Relay basic single-bit message dispatch results back to the source chain (#935)

* relay dispatch result flags back to the source chain

* OnMessagesDelivered callback

* add lane id to OnDeliveredMessages callback

* fix benchmarks && upate weights

* clippy

* clippy

* clipy another try

* OnMessagesDelivered -> OnDeliveryConfirmed

* Update primitives/messages/src/source_chain.rs

Co-authored-by: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

Co-authored-by: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

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

@@ -384,6 +384,7 @@ impl pallet_bridge_messages::Config<WithRialtoMessagesInstance> for Runtime {
 		GetDeliveryConfirmationTransactionFee,
 		RootAccountForPayments,
 	>;
+	type OnDeliveryConfirmed = ();
 
 	type SourceHeaderChain = crate::rialto_messages::Rialto;
 	type MessageDispatch = crate::rialto_messages::FromRialtoMessageDispatch;
@@ -702,6 +703,7 @@ mod tests {
 		let max_incoming_inbound_lane_data_proof_size = bp_messages::InboundLaneData::<()>::encoded_size_hint(
 			bp_millau::MAXIMAL_ENCODED_ACCOUNT_ID_SIZE,
 			bp_rialto::MAX_UNREWARDED_RELAYER_ENTRIES_AT_INBOUND_LANE as _,
+			bp_rialto::MAX_UNCONFIRMED_MESSAGES_AT_INBOUND_LANE as _,
 		)
 		.unwrap_or(u32::MAX);
 		pallet_bridge_messages::ensure_able_to_receive_confirmation::<Weights>(

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

@@ -113,8 +113,11 @@ impl messages::ThisChainWithMessages for Millau {
 	}
 
 	fn estimate_delivery_confirmation_transaction() -> MessageTransaction<Weight> {
-		let inbound_data_size =
-			InboundLaneData::<bp_millau::AccountId>::encoded_size_hint(bp_millau::MAXIMAL_ENCODED_ACCOUNT_ID_SIZE, 1)
+		let inbound_data_size = InboundLaneData::<bp_millau::AccountId>::encoded_size_hint(
+			bp_millau::MAXIMAL_ENCODED_ACCOUNT_ID_SIZE,
+			1,
+			1,
+		)
 		.unwrap_or(u32::MAX);
 
 		MessageTransaction {

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

@@ -491,6 +491,7 @@ impl pallet_bridge_messages::Config<WithMillauMessagesInstance> for Runtime {
 		GetDeliveryConfirmationTransactionFee,
 		RootAccountForPayments,
 	>;
+	type OnDeliveryConfirmed = ();
 
 	type SourceHeaderChain = crate::millau_messages::Millau;
 	type MessageDispatch = crate::millau_messages::FromMillauMessageDispatch;
@@ -1028,7 +1029,7 @@ impl_runtime_apis! {
 						.map(|event_record| event_record.event)
 						.any(|event| matches!(
 							event,
-							Event::pallet_bridge_dispatch(pallet_bridge_dispatch::Event::<Runtime, _>::MessageDispatched(
+							Event::BridgeDispatch(pallet_bridge_dispatch::Event::<Runtime, _>::MessageDispatched(
 								_, ([0, 0, 0, 0], nonce_from_event), _,
 							)) if nonce_from_event == nonce
 						))
@@ -1144,6 +1145,7 @@ mod tests {
 		let max_incoming_inbound_lane_data_proof_size = bp_messages::InboundLaneData::<()>::encoded_size_hint(
 			bp_rialto::MAXIMAL_ENCODED_ACCOUNT_ID_SIZE,
 			bp_millau::MAX_UNREWARDED_RELAYER_ENTRIES_AT_INBOUND_LANE as _,
+			bp_millau::MAX_UNCONFIRMED_MESSAGES_AT_INBOUND_LANE as _,
 		)
 		.unwrap_or(u32::MAX);
 		pallet_bridge_messages::ensure_able_to_receive_confirmation::<Weights>(

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

@@ -113,8 +113,11 @@ impl messages::ThisChainWithMessages for Rialto {
 	}
 
 	fn estimate_delivery_confirmation_transaction() -> MessageTransaction<Weight> {
-		let inbound_data_size =
-			InboundLaneData::<bp_rialto::AccountId>::encoded_size_hint(bp_rialto::MAXIMAL_ENCODED_ACCOUNT_ID_SIZE, 1)
+		let inbound_data_size = InboundLaneData::<bp_rialto::AccountId>::encoded_size_hint(
+			bp_rialto::MAXIMAL_ENCODED_ACCOUNT_ID_SIZE,
+			1,
+			1,
+		)
 		.unwrap_or(u32::MAX);
 
 		MessageTransaction {

bridges/modules/dispatch/src/lib.rs

@@ -154,6 +154,7 @@ impl<T: Config<I>, I: Instance> MessageDispatch<T::AccountId, T::MessageId> for
 				);
 				Self::deposit_event(RawEvent::MessageRejected(source_chain, id));
 				return MessageDispatchResult {
+					dispatch_result: false,
 					unspent_weight: 0,
 					dispatch_fee_paid_during_dispatch: false,
 				};
@@ -163,6 +164,7 @@ impl<T: Config<I>, I: Instance> MessageDispatch<T::AccountId, T::MessageId> for
 		// verify spec version
 		// (we want it to be the same, because otherwise we may decode Call improperly)
 		let mut dispatch_result = MessageDispatchResult {
+			dispatch_result: false,
 			unspent_weight: message.weight,
 			dispatch_fee_paid_during_dispatch: false,
 		};
@@ -303,6 +305,7 @@ impl<T: Config<I>, I: Instance> MessageDispatch<T::AccountId, T::MessageId> for
 		log::trace!(target: "runtime::bridge-dispatch", "Message being dispatched is: {:.4096?}", &call);
 		let result = call.dispatch(origin);
 		let actual_call_weight = extract_actual_weight(&result, &dispatch_info);
+		dispatch_result.dispatch_result = result.is_ok();
 		dispatch_result.unspent_weight = message.weight.saturating_sub(actual_call_weight);
 
 		log::trace!(
@@ -573,6 +576,7 @@ mod tests {
 			System::set_block_number(1);
 			let result = Dispatch::dispatch(SOURCE_CHAIN_ID, TARGET_CHAIN_ID, id, Ok(message), |_, _| unreachable!());
 			assert_eq!(result.unspent_weight, weight);
+			assert!(!result.dispatch_result);
 
 			assert_eq!(
 				System::events(),
@@ -601,6 +605,7 @@ mod tests {
 			System::set_block_number(1);
 			let result = Dispatch::dispatch(SOURCE_CHAIN_ID, TARGET_CHAIN_ID, id, Ok(message), |_, _| unreachable!());
 			assert_eq!(result.unspent_weight, 7);
+			assert!(!result.dispatch_result);
 
 			assert_eq!(
 				System::events(),
@@ -633,6 +638,7 @@ mod tests {
 			System::set_block_number(1);
 			let result = Dispatch::dispatch(SOURCE_CHAIN_ID, TARGET_CHAIN_ID, id, Ok(message), |_, _| unreachable!());
 			assert_eq!(result.unspent_weight, weight);
+			assert!(!result.dispatch_result);
 
 			assert_eq!(
 				System::events(),
@@ -683,6 +689,7 @@ mod tests {
 			System::set_block_number(1);
 			let result = Dispatch::dispatch(SOURCE_CHAIN_ID, TARGET_CHAIN_ID, id, Ok(message), |_, _| unreachable!());
 			assert_eq!(result.unspent_weight, weight);
+			assert!(!result.dispatch_result);
 
 			assert_eq!(
 				System::events(),
@@ -711,6 +718,7 @@ mod tests {
 			System::set_block_number(1);
 			let result = Dispatch::dispatch(SOURCE_CHAIN_ID, TARGET_CHAIN_ID, id, Ok(message), |_, _| unreachable!());
 			assert_eq!(result.unspent_weight, weight);
+			assert!(!result.dispatch_result);
 
 			assert_eq!(
 				System::events(),
@@ -739,12 +747,13 @@ mod tests {
 			System::set_block_number(1);
 			let result = Dispatch::dispatch(SOURCE_CHAIN_ID, TARGET_CHAIN_ID, id, Ok(message), |_, _| Err(()));
 			assert_eq!(result.unspent_weight, weight);
+			assert!(!result.dispatch_result);
 
 			assert_eq!(
 				System::events(),
 				vec![EventRecord {
 					phase: Phase::Initialization,
-					event: Event::call_dispatch(call_dispatch::Event::<TestRuntime>::MessageDispatchPaymentFailed(
+					event: Event::Dispatch(call_dispatch::Event::<TestRuntime>::MessageDispatchPaymentFailed(
 						SOURCE_CHAIN_ID,
 						id,
 						AccountIdConverter::convert(derive_account_id::<AccountId>(
@@ -771,12 +780,13 @@ mod tests {
 			System::set_block_number(1);
 			let result = Dispatch::dispatch(SOURCE_CHAIN_ID, TARGET_CHAIN_ID, id, Ok(message), |_, _| Ok(()));
 			assert!(result.dispatch_fee_paid_during_dispatch);
+			assert!(result.dispatch_result);
 
 			assert_eq!(
 				System::events(),
 				vec![EventRecord {
 					phase: Phase::Initialization,
-					event: Event::call_dispatch(call_dispatch::Event::<TestRuntime>::MessageDispatched(
+					event: Event::Dispatch(call_dispatch::Event::<TestRuntime>::MessageDispatched(
 						SOURCE_CHAIN_ID,
 						id,
 						Ok(())
@@ -787,6 +797,34 @@ mod tests {
 		});
 	}
 
+	#[test]
+	fn should_return_dispatch_failed_flag_if_dispatch_happened_but_failed() {
+		new_test_ext().execute_with(|| {
+			let id = [0; 4];
+
+			let call = Call::System(<frame_system::Call<TestRuntime>>::set_heap_pages(1));
+			let message = prepare_target_message(call);
+
+			System::set_block_number(1);
+			let result = Dispatch::dispatch(SOURCE_CHAIN_ID, TARGET_CHAIN_ID, id, Ok(message), |_, _| unreachable!());
+			assert!(!result.dispatch_fee_paid_during_dispatch);
+			assert!(!result.dispatch_result);
+
+			assert_eq!(
+				System::events(),
+				vec![EventRecord {
+					phase: Phase::Initialization,
+					event: Event::Dispatch(call_dispatch::Event::<TestRuntime>::MessageDispatched(
+						SOURCE_CHAIN_ID,
+						id,
+						Err(sp_runtime::DispatchError::BadOrigin)
+					)),
+					topics: vec![],
+				}],
+			);
+		})
+	}
+
 	#[test]
 	fn should_dispatch_bridge_message_from_root_origin() {
 		new_test_ext().execute_with(|| {
@@ -796,6 +834,7 @@ mod tests {
 			System::set_block_number(1);
 			let result = Dispatch::dispatch(SOURCE_CHAIN_ID, TARGET_CHAIN_ID, id, Ok(message), |_, _| unreachable!());
 			assert!(!result.dispatch_fee_paid_during_dispatch);
+			assert!(result.dispatch_result);
 
 			assert_eq!(
 				System::events(),
@@ -823,6 +862,7 @@ mod tests {
 			System::set_block_number(1);
 			let result = Dispatch::dispatch(SOURCE_CHAIN_ID, TARGET_CHAIN_ID, id, Ok(message), |_, _| unreachable!());
 			assert!(!result.dispatch_fee_paid_during_dispatch);
+			assert!(result.dispatch_result);
 
 			assert_eq!(
 				System::events(),
@@ -850,6 +890,7 @@ mod tests {
 			System::set_block_number(1);
 			let result = Dispatch::dispatch(SOURCE_CHAIN_ID, TARGET_CHAIN_ID, id, Ok(message), |_, _| unreachable!());
 			assert!(!result.dispatch_fee_paid_during_dispatch);
+			assert!(result.dispatch_result);
 
 			assert_eq!(
 				System::events(),

bridges/modules/messages/Cargo.toml

@@ -7,6 +7,7 @@ edition = "2018"
 license = "GPL-3.0-or-later WITH Classpath-exception-2.0"
 
