netdev - Re: Re: Clarification on bpftool dual licensing

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Date:   Wed, 17 Nov 2021 16:37:28 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Martin Kelly <martin.kelly@...wdstrike.com>
Cc:     "daniel@...earbox.net" <daniel@...earbox.net>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "ast@...nel.org" <ast@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "kernel-team@...com" <kernel-team@...com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "andrii@...nel.org" <andrii@...nel.org>
Subject: Re: Re: Clarification on bpftool dual licensing

On Wed, Nov 17, 2021 at 4:32 PM Martin Kelly
<martin.kelly@...wdstrike.com> wrote:
>
> >
> > 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).
>
>  Thanks everyone, that's what I assumed as well. Any objection to a patch clarifying this more explicitly?
>
> One other, related question: vmlinux.h (generated by "bpftool btf dump file /sys/kernel/btf/vmlinux format c"), does not currently contain a license declaration. I assume this would have to be a GPL header, since vmlinux.h references many GPL'd Linux kernel structs and similar, though again I'm not a lawyer and therefore am not certain. Would you all agree with this? If so, any objection to a patch adding an SPDX line to the generated vmlinux.h?

Is vmlinux DWARF data GPL'ed? I certainly hope not. So vmlinux.h
shouldn't be licensed under GPL.