[Open-FCoE] [PATCH] libfc: Validating SOF, EOF, SEQ_ID, SEQ_CNT, f_ctl for response frames

Ma, Steve steve.ma at intel.com
Thu Jul 16 21:19:45 UTC 2009



>-----Original Message-----
>From: Joe Eykholt [mailto:jeykholt at cisco.com]
>Sent: Thursday, July 16, 2009 2:12 PM
>To: Ma, Steve
>Cc: devel at open-fcoe.org
>Subject: Re: [Open-FCoE] [PATCH] libfc: Validating SOF, EOF, SEQ_ID,
>SEQ_CNT, f_ctl for response frames
>
>Ma, Steve wrote:
>>
>>> -----Original Message-----
>>> From: Joe Eykholt [mailto:jeykholt at cisco.com]
>>> Sent: Wednesday, July 15, 2009 2:40 PM
>>> To: Ma, Steve
>>> Cc: devel at open-fcoe.org
>>> Subject: Re: [Open-FCoE] [PATCH] libfc: Validating SOF, EOF, SEQ_ID,
>>> SEQ_CNT, f_ctl for response frames
>>>
>>> Steve Ma wrote:
>>>> This patch is for handling the received frames where the other end
>>>> is originating the sequence in response to the exchange originated
>>>> by the initiator.
>>>>
>>>> The current code is weak in validation of SOF,EOF,SEQ_ID,SEQ_CNT,f_ctl
>>>> for response frames, or no validations for SEQ_CNT.
>>>>
>>>> This patch is to add code to perform the validations of f_ctl in the
>>>> frame header for FC_FC_LAST_SEQ, FC_FC_END_SEQ, and FC_FC_SEQ_INIT
>>>> bits. The frame will be dropped (i.e. freed) if it fails the
>validation.
>>>>
>>>> Signed-off-by: Steve Ma <steve.ma at intel.com>
>>>> ---
>>>>
>>>>  drivers/scsi/libfc/fc_exch.c |   59
>>> ++++++++++++++++++++++++++++++++++++------
>>>>  1 files changed, 51 insertions(+), 8 deletions(-)
>>>>
>>>> diff --git a/drivers/scsi/libfc/fc_exch.c
>b/drivers/scsi/libfc/fc_exch.c
>>>> index f42695e..d86eda8 100644
>>>> --- a/drivers/scsi/libfc/fc_exch.c
>>>> +++ b/drivers/scsi/libfc/fc_exch.c
>>>> @@ -1124,7 +1124,9 @@ static void fc_exch_recv_seq_resp(struct
>>> fc_exch_mgr *mp, struct fc_frame *fp)
>>>>  	struct fc_seq *sp;
>>>>  	struct fc_exch *ep;
>>>>  	enum fc_sof sof;
>>>> +	enum fc_eof eof;
>>>>  	u32 f_ctl;
>>>> +	u16 cnt;
>>>>  	void (*resp)(struct fc_seq *, struct fc_frame *fp, void *arg);
>>>>  	void *ex_resp_arg;
>>>>  	int rc;
>>>> @@ -1149,29 +1151,70 @@ static void fc_exch_recv_seq_resp(struct
>>> fc_exch_mgr *mp, struct fc_frame *fp)
>>>>  		atomic_inc(&mp->stats.xid_not_found);
>>>>  		goto rel;
>>>>  	}
>>>> +
>>>>  	sof = fr_sof(fp);
>>>> -	if (fc_sof_is_init(sof)) {
>>>> +	eof = fr_eof(fp);
>>>> +	cnt = ntohs(fh->fh_seq_cnt);
>>>> +	f_ctl = ntoh24(fh->fh_f_ctl);
>>>> +
>>>> +	if ((sof ==  FC_SOF_I3 && eof == FC_EOF_T)) {
>>> Remove extra parens and extra space after the first ==.
>>>
>>> 	if (sof == FC_SOF_I3 && eof == FC_EOF_T) {
>>>
>>>> +		/* first and last frame in a sequence */
>>>>  		sp = fc_seq_start_next(&ep->seq);
>>>> +		if ((cnt && (cnt != sp->cnt + 1)) ||
>>>> +		    (!(f_ctl & FC_FC_END_SEQ))) {
>>> Since it's the only frame of the sequence, shouldn't cnt be zero?
>>
>> Because the sequence may not be the first sequence of the exchange,
> > the SEQ_CNT can be either zero or continuously increasing. FC-FS-2,
>9.10.
>
>Good point.  I forgot about continuously increasing sequence count.
>
>>> 		if (!cnt || !(f_ctl & FC_FC_END_SEQ)) {
>>>
>>> Avoid extra parens.
>>>
>>>> +			atomic_inc(&mp->stats.seq_not_found);
>>>> +			goto rel;
>>>> +		}
>>>> +		sp->cnt = cnt;
>>>>  		sp->id = fh->fh_seq_id;
>>>>  		sp->ssb_stat |= SSB_ST_RESP;
>>>> -	} else {
>>>> +		ep->esb_stat |= ESB_ST_SEQ_INIT;
>>>> +	} else if ((sof ==  FC_SOF_I3 && eof == FC_EOF_N)) {
>>> remove extra parens and extra space after first ==
>>>
>>>> +		/* first and not last frame in a sequence */
>>>> +		sp = fc_seq_start_next(&ep->seq);
>>>> +		if ((cnt && (cnt != sp->cnt + 1)) ||
>>> Again, shouldn't cnt be zero?
>>>
>> Same as above.
>>
>>>> +		    (f_ctl & (FC_FC_LAST_SEQ | FC_FC_END_SEQ)) ||
>>> LAST_SEQ is allowed on any frame in the last sequence, although
>>> it is only required on the last frame.  So, don't check that here.
>>> See FC-FS-2, section 9.7.5.
>>>
>>>> +		    (f_ctl & FC_FC_SEQ_INIT)) {
>>>> +			atomic_inc(&mp->stats.seq_not_found);
>>>> +			goto rel;
>>>> +		}
>>>> +		sp->cnt = cnt;
>>>> +		sp->id = fh->fh_seq_id;
>>>> +		sp->ssb_stat |= SSB_ST_RESP;
>>>> +		ep->esb_stat |= ESB_ST_SEQ_INIT;
>>>> +	} else if ((sof ==  FC_SOF_N3) && (eof == FC_EOF_N)) {
>>>> +		/* middle frame in a sequence */
>>>>  		sp = &ep->seq;
>>>> -		if (sp->id != fh->fh_seq_id) {
>>>> +		if ((sp->id != fh->fh_seq_id) ||
>>>> +		    (sp->cnt + 1 != cnt) ||
>>>> +		    (f_ctl & (FC_FC_LAST_SEQ | FC_FC_END_SEQ)) ||
>>>> +		    (f_ctl & FC_FC_SEQ_INIT)) {
>>> Don't check LAST_SEQ here, either.
>>> Suggest removing extra parens around comparisons.
>>>
>>>> +			atomic_inc(&mp->stats.seq_not_found);
>>>> +			goto rel;
>>>> +		}
>>>> +		sp->cnt++;
>>>> +	} else if ((sof ==  FC_SOF_N3) && (eof == FC_EOF_T)) {
>>>> +		/* last frame in a sequence */
>>>> +		sp = &ep->seq;
>>>> +		if ((sp->id != fh->fh_seq_id) ||
>>>> +		    (sp->cnt + 1 != cnt) ||
>>> We do see reordering of frames for FCP when interrupt
>>> migration moves the receive interrupt to another CPU.
>>> So the sequence comparison shouldn't be done unless we somehow
>>> figure out how to preserve order in this case.
>>>
>>> BTW, the only non-FCP sequences that we handle as multiple frames
>>> are CT GPN_FT responses.  fc_disc.c already checks that they
>>> arrive in order, so we really don't need to check it here.
>>>
>> I have also seen multiple response frames when sending ECHO of 256 bytes
>to a SANBlaze target.
>
>OK, sure.  Still, we can get reordering, so checking sequence count is a
>problem.
>I think it's better to let the upper level (FCP or fc_disc or fcping)
>handle it.

