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, 72 insertions, 0 deletions

diff --git a/net/netfilter/nf_conntrack_labels.c b/net/netfilter/nf_conntrack_labels.c
new file mode 100644
index 000000000000..0c542f41f338
--- /dev/null
+++ b/net/netfilter/nf_conntrack_labels.c
@@ -0,0 +1,72 @@
+/*
+ * test/set flag bits stored in conntrack extension area.
+ *
+ * (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/ctype.h>
+#include <linux/export.h>
+#include <linux/jhash.h>
+#include <linux/spinlock.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+
+#include <net/netfilter/nf_conntrack_ecache.h>
+#include <net/netfilter/nf_conntrack_labels.h>
+
+static unsigned int label_bits(const struct nf_conn_labels *l)
+{
+	unsigned int longs = l->words;
+	return longs * BITS_PER_LONG;
+}
+
+bool nf_connlabel_match(const struct nf_conn *ct, u16 bit)
+{
+	struct nf_conn_labels *labels = nf_ct_labels_find(ct);
+
+	if (!labels)
+		return false;
+
+	return bit < label_bits(labels) && test_bit(bit, labels->bits);
+}
+EXPORT_SYMBOL_GPL(nf_connlabel_match);
+
+int nf_connlabel_set(struct nf_conn *ct, u16 bit)
+{
+	struct nf_conn_labels *labels = nf_ct_labels_find(ct);
+
+	if (!labels || bit >= label_bits(labels))
+		return -ENOSPC;
+
+	if (test_bit(bit, labels->bits))
+		return 0;
+
+	if (test_and_set_bit(bit, labels->bits))
+		return 0;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(nf_connlabel_set);
+
+static struct nf_ct_ext_type labels_extend __read_mostly = {
+	.len    = sizeof(struct nf_conn_labels),
+	.align  = __alignof__(struct nf_conn_labels),
+	.id     = NF_CT_EXT_LABELS,
+};
+
+int nf_conntrack_labels_init(struct net *net)
+{
+	if (net_eq(net, &init_net))
+		return nf_ct_extend_register(&labels_extend);
+	return 0;
+}
+
+void nf_conntrack_labels_fini(struct net *net)
+{
+	if (net_eq(net, &init_net))
+		nf_ct_extend_unregister(&labels_extend);
+}