NAME
    IO::Socket::DNS - IO::Socket like interface using DNS to access an
    IO::Socket::DNS::Server backend.

SYNOPSIS
      use IO::Socket::DNS;

      my $sock = new IO::Socket::DNS
        PeerAddr => $ip,
        PeerPort => $port,
        Suffix   => $dns_suffix,
        Password => $secret,
        Verbose  => 1,
          or die "Unable to connect to $ip:$port";

DESCRIPTION
    I originally used this module for my own purposes and never intended to
    show anyone, but there have been so many requests that I've decided to
    release it to the public.

    Have you ever been away from your home with your computer and needed to
    use the Internet, but all you can find is a crippled WiFi Access Point
    that doesn't give full Internet? When you try to visit a website, it
    asks for an annoying login or asks you to pay money or some other silly
    thing in order to be able to use the Internet. However, usually if you
    actually try a dig or nslookup, you'll notice that DNS is working
    perfectly fine. If so, then this is exactly what you need!

    It translates TCP connection packets into DNS queries. So now you can
    finally reach that external SSH server you've been needing to reach,
    even though your Internet connection is too crippled to connect to it
    directly. Actually, you can connect to any TCP server, such as a Web
    server or a Squid proxy or even a remote SOCKS server. The client module
    IO::Socket::DNS communicates with the server module
    IO::Socket::DNS::Server to tunnel the connection for the client using
    only DNS queries as its transport. The only thing that the Internet
    Service Provider will see is a bunch of DNS queries.

    Be aware that this is much slower than full Internet access. This is
    only intended for proof of concept or emergency use.

SOCKS
    SOCKS is a popular protocol used for proxying connections which works
    very well in conjuction with this module. Here is one simple way to
    utilize SOCKS using "dnsc", which comes with this distribution.

  1. Start SSH proxy
    Note that you need an SSH account somewhere, say $USER@server.com

      dnsc --suffix=d.example.com --listen_port=2222 server.com:22

    But if you have SSH access directly to d.example.com, the DNS authority,
    it is recommended to connect to "127.0.0.1" for better performance,
    i.e.:

      dnsc --suffix=d.example.com --listen_port=2222 127.0.0.1:22

  2. Start SOCKS tunnelling server
    The ssh option "-D" implements a tunnelled SOCKS server. Make sure that
    $USER is a valid SSH account whatever destination you chose in step 1,
    then connect:

      ssh -D127.0.0.1:1080 -p2222 $USER@127.0.0.1

    Or if you have lots of other people on your client network that don't
    like the crippled Internet and also want to use your SOCKS server, then
    you'll need to know the IP address of your computer and bind to that
    instead of the 127.0.0.1 default, i.e.:

      ssh -D192.168.0.101:1080 -p2222 $USER@127.0.0.1

  3. Configure Network Settings on browser
    On Firefox => Options => Advanced => Network => Settings => [X] Manual
    proxy configuration => SOCKS Host: 192.168.0.101 Port: 1080 (or whatever
    IP:Port used for -D in step 2) => [OK]

    Then surf away.

CONSTRUCTOR
    The "new" constructor takes arguments in key-value pairs:

      PeerAddr     Remote host address      <hostname>[:<port>]
      PeerHost     Synonym for PeerAddr     <hostname>[:<port>]
      PeerPort     Remote port              <port>
      Suffix       Proxy DNS Suffix         <domain>
      Password     Access password          <password>
      Verbose      Used for debugging       <level>

    If only one argument is passed, it is considered to be "PeerAddr". The
    "PeerAddr" can be a hostname or IP-Address.

    The "PeerPort" specification can also be embedded in the "PeerAddr" by
    preceding it with a ":". The "PeerPort" must be in numeric form.

    The "Password" setting is to prove to the server that you are authorized
    to use it.

    If "Verbose" is specified, additional diagnostic information will be
    sent to STDERR.

    The "Suffix" argument must be a real domain name or subdomain that
    points to an IP running the IO::Socket::DNS::Server instance. The
    environment variable DNS_SUFFIX may also be used to define this setting.
    This is required.

EXAMPLES
      my $sock = IO::Socket::DNS->new(
        PeerAddr => "www.perl.org",
        PeerPort => 80,
        Verbose  => 1,
        Suffix   => "d.example.com",
      ) or die "connect: $!";

      $ENV{DNS_SUFFIX} = "d.example.com";
      my $sock = new IO::Socket::DNS "www.perl.org:80";

KNOWN ISSUES
    It is still very slow. There are several optimizations that can be done
    in order to improve the performance to make it faster, but none of these
    have been implemented yet.

    The Password setting is not implemented yet. So anyone can use your
    server without your permission fairly easily and you could be blamed for
    any malicious traffic tunnelled through it.

    Sockets idle for more than 120 are automatically closed on the server
    side. You have to keep probing to keep the connection alive.

    Since DNS, for the most part, is UDP, which is a "connectionless"
    protocol, IO::Socket::DNS does not implement the FILENO hook for its
    TIEHANDLE, so things like IO::Select won't work as expected.

    Only TCP protocol is supported at this time.

    Patches are welcome, or if you have other ideas for improvements, let me
    know.

DISCLAIMER
    This software is provided AS-IS for proof of concept purposes only. I
    can not be held liable for any loss or damages due to misuse or illegal
    or unlawful violations in conjunction with this software. Use at your
    own risk of punishing condemnation of all types of ISPs and law
    enforcement everywhere. If you do get in trouble, just DON'T BLAME ME!
    And please don't abuse this too much or else hotspot admins everywhere
    will wise up and start locking out all DNS queries!

SEE ALSO
    Net::DNS, IO::Socket, dnsc, iodine

AUTHOR
    Rob Brown, <bbb@cpan.org>

COPYRIGHT AND LICENSE
    Copyright (C) 2011 by Rob Brown

    This library is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself, either Perl version 5.8.9 or, at
    your option, any later version of Perl 5 you may have available.

