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>
2026-06-13 03:31:10 +00:00 · 2023-10-18 23:22:25 +08:00
parent 1cf7d3aafa
commit 3dece311be
99 changed files with 2229 additions and 468 deletions
@@ -31,38 +31,63 @@ use SendError::*;

 /// Simple value-bearing trait for determining/expressing the assets required to be paid for a
 /// messages to be delivered to a parachain.
-pub trait PriceForParachainDelivery {
+pub trait PriceForMessageDelivery {
+	/// Type used for charging different prices to different destinations
+	type Id;
 	/// Return the assets required to deliver `message` to the given `para` destination.
-	fn price_for_parachain_delivery(para: ParaId, message: &Xcm<()>) -> MultiAssets;
+	fn price_for_delivery(id: Self::Id, message: &Xcm<()>) -> MultiAssets;
 }
-impl PriceForParachainDelivery for () {
-	fn price_for_parachain_delivery(_: ParaId, _: &Xcm<()>) -> MultiAssets {
+impl PriceForMessageDelivery for () {
+	type Id = ();
+
+	fn price_for_delivery(_: Self::Id, _: &Xcm<()>) -> MultiAssets {
 		MultiAssets::new()
 	}
 }

-/// Implementation of `PriceForParachainDelivery` which returns a fixed price.
+pub struct NoPriceForMessageDelivery<Id>(PhantomData<Id>);
+impl<Id> PriceForMessageDelivery for NoPriceForMessageDelivery<Id> {
+	type Id = Id;
+
+	fn price_for_delivery(_: Self::Id, _: &Xcm<()>) -> MultiAssets {
+		MultiAssets::new()
+	}
+}
+
+/// Implementation of [`PriceForMessageDelivery`] which returns a fixed price.
 pub struct ConstantPrice<T>(sp_std::marker::PhantomData<T>);
-impl<T: Get<MultiAssets>> PriceForParachainDelivery for ConstantPrice<T> {
-	fn price_for_parachain_delivery(_: ParaId, _: &Xcm<()>) -> MultiAssets {
+impl<T: Get<MultiAssets>> PriceForMessageDelivery for ConstantPrice<T> {
+	type Id = ();
+
+	fn price_for_delivery(_: Self::Id, _: &Xcm<()>) -> MultiAssets {
 		T::get()
 	}
 }

-/// Implementation of `PriceForParachainDelivery` which returns an exponentially increasing price.
-/// The `A` type parameter is used to denote the asset ID that will be used for paying the delivery
-/// fee.
-///
+/// Implementation of [`PriceForMessageDelivery`] which returns an exponentially increasing price.
 /// The formula for the fee is based on the sum of a base fee plus a message length fee, multiplied
-/// by a specified factor. In mathematical form, it is `F * (B + encoded_msg_len * M)`.
+/// by a specified factor. In mathematical form:
+///
+/// `F * (B + encoded_msg_len * M)`
+///
+/// Thus, if F = 1 and M = 0, this type is equivalent to [`ConstantPrice<B>`].
+///
+/// The type parameters are understood as follows:
+///
+/// - `A`: Used to denote the asset ID that will be used for paying the delivery fee.
+/// - `B`: The base fee to pay for message delivery.
+/// - `M`: The fee to pay for each and every byte of the message after encoding it.
+/// - `F`: A fee factor multiplier. It can be understood as the exponent term in the formula.
 pub struct ExponentialPrice<A, B, M, F>(sp_std::marker::PhantomData<(A, B, M, F)>);
-impl<A: Get<AssetId>, B: Get<u128>, M: Get<u128>, F: FeeTracker> PriceForParachainDelivery
+impl<A: Get<AssetId>, B: Get<u128>, M: Get<u128>, F: FeeTracker> PriceForMessageDelivery
 	for ExponentialPrice<A, B, M, F>
 {
-	fn price_for_parachain_delivery(para: ParaId, msg: &Xcm<()>) -> MultiAssets {
+	type Id = F::Id;
+
+	fn price_for_delivery(id: Self::Id, msg: &Xcm<()>) -> MultiAssets {
 		let msg_fee = (msg.encoded_size() as u128).saturating_mul(M::get());
 		let fee_sum = B::get().saturating_add(msg_fee);
-		let amount = F::get_fee_factor(para).saturating_mul_int(fee_sum);
+		let amount = F::get_fee_factor(id).saturating_mul_int(fee_sum);
 		(A::get(), amount).into()
 	}
 }
@@ -70,8 +95,10 @@ impl<A: Get<AssetId>, B: Get<u128>, M: Get<u128>, F: FeeTracker> PriceForParacha
 /// XCM sender for relay chain. It only sends downward message.
 pub struct ChildParachainRouter<T, W, P>(PhantomData<(T, W, P)>);

