/*
   *	"LAPB via ethernet" driver release 001
   *
   *	This code REQUIRES 2.1.15 or higher/ NET3.038
   *
   *	This module:
   *		This module is free software; you can redistribute it and/or
   *		modify it under the terms of the GNU General Public License
   *		as published by the Free Software Foundation; either version
   *		2 of the License, or (at your option) any later version.
   *
   *	This is a "pseudo" network driver to allow LAPB over Ethernet.
   *
   *	This driver can use any ethernet destination address, and can be 
   *	limited to accept frames from one dedicated ethernet card only.
   *
   *	History
   *	LAPBETH 001	Jonathan Naylor		Cloned from bpqether.c
   *	2000-10-29	Henner Eisen	lapb_data_indication() return status.
   *	2000-11-14	Henner Eisen	dev_hold/put, NETDEV_GOING_DOWN support
   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #include <linux/errno.h>
  #include <linux/types.h>
  #include <linux/socket.h>
  #include <linux/in.h>

  #include <linux/slab.h>

  #include <linux/kernel.h>
  #include <linux/string.h>
  #include <linux/net.h>
  #include <linux/inet.h>
  #include <linux/netdevice.h>
  #include <linux/if_arp.h>
  #include <linux/skbuff.h>
  #include <net/sock.h>

  #include <asm/uaccess.h>
  #include <linux/mm.h>
  #include <linux/interrupt.h>
  #include <linux/notifier.h>
  #include <linux/stat.h>

  #include <linux/module.h>
  #include <linux/lapb.h>
  #include <linux/init.h>
  
  #include <net/x25device.h>

  static const u8 bcast_addr[6] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };

  
  /* If this number is made larger, check that the temporary string buffer
   * in lapbeth_new_device is large enough to store the probe device name.*/
  #define MAXLAPBDEV 100
  
  struct lapbethdev {
  	struct list_head	node;
  	struct net_device	*ethdev;	/* link to ethernet device */
  	struct net_device	*axdev;		/* lapbeth device (lapb#) */

  };

  static LIST_HEAD(lapbeth_devices);

  
  /* ------------------------------------------------------------------------ */
  
  /*
   *	Get the LAPB device for the ethernet device
   */
  static struct lapbethdev *lapbeth_get_x25_dev(struct net_device *dev)
  {
  	struct lapbethdev *lapbeth;
  
  	list_for_each_entry_rcu(lapbeth, &lapbeth_devices, node) {
  		if (lapbeth->ethdev == dev) 
  			return lapbeth;
  	}
  	return NULL;
  }
  
  static __inline__ int dev_is_ethdev(struct net_device *dev)
  {
  	return dev->type == ARPHRD_ETHER && strncmp(dev->name, "dummy", 5);
  }
  
  /* ------------------------------------------------------------------------ */
  
  /*
   *	Receive a LAPB frame via an ethernet interface.
   */

  static int lapbeth_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *ptype, struct net_device *orig_dev)

  {
  	int len, err;
  	struct lapbethdev *lapbeth;

  	if (dev_net(dev) != &init_net)

  		goto drop;

  	if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)
  		return NET_RX_DROP;
  
  	if (!pskb_may_pull(skb, 2))
  		goto drop;
  
  	rcu_read_lock();
  	lapbeth = lapbeth_get_x25_dev(dev);
  	if (!lapbeth)
  		goto drop_unlock;
  	if (!netif_running(lapbeth->axdev))
  		goto drop_unlock;

  	len = skb->data[0] + skb->data[1] * 256;

  	dev->stats.rx_packets++;
  	dev->stats.rx_bytes += len;

  
  	skb_pull(skb, 2);	/* Remove the length bytes */
  	skb_trim(skb, len);	/* Set the length of the data */
  
  	if ((err = lapb_data_received(lapbeth->axdev, skb)) != LAPB_OK) {
  		printk(KERN_DEBUG "lapbether: lapb_data_received err - %d
  ", err);
  		goto drop_unlock;
  	}
  out:
  	rcu_read_unlock();
  	return 0;
  drop_unlock:
  	kfree_skb(skb);
  	goto out;
  drop:
  	kfree_skb(skb);
  	return 0;
  }
  
  static int lapbeth_data_indication(struct net_device *dev, struct sk_buff *skb)
  {
  	unsigned char *ptr;
  
  	skb_push(skb, 1);
  
  	if (skb_cow(skb, 1))
  		return NET_RX_DROP;
  
  	ptr  = skb->data;

  	*ptr = X25_IFACE_DATA;

  
  	skb->protocol = x25_type_trans(skb, dev);

  	return netif_rx(skb);
  }
  
  /*
   *	Send a LAPB frame via an ethernet interface
   */

  static netdev_tx_t lapbeth_xmit(struct sk_buff *skb,
  				      struct net_device *dev)

