On Thursday 28 May 2009 20:00:46 ext Nivedita Singhvi wrote:

After some discussion offline with Christoph Lameter and David Stevens
regarding multicast behaviour in Linux, I'm submitting a slightly
modified patch from the one Christoph submitted earlier.

This patch provides a new socket option IP_MULTICAST_ALL.

In this case, default behaviour is _unchanged_ from the current
Linux standard. The socket option is set by default to provide
original behaviour. Sockets wishing to receive data only from
multicast groups they join explicitly will need to clear this
socket option.

You can already achieve this by checking the destination address in the 
SOL_PKTINFO ancilliary data. Sure, it will cause extra context switches to 
process unwanted packets but it will work with any kernel version.

-- 
Rémi Denis-Courmont
Nokia Devices R&D, Maemo Software, Helsinki