don't forward messages with source ourselves but not published by ourselves

per stebalien's request.

gossipsub.go

@@ -556,6 +556,12 @@ func (gs *GossipSubRouter) connector() {
 }
 
 func (gs *GossipSubRouter) Publish(msg *Message) {
+	self := gs.p.host.ID()
+	if peer.ID(msg.GetFrom()) == self && msg.ReceivedFrom != self {
+		// we don't forward messages claiming to be from us but not published by ourselves
+		return
+	}
+
 	gs.mcache.Put(msg.Message)
 	from := msg.ReceivedFrom
 
@@ -567,7 +573,7 @@ func (gs *GossipSubRouter) Publish(msg *Message) {
 			continue
 		}
 
-		if gs.floodPublish && from == gs.p.host.ID() {
+		if gs.floodPublish && from == self {
 			for p := range tmap {
 				if gs.score.Score(p) >= gs.publishThreshold {
 					tosend[p] = struct{}{}