From mboxrd@z Thu Jan  1 00:00:00 1970
From: Cong Wang <xiyou.wangcong@gmail.com>
Subject: Re: [PATCH net] ipv6: no need to return rt->dst.error if it is not
 null entry.
Date: Thu, 27 Jul 2017 21:56:08 -0700
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Cc: Roopa Prabhu <roopa@cumulusnetworks.com>,
        Hangbin Liu <liuhangbin@gmail.com>,
        network dev <netdev@vger.kernel.org>
To: David Ahern <dsahern@gmail.com>
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On Wed, Jul 26, 2017 at 11:49 AM, David Ahern <dsahern@gmail.com> wrote:
> On 7/26/17 12:27 PM, Roopa Prabhu wrote:
>> agreed...so looks like the check in v3 should be
>>
>>
>> +       if ( rt == net->ipv6.ip6_null_entry ||
>> +            (rt->dst.error &&
>> + #ifdef CONFIG_IPV6_MULTIPLE_TABLES
>> +              rt != net->ipv6.ip6_prohibit_entry &&
>> +              rt != net->ipv6.ip6_blk_hole_entry &&
>> +#endif
>> +             )) {
>>                 err = rt->dst.error;
>>                 ip6_rt_put(rt);
>>                 goto errout;
>>
>
> I don't think so. If I add a prohibit route and use the fibmatch
> attribute, I want to see the route from the FIB that was matched.

But net->ipv6.ip6_prohibit_entry is not the prohibit route you can
add in user-space, it is only used by rule actions. So do you really
want to dump it?? My gut feeling is no, but I am definitely not sure.

When you add a prohibit route, a new rt is allocated dynamically,
net->ipv6.ip6_prohibit_entry is relatively static, internal and is the
only one per netns. (Same for net->ipv6.ip6_blk_hole_entry)

I think Hangbin's example doesn't have ip rules, so this case
is not shown up.