[tor-bugs] #8240 [Tor]: Raise our guard rotation period

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#8240: Raise our guard rotation period
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 Reporter:  arma                                    |          Owner:                    
     Type:  defect                                  |         Status:  needs_revision    
 Priority:  major                                   |      Milestone:  Tor: 0.2.4.x-final
Component:  Tor                                     |        Version:                    
 Keywords:  tor-client needs-proposal 023-backport  |         Parent:                    
   Points:                                          |   Actualpoints:                    
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Changes (by arma):

  * status:  needs_review => needs_revision


Comment:

 Replying to [comment:1 nickm]:
 > See branch "bug8240".

 guards_get_lifetime()'s comments says it's about "directory guards", but I
 think it's about the other kinds of guards too, yes?

 I believe I misremembered the code when making some of the above comments
 -- I now believe setting GuardLifetime to 9 months will make your guards
 last between 8 and 9 months (as opposed to between 9 and 10 months). Since
 your consensus param wants to be "minimum lifetime" (which is a fine
 choice), we should deal with that fencepost issue internally by adding on
 an extra fencepost or something.

 I notice that our time_units array doesn't know what a month is. (I
 noticed because if we add a month and define it as 30 days, then 2 months,
 which is the current value, will be under your MIN_GUARD_LIFETIME value.)
 (That said, see the above fencepost issue -- I think the current value is
 actually best described as "1 month", meaning "at least 1 month", i.e.
 when it chooses an expiration time it chooses it up to 30 days in the
 past, and when it checks for expiration it checks if 60 days have passed.)

 Your patch doesn't change the two comments in
 remove_obsolete_entry_guards() that say "2 months".

 I'd be fine changing the value to "at least 2 months" while we're
 discussing how to deal with the weights issue.

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/8240#comment:14>
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