rewrite Location header?

[3molo]

Hi.

Running nginx as a reverse proxy for trac. Reaching trac etc works, but when posting login credentials, trac returns a Location: header as seen below.

POST /somesite/login HTTP/1.1
Host: dev.somesite.co.za:8001
Referer: http://dev.somesite.co.za:8001/somesite/login
__FORM_TOKEN=ec42989d17edbcdec96290d6&referer=http%3A%2F%2Fdev.somesite.co.za%3A8001%2Fsomesite&user=user&password=pass
-
HTTP/1.x 303 See Other
Server: tracd/0.11.6 Python/2.5.2
Date: Wed, 03 Feb 2010 13:37:16 GMT
Location: http://dev.somesite.co.za:8001/somesite

This is the case when going through nginx too, but I now need to rewrite the Location response header to http://ip_to_nginx:port/ instead, as the trac server is not reachable from the outside.
Im kind of stuck :(

Here's the simple proxy_pass config:
      location /somesite {
               proxy_pass http://192.168.1.9:8001/somesite;
      }

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,49946,49946#msg-49946