In Icecast parlance this is called a per mount relay and is a built in feature.
As this was trivial, I quickly made you a working config snippet, that you just need to insert into your icecast.xml config:
<relay>
<server>204.45.41.148</server>
<port>80</port>
<mount>/</mount>
<local-mount>/desi-radio.mp3</local-mount>
<on-demand>1</on-demand>
<relay-shoutcast-metadata>1</relay-shoutcast-metadata>
</relay>
For details as to how this works:
Icecast docs on relaying
Icecast docs on config file options, relaying section
Please note how I set this to on-demand, this means that the stream will only be pulled from the original server if there are local listeners.
This is generally a very nice feature to reduce bandwidth use on tight network connections as you only have one stream coming from the internet, while many users can locally connect to:
http://YOURLANIP:8000/desi-radio.mp3