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/bridge-hubs/bridge-hub-kusama/src/lib.rs

@@ -26,6 +26,8 @@ mod weights;
 pub mod xcm_config;
 
 use cumulus_pallet_parachain_system::RelayNumberStrictlyIncreases;
+use cumulus_primitives_core::ParaId;
+use polkadot_runtime_common::xcm_sender::NoPriceForMessageDelivery;
 use sp_api::impl_runtime_apis;
 use sp_core::{crypto::KeyTypeId, OpaqueMetadata};
 use sp_runtime::{
@@ -75,7 +77,7 @@ use parachains_common::{
 };
 
 // XCM Imports
-use xcm::latest::prelude::BodyId;
+use xcm::latest::prelude::*;
 use xcm_executor::XcmExecutor;
 
 /// The address format for describing accounts.
@@ -314,7 +316,7 @@ impl cumulus_pallet_xcmp_queue::Config for Runtime {
 	type ControllerOrigin = RootOrFellows;
 	type ControllerOriginConverter = XcmOriginToTransactDispatchOrigin;
 	type WeightInfo = weights::cumulus_pallet_xcmp_queue::WeightInfo<Runtime>;
-	type PriceForSiblingDelivery = ();
+	type PriceForSiblingDelivery = NoPriceForMessageDelivery<ParaId>;
 }
 
 impl cumulus_pallet_dmp_queue::Config for Runtime {
@@ -671,9 +673,21 @@ impl_runtime_apis! {
 			use xcm::latest::prelude::*;
 			use xcm_config::KsmRelayLocation;
 
+			parameter_types! {
+				pub ExistentialDepositMultiAsset: Option<MultiAsset> = Some((
+					xcm_config::KsmRelayLocation::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(KsmRelayLocation::get())
 				}
@@ -714,6 +728,7 @@ 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/bridge-hubs/bridge-hub-kusama/src/xcm_config.rs

@@ -16,7 +16,8 @@
 
 use super::{
 	AccountId, AllPalletsWithSystem, Balances, ParachainInfo, ParachainSystem, PolkadotXcm,
-	Runtime, RuntimeCall, RuntimeEvent, RuntimeOrigin, WeightToFee, XcmpQueue,
+	Runtime, RuntimeCall, RuntimeEvent, RuntimeOrigin, TransactionByteFee, WeightToFee, XcmpQueue,
+	CENTS,
 };
 use frame_support::{
 	match_types, parameter_types,
@@ -26,6 +27,7 @@ use frame_system::EnsureRoot;
 use pallet_xcm::XcmPassthrough;
 use parachains_common::{impls::ToStakingPot, xcm_config::ConcreteAssetFromSystem};
 use polkadot_parachain_primitives::primitives::Sibling;
+use polkadot_runtime_common::xcm_sender::ExponentialPrice;
 use xcm::latest::prelude::*;
 use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
@@ -220,11 +222,21 @@ impl xcm_executor::Config for XcmConfig {
 /// Forms the basis for local origins sending/executing XCMs.
 pub type LocalOriginToLocation = SignedToAccountId32<RuntimeOrigin, AccountId, RelayNetwork>;
 
+parameter_types! {
+	/// The asset ID for the asset that we use to pay for message delivery fees.
+	pub FeeAssetId: AssetId = Concrete(KsmRelayLocation::get());
+	/// The base fee for the message delivery fees.
+	pub const BaseDeliveryFee: u128 = CENTS.saturating_mul(3);
+}
+
+pub type PriceForParentDelivery =
+	ExponentialPrice<FeeAssetId, BaseDeliveryFee, TransactionByteFee, ParachainSystem>;
+
 /// The means for routing XCM messages which are not for local execution into the right message
 /// queues.
 pub type XcmRouter = WithUniqueTopic<(
 	// 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,
 )>;

cumulus/parachains/runtimes/bridge-hubs/bridge-hub-polkadot/src/lib.rs

@@ -26,6 +26,8 @@ mod weights;
 pub mod xcm_config;
 
 use cumulus_pallet_parachain_system::RelayNumberStrictlyIncreases;
+use cumulus_primitives_core::ParaId;
+use polkadot_runtime_common::xcm_sender::NoPriceForMessageDelivery;
 use sp_api::impl_runtime_apis;
 use sp_core::{crypto::KeyTypeId, OpaqueMetadata};
 use sp_runtime::{
@@ -75,7 +77,7 @@ use parachains_common::{
 	HOURS, MAXIMUM_BLOCK_WEIGHT, NORMAL_DISPATCH_RATIO, SLOT_DURATION,
 };
 // XCM Imports
-use xcm::latest::prelude::BodyId;
+use xcm::latest::prelude::*;
 use xcm_executor::XcmExecutor;
 
