[tor-bugs] #16069 [Tor]: ipv4 + ipv6 exit : v6 policy is displayed twice, v4 isn't displayed

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#16069: ipv4 + ipv6 exit : v6 policy is displayed twice, v4 isn't displayed
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     Reporter:  toralf    |      Owner:
         Type:  defect    |     Status:  needs_review
     Priority:  critical  |  Milestone:  Tor: 0.2.7.x-final
    Component:  Tor       |    Version:  Tor: 0.2.7
   Resolution:            |   Keywords:  026-backport, ipv6, PostFreeze027
Actual Points:            |  Parent ID:
       Points:            |
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Comment (by teor):

 Replying to [comment:30 teor]:
 > Replying to [comment:29 nickm]:
 > > okay, thoughts!
 > >
 > > {{{
 > > +      log_notice(LD_GENERAL,
 > > +                 "accept/reject * expands into rules which apply to
 all IPv4 "
 > > +                 "and IPv6 addresses.");
 > > }}}
 > >
 > > Maybe this should:
 > ...
 > >    * tell the user what to do if they only wanted it to apply to IPv4?
 > >    * not happen once per policy line per hup. :)
 > >    * Give the user some way to avoid the message if they really did
 mean "all ipv4 and ipv6".
 >
 > Hmm, yes, this is a complex one to fix. I suggest a split solution:
 >  * downgrading the severity of the every-line-every-hup message to INFO
 or DEBUG
 >  * telling the user to use *4 for IPv4 or *6 for IPv6
 >
 > Then creating another message that is NOTICE that only occurs once per
 torrc parse when:
 >  * the policy has an `accept *:*` or `reject *:*` line
 >  * other lines occur after that line (and will be ignored)
 > We can then create a message telling the user:
 >  * that lines after `accept/reject *:*` are being ignored
 >  * to use *4 for IPv4 or *6 for IPv6 or put `accept/reject *:*` at the
 end of the policy to silence this notice
 >
 > For toralf's torrc and similar torrcs:
 > * this patch makes the IPv6 section would now be IPv6 only
 > * the accept/reject section would only apply to IPv4 due to `ExitPolicy
 reject6 *:*` at the end of the accept6/reject6 section
 > * no warnings would be issued, as `reject *:*` occurs last
 >
 > If someone goes against the advice to end with `accept/reject *:*`, and
 puts `accept6/reject6/accept/reject` after an `accept/reject *:*`, then
 they will get this NOTICE once on every torrc parse.

 Now that I think about it, any ExitPolicy lines after `accept/reject *:*`
 are almost certainly a misconfiguration. Should we elevate them to WARN?

 (Note we won't WARN on policies of the form `accept *:N,reject *6:N,accept
 *:*`. I think this is ok, as it's unclear if they are intentional or not,
 and deciding whether they are or not is non-trivial. We could NOTICE/INFO
 when rules override each other, but this is often intentional. Maybe we
 coulod issue a single NOTICE with the resultant policy per torrc parse?)

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/16069#comment:32>
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