Get dispatch weight from the target chain (when DispatchFeePayment::AtTargetChain is used) (#1430)

* reintroduce From<SourceChain>InboundLaneApi

* impl From<Chain>InboundLaneApi for testnet runtimes

* use inboundlaneapi in relay

* remove unused OutboundXcmWeigher

* spelling

* added the only test to messages pallet

* fmt

bridges/bin/millau/runtime/src/lib.rs

@@ -833,16 +833,26 @@ impl_runtime_apis! {
 			lane: bp_messages::LaneId,
 			begin: bp_messages::MessageNonce,
 			end: bp_messages::MessageNonce,
-		) -> Vec<bp_messages::MessageDetails<Balance>> {
+		) -> Vec<bp_messages::OutboundMessageDetails<Balance>> {
 			bridge_runtime_common::messages_api::outbound_message_details::<
 				Runtime,
 				WithRialtoMessagesInstance,
-				WithRialtoMessageBridge,
-				xcm_config::OutboundXcmWeigher,
 			>(lane, begin, end)
 		}
 	}
 
+	impl bp_rialto::FromRialtoInboundLaneApi<Block, bp_rialto::Balance> for Runtime {
+		fn message_details(
+			lane: bp_messages::LaneId,
+			messages: Vec<(bp_messages::MessagePayload, bp_messages::OutboundMessageDetails<bp_rialto::Balance>)>,
+		) -> Vec<bp_messages::InboundMessageDetails> {
+			bridge_runtime_common::messages_api::inbound_message_details::<
+				Runtime,
+				WithRialtoMessagesInstance,
+			>(lane, messages)
+		}
+	}
+
 	impl bp_rialto_parachain::ToRialtoParachainOutboundLaneApi<Block, Balance, ToRialtoParachainMessagePayload> for Runtime {
 		fn estimate_message_delivery_and_dispatch_fee(
 			_lane_id: bp_messages::LaneId,
@@ -860,16 +870,26 @@ impl_runtime_apis! {
 			lane: bp_messages::LaneId,
 			begin: bp_messages::MessageNonce,
 			end: bp_messages::MessageNonce,
-		) -> Vec<bp_messages::MessageDetails<Balance>> {
+		) -> Vec<bp_messages::OutboundMessageDetails<Balance>> {
 			bridge_runtime_common::messages_api::outbound_message_details::<
 				Runtime,
 				WithRialtoParachainMessagesInstance,
-				WithRialtoParachainMessageBridge,
-				xcm_config::OutboundXcmWeigher,
 			>(lane, begin, end)
 		}
 	}
 
+	impl bp_rialto_parachain::FromRialtoParachainInboundLaneApi<Block, bp_rialto_parachain::Balance> for Runtime {
+		fn message_details(
+			lane: bp_messages::LaneId,
+			messages: Vec<(bp_messages::MessagePayload, bp_messages::OutboundMessageDetails<bp_rialto_parachain::Balance>)>,
+		) -> Vec<bp_messages::InboundMessageDetails> {
+			bridge_runtime_common::messages_api::inbound_message_details::<
+				Runtime,
+				WithRialtoParachainMessagesInstance,
+			>(lane, messages)
+		}
+	}
+
 	#[cfg(feature = "runtime-benchmarks")]
 	impl frame_benchmarking::Benchmark<Block> for Runtime {
 		fn benchmark_metadata(extra: bool) -> (

bridges/bin/millau/runtime/src/xcm_config.rs

@@ -122,8 +122,6 @@ pub type Barrier = (
 	AllowKnownQueryResponses<XcmPallet>,
 );
 
-/// Outbound XCM weigher type.
-pub type OutboundXcmWeigher = xcm_builder::FixedWeightBounds<BaseXcmWeight, (), MaxInstructions>;
 /// XCM weigher type.
 pub type XcmWeigher = xcm_builder::FixedWeightBounds<BaseXcmWeight, Call, MaxInstructions>;
 

bridges/bin/rialto-parachain/runtime/src/lib.rs

@@ -383,8 +383,6 @@ pub type Barrier = (
 	// ^^^ Parent & its unit plurality gets free execution
 );
 
-/// Outbound XCM weigher type.
-pub type OutboundXcmWeigher = FixedWeightBounds<UnitWeightCost, (), MaxInstructions>;
 /// XCM weigher type.
 pub type XcmWeigher = FixedWeightBounds<UnitWeightCost, Call, MaxInstructions>;
 
@@ -708,16 +706,26 @@ impl_runtime_apis! {
 			lane: bp_messages::LaneId,
 			begin: bp_messages::MessageNonce,
 			end: bp_messages::MessageNonce,
-		) -> Vec<bp_messages::MessageDetails<Balance>> {
+		) -> Vec<bp_messages::OutboundMessageDetails<Balance>> {
 			bridge_runtime_common::messages_api::outbound_message_details::<
 				Runtime,
 				WithMillauMessagesInstance,
-				WithMillauMessageBridge,
-				OutboundXcmWeigher,
 			>(lane, begin, end)
 		}
 	}
 
+	impl bp_millau::FromMillauInboundLaneApi<Block, bp_millau::Balance> for Runtime {
+		fn message_details(
+			lane: bp_messages::LaneId,
+			messages: Vec<(bp_messages::MessagePayload, bp_messages::OutboundMessageDetails<bp_millau::Balance>)>,
+		) -> Vec<bp_messages::InboundMessageDetails> {
+			bridge_runtime_common::messages_api::inbound_message_details::<
+				Runtime,
+				WithMillauMessagesInstance,
+			>(lane, messages)
+		}
+	}
+
 	#[cfg(feature = "runtime-benchmarks")]
 	impl frame_benchmarking::Benchmark<Block> for Runtime {
 		fn dispatch_benchmark(

