From 18d69a5c41c03f493a9f80073ea304b9693350ac Mon Sep 17 00:00:00 2001
From: Giovanni Petrantoni <7008900+sinkingsugar@users.noreply.github.com>
Date: Wed, 16 Dec 2020 03:32:11 +0900
Subject: [PATCH] Workaround the gossipsub table race condition (#486)

---
 libp2p/protocols/pubsub/floodsub.nim  | 12 ++++++++++++
 libp2p/protocols/pubsub/gossipsub.nim | 16 ++++++++++++----
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/libp2p/protocols/pubsub/floodsub.nim b/libp2p/protocols/pubsub/floodsub.nim
index 0bf053da6..446e6c8d5 100644
--- a/libp2p/protocols/pubsub/floodsub.nim
+++ b/libp2p/protocols/pubsub/floodsub.nim
@@ -33,6 +33,18 @@ method subscribeTopic*(f: FloodSub,
                        topic: string,
                        subscribe: bool,
                        peer: PubsubPeer) {.gcsafe.} =
+  logScope:
+    peer
+    topic
+
+  # this is a workaround for a race condition 
+  # that can happen if we disconnect the peer very early
+  # in the future we might use this as a test case 
+  # and eventually remove this workaround
+  if subscribe and peer.peerId notin f.peers:
+    trace "ignoring unknown peer"
+    return
+
   procCall PubSub(f).subscribeTopic(topic, subscribe, peer)
 
   if topic notin f.floodsub:
diff --git a/libp2p/protocols/pubsub/gossipsub.nim b/libp2p/protocols/pubsub/gossipsub.nim
index 349088121..529005c79 100644
--- a/libp2p/protocols/pubsub/gossipsub.nim
+++ b/libp2p/protocols/pubsub/gossipsub.nim
@@ -909,17 +909,25 @@ method subscribeTopic*(g: GossipSub,
                        topic: string,
                        subscribe: bool,
                        peer: PubSubPeer) {.gcsafe.} =
-  # Skip floodsub - we don't want it to add the peer to `g.floodsub`
-  procCall PubSub(g).subscribeTopic(topic, subscribe, peer)
-
   logScope:
     peer
     topic
 
-  g.onNewPeer(peer)
+  # this is a workaround for a race condition 
+  # that can happen if we disconnect the peer very early
+  # in the future we might use this as a test case 
+  # and eventually remove this workaround
+  if subscribe and peer.peerId notin g.peers:
+    trace "ignoring unknown peer"
+    return
+  
+  # Skip floodsub - we don't want it to add the peer to `g.floodsub`
+  procCall PubSub(g).subscribeTopic(topic, subscribe, peer)
 
   if subscribe:
     trace "peer subscribed to topic"
+    # populate scoring structs and such
+    g.onNewPeer(peer)
     # subscribe remote peer to the topic
     discard g.gossipsub.addPeer(topic, peer)
     if peer.peerId in g.parameters.directPeers: