track the icmp packet.

[ratheesh kannoth <ratheesh.ksz@xxxxxxxxx>]

I have a  linux machine (2.6.32 kernel )
ip address is 192.168.0.102 and default gw is 192.168.0.1


I want to do some "printk " when an echo request is sent from the
machine to the gateway
ie ...
# ping  192.168.0.1       // command should do some printk.

I found a program at
http://www.netfilter.org/documentation/HOWTO/netfilter-hacking-HOWTO.txt.
I modified a little for my purpose. But it is not working. Could you
please guide me.



@@@@@@@  conn-track-01.c @@@@@@@@@@@@
// copied from http://www.netfilter.org/documentation/HOWTO/netfilter-hacking-HOWTO.txt
// and modified

#define FOO_PORT        111
#include <linux/module.h>
#include <linux/kernel.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <linux/ip.h>
#include <net/netfilter/nf_conntrack_expect.h>


static char * dst_ipaddress = "192.168.0.1" ; // my gateway ip address
is 192.168.0.1
module_param(dst_ipaddress, charp, 0000);

static const struct nf_conntrack_expect_policy my_expect_policy = {
       .max_expected           = 3,
       .timeout                = 180,
};


static int foo_expectfn(struct nf_conntrack *new)
{

       return 0;
}

static int foo_help(struct sk_buff *skb,
                   unsigned int protoff,
                  struct nf_conn *ct,
                   enum ip_conntrack_info conntrackinfo)
{
       printk (KERN_INFO "RAT: called the  helper \n");
       return NF_ACCEPT;
}

static struct nf_conntrack_helper foo;

int init_conntrack_module(void)
{
       memset(&foo, 0, sizeof(struct nf_conntrack_helper));

       foo.name = "foo";
       foo.me = THIS_MODULE;

       foo.tuple.dst.protonum = IPPROTO_ICMP;
       foo.tuple.dst.u.icmp.type = 8;
       foo.tuple.dst.u.icmp.code  = 0;
       foo.tuple.src.l3num = AF_INET;
       foo.help = foo_help;
       foo.expect_policy = &my_expect_policy;
       {
         int i = 0;
         int addr = 0;
         char *p = (char *)&addr;
         int a[4];
         sscanf(dst_ipaddress, "%d.%d.%d.%d", &a[3], &a[2], &a[1], &a[0]);
         while(i != 4 ) {
                *(p + i ) = a[i];
                 i++;
         }
         foo.tuple.dst.u3.ip = addr;
         foo.tuple.src.u3.ip = 0xc0a80066; //my linux machine  ip
address is 192.168.0.102
       }

       return nf_conntrack_helper_register(&foo);
}

void  fini_conntrack_module(void)
{
       nf_conntrack_helper_unregister(&foo);
}

module_init(init_conntrack_module);
module_exit(fini_conntrack_module);

//end of program

-Ratheesh
--
To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html