bridges/bin/rialto/runtime/src/lib.rs

@@ -893,15 +893,25 @@ impl_runtime_apis! {
 			lane: bp_messages::LaneId,
 			begin: bp_messages::MessageNonce,
 			end: bp_messages::MessageNonce,
-		) -> Vec<bp_messages::MessageDetails<Balance>> {
+		) -> Vec<bp_messages::OutboundMessageDetails<Balance>> {
 			bridge_runtime_common::messages_api::outbound_message_details::<
 				Runtime,
 				WithMillauMessagesInstance,
-				WithMillauMessageBridge,
-				xcm_config::OutboundXcmWeigher,
 			>(lane, begin, end)
 		}
 	}
+
+	impl bp_millau::FromMillauInboundLaneApi<Block, bp_millau::Balance> for Runtime {
+		fn message_details(
+			lane: bp_messages::LaneId,
+			messages: Vec<(bp_messages::MessagePayload, bp_messages::OutboundMessageDetails<bp_millau::Balance>)>,
+		) -> Vec<bp_messages::InboundMessageDetails> {
+			bridge_runtime_common::messages_api::inbound_message_details::<
+				Runtime,
+				WithMillauMessagesInstance,
+			>(lane, messages)
+		}
+	}
 }
 
 #[cfg(test)]

bridges/bin/rialto/runtime/src/xcm_config.rs

@@ -122,8 +122,6 @@ pub type Barrier = (
 	AllowKnownQueryResponses<XcmPallet>,
 );
 
-/// Outbound XCM weigher type.
-pub type OutboundXcmWeigher = xcm_builder::FixedWeightBounds<BaseXcmWeight, (), MaxInstructions>;
 /// Incoming XCM weigher type.
 pub type XcmWeigher = xcm_builder::FixedWeightBounds<BaseXcmWeight, Call, MaxInstructions>;
 

bridges/bin/runtime-common/src/messages_api.rs

@@ -16,68 +16,54 @@
 
 //! Helpers for implementing various message-related runtime API mthods.
 
-use crate::messages::{target::FromBridgedChainMessagePayload, MessageBridge};
+use bp_messages::{
-
+	InboundMessageDetails, LaneId, MessageNonce, MessagePayload, OutboundMessageDetails,
-use bp_messages::{LaneId, MessageDetails, MessageKey, MessageNonce};
+};
-use codec::Decode;
-use frame_support::weights::Weight;
 use sp_std::vec::Vec;
 
 /// Implementation of the `To*OutboundLaneApi::message_details`.
-pub fn outbound_message_details<Runtime, MessagesPalletInstance, BridgeConfig, XcmWeigher>(
+pub fn outbound_message_details<Runtime, MessagesPalletInstance>(
 	lane: LaneId,
 	begin: MessageNonce,
 	end: MessageNonce,
-) -> Vec<MessageDetails<Runtime::OutboundMessageFee>>
+) -> Vec<OutboundMessageDetails<Runtime::OutboundMessageFee>>
 where
 	Runtime: pallet_bridge_messages::Config<MessagesPalletInstance>,
 	MessagesPalletInstance: 'static,
-	BridgeConfig: MessageBridge,
-	XcmWeigher: xcm_executor::traits::WeightBounds<()>,
 {
 	(begin..=end)
 		.filter_map(|nonce| {
 			let message_data =
 				pallet_bridge_messages::Pallet::<Runtime, MessagesPalletInstance>::outbound_message_data(lane, nonce)?;
-			Some(MessageDetails {
+			Some(OutboundMessageDetails {
 				nonce,
-				// this shall match the similar code in the `FromBridgedChainMessageDispatch` - if we have failed
+				// dispatch message weight is always zero at the source chain, since we're paying for
-				// to decode or estimate dispatch weight, we'll just return 0 to disable actual execution
+				// dispatch at the target chain
-				dispatch_weight: compute_message_weight::<XcmWeigher>(
+				dispatch_weight: 0,
-					MessageKey { lane_id: lane, nonce },
-					&message_data.payload,
-				).unwrap_or(0),
 				size: message_data.payload.len() as _,
 				delivery_and_dispatch_fee: message_data.fee,
+				// we're delivering XCM messages here, so fee is always paid at the target chain
 				dispatch_fee_payment: bp_runtime::messages::DispatchFeePayment::AtTargetChain,
 			})
 		})
 		.collect()
 }
 
-// at the source chain we don't know the type of target chain `Call` => `()` is used (it is
+/// Implementation of the `To*InboundLaneApi::message_details`.
-// similarly currently used in Polkadot codebase)
+pub fn inbound_message_details<Runtime, MessagesPalletInstance>(
-fn compute_message_weight<XcmWeigher: xcm_executor::traits::WeightBounds<()>>(
+	lane: LaneId,
-	message_key: MessageKey,
+	messages: Vec<(MessagePayload, OutboundMessageDetails<Runtime::InboundMessageFee>)>,
-	encoded_payload: &[u8],
+) -> Vec<InboundMessageDetails>
-) -> Result<Weight, ()> {
+where
-	let mut payload = FromBridgedChainMessagePayload::<()>::decode(&mut &encoded_payload[..])
+	Runtime: pallet_bridge_messages::Config<MessagesPalletInstance>,
-		.map_err(|e| {
+	MessagesPalletInstance: 'static,
-			log::debug!(
+{
-				target: "runtime::bridge-dispatch",
+	messages
-				"Failed to decode outbound XCM message {:?}: {:?}",
+		.into_iter()
-				message_key,
+		.map(|(payload, details)| {
-				e,
+			pallet_bridge_messages::Pallet::<Runtime, MessagesPalletInstance>::inbound_message_data(
-			);
+				lane, payload, details,
-		})?;
+			)
-	let weight = XcmWeigher::weight(&mut payload.xcm.1);
+		})
-	let weight = weight.map_err(|e| {
+		.collect()
-		log::debug!(
-			target: "runtime::bridge-dispatch",
-			"Failed to compute dispatch weight of outbound XCM message {:?}: {:?}",
-			message_key,
-			e,
-		);
-	})?;
-	Ok(weight)
 }

