feat(swarm)!: allow NetworkBehaviours to manage connections

Previously, a `ConnectionHandler` was immediately requested from the `NetworkBehaviour` as soon as a new dial was initiated or a new incoming connection accepted.

With this patch, we delay the creation of the handler until the connection is actually established and fully upgraded, i.e authenticated and multiplexed.

As a consequence, `NetworkBehaviour::new_handler` is now deprecated in favor of a new set of callbacks:

- `NetworkBehaviour::handle_pending_inbound_connection`
- `NetworkBehaviour::handle_pending_outbound_connection`
- `NetworkBehaviour::handle_established_inbound_connection`
- `NetworkBehaviour::handle_established_outbound_connection`

All callbacks are fallible, allowing the `NetworkBehaviour` to abort the connection either immediately or after it is fully established. All callbacks also receive a `ConnectionId` parameter which uniquely identifies the connection. For example, in case a `NetworkBehaviour` issues a dial via `NetworkBehaviourAction::Dial`, it can unambiguously detect this dial in these lifecycle callbacks via the `ConnectionId`.

Finally, `NetworkBehaviour::handle_pending_outbound_connection` also replaces `NetworkBehaviour::addresses_of_peer` by allowing the behaviour to return more addresses to be used for the dial.

Resolves #2824.

Pull-Request: #3254.

protocols/identify/src/behaviour.rs

@@ -18,16 +18,16 @@
 // FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
 
-use crate::handler::{self, InEvent, Proto};
+use crate::handler::{self, Handler, InEvent};
 use crate::protocol::{Info, Protocol, UpgradeError};
-use libp2p_core::{multiaddr, ConnectedPoint, Multiaddr, PeerId, PublicKey};
+use libp2p_core::{multiaddr, ConnectedPoint, Endpoint, Multiaddr, PeerId, PublicKey};
+use libp2p_swarm::behaviour::{ConnectionClosed, ConnectionEstablished, DialFailure, FromSwarm};
 use libp2p_swarm::{
-    behaviour::{ConnectionClosed, ConnectionEstablished, DialFailure, FromSwarm},
-    dial_opts::DialOpts,
-    AddressScore, ConnectionHandlerUpgrErr, ConnectionId, DialError, ExternalAddresses,
-    ListenAddresses, NetworkBehaviour, NetworkBehaviourAction, NotifyHandler, PollParameters,
-    THandlerInEvent, THandlerOutEvent,
+    dial_opts::DialOpts, AddressScore, ConnectionDenied, ConnectionHandlerUpgrErr, DialError,
+    ExternalAddresses, ListenAddresses, NetworkBehaviour, NetworkBehaviourAction, NotifyHandler,
+    PollParameters, THandlerInEvent,
 };
+use libp2p_swarm::{ConnectionId, THandler, THandlerOutEvent};
 use lru::LruCache;
 use std::num::NonZeroUsize;
 use std::{
@@ -234,17 +234,43 @@ impl Behaviour {
 }
 
 impl NetworkBehaviour for Behaviour {
-    type ConnectionHandler = Proto;
+    type ConnectionHandler = Handler;
     type OutEvent = Event;
 
-    fn new_handler(&mut self) -> Self::ConnectionHandler {
-        Proto::new(
+    fn handle_established_inbound_connection(
+        &mut self,
+        _: ConnectionId,
+        peer: PeerId,
+        _: &Multiaddr,
+        remote_addr: &Multiaddr,
+    ) -> Result<THandler<Self>, ConnectionDenied> {
+        Ok(Handler::new(
             self.config.initial_delay,
             self.config.interval,
+            peer,
             self.config.local_public_key.clone(),
             self.config.protocol_version.clone(),
             self.config.agent_version.clone(),
-        )
+            remote_addr.clone(),
+        ))
+    }
+
+    fn handle_established_outbound_connection(
+        &mut self,
+        _: ConnectionId,
+        peer: PeerId,
+        addr: &Multiaddr,
+        _: Endpoint,
+    ) -> Result<THandler<Self>, ConnectionDenied> {
+        Ok(Handler::new(
+            self.config.initial_delay,
+            self.config.interval,
+            peer,
+            self.config.local_public_key.clone(),
+            self.config.protocol_version.clone(),
+            self.config.agent_version.clone(),
+            addr.clone(), // TODO: This is weird? That is the public address we dialed, shouldn't need to tell the other party?
+        ))
     }
 
     fn on_connection_handler_event(
@@ -352,8 +378,19 @@ impl NetworkBehaviour for Behaviour {
         }
     }
 
-    fn addresses_of_peer(&mut self, peer: &PeerId) -> Vec<Multiaddr> {
-        self.discovered_peers.get(peer)
+    fn handle_pending_outbound_connection(
+        &mut self,
+        _connection_id: ConnectionId,
+        maybe_peer: Option<PeerId>,
+        _addresses: &[Multiaddr],
+        _effective_role: Endpoint,
+    ) -> Result<Vec<Multiaddr>, ConnectionDenied> {
+        let peer = match maybe_peer {
+            None => return Ok(vec![]),
+            Some(peer) => peer,
+        };
+
+        Ok(self.discovered_peers.get(&peer))
     }
 
     fn on_swarm_event(&mut self, event: FromSwarm<Self::ConnectionHandler>) {