[tor-bugs] #21415 [Core Tor/Tor]: tor_bug_occurred_: Bug: src/or/entrynodes.c:1845: select_entry_guard_for_circuit: Non-fatal assertion !(!guard_has_descriptor(guard)) failed.

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#21415: tor_bug_occurred_: Bug: src/or/entrynodes.c:1845:
select_entry_guard_for_circuit: Non-fatal assertion
!(!guard_has_descriptor(guard)) failed.
-----------------------------+------------------------------------
 Reporter:  cypherpunks      |          Owner:  nickm
     Type:  defect           |         Status:  needs_review
 Priority:  Medium           |      Milestone:  Tor: 0.3.0.x-final
Component:  Core Tor/Tor     |        Version:  Tor: 0.3.0.3-alpha
 Severity:  Normal           |     Resolution:
 Keywords:  review-group-16  |  Actual Points:
Parent ID:                   |         Points:
 Reviewer:  asn              |        Sponsor:
-----------------------------+------------------------------------

Comment (by teor):

 Replying to [comment:16 teor]:
 > Replying to [comment:15 nickm]:
 > > Either that, or just adding 1 to num_primary?
 >
 > Circuits can be up to 8 hops long in pathological cases:
 >
 > Having only 2 primary guards with descriptors fails in the scenario
 where we pick one guard as the exit, and the other as the middle.
 >
 > Having only 3 primary guards with descriptors fails in the scenario
 where we cannibalise a circuit, and one guard is the exit, and the others
 are middles.
 >
 > Having only 3 to (max_intro_points + 2) = 12 primary guards with
 descriptors fails in the scenario where a client fails to connect to an
 intro point, and so it extends to the next intro point repeatedly, up to
 10 intro points. Of course, we're only allowed to send 8 RELAY_EARLY
 cells, so this is bounded by the maximum path length.

 These are wrong, we pick exit, guard, middle(s).

 But having only N primary guards with descriptors fails in the scenario
 where all our primary guards are in the exit's IPv4 /16, or the exit's
 family.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/21415#comment:17>
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