Add x_forwarded_host, which will forward the original Host header using the X-Forwarded-Host request header

This way, the origin server can optionally use that value to generate absolute URLs, etc.

Author: jjthrash

lib/rack/reverse_proxy.rb

@@ -24,6 +24,7 @@ def call(env)
         end
       }
       headers['HOST'] = uri.host if all_opts[:preserve_host]
+      headers['X-Forwarded-Host'] = rackreq.host if all_opts[:x_forwarded_host]
 
       session = Net::HTTP.new(uri.host, uri.port)
       session.read_timeout=all_opts[:timeout] if all_opts[:timeout]