From: Willy Tarreau <w@1wt.eu>
Date: Wed, 31 Dec 2025 11:35:24 +0000 (+0100)
Subject: BUG/MINOR: backend: inspect request not response buffer to check for TFO
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=933cb76461795cf5ca9754cd821a409d1f8dec95;p=thirdparty%2Fhaproxy.git

BUG/MINOR: backend: inspect request not response buffer to check for TFO

In 2.6, do_connect_server() was introduced by commit 0a4dcb65f ("MINOR:
stream-int/backend: Move si_connect() in the backend scope") and changed
the approach to work with a stream instead of a stream-interface. However
si_oc(si) was wrongly turned to &s->res instead of &s->req, which breaks
TFO by always inspecting the response channel to figure whether there are
data pending.

This fix can be backported to all versions till 2.6.
---

diff --git a/src/backend.c b/src/backend.c
index b13922d65..c8adf38a3 100644
--- a/src/backend.c
+++ b/src/backend.c
@@ -1445,7 +1445,7 @@ static int do_connect_server(struct stream *s, struct connection *conn)
 	if (unlikely(!conn || !conn->ctrl || !conn->ctrl->connect))
 		return SF_ERR_INTERNAL;
 
-	if (co_data(&s->res))
+	if (co_data(&s->req))
 		conn_flags |= CONNECT_HAS_DATA;
 	if (s->conn_retries == 0)
 		conn_flags |= CONNECT_CAN_USE_TFO;