// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      LAPB release 002
 *
 *      This code REQUIRES 2.1.15 or higher/ NET3.038
 *
 *      History
 *      LAPB 001        Jonathan Naylor Started Coding
 *      LAPB 002        Jonathan Naylor New timer architecture.
 *      2000-10-29      Henner Eisen    lapb_data_indication() return status.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/jiffies.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/inet.h>
#include <linux/if_arp.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <linux/uaccess.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <net/lapb.h>

static LIST_HEAD(lapb_list);
static DEFINE_RWLOCK(lapb_list_lock);

/*
 *      Free an allocated lapb control block.
 */
static void lapb_free_cb(struct lapb_cb *lapb)
{
        kfree(lapb);
}

static __inline__ void lapb_hold(struct lapb_cb *lapb)
{
        refcount_inc(&lapb->refcnt);
}

static __inline__ void lapb_put(struct lapb_cb *lapb)
{
        if (refcount_dec_and_test(&lapb->refcnt))
                lapb_free_cb(lapb);
}

/*
 *      Socket removal during an interrupt is now safe.
 */
static void __lapb_remove_cb(struct lapb_cb *lapb)
{
        if (lapb->node.next) {
                list_del(&lapb->node);
                lapb_put(lapb);
        }
}

/*
 *      Add a socket to the bound sockets list.
 */
static void __lapb_insert_cb(struct lapb_cb *lapb)
{
        list_add(&lapb->node, &lapb_list);
        lapb_hold(lapb);
}

static struct lapb_cb *__lapb_devtostruct(struct net_device *dev)
{
        struct lapb_cb *lapb, *use = NULL;

        list_for_each_entry(lapb, &lapb_list, node) {
                if (lapb->dev == dev) {
                        use = lapb;
                        break;
                }
        }

        if (use)
                lapb_hold(use);

        return use;
}

static struct lapb_cb *lapb_devtostruct(struct net_device *dev)
{
        struct lapb_cb *rc;

        read_lock_bh(&lapb_list_lock);
        rc = __lapb_devtostruct(dev);
        read_unlock_bh(&lapb_list_lock);

        return rc;
}
/*
 *      Create an empty LAPB control block.
 */
static struct lapb_cb *lapb_create_cb(void)
{
        struct lapb_cb *lapb = kzalloc_obj(*lapb, GFP_ATOMIC);

        if (!lapb)
                goto out;

        skb_queue_head_init(&lapb->write_queue);
        skb_queue_head_init(&lapb->ack_queue);

        timer_setup(&lapb->t1timer, NULL, 0);
        timer_setup(&lapb->t2timer, NULL, 0);
        lapb->t1timer_running = false;
        lapb->t2timer_running = false;

        lapb->t1      = LAPB_DEFAULT_T1;
        lapb->t2      = LAPB_DEFAULT_T2;
        lapb->n2      = LAPB_DEFAULT_N2;
        lapb->mode    = LAPB_DEFAULT_MODE;
        lapb->window  = LAPB_DEFAULT_WINDOW;
        lapb->state   = LAPB_STATE_0;

        spin_lock_init(&lapb->lock);
        refcount_set(&lapb->refcnt, 1);
out:
        return lapb;
}

int lapb_register(struct net_device *dev,
                  const struct lapb_register_struct *callbacks)
{
        struct lapb_cb *lapb;
        int rc = LAPB_BADTOKEN;

        write_lock_bh(&lapb_list_lock);

        lapb = __lapb_devtostruct(dev);
        if (lapb) {
                lapb_put(lapb);
                goto out;
        }

        lapb = lapb_create_cb();
        rc = LAPB_NOMEM;
        if (!lapb)
                goto out;

        lapb->dev       = dev;
        lapb->callbacks = callbacks;

        __lapb_insert_cb(lapb);

        lapb_start_t1timer(lapb);

        rc = LAPB_OK;
out:
        write_unlock_bh(&lapb_list_lock);
        return rc;
}
EXPORT_SYMBOL(lapb_register);

int lapb_unregister(struct net_device *dev)
{
        struct lapb_cb *lapb;
        int rc = LAPB_BADTOKEN;

        write_lock_bh(&lapb_list_lock);
        lapb = __lapb_devtostruct(dev);
        if (!lapb)
                goto out;
        lapb_put(lapb);

