In my short time poking around, my belief is discoveryd gets wedged into a state where it thinks DNS queries aren't resolving, and so it doesn't try to resolve them. I'm not sure what exactly is going on there, either all the queries are blocked somehow on some long-lived query that has no response and no timeout, or discoveryd thinks the network is broken and is waiting for it to come back (those are just guesses). Either way, the command tells discoveryd to restart any outstanding "questions" (which presumably means queries). When I had the issue, that was sufficient to flush out whatever it was that was blocking everything, as my machine instantly started working properly again.
In my short time poking around, my belief is discoveryd gets wedged into a state where it thinks DNS queries aren't resolving, and so it doesn't try to resolve them. I'm not sure what exactly is going on there, either all the queries are blocked somehow on some long-lived query that has no response and no timeout, or discoveryd thinks the network is broken and is waiting for it to come back (those are just guesses). Either way, the command tells discoveryd to restart any outstanding "questions" (which presumably means queries). When I had the issue, that was sufficient to flush out whatever it was that was blocking everything, as my machine instantly started working properly again.