tree ac307d6fd960b5b83062e3623ed3e1529b735b7a
parent c3f67cdac3c23db5d4487130121690ed2c332c68
author Christopher Faulet <cfaulet@haproxy.com> 1610981223 +0100
committer Christopher Faulet <cfaulet@haproxy.com> 1611654086 +0100

BUG/MEDIUM: tcpcheck: Don't destroy connection in the wake callback context

When a tcpcheck ruleset uses multiple connections, the existing one must be
closed and destroyed before openning the new one. This part is handled in
the tcpcheck_main() function, when called from the wake callback function
(wake_srv_chk). But it is indeed a problem, because this function may be
called from the mux layer. This means a mux may call the wake callback
function of the data layer, which may release the connection and the mux. It
is easy to see how it is hazardous. And actually, depending on the
scheduling, it leads to crashes.

Thus, we must avoid to release the connection in the wake callback context,
and move this part in the check's process function instead. To do so, we
rely on the CHK_ST_CLOSE_CONN flags. When a connection must be replaced by a
new one, this flag is set on the check, in tcpcheck_main() function, and the
check's task is woken up. Then, the connection is really closed in
process_chk_conn() function.

This patch must be backported as far as 2.2, with some adaptations however
because the code is not exactly the same.

(cherry picked from commit 8f100427c4bf56acff967e313cd9cb8d42da035d)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>