bsd/man/man4/faith.4

   1 .\"     $KAME: faith.4,v 1.9 2001/04/27 17:26:35 itojun Exp $
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  30 .\"     $FreeBSD: src/share/man/man4/faith.4,v 1.6.2.3 2001/07/03 11:01:24 ume Exp $
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  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
  41 The
  42 .Nm
  43 interface captures IPv6 TCP traffic,
  44 for implementing userland IPv6-to-IPv4 TCP relay
  45 like
  46 .Xr faithd 8 .
  47 .Pp
  48 Special action will be taken when IPv6 TCP traffic is seen on a router,
  49 and routing table suggests to route it to
  50 .Nm
  51 interface.
  52 In this case, the packet will be accepted by the router,
  53 regardless of list of IPv6 interface addresses assigned to the router.
  54 The packet will be captured by an IPv6 TCP socket, if it has
  55 .Dv IN6P_FAITH
  56 flag turned on and it has matching address/port pairs.
  57 In result,
  58 .Nm
  59 will let you capture IPv6 TCP traffic to some specific destination addresses.
  60 Userland programs, such as
  61 .Xr faithd 8
  62 can use this behavior to relay IPv6 TCP traffic to IPv4 TCP traffic.
  63 The program can accept some specific IPv6 TCP traffic, perform
  64 .Xr getsockname 2
  65 to get the IPv6 destination address specified by the client,
  66 and perform application-specific address mapping to relay IPv6 TCP to IPv4 TCP.
  67 .Pp
  68 The
  69 .Dv IN6P_FAITH
  70 flag on IPv6 TCP socket can be set by using
  71 .Xr setsockopt 2 ,
  72 with level equals to
  73 .Dv IPPROTO_IPV6
  74 and optname equals to
  75 .Dv IPv6_FAITH .
  76 .Pp
  77 To handle error reports by ICMPv6, some of ICMPv6 packets routed to
  78 .Nm
  79 interface will be delivered to IPv6 TCP, as well.
  80 .Pp
  81 To understand how
  82 .Nm
  83 can be used, take a look at source code of
  84 .Xr faithd 8 .
  85 .Pp
  86 As
  87 .Nm
  88 interface implements potentially dangerous operation,
  89 great care must be taken when configuring
  90 .Nm
  91 interface.
  92 To avoid possible misuse,
  93 .Xr sysctl 8
  94 variable
  95 .Li net.inet6.ip6.keepfaith
  96 must be set to
  97 .Li 1
  98 prior to the use of the interface.
  99 When
 100 .Li net.inet6.ip6.keepfaith
 101 is
 102 .Li 0 ,
 103 no packet will be captured by
 104 .Nm
 105 interface.
 106 .Pp
 107 .Nm
 108 interface 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
 123 The FAITH IPv6-to-IPv4 TCP relay translator was first appeared in
 124 WIDE hydrangea IPv6 stack.