netdev - Re: [PATCH net-next 3/3] GRE: Add TCP segmentation offload for GRE

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Date:	Thu, 14 Feb 2013 17:39:49 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Pravin B Shelar <pshelar@...ira.com>
Cc:	netdev@...r.kernel.org, edumazet@...gle.com, jesse@...ira.com,
	bhutchings@...arflare.com, mirqus@...il.com
Subject: Re: [PATCH net-next 3/3] GRE: Add TCP segmentation offload for GRE

On Thu, 2013-02-14 at 11:45 -0800, Pravin B Shelar wrote:
> Following patch adds GRE protocol offload handler so that
> skb_gso_segment() can segment GRE packets.
> SKB GSO CB is added to keep track of total header length so that
> skb_segment can push entire header. e.g. in case of GRE, skb_segment
> need to push inner and outer headers to every segment.
> New NETIF_F_GRE_GSO feature is added for devices which support HW
> GRE TSO offload. Currently none of devices support it therefore GRE GSO
> always fall backs to software GSO.
> 
> Signed-off-by: Pravin B Shelar <pshelar@...ira.com>
> ---
> Fixed according to comments from Jesse and Eric.
> v2-v3:
>  - Use device features to segment inner packet.
>  - Moved skb_mac_gso_segment to separate patch.
>  - simplified gre_gso_segment().
>  - Added NETIF_F_GRE_GSO feature.
> 
> v1-v2:
>  - Factored a MAC layer handler out of skb_gso_segment().
>  - Eliminated copy operation from gre_gso_segment().
>  - Refresh header pointer after pskb_may_pull().
> ---

Seems very good to me, thanks !

The only thing that puzzles me is the ip_select_ident() in
ipgre_tunnel_xmit()

Do we care of the IP identifiers being 0, 1, 2, 3, ... on the outer
headers ?

Without TSO, we are using 0 IP identifiers (DF being set)

Also if we can't unclone the skb in handle_offloads(), we should
increment tx_dropped or tx_errors.




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