Re: [PATCH net] net/sched: act_ife: use mac_len for ingress header offset

On Tue, Aug 11, 2026 at 9:45 PM Jakub Kicinski <[email protected]> wrote:
>
> On Mon, 10 Aug 2026 11:42:01 -0300 Victor Nogueira wrote:
> > On ingress, the L2 header stripped from the frame is skb->mac_len, not
> > skb->dev->hard_header_len. Use it for the skb_push/skb_pull offsets in
> > tcf_ife_encode()/tcf_ife_decode() and the matching header length inside
> > ife_encode()/ife_decode(). On egress keep hard_header_len.
> >
> > For devices where hard_header_len differs from mac_len (e.g. PPP, which
> > reports 4 vs 0), the previous code pushed/pulled the wrong amount and
> > could hit skb_under_panic on ingress when headroom was tight.
>
> Clashiko points out that act_ife operates on Ethernet headers
> pretty explicitly. IOW we're fixing a crash in a case that
> functionally won't work, anyway.
>
> Should we not simply drop all the packets if they are are destined
> for a non ARPHRD_ETHER device?

You have a point, but I need to double check.
I'll discuss this with Jamal and get back to you.

cheers,
Victor