feature request: command (or documentation on existing commands) for determining controller connection status

[lantz]

I'd like to be able to determine whether IVS is connected to a controller. For OVS, this can be done using ovs-vsctl get Bridge s1 Controller, and for the reference user switch it can be done with dpctl status tcp:127.0.0.1:6634, but I can't discern how to do it with IVS.

This would be very useful since I'd like to solve the problem of system-level tests in mininet (notably --pingall) which should not begin until all switches have connected to the controller, which I may not have access to (for example it could be a custom controller running on a remote server.) Providing switch status is also generally useful since it's nice to know if your network control plane is at least connected!!

For UserSwitch and OVSSwitch I was able to implement a connected() method using the above commands, but I'm not sure how to do this with IVS since ivs-ctl doesn't seem to support it (and I wasn't able to immediately find documentation on other methods of configuring IVS, for example using a REST or JSON API.)