Dispatchable for teleporting assets (#2995)

* Dispatchable for teleporting assets

* Fixes

* Fixes

* Fixes

* Fixes

* Fixes

* Update node/network/protocol/src/peer_set.rs

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>

* Update xcm/src/v0/traits.rs

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>

polkadot/runtime/kusama/src/lib.rs

@@ -52,7 +52,7 @@ use runtime_parachains::scheduler as parachains_scheduler;
 use runtime_parachains::reward_points as parachains_reward_points;
 use runtime_parachains::runtime_api_impl::v1 as parachains_runtime_api_impl;
 
-use xcm::v0::{MultiLocation, NetworkId, BodyId, Xcm};
+use xcm::v0::{MultiLocation, NetworkId, BodyId, Xcm, MultiAsset};
 use xcm_builder::{
 	AccountId32Aliases, ChildParachainConvertsVia, SovereignSignedViaLocation, CurrencyAdapter as XcmCurrencyAdapter,
 	ChildParachainAsNative, SignedAccountId32AsNative, ChildSystemParachainAsSuperuser, LocationInverter,
@@ -1217,6 +1217,8 @@ impl pallet_xcm::Config for Runtime {
 	// ...but they must match our filter, which requires them to be a simple withdraw + teleport.
 	type XcmExecuteFilter = OnlyWithdrawTeleportForAccounts;
 	type XcmExecutor = XcmExecutor<XcmConfig>;
+	type XcmTeleportFilter = All<(MultiLocation, Vec<MultiAsset>)>;
+	type Weigher = FixedWeightBounds<BaseXcmWeight, Call>;
 }
 
 construct_runtime! {

polkadot/runtime/rococo/src/lib.rs

@@ -110,7 +110,7 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	spec_name: create_runtime_str!("rococo"),
 	impl_name: create_runtime_str!("parity-rococo-v1.5"),
 	authoring_version: 0,
-	spec_version: 9000,
+	spec_version: 9001,
 	impl_version: 0,
 	#[cfg(not(feature = "disable-runtime-api"))]
 	apis: RUNTIME_API_VERSIONS,
@@ -714,6 +714,8 @@ impl pallet_xcm::Config for Runtime {
 	// ...but they must match our filter, which requires them to be a simple withdraw + teleport.
 	type XcmExecuteFilter = OnlyWithdrawTeleportForAccounts;
 	type XcmExecutor = XcmExecutor<XcmConfig>;
+	type XcmTeleportFilter = All<(MultiLocation, Vec<MultiAsset>)>;
+	type Weigher = FixedWeightBounds<BaseXcmWeight, Call>;
 }
 
 impl parachains_session_info::Config for Runtime {}

polkadot/runtime/westend/src/lib.rs

@@ -53,7 +53,7 @@ use runtime_parachains::scheduler as parachains_scheduler;
 use runtime_parachains::reward_points as parachains_reward_points;
 use runtime_parachains::runtime_api_impl::v1 as parachains_runtime_api_impl;
 
-use xcm::v0::{MultiLocation, NetworkId, Xcm};
+use xcm::v0::{MultiLocation, NetworkId, Xcm, MultiAsset};
 use xcm_executor::XcmExecutor;
 use xcm_builder::{
 	AccountId32Aliases, ChildParachainConvertsVia, SovereignSignedViaLocation, CurrencyAdapter as XcmCurrencyAdapter,
@@ -922,6 +922,8 @@ impl pallet_xcm::Config for Runtime {
 	// ...but they must match our filter, which requires them to be a simple withdraw + teleport.
 	type XcmExecuteFilter = OnlyWithdrawTeleportForAccounts;
 	type XcmExecutor = XcmExecutor<XcmConfig>;
+	type XcmTeleportFilter = All<(MultiLocation, Vec<MultiAsset>)>;
+	type Weigher = FixedWeightBounds<BaseXcmWeight, Call>;
 }
 
 construct_runtime! {

polkadot/xcm/pallet-xcm/src/lib.rs

@@ -18,9 +18,9 @@
 
 #![cfg_attr(not(feature = "std"), no_std)]
 
