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Date: Tue, 11 Jun 2019 01:45:57 +0200
From: Linus =?utf-8?Q?L=C3=BCssing?= <linus.luessing@c0d3.blue>
Subject: Re: [PATCH v4 1/2] batman-adv: mcast: detect, distribute and
 maintain multicast router presence
Message-ID: <20190610234557.GB10498@otheros>
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To: The list for a Better Approach To Mobile Ad-hoc Networking <b.a.t.m.a.n@lists.open-mesh.org>

On Tue, Jun 11, 2019 at 01:14:14AM +0200, Linus Lüssing wrote:
> On Mon, Jun 10, 2019 at 09:24:26AM +0200, Sven Eckelmann wrote:
> > On Monday, 10 June 2019 02:45:34 CEST Linus Lüssing wrote:
> > > @@ -107,12 +107,20 @@ enum batadv_icmp_packettype {
> > >   * @BATADV_MCAST_WANT_ALL_UNSNOOPABLES: we want all packets destined for
> > >   *  224.0.0.0/24 or ff02::1
> > >   * @BATADV_MCAST_WANT_ALL_IPV4: we want all IPv4 multicast packets
> > > + *  (both link-local and routeable ones)
> > >   * @BATADV_MCAST_WANT_ALL_IPV6: we want all IPv6 multicast packets
> > > + *  (both link-local and routable ones)
> > > + * @BATADV_MCAST_WANT_NO_RTR4: we have no IPv4 multicast router and therefore
> > > + * only need routeable IPv4 multicast packets we signed up for explicitly
> > > + * @BATADV_MCAST_WANT_NO_RTR6: we have no IPv6 multicast router and therefore
> > > + * only need routeable IPv6 multicast packets we signed up for explicitly
> > >   */
> > >  enum batadv_mcast_flags {
> > >         BATADV_MCAST_WANT_ALL_UNSNOOPABLES      = 1UL << 0,
> > >         BATADV_MCAST_WANT_ALL_IPV4              = 1UL << 1,
> > >         BATADV_MCAST_WANT_ALL_IPV6              = 1UL << 2,
> > > +       BATADV_MCAST_WANT_NO_RTR4               = 1UL << 3,
> > > +       BATADV_MCAST_WANT_NO_RTR6               = 1UL << 4,
> > >  };
> > 
> > I wonder what a good interpretation of 0x1f would be (all bits set). The code 
> > doesn't seem to be able to handle this but an interpretation would be:
> > 
> > * get all unsnoopable
> > * get all link-local but not rtr

Hrm, in hindsight I would have prefered a much cleaner, more clear
and more flexible flag set like:

enum batadv_mcast_flags {
	BATADV_MCAST_WANT_ALL_LL4	= 1UL << 0,
	BATADV_MCAST_WANT_ALL_LL6	= 1UL << 1,
	BATADV_MCAST_WANT_ALL_RTR4	= 1UL << 2,
	BATADV_MCAST_WANT_ALL_RTR6	= 1UL << 3,
}

The IPv4 unsnoopable case would have been equivalent to
BATADV_MCAST_WANT_ALL_LL4. And for the IPv6 unsnoopable case,
which is just the ff02::1 address which does not get any MLD
reports, we could have injected a TT entry for 33:33:00:00:00:01
instead (or just always flooding ff02::1).

Well, I guess that's too late now.