// SPDX-License-Identifier: GPL-2.0-only
/*
 * File: pn_dev.c
 *
 * Phonet network device
 *
 * Copyright (C) 2008 Nokia Corporation.
 *
 * Authors: Sakari Ailus <sakari.ailus@nokia.com>
 *          Rémi Denis-Courmont
 */

#include <linux/kernel.h>
#include <linux/net.h>
#include <linux/slab.h>
#include <linux/netdevice.h>
#include <linux/phonet.h>
#include <linux/proc_fs.h>
#include <linux/if_arp.h>
#include <net/sock.h>
#include <net/netns/generic.h>
#include <net/phonet/pn_dev.h>

struct phonet_routes {
	struct mutex		lock;
	struct net_device __rcu	*table[64];
};

struct phonet_net {
	struct phonet_device_list pndevs;
	struct phonet_routes routes;
};

static unsigned int phonet_net_id __read_mostly;

static struct phonet_net *phonet_pernet(struct net *net)
{
	return net_generic(net, phonet_net_id);
}

struct phonet_device_list *phonet_device_list(struct net *net)
{
	struct phonet_net *pnn = phonet_pernet(net);
	return &pnn->pndevs;
}

/* Allocate new Phonet device. */
static struct phonet_device *__phonet_device_alloc(struct net_device *dev)
{
	struct phonet_device_list *pndevs = phonet_device_list(dev_net(dev));
	struct phonet_device *pnd = kmalloc(sizeof(*pnd), GFP_ATOMIC);
	if (pnd == NULL)
		return NULL;
	pnd->netdev = dev;
	bitmap_zero(pnd->addrs, 64);

	BUG_ON(!mutex_is_locked(&pndevs->lock));
	list_add_rcu(&pnd->list, &pndevs->list);
	return pnd;
}

static struct phonet_device *__phonet_get(struct net_device *dev)
{
	struct phonet_device_list *pndevs = phonet_device_list(dev_net(dev));
	struct phonet_device *pnd;

	BUG_ON(!mutex_is_locked(&pndevs->lock));
	list_for_each_entry(pnd, &pndevs->list, list) {
		if (pnd->netdev == dev)
			return pnd;
	}
	return NULL;
}

static struct phonet_device *__phonet_get_rcu(struct net_device *dev)
{
	struct phonet_device_list *pndevs = phonet_device_list(dev_net(dev));
	struct phonet_device *pnd;

	list_for_each_entry_rcu(pnd, &pndevs->list, list) {
		if (pnd->netdev == dev)
			return pnd;
	}
	return NULL;
}

static void phonet_device_destroy(struct net_device *dev)
{
	struct phonet_device_list *pndevs = phonet_device_list(dev_net(dev));
	struct phonet_device *pnd;

	ASSERT_RTNL();

	mutex_lock(&pndevs->lock);
	pnd = __phonet_get(dev);
	if (pnd)
		list_del_rcu(&pnd->list);
	mutex_unlock(&pndevs->lock);

	if (pnd) {
		u8 addr;

		for_each_set_bit(addr, pnd->addrs, 64)
			phonet_address_notify(RTM_DELADDR, dev, addr);
		kfree(pnd);
	}
}

struct net_device *phonet_device_get(struct net *net)
{
	struct phonet_device_list *pndevs = phonet_device_list(net);
	struct phonet_device *pnd;
	struct net_device *dev = NULL;

	rcu_read_lock();
	list_for_each_entry_rcu(pnd, &pndevs->list, list) {
		dev = pnd->netdev;
		BUG_ON(!dev);

		if ((dev->reg_state == NETREG_REGISTERED) &&
			((pnd->netdev->flags & IFF_UP)) == IFF_UP)
			break;
		dev = NULL;
	}
	dev_hold(dev);
	rcu_read_unlock();
	return dev;
}

int phonet_address_add(struct net_device *dev, u8 addr)
{
	struct phonet_device_list *pndevs = phonet_device_list(dev_net(dev));
	struct phonet_device *pnd;
	int err = 0;

	mutex_lock(&pndevs->lock);
	/* Find or create Phonet-specific device data */
	pnd = __phonet_get(dev);
	if (pnd == NULL)
		pnd = __phonet_device_alloc(dev);
	if (unlikely(pnd == NULL))
		err = -ENOMEM;
	else if (test_and_set_bit(addr >> 2, pnd->addrs))
		err = -EEXIST;
	mutex_unlock(&pndevs->lock);
	return err;
}

