OpenWrt hotplug iface ifupdate

im using the netifd/files/etc/hotplug.d/iface script file to detect network disconnect.
but i find the interface is in ifupdate,
what is the define of ifupdate?

how about the command ubus call network.interface.wan status ?

https://openwrt.org/docs/guide-user/base-system/hotplug?s=ifupdate#iface

i have seen the doc , so i still dont understand it

How about DHCP renew?