Consistent tracking of disconnected peers (#2650)

## Issue Addressed

N/A

## Proposed Changes

When peers switching to a disconnecting state, decrement the disconnected peers counter. This also downgrades some crit logs to errors. 

I've also added a re-sync point when peers get unbanned the disconnected peer count will match back to the number of disconnected peers if it has gone out of sync previously.

beacon_node/eth2_libp2p/src/peer_manager/mod.rs

@@ -13,7 +13,7 @@ use futures::Stream;
 use hashset_delay::HashSetDelay;
 use libp2p::core::ConnectedPoint;
 use libp2p::identify::IdentifyInfo;
-use slog::{crit, debug, error, warn};
+use slog::{debug, error, warn};
 use smallvec::SmallVec;
 use std::{
     pin::Pin,
@@ -529,7 +529,7 @@ impl<TSpec: EthSpec> PeerManager<TSpec> {
                 };
             }
         } else {
-            crit!(self.log, "Received an Identify response from an unknown peer"; "peer_id" => peer_id.to_string());
+            error!(self.log, "Received an Identify response from an unknown peer"; "peer_id" => peer_id.to_string());
         }
     }
 
@@ -672,7 +672,7 @@ impl<TSpec: EthSpec> PeerManager<TSpec> {
                 self.events.push(PeerManagerEvent::MetaData(*peer_id));
             }
         } else {
-            crit!(self.log, "Received a PING from an unknown peer";
+            error!(self.log, "Received a PING from an unknown peer";
                 "peer_id" => %peer_id);
         }
     }
@@ -696,7 +696,7 @@ impl<TSpec: EthSpec> PeerManager<TSpec> {
                 self.events.push(PeerManagerEvent::MetaData(*peer_id));
             }
         } else {
-            crit!(self.log, "Received a PONG from an unknown peer"; "peer_id" => %peer_id);
+            error!(self.log, "Received a PONG from an unknown peer"; "peer_id" => %peer_id);
         }
     }
 
@@ -720,7 +720,7 @@ impl<TSpec: EthSpec> PeerManager<TSpec> {
             }
             peer_info.meta_data = Some(meta_data);
         } else {
-            crit!(self.log, "Received METADATA from an unknown peer";
+            error!(self.log, "Received METADATA from an unknown peer";
                 "peer_id" => %peer_id);
         }
     }
@@ -842,7 +842,7 @@ impl<TSpec: EthSpec> PeerManager<TSpec> {
             let mut peerdb = self.network_globals.peers.write();
             if !matches!(peerdb.ban_status(peer_id), BanResult::NotBanned) {
                 // don't connect if the peer is banned
-                slog::crit!(self.log, "Connection has been allowed to a banned peer"; "peer_id" => %peer_id);
+                error!(self.log, "Connection has been allowed to a banned peer"; "peer_id" => %peer_id);
             }
 
             match connection {

beacon_node/eth2_libp2p/src/peer_manager/peerdb.rs

@@ -515,10 +515,15 @@ impl<TSpec: EthSpec> PeerDB<TSpec> {
     /// Notifies the peer manager that the peer is undergoing a normal disconnect. Optionally tag
     /// the peer to be banned after the disconnect.
     pub fn notify_disconnecting(&mut self, peer_id: PeerId, to_ban_afterwards: bool) {
-        self.peers
-            .entry(peer_id)
-            .or_default()
-            .disconnecting(to_ban_afterwards);
+        let peer_info = self.peers.entry(peer_id).or_default();
+
+        if matches!(
+            peer_info.connection_status(),
+            PeerConnectionStatus::Disconnected { .. }
+        ) {
+            self.disconnected_peers = self.disconnected_peers.saturating_sub(1);
+        }
+        peer_info.disconnecting(to_ban_afterwards);
     }
 
     /// Marks a peer to be disconnected and then banned.
@@ -609,7 +614,7 @@ impl<TSpec: EthSpec> PeerDB<TSpec> {
         info.update_state();
 
         // This transitions a banned peer to a disconnected peer
-        self.disconnected_peers = self.disconnected_peers.saturating_add(1);
+        self.disconnected_peers = self.disconnected_peers().count().saturating_add(1);
         self.shrink_to_fit();
         Ok(())
     }

beacon_node/eth2_libp2p/src/service.rs

@@ -138,14 +138,14 @@ impl<TSpec: EthSpec> Service<TSpec> {
                 .with_max_established_incoming(Some(
                     (config.target_peers as f32
                         * (1.0 + PEER_EXCESS_FACTOR - MIN_OUTBOUND_ONLY_FACTOR))
-                        as u32,
+                        .ceil() as u32,
                 ))
                 .with_max_established_outgoing(Some(
-                    (config.target_peers as f32 * (1.0 + PEER_EXCESS_FACTOR)) as u32,
+                    (config.target_peers as f32 * (1.0 + PEER_EXCESS_FACTOR)).ceil() as u32,
                 ))
                 .with_max_established(Some(
                     (config.target_peers as f32 * (1.0 + PEER_EXCESS_FACTOR + PRIORITY_PEER_EXCESS))
-                        as u32,
+                        .ceil() as u32,
                 ))
                 .with_max_established_per_peer(Some(MAX_CONNECTIONS_PER_PEER));
 

beacon_node/network/src/sync/manager.rs

@@ -672,7 +672,7 @@ impl<T: BeaconChainTypes> SyncManager<T> {
             }
             peer_info.is_connected()
         } else {
-            crit!(self.log, "Status'd peer is unknown"; "peer_id" => %peer_id);
+            error!(self.log, "Status'd peer is unknown"; "peer_id" => %peer_id);
             false
         }
     }