python.org coming back as unreachable in Dillo (IPv6 routing error?)

["Martin v. Löwis"]

> Have any network changes taken place at python.org (particularly IPv6 or
> DNS related) recently?

Yes, python.org has IPv6 connectivity now, and many systems (except for
mail) have IPv6 DNS entries (AAAA).

> Some of the configuration details from my machine:
> 
> tim at rubbish:~$ ip -f inet6 route
> fe80::/64 dev eth0  metric 256  expires 21252543sec mtu 1500 advmss 1440
> hoplimit 4294967295

Ok, so you don't have IPv6 connectivity, right? You can reach the
link-local network fe80::/64, but none of the global IPv6 internet
(2000::/3).

> tim at rubbish:~$ traceroute -6 docs.python.org
> traceroute to docs.python.org (2001:888:2000:d::a2), 30 hops max, 40
> byte packets
> connect: Network is unreachable

Right. Your IP stack determines that it has no v6 route to
docs.python.org (or any other IPv6 system in the world), so it reports
"network unreachable".

> If output of other commands would be helpful, just ask as I don't know
> enough about IPv6 to troubleshoot the best solution to this.

If you want to use IPv6 connectivity, you need to get it from somewhere,
e.g. from your ISP (although chances are high that your ISP doesn't
offer IPv6 connectivity right now - you could then try a tunnel broker
such as www.sixxs.net).

> It may be possible to just disable IPv6, but it would be nice to allow
> IPv6 to remain enabled *and* configured correctly :)

You shouldn't need to do anything. It should be no problem that you
can't reach www.python.org through IPv6, since all your applications
will immediately fall back to using IPv4 on their own.

It may be that some application misbehaves, i.e. it tries to get an
IPv6 connection, which it can't, and then gives up. This would be
very bad programming, and the authors should never had added IPv6
support to that application in the first place (applications that
predate IPv6 only use gethostbyname, only find IPv4 addresses, and
never even try IPv6).

Regards,
Martin