netdev - Re: [PATCH 1/1] tun: change speed from 10M to dynamically configured

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Message-ID: <20150220023500.GK580@gospo.home.greyhouse.net>
Date:	Thu, 19 Feb 2015 21:35:00 -0500
From:	Andy Gospodarek <gospo@...ulusnetworks.com>
To:	David Miller <davem@...emloft.net>
Cc:	stephen@...workplumber.org, Yanjun.Zhu@...driver.com,
	romieu@...zoreil.com, netdev@...r.kernel.org, mst@...hat.com,
	jasowang@...hat.com, viro@...iv.linux.org.uk,
	sergei.shtylyov@...entembedded.com, jonathon.reinhart@...il.com
Subject: Re: [PATCH 1/1] tun: change speed from 10M to dynamically configured

On Thu, Feb 19, 2015 at 03:40:41PM -0500, David Miller wrote:
> From: Stephen Hemminger <stephen@...workplumber.org>
> Date: Mon, 16 Feb 2015 12:03:45 -0500
> 
> > I would like to propose this is as a more complete alternative.
> > 
> > From: Stephen Hemminger <stephen@...workpluber.org>
> > Subject: [PATCH] tun: support overriding ethtool information
> > 
> > Extensions to allow masqurade of ethtool info and device statistics.
> > This is useful to provide correct information to SNMP and OSPF routing
> > daemons when doing hw/sw offload of network device.
> > 
> > Signed-off-by: Stephen Hemminger <stephen@...workplumber.org>
> 
> We need a consistent policy regarding link attributes of encapsulating
> "software" devices.

I think this is a great point and though I like Stephen's patch due to
how useful it would be to me, I had some concerns about whether or not
others would accept it without a bit more of 'a plan' for functions like
this.

> 
> I see three realistic options:
> 
> 1) Create a link state indication which means "I am a software device,
>    so I don't really have a link state in the traditional sense"
> 
> 2) Don't implement the link set/get operations at all on software
>    devices.
> 
>    People can use ETHTOOL_GLINK to see if the thing is "up"
> 
> 3) Propagate the ultimate physical transport parameters into what
>    the software device advertises.
> 
> It's important to carefully pick one of these, and consistently apply
> it to all of our software devices.
> 
> I don't want TUN doing one thing, ipv4 tunnels doing another, etc.

I would prefer option #3 as it relates to the ability to transport
offload statistics and parameters to software devices.  This could be
useful for hardware with some form of offload vxlan/gre/etc that may be
backed by hardare statistics (a callback to the upper device's ndo op
could be made by the native hardware driver) or any other device without
a proper in-kernel driver like a userspace user of tuntap that might be
backed by something like OpenVPN.

That might help provide some more detailed, ethtool-like statistics in
the format that is more easily readable by common monitoring tools
without the need to have those applications look at anything except an
ethtool/kernel interface.

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