/*

   * 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/workqueue.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 {
  	struct rhashtable		ht;

  	struct delayed_work		gc_work;

  };

  struct nft_hash_elem {

  	struct rhash_head		node;

  	struct nft_set_ext		ext;

  };

  struct nft_hash_cmp_arg {
  	const struct nft_set		*set;

  	const u32			*key;

  	u8				genmask;

  };

  static const struct rhashtable_params nft_hash_params;

  static inline u32 nft_hash_key(const void *data, u32 len, u32 seed)
  {
  	const struct nft_hash_cmp_arg *arg = data;
  
  	return jhash(arg->key, len, seed);
  }
  
  static inline u32 nft_hash_obj(const void *data, u32 len, u32 seed)
  {
  	const struct nft_hash_elem *he = data;

  	return jhash(nft_set_ext_key(&he->ext), len, seed);

  }
  
  static inline int nft_hash_cmp(struct rhashtable_compare_arg *arg,
  			       const void *ptr)
  {
  	const struct nft_hash_cmp_arg *x = arg->key;
  	const struct nft_hash_elem *he = ptr;

  	if (memcmp(nft_set_ext_key(&he->ext), x->key, x->set->klen))

  		return 1;

  	if (nft_set_elem_expired(&he->ext))
  		return 1;

  	if (!nft_set_elem_active(&he->ext, x->genmask))
  		return 1;

  	return 0;
  }

  static bool nft_hash_lookup(const struct nft_set *set, const u32 *key,

  			    const struct nft_set_ext **ext)

  {

  	struct nft_hash *priv = nft_set_priv(set);

  	const struct nft_hash_elem *he;

  	struct nft_hash_cmp_arg arg = {

  		.genmask = nft_genmask_cur(read_pnet(&set->pnet)),

  		.set	 = set,
  		.key	 = key,
  	};

  	he = rhashtable_lookup_fast(&priv->ht, &arg, nft_hash_params);

  	if (he != NULL)
  		*ext = &he->ext;

  	return !!he;

  }

  static bool nft_hash_update(struct nft_set *set, const u32 *key,

  			    void *(*new)(struct nft_set *,
  					 const struct nft_expr *,

  					 struct nft_regs *regs),

  			    const struct nft_expr *expr,

  			    struct nft_regs *regs,

  			    const struct nft_set_ext **ext)
  {
  	struct nft_hash *priv = nft_set_priv(set);
  	struct nft_hash_elem *he;
  	struct nft_hash_cmp_arg arg = {
  		.genmask = NFT_GENMASK_ANY,
  		.set	 = set,
  		.key	 = key,
  	};
  
  	he = rhashtable_lookup_fast(&priv->ht, &arg, nft_hash_params);
  	if (he != NULL)
  		goto out;

  	he = new(set, expr, regs);

  	if (he == NULL)
  		goto err1;
  	if (rhashtable_lookup_insert_key(&priv->ht, &arg, &he->node,
  					 nft_hash_params))
  		goto err2;
  out:
  	*ext = &he->ext;
  	return true;
  
  err2:
  	nft_set_elem_destroy(set, he);
  err1:
  	return false;
  }

  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 = elem->priv;

  	struct nft_hash_cmp_arg arg = {

  		.genmask = nft_genmask_next(read_pnet(&set->pnet)),

  		.set	 = set,

  		.key	 = elem->key.val.data,

  	};

  	return rhashtable_lookup_insert_key(&priv->ht, &arg, &he->node,
  					    nft_hash_params);

  }

  static void nft_hash_activate(const struct nft_set *set,
  			      const struct nft_set_elem *elem)

  {

  	struct nft_hash_elem *he = elem->priv;

  	nft_set_elem_change_active(set, &he->ext);

  	nft_set_elem_clear_busy(&he->ext);

  }

  static void *nft_hash_deactivate(const struct nft_set *set,
  				 const struct nft_set_elem *elem)

  {

  	struct nft_hash *priv = nft_set_priv(set);

  	struct nft_hash_elem *he;

  	struct nft_hash_cmp_arg arg = {

  		.genmask = nft_genmask_next(read_pnet(&set->pnet)),

  		.set	 = set,

  		.key	 = elem->key.val.data,

  	};

  	rcu_read_lock();

  	he = rhashtable_lookup_fast(&priv->ht, &arg, nft_hash_params);

  	if (he != NULL) {
  		if (!nft_set_elem_mark_busy(&he->ext))
  			nft_set_elem_change_active(set, &he->ext);
  		else
  			he = NULL;
  	}
  	rcu_read_unlock();

  	return he;
  }

  static void nft_hash_remove(const struct nft_set *set,
  			    const struct nft_set_elem *elem)
  {
  	struct nft_hash *priv = nft_set_priv(set);
  	struct nft_hash_elem *he = elem->priv;
  
  	rhashtable_remove_fast(&priv->ht, &he->node, nft_hash_params);