int phonet_address_del(struct net_device *dev, u8 addr)
{
	struct phonet_device_list *pndevs = phonet_device_list(dev_net(dev));
	struct phonet_device *pnd;
	int err = 0;

	mutex_lock(&pndevs->lock);
	pnd = __phonet_get(dev);
	if (!pnd || !test_and_clear_bit(addr >> 2, pnd->addrs)) {
		err = -EADDRNOTAVAIL;
		pnd = NULL;
	} else if (bitmap_empty(pnd->addrs, 64))
		list_del_rcu(&pnd->list);
	else
		pnd = NULL;
	mutex_unlock(&pndevs->lock);

	if (pnd)
		kfree_rcu(pnd, rcu);

	return err;
}

/* Gets a source address toward a destination, through a interface. */
u8 phonet_address_get(struct net_device *dev, u8 daddr)
{
	struct phonet_device *pnd;
	u8 saddr;

	rcu_read_lock();
	pnd = __phonet_get_rcu(dev);
	if (pnd) {
		BUG_ON(bitmap_empty(pnd->addrs, 64));

		/* Use same source address as destination, if possible */
		if (test_bit(daddr >> 2, pnd->addrs))
			saddr = daddr;
		else
			saddr = find_first_bit(pnd->addrs, 64) << 2;
	} else
		saddr = PN_NO_ADDR;
	rcu_read_unlock();

	if (saddr == PN_NO_ADDR) {
		/* Fallback to another device */
		struct net_device *def_dev;

		def_dev = phonet_device_get(dev_net(dev));
		if (def_dev) {
			if (def_dev != dev)
				saddr = phonet_address_get(def_dev, daddr);
			dev_put(def_dev);
		}
	}
	return saddr;
}

int phonet_address_lookup(struct net *net, u8 addr)
{
	struct phonet_device_list *pndevs = phonet_device_list(net);
	struct phonet_device *pnd;
	int err = -EADDRNOTAVAIL;

	rcu_read_lock();
	list_for_each_entry_rcu(pnd, &pndevs->list, list) {
		/* Don't allow unregistering devices! */
		if ((pnd->netdev->reg_state != NETREG_REGISTERED) ||
				((pnd->netdev->flags & IFF_UP)) != IFF_UP)
			continue;

		if (test_bit(addr >> 2, pnd->addrs)) {
			err = 0;
			goto found;
		}
	}
found:
	rcu_read_unlock();
	return err;
}

/* automatically configure a Phonet device, if supported */
static int phonet_device_autoconf(struct net_device *dev)
{
	struct if_phonet_req req;
	int ret;

	if (!dev->netdev_ops->ndo_siocdevprivate)
		return -EOPNOTSUPP;

	ret = dev->netdev_ops->ndo_siocdevprivate(dev, (struct ifreq *)&req,
						  NULL, SIOCPNGAUTOCONF);
	if (ret < 0)
		return ret;

	ASSERT_RTNL();
	ret = phonet_address_add(dev, req.ifr_phonet_autoconf.device);
	if (ret)
		return ret;
	phonet_address_notify(RTM_NEWADDR, dev,
				req.ifr_phonet_autoconf.device);
	return 0;
}

static void phonet_route_autodel(struct net_device *dev)
{
	struct phonet_net *pnn = phonet_pernet(dev_net(dev));
	unsigned int i;
	DECLARE_BITMAP(deleted, 64);

	/* Remove left-over Phonet routes */
	bitmap_zero(deleted, 64);
	mutex_lock(&pnn->routes.lock);
	for (i = 0; i < 64; i++)
		if (rcu_access_pointer(pnn->routes.table[i]) == dev) {
			RCU_INIT_POINTER(pnn->routes.table[i], NULL);
			set_bit(i, deleted);
		}
	mutex_unlock(&pnn->routes.lock);

	if (bitmap_empty(deleted, 64))
		return; /* short-circuit RCU */
	synchronize_rcu();
	for_each_set_bit(i, deleted, 64) {
		rtm_phonet_notify(RTM_DELROUTE, dev, i);
		dev_put(dev);
	}
}

