FAITHD(8) BSD System Manager's Manual FAITHD(8)NAMEfaithd — FAITH IPv6/v4 translator daemon
SYNOPSISfaithd [-dp] [-f configfile] service [serverpath [serverargs]]
faithdDESCRIPTION
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 10.1.1.1.
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
http://www.vermicelli.pasta.cs.uit.no/software/totd.html. 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
commands.
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).
EXIT STATUSfaithd 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 -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 10.0.0.0/8 and 127.0.0.0/8.
# Permit no other connections.
#
2001:0db8:ffff::/48 deny 10.0.0.0/8
2001:0db8:ffff::/48 deny 127.0.0.0/8
2001:0db8:ffff::/48 permit 0.0.0.0/0
SEE ALSOfaith(4), route(8), sysctl(8), pkgsrc/net/totd
Jun-ichiro itojun Hagino and Kazu Yamamoto, "An IPv6-to-IPv4 transport
relay translator", RFC 3142, ftp://ftp.isi.edu/in-notes/rfc3142.txt, June
2001.
HISTORY
The faithd utility 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, 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.
BSD January 9, 2010 BSD
