netdev - Re: [RFC PATCH 7/7] tou: Support for GSO

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Date:	Tue, 24 May 2016 07:59:16 -0700
From:	Alexander Duyck <alexander.duyck@...il.com>
To:	Tom Herbert <tom@...bertland.com>
Cc:	David Miller <davem@...emloft.net>,
	Netdev <netdev@...r.kernel.org>, Kernel Team <kernel-team@...com>
Subject: Re: [RFC PATCH 7/7] tou: Support for GSO

On Mon, May 23, 2016 at 3:48 PM, Tom Herbert <tom@...bertland.com> wrote:
> Add SKB_GSO_TOU. In udp[64]_ufo_fragment check for SKB_GSO_TOU. If this
> is set call skb_udp_tou_segment. skb_udp_tou_segment is very similar
> to skb_udp_tunnel_segment except that we only need to deal with the
> L4 headers.
>
> Signed-off-by: Tom Herbert <tom@...bertland.com>
> ---
>  include/linux/skbuff.h           |   2 +
>  include/net/udp.h                |   2 +
>  net/ipv4/fou.c                   |   2 +
>  net/ipv4/ip_output.c             |   2 +
>  net/ipv4/udp_offload.c           | 164 +++++++++++++++++++++++++++++++++++++--
>  net/ipv6/inet6_connection_sock.c |   3 +
>  net/ipv6/udp_offload.c           | 128 +++++++++++++++---------------
>  7 files changed, 236 insertions(+), 67 deletions(-)
>
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 65968a9..b57e484 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -482,6 +482,8 @@ enum {
>         SKB_GSO_PARTIAL = 1 << 13,
>
>         SKB_GSO_TUNNEL_REMCSUM = 1 << 14,
> +
> +       SKB_GSO_TOU = 1 << 15,
>  };
>

So where do you add the netdev feature bit?  From what I can tell that
was overlooked and as a result devices that support FCoE CRC will end
up corrupting TOU frames because netif_gso_ok currently ands the two
together.

Also I am pretty sure we can offload this on the Intel NICs using the
GSO partial approach as we can just stuff the UDP header into the
space that we would use for IPv4 options or IPv6 extension headers and
it shouldn't complain.

- Alex