Package version does not support "ignore-carrier" configuration option

I have a couple of connections defined which are not on "auto connect" - one wired, one wireless - so that I can control which I want to be on at the same time. Since they share the same IP, leaving NetworkManager to do things automatically doesn't work since at the moment that it has both connections configured, IPv6 duplicate address detection kicks in by detecting itself and disables my IPv6 connection.

Everything works fine this way normally - I just manually connect the connection I want (after disconnecting the other one first if necessary), and everything works.

When I get a power cut, my switch turns off, but as a laptop my main machine effectively has a UPS. In this case, NetworkManager detects a cable disconnect on eth0, and disconnects the connection. When the power comes back on and the cable "reconnects", NetworkManager does nothing.

When I'm away, this kills my connection, even after the power is restored. This breaks my expectation is that everything should be fine as long as the power cut didn't last as long as my battery.

AIUI, this behaviour is by design, but more recent versions of NetworkManager have an "ignore-carrier" configuration option that is intended for my use case and would solve my problem. But Ubuntu doesn't currently ship a version that supports this.

The upstream patch appears to be in http://cgit.freedesktop.org/NetworkManager/NetworkManager/commit/?id=8e37935875ad84c1cdaf13b38535adc884ec188e and I see references to it for example in Red Hat's NetworkManager-config-server package. I have no idea if the upstream patch would apply cleanly and work or not.

It looks like Ubuntu's delta against upstream is quite big. I don't really expect this to be fixed soon, and I'm sure I can find some kind of workaround more easily than trying to patch support in, but I thought it might be helpful to file a bug to track the existence of a real use case where a newer upstream release would be useful.