Hangbin Liu [off-list ref] writes:

On Wed, Oct 28, 2020 at 09:00:41PM -0600, David Ahern wrote:

quoted

quoted

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nope. you need to be able to handle this. Ubuntu 20.10 was just
released, and it has a version of libbpf. If you are going to integrate
libbpf into other packages like iproute2, it needs to just work with
that version.

OK, I can replace bpf_program__section_name by bpf_program__title().

I believe this one can be handled through a compatability check. Looks
the rename / deprecation is fairly recent (78cdb58bdf15f from Sept 2020).

Hi David,

I just come up with another way. In configure, build a temp program and update
the function checking every time is not graceful. How about just check the
libbpf version, since libbpf has exported all functions in src/libbpf.map.

Currently, only bpf_program__section_name() is added in 0.2.0, all other
needed functions are supported in 0.1.0.

So in configure, the new check would like:

Why is this easier than just checking for the function you need? In
xdp-tools configure we have a test like this:

check_perf_consume()
{
    cat >$TMPDIR/libbpftest.c <<EOF
#include <bpf/libbpf.h>
int main(int argc, char **argv) {
    perf_buffer__consume(NULL);
    return 0;
}
EOF
    libbpf_err=$($CC -o $TMPDIR/libbpftest $TMPDIR/libbpftest.c $LIBBPF_CFLAGS $LIBBPF_LDLIBS 2>&1)
    if [ "$?" -eq "0" ]; then
        echo "HAVE_LIBBPF_PERF_BUFFER__CONSUME:=y" >>"$CONFIG"
        echo "yes"
    else
        echo "HAVE_LIBBPF_PERF_BUFFER__CONSUME:=n" >>"$CONFIG"
        echo "no"
    fi
}

Just do that for __section_name(), and you'll also be able to work with
custom libbpf versions using LIBBPF_DIR.

static const char *get_bpf_program__section_name(const struct bpf_program *prog)
{
#ifdef HAVE_LIBBPF_SECTION_NAME
	return bpf_program__section_name(prog);
#else
	return bpf_program__title(prog, false);
#endif
}

This bit is fine :)

-Toke