netdev - Re: [PATCH bpf-next] nfp: bpf: xdp_adjust

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Message-ID: <822c724c-3f97-8175-b3c3-1aae3644f576@iogearbox.net>
Date:   Sat, 4 Aug 2018 22:00:22 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>,
        alexei.starovoitov@...il.com
Cc:     netdev@...r.kernel.org, oss-drivers@...ronome.com
Subject: Re: [PATCH bpf-next] nfp: bpf: xdp_adjust_tail support

On 08/04/2018 07:06 AM, Jakub Kicinski wrote:
> Add support for adjust_tail.  There are no FW changes needed but add
> a FW capability just in case there would be any issue with previously
> released FW, or we will have to change the ABI in the future.
> 
> The helper is trivial and shouldn't be used too often so just inline
> the body of the function.  We add the delta to locally maintained
> packet length register and check for overflow, since add of negative
> value must overflow if result is positive.  Note that if delta of 0
> would be allowed in the kernel this trick stops working and we need
> one more instruction to compare lengths before and after the change.
> 
> Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
> Reviewed-by: Quentin Monnet <quentin.monnet@...ronome.com>

Applied to bpf-next, thanks Jakub!