Properly reset source key gc timers

After fixing #176 the source key garbage collection timers are not
updated if the source key is not adjusted. As a a result, in stable
networks source keys get garbage collected too frequently. Now we
properly reset them.

Signed-off-by: Lee Smet <lee.smet@hotmail.com>

src/router.rs

@@ -1245,6 +1245,10 @@ impl RouterInner {
                     self.expired_source_key_sink.clone(),
                 )
             }
+            // We also reset the garbage collection timer (unless the update is a retraction)
+            else if !metric.is_infinite() {
+                source_table.reset_timer(source_key, self.expired_source_key_sink.clone());
+            }
         }
         // no entry for this source key, so insert it
         else {

src/source_table.rs

@@ -100,6 +100,26 @@ impl SourceTable {
         };
     }
 
+    /// Resets the garbage collection timer for a given source key.
+    ///
+    /// Does nothing if the source key is not present.
+    pub fn reset_timer(&mut self, key: SourceKey, sink: mpsc::Sender<SourceKey>) {
+        self.table
+            .entry(key)
+            .and_modify(|(old_expiration_handle, _)| {
+                // First cancel the existing task
+                old_expiration_handle.abort();
+                // Then set the new one
+                *old_expiration_handle = tokio::spawn(async move {
+                    tokio::time::sleep(SOURCE_HOLD_DURATION).await;
+
+                    if let Err(e) = sink.send(key).await {
+                        error!("Failed to notify router of expired source key {e}");
+                    }
+                });
+            });
+    }
+
     /// Get the [`FeasibilityDistance`] currently associated with the [`SourceKey`].
     pub fn get(&self, key: &SourceKey) -> Option<&FeasibilityDistance> {
         self.table.get(key).map(|(_, v)| v)