Re: [tor-bugs] #33056 [Core Tor/Tor]: Tor relays fail to understand /etc/resolv.conf ipv6 lines with % in them

2020-05-21 Thread Tor Bug Tracker & Wiki 
#33056: Tor relays fail to understand /etc/resolv.conf ipv6 lines with % in them
-+
 Reporter:  arma |  Owner:  (none)
 Type:  defect   | Status:  closed
 Priority:  Medium   |  Milestone:  Tor: 0.4.4.x-final
Component:  Core Tor/Tor |Version:
 Severity:  Normal   | Resolution:  wontfix
 Keywords:  ipv6, libevent, 044-can  |  Actual Points:
Parent ID:   | Points:  1
 Reviewer:   |Sponsor:  Sponsor55-can
-+
Changes (by nickm):

 * status:  new => closed
 * keywords:  ipv6, libevent, 044-should => ipv6, libevent, 044-can
 * resolution:   => wontfix


Comment:

 This is a libevent issue; we can't do anything about it on our end.  The
 answer is "upgrade to a newer libevent when it is out."

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Re: [tor-bugs] #33056 [Core Tor/Tor]: Tor relays fail to understand /etc/resolv.conf ipv6 lines with % in them

2020-05-21 Thread Tor Bug Tracker & Wiki 
#33056: Tor relays fail to understand /etc/resolv.conf ipv6 lines with % in them
+--
 Reporter:  arma|  Owner:  (none)
 Type:  defect  | Status:  new
 Priority:  Medium  |  Milestone:  Tor:
|  0.4.4.x-final
Component:  Core Tor/Tor|Version:
 Severity:  Normal  | Resolution:
 Keywords:  ipv6, libevent, 044-should  |  Actual Points:
Parent ID:  | Points:  1
 Reviewer:  |Sponsor:  Sponsor55-can
+--
Changes (by asn):

 * sponsor:   => Sponsor55-can


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Re: [tor-bugs] #33056 [Core Tor/Tor]: Tor relays fail to understand /etc/resolv.conf ipv6 lines with % in them

2020-01-28 Thread Tor Bug Tracker & Wiki 
#33056: Tor relays fail to understand /etc/resolv.conf ipv6 lines with % in them
+--
 Reporter:  arma|  Owner:  (none)
 Type:  defect  | Status:  new
 Priority:  Medium  |  Milestone:  Tor:
|  0.4.4.x-final
Component:  Core Tor/Tor|Version:
 Severity:  Normal  | Resolution:
 Keywords:  ipv6, libevent, 044-should  |  Actual Points:
Parent ID:  | Points:  1
 Reviewer:  |Sponsor:
+--

Comment (by teor):

 Libevent seems to release every few months, so I think the answer to "when
 will there be a new libevent release" is "soon":
 https://github.com/libevent/libevent/releases

 Although I don't think this change was backported to libevent 2.1, so it
 might be a while before a new stable release:
 https://github.com/libevent/libevent/branches

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Re: [tor-bugs] #33056 [Core Tor/Tor]: Tor relays fail to understand /etc/resolv.conf ipv6 lines with % in them

2020-01-28 Thread Tor Bug Tracker & Wiki 
#33056: Tor relays fail to understand /etc/resolv.conf ipv6 lines with % in them
+--
 Reporter:  arma|  Owner:  (none)
 Type:  defect  | Status:  new
 Priority:  Medium  |  Milestone:  Tor:
|  0.4.4.x-final
Component:  Core Tor/Tor|Version:
 Severity:  Normal  | Resolution:
 Keywords:  ipv6, libevent, 044-should  |  Actual Points:
Parent ID:  | Points:  1
 Reviewer:  |Sponsor:
+--
Changes (by teor):

 * keywords:  ipv6 => ipv6, libevent, 044-should
 * points:   => 1
 * milestone:   => Tor: 0.4.4.x-final


Comment:

 I don't think this change is urgent, so I'm triaging it into Tor 0.4.4.

 It's also worth noting that:
 * tor exits need working DNS
 * tor non-exit relays and bridges only use DNS to discover their own
 address, and:
   * they are configured with a DNS name in the `Address` torrc option
 (failure is an error), or
   * their local hostname resolves via DNS (failure falls back to local
 interface APIs or directory X-Your-Address-Is headers)
 * tor clients don't depend on DNS for anything

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Re: [tor-bugs] #33056 [Core Tor/Tor]: Tor relays fail to understand /etc/resolv.conf ipv6 lines with % in them

2020-01-25 Thread Tor Bug Tracker & Wiki 
#33056: Tor relays fail to understand /etc/resolv.conf ipv6 lines with % in them
--+
 Reporter:  arma  |  Owner:  (none)
 Type:  defect| Status:  new
 Priority:  Medium|  Milestone:
Component:  Core Tor/Tor  |Version:
 Severity:  Normal| Resolution:
 Keywords:  ipv6  |  Actual Points:
Parent ID:| Points:
 Reviewer:|Sponsor:
--+

Comment (by arma):

 Good find!

 So it sounds like some future release of libevent will have this feature,
 and so eventually relay operators will get it. Do we know what version of
 libevent that will be?

 And in the meantime we at Tor have a choice about how we want to handle
 it. Here are some options:

 (A) Do nothing, it was only one user, hope that common distros have the
 new libevent before it really starts to matter.

