*: Dial with handler and return handler on error and closed (#2191)

Require `NetworkBehaviourAction::{DialPeer,DialAddress}` to contain a
`ProtocolsHandler`. This allows a behaviour to attach custom state to its
handler. The behaviour would no longer need to track this state separately
during connection establishment, thus reducing state required in a behaviour.
E.g. in the case of `libp2p-kad` the behaviour can include a `GetRecord` request
in its handler, or e.g. in the case of `libp2p-request-response` the behaviour
can include the first request in the handler.

Return `ProtocolsHandler` on connection error and close. This allows a behaviour
to extract its custom state previously included in the handler on connection
failure and connection closing. E.g. in the case of `libp2p-kad` the behaviour
could extract the attached `GetRecord` from the handler of the failed connection
and then start another connection attempt with a new handler with the same
`GetRecord` or bubble up an error to the user.

Co-authored-by: Thomas Eizinger <thomas@eizinger.io>

protocols/floodsub/src/layer.rs

@@ -29,7 +29,7 @@ use fnv::FnvHashSet;
 use libp2p_core::{connection::ConnectionId, PeerId};
 use libp2p_swarm::{
     DialPeerCondition, NetworkBehaviour, NetworkBehaviourAction, NotifyHandler, OneShotHandler,
-    PollParameters, ProtocolsHandler,
+    PollParameters,
 };
 use log::warn;
 use smallvec::SmallVec;
@@ -40,7 +40,12 @@ use std::{collections::VecDeque, iter};
 /// Network behaviour that handles the floodsub protocol.
 pub struct Floodsub {
     /// Events that need to be yielded to the outside when polling.
-    events: VecDeque<NetworkBehaviourAction<FloodsubRpc, FloodsubEvent>>,
+    events: VecDeque<
+        NetworkBehaviourAction<
+            FloodsubEvent,
+            OneShotHandler<FloodsubProtocol, FloodsubRpc, InnerMessage>,
+        >,
+    >,
 
     config: FloodsubConfig,
 
@@ -101,9 +106,11 @@ impl Floodsub {
         }
 
         if self.target_peers.insert(peer_id) {
+            let handler = self.new_handler();
             self.events.push_back(NetworkBehaviourAction::DialPeer {
                 peer_id,
                 condition: DialPeerCondition::Disconnected,
+                handler,
             });
         }
     }
@@ -302,9 +309,11 @@ impl NetworkBehaviour for Floodsub {
         // We can be disconnected by the remote in case of inactivity for example, so we always
         // try to reconnect.
         if self.target_peers.contains(id) {
+            let handler = self.new_handler();
             self.events.push_back(NetworkBehaviourAction::DialPeer {
                 peer_id: *id,
                 condition: DialPeerCondition::Disconnected,
+                handler,
             });
         }
     }
@@ -426,12 +435,7 @@ impl NetworkBehaviour for Floodsub {
         &mut self,
         _: &mut Context<'_>,
         _: &mut impl PollParameters,
-    ) -> Poll<
-        NetworkBehaviourAction<
-            <Self::ProtocolsHandler as ProtocolsHandler>::InEvent,
-            Self::OutEvent,
-        >,
-    > {
+    ) -> Poll<NetworkBehaviourAction<Self::OutEvent, Self::ProtocolsHandler>> {
         if let Some(event) = self.events.pop_front() {
             return Poll::Ready(event);
         }