Subject: Re: [PATCH v2] sctp: fix the check for path failure detection

From: Vlad Yasevich <[email-masked]>
Date: Tue, 25 Aug 2009 09:31:54 -0400

Luo Chunbo wrote:
> On Tue, 2009-08-25 at 15:36 +0800, Wei Yongjun wrote:
>> Chunbo Luo wrote:
>>> The transport error count should be incremented when an outstanding
>>> HB is not acknowledged. And the path failure detection should be done
>>> before sending out the HB.
>>>   
>>> Signed-off-by: Chunbo Luo <[email-masked]>
>>> ---
>>>  net/sctp/sm_sideeffect.c |    6 +++++-
>>>  net/sctp/sm_statefuns.c  |    8 ++++----
>>>  2 files changed, 9 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c
>>> index 86426aa..fbdf4de 100644
>>> --- a/net/sctp/sm_sideeffect.c
>>> +++ b/net/sctp/sm_sideeffect.c
>>> @@ -446,7 +446,11 @@ static void sctp_do_8_2_transport_strike(struct sctp_association *asoc,
>>>  	if (transport->state != SCTP_UNCONFIRMED)
>>>  		asoc->overall_error_count++;
>>>  
>>> -	if (transport->state != SCTP_INACTIVE &&
>>> +	/*
>>> +	 * The transport error count is incremented when an outstanding HB
>>> +	 * is not acknowledged. 
>>> +	 */
>>>   
>> T3-rtx timer expires also need to increment error count.
> 
> Yes, T3-rtx timer expires need to increment error count.
> 
>>> +	if (transport->hb_sent && transport->state != SCTP_INACTIVE &&
>>>  	    (transport->error_count++ >= transport->pathmaxrxt)) {
>>>  		SCTP_DEBUG_PRINTK_IPADDR("transport_strike:association %p",
>>>  					 " transport IP: port:%d failed.\n",
>>> diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
>>> index 7288192..7f77099 100644
>>> --- a/net/sctp/sm_statefuns.c
>>> +++ b/net/sctp/sm_statefuns.c
>>> @@ -981,10 +981,6 @@ sctp_disposition_t sctp_sf_sendbeat_8_3(const struct sctp_endpoint *ep,
>>>  	 */
>>>  
>>>  	if (transport->param_flags & SPP_HB_ENABLE) {
>>> -		if (SCTP_DISPOSITION_NOMEM ==
>>> -				sctp_sf_heartbeat(ep, asoc, type, arg,
>>> -						  commands))
>>> -			return SCTP_DISPOSITION_NOMEM;
>>>  		/* Set transport error counter and association error counter
>>>  		 * when sending heartbeat.
>>>  		 */
>>> @@ -992,6 +988,10 @@ sctp_disposition_t sctp_sf_sendbeat_8_3(const struct sctp_endpoint *ep,
>>>  				SCTP_TRANSPORT(transport));
>>>  		sctp_add_cmd_sf(commands, SCTP_CMD_TRANSPORT_HB_SENT,
>>>  				SCTP_TRANSPORT(transport));
>>> +		if (SCTP_DISPOSITION_NOMEM ==
>>> +				sctp_sf_heartbeat(ep, asoc, type, arg,
>>> +						  commands))
>>> +			return SCTP_DISPOSITION_NOMEM;
>>>  	}
>>>  	sctp_add_cmd_sf(commands, SCTP_CMD_HB_TIMER_UPDATE,
>>>  			SCTP_TRANSPORT(transport));
>>>   
>> How about this one:
> 
> It is ok to increment the error count. But the path failure detection
> should be done before send HB. Otherwise, an extra HB chunk will be sent
> out before the transport is marked DOWN . So the changes in
> net/sctp/sm_statefuns.c is also needed.

After running a few simulations with all the different patches from this thread,
what we are really after was achieved by the original patch.  Looking back over
the code history, it looks like this was try to implement the old text of
section 8.3 (prior to errata that fixed it).

We still have to send HB on an INACTIVE transport to see if it comes back, so
that comment of my was entirely wrong.  Sorry, don't know what I was thinking at
that time...

So I'll take the original patch Luo submitted.

Thanks
-vlad

> 
> 
> 
>> diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c
>> index 86426aa..fb723dd 100644
>> --- a/net/sctp/sm_sideeffect.c
>> +++ b/net/sctp/sm_sideeffect.c
>> @@ -447,7 +447,7 @@ static void sctp_do_8_2_transport_strike(struct sctp_association *asoc,
>>  		asoc->overall_error_count++;
>>  
>>  	if (transport->state != SCTP_INACTIVE &&
>> -	    (transport->error_count++ >= transport->pathmaxrxt)) {
>> +	    (transport->error_count >= transport->pathmaxrxt)) {
>>  		SCTP_DEBUG_PRINTK_IPADDR("transport_strike:association %p",
>>  					 " transport IP: port:%d failed.\n",
>>  					 asoc,
>> @@ -468,6 +468,7 @@ static void sctp_do_8_2_transport_strike(struct sctp_association *asoc,
>>  	 * that indicates that we have an outstanding HB.
>>  	 */
>>  	if (!is_hb || transport->hb_sent) {
>> +		transport->error_count++;
>>  		transport->last_rto = transport->rto;
>>  		transport->rto = min((transport->rto * 2), transport->asoc->rto_max);
>>  	}
>>
>>
>>
>>
>>
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