1. 根目录:
2. net
3. netfilter
4. nf_conntrack_labels.c

/*
 * 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))
		nf_conntrack_event_cache(IPCT_LABEL, ct);

	return 0;
}
EXPORT_SYMBOL_GPL(nf_connlabel_set);

#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
static void replace_u32(u32 *address, u32 mask, u32 new)
{
	u32 old, tmp;

	do {
		old = *address;
		tmp = (old & mask) ^ new;
	} while (cmpxchg(address, old, tmp) != old);
}

int nf_connlabels_replace(struct nf_conn *ct,
			  const u32 *data,
			  const u32 *mask, unsigned int words32)
{
	struct nf_conn_labels *labels;
	unsigned int size, i;
	u32 *dst;

	labels = nf_ct_labels_find(ct);
	if (!labels)
		return -ENOSPC;

	size = labels->words * sizeof(long);
	if (size < (words32 * sizeof(u32)))
		words32 = size / sizeof(u32);

	dst = (u32 *) labels->bits;
	if (words32) {
		for (i = 0; i < words32; i++)
			replace_u32(&dst[i], mask ? ~mask[i] : 0, data[i]);
	}

	size /= sizeof(u32);
	for (i = words32; i < size; i++) /* pad */
		replace_u32(&dst[i], 0, 0);

	nf_conntrack_event_cache(IPCT_LABEL, ct);
	return 0;
}
EXPORT_SYMBOL_GPL(nf_connlabels_replace);
#endif

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(void)
{
	return nf_ct_extend_register(&labels_extend);
}

void nf_conntrack_labels_fini(void)
{
	nf_ct_extend_unregister(&labels_extend);
}