402 lines
9.7 KiB
Groff
402 lines
9.7 KiB
Groff
.\" $NetBSD: faithd.8,v 1.28 2010/01/15 19:19:32 joerg Exp $
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.\" $KAME: faithd.8,v 1.37 2002/05/09 14:21:23 itojun Exp $
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.\"
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.\" Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
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.\" All rights reserved.
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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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.\" 3. Neither the name of the project nor the names of its contributors
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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 PROJECT 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 PROJECT 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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.Dd January 9, 2010
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.Dt FAITHD 8
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.Os
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.Sh NAME
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.Nm faithd
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.Nd FAITH IPv6/v4 translator daemon
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.Sh SYNOPSIS
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.Nm
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.Op Fl dp
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.Op Fl f Ar configfile
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.Ar service
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.Op Ar serverpath Op Ar serverargs
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.Nm
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.Sh DESCRIPTION
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The
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.Nm
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utility provides IPv6-to-IPv4 TCP relaying.
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It can only be used on an IPv4/v6 dual stack router.
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.Pp
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When
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.Nm
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receives
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.Tn TCPv6
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traffic, it will relay the
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.Tn TCPv6
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traffic to
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.Tn TCPv4 .
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The destination for the relayed
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.Tn TCPv4
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connection will be determined by the last 4 octets of the original
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.Tn IPv6
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destination.
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For example, if
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.Li 2001:0db8:4819:ffff::
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is reserved for
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.Nm ,
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and the
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.Tn TCPv6
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destination address is
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.Li 2001:0db8:4819:ffff::0a01:0101 ,
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the traffic will be relayed to IPv4 destination
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.Li 10.1.1.1 .
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.Pp
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To use the
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.Nm
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translation service,
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an IPv6 address prefix must be reserved for mapping IPv4 addresses into.
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The kernel must be properly configured to route all the TCP connections
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toward the reserved IPv6 address prefix into the
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.Xr faith 4
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pseudo interface, using the
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.Xr route 8
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command.
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Also,
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.Xr sysctl 8
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should be used to configure
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.Dv net.inet6.ip6.keepfaith
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to
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.Dv 1 .
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.Pp
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The router must be configured to capture all the TCP traffic
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for the reserved
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.Tn IPv6
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address prefix, by using
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.Xr route 8
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and
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.Xr sysctl 8
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commands.
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.Pp
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The
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.Nm
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utility needs special name-to-address translation logic, so that
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hostnames gets resolved into the special
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.Tn IPv6
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address prefix.
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For small-scale installations, use
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.Xr hosts 5 ;
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For large-scale installations, it is useful to have
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a DNS server with special address translation support.
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An implementation called
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.Nm totd
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is available at
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.Pa http://www.vermicelli.pasta.cs.uit.no/software/totd.html .
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Make sure you do not propagate translated DNS records over to normal
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DNS, as it can cause severe problems.
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.Ss Daemon mode
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When
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.Nm
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is invoked as a standalone program,
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.Nm
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will daemonize itself.
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.Nm
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will listen to
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.Tn TCPv6
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port
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.Ar service .
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If
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.Tn TCPv6
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traffic to port
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.Ar service
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is found, it relays the connection.
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.Pp
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Since
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.Nm
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listens to TCP port
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.Ar service ,
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it is not possible to run local TCP daemons for port
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.Ar service
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on the router, using
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.Xr inetd 8
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or other standard mechanisms.
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By specifying
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.Ar serverpath
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to
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.Nm ,
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you can run local daemons on the router.
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The
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.Nm
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utility will invoke ia local daemon at
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.Ar serverpath
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if the destination address is a local interface address,
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and will perform translation to IPv4 TCP in other cases.
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You can also specify
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.Ar serverargs
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for the arguments for the local daemon.
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.Pp
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The following options are available:
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.Bl -tag -width indent
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.It Fl d
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Debugging information will be generated using
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.Xr syslog 3 .
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.It Fl f Ar configfile
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Specify a configuration file for access control.
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See below.
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.It Fl p
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Use privileged TCP port number as source port,
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for IPv4 TCP connection toward final destination.
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For relaying
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.Xr ftp 1
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this flag is not necessary as special program code is supplied.
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.El
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.Pp
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.Nm
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will relay both normal and out-of-band TCP data.
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It is capable of emulating TCP half close as well.
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.Nm
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includes special support for protocols used by
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.Xr ftp 1 .
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When translating the FTP protocol,
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.Nm
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translates network level addresses in
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.Li PORT/LPRT/EPRT
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and
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.Li PASV/LPSV/EPSV
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commands.
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.Pp
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Inactive sessions will be disconnected in 30 minutes,
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to prevent stale sessions from chewing up resources.
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This may be inappropriate for some services
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.Pq should this be configurable? .
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.Ss inetd mode
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When
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.Nm
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is invoked via
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.Xr inetd 8 ,
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.Nm
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will handle connections passed from standard input.
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If the connection endpoint is in the reserved IPv6 address prefix,
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.Nm
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will relay the connection.
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Otherwise,
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.Nm
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will invoke a service-specific daemon like
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.Xr telnetd 8 ,
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by using the command argument passed from
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.Xr inetd 8 .
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.Pp
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.Nm
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determines operation mode by the local TCP port number,
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and enables special protocol handling whenever necessary/possible.
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For example, if
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.Nm
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is invoked via
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.Xr inetd 8
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on the FTP port, it will operate as an FTP relay.
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.\".Pp
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.\"The operation mode requires special support for
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.\".Nm
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.\"in
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.\".Xr inetd 8 .
