1.\" $KAME: faith.4,v 1.9 2001/04/27 17:26:35 itojun Exp $ 2.\" 3.\" Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project. 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the project nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" $FreeBSD: src/share/man/man4/faith.4,v 1.6.2.3 2001/07/03 11:01:24 ume Exp $ 31.\" 32.Dd April 10, 1999 33.Dt FAITH 4 34.Os 35.Sh NAME 36.Nm faith 37.Nd IPv6-to-IPv4 TCP relay capturing interface 38.Sh SYNOPSIS 39.Cd "pseudo-device faith" Op Ar count 40.Sh DESCRIPTION 41The 42.Nm 43interface captures IPv6 TCP traffic, 44for implementing userland IPv6-to-IPv4 TCP relay 45like 46.Xr faithd 8 . 47.Pp 48Special action will be taken when IPv6 TCP traffic is seen on a router, 49and routing table suggests to route it to 50.Nm 51interface. 52In this case, the packet will be accepted by the router, 53regardless of list of IPv6 interface addresses assigned to the router. 54The packet will be captured by an IPv6 TCP socket, if it has 55.Dv IN6P_FAITH 56flag turned on and it has matching address/port pairs. 57In result, 58.Nm 59will let you capture IPv6 TCP traffic to some specific destination addresses. 60Userland programs, such as 61.Xr faithd 8 62can use this behavior to relay IPv6 TCP traffic to IPv4 TCP traffic. 63The program can accept some specific IPv6 TCP traffic, perform 64.Xr getsockname 2 65to get the IPv6 destination address specified by the client, 66and perform application-specific address mapping to relay IPv6 TCP to IPv4 TCP. 67.Pp 68The 69.Dv IN6P_FAITH 70flag on IPv6 TCP socket can be set by using 71.Xr setsockopt 2 , 72with level equals to 73.Dv IPPROTO_IPV6 74and optname equals to 75.Dv IPv6_FAITH . 76.Pp 77To handle error reports by ICMPv6, some of ICMPv6 packets routed to 78.Nm 79interface will be delivered to IPv6 TCP, as well. 80.Pp 81To understand how 82.Nm 83can be used, take a look at source code of 84.Xr faithd 8 . 85.Pp 86As 87.Nm 88interface implements potentially dangerous operation, 89great care must be taken when configuring 90.Nm 91interface. 92To avoid possible misuse, 93.Xr sysctl 8 94variable 95.Li net.inet6.ip6.keepfaith 96must be set to 97.Li 1 98prior to the use of the interface. 99When 100.Li net.inet6.ip6.keepfaith 101is 102.Li 0 , 103no packet will be captured by 104.Nm 105interface. 106.Pp 107.Nm 108interface is intended to be used on routers, not on hosts. 109.\" 110.Sh SEE ALSO 111.Xr inet 4 , 112.Xr inet6 4 , 113.Xr faithd 8 114.Rs 115.%A Jun-ichiro itojun Hagino 116.%A Kazu Yamamoto 117.%T "An IPv6-to-IPv4 transport relay translator" 118.%R internet draft 119.%N draft-ietf-ngtrans-tcpudp-relay-04.txt 120.%O work in progress material 121.Re 122.Sh HISTORY 123The FAITH IPv6-to-IPv4 TCP relay translator was first appeared in 124WIDE hydrangea IPv6 stack. 125