/*
 * Copyright (c) 2008-2009 Patrick McHardy <kaber@trash.net>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Development of this code funded by Astaro AG (http://www.astaro.com/)
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/jhash.h>
#include <linux/netlink.h>
#include <linux/netfilter.h>
#include <linux/netfilter/nf_tables.h>
#include <net/netfilter/nf_tables.h>

struct nft_hash {
	struct hlist_head	*hash;
	unsigned int		hsize;
};

struct nft_hash_elem {
	struct hlist_node	hnode;
	struct nft_data		key;
	struct nft_data		data[];
};

static u32 nft_hash_rnd __read_mostly;
static bool nft_hash_rnd_initted __read_mostly;

static unsigned int nft_hash_data(const struct nft_data *data,
				  unsigned int hsize, unsigned int len)
{
	unsigned int h;

	h = jhash(data->data, len, nft_hash_rnd);
	return ((u64)h * hsize) >> 32;
}

static bool nft_hash_lookup(const struct nft_set *set,
			    const struct nft_data *key,
			    struct nft_data *data)
{
	const struct nft_hash *priv = nft_set_priv(set);
	const struct nft_hash_elem *he;
	unsigned int h;

	h = nft_hash_data(key, priv->hsize, set->klen);
	hlist_for_each_entry(he, &priv->hash[h], hnode) {
		if (nft_data_cmp(&he->key, key, set->klen))
			continue;
		if (set->flags & NFT_SET_MAP)
			nft_data_copy(data, he->data);
		return true;
	}
	return false;
}

static void nft_hash_elem_destroy(const struct nft_set *set,
				  struct nft_hash_elem *he)
{
	nft_data_uninit(&he->key, NFT_DATA_VALUE);
	if (set->flags & NFT_SET_MAP)
		nft_data_uninit(he->data, set->dtype);
	kfree(he);
}

static int nft_hash_insert(const struct nft_set *set,
			   const struct nft_set_elem *elem)
{
	struct nft_hash *priv = nft_set_priv(set);
	struct nft_hash_elem *he;
	unsigned int size, h;

	if (elem->flags != 0)
		return -EINVAL;

	size = sizeof(*he);
	if (set->flags & NFT_SET_MAP)
		size += sizeof(he->data[0]);

	he = kzalloc(size, GFP_KERNEL);
	if (he == NULL)
		return -ENOMEM;

	nft_data_copy(&he->key, &elem->key);
	if (set->flags & NFT_SET_MAP)
		nft_data_copy(he->data, &elem->data);

	h = nft_hash_data(&he->key, priv->hsize, set->klen);
	hlist_add_head_rcu(&he->hnode, &priv->hash[h]);
	return 0;
}

static void nft_hash_remove(const struct nft_set *set,
			    const struct nft_set_elem *elem)
{
	struct nft_hash_elem *he = elem->cookie;

	hlist_del_rcu(&he->hnode);
	kfree(he);
}

static int nft_hash_get(const struct nft_set *set, struct nft_set_elem *elem)
{
	const struct nft_hash *priv = nft_set_priv(set);
	struct nft_hash_elem *he;
	unsigned int h;

	h = nft_hash_data(&elem->key, priv->hsize, set->klen);
	hlist_for_each_entry(he, &priv->hash[h], hnode) {
		if (nft_data_cmp(&he->key, &elem->key, set->klen))
			continue;

		elem->cookie = he;
		elem->flags  = 0;
		if (set->flags & NFT_SET_MAP)
			nft_data_copy(&elem->data, he->data);
		return 0;
	}
	return -ENOENT;
}

static void nft_hash_walk(const struct nft_ctx *ctx, const struct nft_set *set,
			  struct nft_set_iter *iter)
{
	const struct nft_hash *priv = nft_set_priv(set);
	const struct nft_hash_elem *he;
	struct nft_set_elem elem;
	unsigned int i;

	for (i = 0; i < priv->hsize; i++) {
		hlist_for_each_entry(he, &priv->hash[i], hnode) {
			if (iter->count < iter->skip)
				goto cont;

			memcpy(&elem.key, &he->key, sizeof(elem.key));
			if (set->flags & NFT_SET_MAP)
				memcpy(&elem.data, he->data, sizeof(elem.data));
			elem.flags = 0;

			iter->err = iter->fn(ctx, set, iter, &elem);
			if (iter->err < 0)
				return;
cont:
			iter->count++;
		}
	}
}

static unsigned int nft_hash_privsize(const struct nlattr * const nla[])
{
	return sizeof(struct nft_hash);
}

static int nft_hash_init(const struct nft_set *set,
			 const struct nlattr * const tb[])
{
	struct nft_hash *priv = nft_set_priv(set);
	unsigned int cnt, i;

	if (unlikely(!nft_hash_rnd_initted)) {
		get_random_bytes(&nft_hash_rnd, 4);
		nft_hash_rnd_initted = true;
	}

	/* Aim for a load factor of 0.75 */
	// FIXME: temporarily broken until we have set descriptions
	cnt = 100;
	cnt = cnt * 4 / 3;

	priv->hash = kcalloc(cnt, sizeof(struct hlist_head), GFP_KERNEL);
	if (priv->hash == NULL)
		return -ENOMEM;
	priv->hsize = cnt;

	for (i = 0; i < cnt; i++)
		INIT_HLIST_HEAD(&priv->hash[i]);

	return 0;
}

static void nft_hash_destroy(const struct nft_set *set)
{
	const struct nft_hash *priv = nft_set_priv(set);
	const struct hlist_node *next;
	struct nft_hash_elem *elem;
	unsigned int i;

	for (i = 0; i < priv->hsize; i++) {
		hlist_for_each_entry_safe(elem, next, &priv->hash[i], hnode) {
			hlist_del(&elem->hnode);
			nft_hash_elem_destroy(set, elem);
		}
	}
	kfree(priv->hash);
}

static struct nft_set_ops nft_hash_ops __read_mostly = {
	.privsize       = nft_hash_privsize,
	.init		= nft_hash_init,
	.destroy	= nft_hash_destroy,
	.get		= nft_hash_get,
	.insert		= nft_hash_insert,
	.remove		= nft_hash_remove,
	.lookup		= nft_hash_lookup,
	.walk		= nft_hash_walk,
	.features	= NFT_SET_MAP,
	.owner		= THIS_MODULE,
};

static int __init nft_hash_module_init(void)
{
	return nft_register_set(&nft_hash_ops);
}

static void __exit nft_hash_module_exit(void)
{
	nft_unregister_set(&nft_hash_ops);
}

module_init(nft_hash_module_init);
module_exit(nft_hash_module_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
MODULE_ALIAS_NFT_SET();