refactor(iroh)!: remove Endpoint::latency (#3717)

## Description

Based on #3593 

This was always just a placeholder, and can now be collected using
`EndpointHooks`.

## Breaking Changes

- remove `Endpoint::latency`

---------

Co-authored-by: varun-doshi <[email protected]>

Author: dignifiedquire

iroh/src/endpoint.rs

@@ -945,13 +945,6 @@ impl Endpoint {
     //
     // Partially they return things passed into the builder.
 
-    /// Returns the currently lowest latency for this endpoint.
-    ///
-    /// Will return `None` if we do not have any address information for the given `endpoint_id`.
-    pub async fn latency(&self, endpoint_id: EndpointId) -> Option<Duration> {
-        self.msock.latency(endpoint_id).await
-    }
-
     /// Returns the DNS resolver used in this [`Endpoint`].
     ///
     /// See [`Builder::dns_resolver`].

iroh/src/magicsock.rs

@@ -391,18 +391,6 @@ impl MagicSock {
         })
     }
 
-    // TODO: Build better info to expose to the user about remote nodes.  We probably want
-    // to expose this as part of path information instead.
-    pub(crate) async fn latency(&self, eid: EndpointId) -> Option<Duration> {
-        let remote_state = self.remote_map.remote_state_actor(eid);
-        let (tx, rx) = oneshot::channel();
-        remote_state
-            .send(RemoteStateMessage::Latency(tx))
-            .await
-            .ok();
-        rx.await.unwrap_or_default()
-    }
-
     /// Stores a new set of direct addresses.
     ///
     /// If the direct addresses have changed from the previous set, they are published to

iroh/src/magicsock/remote_map/remote_state.rs

@@ -348,9 +348,6 @@ impl RemoteStateActor {
             RemoteStateMessage::ResolveRemote(addrs, tx) => {
                 self.handle_msg_resolve_remote(addrs, tx);
             }
-            RemoteStateMessage::Latency(tx) => {
-                self.handle_msg_latency(tx);
-            }
         }
     }
 
@@ -504,29 +501,6 @@ impl RemoteStateActor {
         self.trigger_discovery();
     }
 
-    /// Handles [`RemoteStateMessage::Latency`].
-    fn handle_msg_latency(&self, tx: oneshot::Sender<Option<Duration>>) {
-        let rtt = self.selected_path.get().and_then(|addr| {
-            for conn_state in self.connections.values() {
-                let Some(path_id) = conn_state.path_ids.get(&addr) else {
-                    continue;
-                };
-                if !conn_state.open_paths.contains_key(path_id) {
-                    continue;
-                }
-                if let Some(rtt) = conn_state
-                    .handle
-                    .upgrade()
-                    .and_then(|conn| conn.path_stats(*path_id).map(|stats| stats.rtt))
-                {
-                    return Some(rtt);
-                }
-            }
-            None
-        });
-        tx.send(rtt).ok();
-    }
-
     fn handle_discovery_item(&mut self, item: Option<Result<DiscoveryItem, DiscoveryError>>) {
         match item {
             None => {
@@ -1018,11 +992,6 @@ pub(crate) enum RemoteStateMessage {
         BTreeSet<TransportAddr>,
         oneshot::Sender<Result<(), DiscoveryError>>,
     ),
-    /// Returns the current latency to the remote endpoint.
-    ///
-    /// TODO: This is more of a placeholder message currently.  Check MagicSock::latency.
-    #[debug("Latency(..)")]
-    Latency(oneshot::Sender<Option<Duration>>),
 }
 
 /// A handle to a [`RemoteStateActor`].