XCM Revamp Continued (#2865)

* Introduce plurality XCM locations * Add RelayedFrom * DMP dispatch weight handling. * Add pallet for XCM sending, add routing logic. * Update error types & doc * Fix warnings. * Fixes * Fixes * Fixes * Bump Substrate * Fixes * Docs * Docs * Docs * Fixes * Fixes * Fixes * Update xcm/pallet-xcm/src/lib.rs Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com> * Docs * Fixes * Update lib.rs * Fixes Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>
2026-05-30 17:31:03 +00:00 · 2021-04-09 20:34:28 +02:00
parent 8961628e7c
commit c9102c11a4
18 changed files with 632 additions and 227 deletions
@@ -0,0 +1,182 @@
+// Copyright 2020-2021 Parity Technologies (UK) Ltd.
+// This file is part of Cumulus.
+
+// Cumulus 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.
+
+// Cumulus 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 Cumulus.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Pallet to handle XCM messages.
+
+#![cfg_attr(not(feature = "std"), no_std)]
+
+use sp_std::{marker::PhantomData, convert::TryInto, boxed::Box};
+use codec::{Encode, Decode};
+use xcm::v0::{BodyId, MultiLocation::{self, X1}, Junction::Plurality};
+use sp_runtime::{RuntimeDebug, traits::BadOrigin};
+use frame_support::traits::{EnsureOrigin, OriginTrait, Filter, Get};
+
+pub use pallet::*;
+
+#[frame_support::pallet]
+pub mod pallet {
+	use super::*;
+	use frame_support::pallet_prelude::*;
+	use frame_system::pallet_prelude::*;
+	use xcm::v0::{Xcm, MultiLocation, Error as XcmError, SendXcm, ExecuteXcm};
+
+	#[pallet::pallet]
+	#[pallet::generate_store(pub(super) trait Store)]
+	pub struct Pallet<T>(_);
+
+	#[pallet::config]
+	/// The module configuration trait.
+	pub trait Config: frame_system::Config {
+		/// The overarching event type.
+		type Event: From<Event<Self>> + IsType<<Self as frame_system::Config>::Event>;
+
+		/// Required origin for sending XCM messages. If successful, the it resolves to `MultiLocation`
+		/// which exists as an interior location within this chain's XCM context.
+		type SendXcmOrigin: EnsureOrigin<Self::Origin, Success=MultiLocation>;
+
+		/// The type used to actually dispatch an XCM to its destination.
+		type XcmRouter: SendXcm;
+
+		/// Required origin for executing XCM messages. If successful, the it resolves to `MultiLocation`
+		/// which exists as an interior location within this chain's XCM context.
+		type ExecuteXcmOrigin: EnsureOrigin<Self::Origin, Success=MultiLocation>;
+
+		/// Something to execute an XCM message.
+		type XcmExecutor: ExecuteXcm<Self::Call>;
+	}
+
+	#[pallet::event]
+	#[pallet::generate_deposit(pub(super) fn deposit_event)]
+	pub enum Event<T: Config> {
+		Attempted(xcm::v0::Outcome),
+	}
+
+	#[pallet::error]
+	pub enum Error<T> {
+		Unreachable,
+		SendFailure,
+	}
+
+	#[pallet::hooks]
+	impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {}
+
+	#[pallet::call]
+	impl<T: Config> Pallet<T> {
+		#[pallet::weight(1_000)]
+		fn send(origin: OriginFor<T>, dest: MultiLocation, message: Xcm<()>) -> DispatchResult {
+			let origin_location = T::SendXcmOrigin::ensure_origin(origin)?;
+			Self::send_xcm(origin_location, dest, message)
+				.map_err(|e| match e {
+					XcmError::CannotReachDestination(..) => Error::<T>::Unreachable,
+					_ => Error::<T>::SendFailure,
+				})?;
+			Ok(())
+		}
+
+		/// Execute an XCM message from a local, signed, origin.
+		///
+		/// An event is deposited indicating whether `msg` could be executed completely or only
+		/// partially.
