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

     faithd -- FAITH IPv6/v4 translator	daemon

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

     faithd provides IPv6-to-IPv4 TCP relay.  faithd must be used on an
     IPv4/v6 dual stack	router.

     When faithd receives TCPv6	traffic, faithd	will relay the TCPv6 traffic
     to	TCPv4.	Destination for	relayed	TCPv4 connection will be determined by
     the last 4	octets of the original IPv6 destination.  For example, if
     3ffe:0501:4819:ffff:: is reserved for faithd, and the TCPv6 destination
     address is	3ffe:0501:4819:ffff::0a01:0101,	the traffic will be relayed to
     IPv4 destination

     To	use faithd translation service,	an IPv6	address	prefix must be
     reserved for mapping IPv4 addresses into.	Kernel must be properly	con-
     figured to	route all the TCP connection toward the	reserved IPv6 address
     prefix into the faith(4) pseudo interface,	by using 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 toward
     reserved IPv6 address prefix, by using route(8) and sysctl(8) commands.

     faithd needs a special name-to-address translation	logic, so that host-
     names gets	resolved into special IPv6 address prefix.  For	small-scale
     installation, use hosts(5).  For large-scale installation,	it is useful
     to	have a DNS server with special address translation support.  An	imple-
     mentation called totd is available	at	Make sure you
     do	not propagate translated DNS records to	normal DNS cloud, it is	highly

   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.  faithd will invoke	local daemon at	serverpath if
     the destination address is	local interface	address, and will perform
     translation to IPv4 TCP in	other cases.  You can also specify 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) and
	     rlogin(1),	this flag is not necessary as special program code is

     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) and rlogin(1).  When translating FTP protocol,
     faithd translates network level addresses in PORT/LPRT/EPRT and
     PASV/LPSV/EPSV commands.  For RLOGIN protocol, faithd will	relay back
     connection	from rlogind(8)	on the server to rlogin(1) on client.

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

   inetd mode
     When faithd is invoked via	inetd(8), faithd will handle connection	passed
     from standard input.  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), 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 FTP port, it will operate as a
     FTP relay.

     The operation mode	requires special support for faithd in inetd(8).

   Access control
     To	prevent	malicious accesses, 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 contains
     directives	with the following format:

     +o	 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.

     +o	 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.

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

     Before invoking faithd, faith(4) interface	has to be configured properly.

     # sysctl net.inet6.ip6.accept_rtadv=0
     # sysctl net.inet6.ip6.forwarding=1
     # sysctl net.inet6.ip6.keepfaith=1
     # ifconfig	faith0 up
     # route add -inet6	3ffe:501:4819:ffff:: -prefixlen	96 ::1
     # route change -inet6 3ffe:501:4819: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/local/v6/libexec/telnetd, use	the following command line:

     # faithd telnet /usr/local/v6/libexec/telnetd telnetd

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

     # faithd ftp /usr/local/v6/libexec/ftpd ftpd -l

     Here are some other examples.  You	may need -p to translate rsh/rlogin

     # faithd ssh
     # faithd login /usr/local/v6/libexec/rlogin rlogind
     # faithd shell /usr/local/v6/libexec/rshd rshd

     However, you should be careful when translating rlogin or rsh connec-
     tions.  See SECURITY CONSIDERATIONS for more details.

   inetd mode samples
     Add the following lines into inetd.conf(5).  Syntax may vary depending
     upon your operating system.

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

     inetd(8) will open	listening sockets with enabling	kernel TCP relay sup-
     port.  Whenever connection	comes in, faithd will be invoked by inetd(8).
     If	it 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 3ffe:501:ffff::/48 to	use the	translator,
     # to connect to the following IPv4	destinations:
     # - any location except	and
     # Permit no other connections.
     3ffe:501:ffff::/48	deny
     3ffe:501:ffff::/48	deny
     3ffe:501:ffff::/48	permit

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

     faith(4), route(8), sysctl(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.

     The faithd	command	first appeared in WIDE Hydrangea IPv6 protocol stack

     IPv6 and IPsec support based on the KAME Project (
     stack was initially integrated into FreeBSD 4.0

     It	is very	insecure to use	rhosts(5) and other IP-address based authenti-
     cation, for connections relayed by	faithd (and any	other TCP relaying

     Administrators are	advised	to limit accesses to faithd using faithd.conf,
     or	by using IPv6 packet filters.  It is to	protect	faithd service from
     malicious parties and avoid theft of service/bandwidth.  IPv6 destination
     address can be limited by carefully configuring routing entries that
     points to faith(4), using route(8).  IPv6 source address needs to be fil-
     tered by using packet filters.  Documents listed in SEE ALSO have more
     discussions on this topic.

FreeBSD	11.1			 May 17, 1998			  FreeBSD 11.1


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