/*
 * xt_quota2 - enhanced xt_quota that can count upwards and in packets
 * as a minimal accounting match.
 * by Jan Engelhardt <jengelh@medozas.de>, 2008
 *
 * Originally based on xt_quota.c:
 * 	netfilter module to enforce network quotas
 * 	Sam Johnston <samj@samj.net>
 *
 *	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 of the License, as published by the Free Software Foundation.
 */
#include <linux/list.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/skbuff.h>
#include <linux/spinlock.h>
#include <linux/workqueue.h>
#include <asm/atomic.h>
#include <net/netlink.h>

#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_quota2.h>

#define QUOTA2_SYSFS_WORK_MAX_SIZE 64
#define QUOTA2_SYSFS_NUM_ENVP 3

#ifdef CONFIG_NETFILTER_XT_MATCH_QUOTA2_LOG
/* For compatibility, these definitions are copied from the
 * deprecated header file <linux/netfilter_ipv4/ipt_ULOG.h> */
#define ULOG_MAC_LEN	80
#define ULOG_PREFIX_LEN	32

/* Format of the ULOG packets passed through netlink */
typedef struct ulog_packet_msg {
	unsigned long mark;
	long timestamp_sec;
	long timestamp_usec;
	unsigned int hook;
	char indev_name[IFNAMSIZ];
	char outdev_name[IFNAMSIZ];
	size_t data_len;
	char prefix[ULOG_PREFIX_LEN];
	unsigned char mac_len;
	unsigned char mac[ULOG_MAC_LEN];
	unsigned char payload[0];
} ulog_packet_msg_t;
#endif

/**
 * @lock:	lock to protect quota writers from each other
 */
struct xt_quota_counter {
	u_int64_t quota;
	spinlock_t lock;
	struct list_head list;
	atomic_t ref;
	char name[sizeof(((struct xt_quota_mtinfo2 *)NULL)->name)];
	struct proc_dir_entry *procfs_entry;
	char last_iface[QUOTA2_SYSFS_WORK_MAX_SIZE];
	char last_prefix[QUOTA2_SYSFS_WORK_MAX_SIZE];
	struct work_struct work;
};

#define to_quota_counter(x) container_of(x, struct xt_quota_counter, work)

static struct class *quota_class;
static struct device *quota_device;
static struct kobject *quota_kobj;

static LIST_HEAD(counter_list);
static DEFINE_SPINLOCK(counter_list_lock);

static struct proc_dir_entry *proc_xt_quota;
static unsigned int quota_list_perms = S_IRUGO | S_IWUSR;
static kuid_t quota_list_uid = KUIDT_INIT(0);
static kgid_t quota_list_gid = KGIDT_INIT(0);
module_param_named(perms, quota_list_perms, uint, S_IRUGO | S_IWUSR);

static void quota2_work(struct work_struct *work)
{
	char alert_msg[QUOTA2_SYSFS_WORK_MAX_SIZE];
	char iface_name[QUOTA2_SYSFS_WORK_MAX_SIZE];
	char *envp[QUOTA2_SYSFS_NUM_ENVP] = {alert_msg, iface_name,  NULL};
	struct xt_quota_counter *counter = to_quota_counter(work);

	snprintf(alert_msg, sizeof(alert_msg), "ALERT_NAME=%s", counter->name);
	snprintf(iface_name, sizeof(iface_name), "INTERFACE=%s",
		 counter->last_iface);

	kobject_uevent_env(quota_kobj, KOBJ_CHANGE, envp);
}

static void quota2_log(const struct net_device *in,
		       const struct net_device *out,
		       struct  xt_quota_counter *q,
		       const char *prefix)
{
	if (prefix == NULL)
		return;

	strlcpy(q->last_prefix, prefix, QUOTA2_SYSFS_WORK_MAX_SIZE);

	if (in)
		strlcpy(q->last_iface, in->name, QUOTA2_SYSFS_WORK_MAX_SIZE);
	else if (out)
		strlcpy(q->last_iface, out->name, QUOTA2_SYSFS_WORK_MAX_SIZE);
	else
		strlcpy(q->last_iface, "UNKNOWN", QUOTA2_SYSFS_WORK_MAX_SIZE);

	schedule_work(&q->work);
}

static ssize_t quota_proc_read(struct file *file, char __user *buf,
			   size_t size, loff_t *ppos)
{
	struct xt_quota_counter *e = PDE_DATA(file_inode(file));
	char tmp[24];
	size_t tmp_size;

