FAITHD(8)

NAME
faithd - FAITH IPv6/v4 translator daemon

SYNOPSIS
faithd [-dD] [-f configfile] service ...

DESCRIPTION
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 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.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 hostnames 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 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.

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 standard mechanisms.

The following options are available:

-d  Generate logs via standard error, instead of syslog(3).

-D  Do not become daemon, for debugging purposes.

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

faithd is capable of emulating TCP half close. faithd includes special support for protocols used by ftp(1). When translating FTP protocol, faithd translates network level addresses in EPSV and LPSV command dialogue into PASV command.

  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:

•   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 functionality in inetd(8).

RETURN VALUES
faithd exits with EXIT_SUCCESS (0) on success, and EXIT_FAILURE (1) on error.

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

    # sysctl -w net.inet6.ip6.accept_rtadv=0
    # sysctl -w net.inet6.ip6.forwarding=1
    # sysctl -w 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, invoke faithd as follows:

    # faithd telnet

If you would like to relay multiple services, simply list them on the command line:

    # faithd telnet ftp ssh

  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 ALSO
faith(4), route(8), sysctl(8) Jun-ichiro itojun Hagino, Kazu Yamamoto, An IPv6-to-IPv4 transport relay translator, RFC3142, ftp://ftp.isi.edu/in-notes/rfc3142.txt, June 2001.

HISTORY
The faithd command first appeared in WIDE Hydrangea IPv6 protocol stack kit.

BUGS
We cannot provide local services for port service while faithd is running.

SECURITY CONSIDERATIONS
It is very insecure to use IP-address based authentication, for connections 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. 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 filtered by using packet filters. Documents listed in SEE ALSO have more discussions on this topic.