protocols/relay/src/v2: Remove empty peer entries in self.reservations (

#2464)

When a peer disconnects, reservations associated with that peer are removed from
the set of reservations of the peer. In case the set of reservations for the
peer is now empty, remove the entire peer.

Same when a reservation times out.

CHANGELOG.md

@@ -42,6 +42,11 @@
 
 # `libp2p` facade crate
 
+## Version 0.42.1 [unreleased]
+
+- Update individual crates.
+  - `libp2p-relay`
+
 ## Version 0.42.0 [2022-01-27]
 
 - Update individual crates.

Cargo.toml

@@ -3,7 +3,7 @@ name = "libp2p"
 edition = "2021"
 rust-version = "1.56.1"
 description = "Peer-to-peer networking library"
-version = "0.42.0"
+version = "0.42.1"
 authors = ["Parity Technologies <[email protected]>"]
 license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"
@@ -88,7 +88,7 @@ libp2p-noise = { version = "0.34.0", path = "transports/noise", optional = true
 libp2p-ping = { version = "0.33.0", path = "protocols/ping", optional = true }
 libp2p-plaintext = { version = "0.31.0", path = "transports/plaintext", optional = true }
 libp2p-pnet = { version = "0.22.0", path = "transports/pnet", optional = true }
-libp2p-relay = { version = "0.6.0", path = "protocols/relay", optional = true }
+libp2p-relay = { version = "0.6.1", path = "protocols/relay", optional = true }
 libp2p-rendezvous = { version = "0.3.0", path = "protocols/rendezvous", optional = true }
 libp2p-request-response = { version = "0.15.0", path = "protocols/request-response", optional = true }
 libp2p-swarm = { version = "0.33.0", path = "swarm" }

protocols/relay/CHANGELOG.md

@@ -1,3 +1,9 @@
+# 0.6.1 [unreleased]
+
+- Remove empty peer entries in `reservations` `HashMap`. See [PR 2464].
+
+[PR 2464]: https://github.com/libp2p/rust-libp2p/pull/2464
+
 # 0.6.0 [2022-01-27]
 
 - Update dependencies.

protocols/relay/Cargo.toml

@@ -3,7 +3,7 @@ name = "libp2p-relay"
 edition = "2021"
 rust-version = "1.56.1"
 description = "Communications relaying for libp2p"
-version = "0.6.0"
+version = "0.6.1"
 authors = ["Parity Technologies <[email protected]>", "Max Inden <[email protected]>"]
 license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"

protocols/relay/src/v2/relay.rs

@@ -35,7 +35,7 @@ use libp2p_swarm::{
     NetworkBehaviour, NetworkBehaviourAction, NotifyHandler, PollParameters,
     ProtocolsHandlerUpgrErr,
 };
-use std::collections::{HashMap, HashSet, VecDeque};
+use std::collections::{hash_map, HashMap, HashSet, VecDeque};
 use std::num::NonZeroU32;
 use std::ops::Add;
 use std::task::{Context, Poll};
@@ -214,8 +214,11 @@ impl NetworkBehaviour for Relay {
         _: &ConnectedPoint,
         _handler: Either<handler::Handler, DummyProtocolsHandler>,
     ) {
-        if let Some(connections) = self.reservations.get_mut(peer) {
-            connections.remove(&connection);
+        if let hash_map::Entry::Occupied(mut peer) = self.reservations.entry(*peer) {
+            peer.get_mut().remove(&connection);
+            if peer.get().is_empty() {
+                peer.remove();
+            }
         }
 
         for circuit in self
@@ -353,9 +356,21 @@ impl NetworkBehaviour for Relay {
                 );
             }
             handler::Event::ReservationTimedOut {} => {
-                self.reservations
-                    .get_mut(&event_source)
-                    .map(|cs| cs.remove(&connection));
+                match self.reservations.entry(event_source) {
+                    hash_map::Entry::Occupied(mut peer) => {
+                        peer.get_mut().remove(&connection);
+                        if peer.get().is_empty() {
+                            peer.remove();
+                        }
+                    }
+                    hash_map::Entry::Vacant(_) => {
+                        unreachable!(
+                            "Expect to track timed out reservation with peer {:?} on connection {:?}",
+                            event_source,
+                            connection,
+                        );
+                    }
+                }
 
                 self.queued_actions.push_back(
                     NetworkBehaviourAction::GenerateEvent(Event::ReservationTimedOut {