This method is deprecated or moved on the latest stable version. The last existing version (v1_9_2_180) is shown here.
family()
returns the socket family as an integer.
p Socket::AncillaryData.new(:INET6, :IPV6, :PKTINFO, "").family #=> 10
static VALUE ancillary_family_m(VALUE self) { return INT2NUM(ancillary_family(self)); }