[systemd-devel] Compatibility between D-Bus and kdbus

Thiago Macieira thiago at kde.org
Tue Nov 25 11:27:17 PST 2014

On Tuesday 25 November 2014 17:19:41 Lennart Poettering wrote:
> On Mon, 24.11.14 18:40, Thiago Macieira (thiago at kde.org) wrote:
> > Another thought that comes to mind: should we reserve the entire highest
> > bit in connection IDs for broadcasts? It would allow for the existence of
> > multicast groups in the future.
> I discussed this quickly with the kdbus guys, and while none of us was
> thrilled about the posibility of introducing such a concept we all
> agreed that if it should be introduced one day it really should be
> part of the well-known names concept, not the unique names
> concept. Meaning: you'd put a label on a group, and join the group by
> the label then, rather than via numeric ids...
> In general, numeric ids are about being automatic, and well-known
> names are about discoverability. But mcast memberships should never be
> automatic, but only about discoverability, hence using unique ids for
> identifying them sounds wrong.

Agreed that mcast memberships should not be automatic. Just like IPv4 and 
IPv6, joining a multicast group requires placing a request.

I was thinking more on the fact that 802 MAC addresses have a bit to indicate 
multicast/broadcast data.

Can I suggest the following two changes to kdbus.txt when it comes to 
connection IDs:

1) remove the part that the numbers are not reused
2) say that the highest bit is reserved for future purposes

Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
   Software Architect - Intel Open Source Technology Center
      PGP/GPG: 0x6EF45358; fingerprint:
      E067 918B B660 DBD1 105C  966C 33F5 F005 6EF4 5358

More information about the dbus mailing list