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89 lines
3.7 KiB
Text
89 lines
3.7 KiB
Text
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iodine - IP over DNS is now easy
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http://code.kryo.se/iodine
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********************************
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This is a piece of software that lets you tunnel IPv4 data through a DNS
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server. This can be usable in different situations where internet access is
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firewalled, but DNS queries are allowed.
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HOW TO USE:
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Server side:
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To use this tunnel, you need control over a real domain (like mytunnel.com),
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and a server with a static public IP number that does not yet run a DNS
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server. Then, delegate a subdomain (say, tunnel1.mytunnel.com) to the server.
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If you use BIND for the domain, add these lines to the zone file:
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tunnel1host IN A 10.15.213.99
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tunnel1 IN NS tunnel1host.mytunnel.com.
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Now any DNS querys for domains ending with tunnel1.mytunnnel.com will be sent
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to your server. Start iodined on the server. The first argument is the tunnel
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IP address (like 192.168.99.1) and the second is the assigned domain (in this
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case tunnel1.mytunnel.com). The -f argument will keep iodined running in the
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foreground, which helps when testing. iodined will start a virtual interface,
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and also start listening for DNS queries on UDP port 53. Now everything is
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ready for the client.
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Client side:
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All the setup is done, just start iodine. It also takes two
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arguments, the first is the local relaying DNS server and the second is the
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domain used (tunnel1.mytunnnel.com). If DNS queries are allowed to any
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computer, you can use the tunnel endpoint (example: 10.15.213.99 or
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tunnel1host.mytunnel.com) as the first argument. The tunnel interface will get
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an IP close to the servers (in this case 192.168.99.2) and a suitable MTU. Now
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you should be able to ping the other end of the tunnel from either side.
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MISC. INFO:
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Note that you can have only one client per server at the same time. This is
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because of the fragmentation of big packets going upstream, and will be fixed
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in future versions.
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Try experimenting with the MTU size (-m option) to get maximum bandwidth. It is
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set to 1024 by default, which seems to work with most DNS servers. If you have
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problems, try setting it to below 512.
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If you have problems, try inspecting the traffic with network monitoring tools
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and make sure that the relaying DNS server has not cached the response. A
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cached error message could mean that you started the client before the server.
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The upstream data is sent gzipped encoded in hexadecimal. DNS protocol allows
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one query per packet, and one query can be max 256 chars. Each domain name part
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can be max 63 chars. So your domain name and subdomain should be as short as
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possible to allow maximum throughput.
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PORTABILITY:
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iodine has been tested on Linux (x86 and SPARC64), FreeBSD (x86) and
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OpenBSD (x86). It should work on other unix-like systems as well that has
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TUN/TAP tunneling support. Let us know if you get it to run on other platforms.
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THE NAME:
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The name iodine was chosen since it starts with IOD (IP Over DNS) and since
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iodine has atomic number 53, which happens to be the DNS port number.
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AUTHORS & LICENSE:
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Copyright (c) 2006 Bjorn Andersson <flex@kryo.se>, Erik Ekman <yarrick@kryo.se>
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Permission to use, copy, modify, and distribute this software for any purpose
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with or without fee is hereby granted, provided that the above copyright notice
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and this permission notice appear in all copies.
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
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REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
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FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
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INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
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LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
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OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
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PERFORMANCE OF THIS SOFTWARE.
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