From 009efebdafd21b63f284f70691b1cc39ff75e8bd Mon Sep 17 00:00:00 2001
From: vyzo <vyzo@hackzen.org>
Date: Thu, 22 Feb 2018 11:01:14 +0200
Subject: [PATCH] harden piggybackControl

don't create a control object if the graft/prune are stale and only assign
the relevant fields.
---
 gossipsub.go | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/gossipsub.go b/gossipsub.go
index b50de38..5ff4386 100644
--- a/gossipsub.go
+++ b/gossipsub.go
@@ -520,14 +520,22 @@ func (gs *GossipSubRouter) piggybackControl(p peer.ID, out *RPC, ctl *pb.Control
 		}
 	}
 
+	if len(tograft) == 0 && len(toprune) == 0 {
+		return
+	}
+
 	xctl := out.Control
 	if xctl == nil {
 		xctl = &pb.ControlMessage{}
 		out.Control = xctl
 	}
 
-	xctl.Graft = append(xctl.Graft, tograft...)
-	xctl.Prune = append(xctl.Prune, toprune...)
+	if len(tograft) > 0 {
+		xctl.Graft = append(xctl.Graft, tograft...)
+	}
+	if len(toprune) > 0 {
+		xctl.Prune = append(xctl.Prune, toprune...)
+	}
 }
 
 func (gs *GossipSubRouter) getPeers(topic string, count int, filter func(peer.ID) bool) []peer.ID {