Skip sending IWant if we have received multiple IDontWants for the same msgId

libp2p/protocols/pubsub/gossipsub/behavior.nim

@@ -29,6 +29,7 @@ declareGauge(libp2p_gossipsub_low_peers_topics, "number of topics in mesh with a
 declareGauge(libp2p_gossipsub_healthy_peers_topics, "number of topics in mesh with at least dlow peers (but below dhigh)")
 declareCounter(libp2p_gossipsub_above_dhigh_condition, "number of above dhigh pruning branches ran", labels = ["topic"])
 declareGauge(libp2p_gossipsub_received_iwants, "received iwants", labels = ["kind"])
+declareCounter(libp2p_gossipsub_IWANT_Saves, "number of saved IWANTs based on received IDontWants")
 
 proc grafted*(g: GossipSub, p: PubSubPeer, topic: string) =
   g.withPeerStats(p.peerId) do (stats: var PeerStats):
@@ -249,14 +250,29 @@ proc handleIHave*(g: GossipSub,
       trace "peer sent ihave",
         peer, topicID = ihave.topicID, msgs = ihave.messageIDs
       if ihave.topicID in g.topics:
+        #look here for receieved idontwants for the same message
+        var meshPeers: HashSet[PubSubPeer]
+        g.mesh.withValue(ihave.topicID, peers): meshPeers.incl(peers[])
+
         for msgId in ihave.messageIDs:
           if not g.hasSeen(g.salt(msgId)):
             if peer.iHaveBudget <= 0:
               break
             elif msgId notin res.messageIDs:
-              res.messageIDs.add(msgId)
-              dec peer.iHaveBudget
-              trace "requested message via ihave", messageID=msgId
+              #dont send IWANT if we have received (N number of) IDontWant(s) for a msgID
+              let saltedID = g.salt(msgId)
+              var numFinds: int = 0
+              for meshPeer in meshPeers:
+                for heDontWant in meshPeer.heDontWants:
+                  if saltedID in heDontWant: 
+                    numFinds = numFinds + 1
+                    #break;
+              if numFinds > 0:  #Or wait for N number of IDontWants  
+                libp2p_gossipsub_IWANT_Saves.inc
+              else:
+                res.messageIDs.add(msgId)
+                dec peer.iHaveBudget
+                trace "requested message via ihave", messageID=msgId
     # shuffling res.messageIDs before sending it out to increase the likelihood
     # of getting an answer if the peer truncates the list due to internal size restrictions.
     g.rng.shuffle(res.messageIDs)