netdev - Re: [net-next PATCH 07/10] gre: Use inner_proto to obtain inner header protocol

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Date:	Sat, 6 Feb 2016 12:55:29 -0800
From:	Tom Herbert <tom@...bertland.com>
To:	Alexander Duyck <aduyck@...antis.com>
Cc:	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	Alexander Duyck <alexander.duyck@...il.com>,
	Edward Cree <ecree@...arflare.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [net-next PATCH 07/10] gre: Use inner_proto to obtain inner
 header protocol

On Fri, Feb 5, 2016 at 3:28 PM, Alexander Duyck <aduyck@...antis.com> wrote:
> Instead of parsing headers to determine the inner protocol we can just pull
> the value from inner_proto.
>
> Signed-off-by: Alexander Duyck <aduyck@...antis.com>
> ---
>  net/ipv4/gre_offload.c |    6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
> index c15441b5ff61..003b0ebbcfdd 100644
> --- a/net/ipv4/gre_offload.c
> +++ b/net/ipv4/gre_offload.c
> @@ -20,7 +20,6 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
>  {
>         int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
>         struct sk_buff *segs = ERR_PTR(-EINVAL);
> -       struct gre_base_hdr *greh;
>         u16 mac_offset = skb->mac_header;
>         __be16 protocol = skb->protocol;
>         u16 mac_len = skb->mac_len;
> @@ -48,15 +47,13 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
>         if (unlikely(!pskb_may_pull(skb, tnl_hlen)))
>                 goto out;
>
> -       greh = (struct gre_base_hdr *)skb_transport_header(skb);
> -
>         /* setup inner skb. */
> -       skb->protocol = greh->protocol;
>         skb->encapsulation = 0;
>         __skb_pull(skb, tnl_hlen);
>         skb_reset_mac_header(skb);
>         skb_set_network_header(skb, skb_inner_network_offset(skb));
>         skb->mac_len = skb_inner_network_offset(skb);
> +       skb->protocol = skb->inner_protocol;

Is this going to be a problem if we try to perform GSO with nested
encapsulations? (I suppose that's something not supported).

>
>         need_csum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_GRE_CSUM);
>         skb->encap_hdr_csum = need_csum;
> @@ -75,6 +72,7 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
>         gre_offset = outer_hlen - tnl_hlen;
>         skb = segs;
>         do {
> +               struct gre_base_hdr *greh;
>                 __be32 *pcsum;
>
>                 skb_reset_inner_headers(skb);
>