+		///
+		/// No more than `max_weight` will be used in its attempted execution. If this is less than the
+		/// maximum amount of weight that the message could take to be executed, then no execution
+		/// attempt will be made.
+		///
+		/// NOTE: A successful return to this does *not* imply that the `msg` was executed successfully
+		/// to completion; only that *some* of it was executed.
+		#[pallet::weight(max_weight.saturating_add(1_000u64))]
+		fn execute(origin: OriginFor<T>, message: Box<Xcm<T::Call>>, max_weight: Weight)
+			-> DispatchResult
+		{
+			let origin_location = T::ExecuteXcmOrigin::ensure_origin(origin)?;
+			let outcome = T::XcmExecutor::execute_xcm(origin_location, *message, max_weight);
+			Self::deposit_event(Event::Attempted(outcome));
+			Ok(())
+		}
+	}
+
+	impl<T: Config> Pallet<T> {
+		/// Relay an XCM `message` from a given `interior` location in this context to a given `dest`
+		/// location. A null `dest` is not handled.
+		pub fn send_xcm(interior: MultiLocation, dest: MultiLocation, message: Xcm<()>) -> Result<(), XcmError> {
+			let message = match interior {
+				MultiLocation::Null => message,
+				who => Xcm::<()>::RelayedFrom { who, message: Box::new(message) },
+			};
+			T::XcmRouter::send_xcm(dest, message)
+		}
+	}
+}
+
+/// Origin for the parachains module.
+#[derive(PartialEq, Eq, Clone, Encode, Decode, RuntimeDebug)]
+pub enum Origin {
+	/// It comes from somewhere in the XCM space.
+	Xcm(MultiLocation),
+}
+
+impl From<MultiLocation> for Origin {
+	fn from(location: MultiLocation) -> Origin {
+		Origin::Xcm(location)
+	}
+}
+
+/// Ensure that the origin `o` represents a sibling parachain.
+/// Returns `Ok` with the parachain ID of the sibling or an `Err` otherwise.
+pub fn ensure_xcm<OuterOrigin>(o: OuterOrigin) -> Result<MultiLocation, BadOrigin>
+	where OuterOrigin: Into<Result<Origin, OuterOrigin>>
+{
+	match o.into() {
+		Ok(Origin::Xcm(location)) => Ok(location),
+		_ => Err(BadOrigin),
+	}
+}
+
+/// Filter for `MultiLocation` to find those which represent a strict majority approval of an identified
+/// plurality.
+///
+/// May reasonably be used with `EnsureXcm`.
+pub struct IsMajorityOfBody<Body>(PhantomData<Body>);
+impl<Body: Get<BodyId>> Filter<MultiLocation> for IsMajorityOfBody<Body> {
+	fn filter(l: &MultiLocation) -> bool {
+		matches!(l, X1(Plurality { id, part }) if id == &Body::get() && part.is_majority())
+	}
+}
+
+/// `EnsureOrigin` implementation succeeding with a `MultiLocation` value to recognise and filter the
+/// `Origin::Xcm` item.
+pub struct EnsureXcm<F>(PhantomData<F>);
+impl<O: OriginTrait + From<Origin>, F: Filter<MultiLocation>> EnsureOrigin<O> for EnsureXcm<F>
+	where O::PalletsOrigin: From<Origin> + TryInto<Origin, Error=O::PalletsOrigin>
+{
+	type Success = MultiLocation;
+
+	fn try_origin(outer: O) -> Result<Self::Success, O> {
+		outer.try_with_caller(|caller| caller.try_into()
+			.and_then(|Origin::Xcm(location)|
+				if F::filter(&location) {
+					Ok(location)
+				} else {
+					Err(Origin::Xcm(location).into())
+				}
+			))
+	}
+
+	#[cfg(feature = "runtime-benchmarks")]
+	fn successful_origin() -> O {
+		O::from(Origin::Xcm(MultiLocation::Null))
+	}
+}