1.\" Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
2.\" All rights reserved.
3.\"
4.\" Redistribution and use in source and binary forms, with or without
5.\" modification, are permitted provided that the following conditions
6.\" are met:
7.\" 1. Redistributions of source code must retain the above copyright
8.\" notice, this list of conditions and the following disclaimer.
9.\" 2. Redistributions in binary form must reproduce the above copyright
10.\" notice, this list of conditions and the following disclaimer in the
11.\" documentation and/or other materials provided with the distribution.
12.\" 3. Neither the name of the project nor the names of its contributors
13.\" may be used to endorse or promote products derived from this software
14.\" without specific prior written permission.
15.\"
16.\" THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26.\" SUCH DAMAGE.
27.\"
28.\" $Id: faith.4,v 1.1.1.1 1999/08/08 23:30:37 itojun Exp $
29.\" $FreeBSD: head/share/man/man4/faith.4 76175 2001-05-01 09:15:30Z schweikh $
30.\"
31.Dd April 10, 1999
32.Dt FAITH 4
33.Os
34.Sh NAME
35.Nm faith
36.Nd
37.Tn IPv6-to-IPv4 TCP
38relay capturing interface
39.Sh SYNOPSIS
40.Cd "device faith 1"
41.Sh DESCRIPTION
42The
43.Nm
44interface captures IPv6 TCP traffic
45for implementing userland IPv6-to-IPv4 TCP relays
46like
47.Xr faithd 8 .
48.Pp
49Special action will be taken when IPv6 TCP traffic is seen on a router
50and the routing table suggests to route it to the
51.Nm
52interface.
53In this case the packet will be accepted by the router,
54regardless of the list of IPv6 interface addresses assigned to the router.
55The packet will be captured by an IPv6 TCP socket if it has the
56.Dv IN6P_FAITH
57flag turned on and it has matching address/port pairs.
58As a result,
59.Nm
60will let you divert IPv6 TCP traffic to some specific destination addresses.
61Userland programs, such as
62.Xr faithd 8 ,
63can use this behavior to relay IPv6 TCP traffic to IPv4 TCP traffic.
64The program can accept some specific IPv6 TCP traffic, perform
65.Xr getsockname 2
66to get the IPv6 destination address specified by the client,
67and perform application-specific address mapping to relay IPv6 TCP to IPv4 TCP.
68.Pp
69The
70.Dv IN6P_FAITH
71flag on an IPv6 TCP socket can be set by using
72.Xr setsockopt 2 ,
73with
74.Fa level
75set to
76.Dv IPPROTO_IPV6
77and
78.Fa optname
79set to
80.Dv IPv6_FAITH .
81.Pp
82To handle error reports by ICMPv6 some of the ICMPv6 packets routed to the
83.Nm
84interface will need be delivered to IPv6 TCP as well.
85.Pp
86To understand how
87.Nm
88can be used take a look at the source code of
89.Xr faithd 8 .
90.Pp
91As the
92.Nm
93interface implements potentially dangerous operations,
94great care must be taken when configuring the
95.Nm
96interface.
97To avoid possible misuse the
98.Xr sysctl 8
99variable
100.Li net.inet6.ip6.keepfaith
101must be set to
102.Li 1
103prior to the use of the interface.
104When
105.Li net.inet6.ip6.keepfaith
106is set to
107.Li 0 ,
108no packets will be captured by the
109.Nm
110interface.
111.Pp
112The
113.Nm
114interface is intended to be used on routers, not on hosts.
115.\"
116.Sh SEE ALSO
117.Xr inet 4 ,
118.Xr inet6 4 ,
119.Xr faithd 8
120.\" .Rs
121.\" .%A Jun-ichiro itojun Hagino
122.\" .%A Kazu Yamamoto
123.\" .%T ``FAITH'' IPv6-to-IPv4 TCP relay translator
124.\" .%D July 1999
125.\" .Re
126.\"
127.Sh HISTORY
128The FAITH IPv6-to-IPv4 TCP relay translator first appeared in
129WIDE hydrangea IPv6 stack.
