On Thu, May 13, 2010 at 9:49 PM, Jan Engelhardt <jengelh@xxxxxxxxxx> wrote:
> If you do not have an Ethernet packet, this is going to explode.
I have only one ethernet network interface (eth0 ) with 192.168.1.5 .
I could see in wireshark all packets with ethernet mac addresses .
When i try to prink the mac address or copy , it hangs ..
-Ratheesh
On Thu, May 13, 2010 at 9:49 PM, Jan Engelhardt <jengelh@xxxxxxxxxx> wrote:
>h
> 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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