/*
 * 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/rbtree.h>
#include <linux/netlink.h>
#include <linux/netfilter.h>
#include <linux/netfilter/nf_tables.h>
#include <net/netfilter/nf_tables.h>

struct nft_rbtree {
        struct rb_root          root;
        rwlock_t                lock;
        seqcount_t              count;
        struct delayed_work     gc_work;
};

struct nft_rbtree_elem {
        struct rb_node          node;
        struct nft_set_ext      ext;
};

static bool nft_rbtree_interval_end(const struct nft_rbtree_elem *rbe)
{
        return nft_set_ext_exists(&rbe->ext, NFT_SET_EXT_FLAGS) &&
               (*nft_set_ext_flags(&rbe->ext) & NFT_SET_ELEM_INTERVAL_END);
}

static bool nft_rbtree_interval_start(const struct nft_rbtree_elem *rbe)
{
        return !nft_rbtree_interval_end(rbe);
}

static bool nft_rbtree_equal(const struct nft_set *set, const void *this,
                             const struct nft_rbtree_elem *interval)
{
        return memcmp(this, nft_set_ext_key(&interval->ext), set->klen) == 0;
}

static bool __nft_rbtree_lookup(const struct net *net, const struct nft_set *set,
                                const u32 *key, const struct nft_set_ext **ext,
                                unsigned int seq)
{
        struct nft_rbtree *priv = nft_set_priv(set);
        const struct nft_rbtree_elem *rbe, *interval = NULL;
        u8 genmask = nft_genmask_cur(net);
        const struct rb_node *parent;
        const void *this;
        int d;

        parent = rcu_dereference_raw(priv->root.rb_node);
        while (parent != NULL) {
                if (read_seqcount_retry(&priv->count, seq))
                        return false;

                rbe = rb_entry(parent, struct nft_rbtree_elem, node);

                this = nft_set_ext_key(&rbe->ext);
                d = memcmp(this, key, set->klen);
                if (d < 0) {
                        parent = rcu_dereference_raw(parent->rb_left);
                        if (interval &&
                            nft_rbtree_equal(set, this, interval) &&
                            nft_rbtree_interval_end(rbe) &&
                            nft_rbtree_interval_start(interval))
                                continue;
                        interval = rbe;
                } else if (d > 0)
                        parent = rcu_dereference_raw(parent->rb_right);
                else {
                        if (!nft_set_elem_active(&rbe->ext, genmask)) {
                                parent = rcu_dereference_raw(parent->rb_left);
                                continue;
                        }

                        if (nft_set_elem_expired(&rbe->ext))
                                return false;

                        if (nft_rbtree_interval_end(rbe)) {
                                if (nft_set_is_anonymous(set))
                                        return false;
                                parent = rcu_dereference_raw(parent->rb_left);
                                interval = NULL;
                                continue;
                        }

                        *ext = &rbe->ext;
                        return true;
                }
        }

        if (set->flags & NFT_SET_INTERVAL && interval != NULL &&
            nft_set_elem_active(&interval->ext, genmask) &&
            !nft_set_elem_expired(&interval->ext) &&
            nft_rbtree_interval_start(interval)) {
                *ext = &interval->ext;
                return true;
        }

        return false;
}

static bool nft_rbtree_lookup(const struct net *net, const struct nft_set *set,
                              const u32 *key, const struct nft_set_ext **ext)
{
        struct nft_rbtree *priv = nft_set_priv(set);
        unsigned int seq = read_seqcount_begin(&priv->count);
        bool ret;

        ret = __nft_rbtree_lookup(net, set, key, ext, seq);
        if (ret || !read_seqcount_retry(&priv->count, seq))
                return ret;

        read_lock_bh(&priv->lock);
        seq = read_seqcount_begin(&priv->count);
        ret = __nft_rbtree_lookup(net, set, key, ext, seq);
        read_unlock_bh(&priv->lock);