bridges/modules/messages/src/lib.rs

@@ -56,9 +56,10 @@ use bp_messages::{
 	target_chain::{
 		DispatchMessage, MessageDispatch, ProvedLaneMessages, ProvedMessages, SourceHeaderChain,
 	},
-	total_unrewarded_messages, DeliveredMessages, InboundLaneData, LaneId, MessageData, MessageKey,
+	total_unrewarded_messages, DeliveredMessages, InboundLaneData, InboundMessageDetails, LaneId,
-	MessageNonce, OperatingMode, OutboundLaneData, Parameter as MessagesParameter,
+	MessageData, MessageKey, MessageNonce, MessagePayload, OperatingMode, OutboundLaneData,
-	UnrewardedRelayer, UnrewardedRelayersState,
+	OutboundMessageDetails, Parameter as MessagesParameter, UnrewardedRelayer,
+	UnrewardedRelayersState,
 };
 use bp_runtime::{ChainId, Size};
 use codec::{Decode, Encode};
@@ -156,7 +157,7 @@ pub mod pallet {
 		/// Payload type of inbound messages. This payload is dispatched on this chain.
 		type InboundPayload: Decode;
 		/// Message fee type of inbound messages. This fee is paid on the bridged chain.
-		type InboundMessageFee: Decode;
+		type InboundMessageFee: Decode + Zero;
 		/// Identifier of relayer that deliver messages to this chain. Relayer reward is paid on the
 		/// bridged chain.
 		type InboundRelayer: Parameter;
@@ -762,6 +763,22 @@ pub mod pallet {
 		) -> Option<MessageData<T::OutboundMessageFee>> {
 			OutboundMessages::<T, I>::get(MessageKey { lane_id: lane, nonce })
 		}
+
+		/// Prepare data, related to given inbound message.
+		pub fn inbound_message_data(
+			lane: LaneId,
+			payload: MessagePayload,
+			outbound_details: OutboundMessageDetails<T::InboundMessageFee>,
+		) -> InboundMessageDetails {
+			let mut dispatch_message = DispatchMessage {
+				key: MessageKey { lane_id: lane, nonce: outbound_details.nonce },
+				data: MessageData { payload, fee: outbound_details.delivery_and_dispatch_fee }
+					.into(),
+			};
+			InboundMessageDetails {
+				dispatch_weight: T::MessageDispatch::dispatch_weight(&mut dispatch_message),
+			}
+		}
 	}
 }
 
@@ -2332,4 +2349,25 @@ mod tests {
 			bp_messages::storage_keys::inbound_lane_data_key("Messages", &TEST_LANE_ID).0,
 		);
 	}
+
+	#[test]
+	fn inbound_message_details_works() {
+		run_test(|| {
+			assert_eq!(
+				Pallet::<TestRuntime>::inbound_message_data(
+					TEST_LANE_ID,
+					REGULAR_PAYLOAD.encode(),
+					OutboundMessageDetails {
+						nonce: 0,
+						dispatch_weight: 0,
+						size: 0,
+						delivery_and_dispatch_fee: 0,
+						dispatch_fee_payment:
+							bp_runtime::messages::DispatchFeePayment::AtTargetChain,
+					},
+				),
+				InboundMessageDetails { dispatch_weight: REGULAR_PAYLOAD.declared_weight },
+			);
+		});
+	}
 }

bridges/primitives/chain-kusama/src/lib.rs

@@ -18,7 +18,9 @@
 // RuntimeApi generated functions
 #![allow(clippy::too_many_arguments)]
 
-use bp_messages::{LaneId, MessageDetails, MessageNonce};
+use bp_messages::{
+	InboundMessageDetails, LaneId, MessageNonce, MessagePayload, OutboundMessageDetails,
+};
 use frame_support::weights::{
 	WeightToFeeCoefficient, WeightToFeeCoefficients, WeightToFeePolynomial,
 };
@@ -105,6 +107,9 @@ pub const TO_KUSAMA_ESTIMATE_MESSAGE_FEE_METHOD: &str =
 /// Name of the `ToKusamaOutboundLaneApi::message_details` runtime method.
 pub const TO_KUSAMA_MESSAGE_DETAILS_METHOD: &str = "ToKusamaOutboundLaneApi_message_details";
 
+/// Name of the `FromKusamaInboundLaneApi::message_details` runtime method.
+pub const FROM_KUSAMA_MESSAGE_DETAILS_METHOD: &str = "FromKusamaInboundLaneApi_message_details";
+
 sp_api::decl_runtime_apis! {
 	/// API for querying information about the finalized Kusama headers.
 	///
@@ -143,6 +148,21 @@ sp_api::decl_runtime_apis! {
 			lane: LaneId,
 			begin: MessageNonce,
 			end: MessageNonce,
-		) -> Vec<MessageDetails<OutboundMessageFee>>;
+		) -> Vec<OutboundMessageDetails<OutboundMessageFee>>;
+	}
+
+	/// Inbound message lane API for messages sent by Kusama chain.
+	///
+	/// This API is implemented by runtimes that are receiving messages from Kusama chain, not the
+	/// Kusama runtime itself.
+	///
+	/// Entries of the resulting vector are matching entries of the `messages` vector. Entries of the
+	/// `messages` vector may (and need to) be read using `To<ThisChain>OutboundLaneApi::message_details`.
+	pub trait FromKusamaInboundLaneApi<InboundMessageFee: Parameter> {
+		/// Return details of given inbound messages.
+		fn message_details(
+			lane: LaneId,
+			messages: Vec<(MessagePayload, OutboundMessageDetails<InboundMessageFee>)>,
+		) -> Vec<InboundMessageDetails>;
 	}
 }

bridges/primitives/chain-millau/src/lib.rs

@@ -20,7 +20,9 @@
 
 mod millau_hash;
 
