[tor-bugs] #17873 [Tor]: replacing 0.0.0.0 listeners at runtime fails

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#17873: replacing 0.0.0.0 listeners at runtime fails
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 Reporter:  cypherpunks  |          Owner:
     Type:  defect       |         Status:  new
 Priority:  Medium       |      Milestone:  Tor: 0.2.8.x-final
Component:  Tor          |        Version:
 Severity:  Normal       |     Resolution:
 Keywords:  easy         |  Actual Points:
Parent ID:               |         Points:
  Sponsor:               |
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Changes (by teor):

 * priority:  Low => Medium
 * severity:  Minor => Normal


Comment:

 Replying to [comment:2 cypherpunks]:
 > Requiring a restart to change this setting might be OK, but exiting
 because of an "invalid config" doesn't seem OK to me. For remote machines
 that are only reachable via hidden service SSH, it can actually be
 extremely inconvenient/expensive.

 I see your point.

 > Is there any ticket about making it safer to reload the config, eg,
 falling back to the previously-read config if the new one fails?

 I don't think so, please feel free to open one.

 I'm not entirely sure how this would work, I wonder if it would be bad for
 security/privacy in some cases to not update to the latest config - like
 the one you reported in this ticket.

 > Regardless of that, loading carefully-tested known-to-be-valid configs
 should not cause tor to exit!

 We'd appreciate a patch that swaps the close and bind steps in
 retry_all_listeners/retry_listener_ports.

 The current code assumes that if the old and new addresses don't match,
 then binding to the new address before closing the old won't cause any
 conflicts. This assumption isn't true for:
 * 0.0.0.0
 * [::]
 * Binding to both IPv4 and IPv6 (is this even possible?)

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/17873#comment:3>
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