        return ret;
}

static bool __nft_rbtree_get(const struct net *net, const struct nft_set *set,
                             const u32 *key, struct nft_rbtree_elem **elem,
                             unsigned int seq, unsigned int flags, u8 genmask)
{
        struct nft_rbtree_elem *rbe, *interval = NULL;
        struct nft_rbtree *priv = nft_set_priv(set);
        const struct rb_node *parent;
        const void *this;
        int d;

        parent = rcu_dereference_raw(priv->root.rb_node);
        while (parent != NULL) {
                if (read_seqcount_retry(&priv->count, seq))
                        return false;

                rbe = rb_entry(parent, struct nft_rbtree_elem, node);

                this = nft_set_ext_key(&rbe->ext);
                d = memcmp(this, key, set->klen);
                if (d < 0) {
                        parent = rcu_dereference_raw(parent->rb_left);
                        if (!(flags & NFT_SET_ELEM_INTERVAL_END))
                                interval = rbe;
                } else if (d > 0) {
                        parent = rcu_dereference_raw(parent->rb_right);
                        if (flags & NFT_SET_ELEM_INTERVAL_END)
                                interval = rbe;
                } else {
                        if (!nft_set_elem_active(&rbe->ext, genmask)) {
                                parent = rcu_dereference_raw(parent->rb_left);
                                continue;
                        }

                        if (nft_set_elem_expired(&rbe->ext))
                                return false;

                        if (!nft_set_ext_exists(&rbe->ext, NFT_SET_EXT_FLAGS) ||
                            (*nft_set_ext_flags(&rbe->ext) & NFT_SET_ELEM_INTERVAL_END) ==
                            (flags & NFT_SET_ELEM_INTERVAL_END)) {
                                *elem = rbe;
                                return true;
                        }

                        if (nft_rbtree_interval_end(rbe))
                                interval = NULL;

                        parent = rcu_dereference_raw(parent->rb_left);
                }
        }

        if (set->flags & NFT_SET_INTERVAL && interval != NULL &&
            nft_set_elem_active(&interval->ext, genmask) &&
            !nft_set_elem_expired(&interval->ext) &&
            ((!nft_rbtree_interval_end(interval) &&
              !(flags & NFT_SET_ELEM_INTERVAL_END)) ||
             (nft_rbtree_interval_end(interval) &&
              (flags & NFT_SET_ELEM_INTERVAL_END)))) {
                *elem = interval;
                return true;
        }

        return false;
}

static void *nft_rbtree_get(const struct net *net, const struct nft_set *set,
                            const struct nft_set_elem *elem, unsigned int flags)
{
        struct nft_rbtree *priv = nft_set_priv(set);
        unsigned int seq = read_seqcount_begin(&priv->count);
        struct nft_rbtree_elem *rbe = ERR_PTR(-ENOENT);
        const u32 *key = (const u32 *)&elem->key.val;
        u8 genmask = nft_genmask_cur(net);
        bool ret;

        ret = __nft_rbtree_get(net, set, key, &rbe, seq, flags, genmask);
        if (ret || !read_seqcount_retry(&priv->count, seq))
                return rbe;

        read_lock_bh(&priv->lock);
        seq = read_seqcount_begin(&priv->count);
        ret = __nft_rbtree_get(net, set, key, &rbe, seq, flags, genmask);
        if (!ret)
                rbe = ERR_PTR(-ENOENT);
        read_unlock_bh(&priv->lock);

        return rbe;
}

static int __nft_rbtree_insert(const struct net *net, const struct nft_set *set,
                               struct nft_rbtree_elem *new,
                               struct nft_set_ext **ext)
{
        struct nft_rbtree *priv = nft_set_priv(set);
        u8 genmask = nft_genmask_next(net);
        struct nft_rbtree_elem *rbe;
        struct rb_node *parent, **p;
        bool overlap = false;
        int d;

