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Dd January 9, 2010
Dt FAITHD 8
Os
Sh NAME
Nm faithd
Nd FAITH IPv6/v4 translator daemon
Sh SYNOPSIS
Nm
Op Fl dp
Op Fl f Ar configfile
Ar service
Op Ar serverpath Op Ar serverargs
Nm
Sh DESCRIPTION
The
Nm
utility provides IPv6-to-IPv4 TCP relaying.
It can only be used on an IPv4/v6 dual stack router.
Pp
When
Nm
receives
Tn TCPv6
traffic, it will relay the
Tn TCPv6
traffic to
Tn TCPv4 .
The destination for the relayed
Tn TCPv4
connection will be determined by the last 4 octets of the original
Tn IPv6
destination.
For example, if
Li 2001:0db8:4819:ffff::
is reserved for
Nm ,
and the
Tn TCPv6
destination address is
Li 2001:0db8:4819:ffff::0a01:0101 ,
the traffic will be relayed to IPv4 destination
Li 10.1.1.1 .
Pp
To use the
Nm
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
Xr faith 4
pseudo interface, using the
Xr route 8
command.
Also,
Xr sysctl 8
should be used to configure
Dv net.inet6.ip6.keepfaith
to
Dv 1 .
Pp
The router must be configured to capture all the TCP traffic
for the reserved
Tn IPv6
address prefix, by using
Xr route 8
and
Xr sysctl 8
commands.
Pp
The
Nm
utility needs special name-to-address translation logic, so that
hostnames gets resolved into the special
Tn IPv6
address prefix.
For small-scale installations, use
Xr hosts 5 ;
For large-scale installations, it is useful to have
a DNS server with special address translation support.
An implementation called
Nm totd
is available at
Lk http://www.dillema.net/software/totd.html .
Make sure you do not propagate translated DNS records over to normal
DNS, as it can cause severe problems.
Ss Daemon mode
When
Nm
is invoked as a standalone program,
Nm
will daemonize itself.
Nm
will listen to
Tn TCPv6
port
Ar service .
If
Tn TCPv6
traffic to port
Ar service
is found, it relays the connection.
Pp
Since
Nm
listens to TCP port
Ar service ,
it is not possible to run local TCP daemons for port
Ar service
on the router, using
Xr inetd 8
or other standard mechanisms.
By specifying
Ar serverpath
to
Nm ,
you can run local daemons on the router.
The
Nm
utility will invoke ia local daemon at
Ar serverpath
if the destination address is a local interface address,
and will perform translation to IPv4 TCP in other cases.
You can also specify
Ar serverargs
for the arguments for the local daemon.
Pp
The following options are available:
Bl -tag -width indent
It Fl d
Debugging information will be generated using
Xr syslog 3 .
It Fl f Ar configfile
Specify a configuration file for access control.
See below.
It Fl p
Use privileged TCP port number as source port,
for IPv4 TCP connection toward final destination.
For relaying
Xr ftp 1
this flag is not necessary as special program code is supplied.
El
Pp
Nm
will relay both normal and out-of-band TCP data.
It is capable of emulating TCP half close as well.
Nm
includes special support for protocols used by
Xr ftp 1 .
When translating the FTP protocol,
Nm
translates network level addresses in
Li PORT/LPRT/EPRT
and
Li PASV/LPSV/EPSV
commands.
Pp
Inactive sessions will be disconnected in 30 minutes,
to prevent stale sessions from chewing up resources.
This may be inappropriate for some services
Pq should this be configurable? .
Ss inetd mode
When
Nm
is invoked via
Xr inetd 8 ,
Nm
will handle connections passed from standard input.
If the connection endpoint is in the reserved IPv6 address prefix,
Nm
will relay the connection.
Otherwise,
Nm
will invoke a service-specific daemon like
Xr telnetd 8 ,
by using the command argument passed from
Xr inetd 8 .
Pp
Nm
determines operation mode by the local TCP port number,
and enables special protocol handling whenever necessary/possible.
For example, if
Nm
is invoked via
Xr inetd 8
on the FTP port, it will operate as an FTP relay.
