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