Subject: Re: [PATCH net] gre: Use inner mac length when computing tunnel length

From: Alexander Duyck <[email-masked]>
Date: Thu, 30 Oct 2014 08:52:41 -0700

On 10/30/2014 08:40 AM, Tom Herbert wrote:
> Currently, skb_inner_network_header is used but this does not account
> for Ethernet header for ETH_P_TEB. Use skb_inner_mac_header which
> handles TEB and also should work with IP encapsulation in which case
> inner mac and inner network headers are the same.
>
> Tested: Ran TCP_STREAM over GRE, worked as expected.
>
> Signed-off-by: Tom Herbert <[email-masked]>
> ---
>   net/ipv4/gre_offload.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
> index f6e345c..bb5947b 100644
> --- a/net/ipv4/gre_offload.c
> +++ b/net/ipv4/gre_offload.c
> @@ -47,7 +47,7 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
>
>   	greh = (struct gre_base_hdr *)skb_transport_header(skb);
>
> -	ghl = skb_inner_network_header(skb) - skb_transport_header(skb);
> +	ghl = skb_inner_mac_header(skb) - skb_transport_header(skb);
>   	if (unlikely(ghl < sizeof(*greh)))
>   		goto out;
>
>

This works for me.  We probably need to queue this up for stable as well 
since this bug goes back as far as 3.14.

Acked-by: Alexander Duyck <[email-masked]>