[tor-bugs] #32020 [Core Tor/Tor]: hsv3: Client do not report failing circuit back into HS subsystem

[Tor Bug Tracker & Wiki]

#32020: hsv3: Client do not report failing circuit back into HS subsystem
--------------------------------+------------------------------------
 Reporter:  dgoulet             |          Owner:  dgoulet
     Type:  defect              |         Status:  needs_review
 Priority:  Medium              |      Milestone:  Tor: 0.4.3.x-final
Component:  Core Tor/Tor        |        Version:
 Severity:  Normal              |     Resolution:
 Keywords:  tor-hs, tor-client  |  Actual Points:  1
Parent ID:  #30200              |         Points:  1
 Reviewer:  asn                 |        Sponsor:  Sponsor27-must
--------------------------------+------------------------------------

Comment (by dgoulet):

 Replying to [comment:5 asn]:
 > Replying to [comment:3 dgoulet]:
 > > Related is #26806 which mentions that possibly because the HSv3 client
 is not noticing the introduction timeout (as in the ACK never came back),
 we resend onto that same intro point. Good or bad?
 >
 >
 > Hmm, questions and answers:
 >
 > 1) Why doesn't the ACK or NACK come to the client? Is it because the
 intro point never sent it (why?)? Or because we timeout before receiving
 it? Or just general Tor network SNAFU?

 SNAFU is probably the answer. Circuit collapsing, timing out, etc...

 >
 > 2) If the above happens, why would the client decide to resend on the
 same intro point and same circuit? Is this an explicit decision?

 It doesn't in theory. Depending on the SNAFU (see patch I did), we either
 flag the intro point in the failure cache (see patch I did) or we go on
 with our lives maybe retrying a new one.

 > 3) Regarding "Good or bad?" I would say it's bad-ish because if the NACK
 never came back, I would prefer to retry a different intro point since
 that one might be suffering networking issues, or being overloaded, or
 downright maliciously DoSing the service.

 Yes, in theory, that is what is suppose to happen. The patch I did would
 fix this that is note down the intro point in the failure cache.

 >
 > PS: #26806 mentions "rendezvous circuits" in the title, but I think it
 should be intro circuits

 Yes.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/32020#comment:6>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online