APPLIED: [RFC Focal] UBUNTU: SAUCE: selftests: net: ip_defrag: limit packet to 1000 fragments

[Seth Forshee]

On Wed, Mar 25, 2020 at 01:00:20PM -0300, Thadeu Lima de Souza Cascardo wrote:
> The ip_defrag selftest will fail when run with a conntrack rule because
> it might push more than a 1000 fragments through loopback. This will hit
> the backlog limit, causing fragments to be dropped, leading to test
> failures.
> 
> This is considered a real bug by Eric Dumazet, so the test change is
> just a workaround so we can keep testing for other regressions while
> avoiding this particular failure.
> 
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo at canonical.com>
> ---
> 
> Sending this as an RFC as I didn't have the chance to really test it.
> 
> If you run only the first or second test after the conntrack rule is added on
> ip_defrag.sh, and run ip_defrag.sh under a loop, you will hit this issue after
> a couple of dozen runs or so. If I recall correctly, that is.
> 
> One fix that I did try was changing the backlog to 1250 and reverting it back
> to 1000 after this test is finished. But that could mess up with tests that run
> after this one or in case tests are run in parallel, so this other fix would be
> preferable, but it hasn't been tested.

The test already fails, so little harm in trying this workaround.
Applied, we'll see if it helps. Thanks!