netdev - Re: [RFC bpf-next 4/5] iproute2: Allow compiling against libbpf

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Date:   Thu, 22 Aug 2019 10:58:22 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Toke Høiland-Jørgensen <toke@...hat.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Alexei Starovoitov <ast@...nel.org>
Cc:     Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>,
        Yonghong Song <yhs@...com>, David Miller <davem@...emloft.net>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        andrii.nakryiko@...il.com
Subject: Re: [RFC bpf-next 4/5] iproute2: Allow compiling against libbpf

On 8/20/19 1:47 PM, Toke Høiland-Jørgensen wrote:
> This adds a configure check for libbpf and renames functions to allow
> lib/bpf.c to be compiled with it present. This makes it possible to
> port functionality piecemeal to use libbpf.
> 
> Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
> ---
>   configure          | 16 ++++++++++++++++
>   include/bpf_util.h |  6 +++---
>   ip/ipvrf.c         |  4 ++--
>   lib/bpf.c          | 33 +++++++++++++++++++--------------
>   4 files changed, 40 insertions(+), 19 deletions(-)
> 
> diff --git a/configure b/configure
> index 45fcffb6..5a89ee9f 100755
> --- a/configure
> +++ b/configure
> @@ -238,6 +238,19 @@ check_elf()
>       fi
>   }
>   
> +check_libbpf()
> +{
> +    if ${PKG_CONFIG} libbpf --exists; then
> +	echo "HAVE_LIBBPF:=y" >>$CONFIG
> +	echo "yes"
> +
> +	echo 'CFLAGS += -DHAVE_LIBBPF' `${PKG_CONFIG} libbpf --cflags` >> $CONFIG
> +	echo 'LDLIBS += ' `${PKG_CONFIG} libbpf --libs` >>$CONFIG
> +    else
> +	echo "no"
> +    fi
> +}
> +
>   check_selinux()

More of an implementation detail at this point in time, but want to make sure this
doesn't get missed along the way: as discussed at bpfconf [0] best for iproute2 to
handle libbpf support would be the same way of integration as pahole does, that is,
to integrate it via submodule [1] to allow kernel and libbpf features to be in sync
with iproute2 releases and therefore easily consume extensions we're adding to libbpf
to aide iproute2 integration.

Thanks,
Daniel

   [0] http://vger.kernel.org/bpfconf2019.html#session-4
   [1] https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/?id=21507cd3e97bc5692d97201ee68df044c6767e9a