Connect functions notes

Before we dive into the individual messages, however, it's worth pointing out that the connect functions all have an identical message structure (rearranged slightly, see <sys/iomsg.h> for the original):

struct _io_connect {
    // Internal use
    uint16_t type;
    uint16_t subtype;
    uint32_t file_type;
    uint16_t reply_max;
    uint16_t entry_max;
    uint32_t key;
    uint32_t handle;
    uint32_t ioflag;
    uint32_t mode;
    uint16_t sflag;
    uint16_t access;
    uint16_t zero;
    uint8_t  eflag;

    // End-user parameters
    uint16_t path_len;
    uint8_t  extra_type;
    uint16_t extra_len;
    char     path [1];
};

You'll notice that I've divided the struct _io_connect structure into two areas, an "Internal use" part and an "End-user parameters" part.