Send messages from Polkadot to Ethereum contracts

parachain-template/pallets/template/src/lib.rs

@@ -16,7 +16,9 @@ mod benchmarking;
 
 #[frame_support::pallet]
 pub mod pallet {
-	use frame_support::{dispatch::DispatchResultWithPostInfo, pallet_prelude::*};
+	pub const LOG_TARGET: &str = "parachain-template";
+
+	use frame_support::{dispatch::DispatchResultWithPostInfo, log, pallet_prelude::*};
 	use frame_system::pallet_prelude::*;
 	use sp_std::boxed::Box;
 	use xcm::{v3::prelude::*, VersionedMultiLocation, VersionedXcm};
@@ -26,7 +28,8 @@ pub mod pallet {
 	pub trait Config: frame_system::Config + pallet_xcm::Config {
 		/// Because this pallet emits events, it depends on the runtime's definition of an event.
 		type RuntimeEvent: From<Event<Self>> + IsType<<Self as frame_system::Config>::RuntimeEvent>;
-	}
+		type BridgeXcmSender: SendXcm;
+    }
 
 	#[pallet::pallet]
 	pub struct Pallet<T>(_);
@@ -49,6 +52,8 @@ pub mod pallet {
 		SomethingStored(u32, T::AccountId),
 		/// XCM message sent. \[to, message\]
 		Sent { from: T::AccountId, to: MultiLocation, message: Xcm<()> },
+		/// ExportMessage message was sent
+		SentExportMessage {forwarded_message_id: XcmHash, sender_cost: MultiAssets, message: Xcm<()> },
 	}
 
 	// Errors inform users that something went wrong.
@@ -67,6 +72,8 @@ pub mod pallet {
 		/// The version of the `Versioned` value used is not able to be
 		/// interpreted.
 		BadVersion,
+		/// The bridge call failed.
+		BridgeCallError,
 	}
 
 	#[pallet::hooks]
@@ -137,5 +144,32 @@ pub mod pallet {
 			Self::deposit_event(Event::Sent { from: who, to: dest, message });
 			Ok(())
 		}
+
+		#[pallet::call_index(3)]
+		#[pallet::weight(Weight::from_parts(100_000_000, 0))]
+		pub fn send_export_message_xcm(
+			origin: OriginFor<T>,
+			dest: Box<VersionedMultiLocation>,
+			message: Box<VersionedXcm<()>>,
+		) -> DispatchResult {
+			let _who = ensure_signed(origin)?;
+
+			let dest = MultiLocation::try_from(*dest).map_err(|()| Error::<T>::BadVersion)?;
+			let message: Xcm<()> = (*message).try_into().map_err(|()| Error::<T>::BadVersion)?;
+
+			let (forwarded_message_id, sender_cost) = send_xcm::<T::BridgeXcmSender>(dest, message.clone())
+				.map_err(|e| {
+					log::error!(
+					target: LOG_TARGET,
+					"[T::BridgeXcmSender] SendError occurred, error: {:?}",
+					e
+				);
+					Error::<T>::BridgeCallError
+				})?;
+
+
+			Self::deposit_event(Event::SentExportMessage {forwarded_message_id, sender_cost, message: message });
+			Ok(())
+		}
 	}
 }

parachain-template/runtime/Cargo.toml

@@ -73,6 +73,8 @@ cumulus-primitives-utility = { path = "../../primitives/utility", default-featur
 pallet-collator-selection = { path = "../../pallets/collator-selection", default-features = false }
 parachain-info = { path = "../../parachains/pallets/parachain-info", default-features = false }
 
+pallet-bridge-transfer-primitives = { path = "../../parachains/pallets/bridge-transfer/primitives", default-features = false }
+
 [features]
 default = [
 	"std",
@@ -122,6 +124,7 @@ std = [
 	"xcm-executor/std",
 	"xcm/std",
 	"substrate-wasm-builder",
+	"pallet-bridge-transfer-primitives/std",
 ]
 
 runtime-benchmarks = [

parachain-template/runtime/src/lib.rs

@@ -59,6 +59,7 @@ use xcm_executor::XcmExecutor;
 
