This features which allows you to limit the maximum number of
connections per arbitrary key. The connlimit expression is stateful,
therefore it can be used from meters to dynamically populate a set, this
provides a mapping to the iptables' connlimit match. This patch also
comes that allows you define static connlimit policies.
This extension depends on the nf_conncount infrastructure.
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
v2: - fix spinlock imbalance.
- incorrect reference to NFT_OBJECT_COUNTER.
- missing Kconfig dependencies.
- fix inverted matching criteria.
- reorder function definitions (comestic).
include/uapi/linux/netfilter/nf_tables.h | 21 ++-
net/netfilter/Kconfig | 9 ++
net/netfilter/Makefile | 1 +
net/netfilter/nft_connlimit.c | 265 +++++++++++++++++++++++++++++++
4 files changed, 295 insertions(+), 1 deletion(-)
create mode 100644 net/netfilter/nft_connlimit.c
diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
index 6a3d653d5b27..05cd30063cf4 100644
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -1010,6 +1010,24 @@ enum nft_limit_attributes {
};
#define NFTA_LIMIT_MAX (__NFTA_LIMIT_MAX - 1)
+enum nft_connlimit_flags {
+ NFT_CONNLIMIT_F_INV = (1 << 0),
+};
+
+/**
+ * enum nft_connlimit_attributes - nf_tables connlimit expression netlink attributes
+ *
+ * @NFTA_CONNLIMIT_COUNT: number of connections (NLA_U32)
+ * @NFTA_CONNLIMIT_FLAGS: flags (NLA_U32: enum nft_connlimit_flags)
+ */
+enum nft_connlimit_attributes {
+ NFTA_CONNLIMIT_UNSPEC,
+ NFTA_CONNLIMIT_COUNT,
+ NFTA_CONNLIMIT_FLAGS,
+ __NFTA_CONNLIMIT_MAX
+};
+#define NFTA_CONNLIMIT_MAX (__NFTA_CONNLIMIT_MAX - 1)
+
/**
* enum nft_counter_attributes - nf_tables counter expression netlink attributes
*
@@ -1315,7 +1333,8 @@ enum nft_ct_helper_attributes {
#define NFT_OBJECT_QUOTA 2
#define NFT_OBJECT_CT_HELPER 3
#define NFT_OBJECT_LIMIT 4
-#define __NFT_OBJECT_MAX 5
+#define NFT_OBJECT_CONNLIMIT 5
+#define __NFT_OBJECT_MAX 6
#define NFT_OBJECT_MAX (__NFT_OBJECT_MAX - 1)
/**
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index 44d8a55e9721..2847d1f64647 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -536,6 +536,15 @@ config NFT_COUNTER
This option adds the "counter" expression that you can use to
include packet and byte counters in a rule.
+config NFT_CONNLIMIT
+ tristate "Netfilter nf_tables connlimit module"
+ depends on NF_CONNTRACK
+ depends on NETFILTER_ADVANCED
+ select NETFILTER_CONNCOUNT
+ help
+ This option adds the "connlimit" expression that you can use to
+ ratelimit rule matchings per connections.
+
config NFT_LOG
tristate "Netfilter nf_tables log module"
help
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index fd32bd2c9521..b44dfd34b6bf 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -80,6 +80,7 @@ nf_tables-objs := nf_tables_core.o nf_tables_api.o nft_chain_filter.o \
obj-$(CONFIG_NF_TABLES) += nf_tables.o
obj-$(CONFIG_NFT_COMPAT) += nft_compat.o
+obj-$(CONFIG_NFT_CONNLIMIT) += nft_connlimit.o
obj-$(CONFIG_NFT_EXTHDR) += nft_exthdr.o
obj-$(CONFIG_NFT_META) += nft_meta.o
obj-$(CONFIG_NFT_RT) += nft_rt.o
diff --git a/net/netfilter/nft_connlimit.c b/net/netfilter/nft_connlimit.c
new file mode 100644
index 000000000000..95d95aca3ff4
--- /dev/null
+++ b/net/netfilter/nft_connlimit.c
@@ -0,0 +1,265 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/spinlock.h>
+#include <linux/netlink.h>
