+#ifdef KERNEL_PRIVATE
+/*!
+ @typedef ctl_rcvd_func
+ @discussion The ctl_rcvd_func is called when the client reads data from
+ the kernel control socket. The kernel control can use this callback
+ in combination with ctl_getenqueuespace() to avoid overflowing
+ the socket's receive buffer. When ctl_getenqueuespace() returns
+ 0 or ctl_enqueuedata()/ctl_enqueuembuf() return ENOBUFS, the
+ kernel control can wait until this callback is called before
+ trying to enqueue the data again.
+ @param kctlref The control ref of the kernel control.
+ @param unit The unit number of the kernel control instance.
+ @param unitinfo The user-defined private data initialized by the
+ ctl_connect_func callback.
+ @param flags The recv flags. See the recv(2) man page.
+ */
+typedef void (*ctl_rcvd_func)(kern_ctl_ref kctlref, u_int32_t unit, void *unitinfo,
+ int flags);
+
+/*!
+ @typedef ctl_send_list_func
+ @discussion The ctl_send_list_func is used to receive data sent from
+ the client to the kernel control.
+ @param kctlref The control ref of the kernel control.
+ @param unit The unit number of the kernel control instance the client has
+ connected to.
+ @param unitinfo The user-defined private data initialized by the
+ ctl_connect_func callback.
+ @param m The data sent by the client to the kernel control in an
+ mbuf packet chain. Your function is responsible for releasing
+ mbuf packet chain.
+ @param flags The flags specified by the client when calling
+ send/sendto/sendmsg (MSG_OOB/MSG_DONTROUTE).
+ */
+typedef errno_t (*ctl_send_list_func)(kern_ctl_ref kctlref, u_int32_t unit, void *unitinfo,
+ mbuf_t m, int flags);
+
+/*!
+ @typedef ctl_bind_func
+ @discussion The ctl_bind_func is an optional function that allows the client
+ to set up their unitinfo prior to connecting.
+ @param kctlref The control ref for the kernel control the client is
+ binding to.
+ @param sac The address used to connect to this control. The field sc_unit
+ contains the unit number of the kernel control instance the client is
+ binding to. If CTL_FLAG_REG_ID_UNIT was set when the kernel control
+ was registered, sc_unit is the ctl_unit of the kern_ctl_reg structure.
+ If CTL_FLAG_REG_ID_UNIT was not set when the kernel control was
+ registered, sc_unit is the dynamically allocated unit number of
+ the new kernel control instance that is used for this connection.
+ @param unitinfo A placeholder for a pointer to the optional user-defined
+ private data associated with this kernel control instance. This
+ opaque info will be provided to the user when the rest of the
+ callback routines are executed. For example, it can be used
+ to pass a pointer to an instance-specific data structure in
+ order for the user to keep track of the states related to this
+ kernel control instance.
+ */
+typedef errno_t (*ctl_bind_func)(kern_ctl_ref kctlref,
+ struct sockaddr_ctl *sac,
+ void **unitinfo);
+#endif /* KERNEL_PRIVATE */
+