netfilter: nf_tables: add last expression

Add a new optional expression that tells you when last matching on a
given rule / set element element has happened.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 87 insertions, 0 deletions

diff --git a/net/netfilter/nft_last.c b/net/netfilter/nft_last.c
new file mode 100644
index 0000000000000..913ac45167f24
--- /dev/null
+++ b/net/netfilter/nft_last.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#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 <net/netfilter/nf_tables_core.h>
+#include <net/netfilter/nf_tables.h>
+
+struct nft_last_priv {
+	unsigned long	last_jiffies;
+	unsigned int	last_set;
+};
+
+static const struct nla_policy nft_last_policy[NFTA_LAST_MAX + 1] = {
+	[NFTA_LAST_SET] = { .type = NLA_U32 },
+	[NFTA_LAST_MSECS] = { .type = NLA_U64 },
+};
+
+static int nft_last_init(const struct nft_ctx *ctx, const struct nft_expr *expr,
+			 const struct nlattr * const tb[])
+{
+	struct nft_last_priv *priv = nft_expr_priv(expr);
+	u64 last_jiffies;
+	int err;
+
+	if (tb[NFTA_LAST_MSECS]) {
+		err = nf_msecs_to_jiffies64(tb[NFTA_LAST_MSECS], &last_jiffies);
+		if (err < 0)
+			return err;
+
+		priv->last_jiffies = jiffies + (unsigned long)last_jiffies;
+		priv->last_set = 1;
+	}
+
+	return 0;
+}
+
+static void nft_last_eval(const struct nft_expr *expr,
+			  struct nft_regs *regs, const struct nft_pktinfo *pkt)
+{
+	struct nft_last_priv *priv = nft_expr_priv(expr);
+
+	priv->last_jiffies = jiffies;
+	priv->last_set = 1;
+}
+
+static int nft_last_dump(struct sk_buff *skb, const struct nft_expr *expr)
+{
+	struct nft_last_priv *priv = nft_expr_priv(expr);
+	__be64 msecs;
+
+	if (time_before(jiffies, priv->last_jiffies))
+		priv->last_set = 0;
+
+	if (priv->last_set)
+		msecs = nf_jiffies64_to_msecs(jiffies - priv->last_jiffies);
+	else
+		msecs = 0;
+
+	if (nla_put_be32(skb, NFTA_LAST_SET, htonl(priv->last_set)) ||
+	    nla_put_be64(skb, NFTA_LAST_MSECS, msecs, NFTA_LAST_PAD))
+		goto nla_put_failure;
+
+	return 0;
+
+nla_put_failure:
+	return -1;
+}
+
+static const struct nft_expr_ops nft_last_ops = {
+	.type		= &nft_last_type,
+	.size		= NFT_EXPR_SIZE(sizeof(struct nft_last_priv)),
+	.eval		= nft_last_eval,
+	.init		= nft_last_init,
+	.dump		= nft_last_dump,
+};
+
+struct nft_expr_type nft_last_type __read_mostly = {
+	.name		= "last",
+	.ops		= &nft_last_ops,
+	.policy		= nft_last_policy,
+	.maxattr	= NFTA_LAST_MAX,
+	.flags		= NFT_EXPR_STATEFUL,
+	.owner		= THIS_MODULE,
+};