netdev - Re: [PATCH v8 bpf-next 08/14] bpf: add multi-buff support to the bpf_xdp_adjust

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Date:   Thu, 8 Apr 2021 23:54:54 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Lorenzo Bianconi <lorenzo@...nel.org>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        lorenzo.bianconi@...hat.com, davem@...emloft.net, kuba@...nel.org,
        ast@...nel.org, daniel@...earbox.net, shayagr@...zon.com,
        sameehj@...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
Subject: Re: [PATCH v8 bpf-next 08/14] bpf: add multi-buff support to the
 bpf_xdp_adjust_tail() API

On Thu, Apr 08, 2021 at 10:15:47PM +0300, Vladimir Oltean wrote:
> > +		if (unlikely(offset > ((int)(xdp->data_end - xdp->data) +
> > +				       xdp_sinfo->data_length -
> > +				       ETH_HLEN)))
> 
> Also: should we have some sort of helper for calculating the total
> length of an xdp_frame (head + frags)? Maybe it's just me, but I find it
> slightly confusing that xdp_sinfo->data_length does not account for
> everything.

I see now that xdp_buff :: frame_length is added in patch 10. It is a
bit strange to not use it wherever you can? Could patch 10 be moved
before patch 8?