netdev - Re: [PATCH] openvswitch: Add cutlen info to upcall.

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Message-ID: <CALDO+SZAYACM2An88EMLRsYY+xubDRs6fD4CGfNowQ9XfrNxTQ@mail.gmail.com>
Date:	Thu, 16 Jun 2016 07:28:22 -0700
From:	William Tu <u9012063@...il.com>
To:	pravin shelar <pshelar@....org>
Cc:	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	Pravin Shelar <pshelar@...ira.com>
Subject: Re: [PATCH] openvswitch: Add cutlen info to upcall.

Hi Pravin,

Yes, I think that's better. Instead of cutlen, I will pass the
skb->len to userspace.

Regards,
William

On Wed, Jun 15, 2016 at 7:55 PM, pravin shelar <pshelar@....org> wrote:
> On Wed, Jun 15, 2016 at 7:28 PM, William Tu <u9012063@...il.com> wrote:
>> The commit f2a4d086ed4c ("openvswitch: Add packet truncation support.")
>> introduces packet truncation before sending to userspace upcall receiver.
>> This patch passes the number of bytes truncated in kernel to so that the
>> upcall receiver knows the original packet size. Potentially this will
>> be used by sFlow, where OVS translates sFlow config header=N to a sample
>> action to trunc(N) in kernel datapath. Thus, only N bytes instead of
>> full-packet size will be copied from kernel to userspace, saving the
>> kernel-to-userspace bandwidth.
>>
>> Signed-off-by: William Tu <u9012063@...il.com>
>> Cc: Pravin Shelar <pshelar@...ira.com>
>
> This is passing unnecessary kernel implementation details to
> userspace, can we just pass skb-len to userspace?