text: from django.utils.http import http_date
  
  class ConditionalGetMiddleware(object):
      """
      Handles conditional GET operations. If the response has a ETag or
      Last-Modified header, and the request has If-None-Match or
      If-Modified-Since, the response is replaced by an HttpNotModified.
  
      Also sets the Date and Content-Length response-headers.
      """
      def process_response(self, request, response):
          response['Date'] = http_date()
          if not response.has_header('Content-Length'):
              response['Content-Length'] = str(len(response.content))
  
          if response.has_header('ETag'):
              if_none_match = request.META.get('HTTP_IF_NONE_MATCH', None)
              if if_none_match == response['ETag']:
                  # Setting the status is enough here. The response handling path
                  # automatically removes content for this status code (in
                  # http.conditional_content_removal()).
                  response.status = 304
  
          if response.has_header('Last-Modified'):
              if_modified_since = request.META.get('HTTP_IF_MODIFIED_SINCE', None)
              if if_modified_since == response['Last-Modified']:
                  # Setting the status code is enough here (same reasons as
                  # above).
                  response.status = 304
  
          return response
  
  class SetRemoteAddrFromForwardedFor(object):
      """
      Middleware that sets REMOTE_ADDR based on HTTP_X_FORWARDED_FOR, if the
      latter is set. This is useful if you're sitting behind a reverse proxy that
      causes each request's REMOTE_ADDR to be set to 127.0.0.1.
  
      Note that this does NOT validate HTTP_X_FORWARDED_FOR. If you're not behind
      a reverse proxy that sets HTTP_X_FORWARDED_FOR automatically, do not use
      this middleware. Anybody can spoof the value of HTTP_X_FORWARDED_FOR, and
      because this sets REMOTE_ADDR based on HTTP_X_FORWARDED_FOR, that means
      anybody can "fake" their IP address. Only use this when you can absolutely
      trust the value of HTTP_X_FORWARDED_FOR.
      """
      def process_request(self, request):
          try:
              real_ip = request.META['HTTP_X_FORWARDED_FOR']
          except KeyError:
              return None
          else:
              # HTTP_X_FORWARDED_FOR can be a comma-separated list of IPs. The
              # client's IP will be the first one.
              real_ip = real_ip.split(",")[0].strip()
              request.META['REMOTE_ADDR'] = real_ip
  