        /* Wait for other refs to "lapb" to drop */
        while (refcount_read(&lapb->refcnt) > 2)
                usleep_range(1, 10);

        spin_lock_bh(&lapb->lock);

        lapb_stop_t1timer(lapb);
        lapb_stop_t2timer(lapb);

        lapb_clear_queues(lapb);

        spin_unlock_bh(&lapb->lock);

        /* Wait for running timers to stop */
        timer_delete_sync(&lapb->t1timer);
        timer_delete_sync(&lapb->t2timer);

        __lapb_remove_cb(lapb);

        lapb_put(lapb);
        rc = LAPB_OK;
out:
        write_unlock_bh(&lapb_list_lock);
        return rc;
}
EXPORT_SYMBOL(lapb_unregister);

int lapb_getparms(struct net_device *dev, struct lapb_parms_struct *parms)
{
        int rc = LAPB_BADTOKEN;
        struct lapb_cb *lapb = lapb_devtostruct(dev);

        if (!lapb)
                goto out;

        spin_lock_bh(&lapb->lock);

        parms->t1      = lapb->t1 / HZ;
        parms->t2      = lapb->t2 / HZ;
        parms->n2      = lapb->n2;
        parms->n2count = lapb->n2count;
        parms->state   = lapb->state;
        parms->window  = lapb->window;
        parms->mode    = lapb->mode;

        if (!timer_pending(&lapb->t1timer))
                parms->t1timer = 0;
        else
                parms->t1timer = (lapb->t1timer.expires - jiffies) / HZ;

        if (!timer_pending(&lapb->t2timer))
                parms->t2timer = 0;
        else
                parms->t2timer = (lapb->t2timer.expires - jiffies) / HZ;

        spin_unlock_bh(&lapb->lock);
        lapb_put(lapb);
        rc = LAPB_OK;
out:
        return rc;
}
EXPORT_SYMBOL(lapb_getparms);

int lapb_setparms(struct net_device *dev, struct lapb_parms_struct *parms)
{
        int rc = LAPB_BADTOKEN;
        struct lapb_cb *lapb = lapb_devtostruct(dev);

        if (!lapb)
                goto out;

        spin_lock_bh(&lapb->lock);

        rc = LAPB_INVALUE;
        if (parms->t1 < 1 || parms->t2 < 1 || parms->n2 < 1)
                goto out_put;

        if (lapb->state == LAPB_STATE_0) {
                if (parms->mode & LAPB_EXTENDED) {
                        if (parms->window < 1 || parms->window > 127)
                                goto out_put;
                } else {
                        if (parms->window < 1 || parms->window > 7)
                                goto out_put;
                }
                lapb->mode    = parms->mode;
                lapb->window  = parms->window;
        }

        lapb->t1    = parms->t1 * HZ;
        lapb->t2    = parms->t2 * HZ;
        lapb->n2    = parms->n2;

        rc = LAPB_OK;
out_put:
        spin_unlock_bh(&lapb->lock);
        lapb_put(lapb);
out:
        return rc;
}
EXPORT_SYMBOL(lapb_setparms);

int lapb_connect_request(struct net_device *dev)
{
        struct lapb_cb *lapb = lapb_devtostruct(dev);
        int rc = LAPB_BADTOKEN;

        if (!lapb)
                goto out;

        spin_lock_bh(&lapb->lock);

        rc = LAPB_OK;
        if (lapb->state == LAPB_STATE_1)
                goto out_put;

        rc = LAPB_CONNECTED;
        if (lapb->state == LAPB_STATE_3 || lapb->state == LAPB_STATE_4)
                goto out_put;

        lapb_establish_data_link(lapb);

        lapb_dbg(0, "(%p) S0 -> S1\n", lapb->dev);
        lapb->state = LAPB_STATE_1;

