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

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Date:   Tue, 17 Apr 2018 21:48:30 -0700
From:   "Nikita V. Shirokov" <tehnerd@...nerd.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S. Miller " <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH bpf-next v2 02/11] bpf: make generic xdp compatible w/
 bpf_xdp_adjust_tail

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" <tehnerd@...nerd.com> 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 <ast@...nel.org>
> 
> 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
--
Nikita