netdev - Re: [PATCH bpf-next V1 3/6] bpf: add BPF-helper for reading MTU from net

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Message-ID: <CANP3RGe3S4eF=xVkQ22o=sxtW991jmNfq-bVtbKQQaszsLNZSA@mail.gmail.com>
Date:   Tue, 6 Oct 2020 18:24:28 -0700
From:   Maciej Żenczykowski <maze@...gle.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Jesper Dangaard Brouer <brouer@...hat.com>,
        bpf <bpf@...r.kernel.org>, Linux NetDev <netdev@...r.kernel.org>,
        Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Lorenz Bauer <lmb@...udflare.com>,
        Shaun Crampton <shaun@...era.io>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Marek Majkowski <marek@...udflare.com>,
        John Fastabend <john.fastabend@...il.com>
Subject: Re: [PATCH bpf-next V1 3/6] bpf: add BPF-helper for reading MTU from
 net_device via ifindex

On Tue, Oct 6, 2020 at 6:19 PM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Tue, 6 Oct 2020 18:33:02 +0200 Jesper Dangaard Brouer wrote:
> > > +static const struct bpf_func_proto bpf_xdp_mtu_lookup_proto = {
> > > +   .func           = bpf_xdp_mtu_lookup,
> > > +   .gpl_only       = true,
> > > +   .ret_type       = RET_INTEGER,
> > > +   .arg1_type      = ARG_PTR_TO_CTX,
> > > +   .arg2_type      = ARG_ANYTHING,
> > > +   .arg3_type      = ARG_ANYTHING,
> > > +};
> > > +
> > > +
>
> FWIW
>
> CHECK: Please don't use multiple blank lines
> #112: FILE: net/core/filter.c:5566:

FYI: It would be nice to have a similar function to return a device's
L2 header size (ie. 14 for ethernet) and/or hwtype.

Also, should this be restricted to gpl only?

[I'm not actually sure, I'm actually fed up with non-gpl code atm, and
wouldn't be against all bpf code needing to be gpl'ed...]