/*
   * This program 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.
   *
   * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
   * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
   */
  #include <linux/errno.h>
  #include <linux/types.h>
  #include <linux/socket.h>
  #include <linux/in.h>
  #include <linux/kernel.h>

  #include <linux/timer.h>
  #include <linux/string.h>
  #include <linux/sockios.h>
  #include <linux/spinlock.h>
  #include <linux/net.h>

  #include <linux/gfp.h>

  #include <net/ax25.h>
  #include <linux/inet.h>
  #include <linux/netdevice.h>
  #include <linux/skbuff.h>
  #include <net/sock.h>
  #include <asm/uaccess.h>

  #include <linux/fcntl.h>
  #include <linux/mm.h>
  #include <linux/interrupt.h>
  
  void ax25_ds_nr_error_recovery(ax25_cb *ax25)
  {
  	ax25_ds_establish_data_link(ax25);
  }
  
  /*
   *	dl1bke 960114: transmit I frames on DAMA poll
   */
  void ax25_ds_enquiry_response(ax25_cb *ax25)
  {
  	ax25_cb *ax25o;

  	/* Please note that neither DK4EG's nor DG2FEF's

  	 * DAMA spec mention the following behaviour as seen
  	 * with TheFirmware:
  	 *
  	 * 	DB0ACH->DL1BKE <RR C P R0> [DAMA]
  	 *	DL1BKE->DB0ACH <I NR=0 NS=0>
  	 *	DL1BKE-7->DB0PRA-6 DB0ACH <I C S3 R5>
  	 *	DL1BKE->DB0ACH <RR R F R0>
  	 *
  	 * The Flexnet DAMA Master implementation apparently
  	 * insists on the "proper" AX.25 behaviour:
  	 *
  	 * 	DB0ACH->DL1BKE <RR C P R0> [DAMA]
  	 *	DL1BKE->DB0ACH <RR R F R0>
  	 *	DL1BKE->DB0ACH <I NR=0 NS=0>
  	 *	DL1BKE-7->DB0PRA-6 DB0ACH <I C S3 R5>
  	 *
  	 * Flexnet refuses to send us *any* I frame if we send
  	 * a REJ in case AX25_COND_REJECT is set. It is superfluous in
  	 * this mode anyway (a RR or RNR invokes the retransmission).
  	 * Is this a Flexnet bug?
  	 */
  
  	ax25_std_enquiry_response(ax25);
  
  	if (!(ax25->condition & AX25_COND_PEER_RX_BUSY)) {
  		ax25_requeue_frames(ax25);
  		ax25_kick(ax25);
  	}
  
  	if (ax25->state == AX25_STATE_1 || ax25->state == AX25_STATE_2 || skb_peek(&ax25->ack_queue) != NULL)
  		ax25_ds_t1_timeout(ax25);
  	else
  		ax25->n2count = 0;
  
  	ax25_start_t3timer(ax25);
  	ax25_ds_set_timer(ax25->ax25_dev);

  	spin_lock(&ax25_list_lock);

  	ax25_for_each(ax25o, &ax25_list) {

  		if (ax25o == ax25)
  			continue;
  
  		if (ax25o->ax25_dev != ax25->ax25_dev)
  			continue;
  
  		if (ax25o->state == AX25_STATE_1 || ax25o->state == AX25_STATE_2) {
  			ax25_ds_t1_timeout(ax25o);
  			continue;
  		}
  
  		if (!(ax25o->condition & AX25_COND_PEER_RX_BUSY) && ax25o->state == AX25_STATE_3) {
  			ax25_requeue_frames(ax25o);
  			ax25_kick(ax25o);
  		}
  
  		if (ax25o->state == AX25_STATE_1 || ax25o->state == AX25_STATE_2 || skb_peek(&ax25o->ack_queue) != NULL)
  			ax25_ds_t1_timeout(ax25o);
  
  		/* do not start T3 for listening sockets (tnx DD8NE) */
  
  		if (ax25o->state != AX25_STATE_0)
  			ax25_start_t3timer(ax25o);
  	}

  	spin_unlock(&ax25_list_lock);

  }
  
  void ax25_ds_establish_data_link(ax25_cb *ax25)
  {
  	ax25->condition &= AX25_COND_DAMA_MODE;
  	ax25->n2count    = 0;
  	ax25_calculate_t1(ax25);
  	ax25_start_t1timer(ax25);
  	ax25_stop_t2timer(ax25);
  	ax25_start_t3timer(ax25);
  }
  
  /*
   *	:::FIXME:::
   *	This is a kludge. Not all drivers recognize kiss commands.
   *	We need a driver level  request to switch duplex mode, that does
   *	either SCC changing, PI config or KISS as required. Currently
   *	this request isn't reliable.
   */
  static void ax25_kiss_cmd(ax25_dev *ax25_dev, unsigned char cmd, unsigned char param)
  {
  	struct sk_buff *skb;
  	unsigned char *p;
  
  	if (ax25_dev->dev == NULL)
  		return;
  
  	if ((skb = alloc_skb(2, GFP_ATOMIC)) == NULL)
  		return;

  	skb_reset_network_header(skb);

  	p = skb_put(skb, 2);
  
  	*p++ = cmd;
  	*p++ = param;

  	skb->protocol = ax25_type_trans(skb, ax25_dev->dev);

  
  	dev_queue_xmit(skb);
  }
  
  /*
   *	A nasty problem arises if we count the number of DAMA connections
   *	wrong, especially when connections on the device already existed
   *	and our network node (or the sysop) decides to turn on DAMA Master
   *	mode. We thus flag the 'real' slave connections with
   *	ax25->dama_slave=1 and look on every disconnect if still slave
   *	connections exist.
   */
  static int ax25_check_dama_slave(ax25_dev *ax25_dev)
  {
  	ax25_cb *ax25;
  	int res = 0;

  	spin_lock(&ax25_list_lock);

  	ax25_for_each(ax25, &ax25_list)

  		if (ax25->ax25_dev == ax25_dev && (ax25->condition & AX25_COND_DAMA_MODE) && ax25->state > AX25_STATE_1) {
  			res = 1;
  			break;
  		}

  	spin_unlock(&ax25_list_lock);

  
  	return res;
  }
  
  static void ax25_dev_dama_on(ax25_dev *ax25_dev)
  {
  	if (ax25_dev == NULL)
  		return;
  
  	if (ax25_dev->dama.slave == 0)
  		ax25_kiss_cmd(ax25_dev, 5, 1);
  
  	ax25_dev->dama.slave = 1;
  	ax25_ds_set_timer(ax25_dev);
  }
  
  void ax25_dev_dama_off(ax25_dev *ax25_dev)
  {
  	if (ax25_dev == NULL)
  		return;
  
  	if (ax25_dev->dama.slave && !ax25_check_dama_slave(ax25_dev)) {
  		ax25_kiss_cmd(ax25_dev, 5, 0);
  		ax25_dev->dama.slave = 0;
  		ax25_ds_del_timer(ax25_dev);
  	}
  }
  
  void ax25_dama_on(ax25_cb *ax25)
  {
  	ax25_dev_dama_on(ax25->ax25_dev);
  	ax25->condition |= AX25_COND_DAMA_MODE;
  }
  
  void ax25_dama_off(ax25_cb *ax25)
  {
  	ax25->condition &= ~AX25_COND_DAMA_MODE;
  	ax25_dev_dama_off(ax25->ax25_dev);
  }