[tor-bugs] #20876 [Core Tor/Fallback Scripts]: Avoid contacting fallback operators who are unlikely to be accepted

[Tor Bug Tracker & Wiki]

#20876: Avoid contacting fallback operators who are unlikely to be accepted
---------------------------------------+----------------------------------
 Reporter:  teor                       |          Owner:  (none)
     Type:  enhancement                |         Status:  new
 Priority:  Medium                     |      Milestone:  Tor: unspecified
Component:  Core Tor/Fallback Scripts  |        Version:
 Severity:  Normal                     |     Resolution:
 Keywords:  fallback                   |  Actual Points:
Parent ID:                             |         Points:
 Reviewer:                             |        Sponsor:
---------------------------------------+----------------------------------

Comment (by teor):

 This is the old wiki text:


 === c. Revising the Bandwidth Cutoff (optional) ===

 When we change the number of relays, we need to revise the bandwidth
 cutoff, then re-run the fallback selection process.

 The 3 MByte/s minimum ends up selecting a lot of relays. But we know that
 if we select 200 relays, the lowest relay will actually have N MByte/s. So
 there's not much point in asking operators to opt-in, if their relays will
 never be chosen.

 So impose a limit of 200 relays, then find the minimum bandwidth in the
 list, and re-run "Find Potential Fallbacks" with this minimum bandwidth.

 i. Use the latest whitelist and blacklist
 ii. Output candidate fallbacks (applying the whitelist, output operator
 contact details):
 {{{
 OUTPUT_CANDIDATES = True
 }}}
 {{{
 - MAX_FALLBACK_COUNT = None if OUTPUT_CANDIDATES else 200
 + MAX_FALLBACK_COUNT = 200
 }}}
 {{{
 - INCLUDE_UNLISTED_ENTRIES = True if OUTPUT_CANDIDATES else False
 + INCLUDE_UNLISTED_ENTRIES = False
 }}}
 {{{
 - OUTPUT_SORT_FIELD = 'contact' if OUTPUT_CANDIDATES else 'fingerprint'
 + OUTPUT_SORT_FIELD = 'measured_bandwidth'
 }}}
 iii. Run the fallback selection script, saving the list:
 {{{
 scripts/maint/updateFallbackDirs.py > potential_extra_fallbacks 2>
 potential_extra_fallbacks.log
 }}}

 During the 0.2.9 fallback regeneration in September 2016, the last relay
 was:
 {{{
 youlooksuspicious
 Flags: Fast Guard HSDir Running Stable V2Dir Valid
 Bandwidth: 8.0 MByte/s, Consensus Weight: 16900
 }}}

 So revise the bandwdith cutoff to 8 MByte/s, restore the
 MAX_FALLBACK_COUNT, INCLUDE_UNLISTED_ENTRIES and OUTPUT_SORT_FIELD, and
 re-run "Find Potential Fallbacks":
 {{{
 - MIN_BANDWIDTH = 102.4 * 30.0 * 1024.0
 + MIN_BANDWIDTH = 8.0 * 1024.0 * 1024.0
 }}}

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/20876#comment:6>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online