On 12/17/2010 11:55 AM, Rustad, Mark D wrote:
Hi all,
I am looking into adding support for DCB into iSCSI. I think it is best to do
this in a way that will not require a strong dependency on DCB for iSCSI. That
is, installing open-iscsi should not then require open-lldp to also be
installed. I see at least two ways to do this.
The first is to have open-lldp supply a library that iscsid can link with at
run time (through dlopen/dlsym). In that way, if the library is not there,
iscsid can go on as usual. It also allows lldpad more freedom to change over
time.
The second way is to put a little more code directly in iscsid and have it
interrogate lldpad for the proper priority to set. If the lldpad socket isn't
there, iscsid can go on as usual. I am thinking that open-lldp can supply the
source files that would be placed directly into open-iscsi and updated as
needed. These source files might also be used by other network applications
that want to participate fully in a DCB environment.
I had been leaning toward the first way until I started thinking about
iscsistart and initrds. Then it seemed that the run-time linkage would create
more trouble than it would be worth. It started to seem like over-engineering.
In either case, I was thinking about adding code right before the connect()
call in iscsi_io_tcp_connect to set the socket options based on information
from lldpad. Is anything more than that needed (besides doing something similar
in iscsistart)?
iscsistart uses the same code as iscsid, so you only need to change that
io.c iscsi_io_tcp_connect call.
The socket protocol to lldpad is already versioned, so that should prevent any
terribly rude surprises in the future should mismatched components be used
together.
Does this sound reasonable to you? Would you rather see it done in a different
way? Would you prefer for iscsid to simply send a file descriptor to the lldpad
socket and have lldpad set the socket options itself?
Does you guys know what is up with iscsi offload? Have you guys talked
to them? For something like be2iscsi it seems like it would be done all
in hardware/firmware so like the emulex fcoe driver, lpfc, it would not
use lldpad. But maybe some of the iscsi offload cards that do a lot in
software and do more of direct data placement type of offload, how would
that work?
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