feat(relay): don't close connections upon errors in relay server

To remove the usages of `ConnectionHandlerEvent::Close` from the relay-server, we unify what used to be called `CircuitFailedReason` and `FatalUpgradeError`. Whilst the errors may be fatal for the particular circuit, they are not necessarily fatal for the entire connection.

Related: #3591.
Resolves: #4716.

Pull-Request: #4718.

misc/metrics/src/relay.rs

@@ -66,20 +66,25 @@ impl From<&libp2p_relay::Event> for EventType {
     fn from(event: &libp2p_relay::Event) -> Self {
         match event {
             libp2p_relay::Event::ReservationReqAccepted { .. } => EventType::ReservationReqAccepted,
+            #[allow(deprecated)]
             libp2p_relay::Event::ReservationReqAcceptFailed { .. } => {
                 EventType::ReservationReqAcceptFailed
             }
             libp2p_relay::Event::ReservationReqDenied { .. } => EventType::ReservationReqDenied,
+            #[allow(deprecated)]
             libp2p_relay::Event::ReservationReqDenyFailed { .. } => {
                 EventType::ReservationReqDenyFailed
             }
             libp2p_relay::Event::ReservationTimedOut { .. } => EventType::ReservationTimedOut,
             libp2p_relay::Event::CircuitReqDenied { .. } => EventType::CircuitReqDenied,
+            #[allow(deprecated)]
             libp2p_relay::Event::CircuitReqOutboundConnectFailed { .. } => {
                 EventType::CircuitReqOutboundConnectFailed
             }
+            #[allow(deprecated)]
             libp2p_relay::Event::CircuitReqDenyFailed { .. } => EventType::CircuitReqDenyFailed,
             libp2p_relay::Event::CircuitReqAccepted { .. } => EventType::CircuitReqAccepted,
+            #[allow(deprecated)]
             libp2p_relay::Event::CircuitReqAcceptFailed { .. } => EventType::CircuitReqAcceptFailed,
             libp2p_relay::Event::CircuitClosed { .. } => EventType::CircuitClosed,
         }

protocols/relay/CHANGELOG.md

@@ -1,5 +1,12 @@
 ## 0.17.0 - unreleased
 
+- Don't close connections on protocol failures within the relay-server.
+  To achieve this, error handling was restructured:
+  - `libp2p::relay::outbound::stop::FatalUpgradeError` has been removed.
+  - `libp2p::relay::outbound::stop::{Error, ProtocolViolation}` have been introduced.
+  - Several variants of `libp2p::relay::Event` have been deprecated.
+
+  See [PR 4718](https://github.com/libp2p/rust-libp2p/pull/4718).
 - Fix a rare race condition when making a reservation on a relay that could lead to a failed reservation.
   See [PR 4747](https://github.com/libp2p/rust-lib2pp/pulls/4747).
 - Propagate errors of relay client to the listener / dialer.

