custom validation rule for IP in form

There is a validation rule for valid_ip already no need for a custom one.

You just need to get it like above then run it through the validation.

adding it with hidden field wont work as users can edit it via inspect on browser before sending the form, like i said i don't need this to use the validate_ip rule, i need it to use a rule which i wrote and its not for ip validation. So far i read the user manual few times googled whole day and didn't find how, this forum and users are my last chance  but seems slim as everyone suggest adding hidden field which is the worst practice ever