idontwant with d=dlow-1 and iwant to pull messages!

libp2p/protocols/pubsub/gossipsub.nim

@@ -46,6 +46,9 @@ declareCounter(libp2p_gossipsub_saved_bytes, "bytes saved by gossipsub optimizat
 declareCounter(libp2p_gossipsub_duplicate, "number of duplicates received")
 declareCounter(libp2p_gossipsub_received, "number of messages received (deduplicated)")
 
+export libp2p_gossipsub_duplicate_during_validation, libp2p_gossipsub_idontwant_saved_messages, 
+       libp2p_gossipsub_saved_bytes, libp2p_gossipsub_duplicate, libp2p_gossipsub_received
+
 proc init*(_: type[GossipSubParams]): GossipSubParams =
   GossipSubParams(
       explicit: true,
@@ -270,7 +273,14 @@ proc handleControl(g: GossipSub, peer: PubSubPeer, control: ControlMessage) =
   g.handlePrune(peer, control.prune)
 
   var respControl: ControlMessage
-  g.handleIDontWant(peer, control.idontwant)
+  var respCtrl: ControlMessage  #for idontwant messages
+
+  let ineed = g.handleIDontWant(peer, control.idontwant)
+  if ineed.messageIds.len > 0:
+    respCtrl.iwant.add(ineed)
+    var mess: seq[Message] #g.handleIWant(peer, control.idontwant)
+    g.send(peer, RPCMsg(control: some(respCtrl), messages: mess))
+
   let iwant = g.handleIHave(peer, control.ihave)
   if iwant.messageIds.len > 0:
     respControl.iwant.add(iwant)
@@ -349,13 +359,7 @@ proc validateAndRelay(g: GossipSub,
     toSendPeers.excl(peer)
     toSendPeers.excl(seenPeers)
 
-    # IDontWant is only worth it if the message is substantially
-    # bigger than the messageId
-    if msg.data.len > msgId.len * 10:
-      g.broadcast(toSendPeers, RPCMsg(control: some(ControlMessage(
-          idontwant: @[ControlIWant(messageIds: @[msgId])]
-        ))))
-
+    #we dont send idont want to peers from which we already received idontwant
     for peer in toSendPeers:
       for heDontWant in peer.heDontWants:
         if msgId in heDontWant:
@@ -366,6 +370,21 @@ proc validateAndRelay(g: GossipSub,
     toSendPeers.excl(seenPeers)
 
 
+    # IDontWant is only worth it if the message is substantially bigger than the messageId
+    # We randomly send large message to a maximum of dLow peers, others get idontwant 
+    if msg.data.len > msgId.len * 10:
+      var dontwantPeers: HashSet[PubSubPeer]
+      var lrgMsgPeers = toSendPeers.toSeq()
+      g.rng.shuffle(lrgMsgPeers)
+      for dpeer in lrgMsgPeers:
+        if (lrgMsgPeers.len - dontwantPeers.len) < g.parameters.dLow: break
+        dontwantPeers.incl(dpeer)
+
+      g.broadcast(dontwantPeers, RPCMsg(control: some(ControlMessage(
+          idontwant: @[ControlIWant(messageIds: @[msgId])]
+        ))))
+      toSendPeers.excl(dontwantPeers)
+
     # In theory, if topics are the same in all messages, we could batch - we'd
     # also have to be careful to only include validated messages
     g.broadcast(toSendPeers, RPCMsg(messages: @[msg]))

libp2p/protocols/pubsub/gossipsub/behavior.nim

@@ -266,12 +266,19 @@ proc handleIHave*(g: GossipSub,
 
 proc handleIDontWant*(g: GossipSub,
                       peer: PubSubPeer,
-                      iDontWants: seq[ControlIWant]) =
+                      iDontWants: seq[ControlIWant]): ControlIWant {.raises: [].}=
+  var res: ControlIWant
   for dontWant in iDontWants:
     for messageId in dontWant.messageIds:
       if peer.heDontWants[^1].len > 1000: break
       if messageId.len > 100: continue
       peer.heDontWants[^1].incl(messageId)
+      #we can ask for unreceived message, learnt through idontwantmessage
+      if (not g.hasSeen(messageId)) and messageId notin g.outstandingIWANTs:
+        if peer.score < g.parameters.gossipThreshold: continue    #dont request from low score peer
+        g.outstandingIWANTs[messageId] = IWANTRequest(messageId: messageId, peer: peer, timestamp: Moment.now())  
+        res.messageIds.add(messageId)
+  return res
 
 proc handleIWant*(g: GossipSub,
                  peer: PubSubPeer,