  {

  	int err;

  
  	/*
  	 * Just to be *really* sure not to send anything if the interface
  	 * is down, the ethernet device may have gone.
  	 */

  	if (!netif_running(dev))

  		goto drop;

  
  	switch (skb->data[0]) {

  	case X25_IFACE_DATA:

  		break;

  	case X25_IFACE_CONNECT:

  		if ((err = lapb_connect_request(dev)) != LAPB_OK)

  			pr_err("lapb_connect_request error: %d
  ", err);

  		goto drop;

  	case X25_IFACE_DISCONNECT:

  		if ((err = lapb_disconnect_request(dev)) != LAPB_OK)

  			pr_err("lapb_disconnect_request err: %d
  ", err);

  		/* Fall thru */
  	default:

  		goto drop;

  	}
  
  	skb_pull(skb, 1);
  
  	if ((err = lapb_data_request(dev, skb)) != LAPB_OK) {

  		pr_err("lapb_data_request error - %d
  ", err);

  		goto drop;
  	}

  out:

  	return NETDEV_TX_OK;

  drop:
  	kfree_skb(skb);
  	goto out;
  }
  
  static void lapbeth_data_transmit(struct net_device *ndev, struct sk_buff *skb)
  {
  	struct lapbethdev *lapbeth = netdev_priv(ndev);
  	unsigned char *ptr;
  	struct net_device *dev;
  	int size = skb->len;
  
  	skb->protocol = htons(ETH_P_X25);
  
  	ptr = skb_push(skb, 2);
  
  	*ptr++ = size % 256;
  	*ptr++ = size / 256;

  	ndev->stats.tx_packets++;
  	ndev->stats.tx_bytes += size;

  
  	skb->dev = dev = lapbeth->ethdev;

  	dev_hard_header(skb, dev, ETH_P_DEC, bcast_addr, NULL, 0);

  
  	dev_queue_xmit(skb);
  }
  
  static void lapbeth_connected(struct net_device *dev, int reason)
  {
  	unsigned char *ptr;
  	struct sk_buff *skb = dev_alloc_skb(1);
  
  	if (!skb) {

  		pr_err("out of memory
  ");

  		return;
  	}
  
  	ptr  = skb_put(skb, 1);

  	*ptr = X25_IFACE_CONNECT;

  
  	skb->protocol = x25_type_trans(skb, dev);

  	netif_rx(skb);
  }
  
  static void lapbeth_disconnected(struct net_device *dev, int reason)
  {
  	unsigned char *ptr;
  	struct sk_buff *skb = dev_alloc_skb(1);
  
  	if (!skb) {

  		pr_err("out of memory
  ");

  		return;
  	}
  
  	ptr  = skb_put(skb, 1);

  	*ptr = X25_IFACE_DISCONNECT;

  
  	skb->protocol = x25_type_trans(skb, dev);

  	netif_rx(skb);
  }
  
  /*

   *	Set AX.25 callsign
   */
  static int lapbeth_set_mac_address(struct net_device *dev, void *addr)
  {
  	struct sockaddr *sa = addr;
  	memcpy(dev->dev_addr, sa->sa_data, dev->addr_len);
  	return 0;
  }

  static const struct lapb_register_struct lapbeth_callbacks = {

  	.connect_confirmation    = lapbeth_connected,
  	.connect_indication      = lapbeth_connected,
  	.disconnect_confirmation = lapbeth_disconnected,
  	.disconnect_indication   = lapbeth_disconnected,
  	.data_indication         = lapbeth_data_indication,
  	.data_transmit           = lapbeth_data_transmit,

  };
  
  /*
   * open/close a device
   */
  static int lapbeth_open(struct net_device *dev)
  {
  	int err;
  
  	if ((err = lapb_register(dev, &lapbeth_callbacks)) != LAPB_OK) {

  		pr_err("lapb_register error: %d
  ", err);

  		return -ENODEV;
  	}
  
  	netif_start_queue(dev);
  	return 0;
  }
  
  static int lapbeth_close(struct net_device *dev)
  {
  	int err;
  
  	netif_stop_queue(dev);
  
  	if ((err = lapb_unregister(dev)) != LAPB_OK)

  		pr_err("lapb_unregister error: %d
  ", err);

  
  	return 0;
  }
  
  /* ------------------------------------------------------------------------ */

  static const struct net_device_ops lapbeth_netdev_ops = {
  	.ndo_open	     = lapbeth_open,
  	.ndo_stop	     = lapbeth_close,
  	.ndo_start_xmit	     = lapbeth_xmit,
  	.ndo_set_mac_address = lapbeth_set_mac_address,
  };

  static void lapbeth_setup(struct net_device *dev)
  {

  	dev->netdev_ops	     = &lapbeth_netdev_ops;

  	dev->destructor	     = free_netdev;

  	dev->type            = ARPHRD_X25;
  	dev->hard_header_len = 3;
  	dev->mtu             = 1000;
  	dev->addr_len        = 0;

