Hello,
I have written a kernel module that accesses skbuff
and depending on whether packet is icmp or not it
prints IP checksum and ICMP checksum. But I am getting
sum.c: In function `hook_func1':
sum.c:24: dereferencing pointer to incomplete type
sum.c: In function `hook_func2':
sum.c:40: dereferencing pointer to incomplete type
Whats wrong?
regards,
cranium.
*************************************************
#define __KERNEL__
#define MODULE
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
static struct nf_hook_ops nfho1,nfho2;
unsigned int hook_func1(unsigned int hooknum,struct
sk_buff **skb,
const struct net_device *in,
const struct net_device *out,
int (*okfn)(struct sk_buff *))
{
struct sk_buff *sb = *skb;
if(sb->nh.iph->protocol==1)
{
printk(KERN_DEBUG"ICMP packet\n");
printk(KERN_DEBUG "ICMP cksum=%d,& IP
cksum=%d\n",sb->h.icmph->checksum,sb->nh.iph->check);
}
return NF_ACCEPT;
}
unsigned int hook_func2(unsigned int hooknum,struct
sk_buff **skb,
const struct net_device *in,
const struct net_device *out,
int (*okfn)(struct sk_buff *))
{
struct sk_buff *sb = *skb;
if(sb->nh.iph->protocol==1)
{
printk(KERN_DEBUG"ICMP packet\n");
printk(KERN_DEBUG "ICMP cksum=%d,& IP
cksum=%d\n",sb->h.icmph->checksum,sb->nh.iph->check);
}
return NF_ACCEPT;
}
static int __init init(void)
{
nfho1.hook = hook_func1;
nfho1.hooknum = NF_IP_POST_ROUTING;
nfho1.pf = PF_INET;
nfho1.priority = NF_IP_PRI_FIRST;
nf_register_hook(&nfho1);
nfho2.hook = hook_func2;
nfho2.hooknum = NF_IP_PRE_ROUTING;
nfho2.pf = PF_INET;
nfho2.priority = NF_IP_PRI_FIRST;
nf_register_hook(&nfho2);
return 0;
}
static void __exit fini(void)
{
nf_unregister_hook(&nfho1);
nf_unregister_hook(&nfho2);
}
module_init(init);
module_exit(fini);
MODULE_LICENSE("GPL");
*************************************************************
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