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From help-file :

U32 classifier
CONFIG_NET_CLS_U32
  If you say Y here, you will be able to classify outgoing packets
  according to their destination address. If unsure, say Y.
 
  This code is also available as a module called cls_u32.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