netdev - Re: [PATCH net] bpf: make padding in bpf_tunnel

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Message-ID: <20160329220614.GA20258@ast-mbp.thefacebook.com>
Date:	Tue, 29 Mar 2016 15:06:16 -0700
From:	Alexei Starovoitov <alexei.starovoitov@...il.com>
To:	Daniel Borkmann <daniel@...earbox.net>
Cc:	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH net] bpf: make padding in bpf_tunnel_key explicit

On Wed, Mar 30, 2016 at 12:02:00AM +0200, Daniel Borkmann wrote:
> Make the 2 byte padding in struct bpf_tunnel_key between tunnel_ttl
> and tunnel_label members explicit. No issue has been observed, and
> gcc/llvm does padding for the old struct already, where tunnel_label
> was not yet present, so the current code works, but since it's part
> of uapi, make sure we don't introduce holes in structs.
> 
> Therefore, add tunnel_ext that we can use generically in future
> (f.e. to flag OAM messages for backends, etc). Also add the offset
> to the compat tests to be sure should some compilers not padd the
> tail of the old version of bpf_tunnel_key.
> 
> Fixes: 4018ab1875e0 ("bpf: support flow label for bpf_skb_{set, get}_tunnel_key")
> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>

Acked-by: Alexei Starovoitov <ast@...nel.org>