Subject: Re: [ofa-general] InfiniBand/RDMA merge plans for 2.6.24

From: Roland Dreier <[email-masked]>
Date: Fri, 14 Sep 2007 09:18:01 -0700

> > I've been meaning to track down the bnx2 iscsi offload patch to look
 > > and see if this issue is addressed, since the same problem seems to
 > > exist: it seems an iscsi connection and a main stack tcp connection
 > > might share the same 4-tuple unless something is done to avoid that
 > > happening.

 > iSCSI does not do passive listens, only active connections to the
 > target.  But you're right, the port space is still shared between iSCSI
 > and the main stack.  We currently rely on user apps binding to the main
 > stack to reserve certain ephemeral ports, and telling the iSCSI driver
 > which ports to use.

Got it... I wasn't thinking that clearly, but it is clear that a full
4-tuple collision with only active connections is quite unlikely.  I
guess you would have to make both an offloaded and a non-offloaded
iSCSI connection to the same target and get really unlucky with
ephemeral port allocation.  So in practice I guess it's not an issue
at all with your driver yet.

However, do you have any plans to support iSCSI offload for targets?
Also, looking at the first CNIC patch, I can't help but notice that
you seem to have at least some support for iWARP there.  How does the
CNIC look?  Does it share the same interface/addresses as the
non-offload NIC, or does it create a completely separate netdevice?

I want to make sure that whatever solution we come up with for cxgb3
doesn't cause problems for you.  And of course if you have a better
idea than what Steve has come up with, that would be great :)

 - R.