::ToParentDeliveryHelper<
+					XcmConfig,
+					ExistentialDepositMultiAsset,
+					xcm_config::PriceForParentDelivery,
+				>;
 				fn valid_destination() -> Result<MultiLocation, BenchmarkError> {
 					Ok(TokenLocation::get())
 				}
@@ -1373,6 +1399,7 @@ impl_runtime_apis! {
 			}
 
 			impl pallet_xcm_benchmarks::generic::Config for Runtime {
+				type TransactAsset = Balances;
 				type RuntimeCall = RuntimeCall;
 
 				fn worst_case_response() -> (u64, Response) {

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

@@ -14,10 +14,11 @@
 // limitations under the License.
 
 use super::{
-	AccountId, AllPalletsWithSystem, Assets, Authorship, Balance, Balances, ForeignAssets,
-	ForeignAssetsInstance, ParachainInfo, ParachainSystem, PolkadotXcm, PoolAssets, Runtime,
-	RuntimeCall, RuntimeEvent, RuntimeFlavor, RuntimeOrigin, ToRococoXcmRouter, ToWococoXcmRouter,
-	TransactionByteFee, TrustBackedAssetsInstance, WeightToFee, XcmpQueue,
+	AccountId, AllPalletsWithSystem, Assets, Authorship, Balance, Balances, BaseDeliveryFee,
+	FeeAssetId, ForeignAssets, ForeignAssetsInstance, ParachainInfo, ParachainSystem, PolkadotXcm,
+	PoolAssets, Runtime, RuntimeCall, RuntimeEvent, RuntimeFlavor, RuntimeOrigin,
+	ToRococoXcmRouter, ToWococoXcmRouter, TransactionByteFee, TrustBackedAssetsInstance,
+	WeightToFee, XcmpQueue,
 };
 use assets_common::{
 	local_and_foreign_assets::MatchesLocalAndForeignAssetsMultiLocation,
@@ -31,10 +32,17 @@ use frame_system::EnsureRoot;
 use pallet_xcm::XcmPassthrough;
 use parachains_common::{
 	impls::ToStakingPot,
-	xcm_config::{AssetFeeAsExistentialDepositMultiplier, ConcreteAssetFromSystem},
+	xcm_config::{
+		AssetFeeAsExistentialDepositMultiplier, ConcreteAssetFromSystem,
+		RelayOrOtherSystemParachains,
+	},
+	TREASURY_PALLET_ID,
 };
 use polkadot_parachain_primitives::primitives::Sibling;
-use sp_runtime::traits::ConvertInto;
+use polkadot_runtime_common::xcm_sender::ExponentialPrice;
+use rococo_runtime::Treasury as RococoTreasury;
+use rococo_runtime_constants::system_parachain::SystemParachains;
+use sp_runtime::traits::{AccountIdConversion, ConvertInto};
 use xcm::latest::prelude::*;
 use xcm_builder::{
 	AccountId32Aliases, AllAssets, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
@@ -46,6 +54,7 @@ use xcm_builder::{
 	SiblingParachainConvertsVia, SignedAccountId32AsNative, SignedToAccountId32,
 	SovereignSignedViaLocation, StartsWith, StartsWithExplicitGlobalConsensus, TakeWeightCredit,
 	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	XcmFeesToAccount,
 };
 use xcm_executor::{traits::WithOriginFilter, XcmExecutor};
 
@@ -67,6 +76,7 @@ parameter_types! {
 		PalletInstance(<PoolAssets as PalletInfoAccess>::index() as u8).into();
 	pub CheckingAccount: AccountId = PolkadotXcm::check_account();
 	pub const GovernanceLocation: MultiLocation = MultiLocation::parent();
+	pub TreasuryAccount: Option<AccountId> = Some(TREASURY_PALLET_ID.into_account_truncating());
 }
 
 /// Adapter for resolving `NetworkId` based on `pub storage Flavor: RuntimeFlavor`.
@@ -521,6 +531,23 @@ pub type ForeignAssetFeeAsExistentialDepositMultiplierFeeCharger =
 		ForeignAssetsInstance,
 	>;
 
+parameter_types! {
+	pub RelayTreasuryLocation: MultiLocation = (Parent, PalletInstance(<RococoTreasury as PalletInfoAccess>::index() as u8)).into();
+}
+
+pub struct RelayTreasury;
+impl Contains<MultiLocation> for RelayTreasury {
+	fn contains(location: &MultiLocation) -> bool {
+		let relay_treasury_location = RelayTreasuryLocation::get();
+		*location == relay_treasury_location
+	}
+}
+
+/// Locations that will not be charged fees in the executor,
+/// either execution or delivery.
+/// We only waive fees for system functions, which these locations represent.
+pub type WaivedLocations = (RelayOrOtherSystemParachains<SystemParachains, Runtime>, RelayTreasury);
+
 /// Cases where a remote origin is accepted as trusted Teleporter for a given asset:
 ///
 /// - ROC with the parent Relay Chain and sibling system parachains; and
@@ -588,8 +615,7 @@ impl xcm_executor::Config for XcmConfig {
 	type MaxAssetsIntoHolding = MaxAssetsIntoHolding;
 	type AssetLocker = ();
 	type AssetExchanger = ();
-	// TODO:check-parameter: change and assert in tests when (https://github.com/paritytech/polkadot-sdk/pull/1234) merged
-	type FeeManager = ();
+	type FeeManager = XcmFeesToAccount<Self, WaivedLocations, AccountId, TreasuryAccount>;
 	type MessageExporter = ();
 	type UniversalAliases =
 		(bridging::to_wococo::UniversalAliases, bridging::to_rococo::UniversalAliases);
@@ -602,10 +628,13 @@ impl xcm_executor::Config for XcmConfig {
 /// Forms the basis for local origins sending/executing XCMs.
 pub type LocalOriginToLocation = SignedToAccountId32<RuntimeOrigin, AccountId, RelayNetwork>;
 
+pub type PriceForParentDelivery =
+	ExponentialPrice<FeeAssetId, BaseDeliveryFee, TransactionByteFee, ParachainSystem>;
+
 /// For routing XCM messages which do not cross local consensus boundary.
 type LocalXcmRouter = (
 	// Two routers - use UMP to communicate with the relay chain:
-	cumulus_primitives_utility::ParentAsUmp<ParachainSystem, PolkadotXcm, ()>,
+	cumulus_primitives_utility::ParentAsUmp<ParachainSystem, PolkadotXcm, PriceForParentDelivery>,
 	// ..and XCMP to communicate with the sibling chains.
 	XcmpQueue,
 );