netdev - Re: [PATCH net-next v2] net: ipv6: make sure multicast packets are not forwarded beyond the different scopes

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Message-ID: <CAPF+HwWJz7kkjzW2g5pzTCnBebeOWh22mqPi8enH6Dcmt6PGKQ@mail.gmail.com>
Date:   Wed, 3 May 2017 10:53:56 +0300
From:   Donatas Abraitis <donatas.abraitis@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH net-next v2] net: ipv6: make sure multicast packets are
 not forwarded beyond the different scopes

Looks like there is this test already:

                if (IPV6_ADDR_MC_SCOPE(&ipv6_hdr(skb)->daddr) <=
                    IPV6_ADDR_SCOPE_NODELOCAL &&
                    !(dev->flags & IFF_LOOPBACK)) {
                        kfree_skb(skb);
                        return 0;
                }

On Tue, May 2, 2017 at 9:59 PM, David Miller <davem@...emloft.net> wrote:
> From: Donatas Abraitis <donatas.abraitis@...il.com>
> Date: Thu, 27 Apr 2017 10:12:02 +0300
>
>>           RFC4291 2.7 Routers must not forward any multicast packets
>>           beyond of the scope indicated by the scop field in the
>>           destination multicast address.
>>
>> Signed-off-by: Donatas Abraitis <donatas.abraitis@...il.com>
>
> I think it's a ">=" test which is needed here, not pure equality.
> Scopes are subsets of other scopes and are therefore allowed within
> eachother.
>
> Did you actually see misbehavior due to this issue, or see a real
> bonafide conformance test fail?
>
> If you're just reading the RFC and sticking tests here and there based
> upon what you read, without any testing or real life verification of
> the issue, this is _strongly_ discouraged.
>
> It would even be ok if you merely showed how another open source
> networking stack makes this test.



-- 
Donatas