From help-file :
Routing tables based classifier CONFIG_NET_CLS_ROUTE4 If you say Y here, you will be able to classify outgoing packets according to the route table entry they matched. If unsure, say Y. This code is also available as a module called cls_route.o ( = code which can be inserted in and removed from the running kernel whenever you want). If you want to compile it as a module, say M here and read Documentation/modules.txt.