[PATCH 3/5] IB/ipoib: Make sendonly multicast joins create the mcast group

[Andy Whitcroft]

On Fri, Feb 05, 2016 at 02:11:45PM -0700, tim.gardner at canonical.com wrote:
> From: Doug Ledford <dledford at redhat.com>
> 
> BugLink: http://bugs.launchpad.net/bugs/1542444
> 
> Since IPoIB should, as much as possible, emulate how multicast
> sends work on Ethernet for regular TCP/IP apps, there should be
> no requirement to subscribe to a multicast group before your
> sends are properly sent.  However, due to the difference in how
> multicast is handled on InfiniBand, we must join the appropriate
> multicast group before we can send to it.  Previously we tried
> not to trigger the auto-create feature of the subnet manager when
> doing this because we didn't have tracking of these sendonly
> groups and the auto-creation might never get undone.  The previous
> patch added timing to these sendonly joins and allows us to
> leave them after a reasonable idle expiration time.  So supply
> all of the information needed to auto-create group.
> 
> Signed-off-by: Doug Ledford <dledford at redhat.com>
> (back ported from commit c3852ab0e606212de523c1fb1e15adbf9f431619)
> Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
> 
>  Conflicts:
> 	drivers/infiniband/ulp/ipoib/ipoib_multicast.c
> ---
>  drivers/infiniband/ulp/ipoib/ipoib_multicast.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
> index 4990572..180d10e 100644
> --- a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
> +++ b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
> @@ -500,6 +500,24 @@ static void ipoib_mcast_join(struct net_device *dev, struct ipoib_mcast *mcast,
>  		rec.sl		  = priv->broadcast->mcmember.sl;
>  		rec.flow_label	  = priv->broadcast->mcmember.flow_label;
>  		rec.hop_limit	  = priv->broadcast->mcmember.hop_limit;
> +
> +		/*
> +		 * Send-only IB Multicast joins do not work at the core
> +		 * IB layer yet, so we can't use them here.  However,
> +		 * we are emulating an Ethernet multicast send, which
> +		 * does not require a multicast subscription and will
> +		 * still send properly.  The most appropriate thing to
> +		 * do is to create the group if it doesn't exist as that
> +		 * most closely emulates the behavior, from a user space
> +		 * application perspecitive, of Ethernet multicast
> +		 * operation.  For now, we do a full join, maybe later
> +		 * when the core IB layers support send only joins we
> +		 * will use them.
> +		 */
> +#if 0
> +		if (test_bit(IPOIB_MCAST_FLAG_SENDONLY, &mcast->flags))
> +			rec.join_state = 4;
> +#endif
>  	}
>  
>  	multicast = ib_sa_join_multicast(&ipoib_sa_client, priv->ca, priv->port,

This patch seems to only add code which is commented out ?  I am not
sure this makes sense to me.

-apw