net: Passthough v2 netconfigs in netplan systems

[aciba90]

Proposed Commit Message

net: Passthough v2 raw net_conf in netplan systems

Adhere to Netplan Passthrough documented behavior,
not limiting v2 netplan configs to the subset of
props that cloud-init supports.

LP: #1978543

Additional Context

SC-1120
https://bugs.launchpad.net/cloud-init/+bug/1978543
Netplan Passthrough

Test Steps

cat > /tmp/lp1978543.yaml <<EOF
network:
  version: 2
  ethernets:
    enp0s3:
      dhcp4: false
      addresses: [10.0.4.10/24]
      nameservers:
        addresses: [10.0.4.1]
      routes:
      - to: default
        via: 10.0.4.1
        metric: 100
EOF

lxc init ubuntu-daily:jammy lp1978543
lxc file push /tmp/lp1978543.yaml lp1978543/etc/cloud/cloud.cfg.d/custom-networking.cfg
lxc file push /tmp/lp1978543.yaml lp1978543/root/
lxc start lp1978543
lxc exec lp1978543 -- cloud-init status --wait

lxc exec lp1978543 -- grep -in valueerror /var/log/cloud-init.log
# No errors found
$ lxc exec lp1978543 -- cat /etc/netplan/50-cloud-init.yaml
...
network:
    ethernets:
        enp0s3:
            addresses:
            - 10.0.4.10/24
            dhcp4: false
            nameservers:
                addresses:
                - 10.0.4.1
            routes:
            -   metric: 100
                to: default
                via: 10.0.4.1
    version: 2

lxc exec lp1978543 -- python3 -m cloudinit.cmd.main devel net-convert -m enp0s3,AA -O netplan --k yaml -p lp1978543.yaml -D ubuntu -d out
# No errors found

$ lxc exec lp1978543 -- cat out/etc/netplan/50-cloud-init.yaml
...
network:
    ethernets:
        enp0s3:
            addresses:
            - 10.0.4.10/24
            dhcp4: false
            nameservers:
                addresses:
                - 10.0.4.1
            routes:
            -   metric: 100
                to: default
                via: 10.0.4.1
    version: 2

Checklist:

• My code follows the process laid out in the documentation
• I have updated or added any unit tests accordingly
• I have updated or added any documentation accordingly

[TheRealFalcon]

I left two comments inline. Neither are strongly held though. Otherwise, looks good.

[TheRealFalcon]

Since most of this method is doing the same thing as the beginnning of _write_network_state, I think it might make more sense to fetch the renderer one time at the beginning of apply_network_config and pass it where it's needed.

[aciba90]

Done.

[TheRealFalcon]

I don't like how the network rendering abstraction is leaking into the distro code here. Do you think it's possible to push this section of code down into either parse_net_config_data or even into NetworkStateInterpreter?

[aciba90]

Logic moved to NetworkStateInterpreter. The downside is that we have to pass the renderer around, but it looks more cohesive in this way. Thanks for the comment.

[aciba90]

Thanks, @TheRealFalcon, for the review. I have addressed the comments and this PR is ready to be reviewed.

[TheRealFalcon]

Thanks @aciba90 , nice work here.

The isinstance checks feel a little awkward. Long term, it might make sense for us to add a name property to the renderers and check that instead, but not required for this PR.