dnt_middleware.py

class TrackingCheck(object):
    """
    Allows implementing the HTTP header-based "Do Not Track" mechanism described in
    http://tools.ietf.org/html/draft-mayer-do-not-track-00
    """
    def process_request(self, request):
        # DNT: 1
        optout = request.META.get("HTTP_DNT", False) or request.META.get("HTTP_X_DNT", "0")
        if optout.strip() == "1":
            setattr(request, "tracking_opt_out", True)
            return None

        # X-Do-Not-Track: 1
        optout = request.META.get("HTTP_X_DO_NOT_TRACK", "0")
        if optout.strip() == "1":
            setattr(request, "tracking_opt_out", True)
            return None

        # X-Tracking-Choice: do-not-track
        optout = request.META.get("HTTP_X_TRACKING_CHOICE", False) or request.META.get("HTTP_TRACKING_PREFERENCE", "")
        if optout.strip() == "do-not-track":
            setattr(request, "tracking_opt_out", True)
            return None

    def process_response(self, request, response):
        # We're actually not doing anything with `request.tracking_opt_out` right now.
        response['DNT'] = "0 (sorry)"
        return response