Commit 91dbc6be authored by Laura Garcia Liebana's avatar Laura Garcia Liebana Committed by Pablo Neira Ayuso

netfilter: nf_tables: add number generator expression

This patch adds the numgen expression that allows us to generated
incremental and random numbers, this generator is bound to a upper limit
that is specified by userspace.

This expression is useful to distribute packets in a round-robin fashion
as well as randomly.
Signed-off-by: default avatarLaura Garcia Liebana <nevola@gmail.com>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 3d2f30a1
......@@ -1121,4 +1121,28 @@ enum nft_trace_types {
__NFT_TRACETYPE_MAX
};
#define NFT_TRACETYPE_MAX (__NFT_TRACETYPE_MAX - 1)
/**
* enum nft_ng_attributes - nf_tables number generator expression netlink attributes
*
* @NFTA_NG_DREG: destination register (NLA_U32)
* @NFTA_NG_UNTIL: source value to increment the counter until reset (NLA_U32)
* @NFTA_NG_TYPE: operation type (NLA_U32)
*/
enum nft_ng_attributes {
NFTA_NG_UNSPEC,
NFTA_NG_DREG,
NFTA_NG_UNTIL,
NFTA_NG_TYPE,
__NFTA_NG_MAX
};
#define NFTA_NG_MAX (__NFTA_NG_MAX - 1)
enum nft_ng_types {
NFT_NG_INCREMENTAL,
NFT_NG_RANDOM,
__NFT_NG_MAX
};
#define NFT_NG_MAX (__NFT_NG_MAX - 1)
#endif /* _LINUX_NF_TABLES_H */
......@@ -474,6 +474,12 @@ config NFT_META
This option adds the "meta" expression that you can use to match and
to set packet metainformation such as the packet mark.
config NFT_NUMGEN
tristate "Netfilter nf_tables number generator module"
help
This option adds the number generator expression used to perform
incremental counting and random numbers bound to a upper limit.
config NFT_CT
depends on NF_CONNTRACK
tristate "Netfilter nf_tables conntrack module"
......
......@@ -80,6 +80,7 @@ obj-$(CONFIG_NF_TABLES_NETDEV) += nf_tables_netdev.o
obj-$(CONFIG_NFT_COMPAT) += nft_compat.o
obj-$(CONFIG_NFT_EXTHDR) += nft_exthdr.o
obj-$(CONFIG_NFT_META) += nft_meta.o
obj-$(CONFIG_NFT_NUMGEN) += nft_numgen.o
obj-$(CONFIG_NFT_CT) += nft_ct.o
obj-$(CONFIG_NFT_LIMIT) += nft_limit.o
obj-$(CONFIG_NFT_NAT) += nft_nat.o
......
/*
* Copyright (c) 2016 Laura Garcia <nevola@gmail.com>
*
* 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.
*
*/
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/netlink.h>
#include <linux/netfilter.h>
#include <linux/netfilter/nf_tables.h>
#include <linux/static_key.h>
#include <net/netfilter/nf_tables.h>
#include <net/netfilter/nf_tables_core.h>
static DEFINE_PER_CPU(struct rnd_state, nft_numgen_prandom_state);
struct nft_ng_inc {
enum nft_registers dreg:8;
u32 until;
atomic_t counter;
};
static void nft_ng_inc_eval(const struct nft_expr *expr,
struct nft_regs *regs,
const struct nft_pktinfo *pkt)
{
struct nft_ng_inc *priv = nft_expr_priv(expr);
u32 nval, oval;
do {
oval = atomic_read(&priv->counter);
nval = (oval + 1 < priv->until) ? oval + 1 : 0;
} while (atomic_cmpxchg(&priv->counter, oval, nval) != oval);
memcpy(&regs->data[priv->dreg], &priv->counter, sizeof(u32));
}
static const struct nla_policy nft_ng_policy[NFTA_NG_MAX + 1] = {
[NFTA_NG_DREG] = { .type = NLA_U32 },
[NFTA_NG_UNTIL] = { .type = NLA_U32 },
[NFTA_NG_TYPE] = { .type = NLA_U32 },
};
static int nft_ng_inc_init(const struct nft_ctx *ctx,
const struct nft_expr *expr,
const struct nlattr * const tb[])
{
struct nft_ng_inc *priv = nft_expr_priv(expr);
