netdev - RE: [PATCH v12 bpf-next 10/18] bpf: add multi-buff support to the bpf_xdp_adjust

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Date:   Tue, 31 Aug 2021 17:10:30 -0700
From:   John Fastabend <john.fastabend@...il.com>
To:     Lorenzo Bianconi <lorenzo@...nel.org>, bpf@...r.kernel.org,
        netdev@...r.kernel.org
Cc:     lorenzo.bianconi@...hat.com, davem@...emloft.net, kuba@...nel.org,
        ast@...nel.org, daniel@...earbox.net, shayagr@...zon.com,
        john.fastabend@...il.com, dsahern@...nel.org, brouer@...hat.com,
        echaudro@...hat.com, jasowang@...hat.com,
        alexander.duyck@...il.com, saeed@...nel.org,
        maciej.fijalkowski@...el.com, magnus.karlsson@...el.com,
        tirthendu.sarkar@...el.com, toke@...hat.com
Subject: RE: [PATCH v12 bpf-next 10/18] bpf: add multi-buff support to the
 bpf_xdp_adjust_tail() API

Lorenzo Bianconi wrote:
> From: Eelco Chaudron <echaudro@...hat.com>
> 
> This change adds support for tail growing and shrinking for XDP multi-buff.
> 
> When called on a multi-buffer packet with a grow request, it will always
> work on the last fragment of the packet. So the maximum grow size is the
> last fragments tailroom, i.e. no new buffer will be allocated.
> 
> When shrinking, it will work from the last fragment, all the way down to
> the base buffer depending on the shrinking size. It's important to mention
> that once you shrink down the fragment(s) are freed, so you can not grow
> again to the original size.
> 
> Co-developed-by: Lorenzo Bianconi <lorenzo@...nel.org>
> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> Signed-off-by: Eelco Chaudron <echaudro@...hat.com>
> ---

LGTM.

Acked-by: John Fastabend <john.fastabend@...il.com>