  }

  static void nft_hash_walk(const struct nft_ctx *ctx, const struct nft_set *set,
  			  struct nft_set_iter *iter)

  {

  	struct nft_hash *priv = nft_set_priv(set);

  	struct nft_hash_elem *he;

  	struct rhashtable_iter hti;

  	struct nft_set_elem elem;

  	u8 genmask = nft_genmask_cur(read_pnet(&set->pnet));

  	int err;

  	err = rhashtable_walk_init(&priv->ht, &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;
  			}

  
  			continue;

  		}
  
  		if (iter->count < iter->skip)
  			goto cont;

  		if (nft_set_elem_expired(&he->ext))
  			goto cont;

  		if (!nft_set_elem_active(&he->ext, genmask))
  			goto cont;

  		elem.priv = he;

  
  		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 void nft_hash_gc(struct work_struct *work)
  {

  	struct nft_set *set;

  	struct nft_hash_elem *he;
  	struct nft_hash *priv;
  	struct nft_set_gc_batch *gcb = NULL;
  	struct rhashtable_iter hti;
  	int err;
  
  	priv = container_of(work, struct nft_hash, gc_work.work);
  	set  = nft_set_container_of(priv);
  
  	err = rhashtable_walk_init(&priv->ht, &hti);
  	if (err)
  		goto schedule;
  
  	err = rhashtable_walk_start(&hti);
  	if (err && err != -EAGAIN)
  		goto out;
  
  	while ((he = rhashtable_walk_next(&hti))) {
  		if (IS_ERR(he)) {
  			if (PTR_ERR(he) != -EAGAIN)
  				goto out;
  			continue;
  		}
  
  		if (!nft_set_elem_expired(&he->ext))
  			continue;
  		if (nft_set_elem_mark_busy(&he->ext))
  			continue;
  
  		gcb = nft_set_gc_batch_check(set, gcb, GFP_ATOMIC);
  		if (gcb == NULL)
  			goto out;
  		rhashtable_remove_fast(&priv->ht, &he->node, nft_hash_params);

  		atomic_dec(&set->nelems);

  		nft_set_gc_batch_add(gcb, he);
  	}
  out:
  	rhashtable_walk_stop(&hti);
  	rhashtable_walk_exit(&hti);
  
  	nft_set_gc_batch_complete(gcb);
  schedule:
  	queue_delayed_work(system_power_efficient_wq, &priv->gc_work,
  			   nft_set_gc_interval(set));
  }

  static unsigned int nft_hash_privsize(const struct nlattr * const nla[])
  {

  	return sizeof(struct nft_hash);

  }

  static const struct rhashtable_params nft_hash_params = {

  	.head_offset		= offsetof(struct nft_hash_elem, node),

  	.hashfn			= nft_hash_key,
  	.obj_hashfn		= nft_hash_obj,
  	.obj_cmpfn		= nft_hash_cmp,

  	.automatic_shrinking	= true,

  };

  static int nft_hash_init(const struct nft_set *set,

  			 const struct nft_set_desc *desc,

  			 const struct nlattr * const tb[])
  {

  	struct nft_hash *priv = nft_set_priv(set);

  	struct rhashtable_params params = nft_hash_params;

  	int err;

  
  	params.nelem_hint = desc->size ?: NFT_HASH_ELEMENT_HINT;

  	params.key_len	  = set->klen;

  	err = rhashtable_init(&priv->ht, &params);
  	if (err < 0)
  		return err;
  
  	INIT_DEFERRABLE_WORK(&priv->gc_work, nft_hash_gc);
  	if (set->flags & NFT_SET_TIMEOUT)
  		queue_delayed_work(system_power_efficient_wq, &priv->gc_work,
  				   nft_set_gc_interval(set));
  	return 0;

  }

  static void nft_hash_elem_destroy(void *ptr, void *arg)

  {

  	nft_set_elem_destroy((const struct nft_set *)arg, ptr);

  }

  static void nft_hash_destroy(const struct nft_set *set)
  {

  	struct nft_hash *priv = nft_set_priv(set);

  	cancel_delayed_work_sync(&priv->gc_work);

  	rhashtable_free_and_destroy(&priv->ht, nft_hash_elem_destroy,
  				    (void *)set);

  }

  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 (desc->size) {

  		est->size = sizeof(struct nft_hash) +

  			    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,

  	.elemsize	= offsetof(struct nft_hash_elem, ext),

  	.estimate	= nft_hash_estimate,

  	.init		= nft_hash_init,
  	.destroy	= nft_hash_destroy,

  	.insert		= nft_hash_insert,

  	.activate	= nft_hash_activate,
  	.deactivate	= nft_hash_deactivate,

  	.remove		= nft_hash_remove,
  	.lookup		= nft_hash_lookup,

  	.update		= nft_hash_update,

  	.walk		= nft_hash_walk,

  	.features	= NFT_SET_MAP | NFT_SET_TIMEOUT,

  	.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();