netdev - Re: [PATCHv3 iproute2-next 3/5] lib: add libbpf support

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Date:   Thu, 05 Nov 2020 16:57:55 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     David Ahern <dsahern@...il.com>, Hangbin Liu <haliu@...hat.com>
Cc:     Stephen Hemminger <stephen@...workplumber.org>,
        netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCHv3 iproute2-next 3/5] lib: add libbpf support

David Ahern <dsahern@...il.com> writes:

> On 11/5/20 12:51 AM, Hangbin Liu wrote:
>> On Wed, Nov 04, 2020 at 07:33:40PM -0700, David Ahern wrote:
>>> On 11/4/20 1:22 AM, Hangbin Liu wrote:
>>>> If we move this #ifdef HAVE_LIBBPF to bpf_legacy.c, we need to rename
>>>> them all. With current patch, we limit all the legacy functions in bpf_legacy
>>>> and doesn't mix them with libbpf.h. What do you think?
>>>
>>> Let's rename conflicts with a prefix -- like legacy. In fact, those
>>> iproute2_ functions names could use the legacy_ prefix as well.
>>>
>> 
>> Sorry, when trying to rename the functions. I just found another issue.
>> Even we fix the conflicts right now. What if libbpf add new functions
>> and we got another conflict in future? There are too much bpf functions
>> in bpf_legacy.c which would have more risks for naming conflicts..
>> 
>> With bpf_libbpf.c, there are less functions and has less risk for naming
>> conflicts. So I think it maybe better to not include libbpf.h in bpf_legacy.c.
>> What do you think?
>> 
>>
>
> Is there a way to sort the code such that bpf_legacy.c is not used when
> libbpf is enabled and bpf_libbpf.c is not compiled when libbpf is disabled.

That's basically what we were going for, i.e.:

git mv lib/bpf.c lib/bpf_legacy.c
git add lib/bpf_libbpf.c

and then adding ifdefs to bpf_legacy.c and only including the other if
libbpf support is enabled.

I guess we could split it further into lib/bpf_{libbpf,legacy,glue}.c
and have the two former ones be completely devoid of ifdefs and
conditionally included based on whether or not libbpf support is
enabled?

-Toke