-impl<T: configuration::Config + dmp::Config, W: xcm::WrapVersion, P: PriceForParachainDelivery>
-	SendXcm for ChildParachainRouter<T, W, P>
+impl<T: configuration::Config + dmp::Config, W: xcm::WrapVersion, P> SendXcm
+	for ChildParachainRouter<T, W, P>
+where
+	P: PriceForMessageDelivery<Id = ParaId>,
 {
 	type Ticket = (HostConfiguration<BlockNumberFor<T>>, ParaId, Vec<u8>);

@@ -91,7 +118,7 @@ impl<T: configuration::Config + dmp::Config, W: xcm::WrapVersion, P: PriceForPar
 		let xcm = msg.take().ok_or(MissingArgument)?;
 		let config = <configuration::Pallet<T>>::config();
 		let para = id.into();
-		let price = P::price_for_parachain_delivery(para, &xcm);
+		let price = P::price_for_delivery(para, &xcm);
 		let blob = W::wrap_version(&d, xcm).map_err(|()| DestinationUnsupported)?.encode();
 		<dmp::Pallet<T>>::can_queue_downward_message(&config, &para, &blob)
 			.map_err(Into::<SendError>::into)?;
@@ -109,6 +136,94 @@ impl<T: configuration::Config + dmp::Config, W: xcm::WrapVersion, P: PriceForPar
 	}
 }

