Re: [PATCH net-next] selftests: drv-net: gro: signal over-coalescing more reliably

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

Jakub Kicinski wrote:
> GRO test is very timing-sensitive, packets may be delayed
> by the network or just sent slowly. Because of this we retry
> each test case up to 6 times.
> 
> This makes perfect sense for positive cases, in which we want
> to see coalescing. Negative test cases, which modify headers
> and expect no coalescing should have opposite treatment.
> We should really try 6 times and make sure that each time
> the test failed. This would, however, require that we annotate
> each test to indicate whether its positive or negative.
> Let's start with a simpler improvement. Do not allow
> retries if we detected over-coalescing. Previously the negative
> case would have to get lucky at least once in 6 tries to pass.
> Now the first failure breaks the retry loop.
> 
> For background - NICs tend to ignore the contents of the TCP
> timestamp option, so that test case commonly fails. In NIPA
> having 6 attempts, however, was enough for some NICs to get
> multiple successful runs in a row, getting the test cases
> auto-classified as expected to pass, even tho the NIC does
> not comply with the expectations.
> 
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Reviewed-by: Willem de Bruijn <willemb@google.com>