[tor-bugs] #25886 [Core Tor/Tor]: Have frac_nodes_with_descriptors() take and use for_direct_connect

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#25886: Have frac_nodes_with_descriptors() take and use for_direct_connect
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     Reporter:  nickm         |      Owner:  (none)
         Type:  defect        |     Status:  new
     Priority:  Medium        |  Milestone:  Tor: unspecified
    Component:  Core Tor/Tor  |    Version:
     Severity:  Normal        |   Keywords:
Actual Points:                |  Parent ID:
       Points:                |   Reviewer:
      Sponsor:                |
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 On their review for #25691, teor notes (about for_direct_connect):

 >We should pass for_direct_conn into this function, and use
 node_has_preferred_descriptor().

 >For the mid and exit case:
 >We won't bootstrap unless we have enough actual mid and exit bandwidth,
 even if we have mids or exits listed as our bridges.
 >
 >For the guard case:
 >The guard case is unchanged for non-bridge clients.
 >
 >The bridge client case could be tricky, because:
 >
 >   1. compute_frac_paths_available() only checks guard-flagged nodes, not
 bridges
 >   2. even if it did check bridges, they don't have bandwidths
 >   3. even if we used a weight of 1 for each bridge, we don't require 65%
 of bridges to be up to bootstrap
 >
 >To workaround this issue, I suggest we make f_guard = 1.0 in
 compute_frac_paths_available() if we are using bridges, and have at least
 one bridge with the preferred descriptor.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/25886>
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