	spin_lock_bh(&e->lock);
	tmp_size = scnprintf(tmp, sizeof(tmp), "%llu\n", e->quota);
	spin_unlock_bh(&e->lock);
	return simple_read_from_buffer(buf, size, ppos, tmp, tmp_size);
}

static ssize_t quota_proc_write(struct file *file, const char __user *input,
                            size_t size, loff_t *ppos)
{
	struct xt_quota_counter *e = PDE_DATA(file_inode(file));
	char buf[sizeof("18446744073709551616")];

	if (size > sizeof(buf))
		size = sizeof(buf);
	if (copy_from_user(buf, input, size) != 0)
		return -EFAULT;
	buf[sizeof(buf)-1] = '\0';

	spin_lock_bh(&e->lock);
	e->quota = simple_strtoull(buf, NULL, 0);
	spin_unlock_bh(&e->lock);
	return size;
}

static const struct file_operations q2_counter_fops = {
	.read		= quota_proc_read,
	.write		= quota_proc_write,
	.llseek		= default_llseek,
};

static struct xt_quota_counter *
q2_new_counter(const struct xt_quota_mtinfo2 *q, bool anon)
{
	struct xt_quota_counter *e;
	unsigned int size;

	/* Do not need all the procfs things for anonymous counters. */
	size = anon ? offsetof(typeof(*e), list) : sizeof(*e);
	e = kmalloc(size, GFP_KERNEL);
	if (e == NULL)
		return NULL;

	e->quota = q->quota;
	spin_lock_init(&e->lock);
	if (!anon) {
		INIT_LIST_HEAD(&e->list);
		atomic_set(&e->ref, 1);
		strlcpy(e->name, q->name, sizeof(e->name));
		strlcpy(e->last_prefix, "UNSET", sizeof(e->last_prefix));
		strlcpy(e->last_iface, "UNSET", sizeof(e->last_iface));
		INIT_WORK(&e->work, quota2_work);
	}
	return e;
}

/**
 * q2_get_counter - get ref to counter or create new
 * @name:	name of counter
 */
static struct xt_quota_counter *
q2_get_counter(const struct xt_quota_mtinfo2 *q)
{
	struct proc_dir_entry *p;
	struct xt_quota_counter *e = NULL;
	struct xt_quota_counter *new_e;

	if (*q->name == '\0')
		return q2_new_counter(q, true);

	/* No need to hold a lock while getting a new counter */
	new_e = q2_new_counter(q, false);
	if (new_e == NULL)
		goto out;

	spin_lock_bh(&counter_list_lock);
	list_for_each_entry(e, &counter_list, list)
		if (strcmp(e->name, q->name) == 0) {
			atomic_inc(&e->ref);
			spin_unlock_bh(&counter_list_lock);
			kfree(new_e);
			pr_debug("xt_quota2: old counter name=%s", e->name);
			return e;
		}
	e = new_e;
	pr_debug("xt_quota2: new_counter name=%s", e->name);
	list_add_tail(&e->list, &counter_list);
	/* The entry having a refcount of 1 is not directly destructible.
	 * This func has not yet returned the new entry, thus iptables
	 * has not references for destroying this entry.
	 * For another rule to try to destroy it, it would 1st need for this
	 * func* to be re-invoked, acquire a new ref for the same named quota.
	 * Nobody will access the e->procfs_entry either.
	 * So release the lock. */
	spin_unlock_bh(&counter_list_lock);

	/* create_proc_entry() is not spin_lock happy */
	p = e->procfs_entry = proc_create_data(e->name, quota_list_perms,
	                      proc_xt_quota, &q2_counter_fops, e);

	if (IS_ERR_OR_NULL(p)) {
		spin_lock_bh(&counter_list_lock);
		list_del(&e->list);
		spin_unlock_bh(&counter_list_lock);
		goto out;
	}
	proc_set_user(p, quota_list_uid, quota_list_gid);
	return e;

 out:
	kfree(e);
	return NULL;
}

static int quota_mt2_check(const struct xt_mtchk_param *par)
{
	struct xt_quota_mtinfo2 *q = par->matchinfo;

	pr_debug("xt_quota2: check() flags=0x%04x", q->flags);

	if (q->flags & ~XT_QUOTA_MASK)
		return -EINVAL;

	q->name[sizeof(q->name)-1] = '\0';
	if (*q->name == '.' || strchr(q->name, '/') != NULL) {
		printk(KERN_ERR "xt_quota.3: illegal name\n");
		return -EINVAL;
	}

	q->master = q2_get_counter(q);
	if (q->master == NULL) {
		printk(KERN_ERR "xt_quota.3: memory alloc failure\n");
		return -ENOMEM;
	}

