faithd(8)

NAME

faithd - FAITH IPv6/v4 translator daemon

SYNOPSIS

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

DESCRIPTION

The faithd utility provides IPv6-to-IPv4 TCP relay. It 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 ex

ample, 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 10.1.1.1.

To use faithd translation service, an IPv6 address prefix

must be
reserved for mapping IPv4 addresses into. Kernel must be

properly configured 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.in

et6.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.

The faithd utility needs a special name-to-address transla

tion logic, so
that hostnames gets resolved into special IPv6 address pre

fix. For
small-scale installation, use hosts(5). For large-scale in

stallation, it
is useful to have a DNS server with special address transla

tion support.
An implementation called totd is available at
http://www.vermicelli.pasta.cs.uit.no/ipv6/software.html.

Make sure you
do not propagate translated DNS records to normal DNS cloud,

it is highly
harmful.

Daemon mode

When faithd is invoked as a standalone program, faithd will

daemonize
itself. The faithd utility 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 standard mechanisms. By specifying serverpath to faithd, you

can run local
daemons on the router. The faithd utility will invoke local

daemon at
serverpath if the destination address is local interface ad

dress, 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 sys

log(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 sup

plied.

The faithd utility will relay both normal and out-of-band

TCP data. It
is capable of emulating TCP half close as well. The faithd

utility
includes special support for protocols used by ftp(1). When

translating
FTP protocol, faithd translates network level addresses in

PORT/LPRT/EPRT
and PASV/LPSV/EPSV commands.

Inactive sessions will be disconnected in 30 minutes, to

avoid stale sessions 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 con

nection 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 service-specific daemon like telnetd(8), by using the

command
argument passed from inetd(8).

The faithd utility determines operation mode by the local

TCP port number, and enables special protocol handling whenever neces

sary/possible.
For example, 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 speci

fied 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 connec

tion.

+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 connec

tion.

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 functionality in inetd(8).

EXIT STATUS

The faithd utility exits with EXIT_SUCCESS (0) on success,

and
EXIT_FAILURE (1) on error.

EXAMPLES

Before invoking faithd, faith(4) interface has to be config

ured 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 tel

netd(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 dae

mon:

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

Here are some other examples. You may need -p if the ser

vice checks the
source port range.

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

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 faithd telnetd
ftp stream tcp6/faith nowait root faithd ftpd -l
ssh stream tcp6/faith nowait root faithd

/usr/sbin/sshd -i

inetd(8) will open listening sockets with enabling kernel

TCP relay support. Whenever connection comes in, faithd will be invoked

by inetd(8).
If it the connection endpoint is in the reserved IPv6 ad

dress prefix.
The faithd utility 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 transla

tor,
# to connect to the following IPv4 destinations:
# - any location except 10.0.0.0/8 and 127.0.0.0/8.
# Permit no other connections.
#
3ffe:501:ffff::/48 deny 10.0.0.0/8
3ffe:501:ffff::/48 deny 127.0.0.0/8
3ffe:501:ffff::/48 permit 0.0.0.0/0

SEE ALSO

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

Jun-ichiro itojun Hagino and Kazu Yamamoto, "An IPv6-to-IPv4

transport
relay translator", RFC3142, June 2001, ftp://ftp.isi.edu/innotes/rfc3142.txt.

HISTORY

The faithd utility first appeared in WIDE Hydrangea IPv6

protocol stack
kit.

IPv6 and IPsec support based on the KAME Project

(http://www.kame.net/)
stack was initially integrated into FreeBSD 4.0

SECURITY CONSIDERATIONS

It is very insecure to use IP-address based authentication,

for connections relayed by faithd, and any other TCP relaying ser

vices.

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 en

tries that
points to faith(4), using route(8). IPv6 source address

needs to be filtered by using packet filters. Documents listed in SEE ALSO

have more
discussions on this topic.

BSD May 17, 1998

BSD