Re: [GIT PULL] kdbus for 4.1-rc1

Jiri Kosina
2015-04-21T11:04:05Z

On Tue, 21 Apr 2015, Greg Kroah-Hartman wrote:

> > We do need something for the multicast messaging. Whether that's
> > supporting AF_LOCAL, SOCK_RDP with multicast or something else (POSIX
> > message queue extensions ?). There's no real IP layer reliable ordered
> > multicast delivery system that is low latency and lightweight because
> > once it hits real networks it changes from a hard problem into a
> > seriously hard problem because of multicast implosions and the like.
>
> This was attempted in the past with AF_DBUS, but the networking
> maintainers rightfully pointed out that the model there did not work.

BTW, I don't think this has been brought up in this discussion yet ...
please correct me if I am wrong, my memory is very faint here (*), but
wasn't the main objection to AF_BUS that defining what happens when one of
the subscribed receivers disconnects is a policy matter, and as such
belongs to userspace (which wasn't the case with the submitted AF_BUS
implementation)?

Was that considered unfixable and AF_BUS consequently given up because of
this?

I personally think that AF_BUS makes quite a lot of sense -- it builds on
what we already have (AF_UNIX credential passing, memfd sealing, etc), it
basically "just implements a missing socket semantics" (wrt. reliability
and multicasting).

(*) and I really would like to avoid the digging out and reading thread
similar to this one, about AF_BUS, again

Thanks,

--
Jiri Kosina
SUSE Labs