 /// Import the template pallet.
 pub use pallet_parachain_template;
+use crate::xcm_config::bridging;
 
 /// Alias to 512-bit hash when used in the context of a transaction signature on the chain.
 pub type Signature = MultiSignature;
@@ -460,6 +461,7 @@ impl pallet_collator_selection::Config for Runtime {
 /// Configure the pallet template in pallets/template.
 impl pallet_parachain_template::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
+	type BridgeXcmSender = bridging::BridgeXcmSender;
 }
 
 // Create the runtime by composing the FRAME pallets that were previously configured.

parachain-template/runtime/src/xcm_config.rs

@@ -17,16 +17,16 @@ use xcm_builder::{
 	CurrencyAdapter, DenyReserveTransferToRelayChain, DenyThenTry, EnsureXcmOrigin,
 	FixedWeightBounds, IsConcrete, NativeAsset, ParentIsPreset, RelayChainAsNative,
 	SiblingParachainAsNative, SiblingParachainConvertsVia, SignedAccountId32AsNative,
-	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId,
-	UsingComponents, WithComputedOrigin, WithUniqueTopic,
+	SignedToAccountId32, SovereignPaidRemoteExporter, SovereignSignedViaLocation, TakeWeightCredit,
+	TrailingSetTopicAsId, UsingComponents, WithComputedOrigin, WithUniqueTopic,
 };
 use xcm_executor::XcmExecutor;
 
 parameter_types! {
 	pub const RelayLocation: MultiLocation = MultiLocation::parent();
-	pub const RelayNetwork: Option<NetworkId> = None;
+	pub const RelayNetwork: Option<NetworkId> = Some(NetworkId::Kusama);
 	pub RelayChainOrigin: RuntimeOrigin = cumulus_pallet_xcm::Origin::Relay.into();
-	pub UniversalLocation: InteriorMultiLocation = Parachain(ParachainInfo::parachain_id().into()).into();
+	pub UniversalLocation: InteriorMultiLocation = X2(GlobalConsensus(RelayNetwork::get().unwrap()), Parachain(ParachainInfo::parachain_id().into()));
 }
 
 /// Type for specifying how a `MultiLocation` can be converted into an `AccountId`. This is used
@@ -191,3 +191,45 @@ impl cumulus_pallet_xcm::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type XcmExecutor = XcmExecutor<XcmConfig>;
 }
+
+/// All configuration related to bridging
+pub mod bridging {
+	use pallet_bridge_transfer_primitives::{
+		BridgeConfig, BridgesConfig, BridgesConfigAdapter, BridgesConfigBuilder, MaybePaidLocation,
+	};
+
+	use crate::xcm_config::{
+		Junction::{GlobalConsensus, Parachain},
+		Junctions::X1,
+		MultiLocation, SovereignPaidRemoteExporter, UniversalLocation, XcmRouter,
+	};
+	use frame_support::parameter_types;
+	use xcm::v3::NetworkId;
+
+	parameter_types! {
+		pub BridgeHubKusamaParaId: u32 = 1013;
+		pub BridgeHubKusama: MultiLocation = MultiLocation::new(1, X1(Parachain(BridgeHubKusamaParaId::get())));
+		// Network and location for the local Ethereum testnet.
+		pub EthereumNetwork: NetworkId = NetworkId::Ethereum { chain_id: 15 };
+		pub EthereumLocation: MultiLocation = MultiLocation::new(2, X1(GlobalConsensus(EthereumNetwork::get())));
+		pub Bridges: BridgesConfig = BridgesConfigBuilder::default()
+			.add_or_panic(
+				EthereumNetwork::get(),
+				BridgeConfig::new(
+					MaybePaidLocation {
+						location: BridgeHubKusama::get(),
+						maybe_fee: None,
+					}
+				).add_target_location(
+					MaybePaidLocation {
+						location: EthereumLocation::get(),
+						maybe_fee: None, // No fees supported for ethereum
+					},
+					None,
+				))
+			.build();
+	}
+
+	pub type BridgeXcmSender =
+		SovereignPaidRemoteExporter<BridgesConfigAdapter<Bridges>, XcmRouter, UniversalLocation>;
+}