Re: Clarification on bpftool dual licensing

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
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.