[ofa-general] [PATCH v3] iw_cxgb3: Support "iwarp-only" interfacesto avoid 4-tuple conflicts.

[Glenn Grundstrom]

> -----Original Message-----
> From: Roland Dreier [mailto:rdreier at cisco.com] 
> Sent: Monday, September 24, 2007 2:33 PM
> To: Glenn Grundstrom
> Cc: Steve Wise; sean.hefty at intel.com; general at lists.openfabrics.org
> Subject: Re: [ofa-general] [PATCH v3] iw_cxgb3: Support 
> "iwarp-only" interfacesto avoid 4-tuple conflicts.
> 
>  > I'm sure I had seen a previous email in this thread that 
> suggested using
>  > a userspace library to open a socket
>  > in the shared port space.  It seems that suggestion was 
> dropped without
>  > reason.  Does anyone know why?
> 
> Yes, because it doesn't handle in-kernel uses (eg NFS/RDMA, 
> iSER, etc).

The kernel apps could open a Linux tcp socket and create an RDMA
socket connection.  Both calls are standard Linux kernel architected
routines.  Doesn't NFSoRDMA already open a TCP socket and another for 
RDMA traffic (ports 2049 & 2050 if I remember correctly)?  I currently
don't know if iSER, RDS, etc. already do the same thing, but if they
don't, they probably could very easily.

> 
> Does the neteffect NIC have the same issue as cxgb3 here?  What are
> your thoughts on how to handle this?

Yes, the NetEffect RNIC will have the same issue as Chelsio.  And all
Future RNIC's which support a unified tcp address with Linux will as
well.

Steve has put a lot of thought and energy into the problem, but
I don't think users & admins will be very happy with us in the long run.

In summary, short of having the rdma_cm share kernel port space, I'd
like to see the equivalent in userspace and have the kernel apps handle
the issue in a similar way as described above.  There are a few
technical
issues to work through (like passing the userspace IP address to the
kernel), but I think we can solve that just like other information that
gets passed from user into the IB/RDMA kernel modules.

Glenn.

> 
>  - R.
>