This document is a Mac OS X manual page. Manual pages are a command-line technology for providing documentation. You can view these manual pages locally using the man(1) command. These manual pages come from many different sources, and thus, have a variety of writing styles.

For more information about the manual page format, see the manual page for manpages(5).

FAITH(4)                 BSD Kernel Interfaces Manual                 FAITH(4)

NAME
     faith -- IPv6-to-IPv4 TCP relay capturing interface

SYNOPSIS
     pseudo-device faith [count]

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

     Special action will be taken when IPv6 TCP traffic is seen on a router, and routing table suggests to
     route it to faith interface.  In this case, the packet will be accepted by the router, regardless of
     list of IPv6 interface addresses assigned to the router.  The packet will be captured by an IPv6 TCP
     socket, if it has IN6P_FAITH flag turned on and it has matching address/port pairs.  In result, faith
     will let you capture IPv6 TCP traffic 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 spec-ified specified
     ified by the client, and perform application-specific address mapping to relay IPv6 TCP to IPv4 TCP.

     The IN6P_FAITH flag on IPv6 TCP socket can be set by using setsockopt(2), with level equals to
     IPPROTO_IPV6 and optname equals to IPv6_FAITH.

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

     To understand how faith can be used, take a look at source code of faithd(8).

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

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

SEE ALSO
     inet(4), inet6(4), faithd(8)

     Jun-ichiro itojun Hagino and Kazu Yamamoto, An IPv6-to-IPv4 transport relay translator, internet draft,
     draft-ietf-ngtrans-tcpudp-relay-04.txt, work in progress material.

HISTORY
     The FAITH IPv6-to-IPv4 TCP relay translator was first appeared in WIDE hydrangea IPv6 stack.

BSD                             April 10, 1999                             BSD