Set optional interface variables when there are no providers

Shorewall/Perl/Shorewall/Providers.pm

@@ -794,6 +794,30 @@ sub setup_providers() {
 
 	    emit "fi\n";
 	}
+
+	my $interfaces = find_interfaces_by_option 'optional';
+
+	if ( $interfaces ) {
+	    emit '';
+
+	    my $first = 1;
+
+	    for my $interface ( @$interfaces ) {
+		my $base = uc chain_base( $interface );
+
+		if ( $first ) {
+		    $first = 0;
+		} else {
+		    emit '';
+		}
+
+		emit ( "if interface_is_usable $interface; then" ,
+		       "    ${base}_IS_UP=Yes" ,
+		       'else' ,
+		       "    ${base}_IS_UP=" ,
+		       'fi' );
+	    }
+	}
     }
 
 }