-use sp_std::{marker::PhantomData, convert::TryInto, boxed::Box};
+use sp_std::{prelude::*, marker::PhantomData, convert::TryInto, boxed::Box, vec};
 use codec::{Encode, Decode};
-use xcm::v0::{BodyId, OriginKind, MultiLocation, Junction::Plurality};
+use xcm::v0::prelude::*;
 use xcm_executor::traits::ConvertOrigin;
 use sp_runtime::{RuntimeDebug, traits::BadOrigin};
 use frame_support::traits::{EnsureOrigin, OriginTrait, Filter, Get, Contains};
@@ -32,7 +32,7 @@ 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};
+	use xcm_executor::traits::WeightBounds;
 
 	#[pallet::pallet]
 	#[pallet::generate_store(pub(super) trait Store)]
@@ -51,8 +51,9 @@ pub mod pallet {
 		/// 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.
+		/// Required origin for executing XCM messages, includng the teleport functionality. 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>;
 
 		/// Our XCM filter which messages to be executed using `XcmExecutor` must pass.
@@ -60,6 +61,12 @@ pub mod pallet {
 
 		/// Something to execute an XCM message.
 		type XcmExecutor: ExecuteXcm<Self::Call>;
+
+		/// Our XCM filter which messages to be executed using `XcmExecutor` must pass.
+		type XcmTeleportFilter: Contains<(MultiLocation, Vec<MultiAsset>)>;
+
+		/// Means of measuring the weight consumed by an XCM message locally.
+		type Weigher: WeightBounds<Self::Call>;
 	}
 
 	#[pallet::event]
@@ -75,6 +82,8 @@ pub mod pallet {
 		SendFailure,
 		/// The message execution fails the filter.
 		Filtered,
+		/// The message's weight could not be determined.
+		UnweighableMessage,
 	}
 
 	#[pallet::hooks]
@@ -82,7 +91,7 @@ pub mod pallet {
 
 	#[pallet::call]
 	impl<T: Config> Pallet<T> {
-		#[pallet::weight(1_000)]
+		#[pallet::weight(100_000_000)]
 		fn send(origin: OriginFor<T>, dest: MultiLocation, message: Xcm<()>) -> DispatchResult {
 			let origin_location = T::SendXcmOrigin::ensure_origin(origin)?;
 			Self::send_xcm(origin_location.clone(), dest.clone(), message.clone())
@@ -94,6 +103,66 @@ pub mod pallet {
 			Ok(())
 		}
 
