Method is_response_cacheable

src/proxy/http/HttpTransact.cc:6178–6368

////////////////////////////////////////////////////////////////////////// Name : is_response_cacheable() Description: check if a response is cacheable Input : State, request header, response header Output : true or false Details : //////////////////////////////////////////////////////////////////////////

//
///////////////////////////////////////////////////////////////////////////////
bool
HttpTransact::is_response_cacheable(State *s, HTTPHdr *request, HTTPHdr *response)
{
  // If the use_client_target_addr is specified but the client
  // specified OS addr does not match any of trafficserver's looked up
  // host addresses, do not allow cache.  This may cause DNS cache poisoning
  // of other trafficserver clients. The flag is set in the
  // process_host_db_info method
  if (!s->dns_info.cta_validated_p && s->client_info.is_transparent) {
    TxnDbg(dbg_ctl_http_trans, "Lookup not validated.  Possible DNS cache poison.  Don't cache");
    return false;
  }

  // the plugin may decide we don't want to cache the response
  if (s->api_server_response_no_store) {
    return false;
  }
  // if method is not GET or HEAD, do not cache.
  // Note: POST is also cacheable with Expires or Cache-control.
  // but due to INKqa11567, we are not caching POST responses.
  // Basically, the problem is the resp for POST url1 req should not
  // be served to a GET url1 request, but we just match URL not method.
  int req_method = request->method_get_wksidx();
  if (!(HttpTransactHeaders::is_method_cacheable(s->txn_conf, req_method)) && s->api_req_cacheable == false) {
    TxnDbg(dbg_ctl_http_trans, "only GET, and some HEAD and POST are cacheable");
    return false;
  }
  // TxnDbg(dbg_ctl_http_trans, "[is_response_cacheable] method is cacheable");
  // If the request was not looked up in the cache, the response
  // should not be cached (same subsequent requests will not be
  // looked up, either, so why cache this).
  if (!(is_request_cache_lookupable(s))) {
    TxnDbg(dbg_ctl_http_trans, "request is not cache lookupable, response is not cacheable");
    return false;
  }
  // already has a fresh copy in the cache
  if (s->range_setup == RANGE_NOT_HANDLED) {
    return false;
  }

  // Check whether the response is cacheable based on its cookie
  // If there are cookies in response but a ttl is set, allow caching
  if ((s->cache_control.ttl_in_cache <= 0) &&
      do_cookies_prevent_caching(static_cast<int>(s->txn_conf->cache_responses_to_cookies), request, response)) {
    TxnDbg(dbg_ctl_http_trans, "response has uncachable cookies, response is not cacheable");
    return false;
  }
  // if server spits back a WWW-Authenticate
  if ((s->txn_conf->cache_ignore_auth) == 0 && response->presence(MIME_PRESENCE_WWW_AUTHENTICATE)) {
    TxnDbg(dbg_ctl_http_trans, "response has WWW-Authenticate, response is not cacheable");
    return false;
  }
  // does server explicitly forbid storing?
  // If OS forbids storing but a ttl is set, allow caching
  if (!s->cache_info.directives.does_server_permit_storing && (s->cache_control.ttl_in_cache <= 0)) {
    TxnDbg(dbg_ctl_http_trans, "server does not permit storing and config file does not "
                               "indicate that server directive should be ignored");
    return false;