// SPDX-License-Identifier: GPL-2.0-or-later

  /*

   *
   * 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/spinlock.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 <net/tcp_states.h>

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

  #include <linux/uaccess.h>

  #include <linux/fcntl.h>
  #include <linux/mm.h>
  #include <linux/interrupt.h>

  static void ax25_ds_timeout(struct timer_list *);

  
  /*
   *	Add DAMA slave timeout timer to timer list.
   *	Unlike the connection based timers the timeout function gets
   *	triggered every second. Please note that NET_AX25_DAMA_SLAVE_TIMEOUT
   *	(aka /proc/sys/net/ax25/{dev}/dama_slave_timeout) is still in
   *	1/10th of a second.
   */

  void ax25_ds_setup_timer(ax25_dev *ax25_dev)

  {

  	timer_setup(&ax25_dev->dama.slave_timer, ax25_ds_timeout, 0);

  }
  
  void ax25_ds_del_timer(ax25_dev *ax25_dev)
  {
  	if (ax25_dev)
  		del_timer(&ax25_dev->dama.slave_timer);
  }
  
  void ax25_ds_set_timer(ax25_dev *ax25_dev)
  {
  	if (ax25_dev == NULL)		/* paranoia */
  		return;

  	ax25_dev->dama.slave_timeout =
  		msecs_to_jiffies(ax25_dev->values[AX25_VALUES_DS_TIMEOUT]) / 10;

  	mod_timer(&ax25_dev->dama.slave_timer, jiffies + HZ);

  }
  
  /*
   *	DAMA Slave Timeout
   *	Silently discard all (slave) connections in case our master forgot us...
   */

  static void ax25_ds_timeout(struct timer_list *t)

  {

  	ax25_dev *ax25_dev = from_timer(ax25_dev, t, dama.slave_timer);

  	ax25_cb *ax25;

  
  	if (ax25_dev == NULL || !ax25_dev->dama.slave)
  		return;			/* Yikes! */
  
  	if (!ax25_dev->dama.slave_timeout || --ax25_dev->dama.slave_timeout) {
  		ax25_ds_set_timer(ax25_dev);
  		return;
  	}

  	spin_lock(&ax25_list_lock);

  	ax25_for_each(ax25, &ax25_list) {

  		if (ax25->ax25_dev != ax25_dev || !(ax25->condition & AX25_COND_DAMA_MODE))
  			continue;
  
  		ax25_send_control(ax25, AX25_DISC, AX25_POLLON, AX25_COMMAND);
  		ax25_disconnect(ax25, ETIMEDOUT);
  	}

  	spin_unlock(&ax25_list_lock);

  
  	ax25_dev_dama_off(ax25_dev);
  }
  
  void ax25_ds_heartbeat_expiry(ax25_cb *ax25)
  {
  	struct sock *sk=ax25->sk;
  
  	if (sk)
  		bh_lock_sock(sk);
  
  	switch (ax25->state) {
  
  	case AX25_STATE_0:

  	case AX25_STATE_2:

  		/* Magic here: If we listen() and a new link dies before it
  		   is accepted() it isn't 'dead' so doesn't get removed. */
  		if (!sk || sock_flag(sk, SOCK_DESTROY) ||
  		    (sk->sk_state == TCP_LISTEN &&
  		     sock_flag(sk, SOCK_DEAD))) {
  			if (sk) {
  				sock_hold(sk);
  				ax25_destroy_socket(ax25);

  				bh_unlock_sock(sk);

  				/* Ungrab socket and destroy it */

  				sock_put(sk);

  			} else
  				ax25_destroy_socket(ax25);
  			return;
  		}
  		break;
  
  	case AX25_STATE_3:
  		/*
  		 * Check the state of the receive buffer.
  		 */
  		if (sk != NULL) {
  			if (atomic_read(&sk->sk_rmem_alloc) <

