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

  /*
   *	X.25 Packet Layer release 002
   *
   *	This is ALPHA test software. This code may break your machine,
   *	randomly fail to work with new releases, misbehave and/or generally

   *	screw up. It might even work.

   *
   *	This code REQUIRES 2.1.15 or higher
   *

   *	History
   *	X.25 001	Jonathan Naylor	Started coding.
   *	X.25 002	Jonathan Naylor	New timer architecture.
   *					Centralised disconnection processing.
   */
  
  #include <linux/errno.h>
  #include <linux/jiffies.h>
  #include <linux/timer.h>
  #include <net/sock.h>

  #include <net/tcp_states.h>

  #include <net/x25.h>

  static void x25_heartbeat_expiry(struct timer_list *t);
  static void x25_timer_expiry(struct timer_list *t);

  
  void x25_init_timers(struct sock *sk)
  {
  	struct x25_sock *x25 = x25_sk(sk);

  	timer_setup(&x25->timer, x25_timer_expiry, 0);

  
  	/* initialized by sock_init_data */

  	sk->sk_timer.function = x25_heartbeat_expiry;

  }
  
  void x25_start_heartbeat(struct sock *sk)
  {
  	mod_timer(&sk->sk_timer, jiffies + 5 * HZ);
  }
  
  void x25_stop_heartbeat(struct sock *sk)
  {
  	del_timer(&sk->sk_timer);
  }
  
  void x25_start_t2timer(struct sock *sk)
  {
  	struct x25_sock *x25 = x25_sk(sk);
  
  	mod_timer(&x25->timer, jiffies + x25->t2);
  }
  
  void x25_start_t21timer(struct sock *sk)
  {
  	struct x25_sock *x25 = x25_sk(sk);
  
  	mod_timer(&x25->timer, jiffies + x25->t21);
  }
  
  void x25_start_t22timer(struct sock *sk)
  {
  	struct x25_sock *x25 = x25_sk(sk);
  
  	mod_timer(&x25->timer, jiffies + x25->t22);
  }
  
  void x25_start_t23timer(struct sock *sk)
  {
  	struct x25_sock *x25 = x25_sk(sk);
  
  	mod_timer(&x25->timer, jiffies + x25->t23);
  }
  
  void x25_stop_timer(struct sock *sk)
  {
  	del_timer(&x25_sk(sk)->timer);
  }
  
  unsigned long x25_display_timer(struct sock *sk)
  {
  	struct x25_sock *x25 = x25_sk(sk);
  
  	if (!timer_pending(&x25->timer))
  		return 0;
  
  	return x25->timer.expires - jiffies;
  }

  static void x25_heartbeat_expiry(struct timer_list *t)

  {

  	struct sock *sk = from_timer(sk, t, sk_timer);

  	bh_lock_sock(sk);
  	if (sock_owned_by_user(sk)) /* can currently only occur in state 3 */

  		goto restart_heartbeat;
  
  	switch (x25_sk(sk)->state) {
  
  		case X25_STATE_0:
  			/*
  			 * Magic here: If we listen() and a new link dies
  			 * before it is accepted() it isn't 'dead' so doesn't
  			 * get removed.
  			 */
  			if (sock_flag(sk, SOCK_DESTROY) ||
  			    (sk->sk_state == TCP_LISTEN &&
  			     sock_flag(sk, SOCK_DEAD))) {

  				bh_unlock_sock(sk);

  				x25_destroy_socket_from_timer(sk);

  				return;

  			}
  			break;
  
  		case X25_STATE_3:
  			/*
  			 * Check for the state of the receive buffer.
  			 */
  			x25_check_rbuf(sk);
  			break;
  	}
  restart_heartbeat:
  	x25_start_heartbeat(sk);

  	bh_unlock_sock(sk);
  }
  
  /*
   *	Timer has expired, it may have been T2, T21, T22, or T23. We can tell
   *	by the state machine state.
   */
  static inline void x25_do_timer_expiry(struct sock * sk)
  {
  	struct x25_sock *x25 = x25_sk(sk);
  
  	switch (x25->state) {
  
  		case X25_STATE_3:	/* T2 */
  			if (x25->condition & X25_COND_ACK_PENDING) {
  				x25->condition &= ~X25_COND_ACK_PENDING;
  				x25_enquiry_response(sk);
  			}
  			break;
  
  		case X25_STATE_1:	/* T21 */
  		case X25_STATE_4:	/* T22 */
  			x25_write_internal(sk, X25_CLEAR_REQUEST);
  			x25->state = X25_STATE_2;
  			x25_start_t23timer(sk);
  			break;
  
  		case X25_STATE_2:	/* T23 */
  			x25_disconnect(sk, ETIMEDOUT, 0, 0);
  			break;
  	}
  }

  static void x25_timer_expiry(struct timer_list *t)

  {

  	struct x25_sock *x25 = from_timer(x25, t, timer);
  	struct sock *sk = &x25->sk;

  
  	bh_lock_sock(sk);
  	if (sock_owned_by_user(sk)) { /* can currently only occur in state 3 */
  		if (x25_sk(sk)->state == X25_STATE_3)
  			x25_start_t2timer(sk);
  	} else
  		x25_do_timer_expiry(sk);
  	bh_unlock_sock(sk);
  }