openwrt编译ifb.ko模块问题

<*> kmod-ifb........................... Intermediate Functional Block support

开始时候怎么都编译不了ifb.ko模块
最后通过Kconfig发现

config IFB
        tristate "Intermediate Functional Block support"
        depends on NET_CLS_ACT
        ---help---
          This is an intermediate driver that allows sharing of
          resources.
          To compile this driver as a module, choose M here: the module
          will be called ifb.  If you want to use more than one ifb
          device at a time, you need to compile this driver as a module.
          Instead of 'ifb', the devices will then be called 'ifb0',
          'ifb1' etc.
          Look at the iproute2 documentation directory for usage etc

其实它是依赖这个模块的，内核是你没有选中的
#CONFIG_NET_CLS_ACT is not set

make menuconfig

<*> kmod-sched-connmark................ Traffic shaper conntrack mark support  
-*- kmod-sched-core....................................... Traffic schedulers

查看内核.config文件， CONFIG_NET_CLS_ACT=y

make V=99

最后会发现内核里出现了ifb.ko