Support IPMasquerade

[waipeng]

Affected Puppet, Ruby, OS and module versions/distributions

• Puppet: all
• Ruby: all
• Distribution: all
• Module version: v4.1.0

How to reproduce (e.g Puppet code you use)

Use the following example

include wireguard

wireguard::interface { 'wg1':
  dport     => 51820,
  addresses => [{'Address' => '192.0.2.1/24'}],
  peers     => [
    {
       public_key  => 'foo==',
       preshared_key => '/22q9I+RpWRsU+zshW8skv1p00TvnEE6fTvPJuI2Cp4=',
       allowed_ips => ['192.0.2.2'],
    },
  ],
}

What are you seeing

The code creates the following /etc/systemd/network/wg1.network

[Match]
Name=wg1

[Network]
DHCP=no
IPv6AcceptRA=false
IPForward=yes

# for networkd >= 244 KeepConfiguration stops networkd from
# removing routes on this interface when restarting
KeepConfiguration=yes

[Address]
Address=192.0.2.1/24

Since systemd-networkd can do IP masquerade, we can get that all built in if we have the follow

[Network]
DHCP=no
IPv6AcceptRA=false
IPMasquerade=ipv4