# firewall plugin

## Overview

This plugin creates firewall rules to allow traffic to/from the host network interface given by "ifName".
It does not create any network interfaces and therefore does not set up connectivity by itself.
It is only useful when used in addition to other plugins.

## Operation
The following network configuration file
```
{
  "name": "mynet",
  "type": "firewall",
  "ifName": "cni0"
}
```

will allow the given interface to send/receive traffic via the host.

A successful result would simply be an empty result, unless a previous plugin passed a previous result, in which case this plugin will return that verbatim.

## Backends

This plugin supports multiple firewall backends that implement the desired functionality.
Available backends include `iptables` and `firewalld` and may be selected with the `backend` key.
If no `backend` key is given, the plugin will use firewalld if the service exists on the D-Bus system bus.
If no firewalld service is found, it will fall back to iptables.

When the `iptables` backend is used, the above example will create two new iptables chains in the `filter` table and add rules that allow the given interface to send/receive traffic.
When the `firewalld` backend is used, the above example will place the `cni0` interface into firewalld's `trusted` zone, allowing it to send/receive traffic.