getGossipPeers fixes

libp2p/protocols/pubsub/gossipsub.nim

@@ -178,6 +178,11 @@ proc dropFanoutPeers(g: GossipSub) {.async.} =
     libp2p_gossipsub_peers_per_topic_fanout
       .set(g.fanout.getOrDefault(topic).len.int64, labelValues = [topic])
 
+proc shuffle[T](collection: var seq[T]) = 
+  for i in 0..collection.high:
+    let r = rand(collection.high)
+    swap(collection[i], collection[r])
+
 proc getGossipPeers(g: GossipSub): Table[string, ControlMessage] {.gcsafe.} =
   ## gossip iHave messages to peers
   let topics = toHashSet(toSeq(g.mesh.keys)) + toHashSet(toSeq(g.fanout.keys))
@@ -186,28 +191,22 @@ proc getGossipPeers(g: GossipSub): Table[string, ControlMessage] {.gcsafe.} =
     let fanout: HashSet[string] = g.fanout.getOrDefault(topic)
 
     let gossipPeers = mesh + fanout
-    var extraPeers = g.gossipsub # copy it!
     let mids = g.mcache.window(topic)
     if mids.len > 0:
       let ihave = ControlIHave(topicID: topic,
                                messageIDs: toSeq(mids))
 
-      if topic notin extraPeers:
+      if topic notin g.gossipsub:
         trace "topic not in gossip array, skipping", topicID = topic
         continue
       
-      while result.len < GossipSubD:
-        if extraPeers.getOrDefault(topic).len == 0:
-          trace "no peers for topic, skipping", topicID = topic
-          break
-
-        let id = toSeq(extraPeers.getOrDefault(topic)).sample()
-        if id in extraPeers.getOrDefault(topic):
-          extraPeers[topic].excl(id)
-          if id notin gossipPeers:
-            if id notin result:
-              result[id] = ControlMessage()
-            result[id].ihave.add(ihave)
+      var extraPeers = toSeq(g.gossipsub[topic])
+      shuffle(extraPeers)
+      for peer in extraPeers:
+          if  result.len < GossipSubD and 
+              peer notin gossipPeers and 
+              peer notin result:
+            result[peer] = ControlMessage(ihave: @[ihave])
 
 proc heartbeat(g: GossipSub) {.async.} =
   while g.heartbeatRunning: