我想使用netfilter进行开发，写了一个非常简单的测试例子，如下：

#include	<stdio.h>


#include 	<linux/netfilter.h>  
#include 	<linux/init.h>  
#include 	<linux/module.h>  
#include 	<linux/netfilter_ipv4.h>  
#include 	<linux/ip.h>  
#include 	<linux/inet.h> 

/** 
 * Hook function to be called. 
 * We modify the packet's src IP. 
 */  
unsigned int my_hookfn(unsigned int hooknum,  
    struct sk_buff *skb,  
    const struct net_device *in,  
    const struct net_device *out,  
    int (*okfn)(struct sk_buff *))  
{  
	struct iphdr *iph;  
	iph = ip_hdr(skb);  
  
	/* log the original src IP */  
	printk(KERN_INFO"src IP %pI4\n", &iph->saddr);  
  
	/* modify the packet's src IP */  
	iph->saddr = in_aton("8.8.8.8");  
  
	return NF_ACCEPT;  
}  
  
/* A netfilter instance to use */  
static struct nf_hook_ops nfho = {  
	.hook = my_hookfn,  
	.pf = PF_INET,  
	.hooknum = NF_INET_PRE_ROUTING,  
	.priority = NF_IP_PRI_FIRST,  
	.owner = THIS_MODULE,  
};  
  
static int __init sknf_init(void)  
{  
	if (nf_register_hook(&nfho)) 
	{  
	        printk(KERN_ERR"nf_register_hook() failed\n");  
	        return -1;  
	}  
	return 0;  
}  
  
static void __exit sknf_exit(void)  
{  
	nf_unregister_hook(&nfho);  
}  
  
module_init(sknf_init);  
module_exit(sknf_exit);  
MODULE_AUTHOR("test");  
MODULE_LICENSE("GPL"); 

static	int	test(int argc, char*argv[])
{
	
	printf("--start test--,%d, %s\n",argc, argv[1]);

	

	printf("--end test--\n");
	
	
	return 0;
}

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