Re: [PATCH v4,bpf-next] bpf: Don't redirect packets with invalid pkt_len

[shaozhengchao]

On 2022/9/20 22:42, Lorenz Bauer wrote:
> On Mon, 19 Sep 2022, at 11:55, shaozhengchao wrote:
> > Sorry for the delay. I'm busy testing the TC module recently. I'm very
> > sorry for the user-space breakage.
> >
> > The root cause of this problem is that eth_type_trans() is called when
> > the protocol type of the SKB is parsed. The len value of the SKB is
> > reduced to 0. If the user mode requires that the forwarding succeed, or
> >    if the MAC header is added again after the MAC header is subtracted,
> > is this appropriate?
>
> We don't require forwarding to succeed with a 14 byte input buffer. We also don't look at the MAC header.
>
> I think refusing to forward 0 length packets would be OK. Not 100% certain I understood you correctly, let me know if this helps.
>
> Best
> Lorenz
Hi Lorenz
	Sorry. But how does the rejection of the 0 length affect the
test case? Is the return value abnormal, send packet failure or some
others?

Zhengchao Shao