This is a tiny experiment to write a C program to run on Heroku. It'll read your IP address from the X-Forwarded-For header and return it as JSON.

You can test this program at ipconfig.herokuapp.com:

curl http://ipconfig.herokuapp.com/

I summarized my experiences in a blog post.

Known problems

• Heroku does not filter values for the X-Forwarded-For header: curl -s http://ipconfig.herokuapp.com/ -H 'X-Forwarded-For: ", "attack": true, "foo": "bar' (see #1).