Large number of invalid packets detected
brice+nginx at daysofwonder.com
Sun May 18 18:43:08 MSD 2008
On Sun, May 18, 2008 09:11, Rt Ibmer wrote:
> Hi all - I'm using the latest version of nginx 6 and recently put iptables
> in place.
> I am seeing a significant number of matches for the following iptables
> iptables -A INPUT -m state --state INVALID -j LOG --log-prefix
> iptables -A INPUT -m state --state INVALID -j DROP
You didn't show us what was important: the log that was produced.
If the rejected packet was a ACK/FIN, then it is harmless.
On busy servers conntrack removes the connection from its table as soon as
it gets the FIN packet. When the ACK/FIN then comes, the connection is not
known and this is not a SYN. It logs it as invalid.
This could also have been a scan (nmap can trigger invalid packets too).
What kernel version are you running?
I remember that there was some issues around 126.96.36.199 about tcp reopening
in nf_conntrack, see this commit for more information:
It was definitely fixed around 188.8.131.52. Maybe you encounter this problem.
Days of Wonder
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