// 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 list_head *entry;
  	struct lapb_cb *lapb, *use = NULL;
  
  	list_for_each(entry, &lapb_list) {
  		lapb = list_entry(entry, struct lapb_cb, 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(sizeof(*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->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;

  	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);

  
  	lapb_stop_t1timer(lapb);
  	lapb_stop_t2timer(lapb);
  
  	lapb_clear_queues(lapb);
  
  	__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;
  
  	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;
  
  	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;
  
  	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:
  	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;
  
  	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
  ", lapb->dev);

  	lapb->state = LAPB_STATE_1;
  
  	rc = LAPB_OK;
  out_put:
  	lapb_put(lapb);
  out:
  	return rc;
  }

  EXPORT_SYMBOL(lapb_connect_request);

  
  int lapb_disconnect_request(struct net_device *dev)
  {
  	struct lapb_cb *lapb = lapb_devtostruct(dev);
  	int rc = LAPB_BADTOKEN;
  
  	if (!lapb)
  		goto out;
  
  	switch (lapb->state) {

  	case LAPB_STATE_0:
  		rc = LAPB_NOTCONNECTED;
  		goto out_put;

  	case LAPB_STATE_1:

  		lapb_dbg(1, "(%p) S1 TX DISC(1)
  ", lapb->dev);
  		lapb_dbg(0, "(%p) S1 -> S0
  ", lapb->dev);

  		lapb_send_control(lapb, LAPB_DISC, LAPB_POLLON, LAPB_COMMAND);
  		lapb->state = LAPB_STATE_0;
  		lapb_start_t1timer(lapb);
  		rc = LAPB_NOTCONNECTED;
  		goto out_put;
  
  	case LAPB_STATE_2:
  		rc = LAPB_OK;
  		goto out_put;

  	}
  
  	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)
  ", lapb->dev);
  	lapb_dbg(0, "(%p) S3 -> S2
  ", lapb->dev);

  
  	rc = LAPB_OK;
  out_put:
  	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;
  
  	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:
  	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) {
  		lapb_data_input(lapb, skb);
  		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;
  }

  static int __init lapb_init(void)
  {
  	return 0;
  }
  
  static void __exit lapb_exit(void)
  {
  	WARN_ON(!list_empty(&lapb_list));
  }
  
  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);