How to kill a TCP connection which has status TIME

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Operating Systems Linux Red Hat How to kill a TCP connection which has status TIME_WAIT & no PID Post 302433223 by thiemel on Tuesday 29th of June 2010 03:33:31 AM

06-29-2010

Registered User

Quote:

Originally Posted by Davinder31may

Hi,

I want to kill TCP connections which have status as TIME_WAIT & no PID

(as per the output of the "netstat - p" command).

Is there any command/utility available to kill connections to a specific port or IP address.

The problem is that these connections don't have process ID (see below).

Hi,
there are two ways of "killing" TIME_WAIT connection:
1) change time of ip_conntrack_timeout_time_wait (via sysctl or by writing number of seconds to /proc/sys/net/ipv4/netfilter/ip_conntrack_tcp_timeout_time_wait by "echo" command)
2) use "lsof" (list opened files) command, eg:

Code:

gate1:~# lsof -n -i@127.0.0.1
COMMAND   PID     USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
sshd      878 thiemtom   12u  IPv4 276087      0t0  TCP 127.0.0.1:57480->127.0.0.1:openvpn (ESTABLISHED)
sshd      878 thiemtom   13u  IPv4 276139      0t0  TCP 127.0.0.1:60649->127.0.0.1:xmpp-client (ESTABLISHED)
named    1494     bind   20u  IPv4   5358      0t0  TCP 127.0.0.1:domain (LISTEN)
named    1494     bind   26u  IPv4   5371      0t0  TCP 127.0.0.1:953 (LISTEN)
named    1494     bind  512u  IPv4   5357      0t0  UDP 127.0.0.1:domain 
lwresd   1591     root  512u  IPv4   5589      0t0  UDP 127.0.0.1:921 
ntpd     1605      ntp   18u  IPv4   5618      0t0  UDP 127.0.0.1:ntp 
openvpn  1637   nobody    7u  IPv4 276088      0t0  TCP 127.0.0.1:openvpn->127.0.0.1:57480 (ESTABLISHED)
epmd     1707 ejabberd    4u  IPv4   6890      0t0  TCP 127.0.0.1:4369->127.0.0.1:39726 (ESTABLISHED)
zebra    1708   quagga    9u  IPv4   6480      0t0  TCP 127.0.0.1:zebra (LISTEN)
ospfd    1758   quagga    7u  IPv4   6548      0t0  TCP 127.0.0.1:ospfd (LISTEN)
beam     1816 ejabberd    8u  IPv4   6889      0t0  TCP 127.0.0.1:39726->127.0.0.1:4369 (ESTABLISHED)
beam     1816 ejabberd   20u  IPv4   7591      0t0  TCP 127.0.0.1:5555 (LISTEN)
beam     1816 ejabberd   22u  IPv4   7756      0t0  TCP 127.0.0.1:5555->127.0.0.1:40447 (ESTABLISHED)
beam     1816 ejabberd   24u  IPv4 276140      0t0  TCP 127.0.0.1:xmpp-client->127.0.0.1:60649 (ESTABLISHED)
python   1840   pyicqt    3u  IPv4   7755      0t0  TCP 127.0.0.1:40447->127.0.0.1:5555 (ESTABLISHED)
sshd    29453     root    8u  IPv4 311274      0t0  TCP 127.0.0.1:6010 (LISTEN)

But I don't see the reason why to "kill" TCP_WAIT connection - it will timeout itself after some time (see ip_conntrack_timeout_time_wait)

thiemel

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LEARN ABOUT OSX

kill.d

kill.d(1m)							   USER COMMANDS							kill.d(1m)

NAME

       kill.d - snoop process signals as they occur. Uses DTrace.

SYNOPSIS

       kill.d

DESCRIPTION

       kill.d is a simple DTrace program to print details of process signals as they are sent, such as the PID source and destination, signal num-
       ber and result.

       This program can be used to determine which process is sending signals to which other process.

       Since this uses DTrace, only users with root privileges can run this command.

EXAMPLES

       Default output, print process signals as they are sent.
	      # kill.d

FIELDS

       FROM   source PID

       COMMAND
	      source command name

       TO     destination PID

       SIG    destination signal ("9" for a kill -9)

       RESULT result of signal (-1 is for failure)

DOCUMENTATION

       See the DTraceToolkit for further documentation under the Docs directory. The DTraceToolkit docs may include full worked examples with ver-
       bose descriptions explaining the output.

EXIT

       kill.d will run forever until Ctrl-C is hit.

AUTHOR

       Brendan Gregg [Sydney, Australia]

SEE ALSO

       dtrace(1M), truss(1)

version 0.90							   May 14, 2005 							kill.d(1m)

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