[tor-bugs] #19522 [Core Tor/Tor]: HS intro circuit retry logic fails when network interface is down

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#19522: HS intro circuit retry logic fails when network interface is down
--------------------------+------------------------------
 Reporter:  asn           |          Owner:
     Type:  defect        |         Status:  new
 Priority:  Medium        |      Milestone:  Tor: 0.2.???
Component:  Core Tor/Tor  |        Version:
 Severity:  Normal        |     Resolution:
 Keywords:  tor-hs        |  Actual Points:
Parent ID:  #16387        |         Points:  1.5
 Reviewer:                |        Sponsor:  SponsorR-can
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Comment (by asn):

 Suggested fix #1:

   In the snippet above, if `rend_service_launch_establish_intro()` fails,
 we '''don't''' remove the intro point from `service->intro_nodes` or free
 it. Instead, we just `continue` to the next intro point. This way we will
 keep on retrying the old intro points every second, till the network comes
 back up.

 The ''main assumption'' in the above fix is that
 `rend_service_launch_establish_intro()`  can only fail for local reasons
 (bugs, OOM, interface down, etc.). If this is the case, then there is no
 reason to blame the intro point for this failure and we can just keep on
 retrying it till the local issues get resolved.

 We should verify the assumption above before implementing the suggested
 fix.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/19522#comment:1>
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