Maint: dynamically set allowed VPN input ports

- Feat: allow to change VPN type at runtime
- Feat: allow to change interface name at runtime
- Maint: Add cleanup method to cleanup VPN loop on a vpn shutdown
- Change: allow VPN inputs ports only when tunnel is up

internal/vpn/cleanup.go

@@ -0,0 +1,27 @@
+package vpn
+
+import (
+	"context"
+	"time"
+
+	"github.com/qdm12/gluetun/internal/publicip/models"
+)
+
+func (l *Loop) cleanup(ctx context.Context, pfEnabled bool) {
+	for _, vpnPort := range l.vpnInputPorts {
+		err := l.fw.RemoveAllowedPort(ctx, vpnPort)
+		if err != nil {
+			l.logger.Error("cannot remove allowed input port from firewall: " + err.Error())
+		}
+	}
+
+	l.publicip.SetData(models.IPInfoData{}) // clear public IP address data
+
+	if pfEnabled {
+		const pfTimeout = 100 * time.Millisecond
+		err := l.stopPortForwarding(ctx, pfTimeout)
+		if err != nil {
+			l.logger.Error("cannot stop port forwarding: " + err.Error())
+		}
+	}
+}