Re: [PATCH net-next v6 3/3] selftests: drv-net: Test queue xsk attribute

[Joe Damato <jdamato@fastly.com>]

On Tue, Feb 11, 2025 at 09:45:56AM -0800, Joe Damato wrote:
> On Tue, Feb 11, 2025 at 12:09:50PM +0100, Paolo Abeni wrote:
> > On 2/10/25 8:38 PM, Joe Damato wrote:
> > > +def check_xdp(cfg, nl, xdp_queue_id=0) -> None:
> > > +    test_dir = os.path.dirname(os.path.realpath(__file__))
> > > +    xdp = subprocess.Popen([f"{test_dir}/xdp_helper", f"{cfg.ifindex}", f"{xdp_queue_id}"],
> > > +                           stdin=subprocess.PIPE, stdout=subprocess.PIPE, bufsize=1,
> > > +                           text=True)
> > > +    defer(xdp.kill)
> > > +
> > > +    stdout, stderr = xdp.communicate(timeout=10)
> > > +    rx = tx = False
> > > +
> > > +    queues = nl.queue_get({'ifindex': cfg.ifindex}, dump=True)
> > > +    if not queues:
> > > +        raise KsftSkipEx("Netlink reports no queues")
> > > +
> > > +    for q in queues:
> > > +        if q['id'] == 0:
> > > +            if q['type'] == 'rx':
> > > +                rx = True
> > > +            if q['type'] == 'tx':
> > > +                tx = True
> > > +
> > > +            ksft_eq(q['xsk'], {})
> > > +        else:
> > > +            if 'xsk' in q:
> > > +                _fail("Check failed: xsk attribute set.")
> > > +
> > > +    ksft_eq(rx, True)
> > > +    ksft_eq(tx, True)
> > 
> > This causes self-test failures:
> > 
> > https://netdev-3.bots.linux.dev/vmksft-net-drv/results/987742/4-queues-py/stdout
> > 
> > but I really haven't done any real investigation here.
> 
> I think it's because the test kernel in this case has
> CONFIG_XDP_SOCKETS undefined [1].
> 
> The error printed in the link you mentioned:
> 
>   socket creation failed: Address family not supported by protocol
> 
> is coming from the C program, which fails to create the AF_XDP
> socket.
> 
> I think the immediate reaction is to add more error checking to the
> python to make sure that the subprocess succeeded and if it failed,
> skip.
> 
> But, we may want it to fail for other error states instead of
> skipping? Not sure if there's general guidance on this, but my plan
> was to have the AF_XDP socket creation failure return a different
> error code (I dunno maybe -1?) and only skip the test in that case.
> 
> Will that work or is there a better way? I only want to skip if
> AF_XDP doesn't exist in the test kernel.
> 
> [1]: https://netdev-3.bots.linux.dev/vmksft-net-drv/results/987742/config

I'll give it a few more hours incase anyone has comments before I
resend, but I got something working (tested on kernels with and
without XDP sockets).

xdp_helper returns -1 if (errno == EAFNOSUPPORT). All other error
cases return 1.

Updated the python to do this:

  if xdp.returncode == 255:
      raise KsftSkipEx('AF_XDP unsupported')
  elif xdp.returncode > 0:
      raise KsftFailEx('unable to create AF_XDP socket')

Which seems to work on both types of kernels?

Happy to take feedback; will hold off on respinning for a bit just
incase there's a better way I don't know about.