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

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Message-ID: <20170727160822.GE5465@leo.usersys.redhat.com>
Date:   Fri, 28 Jul 2017 00:08:22 +0800
From:   Hangbin Liu <liuhangbin@...il.com>
To:     David Ahern <dsahern@...il.com>
Cc:     Roopa Prabhu <roopa@...ulusnetworks.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.

Hi David,

On Wed, Jul 26, 2017 at 01:00:26PM -0600, David Ahern wrote:
> >> 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.

Thanks for your explains. Now I know where I made the mistake. I mis-looked
FR_ACT_UNREACHABLE to RTN_UNREACHABLE and thought we return rt =
net->ipv6.ip6_null_entry in fib6_rule_action().

With you help I know we just set rt->dst.error to -EACCES for prohibit
entry in ip6_route_info_create. So remove the rt->dst.error check is enought.

Thanks
Hangbin