BMC redundancy

[Vernon Mauery]

On 02-Feb-2018 11:18 AM, Andrew Jeffery wrote:
>Hi Deepak,
>
>> So several of the existing OpenBMC apps implement specific D-Bus
>> services. What does it take to make remote D-Bus calls to such apps?
>> - It doesn't look like the D-Bus spec or libdbus officially has anything
>> for D-Bus across computers. There are some good notes at
>> https://www.freedesktop.org/wiki/Software/DBusRemote/.
>
>Applications can cannect to remote dbus servers; the --address option to dbus-daemon allows it to listen on a TCP socket and setting DBUS_SESSION_BUS_ADDRESS will point applications in the right direction. So there are probably two ways we could do this:

Putting DBus on an externally-available TCP socket is a security 
architect's nightmare. All command and control of the entire BMC is done 
over DBus; we cannot put that on an externally-available address. I 
suppose if you have an internal connection and switching fabric between 
the nodes, this would be possible.

--Vernon

>1. Slave BMCs connect to the master's DBus daemon, and applications namespace their objects appropriately. Multi-BMC aware applications on the master access the namespaced objects as required
>2. Slave BMCs are willfully ignorant of their role, with the master connecting to the slaves' DBus daemons to form a coherent global view of the bus for its multi-BMC aware applications, which access the remote objects as required.
>
>Given the support DBus has today it might be easier to go for 1 than for 2, if we go down this path at all.
>
>[1] https://dbus.freedesktop.org/doc/dbus-daemon.1.html
>
>> - There are ways to achieve this via Qt D-Bus, but it would involve some
>> amount tweaking with the D-Bus configs.
>> - I'm not aware of any open/active project implementing remote D-Bus.
>
>Here is someone's attempt at making it easier: http://gabriel.sourceforge.net/howto.html though you would struggle to say it's active given the last contribution was 2013-05-14.
>
>> - Thoughts on doing remote D-Bus over WebSockets?
>
>How do websockets come into the picture? Why do we need the extra complication vs normal sockets?
>
>Cheers,
>
>Andrew