 /// The address format for describing accounts.
@@ -314,7 +316,7 @@ impl cumulus_pallet_xcmp_queue::Config for Runtime {
 	type ControllerOrigin = RootOrFellows;
 	type ControllerOriginConverter = XcmOriginToTransactDispatchOrigin;
 	type WeightInfo = weights::cumulus_pallet_xcmp_queue::WeightInfo<Runtime>;
-	type PriceForSiblingDelivery = ();
+	type PriceForSiblingDelivery = NoPriceForMessageDelivery<ParaId>;
 }
 
 impl cumulus_pallet_dmp_queue::Config for Runtime {
@@ -671,9 +673,21 @@ impl_runtime_apis! {
 			use xcm::latest::prelude::*;
 			use xcm_config::DotRelayLocation;
 
+			parameter_types! {
+				pub ExistentialDepositMultiAsset: Option<MultiAsset> = Some((
+					xcm_config::DotRelayLocation::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(DotRelayLocation::get())
 				}
@@ -714,6 +728,7 @@ 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/bridge-hubs/bridge-hub-polkadot/src/xcm_config.rs

@@ -16,7 +16,8 @@
 
 use super::{
 	AccountId, AllPalletsWithSystem, Balances, ParachainInfo, ParachainSystem, PolkadotXcm,
-	Runtime, RuntimeCall, RuntimeEvent, RuntimeOrigin, WeightToFee, XcmpQueue,
+	Runtime, RuntimeCall, RuntimeEvent, RuntimeOrigin, TransactionByteFee, WeightToFee, XcmpQueue,
+	CENTS,
 };
 use frame_support::{
 	match_types, parameter_types,
@@ -26,6 +27,7 @@ use frame_system::EnsureRoot;
 use pallet_xcm::XcmPassthrough;
 use parachains_common::{impls::ToStakingPot, xcm_config::ConcreteAssetFromSystem};
 use polkadot_parachain_primitives::primitives::Sibling;
+use polkadot_runtime_common::xcm_sender::ExponentialPrice;
 use xcm::latest::prelude::*;
 use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
@@ -224,11 +226,21 @@ impl xcm_executor::Config for XcmConfig {
 /// Forms the basis for local origins sending/executing XCMs.
 pub type LocalOriginToLocation = SignedToAccountId32<RuntimeOrigin, AccountId, RelayNetwork>;
 
+parameter_types! {
+	/// The asset ID for the asset that we use to pay for message delivery fees.
+	pub FeeAssetId: AssetId = Concrete(DotRelayLocation::get());
+	/// The base fee for the message delivery fees.
+	pub const BaseDeliveryFee: u128 = CENTS.saturating_mul(3);
+}
+
+pub type PriceForParentDelivery =
+	ExponentialPrice<FeeAssetId, BaseDeliveryFee, TransactionByteFee, ParachainSystem>;
+
 /// The means for routing XCM messages which are not for local execution into the right message
 /// queues.
 pub type XcmRouter = WithUniqueTopic<(
 	// 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,
 )>;

cumulus/parachains/runtimes/bridge-hubs/bridge-hub-rococo/src/lib.rs

@@ -75,6 +75,7 @@ use bp_runtime::HeaderId;
 pub use sp_runtime::BuildStorage;
 
 use polkadot_runtime_common::{BlockHashCount, SlowAdjustingFeeUpdate};
+use xcm::latest::prelude::*;
 
 use weights::{BlockExecutionWeight, ExtrinsicBaseWeight, RocksDbWeight};
 
@@ -362,6 +363,20 @@ 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>;
@@ -371,7 +386,7 @@ impl cumulus_pallet_xcmp_queue::Config for Runtime {
 	type ControllerOrigin = EnsureRoot<AccountId>;
 	type ControllerOriginConverter = XcmOriginToTransactDispatchOrigin;
 	type WeightInfo = weights::cumulus_pallet_xcmp_queue::WeightInfo<Runtime>;
-	type PriceForSiblingDelivery = ();
+	type PriceForSiblingDelivery = PriceForSiblingParachainDelivery;
 }
 
 impl cumulus_pallet_dmp_queue::Config for Runtime {
@@ -1014,9 +1029,21 @@ impl_runtime_apis! {
 			use xcm::latest::prelude::*;
 			use xcm_config::TokenLocation;
 
+			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())
 				}
@@ -1057,6 +1084,7 @@ 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/bridge-hubs/bridge-hub-rococo/src/xcm_config.rs

@@ -15,10 +15,10 @@
 // along with Cumulus.  If not, see <http://www.gnu.org/licenses/>.
 
