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
 }

internal/netlink/route.go

@@ -6,10 +6,16 @@ import (
 	"github.com/vishvananda/netlink"
 )
 
-func (n *NetLink) RouteList(link *Link, family int) (
-	routes []Route, err error) {
-	netlinkLink := linkToNetlinkLink(link)
-	netlinkRoutes, err := netlink.RouteList(netlinkLink, family)
+func (n *NetLink) RouteList(family int) (routes []Route, err error) {
+	// We set the filter to netlink.RT_FILTER_TABLE so that
+	// routes from all tables are listed, as long as the filter
+	// table is set to 0.
+	const filterMask = netlink.RT_FILTER_TABLE
+	// The filter is not left to `nil` otherwise non-main tables
+	// are ignored.
+	filter := &netlink.Route{}
+
+	netlinkRoutes, err := netlink.RouteListFiltered(family, filter, filterMask)
 	if err != nil {
 		return nil, err
 	}

internal/netlink/route_unspecified.go

@@ -2,7 +2,7 @@
 
 package netlink
 
-func (n *NetLink) RouteList(link *Link, family int) (
+func (n *NetLink) RouteList(family int) (
 	routes []Route, err error) {
 	panic("not implemented")
 }