routing.cgi: Allow adding static routes with subnet masks.

It was not possible to enter networks in the subnet mask notation,
which is fixed by this patch.

Fixes #10219.

html/cgi-bin/routing.cgi

@@ -118,6 +118,8 @@ if ($settings{'ACTION'} eq $Lang::tr{'toggle enable disable'}) {
 }
 
 if ($settings{'ACTION'} eq $Lang::tr{'add'}) {
+	# Convert subnet masks to CIDR notation.
+	$settings{'IP'} = &General::iporsubtocidr($settings{'IP'});
 
 # Validate inputs
 	if (( !&General::validip($settings{'IP'})) and ( !&General::validipandmask($settings{'IP'}))){
@@ -443,4 +445,4 @@ sub SortDataFile
 #
 sub BuildConfiguration {
     system '/usr/local/bin/rebuildroutes';
-}
+}