net/netfilter/xt_connmark.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *	xt_connmark - Netfilter module to operate on connection marks
 *
 *	Copyright (C) 2002,2004 MARA Systems AB <https://www.marasystems.com>
 *	by Henrik Nordstrom <hno@marasystems.com>
 *	Copyright © CC Computer Consultants GmbH, 2007 - 2008
 *	Jan Engelhardt <jengelh@medozas.de>
 */

#include <linux/module.h>
#include <linux/skbuff.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_ecache.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_connmark.h>

MODULE_AUTHOR("Henrik Nordstrom <hno@marasystems.com>");
MODULE_DESCRIPTION("Xtables: connection mark operations");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ipt_CONNMARK");
MODULE_ALIAS("ip6t_CONNMARK");
MODULE_ALIAS("ipt_connmark");
MODULE_ALIAS("ip6t_connmark");

static unsigned int
connmark_tg_shift(struct sk_buff *skb, const struct xt_connmark_tginfo2 *info)
{
	enum ip_conntrack_info ctinfo;
	u_int32_t new_targetmark;
	struct nf_conn *ct;
	u_int32_t newmark;
	u_int32_t oldmark;

	ct = nf_ct_get(skb, &ctinfo);
	if (ct == NULL)
		return XT_CONTINUE;

	switch (info->mode) {
	case XT_CONNMARK_SET:
		oldmark = READ_ONCE(ct->mark);
		newmark = (oldmark & ~info->ctmask) ^ info->ctmark;
		if (info->shift_dir == D_SHIFT_RIGHT)
			newmark >>= info->shift_bits;
		else
			newmark <<= info->shift_bits;

		if (READ_ONCE(ct->mark) != newmark) {
			WRITE_ONCE(ct->mark, newmark);
			nf_conntrack_event_cache(IPCT_MARK, ct);
		}
		break;
	case XT_CONNMARK_SAVE:
		new_targetmark = (skb->mark & info->nfmask);
		if (info->shift_dir == D_SHIFT_RIGHT)
			new_targetmark >>= info->shift_bits;
		else
			new_targetmark <<= info->shift_bits;

		newmark = (READ_ONCE(ct->mark) & ~info->ctmask) ^
			  new_targetmark;
		if (READ_ONCE(ct->mark) != newmark) {
			WRITE_ONCE(ct->mark, newmark);
			nf_conntrack_event_cache(IPCT_MARK, ct);
		}
		break;
	case XT_CONNMARK_RESTORE:
		new_targetmark = (READ_ONCE(ct->mark) & info->ctmask);
		if (info->shift_dir == D_SHIFT_RIGHT)
			new_targetmark >>= info->shift_bits;
		else
			new_targetmark <<= info->shift_bits;

		newmark = (skb->mark & ~info->nfmask) ^
			  new_targetmark;
		skb->mark = newmark;
		break;
	}
	return XT_CONTINUE;
}

static unsigned int
connmark_tg(struct sk_buff *skb, const struct xt_action_param *par)
{
	const struct xt_connmark_tginfo1 *info = par->targinfo;
	const struct xt_connmark_tginfo2 info2 = {
		.ctmark	= info->ctmark,
		.ctmask	= info->ctmask,
		.nfmask	= info->nfmask,
		.mode	= info->mode,
	};

	return connmark_tg_shift(skb, &info2);
}

static unsigned int
connmark_tg_v2(struct sk_buff *skb, const struct xt_action_param *par)
{
	const struct xt_connmark_tginfo2 *info = par->targinfo;

	return connmark_tg_shift(skb, info);
}

static int connmark_tg_check(const struct xt_tgchk_param *par)
{
	int ret;

	ret = nf_ct_netns_get(par->net, par->family);
	if (ret < 0)
		pr_info_ratelimited("cannot load conntrack support for proto=%u\n",
				    par->family);
	return ret;
}

