debug - Enable extra debug codepaths, like asserts and extra output. If you want to get meaningful backtraces see https://wiki.gentoo.org/wiki/Project:Quality_Assurance/Backtraces
geoip - Add geoip support for country and city lookup based on IPs
geoipv2 - Enable support for GeoIP2 through dev-libs/libmaxminddb
getline - Use GNU getline() to parse full line requests
ssl - Add support for SSL/TLS connections (Secure Socket Layer / Transport Layer Security)