Redirecting subdomains with the Rails router

We have an application which uses five subdomains. One of those subdomains is changing.

I would like to be able to redirect everyone hitting the old domain to be redirected to the new one, and ideally use the Rails router so that I leave the processing there using Rack.

Is there a way of redirecting all traffic to one domain, to be redirected to another.

e.g all traffic to foo.app.com开发者_开发知识库 get's redirected to bar.foo.com, whilst maintaining the full path & query string.

As I am hosting with Heroku I have no .htaccess.

---

Refraction may be able to help with that.