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@networkplumber.org>
Date: Mon, 16 Feb 2015 12:03:45 -0500

quoted

I would like to propose this is as a more complete alternative.

From: Stephen Hemminger <redacted>
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@networkplumber.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.