On Thu, 21 Jul 2011 19:30:34 -0000, Mathieu Trudel-Lapierre
<email address hidden> wrote:
> Dual-stack and single-stack connections are being tested extensively,
> but at this point the default is already (for an automatically created
> connection, that is) to have IPv6 at Automatic and optional. This
> doesn't apply to connections created by clicking the Add button in nm-
> connection-editor though; see
>
http://cgit.freedesktop.org/NetworkManager/NetworkManager/commit/?id=36db194ae95e35cc7b8f431ab984780dea24656d
> and http://git.gnome.org/browse/network-manager-
> applet/commit/?id=7068b0f7052078f101ad1eccc3456492f03fbb8b. Those will
> get in with the next upload of NM and nm-applet (anytime now).
> 
> Syslog looks correct except for the crash you got, and since you
> confirmed that with the correct settings for the interface the
> connection comes up properly, I'm not overly concerned by any of this
> (though the crash still needs fixing).

If you look closely at the log, you will see that NM does not do anything
at all about IPv6 until I manually change the settings at 15:37:19. Before
that point, the only thing related to IPv6 that is logged at all is from
avahi-daemon saying «Registering new address record for
2001:840:3033:10:230:1bff:febc:7f23 on eth0.*». That is the only thing that
disclose the fact that there is IPv6 service on the network in question.
NM, on the other hand, is ignoring IPv6 completely - in particular, the
«Activation (eth0) Beginning IP6 addrconf» log line never shows up before
the manual settings change.

The connection in question is *not* added manually with
nm-connection-editor, it was automatically created somehow. I don't know
how, precisely; all I did was to pop in the Live CD and boot - «Wired
Connection 1» was there when the system came up, I did not do anything to
create it, and its IPv6 mode was *NOT* «Automatic».

This all appears to run counter to your statement that IPv6 mode Automatic
should now be the default, and it is the reason why I call into question
that the corresponding work item in the desktop-side networking
enhancements blueprint is indeed 100% done.

> One thing to keep in mind is that ipv4 will remain *required*, at least
> for 11.10; and most probably until after the next LTS (because let's
> face it, IPv6 isn't set up everywhere, and things need to work magically
> for users who don't have ipv6... and also should fail magically when
> users don't actually get any dhcp responses). I'll however be happy to
> be convinced that the automatic failing of v4 interfaces that don't
> complete DHCP is no necessary. (Though I believe it makes everyone's
> life easier).

Wait, wait! I am absolutely *NOT* suggesting that things should not «work
magically for users who don't have ipv6»!

I merely suggest leaving the «require» box unchecked by default both for
IPv4 and for IPv6. NM will still require at least one method to succeed in
order for the overall connection to succeed. If the user don't have IPv6,
well, then the IPv6 method will obviously fail every time, in turn making
IPv4 success a necessity for the overall connection to succeed. So for the
IPv4-only users, there will be absolutely *no change in behaviour* by
leaving the «require IPv4» box unchecked by default. In the IPv4-only case,
the connections *will* «fail magically when users don't actually get any
dhcp[v4] responses», so I think your worries are unfounded, at least I
cannot see how leaving both «require» boxes unchecked will cause any
problems for any user, regardless of whether his network is IPv4, IPv6, or
dual-stack.

On the other hand, leaving the «require IPv4» box checked will cause
problems for IPv6 users that have no IPv4 service. While this is perhaps
not too common today, several carriers have announced plans to deploy
IPv6-only service (with NAT64/DNS64). I've already mentioned T-Mobile USA,
and also Network Norway here in my home country and Mobiltel in Slovenia is
doing the same. Verizon Wireless (USA) is mandating IPv6 support for
devices on their LTE network, while leaving IPv4 support optional.

I cannot predict exactly how common IPv6-only networks will be in the
future, but in any case - IPv6-only networks already exist, and I cannot
see what possible harm could be caused by having Ubuntu/NM support these
out of the box by having the «require IPv4» box unticked. And, for what
it's worth, other major operating system do support IPv6-only networks out
of the box (in particular: Microsoft Windows Vista and 7, Apple Mac OS X
Snow Leopard and Lion, as well as recent Apple iOS for the iPad/iPhones).
Ubuntu/NM should follow suit, IMO.

Tore