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202 lines
4.4 KiB
Groff
202 lines
4.4 KiB
Groff
.\" $OpenBSD: tcpdrop.8,v 1.5 2004/05/24 13:57:31 jmc Exp $
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.\"
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.\" Copyright (c) 2009 Juli Mallett <jmallett@FreeBSD.org>
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.\" Copyright (c) 2004 Markus Friedl <markus@openbsd.org>
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.\"
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.\" Permission to use, copy, modify, and distribute this software for any
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.\" purpose with or without fee is hereby granted, provided that the above
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.\" copyright notice and this permission notice appear in all copies.
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.\"
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.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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.\"
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.Dd December 4, 2021
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.Dt TCPDROP 8
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.Os
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.Sh NAME
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.Nm tcpdrop
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.Nd drop TCP connections
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.Sh SYNOPSIS
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.Nm tcpdrop
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.Ar local-address
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.Ar local-port
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.Ar foreign-address
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.Ar foreign-port
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.Nm tcpdrop
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.Op Fl l
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.Fl a
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.Nm tcpdrop
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.Op Fl l
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.Fl C Ar cc-algo
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.Op Fl S Ar stack
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.Op Fl s Ar state
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.Nm tcpdrop
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.Op Fl l
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.Op Fl C Ar cc-algo
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.Fl S Ar stack
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.Op Fl s Ar state
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.Nm tcpdrop
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.Op Fl l
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.Op Fl C Ar cc-algo
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.Op Fl S Ar stack
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.Fl s Ar state
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.Sh DESCRIPTION
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The
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.Nm
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command may be used to drop TCP connections from the command line.
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.Pp
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If
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.Fl a
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is specified then
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.Nm
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will attempt to drop all TCP connections.
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.Pp
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If
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.Fl C Ar cc-algo
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is specified then
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.Nm
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will attempt to drop all connections using the TCP congestion control algorithm
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.Ar cc-algo .
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.Pp
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If
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.Fl S Ar stack
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is specified then
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.Nm
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will attempt to drop all connections using the TCP stack
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.Ar stack .
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.Pp
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If
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.Fl s Ar state
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is specified then
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.Nm
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will attempt to drop all TCP connections being in the state
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.Ar state .
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.Ar state
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is one of
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.Dv SYN_SENT ,
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.Dv SYN_RCVD ,
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.Dv ESTABLISHED ,
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.Dv CLOSE_WAIT ,
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.Dv FIN_WAIT_1 ,
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.Dv CLOSING ,
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.Dv LAST_ACK ,
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.Dv FIN_WAIT_2 , or
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.Dv TIME_WAIT .
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.Pp
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If multiple of
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.Fl C Ar cc-algo ,
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.Fl S Ar stack ,
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and
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.Fl s Ar state
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are specified,
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.Nm
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will attempt to drop all TCP connections using the congestion control algorithm
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.Ar cc-algo ,
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being in the state
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.Ar state ,
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and using the TCP stack
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.Ar stack ,
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if specified.
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Since TCP connections in the
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.Dv TIME_WAIT
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state are not tied to any TCP stack, using the option
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.Fl s Dv TIME_WAIT
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in combination with the
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.Fl S Ar stack
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option results in
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.Nm
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not dropping any TCP connection.
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.Pp
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The
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.Fl l
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flag may be given in addition to the
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.Fl a ,
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.Fl C ,
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.Fl S ,
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or
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.Fl s
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options to list the tcpdrop invocation to drop all corresponding TCP
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connections one at a time.
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.Pp
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If none of the
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.Fl a ,
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.Fl C ,
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.Fl S ,
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or
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.Fl s
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options are specified then only the connection between the given local
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address
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.Ar local-address ,
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port
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.Ar local-port ,
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and the foreign address
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.Ar foreign-address ,
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port
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.Ar foreign-port ,
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will be dropped.
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.Pp
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Addresses and ports may be specified by name or numeric value.
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Both IPv4 and IPv6 address formats are supported.
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.Pp
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The addresses and ports may be separated by periods or colons
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instead of spaces.
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.Sh EXIT STATUS
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.Ex -std
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.Sh EXAMPLES
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If a connection to
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.Xr httpd 8
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is causing congestion on a network link, one can drop the TCP session
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in charge:
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.Bd -literal -offset indent
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# sockstat -c | grep httpd
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www httpd 16525 3 tcp4 \e
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192.168.5.41:80 192.168.5.1:26747
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.Ed
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.Pp
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The following command will drop the connection:
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.Bd -literal -offset indent
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# tcpdrop 192.168.5.41 80 192.168.5.1 26747
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.Ed
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.Pp
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The following command will drop all connections but those to or from
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port 22, the port used by
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.Xr sshd 8 :
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.Bd -literal -offset indent
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# tcpdrop -l -a | grep -vw 22 | sh
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.Ed
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.Pp
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To drop all TCP connections using the new-reno congestion control algorithm use:
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.Bd -literal -offset indent
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# tcpdrop -C new-reno
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.Ed
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.Pp
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The following command will drop all connections using the TCP stack
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rack:
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.Bd -literal -offset indent
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# tcpdrop -S rack
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.Ed
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.Pp
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To drop all TCP connections in the LAST_ACK state use:
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.Bd -literal -offset indent
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# tcpdrop -s LAST_ACK
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.Ed
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.Pp
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To drop all TCP connections using the congestion control algorithm new-reno and
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the TCP stack rack and being in the LAST_ACK state use:
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.Bd -literal -offset indent
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# tcpdrop -C new-reno -S rack -s LAST_ACK
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.Ed
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.Sh SEE ALSO
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.Xr netstat 1 ,
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.Xr sockstat 1 ,
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.Xr tcp 4 ,
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.Xr tcp_functions 9
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.Sh AUTHORS
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.An Markus Friedl Aq Mt markus@openbsd.org
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.An Juli Mallett Aq Mt jmallett@FreeBSD.org
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