netdev - Re: Clarification on bpftool dual licensing

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Message-ID: <CAEf4BzaheW1EGczxS8zXmObBte81gR7pepa9cLi8Z=UvwJdnrg@mail.gmail.com>
Date:   Tue, 16 Nov 2021 14:00:19 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     Martin Kelly <martin.kelly@...wdstrike.com>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "kernel-team@...com" <kernel-team@...com>,
        "David S. Miller" <davem@...emloft.net>,
        Andrii Nakryiko <andrii@...nel.org>
Subject: Re: Clarification on bpftool dual licensing

On Tue, Nov 16, 2021 at 2:16 AM Daniel Borkmann <daniel@...earbox.net> wrote:
>
> On 11/15/21 7:20 PM, Martin Kelly wrote:
> > Hi,
> >
> > I have a question regarding the dual licensing provision of bpftool. I
> > understand that bpftool can be distributed as either GPL 2.0 or BSD 2-clause.
> > That said, bpftool can also auto-generate BPF code that gets specified inline
> > in the skeleton header file, and it's possible that the BPF code generated is
> > GPL. What I'm wondering is what happens if bpftool generates GPL-licensed BPF
> > code inside the skeleton header, so that you get a header like this:
> >
> > something.skel.h:
> > /* this file is BSD 2-clause, by nature of dual licensing */
>
> Fwiw, the generated header contains an SPDX identifier:
>
>   /* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
>   /* THIS FILE IS AUTOGENERATED! */
>
> > /* THIS FILE IS AUTOGENERATED! */
> >
> > /* standard skeleton definitions */
> >
> > ...
> >
> > s->data_sz = XXX;
> > s->data = (void *)"\
> > <eBPF bytecode, produced by GPL 2.0 sources, specified in binary>
> > ";
> >
> > My guess is that, based on the choice to dual-license bpftool, the header is
> > meant to still be BSD 2-clause, and the s->data inline code's GPL license is
> > not meant to change the licensing of the header itself, but I wanted to

Yes, definitely that is the intent (but not a lawyer either).


> > double-check, especially as I am not a lawyer. If this is indeed the intent,
> > is there any opposition to a patch clarifying this more explicitly in
> > Documentation/bpf/bpf_licensing.rst?
>
> Not a lawyer either, but my interpretation is that this point related to "packaging"
> of BPF programs from the bpf_licensing.rst would apply here (given this is what it
> does after all):
>
>    Packaging BPF programs with user space applications
>    ===================================================
>
>    Generally, proprietary-licensed applications and GPL licensed BPF programs
>    written for the Linux kernel in the same package can co-exist because they are
>    separate executable processes. This applies to both cBPF and eBPF programs.

Yep. If someone packages proprietary BPF ELF into a skeleton, that
doesn't make the BPF ELF suddenly GPL or BSD, I'd imagine.