Subject: Re: [PATCH] net: update the usage of CHECKSUM_UNNECESSARY

From: "Michael S. Tsirkin" <[email-masked]>
Date: Tue, 8 May 2012 20:48:32 +0300

On Mon, Mar 19, 2012 at 02:12:41PM -0700, Yi Zou wrote:
> As suggested by Ben, this adds the clarification on the usage of
> CHECKSUM_UNNECESSARY on the outgoing patch. Also add the usage
> description of NETIF_F_FCOE_CRC and CHECKSUM_UNNECESSARY
> for the kernel FCoE protocol driver.
> 
> This is a follow-up to the following:
> http://patchwork.ozlabs.org/patch/147315/
> 
> Signed-off-by: Yi Zou <[email-masked]>
> Cc: Ben Hutchings <[email-masked]>
> Cc: Jeff Kirsher <[email-masked]>
> Cc: www.Open-FCoE.org <[email-masked]>
> ---
> 
>  include/linux/skbuff.h |    7 +++++++
>  1 files changed, 7 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 8dc8257..a2b9953 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -94,6 +94,13 @@
>   *			  about CHECKSUM_UNNECESSARY. 8)
>   *	NETIF_F_IPV6_CSUM about as dumb as the last one but does IPv6 instead.
>   *
> + *	UNNECESSARY: device will do per protocol specific csum. Protocol drivers
> + *	that do not want net to perform the checksum calculation should use
> + *	this flag in their outgoing skbs.
> + *	NETIF_F_FCOE_CRC  this indicates the device can do FCoE FC CRC
> + *			  offload. Correspondingly, the FCoE protocol driver
> + *			  stack should use CHECKSUM_UNNECESSARY.
> + *
>   *	Any questions? No questions, good. 		--ANK
>   */
>  

So just to make sure I understand, you never get
UNNECESSARY packets on tx unless you declared NETIF_F_FCOE_CRC?

Maybe the comment says this somehow but could not figure it out.

> 
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