Configure a Wireguard interface (wg)

Wireguard is a very promising VPN technology but is currently (Alpine 3.9.0) not stable and thus only available via the edge/testing repository. To be able to use it you will need to install a kernel from the edge/testing repository including all the out of tree modules you like to use. This mean when you are running a stable system you will have to pin the edge/testing repository in your repositories file and install it by:

apk add linux-vanilla (or linux-virt)
apk add wireguard-vanilla (or wireguard-virt)

The official documents from wireguard will show examples of how to setup an inteface with the use of wg-quick. In this howto we are not going to use this utility but are going to use the plain wg command and busybox ifupdown.

apk add wireguard-tools-wg

Now that you have all the tools installed we can setup the interface. The setup of your interface config is out of the scope of this document, you should consult the manual page of wg.

After you have finished setting up your wgX interface config you can add it to your /etc/networking/interfaces:

auto wg0
iface wg0 inet static
    address x.x.x.x
    netmask 255.255.255.0
    pre-up ip link add dev wg0 type wireguard
    pre-up wg setconf wg0 /etc/wireguard/wg0.conf
    post-up ip route add x.x.x.x/24 dev wg0
    post-down ip link delete dev wg0

This config will do:

bring the wireguard interface up
assign a config to this interface (which you have previously created)
setup the interface address and netmask
add the route ones the interface is up
remove the interface when it goes down