Feat: OPENVPN_INTERFACE defaulting to tun0

- Fix: custom config with custom network interface name for firewall
- Keep VPN tunnel interface in firewall state
- Vul fix: only allow traffic through vpn interface when needed
- Adapt code to adapt to network interface name
- Remove outdated TUN and TAP constants

internal/vpn/openvpn.go

@@ -29,14 +29,16 @@ func setupOpenVPN(ctx context.Context, fw firewall.VPNConnectionSetter,
 	settings configuration.VPN, starter command.Starter, logger logging.Logger) (
 	runner vpnRunner, serverName string, err error) {
 	var connection models.Connection
+	var netInterface string
 	var lines []string
 	if settings.OpenVPN.Config == "" {
+		netInterface = settings.OpenVPN.Interface
 		connection, err = providerConf.GetConnection(settings.Provider.ServerSelection)
 		if err == nil {
 			lines = providerConf.BuildConf(connection, settings.OpenVPN)
 		}
 	} else {
-		lines, connection, err = custom.BuildConfig(settings.OpenVPN)
+		lines, connection, netInterface, err = custom.BuildConfig(settings.OpenVPN)
 	}
 	if err != nil {
 		return nil, "", fmt.Errorf("%w: %s", errBuildConfig, err)
@@ -53,7 +55,7 @@ func setupOpenVPN(ctx context.Context, fw firewall.VPNConnectionSetter,
 		}
 	}
 
-	if err := fw.SetVPNConnection(ctx, connection); err != nil {
+	if err := fw.SetVPNConnection(ctx, connection, netInterface); err != nil {
 		return nil, "", fmt.Errorf("%w: %s", errFirewall, err)
 	}
 

internal/vpn/portforward.go

@@ -6,9 +6,7 @@ import (
 	"fmt"
 	"time"
 
-	"github.com/qdm12/gluetun/internal/constants"
 	"github.com/qdm12/gluetun/internal/portforward"
-	"github.com/qdm12/gluetun/internal/provider"
 )
 
 var (
@@ -16,24 +14,23 @@ var (
 	errStartPortForwarding   = errors.New("cannot start port forwarding")
 )
 
-func (l *Loop) startPortForwarding(ctx context.Context, enabled bool,
-	portForwarder provider.PortForwarder, serverName string) (err error) {
-	if !enabled {
+func (l *Loop) startPortForwarding(ctx context.Context, data tunnelUpData) (err error) {
+	if !data.portForwarding {
 		return nil
 	}
 
 	// only used for PIA for now
-	gateway, err := l.routing.VPNLocalGatewayIP()
+	gateway, err := l.routing.VPNLocalGatewayIP(data.vpnIntf)
 	if err != nil {
 		return fmt.Errorf("%w: %s", errObtainVPNLocalGateway, err)
 	}
 	l.logger.Info("VPN gateway IP address: " + gateway.String())
 
 	pfData := portforward.StartData{
-		PortForwarder: portForwarder,
+		PortForwarder: data.portForwarder,
 		Gateway:       gateway,
-		ServerName:    serverName,
-		Interface:     constants.TUN,
+		ServerName:    data.serverName,
+		Interface:     data.vpnIntf,
 	}
 	_, err = l.portForward.Start(ctx, pfData)
 	if err != nil {

internal/vpn/tunnelup.go

@@ -11,6 +11,7 @@ import (
 type tunnelUpData struct {
 	// Port forwarding
 	portForwarding bool
+	vpnIntf        string
 	serverName     string
 	portForwarder  provider.PortForwarder
 }
@@ -39,7 +40,7 @@ func (l *Loop) onTunnelUp(ctx context.Context, data tunnelUpData) {
 		}
 	}
 
-	err = l.startPortForwarding(ctx, data.portForwarding, data.portForwarder, data.serverName)
+	err = l.startPortForwarding(ctx, data)
 	if err != nil {
 		l.logger.Error(err.Error())
 	}