[tor-bugs] #24839 [Core Tor/Tor]: Add a torrc option and descriptor line to opt-in as a FallbackDir

[Tor Bug Tracker & Wiki]

#24839: Add a torrc option and descriptor line to opt-in as a FallbackDir
-------------------------------------------------+-------------------------
 Reporter:  teor                                 |          Owner:  (none)
     Type:  task                                 |         Status:  new
 Priority:  Medium                               |      Milestone:  Tor:
                                                 |  unspecified
Component:  Core Tor/Tor                         |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  needs-proposal, fallback, tor-spec,  |  Actual Points:
  034-triage-20180328, 034-removed-20180328,     |
  teor-backlog, network-team-roadmap-2020Q1      |
Parent ID:                                       |         Points:  3
 Reviewer:                                       |        Sponsor:
-------------------------------------------------+-------------------------

Old description:

> This needs:
> * a proposal and a design
> * a patch to dir-spec.txt
> * a patch to the tor man page
> * a tor code patch
> * an updateFallbackDirs.py code patch
> * a wiki update to [[doc/UpdatingFallbackDirectoryMirrors]]
>
> Here's a quick sketch of a design:
>
> 1. Relay operators set `OfferFallbackDirServer 1` to offer their relay as
> a potential FallbackDir.
> 2. Relays with this option set put `offer-fallback-dir-server` in their
> descriptors
> 3. updateFallbackDirs.py loads relay fingerprints with `offer-fallback-
> dir-server`, and from the legacy whitelist (#24838 will make this easier)
> 4. updateFallbackDirs.py applies the blacklist, does stability checks,
> and generates the fallback list

New description:

 This needs:
 * a proposal and a design
 * a patch to dir-spec.txt
 * a patch to the tor man page
 * a tor code patch
 * an updateFallbackDirs.py code patch
 * a wiki update to [[doc/UpdatingFallbackDirectoryMirrors]]

 Here's a quick sketch of a design:

 1. Relay operators set `OfferFallbackDir 1` to offer their relay as a
 potential FallbackDir.
 2. Relays with this option set put `offer-fallback-dir` in their
 descriptors
 3. updateFallbackDirs.py loads relay fingerprints with `offer-fallback-
 dir`, and from the legacy offer list
 4. updateFallbackDirs.py does stability checks, and generates the fallback
 list

--

Comment (by teor):

 Update description, make option shorter.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/24839#comment:12>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online