Re: Emacs can't reach dx.doi.org?

[Simon Leinen <simon.leinen@gmail.com>]

On Mon, Mar 21, 2016 at 8:58 PM, Clément Pit--Claudel
<clement.pit@gmail.com> wrote:
> On 03/19/2016 05:23 AM, Andreas Schwab wrote:
>> Clément Pit--Claudel <clement.pit@gmail.com> writes:
>>
>>>   (url-retrieve
>>>    "http://dx.doi.org/10.1016/s0262-4079(08)62292-7"
>>>    (lambda (&rest args) (message "args: %S" args)))
>>>
>>> I get 'Contacting host: dx.doi.org:80', and nothing. After a few calls list-processes shows this:
>>
>> Do you have IPv6 connectivity problems?  What does `telnet dx.doi.org 80'
>> do?
>
> I'm running into this again today, and it seems that you were right! Thanks:
>
>     $ telnet dx.doi.org 80
>     Trying 2001:550:100:6::138:162...
>
> (hangs for a while)

Works from here:

  : leinen@macsl[foo]; telnet dx.doi.org 80
  Trying 2001:550:100:6::138:163...
  Connected to dx.doi.org.
  Escape character is '^]'.
  ^]
  telnet> close
  Connection closed.

> Is there anything I can do on my side to diagnose this?

traceroute/traceroute6?

You seem to have a public IPv6 address and/or an IPv6 default route,
because otherwise telnet and other programs wouldn't try to connect
over IPv6.  But maybe your IPv6 connectivity is broken/blocked by
firewall/nonexistent.  Or, if IPv6 generally works for you, there may
be a routing problem further "upstream".  As I said, traceroute{,6}
might help.  What is your IPv6 address? There are some IPv6 peering
issues/disputes that may cause disconnectivity between some parts of
the IPv6 Internet, maybe you are being hit by this.  I see dx.doi.org
behind Cogent, who are involved in these disputes.

While the routing issue certainly isn't an Emacs problem, it would be
nice if Emacs would notice the issue and quickly fall back to IPv4, as
per the recommendations in RFC 6555.  I assume IPv4 works for you?
i.e. telnet -4 dx.doi.org 80
-- 
Simon.

: 130leinen@macsl[foo]; traceroute6 -I dx.doi.org
traceroute6: Warning: dx.doi.org has multiple addresses; using
2001:550:100:6::138:162
traceroute6 to dx.doi.org (2001:550:100:6::138:162) from
2001:620:0:69::101, 64 hops max, 16 byte packets
 1  vpngw-b.switch.ch  15.884 ms  11.575 ms  10.809 ms
 2  swiofw1-v15.switch.ch  10.861 ms  9.493 ms  14.564 ms
 3  swiws2-v910.switch.ch  11.518 ms  11.757 ms  15.242 ms
 4  swiws1-v640.switch.ch  13.000 ms  16.052 ms  10.730 ms
 5  swiez1-10ge-4-15.switch.ch  11.239 ms  11.567 ms  22.094 ms
 6  swiba2-10ge-1-4.switch.ch  21.159 ms  10.761 ms  14.005 ms
 7  2001:978:2:3e::2:1  12.614 ms  15.255 ms  26.509 ms
 8  te0-0-0-1.agr12.zrh01.atlas.cogentco.com  17.263 ms  16.212 ms  21.287 ms
 9  *
    te0-7-0-35.ccr21.zrh01.atlas.cogentco.com  15.346 ms  15.956 ms
10  be2295.ccr41.par01.atlas.cogentco.com  33.689 ms  43.170 ms  30.533 ms
11  be2746.ccr41.jfk02.atlas.cogentco.com  103.163 ms  96.974 ms  100.221 ms
12  be2806.ccr41.dca01.atlas.cogentco.com  105.293 ms *  103.563 ms
13  te0-0-1-0.rcr21.iad03.atlas.cogentco.com  112.268 ms  108.030 ms  105.387 ms
14  te0-0-2-3.agr11.iad03.atlas.cogentco.com  110.695 ms  159.057 ms  106.802 ms
15  2001:550:100:6::138:162  104.891 ms  113.060 ms  122.931 ms