-use bp_messages::{LaneId, MessageDetails, MessageNonce};
+use bp_messages::{
+	InboundMessageDetails, LaneId, MessageNonce, MessagePayload, OutboundMessageDetails,
+};
 use bp_runtime::Chain;
 use frame_support::{
 	weights::{constants::WEIGHT_PER_SECOND, DispatchClass, IdentityFee, Weight},
@@ -294,6 +296,9 @@ pub const TO_MILLAU_ESTIMATE_MESSAGE_FEE_METHOD: &str =
 /// Name of the `ToMillauOutboundLaneApi::message_details` runtime method.
 pub const TO_MILLAU_MESSAGE_DETAILS_METHOD: &str = "ToMillauOutboundLaneApi_message_details";
 
+/// Name of the `FromMillauInboundLaneApi::message_details` runtime method.
+pub const FROM_MILLAU_MESSAGE_DETAILS_METHOD: &str = "FromMillauInboundLaneApi_message_details";
+
 sp_api::decl_runtime_apis! {
 	/// API for querying information about the finalized Millau headers.
 	///
@@ -332,7 +337,22 @@ sp_api::decl_runtime_apis! {
 			lane: LaneId,
 			begin: MessageNonce,
 			end: MessageNonce,
-		) -> Vec<MessageDetails<OutboundMessageFee>>;
+		) -> Vec<OutboundMessageDetails<OutboundMessageFee>>;
+	}
+
+	/// Inbound message lane API for messages sent by Millau chain.
+	///
+	/// This API is implemented by runtimes that are receiving messages from Millau chain, not the
+	/// Millau runtime itself.
+	///
+	/// Entries of the resulting vector are matching entries of the `messages` vector. Entries of the
+	/// `messages` vector may (and need to) be read using `To<ThisChain>OutboundLaneApi::message_details`.
+	pub trait FromMillauInboundLaneApi<InboundMessageFee: Parameter> {
+		/// Return details of given inbound messages.
+		fn message_details(
+			lane: LaneId,
+			messages: Vec<(MessagePayload, OutboundMessageDetails<InboundMessageFee>)>,
+		) -> Vec<InboundMessageDetails>;
 	}
 }
 

bridges/primitives/chain-polkadot/src/lib.rs

@@ -18,7 +18,9 @@
 // RuntimeApi generated functions
 #![allow(clippy::too_many_arguments)]
 
-use bp_messages::{LaneId, MessageDetails, MessageNonce};
+use bp_messages::{
+	InboundMessageDetails, LaneId, MessageNonce, MessagePayload, OutboundMessageDetails,
+};
 use frame_support::weights::{
 	WeightToFeeCoefficient, WeightToFeeCoefficients, WeightToFeePolynomial,
 };
@@ -105,6 +107,10 @@ pub const TO_POLKADOT_ESTIMATE_MESSAGE_FEE_METHOD: &str =
 /// Name of the `ToPolkadotOutboundLaneApi::message_details` runtime method.
 pub const TO_POLKADOT_MESSAGE_DETAILS_METHOD: &str = "ToPolkadotOutboundLaneApi_message_details";
 
+/// Name of the `FromPolkadotInboundLaneApi::message_details` runtime method.
+pub const FROM_POLKADOT_MESSAGE_DETAILS_METHOD: &str =
+	"FromPolkadotOutboundLaneApi_message_details";
+
 sp_api::decl_runtime_apis! {
 	/// API for querying information about the finalized Polkadot headers.
 	///
@@ -143,6 +149,21 @@ sp_api::decl_runtime_apis! {
 			lane: LaneId,
 			begin: MessageNonce,
 			end: MessageNonce,
-		) -> Vec<MessageDetails<OutboundMessageFee>>;
+		) -> Vec<OutboundMessageDetails<OutboundMessageFee>>;
+	}
+
+	/// Inbound message lane API for messages sent by Polkadot chain.
+	///
+	/// This API is implemented by runtimes that are receiving messages from Polkadot chain, not the
+	/// Polkadot runtime itself.
+	///
+	/// Entries of the resulting vector are matching entries of the `messages` vector. Entries of the
+	/// `messages` vector may (and need to) be read using `To<ThisChain>OutboundLaneApi::message_details`.
+	pub trait FromPolkadotInboundLaneApi<InboundMessageFee: Parameter> {
+		/// Return details of given inbound messages.
+		fn message_details(
+			lane: LaneId,
+			messages: Vec<(MessagePayload, OutboundMessageDetails<InboundMessageFee>)>,
+		) -> Vec<InboundMessageDetails>;
 	}
 }

bridges/primitives/chain-rialto-parachain/src/lib.rs

@@ -18,7 +18,9 @@
 // RuntimeApi generated functions
 #![allow(clippy::too_many_arguments)]
 
-use bp_messages::{LaneId, MessageDetails, MessageNonce};
+use bp_messages::{
+	InboundMessageDetails, LaneId, MessageNonce, MessagePayload, OutboundMessageDetails,
+};
 use bp_runtime::Chain;
 use frame_support::{
 	weights::{constants::WEIGHT_PER_SECOND, DispatchClass, IdentityFee, Weight},
@@ -210,6 +212,10 @@ pub const TO_RIALTO_PARACHAIN_ESTIMATE_MESSAGE_FEE_METHOD: &str =
 pub const TO_RIALTO_PARACHAIN_MESSAGE_DETAILS_METHOD: &str =
 	"ToRialtoParachainOutboundLaneApi_message_details";
 
