netfilter: add connlabel conntrack extension

similar to connmarks, except labels are bit-based; i.e.
all labels may be attached to a flow at the same time.

Up to 128 labels are supported.  Supporting more labels
is possible, but requires increasing the ct offset delta
from u8 to u16 type due to increased extension sizes.

Mapping of bit-identifier to label name is done in userspace.

The extension is enabled at run-time once "-m connlabel" netfilter
rules are added.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 99 insertions, 0 deletions

diff --git a/net/netfilter/xt_connlabel.c b/net/netfilter/xt_connlabel.c
new file mode 100644
index 000000000000..9f8719df2001
--- /dev/null
+++ b/net/netfilter/xt_connlabel.c
@@ -0,0 +1,99 @@
+/*
+ * (C) 2013 Astaro GmbH & Co KG
+ *
+ * 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/module.h>
+#include <linux/skbuff.h>
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_labels.h>
+#include <linux/netfilter/x_tables.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");
+MODULE_DESCRIPTION("Xtables: add/match connection trackling labels");
+MODULE_ALIAS("ipt_connlabel");
+MODULE_ALIAS("ip6t_connlabel");
+
+static bool
+connlabel_mt(const struct sk_buff *skb, struct xt_action_param *par)
+{
+	const struct xt_connlabel_mtinfo *info = par->matchinfo;
+	enum ip_conntrack_info ctinfo;
+	struct nf_conn *ct;
+	bool invert = info->options & XT_CONNLABEL_OP_INVERT;
+
+	ct = nf_ct_get(skb, &ctinfo);
+	if (ct == NULL || nf_ct_is_untracked(ct))
+		return invert;
+
+	if (info->options & XT_CONNLABEL_OP_SET)
+		return (nf_connlabel_set(ct, info->bit) == 0) ^ invert;
+
+	return nf_connlabel_match(ct, info->bit) ^ invert;
+}
+
+static int connlabel_mt_check(const struct xt_mtchk_param *par)
+{
+	const int options = XT_CONNLABEL_OP_INVERT |
+			    XT_CONNLABEL_OP_SET;
+	struct xt_connlabel_mtinfo *info = par->matchinfo;
+	int ret;
+	size_t words;
+
+	if (info->bit > XT_CONNLABEL_MAXBIT)
+		return -ERANGE;
+
+	if (info->options & ~options) {
+		pr_err("Unknown options in mask %x\n", info->options);
+		return -EINVAL;
+	}
+
+	ret = nf_ct_l3proto_try_module_get(par->family);
+	if (ret < 0) {
+		pr_info("cannot load conntrack support for proto=%u\n",
+							par->family);
+		return ret;
+	}
+
+	par->net->ct.labels_used++;
+	words = BITS_TO_LONGS(info->bit+1);
+	if (words > par->net->ct.label_words)
+		par->net->ct.label_words = words;
+
+	return ret;
+}
+
+static void connlabel_mt_destroy(const struct xt_mtdtor_param *par)
+{
+	par->net->ct.labels_used--;
+	if (par->net->ct.labels_used == 0)
+		par->net->ct.label_words = 0;
+	nf_ct_l3proto_module_put(par->family);
+}
+
+static struct xt_match connlabels_mt_reg __read_mostly = {
+	.name           = "connlabel",
+	.family         = NFPROTO_UNSPEC,
+	.checkentry     = connlabel_mt_check,
+	.match          = connlabel_mt,
+	.matchsize      = sizeof(struct xt_connlabel_mtinfo),
+	.destroy        = connlabel_mt_destroy,
+	.me             = THIS_MODULE,
+};
+
+static int __init connlabel_mt_init(void)
+{
+	return xt_register_match(&connlabels_mt_reg);
+}
+
+static void __exit connlabel_mt_exit(void)
+{
+	xt_unregister_match(&connlabels_mt_reg);
+}
+
+module_init(connlabel_mt_init);
+module_exit(connlabel_mt_exit);