[tor-bugs] #17901 [Tor]: Tor would bind ControlPort to public ip address if it has no localhost interface

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#17901: Tor would bind ControlPort to public ip address if it has no localhost
interface
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 Reporter:  s7r                        |          Owner:  teor
     Type:  defect                     |         Status:  assigned
 Priority:  High                       |      Milestone:  Tor:
Component:  Tor                        |  0.2.8.x-final
 Severity:  Major                      |        Version:  Tor: 0.2.7.6
 Keywords:  027-backport 026-backport  |     Resolution:
Parent ID:                             |  Actual Points:
  Sponsor:                             |         Points:
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Comment (by yawning):

 Replying to [comment:16 teor]:
 > Instead of resolving localhost, we could look through all the interfaces
 and find the first address present on the system that:
 > * is 127.0.0.1, or
 > * is in 127/8.
 >
 > For stability, it would make sense to choose the numerically lowest
 valid 127/8 address.
 > (That is, exclude 127.0.0.0, and choose the address that is closest to
 127.0.0.1.)

 On Linux, when you query the interfaces, you can check the per-interface
 flags for `IFF_LOOPBACK`.  On systems where this information is readily
 available (I think we even already have code that uses the relevant
 ioctl), we should use that to restrict the set of candidate addresses.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/17901#comment:18>
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