Subject: Re: [PATCH net-next] bridge: mdb: add vlan support for user entries

From: Stephen Hemminger <[email-masked]>
Date: Mon, 20 Jul 2015 15:28:17 -0700

On Fri, 10 Jul 2015 08:02:08 -0700
Nikolay Aleksandrov <[email-masked]> wrote:

> diff --git a/include/uapi/linux/if_bridge.h b/include/uapi/linux/if_bridge.h
> index eaaea6208b42..3635b7797508 100644
> --- a/include/uapi/linux/if_bridge.h
> +++ b/include/uapi/linux/if_bridge.h
> @@ -182,6 +182,7 @@ struct br_mdb_entry {
>  #define MDB_TEMPORARY 0
>  #define MDB_PERMANENT 1
>  	__u8 state;
> +	__u16 vid;
>  	struct {
>  		union {
>  			__be32	ip4;

You added a new field into an unused hole in a data
structure shared as part of API with user space.

This seems like it might break when newer iproute
is run on older kernels. The vid would always be 0
on show and ignored when adding entries.