[tor-bugs] #32165 [Core Tor/Tor]: On first boot, Tor mistakenly tells me "The current consensus has no exit nodes"

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#32165: On first boot, Tor mistakenly tells me "The current consensus has no exit
nodes"
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 Reporter:  arma          |          Owner:  (none)
     Type:  defect        |         Status:  new
 Priority:  Medium        |      Milestone:
Component:  Core Tor/Tor  |        Version:
 Severity:  Normal        |     Resolution:
 Keywords:                |  Actual Points:
Parent ID:                |         Points:
 Reviewer:                |        Sponsor:
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Comment (by arma):

 It looks like compute_frac_paths_available() prints that line as a
 log_notice whenever it is called and count_usable_descriptors() returns
 "np" (number present) of 0.

 Specifically, count_usable_descriptors() counts up how many of the exit
 relays in the consensus are "present" and how many are "usable". At the
 beginning, when we've gotten the consensus but no microdescriptors, many
 of the exit relays are "usable" but none of them are "present" yet. But!
 The logic inside count_usable_descriptors() uses the opposite meaning: it
 says to itself that many of the exit relays are "present" in the consensus
 but none of them are "usable" by this Tor yet (because we don't have a
 microdescriptor for them yet).

 So the simple fix is that it needs to check if nu > 0, not np.

 And the broader fix is that maybe we need better words for these two
 notions.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/32165#comment:1>
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