netdev - Re: [PATCH net v2] ipv6: enforce egress device match in per table nexthop lookups

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Message-ID: <a359d93e-c7dd-9558-c7ad-c6a9ca6d4c20@cumulusnetworks.com>
Date:	Thu, 23 Jun 2016 14:33:29 -0600
From:	David Ahern <dsa@...ulusnetworks.com>
To:	Paolo Abeni <pabeni@...hat.com>
Cc:	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	Beniamino Galvani <bgalvani@...hat.com>
Subject: Re: [PATCH net v2] ipv6: enforce egress device match in per table
 nexthop lookups

On 6/23/16 8:39 AM, Paolo Abeni wrote:
> On Thu, 2016-06-23 at 08:29 -0600, David Ahern wrote:
>> On 6/23/16 8:20 AM, David Ahern wrote:
>>>> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
>>>> index 969913d..520b788 100644
>>>> --- a/net/ipv6/route.c
>>>> +++ b/net/ipv6/route.c
>>>> @@ -1782,7 +1782,7 @@ static struct rt6_info
>>>> *ip6_nh_lookup_table(struct net *net,
>>>>      };
>>>>      struct fib6_table *table;
>>>>      struct rt6_info *rt;
>>>> -    int flags = 0;
>>>> +    int flags = RT6_LOOKUP_F_IFACE;
>>>>
>>>>      table = fib6_get_table(net, cfg->fc_table);
>>>>      if (!table)
>>>>
>>>
>>> Acked-by: David Ahern <dsa@...ulusnetworks.com>
>>
>> I take that back.
>>
>> I think RT6_LOOKUP_F_IFACE should only be set if cfg->fc_ifindex is set.
>
> AFAICS the latter condition should not be needed. The related
> information is passed all way down to rt6_score_route(), where it's
> really used:
>
> 	m = rt6_check_dev(rt, oif);
>         if (!m && (strict & RT6_LOOKUP_F_IFACE))
>                 return RT6_NUD_FAIL_HARD;
>
> and 'm' can be 0 only if oif is set: RT6_LOOKUP_F_IFACE has no effect
> ifindex is set.
>

For the simplified lookup yes that is true. Lookups that go through 
ip6_pol_route it is not and for my comment above I was thinking about 
this latter case.

Anyways, your change is fine for the ip6_nh_lookup_table case.