inet value validation

["pgsql-general@xxxxxxxxxxxxxxxx" <pgsql-general@xxxxxxxxxxxxxxxx>]

hello,

I want to write a function to validate an inet data type, but I figure 
that postgres should already have such a function to use before 
inserting values in inet type columns.
is it possible to access postgres's validation function for inet types ? 
I have snooped through the catalogs but I can not find such a function.


thanks,
Razvan Radu