sig
val zero : Cf_socket.protocol_t
val icmp : Cf_socket.protocol_t
val ipv4 : Cf_socket.protocol_t
val ipv6 : Cf_socket.protocol_t
val tcp : Cf_socket.protocol_t
val udp : Cf_socket.protocol_t
val tcp_nodelay :
(bool, [< `AF_INET | `AF_INET6 ], [ `SOCK_STREAM ]) Cf_socket.sockopt_t
end