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

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Date:	Wed, 10 Jul 2013 16:10:58 +0200
From:	Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:	unlisted-recipients:; (no To-header on input)
CC:	netdev@...r.kernel.org, yoshfuji@...ux-ipv6.org,
	petrus.lt@...il.com, davem@...emloft.net,
	hannes@...essinduktion.org
Subject: Re: [PATCH RFC] ipv6: fix route selection if kernel is not compiled
 with CONFIG_IPV6_ROUTER_PREF

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 :
>>> On Wed, Jul 10, 2013 at 11:28:57AM +0200, Nicolas Dichtel wrote:
>>>> Le 10/07/2013 09:54, Nicolas Dichtel a écrit :
>>>>> Le 09/07/2013 23:57, Hannes Frederic Sowa a écrit :
>>>>>> After starting a ping6 2000::1 the box should panic soon, after the
>>>>>> first nexthop entry times out.
>>>>>>
>>>>>> Perhaps you could give me a hint?
>>>>> I will run some tests with your patch. Will see.
>>>> I don't reproduce this panic.
>>>
>>> I just dumped the routes for which it does increase the rt6i_nsiblings
>>> counter in this condition:
>>>
>>>                          /* If we have the same destination and the same
>>>                          metric,
>>>                           * but not the same gateway, then the route we
>>>                           try to
>>>                           * add is sibling to this route, increment our
>>>                           counter
>>>                           * of siblings, and later we will add our route
>>>                           to the
>>>                           * list.
>>>                           * Only static routes (which don't have flag
>>>                           * RTF_EXPIRES) are used for ECMPv6.
>>>                           *
>>>                           * To avoid long list, we only had siblings if the
>>>                           * route have a gateway.
>>>                           */
>>>                          if (rt->rt6i_flags & RTF_GATEWAY &&
>>>                              !(rt->rt6i_flags & RTF_EXPIRES) &&
>>>                              !(iter->rt6i_flags & RTF_EXPIRES))
>>>                                  rt->rt6i_nsiblings++;
>>>                                  dump_route(iter, "(iter)");
>>>                                  dump_route(rt, "(rt)");
>>> 			}
>>>
>>>
>>>
>>> Here:
>>>
>>> [   42.497470] (iter): ffff88011796cc00 dst 2000::1 plen 128 gateway
>>> 2001:db8::32, siblings 2, metric 0, expires 0 gateway 2 idev6
>>> ffff8801139ddc00 dev ffff880117e83000
>>> [   42.505912] (rt): ffff88011796d800 dst 2000::1 plen 128 gateway
>>> fe80::5054:ff:fe82:e153, siblings 1, metric 0, expires 0 gateway 2 idev6
>>> ffff880117edc400 dev ffff8801185cb000
>>> [   42.527241] (iter): ffff88011796d380 dst 2000::1 plen 128 gateway
>>> 2001:db8::33, siblings 2, metric 0, expires 0 gateway 2 idev6
>>> ffff8801139ddc00 dev ffff880117e83000
>>> [   42.536440] (rt): ffff88011796d800 dst 2000::1 plen 128 gateway
>>> fe80::5054:ff:fe82:e153, siblings 2, metric 0, expires 0 gateway 2 idev6
>>> ffff880117edc400 dev ffff8801185cb000
>>>
>>>  From my understanding these two routes should not be aggregated in one
>>> ecmp
>>> route set. Am I seeing this correct? (My configuration is like in the mail
>>> before.)
>> Hmm, why?
>> Routes have the same destination, same metric, are static (expires == 0)
>> and have a gateway.
>
> 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?


Nicolas
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