[client] Refactor/iface pkg (#2646)

Refactor the flat code structure

client/iface/iface_unix.go

@@ -0,0 +1,49 @@
+//go:build (linux && !android) || freebsd
+
+package iface
+
+import (
+	"fmt"
+	"runtime"
+
+	"github.com/pion/transport/v3"
+
+	"github.com/netbirdio/netbird/client/iface/bind"
+	"github.com/netbirdio/netbird/client/iface/device"
+	"github.com/netbirdio/netbird/client/iface/netstack"
+)
+
+// NewWGIFace Creates a new WireGuard interface instance
+func NewWGIFace(iFaceName string, address string, wgPort int, wgPrivKey string, mtu int, transportNet transport.Net, args *device.MobileIFaceArguments, filterFn bind.FilterFn) (*WGIface, error) {
+	wgAddress, err := device.ParseWGAddress(address)
+	if err != nil {
+		return nil, err
+	}
+
+	wgIFace := &WGIface{}
+
+	// move the kernel/usp/netstack preference evaluation to upper layer
+	if netstack.IsEnabled() {
+		wgIFace.tun = device.NewNetstackDevice(iFaceName, wgAddress, wgPort, wgPrivKey, mtu, transportNet, netstack.ListenAddr(), filterFn)
+		wgIFace.userspaceBind = true
+		return wgIFace, nil
+	}
+
+	if device.WireGuardModuleIsLoaded() {
+		wgIFace.tun = device.NewKernelDevice(iFaceName, wgAddress, wgPort, wgPrivKey, mtu, transportNet)
+		wgIFace.userspaceBind = false
+		return wgIFace, nil
+	}
+
+	if !device.ModuleTunIsLoaded() {
+		return nil, fmt.Errorf("couldn't check or load tun module")
+	}
+	wgIFace.tun = device.NewUSPDevice(iFaceName, wgAddress, wgPort, wgPrivKey, mtu, transportNet, nil)
+	wgIFace.userspaceBind = true
+	return wgIFace, nil
+}
+
+// CreateOnAndroid this function make sense on mobile only
+func (w *WGIface) CreateOnAndroid([]string, string, []string) error {
+	return fmt.Errorf("CreateOnAndroid function has not implemented on %s platform", runtime.GOOS)
+}