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/action.rs

@@ -57,6 +57,9 @@ pub(crate) enum Action {
 	/// Report a peer to the network implementation (decreasing/increasing its reputation).
 	ReportPeer(PeerId, UnifiedReputationChange),
 
+	/// Disconnect a peer from the given peer-set without affecting their reputation.
+	DisconnectPeer(PeerId, PeerSet),
+
 	/// A subsystem updates us on the relay chain leaves we consider active.
 	///
 	/// Implementation will send `WireMessage::ViewUpdate` message to peers as appropriate to the
@@ -119,6 +122,9 @@ impl From<polkadot_subsystem::SubsystemResult<FromOverseer<NetworkBridgeMessage>
 			}
 			Ok(FromOverseer::Communication { msg }) => match msg {
 				NetworkBridgeMessage::ReportPeer(peer, rep) => Action::ReportPeer(peer, rep),
+				NetworkBridgeMessage::DisconnectPeer(peer, peer_set) => {
+					Action::DisconnectPeer(peer, peer_set)
+				}
 				NetworkBridgeMessage::SendValidationMessage(peers, msg) => {
 					Action::SendValidationMessages(vec![(peers, msg)])
 				}

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

@@ -297,6 +297,16 @@ where
 				bridge.network_service.report_peer(peer, rep).await?
 			}
 
+			Action::DisconnectPeer(peer, peer_set) => {
+				tracing::debug!(
+					target: LOG_TARGET,
+					action = "DisconnectPeer",
+					?peer,
+					peer_set = ?peer_set,
+				);
+				bridge.network_service.disconnect_peer(peer, peer_set);
+			}
+
 			Action::ActiveLeaves(ActiveLeavesUpdate { activated, deactivated }) => {
 				tracing::debug!(
 					target: LOG_TARGET,

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),