 use super::{
-	AccountId, AllPalletsWithSystem, Balances, BridgeGrandpaRococoInstance,
-	BridgeGrandpaWococoInstance, DeliveryRewardInBalance, ParachainInfo, ParachainSystem,
-	PolkadotXcm, RequiredStakeForStakeAndSlash, Runtime, RuntimeCall, RuntimeEvent, RuntimeFlavor,
-	RuntimeOrigin, WeightToFee, XcmpQueue,
+	AccountId, AllPalletsWithSystem, Balances, BaseDeliveryFee, BridgeGrandpaRococoInstance,
+	BridgeGrandpaWococoInstance, DeliveryRewardInBalance, FeeAssetId, ParachainInfo,
+	ParachainSystem, PolkadotXcm, RequiredStakeForStakeAndSlash, Runtime, RuntimeCall,
+	RuntimeEvent, RuntimeFlavor, RuntimeOrigin, TransactionByteFee, WeightToFee, XcmpQueue,
 };
 use crate::{
 	bridge_hub_rococo_config::ToBridgeHubWococoHaulBlobExporter,
@@ -30,9 +30,16 @@ use frame_support::{
 };
 use frame_system::EnsureRoot;
 use pallet_xcm::XcmPassthrough;
-use parachains_common::{impls::ToStakingPot, xcm_config::ConcreteAssetFromSystem};
+use parachains_common::{
+	impls::ToStakingPot,
+	xcm_config::{ConcreteAssetFromSystem, RelayOrOtherSystemParachains},
+	TREASURY_PALLET_ID,
+};
 use polkadot_parachain_primitives::primitives::Sibling;
+use polkadot_runtime_common::xcm_sender::ExponentialPrice;
+use rococo_runtime_constants::system_parachain::SystemParachains;
 use sp_core::Get;
+use sp_runtime::traits::AccountIdConversion;
 use xcm::latest::prelude::*;
 use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
@@ -41,6 +48,7 @@ use xcm_builder::{
 	ParentIsPreset, RelayChainAsNative, SiblingParachainAsNative, SiblingParachainConvertsVia,
 	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
 	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	XcmFeesToAccount,
 };
 use xcm_executor::{
 	traits::{ExportXcm, WithOriginFilter},
@@ -55,6 +63,7 @@ parameter_types! {
 		X2(GlobalConsensus(RelayNetwork::get()), Parachain(ParachainInfo::parachain_id().into()));
 	pub const MaxInstructions: u32 = 100;
 	pub const MaxAssetsIntoHolding: u32 = 64;
+	pub TreasuryAccount: Option<AccountId> = Some(TREASURY_PALLET_ID.into_account_truncating());
 }
 
 /// Adapter for resolving `NetworkId` based on `pub storage Flavor: RuntimeFlavor`.
@@ -253,7 +262,12 @@ impl xcm_executor::Config for XcmConfig {
 	type SubscriptionService = PolkadotXcm;
 	type PalletInstancesInfo = AllPalletsWithSystem;
 	type MaxAssetsIntoHolding = MaxAssetsIntoHolding;
-	type FeeManager = ();
+	type FeeManager = XcmFeesToAccount<
+		Self,
+		RelayOrOtherSystemParachains<SystemParachains, Runtime>,
+		AccountId,
+		TreasuryAccount,
+	>;
 	type MessageExporter = BridgeHubRococoOrBridgeHubWococoSwitchExporter;
 	type UniversalAliases = Nothing;
 	type CallDispatcher = WithOriginFilter<SafeCallFilter>;
@@ -261,6 +275,9 @@ impl xcm_executor::Config for XcmConfig {
 	type Aliasers = Nothing;
 }
 
+pub type PriceForParentDelivery =
+	ExponentialPrice<FeeAssetId, BaseDeliveryFee, TransactionByteFee, ParachainSystem>;
+
 /// Converts a local signed origin into an XCM multilocation.
 /// Forms the basis for local origins sending/executing XCMs.
 pub type LocalOriginToLocation = SignedToAccountId32<RuntimeOrigin, AccountId, RelayNetwork>;
@@ -269,7 +286,7 @@ pub type LocalOriginToLocation = SignedToAccountId32<RuntimeOrigin, AccountId, R
 /// queues.
 pub type XcmRouter = WithUniqueTopic<(
 	// 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,
 )>;

cumulus/parachains/runtimes/bridge-hubs/test-utils/src/test_cases.rs

@@ -186,7 +186,7 @@ pub fn handle_export_message_from_system_parachain_to_outbound_queue_works<
 					XcmConfig::AssetTransactor::deposit_asset(
 						&ed,
 						&sibling_parachain_location,
-						&XcmContext::with_message_id([0; 32]),
+						Some(&XcmContext::with_message_id([0; 32])),
 					)
 					.expect("deposited ed");
 				}
@@ -194,7 +194,7 @@ pub fn handle_export_message_from_system_parachain_to_outbound_queue_works<
 				XcmConfig::AssetTransactor::deposit_asset(
 					&fee,
 					&sibling_parachain_location,
-					&XcmContext::with_message_id([0; 32]),
+					Some(&XcmContext::with_message_id([0; 32])),
 				)
 				.expect("deposited fee");