 [dependencies]
+bitvec = { version = "0.20", default-features = false, features = ["alloc"] }
 codec = { package = "parity-scale-codec", version = "2.0.0", default-features = false }
 log = { version = "0.4.14", default-features = false }
 num-traits = { version = "0.2", default-features = false }

bridges/modules/messages/README.md

@@ -101,7 +101,14 @@ the `MessageAccepted` event is emitted in the `send_message()` transaction. The
 message lane identifier and nonce that has been assigned to the message. When a message is delivered
 to the target chain, the `MessagesDelivered` event is emitted from the
 `receive_messages_delivery_proof()` transaction. The `MessagesDelivered` contains the message lane
-identifier and inclusive range of delivered message nonces.
+identifier, inclusive range of delivered message nonces and their single-bit dispatch results.
+
+Please note that the meaning of the 'dispatch result' is determined by the message dispatcher at
+the target chain. For example, in case of immediate call dispatcher it will be the `true` if call
+has been successfully dispatched and `false` if it has only been delivered. This simple mechanism
+built into the messages module allows building basic bridge applications, which only care whether
+their messages have been successfully dispatched or not. More sophisticated applications may use
+their own dispatch result delivery mechanism to deliver something larger than single bit.
 
 ### How to plug-in Messages Module to Send Messages to the Bridged Chain?
 

bridges/modules/messages/src/benchmarking.rs

@@ -17,17 +17,25 @@
 //! Messages pallet benchmarking.
 
 use crate::weights_ext::EXPECTED_DEFAULT_MESSAGE_LENGTH;
-use crate::{inbound_lane::InboundLaneStorage, inbound_lane_storage, outbound_lane, Call, Instance};
+use crate::{
+	inbound_lane::InboundLaneStorage, inbound_lane_storage, outbound_lane, outbound_lane::ReceivalConfirmationResult,
+	Call, Instance,
+};
 
 use bp_messages::{
-	source_chain::TargetHeaderChain, target_chain::SourceHeaderChain, InboundLaneData, LaneId, MessageData,
-	MessageNonce, OutboundLaneData, UnrewardedRelayersState,
+	source_chain::TargetHeaderChain, target_chain::SourceHeaderChain, DeliveredMessages, InboundLaneData, LaneId,
+	MessageData, MessageNonce, OutboundLaneData, UnrewardedRelayer, UnrewardedRelayersState,
 };
 use bp_runtime::messages::DispatchFeePayment;
 use frame_benchmarking::{account, benchmarks_instance};
 use frame_support::{traits::Get, weights::Weight};
 use frame_system::RawOrigin;
-use sp_std::{collections::btree_map::BTreeMap, convert::TryInto, ops::RangeInclusive, prelude::*};
+use sp_std::{
+	collections::{btree_map::BTreeMap, vec_deque::VecDeque},
+	convert::TryInto,
+	ops::RangeInclusive,
+	prelude::*,
+};
 
 /// Fee paid by submitter for single message delivery.
 pub const MESSAGE_FEE: u64 = 10_000_000_000;
@@ -471,7 +479,10 @@ benchmarks_instance! {
 		let proof = T::prepare_message_delivery_proof(MessageDeliveryProofParams {
 			lane: T::bench_lane_id(),
 			inbound_lane_data: InboundLaneData {
-				relayers: vec![(1, 1, relayer_id.clone())].into_iter().collect(),
+				relayers: vec![UnrewardedRelayer {
+					relayer: relayer_id.clone(),
+					messages: DeliveredMessages::new(1, true),
+				}].into_iter().collect(),
 				last_confirmed_nonce: 0,
 			},
 			size: ProofSize::Minimal(0),
@@ -506,10 +517,15 @@ benchmarks_instance! {
 			messages_in_oldest_entry: 2,
 			total_messages: 2,
 		};
+		let mut delivered_messages = DeliveredMessages::new(1, true);
+		delivered_messages.note_dispatched_message(true);
 		let proof = T::prepare_message_delivery_proof(MessageDeliveryProofParams {
 			lane: T::bench_lane_id(),
 			inbound_lane_data: InboundLaneData {
-				relayers: vec![(1, 2, relayer_id.clone())].into_iter().collect(),
+				relayers: vec![UnrewardedRelayer {
+					relayer: relayer_id.clone(),
+					messages: delivered_messages,
+				}].into_iter().collect(),
 				last_confirmed_nonce: 0,
 			},
 			size: ProofSize::Minimal(0),
@@ -547,8 +563,14 @@ benchmarks_instance! {
 			lane: T::bench_lane_id(),
 			inbound_lane_data: InboundLaneData {
 				relayers: vec![
-					(1, 1, relayer1_id.clone()),
-					(2, 2, relayer2_id.clone()),
+					UnrewardedRelayer {
+						relayer: relayer1_id.clone(),
+						messages: DeliveredMessages::new(1, true),
+					},
+					UnrewardedRelayer {
+						relayer: relayer2_id.clone(),
+						messages: DeliveredMessages::new(2, true),
+					},
 				].into_iter().collect(),
 				last_confirmed_nonce: 0,
 			},
@@ -783,10 +805,17 @@ benchmarks_instance! {
 			messages_in_oldest_entry: 1,
 			total_messages: i as MessageNonce,
 		};
+		let mut delivered_messages = DeliveredMessages::new(1, true);
+		for nonce in 2..=i {
+			delivered_messages.note_dispatched_message(true);
+		}
 		let proof = T::prepare_message_delivery_proof(MessageDeliveryProofParams {
 			lane: T::bench_lane_id(),
 			inbound_lane_data: InboundLaneData {
-				relayers: vec![(1, i as MessageNonce, relayer_id.clone())].into_iter().collect(),
+				relayers: vec![UnrewardedRelayer {
+					relayer: relayer_id.clone(),
+					messages: delivered_messages,
+				}].into_iter().collect(),
 				last_confirmed_nonce: 0,
 			},
 			size: ProofSize::Minimal(0),
@@ -831,7 +860,10 @@ benchmarks_instance! {
 				relayers: relayers
 					.keys()
 					.enumerate()
-					.map(|(j, relayer_id)| (j as MessageNonce + 1, j as MessageNonce + 1, relayer_id.clone()))
+					.map(|(j, relayer)| UnrewardedRelayer {
+						relayer: relayer.clone(),
+						messages: DeliveredMessages::new(j as MessageNonce + 1, true),
+					})
 					.collect(),
 				last_confirmed_nonce: 0,
 			},
@@ -863,13 +895,29 @@ fn send_regular_message_with_payload<T: Config<I>, I: Instance>(payload: Vec<u8>
 
 fn confirm_message_delivery<T: Config<I>, I: Instance>(nonce: MessageNonce) {
 	let mut outbound_lane = outbound_lane::<T, I>(T::bench_lane_id());
-	assert!(outbound_lane.confirm_delivery(nonce).is_some());
+	let latest_received_nonce = outbound_lane.data().latest_received_nonce;
+	let mut relayers = VecDeque::with_capacity((nonce - latest_received_nonce) as usize);
+	for nonce in latest_received_nonce + 1..=nonce {
+		relayers.push_back(UnrewardedRelayer {
+			relayer: (),
+			messages: DeliveredMessages::new(nonce, true),
+		});
+	}
+	assert!(matches!(
+		outbound_lane.confirm_delivery(nonce, &relayers),
+		ReceivalConfirmationResult::ConfirmedMessages(_),
+	));
 }
 
 fn receive_messages<T: Config<I>, I: Instance>(nonce: MessageNonce) {
 	let mut inbound_lane_storage = inbound_lane_storage::<T, I>(T::bench_lane_id());
 	inbound_lane_storage.set_data(InboundLaneData {
-		relayers: vec![(1, nonce, T::bridged_relayer_id())].into_iter().collect(),
+		relayers: vec![UnrewardedRelayer {
+			relayer: T::bridged_relayer_id(),
+			messages: DeliveredMessages::new(nonce, true),
+		}]
+		.into_iter()
+		.collect(),
 		last_confirmed_nonce: 0,
 	});
 }

bridges/modules/messages/src/inbound_lane.rs

@@ -18,7 +18,7 @@
 
 use bp_messages::{
 	target_chain::{DispatchMessage, DispatchMessageData, MessageDispatch},
-	InboundLaneData, LaneId, MessageKey, MessageNonce, OutboundLaneData,
+	DeliveredMessages, InboundLaneData, LaneId, MessageKey, MessageNonce, OutboundLaneData, UnrewardedRelayer,
 };
 use bp_runtime::messages::MessageDispatchResult;
 use frame_support::RuntimeDebug;
@@ -89,7 +89,7 @@ impl<S: InboundLaneStorage> InboundLane<S> {
 		while data
 			.relayers
 			.front()
-			.map(|(_, nonce_high, _)| *nonce_high <= new_confirmed_nonce)
+			.map(|entry| entry.messages.end <= new_confirmed_nonce)
 			.unwrap_or(false)
 		{
 			data.relayers.pop_front();
@@ -97,8 +97,12 @@ impl<S: InboundLaneStorage> InboundLane<S> {
 		// Secondly, update the next record with lower nonce equal to new confirmed nonce if needed.
 		// Note: There will be max. 1 record to update as we don't allow messages from relayers to overlap.
 		match data.relayers.front_mut() {
-			Some((nonce_low, _, _)) if *nonce_low < new_confirmed_nonce => {
-				*nonce_low = new_confirmed_nonce + 1;
+			Some(entry) if entry.messages.begin < new_confirmed_nonce => {
+				entry.messages.dispatch_results = entry
+					.messages
+					.dispatch_results
+					.split_off((new_confirmed_nonce + 1 - entry.messages.begin) as _);
+				entry.messages.begin = new_confirmed_nonce + 1;
 			}
 			_ => {}
 		}
@@ -132,21 +136,10 @@ impl<S: InboundLaneStorage> InboundLane<S> {
 			return ReceivalResult::TooManyUnconfirmedMessages;
 		}
 
-		let push_new = match data.relayers.back_mut() {
-			Some((_, nonce_high, last_relayer)) if last_relayer == relayer_at_bridged_chain => {
-				*nonce_high = nonce;
-				false
-			}
-			_ => true,
-		};
-		if push_new {
-			data.relayers
-				.push_back((nonce, nonce, (*relayer_at_bridged_chain).clone()));
-		}
-
-		self.storage.set_data(data);
-
-		ReceivalResult::Dispatched(P::dispatch(
+		// dispatch message before updating anything in the storage. If dispatch would panic,
+		// (which should not happen in the runtime) then we simply won't consider message as
+		// delivered (no changes to the inbound lane storage have been made).
+		let dispatch_result = P::dispatch(
 			relayer_at_this_chain,
 			DispatchMessage {
 				key: MessageKey {
@@ -155,7 +148,25 @@ impl<S: InboundLaneStorage> InboundLane<S> {
 				},
 				data: message_data,
 			},
-		))
+		);
+
+		// now let's update inbound lane storage
+		let push_new = match data.relayers.back_mut() {
+			Some(entry) if entry.relayer == *relayer_at_bridged_chain => {
+				entry.messages.note_dispatched_message(dispatch_result.dispatch_result);
+				false
+			}
+			_ => true,
+		};
+		if push_new {
+			data.relayers.push_back(UnrewardedRelayer {
+				relayer: (*relayer_at_bridged_chain).clone(),
+				messages: DeliveredMessages::new(nonce, dispatch_result.dispatch_result),
+			});
+		}
+		self.storage.set_data(data);
+
+		ReceivalResult::Dispatched(dispatch_result)
 	}
 }
 
