On Thursday 2010-05-13 17:45, ratheesh k wrote:
>Why this program cause kernel crash ? , If i comment out "memcpy " ,
>it works fine
>
>/* 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 );
If you do not have an Ethernet packet, this is going to explode.
>
> return NF_ACCEPT; /* Drop ALL packets */
>}
>
>/* Initialisation routine */
>int init_module()
^ void
>{
> /* 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()
^ void
>{
> nf_unregister_hook(&nfho);
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