identify: Move I/O from Networkehaviour,

reply to the Identification requests from the ConnectionHandler.

protocols/identify/src/behaviour.rs

@@ -261,6 +261,12 @@ impl NetworkBehaviour for Behaviour {
                         score: AddressScore::Finite(1),
                     });
             }
+            handler::Event::Identification(peer) => {
+                self.events
+                    .push_back(NetworkBehaviourAction::GenerateEvent(Event::Sent {
+                        peer_id: peer,
+                    }));
+            }
             handler::Event::IdentificationPushed => {
                 self.events
                     .push_back(NetworkBehaviourAction::GenerateEvent(Event::Pushed {

protocols/identify/src/handler.rs

@@ -36,6 +36,7 @@ use libp2p_swarm::{
 };
 use log::warn;
 use smallvec::SmallVec;
+use std::collections::VecDeque;
 use std::{io, pin::Pin, task::Context, task::Poll, time::Duration};
 
 pub struct Proto {
@@ -64,6 +65,17 @@ impl IntoConnectionHandler for Proto {
     }
 }
 
+/// A pending reply to an inbound identification request.
+enum Pending {
+    /// The reply is queued for sending.
+    Queued(Reply),
+    /// The reply is being sent.
+    Sending {
+        peer: PeerId,
+        io: Pin<Box<dyn Future<Output = Result<(), UpgradeError>> + Send>>,
+    },
+}
+
 /// A reply to an inbound identification request.
 #[derive(Debug)]
 pub struct Reply {
@@ -90,6 +102,9 @@ pub struct Handler {
         >; 4],
     >,
 
+    /// Pending replies to send.
+    pending_replies: VecDeque<Pending>,
+
     /// Future that fires when we need to identify the node again.
     trigger_next_identify: Delay,
 
@@ -106,11 +121,13 @@ pub struct Handler {
 pub enum Event {
     /// We obtained identification information from the remote.
     Identified(Info),
+    /// We replied to an identification request from the remote.
+    Identification(PeerId),
     /// We actively pushed our identification information to the remote.
     IdentificationPushed,
     /// We received a request for identification.
     Identify(ReplySubstream<NegotiatedSubstream>),
-    /// Failed to identify the remote.
+    /// Failed to identify the remote, or to reply to an identification request.
     IdentificationError(ConnectionHandlerUpgrErr<UpgradeError>),
 }
 
@@ -130,6 +147,7 @@ impl Handler {
             remote_peer_id,
             inbound_identify_push: Default::default(),
             events: SmallVec::new(),
+            pending_replies: VecDeque::new(),
             trigger_next_identify: Delay::new(initial_delay),
             keep_alive: KeepAlive::Yes,
             interval,
@@ -231,8 +249,15 @@ impl ConnectionHandler for Handler {
                         ),
                     });
             }
-            InEvent::Identify(_) => {
-                todo!()
+            InEvent::Identify(reply) => {
+                if !self.pending_replies.is_empty() {
+                    warn!(
+                        "New inbound identify request from {} while a previous one \
+                         is still pending. Queueing the new one.",
+                        reply.peer,
+                    );
+                }
+                self.pending_replies.push_back(Pending::Queued(reply));
             }
         }
     }
@@ -275,6 +300,39 @@ impl ConnectionHandler for Handler {
             }
         }
 
+        // Check for pending replies to send.
+        if let Some(mut pending) = self.pending_replies.pop_front() {
+            loop {
+                match pending {
+                    Pending::Queued(Reply { peer, io, info }) => {
+                        let io = Box::pin(io.send(info));
+                        pending = Pending::Sending { peer, io };
+                    }
+                    Pending::Sending { peer, mut io } => {
+                        match Future::poll(Pin::new(&mut io), cx) {
+                            Poll::Pending => {
+                                self.pending_replies
+                                    .push_front(Pending::Sending { peer, io });
+                                return Poll::Pending;
+                            }
+                            Poll::Ready(Ok(())) => {
+                                return Poll::Ready(ConnectionHandlerEvent::Custom(
+                                    Event::Identification(peer),
+                                ));
+                            }
+                            Poll::Ready(Err(err)) => {
+                                return Poll::Ready(ConnectionHandlerEvent::Custom(
+                                    Event::IdentificationError(ConnectionHandlerUpgrErr::Upgrade(
+                                        libp2p_core::upgrade::UpgradeError::Apply(err),
+                                    )),
+                                ))
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
         Poll::Pending
     }