Looking at vdsm code, we see, that it recognizes it as iSCSI connection, but then it fails to get all the session's information from the OS:

In multipath.py we go to iscsi.devIsiSCSI and not to FC else section:
------------------------------
            if iscsi.devIsiSCSI(slave):  
>> here it returns true, see below [1]
                devInfo["devtypes"].append(DEV_ISCSI)
                pathInfo["type"] = DEV_ISCSI
                sessionID = iscsi.getiScsiSession(slave)
                if sessionID not in knownSessions:
                    # FIXME: This entire part is for BC. It should be moved to
                    # hsm and not preserved for new APIs. New APIs should keep
                    # numeric types and sane field names.
                    sess = iscsi.getSessionInfo(sessionID)
>> here is the exception thrown, from iscsi.py:
--------------------------------
readSessionInfo:
    sessionName = "session%d" % sessionID
    connectionName = "connection%d:0" % sessionID
    iscsi_session = "/sys/class/iscsi_session/%s/" % sessionName
    iscsi_connection = "/sys/class/iscsi_connection/%s/" % connectionName
    if not os.path.isdir(iscsi_session) or not os.path.isdir(iscsi_connection):
        raise OSError(errno.ENOENT, "No such session")

    targetname = os.path.join(iscsi_session, "targetname")
    iface = os.path.join(iscsi_session, "ifacename")
    tpgt = os.path.join(iscsi_session, "tpgt")

    user = os.path.join(iscsi_session, "username")
    passwd = os.path.join(iscsi_session, "password")

    paddr = os.path.join(iscsi_connection, "persistent_address")
    pport = os.path.join(iscsi_connection, "persistent_port")

    res = []
    for fname in (targetname, tpgt, user, passwd, paddr, pport, iface):
        try:
            with open(fname, "r") as f:
                res.append(f.read().strip())
        except (OSError, IOError):
            res.append("")

    iqn, tpgt, username, password, ip, port, iface = res
    port = int(port)  
>> the failure is here, since no port information is collected, see [2] for details
    tpgt = int(tpgt)
-----------------------------------------
[1] in iscsi.py
def devIsiSCSI(dev):
    hostdir = os.path.realpath(os.path.join("/sys/block", dev, "device/../../.."))
    host = os.path.basename(hostdir)
    iscsi_host = os.path.join(hostdir, constants.STRG_ISCSI_HOST, host)
    scsi_host = os.path.join(hostdir, constants.STRG_SCSI_HOST, host)
    proc_name = os.path.join(scsi_host, "proc_name")
    return (os.path.exists(iscsi_host) and os.path.exists(proc_name))

So hostdir & iscsi_host & scsi_host = TRUE # ll /sys/block/<dev>/device/../../..  IE: 

drwxr-xr-x 3 root root    0 May 24 17:44 iscsi_host
drwxr-xr-x 2 root root    0 May 24 17:45 power
drwxr-xr-x 3 root root    0 May 24 17:44 scsi_host
drwxr-xr-x 6 root root    0 May 24 17:44 session1
lrwxrwxrwx 1 root root    0 May 24 17:44 subsystem -> ../../../bus/scsi
-rw-r--r-- 1 root root 4096 May 24 17:44 uevent

# cat /sys/block/sdc/device/../../../scsi_host/host6/proc_name
iscsi_tcp

return TRUE
---------------------------------------------
[2] in iscsy.py:
def getiScsiSession(dev):
    # FIXME: Use the new session object instead of a string
    device = os.path.realpath(os.path.join("/sys/block", dev, "device"))
    sessiondir = os.path.realpath(os.path.join(device, "../.."))
    session = os.path.basename(sessiondir)
    return int(session[len('session'):])

Again, # ll /sys/block/sdc/device/../..

drwxr-xr-x 4 root root    0 May 24 17:44 connection1:0
drwxr-xr-x 3 root root    0 May 24 17:44 iscsi_session
drwxr-xr-x 2 root root    0 May 24 17:52 power
drwxr-xr-x 5 root root    0 May 24 17:44 target6:0:0
-rw-r--r-- 1 root root 4096 May 24 17:44 uevent

And then we are trying to collect session information and update the session fields, but fail, since on customer side there is no such fields as port:
# ll /sys/block/sdc/device/../../iscsi_session/session1/
[root@phrhv05 ~]# ll /sys/block/sda/device/../../iscsi_session/session1/
total 0
-r--r--r--. 1 root root 4096 May 25 07:40 creator
lrwxrwxrwx. 1 root root    0 May 24 16:00 device -> ../../../session1
drwxr-xr-x. 2 root root    0 May 25 07:40 power
-rw-r--r--. 1 root root 4096 May 24 15:59 recovery_tmo
-r--r--r--. 1 root root 4096 May 25 07:40 state
lrwxrwxrwx. 1 root root    0 May 24 15:59 subsystem -> ../../../../../../../../../class/iscsi_session
-r--r--r--. 1 root root 4096 May 24 15:59 targetname
-r--r--r--. 1 root root 4096 May 24 15:59 tpgt
-rw-r--r--. 1 root root 4096 May 24 15:59 uevent

Following comment #28
marking as verified

This bug is currently attached to errata RHBA-2013:15291. If this change is not to be documented in the text for this errata please either remove it from the errata, set the requires_doc_text flag to 
minus (-), or leave a "Doc Text" value of "--no tech note required" if you do not have permission to alter the flag.

Otherwise to aid in the development of relevant and accurate release documentation, please fill out the "Doc Text" field above with these four (4) pieces of information:

* Cause: What actions or circumstances cause this bug to present.
* Consequence: What happens when the bug presents.
* Fix: What was done to fix the bug.
* Result: What now happens when the actions or circumstances above occur. (NB: this is not the same as 'the bug doesn't present anymore')

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Thanks in advance.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHBA-2014-0040.html