netdev - Re: SFQ on HFSC leaf does not seem to work

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Message-ID: <1324660838.10184.614.camel@denise.theartistscloset.com>
Date:	Fri, 23 Dec 2011 12:20:38 -0500
From:	"John A. Sullivan III" <jsullivan@...nsourcedevel.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: SFQ on HFSC leaf does not seem to work

On Fri, 2011-12-23 at 18:06 +0100, Eric Dumazet wrote:
> Le vendredi 23 décembre 2011 à 11:44 -0500, John A. Sullivan III a
> écrit :
> > On Fri, 2011-12-23 at 17:16 +0100, Eric Dumazet wrote:
> > > Le vendredi 23 décembre 2011 à 10:26 -0500, John A. Sullivan III a
> > > écrit :
> > > 
> > > > Yes.  This is a problem I have with netem on ingress traffic.  I use the
> > > > filter on ffff: to redirect to ifb0 for the ingress traffic shaping.  I
> > > > cannot figure out a way to redirect a second time to ifb1 for the netem
> > > > qdisc.  I tried putting two action mirred statements in the filter but
> > > > that did not work.  Unlike eth1, I cannot attach a filter further down
> > > > the ifb0 hfsc hierarchy because one can't redirect one ifb into another
> > > > ifb.  Thus, the only way I could figure out how to do inbound netem was
> > > > to replace the terminal qdisc with netem rather than SFQ.  I'd love to
> > > > be able to do that differently.  I tried attaching netem to the SFQ but
> > > > that failed (I assume because SFQ is classless) and I tried the other
> > > > way around, attaching SFQ to netem since you mentioned netem could take
> > > > a class but that did not work either.
> > > 
> > > Unfortunately, netem wants to control skbs itself, in a fifo queue.
> > > 
> > > To implement what you want, we would need to setup a second qdisc,
> > > and when packets are dequeued from internal netem fifo, queue them in
> > > second qdisc.
> > > 
> > > 
> > > 
> > I thought I tried to do that but I must have done it incorrectly.  I
> > would think something like:
> > 
> > tc qdisc add dev eth1 ingress
> > tc filter add dev eth1 parent ffff: protocol ip prio 50 u32 match u32 0 0 action mirred egress redirect dev ifb0
> > tc qdisc add  dev ifb0 root handle 4 netem delay 25ms 5ms distribution normal loss 0.1% 30%
> > tc qdisc add dev ifb0 parent 4:0 handle 1: hfsc default 20
> > 
> > but I get:
> > root@...tswitch01:~# tc qdisc add dev ifb0 parent 4:0 handle 1: hfsc default 20
> > RTNETLINK answers: Operation not supported
> > 
> > What did I do wrong? Thanks - John
> > 
> 
> Maybe I was not clear :
> 
> netem currently uses a fifo queue, you cant change this, without
> patching kernel.
> 
> 
> 
OK - that makes sense and explains what I was seeing but, once they are
out the netem fifo, aren't they headed for the NIC driver? How do we
queue them in a second qdisc? I'll gladly give it a try if I know how.
Thanks - John

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