134 lines
3.9 KiB
Groff
134 lines
3.9 KiB
Groff
.\" $KAME: faith.4,v 1.9 2001/04/27 17:26:35 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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.\" $FreeBSD$
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.\"
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.Dd January 23, 2012
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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 IPv6-to-IPv4 TCP relay capturing interface
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.Sh SYNOPSIS
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.Cd "device faith"
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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 relay
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like
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.Xr faithd 8 .
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.Pp
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Each
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.Nm
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interface is created at runtime using interface cloning.
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This is
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most easily done with the
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.Xr ifconfig 8
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.Cm create
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command or using the
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.Va cloned_interfaces
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variable in
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.Xr rc.conf 5 .
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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 default 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 matching address/port pairs.
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As a result,
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.Nm
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will let you capture 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 a IPv6 TCP socket can be set by using
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.Xr setsockopt 2 ,
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with level
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.Dv IPPROTO_IPV6
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and optname
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.Dv IPv6_FAITH .
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.Pp
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To handle error reports by ICMPv6, some ICMPv6 packets routed to an
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.Nm
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interface will 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 it.
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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 using the interface.
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When
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.Li net.inet6.ip6.keepfaith
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is
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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 "An IPv6-to-IPv4 transport relay translator"
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.%O RFC3142
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.Re
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.Sh HISTORY
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The FAITH IPv6-to-IPv4 TCP relay translator first appeared in the
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WIDE hydrangea IPv6 stack.
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