Systemd-networkd generated configuration is wrong when both ipv4 and ipv6 addresses are used

[Rémy Grünblatt]

Hello,

I'm using cloud-init in a proxmox environment, which exposes the configuration as a /dev/sr0.

The generated network-config looks like this:

```

[root@newgate:~]# more /mnt/*|cat
::::::::::::::
/mnt/meta-data
::::::::::::::
instance-id: 550761acf2ff3ad63bf33cab486c12131f73f405
::::::::::::::
/mnt/network-config
::::::::::::::
version: 1
config:
    - type: physical
      name: eth0
      mac_address: 'ae:98:25:fa:36:9e'
      subnets:
      - type: static
        address: '10.0.0.2'
        netmask: '255.255.255.255'
        gateway: '10.0.0.1'
      - type: static6
        address: '2a01:4f8:10a:19d2::4/64'
        gateway: '2a01:4f8:10a:19d2::2'
    - type: nameserver
      address:
      - '100.100.100.100'
      search:
      - 'rgrunbla.github.beta.tailscale.net'
::::::::::::::
/mnt/user-data
::::::::::::::
#cloud-config
hostname: newgate
manage_etc_hosts: true
ssh_authorized_keys:
  - ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIDwZm6kUsK/FrgJPzFi5AgvqIIYfy5S/Se4/rZgB4Edx remy@typhoon
chpasswd:
  expire: False
users:
  - default
package_upgrade: true
::::::::::::::
/mnt/vendor-data
::::::::::::::

```

The problem is that the generated systemd-networkd configuration is wrong. It looks like this:

```

[root@newgate:~]# cat /etc/systemd/network/10-cloud-init-eth0.network
[Match]
MACAddress=ae:98:25:fa:36:9e
Name=eth0

[Network]
DHCP=no
DNS=100.100.100.100
Domains=rgrunbla.github.beta.tailscale.net

[Address]
Address=10.0.0.2/32
Address=2a01:4f8:10a:19d2::4/64

[Route]
Gateway=10.0.0.1
Gateway=2a01:4f8:10a:19d2::2

```

In particular, the systemd-networkd manual says: "As in the [Network] section. This setting is mandatory. Each [Address] section can contain one Address= setting".

This results in errors in systemd:

```

[root@newgate:~]# systemctl status systemd-networkd --no-pager --all
● systemd-networkd.service - Network Configuration
     Loaded: loaded (/etc/systemd/system/systemd-networkd.service; enabled; vendor preset: enabled)
    Drop-In: /nix/store/5bj0s92f35hwc06mgjp9dzc0inncva6d-system-units/systemd-networkd.service.d
             └─overrides.conf
     Active: active (running) since Tue 2022-05-17 07:46:48 UTC; 5min ago
TriggeredBy: ● systemd-networkd.socket
       Docs: man:systemd-networkd.service(8)
   Main PID: 643 (systemd-network)
     Status: "Processing requests..."
         IP: 0B in, 392B out
         IO: 1.6M read, 0B written
      Tasks: 1 (limit: 2354)
     Memory: 2.9M
        CPU: 25ms
     CGroup: /system.slice/systemd-networkd.service
             └─643 /nix/store/9c90b5pmgj1pbdvgnalhldhfcj98p400-systemd-250.4/li…

May 17 07:46:48 newgate systemd[1]: Starting Network Configuration...
May 17 07:46:48 newgate systemd-networkd[643]: /etc/systemd/network/10-cloud-init-eth0.network:12: Address is incompatible, ignoring assignment: 2a01:4f8:10a:19d2::4/64
May 17 07:46:48 newgate systemd-networkd[643]: /etc/systemd/network/10-cloud-init-eth0.network: Gateway= without static address configured. Enabling GatewayOnLink= option.
May 17 07:46:48 newgate systemd-networkd[643]: lo: Link UP
May 17 07:46:48 newgate systemd-networkd[643]: lo: Gained carrier
May 17 07:46:48 newgate systemd-networkd[643]: Enumeration completed
May 17 07:46:48 newgate systemd[1]: Started Network Configuration.
May 17 07:46:48 newgate systemd-networkd[643]: eth0: Link UP
May 17 07:46:48 newgate systemd-networkd[643]: eth0: Gained carrier
May 17 07:46:49 newgate systemd-networkd[643]: eth0: Gained IPv6LL

```

[Chad Smith (chad.smith)]

Thanks for the background and analysis and making cloud-init better.
I can confirm the failure using the following steps:

cat > net.cfg <<EOF
version: 1
config:
    - type: physical
      name: eth0
      mac_address: 'ae:98:25:fa:36:9e'
      subnets:
      - type: static
        address: '10.0.0.2'
        netmask: '255.255.255.255'
        gateway: '10.0.0.1'
      - type: static6
        address: '2a01:4f8:10a:19d2::4/64'
        gateway: '2a01:4f8:10a:19d2::2'
    - type: nameserver
      address:
      - '100.100.100.100'
      search:
      - 'rgrunbla.github.beta.tailscale.net'
EOF

cloud-init devel net-convert -k yaml -p net.cfg -O networkd -d data -D ubuntu
cat data/etc/systemd/network/10-cloud-init-eth0.network
etc/systemd/network/10-cloud-init-eth0.network
[Match]
MACAddress=00:16:3e:76:25:ac
Name=eth0

[Network]
DHCP=no
DNS=100.100.100.100
Domains=rgrunbla.github.beta.tailscale.net

[Address]
Address=10.0.0.2/32
Address=2a01:4f8:10a:19d2::4/64

[Route]
Gateway=10.0.0.1
Gateway=2a01:4f8:10a:19d2::2

cp etc/systemd/network/10-cloud-init-eth0.network /lib/systemd/networkd

sudo service systemd-networkd restart
sudo service systemd-networkd status
..
May 19 20:04:06 dev-bb systemd[1]: Starting Network Service...
May 19 20:04:06 dev-bb systemd-networkd[769]: /lib/systemd/network/10-cloud-init
May 19 20:04:06 dev-bb systemd-networkd[769]: eth0: IPv6 successfully enabled
May 19 20:04:06 dev-bb systemd-networkd[769]: eth0: Gained IPv6LL
May 19 20:04:06 dev-bb systemd-networkd[769]: Enumeration completed
May 19 20:04:06 dev-bb systemd[1]: Started Network Service.
May 19 20:04:06 dev-bb systemd-networkd[769]: eth0: Could not set route: No rout
May 19 20:04:06 dev-bb systemd-networkd[769]: eth0: Configured
lines 1-18/18 (END)

```

[Alberto Contreras (aciba)]

This issue was already fixed by https://github.com/canonical/cloud-init/pull/1685

I added unit-test coverage in: https://github.com/canonical/cloud-init/pull/1747

[Showfom (showfom)]

We have the same problem with IPv4 and IPv6 both enabled

We should add another [Route] for the IPv4 gateway, or IPv4 is not working

[James Falcon (falcojr)]

Showfom, are you saying there's still related work to be done here? If so, can you please open a new bug for it?

[Showfom (showfom)]

James, I have submitted a new bug

https://bugs.launchpad.net/cloud-init/+bug/2003363

[James Falcon (falcojr)]

Tracked in Github Issues as https://github.com/canonical/cloud-init/issues/3975