        /* Detect overlaps as we descend the tree. Set the flag in these cases:
         *
         * a1. _ _ __>|  ?_ _ __|  (insert end before existing end)
         * a2. _ _ ___|  ?_ _ _>|  (insert end after existing end)
         * a3. _ _ ___? >|_ _ __|  (insert start before existing end)
         *
         * and clear it later on, as we eventually reach the points indicated by
         * '?' above, in the cases described below. We'll always meet these
         * later, locally, due to tree ordering, and overlaps for the intervals
         * that are the closest together are always evaluated last.
         *
         * b1. _ _ __>|  !_ _ __|  (insert end before existing start)
         * b2. _ _ ___|  !_ _ _>|  (insert end after existing start)
         * b3. _ _ ___! >|_ _ __|  (insert start after existing end, as a leaf)
         *            '--' no nodes falling in this range
         * b4.          >|_ _   !  (insert start before existing start)
         *
         * Case a3. resolves to b3.:
         * - if the inserted start element is the leftmost, because the '0'
         *   element in the tree serves as end element
         * - otherwise, if an existing end is found immediately to the left. If
         *   there are existing nodes in between, we need to further descend the
         *   tree before we can conclude the new start isn't causing an overlap
         *
         * or to b4., which, preceded by a3., means we already traversed one or
         * more existing intervals entirely, from the right.
         *
         * For a new, rightmost pair of elements, we'll hit cases b3. and b2.,
         * in that order.
         *
         * The flag is also cleared in two special cases:
         *
         * b5. |__ _ _!|<_ _ _   (insert start right before existing end)
         * b6. |__ _ >|!__ _ _   (insert end right after existing start)
         *
         * which always happen as last step and imply that no further
         * overlapping is possible.
         */

        parent = NULL;
        p = &priv->root.rb_node;
        while (*p != NULL) {
                parent = *p;
                rbe = rb_entry(parent, struct nft_rbtree_elem, node);
                d = memcmp(nft_set_ext_key(&rbe->ext),
                           nft_set_ext_key(&new->ext),
                           set->klen);
                if (d < 0) {
                        p = &parent->rb_left;

                        if (nft_rbtree_interval_start(new)) {
                                if (nft_rbtree_interval_end(rbe) &&
                                    nft_set_elem_active(&rbe->ext, genmask) &&
                                    !nft_set_elem_expired(&rbe->ext) && !*p)
                                        overlap = false;
                        } else {
                                overlap = nft_rbtree_interval_end(rbe) &&
                                          nft_set_elem_active(&rbe->ext,
                                                              genmask) &&
                                          !nft_set_elem_expired(&rbe->ext);
                        }
                } else if (d > 0) {
                        p = &parent->rb_right;

                        if (nft_rbtree_interval_end(new)) {
                                overlap = nft_rbtree_interval_end(rbe) &&
                                          nft_set_elem_active(&rbe->ext,
                                                              genmask) &&
                                          !nft_set_elem_expired(&rbe->ext);
                        } else if (nft_set_elem_active(&rbe->ext, genmask) &&
                                   !nft_set_elem_expired(&rbe->ext)) {
                                overlap = nft_rbtree_interval_end(rbe);
                        }
                } else {
                        if (nft_rbtree_interval_end(rbe) &&
                            nft_rbtree_interval_start(new)) {
                                p = &parent->rb_left;

                                if (nft_set_elem_active(&rbe->ext, genmask) &&
                                    !nft_set_elem_expired(&rbe->ext))
                                        overlap = false;
                        } else if (nft_rbtree_interval_start(rbe) &&
                                   nft_rbtree_interval_end(new)) {
                                p = &parent->rb_right;

                                if (nft_set_elem_active(&rbe->ext, genmask) &&
                                    !nft_set_elem_expired(&rbe->ext))
                                        overlap = false;
                        } else if (nft_set_elem_active(&rbe->ext, genmask) &&
                                   !nft_set_elem_expired(&rbe->ext)) {
                                *ext = &rbe->ext;
                                return -EEXIST;
                        } else {
                                p = &parent->rb_left;
                        }
                }
        }

        if (overlap)
                return -ENOTEMPTY;

        rb_link_node_rcu(&new->node, parent, p);
        rb_insert_color(&new->node, &priv->root);
        return 0;
}

static int nft_rbtree_insert(const struct net *net, const struct nft_set *set,
                             const struct nft_set_elem *elem,
                             struct nft_set_ext **ext)
{
        struct nft_rbtree *priv = nft_set_priv(set);
        struct nft_rbtree_elem *rbe = elem->priv;
        int err;

