Clever Geek Handbook

How do I contact the members of struct sk_buff?

I am trying to change the original IP of all packets leaving the machine to what I am specifying in this kernel module, but every time I try to access nh.iph-> saddr I get a compile-time error, in which says Struct sk_buff has no name nh
What am I doing wrong here? Am I missing some title or something similar?

#include <linux/module.h>       
#include <linux/kernel.h>       
#include <linux/init.h>         

#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>

#include <linux/skbuff.h>
#include <linux/ip.h>                  /* For IP header */

#include <linux/inet.h> /* For in_aton(); htonl(); and other related Network utility functions */ 


static struct nf_hook_ops nfho;


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 sk_buff *sb = *skb;
    struct in_addr masterIP;

    masterIP.s_addr = htonl (in_aton("192.168.1.10")); 
    sb->nh.iph->saddr = masterIP.s_addr;
    return NF_ACCEPT;
}

Please note that I am running Ubuntu 10.04 LTS 64 bit
Kernel 2.6.32-33

+3


source to share


2 answers


The version struct sk_buff

has changed in the kernel version . It no longer has these members. To access the IP header you should try:

#include <linux/ip.h>

struct iphdr* iph = ip_hdr(skb);

Then just use a variable iph

to change the addresses, for example:



iph->saddr = ....
iph->daddr = ....

Also, do not forget that you may need to recalculate the ip

possible checksums of the transport packets.

+13


source


You can find the definition of struck sk_buff in 'include / linux / skbuff.h'.



It does not have an nh field that explains the compilation errors you are seeing. It has a "network_header" field, which is probably what you are looking for.

-1


source






More articles:


All Articles