From 2f44e8843a553ef0f9c53c9b27899727de097777 Mon Sep 17 00:00:00 2001
From: Jerome Magnin <jmagnin@haproxy.com>
Date: Sat, 9 Nov 2019 18:00:47 +0100
Subject: [PATCH] BUG/MINOR: stream: init variables when the list is empty

We need to call vars_init() when the list is empty otherwise we
can't use variables in the response scope. This regression was
introduced by cda7f3f5 (MINOR: stream: don't prune variables if
the list is empty).

The following config reproduces the issue:

 defaults
   mode http

 frontend in
   bind *:11223
   http-request set-var(req.foo) str("foo")  if { path /bar }
   http-request set-header bar %[var(req.foo)]  if { var(req.foo) -m found }
   http-response set-var(res.bar) str("bar")
   http-response set-header foo %[var(res.bar)] if { var(res.bar) -m found }
   use_backend out

 backend out
   server s1 127.0.0.1:11224

 listen back
   bind *:11224
   http-request deny deny_status 200

 > GET /ba HTTP/1.1
 > Host: localhost:11223
 > User-Agent: curl/7.66.0
 > Accept: */*
 >
 < HTTP/1.0 200 OK
 < Cache-Control: no-cache
 < Content-Type: text/html

 > GET /bar HTTP/1.1
 > Host: localhost:11223
 > User-Agent: curl/7.66.0
 > Accept: */*
 >
 < HTTP/1.0 200 OK
 < Cache-Control: no-cache
 < Content-Type: text/html
 < foo: bar

This must be backported as far as 1.9.
---
 src/stream.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/src/stream.c b/src/stream.c
index be9a9fabe..535bf6a76 100644
--- a/src/stream.c
+++ b/src/stream.c
@@ -2581,10 +2581,9 @@ struct task *process_stream(struct task *t, void *context, unsigned short state)
 	if (si_state_in(si_b->state, SI_SB_REQ|SI_SB_QUE|SI_SB_TAR|SI_SB_ASS)) {
 		/* prune the request variables and swap to the response variables. */
 		if (s->vars_reqres.scope != SCOPE_RES) {
-			if (!LIST_ISEMPTY(&s->vars_reqres.head)) {
+			if (!LIST_ISEMPTY(&s->vars_reqres.head))
 				vars_prune(&s->vars_reqres, s->sess, s);
-				vars_init(&s->vars_reqres, SCOPE_RES);
-			}
+			vars_init(&s->vars_reqres, SCOPE_RES);
 		}
 
 		do {