+(declare-function network-interface-list "process.c")
+
+(defun dns-servers-up-to-date-p ()
+ "Return false if we need to recheck the list of DNS servers."
+ (and dns-servers
+ (or (eq dns-servers-valid-for-interfaces t)
+ ;; `network-interface-list' was introduced in Emacs 22.1.
+ (not (fboundp 'network-interface-list))
+ (equal dns-servers-valid-for-interfaces
+ (network-interface-list)))))
+