netdev - Re: [PATCH net-next 0/2] veth: a couple of fixes

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Date:   Fri, 18 Nov 2022 09:41:05 +0100
From:   Paolo Abeni <pabeni@...hat.com>
To:     netdev@...r.kernel.org
Cc:     Heng Qi <henqqi@...ux.alibaba.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, bpf@...r.kernel.org
Subject: Re: [PATCH net-next 0/2] veth: a couple of fixes

On Fri, 2022-11-18 at 00:33 +0100, Paolo Abeni wrote:
> Recent changes in the veth driver caused a few regressions
> this series addresses a couple of them, causing oops.
> 
> Paolo Abeni (2):
>   veth: fix uninitialized napi disable
>   veth: fix double napi enable
> 
>  drivers/net/veth.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)

@Xuan Zhuo: another option would be reverting 2e0de6366ac1 ("veth:
Avoid drop packets when xdp_redirect performs") and its follow-up
5e5dc33d5dac ("bpf: veth driver panics when xdp prog attached before
veth_open").

That option would be possibly safer, because I feel there are other
issues with 2e0de6366ac1, and would offer the opportunity to refactor
its logic a bit: the napi enable/disable condition is quite complex and
not used consistently mixing and alternating the gro/xdp/peer xdp check
with the napi ptr dereference.

Ideally it would be better to have an helper alike
napi_should_be_enabled(), use it everywhere, and pair the new code with
some selftests, extending the existing ones.

WDYT?

Side notes:
- Heng Qi address is bouncing 
- the existing veth self-tests would have caught the bug addressed
here, if commit afef88e65554 ("selftests/bpf: Store BPF object files
with .bpf.o extension") would not have broken them meanwhile :(

/P