/*
 * Copyright (c) 2008-2014 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/log2.h>
#include <linux/jhash.h>
#include <linux/netlink.h>
#include <linux/rhashtable.h>
#include <linux/netfilter.h>
#include <linux/netfilter/nf_tables.h>
#include <net/netfilter/nf_tables.h>

/* We target a hash table size of 4, element hint is 75% of final size */
#define NFT_HASH_ELEMENT_HINT 3

struct nft_hash_elem {
	struct rhash_head		node;
	struct nft_data			key;
	struct nft_data			data[];
};

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

	he = rhashtable_lookup(priv, key);
	if (he && set->flags & NFT_SET_MAP)
		nft_data_copy(data, he->data);

	return !!he;
}

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

	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);

	rhashtable_insert(priv, &he->node);

	return 0;
}

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 void nft_hash_remove(const struct nft_set *set,
			    const struct nft_set_elem *elem)
{
	struct rhashtable *priv = nft_set_priv(set);

	rhashtable_remove(priv, elem->cookie);
	synchronize_rcu();
	kfree(elem->cookie);
}

struct nft_compare_arg {
	const struct nft_set *set;
	struct nft_set_elem *elem;
};

static bool nft_hash_compare(void *ptr, void *arg)
{
	struct nft_hash_elem *he = ptr;
	struct nft_compare_arg *x = arg;

	if (!nft_data_cmp(&he->key, &x->elem->key, x->set->klen)) {
		x->elem->cookie = he;
		x->elem->flags = 0;
		if (x->set->flags & NFT_SET_MAP)
			nft_data_copy(&x->elem->data, he->data);

		return true;
	}

	return false;
}

static int nft_hash_get(const struct nft_set *set, struct nft_set_elem *elem)
{
	struct rhashtable *priv = nft_set_priv(set);
	struct nft_compare_arg arg = {
		.set = set,
		.elem = elem,
	};

	if (rhashtable_lookup_compare(priv, &elem->key,
				      &nft_hash_compare, &arg))
		return 0;

	return -ENOENT;
}

static void nft_hash_walk(const struct nft_ctx *ctx, const struct nft_set *set,
			  struct nft_set_iter *iter)
{
	struct rhashtable *priv = nft_set_priv(set);
	const struct nft_hash_elem *he;
	struct rhashtable_iter hti;
	struct nft_set_elem elem;
	int err;

	err = rhashtable_walk_init(priv, &hti);
	iter->err = err;
	if (err)
		return;

	err = rhashtable_walk_start(&hti);
	if (err && err != -EAGAIN) {
		iter->err = err;
		goto out;
	}

	while ((he = rhashtable_walk_next(&hti))) {
		if (IS_ERR(he)) {
			err = PTR_ERR(he);
			if (err != -EAGAIN) {
				iter->err = err;
				goto out;
			}
		}

		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)
			goto out;

cont:
		iter->count++;
	}

out:
	rhashtable_walk_stop(&hti);
	rhashtable_walk_exit(&hti);
}

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

static int nft_hash_init(const struct nft_set *set,
			 const struct nft_set_desc *desc,
			 const struct nlattr * const tb[])
{
	struct rhashtable *priv = nft_set_priv(set);
	struct rhashtable_params params = {
		.nelem_hint = desc->size ? : NFT_HASH_ELEMENT_HINT,
		.head_offset = offsetof(struct nft_hash_elem, node),
		.key_offset = offsetof(struct nft_hash_elem, key),
		.key_len = set->klen,
		.hashfn = jhash,
		.grow_decision = rht_grow_above_75,
		.shrink_decision = rht_shrink_below_30,
	};

	return rhashtable_init(priv, &params);
}

static void nft_hash_destroy(const struct nft_set *set)
{
	struct rhashtable *priv = nft_set_priv(set);
	const struct bucket_table *tbl;
	struct nft_hash_elem *he;
	struct rhash_head *pos, *next;
	unsigned int i;

	/* Stop an eventual async resizing */
	priv->being_destroyed = true;
	mutex_lock(&priv->mutex);

	tbl = rht_dereference(priv->tbl, priv);
	for (i = 0; i < tbl->size; i++) {
		rht_for_each_entry_safe(he, pos, next, tbl, i, node)
			nft_hash_elem_destroy(set, he);
	}
	mutex_unlock(&priv->mutex);

	rhashtable_destroy(priv);
}

static bool nft_hash_estimate(const struct nft_set_desc *desc, u32 features,
			      struct nft_set_estimate *est)
{
	unsigned int esize;

	esize = sizeof(struct nft_hash_elem);
	if (features & NFT_SET_MAP)
		esize += FIELD_SIZEOF(struct nft_hash_elem, data[0]);

	if (desc->size) {
		est->size = sizeof(struct rhashtable) +
			    roundup_pow_of_two(desc->size * 4 / 3) *
			    sizeof(struct nft_hash_elem *) +
			    desc->size * esize;
	} else {
		/* Resizing happens when the load drops below 30% or goes
		 * above 75%. The average of 52.5% load (approximated by 50%)
		 * is used for the size estimation of the hash buckets,
		 * meaning we calculate two buckets per element.
		 */
		est->size = esize + 2 * sizeof(struct nft_hash_elem *);
	}

	est->class = NFT_SET_CLASS_O_1;

	return true;
}

static struct nft_set_ops nft_hash_ops __read_mostly = {
	.privsize       = nft_hash_privsize,
	.estimate	= nft_hash_estimate,
	.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();