Re: [PATCH v9 bpf-next 01/14] net: skbuff: add data_len field to skb_shared_info

[Jakub Kicinski <kuba@kernel.org>]

On Tue, 29 Jun 2021 14:44:56 +0200 Lorenzo Bianconi wrote:
> > On Mon, Jun 14, 2021 at 5:50 AM Lorenzo Bianconi <lorenzo@kernel.org> wrote:  
> > >
> > > data_len field will be used for paged frame len for xdp_buff/xdp_frame.
> > > This is a preliminary patch to properly support xdp-multibuff
> > >
> > > Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> > > ---
> > >  include/linux/skbuff.h | 5 ++++-
> > >  1 file changed, 4 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> > > index dbf820a50a39..332ec56c200d 100644
> > > --- a/include/linux/skbuff.h
> > > +++ b/include/linux/skbuff.h
> > > @@ -522,7 +522,10 @@ struct skb_shared_info {
> > >         struct sk_buff  *frag_list;
> > >         struct skb_shared_hwtstamps hwtstamps;
> > >         unsigned int    gso_type;
> > > -       u32             tskey;
> > > +       union {
> > > +               u32     tskey;
> > > +               u32     data_len;
> > > +       };
> > >  
> > 
> > Rather than use the tskey field why not repurpose the gso_size field?
> > I would think in the XDP paths that the gso fields would be unused
> > since LRO and HW_GRO would be incompatible with XDP anyway.
> 
> ack, I agree. I will fix it in v10.

Why is XDP mb incompatible with LRO? I thought that was one of the use
cases (mentioned by Willem IIRC).