Install shorewall-core by entering the following commands in the terminal:
sudo apt update sudo apt install shorewall-core
Description:
Shorewall core components
This package provides the core Shorewall components, which are required for the rest of the Shorewall packages to work. . There is not an especially good reason to have this package installed all by itself.
Homepage: http://www.shorewall.net
Version: 5.1.12.2-1
Section: universe/net