netdev - WAS ( Re: [PATCH net-next 1/1] net_sched: Introduce skbmod action

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Date:	Thu, 21 Jul 2016 03:27:30 -0400
From:	Jamal Hadi Salim <jhs@...atatu.com>
To:	Daniel Borkmann <daniel@...earbox.net>,
	Cong Wang <xiyou.wangcong@...il.com>
Cc:	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	David Miller <davem@...emloft.net>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
Subject: WAS ( Re: [PATCH net-next 1/1] net_sched: Introduce skbmod action

On 16-07-19 08:23 PM, Daniel Borkmann wrote:
> On 07/19/2016 08:04 PM, Cong Wang wrote:
>> On Tue, Jul 19, 2016 at 8:03 AM, Daniel Borkmann
>> <daniel@...earbox.net> wrote:
>>> On 07/19/2016 03:56 PM, Jamal Hadi Salim wrote:
>>> [...]

[..]
>> I don't think so. 1) checksum is supposed to be done by csum action
>> rather than pedit (or skbmod if it matters), 2) csum action currently
>> already handles that correctly for both egress and ingress: 2a)
>> CHECKSUM_COMPLETE is meaningless on egress; 2b) it forces
>> CHECKSUM_COMPLETE to be CHECKSUM_NONE on ingress
>> and it is correctly respected.
>
> Ahh, right, so it redoes entire csums when worst-case changing one byte
> only, since it cannot know what other actions like pedit did previously.
 >
> But it also means for your l2 mac addr changes to force a CHECKSUM_COMPLETE
> into CHECKSUM_NONE with csum action that you need to call into one of the
> l3/l4 helpers as far as I see.


Forgot about csum which would work with pedit - didnt quiet parse what
you are saying above though:
does changing MAC address require changing to CHECKSUM_NONE? If yes,
then seems like i need to send a patch for act_ife as well to make in
the spirit of mirred?

Having said all that:
This discussion now has gone past the original patch submission.
I really want to see this patch go in and dont want to get Dave to
review all these side comments - for this reason I changed the subject.

cheers,
jamal