Hello,
I am learning the skbuff workings in kenrel for that I added a fake header in TCP/IP with Fake header containing 2 fields of type int ipchksum and tcpchksum taken frpm upper layer and only copied to new header. I directly push it after IP header is added and thus sending packets to destination pc. At
destination side i am able to receive application data(payload) indeed correctly in FTP transfer but when i try to print faker header fields in kernel they are not printed rather gives OOPS message
I am really stuck at this point please help me.
Thanks in advance.
regards,
linux_lover.

How is your printf statement like? It is possible that you have used wrong format string. e.g. %s for an integer value...

i have netfilter kernel module at NF_IP_POST_ROUTING at which i added netfilter hook that pushes new fake header after IP header is skb_put in ip_output.c file.
i did some changes to implementation by changing header values as
struct fake{
char *name;
int num;
}; /*inserted this in skbuff struct*/
In netfilter module i am just assigning values. Then packet is filled with Hardware header. I want to work this on network but right now using 2 computers.
Actually the problem is to retreive header from skb->data. As we know each header is mapped to union raw character format in netif_receive_skb. I dont have union defined in skbuff. i tried that one but not worked as my header position is in between Ethernet and IP.
I am doing
fake=skb->fakehdr;
printk(KERN_DEBUG "my name = %s\n", fake->name);
printk(KERN_DEBUG "num is = %d\n", fake->num);
kernel oops here as i think it is not getting corret pointer in skb->data for new fake header?
please help me if you need any more info please ask me. Theres only i think pointer problem that i am not able to set.