Summer Fun

by Craig Miller

Internet Radio

Can tune to any stream anywhere in the world. Like listening to shortwave, but clearer, don't have to wait until after sunset.

What's inside

Outside

Simple to use buttons along the top, with a 3 line character display.

Outside

Simple construction inside. Single PCB board under the buttons, with wires to the 2.4 Ghz antenna, and speaker.

Outside

The brain inside, an ESP32, no wonder it doesn't support IPv6!

Internet Radio, just another IoT device

Network Diagram

Production Router is also a multi-port firewall (running OpenWrt). IoT devices connect to the Wireguard VPN router via 2.4 Ghz Wifi.

The Internet radio:

Internet Radio has a built in Web Server

The documentation states that the laptop has to be on the same network as the Internet Radio. But my laptop is not on the DMZ network. So how to get there via IPv6?

I used socat running on the router as a reverse proxy.

socat  TCP6-LISTEN:8888,fork,reuseaddr,retry TCP4:192.168.99.36:80

Now to test it with curl

curl http://6nuuanu.hoomaha.net:8888/
<html xmlns='http://www.w3.org/1999/xhtml'>
<head><meta http-equiv='Content-Type' content='text/html; charset=UTF-8' >
<meta http-equiv='Pragma' content='no-cache'>
<meta http-equiv='cache-control' content='no-cache'>
<meta http-equiv='expires' content='-1'>
<meta http-equiv='set-cookie' content='Mon,12 May 2001 00:20:00 GMT'>

<script type="text/javascript">
<!--
window.history.forward();
function Click(){ return false; }
document.oncontextmenu = Click;
-->
</script>
<title>My Favourite</title><script type='text/javascript'>
<!--
document.oncontextmenu = function() { return false; }
-->
</script></head><noscript><font size="3" face="Arial"><font color="#FF0000"><b>This page requires javascript-enabled.</b></font></font><br>
<br>Please enable javacript and reload this page. Thank you.</noscript><frameset border='0' rows='94,*' cols='*' frameborder='no' framespacing='0'>
<frame id='frmHeader' src='http://192.168.99.36/top.cgi' scrolling='no' noresize><frameset border='0' rows='*' cols='24,*' frameborder='no' framespacing='0'>
<frame name='frmMiddle' id='frmMiddle' src='http://192.168.99.36/middle.cgi' frameborder='0' scrolling='no' hidefocus='true' noresize>
<frame name='frmContent' id='frmContent' src='http://192.168.99.36/content.cgi' frameborder='0' scrolling='auto' noresize  hidefocus='true'></frameset><noframes>Sorry, your browser does not handle frames!</noframes></frameset></html>

However the HTML has IPv4 Literals in it.

Need to modify the HTML while proxying, enter nginx. Reverse Proxy is quite easy in nginx Create the foloowing config file:

server {
        listen 80 default_server;
        listen [::]:80 default_server;
        server_name localhost;

        # Setup proxy
        location / {
                # sub module stuff
                sub_filter_once off;
                sub_filter 'http://192.168.99.36' 'http://6wr26.hoomaha.net';
                # rev proxy config
                proxy_pass http://wr26.hoomaha.net/;
                proxy_set_header Host $host;
                proxy_set_header X-Real-IP $remote_addr;
                proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        }

}

nginx reverse proxy config with on the fly HTML modification (sub_filter).

Now curl shows:

curl http://6wr26.hoomaha.net/       
<html xmlns='http://www.w3.org/1999/xhtml'>
<head><meta http-equiv='Content-Type' content='text/html; charset=UTF-8' >
<meta http-equiv='Pragma' content='no-cache'>
<meta http-equiv='cache-control' content='no-cache'>
...
<frame name='frmContent' id='frmContent' src='http://6wr26.hoomaha.net/content.cgi' frameborder='0' scrolling='auto' noresize  hidefocus='true'></frameset>
<noframes>Sorry, your browser does not handle frames!</noframes></frameset></html>

The real test, it works!

Web screen

A Simple reverse Proxy works after all

By looking at the curl output a bit more, it is possible to make a request for just one frames contents in a browser. For example, put the following in into the browser http://6wr26.hoomaha.net/content.cgi

It will bring up just the important part of the page. Looking at the source, there are no IPv4 literals, so it is possible to use that URL with the simple socat proxy. Didn't need nginx after all.

http://6nuuanu.hoomaha.net:8888/content.cgi

More fun with Internet Radios

Peeking in on the web requests to see the real URL of the stream. By running tcpdump on the router where the traffic flows, it is possible to see the URL being requested.

tcpdump -i br-lan  -A 'tcp[((tcp[12:1] & 0xf0) >> 2):4] = 0x47455420'

Options:

The output looks like:

listening on br-lan, link-type EN10MB (Ethernet), capture size 262144 bytes
14:43:27.086452 IP wr26.hoomaha.net.49972 > sc12.lax.llnw.net.80: Flags [P.], seq 471201:471333, ack 2322166818, win 15200, length 132: HTTP: GET /stream/bbcwssc_mp1_ws-einws HTTP/1.1
E...C.....V...c$E....4.P..0..it"P.;`....GET /stream/bbcwssc_mp1_ws-einws HTTP/1.1
Host: bbcwssc.ic.llnwd.net
User-Agent: WR-26/1.0
Icy-MetaData: 1
Content-Length: 0

Where you can see the real URL for the stream is: http://bbcwssc.ic.llnwd.net/stream/bbcwssc_mp1_ws-einws

Other Project:


12 September 2020