@seb128 I have created a new bug report with links to the upstream
commits. The core of the issue is that IPv6 addresses are now being
added in the wrong order, so the kernel prefers SLAAC addresses over
DHCPv6 addresses, which should be the other way around.

As this is a breaking change in source-based IPv6 routing in an LTS
release, I think the impact is severe. In my opinion, this update should
never have reached stable, especially because this bug is known upstream
and fixed in a later version.

I'm already quite stressed how this will turn out at work after the
weekend. We use source-based ACL's on all of our firewalls, giving
static DHCPv6 leases to our client devices. Now all of a sudden those
addresses are no longer being used for outgoing traffic, but instead the
non-controllable SLAAC-addresses are. This will lock everyone out of all

The only way to get the proper addresses to be preferred again seems to
be to disable SLAAC on the router, because any local setting in
NetworkManager no longer works. I can disable SLAAC without issues at
home, because everything is 100% Ubuntu and Debian there. But in
environments with other OS'es that don't support DHCPv6 (like Android),
disabling SLAAC will break IPv6 on all such devices. Moreover, not
everybody controls their own routers, so this really isn't much of a

Other options would be to downgrade and apt-mark hold network-manager on
all Ubuntu 22.04 devices, or to completely change server firewall
infrastructure by whitelisting prefixes. As you can see, none of these
options sound appealing.

So regarding the regression potential: it has severely regressed IPv6
handling, and definitely *not* fixed things.

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