Re: TOE, etc.

[Steve Wise <swise@opengridcomputing.com>]

On Wed, 2006-06-28 at 15:35 +1000, Herbert Xu wrote:
> On Tue, Jun 27, 2006 at 09:43:23PM -0700, David Miller wrote:
> > 
> > Socket state, and that is one thing I don't see them doing yet.
> 
> I wonder what happens when the Linux TCP stack attempts to open a
> connection to a remote host when that connection is already open
> in the RDMA NIC?  For that matter what happens if a Linux application
> decides to listen on a TCP port already listened on by the RDMA
> NIC?
> 

This issue would have to be handled by using seperate IP addresses for
RDMA connections vs native stack TCP.

Consider NFS-RDMA server.  Through administration, it would be
configured to listen on the specific rdma ip addresses, and the native
stack tcp ip addresses and thus support both TCP and RDMA NFS
connections.

There are definitely issues with this that could be resolved via tighter
integration, but that seems to not be a goal of the linux community at
this time...


> The only saving grace is that they're only doing RDMA rather than
> arbitrary TCP.  However, exactly the same infrastructure can be used
> to do arbitrary TCP should they wish to.
>  
> > But we have to realize they've already been given %95 of the
> > interfaces they need to speak IP using our routes and our neighbour
> > entries.
> > 
> > Right?
> 
> Yes, however I think the same argument could be applied to TOE.
> 
> With their RDMA NIC, we'll have TCP/SCTP connections that bypass
> netfilter, tc, IPsec, AF_PACKET/tcpdump and the rest of our stack
> while at the same time it is using the same IP address as us and
> deciding what packets we will or won't see.
> 


Doesn't iSCSI have this same issue?

Steve.