[openib-general] IPv6 All Router Multicast Group

[Hal Rosenstock]

Roland Dreier wrote:
>     Hal> My question was a little unclear; I meant: Why does the
>     Hal> kernel not request a full join in the case of the all routers
>     Hal> and IGMP groups ?  What is the differentiator for this ?
>
> Not sure exactly but I would guess only routers (or nodes running
> routing protocols) would join these groups (as opposed to groups that
> all nodes have to join).  On the other hand I'm not sure who is
> sending packets to these groups either...

I would expect end nodes joining the all routers group to at least be
listening
to router advertisements so just joining send only doesn't make sense. If
the
node is behaving as a router, I would expect a full join as they would need
to
both send and receive.

In terms of IGMP, if the end node is running multicast, it needs to send and
receive as would a multicast router.

So a send only join doesn't make sense to me for these groups.

To state what sounds obvious, the only time a send only join makes sense
would be for some send only application.

Something doesn't quite seem right to me here.

-- Hal