+		/// Teleport some assets from the local chain to some destination chain.
+		///
+		/// - `origin`: Must be capable of withdrawing the `assets` and executing XCM.
+		/// - `dest`: Destination context for the assets. Will typically be `X2(Parent, Parachain(..))` to send
+		///   from parachain to parachain, or `X1(Parachain(..))` to send from relay to parachain.
+		/// - `beneficiary`: A beneficiary location for the assets in the context of `dest`. Will generally be
+		///   an `AccountId32` value.
+		/// - `assets`: The assets to be withdrawn. This should include the assets used to pay the fee on the
+		///   `dest` side.
+		/// - `dest_weight`: Equal to the total weight on `dest` of the XCM message
+		///   `Teleport { assets, effects: [ BuyExecution{..}, DepositAsset{..} ] }`.
+		#[pallet::weight({
+			let mut message = Xcm::WithdrawAsset {
+				assets: assets.clone(),
+				effects: sp_std::vec![ InitiateTeleport {
+					assets: sp_std::vec![ All ],
+					dest: dest.clone(),
+					effects: sp_std::vec![],
+				} ]
+			};
+			T::Weigher::weight(&mut message).map_or(Weight::max_value(), |w| 100_000_000 + w)
+		})]
+		fn teleport_assets(
+			origin: OriginFor<T>,
+			dest: MultiLocation,
+			beneficiary: MultiLocation,
+			assets: Vec<MultiAsset>,
+			dest_weight: Weight,
+		) -> DispatchResult {
+			let origin_location = T::ExecuteXcmOrigin::ensure_origin(origin)?;
+			let value = (origin_location, assets);
+			ensure!(T::XcmTeleportFilter::contains(&value), Error::<T>::Filtered);
+			let (origin_location, assets) = value;
+			let mut message = Xcm::WithdrawAsset {
+				assets,
+				effects: vec![
+					InitiateTeleport {
+						assets: vec![ All ],
+						dest,
+						effects: vec![
+							BuyExecution {
+								fees: All,
+								// Zero weight for additional XCM (since there are none to execute)
+								weight: 0,
+								debt: dest_weight,
+								halt_on_error: false,
+								xcm: vec![],
+							},
+							DepositAsset { assets: vec![ All ], dest: beneficiary },
+						],
+					},
+				],
+			};
+			let weight = T::Weigher::weight(&mut message)
+				.map_err(|()| Error::<T>::UnweighableMessage)?;
+			let outcome = T::XcmExecutor::execute_xcm_in_credit(origin_location, message, weight, weight);
+			Self::deposit_event(Event::Attempted(outcome));
+			Ok(())
+		}
+
 		/// Execute an XCM message from a local, signed, origin.
 		///
 		/// An event is deposited indicating whether `msg` could be executed completely or only
@@ -105,7 +174,7 @@ pub mod pallet {
 		///
 		/// 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))]
+		#[pallet::weight(max_weight.saturating_add(100_000_000u64))]
 		fn execute(origin: OriginFor<T>, message: Box<Xcm<T::Call>>, max_weight: Weight)
 			-> DispatchResult
 		{

polkadot/xcm/src/v0/mod.rs

@@ -33,6 +33,16 @@ pub use multi_location::MultiLocation;
 pub use order::Order;
 pub use traits::{Error, Result, SendXcm, ExecuteXcm, Outcome};
 
+/// A prelude for importing all types typically used when interacting with XCM messages.
+pub mod prelude {
+	pub use super::junction::{Junction::*, NetworkId, BodyId, BodyPart};
+	pub use super::multi_asset::{MultiAsset::{self, *}, AssetInstance::{self, *}};
+	pub use super::multi_location::MultiLocation::{self, *};
+	pub use super::order::Order::{self, *};
+	pub use super::traits::{Error as XcmError, Result as XcmResult, SendXcm, ExecuteXcm, Outcome};
+	pub use super::{Xcm::{self, *}, OriginKind};
+}
+
 // TODO: #2841 #XCMENCODE Efficient encodings for Vec<MultiAsset>, Vec<Order>, using initial byte values 128+ to encode
 //   the number of items in the vector.
 

polkadot/xcm/src/v0/traits.rs

@@ -126,14 +126,34 @@ impl Outcome {
 	}
 }
 
+/// Type of XCM message executor.
 pub trait ExecuteXcm<Call> {
-	type Call;
-	fn execute_xcm(origin: MultiLocation, message: Xcm<Call>, weight_limit: Weight) -> Outcome;
+	/// Execute some XCM `message` from `origin` using no more than `weight_limit` weight. The weight limit is
+	/// a basic hard-limit and the implementation may place further restrictions or requirements on weight and
+	/// other aspects.
+	fn execute_xcm(origin: MultiLocation, message: Xcm<Call>, weight_limit: Weight) -> Outcome {
+		Self::execute_xcm_in_credit(origin, message, weight_limit, 0)
+	}
+
+	/// Execute some XCM `message` from `origin` using no more than `weight_limit` weight.
+	///
+	/// Some amount of `weight_credit` may be provided which, depending on the implementation, may allow
+	/// execution without associated payment.
+	fn execute_xcm_in_credit(
+		origin: MultiLocation,
+		message: Xcm<Call>,
+		weight_limit: Weight,
+		weight_credit: Weight,
+	) -> Outcome;
 }
 
