standards/174938: Problem statement: iSCSI target failure

Asiris asiris at
Thu Jan 3 13:20:00 UTC 2013

>Number:         174938
>Category:       standards
>Synopsis:       Problem statement: iSCSI target failure
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-standards
>State:          open
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Jan 03 13:20:00 UTC 2013
>Originator:     Asiris
>Release:        NAS4Free (revision 531)
Disc Soft Ltd
FreeBSD nas4free.local 9.1-RC3 FreeBSD 9.1-RC3 #0 r243187M: Sat Nov 17 21:59:26 JST 2012      root at nas4free.local:/usr/obj/nas4free/usr/src/sys/NAS4FREE-amd64 amd64
Problem statement: iSCSI target failure

- FreeNAS 0.7.2 (or/and NAS4Free (revision 531) behaves the same way)
- iSCSI target: istgt
- the DVD-ROM target created with istgt
- the iSCSI initiator creates the session with istgt target
- the iSCSI initiator claims the MaxRecvDataSegmentLength=8192 while 
  the session parameter negotiation stage
- the iSCSI initiator issues the SET MODE(10) SCSI command with
  allocation length 0xFFF0 bytes
- the istgt immideately aborts the TCP connection (sends FIN)
- the istgt logfile contains the messages:
  	freenas	istgt[1365]: istgt_lu_dvd.c:3339:istgt_lu_dvd_execute: ***ERROR*** data_alloc_len(8192) too small
	freenas	istgt[1365]: istgt_lu.c:2283:istgt_lu_execute: ***ERROR*** LU2: lu_dvd_execute() failed
	freenas	istgt[1365]: istgt_iscsi.c:3118:istgt_iscsi_op_scsi: ***ERROR*** lu_execute() failed
	freenas	istgt[1365]: istgt_iscsi.c:4400:istgt_iscsi_execute: ***ERROR*** iscsi_op_scsi() failed

If the iSCSI initiator claims the MaxRecvDataSegmentLength=65536, the problem disappears.
But the small iSCSI segments is not acceptable at all for some iSCSI initiators (e.g. embedded systems with limited amount of memory).

Use embedded systems with limited amount of memory, or simulate MaxRecvDataSegmentLength=8192
It is necessary to define at whom the buffer less, and to use with a smaller size


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