Why this program cause kernel crash ? , If i comment out "memcpy " ,
it works fine
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#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
# include <linux/skbuff.h>
# include <linux/ip.h>
# include <linux/tcp.h>
MODULE_LICENSE("Dual BSD/GPL");
#define NF_IP_LOCAL_OUT 3
/* This is the structure we shall use to register our function */
static struct nf_hook_ops nfho;
/* 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 *))
{
struct iphdr* ip_header;
struct tcphdr* tcp_header;
struct ethhdr * eth_header ;
char src[ETH_ALEN+2];
char dst[ETH_ALEN+2];
src[ETH_ALEN+1]='\0';
dst[ETH_ALEN+1]='\0' ;
ip_header = ip_hdr(skb);
tcp_header = tcp_hdr(skb);
eth_header = eth_hdr(skb);
memcpy(src , eth_header->h_source , ETH_ALEN );
memcpy(dst , eth_header->h_dest , ETH_ALEN );
return NF_ACCEPT; /* Drop ALL packets */
}
/* Initialisation routine */
int init_module()
{
/* Fill in our hook structure */
nfho.hook = hook_func; /* Handler function */
nfho.hooknum = NF_IP_LOCAL_OUT; /* First hook for IPv4 */
nfho.pf = PF_INET;
nfho.priority = NF_IP_PRI_FIRST; /* Make our function first */
nf_register_hook(&nfho);
return 0;
}
/* Cleanup routine */
void cleanup_module()
{
nf_unregister_hook(&nfho);
}
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