netfilter: xtables: hardidletimer target implementation

This patch implements a hardidletimer Xtables target that can be used to
identify when interfaces have been idle for a certain period of time.

Timers are identified by labels and are created when a rule is set with a
new label. The rules also take a timeout value (in seconds) as an option.
If more than one rule uses the same timer label, the timer will be
restarted whenever any of the rules get a hit.

One entry for each timer is created in sysfs. This attribute contains the
timer remaining for the timer to expire. The attributes are located under
the xt_idletimer class:

/sys/class/xt_hardidletimer/timers/<label>

When the timer expires, the target module sends a sysfs notification to the
userspace, which can then decide what to do (eg. disconnect to save power)

Compared to xt_IDLETIMER, xt_HARDIDLETIMER can send notifications when CPU
is in suspend too, to notify the timer expiry

Change-Id: I1723d44e02df864d63da7550766ea7d763076de2
Signed-off-by: Bhavya Sokke Mallikarjunappa <bsokke@codeaurora.org>

4 files changed, 450 insertions, 0 deletions

diff --git a/include/uapi/linux/netfilter/xt_HARDIDLETIMER.h b/include/uapi/linux/netfilter/xt_HARDIDLETIMER.h
new file mode 100644
index 000000000000..58ff60899cd2
--- /dev/null
+++ b/include/uapi/linux/netfilter/xt_HARDIDLETIMER.h
@@ -0,0 +1,55 @@
+/*
+ * linux/include/linux/netfilter/xt_HARDIDLETIMER.h
+ *
+ * Header file for Xtables timer target module.
+ *
+ * Copyright (c) 2014, The Linux Foundation. All rights reserved.
+ *
+ * Copyright (C) 2004, 2010 Nokia Corporation
+ *
+ * Written by Timo Teras <ext-timo.teras@nokia.com>
+ *
+ * Converted to x_tables and forward-ported to 2.6.34
+ * by Luciano Coelho <luciano.coelho@nokia.com>
+ *
+ * Contact: Luciano Coelho <luciano.coelho@nokia.com>
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA
+ */
+
+#ifndef _XT_HARDIDLETIMER_H
+#define _XT_HARDIDLETIMER_H
+
+#include <linux/types.h>
+
+#define MAX_HARDIDLETIMER_LABEL_SIZE 28
+#define NLMSG_MAX_SIZE 64
+
+#define NL_EVENT_TYPE_INACTIVE 0
+#define NL_EVENT_TYPE_ACTIVE 1
+
+struct hardidletimer_tg_info {
+	__u32 timeout;
+
+	char label[MAX_HARDIDLETIMER_LABEL_SIZE];
+
+	/* Use netlink messages for notification in addition to sysfs */
+	__u8 send_nl_msg;
+
+	/* for kernel module internal use only */
+	struct hardidletimer_tg *timer __attribute__((aligned(8)));
+};
+
+#endif
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index 273f26b67653..53b592ec040f 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -749,6 +749,20 @@ config NETFILTER_XT_TARGET_IDLETIMER
 
 	  To compile it as a module, choose M here.  If unsure, say N.
 
+config NETFILTER_XT_TARGET_HARDIDLETIMER
+	tristate  "HARDIDLETIMER target support"
+	depends on NETFILTER_ADVANCED
+	help
+
+	  This option adds the `HARDIDLETIMER' target.  Each matching packet
+	  resets the timer associated with label specified when the rule is
+	  added.  When the timer expires, it triggers a sysfs notification.
+	  The remaining time for expiration can be read via sysfs.
+          Compared to IDLETIMER HARDIDLETIMER will send notification when
+          CPU in suspend too.
+
+	  To compile it as a module, choose M here.  If unsure, say N.
+
 config NETFILTER_XT_TARGET_LED
 	tristate '"LED" target support'
 	depends on LEDS_CLASS && LEDS_TRIGGERS
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index ad6a8aa63b1f..fcdc061130d7 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -122,6 +122,7 @@ obj-$(CONFIG_NETFILTER_XT_TARGET_TCPOPTSTRIP) += xt_TCPOPTSTRIP.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_TEE) += xt_TEE.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_TRACE) += xt_TRACE.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_IDLETIMER) += xt_IDLETIMER.o
+obj-$(CONFIG_NETFILTER_XT_TARGET_HARDIDLETIMER) += xt_HARDIDLETIMER.o
 
