slackbuilds_ponce/network/shorewall6

Shorewall6 (IPv6 support package for shorewall)

The Shoreline Firewall, more commonly known as "Shorewall", is a
Netfilter (iptables) based firewall that can be used on a dedicated
firewall system, a multi-function gateway/router/server or on a
standalone GNU/Linux system.

This is the IPv6 part of Shorewall. It only provides IPv6 support.
The IPv6 part is started by /etc/rc.d/rc.shorewall6 from rc.firewall 
(provided by shorewall-common) if both are executable.
rc.shorewall provided by shorewall-common will only start the IPv4
part of the firewall. Both can run simultaneously.

You will also need the shorewall-common and shorewall-perl packages.
Note that you cannot use the shell compiler to have IPv6 support.