netdev - Re: [PATCH v2 0/4] net: Checksum offload changes

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Date:	Thu, 10 Jul 2014 23:40:51 -0600
From:	Sharat Masetty <sharat04@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	Tom Herbert <therbert@...gle.com>,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 0/4] net: Checksum offload changes - Part IV

> Don't do skb_checksum more than once per packet
Was wondering in which cases does the stack perform the checksum more
than once? __skb_checksum_complete_head() already sets the ip_summed
to CHECKSUM_UNNECESSARY, so future checksum calculations are avoided.
What am I missing?

Thanks
Sharat

On Wed, Jun 11, 2014 at 4:46 PM, David Miller <davem@...emloft.net> wrote:
> From: Tom Herbert <therbert@...gle.com>
> Date: Tue, 10 Jun 2014 18:54:03 -0700 (PDT)
>
>> I am working on overhauling RX checksum offload. Goals of this effort
>> are:
>>
>> - Specify what exactly it means when driver returns CHECKSUM_UNNECESSARY
>> - Preserve CHECKSUM_COMPLETE through encapsulation layers
>> - Don't do skb_checksum more than once per packet
>> - Unify GRO and non-GRO csum verification as much as possible
>> - Unify the checksum functions (checksum_init)
>> - Simply code
>>
>> What is in this fourth patch set:
>>
>> - Preserve CHECKSUM_COMPLETE instead of changing it to
>>   CHECKSUM_UNNECESSARY. This allows correct reuse in validating multiple
>>   csums in a packet.
>> - When SW needs to compute the packet checksum, save it as
>>   CHECKSUM_COMPLETE. Also mark that checksum was compute by SW.
>> - Add skb_gro_postpull_rcsum to udp and vxlan to make GRO work with
>>   CHECKSUM_COMPLETE.
>>
>> v2: Removed patch setting skb_encapsulation when validating checksum
>>     in tcp_gro_receive
>>
>> Please review carefully and test if possible, mucking with basic
>> checksum functions is always a little precarious :-)
>
> Series applied, thanks Tom.
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