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

[Wei Yongjun <yjwei@cn.fujitsu.com>]

Luo Chunbo дµÀ:
> On Fri, 2009-08-21 at 17:47 -0400, Vlad Yasevich wrote:
>   
>> Chunbo Luo wrote:
>>     
>>> The transport is marked DOWN immediately after sending the max+1 HB,
>>> which is equal to not sending the max+1 HB at all. We should wait
>>> a next period and make sure the last HB is not acknowledged.
>>>
>>>       
>> I don't think this code does what you want either...
>>
>> Let's say path_max_rxt = 2.  What we'll get is:
>> 	timeout:
>> 		err++ (1)
>> 		if (err > 2) false
>> 		send HB
>> 		reset timer
>> 	timeout:
>> 		err++ (2)
>> 		if (err > 2) false
>> 		send HB
>> 		reset timer
>> 	timeout:
>> 		err++ (3)
>> 		if (err > 2)
>> 			set transport DOWN
>> 		send HB
>> 		reset timer.
>>
>> We only had 2 unacknowledged HB when we should have had 3.
>>     
>
> The error count is increment after the HB was sent, and the error count
> check is before sending HB.
>
> Let's say path_max_rxt =2 . What we really get is:
>
> timeout:
> 	if( err > 2) false
> 	send HB
> 	err++ (1)
> 	reset timer
> timeout:
> 	if( err > 2) false
> 	send HB
> 	err++ (2)
> 	reset timer
> timeout:
> 	if( err > 2) false
> 	send HB
> 	err++ (3)
> 	reset timer
> timeout:
> 	if( err > 2)
> 		set transport DOWN
> 	send HB
> 	reset timer
>
> Here We had 3 unacknowledged HBs


But with Vlad's advice, you just need to do little change to the kernel
codes, may be two lines's patch, and it can do the same thing.