protocols/floodsub: Propagate messages only to target peers (#2360)

Propagate messages only to the target peers and not all connected peers.

Co-authored-by: Victor Ermolaev <victorermolaev@gmail.com>
Co-authored-by: Max Inden <mail@max-inden.de>

protocols/floodsub/CHANGELOG.md

@@ -4,8 +4,12 @@
 
 - Migrate to Rust edition 2021 (see [PR 2339]).
 
+- Propagate messages only to the target peers and not all connected peers (see [PR2360]).
+
 [PR 2339]: https://github.com/libp2p/rust-libp2p/pull/2339
 
+[PR 2360]: https://github.com/libp2p/rust-libp2p/pull/2360/
+
 # 0.32.0 [2021-11-16]
 
 - Update dependencies.

protocols/floodsub/src/layer.rs

@@ -253,6 +253,12 @@ impl Floodsub {
 
         // Send to peers we know are subscribed to the topic.
         for (peer_id, sub_topic) in self.connected_peers.iter() {
+            // Peer must be in a communication list.
+            if !self.target_peers.contains(peer_id) {
+                continue;
+            }
+
+            // Peer must be subscribed for the topic.
             if !sub_topic
                 .iter()
                 .any(|t| message.topics.iter().any(|u| t == u))
@@ -402,6 +408,12 @@ impl NetworkBehaviour for Floodsub {
                     continue;
                 }
 
+                // Peer must be in a communication list.
+                if !self.target_peers.contains(peer_id) {
+                    continue;
+                }
+
+                // Peer must be subscribed for the topic.
                 if !subscr_topics
                     .iter()
                     .any(|t| message.topics.iter().any(|u| t == u))