Not immediately required (it would be nice to have for Canada, possibly) but definitely necessary for Spaun.

As far as I can tell, the IP address of a chip can be read from the sv struct (ip_addr) and is, I assume, formatted the same way as IP addresses for IP tags (i.e., !4B, bewaring that the default appears to be 255.255.0.0).
The real challenge is in determining the co-ordinates of likely chips, though I guess a safe approach would be to always jump 8* (north or east) from the last found ethernet chip and then read eth_addr to get the co-ordinates of the nearest ethernet connected chip.

I initially thought that this process should be part of get_machine... but now I'm not so sure.

Once we have a map of co-ordinates to ethernet addresses it becomes a drop in replacement to MachineController.get_connection, though we should also expose the mapping so that other software (like Nengo) can transmit SDP to SpiNNaker efficiently.

* or 7?

Also: "bewaring" is an awesome word.