problem to print source address and destination address

jooboo · 11-26-2003, 01:07 PM

Please look my code below

#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <linux/spinlock.h>
#include <linux/icmp.h>
#include <linux/udp.h>
#include <linux/tcp.h>
#include <linux/netfilter_ipv4/ip_tables.h>

int init_module(struct sk_buff *skb)
{
struct iphdr *iph;
int i;
printk("SRC : %u.%u.%u.%u \n",NIPQUAD(iph->saddr));
printk("DST : %u.%u.%u.%u \n",NIPQUAD(iph->daddr));
return 0;
}

void cleanup_module()
{
printk("Goodbye\n");
}

That code print source & destination address in /var/log/message below

SRC : 208.1.0.0
DST : 1.0.0.0

I don't understand ,what is ip ? and Where it come from ?

Hko · 11-26-2003, 02:16 PM

Quote:

Code:

 struct iphdr *iph;
/* ... */
printk("SRC : %u.%u.%u.%u \n",NIPQUAD(iph->saddr));

I'm not familiar with programming af kernel modules, but seems to me that iph is a dangling pointer. So you are syslogging random data from an unknown place in memory.

infamous41md · 11-26-2003, 03:24 PM

http://www.linuxquestions.org/questi...hreadid=119823
it would be nice if u read the replies to ur posts b4 asking again. people dont like typing out replies twice.