+/// Name of the `FromRialtoParachainInboundLaneApi::message_details` runtime method.
+pub const FROM_RIALTO_PARACHAIN_MESSAGE_DETAILS_METHOD: &str =
+	"FromRialtoParachainInboundLaneApi_message_details";
+
 // We use this to get the account on RialtoParachain (target) which is derived from Millau's
 // (source) account. We do this so we can fund the derived account on RialtoParachain at Genesis to
 // it can pay transaction fees.
@@ -261,7 +267,22 @@ sp_api::decl_runtime_apis! {
 			lane: LaneId,
 			begin: MessageNonce,
 			end: MessageNonce,
-		) -> Vec<MessageDetails<OutboundMessageFee>>;
+		) -> Vec<OutboundMessageDetails<OutboundMessageFee>>;
+	}
+
+	/// Inbound message lane API for messages sent by RialtoParachain chain.
+	///
+	/// This API is implemented by runtimes that are receiving messages from RialtoParachain chain, not the
+	/// RialtoParachain runtime itself.
+	///
+	/// Entries of the resulting vector are matching entries of the `messages` vector. Entries of the
+	/// `messages` vector may (and need to) be read using `To<ThisChain>OutboundLaneApi::message_details`.
+	pub trait FromRialtoParachainInboundLaneApi<InboundMessageFee: Parameter> {
+		/// Return details of given inbound messages.
+		fn message_details(
+			lane: LaneId,
+			messages: Vec<(MessagePayload, OutboundMessageDetails<InboundMessageFee>)>,
+		) -> Vec<InboundMessageDetails>;
 	}
 }
 

bridges/primitives/chain-rialto/src/lib.rs

@@ -18,7 +18,9 @@
 // RuntimeApi generated functions
 #![allow(clippy::too_many_arguments)]
 
-use bp_messages::{LaneId, MessageDetails, MessageNonce};
+use bp_messages::{
+	InboundMessageDetails, LaneId, MessageNonce, MessagePayload, OutboundMessageDetails,
+};
 use bp_runtime::Chain;
 use frame_support::{
 	weights::{constants::WEIGHT_PER_SECOND, DispatchClass, IdentityFee, Weight},
@@ -250,6 +252,9 @@ pub const TO_RIALTO_ESTIMATE_MESSAGE_FEE_METHOD: &str =
 /// Name of the `ToRialtoOutboundLaneApi::message_details` runtime method.
 pub const TO_RIALTO_MESSAGE_DETAILS_METHOD: &str = "ToRialtoOutboundLaneApi_message_details";
 
+/// Name of the `FromRialtoInboundLaneApi::message_details` runtime method.
+pub const FROM_RIALTO_MESSAGE_DETAILS_METHOD: &str = "FromRialtoInboundLaneApi_message_details";
+
 sp_api::decl_runtime_apis! {
 	/// API for querying information about the finalized Rialto headers.
 	///
@@ -288,7 +293,22 @@ sp_api::decl_runtime_apis! {
 			lane: LaneId,
 			begin: MessageNonce,
 			end: MessageNonce,
-		) -> Vec<MessageDetails<OutboundMessageFee>>;
+		) -> Vec<OutboundMessageDetails<OutboundMessageFee>>;
+	}
+
+	/// Inbound message lane API for messages sent by Rialto chain.
+	///
+	/// This API is implemented by runtimes that are receiving messages from Rialto chain, not the
+	/// Rialto runtime itself.
+	///
+	/// Entries of the resulting vector are matching entries of the `messages` vector. Entries of the
+	/// `messages` vector may (and need to) be read using `To<ThisChain>OutboundLaneApi::message_details`.
+	pub trait FromRialtoInboundLaneApi<InboundMessageFee: Parameter> {
+		/// Return details of given inbound messages.
+		fn message_details(
+			lane: LaneId,
+			messages: Vec<(MessagePayload, OutboundMessageDetails<InboundMessageFee>)>,
+		) -> Vec<InboundMessageDetails>;
 	}
 }
 

bridges/primitives/chain-rococo/src/lib.rs

@@ -18,7 +18,9 @@
 // RuntimeApi generated functions
 #![allow(clippy::too_many_arguments)]
 
-use bp_messages::{LaneId, MessageDetails, MessageNonce};
+use bp_messages::{
+	InboundMessageDetails, LaneId, MessageNonce, MessagePayload, OutboundMessageDetails,
+};
 use frame_support::weights::{
 	Weight, WeightToFeeCoefficient, WeightToFeeCoefficients, WeightToFeePolynomial,
 };
@@ -89,6 +91,9 @@ pub const TO_ROCOCO_ESTIMATE_MESSAGE_FEE_METHOD: &str =
 /// Name of the `ToRococoOutboundLaneApi::message_details` runtime method.
 pub const TO_ROCOCO_MESSAGE_DETAILS_METHOD: &str = "ToRococoOutboundLaneApi_message_details";
 
+/// Name of the `FromRococoInboundLaneApi::message_details` runtime method.
+pub const FROM_ROCOCO_MESSAGE_DETAILS_METHOD: &str = "FromRococoInboundLaneApi_message_details";
+
 /// Existential deposit on Rococo.
 pub const EXISTENTIAL_DEPOSIT: Balance = 1_000_000_000_000 / 100;
 
@@ -139,6 +144,21 @@ sp_api::decl_runtime_apis! {
 			lane: LaneId,
 			begin: MessageNonce,
 			end: MessageNonce,
-		) -> Vec<MessageDetails<OutboundMessageFee>>;
+		) -> Vec<OutboundMessageDetails<OutboundMessageFee>>;
+	}
+
+	/// Inbound message lane API for messages sent by Rococo chain.
+	///
+	/// This API is implemented by runtimes that are receiving messages from Rococo chain, not the
+	/// Rococo runtime itself.
+	///
+	/// Entries of the resulting vector are matching entries of the `messages` vector. Entries of the
+	/// `messages` vector may (and need to) be read using `To<ThisChain>OutboundLaneApi::message_details`.
+	pub trait FromRococoInboundLaneApi<InboundMessageFee: Parameter> {
+		/// Return details of given inbound messages.
+		fn message_details(
+			lane: LaneId,
+			messages: Vec<(MessagePayload, OutboundMessageDetails<InboundMessageFee>)>,
+		) -> Vec<InboundMessageDetails>;
 	}
 }

bridges/primitives/chain-wococo/src/lib.rs

@@ -18,7 +18,9 @@
 // RuntimeApi generated functions
 #![allow(clippy::too_many_arguments)]
 
