linux-kernel - Re: [PATCH] bridge: multicast: add sanity check for query source addresses

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Message-ID: <20140304104032.GB5090@Linus-Debian>
Date:	Tue, 4 Mar 2014 11:43:55 +0100
From:	Linus Lüssing <linus.luessing@....de>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:	netdev@...r.kernel.org, bridge@...ts.linux-foundation.org,
	Stephen Hemminger <stephen@...workplumber.org>,
	"David S. Miller" <davem@...emloft.net>,
	linux-kernel@...r.kernel.org, Jan Stancek <jstancek@...hat.com>,
	Florian Westphal <fwestpha@...hat.com>
Subject: Re: [PATCH] bridge: multicast: add sanity check for query source
 addresses

On Tue, Mar 04, 2014 at 10:06:14AM +0100, Hannes Frederic Sowa wrote:
> > diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
> > index ef66365..fb0e36f 100644
> > --- a/net/bridge/br_multicast.c
> > +++ b/net/bridge/br_multicast.c
> > @@ -1235,6 +1235,12 @@ static int br_ip6_multicast_query(struct net_bridge *br,
> >  	    (port && port->state == BR_STATE_DISABLED))
> >  		goto out;
> >  
> > +	/* RFC2710+RFC3810 (MLDv1+MLDv2) require link-local source addresses */
> > +	if (!(ipv6_addr_type(&ip6h->saddr) & IPV6_ADDR_LINKLOCAL)) {
> > +		err = -EINVAL;
> > +		goto out;
> > +	}
> > +
> 
> Shouldn't we allow empty source address, here?
> 
> Routers are supposed to drop them but bridges care. Linux uses ::
> as source address as long as no valid LL addresses are available,
> e.g. at boot-up (RFC3810 5.2.13.).

RFC3810, 5.2.13. refers to MLD reports, not queries, so that
shouldn't be relevant, section 5.1.14 should apply. Also the
bridge code only issues queries with a valid link-local source
address (see br_ip6_multicast_alloc_query() in
net/bridge/br_multicast.c). Where does Linux use :: for queries?

Cheers, Linus

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