* support maximum history age in _avg_generic_history()
* fix division-by-zero trap in _avg_generic_history()
* skip missing (i.e. null/None) intervals in _avg_generic_history()
* Python timedelta.total_seconds() function not available in 2.6;
replace with equivalent expression
* set DEBUG logging level to make relay exclusion reasons visible
* move CUTOFF_GUARD test to end in order to expose more exclusion
reasons
Patch by "starlight", merge modifications by "teor".
Allow cached or outdated Onionoo data to be used to choose
fallback directories, as long as it's less than a day old.
Modify last modified date checks in preparation for Onionoo change
"Tor has included a feature to fetch the initial consensus from nodes
other than the authorities for a while now. We just haven't shipped a
list of alternate locations for clients to go to yet.
Reasons why we might want to ship tor with a list of additional places
where clients can find the consensus is that it makes authority
reachability and BW less important.
We want them to have been around and using their current key, address,
and port for a while now (120 days), and have been running, a guard,
and a v2 directory mirror for most of that time."
Features:
* whitelist and blacklist for an opt-in/opt-out trial.
* excludes BadExits, tor versions that aren't recommended, and low
consensus weight directory mirrors.
* reduces the weighting of Exits to avoid overloading them.
* places limits on the weight of any one fallback.
* includes an IPv6 address and orport for each FallbackDir, as
implemented in #17327. (Tor won't bootstrap using IPv6 fallbacks
until #17840 is merged.)
* generated output includes timestamps & Onionoo URL for traceability.
* unit test ensures that we successfully load all included default
fallback directories.
Closes ticket #15775. Patch by "teor".
OnionOO script by "weasel", "teor", "gsathya", and "karsten".