 # matches
 obj-$(CONFIG_NETFILTER_XT_MATCH_ADDRTYPE) += xt_addrtype.o
diff --git a/net/netfilter/xt_HARDIDLETIMER.c b/net/netfilter/xt_HARDIDLETIMER.c
new file mode 100644
index 000000000000..1e209b96ec2a
--- /dev/null
+++ b/net/netfilter/xt_HARDIDLETIMER.c
@@ -0,0 +1,380 @@
+/*
+ * linux/net/netfilter/xt_HARDIDLETIMER.c
+ *
+ * Netfilter module to trigger a timer when packet matches.
+ * After timer expires a kevent will be sent.
+ *
+ * Copyright (c) 2014, The Linux Foundation. All rights reserved.
+ *
+ * Copyright (C) 2004, 2010 Nokia Corporation
+ *
+ * Written by Timo Teras <ext-timo.teras@nokia.com>
+ *
+ * Converted to x_tables and reworked for upstream inclusion
+ * by Luciano Coelho <luciano.coelho@nokia.com>
+ *
+ * Contact: Luciano Coelho <luciano.coelho@nokia.com>
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/timer.h>
+#include <linux/alarmtimer.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/netfilter.h>
+#include <linux/netfilter/x_tables.h>
+#include <linux/netfilter/xt_HARDIDLETIMER.h>
+#include <linux/kdev_t.h>
+#include <linux/kobject.h>
+#include <linux/skbuff.h>
+#include <linux/workqueue.h>
+#include <linux/sysfs.h>
+#include <net/net_namespace.h>
+
+struct hardidletimer_tg_attr {
+	struct attribute attr;
+	ssize_t	(*show)(struct kobject *kobj,
+			struct attribute *attr, char *buf);
+};
+
+struct hardidletimer_tg {
+	struct list_head entry;
+	struct alarm alarm;
+	struct work_struct work;
+
+	struct kobject *kobj;
+	struct hardidletimer_tg_attr attr;
+
+	unsigned int refcnt;
+	bool send_nl_msg;
+	bool active;
+};
+
+static LIST_HEAD(hardidletimer_tg_list);
+static DEFINE_MUTEX(list_mutex);
+
+static struct kobject *hardidletimer_tg_kobj;
+
+static void notify_netlink_uevent(const char *iface,
+		struct hardidletimer_tg *timer)
+{
+	char iface_msg[NLMSG_MAX_SIZE];
+	char state_msg[NLMSG_MAX_SIZE];
+	char *envp[] = { iface_msg, state_msg, NULL };
+	int res;
+
+	res = snprintf(iface_msg, NLMSG_MAX_SIZE, "INTERFACE=%s",
+		       iface);
+	if (NLMSG_MAX_SIZE <= res) {
+		pr_err("message too long (%d)", res);
+		return;
+	}
+	res = snprintf(state_msg, NLMSG_MAX_SIZE, "STATE=%s",
+		       timer->active ? "active" : "inactive");
+	if (NLMSG_MAX_SIZE <= res) {
+		pr_err("message too long (%d)", res);
+		return;
+	}
+	pr_debug("putting nlmsg: <%s> <%s>\n", iface_msg, state_msg);
+	kobject_uevent_env(hardidletimer_tg_kobj, KOBJ_CHANGE, envp);
+	return;
+
+
+}
+
+static
+struct hardidletimer_tg *__hardidletimer_tg_find_by_label(const char *label)
+{
+	struct hardidletimer_tg *entry;
+
+	BUG_ON(!label);
+
+	list_for_each_entry(entry, &hardidletimer_tg_list, entry) {
+		if (!strcmp(label, entry->attr.attr.name))
+			return entry;
+	}
+
+	return NULL;
+}
+
+static ssize_t hardidletimer_tg_show(struct kobject *kobj,
+			struct attribute *attr, char *buf)
+{
+	struct hardidletimer_tg *timer;
+	ktime_t expires;
+	struct timespec ktimespec;
+
+	memset(&ktimespec, 0, sizeof(struct timespec));
+	mutex_lock(&list_mutex);
+
+	timer =	__hardidletimer_tg_find_by_label(attr->name);
+	if (timer) {
+		expires = alarm_expires_remaining(&timer->alarm);
+		ktimespec = ktime_to_timespec(expires);
+	}
+
+	mutex_unlock(&list_mutex);
+
+	if (ktimespec.tv_sec >= 0)
