[tor-bugs] #33796 [Core Tor/Tor]: socks: Prefer IPv6 by default on SOCKS port broke torsocks

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#33796: socks: Prefer IPv6 by default on SOCKS port broke torsocks
------------------------------+-----------------------------------
     Reporter:  dgoulet       |      Owner:  (none)
         Type:  defect        |     Status:  new
     Priority:  Medium        |  Milestone:  Tor: 0.4.3.x-final
    Component:  Core Tor/Tor  |    Version:
     Severity:  Normal        |   Keywords:  tor-dns torsocks ipv6
Actual Points:                |  Parent ID:
       Points:                |   Reviewer:
      Sponsor:                |
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 In commit `bf2a399fc0d90df76e091fa3259f7c1b8fb87781` we made all SocksPort
 to prefer IPv6 which means that any DNS resolution answer will pick IPv6,
 if exists, over IPv4.

 For torsocks, this is a problem because by default it tries to resolve an
 IPv4. This can be fixed _except_ when the libc call (ex: `getaddrinfo()`)
 is specifically requesting an IPv4 (`hints.ai_family = AF_INET`).

 There is currently no way for torsocks to ask tor, via the SocksPort, a
 specific INET family and thus torsocks receives back the IPv6 and can't
 handle it because the application was expecting an IPv4.

 So this example fails often as we have more and more Exits are able to
 resolve IPv6:

 {{{
 wget -4 some.url
 }}}

 And still many applications by default will request an IPv4 because they
 don't handle IPv6.

 Bottom line is that torsocks use case is broken for when an application is
 specifically requesting an INET family...

 As a reminder, torsocks can _not_ pass the hostname directly in the SOCKS
 connection because it hijacks libc calls and thus flow can only be 1) DNS
 resolution, 2) `connect()` with an IP address.

 I'm not sure what to do here... I think the ideal scenario would be to
 have a way for our "resolve" SOCKS extension to specify an address family
 value.

 For instance, the `F0` (`RESOLVE` command) would be "return whatever" and
 then we could extend to have `RESOLVE4` and `RESOLVE6`..... HACK-ish but
 those extensions are already a hack so...

 (That prefer IPv6 change went in 043)

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/33796>
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