linux-kernel - [PATCH 4.17 030/101] net_sched: blackhole: tell upper qdisc about dropped packets

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Message-Id: <20180720121424.239595632@linuxfoundation.org>
Date:   Fri, 20 Jul 2018 14:13:36 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.17 030/101] net_sched: blackhole: tell upper qdisc about dropped packets

4.17-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>

[ Upstream commit 7e85dc8cb35abf16455f1511f0670b57c1a84608 ]

When blackhole is used on top of classful qdisc like hfsc it breaks
qlen and backlog counters because packets are disappear without notice.

In HFSC non-zero qlen while all classes are inactive triggers warning:
WARNING: ... at net/sched/sch_hfsc.c:1393 hfsc_dequeue+0xba4/0xe90 [sch_hfsc]
and schedules watchdog work endlessly.

This patch return __NET_XMIT_BYPASS in addition to NET_XMIT_SUCCESS,
this flag tells upper layer: this packet is gone and isn't queued.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/sched/sch_blackhole.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/sched/sch_blackhole.c
+++ b/net/sched/sch_blackhole.c
@@ -21,7 +21,7 @@ static int blackhole_enqueue(struct sk_b
 			     struct sk_buff **to_free)
 {
 	qdisc_drop(skb, sch, to_free);
-	return NET_XMIT_SUCCESS;
+	return NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
 }

 static struct sk_buff *blackhole_dequeue(struct Qdisc *sch)