FAITHD(8)               NetBSD System Manager's Manual               FAITHD(8)

     faithd -- FAITH IPv6/v4 translator daemon

     faithd [-dp] [-f configfile] service [serverpath [serverargs]]

     The faithd utility provides IPv6-to-IPv4 TCP relaying.  It can only be
     used on an IPv4/v6 dual stack router.

     When faithd receives TCPv6 traffic, it will relay the TCPv6 traffic to
     TCPv4.  The destination for the relayed TCPv4 connection will be deter-
     mined by the last 4 octets of the original IPv6 destination.  For exam-
     ple, if 2001:0db8:4819:ffff:: is reserved for faithd, and the TCPv6 des-
     tination address is 2001:0db8:4819:ffff::0a01:0101, the traffic will be
     relayed to IPv4 destination

     To use the faithd translation service, an IPv6 address prefix must be
     reserved for mapping IPv4 addresses into.  The kernel must be properly
     configured to route all the TCP connections toward the reserved IPv6
     address prefix into the faith(4) pseudo interface, using the route(8)
     command.  Also, sysctl(8) should be used to configure
     net.inet6.ip6.keepfaith to 1.

     The router must be configured to capture all the TCP traffic for the
     reserved IPv6 address prefix, by using route(8) and sysctl(8) commands.

     The faithd utility needs special name-to-address translation logic, so
     that hostnames gets resolved into the special IPv6 address prefix.  For
     small-scale installations, use hosts(5); For large-scale installations,
     it is useful to have a DNS server with special address translation sup-
     port.  An implementation called totd is available at .:
     Make sure you do not propagate translated DNS records over to normal DNS,
     as it can cause severe problems.

   Daemon mode
     When faithd is invoked as a standalone program, faithd will daemonize
     itself.  faithd will listen to TCPv6 port service.  If TCPv6 traffic to
     port service is found, it relays the connection.

     Since faithd listens to TCP port service, it is not possible to run local
     TCP daemons for port service on the router, using inetd(8) or other stan-
     dard mechanisms.  By specifying serverpath to faithd, you can run local
     daemons on the router.  The faithd utility will invoke ia local daemon at
     serverpath if the destination address is a local interface address, and
     will perform translation to IPv4 TCP in other cases.  You can also spec-
     ify serverargs for the arguments for the local daemon.

     The following options are available:

     -d      Debugging information will be generated using syslog(3).

     -f configfile
             Specify a configuration file for access control.  See below.

     -p      Use privileged TCP port number as source port, for IPv4 TCP con-
             nection toward final destination.  For relaying ftp(1) this flag
             is not necessary as special program code is supplied.

     faithd will relay both normal and out-of-band TCP data.  It is capable of
     emulating TCP half close as well.  faithd includes special support for
     protocols used by ftp(1).  When translating the FTP protocol, faithd
     translates network level addresses in PORT/LPRT/EPRT and PASV/LPSV/EPSV

     Inactive sessions will be disconnected in 30 minutes, to prevent stale
     sessions from chewing up resources.  This may be inappropriate for some
     services (should this be configurable?).

   inetd mode
     When faithd is invoked via inetd(8), faithd will handle connections
     passed from standard input.  If the connection endpoint is in the
     reserved IPv6 address prefix, faithd will relay the connection.  Other-
     wise, faithd will invoke a service-specific daemon like telnetd(8), by
     using the command argument passed from inetd(8).

     faithd determines operation mode by the local TCP port number, and
     enables special protocol handling whenever necessary/possible.  For exam-
     ple, if faithd is invoked via inetd(8) on the FTP port, it will operate
     as an FTP relay.

   Access control
     To prevent malicious access, faithd implements a simple address-based
     access control.  With /etc/faithd.conf (or configfile specified by -f),
     faithd will avoid relaying unwanted traffic.  The faithd.conf configura-
     tion file contains directives of the following format:

        src/slen deny dst/dlen

         If the source address of a query matches src/slen, and the translated
         destination address matches dst/dlen, deny the connection.

        src/slen permit dst/dlen

         If the source address of a query matches src/slen, and the translated
         destination address matches dst/dlen, permit the connection.

     The directives are evaluated in sequence, and the first matching entry
     will be effective.  If there is no match (if we reach the end of the
     ruleset) the traffic will be denied.

     With inetd mode, traffic may be filtered by using access control func-
     tionality in inetd(8).

     faithd exits with EXIT_SUCCESS (0) on success, and EXIT_FAILURE (1) on

     Before invoking faithd, the faith(4) interface has to be configured prop-

     # sysctl -w net.inet6.ip6.accept_rtadv=0
     # sysctl -w net.inet6.ip6.forwarding=1
     # sysctl -w net.inet6.ip6.keepfaith=1
     # ifconfig faith0 create up
     # route add -inet6 2001:0db8:4819:ffff:: -prefixlen 96 ::1
     # route change -inet6 2001:0db8:4819:ffff:: -prefixlen 96 -ifp faith0

   Daemon mode samples
     To translate telnet service, and provide no local telnet service, invoke
     faithd as follows:

     # faithd telnet

     If you would like to provide local telnet service via telnetd(8) on
     /usr/libexec/telnetd, use the following command line:

     # faithd telnet /usr/libexec/telnetd telnetd

     If you would like to pass extra arguments to the local daemon:

     # faithd ftp /usr/libexec/ftpd ftpd -l

     Here are some other examples.  You may need -p if the service checks the
     source port range.

     # faithd ssh
     # faithd telnet /usr/libexec/telnetd telnetd

   inetd mode samples
     Add the following lines into inetd.conf(5).

     telnet  stream  faith/tcp6  nowait  root  faithd  telnetd
     ftp     stream  faith/tcp6  nowait  root  faithd  ftpd -l
     ssh     stream  faith/tcp6  nowait  root  faithd  /usr/sbin/sshd -i

     inetd(8) will open listening sockets with kernel TCP relay support
     enabled.  Whenever a connection comes in, faithd will be invoked by
     inetd(8).  If the connection endpoint is in the reserved IPv6 address
     prefix.  faithd will relay the connection.  Otherwise, faithd will invoke
     service-specific daemon like telnetd(8).

   Access control samples
     The following illustrates a simple faithd.conf setting.

     # permit anyone from 2001:0db8:ffff::/48 to use the translator,
     # to connect to the following IPv4 destinations:
     # - any location except and
     # Permit no other connections.
     2001:0db8:ffff::/48 deny
     2001:0db8:ffff::/48 deny
     2001:0db8:ffff::/48 permit

     faith(4), route(8), sysctl(8), pkgsrc/net/totd

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

     The faithd utility first appeared in the WIDE Hydrangea IPv6 protocol
     stack kit.

     It is very insecure to use IP-address based authentication, for connec-
     tions relayed by faithd, and any other TCP relaying services.

     Administrators are advised to limit accesses to faithd using faithd.conf,
     or by using IPv6 packet filters, to protect the faithd service from mali-
     cious parties, and to avoid theft of service/bandwidth.  IPv6 destination
     addresses can be limited by carefully configuring routing entries that
     point to faith(4), using route(8).  The IPv6 source address needs to be
     filtered using packet filters.  The documents listed in SEE ALSO have
     more information on this topic.

NetBSD 9.0                      January 9, 2010                     NetBSD 9.0

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