	return 0;
}

static void quota_mt2_destroy(const struct xt_mtdtor_param *par)
{
	struct xt_quota_mtinfo2 *q = par->matchinfo;
	struct xt_quota_counter *e = q->master;

	if (*q->name == '\0') {
		kfree(e);
		return;
	}

	spin_lock_bh(&counter_list_lock);
	if (!atomic_dec_and_test(&e->ref)) {
		spin_unlock_bh(&counter_list_lock);
		return;
	}

	list_del(&e->list);
	remove_proc_entry(e->name, proc_xt_quota);
	spin_unlock_bh(&counter_list_lock);
	kfree(e);
}

static bool
quota_mt2(const struct sk_buff *skb, struct xt_action_param *par)
{
	struct xt_quota_mtinfo2 *q = (void *)par->matchinfo;
	struct xt_quota_counter *e = q->master;
	bool ret = q->flags & XT_QUOTA_INVERT;

	spin_lock_bh(&e->lock);
	if (q->flags & XT_QUOTA_GROW) {
		/*
		 * While no_change is pointless in "grow" mode, we will
		 * implement it here simply to have a consistent behavior.
		 */
		if (!(q->flags & XT_QUOTA_NO_CHANGE)) {
			e->quota += (q->flags & XT_QUOTA_PACKET) ? 1 : skb->len;
		}
		ret = true;
	} else {
		if (e->quota >= skb->len) {
			if (!(q->flags & XT_QUOTA_NO_CHANGE))
				e->quota -= (q->flags & XT_QUOTA_PACKET) ? 1 : skb->len;
			ret = !ret;
		} else {
			/* We are transitioning, log that fact. */
			if (e->quota) {
				quota2_log(par->in, par->out, e, q->name);
			}
			/* we do not allow even small packets from now on */
			e->quota = 0;
		}
	}
	spin_unlock_bh(&e->lock);
	return ret;
}

static struct xt_match quota_mt2_reg[] __read_mostly = {
	{
		.name       = "quota2",
		.revision   = 3,
		.family     = NFPROTO_IPV4,
		.checkentry = quota_mt2_check,
		.match      = quota_mt2,
		.destroy    = quota_mt2_destroy,
		.matchsize  = sizeof(struct xt_quota_mtinfo2),
		.me         = THIS_MODULE,
	},
	{
		.name       = "quota2",
		.revision   = 3,
		.family     = NFPROTO_IPV6,
		.checkentry = quota_mt2_check,
		.match      = quota_mt2,
		.destroy    = quota_mt2_destroy,
		.matchsize  = sizeof(struct xt_quota_mtinfo2),
		.me         = THIS_MODULE,
	},
};

static int __init quota_mt2_init(void)
{
	int ret;
	pr_debug("xt_quota2: init()");

	quota_class = class_create(THIS_MODULE, "xt_quota2");
	ret = PTR_ERR(quota_class);
	if (IS_ERR(quota_class)) {
		pr_err("xt_quota2: couldn't create class");
		class_destroy(quota_class);
		return ret;
	}

	quota_device = device_create(quota_class, NULL, MKDEV(0, 0), NULL,
				     "counters");
	ret = PTR_ERR(quota_device);
	if (IS_ERR(quota_device)) {
		pr_err("xt_quota2: couldn't create device");
		device_destroy(quota_class, MKDEV(0, 0));
		class_destroy(quota_class);
		return ret;
	}

	quota_kobj = &quota_device->kobj;

	proc_xt_quota = proc_mkdir("xt_quota", init_net.proc_net);
	if (proc_xt_quota == NULL)
		return -EACCES;

	ret = xt_register_matches(quota_mt2_reg, ARRAY_SIZE(quota_mt2_reg));
	if (ret < 0)
		remove_proc_entry("xt_quota", init_net.proc_net);
	pr_debug("xt_quota2: init() %d", ret);
	return ret;
}

static void __exit quota_mt2_exit(void)
{
	xt_unregister_matches(quota_mt2_reg, ARRAY_SIZE(quota_mt2_reg));
	remove_proc_entry("xt_quota", init_net.proc_net);
	device_destroy(quota_class, MKDEV(0, 0));
	class_destroy(quota_class);
}

module_init(quota_mt2_init);
module_exit(quota_mt2_exit);
MODULE_DESCRIPTION("Xtables: countdown quota match; up counter");
MODULE_AUTHOR("Sam Johnston <samj@samj.net>");
MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ipt_quota2");
MODULE_ALIAS("ip6t_quota2");