netdev - Re: [Bridge] [PATCH net] net: bridge: remove ipv6 zero address check in mcast queries

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Date:   Sun, 28 Oct 2018 08:20:23 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
Cc:     netdev@...r.kernel.org, roopa@...ulusnetworks.com,
        bridge@...ts.linux-foundation.org, yinxu@...hat.com,
        liuhangbin@...il.com, davem@...emloft.net
Subject: Re: [Bridge] [PATCH net] net: bridge: remove ipv6 zero address
 check in mcast queries

On Sat, 27 Oct 2018 12:07:47 +0300
Nikolay Aleksandrov <nikolay@...ulusnetworks.com> wrote:

> Recently a check was added which prevents marking of routers with zero
> source address, but for IPv6 that cannot happen as the relevant RFCs
> actually forbid such packets:
> RFC 2710 (MLDv1):
> "To be valid, the Query message MUST
>  come from a link-local IPv6 Source Address, be at least 24 octets
>  long, and have a correct MLD checksum."
> 
> Same goes for RFC 3810.
> 
> And also it can be seen as a requirement in ipv6_mc_check_mld_query()
> which is used by the bridge to validate the message before processing
> it. Thus any queries with :: source address won't be processed anyway.
> So just remove the check for zero IPv6 source address from the query
> processing function.
> 
> Fixes: 5a2de63fd1a5 ("bridge: do not add port to router list when receives query with source 0.0.0.0")
> Signed-off-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>

What about a broken/malicious sender? Could an all zero source be used
to poison the multicast table?