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SubjectRe: [PATCH RFC net-next 07/14] bpf: expand BPF syscall with program load/unload
On Sat, Jun 28, 2014 at 8:35 AM, Andy Lutomirski <> wrote:
> On Sat, Jun 28, 2014 at 8:21 AM, Greg KH <> wrote:
>> On Sat, Jun 28, 2014 at 12:26:14AM -0700, Alexei Starovoitov wrote:
>>> On Fri, Jun 27, 2014 at 11:28 PM, Andy Lutomirski <> wrote:
>>> > On Fri, Jun 27, 2014 at 11:12 PM, Alexei Starovoitov <> wrote:
>>> > If you want to add GPL-only functions in the future, that would be one
>>> > thing. But if someone writes a nice eBPF compiler, and someone else
>>> > writes a little program that filters on network packets, I see no
>>> > reason to claim that the little program is a derivative work of the
>>> > kernel and therefore must be GPL.
>>> I think we have to draw a line somewhere. Say, tomorrow I want
>>> to modify libpcap to emit eBPF based on existing tcpdump syntax.
>>> Would it mean that tcpdump filter strings are GPLed? Definitely not,
>>> since they existed before and can function without new libpcap.
>>> But if I write a new packet filtering program in C, compile it
>>> using LLVM->eBPF and call into in-kernel helper functions
>>> (like bpf_map_lookup_elem()), I think it's exactly the derivative work.
>>> It's analogous to kernel modules. If module wants to call
>>> export_symbol_gpl() functions, it needs to be GPLed. Here all helper
>>> functions are GPL. So we just have a blank check for eBPF program.
>> I agree, these eBFP programs should be GPL-compatible licensed as well.
> I think I'd be happy with an export_symbol_gpl analogue. I might
> argue that bpf_map_lookup_elem shouldn't be gpl-only, though.

ok. sounds like module-like approach will be more acceptable to potential
user base. Will change it. Last thing I want to do is to scary users away.

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