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NAME    [Toc]    [Back]

     faith - IPv6-to-IPv4 TCP relay capturing interface

SYNOPSIS    [Toc]    [Back]

     pseudo-device faith [count]

DESCRIPTION    [Toc]    [Back]

     The faith interface captures IPv6 TCP  traffic,  for  implementing userland
     IPv6-to-IPv4 TCP relay similar to faithd(8).

     A  faith  interface  can  be  created  at  runtime using the
ifconfig faithN
     create command or by setting up a hostname.if(5)  configuration file for

     Special  action  will be taken when IPv6 TCP traffic is seen
on a router,
     and the routing table suggests routing it to the  faith  interface.  In
     this  case,  the  packet will be accepted by the router, regardless of the
     list of IPv6 interface addresses  assigned  to  the  router.
The packet is
     captured  by  an  IPv6  TCP socket, if it has the IN6P_FAITH
flag turned on
     and it has matching address/port pairs.  Thus, faith  allows
captured IPv6
     TCP  traffic  to be relayed to some specific destination addresses.  Userland
 programs, such as faithd(8) can use  this  behavior  to
relay IPv6 TCP
     traffic  to  IPv4  TCP traffic.  The program can accept some
specific IPv6
     TCP traffic, perform getsockname(2) to get the IPv6 destination address
     specified  by  the  client, and perform application-specific
address mapping
     to relay IPv6 TCP to IPv4 TCP.

     The IN6P_FAITH flag on an IPv6 TCP socket can be set by  using
     setsockopt(2),  with  level  set to IPPROTO_IPV6 and optname
set to

     To handle error reports by ICMPv6, some of the ICMPv6  packets routed to
     the  faith interface will be delivered to IPv6 TCP, as well.

     To understand how faith can be used,  take  a  look  at  the
source code of

     As  the  faith  interface implements a potentially dangerous
     great care must be taken when configuring the  faith  interface.  To avoid
     possible  misuse, the sysctl(8) variable net.inet6.ip6.keepfaith must be
     set to 1 prior  to  use  of  the  interface.   When  net.inet6.ip6.keepfaith is
     0, no packet is captured by the faith interface.

     The  faith  interface is intended to be used on routers, not
on hosts.

SEE ALSO    [Toc]    [Back]

     inet(4), inet6(4), hostname.if(5), faithd(8), netstart(8)

     Jun-ichiro itojun Hagino and Kazu Yamamoto, "An IPv6-to-IPv4
     relay      translator",     RFC     3142,     June     2001,

HISTORY    [Toc]    [Back]

     The FAITH IPv6-to-IPv4 TCP relay translator  first  appeared
     hydrangea IPv6 stack.

OpenBSD      3.6                          April      10,     1999
[ Back ]
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