Controller should support more than 254 connected units

[cotosso]

Actual Behavior

The controller can currently connect up to 254 units (a /24 network)

Expected Behavior

The controller should support a maximum of approximately 4000 units (a /20 network)

Proposed solution

• Subnet Mask Extension: Allow the use of a subnet mask down to /20 (more than 4,000 units) with a parameterizable limit that can be modified via a prop.
• Bulk Actions: Limit the maximum number of units involved in UI bulk actions.

Additional Notes

• UI Impact: A very large number of units could become very difficult to manage with the current UI; that being said, do not modify the UI for now as it could be an overkill.

• Controllers unification:Users wishing to unify multiple controllers can migrate them manually over time.

[Tbaile]

QA:

• Fresh install:
  • install the controller using ghcr.io/nethserver/nethsecurity-controller:2.3.0-dev.5
  • check that in the configuration steps you can enter a network that can be max a /20 and min a /24
  • configure the module and connect a unit to the controller. Use a latest dev for the unit since otherwise you cannot access the UI.
• Update:
  • start a fresh stable instance of the controller
  • connect a unit to it
  • update the controller with ghcr.io/nethserver/nethsecurity-controller:2.3.0-dev.5
  • check that the unit is still reachable (nothing actually changed)
• Change VPN network
  • from the previous steps, now follow the instructions over at: https://docs.nethsecurity.org/pr-preview/pr-313/docs/administrator-manual/system/controller#controller_vpn_network-section
  • change the VPN network by expanding it, making sure that:
    • the action shouldn't let you change the network if it's outside the current set one
    • limits changes from /20 narrowing to /24
    • force works and skips these changes

Suggestion, instead of installing a dev unit and flashing, you can start with a clean 8.8.0 and use the following command to update the packages to allow access from the controller:

echo 'set repo_channel=staging' > /etc/apk/repositories.d/98-override.list && echo 'set endpoint=updates.nethsecurity.nethserver.org/${repo_channel}' >> /etc/apk/repositories.d/98-override.list && apk update && apk upgrade && rm /etc/apk/repositories.d/98-override.list