 impl<C> ExecuteXcm<C> for () {
-	type Call = C;
-	fn execute_xcm(_origin: MultiLocation, _message: Xcm<C>, _weight_limit: Weight) -> Outcome {
+	fn execute_xcm_in_credit(
+		_origin: MultiLocation,
+		_message: Xcm<C>,
+		_weight_limit: Weight,
+		_weight_credit: Weight,
+	) -> Outcome {
 		Outcome::Error(Error::Unimplemented)
 	}
 }

polkadot/xcm/xcm-builder/src/weight.rs

@@ -32,7 +32,8 @@ impl<T: Get<Weight>, C: Decode + GetDispatchInfo> WeightBounds<C> for FixedWeigh
 			Xcm::RelayedFrom { ref mut message, .. } => T::get() + Self::shallow(message.as_mut())?,
 			Xcm::WithdrawAsset { effects, .. }
 			| Xcm::ReserveAssetDeposit { effects, .. }
-			| Xcm::TeleportAsset { effects, .. } => {
+			| Xcm::TeleportAsset { effects, .. }
+			=> {
 				let inner: Weight = effects.iter_mut()
 					.map(|effect| match effect {
 						Order::BuyExecution { .. } => {

polkadot/xcm/xcm-executor/src/lib.rs

@@ -40,8 +40,12 @@ pub use config::Config;
 pub struct XcmExecutor<Config>(PhantomData<Config>);
 
 impl<Config: config::Config> ExecuteXcm<Config::Call> for XcmExecutor<Config> {
-	type Call = Config::Call;
-	fn execute_xcm(origin: MultiLocation, message: Xcm<Config::Call>, weight_limit: Weight) -> Outcome {
+	fn execute_xcm_in_credit(
+		origin: MultiLocation,
+		message: Xcm<Config::Call>,
+		weight_limit: Weight,
+		mut weight_credit: Weight,
+	) -> Outcome {
 		// TODO: #2841 #HARDENXCM We should identify recursive bombs here and bail.
 		let mut message = Xcm::<Config::Call>::from(message);
 		let shallow_weight = match Config::Weigher::shallow(&mut message) {
@@ -60,7 +64,7 @@ impl<Config: config::Config> ExecuteXcm<Config::Call> for XcmExecutor<Config> {
 			return Outcome::Error(XcmError::WeightLimitReached(maximum_weight));
 		}
 		let mut trader = Config::Trader::new();
-		let result = Self::do_execute_xcm(origin, true, message, &mut 0, Some(shallow_weight), &mut trader);
+		let result = Self::do_execute_xcm(origin, true, message, &mut weight_credit, Some(shallow_weight), &mut trader);
 		drop(trader);
 		match result {
 			Ok(surplus) => Outcome::Complete(maximum_weight.saturating_sub(surplus)),

polkadot/xcm/xcm-executor/src/traits/weight.rs

@@ -15,7 +15,7 @@
 // along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
 
 use sp_std::result::Result;
-use xcm::v0::{Xcm, MultiAsset, Error};
+use xcm::v0::{Xcm, MultiAsset, MultiLocation, Error};
 use frame_support::weights::Weight;
 use crate::Assets;
 
@@ -43,6 +43,18 @@ pub trait WeightBounds<Call> {
 	/// any internal effects. Inner XCM messages may be executed by:
 	/// - Order::BuyExecution
 	fn deep(message: &mut Xcm<Call>) -> Result<Weight, ()>;
+
+	/// Return the total weight for executing `message`.
+	fn weight(message: &mut Xcm<Call>) -> Result<Weight, ()> {
+		Self::shallow(message)?.checked_add(Self::deep(message)?).ok_or(())
+	}
+}
+
+/// A means of getting approximate weight consumption for a given destination message executor and a
+/// message.
+pub trait UniversalWeigher {
+	/// Get the upper limit of weight required for `dest` to execute `message`.
+	fn weigh(dest: MultiLocation, message: Xcm<()>) -> Result<Weight, ()>;
 }
 
 /// Charge for weight in order to execute XCM.