GuardMgr: Launch a background task to keep the list of bridge

descriptors updated as appropriate.

crates/tor-guardmgr/src/daemon.rs

@@ -116,3 +116,31 @@ pub(crate) async fn keep_netdir_updated<RT: tor_rtcompat::Runtime>(
         }
     }
 }
+
+/// Background task to keep a guard manager up-to-date with a given bridge
+/// descriptor provider.
+#[cfg(feature = "bridge-client")]
+pub(crate) async fn keep_bridge_descs_updated<RT: tor_rtcompat::Runtime>(
+    runtime: RT,
+    inner: Weak<Mutex<GuardMgrInner>>,
+    bridge_desc_provider: Weak<dyn crate::bridge::BridgeDescProvider>,
+) {
+    use crate::bridge::BridgeDescEvent as E;
+    let mut event_stream = match bridge_desc_provider.upgrade().map(|p| p.events()) {
+        Some(s) => s,
+        None => return,
+    };
+
+    while let Some(event) = event_stream.next().await {
+        match event {
+            E::SomethingChanged => {
+                if let Some(inner) = inner.upgrade() {
+                    let mut inner = inner.lock().expect("Poisoned lock");
+                    inner.update(runtime.wallclock());
+                } else {
+                    return;
+                }
+            }
+        }
+    }
+}

crates/tor-guardmgr/src/lib.rs

@@ -394,7 +394,16 @@ impl<R: Runtime> GuardMgr<R> {
             let mut inner = self.inner.lock().expect("Poisoned lock");
             inner.bridge_desc_provider = Some(weak_provider.clone());
         }
-        // TODO pt-client: launch a keep_bridge_descs_updated task.
+
+        let weak_inner = Arc::downgrade(&self.inner);
+        let rt_clone = self.runtime.clone();
+        self.runtime
+            .spawn(daemon::keep_bridge_descs_updated(
+                rt_clone,
+                weak_inner,
+                weak_provider,
+            ))
+            .map_err(|e| GuardMgrError::from_spawn("periodic guard netdir updater", e))?;
 
         Ok(())
     }