#include <linux/module.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
static struct nf_hook_ops netfilter_ops_in; /* NF_IP_PRE_ROUTING */
/* Function prototype in <linux/netfilter> */
unsigned int main_hook(unsigned int hooknum,  
                  struct sk_buff **skb,
                  const struct net_device *in,
                  const struct net_device *out,
                  int (*okfn)(struct sk_buff*))
{
struct sk_buff* sk;
sk = (*skb);

unsigned char* rawp;
rawp = sk->mac.raw; //Accessing the MAC Header
return NF_ACCEPT;
}
int init_module()
{
        netfilter_ops_in.hook                   =       main_hook;
        netfilter_ops_in.pf                     =       PF_INET;
        netfilter_ops_in.hooknum                =       NF_IP_PRE_ROUTING;
        netfilter_ops_in.priority               =       NF_IP_PRI_FIRST;
      

        nf_register_hook(&netfilter_ops_in); /* register NF_IP_PRE_ROUTING hook */
      
return 0;
}
void cleanup_module()
{
nf_unregister_hook(&netfilter_ops_in); /*unregister NF_IP_PRE_ROUTING hook*/
}