[stable2409] Backport #6690 (#6799)

Backport #6690 into `stable2409` from alexggh.

See the
[documentation](https://github.com/paritytech/polkadot-sdk/blob/master/docs/BACKPORT.md)
on how to use this bot.

<!--
  # To be used by other automation, do not modify:
  original-pr-number: #${pull_number}
-->

Co-authored-by: Alexandru Gheorghe <[email protected]>

polkadot/node/network/approval-distribution/src/lib.rs

@@ -163,8 +163,6 @@ enum ApprovalEntryError {
 	InvalidCandidateIndex,
 	DuplicateApproval,
 	UnknownAssignment,
-	#[allow(dead_code)]
-	AssignmentsFollowedDifferentPaths(RequiredRouting, RequiredRouting),
 }
 
 impl ApprovalEntry {
@@ -571,7 +569,7 @@ impl BlockEntry {
 		&mut self,
 		approval: IndirectSignedApprovalVoteV2,
 	) -> Result<(RequiredRouting, HashSet<PeerId>), ApprovalEntryError> {
-		let mut required_routing = None;
+		let mut required_routing: Option<RequiredRouting> = None;
 		let mut peers_randomly_routed_to = HashSet::new();
 
 		if self.candidates.len() < approval.candidate_indices.len() as usize {
@@ -598,16 +596,11 @@ impl BlockEntry {
 				peers_randomly_routed_to
 					.extend(approval_entry.routing_info().peers_randomly_routed.iter());
 
-				if let Some(required_routing) = required_routing {
-					if required_routing != approval_entry.routing_info().required_routing {
-						// This shouldn't happen since the required routing is computed based on the
-						// validator_index, so two assignments from the same validators will have
-						// the same required routing.
-						return Err(ApprovalEntryError::AssignmentsFollowedDifferentPaths(
-							required_routing,
-							approval_entry.routing_info().required_routing,
-						))
-					}
+				if let Some(current_required_routing) = required_routing {
+					required_routing = Some(
+						current_required_routing
+							.combine(approval_entry.routing_info().required_routing),
+					);
 				} else {
 					required_routing = Some(approval_entry.routing_info().required_routing)
 				}

polkadot/node/network/protocol/src/grid_topology.rs

@@ -575,6 +575,22 @@ impl RequiredRouting {
 			_ => false,
 		}
 	}
+
+	/// Combine two required routing sets into one that would cover both routing modes.
+	pub fn combine(self, other: Self) -> Self {
+		match (self, other) {
+			(RequiredRouting::All, _) | (_, RequiredRouting::All) => RequiredRouting::All,
+			(RequiredRouting::GridXY, _) | (_, RequiredRouting::GridXY) => RequiredRouting::GridXY,
+			(RequiredRouting::GridX, RequiredRouting::GridY) |
+			(RequiredRouting::GridY, RequiredRouting::GridX) => RequiredRouting::GridXY,
+			(RequiredRouting::GridX, RequiredRouting::GridX) => RequiredRouting::GridX,
+			(RequiredRouting::GridY, RequiredRouting::GridY) => RequiredRouting::GridY,
+			(RequiredRouting::None, RequiredRouting::PendingTopology) |
+			(RequiredRouting::PendingTopology, RequiredRouting::None) => RequiredRouting::PendingTopology,
+			(RequiredRouting::None, _) | (RequiredRouting::PendingTopology, _) => other,
+			(_, RequiredRouting::None) | (_, RequiredRouting::PendingTopology) => self,
+		}
+	}
 }
 
 #[cfg(test)]
@@ -587,6 +603,50 @@ mod tests {
 		rand_chacha::ChaCha12Rng::seed_from_u64(12345)
 	}
 
+	#[test]
+	fn test_required_routing_combine() {
+		assert_eq!(RequiredRouting::All.combine(RequiredRouting::None), RequiredRouting::All);
+		assert_eq!(RequiredRouting::All.combine(RequiredRouting::GridXY), RequiredRouting::All);
+		assert_eq!(RequiredRouting::GridXY.combine(RequiredRouting::All), RequiredRouting::All);
+		assert_eq!(RequiredRouting::None.combine(RequiredRouting::All), RequiredRouting::All);
+		assert_eq!(RequiredRouting::None.combine(RequiredRouting::None), RequiredRouting::None);
+		assert_eq!(
+			RequiredRouting::PendingTopology.combine(RequiredRouting::GridX),
+			RequiredRouting::GridX
+		);
+
+		assert_eq!(
+			RequiredRouting::GridX.combine(RequiredRouting::PendingTopology),
+			RequiredRouting::GridX
+		);
+		assert_eq!(RequiredRouting::GridX.combine(RequiredRouting::GridY), RequiredRouting::GridXY);
+		assert_eq!(RequiredRouting::GridY.combine(RequiredRouting::GridX), RequiredRouting::GridXY);
+		assert_eq!(
+			RequiredRouting::GridXY.combine(RequiredRouting::GridXY),
+			RequiredRouting::GridXY
+		);
+		assert_eq!(RequiredRouting::GridX.combine(RequiredRouting::GridX), RequiredRouting::GridX);
+		assert_eq!(RequiredRouting::GridY.combine(RequiredRouting::GridY), RequiredRouting::GridY);
+
+		assert_eq!(RequiredRouting::None.combine(RequiredRouting::GridY), RequiredRouting::GridY);
+		assert_eq!(RequiredRouting::None.combine(RequiredRouting::GridX), RequiredRouting::GridX);
+		assert_eq!(RequiredRouting::None.combine(RequiredRouting::GridXY), RequiredRouting::GridXY);
+
+		assert_eq!(RequiredRouting::GridY.combine(RequiredRouting::None), RequiredRouting::GridY);
+		assert_eq!(RequiredRouting::GridX.combine(RequiredRouting::None), RequiredRouting::GridX);
+		assert_eq!(RequiredRouting::GridXY.combine(RequiredRouting::None), RequiredRouting::GridXY);
+
+		assert_eq!(
+			RequiredRouting::PendingTopology.combine(RequiredRouting::None),
+			RequiredRouting::PendingTopology
+		);
+
+		assert_eq!(
+			RequiredRouting::None.combine(RequiredRouting::PendingTopology),
+			RequiredRouting::PendingTopology
+		);
+	}
+
 	#[test]
 	fn test_random_routing_sample() {
 		// This test is fragile as it relies on a specific ChaCha12Rng

prdoc/pr_6690.prdoc

@@ -0,0 +1,17 @@
+# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
+# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
+
+title: Fix Possible bug, Vote import failed after aggression is enabled
+
+doc:
+  - audience: Node Dev
+    description: |
+      Fix the appearance of Possible bug: Vote import failed after aggression is enabled, the log itself is
+      harmless because approval gets imported anyway and aggression is able to distribute it, nevertheless
+      is something that can be easily be fixed by picking the highest required routing possible.
+
+crates:
+  - name: polkadot-node-network-protocol
+    bump: minor
+  - name: polkadot-approval-distribution
+    bump: minor