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

Daniel Borkmann [off-list ref] writes:

On 8/20/19 1:47 PM, Toke Høiland-Jørgensen wrote:

quoted

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 <redacted>
---
  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.

I can sorta see the point wrt keeping in sync with kernel features. But
how will this work with distros that package libbpf as a regular
library? Have you guys given up on regular library symbol versioning for
libbpf?

   [0] http://vger.kernel.org/bpfconf2019.html#session-4

Thanks for that link! Didn't manage to find any of the previous
discussions on iproute2 compatibility.

-Toke