rfc3779 - Enable support for RFC 3779 (X.509 Extensions for IP Addresses and AS Identifiers)
sctp - Support for Stream Control Transmission Protocol
sslv2 - Support for the old/insecure SSLv2 protocol -- note: not required for TLS/https
sslv3 - Support for the old/insecure SSLv3 protocol -- note: not required for TLS/https
static-libs - Build static versions of dynamic libraries as well
test - Enable dependencies and/or preparations necessary to run tests (usually controlled by FEATURES=test but can be toggled independently)
tls-compression - Enable support for discouraged TLS compression
tls-heartbeat - Enable the Heartbeat Extension in TLS and DTLS
vanilla - Do not add extra patches which change default behaviour; DO NOT USE THIS ON A GLOBAL SCALE as the severity of the meaning changes drastically
verify-sig - Verify upstream signatures on distfiles
weak-ssl-ciphers - Build support for SSL/TLS ciphers that are considered "weak"