readconfiguration.c

Linux下kernel与userspace的通信实现。主要功能为可修改linux的防火墙设置进行通信控制。Linux下调试通过。

/*  Reading data
 */

#include <linux/module.h>  /* Needed by all modules */
#include <linux/kernel.h>  /* Needed for KERN_ALERT */
#include <linux/proc_fs.h> 
#include <asm/uaccess.h>
#include "../include/firewall.h"

MODULE_AUTHOR ("Eike Ritter <[e-mail]>");
MODULE_DESCRIPTION ("Reading data") ;
MODULE_LICENSE("GPL");


struct proc_dir_entry *procFirewall; /* the handler for the proc-file */


/* reads the data from the buffer into the kernel */
struct ConfigKernelEntry *parseBuffer (char *buffer, int count, int *errno) {
  int progLength;
  
  struct ConfigKernelEntry *entry;

  printk (KERN_INFO "tableRead parseBuffer: count = %d \n", count);
  *errno = 0;
  if (count < 2 * sizeof (int)) {

    *errno = -ENOMEM;
    return NULL;
  }
  
  entry = kmalloc (sizeof (*entry), GFP_KERNEL);
  if (!entry) {
    *errno = -ENOMEM;
    return NULL;
  }
  
  /* reads port number */
  memcpy (&(entry->port), buffer, sizeof (int));

  /* reads lengths of the program string */
  memcpy (&progLength, buffer + sizeof (int), sizeof (int));

  /* allocate space in kernel memory for program name */
  entry->program = kmalloc (progLength, GFP_KERNEL);
  if (!entry->program) {
    kfree (entry);
    *errno = -ENOMEM;
    return NULL;
  }

  if (count < 2 *sizeof (int) + progLength + sizeof (IPAddressByteType)) {
    *errno = -ENOMEM;
    kfree (entry->program);
    kfree (entry);
    return NULL;
  }

  /* read program name */
  memcpy (entry->program, buffer + 2*sizeof (int), progLength);

  /* read IP-address */
  memcpy (&(entry->IPAddress), buffer + (2 *sizeof (int) + progLength), sizeof (IPAddressByteType));
  
  return entry;
}



/* This function reads in data from the user into the kernel */
int fwTableRead (struct file *file, const char *userBuffer, unsigned long count, void *data) {
 

  char *buffer;
  int errno = 0;
  struct ConfigKernelEntry *entry;
  

  /* allocate temporary kernel buffer */
  buffer = kmalloc (count, GFP_KERNEL);
  if (!buffer) {
    return -ENOMEM;
  }

  /* copy data from user space */
  if (copy_from_user (buffer, userBuffer, count)) { 
    printk (KERN_INFO "tableRead copying data from user space failed \n");
    kfree (buffer);
    return -EFAULT;
  }

  entry = parseBuffer (buffer, count, &errno);
  if (!entry) {
    kfree (buffer);
    return errno;
  }

  kfree (buffer); /* temporary buffer no longer needed */
  /* print the results */
  printk (KERN_INFO "program = %s\n", entry->program);
  printk (KERN_INFO "port = %d\n", entry->port);
  printk (KERN_INFO "tableRead Destination address = %u.%u.%u.%u\n", NIPQUAD(entry->IPAddress));
  return count;
}


int init_module(void)
{
   printk(KERN_INFO "tableRead module loaded.\n");
	

   /* create the proc-file */
   procFirewall = create_proc_entry ("net/firewall", S_IWUSR | S_IRUGO, NULL);

   if (!procFirewall) {
     return -ENOMEM;
   }


   procFirewall->owner = THIS_MODULE; /* required for using proc-structure within module */
   /* specify the procedure which reads data */
   procFirewall->write_proc = fwTableRead;


   return 0;
}
  
void cleanup_module(void)
{


  remove_proc_entry ("net/firewall", NULL); /* do this first to prevent any concurrency problems */

  printk(KERN_INFO "tableRead module unloaded.\n");
  
}