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 XFREE86

kill

KILL(1)                                                            User Commands                                                           KILL(1)

NAME

       kill - send a signal to a process

SYNOPSIS

       kill [options] <pid> [...]

DESCRIPTION

       The  default  signal  for kill is TERM.  Use -l or -L to list available signals.  Particularly useful signals include HUP, INT, KILL, STOP,
       CONT, and 0.  Alternate signals may be specified in three ways: -9, -SIGKILL or -KILL.  Negative PID values may be  used  to  choose  whole
       process  groups;  see  the  PGID  column  in ps command output.  A PID of -1 is special; it indicates all processes except the kill process
       itself and init.

OPTIONS

       <pid> [...]
              Send signal to every <pid> listed.

       -<signal>
       -s <signal>
       --signal <signal>
              Specify the signal to be sent.  The signal can be specified by using name or number.  The behavior of signals is explained  in  sig-
              nal(7) manual page.

       -l, --list [signal]
              List signal names.  This option has optional argument, which will convert signal number to signal name, or other way round.

       -L, --table
              List signal names in a nice table.

       NOTES  Your shell (command line interpreter) may have a built-in kill command.  You may need to run the command described here as /bin/kill
              to solve the conflict.

EXAMPLES

       kill -9 -1
              Kill all processes you can kill.

       kill -l 11
              Translate number 11 into a signal name.

       kill -L
              List the available signal choices in a nice table.

       kill 123 543 2341 3453
              Send the default signal, SIGTERM, to all those processes.

SEE ALSO

       kill(2), killall(1), nice(1), pkill(1), renice(1), signal(7), skill(1)

STANDARDS

       This command meets appropriate standards. The -L flag is Linux-specific.

AUTHOR

       Albert Cahalan <albert@users.sf.net> wrote kill in 1999 to replace a bsdutils one that was not standards  compliant.   The  util-linux  one
       might also work correctly.

REPORTING BUGS

       Please send bug reports to <procps@freelists.org>

procps-ng                                                          October 2011                                                            KILL(1)

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