[openib-general] IB mcast question

[Steve Wise]

IB experts,

I'm playing around with UD QPs over IB, and using the librdma services
to join and send to multicast groups.  I can run seans mckey example
program and it works.  I've written a simply program to echo stdin to a
mcast address and another program to read mcast packets and echo to
stout.  I run this on two hosts connected p2p via IB.  And it works as
expected. 

However, if I run 2 instances of the app that reads mcasts and dumps
them to stdout, I only get the mcast packets delivered to one of the
applications.  Namely the first one who joins the group seems to get the
mcasts.  I know for UDP/IP multicast, all applications bound to the same
port and joined to the IP mcast addr will get a copy of incoming mcast
packets.  Is this not true for IB mcast?   It appears not based on my
tests...


Thanks,


Stevo.