Re: [PATCH v3] net: fix wrong network header length

[Lina Wang]

On Thu, 2022-02-17 at 09:05 -0800, Alexei Starovoitov wrote:
> On Thu, Feb 17, 2022 at 12:45 AM Paolo Abeni <pabeni@xxxxxxxxxx>
> wrote:
> > To clarify: Alexei is asking to add a test under:
> > 
> > tools/testing/selftests/net/
> > 
> > to cover this specific case. You can propbably extend the existing
> > udpgro_fwd.sh.
> 
> Exactly.
> I suspect the setup needs a bit more than just iperf udp test.
> Does it need a specific driver and hw?

My hw is Android phone, Android system has improved clatd with bpf. When 
clatd starts, cls_bpf_classify will handle ingress packets with bpf progs.
bpf_skb_proto_6_to_4 is used here.

> Can it be reproduced with veth or other virtual netdev?

I am not sure. I have no idea how to verify it in linux system. 

> Also commit talks about bpf_skb_proto_6_to_4.
> So that bpf helper has to be somehow involved, but iperf udp test
> says nothing about it.
> Please craft a _complete_ selftest.

Thanks!