hotfix(pmtud,ipv6): detect IPv6 after tunnel is up

Author: qdm12

internal/vpn/run.go

@@ -59,7 +59,6 @@ func (l *Loop) Run(ctx context.Context, done chan<- struct{}) {
 				enabled:   settings.Type != vpn.Wireguard || *settings.Wireguard.MTU == 0,
 				vpnType:   settings.Type,
 				network:   connection.Protocol,
-				ipv6:      l.isIPv6Used(settings),
 				icmpAddrs: settings.PMTUD.ICMPAddresses,
 				tcpAddrs:  settings.PMTUD.TCPAddresses,
 			},

internal/vpn/tunnelup.go

@@ -41,8 +41,6 @@ type tunnelUpPMTUDData struct {
 	// network is used to find the network level header overhead.
 	// It can be [constants.UDP] or [constants.TCP].
 	network string
-	// ipv6 is true if the VPN connection supports IPv6.
-	ipv6 bool
 	// icmpAddrs is the list of addresses to use for ICMP path MTU discovery.
 	// Each address should handle ICMP packets for PMTUD to work.
 	icmpAddrs []netip.Addr
@@ -52,7 +50,8 @@ type tunnelUpPMTUDData struct {
 }
 
 func (l *Loop) onTunnelUp(ctx, loopCtx context.Context, data tunnelUpData) {
-	switch vpnType := l.GetSettings().Type; vpnType {
+	vpnSettings := l.GetSettings()
+	switch vpnType := vpnSettings.Type; vpnType {
 	case vpn.Wireguard, vpn.AmneziaWg:
 		l.logger.Infof("%s setup is complete. "+
 			"Note %s is a silent protocol and it may or may not work, without giving any error message. "+
@@ -71,8 +70,9 @@ func (l *Loop) onTunnelUp(ctx, loopCtx context.Context, data tunnelUpData) {
 
 	if data.pmtud.enabled {
 		mtuLogger := l.logger.New(log.SetComponent("MTU discovery"))
+		ipv6 := l.isIPv6Used(vpnSettings)
 		err := updateToMaxMTU(ctx, data.vpnIntf, data.pmtud.vpnType,
-			data.pmtud.network, data.pmtud.ipv6, data.pmtud.icmpAddrs, data.pmtud.tcpAddrs,
+			data.pmtud.network, ipv6, data.pmtud.icmpAddrs, data.pmtud.tcpAddrs,
 			l.netLinker, l.routing, l.fw, mtuLogger)
 		if err != nil {
 			mtuLogger.Error(err.Error())