+#include <linux/netfilter.h>
+#include <linux/netfilter/nf_tables.h>
+#include <net/netfilter/nf_tables.h>
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_count.h>
+#include <net/netfilter/nf_conntrack_core.h>
+#include <net/netfilter/nf_conntrack_tuple.h>
+#include <net/netfilter/nf_conntrack_zones.h>
+
+static struct kmem_cache *nft_connlimit_cachep;
+
+struct nft_connlimit {
+ spinlock_t lock;
+ struct hlist_head hhead;
+ u32 limit;
+ bool invert;
+};
+
+static inline void nft_connlimit_do_eval(struct nft_connlimit *priv,
+ struct nft_regs *regs,
+ const struct nft_pktinfo *pkt)
+{
+ const struct nf_conntrack_zone *zone = &nf_ct_zone_dflt;
+ const struct nf_conntrack_tuple *tuple_ptr;
+ struct nf_conntrack_tuple tuple;
+ enum ip_conntrack_info ctinfo;
+ const struct nf_conn *ct;
+ unsigned int count;
+ bool addit;
+
+ tuple_ptr = &tuple;
+
+ ct = nf_ct_get(pkt->skb, &ctinfo);
+ if (ct != NULL) {
+ tuple_ptr = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
+ zone = nf_ct_zone(ct);
+ } else if (!nf_ct_get_tuplepr(pkt->skb, skb_network_offset(pkt->skb),
+ nft_pf(pkt), nft_net(pkt), &tuple)) {
+ regs->verdict.code = NF_DROP;
+ return;
+ }
+
+ spin_lock_bh(&priv->lock);
+ count = nf_conncount_lookup(nft_net(pkt), nft_connlimit_cachep,
+ &priv->hhead, tuple_ptr, zone,
+ &addit);
+
+ if (!addit)
+ goto out;
+
+ if (!nf_conncount_add(nft_connlimit_cachep, &priv->hhead, tuple_ptr)) {
+ regs->verdict.code = NF_DROP;
+ spin_unlock_bh(&priv->lock);
+ return;
+ }
+ count++;
+out:
+ spin_unlock_bh(&priv->lock);
+
+ if ((count > priv->limit) ^ priv->invert) {
+ regs->verdict.code = NFT_BREAK;
+ return;
+ }
+}
+
+static int nft_connlimit_do_init(const struct nft_ctx *ctx,
+ const struct nlattr * const tb[],
+ struct nft_connlimit *priv)
+{
+ u32 flags;
+
+ if (!tb[NFTA_CONNLIMIT_COUNT])
+ return -EINVAL;
+
+ priv->limit = ntohl(nla_get_be32(tb[NFTA_CONNLIMIT_COUNT]));
+
+ if (tb[NFTA_CONNLIMIT_FLAGS]) {
+ flags = ntohl(nla_get_be32(tb[NFTA_CONNLIMIT_FLAGS]));
+ if (flags & ~NFT_CONNLIMIT_F_INV)
+ return -EOPNOTSUPP;
+ if (flags & NFT_CONNLIMIT_F_INV)
+ priv->invert = true;
+ }
+
+ spin_lock_init(&priv->lock);
+ INIT_HLIST_HEAD(&priv->hhead);
+
+ return nf_ct_netns_get(ctx->net, ctx->family);
+}
+
+static void nft_connlimit_do_destroy(const struct nft_ctx *ctx,
+ struct nft_connlimit *priv)
+{
+ nf_ct_netns_put(ctx->net, ctx->family);
+ nf_conncount_cache_free(nft_connlimit_cachep, &priv->hhead);
+}
+
+static int nft_connlimit_do_dump(struct sk_buff *skb,
+ struct nft_connlimit *priv)
+{
+ if (nla_put_be32(skb, NFTA_CONNLIMIT_COUNT, htonl(priv->limit)))
+ goto nla_put_failure;
+ if (priv->invert &&
+ nla_put_be32(skb, NFTA_CONNLIMIT_FLAGS, htonl(NFT_CONNLIMIT_F_INV)))
+ goto nla_put_failure;
+
+ return 0;
+
+nla_put_failure:
+ return -1;
+}
+
+static inline void nft_connlimit_obj_eval(struct nft_object *obj,
+ struct nft_regs *regs,
+ const struct nft_pktinfo *pkt)
+{
+ struct nft_connlimit *priv = nft_obj_data(obj);
+
+ nft_connlimit_do_eval(priv, regs, pkt);
+}
+
+static int nft_connlimit_obj_init(const struct nft_ctx *ctx,
+ const struct nlattr * const tb[],
+ struct nft_object *obj)
+{
+ struct nft_connlimit *priv = nft_obj_data(obj);
+
+ return nft_connlimit_do_init(ctx, tb, priv);
+}
+
+static void nft_connlimit_obj_destroy(const struct nft_ctx *ctx,
+ struct nft_object *obj)
+{
+ struct nft_connlimit *priv = nft_obj_data(obj);
