Re: xdp-cpumap-tc multi queue schema and traffic mirroring

On Thu, 07 Oct 2021 19:02:58 +0200
Toke Høiland-Jørgensen <[email protected]> wrote:

> "Ethy H. Brito" <[email protected]> writes:
> 
> > Hi All
> >
> > Before I moved to XDP cpumap bandwidth control "philosophy" I used to snoop
> > inside the htb classes (mainly the default one) mirroring traffic to a
> > dummy interface then run tcpdump on that like:
> >
> > 	tc filter add dev eth0 parent 1: protocol all prio 0xffff \
> > 	u32 match u32 0 0 flowid 1:$shp action mirred egress mirror dev
> > dummy0
> >
> > Then "tcpdump -npi dummy0" used to show me all that classid "1:$shp" was
> > carrying.
> >
> > Now, with the multi queue environment XDP creates, I can't make mirroring
> > to work. For instance: I need to see what is going on with HTB classid
> > e:102, so I tried: 
> > 	tc filter add dev eth0 parent e: ... e:102 action mirred egress ...
> >
> > and "tcpdump -npi dummy0" prints traffic that has nothing to do with
> > classid e:102. I can confirm the traffic is pored thru the class since its
> > bandwidth is controlled/limited correctly.  


Hi Toke, et All.

> 
> The xdp-cpumap-tc utility will attach a filter to the egress interface,
> presumably that is taking priority and short-circuit your mirred filter?

This makes sense. 
But How to circumvent this??

Snooping the default class (classes, in xdp-cpumap case) is essencial to catch misconfigured mappings.

Regards

Ethy