NAME

       ptunnel - tunnel TCP connections over ICMP echo request/reply packets.

SYNOPSIS

       ptunnel  -p  proxy_address  -lp  listen_port  -da  destination_address  -dp  dest_port [-c
       network_device] [-v verbosity] [-f file] [-udp] [-syslog]

       ptunnel [-c network_device] [-v verbosity] [-f file] [-udp] [-syslog] [-daemon file]

       ptunnel [-u] [-x password] [-setuid user] [-setgid group] [-chroot dir] [-setcon context]

       ptunnel -h

DESCRIPTION

       ptunnel is an application that allows you to reliably tunnel TCP connections to  a  remote
       host  using  ICMP  echo  request  and  reply  packets, commonly known as ping requests and
       replies. At first glance, this might seem like a rather useless thing to do,  but  it  can
       actually  come  in  handy  in  some  cases.  The  following  example  illustrates the main
       motivation in creating ptunnel:

       Setting: You're on the go, and stumble across an open wireless network. The network  gives
       you  an  IP  address,  but  won't  let  you send TCP or UDP packets out to the rest of the
       internet, for instance to check your mail. What to do? By chance, you  discover  that  the
       network will allow you to ping any computer on the rest of the internet. With ptunnel, you
       can utilize this feature to check your mail, or do other things that require TCP.

OPTIONS

       Client options:

       -p proxy_address
              Specify the host on which the proxy is running.

       -lp listen_port
              Specifies the port on which the client will listen for incoming TCP connections.

       -da destination_addr
              Specifies the address to which you want your packets tunneled  after  reaching  the
              proxy when in client mode, or restricts the destination packets can be forwarded to
              when in server mode.

       -dp destination_port
              Specifies/restrict the port that the proxy should tunnel the TCP connection to.

       Shared options:

       -c network_device
              Specify the network interface to capture packets from. Note that  packet  capturing
              isn't  always  necessary,  but  you should try this if you experience problems with
              ptunnel.

       -v verbosity
              Controls the verbosity level. -1 is no output, 0 shows errors only,  1  shows  info
              messages,  2 gives more output, 3 provides even more output, level 4 displays debug
              info and level 5 displays absolutely everything, including  the  nasty  details  of
              sends and receives.

       -udp   Enables tunneling over UDP port 53 (DNS) instead of using ICMP. This will only work
              if your proxy can accept incoming traffic on port 53, and the  client  is  able  to
              send  data  to  the proxy on port 53. Note that this option does not wrap ptunnel's
              data in DNS-compliant packets. This option must be given  on  both  the  proxy  and
              client side for things to work correctly.

       -syslog (Not available on Windows.)
              Changes logging to use the built-in syslog fascility.

       -daemon file (Not available on Windows.)
              Run in background, writing PID in file.

       -u     Attempts  to  run  ptunnel  without  privileges. This doesn't usually work! On UNIX
              systems please consider using the following three options instead:

       -setuid user (Not available on Windows.)
              When started in privileged mode, drop down to user's rights as soon as possible.

       -setgid group (Not available on Windows.)
              When started in privileged mode, drop down to group's rights as soon as possible.

       -chroot dir (Not available on Windows.)
              When started in privileged mode, restrict file access to the specified directory.

       -setcon context (Not available on Windows.)
              Set SELinux context when all there is left to do are network  I/O  operations.   In
              order  to  be  able  to  combine  with -chroot you will have to `mount --bind /proc
              /chrootdir/proc`

       -x password
              Specifies a password or passphrase to use. This will allow you to protect the proxy
              from  use  by  others who don't know the password. It needs to be specified on both
              proxy and client.

       -f file
              Specifies a log file. If you specify -syslog, syslog is always used instead.

       -h     Displays brief usage information.

EXAMPLES

       The following assumes that ptunnel is run as root, both on the proxy and client. To tunnel
       ssh connections from the client machine via a proxy running on proxy.pingtunnel.com to the
       computer login.domain.com, the following command line would be used:

       ptunnel -p proxy.pingtunnel.com -lp 8000 -da login.domain.com -dp 22

       An ssh connection to login.domain.com can now be established as follows:

       ssh -p 8000 localhost

       If ssh complains about potential man-in-the-middle attacks, simply  remove  the  offending
       key  from the known_hosts file. The warning/error is expected if you have previously ssh'd
       to your local computer (i.e., ssh localhost), or you have  used  ptunnel  to  forward  ssh
       connections to different hosts.

       Of  course,  for  all  of this to work, you need to start the proxy on your proxy-computer
       (proxy.pingtunnel.com). Doing this is very simple:

       ptunnel

       If you find that the proxy isn't working, you will need to enable packet capturing on  the
       main  network  device.  Currently  this  device is assumed to be an ethernet-device (i.e.,
       ethernet or wireless). Packet capturing is enabled by giving the -c switch, and  supplying
       the  device  name  to capture packets on (for instance eth0 or en1). The same goes for the
       client. On Mac OS X, packet capturing must always be enabled (both for proxy and  client),
       as resent packets won't be received otherwise.

       To  protect  yourself  from  others  using your proxy, you can protect access to it with a
       password using the <tt>-x</tt> switch. The password is never sent in the clear,  but  keep
       in  mind  that  it may be visible from tools like top or ps, which can display the command
       line used to start an application.

EXIT STATUS

       ptunnel does not exit until forced to do so by an interrupt (Ctrl-C) or if it crashes.

BUGS

       ptunnel currently does not handle  packet  capturing  on  network  interfaces  other  than
       ethernet or wireless correctly.

AUTHORS

       Daniel Stoedle (daniels@cs.uit.no)

       Mike Miller (mike@mikeage.net)

       Sebastien Raveau (sebastien.raveau@epita.fr)

LICENSE

       ptunnel is licensed under the BSD License.

AVAILABILITY

       The ptunnel homepage is currently located here:
              http://www.cs.uit.no/~daniels/PingTunnel/

       The freshmeat project page is located here:
              http://freshmeat.net/projects/ptunnel/

       Please take the time to rate ptunnel if you find it useful. Thanks!