  			    (sk->sk_rcvbuf >> 1) &&

  			    (ax25->condition & AX25_COND_OWN_RX_BUSY)) {
  				ax25->condition &= ~AX25_COND_OWN_RX_BUSY;
  				ax25->condition &= ~AX25_COND_ACK_PENDING;
  				break;
  			}
  		}
  		break;
  	}
  
  	if (sk)
  		bh_unlock_sock(sk);
  
  	ax25_start_heartbeat(ax25);
  }
  
  /* dl1bke 960114: T3 works much like the IDLE timeout, but
   *                gets reloaded with every frame for this
   *		  connection.
   */
  void ax25_ds_t3timer_expiry(ax25_cb *ax25)
  {
  	ax25_send_control(ax25, AX25_DISC, AX25_POLLON, AX25_COMMAND);
  	ax25_dama_off(ax25);
  	ax25_disconnect(ax25, ETIMEDOUT);
  }
  
  /* dl1bke 960228: close the connection when IDLE expires.
   *		  unlike T3 this timer gets reloaded only on
   *		  I frames.
   */
  void ax25_ds_idletimer_expiry(ax25_cb *ax25)
  {
  	ax25_clear_queues(ax25);
  
  	ax25->n2count = 0;
  	ax25->state = AX25_STATE_2;
  
  	ax25_calculate_t1(ax25);
  	ax25_start_t1timer(ax25);
  	ax25_stop_t3timer(ax25);
  
  	if (ax25->sk != NULL) {
  		bh_lock_sock(ax25->sk);
  		ax25->sk->sk_state     = TCP_CLOSE;
  		ax25->sk->sk_err       = 0;
  		ax25->sk->sk_shutdown |= SEND_SHUTDOWN;
  		if (!sock_flag(ax25->sk, SOCK_DEAD)) {
  			ax25->sk->sk_state_change(ax25->sk);
  			sock_set_flag(ax25->sk, SOCK_DEAD);
  		}
  		bh_unlock_sock(ax25->sk);
  	}
  }
  
  /* dl1bke 960114: The DAMA protocol requires to send data and SABM/DISC
   *                within the poll of any connected channel. Remember
   *                that we are not allowed to send anything unless we
   *                get polled by the Master.
   *
   *                Thus we'll have to do parts of our T1 handling in
   *                ax25_enquiry_response().
   */
  void ax25_ds_t1_timeout(ax25_cb *ax25)
  {
  	switch (ax25->state) {
  	case AX25_STATE_1:
  		if (ax25->n2count == ax25->n2) {
  			if (ax25->modulus == AX25_MODULUS) {
  				ax25_disconnect(ax25, ETIMEDOUT);
  				return;
  			} else {
  				ax25->modulus = AX25_MODULUS;
  				ax25->window  = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
  				ax25->n2count = 0;
  				ax25_send_control(ax25, AX25_SABM, AX25_POLLOFF, AX25_COMMAND);
  			}
  		} else {
  			ax25->n2count++;
  			if (ax25->modulus == AX25_MODULUS)
  				ax25_send_control(ax25, AX25_SABM, AX25_POLLOFF, AX25_COMMAND);
  			else
  				ax25_send_control(ax25, AX25_SABME, AX25_POLLOFF, AX25_COMMAND);
  		}
  		break;
  
  	case AX25_STATE_2:
  		if (ax25->n2count == ax25->n2) {
  			ax25_send_control(ax25, AX25_DISC, AX25_POLLON, AX25_COMMAND);

  			if (!sock_flag(ax25->sk, SOCK_DESTROY))
  				ax25_disconnect(ax25, ETIMEDOUT);

  			return;
  		} else {
  			ax25->n2count++;
  		}
  		break;
  
  	case AX25_STATE_3:
  		if (ax25->n2count == ax25->n2) {
  			ax25_send_control(ax25, AX25_DM, AX25_POLLON, AX25_RESPONSE);
  			ax25_disconnect(ax25, ETIMEDOUT);
  			return;
  		} else {
  			ax25->n2count++;
  		}
  		break;
  	}
  
  	ax25_calculate_t1(ax25);
  	ax25_start_t1timer(ax25);
  }