/usr/src/xtables-addons-2.10/extensions/xt_condition.c is in xtables-addons-dkms 2.10-1build1.
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* "condition" match extension for Xtables
*
* Description: This module allows firewall rules to match using
* condition variables available through procfs.
*
* Authors:
* Stephane Ouellette <ouellettes [at] videotron ca>, 2002-10-22
* Massimiliano Hofer <max [at] nucleus it>, 2006-05-15
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License; either version 2
* or 3 of the License, as published by the Free Software Foundation.
*/
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/version.h>
#include <linux/netfilter/x_tables.h>
#include <asm/uaccess.h>
#include "xt_condition.h"
#include "compat_xtables.h"
#ifndef CONFIG_PROC_FS
# error "proc file system support is required for this module"
#endif
/* Defaults, these can be overridden on the module command-line. */
static unsigned int condition_list_perms = S_IRUGO | S_IWUSR;
static unsigned int condition_uid_perms = 0;
static unsigned int condition_gid_perms = 0;
MODULE_AUTHOR("Stephane Ouellette <ouellettes@videotron.ca>");
MODULE_AUTHOR("Massimiliano Hofer <max@nucleus.it>");
MODULE_AUTHOR("Jan Engelhardt ");
MODULE_DESCRIPTION("Allows rules to match against condition variables");
MODULE_LICENSE("GPL");
module_param(condition_list_perms, uint, S_IRUSR | S_IWUSR);
MODULE_PARM_DESC(condition_list_perms, "permissions on /proc/net/nf_condition/* files");
module_param(condition_uid_perms, uint, S_IRUSR | S_IWUSR);
MODULE_PARM_DESC(condition_uid_perms, "user owner of /proc/net/nf_condition/* files");
module_param(condition_gid_perms, uint, S_IRUSR | S_IWUSR);
MODULE_PARM_DESC(condition_gid_perms, "group owner of /proc/net/nf_condition/* files");
MODULE_ALIAS("ipt_condition");
MODULE_ALIAS("ip6t_condition");
struct condition_variable {
struct list_head list;
struct proc_dir_entry *status_proc;
unsigned int refcount;
bool enabled;
char name[sizeof(((struct xt_condition_mtinfo *)NULL)->name)];
};
/* proc_lock is a user context only semaphore used for write access */
/* to the conditions' list. */
static DEFINE_MUTEX(proc_lock);
static LIST_HEAD(conditions_list);
static struct proc_dir_entry *proc_net_condition;
static int condition_proc_show(struct seq_file *m, void *data)
{
const struct condition_variable *var = m->private;
seq_printf(m, var->enabled ? "1\n" : "0\n");
return 0;
}
static int condition_proc_open(struct inode *inode, struct file *file)
{
return single_open(file, condition_proc_show, PDE_DATA(inode));
}
static ssize_t
condition_proc_write(struct file *file, const char __user *buffer,
size_t length, loff_t *loff)
{
struct condition_variable *var = PDE_DATA(file_inode(file));
char newval;
if (length > 0) {
if (get_user(newval, buffer) != 0)
return -EFAULT;
/* Match only on the first character */
switch (newval) {
case '0':
var->enabled = false;
break;
case '1':
var->enabled = true;
break;
}
}
return length;
}
static const struct file_operations condition_proc_fops = {
.open = condition_proc_open,
.read = seq_read,
.llseek = seq_lseek,
.write = condition_proc_write,
.release = single_release,
};
static bool
condition_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
const struct xt_condition_mtinfo *info = par->matchinfo;
const struct condition_variable *var = info->condvar;
return var->enabled ^ info->invert;
}
static int condition_mt_check(const struct xt_mtchk_param *par)
{
struct xt_condition_mtinfo *info = par->matchinfo;
struct condition_variable *var;
/* Forbid certain names */
if (*info->name == '\0' || *info->name == '.' ||
info->name[sizeof(info->name)-1] != '\0' ||
memchr(info->name, '/', sizeof(info->name)) != NULL) {
printk(KERN_INFO KBUILD_MODNAME ": name not allowed or too "
"long: \"%.*s\"\n", (unsigned int)sizeof(info->name),
info->name);
return -EINVAL;
}
/*
* Let's acquire the lock, check for the condition and add it
* or increase the reference counter.
*/
mutex_lock(&proc_lock);
list_for_each_entry(var, &conditions_list, list) {
if (strcmp(info->name, var->name) == 0) {
var->refcount++;
mutex_unlock(&proc_lock);
info->condvar = var;
return 0;
}
}
/* At this point, we need to allocate a new condition variable. */
var = kmalloc(sizeof(struct condition_variable), GFP_KERNEL);
if (var == NULL) {
mutex_unlock(&proc_lock);
return -ENOMEM;
}
memcpy(var->name, info->name, sizeof(info->name));
/* Create the condition variable's proc file entry. */
var->status_proc = proc_create_data(info->name, condition_list_perms,
proc_net_condition, &condition_proc_fops, var);
if (var->status_proc == NULL) {
kfree(var);
mutex_unlock(&proc_lock);
return -ENOMEM;
}
proc_set_user(var->status_proc,
make_kuid(&init_user_ns, condition_uid_perms),
make_kgid(&init_user_ns, condition_gid_perms));
var->refcount = 1;
var->enabled = false;
wmb();
list_add(&var->list, &conditions_list);
mutex_unlock(&proc_lock);
info->condvar = var;
return 0;
}
static void condition_mt_destroy(const struct xt_mtdtor_param *par)
{
const struct xt_condition_mtinfo *info = par->matchinfo;
struct condition_variable *var = info->condvar;
mutex_lock(&proc_lock);
if (--var->refcount == 0) {
list_del(&var->list);
proc_remove(var->status_proc);
mutex_unlock(&proc_lock);
kfree(var);
return;
}
mutex_unlock(&proc_lock);
}
static struct xt_match condition_mt_reg[] __read_mostly = {
{
.name = "condition",
.revision = 1,
.family = NFPROTO_IPV4,
.matchsize = sizeof(struct xt_condition_mtinfo),
.match = condition_mt,
.checkentry = condition_mt_check,
.destroy = condition_mt_destroy,
.me = THIS_MODULE,
},
{
.name = "condition",
.revision = 1,
.family = NFPROTO_IPV6,
.matchsize = sizeof(struct xt_condition_mtinfo),
.match = condition_mt,
.checkentry = condition_mt_check,
.destroy = condition_mt_destroy,
.me = THIS_MODULE,
},
};
static const char *const dir_name = "nf_condition";
static int __init condition_mt_init(void)
{
int ret;
mutex_init(&proc_lock);
proc_net_condition = proc_mkdir(dir_name, init_net.proc_net);
if (proc_net_condition == NULL)
return -EACCES;
ret = xt_register_matches(condition_mt_reg, ARRAY_SIZE(condition_mt_reg));
if (ret < 0) {
remove_proc_entry(dir_name, init_net.proc_net);
return ret;
}
return 0;
}
static void __exit condition_mt_exit(void)
{
xt_unregister_matches(condition_mt_reg, ARRAY_SIZE(condition_mt_reg));
remove_proc_entry(dir_name, init_net.proc_net);
}
module_init(condition_mt_init);
module_exit(condition_mt_exit);
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