VMS Help TCPIP Services, Programming Interfaces, Sockets API, ioctl(), Argument  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 s
    Specifies the socket descriptor of the requested network device.
 request
    Specifies the type of ioctl command to be performed on the
    device. The request types are grouped as follows:
    o  Socket operations
    o  File operations
    o  Interface operations
    o  ARP cache operations
    o  Routing table operations
    Refer to <REFERENCE>(app_ioctl_commands) for a complete list of
    IOCTL commands.
 arg
    Specifies arguments for this request. The type of arg is
    dependent on the specific ioctl() request and device to which
    the ioctl call is targeted.