2.\" All rights reserved.
3.\"
4.\" Redistribution and use in source and binary forms, with or without
5.\" modification, are permitted provided that the following conditions
6.\" are met:
7.\" 1. Redistributions of source code must retain the above copyright
8.\" notice, this list of conditions and the following disclaimer.
9.\" 2. Redistributions in binary form must reproduce the above copyright
10.\" notice, this list of conditions and the following disclaimer in the
11.\" documentation and/or other materials provided with the distribution.
12.\" 3. Neither the name of the project nor the names of its contributors
13.\" may be used to endorse or promote products derived from this software
14.\" without specific prior written permission.
15.\"
16.\" THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26.\" SUCH DAMAGE.
27.\"
28.\" $Id: faith.4,v 1.1.1.1 1999/08/08 23:30:37 itojun Exp $
29.\" $FreeBSD: head/share/man/man4/faith.4 76175 2001-05-01 09:15:30Z schweikh $
30.\"
31.Dd April 10, 1999
32.Dt FAITH 4
33.Os
34.Sh NAME
35.Nm faith
36.Nd
37.Tn IPv6-to-IPv4 TCP
38relay capturing interface
39.Sh SYNOPSIS
40.Cd "device faith 1"
41.Sh DESCRIPTION
42The
43.Nm
44interface captures IPv6 TCP traffic
45for implementing userland IPv6-to-IPv4 TCP relays
46like
47.Xr faithd 8 .
48.Pp
49Special action will be taken when IPv6 TCP traffic is seen on a router
50and the routing table suggests to route it to the
51.Nm
52interface.
53In this case the packet will be accepted by the router,
54regardless of the list of IPv6 interface addresses assigned to the router.
55The packet will be captured by an IPv6 TCP socket if it has the
56.Dv IN6P_FAITH
57flag turned on and it has matching address/port pairs.
58As a result,
59.Nm
60will let you divert IPv6 TCP traffic to some specific destination addresses.
61Userland programs, such as
62.Xr faithd 8 ,
63can use this behavior to relay IPv6 TCP traffic to IPv4 TCP traffic.
64The program can accept some specific IPv6 TCP traffic, perform
65.Xr getsockname 2
66to get the IPv6 destination address specified by the client,
67and perform application-specific address mapping to relay IPv6 TCP to IPv4 TCP.
68.Pp
69The
70.Dv IN6P_FAITH
71flag on an IPv6 TCP socket can be set by using
72.Xr setsockopt 2 ,
73with
74.Fa level
75set to
76.Dv IPPROTO_IPV6
77and
78.Fa optname
79set to
80.Dv IPv6_FAITH .
81.Pp
82To handle error reports by ICMPv6 some of the ICMPv6 packets routed to the
83.Nm
84interface will need be delivered to IPv6 TCP as well.
85.Pp
86To understand how
87.Nm
88can be used take a look at the source code of
89.Xr faithd 8 .
90.Pp
91As the
92.Nm
93interface implements potentially dangerous operations,
94great care must be taken when configuring the
95.Nm
96interface.
97To avoid possible misuse the
98.Xr sysctl 8
99variable
100.Li net.inet6.ip6.keepfaith
101must be set to
102.Li 1
103prior to the use of the interface.
104When
105.Li net.inet6.ip6.keepfaith
106is set to
107.Li 0 ,
108no packets will be captured by the
109.Nm
110interface.
111.Pp
112The
113.Nm
114interface is intended to be used on routers, not on hosts.
115.\"
116.Sh SEE ALSO
117.Xr inet 4 ,
118.Xr inet6 4 ,
119.Xr faithd 8
120.\" .Rs
121.\" .%A Jun-ichiro itojun Hagino
122.\" .%A Kazu Yamamoto
123.\" .%T ``FAITH'' IPv6-to-IPv4 TCP relay translator
124.\" .%D July 1999
125.\" .Re
126.\"
127.Sh HISTORY
128The FAITH IPv6-to-IPv4 TCP relay translator first appeared in
129WIDE hydrangea IPv6 stack.