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Laura Garcia Liebanaummakynes
Laura Garcia Liebana
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ummakynes
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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: Laura Garcia Liebana <[email protected]> Signed-off-by: Pablo Neira Ayuso <[email protected]>
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‎include/uapi/linux/netfilter/nf_tables.h

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@@ -1121,4 +1121,28 @@ enum nft_trace_types {
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__NFT_TRACETYPE_MAX
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};
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#define NFT_TRACETYPE_MAX (__NFT_TRACETYPE_MAX - 1)
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/**
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* enum nft_ng_attributes - nf_tables number generator expression netlink attributes
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*
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* @NFTA_NG_DREG: destination register (NLA_U32)
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* @NFTA_NG_UNTIL: source value to increment the counter until reset (NLA_U32)
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* @NFTA_NG_TYPE: operation type (NLA_U32)
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*/
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enum nft_ng_attributes {
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NFTA_NG_UNSPEC,
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NFTA_NG_DREG,
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NFTA_NG_UNTIL,
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NFTA_NG_TYPE,
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__NFTA_NG_MAX
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};
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#define NFTA_NG_MAX (__NFTA_NG_MAX - 1)
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enum nft_ng_types {
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NFT_NG_INCREMENTAL,
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NFT_NG_RANDOM,
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__NFT_NG_MAX
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};
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#define NFT_NG_MAX (__NFT_NG_MAX - 1)
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#endif /* _LINUX_NF_TABLES_H */

‎net/netfilter/Kconfig

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@@ -474,6 +474,12 @@ config NFT_META
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This option adds the "meta" expression that you can use to match and
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to set packet metainformation such as the packet mark.
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config NFT_NUMGEN
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tristate "Netfilter nf_tables number generator module"
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help
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This option adds the number generator expression used to perform
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incremental counting and random numbers bound to a upper limit.
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config NFT_CT
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depends on NF_CONNTRACK
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tristate "Netfilter nf_tables conntrack module"

‎net/netfilter/Makefile

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Original file line numberDiff line numberDiff line change
@@ -80,6 +80,7 @@ obj-$(CONFIG_NF_TABLES_NETDEV) += nf_tables_netdev.o
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obj-$(CONFIG_NFT_COMPAT) += nft_compat.o
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obj-$(CONFIG_NFT_EXTHDR) += nft_exthdr.o
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obj-$(CONFIG_NFT_META) += nft_meta.o
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obj-$(CONFIG_NFT_NUMGEN) += nft_numgen.o
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obj-$(CONFIG_NFT_CT) += nft_ct.o
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obj-$(CONFIG_NFT_LIMIT) += nft_limit.o
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obj-$(CONFIG_NFT_NAT) += nft_nat.o

‎net/netfilter/nft_numgen.c

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,192 @@
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/*
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* Copyright (c) 2016 Laura Garcia <[email protected]>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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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/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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static DEFINE_PER_CPU(struct rnd_state, nft_numgen_prandom_state);
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struct nft_ng_inc {
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enum nft_registers dreg:8;
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u32 until;
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atomic_t counter;
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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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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->until) ? oval + 1 : 0;
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} while (atomic_cmpxchg(&priv->counter, oval, nval) != oval);
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memcpy(&regs->data[priv->dreg], &priv->counter, sizeof(u32));
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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_UNTIL] = { .type = NLA_U32 },
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[NFTA_NG_TYPE] = { .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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priv->until = ntohl(nla_get_be32(tb[NFTA_NG_UNTIL]));
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if (priv->until == 0)
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return -ERANGE;
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priv->dreg = nft_parse_register(tb[NFTA_NG_DREG]);
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atomic_set(&priv->counter, 0);
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return nft_validate_register_store(ctx, priv->dreg, NULL,
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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 until, enum nft_ng_types type)
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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 (nft_dump_register(skb, NFTA_NG_UNTIL, until))
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goto nla_put_failure;
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if (nft_dump_register(skb, NFTA_NG_TYPE, type))
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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->until, NFT_NG_INCREMENTAL);
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}
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struct nft_ng_random {
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enum nft_registers dreg:8;
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u32 until;
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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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struct rnd_state *state = this_cpu_ptr(&nft_numgen_prandom_state);
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regs->data[priv->dreg] = reciprocal_scale(prandom_u32_state(state),
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priv->until);
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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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111+
priv->until = ntohl(nla_get_be32(tb[NFTA_NG_UNTIL]));
112+
if (priv->until == 0)
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return -ERANGE;
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prandom_init_once(&nft_numgen_prandom_state);
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priv->dreg = nft_parse_register(tb[NFTA_NG_DREG]);
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119+
return nft_validate_register_store(ctx, priv->dreg, NULL,
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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->until, NFT_NG_RANDOM);
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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;
151+
152+
if (!tb[NFTA_NG_DREG] ||
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!tb[NFTA_NG_UNTIL] ||
154+
!tb[NFTA_NG_TYPE])
155+
return ERR_PTR(-EINVAL);
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157+
type = ntohl(nla_get_be32(tb[NFTA_NG_TYPE]));
158+
159+
switch (type) {
160+
case NFT_NG_INCREMENTAL:
161+
return &nft_ng_inc_ops;
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case NFT_NG_RANDOM:
163+
return &nft_ng_random_ops;
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}
165+
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return ERR_PTR(-EINVAL);
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}
168+
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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)
183+
{
184+
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 <[email protected]>");
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MODULE_ALIAS_NFT_EXPR("numgen");

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