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

include/uapi/linux/netfilter/nf_tables.h

+24 −0
Original line number Diff line number Diff line
@@ -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 */

net/netfilter/Kconfig

+6 −0
Original line number Diff line number Diff line
@@ -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"

net/netfilter/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -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

net/netfilter/nft_numgen.c

0 → 100644
+192 −0
Original line number Diff line number Diff line 
/*

 * 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");