From b508ea5f95269761794731dbb8a1e4f7b21c786d Mon Sep 17 00:00:00 2001
From: Paolo Capriotti <paolo@capriotti.io>
Date: Mon, 29 Nov 2021 11:28:52 +0100
Subject: [PATCH] Make sure connection preface is always sent first

This fixes a race condition in the client between the `frameSender`
thread and the main thread, in the case where a SETTINGS frame is sent
in response to a server SETTINGS frame before the connection preface has
had a chance to be sent.
---
 Network/HTTP2/Client/Run.hs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Network/HTTP2/Client/Run.hs b/Network/HTTP2/Client/Run.hs
index 49e782af..f13f023f 100644
--- a/Network/HTTP2/Client/Run.hs
+++ b/Network/HTTP2/Client/Run.hs
@@ -24,11 +24,11 @@ run ClientConfig{..} conf@Config{..} client = do
     clientInfo <- newClientInfo scheme authority cacheLimit
     ctx <- newContext clientInfo
     mgr <- start confTimeoutManager
+    exchangeSettings conf ctx
     tid0 <- forkIO $ frameReceiver ctx confReadN
     -- fixme: if frameSender is terminated but the main thread is alive,
     --        what will happen?
     tid1 <- forkIO $ frameSender ctx conf mgr
-    exchangeSettings conf ctx
     client (sendRequest ctx scheme authority) `E.finally` do
         stop mgr
         killThread tid0