From 91dbc6be0a62d3bcea98287734d593610aed507d Mon Sep 17 00:00:00 2001 From: Laura Garcia Liebana Date: Thu, 18 Aug 2016 12:13:13 +0200 Subject: [PATCH] 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 Signed-off-by: Pablo Neira Ayuso --- include/uapi/linux/netfilter/nf_tables.h | 24 +++ net/netfilter/Kconfig | 6 + net/netfilter/Makefile | 1 + net/netfilter/nft_numgen.c | 192 +++++++++++++++++++++++ 4 files changed, 223 insertions(+) create mode 100644 net/netfilter/nft_numgen.c diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h index 784fbf15ab3d..8c9d6ff70ec0 100644 --- a/include/uapi/linux/netfilter/nf_tables.h +++ b/include/uapi/linux/netfilter/nf_tables.h @@ -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 */ diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig index 29a8078deafa..e8d56d9a4df2 100644 --- a/net/netfilter/Kconfig +++ b/net/netfilter/Kconfig @@ -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" diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile index 0fc42df19b8c..0c8581100ac6 100644 --- a/net/netfilter/Makefile +++ b/net/netfilter/Makefile @@ -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 diff --git a/net/netfilter/nft_numgen.c b/net/netfilter/nft_numgen.c new file mode 100644 index 000000000000..176e26d5bbd0 --- /dev/null +++ b/net/netfilter/nft_numgen.c @@ -0,0 +1,192 @@ +/* + * Copyright (c) 2016 Laura Garcia + * + * 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 +#include +#include +#include +#include +#include +#include +#include +#include + +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(®s->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 "); +MODULE_ALIAS_NFT_EXPR("numgen");