netfilter: adding the original quota2 from xtables-addons

The original xt_quota in the kernel is plain broken:
  - counts quota at a per CPU level
    (was written back when ubiquitous SMP was just a dream)
  - provides no way to count across IPV4/IPV6.

This patch is the original unaltered code from:
  http://sourceforge.net/projects/xtables-addons

  at commit e84391ce665cef046967f796dd91026851d6bbf3

Change-Id: I19d49858840effee9ecf6cff03c23b45a97efdeb
Signed-off-by: JP Abgrall <jpa@google.com>

2 files changed, 299 insertions, 0 deletions

diff --git a/include/linux/netfilter/xt_quota2.h b/include/linux/netfilter/xt_quota2.h
new file mode 100644
index 00000000000..eadc6903314
--- /dev/null
+++ b/include/linux/netfilter/xt_quota2.h
@@ -0,0 +1,25 @@
+#ifndef _XT_QUOTA_H
+#define _XT_QUOTA_H
+
+enum xt_quota_flags {
+	XT_QUOTA_INVERT    = 1 << 0,
+	XT_QUOTA_GROW      = 1 << 1,
+	XT_QUOTA_PACKET    = 1 << 2,
+	XT_QUOTA_NO_CHANGE = 1 << 3,
+	XT_QUOTA_MASK      = 0x0F,
+};
+
+struct xt_quota_counter;
+
+struct xt_quota_mtinfo2 {
+	char name[15];
+	u_int8_t flags;
+
+	/* Comparison-invariant */
+	aligned_u64 quota;
+
+	/* Used internally by the kernel */
+	struct xt_quota_counter *master __attribute__((aligned(8)));
+};
+
+#endif /* _XT_QUOTA_H */
diff --git a/net/netfilter/xt_quota2.c b/net/netfilter/xt_quota2.c
new file mode 100644
index 00000000000..4857008f1eb
--- /dev/null
+++ b/net/netfilter/xt_quota2.c
@@ -0,0 +1,274 @@
+/*
+ * 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/proc_fs.h>
+#include <linux/skbuff.h>
+#include <linux/spinlock.h>
+#include <asm/atomic.h>
+
+#include <linux/netfilter/x_tables.h>
+#include "xt_quota2.h"
+#include "compat_xtables.h"
+
+/**
+ * @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;
+};
+
+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 unsigned int quota_list_uid   = 0;
+static unsigned int quota_list_gid   = 0;
+module_param_named(perms, quota_list_perms, uint, S_IRUGO | S_IWUSR);
+module_param_named(uid, quota_list_uid, uint, S_IRUGO | S_IWUSR);
+module_param_named(gid, quota_list_gid, uint, S_IRUGO | S_IWUSR);
+
+static int quota_proc_read(char *page, char **start, off_t offset,
+                           int count, int *eof, void *data)
+{
+	struct xt_quota_counter *e = data;
+	int ret;
+
+	spin_lock_bh(&e->lock);
+	ret = snprintf(page, PAGE_SIZE, "%llu\n", e->quota);
+	spin_unlock_bh(&e->lock);
+	return ret;
+}
+
+static int quota_proc_write(struct file *file, const char __user *input,
+                            unsigned long size, void *data)
+{
+	struct xt_quota_counter *e = data;
+	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 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);
+		strncpy(e->name, q->name, sizeof(e->name));
+	}
+	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;
+
+	if (*q->name == '\0')
+		return q2_new_counter(q, true);
+
+	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);
+			return e;
+		}
+
+	e = q2_new_counter(q, false);
+	if (e == NULL)
+		goto out;
+
+	p = e->procfs_entry = create_proc_entry(e->name, quota_list_perms,
+	                      proc_xt_quota);
+	if (p == NULL || IS_ERR(p))
+		goto out;
+
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2, 6, 29)
+	p->owner        = THIS_MODULE;
+#endif
+	p->data         = e;
+	p->read_proc    = quota_proc_read;
+	p->write_proc   = quota_proc_write;
+	p->uid          = quota_list_uid;
+	p->gid          = quota_list_gid;
+	list_add_tail(&e->list, &counter_list);
+	spin_unlock_bh(&counter_list_lock);
+	return e;
+
+ out:
+	spin_unlock_bh(&counter_list_lock);
+	kfree(e);
+	return NULL;
+}
+
+static int quota_mt2_check(const struct xt_mtchk_param *par)
+{
+	struct xt_quota_mtinfo2 *q = par->matchinfo;
+
+	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;
+			q->quota = e->quota;
+		}
+		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 do not allow even small packets from now on */
+			e->quota = 0;
+		}
+		q->quota = e->quota;
+	}
+	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;
+
+	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);
+	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);
+}
+
+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");