#ifndef __KERNEL__

#define __KERNEL__

#endif

#ifndef MODULE

#define MODULE

#endif

#include <linux/module.h>

#include <linux/sched.h>

#include <linux/kernel.h>

#include <linux/netdevice.h>

#include <linux/ip.h>

#include <linux/tcp.h>

#include <linux/skbuff.h>

#include <linux/proc_fs.h>

#include <linux/if.h>

#include <linux/in.h>

#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/skbuff.h>

#include <linux/netfilter_ipv4.h>

#include <linux/ip.h>

#define PERMIT_PORT 80

static unsigned int test_firewall(unsigned int hooknum ,struct sk_buff **skb,

const struct net_device *in ,

const struct net_device *out,

int(*okfn)(struct sk_buff*))

{

//struct tcphdr *tcph;

struct iphdr *iph;

// struct sk_buff *skb=*pskb;

if((*skb)->protocol==htons(ETH_P_IP))

{

iph=(*skb)->nh.iph;

if (iph->protocol==IPPROTO_ICMP)

{

printk("\nDROP a ICMP Packet");

return NF_DROP;

}

if(iph->protocol==IPPROTO_TCP){

printk("\nPermit a valid access");

return NF_ACCEPT;

}

}

return NF_ACCEPT;

}

static struct nf_hook_ops ipl1 =

{

{NULL,NULL},

test_firewall,

PF_INET,

NF_IP_PRE_ROUTING,

NF_IP_PRI_FILTER -1

};

int init_module()

{

return nf_register_hook(&ipl1);

}

void cleanup_module()

{

printk("goodbye1");

nf_unregister_hook(&ipl1);

}