Comment 12 for bug 761558

On Fri, Jul 22, 2011 at 2:46 AM, Tore Anderson <email address hidden> wrote:
> 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.

My bad, I've just confirmed it is indeed the case: there is something
wrong in the LiveCD, and we'll definitely fix that. Connections should
definitely be set to IPv6 automatic (and optional) in both the LiveCD
and the subsequent install. I could have sworn things were fine in the
install; but the LiveCD case proves it is probably not the case and
needs some more work -- this bug will track that issue.

>> 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»!

That's not what I thought you meant, sorry if there was any confusion;
see below.

> 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,
[...]
> 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.

After re-reading this, I also got to the same conclusion (and also
with Stephane's careful analysis and testing); IPv4 could
theoretically be set to "optional" as well, *however*...

> 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.

While I agree that IPv6 deployment is being planned in carriers (and
ipv6-only also is), I believe majority still will remain, at least
until Oneiric + 1, that dual-stack IPv4 and IPv6 would be what will
get deployed if anything. Other networks with specific requirements
can obviously set a different setting, it's not very far in the
dialogs.

In other words, let's aim to change that in the release after Oneiric.

I was unfortunately bitten by a side-effect of setting IPv4 to
optional in dual-stack networks: users of dual-stack networks, when
networks fail to provide IPv4 addresses but do provide IPv6 (my
router's DHCP process had somehow stopped giving IPv4), will be faced
with a connection coming up because IPv6 is available. This will mean
they would get NM to say it's online, although only IPv6 is. They
would be able to connect to some services that do allow IPv6 (e.g.
Freenode, Google, some others), but wouldn't get access to IPv4-only
networks. In order to avoid cater to most users and avoid getting bugs
against NetworkManager for what is ultimately a network fault, I think
for the time being it is still best to keep the IPv4 setting to
required.

What do you think?

Mathieu Trudel-Lapierre <email address hidden>
Freenode: cyphermox, Jabber: <email address hidden>
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