Fix detection of wireguard kernel module on non-amd64 archs (#200)

iface/iface_linux.go

@@ -1,16 +1,42 @@
 package iface
 
 import (
+	"errors"
 	"fmt"
+	"math"
+	"os"
+	"syscall"
+
 	log "github.com/sirupsen/logrus"
 	"github.com/vishvananda/netlink"
-	"os"
+)
+
+const (
+	wireguarModuleName = "wireguard"
 )
 
 type NativeLink struct {
 	Link *netlink.Link
 }
 
+func WireguardModExists() bool {
+	link := newWGLink("mustnotexist")
+
+	// We willingly try to create a device with an invalid
+	// MTU here as the validation of the MTU will be performed after
+	// the validation of the link kind and hence allows us to check
+	// for the existance of the wireguard module without actually
+	// creating a link.
+	//
+	// As a side-effect, this will also let the kernel lazy-load
+	// the wireguard module.
+	link.attrs.MTU = math.MaxInt
+
+	err := netlink.LinkAdd(link)
+
+	return errors.Is(err, syscall.EINVAL)
+}
+
 // Create Creates a new Wireguard interface, sets a given IP and brings it up.
 // Will reuse an existing one.
 func (w *WGIface) Create() error {