  }
  
  /*
   *	Setup a new device.
   */
  static int lapbeth_new_device(struct net_device *dev)
  {
  	struct net_device *ndev;
  	struct lapbethdev *lapbeth;
  	int rc = -ENOMEM;
  
  	ASSERT_RTNL();

  	ndev = alloc_netdev(sizeof(*lapbeth), "lapb%d", NET_NAME_UNKNOWN,
  			    lapbeth_setup);

  	if (!ndev)
  		goto out;
  
  	lapbeth = netdev_priv(ndev);
  	lapbeth->axdev = ndev;
  
  	dev_hold(dev);
  	lapbeth->ethdev = dev;

  	rc = -EIO;
  	if (register_netdevice(ndev))
  		goto fail;
  
  	list_add_rcu(&lapbeth->node, &lapbeth_devices);
  	rc = 0;
  out:
  	return rc;
  fail:
  	dev_put(dev);
  	free_netdev(ndev);
  	kfree(lapbeth);
  	goto out;
  }
  
  /*
   *	Free a lapb network device.
   */
  static void lapbeth_free_device(struct lapbethdev *lapbeth)
  {
  	dev_put(lapbeth->ethdev);
  	list_del_rcu(&lapbeth->node);
  	unregister_netdevice(lapbeth->axdev);
  }
  
  /*
   *	Handle device status changes.
   *
   * Called from notifier with RTNL held.
   */
  static int lapbeth_device_event(struct notifier_block *this,
  				unsigned long event, void *ptr)
  {
  	struct lapbethdev *lapbeth;

  	struct net_device *dev = netdev_notifier_info_to_dev(ptr);

  	if (dev_net(dev) != &init_net)

  		return NOTIFY_DONE;

  	if (!dev_is_ethdev(dev))
  		return NOTIFY_DONE;
  
  	switch (event) {
  	case NETDEV_UP:
  		/* New ethernet device -> new LAPB interface	 */
  		if (lapbeth_get_x25_dev(dev) == NULL)
  			lapbeth_new_device(dev);
  		break;
  	case NETDEV_DOWN:	
  		/* ethernet device closed -> close LAPB interface */
  		lapbeth = lapbeth_get_x25_dev(dev);
  		if (lapbeth) 
  			dev_close(lapbeth->axdev);
  		break;
  	case NETDEV_UNREGISTER:
  		/* ethernet device disappears -> remove LAPB interface */
  		lapbeth = lapbeth_get_x25_dev(dev);
  		if (lapbeth)
  			lapbeth_free_device(lapbeth);
  		break;
  	}
  
  	return NOTIFY_DONE;
  }
  
  /* ------------------------------------------------------------------------ */

  static struct packet_type lapbeth_packet_type __read_mostly = {

  	.type = cpu_to_be16(ETH_P_DEC),

  	.func = lapbeth_rcv,
  };
  
  static struct notifier_block lapbeth_dev_notifier = {
  	.notifier_call = lapbeth_device_event,
  };

  static const char banner[] __initconst =

  	KERN_INFO "LAPB Ethernet driver version 0.02
  ";

  
  static int __init lapbeth_init_driver(void)
  {
  	dev_add_pack(&lapbeth_packet_type);
  
  	register_netdevice_notifier(&lapbeth_dev_notifier);
  
  	printk(banner);
  
  	return 0;
  }
  module_init(lapbeth_init_driver);
  
  static void __exit lapbeth_cleanup_driver(void)
  {
  	struct lapbethdev *lapbeth;
  	struct list_head *entry, *tmp;
  
  	dev_remove_pack(&lapbeth_packet_type);
  	unregister_netdevice_notifier(&lapbeth_dev_notifier);
  
  	rtnl_lock();
  	list_for_each_safe(entry, tmp, &lapbeth_devices) {
  		lapbeth = list_entry(entry, struct lapbethdev, node);

  		dev_put(lapbeth->ethdev);

  		unregister_netdevice(lapbeth->axdev);
  	}
  	rtnl_unlock();
  }
  module_exit(lapbeth_cleanup_driver);
  
  MODULE_AUTHOR("Jonathan Naylor <g4klx@g4klx.demon.co.uk>");
  MODULE_DESCRIPTION("The unofficial LAPB over Ethernet driver");
  MODULE_LICENSE("GPL");