What is "firewalld"

FirewallD is a firewall management tool for Linux operating systems. It provides firewall features by acting as a front-end for the iptables packet filtering system provided by the Linux kernel. The name firewalld adheres to the Unix convention of naming system daemons by appending the letter “d”.

FirewallD is written in Python. It was intended to be ported to C++, but the porting project was abandoned in January 2015.