@@ -165,8 +176,8 @@ mod tests {
 	use crate::{
 		inbound_lane,
 		mock::{
-			dispatch_result, message_data, run_test, TestMessageDispatch, TestRuntime, REGULAR_PAYLOAD, TEST_LANE_ID,
-			TEST_RELAYER_A, TEST_RELAYER_B, TEST_RELAYER_C,
+			dispatch_result, message_data, run_test, unrewarded_relayer, TestMessageDispatch, TestRuntime,
+			REGULAR_PAYLOAD, TEST_LANE_ID, TEST_RELAYER_A, TEST_RELAYER_B, TEST_RELAYER_C,
 		},
 		DefaultInstance, RuntimeInboundLaneStorage,
 	};
@@ -238,7 +249,10 @@ mod tests {
 			receive_regular_message(&mut lane, 2);
 			receive_regular_message(&mut lane, 3);
 			assert_eq!(lane.storage.data().last_confirmed_nonce, 0);
-			assert_eq!(lane.storage.data().relayers, vec![(1, 3, TEST_RELAYER_A)]);
+			assert_eq!(
+				lane.storage.data().relayers,
+				vec![unrewarded_relayer(1, 3, TEST_RELAYER_A)]
+			);
 
 			assert_eq!(
 				lane.receive_state_update(OutboundLaneData {
@@ -248,7 +262,10 @@ mod tests {
 				Some(2),
 			);
 			assert_eq!(lane.storage.data().last_confirmed_nonce, 2);
-			assert_eq!(lane.storage.data().relayers, vec![(3, 3, TEST_RELAYER_A)]);
+			assert_eq!(
+				lane.storage.data().relayers,
+				vec![unrewarded_relayer(3, 3, TEST_RELAYER_A)]
+			);
 
 			assert_eq!(
 				lane.receive_state_update(OutboundLaneData {
@@ -269,10 +286,16 @@ mod tests {
 			let mut seed_storage_data = lane.storage.data();
 			// Prepare data
 			seed_storage_data.last_confirmed_nonce = 0;
-			seed_storage_data.relayers.push_back((1, 1, TEST_RELAYER_A));
+			seed_storage_data
+				.relayers
+				.push_back(unrewarded_relayer(1, 1, TEST_RELAYER_A));
 			// Simulate messages batch (2, 3, 4) from relayer #2
-			seed_storage_data.relayers.push_back((2, 4, TEST_RELAYER_B));
-			seed_storage_data.relayers.push_back((5, 5, TEST_RELAYER_C));
+			seed_storage_data
+				.relayers
+				.push_back(unrewarded_relayer(2, 4, TEST_RELAYER_B));
+			seed_storage_data
+				.relayers
+				.push_back(unrewarded_relayer(5, 5, TEST_RELAYER_C));
 			lane.storage.set_data(seed_storage_data);
 			// Check
 			assert_eq!(
@@ -285,7 +308,10 @@ mod tests {
 			assert_eq!(lane.storage.data().last_confirmed_nonce, 3);
 			assert_eq!(
 				lane.storage.data().relayers,
-				vec![(4, 4, TEST_RELAYER_B), (5, 5, TEST_RELAYER_C)]
+				vec![
+					unrewarded_relayer(4, 4, TEST_RELAYER_B),
+					unrewarded_relayer(5, 5, TEST_RELAYER_C)
+				]
 			);
 		});
 	}
@@ -418,7 +444,11 @@ mod tests {
 			);
 			assert_eq!(
 				lane.storage.data().relayers,
-				vec![(1, 1, TEST_RELAYER_A), (2, 2, TEST_RELAYER_B), (3, 3, TEST_RELAYER_A)]
+				vec![
+					unrewarded_relayer(1, 1, TEST_RELAYER_A),
+					unrewarded_relayer(2, 2, TEST_RELAYER_B),
+					unrewarded_relayer(3, 3, TEST_RELAYER_A)
+				]
 			);
 		});
 	}

bridges/modules/messages/src/lib.rs

@@ -43,21 +43,23 @@ pub use crate::weights_ext::{
 };
 
 use crate::inbound_lane::{InboundLane, InboundLaneStorage, ReceivalResult};
-use crate::outbound_lane::{OutboundLane, OutboundLaneStorage};
+use crate::outbound_lane::{OutboundLane, OutboundLaneStorage, ReceivalConfirmationResult};
 use crate::weights::WeightInfo;
 
 use bp_messages::{
-	source_chain::{LaneMessageVerifier, MessageDeliveryAndDispatchPayment, RelayersRewards, TargetHeaderChain},
+	source_chain::{
+		LaneMessageVerifier, MessageDeliveryAndDispatchPayment, OnDeliveryConfirmed, RelayersRewards, TargetHeaderChain,
+	},
 	target_chain::{DispatchMessage, MessageDispatch, ProvedLaneMessages, ProvedMessages, SourceHeaderChain},
-	total_unrewarded_messages, InboundLaneData, LaneId, MessageData, MessageKey, MessageNonce, OperatingMode,
-	OutboundLaneData, Parameter as MessagesParameter, UnrewardedRelayersState,
+	total_unrewarded_messages, DeliveredMessages, InboundLaneData, LaneId, MessageData, MessageKey, MessageNonce,
+	OperatingMode, OutboundLaneData, Parameter as MessagesParameter, UnrewardedRelayersState,
 };
 use bp_runtime::Size;
 use codec::{Decode, Encode};
 use frame_support::{
 	decl_error, decl_event, decl_module, decl_storage,
 	dispatch::DispatchResultWithPostInfo,
-	ensure,
+	ensure, fail,
 	traits::Get,
 	weights::{DispatchClass, Pays, PostDispatchInfo, Weight},
 	Parameter, StorageMap,
@@ -146,6 +148,8 @@ pub trait Config<I = DefaultInstance>: frame_system::Config {
 	type LaneMessageVerifier: LaneMessageVerifier<Self::AccountId, Self::OutboundPayload, Self::OutboundMessageFee>;
 	/// Message delivery payment.
 	type MessageDeliveryAndDispatchPayment: MessageDeliveryAndDispatchPayment<Self::AccountId, Self::OutboundMessageFee>;
+	/// Handler for delivered messages.
+	type OnDeliveryConfirmed: OnDeliveryConfirmed;
 
 	// Types that are used by inbound_lane (on target chain).
 
@@ -186,6 +190,8 @@ decl_error! {
 		InvalidMessagesDispatchWeight,
 		/// Invalid messages delivery proof has been submitted.
 		InvalidMessagesDeliveryProof,
+		/// The bridged chain has invalid `UnrewardedRelayers` in its storage (fatal for the lane).
+		InvalidUnrewardedRelayers,
 		/// The relayer has declared invalid unrewarded relayers state in the `receive_messages_delivery_proof` call.
 		InvalidUnrewardedRelayersState,
 		/// The message someone is trying to work with (i.e. increase fee) is already-delivered.
@@ -236,8 +242,8 @@ decl_event!(
 		ParameterUpdated(Parameter),
 		/// Message has been accepted and is waiting to be delivered.
 		MessageAccepted(LaneId, MessageNonce),
-		/// Messages in the inclusive range have been delivered and processed by the bridged chain.
-		MessagesDelivered(LaneId, MessageNonce, MessageNonce),
+		/// Messages in the inclusive range have been delivered to the bridged chain.
+		MessagesDelivered(LaneId, DeliveredMessages),
 		/// Phantom member, never used.
 		Dummy(PhantomData<(AccountId, I)>),
 	}
@@ -620,19 +626,36 @@ decl_module! {
 			let mut lane = outbound_lane::<T, I>(lane_id);
 			let mut relayers_rewards: RelayersRewards<_, T::OutboundMessageFee> = RelayersRewards::new();
 			let last_delivered_nonce = lane_data.last_delivered_nonce();
-			let received_range = lane.confirm_delivery(last_delivered_nonce);
-			if let Some(received_range) = received_range {
-				Self::deposit_event(RawEvent::MessagesDelivered(lane_id, received_range.0, received_range.1));
+			let confirmed_messages = match lane.confirm_delivery(last_delivered_nonce, &lane_data.relayers) {
+				ReceivalConfirmationResult::ConfirmedMessages(confirmed_messages) => Some(confirmed_messages),
+				ReceivalConfirmationResult::NoNewConfirmations => None,
+				error => {
+					log::trace!(
+						target: "runtime::bridge-messages",
+						"Messages delivery proof contains invalid unrewarded relayers vec: {:?}",
+						error,
+					);
+
+					fail!(Error::<T, I>::InvalidUnrewardedRelayers);
+				},
+			};
+			if let Some(confirmed_messages) = confirmed_messages {
+				// handle messages delivery confirmation
+				T::OnDeliveryConfirmed::on_messages_delivered(&lane_id, &confirmed_messages);
+
+				// emit 'delivered' event
+				let received_range = confirmed_messages.begin..=confirmed_messages.end;
+				Self::deposit_event(RawEvent::MessagesDelivered(lane_id, confirmed_messages));
 
 				// remember to reward relayers that have delivered messages
 				// this loop is bounded by `T::MaxUnrewardedRelayerEntriesAtInboundLane` on the bridged chain
-				for (nonce_low, nonce_high, relayer) in lane_data.relayers {
-					let nonce_begin = sp_std::cmp::max(nonce_low, received_range.0);
-					let nonce_end = sp_std::cmp::min(nonce_high, received_range.1);
+				for entry in lane_data.relayers {
+					let nonce_begin = sp_std::cmp::max(entry.messages.begin, *received_range.start());
+					let nonce_end = sp_std::cmp::min(entry.messages.end, *received_range.end());
 
