chore!(amneziawg): refactor to be separate from wireguard

- amneziawg is now a VPN protocol and no longer a Wireguard implementation
- Use it with VPN_TYPE=amneziawg
- document AMNEZIAWG_* options in Dockerfile
- document amneziawg support in readme
- separate amneziawg settings and code from wireguard
- re-use code from wireguard whenever possible

internal/amneziawg/run.go

@@ -0,0 +1,133 @@
+package amneziawg
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net"
+
+	amneziaconn "github.com/amnezia-vpn/amneziawg-go/conn"
+	amneziadevice "github.com/amnezia-vpn/amneziawg-go/device"
+	amneziatun "github.com/amnezia-vpn/amneziawg-go/tun"
+	"github.com/qdm12/gluetun/internal/cleanup"
+	"github.com/qdm12/gluetun/internal/wireguard"
+)
+
+var (
+	errTunNameMismatch = errors.New("TUN device name is mismatching")
+	errDeviceWaited    = errors.New("device waited for")
+)
+
+// Run runs the amneziawg interface and waits until the context is done, then it cleans up the
+// interface and returns any error that occurred during setup or waiting. It sends an error to
+// waitError if any error occurs during setup or waiting, otherwise it sends nil when the context
+// is done. It sends a signal to ready when the setup is complete and the interface is ready to use.
+// See https://github.com/amnezia-vpn/amneziawg-go/blob/master/main.go
+func (a *Amneziawg) Run(ctx context.Context, waitError chan<- error, ready chan<- struct{}) {
+	setup := func(ctx context.Context, cleanups *cleanup.Cleanups) (
+		linkIndex uint32, waitAndCleanup func() error, err error,
+	) {
+		return setupUserspace(ctx, a.settings.Wireguard.InterfaceName,
+			a.netlink, a.settings.Wireguard.MTU, cleanups, a.logger, a.settings)
+	}
+
+	wireguard.Run(ctx, waitError, ready, setup, a.settings.Wireguard, a.netlink, a.logger)
+}
+
+func setupUserspace(ctx context.Context,
+	interfaceName string, netLinker NetLinker, mtu uint32,
+	cleanups *cleanup.Cleanups, logger Logger,
+	settings Settings,
+) (
+	linkIndex uint32, waitAndCleanup func() error, err error,
+) {
+	tun, err := amneziatun.CreateTUN(interfaceName, int(mtu))
+	if err != nil {
+		return 0, nil, fmt.Errorf("creating TUN device: %w", err)
+	}
+
+	cleanups.Add("closing TUN device", 7, tun.Close)
+
+	tunName, err := tun.Name()
+	if err != nil {
+		return 0, nil, fmt.Errorf("getting created TUN device name: %w", err)
+	} else if tunName != interfaceName {
+		return 0, nil, fmt.Errorf("%w: expected %q and got %q",
+			errTunNameMismatch, interfaceName, tunName)
+	}
+
+	link, err := netLinker.LinkByName(interfaceName)
+	if err != nil {
+		return 0, nil, fmt.Errorf("finding link %s: %w", interfaceName, err)
+	}
+	cleanups.Add("deleting link", 5, func() error {
+		return netLinker.LinkDel(link.Index)
+	})
+
+	bind := amneziaconn.NewDefaultBind()
+	cleanups.Add("closing bind", 7, bind.Close)
+
+	deviceLogger := amneziadevice.Logger{
+		Verbosef: logger.Debugf,
+		Errorf:   logger.Errorf,
+	}
+	device := amneziadevice.NewDevice(tun, bind, &deviceLogger)
+
+	cleanups.Add("closing Wireguard device", 6, func() error {
+		device.Close()
+		return nil
+	})
+
+	uapiFile, err := wireguard.UAPIOpen(interfaceName)
+	if err != nil {
+		return 0, nil, fmt.Errorf("opening UAPI socket: %w", err)
+	}
+	cleanups.Add("closing UAPI file", 3, uapiFile.Close)
+
+	uapiListener, err := wireguard.UAPIListen(interfaceName, uapiFile)
+	if err != nil {
+		return 0, nil, fmt.Errorf("listening on UAPI socket: %w", err)
+	}
+	cleanups.Add("closing UAPI listener", 2, uapiListener.Close)
+
+	uapiConfig := settings.uapiConfig()
+	err = device.IpcSet(uapiConfig)
+	if err != nil {
+		return 0, nil, fmt.Errorf("setting amneziawg uapi config: %w", err)
+	}
+
+	// acceptAndHandle exits when uapiListener is closed
+	uapiAcceptErrorCh := make(chan error)
+	go acceptAndHandle(uapiListener, device, uapiAcceptErrorCh)
+	waitAndCleanup = func() error {
+		select {
+		case <-ctx.Done():
+			err = ctx.Err()
+		case err = <-uapiAcceptErrorCh:
+			close(uapiAcceptErrorCh)
+		case <-device.Wait():
+			err = errDeviceWaited
+		}
+
+		cleanups.Cleanup(logger)
+
+		<-uapiAcceptErrorCh // wait for acceptAndHandle to exit
+
+		return err
+	}
+
+	return link.Index, waitAndCleanup, nil
+}
+
+func acceptAndHandle(uapi net.Listener, device *amneziadevice.Device,
+	uapiAcceptErrorCh chan<- error,
+) {
+	for { // stopped by uapiFile.Close()
+		conn, err := uapi.Accept()
+		if err != nil {
+			uapiAcceptErrorCh <- err
+			return
+		}
+		go device.IpcHandle(conn)
+	}
+}