Re: TCP connection tracking timeout

[Patrick McHardy <kaber@trash.net>]

Jozsef Kadlecsik wrote:
> Hi,
> 
> On Tue, 29 Jul 2008, Patrick McHardy wrote:
> 
>> Herbert Xu wrote:
>>> On Tue, Jul 29, 2008 at 07:00:46AM +0200, Patrick McHardy wrote:
>>>>> That sounds like a pretty neat idea. I'm testing a patch now, I'll
>>>>> send it over in a few minutes if it survives :)
>>>   
>>>> This seems to work. I'm wondering however if this will really help.
>>>> We already track retransmissions and decrease the timeout on the
>>>> 3rd retransmission, so this should only help if both the sender and
>>>> the receiver went down.
>>> The problem with requiring a 3rd retransmit is that once a socket
>>> is orphaned (closed) on Linux, we fast-track the retransmit timeout
>>> process.  In particular, if it's already maxed out the RTO prior
>>> to closing, we'll kill it straight away.
>>>
>>> This is in violation of the RFCs but it's an important optimisation.
>> Thanks for this explanation. Unless Jozsef sees something wrong with this
>> patch, I'll queue it with a proper changelog. Its small enough, so perhaps
>> we can even put this in 2.6.27.
> 
> Seems to be fine - as we cannot assume everything runs Linux (;-), the 
> only risk is that we may kill the conntrack entry too early and then it'll 
> mark packets as INVALID unnecessarily. But 5min timeout when there are 
> unacknowledged data should be enough to avoid it.

Thanks, I've queued the patch.