imp1_k.c

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/*imp1_k.c*/
#ifndef __KERNEL__
#define __KERNEL__
#endif

#ifndef MODULE
#define MODULE
#endif

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/netfilter_ipv4.h>
#include <linux/init.h>
#include <asm/uaccess.h>
#include "imp1.h"

#define KMSG      "a message from kernel\n"
#define KMSG_LEN  sizeof("a message from kernel\n")

static int data_to_kernel(struct sock *sk, int cmd, void *user,
			  unsigned int len)
{
  switch(cmd)
    {
    case IMP1_SET:
      {
        char umsg[64];
	memset(umsg, 0, sizeof(char)*64);
        copy_from_user(umsg, user, sizeof(char)*64);
        printk("umsg: %s", umsg);
      }
      break;
    }
  return 0;
}

static int data_from_kernel(struct sock *sk, int cmd, void *user, int *len)
{
  switch(cmd)
    {
    case IMP1_GET:
      {
        copy_to_user(user, KMSG, KMSG_LEN);
      }
      break;
    }
  return 0;
}

static struct nf_sockopt_ops imp1_sockops =
{
  .pf = PF_INET,
  .set_optmin = IMP1_SET,
  .set_optmax = IMP1_MAX,
  .set = data_to_kernel,
  .get_optmin = IMP1_GET,
  .get_optmax = IMP1_MAX,
  .get = data_from_kernel,
};

static int __init init(void)
{
  return nf_register_sockopt(&imp1_sockops);
}

static void __exit fini(void)
{
  nf_unregister_sockopt(&imp1_sockops);
}

module_init(init);
module_exit(fini);