/* notify Phonet of device events */
static int phonet_device_notify(struct notifier_block *me, unsigned long what,
				void *ptr)
{
	struct net_device *dev = netdev_notifier_info_to_dev(ptr);

	switch (what) {
	case NETDEV_REGISTER:
		if (dev->type == ARPHRD_PHONET)
			phonet_device_autoconf(dev);
		break;
	case NETDEV_UNREGISTER:
		phonet_device_destroy(dev);
		phonet_route_autodel(dev);
		break;
	}
	return 0;

}

static struct notifier_block phonet_device_notifier = {
	.notifier_call = phonet_device_notify,
	.priority = 0,
};

/* Per-namespace Phonet devices handling */
static int __net_init phonet_init_net(struct net *net)
{
	struct phonet_net *pnn = phonet_pernet(net);

	if (!proc_create_net("phonet", 0, net->proc_net, &pn_sock_seq_ops,
			sizeof(struct seq_net_private)))
		return -ENOMEM;

	INIT_LIST_HEAD(&pnn->pndevs.list);
	mutex_init(&pnn->pndevs.lock);
	mutex_init(&pnn->routes.lock);
	return 0;
}

static void __net_exit phonet_exit_net(struct net *net)
{
	struct phonet_net *pnn = phonet_pernet(net);

	remove_proc_entry("phonet", net->proc_net);
	WARN_ON_ONCE(!list_empty(&pnn->pndevs.list));
}

static struct pernet_operations phonet_net_ops = {
	.init = phonet_init_net,
	.exit = phonet_exit_net,
	.id   = &phonet_net_id,
	.size = sizeof(struct phonet_net),
};

/* Initialize Phonet devices list */
int __init phonet_device_init(void)
{
	int err = register_pernet_subsys(&phonet_net_ops);
	if (err)
		return err;

	proc_create_net("pnresource", 0, init_net.proc_net, &pn_res_seq_ops,
			sizeof(struct seq_net_private));
	register_netdevice_notifier(&phonet_device_notifier);
	err = phonet_netlink_register();
	if (err)
		phonet_device_exit();
	return err;
}

void phonet_device_exit(void)
{
	rtnl_unregister_all(PF_PHONET);
	unregister_netdevice_notifier(&phonet_device_notifier);
	unregister_pernet_subsys(&phonet_net_ops);
	remove_proc_entry("pnresource", init_net.proc_net);
}

int phonet_route_add(struct net_device *dev, u8 daddr)
{
	struct phonet_net *pnn = phonet_pernet(dev_net(dev));
	struct phonet_routes *routes = &pnn->routes;
	int err = -EEXIST;

	daddr = daddr >> 2;
	mutex_lock(&routes->lock);
	if (routes->table[daddr] == NULL) {
		rcu_assign_pointer(routes->table[daddr], dev);
		dev_hold(dev);
		err = 0;
	}
	mutex_unlock(&routes->lock);
	return err;
}

int phonet_route_del(struct net_device *dev, u8 daddr)
{
	struct phonet_net *pnn = phonet_pernet(dev_net(dev));
	struct phonet_routes *routes = &pnn->routes;

	daddr = daddr >> 2;
	mutex_lock(&routes->lock);
	if (rcu_access_pointer(routes->table[daddr]) == dev)
		RCU_INIT_POINTER(routes->table[daddr], NULL);
	else
		dev = NULL;
	mutex_unlock(&routes->lock);

	if (!dev)
		return -ENOENT;
	synchronize_rcu();
	dev_put(dev);
	return 0;
}

struct net_device *phonet_route_get_rcu(struct net *net, u8 daddr)
{
	struct phonet_net *pnn = phonet_pernet(net);
	struct phonet_routes *routes = &pnn->routes;
	struct net_device *dev;

	daddr >>= 2;
	dev = rcu_dereference(routes->table[daddr]);
	return dev;
}

struct net_device *phonet_route_output(struct net *net, u8 daddr)
{
	struct phonet_net *pnn = phonet_pernet(net);
	struct phonet_routes *routes = &pnn->routes;
	struct net_device *dev;

	daddr >>= 2;
	rcu_read_lock();
	dev = rcu_dereference(routes->table[daddr]);
	dev_hold(dev);
	rcu_read_unlock();

	if (!dev)
		dev = phonet_device_get(net); /* Default route */
	return dev;
}