2006-09-03 03:40:22 +04:00
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.\" $NetBSD: lo.4,v 1.10 2006/09/02 23:40:22 wiz Exp $
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1994-11-30 19:22:03 +03:00
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.\"
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.\" Copyright (c) 1983, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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1993-03-21 12:45:37 +03:00
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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2003-08-07 14:30:41 +04:00
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.\" 3. Neither the name of the University nor the names of its contributors
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1993-03-21 12:45:37 +03:00
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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1994-11-30 19:22:03 +03:00
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.\" @(#)lo.4 8.1 (Berkeley) 6/5/93
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1993-03-21 12:45:37 +03:00
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.\"
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2006-09-03 03:40:22 +04:00
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.Dd September 3, 2006
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1993-03-21 12:45:37 +03:00
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.Dt LO 4
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1999-03-16 04:19:14 +03:00
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.Os
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1993-03-21 12:45:37 +03:00
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.Sh NAME
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.Nm lo
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.Nd software loopback network interface
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.Sh SYNOPSIS
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2004-12-04 19:47:10 +03:00
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.Cd "pseudo-device loop"
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1993-03-21 12:45:37 +03:00
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.Sh DESCRIPTION
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The
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.Nm loop
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interface is a software loopback mechanism which may be used for
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performance analysis, software testing, and/or local communication.
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1993-03-21 12:45:37 +03:00
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As with other network interfaces, the loopback interface must have
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network addresses assigned for each address family with which it
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is to be used.
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These addresses may be set or changed with the
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1993-03-21 12:45:37 +03:00
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.Dv SIOCSIFADDR
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.Xr ioctl 2 .
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2004-12-04 20:03:04 +03:00
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The loopback interface should be the last interface configured, as
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protocols may use the order of configuration as an indication of
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priority.
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1993-03-21 12:45:37 +03:00
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The loopback should
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.Em never
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2004-12-04 20:03:04 +03:00
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be configured first unless no hardware interfaces exist.
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2004-12-04 19:47:10 +03:00
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.Pp
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The loopback interface
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.Nm lo0
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2004-12-04 20:03:04 +03:00
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is created at boottime, it always exists and cannot be destroyed
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with
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2004-12-04 19:47:10 +03:00
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.Xr ifconfig 8 .
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Additional loopback interfaces can be created by using the
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.Xr ifconfig 8
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2004-12-04 20:03:04 +03:00
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.Cm create
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2004-12-04 19:47:10 +03:00
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command.
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1993-03-21 12:45:37 +03:00
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.Sh DIAGNOSTICS
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.Bl -diag
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2001-09-22 05:22:48 +04:00
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.It lo%d: can't handle af%d .
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2004-12-04 20:03:04 +03:00
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The interface was handed a message with addresses formatted in an
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unsuitable address family; the packet was dropped.
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1993-03-21 12:45:37 +03:00
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.El
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.Sh SEE ALSO
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.Xr inet 4 ,
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2001-09-22 05:22:48 +04:00
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.Xr intro 4 ,
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.Xr ifconfig 8
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1993-03-21 12:45:37 +03:00
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.Sh HISTORY
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The
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.Nm
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device appeared in
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.Bx 4.2 .
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.Sh BUGS
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Previous versions of the system enabled the loopback interface
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automatically, using a nonstandard Internet address (127.1).
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Use of that address is now discouraged; a reserved host address
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for the local network should be used instead.
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