Reverse Address Resolution Cache

ze-filter maintains a cache with reverse DNS resolution of IP addresses. The goal isn't to use this to handle new connections but to accelerate reporting. E.g., if you ask the filter to show you all SMTP clients which connected to your server, the cache will provide hostnames associated to IP addresses without querying DNS to solve it.

The following four parameters are used to enable and tune the cache.

RESOLVE_CACHE_ENABLE               YES
RESOLVE_CACHE_SYNC                 1m
RESOLVE_CACHE_CHECK                1h
RESOLVE_CACHE_EXPIRE               2d