22.04 DHCPv6 IPv6 broken (at least on Oracle OCI)

[Tim K.]

Ubuntu 22.04.2 LTS
kernel 5.15.0-1038-oracle
systemd 249.11-0ubuntu3.9

After an update a couple weeks ago, Ubuntu 22.04 can no longer get IPv6 via DHCPv6 systemd-networkd, at least on Oracle OCI, but there are also other similar reports, e.g.

https://ubuntuforums.org/showthread.php?t=2487465&p=14146758

Oracle seems to be aware of the issue but they claim it's a Ubuntu 22.04 bug:

https://community.oracle.com/customerconnect/discussion/687610/oci-ipv6-address-not-assigned-to-oci-ubuntu-instance-by-dhcp

The workaround to assign a static IPv6 is not great when managing multiple cloud instances.

[Tim K. (tkubnt)]

Running `sudo dhclient -6 <interface>` appears to work, the problem seems to be with the systemd-networkd DHCPv6 client.

[Dominic (triatic)]

Oracle seem to have started sending invalid bytes at the end of dhcpv6 packets.

Systemd has just issued a patch to work around this.

Can this patch be backported into Ubuntu 22.04?

https://github.com/systemd/systemd/commit/1d2b93ff89f28b18c222321c8c7bc48be2185375

[Nick Rosbrook (enr0n)]

This does seem like a reasonable thing to backport, yeah.

The patch does not actually apply to v249.11 cleanly, but from a quick look around this is just because of some re-factoring and moving things around. So it should be simple to adapt the patch for the v249.11 codebase.

I will look into patching and testing this out myself. I don't currently have access to Oracle OCI, however.

[Nick Rosbrook (enr0n)]

Did Oracle make any changes around this or is it still an issue? I have not had the time to try and test this or access to OCI.

[Jan De Luyck (jdeluyck)]

As far as I'm aware nothing has changed on OCI.

[Dominic (triatic)]

Oracle seem to have corrected the DHCPv6 server. When I load up an unmodified stock instance of Ubuntu, I now get an IPv6 address immediately like I did before they broke it.

[Tim K. (tkubnt)]

Interesting because Oracle claimed that it was Ubuntu/systemd that was broken, not their DHCPv6 server, their argument was that the `dhclient -6` works fine.

[Dominic (triatic)]

It eventually became apparent that Oracle started appending a null byte to DHCPv6 packets a few weeks ago. `dhclient -6` is more tolerant of malformed DHCPv6 packets than networkd's DHCPv6 client.

[Jan De Luyck (jdeluyck)]

I just tried rebooting my OCI ubuntu 2204 box. Still no ipv6 address until I run dhclient -6.

[Brian Murray (brian-murray)]

Ubuntu 23.04 (Lunar Lobster) has reached end of life, so this bug will not be fixed for that specific release.

[Nick Rosbrook (enr0n)]

The mentioned fix is included in v255, which is now in Noble.