netdev - Re: TCP 2MSL on loopback

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Date:	Tue, 6 Mar 2007 11:42:00 +0100
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Howard Chu <hyc@...as.com>
Cc:	netdev@...r.kernel.org
Subject: Re: TCP 2MSL on loopback

On Tuesday 06 March 2007 10:22, Howard Chu wrote:

>
> It's a combination of 2MSL and /proc/sys/net/ipv4/ip_local_port_range -
> on my system the default port range is 32768-61000. That means if I use
> up 28232 ports in less than 2MSL then everything stops. netstat will
> show that all the available port numbers are in TIME_WAIT state. And
> this is particularly bad because while waiting for the timeout, I can't
> initiate any new outbound connections of any kind at all - telnet, ssh,
> whatever, you have to wait for at least one port to free up.
> (Interesting denial of service there....)
>
> Granted, I was running my test on 2.6.18, perhaps 2.6.21 behaves
> differently.

Could you try this attached program and tell me whats happen ?

$ gcc -O2 -o socktest socktest.c -lpthread
$ time ./socktest -n 100000
nb_conn=99999 nb_accp=99999

real    0m5.058s
user    0m0.212s
sys     0m4.844s

(on my small machine, dell d610 :) )


View attachment "socktest.c" of type "text/plain" (3409 bytes)