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

Steve Wise
2010-06-23T20:11:27Z

Jason Gunthorpe wrote:
> On Wed, Jun 23, 2010 at 02:42:43PM -0500, Steve Wise wrote:
>
>>> 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.
>>
>
> That is what RDMA does.. So that means that the IP used for iscsi is
> actually an IP assigned to the interface?
>
>

The IP address assigned for the cxgb3i iscsi device is _not_ assigned to
a netdev interface via ifconfig, as far as I understand it (by looking
at the cxgb3i code). So the host stack doesn't know about this
address. There is an administrative requirement, I assume, that the
secret iscsi ipaddr is within a subnet that is bound to the T3 ethX
interface. Otherwise the routing lookup wouldn't work.

Steve.