Cockpit uses firewalld to interact with the system's firewall. No firewall configuration UI will be shown if firewalld is not installed.
Firewalld controls access to its APIs via PolicyKit. The user logged into Cockpit needs to have the appropriate permissions to view or modify the settings.
Cockpit can currently only show, add, and remove predefined firewalld services in the default zone.
To perform similar tasks from the command line, use firewall-cmd. For example, to get the same list of allowed services that Cockpit displays:
$ sudo firewall-cmd --list-services dhcpv6-client samba-client mdns ssh cockpit
To enable an additional service, use:
$ firewall-cmd --add-service pop3 success