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 standard 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 specify 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 connection 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. Otherwise, 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 example, 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 configuration 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 functionality in inetd(8).

# 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