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

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Message-ID: <CAOrHB_CNe19U8wSOEAc6zi1+83ZH8GNQ3D+H_syG2SWNS5eUhA@mail.gmail.com>
Date:	Wed, 15 Jun 2016 19:55:40 -0700
From:	pravin shelar <pshelar@....org>
To:	William Tu <u9012063@...il.com>
Cc:	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	Pravin Shelar <pshelar@...ira.com>
Subject: Re: [PATCH] openvswitch: Add cutlen info to upcall.

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?