invalid pointer initialization

[ricardopf]

Hello all,

I'm facing some problems to compile a new module for Linux Ubuntu 8.04, kernel version 2.6. Above are two pieces of code related to the problem.

linux/netfilter.h

//begin netfilter
...
typedef unsigned int nf_hookfn(unsigned int hooknum, struct sk_buff *skb, const struct net_devide *in, const struct net_device *out, int (*okfn)(struct sk_buff *));
...
struct nf_hook_ops {
struct list_head list;
nf_hookfn *hook;
struct module *owner;
int pf;
int hooknum;
int priority;
};
...
// end netfilter

myfile.h

// begin myfile
...
#include <netfilter.h>
...
unsigned int my_nf_hook(unsigned int hook, struct sk_buff **skb, const struct net_device *indev, const struct net_device *outdev, int (*okfn)(struct sk_buff *)); // It is a function that is further implemented
...
static struct nf_hook_ops nfh_pre = {
{NULL, NULL},
my_nf_hook,
THIS_MODULE,
PF_INET,
NF_IP_PRE_ROUTING,
NF_IP_PRI_FILTER+1
};
...
// end myfile

When I execute the 'make myfile.ko' to compile the module, it gives me the following warning:

... warning: initialization from incompatible pointer type

This warning is pointing the line '9. my_nf_hook' inside the struct nfh_pre initialization.

Well, after compiling, the ko file is generated. However, when I execute the command 'insmod myfile.ko' to load the module, it results in kernel panic. I believe that the warning is directed related to the problem.

Finally, my question: does anybody know where is the problem in the code above? What could be missing?

Thanks a lot in advance for repliers.

[newb16]

Is it struct sk_buff **skb or struct sk_buff *skb in function args ? ( number of *'s )

[ricardopf]

That's right... it is **

[ricardopf]

Problem solved

Indeed, the pointer to pointer was the problem.
However, who is implementing with netfilter.h needs to be careful about that. From kernel 2.6.20 (I guess) it is a pointer only to skb sk_buff structure. But, from 2.6.19 version and lesser ones it is a double pointer (**skb).