Reuse and reallocate TCP/UDP port range

[DavidePrincipi]

The current implementation of TCP and UDP ports allocation has two limitations:

1. Modules like NethVoice allocates a wide range of port numbers, leading to possible node port exhaustion. When an instance is removed, used ports must be reclaimed by the node agent.
2. By time, the number of ports required by a module may change. For instance, Mattermost received an additional TCP port for the Calls plugin. As the ports are allocated by the add-module action, the only way to require more ports is with backup/restore or instance clone.

Proposed solution

• [x] Reclaim and reuse a port range after an instance is removed.
• [x] Implement a node action that a module can invoke to receive a new range of ports (both TCP and UDP).
• [x] Migrate existing range allocations from module/ID/environment keys to the new (trusted) allocation storage

Alternative solutions

This feature is required. Keeping things as they are makes difficult to install NethVoice and manage the update of applications that increase their port requirements.

See also

Discussion https://mattermost.nethesis.it/nethesis/pl/5s131bmj7jdwzj7gaogukb5z6a

[DavidePrincipi]

Acceptance tests

• [x] Upgrade an existing system. Existing TCP and UDP ports allocation are migrated to /var/lib/nethserver/node/ports.sqlite DB for each cluster node.
• [x] Redis keys *_ports_sequence are removed.
• [ ] Modules with role portsadm can run allocate-ports and deallocate-ports actions on the local node agent.
• [ ] Port ranges are allocated without conflicts.
• [ ] Port ranges are deallocated and can be reallocated later.

Useful commands

Dump the ports.sqlite DB with

podman run -i --rm --volume /var/lib/nethserver/node/state/ports.sqlite:/srv/ports.sqlite:z alpine ash -c 'apk add sqlite ; sqlite3 /srv/ports.sqlite' <<<"SELECT *, 'tcp' FROM TCP_PORTS UNION SELECT *, 'udp' FROM UDP_PORTS;"