Redirect based on header value.

[zestriddle]

Let assume that server called n1 is reverse proxy (SSL) for http server s1. Client c1 connects to n1 using given URL https://n1/index.html and in the end reads web page from /var/www/index.html on s1. What I want to do is to change URL sent to s1 depending on some header value sent by client. Namely, c1 connects to n1 with URL https://n1/index.html and with header "some_header=123" then n1 checks in some configuration file what to do if some_header has the value of 123 and changes the URL http://s1/123/index.html (as an example).  I did the same thing on Apache using *.map files and RewriteRule how I can do the same thing in nginx ?

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,23791,23791#msg-23791