        write_lock_bh(&priv->lock);
        write_seqcount_begin(&priv->count);
        err = __nft_rbtree_insert(net, set, rbe, ext);
        write_seqcount_end(&priv->count);
        write_unlock_bh(&priv->lock);

        return err;
}

static void nft_rbtree_remove(const struct net *net,
                              const struct nft_set *set,
                              const struct nft_set_elem *elem)
{
        struct nft_rbtree *priv = nft_set_priv(set);
        struct nft_rbtree_elem *rbe = elem->priv;

        write_lock_bh(&priv->lock);
        write_seqcount_begin(&priv->count);
        rb_erase(&rbe->node, &priv->root);
        write_seqcount_end(&priv->count);
        write_unlock_bh(&priv->lock);
}

static void nft_rbtree_activate(const struct net *net,
                                const struct nft_set *set,
                                const struct nft_set_elem *elem)
{
        struct nft_rbtree_elem *rbe = elem->priv;

        nft_set_elem_change_active(net, set, &rbe->ext);
        nft_set_elem_clear_busy(&rbe->ext);
}

static bool nft_rbtree_flush(const struct net *net,
                             const struct nft_set *set, void *priv)
{
        struct nft_rbtree_elem *rbe = priv;

        if (!nft_set_elem_mark_busy(&rbe->ext) ||
            !nft_is_active(net, &rbe->ext)) {
                nft_set_elem_change_active(net, set, &rbe->ext);
                return true;
        }
        return false;
}

static void *nft_rbtree_deactivate(const struct net *net,
                                   const struct nft_set *set,
                                   const struct nft_set_elem *elem)
{
        const struct nft_rbtree *priv = nft_set_priv(set);
        const struct rb_node *parent = priv->root.rb_node;
        struct nft_rbtree_elem *rbe, *this = elem->priv;
        u8 genmask = nft_genmask_next(net);
        int d;

        while (parent != NULL) {
                rbe = rb_entry(parent, struct nft_rbtree_elem, node);

                d = memcmp(nft_set_ext_key(&rbe->ext), &elem->key.val,
                                           set->klen);
                if (d < 0)
                        parent = parent->rb_left;
                else if (d > 0)
                        parent = parent->rb_right;
                else {
                        if (nft_rbtree_interval_end(rbe) &&
                            nft_rbtree_interval_start(this)) {
                                parent = parent->rb_left;
                                continue;
                        } else if (nft_rbtree_interval_start(rbe) &&
                                   nft_rbtree_interval_end(this)) {
                                parent = parent->rb_right;
                                continue;
                        } else if (!nft_set_elem_active(&rbe->ext, genmask)) {
                                parent = parent->rb_left;
                                continue;
                        }
                        nft_rbtree_flush(net, set, rbe);
                        return rbe;
                }
        }
        return NULL;
}

static void nft_rbtree_walk(const struct nft_ctx *ctx,
                            struct nft_set *set,
                            struct nft_set_iter *iter)
{
        struct nft_rbtree *priv = nft_set_priv(set);
        struct nft_rbtree_elem *rbe;
        struct nft_set_elem elem;
        struct rb_node *node;

        read_lock_bh(&priv->lock);
        for (node = rb_first(&priv->root); node != NULL; node = rb_next(node)) {
                rbe = rb_entry(node, struct nft_rbtree_elem, node);

                if (iter->count < iter->skip)
                        goto cont;
                if (nft_set_elem_expired(&rbe->ext))
                        goto cont;
                if (!nft_set_elem_active(&rbe->ext, iter->genmask))
                        goto cont;

                elem.priv = rbe;

