netplan accept-ra disables slaac

[Martin Pels]

Hello,

The netplan flag configuration "accept-ra" does not only enable or disable the use of router advertisements, but also stateless configuration of addresses. This makes it impossible to configure a host with only a static IPv6 address, but with a gateway received through RA's (equivalent to sysctl autoconf=0 and accept_ra=1).

[Šádek (ksadek36)]

I have the same problem here. We depend on RAs for gateway configuration as router belongs to our provider, but we utilize specific OUTBOUND IPv6 for our services.

[Ryan Harper (raharper)]

Thanks for filing the bug.

Can you provide the netplan you used?

Also, if possible, could you run:

mkdir /etc/systemd/system/systemd-networkd.service.d/
echo -e "[Service]\nEnvironment=SYSTEMD_LOG_LEVEL=debug" > /etc/systemd/system/systemd-networkd.service.d/10-debug.conf

Reboot and then provide the output from the journal like so?

journalctl -b 0 -o short-monotonic -u systemd-networkd.service

And tar up whatever is in /run/systemd/network/* ?

Lastly, if you do not specify accept_ra at all, does this affect the results?

Thanks!

[Martin Pels (martin-rodecker)]

Hi Ryan,

On 26/08/19 21:17, Ryan Harper wrote:
> Thanks for filing the bug.
>
> Can you provide the netplan you used?

netplan.io 0.97-0ubuntu1~18.04.1

> Also, if possible, could you run:
>
> mkdir /etc/systemd/system/systemd-networkd.service.d/
> echo -e "[Service]\nEnvironment=SYSTEMD_LOG_LEVEL=debug" > /etc/systemd/system/systemd-networkd.service.d/10-debug.conf
>
>
> Reboot and then provide the output from the journal like so?
>
> journalctl -b 0 -o short-monotonic -u systemd-networkd.service

See attached (netplandebug.log)

> And tar up whatever is in /run/systemd/network/* ?

See attached (run_systemd_network)

> Lastly, if you do not specify accept_ra at all, does this affect the results?

This gives the same result als specifying accept_ra=true. Stateless
autoconfig addresses are added as well as gateways received through
RA's. With accept_ra=false neither autoconfig addresses or RA gateways
are added.

The only difference is that with accept_ra=true the file in
/run/systemd/network/ shows 'IPv6AcceptRA=yes', whereas if accept_ra is
not specified this line is not shown.

I hope this helps.

Kind regards,
Martin

[Launchpad Janitor (janitor)]

[Expired for netplan because there has been no activity for 60 days.]

[Launchpad Janitor (janitor)]

[Expired for netplan.io (Ubuntu) because there has been no activity for 60 days.]

[Tom Hetmer (totocz)]

Can we get this reopened (and solved)?

Let's have this config

# This is the network config written by 'subiquity'
network:
  ethernets:
    eno1:
      dhcp4: false
      dhcp6: false
      addresses:
        - 2a09:e201:0:2:921b:eff:feae:82e5/64

What happens now is the system gets the static IPv6 AND autoconf.

    inet6 2a09:e201::921b:eff:feae:82e5/64 scope global dynamic mngtmpaddr noprefixroute
       valid_lft 2591614sec preferred_lft 604414sec
    inet6 2a09:e201:0:2:921b:eff:feae:82e5/64 scope global
       valid_lft forever preferred_lft forever

I know it's a bug on the network, but there should be a way to do autoconf=0 accept_ra=1.
systemd-networks is kinda weird and I didn't manage to configure it properly with

[IPv6AcceptRA]
UseAutonomousPrefix=no
UseOnLinkPrefix=no

It does nothing.
I don't want accept-ra: false because I'd like to keep using RA acquired gateway.

In Alpine it's as easy as

auto eth1
iface eth1 inet static
  address 2a09:e201:0:2:216:3eff:fe0d:10a6
  netmask 64

net.ipv6.conf.eth1.autoconf=0
net.ipv6.conf.eth1.use_tempaddr=0

There's something weird with netplan + networkd.

[Tom Hetmer (totocz)]

After testing on Arch (no netplan)

[IPv6AcceptRA]
UseAutonomousPrefix=no
UseOnLinkPrefix=no

in /etc/systemd/network/eth1.network will get applied.
Anywhere else it won't.

So it's up to netplan to add this config option so it can be generated into /run/systemd/network files.

[XSpielinbox (xspielinbox)]

I can still reproduce this issue with the newest Version of Netplan in Ubuntu 22.04 as well as Ubuntu 22.10.

If 'accept-ra: false' is set the systemd-networkd config contains 'IPv6AcceptRA=no'.
If 'accept-ra' is unset, the systemd-networkd config does not contain any 'IPv6AcceptRA' statement.
That is the only change I could find between these two options.

Independent of the config in systmed-networkd/Netplan 'sysctl net.ipv6.conf.<iface>.accept_ra' always returns 0. Also see LP#1862481 for that.

Also independent of the config in systmed-networkd/Netplan 'sysctl net.ipv6.conf.<iface>.autoconf' always returns 1. It is very unclear to me how setting 'accept-ra: false' in Netplan disables SLAAC, that is working when 'accept-ra' is unset or 'accept.ra: true' is set.

I agree, that this should not be the case. Additionally, I strongly suggest, that there is be a separate option to disable SLAAC, as I am currently unaware of any other method to disable SLAAC wouldn't it be for this very strange side effect of 'accept-ra'.

[Lukas Märdian (slyon)]

seems to be related to bug #1858503