Re: rxe mcast

[Jason Gunthorpe <jgg@nvidia.com>]

On Wed, Nov 01, 2023 at 01:07:28PM -0500, Bob Pearson wrote:
> Jason,
> 
> I wrote a test program to verify that multicast is working in rxe
> since there don't seem to be any pyverbs tests that actually test this.
> It turns out that it doesn't work for several reasons most of which
> I have fixed. But there is one that I can't figure out.
> 
> The rxe driver calls dev_mc_add() with a MAC address to add the
> multicast MAC address to the device which shows up when you type
> 'ip maddr'. But nothing comes through from the network to the driver.
> Wireshark does see the packets but they don't get to the IP or
> UDP layers in the netdev stack.

I think you also need to attach a multicast IP address to the RXE
socket ?

> So creating the IP mcast address seems critical to letting the
> netdev stack receive traffic.

Yes
 
> I tried creating a separate UDP socket bound to the mcast address
> but it doesn't seem to create the required IP address.

I don't think that is how you do it... There is a set sock opt thing
you need, IIRC. It has been a long time since I last wrote code for it

Check what iperf did and that will be the basic thing that has to be
cloned in the kernel

Jason