priv->until = ntohl(nla_get_be32(tb[NFTA_NG_UNTIL]));
if (priv->until == 0)
return -ERANGE;
priv->dreg = nft_parse_register(tb[NFTA_NG_DREG]);
atomic_set(&priv->counter, 0);
return nft_validate_register_store(ctx, priv->dreg, NULL,
NFT_DATA_VALUE, sizeof(u32));
}
static int nft_ng_dump(struct sk_buff *skb, enum nft_registers dreg,
u32 until, enum nft_ng_types type)
{
if (nft_dump_register(skb, NFTA_NG_DREG, dreg))
goto nla_put_failure;
if (nft_dump_register(skb, NFTA_NG_UNTIL, until))
goto nla_put_failure;
if (nft_dump_register(skb, NFTA_NG_TYPE, type))
goto nla_put_failure;
return 0;
nla_put_failure:
return -1;
}
static int nft_ng_inc_dump(struct sk_buff *skb, const struct nft_expr *expr)
{
const struct nft_ng_inc *priv = nft_expr_priv(expr);
return nft_ng_dump(skb, priv->dreg, priv->until, NFT_NG_INCREMENTAL);
}
struct nft_ng_random {
enum nft_registers dreg:8;
u32 until;
};
static void nft_ng_random_eval(const struct nft_expr *expr,
struct nft_regs *regs,
const struct nft_pktinfo *pkt)
{
struct nft_ng_random *priv = nft_expr_priv(expr);
struct rnd_state *state = this_cpu_ptr(&nft_numgen_prandom_state);
regs->data[priv->dreg] = reciprocal_scale(prandom_u32_state(state),
priv->until);
}
static int nft_ng_random_init(const struct nft_ctx *ctx,
const struct nft_expr *expr,
const struct nlattr * const tb[])
{
struct nft_ng_random *priv = nft_expr_priv(expr);
priv->until = ntohl(nla_get_be32(tb[NFTA_NG_UNTIL]));
if (priv->until == 0)
return -ERANGE;
prandom_init_once(&nft_numgen_prandom_state);
priv->dreg = nft_parse_register(tb[NFTA_NG_DREG]);
return nft_validate_register_store(ctx, priv->dreg, NULL,
NFT_DATA_VALUE, sizeof(u32));
}
static int nft_ng_random_dump(struct sk_buff *skb, const struct nft_expr *expr)
{
const struct nft_ng_random *priv = nft_expr_priv(expr);
return nft_ng_dump(skb, priv->dreg, priv->until, NFT_NG_RANDOM);
}
static struct nft_expr_type nft_ng_type;
static const struct nft_expr_ops nft_ng_inc_ops = {
.type = &nft_ng_type,
.size = NFT_EXPR_SIZE(sizeof(struct nft_ng_inc)),
.eval = nft_ng_inc_eval,
.init = nft_ng_inc_init,
.dump = nft_ng_inc_dump,
};
static const struct nft_expr_ops nft_ng_random_ops = {
.type = &nft_ng_type,
.size = NFT_EXPR_SIZE(sizeof(struct nft_ng_random)),
.eval = nft_ng_random_eval,
.init = nft_ng_random_init,
.dump = nft_ng_random_dump,
};
static const struct nft_expr_ops *
nft_ng_select_ops(const struct nft_ctx *ctx, const struct nlattr * const tb[])
{
u32 type;
if (!tb[NFTA_NG_DREG] ||
!tb[NFTA_NG_UNTIL] ||
!tb[NFTA_NG_TYPE])
return ERR_PTR(-EINVAL);
type = ntohl(nla_get_be32(tb[NFTA_NG_TYPE]));
switch (type) {
case NFT_NG_INCREMENTAL:
return &nft_ng_inc_ops;
case NFT_NG_RANDOM:
return &nft_ng_random_ops;
}
return ERR_PTR(-EINVAL);
}
static struct nft_expr_type nft_ng_type __read_mostly = {
.name = "numgen",
.select_ops = &nft_ng_select_ops,
.policy = nft_ng_policy,
.maxattr = NFTA_NG_MAX,
.owner = THIS_MODULE,
};
static int __init nft_ng_module_init(void)
{
return nft_register_expr(&nft_ng_type);
}
static void __exit nft_ng_module_exit(void)
{
nft_unregister_expr(&nft_ng_type);
}
module_init(nft_ng_module_init);
module_exit(nft_ng_module_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>");
MODULE_ALIAS_NFT_EXPR("numgen");
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