netdev - Re: [PATCH RFC] ipv6: fix route selection if kernel is not compiled with CONFIG_IPV6_ROUTER

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Message-ID: <20130710163537.GJ15411@order.stressinduktion.org>
Date:	Wed, 10 Jul 2013 18:35:37 +0200
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Nicolas Dichtel <nicolas.dichtel@...nd.com>,
	netdev@...r.kernel.org, yoshfuji@...ux-ipv6.org,
	petrus.lt@...il.com, davem@...emloft.net
Subject: Re: [PATCH RFC] ipv6: fix route selection if kernel is not compiled with CONFIG_IPV6_ROUTER_PREF

On Wed, Jul 10, 2013 at 05:59:04PM +0200, Hannes Frederic Sowa wrote:
> On Wed, Jul 10, 2013 at 05:20:01PM +0200, Hannes Frederic Sowa wrote:
> > On Wed, Jul 10, 2013 at 04:10:58PM +0200, Nicolas Dichtel wrote:
> > > Le 10/07/2013 15:21, Hannes Frederic Sowa a écrit :
> > > >On Wed, Jul 10, 2013 at 02:22:55PM +0200, Nicolas Dichtel wrote:
> > > >>Le 10/07/2013 12:53, Hannes Frederic Sowa a écrit :
> > > >The route with rt6i_gateway does actually expire because I got it from
> > > >autoconf and ip -6 r l confirms this, too. It seems this is only the cached
> > > >route (I will confirm shortly). Is this still ok?
> > > I wonder why expires is 0. Even if this route is cached, the flag 
> > > RTF_EXPIRES should be set. Am I wrong?
> > 
> > It seems it is possible cached route gets its expiration updated. As
> > such it is not counted in the iteration but it is found as a sibling and its
> > nsiblings count is updated again.
> 
> ip6_link_failure is the problem. We need to remove the route directly instead
> of calling rt6_update_expires:
> 
> static void ip6_link_failure(struct sk_buff *skb)
> {
>         struct rt6_info *rt;
> 
>         icmpv6_send(skb, ICMPV6_DEST_UNREACH, ICMPV6_ADDR_UNREACH, 0);
> 
>         rt = (struct rt6_info *) skb_dst(skb);
>         if (rt) {
>                 if (rt->rt6i_flags & RTF_CACHE)
>                         rt6_update_expires(rt, 0);
>                 else if (rt->rt6i_node && (rt->rt6i_flags & RTF_DEFAULT))
>                         rt->rt6i_node->fn_sernum = -1;
>         }
> }

With this patch I do not get the panic any more and the routing table
stabilizes and discarded all NUD nonavailable routes. I'll need to review
it myself, first. Thanks for your help!

--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1096,10 +1096,12 @@ static void ip6_link_failure(struct sk_buff *skb)
 
        rt = (struct rt6_info *) skb_dst(skb);
        if (rt) {
-               if (rt->rt6i_flags & RTF_CACHE)
-                       rt6_update_expires(rt, 0);
-               else if (rt->rt6i_node && (rt->rt6i_flags & RTF_DEFAULT))
+               if (rt->rt6i_flags & RTF_CACHE) {
+                       dst_hold(&rt->dst);
+                       ip6_del_rt(rt);
+               } else if (rt->rt6i_node && (rt->rt6i_flags & RTF_DEFAULT)) {
                        rt->rt6i_node->fn_sernum = -1;
+               }
        }
 }
 


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