From 02b20440f268da7ffd69a528544c1df5543caeb3 Mon Sep 17 00:00:00 2001
From: Giovanni Petrantoni <7008900+sinkingsugar@users.noreply.github.com>
Date: Sat, 28 Nov 2020 16:27:39 +0900
Subject: [PATCH] Limit ihave emission (#462)

* add some limits to ihave emission, go has them, rust does not actually

* restore shuffling of IDs

* add some context
---
 libp2p/protocols/pubsub/gossipsub.nim | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/libp2p/protocols/pubsub/gossipsub.nim b/libp2p/protocols/pubsub/gossipsub.nim
index fd094d0..faa4570 100644
--- a/libp2p/protocols/pubsub/gossipsub.nim
+++ b/libp2p/protocols/pubsub/gossipsub.nim
@@ -57,6 +57,10 @@ const
   BackoffSlackTime = 2 # seconds
   IWantPeerBudget = 25 # 25 messages per second ( reset every heartbeat )
   IHavePeerBudget = 10
+  # the max amount of IHave to expose, not by spec, but go as example
+  # rust sigp: https://github.com/sigp/rust-libp2p/blob/f53d02bc873fef2bf52cd31e3d5ce366a41d8a8c/protocols/gossipsub/src/config.rs#L572
+  # go: https://github.com/libp2p/go-libp2p-pubsub/blob/08c17398fb11b2ab06ca141dddc8ec97272eb772/gossipsub.go#L155
+  IHaveMaxLength = 5000
 
 type
   TopicInfo* = object
@@ -618,7 +622,14 @@ proc getGossipPeers(g: GossipSub): Table[PubSubPeer, ControlMessage] {.gcsafe.}
     if not mids.len > 0:
       continue
 
-    let ihave = ControlIHave(topicID: topic, messageIDs: toSeq(mids))
+    var midsSeq = toSeq(mids)
+    # not in spec
+    # similar to rust: https://github.com/sigp/rust-libp2p/blob/f53d02bc873fef2bf52cd31e3d5ce366a41d8a8c/protocols/gossipsub/src/behaviour.rs#L2101
+    # and go https://github.com/libp2p/go-libp2p-pubsub/blob/08c17398fb11b2ab06ca141dddc8ec97272eb772/gossipsub.go#L582
+    if midsSeq.len > IHaveMaxLength:
+      shuffle(midsSeq)
+      midsSeq.setLen(IHaveMaxLength)
+    let ihave = ControlIHave(topicID: topic, messageIDs: midsSeq)
 
     let mesh = g.mesh.getOrDefault(topic)
     let fanout = g.fanout.getOrDefault(topic)