Re: [PATCH bpf-next] samples: bpf: avoid name collision with kernel enum values

["Toke Høiland-Jørgensen" <toke@redhat.com>]

Kumar Kartikeya Dwivedi <memxor@gmail.com> writes:

> On Mon, Sep 27, 2021 at 06:07:30PM IST, Toke Høiland-Jørgensen wrote:
>> Kumar Kartikeya Dwivedi <memxor@gmail.com> writes:
>>
>> > In xdp_redirect_map_multi.bpf.c, on newer kernels samples compilation
>> > fails when vmlinux.h is generated from a kernel supporting broadcast for
>> > devmap. Hence, avoid naming collisions to prevent build failure.
>>
>> Hmm, shouldn't the sample just be getting the value from the kernel in
>> the first place instead of re-defining it?
>>
>
> True, but in general my assumption was that it could be built with a older
> kernel's vmlinux.h, but be ran on a newer one. If that's not strictly needed, I
> can just drop it.

But the code is still making assumptions about the contents of
vmlinux.h, isn't it? Like the size (and existence) of struct
bpf_devmap_val.

> This can also be the case if you haven't built the kernel in the tree
> (just did a make headers_install), it then falls back to generating
> the vmlinux.h from the running kernel.

This seems a bit brittle. Given that the samples are distributed with
the kernel sources, I would expect them to always correspond to the
kernel version in the source tree they're in and not randomly break if
the running kernel is different...

-Toke