[tor-bugs] #21044 [Core Tor/Tor]: ORPort self reachability test happens also when it shouldn't

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#21044: ORPort self reachability test happens also when it shouldn't
------------------------------+--------------------------------
     Reporter:  s7r           |      Owner:
         Type:  defect        |     Status:  new
     Priority:  Medium        |  Milestone:
    Component:  Core Tor/Tor  |    Version:  Tor: 0.3.0.1-alpha
     Severity:  Normal        |   Keywords:
Actual Points:                |  Parent ID:
       Points:                |   Reviewer:
      Sponsor:                |
------------------------------+--------------------------------
 I think we did not cover all cases when the self reachability test before
 publishing descriptors was introduced.

 I am running a bridge with `PublishServerDescriptor 0` and `ORPort
 127.0.0.1:443` because I want to run it just to do some responsible
 testing without hammering the public Guards used by other clients. The
 bridge is configured with `PublishServerDescriptor 0` so it means I don't
 need a descriptor, I don't intend to make the bridge (or relay) public.

 When a bridge is run in the conditions described above the log is spammed
 (exactly one log message at every 20 minutes) with:

 {{{
 [warn] Your server (PUBLIC_IP:443) has not managed to confirm that its
 ORPort is reachable. Relays do not publish descriptors until their ORPort
 and DirPort are reachable. Please check your firewalls, ports, address,
 /etc/hosts file, etc.
 }}}

 and

 {{{
 [warn] The IPv4 ORPort address 127.0.0.1 does not match the descriptor
 address PUBLIC_IP. If you have a static public IPv4 address, use 'Address
 <IPv4>' and 'OutboundBindAddress <IPv4>'. If you are behind a NAT, use two
 ORPort lines: 'ORPort <PublicPort> NoListen' and 'ORPort <InternalPort>
 NoAdvertise'.
 }}}

 What it did wrong:
 - It guessed the public IP address and tried to make the self test on that
 address, regardless it's not the address explicitly configured at
 `ORPort`. `Address` is not set in this setup.

 - Based on the second log message, I think it even overwritten the address
 used with `ORPort` with the public IP address that it guessed and built
 the descriptor.

 - It infinitely tries once every 20 minutes and logs a message that the
 descriptor cannot be published (and my intention based on the options
 configured is exactly not to publish one even if the tests were
 successful).

 What Tor should do:
 - Bypass the protocol to guess `Address` (the public IP address) when
 `ORPort` / `DirPort` is explicitly configured as a loopback address or NAT
 address. This will have a logic follow-up (which I think we already do,
 but want to make sure) like this:

 - Bypass self tests when `ORPort` / `DirPort` address is explicitly
 configured as a loopback address or NAT address (simplest thing would be
 to treat these cases as like `AssumeReachable 1` is set). Such addresses
 cannot be tested from the public internet anyway.

 - `PublishServerDescriptor 0` maybe should not even build a descriptor at
 all, or at least bypass the self tests in this case too, it does not make
 sense to try to test something we never want to publish. Or, only make 1
 attempt to test and log a message stating success or failure.

 #19919 is kind of related, it treats as it should the cases where `ORPort`
 is explicitly configured as a public address. In this ticket we cover an
 extension for cases where `ORPort` is a loopback or NAT address.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/21044>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online
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