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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (c) 2016 Laura Garcia <nevola@gmail.com>
*/
#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 {
u8 dreg;
u32 modulus;
atomic_t counter;
u32 offset;
};
static u32 nft_ng_inc_gen(struct nft_ng_inc *priv)
{
u32 nval, oval;
do {
oval = atomic_read(&priv->counter);
nval = (oval + 1 < priv->modulus) ? oval + 1 : 0;
} while (atomic_cmpxchg(&priv->counter, oval, nval) != oval);
return nval + priv->offset;
}
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);
regs->data[priv->dreg] = nft_ng_inc_gen(priv);
}
static const struct nla_policy nft_ng_policy[NFTA_NG_MAX + 1] = {
[NFTA_NG_DREG] = { .type = NLA_U32 },
[NFTA_NG_MODULUS] = { .type = NLA_U32 },
[NFTA_NG_TYPE] = { .type = NLA_U32 },
[NFTA_NG_OFFSET] = { .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);
if (tb[NFTA_NG_OFFSET])
priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET]));
priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS]));
if (priv->modulus == 0)
return -ERANGE;
if (priv->offset + priv->modulus - 1 < priv->offset)
return -EOVERFLOW;
atomic_set(&priv->counter, priv->modulus - 1);
return nft_parse_register_store(ctx, tb[NFTA_NG_DREG], &priv->dreg,
NULL, NFT_DATA_VALUE, sizeof(u32));
}
static int nft_ng_dump(struct sk_buff *skb, enum nft_registers dreg,
u32 modulus, enum nft_ng_types type, u32 offset)
{
if (nft_dump_register(skb, NFTA_NG_DREG, dreg))
goto nla_put_failure;
if (nla_put_be32(skb, NFTA_NG_MODULUS, htonl(modulus)))
goto nla_put_failure;
if (nla_put_be32(skb, NFTA_NG_TYPE, htonl(type)))
goto nla_put_failure;
if (nla_put_be32(skb, NFTA_NG_OFFSET, htonl(offset)))
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->modulus, NFT_NG_INCREMENTAL,
priv->offset);
}
struct nft_ng_random {
u8 dreg;
u32 modulus;
u32 offset;
};
static u32 nft_ng_random_gen(struct nft_ng_random *priv)
{
struct rnd_state *state = this_cpu_ptr(&nft_numgen_prandom_state);
return reciprocal_scale(prandom_u32_state(state), priv->modulus) +
priv->offset;
}
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);
regs->data[priv->dreg] = nft_ng_random_gen(priv);
}
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);
if (tb[NFTA_NG_OFFSET])
priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET]));
priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS]));
if (priv->modulus == 0)
return -ERANGE;
if (priv->offset + priv->modulus - 1 < priv->offset)
return -EOVERFLOW;
prandom_init_once(&nft_numgen_prandom_state);
return nft_parse_register_store(ctx, tb[NFTA_NG_DREG], &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->modulus, NFT_NG_RANDOM,
priv->offset);
}
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_MODULUS] ||
!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");
MODULE_DESCRIPTION("nftables number generator module");
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