feat(wireguard): add debug logs for IPv6 detection

- To debug issue #998
- Enable with `LOG_LEVEL=debug`

internal/wireguard/ipv6.go

@@ -12,16 +12,23 @@ func (w *Wireguard) isIPv6Supported() (supported bool, err error) {
 		return false, fmt.Errorf("cannot list links: %w", err)
 	}
 
+	w.logger.Debug("Checking for IPv6 support...")
 	for _, link := range links {
+		linkName := link.Attrs().Name
 		routes, err := w.netlink.RouteList(link, netlink.FAMILY_V6)
 		if err != nil {
-			return false, fmt.Errorf("cannot list routes: %w", err)
+			return false, fmt.Errorf("cannot list routes for link %s: %w", linkName, err)
 		}
 
-		if len(routes) > 0 {
-			return true, nil
+		if len(routes) == 0 {
+			w.logger.Debugf("Link %s has no IPv6 route", linkName)
+			continue
 		}
+
+		w.logger.Debugf("Link %s has IPv6 routes: %#v",
+			linkName, routes)
+		supported = true
 	}
 
-	return false, nil
+	return supported, nil
 }