RE: [PATCH 1/1] tun: change speed from 10M to dynamically configured

From: David Miller
...

We need a consistent policy regarding link attributes of encapsulating
"software" devices.

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.

You also need to be careful to not break existing 'stuff'.

We've connected a single USB ethernet port into a 'bond' (with
nothing else) in order to get a stable interface and IP address
that doesn't bounce on transient USB errors.

If the absence of the physical interface caused the state of bond0
to change and that got propagated through the routing tables then
we'd get TCP disconnects reported for things that would only see
recovered packet loss.

	David