In this directory, you can create the following filenames to add
custom rules at each section of the firewall script:

ipv4_custom_allowedports   ipv4_custom_mssclamp     ipv4_custom_proto
ipv4_custom_blockincoming  ipv4_custom_nat          ipv4_custom_routing
ipv4_custom_blockoutports  ipv4_custom_notrack      ipv4_custom_flush
ipv4_custom_conntrack      ipv4_custom_portforward  ipv4_custom_trust
ipv4_custom_blockip	   ipv4_custom_mark

ipv6_custom_flush          ipv6_custom_trust        ipv6_custom_mssclamp
ipv6_custom_blockoutports  ipv6_custom_allowedports ipv6_custom_conntrack
ipv6_custom_routing        ipv6_custom_blockincoming ipv6_custom_conntrack