Rails server environment info can be accessed from your views with the following syntax

request.env["NAME_OF_VARIABLE"]

for example
request.env["REQUEST_ADDR"] should return the referring address


From the Rails wiki
http://wiki.rubyonrails.org/rails/pages/VariablesInRequestEnv

request.env is a Ruby Array that contains information about a visiting user’s and server environments.

This is similar to the php variable $_SERVER.

request.env is accessible on all pages hosted in a ruby on rails site. The Array contains the following key/value pairs:

    * SERVER_NAME
    * PATH_INFO
    * REMOTE_HOST
    * HTTP_ACCEPT_ENCODING
    * HTTP_USER_AGENT
    * SERVER_PROTOCOL
    * HTTP_CACHE_CONTROL
    * HTTP_ACCEPT_LANGUAGE
    * HTTP_HOST
    * REMOTE_ADDR
    * SERVER_SOFTWARE
    * HTTP_KEEP_ALIVE
    * HTTP_REFERER
    * HTTP_COOKIE
    * HTTP_ACCEPT_CHARSET
    * REQUEST_URI
    * SERVER_PORT
    * GATEWAY_INTERFACE
    * QUERY_STRING
    * REMOTE_USER
    * HTTP_ACCEPT
    * REQUEST_METHOD
    * HTTP_CONNECTION