 					// loop won't proceed if current entry is ahead of received range (begin > end).
 					// this loop is bound by `T::MaxUnconfirmedMessagesAtInboundLane` on the bridged chain
-					let mut relayer_reward = relayers_rewards.entry(relayer).or_default();
+					let mut relayer_reward = relayers_rewards.entry(entry.relayer).or_default();
 					for nonce in nonce_begin..nonce_end + 1 {
 						let message_data = OutboundMessages::<T, I>::get(MessageKey {
 							lane_id,
@@ -697,7 +720,10 @@ impl<T: Config<I>, I: Instance> Pallet<T, I> {
 		let relayers = InboundLanes::<T, I>::get(&lane).relayers;
 		bp_messages::UnrewardedRelayersState {
 			unrewarded_relayer_entries: relayers.len() as _,
-			messages_in_oldest_entry: relayers.front().map(|(begin, end, _)| 1 + end - begin).unwrap_or(0),
+			messages_in_oldest_entry: relayers
+				.front()
+				.map(|entry| 1 + entry.messages.end - entry.messages.begin)
+				.unwrap_or(0),
 			total_messages: total_unrewarded_messages(&relayers).unwrap_or(MessageNonce::MAX),
 		}
 	}
@@ -920,11 +946,12 @@ fn verify_and_decode_messages_proof<Chain: SourceHeaderChain<Fee>, Fee, Dispatch
 mod tests {
 	use super::*;
 	use crate::mock::{
-		message, message_payload, run_test, Event as TestEvent, Origin, TestMessageDeliveryAndDispatchPayment,
-		TestMessagesDeliveryProof, TestMessagesParameter, TestMessagesProof, TestRuntime, TokenConversionRate,
-		PAYLOAD_REJECTED_BY_TARGET_CHAIN, REGULAR_PAYLOAD, TEST_LANE_ID, TEST_RELAYER_A, TEST_RELAYER_B,
+		message, message_payload, run_test, unrewarded_relayer, Event as TestEvent, Origin,
+		TestMessageDeliveryAndDispatchPayment, TestMessagesDeliveryProof, TestMessagesParameter, TestMessagesProof,
+		TestRuntime, TokenConversionRate, PAYLOAD_REJECTED_BY_TARGET_CHAIN, REGULAR_PAYLOAD, TEST_LANE_ID,
+		TEST_RELAYER_A, TEST_RELAYER_B,
 	};
-	use bp_messages::UnrewardedRelayersState;
+	use bp_messages::{UnrewardedRelayer, UnrewardedRelayersState};
 	use frame_support::{assert_noop, assert_ok};
 	use frame_system::{EventRecord, Pallet as System, Phase};
 	use hex_literal::hex;
@@ -938,6 +965,10 @@ mod tests {
 	fn send_regular_message() {
 		get_ready_for_events();
 
+		let message_nonce = outbound_lane::<TestRuntime, DefaultInstance>(TEST_LANE_ID)
+			.data()
+			.latest_generated_nonce
+			+ 1;
 		assert_ok!(Pallet::<TestRuntime>::send_message(
 			Origin::signed(1),
 			TEST_LANE_ID,
@@ -950,7 +981,7 @@ mod tests {
 			System::<TestRuntime>::events(),
 			vec![EventRecord {
 				phase: Phase::Initialization,
-				event: TestEvent::Messages(RawEvent::MessageAccepted(TEST_LANE_ID, 1)),
+				event: TestEvent::Messages(RawEvent::MessageAccepted(TEST_LANE_ID, message_nonce)),
 				topics: vec![],
 			}],
 		);
@@ -972,17 +1003,29 @@ mod tests {
 				TEST_LANE_ID,
 				InboundLaneData {
 					last_confirmed_nonce: 1,
-					..Default::default()
+					relayers: vec![UnrewardedRelayer {
+						relayer: 0,
+						messages: DeliveredMessages::new(1, true),
+					}]
+					.into_iter()
+					.collect(),
 				},
 			))),
-			Default::default(),
+			UnrewardedRelayersState {
+				unrewarded_relayer_entries: 1,
+				total_messages: 1,
+				..Default::default()
+			},
 		));
 
 		assert_eq!(
 			System::<TestRuntime>::events(),
 			vec![EventRecord {
 				phase: Phase::Initialization,
-				event: TestEvent::Messages(RawEvent::MessagesDelivered(TEST_LANE_ID, 1, 1)),
+				event: TestEvent::Messages(RawEvent::MessagesDelivered(
+					TEST_LANE_ID,
+					DeliveredMessages::new(1, true),
+				)),
 				topics: vec![],
 			}],
 		);
@@ -1333,7 +1376,10 @@ mod tests {
 				TEST_LANE_ID,
 				InboundLaneData {
 					last_confirmed_nonce: 8,
-					relayers: vec![(9, 9, TEST_RELAYER_A), (10, 10, TEST_RELAYER_B)]
+					relayers: vec![
+						unrewarded_relayer(9, 9, TEST_RELAYER_A),
+						unrewarded_relayer(10, 10, TEST_RELAYER_B),
+					]
 					.into_iter()
 					.collect(),
 				},
@@ -1366,7 +1412,10 @@ mod tests {
 				InboundLanes::<TestRuntime>::get(TEST_LANE_ID),
 				InboundLaneData {
 					last_confirmed_nonce: 9,
-					relayers: vec![(10, 10, TEST_RELAYER_B), (11, 11, TEST_RELAYER_A)]
+					relayers: vec![
+						unrewarded_relayer(10, 10, TEST_RELAYER_B),
+						unrewarded_relayer(11, 11, TEST_RELAYER_A)
+					]
 					.into_iter()
 					.collect(),
 				},
@@ -1465,7 +1514,7 @@ mod tests {
 				TestMessagesDeliveryProof(Ok((
 					TEST_LANE_ID,
 					InboundLaneData {
-						relayers: vec![(1, 1, TEST_RELAYER_A)].into_iter().collect(),
+						relayers: vec![unrewarded_relayer(1, 1, TEST_RELAYER_A)].into_iter().collect(),
 						..Default::default()
 					}
 				))),
@@ -1490,7 +1539,10 @@ mod tests {
 				TestMessagesDeliveryProof(Ok((
 					TEST_LANE_ID,
 					InboundLaneData {
-						relayers: vec![(1, 1, TEST_RELAYER_A), (2, 2, TEST_RELAYER_B)]
+						relayers: vec![
+							unrewarded_relayer(1, 1, TEST_RELAYER_A),
+							unrewarded_relayer(2, 2, TEST_RELAYER_B)
+						]
 						.into_iter()
 						.collect(),
 						..Default::default()
@@ -1537,7 +1589,10 @@ mod tests {
 					TestMessagesDeliveryProof(Ok((
 						TEST_LANE_ID,
 						InboundLaneData {
-							relayers: vec![(1, 1, TEST_RELAYER_A), (2, 2, TEST_RELAYER_B)]
+							relayers: vec![
+								unrewarded_relayer(1, 1, TEST_RELAYER_A),
+								unrewarded_relayer(2, 2, TEST_RELAYER_B)
+							]
 							.into_iter()
 							.collect(),
 							..Default::default()
@@ -1559,7 +1614,10 @@ mod tests {
 					TestMessagesDeliveryProof(Ok((
 						TEST_LANE_ID,
 						InboundLaneData {
-							relayers: vec![(1, 1, TEST_RELAYER_A), (2, 2, TEST_RELAYER_B)]
+							relayers: vec![
+								unrewarded_relayer(1, 1, TEST_RELAYER_A),
+								unrewarded_relayer(2, 2, TEST_RELAYER_B)
+							]
 							.into_iter()
 							.collect(),
 							..Default::default()
@@ -1791,4 +1849,70 @@ mod tests {
 			);
 		});
 	}
+
+	#[test]
+	fn messages_delivered_callbacks_are_called() {
+		run_test(|| {
+			send_regular_message();
+			send_regular_message();
+			send_regular_message();
+
+			// messages 1+2 are confirmed in 1 tx, message 3 in a separate tx
+			// dispatch of message 2 has failed
+			let mut delivered_messages_1_and_2 = DeliveredMessages::new(1, true);
+			delivered_messages_1_and_2.note_dispatched_message(false);
+			let messages_1_and_2_proof = Ok((
+				TEST_LANE_ID,
+				InboundLaneData {
+					last_confirmed_nonce: 0,
+					relayers: vec![UnrewardedRelayer {
+						relayer: 0,
+						messages: delivered_messages_1_and_2.clone(),
+					}]
+					.into_iter()
+					.collect(),
+				},
+			));
+			let delivered_message_3 = DeliveredMessages::new(3, true);
+			let messages_3_proof = Ok((
+				TEST_LANE_ID,
+				InboundLaneData {
+					last_confirmed_nonce: 0,
+					relayers: vec![UnrewardedRelayer {
+						relayer: 0,
+						messages: delivered_message_3.clone(),
+					}]
+					.into_iter()
+					.collect(),
+				},
+			));
+
+			// first tx with messages 1+2
+			assert_ok!(Pallet::<TestRuntime>::receive_messages_delivery_proof(
+				Origin::signed(1),
+				TestMessagesDeliveryProof(messages_1_and_2_proof),
+				UnrewardedRelayersState {
+					unrewarded_relayer_entries: 1,
+					total_messages: 2,
+					..Default::default()
+				},
+			));
+			// second tx with message 3
+			assert_ok!(Pallet::<TestRuntime>::receive_messages_delivery_proof(
+				Origin::signed(1),
+				TestMessagesDeliveryProof(messages_3_proof),
+				UnrewardedRelayersState {
+					unrewarded_relayer_entries: 1,
+					total_messages: 1,
+					..Default::default()
+				},
+			));
+
+			// ensure that both callbacks have been called twice: for 1+2, then for 3
+			crate::mock::TestOnDeliveryConfirmed1::ensure_called(&TEST_LANE_ID, &delivered_messages_1_and_2);
+			crate::mock::TestOnDeliveryConfirmed1::ensure_called(&TEST_LANE_ID, &delivered_message_3);
+			crate::mock::TestOnDeliveryConfirmed2::ensure_called(&TEST_LANE_ID, &delivered_messages_1_and_2);
+			crate::mock::TestOnDeliveryConfirmed2::ensure_called(&TEST_LANE_ID, &delivered_message_3);
+		});
+	}
 }

bridges/modules/messages/src/mock.rs

@@ -19,13 +19,15 @@
 
 use crate::Config;
 
+use bitvec::prelude::*;
 use bp_messages::{
 	source_chain::{
-		LaneMessageVerifier, MessageDeliveryAndDispatchPayment, RelayersRewards, Sender, TargetHeaderChain,
+		LaneMessageVerifier, MessageDeliveryAndDispatchPayment, OnDeliveryConfirmed, RelayersRewards, Sender,
+		TargetHeaderChain,
 	},
 	target_chain::{DispatchMessage, MessageDispatch, ProvedLaneMessages, ProvedMessages, SourceHeaderChain},
-	InboundLaneData, LaneId, Message, MessageData, MessageKey, MessageNonce, OutboundLaneData,
-	Parameter as MessagesParameter,
+	DeliveredMessages, InboundLaneData, LaneId, Message, MessageData, MessageKey, MessageNonce, OutboundLaneData,
+	Parameter as MessagesParameter, UnrewardedRelayer,
 };
 use bp_runtime::{messages::MessageDispatchResult, Size};
 use codec::{Decode, Encode};
@@ -169,6 +171,7 @@ impl Config for TestRuntime {
 	type TargetHeaderChain = TestTargetHeaderChain;
 	type LaneMessageVerifier = TestLaneMessageVerifier;
 	type MessageDeliveryAndDispatchPayment = TestMessageDeliveryAndDispatchPayment;
+	type OnDeliveryConfirmed = (TestOnDeliveryConfirmed1, TestOnDeliveryConfirmed2);
 
 	type SourceHeaderChain = TestSourceHeaderChain;
 	type MessageDispatch = TestMessageDispatch;
@@ -345,6 +348,44 @@ impl MessageDeliveryAndDispatchPayment<AccountId, TestMessageFee> for TestMessag
 	}
 }
 
