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

Steve Wise
2010-06-23T19:42:43Z

Jason Gunthorpe wrote:
> On Wed, Jun 23, 2010 at 01:46:47PM -0500, Steve Wise wrote:
>
>
>> 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 wonder how does neighbor discovery, routing, etc work with iscsi?
>
>

For cxgb3i:

ND is handled by initiating ND via exported kernel services
(neigh_event_send()) and registering for NETEVENT_NEIGH_UPDATE net
events to get updated neigh entries.

The host routing table is consulted via ip_route_output_flow() to map a
destination ip address to a local netdev, and then if that device is T3,
it will do the iscsi offload.

>> 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. :(
>>
>
> Well, maybe you can get netdev to agree on some way to create an
> interface that has all the IP services, but no TCP protocol binding?
> Then the configuration could be largely the same. If you could share
> that with the iscsi world then maybe it isn't so bad?
>

Maybe. I fear this will meet the same resistance from the netdev folks.

Steve.