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/contracts/contracts-rococo/Cargo.toml

@@ -54,13 +54,14 @@ pallet-contracts = { path = "../../../../../substrate/frame/contracts", default-
 pallet-contracts-primitives = { path = "../../../../../substrate/frame/contracts/primitives", default-features = false}
 
 # Polkadot
-pallet-xcm = { path = "../../../../../polkadot/xcm/pallet-xcm", default-features = false}
-polkadot-core-primitives = { path = "../../../../../polkadot/core-primitives", default-features = false}
-polkadot-parachain-primitives = { path = "../../../../../polkadot/parachain", default-features = false}
-polkadot-runtime-common = { path = "../../../../../polkadot/runtime/common", default-features = false}
-xcm = { package = "staging-xcm", path = "../../../../../polkadot/xcm", default-features = false}
-xcm-builder = { package = "staging-xcm-builder", path = "../../../../../polkadot/xcm/xcm-builder", default-features = false}
-xcm-executor = { package = "staging-xcm-executor", path = "../../../../../polkadot/xcm/xcm-executor", default-features = false}
+pallet-xcm = { path = "../../../../../polkadot/xcm/pallet-xcm", default-features = false }
+polkadot-core-primitives = { path = "../../../../../polkadot/core-primitives", default-features = false }
+polkadot-parachain-primitives = { path = "../../../../../polkadot/parachain", default-features = false }
+polkadot-runtime-common = { path = "../../../../../polkadot/runtime/common", default-features = false }
+rococo-runtime-constants = { path = "../../../../../polkadot/runtime/rococo/constants", default-features = false }
+xcm = { package = "staging-xcm", path = "../../../../../polkadot/xcm", default-features = false }
+xcm-builder = { package = "staging-xcm-builder", path = "../../../../../polkadot/xcm/xcm-builder", default-features = false }
+xcm-executor = { package = "staging-xcm-executor", path = "../../../../../polkadot/xcm/xcm-executor", default-features = false }
 
 # Cumulus
 cumulus-pallet-aura-ext = { path = "../../../../pallets/aura-ext", default-features = false }
@@ -115,6 +116,7 @@ std = [
 	"polkadot-core-primitives/std",
 	"polkadot-parachain-primitives/std",
 	"polkadot-runtime-common/std",
+	"rococo-runtime-constants/std",
 	"scale-info/std",
 	"sp-api/std",
 	"sp-block-builder/std",

cumulus/parachains/runtimes/contracts/contracts-rococo/src/lib.rs

@@ -224,13 +224,17 @@ impl pallet_balances::Config for Runtime {
 	type MaxFreezes = ConstU32<0>;
 }
 
+parameter_types! {
+	pub const TransactionByteFee: Balance = MILLICENTS;
+}
+
 impl pallet_transaction_payment::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type OnChargeTransaction =
 		pallet_transaction_payment::CurrencyAdapter<Balances, DealWithFees<Runtime>>;
 	type WeightToFee = WeightToFee;
 	/// Relay Chain `TransactionByteFee` / 10
-	type LengthToFee = ConstantMultiplier<Balance, ConstU128<MILLICENTS>>;
+	type LengthToFee = ConstantMultiplier<Balance, TransactionByteFee>;
 	type FeeMultiplierUpdate = SlowAdjustingFeeUpdate<Self>;
 	type OperationalFeeMultiplier = ConstU8<5>;
 }

cumulus/parachains/runtimes/contracts/contracts-rococo/src/xcm_config.rs

@@ -15,8 +15,9 @@
 
 use super::{
 	AccountId, AllPalletsWithSystem, Balances, ParachainInfo, ParachainSystem, PolkadotXcm,
-	Runtime, RuntimeCall, RuntimeEvent, RuntimeOrigin, WeightToFee, XcmpQueue,
+	Runtime, RuntimeCall, RuntimeEvent, RuntimeOrigin, TransactionByteFee, WeightToFee, XcmpQueue,
 };
+use crate::common::rococo::currency::CENTS;
 use frame_support::{
 	match_types, parameter_types,
 	traits::{ConstU32, EitherOfDiverse, Everything, Nothing},
@@ -24,8 +25,14 @@ use frame_support::{
 };
 use frame_system::EnsureRoot;
 use pallet_xcm::{EnsureXcm, IsMajorityOfBody, XcmPassthrough};
-use parachains_common::xcm_config::ConcreteAssetFromSystem;
+use parachains_common::{
+	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_runtime::traits::AccountIdConversion;
 use xcm::latest::prelude::*;
 use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
@@ -34,7 +41,7 @@ use xcm_builder::{
 	NativeAsset, ParentAsSuperuser, ParentIsPreset, RelayChainAsNative, SiblingParachainAsNative,
 	SiblingParachainConvertsVia, SignedAccountId32AsNative, SignedToAccountId32,
 	SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId, UsingComponents,
-	WithComputedOrigin, WithUniqueTopic,
+	WithComputedOrigin, WithUniqueTopic, XcmFeesToAccount,
 };
 use xcm_executor::XcmExecutor;
 
@@ -44,7 +51,7 @@ parameter_types! {
 	pub RelayChainOrigin: RuntimeOrigin = cumulus_pallet_xcm::Origin::Relay.into();
 	pub UniversalLocation: InteriorMultiLocation = Parachain(ParachainInfo::parachain_id().into()).into();
 	pub const ExecutiveBody: BodyId = BodyId::Executive;
-	pub CheckingAccount: AccountId = PolkadotXcm::check_account();
+	pub TreasuryAccount: Option<AccountId> = Some(TREASURY_PALLET_ID.into_account_truncating());
 }
 
 /// We allow root and the Relay Chain council to execute privileged collator selection operations.
@@ -167,7 +174,12 @@ impl xcm_executor::Config for XcmConfig {
 	type MaxAssetsIntoHolding = ConstU32<8>;
 	type AssetLocker = ();
 	type AssetExchanger = ();
-	type FeeManager = ();
+	type FeeManager = XcmFeesToAccount<
+		Self,
+		RelayOrOtherSystemParachains<SystemParachains, Runtime>,
+		AccountId,
+		TreasuryAccount,
+	>;
 	type MessageExporter = ();
 	type UniversalAliases = Nothing;
 	type CallDispatcher = RuntimeCall;
@@ -179,11 +191,14 @@ 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>;
+
 /// 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,
 )>;
@@ -231,6 +246,20 @@ impl cumulus_pallet_xcm::Config for Runtime {
 	type XcmExecutor = XcmExecutor<XcmConfig>;
 }
 
+parameter_types! {
+	/// The asset ID for the asset that we use to pay for message delivery fees.
+	pub FeeAssetId: AssetId = Concrete(RelayLocation::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>;
@@ -243,7 +272,7 @@ impl cumulus_pallet_xcmp_queue::Config for Runtime {
 	>;
 	type ControllerOriginConverter = XcmOriginToTransactDispatchOrigin;
 	type WeightInfo = cumulus_pallet_xcmp_queue::weights::SubstrateWeight<Runtime>;
-	type PriceForSiblingDelivery = ();
+	type PriceForSiblingDelivery = PriceForSiblingParachainDelivery;
 }
 
 impl cumulus_pallet_dmp_queue::Config for Runtime {