+/// First on-messages-delivered callback.
+#[derive(Debug)]
+pub struct TestOnDeliveryConfirmed1;
+
+impl TestOnDeliveryConfirmed1 {
+	/// Verify that the callback has been called with given delivered messages.
+	pub fn ensure_called(lane: &LaneId, messages: &DeliveredMessages) {
+		let key = (b"TestOnDeliveryConfirmed1", lane, messages).encode();
+		assert_eq!(frame_support::storage::unhashed::get(&key), Some(true));
+	}
+}
+
+impl OnDeliveryConfirmed for TestOnDeliveryConfirmed1 {
+	fn on_messages_delivered(lane: &LaneId, messages: &DeliveredMessages) {
+		let key = (b"TestOnDeliveryConfirmed1", lane, messages).encode();
+		frame_support::storage::unhashed::put(&key, &true);
+	}
+}
+
+/// Seconde on-messages-delivered callback.
+#[derive(Debug)]
+pub struct TestOnDeliveryConfirmed2;
+
+impl TestOnDeliveryConfirmed2 {
+	/// Verify that the callback has been called with given delivered messages.
+	pub fn ensure_called(lane: &LaneId, messages: &DeliveredMessages) {
+		let key = (b"TestOnDeliveryConfirmed2", lane, messages).encode();
+		assert_eq!(frame_support::storage::unhashed::get(&key), Some(true));
+	}
+}
+
+impl OnDeliveryConfirmed for TestOnDeliveryConfirmed2 {
+	fn on_messages_delivered(lane: &LaneId, messages: &DeliveredMessages) {
+		let key = (b"TestOnDeliveryConfirmed2", lane, messages).encode();
+		frame_support::storage::unhashed::put(&key, &true);
+	}
+}
+
 /// Source header chain that is used in tests.
 #[derive(Debug)]
 pub struct TestSourceHeaderChain;
@@ -421,11 +462,32 @@ pub fn message_data(payload: TestPayload) -> MessageData<TestMessageFee> {
 /// Returns message dispatch result with given unspent weight.
 pub const fn dispatch_result(unspent_weight: Weight) -> MessageDispatchResult {
 	MessageDispatchResult {
+		dispatch_result: true,
 		unspent_weight,
 		dispatch_fee_paid_during_dispatch: true,
 	}
 }
 
+/// Constructs unrewarded relayer entry from nonces range and relayer id.
+pub fn unrewarded_relayer(
+	begin: MessageNonce,
+	end: MessageNonce,
+	relayer: TestRelayer,
+) -> UnrewardedRelayer<TestRelayer> {
+	UnrewardedRelayer {
+		relayer,
+		messages: DeliveredMessages {
+			begin,
+			end,
+			dispatch_results: if end >= begin {
+				bitvec![Msb0, u8; 1; (end - begin + 1) as _]
+			} else {
+				Default::default()
+			},
+		},
+	}
+}
+
 /// Run pallet test.
 pub fn run_test<T>(test: impl FnOnce() -> T) -> T {
 	let mut t = frame_system::GenesisConfig::default()

bridges/modules/messages/src/outbound_lane.rs

@@ -16,7 +16,12 @@
 
 //! Everything about outgoing messages sending.
 
-use bp_messages::{LaneId, MessageData, MessageNonce, OutboundLaneData};
+use bitvec::prelude::*;
+use bp_messages::{
+	DeliveredMessages, DispatchResultsBitVec, LaneId, MessageData, MessageNonce, OutboundLaneData, UnrewardedRelayer,
+};
+use frame_support::RuntimeDebug;
+use sp_std::collections::vec_deque::VecDeque;
 
 /// Outbound lane storage.
 pub trait OutboundLaneStorage {
@@ -38,6 +43,28 @@ pub trait OutboundLaneStorage {
 	fn remove_message(&mut self, nonce: &MessageNonce);
 }
 
+/// Result of messages receival confirmation.
+#[derive(RuntimeDebug, PartialEq, Eq)]
+pub enum ReceivalConfirmationResult {
+	/// New messages have been confirmed by the confirmation transaction.
+	ConfirmedMessages(DeliveredMessages),
+	/// Confirmation transaction brings no new confirmation. This may be a result of relayer
+	/// error or several relayers runnng.
+	NoNewConfirmations,
+	/// Bridged chain is trying to confirm more messages than we have generated. May be a result
+	/// of invalid bridged chain storage.
+	FailedToConfirmFutureMessages,
+	/// The unrewarded relayers vec contains an empty entry. May be a result of invalid bridged
+	/// chain storage.
+	EmptyUnrewardedRelayerEntry,
+	/// The unrewarded relayers vec contains non-consecutive entries. May be a result of invalid bridged
+	/// chain storage.
+	NonConsecutiveUnrewardedRelayerEntries,
+	/// The unrewarded relayers vec contains entry with mismatched number of dispatch results. May be
+	/// a result of invalid bridged chain storage.
+	InvalidNumberOfDispatchResults,
+}
+
 /// Outbound messages lane.
 pub struct OutboundLane<S> {
 	storage: S,
@@ -69,20 +96,34 @@ impl<S: OutboundLaneStorage> OutboundLane<S> {
 	}
 
 	/// Confirm messages delivery.
-	///
-	/// Returns `None` if confirmation is wrong/duplicate.
-	/// Returns `Some` with inclusive ranges of message nonces that have been received.
-	pub fn confirm_delivery(&mut self, latest_received_nonce: MessageNonce) -> Option<(MessageNonce, MessageNonce)> {
+	pub fn confirm_delivery<RelayerId>(
+		&mut self,
+		latest_received_nonce: MessageNonce,
+		relayers: &VecDeque<UnrewardedRelayer<RelayerId>>,
+	) -> ReceivalConfirmationResult {
 		let mut data = self.storage.data();
-		if latest_received_nonce <= data.latest_received_nonce || latest_received_nonce > data.latest_generated_nonce {
-			return None;
+		if latest_received_nonce <= data.latest_received_nonce {
+			return ReceivalConfirmationResult::NoNewConfirmations;
 		}
+		if latest_received_nonce > data.latest_generated_nonce {
+			return ReceivalConfirmationResult::FailedToConfirmFutureMessages;
+		}
+
+		let dispatch_results =
+			match extract_dispatch_results(data.latest_received_nonce, latest_received_nonce, relayers) {
+				Ok(dispatch_results) => dispatch_results,
+				Err(extract_error) => return extract_error,
+			};
 
 		let prev_latest_received_nonce = data.latest_received_nonce;
 		data.latest_received_nonce = latest_received_nonce;
 		self.storage.set_data(data);
 
-		Some((prev_latest_received_nonce + 1, latest_received_nonce))
+		ReceivalConfirmationResult::ConfirmedMessages(DeliveredMessages {
+			begin: prev_latest_received_nonce + 1,
+			end: latest_received_nonce,
+			dispatch_results,
+		})
 	}
 
 	/// Prune at most `max_messages_to_prune` already received messages.
@@ -108,13 +149,108 @@ impl<S: OutboundLaneStorage> OutboundLane<S> {
 	}
 }
 
+/// Extract new dispatch results from the unrewarded relayers vec.
+///
+/// Returns `Err(_)` if unrewarded relayers vec contains invalid data, meaning that the bridged
+/// chain has invalid runtime storage.
+fn extract_dispatch_results<RelayerId>(
+	prev_latest_received_nonce: MessageNonce,
+	latest_received_nonce: MessageNonce,
+	relayers: &VecDeque<UnrewardedRelayer<RelayerId>>,
+) -> Result<DispatchResultsBitVec, ReceivalConfirmationResult> {
+	// the only caller of this functions checks that the prev_latest_received_nonce..=latest_received_nonce
+	// is valid, so we're ready to accept messages in this range
+	// => with_capacity call must succeed here or we'll be unable to receive confirmations at all
+	let mut received_dispatch_result =
+		BitVec::with_capacity((latest_received_nonce - prev_latest_received_nonce + 1) as _);
+	let mut last_entry_end: Option<MessageNonce> = None;
+	for entry in relayers {
+		// unrewarded relayer entry must have at least 1 unconfirmed message
+		// (guaranteed by the `InboundLane::receive_message()`)
+		if entry.messages.end < entry.messages.begin {
+			return Err(ReceivalConfirmationResult::EmptyUnrewardedRelayerEntry);
+		}
+		// every entry must confirm range of messages that follows previous entry range
+		// (guaranteed by the `InboundLane::receive_message()`)
+		if let Some(last_entry_end) = last_entry_end {
+			let expected_entry_begin = last_entry_end.checked_add(1);
+			if expected_entry_begin != Some(entry.messages.begin) {
+				return Err(ReceivalConfirmationResult::NonConsecutiveUnrewardedRelayerEntries);
+			}
+		}
+		last_entry_end = Some(entry.messages.end);
+		// entry can't confirm messages larger than `inbound_lane_data.latest_received_nonce()`
+		// (guaranteed by the `InboundLane::receive_message()`)
+		if entry.messages.end > latest_received_nonce {
+			// technically this will be detected in the next loop iteration as `InvalidNumberOfDispatchResults`
+			// but to guarantee safety of loop operations below this is detected now
+			return Err(ReceivalConfirmationResult::FailedToConfirmFutureMessages);
+		}
+		// entry must have single dispatch result for every message
+		// (guaranteed by the `InboundLane::receive_message()`)
+		if entry.messages.dispatch_results.len() as MessageNonce != entry.messages.end - entry.messages.begin + 1 {
+			return Err(ReceivalConfirmationResult::InvalidNumberOfDispatchResults);
+		}
+
+		// now we know that the entry is valid
+		// => let's check if it brings new confirmations
+		let new_messages_begin = sp_std::cmp::max(entry.messages.begin, prev_latest_received_nonce + 1);
+		let new_messages_end = sp_std::cmp::min(entry.messages.end, latest_received_nonce);
+		let new_messages_range = new_messages_begin..=new_messages_end;
+		if new_messages_range.is_empty() {
+			continue;
+		}
+
+		// now we know that entry brings new confirmations
+		// => let's extract dispatch results
+		received_dispatch_result.extend_from_bitslice(
+			&entry.messages.dispatch_results[(new_messages_begin - entry.messages.begin) as usize..],
+		);
+	}
+
+	Ok(received_dispatch_result)
+}
+
 #[cfg(test)]
 mod tests {
 	use super::*;
 	use crate::{
-		mock::{message_data, run_test, TestRuntime, REGULAR_PAYLOAD, TEST_LANE_ID},
+		mock::{message_data, run_test, unrewarded_relayer, TestRelayer, TestRuntime, REGULAR_PAYLOAD, TEST_LANE_ID},
 		outbound_lane,
 	};
+	use sp_std::ops::RangeInclusive;
+
+	fn unrewarded_relayers(nonces: RangeInclusive<MessageNonce>) -> VecDeque<UnrewardedRelayer<TestRelayer>> {
+		vec![unrewarded_relayer(*nonces.start(), *nonces.end(), 0)]
+			.into_iter()
+			.collect()
+	}
+
+	fn delivered_messages(nonces: RangeInclusive<MessageNonce>) -> DeliveredMessages {
+		DeliveredMessages {
+			begin: *nonces.start(),
+			end: *nonces.end(),
+			dispatch_results: bitvec![Msb0, u8; 1; (nonces.end() - nonces.start() + 1) as _],
+		}
+	}
+
+	fn assert_3_messages_confirmation_fails(
+		latest_received_nonce: MessageNonce,
+		relayers: &VecDeque<UnrewardedRelayer<TestRelayer>>,
+	) -> ReceivalConfirmationResult {
+		run_test(|| {
+			let mut lane = outbound_lane::<TestRuntime, _>(TEST_LANE_ID);
+			lane.send_message(message_data(REGULAR_PAYLOAD));
+			lane.send_message(message_data(REGULAR_PAYLOAD));
+			lane.send_message(message_data(REGULAR_PAYLOAD));
+			assert_eq!(lane.storage.data().latest_generated_nonce, 3);
+			assert_eq!(lane.storage.data().latest_received_nonce, 0);
+			let result = lane.confirm_delivery(latest_received_nonce, relayers);
+			assert_eq!(lane.storage.data().latest_generated_nonce, 3);
+			assert_eq!(lane.storage.data().latest_received_nonce, 0);
+			result
+		})
+	}
 
