sock_buff is NULL !

[Kesava Srinivas]

Thanks Jeff for the reply. Yes; after changing the double pointer to a
Normal Pointer., I can see that ., "if" block was skipped.

-Thnx,
VKS

On Tue, Nov 22, 2011 at 12:50 AM, Jeff Haran <jharan at bytemobile.com> wrote:

> ** **
>
> ** **
>
> *From:* kernelnewbies-bounces at kernelnewbies.org [mailto:
> kernelnewbies-bounces at kernelnewbies.org] *On Behalf Of *Kesava Srinivas
> *Sent:* Monday, November 21, 2011 11:03 AM
> *To:* kernelnewbies at kernelnewbies.org
> *Subject:* sock_buff is NULL !****
>
> ** **
>
> HI Team,
>
> Trying to make this code work; but some how it is entering the if
> condition mentioned below.sock_buff is still a NULL Pointer.I can see that
> Function was registered with the Ipv4 Hooks. Any ideas/scenarios where the
> sock_buff remains as NULL Pointer??? Testing this code by trying to do ssh
> with this machine.
>
> Any Help is really appreciated !!
>
> #########
> static struct nf_hook_ops netfilter_ops;
> struct sk_buff *sock_buff;
>
> 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*)) {
>  sock_buff = *skb;
>         if(!sock_buff){
>            printk(KERN_ERR "Entered unexpected loop \n");
>                return NF_ACCEPT;
>          }/* Check for sk_buff NULL */
> }
> int init_module()
> {
>         netfilter_ops.hook              =       (nf_hookfn *) main_hook;
>         netfilter_ops.hooknum           =       NF_INET_PRE_ROUTING;
>         netfilter_ops.pf                =       PF_INET;
>         netfilter_ops.priority          =       NF_IP_PRI_FIRST;
>         nf_register_hook(&netfilter_ops);
>
>
> }
> ######################
>
>
> -Thnx,
> VKS****
>
> ** **
>
> Which kernel version are you using? The function prototype of a netfilter
> hook does vary from kernel version to kernel version, but in the kernels
> I’ve seen the skb parameter is a typed sk_buff *skb, not sk_buff **skb. In
> other words, you get passed a pointer to the sk_buff, not the address of a
> pointer to an sk_buff.****
>
> ** **
>
> Jeff Haran****
>
> ** **
>



-- 
-VKS
Masters,Computer Science&Engineering.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.kernelnewbies.org/pipermail/kernelnewbies/attachments/20111122/4a60b76c/attachment.html