Netplan default routes does not accept 0/0 notation

[Jason Leschnik]

The documentation `man netplan` indicates that {default, 0/0, 0.0.0.0/0} are all equivalent tokens for the default route.

Documentation
=============
`man netplan`
<snip>
                routes:
                - to: default # could be 0/0 or 0.0.0.0/0 optionally
                  via: 10.0.0.1
</snip>

Configuration
=============
network:
  version: 2
  renderer: networkd
  ethernets:
    enp0s31f6:
      dhcp4: no
      addresses:
        - 192.168.1.11/26
      routes:
        - to: 0/0 <<<<<<<<<<<< (Ok when 0.0.0.0/0 or default)
          via: 192.168.1.1
          on-link: true
      nameservers:
        addresses: [1.1.1.3, 1.0.0.3]

Error
=====
When using `0/0` notation in netplan configuration, the follow error occurs.

<snip>
jason@HIDDEN:~$ sudo netplan apply
/etc/netplan/00-installer-config.yaml:10:15: Error in network definition: invalid IP family '-1'
        - to: 0/0
              ^
</snip>

Version
=======
jason@HIDDEN:~$ dpkg --list | egrep netplan
ii libnetplan0:amd64 0.105-0ubuntu2~22.04.1 amd64 YAML network configuration abstraction runtime library
ii netplan.io 0.105-0ubuntu2~22.04.1 amd64 YAML network configuration abstraction for various backends

Seen on a fresh install of 22.04.1 LTS Server

<snip>
jason@HIDDEN:~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 22.04.1 LTS
Release: 22.04
Codename: jammy

jason@HIDDEN:~$ uname -a
Linux HIDDEN 5.15.0-53-generic #59-Ubuntu SMP Mon Oct 17 18:53:30 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
</snip>

[Jason Leschnik (jleschnik)]

Seen on a fresh install of 22.04.1 LTS Server, Issue also seen in latest 22.10 (kinetic) Server AMD64

<snip>
jason@HIDDEN:~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 22.04.1 LTS
Release: 22.04
Codename: jammy

jason@HIDDEN:~$ uname -a
Linux HIDDEN 5.15.0-53-generic #59-Ubuntu SMP Mon Oct 17 18:53:30 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
</snip>

[Lukas Märdian (slyon)]

Alright, let's fix the documentation right now and keep the bug open to eventually accept the 0/0 notation as well.

[Lukas Märdian (slyon)]

https://github.com/canonical/netplan/commit/53e33fc716be10498f2fe789114e9339a38b281d