Re: [PATCH v2] RDMA/CMA: fix iWARP adapter TCP port space usage

Steve Wise
2010-06-23T18:46:47Z

Roland Dreier wrote:
> > Roland, do you think the iSCSI approach is a "good design" for iWARP
> > devices?
>
> Well, it's a different problem since as I said the port collision
> problem is a non-issue for iSCSI anyway. But yes having a separate
> interface to assign an iWARP IP address to an RNIC does seem to avoid
> the immediate problem.
>
> I actually don't know what the right answer is -- having a separate IP
> address for iWARP does seem to lead to having to duplicate everything
> for configuring it. (And this is the approach for the cxgb[34] iSCSI
> drivers, right?)
>
>

Yes. Perusing the drivers/scsi/cxgb3i code I see the iscsi ipaddr is
actually stored in the port_info struct which is hung of the netdev_priv
of the cxgb3 device. It is set by cxgb3i_host_set_param() which is part
of the iscsi transport interface.

I just think the customer looses when we add iwarp-specific tools,
ipaddrs, subnets, etc etc. And what about software iwarp? Will it use
the host stack tools and not these new tools? So then we end up with 2
sets of tools for iwarp devices. :(

> On the other hand trying to hook offloaded iWARP into the normal stack
> does seem to lead to a mess. I see DaveM's point: TCP port space is
> just the beginning -- filtering, queueing, etc also have config that
> ultimately an offload device would want to hook too.
>
> Maybe the sanest out of a bad set of options would be to come up with a
> standard way to configure independent TCP/IP stacks that share a link.
>
> really, dunno.
>
> - R.