Evict inactive peers from the collator protocol peer-set (#2680)

* malicious reputation cost is fatal

* make ReportBad a malicious cost

* futures control-flow for cleaning up inactive collator peers

* guide: network bridge updates

* add `PeerDisconnected` message

* guide: update

* reverse order

* remember to match

* implement disconnect peer in network bridge

* implement disconnect_inactive_peers

* test

* remove println

* don't hardcore policy

* add fuse outside of loop

* use default eviction policy

polkadot/node/network/bridge/src/network.rs

@@ -90,6 +90,8 @@ where
 pub enum NetworkAction {
 	/// Note a change in reputation for a peer.
 	ReputationChange(PeerId, Rep),
+	/// Disconnect a peer from the given peer-set.
+	DisconnectPeer(PeerId, PeerSet),
 	/// Write a notification to a given peer on the given peer-set.
 	WriteNotification(PeerId, PeerSet, Vec<u8>),
 }
@@ -130,6 +132,20 @@ pub trait Network: Send + 'static {
 		.boxed()
 	}
 
+	/// Disconnect a given peer from the peer set specified without harming reputation.
+	fn disconnect_peer(
+		&mut self,
+		who: PeerId,
+		peer_set: PeerSet,
+	) -> BoxFuture<SubsystemResult<()>> {
+		async move {
+			self.action_sink()
+				.send(NetworkAction::DisconnectPeer(who, peer_set))
+				.await
+		}
+		.boxed()
+	}
+
 	/// Write a notification to a peer on the given peer-set's protocol.
 	fn write_notification(
 		&mut self,
@@ -179,6 +195,9 @@ impl Network for Arc<NetworkService<Block, Hash>> {
 						);
 						self.0.report_peer(peer, cost_benefit.into_base_rep())
 					}
+					NetworkAction::DisconnectPeer(peer, peer_set) => self
+						.0
+						.disconnect_peer(peer, peer_set.into_protocol_name()),
 					NetworkAction::WriteNotification(peer, peer_set, message) => self
 						.0
 						.write_notification(peer, peer_set.into_protocol_name(), message),