+
+ nft_connlimit_do_destroy(ctx, priv);
+}
+
+static int nft_connlimit_obj_dump(struct sk_buff *skb,
+ struct nft_object *obj, bool reset)
+{
+ struct nft_connlimit *priv = nft_obj_data(obj);
+
+ return nft_connlimit_do_dump(skb, priv);
+}
+
+static const struct nla_policy nft_connlimit_policy[NFTA_CONNLIMIT_MAX + 1] = {
+ [NFTA_CONNLIMIT_COUNT] = { .type = NLA_U32 },
+ [NFTA_CONNLIMIT_FLAGS] = { .type = NLA_U32 },
+};
+
+static struct nft_object_type nft_connlimit_obj_type;
+static const struct nft_object_ops nft_connlimit_obj_ops = {
+ .type = &nft_connlimit_obj_type,
+ .size = sizeof(struct nft_connlimit),
+ .eval = nft_connlimit_obj_eval,
+ .init = nft_connlimit_obj_init,
+ .destroy = nft_connlimit_obj_destroy,
+ .dump = nft_connlimit_obj_dump,
+};
+
+static struct nft_object_type nft_connlimit_obj_type __read_mostly = {
+ .type = NFT_OBJECT_CONNLIMIT,
+ .ops = &nft_connlimit_obj_ops,
+ .maxattr = NFTA_CONNLIMIT_MAX,
+ .policy = nft_connlimit_policy,
+ .owner = THIS_MODULE,
+};
+
+static void nft_connlimit_eval(const struct nft_expr *expr,
+ struct nft_regs *regs,
+ const struct nft_pktinfo *pkt)
+{
+ struct nft_connlimit *priv = nft_expr_priv(expr);
+
+ nft_connlimit_do_eval(priv, regs, pkt);
+}
+
+static int nft_connlimit_dump(struct sk_buff *skb, const struct nft_expr *expr)
+{
+ struct nft_connlimit *priv = nft_expr_priv(expr);
+
+ return nft_connlimit_do_dump(skb, priv);
+}
+
+static int nft_connlimit_init(const struct nft_ctx *ctx,
+ const struct nft_expr *expr,
+ const struct nlattr * const tb[])
+{
+ struct nft_connlimit *priv = nft_expr_priv(expr);
+
+ return nft_connlimit_do_init(ctx, tb, priv);
+}
+
+static void nft_connlimit_destroy(const struct nft_ctx *ctx,
+ const struct nft_expr *expr)
+{
+ struct nft_connlimit *priv = nft_expr_priv(expr);
+
+ nft_connlimit_do_destroy(ctx, priv);
+}
+
+static struct nft_expr_type nft_connlimit_type;
+static const struct nft_expr_ops nft_connlimit_ops = {
+ .type = &nft_connlimit_type,
+ .size = NFT_EXPR_SIZE(sizeof(struct nft_connlimit)),
+ .eval = nft_connlimit_eval,
+ .init = nft_connlimit_init,
+ .destroy = nft_connlimit_destroy,
+ .dump = nft_connlimit_dump,
+};
+
+static struct nft_expr_type nft_connlimit_type __read_mostly = {
+ .name = "connlimit",
+ .ops = &nft_connlimit_ops,
+ .policy = nft_connlimit_policy,
+ .maxattr = NFTA_CONNLIMIT_MAX,
+ .flags = NFT_EXPR_STATEFUL,
+ .owner = THIS_MODULE,
+};
+
+static int __init nft_connlimit_module_init(void)
+{
+ int err;
+
+ nft_connlimit_cachep = nf_conncount_cache_alloc("nft_connlimit");
+ if (IS_ERR(nft_connlimit_cachep))
+ return -ENOMEM;
+
+ err = nft_register_obj(&nft_connlimit_obj_type);
+ if (err < 0)
+ goto err1;
+
+ err = nft_register_expr(&nft_connlimit_type);
+ if (err < 0)
+ goto err2;
+
+ return 0;
+err2:
+ nft_unregister_obj(&nft_connlimit_obj_type);
+err1:
+ kmem_cache_destroy(nft_connlimit_cachep);
+ return err;
+}
+
+static void __exit nft_connlimit_module_exit(void)
+{
+ nft_unregister_expr(&nft_connlimit_type);
+ nft_unregister_obj(&nft_connlimit_obj_type);
+ kmem_cache_destroy(nft_connlimit_cachep);
+}
+
+module_init(nft_connlimit_module_init);
+module_exit(nft_connlimit_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Pablo Neira Ayuso");
+MODULE_ALIAS_NFT_EXPR("connlimit");
+MODULE_ALIAS_NFT_OBJ(NFT_OBJECT_CONNLIMIT);
--
2.11.0
--
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