 	#[test]
 	fn send_message_works() {
@@ -136,7 +272,10 @@ mod tests {
 			assert_eq!(lane.send_message(message_data(REGULAR_PAYLOAD)), 3);
 			assert_eq!(lane.storage.data().latest_generated_nonce, 3);
 			assert_eq!(lane.storage.data().latest_received_nonce, 0);
-			assert_eq!(lane.confirm_delivery(3), Some((1, 3)));
+			assert_eq!(
+				lane.confirm_delivery(3, &unrewarded_relayers(1..=3)),
+				ReceivalConfirmationResult::ConfirmedMessages(delivered_messages(1..=3)),
+			);
 			assert_eq!(lane.storage.data().latest_generated_nonce, 3);
 			assert_eq!(lane.storage.data().latest_received_nonce, 3);
 		});
@@ -151,12 +290,21 @@ mod tests {
 			lane.send_message(message_data(REGULAR_PAYLOAD));
 			assert_eq!(lane.storage.data().latest_generated_nonce, 3);
 			assert_eq!(lane.storage.data().latest_received_nonce, 0);
-			assert_eq!(lane.confirm_delivery(3), Some((1, 3)));
-			assert_eq!(lane.confirm_delivery(3), None);
+			assert_eq!(
+				lane.confirm_delivery(3, &unrewarded_relayers(1..=3)),
+				ReceivalConfirmationResult::ConfirmedMessages(delivered_messages(1..=3)),
+			);
+			assert_eq!(
+				lane.confirm_delivery(3, &unrewarded_relayers(1..=3)),
+				ReceivalConfirmationResult::NoNewConfirmations,
+			);
 			assert_eq!(lane.storage.data().latest_generated_nonce, 3);
 			assert_eq!(lane.storage.data().latest_received_nonce, 3);
 
-			assert_eq!(lane.confirm_delivery(2), None);
+			assert_eq!(
+				lane.confirm_delivery(2, &unrewarded_relayers(1..=1)),
+				ReceivalConfirmationResult::NoNewConfirmations,
+			);
 			assert_eq!(lane.storage.data().latest_generated_nonce, 3);
 			assert_eq!(lane.storage.data().latest_received_nonce, 3);
 		});
@@ -164,17 +312,70 @@ mod tests {
 
 	#[test]
 	fn confirm_delivery_rejects_nonce_larger_than_last_generated() {
-		run_test(|| {
-			let mut lane = outbound_lane::<TestRuntime, _>(TEST_LANE_ID);
-			lane.send_message(message_data(REGULAR_PAYLOAD));
-			lane.send_message(message_data(REGULAR_PAYLOAD));
-			lane.send_message(message_data(REGULAR_PAYLOAD));
-			assert_eq!(lane.storage.data().latest_generated_nonce, 3);
-			assert_eq!(lane.storage.data().latest_received_nonce, 0);
-			assert_eq!(lane.confirm_delivery(10), None);
-			assert_eq!(lane.storage.data().latest_generated_nonce, 3);
-			assert_eq!(lane.storage.data().latest_received_nonce, 0);
-		});
+		assert_eq!(
+			assert_3_messages_confirmation_fails(10, &unrewarded_relayers(1..=10),),
+			ReceivalConfirmationResult::FailedToConfirmFutureMessages,
+		);
+	}
+
+	#[test]
+	fn confirm_delivery_fails_if_entry_confirms_future_messages() {
+		assert_eq!(
+			assert_3_messages_confirmation_fails(
+				3,
+				&unrewarded_relayers(1..=1)
+					.into_iter()
+					.chain(unrewarded_relayers(2..=30).into_iter())
+					.chain(unrewarded_relayers(3..=3).into_iter())
+					.collect(),
+			),
+			ReceivalConfirmationResult::FailedToConfirmFutureMessages,
+		);
+	}
+
+	#[test]
+	#[allow(clippy::reversed_empty_ranges)]
+	fn confirm_delivery_fails_if_entry_is_empty() {
+		assert_eq!(
+			assert_3_messages_confirmation_fails(
+				3,
+				&unrewarded_relayers(1..=1)
+					.into_iter()
+					.chain(unrewarded_relayers(2..=1).into_iter())
+					.chain(unrewarded_relayers(2..=3).into_iter())
+					.collect(),
+			),
+			ReceivalConfirmationResult::EmptyUnrewardedRelayerEntry,
+		);
+	}
+
+	#[test]
+	fn confirm_delivery_fails_if_entries_are_non_consecutive() {
+		assert_eq!(
+			assert_3_messages_confirmation_fails(
+				3,
+				&unrewarded_relayers(1..=1)
+					.into_iter()
+					.chain(unrewarded_relayers(3..=3).into_iter())
+					.chain(unrewarded_relayers(2..=2).into_iter())
+					.collect(),
+			),
+			ReceivalConfirmationResult::NonConsecutiveUnrewardedRelayerEntries,
+		);
+	}
+
+	#[test]
+	fn confirm_delivery_fails_if_number_of_dispatch_results_in_entry_is_invalid() {
+		let mut relayers: VecDeque<_> = unrewarded_relayers(1..=1)
+			.into_iter()
+			.chain(unrewarded_relayers(2..=2).into_iter())
+			.chain(unrewarded_relayers(3..=3).into_iter())
+			.collect();
+		relayers[0].messages.dispatch_results.clear();
+		assert_eq!(
+			assert_3_messages_confirmation_fails(3, &relayers),
+			ReceivalConfirmationResult::InvalidNumberOfDispatchResults,
+		);
 	}
 
 	#[test]
@@ -191,11 +392,17 @@ mod tests {
 			assert_eq!(lane.prune_messages(100), 0);
 			assert_eq!(lane.storage.data().oldest_unpruned_nonce, 1);
 			// after confirmation, some messages are received
-			assert_eq!(lane.confirm_delivery(2), Some((1, 2)));
+			assert_eq!(
+				lane.confirm_delivery(2, &unrewarded_relayers(1..=2)),
+				ReceivalConfirmationResult::ConfirmedMessages(delivered_messages(1..=2)),
+			);
 			assert_eq!(lane.prune_messages(100), 2);
 			assert_eq!(lane.storage.data().oldest_unpruned_nonce, 3);
 			// after last message is confirmed, everything is pruned
-			assert_eq!(lane.confirm_delivery(3), Some((3, 3)));
+			assert_eq!(
+				lane.confirm_delivery(3, &unrewarded_relayers(3..=3)),
+				ReceivalConfirmationResult::ConfirmedMessages(delivered_messages(3..=3)),
+			);
 			assert_eq!(lane.prune_messages(100), 1);
 			assert_eq!(lane.storage.data().oldest_unpruned_nonce, 4);
 		});

