Re: [PATCH net-next 1/2] netdevsim: add link speed support

[Hangbin Liu <hangbin.liu@linux.dev>]

On Mon, Aug 31, 2026 at 03:08:18PM -0700, Jakub Kicinski wrote:
> On Mon, 31 Aug 2026 11:28:10 +0800 Hangbin Liu wrote:
> > Add ethtool get/set_link_ksettings callbacks to netdevsim so the simulated
> > link speed and duplex can be queried and configured from userspace.
> > 
> > Move NSIM_LINK_SPEED_MAX and NSIM_LINK_SPEED_UNIT from dev.c to netdevsim.h
> > so they are available to both the devlink rate path and the new ethtool
> > code. The set callback rejects speeds exceeding NSIM_LINK_SPEED_MAX.
> > 
> > The default link speed is set to SPEED_5000 with DUPLEX_FULL, matching the
> > existing NSIM_LINK_SPEED_MAX definition.
> 
> This breaks TDC which uses netdevsim for taprio testing.

Sigh, I really didn't expect a speed feature could break the tc qdisc
testing... I will check the reason.

> You posted 2 series for net-next and both broke tests.
> Please try harder to test stuff locally.

Sorry for the extra work this caused you. You know I did not mean for this
to happen.

Every time I prepare a patch, I build it locally, run the relevant selftests,
and get an AI review before posting.

The selftest lib patch touches too many files. The fib_test failed locally
without producing any useful error output: it returns 1, but I cannot spot
the it by human viewing. The netdevsim test failed during tc testing, which
I did not expect at all.

> Matt added support for Docker to NIPA so you should be able
> to repro all ksfts locally. If something doesn't work please 
> report back.

I will give this a try. NIPA could help capture this return‑1 failure.

Regarding the tc‑related failures: do you run the full set of network
selftests for every single patch, or are there rules to select tests based
on the changes? As you know, not all companies have testing resources
comparable to RedHat. I have to run all these tests on my personal laptop.

Thanks
Hangbin