Re: An inconsistency/bug in ingress netem timestamps

[Alex Sidorenko <alexandre.sidorenko@hp.com>]

On April 15, 2009 03:50:22 pm Jarek Poplawski wrote:

> I agree there is an inconsistency, but it seems 100 ms isn't the
> "right" thing to show here. It shows an internal delay added on ifb by
> any packet scheduler, so probably not what a user usually expects.

Hi Jarek,

thank you for your comments. Yes, I understand that it just looked OK in this 
case even though technically the value was not quite correct.

> > The strange thing is that as soon as there is any ptype_all handler
> > installed, skb->tstamp is updated properly. Unfortunately, my knowledge
> > of TC internals is not good enough to find how exactly this happens.
>
> Isn't it when act_mirred calls dev_queue_xmit with dev_queue_xmit_nit?
> But, as above mentioned, I doubt it's "updated properly" in this case.

I can see that dev_queue_xmit_nit calls net_timestamp(skb) unconditionally. I 
agree that to fix this properly we need to update tstamp in another place 
explicitly (in ifb or netem?).

Thanks,
Alex

-- 
------------------------------------------------------------------
Alexandre Sidorenko             email: asid@hp.com
WTEC Linux			Hewlett-Packard (Canada)
------------------------------------------------------------------