+/// Implementation of `pallet_xcm_benchmarks::EnsureDelivery` which helps to ensure delivery to the
+/// `ParaId` parachain (sibling or child). Deposits existential deposit for origin (if needed).
+/// Deposits estimated fee to the origin account (if needed).
+/// Allows to trigger additional logic for specific `ParaId` (e.g. open HRMP channel) (if neeeded).
+#[cfg(feature = "runtime-benchmarks")]
+pub struct ToParachainDeliveryHelper<
+	XcmConfig,
+	ExistentialDeposit,
+	PriceForDelivery,
+	ParaId,
+	ToParaIdHelper,
+>(
+	sp_std::marker::PhantomData<(
+		XcmConfig,
+		ExistentialDeposit,
+		PriceForDelivery,
+		ParaId,
+		ToParaIdHelper,
+	)>,
+);
+
+#[cfg(feature = "runtime-benchmarks")]
+impl<
+		XcmConfig: xcm_executor::Config,
+		ExistentialDeposit: Get<Option<MultiAsset>>,
+		PriceForDelivery: PriceForMessageDelivery<Id = ParaId>,
+		Parachain: Get<ParaId>,
+		ToParachainHelper: EnsureForParachain,
+	> pallet_xcm_benchmarks::EnsureDelivery
+	for ToParachainDeliveryHelper<
+		XcmConfig,
+		ExistentialDeposit,
+		PriceForDelivery,
+		Parachain,
+		ToParachainHelper,
+	>
+{
+	fn ensure_successful_delivery(
+		origin_ref: &MultiLocation,
+		_dest: &MultiLocation,
+		fee_reason: xcm_executor::traits::FeeReason,
+	) -> (Option<xcm_executor::FeesMode>, Option<MultiAssets>) {
+		use xcm_executor::{
+			traits::{FeeManager, TransactAsset},
+			FeesMode,
+		};
+
+		let mut fees_mode = None;
+		if !XcmConfig::FeeManager::is_waived(Some(origin_ref), fee_reason) {
+			// if not waived, we need to set up accounts for paying and receiving fees
+
+			// mint ED to origin if needed
+			if let Some(ed) = ExistentialDeposit::get() {
+				XcmConfig::AssetTransactor::deposit_asset(&ed, &origin_ref, None).unwrap();
+			}
+
+			// overestimate delivery fee
+			let overestimated_xcm = vec![ClearOrigin; 128].into();
+			let overestimated_fees =
+				PriceForDelivery::price_for_delivery(Parachain::get(), &overestimated_xcm);
+
+			// mint overestimated fee to origin
+			for fee in overestimated_fees.inner() {
+				XcmConfig::AssetTransactor::deposit_asset(&fee, &origin_ref, None).unwrap();
+			}
+
+			// allow more initialization for target parachain
+			ToParachainHelper::ensure(Parachain::get());
+
+			// expected worst case - direct withdraw
+			fees_mode = Some(FeesMode { jit_withdraw: true });
+		}
+		(fees_mode, None)
+	}
+}
+
+/// Ensure more initialization for `ParaId`. (e.g. open HRMP channels, ...)
+#[cfg(feature = "runtime-benchmarks")]
+pub trait EnsureForParachain {
+	fn ensure(para_id: ParaId);
+}
+#[cfg(feature = "runtime-benchmarks")]
+impl EnsureForParachain for () {
+	fn ensure(_: ParaId) {
+		// doing nothing
+	}
+}
+
 #[cfg(test)]
 mod tests {
 	use super::*;
@@ -124,7 +239,17 @@ mod tests {

 	struct TestFeeTracker;
 	impl FeeTracker for TestFeeTracker {
-		fn get_fee_factor(_: ParaId) -> FixedU128 {
+		type Id = ParaId;
+
+		fn get_fee_factor(_: Self::Id) -> FixedU128 {
+			FixedU128::from_rational(101, 100)
+		}
+
+		fn increase_fee_factor(_: Self::Id, _: FixedU128) -> FixedU128 {
+			FixedU128::from_rational(101, 100)
+		}
+
+		fn decrease_fee_factor(_: Self::Id) -> FixedU128 {
 			FixedU128::from_rational(101, 100)
 		}
 	}
@@ -142,21 +267,21 @@ mod tests {
 		// message_length = 1
 		let result: u128 = TestFeeTracker::get_fee_factor(id).saturating_mul_int(b + m);
 		assert_eq!(
-			TestExponentialPrice::price_for_parachain_delivery(id, &Xcm(vec![])),
+			TestExponentialPrice::price_for_delivery(id, &Xcm(vec![])),
 			(FeeAssetId::get(), result).into()
 		);

 		// message size = 2
 		let result: u128 = TestFeeTracker::get_fee_factor(id).saturating_mul_int(b + (2 * m));
 		assert_eq!(
-			TestExponentialPrice::price_for_parachain_delivery(id, &Xcm(vec![ClearOrigin])),
+			TestExponentialPrice::price_for_delivery(id, &Xcm(vec![ClearOrigin])),
 			(FeeAssetId::get(), result).into()
 		);

 		// message size = 4
 		let result: u128 = TestFeeTracker::get_fee_factor(id).saturating_mul_int(b + (4 * m));
 		assert_eq!(
-			TestExponentialPrice::price_for_parachain_delivery(
+			TestExponentialPrice::price_for_delivery(
 				id,
 				&Xcm(vec![SetAppendix(Xcm(vec![ClearOrigin]))])
 			),