client_data_usage/cdu_nf_events.c

/* cdu_nf_events.c
 *
 * This file handles client data usage netfilter conntrack events.
 *
 * 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/module.h>
#include <linux/netfilter/x_tables.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_core.h>

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

#ifndef CONFIG_NF_CONNTRACK_CHAIN_EVENTS
#error Can not use this module without conntrack events
#endif

static u_int8_t nf_registered;

static int cdu_nf_event(struct notifier_block *this, unsigned long events, void *ptr)
{
	struct nf_ct_event *item = (struct nf_ct_event *)ptr;
	struct nf_conn *ct = item->ct;

	if (!ct) {
		CDU_DEBUG("No ct available\n");
		return -EINVAL;
	}

	if (ct->orig_direction == CDU_DIR_NOT_SET) {
		/* This ct does not have a direction information because it didn't
		 * travel through the xt hook, which means that we don't care
		 * about this traffic
		 */
		return NOTIFY_DONE;
	}

	/* Update data usage htable entry on end of flow trigger */
	if (events & (1 << IPCT_DESTROY)) {
		CDU_DEBUG("Caught %s NF event. mac=%pM, dir %s, ct %p\n",
			events & (1 << IPCT_NEW)?"NEW":"DESTROY", ct->mac,
			(ct->orig_direction == CDU_DIR_SRC)?"DIR_SRC":"DIR_DEST", ct);

		cdu_db_update_entry(ct, CDU_DB_UPDATE_PERMA_SET, CDU_DB_CONNTR_NOCLEAR);
	}

	return NOTIFY_DONE;
}

static struct notifier_block cdu_nf_notifier = {
	.notifier_call	= cdu_nf_event,
};

int cdu_nf_events_register(void)
{
	int result;

	if (!nf_registered) {
		result = nf_conntrack_register_notifier(&init_net, &cdu_nf_notifier);
		if (result < 0) {
			CDU_INFO("Failed to register conntrack notifier %d\n", result);
			return result;
		}
		nf_registered = 1;
	}

	CDU_DEBUG("initialized\n");
	return 0;
}

void cdu_nf_events_unregister(void)
{
	if (nf_registered) {
		nf_conntrack_unregister_notifier(&init_net, &cdu_nf_notifier);
		CDU_DEBUG("uninitialized\n");
	}
}