ipv6: temp address does not renew

[Andreas B <panden@gmail.com>]

Hi,

I'm very puzzled by the behaviour of ipv6 temp addresses on Debian 12.

Expected behaviour: as soon as a temp address becomes deprecated, a
new one is generated. This is the behaviour on Debian 11.

What actually happens: When the (first) temp address becomes
deprecated (in my case, this happens in practice 24h after boot, i.e.
after the interface is brought up), no new temp address is generated.

When the temp address is deprecated, outgoing connections start to use
the eui64 address. I.e., my mac address is being used on the internet.
This seems very weird to me, and cannot  possibly be intended?

I did some checking to try to find out why this is (not relevant as it
turns out, but still).

As far as I can tell, the relevant ipv6-settings is the same on both
Debian 11 and Debian 12:

net.ipv6.conf.all.temp_prefered_lft = 86400 (= 24h)
net.ipv6.conf.all.temp_valid_lft = 604800 (= 7d)
net.ipv6.conf.<if>.use_tempaddr = 2

NetworkManager version differences:

NetworkManager version in Debian 11: 1.30.6
NetworkManager version in Debian 12: 1.42.4

I wanted to downgrade the version on Debian 12, but no old version is available.

I then disabled NetworkManager and used /etc/network/interfaces (with
privext = 2) to administer my interface to see if that made a
difference, but the problem is the same.

Tested on two different machines; the problem exist on both.

Best regards,
Andreas