// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (c) 2017 Pablo Neira Ayuso <pablo@netfilter.org>
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*/
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/list.h>
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#include <linux/netlink.h>
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#include <linux/netfilter.h>
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#include <linux/netfilter/nf_tables.h>
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#include <net/netfilter/nf_tables_core.h>
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struct nft_bitmap_elem {
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struct list_head head;
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struct nft_set_ext ext;
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};
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/* This bitmap uses two bits to represent one element. These two bits determine
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* the element state in the current and the future generation.
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*
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* An element can be in three states. The generation cursor is represented using
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* the ^ character, note that this cursor shifts on every succesful transaction.
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* If no transaction is going on, we observe all elements are in the following
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* state:
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*
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* 11 = this element is active in the current generation. In case of no updates,
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* ^ it stays active in the next generation.
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* 00 = this element is inactive in the current generation. In case of no
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* ^ updates, it stays inactive in the next generation.
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*
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* On transaction handling, we observe these two temporary states:
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*
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* 01 = this element is inactive in the current generation and it becomes active
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* ^ in the next one. This happens when the element is inserted but commit
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* path has not yet been executed yet, so activation is still pending. On
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* transaction abortion, the element is removed.
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* 10 = this element is active in the current generation and it becomes inactive
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* ^ in the next one. This happens when the element is deactivated but commit
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* path has not yet been executed yet, so removal is still pending. On
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* transation abortion, the next generation bit is reset to go back to
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* restore its previous state.
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*/
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struct nft_bitmap {
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struct list_head list;
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u16 bitmap_size;
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u8 bitmap[];
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};
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static inline void nft_bitmap_location(const struct nft_set *set,
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const void *key,
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u32 *idx, u32 *off)
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{
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u32 k;
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if (set->klen == 2)
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k = *(u16 *)key;
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else
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k = *(u8 *)key;
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k <<= 1;
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*idx = k / BITS_PER_BYTE;
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*off = k % BITS_PER_BYTE;
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}
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/* Fetch the two bits that represent the element and check if it is active based
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* on the generation mask.
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*/
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static inline bool
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nft_bitmap_active(const u8 *bitmap, u32 idx, u32 off, u8 genmask)
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{
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return (bitmap[idx] & (0x3 << off)) & (genmask << off);
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}
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static bool nft_bitmap_lookup(const struct net *net, const struct nft_set *set,
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const u32 *key, const struct nft_set_ext **ext)
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{
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const struct nft_bitmap *priv = nft_set_priv(set);
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u8 genmask = nft_genmask_cur(net);
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u32 idx, off;
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nft_bitmap_location(set, key, &idx, &off);
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return nft_bitmap_active(priv->bitmap, idx, off, genmask);
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}
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static struct nft_bitmap_elem *
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nft_bitmap_elem_find(const struct nft_set *set, struct nft_bitmap_elem *this,
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u8 genmask)
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{
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const struct nft_bitmap *priv = nft_set_priv(set);
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struct nft_bitmap_elem *be;
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list_for_each_entry_rcu(be, &priv->list, head) {
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if (memcmp(nft_set_ext_key(&be->ext),
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nft_set_ext_key(&this->ext), set->klen) ||
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!nft_set_elem_active(&be->ext, genmask))
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continue;
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return be;
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}
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return NULL;
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}
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static void *nft_bitmap_get(const struct net *net, const struct nft_set *set,
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const struct nft_set_elem *elem, unsigned int flags)
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{
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const struct nft_bitmap *priv = nft_set_priv(set);
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u8 genmask = nft_genmask_cur(net);
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struct nft_bitmap_elem *be;
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list_for_each_entry_rcu(be, &priv->list, head) {
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if (memcmp(nft_set_ext_key(&be->ext), elem->key.val.data, set->klen) ||
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!nft_set_elem_active(&be->ext, genmask))
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continue;
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return be;
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}
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return ERR_PTR(-ENOENT);
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}
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static int nft_bitmap_insert(const struct net *net, const struct nft_set *set,
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const struct nft_set_elem *elem,
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struct nft_set_ext **ext)
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{
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struct nft_bitmap *priv = nft_set_priv(set);
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struct nft_bitmap_elem *new = elem->priv, *be;
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u8 genmask = nft_genmask_next(net);
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u32 idx, off;
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be = nft_bitmap_elem_find(set, new, genmask);
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if (be) {
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*ext = &be->ext;
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return -EEXIST;
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}
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nft_bitmap_location(set, nft_set_ext_key(&new->ext), &idx, &off);
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/* Enter 01 state. */
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priv->bitmap[idx] |= (genmask << off);
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list_add_tail_rcu(&new->head, &priv->list);
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return 0;
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}
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static void nft_bitmap_remove(const struct net *net,
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const struct nft_set *set,
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const struct nft_set_elem *elem)
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{
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struct nft_bitmap *priv = nft_set_priv(set);
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struct nft_bitmap_elem *be = elem->priv;
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u8 genmask = nft_genmask_next(net);
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u32 idx, off;