Here I just want to point out there are other cases to get multiple response frames. I have consulted the entire team and Chris has already made nice comment. I will resubmit the patch based on all the input I got so far.

>>>> +		    (!(f_ctl & FC_FC_END_SEQ))) {
>>>>  			atomic_inc(&mp->stats.seq_not_found);
>>>>  			goto rel;
>>>>  		}
>>>> +		sp->cnt++;
>>> Need to test for SEQ_INIT here, too.
>>>
>>>> +	} else {
>>>> +		atomic_inc(&mp->stats.seq_not_found);
>>>> +		goto rel;
>>>>  	}
>>>> -	f_ctl = ntoh24(fh->fh_f_ctl);
>>>> -	fr_seq(fp) = sp;
>>>> -	if (f_ctl & FC_FC_SEQ_INIT)
>>>> -		ep->esb_stat |= ESB_ST_SEQ_INIT;
>>>>
>>>> +	fr_seq(fp) = sp;
>>>>  	if (fc_sof_needs_ack(sof))
>>>>  		fc_seq_send_ack(sp, fp);
>>>>  	resp = ep->resp;
>>>>  	ex_resp_arg = ep->arg;
>>>>
>>>> -	if (fh->fh_type != FC_TYPE_FCP && fr_eof(fp) == FC_EOF_T &&
>>>> +	if (fh->fh_type != FC_TYPE_FCP && eof == FC_EOF_T &&
>>>>  	    (f_ctl & (FC_FC_LAST_SEQ | FC_FC_END_SEQ)) ==
>>>>  	    (FC_FC_LAST_SEQ | FC_FC_END_SEQ)) {
>>>>  		spin_lock_bh(&ep->ex_lock);
>>>>
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>>




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