TNAT64(8)						      System Manager's Manual							 TNAT64(8)

NAME

       tnat64 - Library for intercepting outgoing network connections and redirecting them through the NAT64.

SYNOPSIS

       Set LD_PRELOAD to load the library then use applications as normal

       The syntax to force preload of the library for different shells is specified below:

       Bash, Ksh and Bourne shell -

       export LD_PRELOAD=/usr/lib/tnat64/libtnat64.so

       C Shell -

       setenv LD_PRELOAD=/usr/lib/tnat64/libtnat64.so

       This  process can be automated (for Bash, Bourne and Korn shell users) for a single command or for all commands in a shell session by using
       the tnat64(1) script

       You can also setup tnat64 in such a way that all processes automatically use it, a very useful configuration. For more information on  this
       configuration see the CAVEATS section of this manual page.

DESCRIPTION

       tnat64  is a library to allow IPv4-only application to access IPv4 hosts on IPv6-only systems by using NAT64. It wraps the normal connect()
       function. When a connection is attempted, it consults the  configuration  file  (which  is  defined  at	configure  time  but  defaults	to
       /etc/tnat64.conf)  and  determines  if  the  IP	address  specified is local. If it is not, the library redirects the connection to an IPv6
       address inside the NAT64 prefix that is specified in the configuration file. The redirection is performed only if the destination  host	is
       unreachable  (when  there's no route to host). Also, after the first successful redirection all the following connection attempts are redi-
       rected immediately without even trying to connect to the host via IPv4. When the destination host cannot be reached via IPv6, the redirect-
       ion is disabled.

       tnat64  avoids  the need to recompile applications so they can use reach hosts even if they do not support IPv6 and there's no IPv4 connec-
       tivity.

       tnat64 is heavily based on the source code of tsocks, a library that intercepts outgoing TCP connections and redirects  them  though  SOCKS
       proxy. Many thanks for tsocks author, Shaun Clowes!

   ARGUMENTS
       Most  arguments	to  tnat64  are  provided  in  the  configuration  file (the location of which is defined at configure time by the --with-
       conf=<file> argument but defaults to /etc/tnat64.conf). The structure of this file is documented in tnat64.conf(8)

       Some configuration options can be specified at run time using environment variables as follows:

       TNAT64_CONF_FILE
	      This environment variable overrides the default location of the tnat64 configuration file. This variable is not honored if the  pro-
	      gram tnat64 is embedded in is setuid. In addition this environment variable can be compiled out of tnat64 with the --disable-envconf
	      argument to configure at build time

       TNAT64_DEBUG
	      This environment variable sets the level of debug output that should be generated by tnat64 (debug output is generated in  the  form
	      of  output  to  standard	error). If this variable is not present by default the logging level is set to 0 which indicates that only
	      error messages should be output.	Setting it to higher values will cause tnat64 to generate more	messages  describing  what  it	is
	      doing.  If  set  to -1 tnat64 will output absolutely no error or debugging messages. This is only needed if tnat64 output interferes
	      with a program it is embedded in. Message output can be permanently compiled out of tnat64 by specifying the --disable-debug  option
	      to configure at build time

       TNAT64_DEBUG_FILE
	      This  option  can be used to redirect the tnat64 output (which would normally be sent to standard error) to a file. This variable is
	      not honored if the program tnat64 is embedded in is setuid. For programs where tnat64 output interferes with normal  operation  this
	      option is generally better than disabling messages (with TNAT64_DEBUG = -1)

   ERRORS
       tnat64  will generate error messages and print them to stderr when there are problems with the configuration file if the TNAT64_DEBUG envi-
       ronment variable is not set to -1 or and --disable-debug was not specified at compile time. This output may cause some problems	with  pro-
       grams that redirect standard error.

   CAVEATS
       tnat64  will  not  in  the  above  configuration be able to provide proxying to setuid applications or applications that are not run from a
       shell. You can force all applications to LD_PRELOAD the library by placing the path to libtnat64 in /etc/ld.so.preload.	Please	make  sure
       you  correctly  enter the full path to the library in this file if you do this. If you get it wrong, you will be UNABLE TO DO ANYTHING with
       the machine and will have to boot it with a rescue disk and remove the file (or try the saveme program,	see  the  INSTALL  file  for  more
       info).	THIS IS A ***WARNING***, please be careful. Also be sure the library is in the root filesystem as all hell will break loose if the
       directory it is in is not available at boot time.

BUGS

       tnat64 can only proxy outgoing TCP connections

       tnat64 does NOT work correctly with asynchronous sockets (though it does work with non blocking sockets). This bug would be very  difficult
       to fix and there appears to be no demand for it (I know of no major application that uses asynchronous sockets)

       tnat64  uses ELF dynamic loader features to intercept dynamic function calls from programs in which it is embedded.  As a result, it cannot
       trace the actions of statically linked executables, non-ELF executables, or executables that make system calls  directly  with  the  system
       call trap or through the syscall() routine.

FILES

       /etc/tnat64.conf - default tnat64 configuration file

SEE ALSO

       tnat64.conf(5) tnat64(1)

AUTHORS

       Andrew O. Shadura (bugzilla@tut.by), Shaun Clowes (delius@progsoc.uts.edu.au)

COPYRIGHT

       Copyright 2011 Andrew O. Shadura

       Original tsocks manual page, copyright 2000 Shaun Clowes

       tnat64  and  its  documentation may be freely copied under the terms and conditions of version 2 of the GNU General Public License, as pub-
       lished by the Free Software Foundation (Cambridge, Massachusetts, United States of America).

       This documentation is heavily based on the documentation for tsocks, transparent SOCKSification	library,  whose  documentation	itself	is
       based  on the documentation for logwrites, another shared library interceptor. One line of code from it was used in tsocks and a lot of the
       documentation :) logwrites is by adam@yggdrasil.com (Adam J. Richter) and can be had from ftp.yggdrasil.com pub/dist/pkg

TNAT64																	 TNAT64(8)