nf_conntrack_count versus '/proc/net/nf_conntrack | wc -l' count

[Afi Gjermund <afigjermund@gmail.com>]

Hi all,

I am running into an odd issue where the kernel begins to drop packets
because the connection tracking table is full. (I am running
2.6.26.5).

A 'cat /proc/sys/net/netfilter/nf_conntrack_count' says 4096.  But if
I do a 'cat /proc/net/nf_conntrack | wc -l' then it says 4.

A tail on /var/log/messages has:

Feb 15 16:45:33 titan user.warn kernel: __ratelimit: 20 messages suppressed
Feb 15 16:45:33 titan user.warn kernel: nf_conntrack: table full,
dropping packet.

I have an interface that allows me to do a 'nf_conntrack_flush' in
kernel, but that seems to only clear the table of
/proc/net/nf_conntrack and not the count the kernel has.

I need a way to ensure that at say 95% there is a way to clear the
"actual" table as well as the count...whichever that may be.  There
seems to be a disconnect between the implementation versus my
understanding of how the system is working. Any help is appreciated.

Afi