UPDATE: This issue is fixed! System working in normal operation again.
While download.opensuse.org is still up and running, our rsync.opensuse.org mirror is currently down (reason: lost network connection completely after trying to re-establish IPv6 connectivity - might be a configuration problem).
We are currently trying to reach out to the data center folks to get remote access to the machine - if this fails, we need to travel to the location, which will take some time.
We need to travel to the external data center to bring the machine up again. This will happen on Monday, 2017-06-26. Stay tuned. (happened)