-use bp_messages::{LaneId, MessageDetails, MessageNonce};
+use bp_messages::{
+	InboundMessageDetails, LaneId, MessageNonce, MessagePayload, OutboundMessageDetails,
+};
 use sp_runtime::FixedU128;
 use sp_std::prelude::*;
 
@@ -58,6 +60,9 @@ pub const TO_WOCOCO_ESTIMATE_MESSAGE_FEE_METHOD: &str =
 /// Name of the `ToWococoOutboundLaneApi::message_details` runtime method.
 pub const TO_WOCOCO_MESSAGE_DETAILS_METHOD: &str = "ToWococoOutboundLaneApi_message_details";
 
+/// Name of the `FromWococoInboundLaneApi::message_details` runtime method.
+pub const FROM_WOCOCO_MESSAGE_DETAILS_METHOD: &str = "FromWococoInboundLaneApi_message_details";
+
 sp_api::decl_runtime_apis! {
 	/// API for querying information about the finalized Wococo headers.
 	///
@@ -96,6 +101,21 @@ sp_api::decl_runtime_apis! {
 			lane: LaneId,
 			begin: MessageNonce,
 			end: MessageNonce,
-		) -> Vec<MessageDetails<OutboundMessageFee>>;
+		) -> Vec<OutboundMessageDetails<OutboundMessageFee>>;
+	}
+
+	/// Inbound message lane API for messages sent by Wococo chain.
+	///
+	/// This API is implemented by runtimes that are receiving messages from Wococo chain, not the
+	/// Wococo runtime itself.
+	///
+	/// Entries of the resulting vector are matching entries of the `messages` vector. Entries of the
+	/// `messages` vector may (and need to) be read using `To<ThisChain>OutboundLaneApi::message_details`.
+	pub trait FromWococoInboundLaneApi<InboundMessageFee: Parameter> {
+		/// Return details of given inbound messages.
+		fn message_details(
+			lane: LaneId,
+			messages: Vec<(MessagePayload, OutboundMessageDetails<InboundMessageFee>)>,
+		) -> Vec<InboundMessageDetails>;
 	}
 }

bridges/primitives/messages/src/lib.rs

@@ -176,12 +176,15 @@ impl<RelayerId> InboundLaneData<RelayerId> {
 	}
 }
 
-/// Message details, returned by runtime APIs.
+/// Outbound message details, returned by runtime APIs.
 #[derive(Clone, Encode, Decode, RuntimeDebug, PartialEq, Eq)]
-pub struct MessageDetails<OutboundMessageFee> {
+pub struct OutboundMessageDetails<OutboundMessageFee> {
 	/// Nonce assigned to the message.
 	pub nonce: MessageNonce,
-	/// Message dispatch weight, declared by the submitter.
+	/// Message dispatch weight.
+	///
+	/// Depending on messages pallet configuration, it may be declared by the message submitter,
+	/// computed automatically or just be zero if dispatch fee is paid at the target chain.
 	pub dispatch_weight: Weight,
 	/// Size of the encoded message.
 	pub size: u32,
@@ -191,6 +194,18 @@ pub struct MessageDetails<OutboundMessageFee> {
 	pub dispatch_fee_payment: DispatchFeePayment,
 }
 
+/// Inbound message details, returned by runtime APIs.
+#[derive(Clone, Encode, Decode, RuntimeDebug, PartialEq, Eq)]
+pub struct InboundMessageDetails {
+	/// Computed message dispatch weight.
+	///
+	/// Runtime API guarantees that it will match the value, returned by
+	/// `target_chain::MessageDispatch::dispatch_weight`. This means that if the runtime
+	/// has failed to decode the message, it will be zero - that's because `undecodable`
+	/// message cannot be dispatched.
+	pub dispatch_weight: Weight,
+}
+
 /// Bit vector of message dispatch results.
 pub type DispatchResultsBitVec = BitVec<u8, Msb0>;
 

bridges/primitives/messages/src/target_chain.rs

@@ -93,8 +93,9 @@ pub trait MessageDispatch<AccountId, Fee> {
 
 	/// Estimate dispatch weight.
 	///
-	/// This function must: (1) be instant and (2) return correct upper bound
+	/// This function must return correct upper bound of dispatch weight. The return value
-	/// of dispatch weight.
+	/// of this function is expected to match return value of the corresponding
+	/// `From<Chain>InboundLaneApi::message_details().dispatch_weight` call.
 	fn dispatch_weight(message: &mut DispatchMessage<Self::DispatchPayload, Fee>) -> Weight;
 
 	/// Called when inbound message is received.

bridges/relays/client-kusama/src/lib.rs

@@ -79,6 +79,8 @@ impl ChainWithMessages for Kusama {
 		bp_kusama::WITH_KUSAMA_MESSAGES_PALLET_NAME;
 	const TO_CHAIN_MESSAGE_DETAILS_METHOD: &'static str =
 		bp_kusama::TO_KUSAMA_MESSAGE_DETAILS_METHOD;
+	const FROM_CHAIN_MESSAGE_DETAILS_METHOD: &'static str =
+		bp_kusama::FROM_KUSAMA_MESSAGE_DETAILS_METHOD;
 	const PAY_INBOUND_DISPATCH_FEE_WEIGHT_AT_CHAIN: Weight =
 		bp_kusama::PAY_INBOUND_DISPATCH_FEE_WEIGHT;
 	const MAX_UNREWARDED_RELAYERS_IN_CONFIRMATION_TX: MessageNonce =

bridges/relays/client-millau/src/lib.rs

@@ -63,6 +63,8 @@ impl ChainWithMessages for Millau {
 		bp_millau::WITH_MILLAU_MESSAGES_PALLET_NAME;
 	const TO_CHAIN_MESSAGE_DETAILS_METHOD: &'static str =
 		bp_millau::TO_MILLAU_MESSAGE_DETAILS_METHOD;
+	const FROM_CHAIN_MESSAGE_DETAILS_METHOD: &'static str =
+		bp_millau::FROM_MILLAU_MESSAGE_DETAILS_METHOD;
 	const PAY_INBOUND_DISPATCH_FEE_WEIGHT_AT_CHAIN: Weight =
 		bp_millau::PAY_INBOUND_DISPATCH_FEE_WEIGHT;
 	const MAX_UNREWARDED_RELAYERS_IN_CONFIRMATION_TX: MessageNonce =

