Re: [PATCH net-next v3 3/3] tc-testing: add a test case for ETS offload

[Davide Caratti <dcaratti@redhat.com>]

On Wed, Mar 18, 2026 at 12:26:25PM -0300, Victor Nogueira wrote:
> On Tue, Mar 17, 2026 at 12:11 PM Davide Caratti <dcaratti@redhat.com> wrote:
> >
> > While reviewing the fix for unintentional u32 overflows in ets offload
> > code, Jamal said:
> >
> >  [...]
> >
> >  > otherwise a tdc test should cover it fine (when you get to the
> >  > netdevsim change perhaps)
> >
> > Add a test case to reproduce the division by zero fixed in [1].
> >
> > [1] https://lore.kernel.org/all/CAM0EoMm17wsYZmdFLshH3_-GrZtzd=i0xnoO2yiVB=-N4761mw@mail.gmail.com/
> >
> > Suggested-by: Jamal Hadi Salim <jhs@mojatatu.com>
> > Reviewed-by: Jamal Hadi Salim <jhs@mojatatu.com>
> > Reviewed-by: Victor Nogueira <victor@mojatatu.com>
> > Signed-off-by: Davide Caratti <dcaratti@redhat.com>

hello Victor, thanks for investigating!
 
> Sorry for not noticing this earlier.
> I tried some approaches with Jamal to avoid changing your patch,
> but changing it seems to be the cleanest way to do this.
> The issue is that tdc overwrites the environment when running
> the shell command from python so it can't find ethtool.
> We believe the cleanest approach here is to specify
> ethtool's path in tdc_config.py (as is done with tc and ip).
> Am sending a proposed change as an attached diff in this
> reply.

[...]

> diff --git a/tools/testing/selftests/tc-testing/tdc_config.py b/tools/testing/selftests/tc-testing/tdc_config.py
> index ccb0f06ef9e3..9488b03cbc2c 100644
> --- a/tools/testing/selftests/tc-testing/tdc_config.py
> +++ b/tools/testing/selftests/tc-testing/tdc_config.py
> @@ -17,6 +17,7 @@ NAMES = {
>            'DEV1': 'v0p1',
>            'DEV2': '',
>            'DUMMY': 'dummy1',
> +          'ETHTOOL': '/usr/sbin/ethtool',
>  	  'ETH': 'eth0',
>            'BATCH_FILE': './batch.txt',
>            'BATCH_DIR': 'tmp',

I see, and maybe now understand why I didn't see this problem before. My
fedora test setup does:

root@localhost:net# which ethtool 
/usr/bin/ethtool

and inside virtme-ng:

root@virtme-ng:net# which ethtool
/bin/ethtool

Moreover {,/usr}/sbin is a symlink because of [1], so it always finds
ethtool _ and would find ethtool also with the $ETHTOOL assignment
you did above; I'm ok for editing patch 3/3 adding the above hunks.

-- 
davide

[1] https://fedoraproject.org/wiki/Changes/Unify_bin_and_sbin