 (B) Change Tor's error handling in the above log message, to check for a %
 character, and if it's present, say something more helpful, like that the
 warning is fine to ignore if they have other working nameservers, and if
 they really need that one, here's the version of libevent to upgrade to.

 (C) Teach Tor to work around libevent's missing feature by somehow parsing
 the line ourselves or something.

 I am fine with all three of these choices, and maybe there are other
 options to consider as well. Left to my own devices I would probably pick
 approach 'B'.

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Re: [tor-bugs] #33056 [Core Tor/Tor]: Tor relays fail to understand /etc/resolv.conf ipv6 lines with % in them

2020-01-25 Thread Tor Bug Tracker & Wiki 
#33056: Tor relays fail to understand /etc/resolv.conf ipv6 lines with % in them
--+
 Reporter:  arma  |  Owner:  (none)
 Type:  defect| Status:  new
 Priority:  Medium|  Milestone:
Component:  Core Tor/Tor  |Version:
 Severity:  Normal| Resolution:
 Keywords:  ipv6  |  Actual Points:
Parent ID:| Points:
 Reviewer:|Sponsor:
--+

Comment (by Hello71):

 
https://github.com/libevent/libevent/commit/9fecb59a94ef246088d7f3e0365c2fe80d0df2f4

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Re: [tor-bugs] #33056 [Core Tor/Tor]: Tor relays fail to understand /etc/resolv.conf ipv6 lines with % in them

2020-01-25 Thread Tor Bug Tracker & Wiki 
#33056: Tor relays fail to understand /etc/resolv.conf ipv6 lines with % in them
--+
 Reporter:  arma  |  Owner:  (none)
 Type:  defect| Status:  new
 Priority:  Medium|  Milestone:
Component:  Core Tor/Tor  |Version:
 Severity:  Normal| Resolution:
 Keywords:  ipv6  |  Actual Points:
Parent ID:| Points:
 Reviewer:|Sponsor:
--+
Description changed by arma:

Old description:

> We had a relay operator on irc just now who has this line in their
> /etc/resolv.conf:
> {{{
> nameserver fe80::7e2ebdff:fe99:4cb9%enp2s0
> }}}
>
> Apparently this is a totally normal thing: the % indicates a link local
> name server.
>
> Two more hints that % is a standard thing:
> * https://bugs.launchpad.net/ubuntu/+source/wide-dhcpv6/+bug/1620221 "The
> link local name servers should be suffixed with the scope, e.g. "%eth0"."
> * https://tools.ietf.org/html/rfc4007#section-11 "to specify an IPv6 non-
> global address without ambiguity, an intended scope zone should be
> specified as well."
>
> Tor is unable to handle this % syntax in a resolv.conf line:
> {{{
> Jan 25 17:03:00.171 [warn] eventdns: Unable to parse nameserver address
> fe80::7e2ebdff:fe99:4cb9%enp2s0
> }}}
>
> It's not as bad as it could be, because Tor skips that line and uses
> whatever other lines there are. But (a) maybe we're not doing as well as
> we can do, and (b) maybe there are situations where that's the only
> configured nameserver and everything works on the host except Tor
> doesn't.
>
> I think technically this might be a libevent bug (aka missing feature),
> since it's libevent's evdns_base_nameserver_ip_add() which calls
> evutil_parse_sockaddr_port() which helpfully explains that
> {{{
> /* recognized formats are:
>  * [ipv6]:port
>  * ipv6
>  * [ipv6]
>  * ipv4:port
>  * ipv4
>  */
> }}}
> none of which are the % syntax. But I will file it here a Tor ticket,
> since it's a Tor bug too, and then we can figure out where best to fix
> it.

New description:

 We had a relay operator on irc just now who has this line in their
 /etc/resolv.conf:
 {{{
 nameserver fe80::7e2ebdff:fe99:4cb9%enp2s0
 }}}

 Apparently this is a totally normal thing: the % indicates a link local
 name server.

 Two more hints that % is a standard thing:
 * https://bugs.launchpad.net/ubuntu/+source/wide-dhcpv6/+bug/1620221 "The
 link local name servers should be suffixed with the scope, e.g. "%eth0"."
 * https://tools.ietf.org/html/rfc4007#section-11 "to specify an IPv6 non-
 global address without ambiguity, an intended scope zone should be
 specified as well."

 Tor is unable to handle this % syntax in a resolv.conf line:
 {{{
 Jan 25 17:03:00.171 [warn] eventdns: Unable to parse nameserver address
 fe80::7e2ebdff:fe99:4cb9%enp2s0
 }}}

 It's not as bad as it could be, because Tor skips that line and uses
 whatever other lines there are. But (a) maybe we're not doing as well as
 we can do, and (b) maybe there are situations where that's the only
 configured nameserver and everything works on the host except Tor doesn't.

 I think technically this might be a libevent bug (aka missing feature),
 since it's libevent's evdns_base_nameserver_ip_add() which calls
 evutil_parse_sockaddr_port() which helpfully explains that
 {{{
 /* recognized formats are:
  * [ipv6]:port
  * ipv6
  * [ipv6]
  * ipv4:port
  * ipv4
  */
 }}}
 none of which are the % syntax. But I will file it here as a Tor ticket,
 since it's a Tor bug too, and then we can figure out where best to fix it.

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