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.Ss Access control
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To prevent malicious access,
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.Nm
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implements a simple address-based access control.
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With
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.Pa /etc/faithd.conf
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.Po
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or
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.Ar configfile
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specified by
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.Fl f
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.Pc ,
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.Nm
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will avoid relaying unwanted traffic.
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The
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.Pa faithd.conf
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configuration file contains directives of the following format:
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.Bl -bullet
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.It
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.Xo
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.Ar src/slen Li deny Ar dst/dlen
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.Xc
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.Pp
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If the source address of a query matches
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.Ar src/slen ,
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and the translated destination address matches
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.Ar dst/dlen ,
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deny the connection.
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.It
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.Xo
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.Ar src/slen Li permit Ar dst/dlen
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.Xc
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.Pp
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If the source address of a query matches
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.Ar src/slen ,
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and the translated destination address matches
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.Ar dst/dlen ,
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permit the connection.
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.El
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.Pp
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The directives are evaluated in sequence,
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and the first matching entry will be effective.
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If there is no match
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.Pq if we reach the end of the ruleset
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the traffic will be denied.
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.Pp
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With inetd mode,
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traffic may be filtered by using access control functionality in
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.Xr inetd 8 .
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.Sh EXIT STATUS
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.Nm
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exits with
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.Dv EXIT_SUCCESS
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.Pq 0
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on success, and
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.Dv EXIT_FAILURE
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.Pq 1
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on error.
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.Sh EXAMPLES
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Before invoking
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.Nm ,
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the
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.Xr faith 4
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interface has to be configured properly.
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.Bd -literal
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# sysctl -w net.inet6.ip6.accept_rtadv=0
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# sysctl -w net.inet6.ip6.forwarding=1
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# sysctl -w net.inet6.ip6.keepfaith=1
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# ifconfig faith0 create up
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# route add -inet6 2001:0db8:4819:ffff:: -prefixlen 96 ::1
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# route change -inet6 2001:0db8:4819:ffff:: -prefixlen 96 -ifp faith0
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.Ed
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.Ss Daemon mode samples
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To translate
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.Li telnet
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service, and provide no local telnet service, invoke
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.Nm
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as follows:
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.Bd -literal
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# faithd telnet
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.Ed
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.Pp
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If you would like to provide local telnet service via
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.Xr telnetd 8
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on
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.Pa /usr/libexec/telnetd ,
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use the following command line:
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.Bd -literal
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# faithd telnet /usr/libexec/telnetd telnetd
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.Ed
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.Pp
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If you would like to pass extra arguments to the local daemon:
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.Bd -literal
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# faithd ftp /usr/libexec/ftpd ftpd -l
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.Ed
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.Pp
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Here are some other examples.
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You may need
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.Fl p
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if the service checks the source port range.
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.Bd -literal
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# faithd ssh
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# faithd telnet /usr/libexec/telnetd telnetd
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.Ed
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.Ss inetd mode samples
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Add the following lines into
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.Xr inetd.conf 5 .
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.\"Syntax may vary depending upon your operating system.
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.Bd -literal
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telnet stream faith/tcp6 nowait root faithd telnetd
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ftp stream faith/tcp6 nowait root faithd ftpd -l
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ssh stream faith/tcp6 nowait root faithd /usr/sbin/sshd -i
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.Ed
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.Pp
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.Xr inetd 8
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will open listening sockets with kernel TCP relay support enabled.
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Whenever a connection comes in,
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.Nm
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will be invoked by
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.Xr inetd 8 .
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If the connection endpoint is in the reserved IPv6 address prefix.
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.Nm
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will relay the connection.
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Otherwise,
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.Nm
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will invoke service-specific daemon like
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.Xr telnetd 8 .
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.Ss Access control samples
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The following illustrates a simple
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.Pa faithd.conf
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setting.
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.Bd -literal
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# permit anyone from 2001:0db8:ffff::/48 to use the translator,
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# to connect to the following IPv4 destinations:
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# - any location except 10.0.0.0/8 and 127.0.0.0/8.
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# Permit no other connections.
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#
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2001:0db8:ffff::/48 deny 10.0.0.0/8
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2001:0db8:ffff::/48 deny 127.0.0.0/8
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2001:0db8:ffff::/48 permit 0.0.0.0/0
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.Ed
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.Sh SEE ALSO
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.Xr faith 4 ,
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.Xr route 8 ,
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.Xr sysctl 8 ,
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.Pa pkgsrc/net/totd
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.Rs
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.%A Jun-ichiro itojun Hagino
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.%A Kazu Yamamoto
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.%T "An IPv6-to-IPv4 transport relay translator"
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.%B RFC 3142
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.%U ftp://ftp.isi.edu/in-notes/rfc3142.txt
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.%D June 2001
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.Re
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.\"
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.Sh HISTORY
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The
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.Nm
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utility first appeared in the WIDE Hydrangea IPv6 protocol stack kit.
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.\"
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.Sh SECURITY CONSIDERATIONS
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It is very insecure to use IP-address based authentication, for connections relayed by
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.Nm ,
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and any other TCP relaying services.
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.Pp
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Administrators are advised to limit accesses to
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.Nm
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using
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.Pa faithd.conf ,
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or by using IPv6 packet filters, to protect the
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.Nm
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service from malicious parties, and to avoid theft of service/bandwidth.
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IPv6 destination addresses can be limited by
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carefully configuring routing entries that point to
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.Xr faith 4 ,
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using
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.Xr route 8 .
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The IPv6 source address needs to be filtered using packet filters.
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The documents listed in
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.Sx SEE ALSO
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have more information on this topic.
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