Re: [PATCH net-next 7/7] testing: net-drv: add a driver test for stats reporting

[Petr Machata <petrm@nvidia.com>]

Jakub Kicinski <kuba@kernel.org> writes:

> On Tue, 2 Apr 2024 18:37:44 +0200 Petr Machata wrote:
>> Yeah, this would be usually done through context managers, as I mention
>> in the other e-mail. But then cfg would be lexically scoped, which IMHO
>> is a good thing, but then it needs to be passed around as an argument,
>> and that makes the ksft_run() invocation a bit messy:
>> 
>>     with NetDrvEnv(__file__) as cfg:
>>         ksft_run([lambda: check_pause(cfg),
>>                   lambda: check_fec(cfg),
>>                   lambda: pkt_byte_sum(cfg)])
>> 
>> Dunno, maybe it could forward *args **kwargs to the cases? But then it
>> loses some of the readability again.
>
> Yes, I was wondering about that. It must be doable, IIRC 
> the multi-threading API "injects" args from a tuple.
> I was thinking something along the lines of:
>
>     with NetDrvEnv(__file__) as cfg:
>         ksft_run([check_pause, check_fec, pkt_byte_sum],
>                  args=(cfg, ))
>
> I got lazy, let me take a closer look. Another benefit
> will be that once we pass in "env" / cfg - we can "register" 
> objects in there for auto-cleanup (in the future, current
> tests don't need cleanup)

Yeah, though some of those should probably just be their own context
managers IMHO, not necessarily hooked to cfg. I'm thinking something
fairly general, so that the support boilerplate doesn't end up costing
an arm and leg:

    with build("ip route add 192.0.2.1/28 nexthop via 192.0.2.17",
               "ip route del 192.0.2.1/28"),
         build("ip link set dev %s master %s" % (swp1, h1),
               "ip link set dev %s nomaster" % swp1):
        le_test()

Dunno. I guess it makes sense to have some of the common stuff
predefined, e.g. "with vrf() as h1". And then the stuff that's typically
in lib.sh's setup() and cleanup(), can be losslessly hooked up to cfg.

This is what I ended up gravitating towards after writing a handful of
LNST tests anyway. The scoping makes it clear where the object exists,
lifetime is taken care of, it's all ponies rainbows basically. At least
as long as your object lifetimes can be cleanly nested, which admittedly
is not always.