Re: [PATCH ipsec 1/3] ipv6: wire up skb->encapsulation

Hannes Frederic Sowa
2013-08-17T18:07:39Z

Hi Simon!

On Sat, Aug 17, 2013 at 07:51:16PM +0200, Hannes Frederic Sowa wrote:
> When pushing a new header before current one call skb_reset_inner_headers
> to record the position of the inner headers in the various ipv6 tunnel
> protocols.
>
> We later need this to correctly identify the addresses needed to send
> back an error in the xfrm layer.
>
> This change is safe, because skb->protocol is always checked before
> dereferencing data from the inner protocol.
>
> Cc: Steffen Klassert <steffen.klassert@secunet.com>
> Cc: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
> Cc: Nicolas Dichtel <nicolas.dichtel@6wind.com>
> Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
> ---
>
> This patch is based on Steffen Klassert's ipsec tree.
>
> net/ipv6/ip6_gre.c | 5 +++++
> net/ipv6/ip6_tunnel.c | 6 ++++++
> net/ipv6/sit.c | 5 +++++
> 3 files changed, 16 insertions(+)
>
> diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
> index ecd6073..90747f1 100644
> --- a/net/ipv6/ip6_gre.c
> +++ b/net/ipv6/ip6_gre.c
> @@ -724,6 +724,11 @@ static netdev_tx_t ip6gre_xmit2(struct sk_buff *skb,
> ipv6_push_nfrag_opts(skb, &opt.ops, &proto, NULL);
> }
>
> + if (likely(!skb->encapsulation)) {
> + skb_reset_inner_headers(skb);
> + skb->encapsulation = 1;
> + }
> +

While doing these patches, I wondered how skb->inner_protocol will be
used in future (you added it in 0d89d2035fe063461a5ddb609b2c12e7fb006e44
("MPLS: Add limited GSO support")). Current use by tunnels seems safe to
me, but I wondered how you would extend its use?

Thanks,

Hannes