[tor-bugs] #18620 [Core Tor/Tor]: HSFORGET command to clear cached client state for a HS

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#18620: HSFORGET command to clear cached client state for a HS
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 Reporter:  str4d                                |          Owner:  str4d
     Type:  enhancement                          |         Status:
 Priority:  Medium                               |  needs_revision
Component:  Core Tor/Tor                         |      Milestone:  Tor:
 Severity:  Normal                               |  0.2.9.x-final
 Keywords:  tor-hs, 029-accepted, review-        |        Version:  Tor:
  group-3                                        |  0.2.7.6
Parent ID:                                       |     Resolution:
 Reviewer:  asn, special                         |  Actual Points:
                                                 |         Points:  1
                                                 |        Sponsor:
                                                 |  SponsorR-can
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Comment (by timonh):

 I think this is connected to #19522. If a HS changes it's ip address and
 choses new intro point because of #19522 then a client with a cached
 descriptor will retry the old intro points before fetching the descriptor
 again. The old intro points won't notice that their circuits to the HS are
 gone until the entry guard experiences a TCP timeout and sends a destroy
 cell. On Linux this might take up to 30 minutes.
 So an application detecting that the connection to a HS broke (e.g. using
 ACKs) might use HSFORGET to avoid the described case.
 If #19522 gets fixed and a HS therefore sticks to it's intro points then
 this might not be necessary anymore.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/18620#comment:25>
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