fix(relay): make reservation to our closest peers

ant-networking/src/relay_manager.rs

@@ -7,12 +7,13 @@
 // permissions and limitations relating to use of the SAFE Network Software.
 
 use crate::driver::{BadNodes, NodeBehaviour};
+use ant_protocol::NetworkAddress;
 use itertools::Itertools;
 use libp2p::{
     core::transport::ListenerId, multiaddr::Protocol, Multiaddr, PeerId, StreamProtocol, Swarm,
 };
 use rand::Rng;
-use std::collections::{BTreeMap, HashMap, HashSet, VecDeque};
+use std::collections::{BTreeMap, HashMap, HashSet};
 
 const MAX_CONCURRENT_RELAY_CONNECTIONS: usize = 4;
 const MAX_POTENTIAL_CANDIDATES: usize = 1000;
@@ -28,7 +29,7 @@ pub(crate) fn is_a_relayed_peer(addrs: &HashSet<Multiaddr>) -> bool {
 #[derive(Debug)]
 pub(crate) struct RelayManager {
     self_peer_id: PeerId,
-    candidates: VecDeque<(PeerId, Multiaddr)>,
+    candidates: Vec<(PeerId, Multiaddr)>,
     waiting_for_reservation: BTreeMap<PeerId, Multiaddr>,
     connected_relays: BTreeMap<PeerId, Multiaddr>,
 
@@ -72,7 +73,7 @@ impl RelayManager {
                 // Hence here can add the addr directly.
                 if let Some(relay_addr) = Self::craft_relay_address(addr, Some(*peer_id)) {
                     debug!("Adding {peer_id:?} with {relay_addr:?} as a potential relay candidate");
-                    self.candidates.push_back((*peer_id, relay_addr));
+                    self.candidates.push((*peer_id, relay_addr));
                 }
             }
         } else {
@@ -101,44 +102,47 @@ impl RelayManager {
             // todo: should we remove all our other `listen_addr`? And should we block from adding `add_external_address` if
             // we're behind nat?
 
-            // Pick a random candidate from the vector. Check if empty, or `gen_range` panics for empty range.
+            // Pick a random closest candidate from the vector. Check if empty, or `gen_range` panics for empty range.
+            let self_peer_id = NetworkAddress::from_peer(self.self_peer_id);
+            self.candidates.sort_by_key(|(peer_id, _)| {
+                self_peer_id.distance(&NetworkAddress::from_peer(*peer_id))
+            });
             let index = if self.candidates.is_empty() {
                 debug!("No more relay candidates.");
                 break;
             } else {
-                rand::thread_rng().gen_range(0..self.candidates.len())
+                let max_range = std::cmp::min(self.candidates.len(), 5);
+                rand::thread_rng().gen_range(0..max_range)
             };
 
-            if let Some((peer_id, relay_addr)) = self.candidates.remove(index) {
-                // skip if detected as a bad node
-                if let Some((_, is_bad)) = bad_nodes.get(&peer_id) {
-                    if *is_bad {
-                        debug!("Peer {peer_id:?} is considered as a bad node. Skipping it.");
-                        continue;
-                    }
-                }
-
-                if self.connected_relays.contains_key(&peer_id)
-                    || self.waiting_for_reservation.contains_key(&peer_id)
-                {
-                    debug!("We are already using {peer_id:?} as a relay server. Skipping.");
+            let (peer_id, relay_addr) = self.candidates.swap_remove(index);
+            // skip if detected as a bad node
+            if let Some((_, is_bad)) = bad_nodes.get(&peer_id) {
+                if *is_bad {
+                    debug!("Peer {peer_id:?} is considered as a bad node. Skipping it.");
                     continue;
                 }
+            }
+
+            if self.connected_relays.contains_key(&peer_id)
+                || self.waiting_for_reservation.contains_key(&peer_id)
+            {
+                debug!("We are already using {peer_id:?} as a relay server. Skipping.");
+                continue;
+            }
 
-                match swarm.listen_on(relay_addr.clone()) {
-                    Ok(id) => {
-                        info!("Sending reservation to relay {peer_id:?} on {relay_addr:?}");
-                        self.waiting_for_reservation.insert(peer_id, relay_addr);
-                        self.relayed_listener_id_map.insert(id, peer_id);
-                        n_reservations += 1;
-                    }
-                    Err(err) => {
-                        error!("Error while trying to listen on the relay addr: {err:?} on {relay_addr:?}");
-                    }
+            match swarm.listen_on(relay_addr.clone()) {
+                Ok(id) => {
+                    info!("Sending reservation to relay {peer_id:?} on {relay_addr:?}");
+                    self.waiting_for_reservation.insert(peer_id, relay_addr);
+                    self.relayed_listener_id_map.insert(id, peer_id);
+                    n_reservations += 1;
+                }
+                Err(err) => {
+                    error!(
+                        "Error while trying to listen on the relay addr: {err:?} on {relay_addr:?}"
+                    );
                 }
-            } else {
-                debug!("No more relay candidates.");
-                break;
             }
         }
     }