RE: iSCSI: need for new data SNACK code?

[Dave Sheehy <dbs@acropora.rose.agilent.com>]

> > If the target makes
> > its own choice to resegment, and the initiator doesn't think the
> > target resegmented, there are error scenarios that combine this with
> > corrupt Data PDU headers to cause the initiator to successfully
> > complete a SCSI command that has not delivered all its data
> > (the resegmented PDUs caused the Data PDU count to match the ExpDataSN
> > value in the response that should have been discarded, but wasn't).
> > While these should be rare, their consequences can be catastrophic.
> 
> What do you mean by "if the target makes it's own choice to resegment"?
> Sounds like a target bug to me.  It feels like you're making this look more
> complicated than it really is.

The only promise the target has made to the initiator is that it will not
send a segment larger than MaxRecvDataSegmentLength. It is free to segment
to any size <= to that and to change that size, for its own purposes, at
any point in time w/o notifying the initiator. I don't think the spec says
anything about requiring the target to use a constant segment size. 
Therefore, the described behavior is perfectly legal and not a bug as you 
seem to believe.

Dave