netdev - Re: [PATCH net] ipv6: no need to return rt->dst.error if it is not null entry.

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Date:   Wed, 26 Jul 2017 13:00:26 -0600
From:   David Ahern <dsahern@...il.com>
To:     Roopa Prabhu <roopa@...ulusnetworks.com>
Cc:     Hangbin Liu <liuhangbin@...il.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        network dev <netdev@...r.kernel.org>
Subject: Re: [PATCH net] ipv6: no need to return rt->dst.error if it is not
 null entry.

On 7/26/17 12:55 PM, Roopa Prabhu wrote:
> On Wed, Jul 26, 2017 at 11:49 AM, David Ahern <dsahern@...il.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.
> 
> 
> yes, exactly. wouldn't  'rt != net->ipv6.ip6_prohibit_entry' above let
> it fall through to the route fill code ?
> 
> ah...but i guess you are saying that they will have rt6_info's of
> their own and will not match. got it. ack.
> 

This:

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 4d30c96a819d..24de81c804c2 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -3637,11 +3637,6 @@ static int inet6_rtm_getroute(struct sk_buff
*in_skb, struct nlmsghdr *nlh,
                dst = ip6_route_lookup(net, &fl6, 0);

        rt = container_of(dst, struct rt6_info, dst);
-       if (rt->dst.error) {
-               err = rt->dst.error;
-               ip6_rt_put(rt);
-               goto errout;
-       }

        if (rt == net->ipv6.ip6_null_entry) {
                err = rt->dst.error;

Puts back the original behavior. In that case, only rt == null_entry
drops to the error path which is correct. All other rt values will drop
to rt6_fill_node and return rt data.