Attempts to cache the sent entity by its ETag, either supplied or generated by the hash algorithm specified by the INI setting http.etag.mode.
If the clients If-None-Match header matches the supplied/calculated ETag, the body is considered cached on the clients side and a 304 Not Modified status code is issued.
A log entry is written to the cache log if the INI setting http.log.cache is set and the cache attempt was successful.