        rc = LAPB_OK;
out_put:
        spin_unlock_bh(&lapb->lock);
        lapb_put(lapb);
out:
        return rc;
}
EXPORT_SYMBOL(lapb_connect_request);

static int __lapb_disconnect_request(struct lapb_cb *lapb)
{
        switch (lapb->state) {
        case LAPB_STATE_0:
                return LAPB_NOTCONNECTED;

        case LAPB_STATE_1:
                lapb_dbg(1, "(%p) S1 TX DISC(1)\n", lapb->dev);
                lapb_dbg(0, "(%p) S1 -> S0\n", lapb->dev);
                lapb_send_control(lapb, LAPB_DISC, LAPB_POLLON, LAPB_COMMAND);
                lapb->state = LAPB_STATE_0;
                lapb_start_t1timer(lapb);
                return LAPB_NOTCONNECTED;

        case LAPB_STATE_2:
                return LAPB_OK;
        }

        lapb_clear_queues(lapb);
        lapb->n2count = 0;
        lapb_send_control(lapb, LAPB_DISC, LAPB_POLLON, LAPB_COMMAND);
        lapb_start_t1timer(lapb);
        lapb_stop_t2timer(lapb);
        lapb->state = LAPB_STATE_2;

        lapb_dbg(1, "(%p) S3 DISC(1)\n", lapb->dev);
        lapb_dbg(0, "(%p) S3 -> S2\n", lapb->dev);

        return LAPB_OK;
}

int lapb_disconnect_request(struct net_device *dev)
{
        struct lapb_cb *lapb = lapb_devtostruct(dev);
        int rc = LAPB_BADTOKEN;

        if (!lapb)
                goto out;

        spin_lock_bh(&lapb->lock);

        rc = __lapb_disconnect_request(lapb);

        spin_unlock_bh(&lapb->lock);
        lapb_put(lapb);
out:
        return rc;
}
EXPORT_SYMBOL(lapb_disconnect_request);

int lapb_data_request(struct net_device *dev, struct sk_buff *skb)
{
        struct lapb_cb *lapb = lapb_devtostruct(dev);
        int rc = LAPB_BADTOKEN;

        if (!lapb)
                goto out;

        spin_lock_bh(&lapb->lock);

        rc = LAPB_NOTCONNECTED;
        if (lapb->state != LAPB_STATE_3 && lapb->state != LAPB_STATE_4)
                goto out_put;

        skb_queue_tail(&lapb->write_queue, skb);
        lapb_kick(lapb);
        rc = LAPB_OK;
out_put:
        spin_unlock_bh(&lapb->lock);
        lapb_put(lapb);
out:
        return rc;
}
EXPORT_SYMBOL(lapb_data_request);

int lapb_data_received(struct net_device *dev, struct sk_buff *skb)
{
        struct lapb_cb *lapb = lapb_devtostruct(dev);
        int rc = LAPB_BADTOKEN;

        if (lapb) {
                spin_lock_bh(&lapb->lock);
                lapb_data_input(lapb, skb);
                spin_unlock_bh(&lapb->lock);
                lapb_put(lapb);
                rc = LAPB_OK;
        }

        return rc;
}
EXPORT_SYMBOL(lapb_data_received);

void lapb_connect_confirmation(struct lapb_cb *lapb, int reason)
{
        if (lapb->callbacks->connect_confirmation)
                lapb->callbacks->connect_confirmation(lapb->dev, reason);
}

void lapb_connect_indication(struct lapb_cb *lapb, int reason)
{
        if (lapb->callbacks->connect_indication)
                lapb->callbacks->connect_indication(lapb->dev, reason);
}

void lapb_disconnect_confirmation(struct lapb_cb *lapb, int reason)
{
        if (lapb->callbacks->disconnect_confirmation)
                lapb->callbacks->disconnect_confirmation(lapb->dev, reason);
}

void lapb_disconnect_indication(struct lapb_cb *lapb, int reason)
{
        if (lapb->callbacks->disconnect_indication)
                lapb->callbacks->disconnect_indication(lapb->dev, reason);
}

