fix(netlink): RouteList list routes from all tables

- Do not filter by link anymore
- IPv6 detection simplified

internal/netlink/ipv6.go

@@ -5,35 +5,28 @@ import (
 )
 
 func (n *NetLink) IsIPv6Supported() (supported bool, err error) {
-	links, err := n.LinkList()
+	routes, err := n.RouteList(FamilyV6)
 	if err != nil {
-		return false, fmt.Errorf("listing links: %w", err)
+		return false, fmt.Errorf("listing IPv6 routes: %w", err)
 	}
 
-	var totalRoutes uint
-	for _, link := range links {
-		link := link
-		routes, err := n.RouteList(&link, FamilyV6)
-		if err != nil {
-			return false, fmt.Errorf("listing IPv6 routes for link %s: %w",
-				link.Name, err)
-		}
-
-		// Check each route for IPv6 due to Podman bug listing IPv4 routes
-		// as IPv6 routes at container start, see:
-		// https://github.com/qdm12/gluetun/issues/1241#issuecomment-1333405949
-		for _, route := range routes {
-			sourceIsIPv6 := route.Src.IsValid() && route.Src.Is6()
-			destinationIsIPv6 := route.Dst.IsValid() && route.Dst.Addr().Is6()
-			if sourceIsIPv6 || destinationIsIPv6 {
-				n.debugLogger.Debugf("IPv6 is supported by link %s", link.Name)
-				return true, nil
+	// Check each route for IPv6 due to Podman bug listing IPv4 routes
+	// as IPv6 routes at container start, see:
+	// https://github.com/qdm12/gluetun/issues/1241#issuecomment-1333405949
+	for _, route := range routes {
+		sourceIsIPv6 := route.Src.IsValid() && route.Src.Is6()
+		destinationIsIPv6 := route.Dst.IsValid() && route.Dst.Addr().Is6()
+		if sourceIsIPv6 || destinationIsIPv6 {
+			link, err := n.LinkByIndex(route.LinkIndex)
+			if err != nil {
+				return false, fmt.Errorf("finding IPv6 supported link: %w", err)
 			}
-			totalRoutes++
+			n.debugLogger.Debugf("IPv6 is supported by link %s", link.Name)
+			return true, nil
 		}
 	}
 
-	n.debugLogger.Debugf("IPv6 is not supported after searching %d links and %d routes",
-		len(links), totalRoutes)
+	n.debugLogger.Debugf("IPv6 is not supported after searching %d routes",
+		len(routes))
 	return false, nil
 }