\".Pp
\"The operation mode requires special support for
\".Nm
\"in
\".Xr inetd 8 .
Ss Access control
To prevent malicious access,
Nm
implements a simple address-based access control.
With
Pa /etc/faithd.conf
Po
or
Ar configfile
specified by
Fl f
Pc ,
Nm
will avoid relaying unwanted traffic.
The
Pa faithd.conf
configuration file contains directives of the following format:
Bl -bullet
It
Xo
Ar src/slen Li deny Ar dst/dlen
Xc
Pp
If the source address of a query matches
Ar src/slen ,
and the translated destination address matches
Ar dst/dlen ,
deny the connection.
It
Xo
Ar src/slen Li permit Ar dst/dlen
Xc
Pp
If the source address of a query matches
Ar src/slen ,
and the translated destination address matches
Ar dst/dlen ,
permit the connection.
El
Pp
The directives are evaluated in sequence,
and the first matching entry will be effective.
If there is no match
Pq if we reach the end of the ruleset
the traffic will be denied.
Pp
With inetd mode,
traffic may be filtered by using access control functionality in
Xr inetd 8 .
Sh EXIT STATUS
Nm
exits with
Dv EXIT_SUCCESS
Pq 0
on success, and
Dv EXIT_FAILURE
Pq 1
on error.
Sh EXAMPLES
Before invoking
Nm ,
the
Xr faith 4
interface has to be configured properly.
Bd -literal
# 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
Ed
Ss Daemon mode samples
To translate
Li telnet
service, and provide no local telnet service, invoke
Nm
as follows:
Bd -literal
# faithd telnet
Ed
Pp
If you would like to provide local telnet service via
Xr telnetd 8
on
Pa /usr/libexec/telnetd ,
use the following command line:
Bd -literal
# faithd telnet /usr/libexec/telnetd telnetd
Ed
Pp
If you would like to pass extra arguments to the local daemon:
Bd -literal
# faithd ftp /usr/libexec/ftpd ftpd -l
Ed
Pp
Here are some other examples.
You may need
Fl p
if the service checks the source port range.
Bd -literal
# faithd ssh
# faithd telnet /usr/libexec/telnetd telnetd
Ed
Ss inetd mode samples
Add the following lines into
Xr inetd.conf 5 .
\"Syntax may vary depending upon your operating system.
Bd -literal
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
Ed
Pp
Xr inetd 8
will open listening sockets with kernel TCP relay support enabled.
Whenever a connection comes in,
Nm
will be invoked by
Xr inetd 8 .
If the connection endpoint is in the reserved IPv6 address prefix.
Nm
will relay the connection.
Otherwise,
Nm
will invoke service-specific daemon like
Xr telnetd 8 .
Ss Access control samples
The following illustrates a simple
Pa faithd.conf
setting.
Bd -literal
# 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
Ed
Sh SEE ALSO
Xr faith 4 ,
Xr route 8 ,
Xr sysctl 8 ,
Pa pkgsrc/net/totd
Rs
%A Jun-ichiro itojun Hagino
%A Kazu Yamamoto
%T "An IPv6-to-IPv4 transport relay translator"
%B RFC 3142
%U http://www.ietf.org/rfc/rfc3142.txt
%D June 2001
Re
\"
Sh HISTORY
The
Nm
utility first appeared in the WIDE Hydrangea IPv6 protocol stack kit.
\"
Sh SECURITY CONSIDERATIONS
It is very insecure to use IP-address based authentication, for connections relayed by
Nm ,
and any other TCP relaying services.
Pp
Administrators are advised to limit accesses to
Nm
using
Pa faithd.conf ,
or by using IPv6 packet filters, to protect the
Nm
service from malicious parties, and to avoid theft of service/bandwidth.
IPv6 destination addresses can be limited by
carefully configuring routing entries that point to
Xr faith 4 ,
using
Xr route 8 .
The IPv6 source address needs to be filtered using packet filters.
The documents listed in
Sx SEE ALSO
have more information on this topic.

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