Re: [LARTC] howto mark packet's dscp value

[Maria Joana Urbano <stmaria@dei.uc.pt>]

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Hi Philip,


>I guess dsmark qdisc is runned before iptables PREROUTING phase, right?
>

Hummm, I actually use dsmark after all iptables hooks, at the QoS Egress, 
just before the packet leaves the interface (please see KPTD at www.docum.org).

Probably you can do it before the routing code, using the IMQ, but I 
haven't try it and I am not sure if this is possible...

Regards,
Joana Urbano



> > >
> > >can anyone tell me how to mark packet's DSCP value using tc?
> > >
> >
> > Hi,
> >
> > You can use the dsmark qdisc. Something like (example):
> >
> > tc qdisc add dev $DEV handle 1:0 root dsmark indices 64 set_tc_index
> > (...)
> > tc class change $DEV parent 1:0 classid 1:1 dsmark 0x3 value 0xb8 # EF
> > (...)
> > tc filter add dev $DEV parent 1:0 prio 4 u32 ip dst y.y.y.y classid 1:1
> >
> > This way, packets going to y.y.y.y get EF mark.
> >
> > Iproute2 packages comes with some examples. The "Differentiated Services on
> > Linux" draft by Almesberger, Jamal and Alexey Kuznetsov is another good
> > source, including commented and easy to understand examples.
> >
> > Regards,
> > Joana Urbano
> >