When we think we're unreachable, we seem to be launching a new reachability testing circuit every second.
To see this in action, start Tor with an unreachable ORPort, and run logs at the Info level. For a minute or so you won't see these, but starting then, once a second, you'll see something like:
Aug 03 14:36:27.000 [notice] Testing reachability of my ORPort: [...]
Aug 03 14:36:28.000 [notice] Testing reachability of my ORPort: [...]
Aug 03 14:36:29.000 [notice] Testing reachability of my ORPort: [...]
Aug 03 14:36:30.000 [notice] Testing reachability of my ORPort: [...]
Aug 03 14:36:31.000 [notice] Testing reachability of my ORPort: [...]
Aug 03 14:36:32.000 [notice] Testing reachability of my ORPort: [...]
Can that really be what we wanted?
Paging @arma.
Edited by Nick Mathewson