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

  /*

   *
   * Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk)
   * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
   * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
   * Copyright (C) Frederic Rible F1OAT (frible@teaser.fr)
   */
  #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/net.h>
  #include <net/ax25.h>
  #include <linux/inet.h>
  #include <linux/netdevice.h>
  #include <linux/skbuff.h>
  #include <net/sock.h>

  #include <net/tcp_states.h>

  #include <linux/uaccess.h>

  #include <linux/fcntl.h>
  #include <linux/mm.h>
  #include <linux/interrupt.h>
  
  void ax25_std_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:
  	case AX25_STATE_4:
  		/*
  		 * 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;
  				ax25_send_control(ax25, AX25_RR, AX25_POLLOFF, AX25_RESPONSE);
  				break;
  			}
  		}
  	}
  
  	if (sk)
  		bh_unlock_sock(sk);
  
  	ax25_start_heartbeat(ax25);
  }
  
  void ax25_std_t2timer_expiry(ax25_cb *ax25)
  {
  	if (ax25->condition & AX25_COND_ACK_PENDING) {
  		ax25->condition &= ~AX25_COND_ACK_PENDING;
  		ax25_std_timeout_response(ax25);
  	}
  }
  
  void ax25_std_t3timer_expiry(ax25_cb *ax25)
  {
  	ax25->n2count = 0;
  	ax25_std_transmit_enquiry(ax25);
  	ax25->state   = AX25_STATE_4;
  }
  
  void ax25_std_idletimer_expiry(ax25_cb *ax25)
  {
  	ax25_clear_queues(ax25);
  
  	ax25->n2count = 0;
  	ax25_send_control(ax25, AX25_DISC, AX25_POLLON, AX25_COMMAND);
  	ax25->state   = AX25_STATE_2;
  
  	ax25_calculate_t1(ax25);
  	ax25_start_t1timer(ax25);
  	ax25_stop_t2timer(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);
  	}
  }
  
  void ax25_std_t1timer_expiry(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_POLLON, AX25_COMMAND);
  			}
  		} else {
  			ax25->n2count++;
  			if (ax25->modulus == AX25_MODULUS)
  				ax25_send_control(ax25, AX25_SABM, AX25_POLLON, AX25_COMMAND);
  			else
  				ax25_send_control(ax25, AX25_SABME, AX25_POLLON, 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++;
  			ax25_send_control(ax25, AX25_DISC, AX25_POLLON, AX25_COMMAND);
  		}
  		break;
  
  	case AX25_STATE_3:
  		ax25->n2count = 1;
  		ax25_std_transmit_enquiry(ax25);
  		ax25->state   = AX25_STATE_4;
  		break;
  
  	case AX25_STATE_4:
  		if (ax25->n2count == ax25->n2) {
  			ax25_send_control(ax25, AX25_DM, AX25_POLLON, AX25_RESPONSE);
  			ax25_disconnect(ax25, ETIMEDOUT);
  			return;
  		} else {
  			ax25->n2count++;
  			ax25_std_transmit_enquiry(ax25);
  		}
  		break;
  	}
  
  	ax25_calculate_t1(ax25);
  	ax25_start_t1timer(ax25);
  }