protocols/relay/src/behaviour.rs

@@ -34,7 +34,7 @@ use libp2p_identity::PeerId;
 use libp2p_swarm::behaviour::{ConnectionClosed, FromSwarm};
 use libp2p_swarm::{
     dummy, ConnectionDenied, ConnectionId, ExternalAddresses, NetworkBehaviour, NotifyHandler,
-    StreamUpgradeError, THandler, THandlerInEvent, THandlerOutEvent, ToSwarm,
+    THandler, THandlerInEvent, THandlerOutEvent, ToSwarm,
 };
 use std::collections::{hash_map, HashMap, HashSet, VecDeque};
 use std::num::NonZeroU32;
@@ -169,16 +169,22 @@ pub enum Event {
         renewed: bool,
     },
     /// Accepting an inbound reservation request failed.
+    #[deprecated(
+        note = "Will be removed in favor of logging them internally, see <https://github.com/libp2p/rust-libp2p/issues/4757> for details."
+    )]
     ReservationReqAcceptFailed {
         src_peer_id: PeerId,
-        error: inbound_hop::UpgradeError,
+        error: inbound_hop::Error,
     },
     /// An inbound reservation request has been denied.
     ReservationReqDenied { src_peer_id: PeerId },
     /// Denying an inbound reservation request has failed.
+    #[deprecated(
+        note = "Will be removed in favor of logging them internally, see <https://github.com/libp2p/rust-libp2p/issues/4757> for details."
+    )]
     ReservationReqDenyFailed {
         src_peer_id: PeerId,
-        error: inbound_hop::UpgradeError,
+        error: inbound_hop::Error,
     },
     /// An inbound reservation has timed out.
     ReservationTimedOut { src_peer_id: PeerId },
@@ -188,27 +194,36 @@ pub enum Event {
         dst_peer_id: PeerId,
     },
     /// Denying an inbound circuit request failed.
+    #[deprecated(
+        note = "Will be removed in favor of logging them internally, see <https://github.com/libp2p/rust-libp2p/issues/4757> for details."
+    )]
     CircuitReqDenyFailed {
         src_peer_id: PeerId,
         dst_peer_id: PeerId,
-        error: inbound_hop::UpgradeError,
+        error: inbound_hop::Error,
     },
     /// An inbound cirucit request has been accepted.
     CircuitReqAccepted {
         src_peer_id: PeerId,
         dst_peer_id: PeerId,
     },
     /// An outbound connect for an inbound cirucit request failed.
+    #[deprecated(
+        note = "Will be removed in favor of logging them internally, see <https://github.com/libp2p/rust-libp2p/issues/4757> for details."
+    )]
     CircuitReqOutboundConnectFailed {
         src_peer_id: PeerId,
         dst_peer_id: PeerId,
-        error: StreamUpgradeError<outbound_stop::CircuitFailedReason>,
+        error: outbound_stop::Error,
     },
     /// Accepting an inbound circuit request failed.
+    #[deprecated(
+        note = "Will be removed in favor of logging them internally, see <https://github.com/libp2p/rust-libp2p/issues/4757> for details."
+    )]
     CircuitReqAcceptFailed {
         src_peer_id: PeerId,
         dst_peer_id: PeerId,
-        error: inbound_hop::UpgradeError,
+        error: inbound_hop::Error,
     },
     /// An inbound circuit has closed.
     CircuitClosed {
@@ -455,6 +470,7 @@ impl NetworkBehaviour for Behaviour {
                 ));
             }
             handler::Event::ReservationReqAcceptFailed { error } => {
+                #[allow(deprecated)]
                 self.queued_actions.push_back(ToSwarm::GenerateEvent(
                     Event::ReservationReqAcceptFailed {
                         src_peer_id: event_source,
@@ -470,6 +486,7 @@ impl NetworkBehaviour for Behaviour {
                 ));
             }
             handler::Event::ReservationReqDenyFailed { error } => {
+                #[allow(deprecated)]
                 self.queued_actions.push_back(ToSwarm::GenerateEvent(
                     Event::ReservationReqDenyFailed {
                         src_peer_id: event_source,
@@ -592,6 +609,7 @@ impl NetworkBehaviour for Behaviour {
                     self.circuits.remove(circuit_id);
                 }
 
+                #[allow(deprecated)]
                 self.queued_actions.push_back(ToSwarm::GenerateEvent(
                     Event::CircuitReqDenyFailed {
                         src_peer_id: event_source,
@@ -637,6 +655,7 @@ impl NetworkBehaviour for Behaviour {
                         status,
                     }),
                 });
+                #[allow(deprecated)]
                 self.queued_actions.push_back(ToSwarm::GenerateEvent(
                     Event::CircuitReqOutboundConnectFailed {
                         src_peer_id,
@@ -662,6 +681,7 @@ impl NetworkBehaviour for Behaviour {
                 error,
             } => {
                 self.circuits.remove(circuit_id);
+                #[allow(deprecated)]
                 self.queued_actions.push_back(ToSwarm::GenerateEvent(
                     Event::CircuitReqAcceptFailed {
                         src_peer_id: event_source,