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From: Stephen Hemminger <stephen@networkplumber.org>
To: netdev@vger.kernel.org
Cc: Stephen Hemminger <stephen@networkplumber.org>,
	Simon Horman <horms@kernel.org>,
	Jamal Hadi Salim <jhs@mojatatu.com>,
	Jiri Pirko <jiri@resnulli.us>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	linux-kernel@vger.kernel.org (open list)
Subject: [PATCH net v4 2/8] net/sched: netem: fix queue limit check to include reordered packets
Date: Mon,  6 Apr 2026 10:25:10 -0700	[thread overview]
Message-ID: <20260406172627.210894-3-stephen@networkplumber.org> (raw)
In-Reply-To: <20260406172627.210894-1-stephen@networkplumber.org>

The queue limit check in netem_enqueue() uses q->t_len which only
counts packets in the internal tfifo. Packets placed in sch->q by
the reorder path (__qdisc_enqueue_head) are not counted, allowing
the total queue occupancy to exceed sch->limit under reordering.

Include sch->q.qlen in the limit check.

Fixes: 50612537e9ab ("netem: fix classful handling")
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Reviewed-by: Simon Horman <horms@kernel.org>
---
 net/sched/sch_netem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 8ee72cac1faf..d400a730eadd 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -524,7 +524,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 				1 << get_random_u32_below(8);
 	}
 
-	if (unlikely(q->t_len >= sch->limit)) {
+	if (unlikely(sch->q.qlen >= sch->limit)) {
 		/* re-link segs, so that qdisc_drop_all() frees them all */
 		skb->next = segs;
 		qdisc_drop_all(skb, sch, to_free);
-- 
2.53.0


  parent reply	other threads:[~2026-04-06 17:26 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-04-06 17:25 [PATCH net v4 0/8] net/sched: netem bug fixes Stephen Hemminger
2026-04-06 17:25 ` [PATCH net v4 1/8] net/sched: netem: fix probability gaps in 4-state loss model Stephen Hemminger
2026-04-06 17:25 ` Stephen Hemminger [this message]
2026-04-06 17:25 ` [PATCH net v4 3/8] net/sched: netem: only reseed PRNG when seed is explicitly provided Stephen Hemminger
2026-04-06 17:25 ` [PATCH net v4 4/8] net/sched: netem: refactor dequeue into helper functions Stephen Hemminger
2026-04-06 17:25 ` [PATCH net v4 5/8] net/sched: netem: batch-transfer ready packets to avoid child re-entrancy Stephen Hemminger
2026-04-06 17:25 ` [PATCH net v4 6/8] net/sched: netem: null-terminate tfifo linear queue tail Stephen Hemminger
2026-04-06 17:25 ` [PATCH net v4 7/8] net/sched: netem: check for invalid slot range Stephen Hemminger
2026-04-06 17:25 ` [PATCH net v4 8/8] net/sched: netem: fix slot delay calculation overflow Stephen Hemminger

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