[libvirt] [PATCH] build: force libnl1 if netcf also used libnl1

[Gene Czarcinski]

On 09/07/2012 06:42 PM, Eric Blake wrote:
> Recent spec file changes ensure that in distro situations, netcf
> and libvirt will link against the same libnl in order to avoid
> dumping core.  But for every-day development, if you are F17 and
> have the libnl3-devel headers available, libvirt was blindly
> linking against libnl3 even though F17 netcf still links against
> libnl1, making testing a self-built binary on F17 impossible.
>
> By making configure a little bit smarter, we can avoid this
> situation.  I intentionally wrote the test so that we still favor
> libnl-3 if netcf is not installed or if we couldn't use ldd
> to determine which library netcf linked against.
>
> * configure.ac (LIBNL): Don't probe libnl3 if netcf doesn't use it.
> ---
>
> Does this patch look safe enough to use?  It was sufficient to
> let me resume self-tests on my F17 box, where I had intentionally
> installed libnl3-devel.

The problem that this patch is attempting to fix is both real and takes 
a little digging to find ... as happened to me.

While is might be nice to have the option of using libnl-3 on a Fedora 
17 system, it should then require the correct netcf.

Gene
>
>   configure.ac | 28 +++++++++++++++++++---------
>   1 file changed, 19 insertions(+), 9 deletions(-)
>
> diff --git a/configure.ac b/configure.ac
> index 47a72b9..7528894 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -2902,14 +2902,24 @@ LIBNL_LIBS=""
>   have_libnl=no
>
>   if test "$with_linux" = "yes"; then
> -    PKG_CHECK_MODULES([LIBNL], [libnl-3.0], [
> -        have_libnl=yes
> -        AC_DEFINE([HAVE_LIBNL3], [1], [Use libnl-3.0])
> -        AC_DEFINE([HAVE_LIBNL], [1], [whether the netlink library is available])
> -        PKG_CHECK_MODULES([LIBNL_ROUTE3], [libnl-route-3.0])
> -        LIBNL_CFLAGS="$LIBNL_CFLAGS $LIBNL_ROUTE3_CFLAGS"
> -        LIBNL_LIBS="$LIBNL_LIBS $LIBNL_ROUTE3_LIBS"
> -    ], [PKG_CHECK_MODULES([LIBNL], [libnl-1 >= $LIBNL_REQUIRED], [
> +    # When linking with netcf, we must ensure that we pick the same version
> +    # of libnl that netcf picked.  Prefer libnl-3 unless we can prove
> +    # netcf linked against libnl-1.
> +    ncftool=`which ncftool`
> +    case `(ldd "$ncftool") 2>&1` in
> +        *libnl.so.1*) ;;
> +        *)
> +        PKG_CHECK_MODULES([LIBNL], [libnl-3.0], [
> +            have_libnl=yes
> +            AC_DEFINE([HAVE_LIBNL3], [1], [Use libnl-3.0])
> +            AC_DEFINE([HAVE_LIBNL], [1], [whether the netlink library is available])
> +            PKG_CHECK_MODULES([LIBNL_ROUTE3], [libnl-route-3.0])
> +            LIBNL_CFLAGS="$LIBNL_CFLAGS $LIBNL_ROUTE3_CFLAGS"
> +            LIBNL_LIBS="$LIBNL_LIBS $LIBNL_ROUTE3_LIBS"
> +        ], []) ;;
> +    esac
> +    if test "$have_libnl" = no; then
> +        PKG_CHECK_MODULES([LIBNL], [libnl-1 >= $LIBNL_REQUIRED], [
>               have_libnl=yes
>               AC_DEFINE_UNQUOTED([HAVE_LIBNL], [1],
>                [whether the netlink library is available])
> @@ -2920,7 +2930,7 @@ if test "$with_linux" = "yes"; then
>                   AC_MSG_ERROR([libnl-devel >= $LIBNL_REQUIRED is required for macvtap support])
>               fi
>           ])
> -    ])
> +    fi
>   fi
>   AM_CONDITIONAL([HAVE_LIBNL], [test "$have_libnl" = "yes"])
>