DHCPv6 *still* broken for F17 alpha

[Tore Anderson]

* Paul Wouters

> Can we please address the following bug that is almsot two years old.
> This bug causes long delays for people enabling IPV6, and causes
> Fedora to not get any connectivity on IPv6 only networks, unless you
> disable/reconfigure ip6tables manually

I find the fact that this bug is not yet fixed quite unbelievable.
Ubuntu, Windows, Mac OS X, and iOS all allow DHCPv6 by default with no
apparent ill effects. When you also take into account that DHCPv4 and
ICMPv6 Router Advertisements (which can be used for similar
auto-configuration of IPv6 network connectivity) are allowed by default
in Fedora, the entire situation becomes borderline bizarre. What on
earth is it about DHCPv6 specifically that causes Fedora to consider it
too insecure to be allowed by default?

However, this is not the only problem related to IPv6. I just tested the
F17 Alpha Live CD, and one particular egregious issue is that by
default, the toggle «Require IPv4 addressing for this connection to
complete» is enabled in NM's connection profiles. This essentially means
that IPv6-only networks are not supported out by default. If I try to
connect the F17 Alpha to an IPv6-only WLAN (not making any changes to the
default settings), the connection is successfully activated and remains
fully functional for about 40 seconds, at which point NM gives up on
waiting for replies from the non-existent DHCPv4 server. Then the entire
connection is torn down, IPv6 included, before the process starts over
again in a seemingly endless loop.

There is no good reason for leaving the «Require IPv4» setting default
enabled as far as I can tell. At least one protocol must still succeed
even with both «Require IPv4» and «Require IPv6» disabled, so for the
99.5% of users that have no IPv6, IPv4 will still remain actually
required, even if the setting in the connection profile is disabled.
(Also, for what it's worth, Windows, Mac OS X, and iOS will all
successfully connect to an IPv6-only network when using their default
settings.)

I have a two-year old bug report about this problem too:

https://bugzilla.redhat.com/show_bug.cgi?id=538499

I have submitted patches to fix the problem:

http://mail.gnome.org/archives/networkmanager-list/2011-August/msg00063.html
http://mail.gnome.org/archives/networkmanager-list/2011-August/msg00062.html

But still the problem remains. I don't know what else I can do to
improve the situation. It is really, really frustrating.

When ranting about the sad state of affairs of IPv6 support in Fedora
like I do now, I like to remind people about the following statement:

> 4.2.2. Enhanced IPv6 support in NetworkManager
> For non-GUI users, and those that use ifcfg files directly,
> NetworkManager should bring up the interface with IPv6 connectivity
> correctly at boot. No modification of the ifcfg files should be
> necessary.
> For GUI users, a new IPv6 tab will appear in the connection editor
> which will allow for control if the IPv6 settings similar to control
> of IPv4 settings already. After selecting the configuration method
> (auto is the default, which will honor router-advertisements and
> attempt to retrieve DNS information with DHCPv6 information-only
> mode) and entering any additional settings they may wish to use, then
> saving the connection, activating that connection should configure
> the interface fully with IPv6 as requested by the user.

That's from the Fedora 12 release notes. Sounds good, right? Only
problem is, it was completely and utterly false. Today, more than two
years and four releases later, it still is false. *sigh*

> It would be REALLY nice if we can get this into F17 this time.

+1

The changes required to make Fedora properly support IPv6 out of the box
are few and trivial. Please don't drag them out for yet another release.
I'd be more than happy to help test and verify.

-- 
Tore Anderson