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

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Date:   Fri, 6 Nov 2020 08:41:03 +0800
From:   Hangbin Liu <haliu@...hat.com>
To:     David Ahern <dsahern@...il.com>
Cc:     Stephen Hemminger <stephen@...workplumber.org>,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        Toke Høiland-Jørgensen <toke@...hat.com>
Subject: Re: [PATCHv3 iproute2-next 3/5] lib: add libbpf support

On Thu, Nov 05, 2020 at 08:25:12AM -0700, David Ahern wrote:
> > 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 what the current code did. In lib/Makefile we only compile bpf_libbpf.o
when libbpf enabled.

ifeq ($(HAVE_LIBBPF),y)
UTILOBJ += bpf_libbpf.o
endif

But bpf code in ipvrf.c is special as it calls both legacy code an libbpf code.
If we put it in bpf_legacy.c, then bpf_legacy.c will be corrupt by libbpf.h.
If we put it in bpf_libbpf.c, then we can't build without bpf_libbpf.o when
libbpf disable.

I haven't figured out a better solution.

Thanks
Hangbin