Subject: Re: [PATCH v2 net] fq_codel: fix NET_XMIT_CN behavior

From: Jamal Hadi Salim <[email-masked]>
Date: Mon, 6 Jun 2016 06:49:26 -0400

On 16-06-05 07:30 PM, Cong Wang wrote:

> Potentially all of the following:
>
> net/sched/sch_choke.c:  return NET_XMIT_CN;
> net/sched/sch_fifo.c:   return NET_XMIT_CN;
> net/sched/sch_generic.c:        return NET_XMIT_CN;
> net/sched/sch_gred.c:   return NET_XMIT_CN;
> net/sched/sch_hhf.c:            return NET_XMIT_CN;
> net/sched/sch_red.c:    return NET_XMIT_CN;
> net/sched/sch_sfb.c:    return NET_XMIT_CN;
> net/sched/sch_sfq.c:            return NET_XMIT_CN;
>

As long as we are not loosing the stat that the packet
is dropped. Some qdiscs have a counter which indicates
congestion drops(look at RED variants of early drops);
maybe codel needs one. The parent also must account for
childs drops.
BTW, returning NET_XMIT_CN could be confusing to tcp;
it does not mean that the packet that we are getting return
code for was dropped; it could mean _another_ packet in
the queue was dropped.

cheers,
jamal