netdev - Re: [PATCH net-next 0/1 v2] skbuff: Extend gso

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Message-ID: <1491677732.10124.94.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Sat, 08 Apr 2017 11:55:32 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Steffen Klassert <steffen.klassert@...unet.com>
Cc:     David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
        Eric Dumazet <edumazet@...gle.com>,
        Alexander Duyck <alexander.duyck@...il.com>
Subject: Re: [PATCH net-next 0/1 v2] skbuff: Extend gso_type to unsigned int.

On Sat, 2017-04-08 at 20:36 +0200, Steffen Klassert wrote:
> All available gso_type flags are currently in use, so
> extend gso_type from 'unsigned short' to 'unsigned int'
> to be able to add further flags.
> 
> We reorder the struct skb_shared_info to use
> two bytes of the four byte hole before dataref.
> All fields before dataref are cleared, i.e.
> four bytes more than before the change.
> 
> The remaining two byte hole is moved to the
> beginning of the structure, this protects us
> from immediate overwites on out of bound writes
> to the sk_buff head.

> Signed-off-by: Steffen Klassert <steffen.klassert@...unet.com>
> ---
>  include/linux/skbuff.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index c776abd..741d75c 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -413,14 +413,15 @@ struct ubuf_info {
>   * the end of the header data, ie. at skb->end.
>   */
>  struct skb_shared_info {
> +	unsigned short	_unused;
>  	unsigned char	nr_frags;
>  	__u8		tx_flags;
>  	unsigned short	gso_size;
>  	/* Warning: this field is not always filled in (UFO)! */
>  	unsigned short	gso_segs;
> -	unsigned short  gso_type;
>  	struct sk_buff	*frag_list;
>  	struct skb_shared_hwtstamps hwtstamps;
> +	unsigned int	gso_type;
>  	u32		tskey;
>  	__be32          ip6_frag_id;
>  

This looks much better, thanks Steffen.

Acked-by: Eric Dumazet <edumazet@...gle.com>