// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (c) 2016 Laura Garcia <nevola@gmail.com>
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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/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 <linux/random.h>
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#include <linux/static_key.h>
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#include <net/netfilter/nf_tables.h>
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#include <net/netfilter/nf_tables_core.h>
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struct nft_ng_inc {
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u8 dreg;
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u32 modulus;
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atomic_t counter;
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u32 offset;
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};
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static u32 nft_ng_inc_gen(struct nft_ng_inc *priv)
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{
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u32 nval, oval;
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do {
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oval = atomic_read(&priv->counter);
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nval = (oval + 1 < priv->modulus) ? oval + 1 : 0;
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} while (atomic_cmpxchg(&priv->counter, oval, nval) != oval);
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return nval + priv->offset;
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}
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static void nft_ng_inc_eval(const struct nft_expr *expr,
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struct nft_regs *regs,
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const struct nft_pktinfo *pkt)
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{
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struct nft_ng_inc *priv = nft_expr_priv(expr);
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regs->data[priv->dreg] = nft_ng_inc_gen(priv);
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}
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static const struct nla_policy nft_ng_policy[NFTA_NG_MAX + 1] = {
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[NFTA_NG_DREG] = { .type = NLA_U32 },
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[NFTA_NG_MODULUS] = { .type = NLA_U32 },
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[NFTA_NG_TYPE] = { .type = NLA_U32 },
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[NFTA_NG_OFFSET] = { .type = NLA_U32 },
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};
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static int nft_ng_inc_init(const struct nft_ctx *ctx,
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const struct nft_expr *expr,
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const struct nlattr * const tb[])
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{
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struct nft_ng_inc *priv = nft_expr_priv(expr);
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if (tb[NFTA_NG_OFFSET])
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priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET]));
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priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS]));
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if (priv->modulus == 0)
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return -ERANGE;
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if (priv->offset + priv->modulus - 1 < priv->offset)
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return -EOVERFLOW;
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atomic_set(&priv->counter, priv->modulus - 1);
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return nft_parse_register_store(ctx, tb[NFTA_NG_DREG], &priv->dreg,
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NULL, NFT_DATA_VALUE, sizeof(u32));
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}
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static int nft_ng_dump(struct sk_buff *skb, enum nft_registers dreg,
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u32 modulus, enum nft_ng_types type, u32 offset)
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{
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if (nft_dump_register(skb, NFTA_NG_DREG, dreg))
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goto nla_put_failure;
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if (nla_put_be32(skb, NFTA_NG_MODULUS, htonl(modulus)))
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goto nla_put_failure;
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if (nla_put_be32(skb, NFTA_NG_TYPE, htonl(type)))
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goto nla_put_failure;
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if (nla_put_be32(skb, NFTA_NG_OFFSET, htonl(offset)))
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goto nla_put_failure;
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return 0;
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nla_put_failure:
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return -1;
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}
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static int nft_ng_inc_dump(struct sk_buff *skb, const struct nft_expr *expr)
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{
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const struct nft_ng_inc *priv = nft_expr_priv(expr);
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return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_INCREMENTAL,
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priv->offset);
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}
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struct nft_ng_random {
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u8 dreg;
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u32 modulus;
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u32 offset;
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};
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static u32 nft_ng_random_gen(const struct nft_ng_random *priv)
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{
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return reciprocal_scale(get_random_u32(), priv->modulus) + priv->offset;
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}
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static void nft_ng_random_eval(const struct nft_expr *expr,
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struct nft_regs *regs,
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const struct nft_pktinfo *pkt)
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{
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struct nft_ng_random *priv = nft_expr_priv(expr);
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regs->data[priv->dreg] = nft_ng_random_gen(priv);
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}
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static int nft_ng_random_init(const struct nft_ctx *ctx,
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const struct nft_expr *expr,
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const struct nlattr * const tb[])
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{
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struct nft_ng_random *priv = nft_expr_priv(expr);
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if (tb[NFTA_NG_OFFSET])
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priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET]));
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priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS]));
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if (priv->modulus == 0)
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return -ERANGE;
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if (priv->offset + priv->modulus - 1 < priv->offset)
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return -EOVERFLOW;
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return nft_parse_register_store(ctx, tb[NFTA_NG_DREG], &priv->dreg,
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NULL, NFT_DATA_VALUE, sizeof(u32));
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}
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static int nft_ng_random_dump(struct sk_buff *skb, const struct nft_expr *expr)
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{
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const struct nft_ng_random *priv = nft_expr_priv(expr);
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return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_RANDOM,
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priv->offset);
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}
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static struct nft_expr_type nft_ng_type;
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static const struct nft_expr_ops nft_ng_inc_ops = {
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.type = &nft_ng_type,
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.size = NFT_EXPR_SIZE(sizeof(struct nft_ng_inc)),
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.eval = nft_ng_inc_eval,
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.init = nft_ng_inc_init,
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.dump = nft_ng_inc_dump,
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};
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static const struct nft_expr_ops nft_ng_random_ops = {
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.type = &nft_ng_type,
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.size = NFT_EXPR_SIZE(sizeof(struct nft_ng_random)),
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.eval = nft_ng_random_eval,
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.init = nft_ng_random_init,
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.dump = nft_ng_random_dump,
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};
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static const struct nft_expr_ops *
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nft_ng_select_ops(const struct nft_ctx *ctx, const struct nlattr * const tb[])
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{
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u32 type;
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if (!tb[NFTA_NG_DREG] ||
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!tb[NFTA_NG_MODULUS] ||
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!tb[NFTA_NG_TYPE])
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return ERR_PTR(-EINVAL);
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type = ntohl(nla_get_be32(tb[NFTA_NG_TYPE]));
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switch (type) {
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case NFT_NG_INCREMENTAL:
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return &nft_ng_inc_ops;
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case NFT_NG_RANDOM:
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return &nft_ng_random_ops;
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}
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return ERR_PTR(-EINVAL);
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}
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static struct nft_expr_type nft_ng_type __read_mostly = {
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.name = "numgen",
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.select_ops = nft_ng_select_ops,
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.policy = nft_ng_policy,
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.maxattr = NFTA_NG_MAX,
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.owner = THIS_MODULE,
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};
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static int __init nft_ng_module_init(void)
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{
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return nft_register_expr(&nft_ng_type);
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}
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static void __exit nft_ng_module_exit(void)
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{
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nft_unregister_expr(&nft_ng_type);
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}
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module_init(nft_ng_module_init);
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module_exit(nft_ng_module_exit);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>");
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MODULE_ALIAS_NFT_EXPR("numgen");
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MODULE_DESCRIPTION("nftables number generator module");
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