Re: [PATCH net v8 2/6] net/sched: netem: fix queue limit check to include reordered packets

[Simon Horman]

On Fri, Apr 17, 2026 at 08:19:40PM -0700, Stephen Hemminger wrote:
> 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: f8d4bc455047 ("net/sched: netem: account for backlog updates from child qdisc")
> Signed-off-by: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>
> Reviewed-by: Simon Horman <horms@xxxxxxxxxx>

I acknowledge that Sashiko has provided review of this patch.

In the case of the commentary on the use of sch->q.qlen in place of q->t_len:
this is exactly the intention of this patch; to address shortcomings
in commit f8d4bc455047. Follow-up issues can be treated as such.

In the case of feedback on us of qdisc_drop_all(): if this is a problem
then it predates this patch and can be addressed separately to this
patch-set.

...