Subject: Re: [PATCH bpf-next v2 02/11] bpf: make generic xdp compatible w/ bpf_xdp_adjust_tail

From: "Nikita V. Shirokov" <[email-masked]>
Date: Tue, 17 Apr 2018 21:48:30 -0700

On Wed, Apr 18, 2018 at 02:48:18PM +0200, Jesper Dangaard Brouer wrote:
> On Tue, 17 Apr 2018 21:29:42 -0700
> "Nikita V. Shirokov" <[email-masked]> wrote:
> 
> > w/ bpf_xdp_adjust_tail helper xdp's data_end pointer could be changed as
> > well (only "decrease" of pointer's location is going to be supported).
> > changing of this pointer will change packet's size.
> > for generic XDP we need to reflect this packet's length change by
> > adjusting skb's tail pointer
> > 
> > Acked-by: Alexei Starovoitov <[email-masked]>
> 
> You are missing your own Signed-off-by: line on all of the patches.
> 
yeah, somehow lost it between v1 and v2 :) thanks !
> BTW, thank you for working on this! It have been on my todo-list for a
> while now!
> 
> _After_ this patchset, I would like to see adding support for
> "increasing" the data_end location to create a larger packet.  For that
> we should likely add a data_hard_end pointer.  This, would also be
> helpful in cpu_map_build_skb() to know the data_hard_end, to determine
> the frame size (as some driver doesn't use PAGE_SIZE frames, ixgbe).
> 
yeah, increasing the size would be nice to have, but will require more
thinking / rework on drivers side (as you pointed out it's not as easy
as "every driver have at least PAGE_SIZE of data available for xdp".).
will add to my TODO
> 
> -- 
> Best regards,
>   Jesper Dangaard Brouer
>   MSc.CS, Principal Kernel Engineer at Red Hat
>   LinkedIn: http://www.linkedin.com/in/brouer