This ioctl is sent downstream by the x25netd process to configure a newly linked driver below the X.25 multiplexor. It supplies the parameters necessary to identify the link via the identifier and to register the mode of the lower driver.
This ioctl is only used when X.25 is initializing. As it affects currently open connections and could therefore disrupt users significantly, it can only be used by root. It should not be used by user applications, as it may be withdrawn from future versions of Solstice X.25.