Requirements

1. Ansible installed:

sudo apt install python3
python3 -m ensurepip --upgrade
pip3 install ansible

Required variables

Review the variables as shown in defaults.

You can add a firewall definition to the variables for your host (../host_vars/[host_name].yaml), group of hosts (../group_vars/[group_name].yaml) using the following structure (see molecule.default.vars/test.yaml for an example):

# this variable point to the rules that are pushed to the remote host
# it is a dict of tables, with chain, with rules, see molecule/default/vars/test.yaml
nftables_ruleset:
  # keys of this become tables
  # they must be:
  # firewall family and name, e.g."
  "inet firewall":

    # description of the table
    comment: "firewall of device"

    chains:

      # name of the respective chain
      input:
        # name of the variable from nftables_rules
        # that you would like to put in this chain
        - input_hook
        - valid_connections
        - ...

  # another table with the same structure
  # valid families are things like inet, inet6, netdev, and inet,
  # see nftables docs for the full reference
  "inet foo":

# the potential rules are defined under `nftables_rules`
# every rule has two attributes:
# -> def: the definition of the rules or set of rules in valid nftables syntax
# -> depends_on: optional list of dependencies of variables from nftables_variables
# see molecule/default/vars/test.yaml for an example

nftables_rules:
  input_hook: >
    type filter hook input priority 0; policy drop;
  valid_connections:
    def: |
        ct state established, related accept
        ct state invalid drop

  new_connections:
    def: |
        ct state new accept


# these are the variable definition, which are included with depends_on
# make sure the keys match
# see molecule/default/vars/test.yaml for an example
nftables_variables:

  tcp_ports:
    comment: tcp ports configuration
    def: |
      {% if nftables_open_tcp_ports_global %}define OPEN_TCP_PORTS = { {{ nftables_open_tcp_ports_global | join(",") }} }{% endif +%}
      {% if nftables_open_tcp_ports_local %}define LOCAL_OPEN_TCP_PORTS = { {{ nftables_open_tcp_ports_local | join(",") }} }{% endif +%}
      {% if nftables_open_tcp_ports_vpn %}define VPN_TCP_PORTS = { {{ nftables_open_tcp_ports_vpn | join(",") }} }{% endif +%}

  ...

The ansible playbook will validate whether the correct variables are passed to the role using an argument_spec.

Example playbook

Minimal (assuming you passed variables elsewhere):

hosts:
  - foo
roles:
  - pimvh.nftables

TLDR - What will happen if I run this

• validate whether rules/some other variables are defined
• install nftables, and python interface
• create required nftable tables
• create dynamic tables as empty tables
• create an empty blocklist
• copy a nftables template to nftables directory
• edit nftables service to point to our new main file
• create script to reload firewall, which dumps tables outside of our control to files, and reloads the firewall after
• when nftables_abuseip_api_key is defined, add a script to pull the blocklist using their api, and make that a systemd service
• enable nftable service when requested
• uninstall iptables when requested

Future Improvements

• Simply structure of rules that needs to be passed
• Improve argument_specs for nftables_variables and nftables_ruleset