Tor clients on 0.3.5.6-rc? and later will use a consensus that will become
valid up to 24 hours in the future.
Clients on 0.3.5.5-alpha? and earlier won't accept future consensuses.
Update the fallback expiry tolerance to match tor's checks.
Part of 28768, follow-up on 28591.
Tor clients will use a consensus that expired up to 24 hours ago.
Clients on 0.3.5.5-alpha? and earlier won't select guards from an expired
consensus, but they can still bootstrap if they have existing guards.
Update the fallback expiry tolerance to match tor's checks.
Part of 28768, follow-up on 24661.