netdev - Re: [PATCH bpf-next] samples/bpf: xdp_redirect_cpu: Add mprog-disable to optstring.

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Date:   Thu, 5 Aug 2021 00:50:31 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Matt Cover <werekraken@...il.com>,
        Kumar Kartikeya Dwivedi <memxor@...il.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Matthew Cover <matthew.cover@...ckpath.com>,
        netdev <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next] samples/bpf: xdp_redirect_cpu: Add mprog-disable
 to optstring.

On 8/4/21 7:57 PM, Matt Cover wrote:
> On Sat, Jul 31, 2021 at 8:25 AM Kumar Kartikeya Dwivedi
> <memxor@...il.com> wrote:
>>
>> On Sat, Jul 31, 2021 at 06:26:32AM IST, Matthew Cover wrote:
>>> Commit ce4dade7f12a ("samples/bpf: xdp_redirect_cpu: Load a eBPF program
>>> on cpumap") added the following option, but missed adding it to optstring:
>>> - mprog-disable: disable loading XDP program on cpumap entries
>>>
>>> Add the missing option character.
>>
>> I made some changes in this area in [0], since the support was primarily to do
>> redirection from the cpumap prog, so by default we don't install anything now
>> and only do so if a redirection interface is specified (and use devmap instead).
>> So this option won't be used anyway going forward (since we don't install a
>> dummy XDP_PASS program anymore) if it gets accepted.
>>
>> [0]: https://lore.kernel.org/bpf/20210728165552.435050-1-memxor@gmail.com
>>
>> PS: I can restore it again if this is something really used beyond redirecting
>> to another device (i.e. with custom BPF programs). Any feedback would be helpful.
> 
> Hey Kartikeya. I happened to be looking through this code to get a
> feel for using CPUMAP for custom steering (e.g. RSS on encapsulated
> packets) in XDP and noticed the missing option character. Figured it
> was worth doing a quick patch and test.
> 
> Unfortunately, I'm not able to say much on your changes as I'm still
> getting familiarized with this code. It looks like your submission is
> in need of a rebase; v3 has been marked "Changes Requested" in
> patchwork [0]. As I see things, It'd be good to get this fix in there
> for now, whether or not the code is removed later.

Yeap, given this fix in here is tiny & valid either way, I took it in for now, and
when Kartikeya's rework eventually drops the whole option, so be it. ;)

Applied, thanks!