FAITHD(8) BSD System Manager's Manual FAITHD(8)NAMEfaithd - FAITH IPv6/v4 translator daemon
SYNOPSISfaithd [-dp] [-f configfile] service [serverpath [serverargs]]
DESCRIPTIONfaithd provides an 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. The destination for the relayed TCPv4 connection is 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 is relayed to IPv4
destination 10.1.1.1.
To use the faithd translation service, an IPv6 address prefix must be
reserved for mapping IPv4 addresses onto. The kernel must be properly
configured to route all the TCP connections toward the reserved IPv6 ad-
dress prefix into the faith(4) pseudo interface, by 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 a given
reserved IPv6 address prefix, by using the route(8) and sysctl(8) com-
mands.
faithd needs a special name-to-address translation logic, so that host-
names get resolved into a 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 implemen-
tation 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. When faithd is invoked, 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. Local daemons can be run on the router by specifying a
serverpath to faithd. faithd will invoke a local daemon at serverpath if
the destination address is a local interface address, and will perform
translation to IPv4 TCP in other cases. Serverargs can also be specified
as 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 the privileged TCP port number as a source port, for an IPv4
TCP connection toward the 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 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 ses-
sions from chewing up resources. This may be inappropriate for some of
the services (should this be configurable?).
Access control
To prevent malicious access, faithd implements a simple address-based ac-
cess control. With /etc/faithd.conf (or configfile specified by -f),
faithd will avoid relaying unwanted traffic. faithd.conf contains direc-
tives with 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 (the end of the ruleset has been
reached), the traffic is denied.
RETURN VALUESfaithd exits with EXIT_SUCCESS (0) on success, and EXIT_FAILURE (1) on
error.
EXAMPLES
Before invoking faithd, the faith(4) interface has to be configured prop-
erly:
# 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
To translate telnet service, and provide no local telnet service, invoke
faithd as follows:
# faithd telnet
Pass extra arguments to the local daemon:
# faithd ftp /usr/libexec/ftpd ftpd -l
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 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 ALSOfaith(4), route(8), sysctl(8)
Jun-ichiro itojun Hagino and Kazu Yamamoto, "An IPv6-to-IPv4 transport
relay translator", RFC 3142, June 2001, ftp://ftp.isi.edu/in-
notes/rfc3142.txt.
HISTORY
The faithd command first appeared in the WIDE Hydrangea IPv6 protocol
stack kit.
SECURITY CONSIDERATIONS
It is very insecure to use IP-address-based authentication for connec-
tions relayed by faithd.
Administrators are advised to limit access to faithd using faithd.conf,
or by using IPv6 packet filters, to protect the faithd service from mali-
cious parties and avoid theft of service/bandwidth. IPv6 destination ad-
dresses can be limited by carefully configuring routing entries that
point to faith(4), using route(8). IPv6 source addresses need to be fil-
tered using a packet filter. The documents listed in SEE ALSO have more
discussions on this topic.
MirOS BSD #10-current May 17, 1998 2
