Xen devel - Nov 2007 - RFC: multicast add/remove for network frontend

Network frontends currently have no way to express the set of  
ethernet multicast groups that they are interested in. As a  
consequence we deliver all multicast traffic to them. A subsequent  
consequence is that network interfaces used in the IO domain  
typically end up in promiscuous mode, which is generally undesirable.

I''d like to slightly extend the inter-domain protocol to allow a  
frontend to add and remove ethernet multicast addresses from the set  
in which it is interested. The backend can use this information to  
deliver only the relevant multicast traffic to the frontend and, as a  
result, can often avoid pushing physical interfaces into promiscuous  
mode.

The use of this feature would be controlled using "feature" and  
"request" flags in xenstore (i.e. the backend would advertise the  
feature and the frontend would request that it be enabled).

Changes to the current OpenSolaris implementation to provide this are  
at http://dme.org/solaris/webrev/x24, with the changes to the inter- 
domain protocol expressed in the diffs to netif.h (this is based on  
3.0.4-2 at the moment).

There''s no requirement to change an implementation other than  
OpenSolaris with this approach - we''d continue to support frontends  
that don''t use the add/remove calls.

Any thoughts?

dme.
-- 
David Edmondson, Solaris Engineering, http://dme.org



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