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

       Andrej Shadura (andrew@shadura.me), Shaun Clowes (delius@progsoc.uts.edu.au)

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.

       Copyright 2011 Andrej 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 published 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)

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  redirected  immediately  without  even
       trying  to  connect  to  the  host  via  IPv4.  When the destination host cannot be reached via IPv6, the
       redirection 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 connectivity.

       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  program  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)

   ERRORStnat64 will generate error  messages  and  print  them  to  stderr  when  there  are  problems  with  the
       configuration  file  if the TNAT64_DEBUG environment variable is not set to -1 or and --disable-debug was
       not specified at compile time. This output may cause some problems with programs that  redirect  standard
       error.

   CAVEATStnat64  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.

       /etc/tnat64.conf - default tnat64 configuration file

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

tnat64.conf(5) tnat64(1)

       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.