[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.

[Tor Bug Tracker & Wiki]

#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: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.

 Really, we need to check that we have path_length primary guards with
 descriptors available, or if we don't know the path length at this point,
 max_path_length. And we should BUG out if the actual path length is
 greater than this.

 > And in this case, should we leave the BUG() check in for now?

 Oh gosh yes!

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/21415#comment:16>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online