+		return snprintf(buf, PAGE_SIZE, "%ld\n", ktimespec.tv_sec);
+
+	if (timer->send_nl_msg)
+		return snprintf(buf, PAGE_SIZE, "0 %ld\n", ktimespec.tv_sec);
+	else
+		return snprintf(buf, PAGE_SIZE, "0\n");
+}
+
+static void hardidletimer_tg_work(struct work_struct *work)
+{
+	struct hardidletimer_tg *timer = container_of(work,
+				struct hardidletimer_tg, work);
+
+	sysfs_notify(hardidletimer_tg_kobj, NULL, timer->attr.attr.name);
+
+	if (timer->send_nl_msg)
+		notify_netlink_uevent(timer->attr.attr.name, timer);
+}
+
+static enum alarmtimer_restart hardidletimer_tg_alarmproc(struct alarm *alarm,
+							ktime_t now)
+{
+	struct hardidletimer_tg *timer = alarm->data;
+
+	pr_debug("alarm %s expired\n", timer->attr.attr.name);
+
+	timer->active = false;
+	schedule_work(&timer->work);
+	return ALARMTIMER_NORESTART;
+}
+
+static int hardidletimer_tg_create(struct hardidletimer_tg_info *info)
+{
+	int ret;
+	ktime_t tout;
+
+	info->timer = kmalloc(sizeof(*info->timer), GFP_KERNEL);
+	if (!info->timer) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	info->timer->attr.attr.name = kstrdup(info->label, GFP_KERNEL);
+	if (!info->timer->attr.attr.name) {
+		ret = -ENOMEM;
+		goto out_free_timer;
+	}
+	info->timer->attr.attr.mode = S_IRUGO;
+	info->timer->attr.show = hardidletimer_tg_show;
+
+	ret = sysfs_create_file(hardidletimer_tg_kobj, &info->timer->attr.attr);
+	if (ret < 0) {
+		pr_debug("couldn't add file to sysfs");
+		goto out_free_attr;
+	}
+
+	list_add(&info->timer->entry, &hardidletimer_tg_list);
+
+	alarm_init(&info->timer->alarm, ALARM_BOOTTIME,
+				hardidletimer_tg_alarmproc);
+	info->timer->alarm.data = info->timer;
+	info->timer->refcnt = 1;
+	info->timer->send_nl_msg = (info->send_nl_msg == 0) ? false : true;
+	info->timer->active = true;
+	tout = ktime_set(info->timeout, 0);
+	alarm_start_relative(&info->timer->alarm, tout);
+
+	INIT_WORK(&info->timer->work, hardidletimer_tg_work);
+
+	return 0;
+
+out_free_attr:
+	kfree(info->timer->attr.attr.name);
+out_free_timer:
+	kfree(info->timer);
+out:
+	return ret;
+}
+
+/* The actual xt_tables plugin. */
+static unsigned int hardidletimer_tg_target(struct sk_buff *skb,
+					 const struct xt_action_param *par)
+{
+	const struct hardidletimer_tg_info *info = par->targinfo;
+	ktime_t tout;
+
+	pr_debug("resetting timer %s, timeout period %u\n",
+		 info->label, info->timeout);
+
+	BUG_ON(!info->timer);
+
+	if (info->timer->active == false) {
+		schedule_work(&info->timer->work);
+		pr_debug("Starting timer %s\n", info->label);
+	}
+
+	info->timer->active = true;
+	/* TODO: Avoid modifying timers on each packet */
+	tout = ktime_set(info->timeout, 0);
+	alarm_start_relative(&info->timer->alarm, tout);
+
+	return XT_CONTINUE;
+}
+
+static int hardidletimer_tg_checkentry(const struct xt_tgchk_param *par)
+{
+	struct hardidletimer_tg_info *info = par->targinfo;
+	int ret;
+	ktime_t tout;
+
+	pr_debug("checkentry targinfo %s\n", info->label);
+
+	if (info->timeout == 0) {
+		pr_debug("timeout value is zero\n");
+		return -EINVAL;
+	}
+
+	if (info->label[0] == '\0' ||
+	    strnlen(info->label, MAX_HARDIDLETIMER_LABEL_SIZE)
+				== MAX_HARDIDLETIMER_LABEL_SIZE) {
+		pr_debug("label is empty or not nul-terminated\n");