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nft_bitmap_location(set, nft_set_ext_key(&be->ext), &idx, &off);
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/* Enter 00 state. */
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priv->bitmap[idx] &= ~(genmask << off);
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list_del_rcu(&be->head);
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}
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static void nft_bitmap_activate(const struct net *net,
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const struct nft_set *set,
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const struct nft_set_elem *elem)
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{
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struct nft_bitmap *priv = nft_set_priv(set);
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struct nft_bitmap_elem *be = elem->priv;
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u8 genmask = nft_genmask_next(net);
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u32 idx, off;
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nft_bitmap_location(set, nft_set_ext_key(&be->ext), &idx, &off);
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/* Enter 11 state. */
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priv->bitmap[idx] |= (genmask << off);
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nft_set_elem_change_active(net, set, &be->ext);
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}
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static bool nft_bitmap_flush(const struct net *net,
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const struct nft_set *set, void *_be)
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{
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struct nft_bitmap *priv = nft_set_priv(set);
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u8 genmask = nft_genmask_next(net);
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struct nft_bitmap_elem *be = _be;
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u32 idx, off;
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nft_bitmap_location(set, nft_set_ext_key(&be->ext), &idx, &off);
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/* Enter 10 state, similar to deactivation. */
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priv->bitmap[idx] &= ~(genmask << off);
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nft_set_elem_change_active(net, set, &be->ext);
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return true;
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}
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static void *nft_bitmap_deactivate(const struct net *net,
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const struct nft_set *set,
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const struct nft_set_elem *elem)
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{
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struct nft_bitmap *priv = nft_set_priv(set);
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struct nft_bitmap_elem *this = elem->priv, *be;
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u8 genmask = nft_genmask_next(net);
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u32 idx, off;
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nft_bitmap_location(set, elem->key.val.data, &idx, &off);
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be = nft_bitmap_elem_find(set, this, genmask);
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if (!be)
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return NULL;
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/* Enter 10 state. */
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priv->bitmap[idx] &= ~(genmask << off);
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nft_set_elem_change_active(net, set, &be->ext);
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return be;
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}
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static void nft_bitmap_walk(const struct nft_ctx *ctx,
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struct nft_set *set,
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struct nft_set_iter *iter)
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{
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const struct nft_bitmap *priv = nft_set_priv(set);
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struct nft_bitmap_elem *be;
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struct nft_set_elem elem;
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list_for_each_entry_rcu(be, &priv->list, head) {
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if (iter->count < iter->skip)
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goto cont;
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if (!nft_set_elem_active(&be->ext, iter->genmask))
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goto cont;
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elem.priv = be;
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iter->err = iter->fn(ctx, set, iter, &elem);
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if (iter->err < 0)
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return;
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cont:
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iter->count++;
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}
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}
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/* The bitmap size is pow(2, key length in bits) / bits per byte. This is
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* multiplied by two since each element takes two bits. For 8 bit keys, the
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* bitmap consumes 66 bytes. For 16 bit keys, 16388 bytes.
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*/
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static inline u32 nft_bitmap_size(u32 klen)
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{
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return ((2 << ((klen * BITS_PER_BYTE) - 1)) / BITS_PER_BYTE) << 1;
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}
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static inline u64 nft_bitmap_total_size(u32 klen)
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{
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return sizeof(struct nft_bitmap) + nft_bitmap_size(klen);
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}
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static u64 nft_bitmap_privsize(const struct nlattr * const nla[],
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const struct nft_set_desc *desc)
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{
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u32 klen = ntohl(nla_get_be32(nla[NFTA_SET_KEY_LEN]));
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return nft_bitmap_total_size(klen);
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}
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static int nft_bitmap_init(const struct nft_set *set,
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const struct nft_set_desc *desc,
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const struct nlattr * const nla[])
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{
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struct nft_bitmap *priv = nft_set_priv(set);
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INIT_LIST_HEAD(&priv->list);
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priv->bitmap_size = nft_bitmap_size(set->klen);
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return 0;
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}
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static void nft_bitmap_destroy(const struct nft_set *set)
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{
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struct nft_bitmap *priv = nft_set_priv(set);
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struct nft_bitmap_elem *be, *n;
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list_for_each_entry_safe(be, n, &priv->list, head)
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nft_set_elem_destroy(set, be, true);
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}
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static bool nft_bitmap_estimate(const struct nft_set_desc *desc, u32 features,
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struct nft_set_estimate *est)
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{
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/* Make sure bitmaps we don't get bitmaps larger than 16 Kbytes. */
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if (desc->klen > 2)
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return false;
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else if (desc->expr)
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return false;
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est->size = nft_bitmap_total_size(desc->klen);
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est->lookup = NFT_SET_CLASS_O_1;
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est->space = NFT_SET_CLASS_O_1;
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return true;
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}
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const struct nft_set_type nft_set_bitmap_type = {
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.ops = {
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.privsize = nft_bitmap_privsize,
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.elemsize = offsetof(struct nft_bitmap_elem, ext),
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.estimate = nft_bitmap_estimate,
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.init = nft_bitmap_init,
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.destroy = nft_bitmap_destroy,
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.insert = nft_bitmap_insert,
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.remove = nft_bitmap_remove,
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.deactivate = nft_bitmap_deactivate,
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.flush = nft_bitmap_flush,
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.activate = nft_bitmap_activate,
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.lookup = nft_bitmap_lookup,
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.walk = nft_bitmap_walk,
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.get = nft_bitmap_get,
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},
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};
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