bridges/relays/client-polkadot/src/lib.rs

@@ -80,6 +80,8 @@ impl ChainWithMessages for Polkadot {
 		bp_polkadot::WITH_POLKADOT_MESSAGES_PALLET_NAME;
 	const TO_CHAIN_MESSAGE_DETAILS_METHOD: &'static str =
 		bp_polkadot::TO_POLKADOT_MESSAGE_DETAILS_METHOD;
+	const FROM_CHAIN_MESSAGE_DETAILS_METHOD: &'static str =
+		bp_polkadot::FROM_POLKADOT_MESSAGE_DETAILS_METHOD;
 	const PAY_INBOUND_DISPATCH_FEE_WEIGHT_AT_CHAIN: Weight =
 		bp_polkadot::PAY_INBOUND_DISPATCH_FEE_WEIGHT;
 	const MAX_UNREWARDED_RELAYERS_IN_CONFIRMATION_TX: MessageNonce =

bridges/relays/client-rialto-parachain/src/lib.rs

@@ -88,6 +88,8 @@ impl ChainWithMessages for RialtoParachain {
 		bp_rialto_parachain::WITH_RIALTO_PARACHAIN_MESSAGES_PALLET_NAME;
 	const TO_CHAIN_MESSAGE_DETAILS_METHOD: &'static str =
 		bp_rialto_parachain::TO_RIALTO_PARACHAIN_MESSAGE_DETAILS_METHOD;
+	const FROM_CHAIN_MESSAGE_DETAILS_METHOD: &'static str =
+		bp_rialto_parachain::FROM_RIALTO_PARACHAIN_MESSAGE_DETAILS_METHOD;
 	const PAY_INBOUND_DISPATCH_FEE_WEIGHT_AT_CHAIN: Weight =
 		bp_rialto_parachain::PAY_INBOUND_DISPATCH_FEE_WEIGHT;
 	const MAX_UNREWARDED_RELAYERS_IN_CONFIRMATION_TX: MessageNonce =

bridges/relays/client-rialto/src/lib.rs

@@ -85,6 +85,8 @@ impl ChainWithMessages for Rialto {
 		bp_rialto::WITH_RIALTO_MESSAGES_PALLET_NAME;
 	const TO_CHAIN_MESSAGE_DETAILS_METHOD: &'static str =
 		bp_rialto::TO_RIALTO_MESSAGE_DETAILS_METHOD;
+	const FROM_CHAIN_MESSAGE_DETAILS_METHOD: &'static str =
+		bp_rialto::FROM_RIALTO_MESSAGE_DETAILS_METHOD;
 	const PAY_INBOUND_DISPATCH_FEE_WEIGHT_AT_CHAIN: Weight =
 		bp_rialto::PAY_INBOUND_DISPATCH_FEE_WEIGHT;
 	const MAX_UNREWARDED_RELAYERS_IN_CONFIRMATION_TX: MessageNonce =

bridges/relays/client-rococo/src/lib.rs

@@ -82,6 +82,8 @@ impl ChainWithMessages for Rococo {
 		bp_rococo::WITH_ROCOCO_MESSAGES_PALLET_NAME;
 	const TO_CHAIN_MESSAGE_DETAILS_METHOD: &'static str =
 		bp_rococo::TO_ROCOCO_MESSAGE_DETAILS_METHOD;
+	const FROM_CHAIN_MESSAGE_DETAILS_METHOD: &'static str =
+		bp_rococo::FROM_ROCOCO_MESSAGE_DETAILS_METHOD;
 	const PAY_INBOUND_DISPATCH_FEE_WEIGHT_AT_CHAIN: Weight =
 		bp_rococo::PAY_INBOUND_DISPATCH_FEE_WEIGHT;
 	const MAX_UNREWARDED_RELAYERS_IN_CONFIRMATION_TX: MessageNonce =

bridges/relays/client-substrate/src/chain.rs

@@ -105,6 +105,10 @@ pub trait ChainWithMessages: Chain {
 	/// The method is provided by the runtime that is bridged with this `ChainWithMessages`.
 	const TO_CHAIN_MESSAGE_DETAILS_METHOD: &'static str;
 
+	/// Name of the `From<ChainWithMessages>InboundLaneApi::message_details` runtime API method.
+	/// The method is provided by the runtime that is bridged with this `ChainWithMessages`.
+	const FROM_CHAIN_MESSAGE_DETAILS_METHOD: &'static str;
+
 	/// Additional weight of the dispatch fee payment if dispatch is paid at the target chain
 	/// and this `ChainWithMessages` is the target chain.
 	const PAY_INBOUND_DISPATCH_FEE_WEIGHT_AT_CHAIN: Weight;

bridges/relays/client-wococo/src/lib.rs

@@ -82,6 +82,8 @@ impl ChainWithMessages for Wococo {
 		bp_wococo::WITH_WOCOCO_MESSAGES_PALLET_NAME;
 	const TO_CHAIN_MESSAGE_DETAILS_METHOD: &'static str =
 		bp_wococo::TO_WOCOCO_MESSAGE_DETAILS_METHOD;
+	const FROM_CHAIN_MESSAGE_DETAILS_METHOD: &'static str =
+		bp_wococo::FROM_WOCOCO_MESSAGE_DETAILS_METHOD;
 	const PAY_INBOUND_DISPATCH_FEE_WEIGHT_AT_CHAIN: Weight =
 		bp_wococo::PAY_INBOUND_DISPATCH_FEE_WEIGHT;
 	const MAX_UNREWARDED_RELAYERS_IN_CONFIRMATION_TX: MessageNonce =

