NAT traversal

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NAT traversal
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todo
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= pwnat =
{{Unsupported}}

* https://samy.pl/pwnat
* https://github.com/samyk/pwnat

To make the client’s browser access <code><nowiki>http://127.0.0.1</nowiki></code> (port <code>80</code>) and get your HTTP server behind NAT, here’s the correct setup:

On Your Server (behind NAT, running the HTTP service on port <code>8080</code>):

{{CodeSelect|code=
sudo ./pwnat -s 0.0.0.0 2222 127.0.0.1:8080
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This:

* Listens for <code>pwnat</code> clients on UDP port <code>2222</code>
* Only allows proxy access to your local port <code>8080</code> (your HTTP server)

Make sure your HTTP server is running:

{{CodeSelect|code=
python3 -m http.server 8080
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On the Client (behind another NAT, allows browser to connect):

<u>Note:</u> Replace <code>your.server.public.ip</code> with the actual IP address of your server.

{{CodeSelect|code=
sudo ./pwnat -c 0.0.0.0 80 your.server.public.ip 2222 127.0.0.1 8080
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This:

* Binds to port <code>80</code> on the client (accessible via <code><nowiki>http://127.0.0.1</nowiki></code>)
* Proxies requests through your server’s <code>pwnat</code> to its local <code>8080</code>
* Now, on the client machine, just open:

{{CodeSelect|code=
http://127.0.0.1
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Expected result:

Client should see the server’s content.

== Actual Result ==

client:

<pre>
Listening on TCP 0.0.0.0:80
</pre>

Then nothing happening.

server:

<pre>
Listening on UDP 0.0.0.0:2222
</pre>

Then nothing happening.

Setup:

* server: ISP home router -> notebook -> Qubes -> VM (with direct internet connection)
* client test 1: ISP home router -> notebook -> Qubes -> different VM (with direct internet connection)
* client test 1: ISP home router -> notebook -> Qubes -> different VM (with VPN connection)

Functionality tests:

* HTTP server is functional locally on the server: Yes. Command <code>curl 127.0.0.1:8080</code> shows HTML output.
* Behind normal NAT according to https://tomchen.github.io/symmetric-nat-test/. (Not behind symmetric NAT.)
* server internet functionality test (visit any website): yes
* client test 1 internet functionality test (visit any website): yes
* client test 2 internet functionality test (visit any website): yes

== Debian ==
* https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=930966

= See Also =
* https://tomchen.github.io/symmetric-nat-test/
* GNUnet's Probabilistic NAT Traversal
* libp2p
** https://libp2p.io/
* slipstream
** https://samy.pl/slipstream/
** https://github.com/samyk/slipstream

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