首先找到模塊的名字,然后去源碼中x86/x86_build/output/build/linux-4.0找到模塊對應的iptable_nat.c文件
在x86/x86_build/output/build/linux-4.0/目錄下grep -rn "iptable_nat.o"找到
x86/x86_build/output/build/linux-4.0/net/ipv4/netfilter/Makefile52: \
obj-$(CONFIG_IP_NF_NAT) \+= iptable_nat.o
得到配置變量是CONFIG_IP_NAT
繼續在linux4.0下grep -rn "IP_NAT"
找到x86/x86_build/output/build/linux-4.0/output/build/linux-4.0/net/ipv4/netfilter/Kconfig:248:config IP_NF_NAT

config IP_NF_NAT
    tristate "iptables NAT support"   //即是內核中的開啟該選項的地方
    depends on NF_CONNTRACK_IPV4      //注意這些depend選項必須先打開才能看到你想要打開的選項
    default m if NETFILTER_ADVANCED=n
    select NF_NAT
    select NF_NAT_IPV4
    select NETFILTER_XT_NAT
    help
    This enables the `nat' table in iptables. This allows masquerading,
    port forwarding and other forms of full Network Address Port
    Translation.
    
    To compile it as a module, choose M here.  If unsure, say N.
    
if IP_NF_NAT