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

static void nft_rbtree_gc(struct work_struct *work)
{
        struct nft_rbtree_elem *rbe, *rbe_end = NULL, *rbe_prev = NULL;
        struct nft_set_gc_batch *gcb = NULL;
        struct nft_rbtree *priv;
        struct rb_node *node;
        struct nft_set *set;

        priv = container_of(work, struct nft_rbtree, gc_work.work);
        set  = nft_set_container_of(priv);

        write_lock_bh(&priv->lock);
        write_seqcount_begin(&priv->count);
        for (node = rb_first(&priv->root); node != NULL; node = rb_next(node)) {
                rbe = rb_entry(node, struct nft_rbtree_elem, node);

                if (nft_rbtree_interval_end(rbe)) {
                        rbe_end = rbe;
                        continue;
                }
                if (!nft_set_elem_expired(&rbe->ext))
                        continue;
                if (nft_set_elem_mark_busy(&rbe->ext))
                        continue;

                if (rbe_prev) {
                        rb_erase(&rbe_prev->node, &priv->root);
                        rbe_prev = NULL;
                }
                gcb = nft_set_gc_batch_check(set, gcb, GFP_ATOMIC);
                if (!gcb)
                        break;

                atomic_dec(&set->nelems);
                nft_set_gc_batch_add(gcb, rbe);
                rbe_prev = rbe;

                if (rbe_end) {
                        atomic_dec(&set->nelems);
                        nft_set_gc_batch_add(gcb, rbe_end);
                        rb_erase(&rbe_end->node, &priv->root);
                        rbe_end = NULL;
                }
                node = rb_next(node);
                if (!node)
                        break;
        }
        if (rbe_prev)
                rb_erase(&rbe_prev->node, &priv->root);
        write_seqcount_end(&priv->count);
        write_unlock_bh(&priv->lock);

        nft_set_gc_batch_complete(gcb);

        queue_delayed_work(system_power_efficient_wq, &priv->gc_work,
                           nft_set_gc_interval(set));
}

static u64 nft_rbtree_privsize(const struct nlattr * const nla[],
                               const struct nft_set_desc *desc)
{
        return sizeof(struct nft_rbtree);
}

static int nft_rbtree_init(const struct nft_set *set,
                           const struct nft_set_desc *desc,
                           const struct nlattr * const nla[])
{
        struct nft_rbtree *priv = nft_set_priv(set);

        rwlock_init(&priv->lock);
        seqcount_init(&priv->count);
        priv->root = RB_ROOT;

        INIT_DEFERRABLE_WORK(&priv->gc_work, nft_rbtree_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_rbtree_destroy(const struct nft_set *set)
{
        struct nft_rbtree *priv = nft_set_priv(set);
        struct nft_rbtree_elem *rbe;
        struct rb_node *node;

        cancel_delayed_work_sync(&priv->gc_work);
        rcu_barrier();
        while ((node = priv->root.rb_node) != NULL) {
                rb_erase(node, &priv->root);
                rbe = rb_entry(node, struct nft_rbtree_elem, node);
                nft_set_elem_destroy(set, rbe, true);
        }
}

static bool nft_rbtree_estimate(const struct nft_set_desc *desc, u32 features,
                                struct nft_set_estimate *est)
{
        if (desc->field_count > 1)
                return false;

        if (desc->size)
                est->size = sizeof(struct nft_rbtree) +
                            desc->size * sizeof(struct nft_rbtree_elem);
        else
                est->size = ~0;

        est->lookup = NFT_SET_CLASS_O_LOG_N;
        est->space  = NFT_SET_CLASS_O_N;

        return true;
}

struct nft_set_type nft_set_rbtree_type __read_mostly = {
        .owner          = THIS_MODULE,
        .features       = NFT_SET_INTERVAL | NFT_SET_MAP | NFT_SET_OBJECT | NFT_SET_TIMEOUT,
        .ops            = {
                .privsize       = nft_rbtree_privsize,
                .elemsize       = offsetof(struct nft_rbtree_elem, ext),
                .estimate       = nft_rbtree_estimate,
                .init           = nft_rbtree_init,
                .destroy        = nft_rbtree_destroy,
                .insert         = nft_rbtree_insert,
                .remove         = nft_rbtree_remove,
                .deactivate     = nft_rbtree_deactivate,
                .flush          = nft_rbtree_flush,
                .activate       = nft_rbtree_activate,
                .lookup         = nft_rbtree_lookup,
                .walk           = nft_rbtree_walk,
                .get            = nft_rbtree_get,
        },
};