[PATCH] net_sched: blackhole: tell upper qdisc about dropped packets

From: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
To: netdev@vger.kernel.org, "David S. Miller" <davem@davemloft.net>
Cc: Cong Wang <xiyou.wangcong@gmail.com>,
	Jiri Pirko <jiri@resnulli.us>,
	Jamal Hadi Salim <jhs@mojatatu.com>
Subject: [PATCH] net_sched: blackhole: tell upper qdisc about dropped packets
Date: Fri, 15 Jun 2018 13:27:31 +0300	[thread overview]
Message-ID: <152905845136.88583.6197221349040585517.stgit@buzz> (raw)

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@yandex-team.ru>
---
 net/sched/sch_blackhole.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/sch_blackhole.c b/net/sched/sch_blackhole.c
index c98a61e980ba..9c4c2bb547d7 100644
--- a/net/sched/sch_blackhole.c
+++ b/net/sched/sch_blackhole.c
@@ -21,7 +21,7 @@ static int blackhole_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 			     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)
