Hi Arshad,
On Wed, 2014-01-22 at 11:10 +0530, Arshad Hussain wrote:
> On 1/16/2014 3:43 PM, Arshad Hussain wrote:
> > Hi,
> >
> > I want to report an error in target. I am trying to confirm SNACK-R2T
> > that the target properly responds to a SNACK request. Whenever I
> > am putting runLength>0 it is crashing the target (machine reboot).
> >
> > Sequence of PDU is like below.
> >
> > I->T SCSI WRITE Command for 512B // Send out write
> > T->I R2T // Got R2T.
> > I->T SNACK BegRun=0 RunLength=1 // This crashes the Target.
> > /*
> > Send out SNACK
> > BegRun = First PDU whose retransmission is requested. (r2tsn)
> > RunLength = Number of PDU whose retransmission is requested.
> > */
> >
> > However, if the begrun and runlength is modified to 0 (Send all) it
> > works.
> >
> > I->T SCSI WRITE Command for 512B // Send out write
> > T->I R2T // Got R2T.
> > I->T SNACK BegRun=0 RunLength=0 // Works correctly.
> >
> > My Machine Details.
> >
> > [root@localhost test_suite_iscsi]# cat /sys/kernel/config/target/version
> > Target Engine Core ConfigFS Infrastructure v4.1.0-rc2-ml on
> > Linux/x86_64 on 3.10.13-101.fc18.x86_64
> > [root@localhost test_suite_iscsi]#
> >
> > [root@localhost test_suite_iscsi]# uname -a
> > Linux localhost.localdomain 3.10.13-101.fc18.x86_64 #1 SMP Fri Sep 27
> > 20:22:12 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
> > [root@localhost test_suite_iscsi]#
> >
> > Thanks,
> > Arshad
> >
> >
> >
> Hi,
>
> I Regret the slow turnaround.
>
> What I got is, if I do not convert from host to network byte order
> and assign BegRun and RunLength values greater than 0. ( of course 0 is
> same for both endian ) it crashes the machine.
>
> This was of course error on my side. However should this have crashed
> the target.? Shoud not this have returned an error and stopped.
> Your comments please.
>
Looking at the code in iscsi_target_erl1.c:iscsit_handle_r2t_snack(), it
is checking the validity of received BegRun + RunLength values, in that
they don't exceed what R2TSN has already been put on the wire:
if (runlength) {
if ((begrun + runlength) > cmd->r2t_sn) {
pr_err("Command ITT: 0x%08x received R2T SNACK"
" with BegRun: 0x%08x, RunLength: 0x%08x, exceeds"
" current R2TSN: 0x%08x, protocol error.\n",
cmd->init_task_tag, begrun, runlength, cmd->r2t_sn);
return iscsit_reject_cmd(cmd,
ISCSI_REASON_BOOKMARK_INVALID, buf);
}
last_r2tsn = (begrun + runlength);
} else
last_r2tsn = cmd->r2t_sn;
Can you confirm your bug is with R2T SNACKs, and not a different type of
SNACK..?
Also, a wireshark dump and/or access to the test that is generating this
particular scenario would be extremely helpful for tracking down the
bug.
Thanks!
--nab
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