Messages in this thread | | | Date | Sat, 1 Jan 2005 00:08:49 -0800 (PST) | From | linux lover <> | Subject | Is my module program is giving correct output? |
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Hello all, While writing kernel module packet sniffer i start with first accessing packets length and its data part.so, to start i try to access packet data first and copy it to other variable to dump its contents but i am facing a problem while accessing the packet's data. As i have studied i found that data in packet at any layer resides in between data and tail pointers. So if i have to print it or copy it in any unsigned string then how to do that? I tried with following example which receives packet and print data part at IP layer. But I am not sure whether am i getting packet dump or address of string packet? Thanks in advance. regards, linux_lover
#define MODULE #define __KERNEL__
#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>
#include <linux/string.h>
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; printk(KERN_DEBUG "calling hook_func at NF_IP_LOCAL_OUT\n"); unsigned char *packet; unsigned int buflen; int i=0; buflen=sb->len; packet=kmalloc(buflen,GFP_USER); memset(packet,'\0',buflen); printk(KERN_DEBUG "Length of skb->data in hook function = %d\n", buflen); strncpy(packet,sb->data,buflen); printk(KERN_DEBUG "packet contents of sb->data in hook function = %x\n", packet);
return NF_ACCEPT; }
static int __init init(void) { nfho.hook = hook_func; nfho.hooknum = NF_IP_LOCAL_OUT; nfho.pf = PF_INET; nfho.priority = NF_IP_PRI_FIRST; nf_register_hook(&nfho1); return 0; }
static void __exit fini(void) { nf_unregister_hook(&nfho1); } module_init(init); module_exit(fini); MODULE_LICENSE("GPL");
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