[tor-bugs] #19919 [Core Tor/Tor]: If ORPort address is publicly routable, use it to guess Address

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#19919: If ORPort address is publicly routable, use it to guess Address
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 Reporter:  teor          |          Owner:
     Type:  defect        |         Status:  new
 Priority:  Medium        |      Milestone:  Tor: 0.2.???
Component:  Core Tor/Tor  |        Version:  Tor: 0.2.5.10
 Severity:  Normal        |     Resolution:
 Keywords:  030-proposed  |  Actual Points:
Parent ID:                |         Points:  1
 Reviewer:                |        Sponsor:
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Comment (by teor):

 Replying to [comment:3 s7r]:
 > I think this ticket can fix the behavior permanently by assuming
 `Address` = The first *Advertised* ORPort (and DirPort?)of course publicly
 routable, unless otherwise explicitly set by the user in torrc.

 Let's just use ORPort for consistency between IPv4 and IPv6.
 If the user sets a different DirPort address, #13953 in 0.2.9 will warn
 them.
 And if they set the same one, that's perfectly ok.

 > Also, I think it's fine to also assume `OutboundBindAddress` is the same
 IP address (first publicly routable Advertised ORPort), unless otherwise
 explicitly set in torrc. This can apply to both IPv4 and IPv6 without any
 problems.

 Not when the relay is behind a NAT: OutboundBindAddress is the *internal*
 address.
 And if we use this default, there's no way to specify "your default
 interface", which is the current default behaviour. Unless there's a
 specific issue here that's causing confusion, let's just leave this alone.
 Or tackle it in a separate ticket.

 > If there's no IP address set with ORPort, and Address is not set,
 maintain the current behavior to guess `Address` and build the descriptor
 - the current behavior to guess `Address` is not broken in any way, to the
 contrary it works good, we just need to add this improvement for boxes
 with multiple public IP addresses and/or multiple Tor instances.

 We can do this, it just involves adding a small amount of code to
 `resolve_my_address()`, right before we use `get_interface_address()` to
 do the guess, we should instead use the first advertised IPv4 ORPort
 address from `get_first_advertised_addr_by_type_af(CONN_TYPE_OR_LISTENER,
 AF_INET);`

 (There's some duplicate code in `resolve_my_address()`, let's refactor it
 out before changing it.)

 The code might be similar to
 `router_check_descriptor_address_port_consistency()`, but will likely be
 much simpler.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/19919#comment:4>
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