statement-distribution: fix filtering of statements for elastic parachains (#3879)

fixes https://github.com/paritytech/polkadot-sdk/issues/3775

Additionally moves the claim queue fetch utilities into
`subsystem-util`.

TODO:
- [x] fix tests
- [x] add elastic scaling tests

---------

Signed-off-by: Andrei Sandu <andrei-mihail@parity.io>

polkadot/node/network/statement-distribution/src/v2/tests/cluster.rs

@@ -312,6 +312,66 @@ fn useful_cluster_statement_from_non_cluster_peer_rejected() {
 	});
 }
 
+// Both validators in the test are part of backing groups assigned to same parachain
+#[test]
+fn elastic_scaling_useful_cluster_statement_from_non_cluster_peer_rejected() {
+	let config = TestConfig {
+		validator_count: 20,
+		group_size: 3,
+		local_validator: LocalRole::Validator,
+		async_backing_params: None,
+	};
+
+	let relay_parent = Hash::repeat_byte(1);
+	let peer_a = PeerId::random();
+
+	test_harness(config, |state, mut overseer| async move {
+		let candidate_hash = CandidateHash(Hash::repeat_byte(42));
+
+		let test_leaf = state.make_dummy_leaf_with_multiple_cores_per_para(relay_parent, 3);
+
+		// Peer A is not in our group, but its group is assigned to same para as we are.
+		let not_our_group = GroupIndex(1);
+
+		let that_group_validators = state.group_validators(not_our_group, false);
+		let v_non = that_group_validators[0];
+
+		connect_peer(
+			&mut overseer,
+			peer_a.clone(),
+			Some(vec![state.discovery_id(v_non)].into_iter().collect()),
+		)
+		.await;
+
+		send_peer_view_change(&mut overseer, peer_a.clone(), view![relay_parent]).await;
+		activate_leaf(&mut overseer, &test_leaf, &state, true, vec![]).await;
+
+		let statement = state
+			.sign_statement(
+				v_non,
+				CompactStatement::Seconded(candidate_hash),
+				&SigningContext { parent_hash: relay_parent, session_index: 1 },
+			)
+			.as_unchecked()
+			.clone();
+
+		send_peer_message(
+			&mut overseer,
+			peer_a.clone(),
+			protocol_v2::StatementDistributionMessage::Statement(relay_parent, statement),
+		)
+		.await;
+
+		assert_matches!(
+			overseer.recv().await,
+			AllMessages::NetworkBridgeTx(NetworkBridgeTxMessage::ReportPeer(ReportPeerMessage::Single(p, r)))
+				if p == peer_a && r == COST_UNEXPECTED_STATEMENT_INVALID_SENDER.into() => { }
+		);
+
+		overseer
+	});
+}
+
 #[test]
 fn statement_from_non_cluster_originator_unexpected() {
 	let config = TestConfig {

polkadot/node/network/statement-distribution/src/v2/tests/grid.rs

@@ -1829,9 +1829,7 @@ fn advertisement_not_re_sent_when_peer_re_enters_view() {
 	});
 }
 
-// Grid statements imported to backing once candidate enters hypothetical frontier.
-#[test]
-fn grid_statements_imported_to_backing() {
+fn inner_grid_statements_imported_to_backing(groups_for_first_para: usize) {
 	let validator_count = 6;
 	let group_size = 3;
 	let config = TestConfig {
@@ -1851,9 +1849,12 @@ fn grid_statements_imported_to_backing() {
 		let local_group_index = local_validator.group_index.unwrap();
 
 		let other_group = next_group_index(local_group_index, validator_count, group_size);
-		let other_para = ParaId::from(other_group.0);
 
-		let test_leaf = state.make_dummy_leaf(relay_parent);
+		// Other para is same para for elastic scaling test (groups_for_first_para > 1)
+		let other_para = ParaId::from((groups_for_first_para == 1) as u32);
+
+		let test_leaf =
+			state.make_dummy_leaf_with_multiple_cores_per_para(relay_parent, groups_for_first_para);
 
 		let (candidate, pvd) = make_candidate(
 			relay_parent,
@@ -2018,6 +2019,18 @@ fn grid_statements_imported_to_backing() {
 		overseer
 	});
 }
+// Grid statements imported to backing once candidate enters hypothetical frontier.
+#[test]
+fn grid_statements_imported_to_backing() {
+	inner_grid_statements_imported_to_backing(1);
+}
+
+// Grid statements imported to backing once candidate enters hypothetical frontier.
+// All statements are for candidates of the same parachain but from different backing groups.
+#[test]
+fn elastic_scaling_grid_statements_imported_to_backing() {
+	inner_grid_statements_imported_to_backing(2);
+}
 
 #[test]
 fn advertisements_rejected_from_incorrect_peers() {

polkadot/node/network/statement-distribution/src/v2/tests/mod.rs

@@ -177,20 +177,39 @@ impl TestState {
 	}
 
 	fn make_dummy_leaf(&self, relay_parent: Hash) -> TestLeaf {
+		self.make_dummy_leaf_with_multiple_cores_per_para(relay_parent, 1)
+	}
+
+	fn make_dummy_leaf_with_multiple_cores_per_para(
+		&self,
+		relay_parent: Hash,
+		groups_for_first_para: usize,
+	) -> TestLeaf {
 		TestLeaf {
 			number: 1,
 			hash: relay_parent,
 			parent_hash: Hash::repeat_byte(0),
 			session: 1,
 			availability_cores: self.make_availability_cores(|i| {
-				CoreState::Scheduled(ScheduledCore {
-					para_id: ParaId::from(i as u32),
-					collator: None,
-				})
+				let para_id = if i < groups_for_first_para {
+					ParaId::from(0u32)
+				} else {
+					ParaId::from(i as u32)
+				};
+
+				CoreState::Scheduled(ScheduledCore { para_id, collator: None })
 			}),
 			disabled_validators: Default::default(),
 			para_data: (0..self.session_info.validator_groups.len())
-				.map(|i| (ParaId::from(i as u32), PerParaData::new(1, vec![1, 2, 3].into())))
+				.map(|i| {
+					let para_id = if i < groups_for_first_para {
+						ParaId::from(0u32)
+					} else {
+						ParaId::from(i as u32)
+					};
+
+					(para_id, PerParaData::new(1, vec![1, 2, 3].into()))
+				})
 				.collect(),
 			minimum_backing_votes: 2,
 		}