netfilter 例子改写1

netfilter is on linux kernel 2.4, now it is rewrite on linux kernel 3.2.0
------------------Begin---------------------------
/* Sample code to install a Netfilter hook function that will
 * drop all incoming packets on an interface we specify */
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
/* This is the structure we shall use to register our function */
static struct nf_hook_ops nfho;

/* Name of the interface we want to drop packets from */
static char *drop_if = "lo";

/* This is the hook function itself */
unsigned int hook_func(unsigned int hooknum,
                       struct sk_buff *skb,
                       const struct net_device *in,
                       const struct net_device *out,
                       int (*okfn)(struct sk_buff *))
{
    if (strcmp(in->name, drop_if) == 0) {
        printk("Dropped packet on %s...\n", drop_if);
        return NF_DROP;
    } else {
        return NF_ACCEPT;
    }
}

/* Initialisation routine */
int init_module()
{
    /* Fill in our hook structure */
    nfho.hook     = hook_func;         /* Handler function */
    nfho.hooknum  = NF_INET_PRE_ROUTING; //NF_IP_PRE_ROUTING; /* First hook for IPv4 */
    nfho.pf       = PF_INET;
    nfho.priority = NF_IP_PRI_FIRST;   /* Make our function first */

    nf_register_hook(&nfho);
    printk("init_module 1\n");
    return 0;
}

/* Cleanup routine */
void cleanup_module()
{
    printk("cleanup module 2\n");
    nf_unregister_hook(&nfho);
}
-----------------End------------------------
Makefile
------------------Begin---------------------------
ifneq ($(KERNELRELEASE),)
mymodule-objs:=filter_if.o
obj-m:=filter_if.o
else
PWD:=$(shell pwd)
KVER:=$(shell uname -r)

#KDIR:=/usr/src/linux-source-2.6.32/
KDIR:=/usr/src/linux-source-3.2.0/linux-source-3.2.0
all:
        $(MAKE) -C $(KDIR) M=$(PWD)
clean:
        @rm -rf .*.com *.o *.mod.c *.ko .tmp_versions modules.order Module.symvers
endif
--------------------End----------------------------------