client_data_usage/cdu_xt_target.c

/* cdu_xt_target.c
 *
 * This file defines client data usage xtables target.
 *
 * Author: Cradlepoint Technology, Inc.  <source@cradlepoint.com>
 *		Adrian Sitterle <asitterle@cradlepoint.com>
 *
 * Copyright (C) 2019 Cradlepoint Technology, Inc.
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/version.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/netfilter/xt_usage.h>
#include <linux/netfilter/x_tables.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <linux/netfilter/nf_conntrack_common.h>
#include <linux/etherdevice.h>


#include "cdu_types.h"
#include "cdu_xt_target.h"
#include "cdu_nf_events.h"
#include "cdu_seq_file.h"
#include "cdu_db.h"

static unsigned int usage_tg(struct sk_buff *skb, const struct xt_action_param *par)
{
	struct nf_conn *ct;
	enum ip_conntrack_info ctinfo;
	const struct xt_usage_tginfo *info = par->targinfo;
	unsigned char direction = (info->src == 1);

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

	if (likely(ct->orig_direction != CDU_DIR_NOT_SET))
		return XT_CONTINUE;

	if (direction) {

		if (ctinfo == IP_CT_NEW)
			ct->orig_direction = CDU_DIR_SRC;
		else if (ctinfo == IP_CT_IS_REPLY)
			ct->orig_direction = CDU_DIR_DEST;
		else
			return XT_CONTINUE;

		ether_addr_copy(ct->mac, eth_hdr(skb)->h_source);

		cdu_db_add_entry_ifmissing(ct);
	}


	return XT_CONTINUE;
}

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

	if (!info->priv) {
		info->priv = cdu_seq_file_create(info->name, info->readreset);
		if (!info->priv)
			return -ENOMEM;
		cdu_nf_events_register();
	}

	(info->priv->usecount)++;

	return 0;
}

static void xt_usage_destroy(const struct xt_tgdtor_param *par)
{
	struct xt_usage_tginfo *info = par->targinfo;

	if (info->priv) {
		CDU_DEBUG("usecount=%u\n", info->priv->usecount);
		(info->priv->usecount)--;
		if (info->priv->usecount <= 0) {
			cdu_seq_file_destroy(info->priv);
			info->priv = NULL;
			cdu_nf_events_unregister();
		}
	}
}

static struct xt_target usage_tg_reg __read_mostly = {
	.name      = "USAGE",
	.revision  = 0,
	.family    = NFPROTO_UNSPEC,
	.target    = usage_tg,
	.checkentry = xt_usage_check,
	.destroy   = xt_usage_destroy,
	.targetsize = sizeof(struct xt_usage_tginfo),
	.hooks     = (1 << NF_INET_PRE_ROUTING) | (1 << NF_INET_LOCAL_IN) |
		     (1 << NF_INET_FORWARD) | (1 << NF_INET_POST_ROUTING) |
		     (1 << NF_INET_LOCAL_OUT),
	.me        = THIS_MODULE,
};

int cdu_xt_target_register(void)
{
	int result = xt_register_target(&usage_tg_reg);

	if (result < 0) {
		CDU_INFO("Failed to register xt target notifier %d\n", result);
		return result;
	}
	CDU_DEBUG("initialized\n");
	return 0;
}

void cdu_xt_target_unregister(void)
{
	xt_unregister_target(&usage_tg_reg);
	CDU_DEBUG("uninitialized\n");
}