From: Amaury Denoyelle <adenoyelle@haproxy.com>
Date: Mon, 23 May 2022 06:52:58 +0000 (+0200)
Subject: BUG/MEDIUM: mux-quic: adjust buggy proxy closing support
X-Git-Tag: v2.6-dev12~146
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d0c62328afe290e6009ae17e092b7df17d73c29b;p=thirdparty%2Fhaproxy.git

BUG/MEDIUM: mux-quic: adjust buggy proxy closing support

The wake handler detects if the frontend is closed. This can happen if
the proxy has been disabled individually or even on process soft-stop.
Before this patch, in this condition QCS instances were freed before
being detached from the cs_endpoint. This clearly violates the haproxy
connection architecture and cause a BUG_ON statement crash in cs_free().

To handle this properly, cs_endpoint is notified by setting RD_SH|WR_SH
on connection flags. The cs_endpoint will thus use the detach operation
which allows the QCS instance to be freed.

This code allows the soft-stop process to complete as soon as possible.
However, the client is not notified about the connection closing. It
should be done by emitting a H3 GOAWAY + CONNECTION_CLOSE. Sadly, this
is impossible at this stage because the listener sockets are closed so
the quic-conn cannot use it to emit new frames. At this stage the client
will most probably detect connection closing on its idle timeout
expiration.

Thus, to completely support proxy closing/soft-stop, important
architecture changes are required in QUIC socket management. This is
also linked with the reload feature.
---

diff --git a/src/mux_quic.c b/src/mux_quic.c
index 4c240c8b22..c1cea6fa3c 100644
--- a/src/mux_quic.c
+++ b/src/mux_quic.c
@@ -1566,12 +1566,15 @@ static int qc_wake(struct connection *conn)
 	TRACE_ENTER(QMUX_EV_QCC_WAKE, conn);
 
 	/* Check if a soft-stop is in progress.
-	 * Release idling front connection if this is the case.
 	 *
 	 * TODO this is revelant for frontend connections only.
+	 *
+	 * TODO Client should be notified with a H3 GOAWAY and then a
+	 * CONNECTION_CLOSE. However, quic-conn uses the listener socket for
+	 * sending which at this stage is already closed.
 	 */
 	if (unlikely(prx->flags & (PR_FL_DISABLED|PR_FL_STOPPED)))
-		goto release;
+		qcc->conn->flags |= (CO_FL_SOCK_RD_SH|CO_FL_SOCK_WR_SH);
 
 	if (conn->handle.qc->flags & QUIC_FL_CONN_NOTIFY_CLOSE)
 		qcc->conn->flags |= (CO_FL_SOCK_RD_SH|CO_FL_SOCK_WR_SH);