Add NewBestBlockNumber event.

substrate/client/network/sync/src/engine.rs

@@ -839,6 +839,9 @@ where
 			ToServiceCommand::SetSyncForkRequest(peers, hash, number) => {
 				self.strategy.set_sync_fork_request(peers, &hash, number);
 			},
+			ToServiceCommand::NewBestBlockNumber(number) => {
+				self.strategy.update_common_number_for_peers(number);
+			},
 			ToServiceCommand::EventStream(tx) => self.event_streams.push(tx),
 			ToServiceCommand::RequestJustification(hash, number) =>
 				self.strategy.request_justification(&hash, number),

substrate/client/network/sync/src/service/syncing_service.rs

@@ -36,6 +36,7 @@ use std::{
 
 /// Commands send to `SyncingEngine`
 pub enum ToServiceCommand<B: BlockT> {
+	NewBestBlockNumber(NumberFor<B>),
 	SetSyncForkRequest(Vec<PeerId>, B::Hash, NumberFor<B>),
 	RequestJustification(B::Hash, NumberFor<B>),
 	ClearJustificationRequests,
@@ -91,6 +92,10 @@ impl<B: BlockT> SyncingService<B> {
 		rx.await
 	}
 
+	pub fn new_best_number(&self, number: NumberFor<B>) {
+		let _ = self.tx.unbounded_send(ToServiceCommand::NewBestBlockNumber(number));
+	}
+
 	/// Get best seen block.
 	pub async fn best_seen_block(&self) -> Result<Option<NumberFor<B>>, oneshot::Canceled> {
 		let (tx, rx) = oneshot::channel();

substrate/client/network/sync/src/strategy.rs

@@ -200,6 +200,15 @@ where
 		}
 	}
 
+	pub fn update_common_number_for_peers(&mut self, number: NumberFor<B>) {
+		match self {
+			SyncingStrategy::WarpSyncStrategy(_) => {},
+			SyncingStrategy::StateSyncStrategy(_) => {},
+			SyncingStrategy::ChainSyncStrategy(strategy) =>
+				strategy.update_common_number_for_peers(number),
+		}
+	}
+
 	/// Request extra justification.
 	pub fn request_justification(&mut self, hash: &B::Hash, number: NumberFor<B>) {
 		match self {

substrate/client/network/sync/src/strategy/chain_sync.rs

@@ -1287,6 +1287,16 @@ where
 		}
 	}
 
+	pub fn update_common_number_for_peers(&mut self, new_common: NumberFor<B>) {
+		for peer in self.peers.values_mut() {
+			if peer.best_number >= new_common {
+				peer.update_common_number(new_common);
+			} else {
+				peer.update_common_number(peer.best_number);
+			}
+		}
+	}
+
 	/// Called when a block has been queued for import.
 	///
 	/// Updates our internal state for best queued block and then goes