quoted

Suddenly does something else.

Indeed!

quoted

Is this an ABI break? How do we make this reliable so implementing
more loopbacks at different levels does not change how you use
--set-loopback?

Isn't this somewhat similar to what we have with ifindex/phy_index,
but potentially unstable when modules are swapped/changed?

If you hot plug hardware, a new PHY pops into existence, i don't think
it is too unreasonable for the hot plugable parts to change ids. I
would however expect the fixed parts to keep there IDs.

But here we are talking about software, a kernel upgrade/downgrade
causing the IDs to change.
 

Instead of ids, use string name and/or topology indices (e.g.
phy_index)? All three -- owner, phy_index, name tuple?

Probably.

	Andrew