protocols/kad: Add Kademlia::get_closest_local_peers (#2436)

Co-authored-by: Max Inden <[email protected]>

Author: folex

protocols/kad/CHANGELOG.md

@@ -8,9 +8,12 @@
 
 - Derive `Serialize`, `Deserialize` for `store::record::Key` (see [PR 2408])
 
+- Add `get_closest_local_peers` to `Kademlia` (see [PR 2436])
+
 [PR 2339]: https://github.com/libp2p/rust-libp2p/pull/2339
 [PR 2411]: https://github.com/libp2p/rust-libp2p/pull/2411
 [PR 2408]: https://github.com/libp2p/rust-libp2p/pull/2408
+[PR 2436]: https://github.com/libp2p/rust-libp2p/pull/2436
 
 # 0.33.0 [2021-11-16]
 

protocols/kad/src/behaviour.rs

@@ -667,6 +667,14 @@ where
         self.queries.add_iter_closest(target.clone(), peers, inner)
     }
 
+    /// Returns closest peers to the given key; takes peers from local routing table only.
+    pub fn get_closest_local_peers<'a, K: Clone>(
+        &'a mut self,
+        key: &'a kbucket::Key<K>,
+    ) -> impl Iterator<Item = kbucket::Key<PeerId>> + 'a {
+        self.kbuckets.closest_keys(key)
+    }
+
     /// Performs a lookup for a record in the DHT.
     ///
     /// The result of this operation is delivered in a