bridges/modules/messages/src/weights.rs

@@ -17,7 +17,7 @@
 //! Autogenerated weights for pallet_bridge_messages
 //!
 //! THIS FILE WAS AUTO-GENERATED USING THE SUBSTRATE BENCHMARK CLI VERSION 3.0.0
-//! DATE: 2021-06-15, STEPS: [50, ], REPEAT: 20
+//! DATE: 2021-06-18, STEPS: [50, ], REPEAT: 20
 //! LOW RANGE: [], HIGH RANGE: []
 //! EXECUTION: Some(Wasm), WASM-EXECUTION: Compiled
 //! CHAIN: Some("dev"), DB CACHE: 128
@@ -74,110 +74,110 @@ pub trait WeightInfo {
 pub struct RialtoWeight<T>(PhantomData<T>);
 impl<T: frame_system::Config> WeightInfo for RialtoWeight<T> {
 	fn send_minimal_message_worst_case() -> Weight {
-		(154_371_000 as Weight)
+		(159_305_000 as Weight)
 			.saturating_add(T::DbWeight::get().reads(5 as Weight))
 			.saturating_add(T::DbWeight::get().writes(12 as Weight))
 	}
 	fn send_1_kb_message_worst_case() -> Weight {
-		(157_479_000 as Weight)
+		(164_394_000 as Weight)
 			.saturating_add(T::DbWeight::get().reads(5 as Weight))
 			.saturating_add(T::DbWeight::get().writes(12 as Weight))
 	}
 	fn send_16_kb_message_worst_case() -> Weight {
-		(186_840_000 as Weight)
+		(223_521_000 as Weight)
 			.saturating_add(T::DbWeight::get().reads(5 as Weight))
 			.saturating_add(T::DbWeight::get().writes(12 as Weight))
 	}
 	fn increase_message_fee() -> Weight {
-		(4_377_567_000 as Weight)
+		(6_709_925_000 as Weight)
 			.saturating_add(T::DbWeight::get().reads(5 as Weight))
 			.saturating_add(T::DbWeight::get().writes(3 as Weight))
 	}
 	fn receive_single_message_proof() -> Weight {
-		(205_350_000 as Weight)
+		(206_769_000 as Weight)
 			.saturating_add(T::DbWeight::get().reads(5 as Weight))
 			.saturating_add(T::DbWeight::get().writes(3 as Weight))
 	}
 	fn receive_two_messages_proof() -> Weight {
-		(337_102_000 as Weight)
+		(343_982_000 as Weight)
 			.saturating_add(T::DbWeight::get().reads(5 as Weight))
 			.saturating_add(T::DbWeight::get().writes(3 as Weight))
 	}
 	fn receive_single_message_proof_with_outbound_lane_state() -> Weight {
-		(218_825_000 as Weight)
+		(223_738_000 as Weight)
 			.saturating_add(T::DbWeight::get().reads(5 as Weight))
 			.saturating_add(T::DbWeight::get().writes(3 as Weight))
 	}
 	fn receive_single_message_proof_1_kb() -> Weight {
-		(230_759_000 as Weight)
+		(235_369_000 as Weight)
 			.saturating_add(T::DbWeight::get().reads(5 as Weight))
 			.saturating_add(T::DbWeight::get().writes(3 as Weight))
 	}
 	fn receive_single_message_proof_16_kb() -> Weight {
-		(490_522_000 as Weight)
+		(510_338_000 as Weight)
 			.saturating_add(T::DbWeight::get().reads(5 as Weight))
 			.saturating_add(T::DbWeight::get().writes(3 as Weight))
 	}
 	fn receive_single_prepaid_message_proof() -> Weight {
-		(136_550_000 as Weight)
+		(141_536_000 as Weight)
 			.saturating_add(T::DbWeight::get().reads(3 as Weight))
 			.saturating_add(T::DbWeight::get().writes(1 as Weight))
 	}
 	fn receive_delivery_proof_for_single_message() -> Weight {
-		(131_397_000 as Weight)
+		(128_805_000 as Weight)
 			.saturating_add(T::DbWeight::get().reads(6 as Weight))
 			.saturating_add(T::DbWeight::get().writes(3 as Weight))
 	}
 	fn receive_delivery_proof_for_two_messages_by_single_relayer() -> Weight {
-		(137_946_000 as Weight)
+		(137_143_000 as Weight)
 			.saturating_add(T::DbWeight::get().reads(7 as Weight))
 			.saturating_add(T::DbWeight::get().writes(3 as Weight))
 	}
 	fn receive_delivery_proof_for_two_messages_by_two_relayers() -> Weight {
-		(194_448_000 as Weight)
+		(193_108_000 as Weight)
 			.saturating_add(T::DbWeight::get().reads(8 as Weight))
 			.saturating_add(T::DbWeight::get().writes(4 as Weight))
 	}
 	fn send_messages_of_various_lengths(i: u32) -> Weight {
-		(142_576_000 as Weight)
-			.saturating_add((2_000 as Weight).saturating_mul(i as Weight))
+		(133_632_000 as Weight)
+			.saturating_add((4_000 as Weight).saturating_mul(i as Weight))
 			.saturating_add(T::DbWeight::get().reads(5 as Weight))
 			.saturating_add(T::DbWeight::get().writes(12 as Weight))
 	}
 	fn receive_multiple_messages_proof(i: u32) -> Weight {
 		(0 as Weight)
-			.saturating_add((138_341_000 as Weight).saturating_mul(i as Weight))
+			.saturating_add((145_006_000 as Weight).saturating_mul(i as Weight))
 			.saturating_add(T::DbWeight::get().reads(5 as Weight))
 			.saturating_add(T::DbWeight::get().writes(3 as Weight))
 	}
 	fn receive_message_proofs_with_extra_nodes(i: u32) -> Weight {
-		(472_752_000 as Weight)
-			.saturating_add((9_000 as Weight).saturating_mul(i as Weight))
+		(486_301_000 as Weight)
+			.saturating_add((10_000 as Weight).saturating_mul(i as Weight))
 			.saturating_add(T::DbWeight::get().reads(5 as Weight))
 			.saturating_add(T::DbWeight::get().writes(3 as Weight))
 	}
 	fn receive_message_proofs_with_large_leaf(i: u32) -> Weight {
-		(175_300_000 as Weight)
-			.saturating_add((6_000 as Weight).saturating_mul(i as Weight))
+		(178_139_000 as Weight)
+			.saturating_add((7_000 as Weight).saturating_mul(i as Weight))
 			.saturating_add(T::DbWeight::get().reads(5 as Weight))
 			.saturating_add(T::DbWeight::get().writes(3 as Weight))
 	}
 	fn receive_multiple_messages_proof_with_outbound_lane_state(i: u32) -> Weight {
 		(0 as Weight)
-			.saturating_add((142_176_000 as Weight).saturating_mul(i as Weight))
+			.saturating_add((150_844_000 as Weight).saturating_mul(i as Weight))
 			.saturating_add(T::DbWeight::get().reads(5 as Weight))
 			.saturating_add(T::DbWeight::get().writes(3 as Weight))
 	}
 	fn receive_delivery_proof_for_multiple_messages_by_single_relayer(i: u32) -> Weight {
-		(127_372_000 as Weight)
-			.saturating_add((7_927_000 as Weight).saturating_mul(i as Weight))
+		(113_140_000 as Weight)
+			.saturating_add((7_656_000 as Weight).saturating_mul(i as Weight))
 			.saturating_add(T::DbWeight::get().reads(5 as Weight))
 			.saturating_add(T::DbWeight::get().reads((1 as Weight).saturating_mul(i as Weight)))
 			.saturating_add(T::DbWeight::get().writes(3 as Weight))
 	}
 	fn receive_delivery_proof_for_multiple_messages_by_multiple_relayers(i: u32) -> Weight {
-		(99_781_000 as Weight)
-			.saturating_add((64_001_000 as Weight).saturating_mul(i as Weight))
+		(97_424_000 as Weight)
+			.saturating_add((63_128_000 as Weight).saturating_mul(i as Weight))
 			.saturating_add(T::DbWeight::get().reads(5 as Weight))
 			.saturating_add(T::DbWeight::get().reads((2 as Weight).saturating_mul(i as Weight)))
 			.saturating_add(T::DbWeight::get().writes(3 as Weight))
@@ -188,110 +188,110 @@ impl<T: frame_system::Config> WeightInfo for RialtoWeight<T> {
 // For backwards compatibility and tests
 impl WeightInfo for () {
 	fn send_minimal_message_worst_case() -> Weight {
-		(154_371_000 as Weight)
+		(159_305_000 as Weight)
 			.saturating_add(RocksDbWeight::get().reads(5 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(12 as Weight))
 	}
 	fn send_1_kb_message_worst_case() -> Weight {
-		(157_479_000 as Weight)
+		(164_394_000 as Weight)
 			.saturating_add(RocksDbWeight::get().reads(5 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(12 as Weight))
 	}
 	fn send_16_kb_message_worst_case() -> Weight {
-		(186_840_000 as Weight)
+		(223_521_000 as Weight)
 			.saturating_add(RocksDbWeight::get().reads(5 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(12 as Weight))
 	}
 	fn increase_message_fee() -> Weight {
-		(4_377_567_000 as Weight)
+		(6_709_925_000 as Weight)
 			.saturating_add(RocksDbWeight::get().reads(5 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(3 as Weight))
 	}
 	fn receive_single_message_proof() -> Weight {
-		(205_350_000 as Weight)
+		(206_769_000 as Weight)
 			.saturating_add(RocksDbWeight::get().reads(5 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(3 as Weight))
 	}
 	fn receive_two_messages_proof() -> Weight {
-		(337_102_000 as Weight)
+		(343_982_000 as Weight)
 			.saturating_add(RocksDbWeight::get().reads(5 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(3 as Weight))
 	}
 	fn receive_single_message_proof_with_outbound_lane_state() -> Weight {
-		(218_825_000 as Weight)
+		(223_738_000 as Weight)
 			.saturating_add(RocksDbWeight::get().reads(5 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(3 as Weight))
 	}
 	fn receive_single_message_proof_1_kb() -> Weight {
-		(230_759_000 as Weight)
+		(235_369_000 as Weight)
 			.saturating_add(RocksDbWeight::get().reads(5 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(3 as Weight))
 	}
 	fn receive_single_message_proof_16_kb() -> Weight {
-		(490_522_000 as Weight)
+		(510_338_000 as Weight)
 			.saturating_add(RocksDbWeight::get().reads(5 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(3 as Weight))
 	}
 	fn receive_single_prepaid_message_proof() -> Weight {
-		(136_550_000 as Weight)
+		(141_536_000 as Weight)
 			.saturating_add(RocksDbWeight::get().reads(3 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(1 as Weight))
 	}
 	fn receive_delivery_proof_for_single_message() -> Weight {
-		(131_397_000 as Weight)
+		(128_805_000 as Weight)
 			.saturating_add(RocksDbWeight::get().reads(6 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(3 as Weight))
 	}
 	fn receive_delivery_proof_for_two_messages_by_single_relayer() -> Weight {
-		(137_946_000 as Weight)
+		(137_143_000 as Weight)
 			.saturating_add(RocksDbWeight::get().reads(7 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(3 as Weight))
 	}
 	fn receive_delivery_proof_for_two_messages_by_two_relayers() -> Weight {
-		(194_448_000 as Weight)
+		(193_108_000 as Weight)
 			.saturating_add(RocksDbWeight::get().reads(8 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(4 as Weight))
 	}
 	fn send_messages_of_various_lengths(i: u32) -> Weight {
-		(142_576_000 as Weight)
-			.saturating_add((2_000 as Weight).saturating_mul(i as Weight))
+		(133_632_000 as Weight)
+			.saturating_add((4_000 as Weight).saturating_mul(i as Weight))
 			.saturating_add(RocksDbWeight::get().reads(5 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(12 as Weight))
 	}
 	fn receive_multiple_messages_proof(i: u32) -> Weight {
 		(0 as Weight)
-			.saturating_add((138_341_000 as Weight).saturating_mul(i as Weight))
+			.saturating_add((145_006_000 as Weight).saturating_mul(i as Weight))
 			.saturating_add(RocksDbWeight::get().reads(5 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(3 as Weight))
 	}
 	fn receive_message_proofs_with_extra_nodes(i: u32) -> Weight {
-		(472_752_000 as Weight)
-			.saturating_add((9_000 as Weight).saturating_mul(i as Weight))
+		(486_301_000 as Weight)
+			.saturating_add((10_000 as Weight).saturating_mul(i as Weight))
 			.saturating_add(RocksDbWeight::get().reads(5 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(3 as Weight))
 	}
 	fn receive_message_proofs_with_large_leaf(i: u32) -> Weight {
-		(175_300_000 as Weight)
-			.saturating_add((6_000 as Weight).saturating_mul(i as Weight))
+		(178_139_000 as Weight)
+			.saturating_add((7_000 as Weight).saturating_mul(i as Weight))
 			.saturating_add(RocksDbWeight::get().reads(5 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(3 as Weight))
 	}
 	fn receive_multiple_messages_proof_with_outbound_lane_state(i: u32) -> Weight {
 		(0 as Weight)
-			.saturating_add((142_176_000 as Weight).saturating_mul(i as Weight))
+			.saturating_add((150_844_000 as Weight).saturating_mul(i as Weight))
 			.saturating_add(RocksDbWeight::get().reads(5 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(3 as Weight))
 	}
 	fn receive_delivery_proof_for_multiple_messages_by_single_relayer(i: u32) -> Weight {
-		(127_372_000 as Weight)
-			.saturating_add((7_927_000 as Weight).saturating_mul(i as Weight))
+		(113_140_000 as Weight)
+			.saturating_add((7_656_000 as Weight).saturating_mul(i as Weight))
 			.saturating_add(RocksDbWeight::get().reads(5 as Weight))
 			.saturating_add(RocksDbWeight::get().reads((1 as Weight).saturating_mul(i as Weight)))
 			.saturating_add(RocksDbWeight::get().writes(3 as Weight))
 	}
 	fn receive_delivery_proof_for_multiple_messages_by_multiple_relayers(i: u32) -> Weight {
-		(99_781_000 as Weight)
-			.saturating_add((64_001_000 as Weight).saturating_mul(i as Weight))
+		(97_424_000 as Weight)
+			.saturating_add((63_128_000 as Weight).saturating_mul(i as Weight))
 			.saturating_add(RocksDbWeight::get().reads(5 as Weight))
 			.saturating_add(RocksDbWeight::get().reads((2 as Weight).saturating_mul(i as Weight)))
 			.saturating_add(RocksDbWeight::get().writes(3 as Weight))

bridges/primitives/messages/Cargo.toml

@@ -7,7 +7,9 @@ edition = "2018"
 license = "GPL-3.0-or-later WITH Classpath-exception-2.0"
 
 [dependencies]
-codec = { package = "parity-scale-codec", version = "2.0.0", default-features = false, features = ["derive"] }
+bitvec = { version = "0.20", default-features = false, features = ["alloc"] }
+codec = { package = "parity-scale-codec", version = "2.0.0", default-features = false, features = ["derive", "bit-vec"] }
+impl-trait-for-tuples = "0.2"
 serde = { version = "1.0.101", optional = true, features = ["derive"] }
 
 # Bridge dependencies

bridges/primitives/messages/src/lib.rs

@@ -22,6 +22,7 @@
 // Generated by `DecodeLimit::decode_with_depth_limit`
 #![allow(clippy::unnecessary_mut_passed)]
 
+use bitvec::prelude::*;
 use codec::{Decode, Encode};
 use frame_support::RuntimeDebug;
 use sp_std::{collections::vec_deque::VecDeque, prelude::*};
@@ -120,7 +121,7 @@ pub struct InboundLaneData<RelayerId> {
 	/// When a relayer sends a single message, both of MessageNonces are the same.
 	/// When relayer sends messages in a batch, the first arg is the lowest nonce, second arg the highest nonce.
 	/// Multiple dispatches from the same relayer are allowed.
-	pub relayers: VecDeque<(MessageNonce, MessageNonce, RelayerId)>,
+	pub relayers: VecDeque<UnrewardedRelayer<RelayerId>>,
 
