[tor-relays] What causes circuits to collapse?

[Igor Mitrofanov]

Hi,

I have configured a Tor bridge to go through a particular Tor guard
relay (that I also own), as an experiment.
Upon initialization I am getting this warning:

"Your guard [fingerprint] is failing an extremely large amount of
circuits. This could indicate a route manipulation attack, extreme
network overload, or a bug. Success counts are 52/275. Use counts are
67/67. 268 circuits completed, 0 were unusable, 217 collapsed and 1
timed out. For reference, your timeout cutoff is 60 seconds".

Both relays are running Tor 3.0.10.

I have never received this warning before. How do I interpret the
numbers above, and debug the issue?

The guard is far from saturating its network bandwidth. It has 98%
idle CPU and plenty of free memory. I am not running any attacks
against it. It does use a tuned-up sysctl.conf but I have never had
any problems with it. "tcpdump icmp" does not show anything
interesting. There are no warnings in the guard's log.

Thanks,
Igor