int lapb_data_indication(struct lapb_cb *lapb, struct sk_buff *skb)
{
        if (lapb->callbacks->data_indication)
                return lapb->callbacks->data_indication(lapb->dev, skb);

        kfree_skb(skb);
        return NET_RX_SUCCESS; /* For now; must be != NET_RX_DROP */
}

int lapb_data_transmit(struct lapb_cb *lapb, struct sk_buff *skb)
{
        int used = 0;

        if (lapb->callbacks->data_transmit) {
                lapb->callbacks->data_transmit(lapb->dev, skb);
                used = 1;
        }

        return used;
}

/* Handle device status changes. */
static int lapb_device_event(struct notifier_block *this, unsigned long event,
                             void *ptr)
{
        struct net_device *dev = netdev_notifier_info_to_dev(ptr);
        struct lapb_cb *lapb;

        if (!net_eq(dev_net(dev), &init_net))
                return NOTIFY_DONE;

        if (dev->type != ARPHRD_X25)
                return NOTIFY_DONE;

        lapb = lapb_devtostruct(dev);
        if (!lapb)
                return NOTIFY_DONE;

        spin_lock_bh(&lapb->lock);

        switch (event) {
        case NETDEV_UP:
                lapb_dbg(0, "(%p) Interface up: %s\n", dev, dev->name);

                if (netif_carrier_ok(dev)) {
                        lapb_dbg(0, "(%p): Carrier is already up: %s\n", dev,
                                 dev->name);
                        if (lapb->mode & LAPB_DCE) {
                                lapb_start_t1timer(lapb);
                        } else {
                                if (lapb->state == LAPB_STATE_0) {
                                        lapb->state = LAPB_STATE_1;
                                        lapb_establish_data_link(lapb);
                                }
                        }
                }
                break;
        case NETDEV_GOING_DOWN:
                if (netif_carrier_ok(dev))
                        __lapb_disconnect_request(lapb);
                break;
        case NETDEV_DOWN:
                lapb_dbg(0, "(%p) Interface down: %s\n", dev, dev->name);
                lapb_dbg(0, "(%p) S%d -> S0\n", dev, lapb->state);
                lapb_clear_queues(lapb);
                lapb->state = LAPB_STATE_0;
                lapb->n2count   = 0;
                lapb_stop_t1timer(lapb);
                lapb_stop_t2timer(lapb);
                break;
        case NETDEV_CHANGE:
                if (netif_carrier_ok(dev)) {
                        lapb_dbg(0, "(%p): Carrier detected: %s\n", dev,
                                 dev->name);
                        if (lapb->mode & LAPB_DCE) {
                                lapb_start_t1timer(lapb);
                        } else {
                                if (lapb->state == LAPB_STATE_0) {
                                        lapb->state = LAPB_STATE_1;
                                        lapb_establish_data_link(lapb);
                                }
                        }
                } else {
                        lapb_dbg(0, "(%p) Carrier lost: %s\n", dev, dev->name);
                        lapb_dbg(0, "(%p) S%d -> S0\n", dev, lapb->state);
                        lapb_clear_queues(lapb);
                        lapb->state = LAPB_STATE_0;
                        lapb->n2count   = 0;
                        lapb_stop_t1timer(lapb);
                        lapb_stop_t2timer(lapb);
                }
                break;
        }

        spin_unlock_bh(&lapb->lock);
        lapb_put(lapb);
        return NOTIFY_DONE;
}

static struct notifier_block lapb_dev_notifier = {
        .notifier_call = lapb_device_event,
};

static int __init lapb_init(void)
{
        return register_netdevice_notifier(&lapb_dev_notifier);
}

static void __exit lapb_exit(void)
{
        WARN_ON(!list_empty(&lapb_list));

        unregister_netdevice_notifier(&lapb_dev_notifier);
}

MODULE_AUTHOR("Jonathan Naylor <g4klx@g4klx.demon.co.uk>");
MODULE_DESCRIPTION("The X.25 Link Access Procedure B link layer protocol");
MODULE_LICENSE("GPL");

module_init(lapb_init);
module_exit(lapb_exit);