Add a JSON-RPC layer for reserved nodes (#8704)

* Add boilerplate for JSON-RPC layer for reserved nodes

* Add more boilerplate for JSON-RPC layer for reserved nodes

* Make JSON-RPC layer for reserved nodes async

* Use more realistic data in reserver_peers tests

* Make JSON-RPC layer for reserved nodes blocking

* Apply tomaka's suggestion to reduce .into_iter() for an iter

Co-authored-by: Pierre Krieger <pierre.krieger1708@gmail.com>

Co-authored-by: Pierre Krieger <pierre.krieger1708@gmail.com>

substrate/client/network/src/protocol.rs

@@ -1014,6 +1014,11 @@ impl<B: BlockT> Protocol<B> {
 		self.peerset_handle.remove_reserved_peer(HARDCODED_PEERSETS_SYNC, peer.clone());
 	}
 
+	/// Returns the list of reserved peers.
+	pub fn reserved_peers(&self) -> impl Iterator<Item = &PeerId> {
+		self.behaviour.reserved_peers(HARDCODED_PEERSETS_SYNC)
+	}
+
 	/// Adds a `PeerId` to the list of reserved peers for syncing purposes.
 	pub fn add_reserved_peer(&self, peer: PeerId) {
 		self.peerset_handle.add_reserved_peer(HARDCODED_PEERSETS_SYNC, peer.clone());

substrate/client/network/src/protocol/notifications/behaviour.rs

@@ -555,6 +555,11 @@ impl Notifications {
 			.map(|((id, _), _)| id)
 	}
 
+	/// Returns the list of reserved peers.
+	pub fn reserved_peers<'a>(&'a self, set_id: sc_peerset::SetId) -> impl Iterator<Item = &'a PeerId> + 'a {
+		self.peerset.reserved_peers(set_id)
+	}
+
 	/// Sends a notification to a peer.
 	///
 	/// Has no effect if the custom protocol is not open with the given peer.

substrate/client/network/src/service.rs

@@ -619,6 +619,11 @@ impl<B: BlockT + 'static, H: ExHashT> NetworkWorker<B, H> {
 	pub fn add_reserved_peer(&self, peer: String) -> Result<(), String> {
 		self.service.add_reserved_peer(peer)
 	}
+
+	/// Returns the list of reserved peers.
+	pub fn reserved_peers(&self) -> impl Iterator<Item = &PeerId> {
+		self.network_service.behaviour().user_protocol().reserved_peers()
+	}
 }
 
 impl<B: BlockT + 'static, H: ExHashT> NetworkService<B, H> {