+		return -EINVAL;
+	}
+
+	mutex_lock(&list_mutex);
+
+	info->timer = __hardidletimer_tg_find_by_label(info->label);
+	if (info->timer) {
+		info->timer->refcnt++;
+		if (info->timer->active == false) {
+				schedule_work(&info->timer->work);
+				pr_debug("Starting Checkentry timer\n");
+		}
+
+		info->timer->active = true;
+		tout = ktime_set(info->timeout, 0);
+		alarm_start_relative(&info->timer->alarm, tout);
+
+		pr_debug("increased refcnt of timer %s to %u\n",
+			 info->label, info->timer->refcnt);
+	} else {
+		ret = hardidletimer_tg_create(info);
+		if (ret < 0) {
+			pr_debug("failed to create timer\n");
+			mutex_unlock(&list_mutex);
+			return ret;
+		}
+	}
+
+	mutex_unlock(&list_mutex);
+
+	return 0;
+}
+
+static void hardidletimer_tg_destroy(const struct xt_tgdtor_param *par)
+{
+	const struct hardidletimer_tg_info *info = par->targinfo;
+
+	pr_debug("destroy targinfo %s\n", info->label);
+
+	mutex_lock(&list_mutex);
+
+	if (--info->timer->refcnt == 0) {
+		pr_debug("deleting timer %s\n", info->label);
+
+		list_del(&info->timer->entry);
+		alarm_cancel(&info->timer->alarm);
+		sysfs_remove_file(hardidletimer_tg_kobj,
+				&info->timer->attr.attr);
+		kfree(info->timer->attr.attr.name);
+		kfree(info->timer);
+	} else {
+		pr_debug("decreased refcnt of timer %s to %u\n",
+		info->label, info->timer->refcnt);
+	}
+
+	mutex_unlock(&list_mutex);
+}
+
+static struct xt_target hardidletimer_tg __read_mostly = {
+	.name		= "HARDIDLETIMER",
+	.revision	= 1,
+	.family		= NFPROTO_UNSPEC,
+	.target		= hardidletimer_tg_target,
+	.targetsize     = sizeof(struct hardidletimer_tg_info),
+	.checkentry	= hardidletimer_tg_checkentry,
+	.destroy        = hardidletimer_tg_destroy,
+	.me		= THIS_MODULE,
+};
+
+static struct class *hardidletimer_tg_class;
+
+static struct device *hardidletimer_tg_device;
+
+static int __init hardidletimer_tg_init(void)
+{
+	int err;
+
+	hardidletimer_tg_class = class_create(THIS_MODULE, "xt_hardidletimer");
+	err = PTR_ERR(hardidletimer_tg_class);
+	if (IS_ERR(hardidletimer_tg_class)) {
+		pr_debug("couldn't register device class\n");
+		goto out;
+	}
+
+	hardidletimer_tg_device = device_create(hardidletimer_tg_class, NULL,
+					    MKDEV(0, 0), NULL, "timers");
+	err = PTR_ERR(hardidletimer_tg_device);
+	if (IS_ERR(hardidletimer_tg_device)) {
+		pr_debug("couldn't register system device\n");
+		goto out_class;
+	}
+
+	hardidletimer_tg_kobj = &hardidletimer_tg_device->kobj;
+
+	err = xt_register_target(&hardidletimer_tg);
+	if (err < 0) {
+		pr_debug("couldn't register xt target\n");
+		goto out_dev;
+	}
+
+	return 0;
+out_dev:
+	device_destroy(hardidletimer_tg_class, MKDEV(0, 0));
+out_class:
+	class_destroy(hardidletimer_tg_class);
+out:
+	return err;
+}
+
+static void __exit hardidletimer_tg_exit(void)
+{
+	xt_unregister_target(&hardidletimer_tg);
+
+	device_destroy(hardidletimer_tg_class, MKDEV(0, 0));
+	class_destroy(hardidletimer_tg_class);
+}
+
+module_init(hardidletimer_tg_init);
+module_exit(hardidletimer_tg_exit);
+
+MODULE_AUTHOR("Timo Teras <ext-timo.teras@nokia.com>");
+MODULE_AUTHOR("Luciano Coelho <luciano.coelho@nokia.com>");
+MODULE_DESCRIPTION("Xtables: idle time monitor");
+MODULE_LICENSE("GPL v2");
+