feat(vpn): auto detection of IPv6 support

- `OPENVPN_IPV6` removed
- Affects OpenVPN
- Use the same mechanism for OpenVPN and Wireguard
- Check only once at program start since this is unlikely to change at runtime
- Log if IPv6 is supported
- Remove `IPv6` boolean from settings structs
- Move IPv6 detection as a method on NetLinker

internal/vpn/loop.go

@@ -21,6 +21,7 @@ type Loop struct {
 	// Fixed parameters
 	buildInfo     models.BuildInformation
 	versionInfo   bool
+	ipv6Supported bool
 	vpnInputPorts []uint16 // TODO make changeable through stateful firewall
 	// Configurators
 	openvpnConf OpenVPN
@@ -48,7 +49,7 @@ const (
 	defaultBackoffTime = 15 * time.Second
 )
 
-func NewLoop(vpnSettings settings.VPN, vpnInputPorts []uint16,
+func NewLoop(vpnSettings settings.VPN, ipv6Supported bool, vpnInputPorts []uint16,
 	providers Providers, storage Storage, openvpnConf OpenVPN,
 	netLinker NetLinker, fw Firewall, routing Routing,
 	portForward PortForward, starter command.Starter,
@@ -70,6 +71,7 @@ func NewLoop(vpnSettings settings.VPN, vpnInputPorts []uint16,
 		storage:       storage,
 		buildInfo:     buildInfo,
 		versionInfo:   versionInfo,
+		ipv6Supported: ipv6Supported,
 		vpnInputPorts: vpnInputPorts,
 		openvpnConf:   openvpnConf,
 		netLinker:     netLinker,

internal/vpn/openvpn.go

@@ -14,14 +14,14 @@ import (
 // It returns a serverName for port forwarding (PIA) and an error if it fails.
 func setupOpenVPN(ctx context.Context, fw Firewall,
 	openvpnConf OpenVPN, providerConf provider.Provider,
-	settings settings.VPN, starter command.Starter, logger openvpn.Logger) (
-	runner *openvpn.Runner, serverName string, err error) {
+	settings settings.VPN, ipv6Supported bool, starter command.Starter,
+	logger openvpn.Logger) (runner *openvpn.Runner, serverName string, err error) {
 	connection, err := providerConf.GetConnection(settings.Provider.ServerSelection)
 	if err != nil {
 		return nil, "", fmt.Errorf("failed finding a valid server connection: %w", err)
 	}
 
-	lines := providerConf.OpenVPNConfig(connection, settings.OpenVPN)
+	lines := providerConf.OpenVPNConfig(connection, settings.OpenVPN, ipv6Supported)
 
 	if err := openvpnConf.WriteConfig(lines); err != nil {
 		return nil, "", fmt.Errorf("failed writing configuration to file: %w", err)

internal/vpn/run.go

@@ -32,10 +32,11 @@ func (l *Loop) Run(ctx context.Context, done chan<- struct{}) {
 		if settings.Type == vpn.OpenVPN {
 			vpnInterface = settings.OpenVPN.Interface
 			vpnRunner, serverName, err = setupOpenVPN(ctx, l.fw,
-				l.openvpnConf, providerConf, settings, l.starter, subLogger)
+				l.openvpnConf, providerConf, settings, l.ipv6Supported, l.starter, subLogger)
 		} else { // Wireguard
 			vpnInterface = settings.Wireguard.Interface
-			vpnRunner, serverName, err = setupWireguard(ctx, l.netLinker, l.fw, providerConf, settings, subLogger)
+			vpnRunner, serverName, err = setupWireguard(ctx, l.netLinker, l.fw,
+				providerConf, settings, l.ipv6Supported, subLogger)
 		}
 		if err != nil {
 			l.crashed(ctx, err)

internal/vpn/wireguard.go

@@ -14,14 +14,14 @@ import (
 // It returns a serverName for port forwarding (PIA) and an error if it fails.
 func setupWireguard(ctx context.Context, netlinker NetLinker,
 	fw Firewall, providerConf provider.Provider,
-	settings settings.VPN, logger wireguard.Logger) (
+	settings settings.VPN, ipv6Supported bool, logger wireguard.Logger) (
 	wireguarder *wireguard.Wireguard, serverName string, err error) {
 	connection, err := providerConf.GetConnection(settings.Provider.ServerSelection)
 	if err != nil {
 		return nil, "", fmt.Errorf("failed finding a VPN server: %w", err)
 	}
 
-	wireguardSettings := utils.BuildWireguardSettings(connection, settings.Wireguard)
+	wireguardSettings := utils.BuildWireguardSettings(connection, settings.Wireguard, ipv6Supported)
 
 	logger.Debug("Wireguard server public key: " + wireguardSettings.PublicKey)
 	logger.Debug("Wireguard client private key: " + wireguardSettings.PrivateKey)