bridges/relays/lib-substrate-relay/src/messages_source.rs

@@ -31,8 +31,10 @@ use async_std::sync::Arc;
 use async_trait::async_trait;
 use bp_messages::{
 	storage_keys::{operating_mode_key, outbound_lane_data_key},
-	LaneId, MessageNonce, OperatingMode, OutboundLaneData, UnrewardedRelayersState,
+	InboundMessageDetails, LaneId, MessageData, MessageNonce, OperatingMode, OutboundLaneData,
+	OutboundMessageDetails, UnrewardedRelayersState,
 };
+use bp_runtime::messages::DispatchFeePayment;
 use bridge_runtime_common::messages::{
 	source::FromBridgedChainMessagesDeliveryProof, target::FromBridgedChainMessagesProof,
 };
@@ -54,7 +56,7 @@ use relay_substrate_client::{
 use relay_utils::{relay_loop::Client as RelayClient, HeaderId};
 use sp_core::{Bytes, Pair};
 use sp_runtime::{traits::Header as HeaderT, DeserializeOwned};
-use std::ops::RangeInclusive;
+use std::{collections::HashMap, ops::RangeInclusive};
 
 /// Intermediate message proof returned by the source Substrate node. Includes everything
 /// required to submit to the target node: cumulative dispatch weight of bundled messages and
@@ -199,11 +201,97 @@ where
 			)
 			.await?;
 
-		make_message_details_map::<P::SourceChain>(
+		let mut messages = make_message_details_map::<P::SourceChain>(
 			Decode::decode(&mut &encoded_response.0[..])
 				.map_err(SubstrateError::ResponseParseFailed)?,
 			nonces,
+		)?;
+
+		// prepare arguments of the inbound message details call (if we need it)
+		let mut messages_to_refine = HashMap::new();
+		for (message_nonce, message) in &messages {
+			if message.dispatch_fee_payment != DispatchFeePayment::AtTargetChain {
+				continue
+			}
+
+			// for pay-at-target messages we may want to ask target chain for
+			// refined dispatch weight
+			let message_key = bp_messages::storage_keys::message_key(
+				P::TargetChain::WITH_CHAIN_MESSAGES_PALLET_NAME,
+				&self.lane_id,
+				*message_nonce,
+			);
+			let message_data: MessageData<BalanceOf<P::SourceChain>> =
+				self.source_client.storage_value(message_key, Some(id.1)).await?.ok_or_else(
+					|| {
+						SubstrateError::Custom(format!(
+							"Message to {} {:?}/{} is missing from runtime the storage of {} at {:?}",
+							P::TargetChain::NAME,
+							self.lane_id,
+							message_nonce,
+							P::SourceChain::NAME,
+							id,
+						))
+					},
+				)?;
+			let message_payload = message_data.payload;
+			messages_to_refine.insert(
+				*message_nonce,
+				(
+					message_payload,
+					OutboundMessageDetails {
+						nonce: *message_nonce,
+						dispatch_weight: message.dispatch_weight,
+						size: message.size,
+						delivery_and_dispatch_fee: message.reward,
+						dispatch_fee_payment: DispatchFeePayment::AtTargetChain,
+					},
+				),
+			);
+		}
+
+		// request inbound message details from the target client
+		if !messages_to_refine.is_empty() {
+			let refined_messages_encoded = self
+				.target_client
+				.state_call(
+					P::SourceChain::FROM_CHAIN_MESSAGE_DETAILS_METHOD.into(),
+					Bytes((self.lane_id, messages_to_refine.values().collect::<Vec<_>>()).encode()),
+					None,
 				)
+				.await?;
+			let refined_messages =
+				Vec::<InboundMessageDetails>::decode(&mut &refined_messages_encoded.0[..])
+					.map_err(SubstrateError::ResponseParseFailed)?;
+			if refined_messages.len() != messages_to_refine.len() {
+				return Err(SubstrateError::Custom(format!(
+					"Call of {} at {} has returned {} entries instead of expected {}",
+					P::SourceChain::FROM_CHAIN_MESSAGE_DETAILS_METHOD,
+					P::TargetChain::NAME,
+					refined_messages.len(),
+					messages_to_refine.len(),
+				)))
+			}
+
+			for (nonce, refined_message) in messages_to_refine.keys().zip(refined_messages) {
+				let message = messages
+					.get_mut(nonce)
+					.expect("`messages_to_refine` is a subset of `messages`; qed");
+				log::trace!(
+					target: "bridge",
+					"Refined weight of {}->{} message {:?}/{}: at-source: {}, at-target: {}",
+					P::SourceChain::NAME,
+					P::TargetChain::NAME,
+					self.lane_id,
+					nonce,
+					message.dispatch_weight,
+					refined_message.dispatch_weight,
+				);
+				message.dispatch_weight = refined_message.dispatch_weight;
+			}
+		}
+
+		Ok(messages)
 	}
 
 	async fn prove_messages(
@@ -483,7 +571,7 @@ where
 }
 
 fn make_message_details_map<C: Chain>(
-	weights: Vec<bp_messages::MessageDetails<C::Balance>>,
+	weights: Vec<bp_messages::OutboundMessageDetails<C::Balance>>,
 	nonces: RangeInclusive<MessageNonce>,
 ) -> Result<MessageDetailsMap<C::Balance>, SubstrateError> {
 	let make_missing_nonce_error = |expected_nonce| {
@@ -558,10 +646,10 @@ mod tests {
 
 	fn message_details_from_rpc(
 		nonces: RangeInclusive<MessageNonce>,
-	) -> Vec<bp_messages::MessageDetails<bp_wococo::Balance>> {
+	) -> Vec<bp_messages::OutboundMessageDetails<bp_wococo::Balance>> {
 		nonces
 			.into_iter()
-			.map(|nonce| bp_messages::MessageDetails {
+			.map(|nonce| bp_messages::OutboundMessageDetails {
 				nonce,
 				dispatch_weight: 0,
 				size: 0,