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Re: DoS attack against TCP services



On Mon, 19 Jan 2015, Michael van Elst wrote:

Date: Mon, 19 Jan 2015 09:24:02 +0000 (UTC)
From: Michael van Elst <mlelstv%serpens.de@localhost>
To: current-users%netbsd.org@localhost
Newsgroups: lists.netbsd.current-users
Subject: Re: DoS attack against TCP services

6bone%6bone.informatik.uni-leipzig.de@localhost writes:

Unfortunately, all TCP connections are now in the TIME_WAIT state.

bash-4.3 # netstat -a -n | grep TIME_WAIT | wc -l
     34611

Is there a way to remove it without rebooting the server?

tcpdrop(8)?

It works. But why doesn't drop the kernel it automatically?


TCP connections in TIME_WAIT will expire after some time, usually between
10 and 60 seconds after a connection is closed. The timeout depends on
the distance of the remote machine.

Yes, but in my case the connections are not expired after over one hour.


Uwe



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