Re: conntrack EILSEQ followed by ENOBUFS

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Thu, Oct 13, 2011 at 12:50:55PM +0000, abirvalg@lavabit.com wrote:
> Sorry for not being sufficiently specific. Since you showed more interest, I feel empowered to go into further detail.

You're reporting problems, I'm not a wizard, if you don't provide
details, it's way harder for me to guess what's wrong ;-)

> My app uses libnetfilter_queue. When it NF_ACCEPTs a packet, it immediately goes on to set a mark on the connection of which the ACCEPTed packet is part of. But in order to set the mark on the connection, it first NFCT_Q_GETs that conntrack (because it knows srcIP, destIP, srcPort, destPort, L4proto, L3proto). Once it got the conntrack, it can proceed to set a mark on it using NFCT_Q_UPDATE.
> 
> I'm hitting EBUSY with NFCT_Q_GET.
> My impression was that it was ok to hit EBUSY, since I'm making such a heavy use of conntrack table, contantly updating in. Besides I have watch -n 1 'conntrack -L' running in another console. So it's double pressure.
> It may be beside the point, but apart from this GETing and UPDATEing, I have another thread (that uses a different handle) which every minute or so does NFCT_Q_DUMP (that's 1000+ entries) and the handle's callback then NFCT_Q_DESTROYS (based on the nfmark) approx. 80% of the dump. 

There are different situations in which you may hit EBUSY:

For example, if you call NFCT_Q_DUMP after some unconcluded dumping
(one previous NFCT_Q_DUMP operation that is still on the way).

Regarding threads, it's a bad idea to share conntrack handlers between
different threads.

As said, I need some code to look at for better helping.