[OE-core] busybox: udhcpc: fix IPv6 support when using udhcpc

[Quentin Schulz]

Hi all,

On Mon, May 14, 2018 at 04:44:15PM +0200, Stefan Agner wrote:
> From: Stefan Agner <stefan.agner at toradex.com>
> 
> The udhcpc script calls ip addr flush .. which flushes addresses
> of any address family, including IPv6. However, busybox udhcpc is
> IPv4 only and should not influence IPv6 addressing. Hence use ip
> addr flush with family constrait.
> 
> The script particularly broke IPv6 SLAAC: Typically when udhcpc
> calls the script the kernel already assigned the IPv6 link-local
> address. The flush removes the link-local IPv6 address again and
> prohibits proper IPv6 operation such as SLAAC since neighbor
> discovery protocol relies on IPv6 link-local addressing.
> 
> Signed-off-by: Stefan Agner <stefan.agner at toradex.com>
> ---
>  meta/recipes-core/busybox/files/simple.script | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/meta/recipes-core/busybox/files/simple.script b/meta/recipes-core/busybox/files/simple.script
> index 6ed0293525..8b5eb53633 100644
> --- a/meta/recipes-core/busybox/files/simple.script
> +++ b/meta/recipes-core/busybox/files/simple.script
> @@ -28,7 +28,7 @@ case "$1" in
>  		fi
>  		if ! root_is_nfs ; then
>                          if [ $have_bin_ip -eq 1 ]; then
> -                                /SBIN_DIR/ip addr flush dev $interface
> +                                /SBIN_DIR/ip -4 addr flush dev $interface
>                                  /SBIN_DIR/ip link set dev $interface up
>                          else
>                                  /SBIN_DIR/ifconfig $interface 0.0.0.0

Kindly pinging, happened to us as well many times.

OT: Didn't have the original mail, so hopefully getting the mbox file
and answering to it didn't trigger anything weird somewhere :)

Thanks,
Quentin