 	/// Nonce of the last message that
 	/// a) has been delivered to the target (this) chain and
@@ -147,18 +148,22 @@ impl<RelayerId> InboundLaneData<RelayerId> {
 	/// size of each entry.
 	///
 	/// Returns `None` if size overflows `u32` limits.
-	pub fn encoded_size_hint(relayer_id_encoded_size: u32, relayers_entries: u32) -> Option<u32> {
+	pub fn encoded_size_hint(relayer_id_encoded_size: u32, relayers_entries: u32, messages_count: u32) -> Option<u32> {
 		let message_nonce_size = 8;
 		let relayers_entry_size = relayer_id_encoded_size.checked_add(2 * message_nonce_size)?;
 		let relayers_size = relayers_entries.checked_mul(relayers_entry_size)?;
-		relayers_size.checked_add(message_nonce_size)
+		let dispatch_results_per_byte = 8;
+		let dispatch_result_size = sp_std::cmp::max(relayers_entries, messages_count / dispatch_results_per_byte);
+		relayers_size
+			.checked_add(message_nonce_size)
+			.and_then(|result| result.checked_add(dispatch_result_size))
 	}
 
 	/// Nonce of the last message that has been delivered to this (target) chain.
 	pub fn last_delivered_nonce(&self) -> MessageNonce {
 		self.relayers
 			.back()
-			.map(|(_, last_nonce, _)| *last_nonce)
+			.map(|entry| entry.messages.end)
 			.unwrap_or(self.last_confirmed_nonce)
 	}
 }
@@ -176,6 +181,71 @@ pub struct MessageDetails<OutboundMessageFee> {
 	pub delivery_and_dispatch_fee: OutboundMessageFee,
 }
 
+/// Bit vector of message dispatch results.
+pub type DispatchResultsBitVec = BitVec<Msb0, u8>;
+
+/// Unrewarded relayer entry stored in the inbound lane data.
+///
+/// This struct represents a continuous range of messages that have been delivered by the same relayer
+/// and whose confirmations are still pending.
+#[derive(Encode, Decode, Clone, RuntimeDebug, PartialEq, Eq)]
+pub struct UnrewardedRelayer<RelayerId> {
+	/// Identifier of the relayer.
+	pub relayer: RelayerId,
+	/// Messages range, delivered by this relayer.
+	pub messages: DeliveredMessages,
+}
+
+/// Delivered messages with their dispatch result.
+#[derive(Clone, Default, Encode, Decode, RuntimeDebug, PartialEq, Eq)]
+pub struct DeliveredMessages {
+	/// Nonce of the first message that has been delivered (inclusive).
+	pub begin: MessageNonce,
+	/// Nonce of the last message that has been delivered (inclusive).
+	pub end: MessageNonce,
+	/// Dispatch result (`false`/`true`), returned by the message dispatcher for every
+	/// message in the `[begin; end]` range. See `dispatch_result` field of the
+	/// `bp_runtime::messages::MessageDispatchResult` structure for more information.
+	pub dispatch_results: DispatchResultsBitVec,
+}
+
+impl DeliveredMessages {
+	/// Create new `DeliveredMessages` struct that confirms delivery of single nonce with given dispatch result.
+	pub fn new(nonce: MessageNonce, dispatch_result: bool) -> Self {
+		DeliveredMessages {
+			begin: nonce,
+			end: nonce,
+			dispatch_results: bitvec![Msb0, u8; if dispatch_result { 1 } else { 0 }],
+		}
+	}
+
+	/// Note new dispatched message.
+	pub fn note_dispatched_message(&mut self, dispatch_result: bool) {
+		self.end += 1;
+		self.dispatch_results.push(dispatch_result);
+	}
+
+	/// Returns true if delivered messages contain message with given nonce.
+	pub fn contains_message(&self, nonce: MessageNonce) -> bool {
+		(self.begin..=self.end).contains(&nonce)
+	}
+
+	/// Get dispatch result flag by message nonce.
+	///
+	/// Dispatch result flag must be interpreted using the knowledge of dispatch mechanism
+	/// at the target chain. See `dispatch_result` field of the
+	/// `bp_runtime::messages::MessageDispatchResult` structure for more information.
+	///
+	/// Panics if message nonce is not in the `begin..=end` range. Typically you'll first
+	/// check if message is within the range by calling `contains_message`.
+	pub fn message_dispatch_result(&self, nonce: MessageNonce) -> bool {
+		const INVALID_NONCE: &str = "Invalid nonce used to index dispatch_results";
+
+		let index = nonce.checked_sub(self.begin).expect(INVALID_NONCE) as usize;
+		*self.dispatch_results.get(index).expect(INVALID_NONCE)
+	}
+}
+
 /// Gist of `InboundLaneData::relayers` field used by runtime APIs.
 #[derive(Clone, Default, Encode, Decode, RuntimeDebug, PartialEq, Eq)]
 pub struct UnrewardedRelayersState {
@@ -214,12 +284,10 @@ impl Default for OutboundLaneData {
 /// Returns total number of messages in the `InboundLaneData::relayers` vector.
 ///
 /// Returns `None` if there are more messages that `MessageNonce` may fit (i.e. `MessageNonce + 1`).
-pub fn total_unrewarded_messages<RelayerId>(
-	relayers: &VecDeque<(MessageNonce, MessageNonce, RelayerId)>,
-) -> Option<MessageNonce> {
+pub fn total_unrewarded_messages<RelayerId>(relayers: &VecDeque<UnrewardedRelayer<RelayerId>>) -> Option<MessageNonce> {
 	match (relayers.front(), relayers.back()) {
-		(Some((begin, _, _)), Some((_, end, _))) => {
-			if let Some(difference) = end.checked_sub(*begin) {
+		(Some(front), Some(back)) => {
+			if let Some(difference) = back.messages.end.checked_sub(front.messages.begin) {
 				difference.checked_add(1)
 			} else {
 				Some(0)
@@ -237,7 +305,16 @@ mod tests {
 	fn total_unrewarded_messages_does_not_overflow() {
 		assert_eq!(
 			total_unrewarded_messages(
-				&vec![(0, 0, 1), (MessageNonce::MAX, MessageNonce::MAX, 2)]
+				&vec![
+					UnrewardedRelayer {
+						relayer: 1,
+						messages: DeliveredMessages::new(0, true)
+					},
+					UnrewardedRelayer {
+						relayer: 2,
+						messages: DeliveredMessages::new(MessageNonce::MAX, true)
+					},
+				]
 				.into_iter()
 				.collect()
 			),
@@ -247,19 +324,60 @@ mod tests {
 
 	#[test]
 	fn inbound_lane_data_returns_correct_hint() {
-		let expected_size = InboundLaneData::<u8>::encoded_size_hint(1, 13);
+		let test_cases = vec![
+			// single relayer, multiple messages
+			(1, 128u8),
+			// multiple relayers, single message per relayer
+			(128u8, 128u8),
+			// several messages per relayer
+			(13u8, 128u8),
+		];
+		for (relayer_entries, messages_count) in test_cases {
+			let expected_size = InboundLaneData::<u8>::encoded_size_hint(1, relayer_entries as _, messages_count as _);
 			let actual_size = InboundLaneData {
-			relayers: (1u8..=13u8).map(|i| (i as _, i as _, i)).collect(),
-			last_confirmed_nonce: 13,
+				relayers: (1u8..=relayer_entries)
+					.map(|i| {
+						let mut entry = UnrewardedRelayer {
+							relayer: i,
+							messages: DeliveredMessages::new(i as _, true),
+						};
+						entry.messages.dispatch_results = bitvec![
+							Msb0, u8;
+							1;
+							(messages_count / relayer_entries) as _
+						];
+						entry
+					})
+					.collect(),
+				last_confirmed_nonce: messages_count as _,
 			}
 			.encode()
 			.len();
 			let difference = (expected_size.unwrap() as f64 - actual_size as f64).abs();
 			assert!(
 				difference / (std::cmp::min(actual_size, expected_size.unwrap() as usize) as f64) < 0.1,
-			"Too large difference between actual ({}) and expected ({:?}) inbound lane data size",
+				"Too large difference between actual ({}) and expected ({:?}) inbound lane data size. Test case: {}+{}",
 				actual_size,
 				expected_size,
+				relayer_entries,
+				messages_count,
 			);
 		}
+	}
+
+	#[test]
+	fn message_dispatch_result_works() {
+		let delivered_messages = DeliveredMessages {
+			begin: 100,
+			end: 150,
+			dispatch_results: bitvec![Msb0, u8; 1; 151],
+		};
+
+		assert!(!delivered_messages.contains_message(99));
+		assert!(delivered_messages.contains_message(100));
+		assert!(delivered_messages.contains_message(150));
+		assert!(!delivered_messages.contains_message(151));
+
+		assert!(delivered_messages.message_dispatch_result(125));
+	}
 }

bridges/primitives/messages/src/source_chain.rs

@@ -16,7 +16,7 @@
 
 //! Primitives of messages module, that are used on the source chain.
 
-use crate::{InboundLaneData, LaneId, MessageNonce, OutboundLaneData};
+use crate::{DeliveredMessages, InboundLaneData, LaneId, MessageNonce, OutboundLaneData};
 
 use bp_runtime::Size;
 use frame_support::{Parameter, RuntimeDebug};
@@ -135,6 +135,15 @@ pub trait MessageDeliveryAndDispatchPayment<AccountId, Balance> {
 	}
 }
 
+/// Handler for messages delivery confirmation.
+#[impl_trait_for_tuples::impl_for_tuples(30)]
+pub trait OnDeliveryConfirmed {
+	/// Called when we receive confirmation that our messages have been delivered to the
+	/// target chain. The confirmation also has single bit dispatch result for every
+	/// confirmed message (see `DeliveredMessages` for details).
+	fn on_messages_delivered(_lane: &LaneId, _messages: &DeliveredMessages) {}
+}
+
 /// Structure that may be used in place of `TargetHeaderChain`, `LaneMessageVerifier` and
 /// `MessageDeliveryAndDispatchPayment` on chains, where outbound messages are forbidden.
 pub struct ForbidOutboundMessages;

bridges/primitives/messages/src/target_chain.rs

@@ -164,6 +164,7 @@ impl<AccountId, Fee> MessageDispatch<AccountId, Fee> for ForbidInboundMessages {
 
 	fn dispatch(_: &AccountId, _: DispatchMessage<Self::DispatchPayload, Fee>) -> MessageDispatchResult {
 		MessageDispatchResult {
+			dispatch_result: false,
 			unspent_weight: 0,
 			dispatch_fee_paid_during_dispatch: false,
 		}

bridges/primitives/runtime/src/messages.rs

@@ -36,6 +36,12 @@ pub enum DispatchFeePayment {
 /// Message dispatch result.
 #[derive(Encode, Decode, RuntimeDebug, Clone, PartialEq, Eq)]
 pub struct MessageDispatchResult {
+	/// Dispatch result flag. This flag is relayed back to the source chain and, generally
+	/// speaking, may bring any (that fits in single bit) information from the dispatcher at
+	/// the target chain to the message submitter at the source chain. If you're using immediate
+	/// call dispatcher, then it'll be result of the dispatch - `true` if dispatch has succeeded
+	/// and `false` otherwise.
+	pub dispatch_result: bool,
 	/// Unspent dispatch weight. This weight that will be deducted from total delivery transaction
 	/// weight, thus reducing the transaction cost. This shall not be zero in (at least) two cases:
 	///

bridges/relays/bin-substrate/src/messages_lane.rs

@@ -204,7 +204,7 @@ mod tests {
 			// reserved for messages dispatch allows dispatch of non-trivial messages.
 			//
 			// Any significant change in this values should attract additional attention.
-			(814, 216_583_333_334),
+			(782, 216_583_333_334),
 		);
 	}
 }