On Wed, Dec 26, 2018 at 09:27:59PM +0100, Denis Fondras wrote:
> Resend because of nasty typo :/
>
> On Mon, Dec 24, 2018 at 08:43:10PM -0200, Martin Pieuchot wrote:
> > I'm not happy with adding the IFF_MULTICAST flag and SIOC{ADD,DEL}MULTI
> > ioctls. It seems to be a common pattern between in existing pseudo-driver,
> > so this shouldn't block you. However I'd greatly appreciate if you
> > could explain to us which code is asking for this and if this could be
> > improved.
> >
>
> Interface needs IFF_MULTICAST when enabling IPv6 as per in6_ifattach().
> When an address is configured, the interface joins multicast groups with
> in6_joingroup() (hence use SIOCADDMULTI) but only if IFF_MULTICAST is set. It
> is
> useful for interfaces extern-facing interfaces, not so much for internal (like
> mpe) as they won't process all-{nodes, routers} packets.
>
> We may remove the test in in6_ifattach() because there are many tests through
> the stack. It works if I disable the test in in6_ifattach() and remove the
> IFF_MULTICAST. However I haven't tested further so it may break elsewhere.
>
Doing IFF_MULTICAST on a true IFF_POINTOPOINT interface is indeed trivial
and save. I think that bit of the mpe(4) diff is OK and I would not go and
try to work around this in in6 code. IPv6 requires multicast and it was an
oversight in mpe(4) to not add it.
--
:wq Claudio
