Re: [PATCH 6/10][CTNETLINK] dump counters iif connection ended or counters filled up

[Patrick McHardy <kaber@trash.net>]

Pablo Neira Ayuso wrote:
> Patrick McHardy wrote:
> 
>> Pablo Neira Ayuso wrote:
>>
>>> I think that this patch should also reset counters upon fill up event,
>>> comments?
>>
>>
>> Not sure, do you know any users of the counters besides conntrackd?
> 
> 
> I don't know any ctnetlink user of the counters. Thinking it well this
> "counters fill up" issue is tricky. Since netlink is unreliable, what if
> the fill up event gets lost? we could reset counters and nobody would
> apparently notice. I think that we need an overflow bit in the conntrack
> that must be set whenever and overflow happens and unset such bit once
> the overflow event has been caught.


If a message is lost userspace simply _must_ resync if it wants
reliability. If we reset the counter its impossible for userspace
to reconstruct the value at which it overflowed, so I don't think
we should do that. But you raise a good point, how should userspace
react to lost DESTROY messages that contain new information (like
counter values)? I don't see how it could reliable handle that case.