static int connmark_tg_check_v2(const struct xt_tgchk_param *par)
{
	const struct xt_connmark_tginfo2 *info = par->targinfo;

	if (info->shift_dir > D_SHIFT_RIGHT || info->shift_bits >= 32)
		return -EINVAL;

	return connmark_tg_check(par);
}

static void connmark_tg_destroy(const struct xt_tgdtor_param *par)
{
	nf_ct_netns_put(par->net, par->family);
}

static bool
connmark_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
	const struct xt_connmark_mtinfo1 *info = par->matchinfo;
	enum ip_conntrack_info ctinfo;
	const struct nf_conn *ct;

	ct = nf_ct_get(skb, &ctinfo);
	if (ct == NULL)
		return false;

	return ((READ_ONCE(ct->mark) & info->mask) == info->mark) ^ info->invert;
}

static int connmark_mt_check(const struct xt_mtchk_param *par)
{
	int ret;

	ret = nf_ct_netns_get(par->net, par->family);
	if (ret < 0)
		pr_info_ratelimited("cannot load conntrack support for proto=%u\n",
				    par->family);
	return ret;
}

static void connmark_mt_destroy(const struct xt_mtdtor_param *par)
{
	nf_ct_netns_put(par->net, par->family);
}

static struct xt_target connmark_tg_reg[] __read_mostly = {
	{
		.name           = "CONNMARK",
		.revision       = 1,
		.family         = NFPROTO_IPV4,
		.checkentry     = connmark_tg_check,
		.target         = connmark_tg,
		.targetsize     = sizeof(struct xt_connmark_tginfo1),
		.destroy        = connmark_tg_destroy,
		.me             = THIS_MODULE,
	},
	{
		.name           = "CONNMARK",
		.revision       = 2,
		.family         = NFPROTO_IPV4,
		.checkentry     = connmark_tg_check_v2,
		.target         = connmark_tg_v2,
		.targetsize     = sizeof(struct xt_connmark_tginfo2),
		.destroy        = connmark_tg_destroy,
		.me             = THIS_MODULE,
	},
#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
	{
		.name           = "CONNMARK",
		.revision       = 1,
		.family         = NFPROTO_IPV6,
		.checkentry     = connmark_tg_check,
		.target         = connmark_tg,
		.targetsize     = sizeof(struct xt_connmark_tginfo1),
		.destroy        = connmark_tg_destroy,
		.me             = THIS_MODULE,
	},
	{
		.name           = "CONNMARK",
		.revision       = 2,
		.family         = NFPROTO_IPV6,
		.checkentry     = connmark_tg_check_v2,
		.target         = connmark_tg_v2,
		.targetsize     = sizeof(struct xt_connmark_tginfo2),
		.destroy        = connmark_tg_destroy,
		.me             = THIS_MODULE,
	},
#endif
};

static struct xt_match connmark_mt_reg __read_mostly = {
	.name           = "connmark",
	.revision       = 1,
	.family         = NFPROTO_UNSPEC,
	.checkentry     = connmark_mt_check,
	.match          = connmark_mt,
	.matchsize      = sizeof(struct xt_connmark_mtinfo1),
	.destroy        = connmark_mt_destroy,
	.me             = THIS_MODULE,
};

static int __init connmark_mt_init(void)
{
	int ret;

	ret = xt_register_targets(connmark_tg_reg,
				  ARRAY_SIZE(connmark_tg_reg));
	if (ret < 0)
		return ret;
	ret = xt_register_match(&connmark_mt_reg);
	if (ret < 0) {
		xt_unregister_targets(connmark_tg_reg,
				      ARRAY_SIZE(connmark_tg_reg));
		return ret;
	}
	return 0;
}

static void __exit connmark_mt_exit(void)
{
	xt_unregister_match(&connmark_mt_reg);
	xt_unregister_targets(connmark_tg_reg, ARRAY_SIZE(connmark_tg_reg));
}

module_init(connmark_mt_init);
module_exit(connmark_mt_exit);