On Thu, Dec 02, 2021 at 02:36:48PM +0100, Christoph Lameter wrote: > The rdma_create_qp createflags option IBV_QP_CREATE_BLOCK_SELF_MCAST_LB > should prevent multicast loopback. However, this feature seems to be > broken on a lot of RDMA NICs and there is no way to test this with the > existing RDMA tools. So add an option to mckey in order to allow to send > multicast messages without loopback. mckey's default has been and will > continue to be to loopback all multicast messages. > > Loopback of multicast messages can have surprising effects because all > messages sent out also have to be processed locally by all members of > the multicast group. This usually also includes the sender. > > In order to test multicast loop execute the following in two windows > on a host connected to an RDMA fabric. > > First session (Receiver) > > mckey -b <RDMA IP address> -m239.1.2.1 > > Second session (Sender) > > mckey -b <RDMA IP address> -m239.1.2.2 -s -l > > > The sender will send 10 messages and the receiver will terminate > after 10 messages have been received. > > If loopback prevention would work then the receiver should only > terminate on its own when the -l option has not been specified. > > Signed-off-by: Christoph Lameter <cl@xxxxxxxxx> Christoph, How can I apply your patch? Can you send it as a PR to rdma-core github? Thanks
