Disconnect peers (#1484)

## Issue Addressed

Peers that connected after the peer limit may remain connected in some circumstances. 

This ensures peers not in the peer manager's list get disconnected. Further logging is also added to track this behaviour.

beacon_node/eth2_libp2p/src/behaviour/handler/delegate.rs

@@ -49,7 +49,7 @@ impl<TSpec: EthSpec> DelegatingHandler<TSpec> {
     }
 
     /// Gives access to identify's handler.
-    pub fn identify(&self) -> &IdentifyHandler {
+    pub fn _identify(&self) -> &IdentifyHandler {
         &self.identify_handler
     }
 }

beacon_node/eth2_libp2p/src/behaviour/handler/mod.rs

@@ -77,7 +77,7 @@ impl<TSpec: EthSpec> ProtocolsHandler for BehaviourHandler<TSpec> {
     fn inject_event(&mut self, event: Self::InEvent) {
         match event {
             BehaviourHandlerIn::Delegate(delegated_ev) => self.delegate.inject_event(delegated_ev),
-            /* Events comming from the behaviour */
+            /* Events coming from the behaviour */
             BehaviourHandlerIn::Shutdown(last_message) => {
                 self.shutting_down = true;
                 self.delegate.rpc_mut().shutdown(last_message);
@@ -113,12 +113,9 @@ impl<TSpec: EthSpec> ProtocolsHandler for BehaviourHandler<TSpec> {
         >,
     > {
         // Disconnect if the sub-handlers are ready.
-        if self.shutting_down {
-            let rpc_keep_alive = self.delegate.rpc().connection_keep_alive();
-            let identify_keep_alive = self.delegate.identify().connection_keep_alive();
-            if KeepAlive::No == rpc_keep_alive.max(identify_keep_alive) {
-                return Poll::Ready(ProtocolsHandlerEvent::Close(DelegateError::Disconnected));
-            }
+        // Currently we only respect the RPC handler.
+        if self.shutting_down && KeepAlive::No == self.delegate.rpc().connection_keep_alive() {
+            return Poll::Ready(ProtocolsHandlerEvent::Close(DelegateError::Disconnected));
         }
 
         match self.delegate.poll(cx) {

beacon_node/eth2_libp2p/src/behaviour/mod.rs

@@ -694,15 +694,28 @@ impl<TSpec: EthSpec> NetworkBehaviour for Behaviour<TSpec> {
         conn_id: &ConnectionId,
         endpoint: &ConnectedPoint,
     ) {
+        // If the peer manager (and therefore the behaviour's) believe this peer connected, inform
+        // about the disconnection.
+        if self.network_globals.peers.read().is_connected(&peer_id) {
+            return;
+        }
         delegate_to_behaviours!(self, inject_connection_closed, peer_id, conn_id, endpoint);
     }
 
     // This gets called once there are no more active connections.
     fn inject_disconnected(&mut self, peer_id: &PeerId) {
+        // If the application/behaviour layers thinks this peer has connected inform it of the disconnect.
+        if self.network_globals.peers.read().is_connected(&peer_id) {
+            // Inform the application.
+            self.add_event(BehaviourEvent::PeerDisconnected(peer_id.clone()));
+            // Inform the behaviour.
+            delegate_to_behaviours!(self, inject_disconnected, peer_id);
+        }
         // Inform the peer manager.
+        // NOTE: It may be the case that a rejected node, due to too many peers is disconnected
+        // here and the peer manager has no knowledge of its connection. We insert it here for
+        // reference so that peer manager can track this peer.
         self.peer_manager.notify_disconnect(&peer_id);
-        // Inform the application.
-        self.add_event(BehaviourEvent::PeerDisconnected(peer_id.clone()));
 
         // Update the prometheus metrics
         metrics::inc_counter(&metrics::PEER_DISCONNECT_EVENT_COUNT);
@@ -710,9 +723,6 @@ impl<TSpec: EthSpec> NetworkBehaviour for Behaviour<TSpec> {
             &metrics::PEERS_CONNECTED,
             self.network_globals.connected_peers() as i64,
         );
-
-        // Inform the behaviour.
-        delegate_to_behaviours!(self, inject_disconnected, peer_id);
     }
 
     // This gets called every time a connection is established.
@@ -741,6 +751,7 @@ impl<TSpec: EthSpec> NetworkBehaviour for Behaviour<TSpec> {
         };
 
         if goodbye_reason.is_some() {
+            debug!(self.log, "Disconnecting newly connected peer"; "peer_id" => peer_id.to_string(), "reason" => goodbye_reason.as_ref().expect("Is some").to_string());
             self.peers_to_dc
                 .push_back((peer_id.clone(), goodbye_reason));
             return;
@@ -771,18 +782,8 @@ impl<TSpec: EthSpec> NetworkBehaviour for Behaviour<TSpec> {
 
     // This gets called on the initial connection establishment.
     fn inject_connected(&mut self, peer_id: &PeerId) {
-        // Drop any connection from a banned peer. The goodbye and disconnects are handled in
-        // `inject_connection_established()`, which gets called first.
-        // The same holds if we reached the peer limit and the connected peer has no future duty.
-        if self.peer_manager.is_banned(peer_id)
-            || (self.peer_manager.peer_limit_reached()
-                && self
-                    .network_globals
-                    .peers
-                    .read()
-                    .peer_info(peer_id)
-                    .map_or(true, |i| !i.has_future_duty()))
-        {
+        // If the PeerManager has connected this peer, inform the behaviours
+        if !self.network_globals.peers.read().is_connected(&peer_id) {
             return;
         }