I'm guessing we should also allow IPv6 control as well here. Something like:

```
if node['platform'] == 'debian'
  sysctl_param 'net.ipv4.ip_forward' do
    value 1
    only_if { node['docker']['ipv4_forward'] }
  end
  sysctl_param 'net.ipv6.conf.all.forwarding' do
    value 1
    only_if { node['docker']['ipv6_forward'] }
  end
end
```