129 lines
3.8 KiB
Groff
129 lines
3.8 KiB
Groff
.\" 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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.\" $Id: faith.4,v 1.1.1.1 1999/08/08 23:30:37 itojun Exp $
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.\" $FreeBSD$
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.\"
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.Dd April 10, 1999
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.Dt FAITH 4
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.Os
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.Sh NAME
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.Nm faith
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.Nd
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.Tn IPv6-to-IPv4 TCP relay capturing interface
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.Sh SYNOPSIS
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.Cd "pseudo-device faith 1"
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.Sh DESCRIPTION
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The
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.Nm
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interface captures IPv6 TCP traffic
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for implementing userland IPv6-to-IPv4 TCP relays
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like
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.Xr faithd 8 .
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.Pp
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Special action will be taken when IPv6 TCP traffic is seen on a router
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and the routing table suggests to route it to the
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.Nm
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interface.
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In this case the packet will be accepted by the router,
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regardless of the list of IPv6 interface addresses assigned to the router.
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The packet will be captured by an IPv6 TCP socket if it has the
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.Dv IN6P_FAITH
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flag turned on and it has matching address/port pairs.
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As a result,
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.Nm
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will let you divert IPv6 TCP traffic to some specific destination addresses.
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Userland programs, such as
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.Xr faithd 8 ,
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can use this behavior to relay IPv6 TCP traffic to IPv4 TCP traffic.
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The program can accept some specific IPv6 TCP traffic, perform
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.Xr getsockname 2
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to get the IPv6 destination address specified by the client,
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and perform application-specific address mapping to relay IPv6 TCP to IPv4 TCP.
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.Pp
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The
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.Dv IN6P_FAITH
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flag on an IPv6 TCP socket can be set by using
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.Xr setsockopt 2 ,
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with
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.Fa level
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set to
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.Dv IPPROTO_IPV6
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and
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.Fa optname
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set to
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.Dv IPv6_FAITH .
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.Pp
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To handle error reports by ICMPv6 some of the ICMPv6 packets routed to the
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.Nm
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interface will need be delivered to IPv6 TCP as well.
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.Pp
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To understand how
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.Nm
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can be used take a look at the source code of
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.Xr faithd 8 .
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.Pp
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As the
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.Nm
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interface implements potentially dangerous operations,
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great care must be taken when configuring the
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.Nm
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interface.
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To avoid possible misuse the
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.Xr sysctl 8
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variable
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.Li net.inet6.ip6.keepfaith
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must be set to
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.Li 1
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prior to the use of the interface.
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When
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.Li net.inet6.ip6.keepfaith
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is set to
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.Li 0 ,
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no packets will be captured by the
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.Nm
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interface.
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.Pp
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The
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.Nm
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interface is intended to be used on routers, not on hosts.
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.\"
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.Sh SEE ALSO
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.Xr inet 4 ,
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.Xr inet6 4 ,
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.Xr faithd 8
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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 ``FAITH'' IPv6-to-IPv4 TCP relay translator
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.\" .%D July 1999
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.\" .Re
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.\"
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.Sh HISTORY
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The FAITH IPv6-to-IPv4 TCP relay translator first appeared in
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WIDE hydrangea IPv6 stack.
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