// SPDX-License-Identifier: GPL-2.0

  /*
   * DECnet       An implementation of the DECnet protocol suite for the LINUX
   *              operating system.  DECnet is implemented using the  BSD Socket
   *              interface as the means of communication with the user level.
   *
   *              DECnet Socket Timer Functions
   *
   * Author:      Steve Whitehouse <SteveW@ACM.org>
   *
   *
   * Changes:
   *       Steve Whitehouse      : Made keepalive timer part of the same
   *                               timer idea.
   *       Steve Whitehouse      : Added checks for sk->sock_readers
   *       David S. Miller       : New socket locking
   *       Steve Whitehouse      : Timer grabs socket ref.
   */
  #include <linux/net.h>
  #include <linux/socket.h>
  #include <linux/skbuff.h>
  #include <linux/netdevice.h>
  #include <linux/timer.h>
  #include <linux/spinlock.h>
  #include <net/sock.h>

  #include <linux/atomic.h>

  #include <linux/jiffies.h>

  #include <net/flow.h>
  #include <net/dn.h>
  
  /*
   * Slow timer is for everything else (n * 500mS)
   */
  
  #define SLOW_INTERVAL (HZ/2)

  static void dn_slow_timer(struct timer_list *t);

  
  void dn_start_slow_timer(struct sock *sk)
  {

  	timer_setup(&sk->sk_timer, dn_slow_timer, 0);

  	sk_reset_timer(sk, &sk->sk_timer, jiffies + SLOW_INTERVAL);

  }
  
  void dn_stop_slow_timer(struct sock *sk)
  {

  	sk_stop_timer(sk, &sk->sk_timer);

  }

  static void dn_slow_timer(struct timer_list *t)

  {

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

  	struct dn_scp *scp = DN_SK(sk);

  	bh_lock_sock(sk);
  
  	if (sock_owned_by_user(sk)) {

  		sk_reset_timer(sk, &sk->sk_timer, jiffies + HZ / 10);

  		goto out;
  	}
  
  	/*
  	 * The persist timer is the standard slow timer used for retransmits
  	 * in both connection establishment and disconnection as well as
  	 * in the RUN state. The different states are catered for by changing
  	 * the function pointer in the socket. Setting the timer to a value
  	 * of zero turns it off. We allow the persist_fxn to turn the
  	 * timer off in a permant way by returning non-zero, so that
  	 * timer based routines may remove sockets. This is why we have a
  	 * sock_hold()/sock_put() around the timer to prevent the socket
  	 * going away in the middle.
  	 */
  	if (scp->persist && scp->persist_fxn) {
  		if (scp->persist <= SLOW_INTERVAL) {
  			scp->persist = 0;
  
  			if (scp->persist_fxn(sk))
  				goto out;
  		} else {
  			scp->persist -= SLOW_INTERVAL;
  		}
  	}
  
  	/*
  	 * Check for keepalive timeout. After the other timer 'cos if
  	 * the previous timer caused a retransmit, we don't need to
  	 * do this. scp->stamp is the last time that we sent a packet.
  	 * The keepalive function sends a link service packet to the
  	 * other end. If it remains unacknowledged, the standard
  	 * socket timers will eventually shut the socket down. Each
  	 * time we do this, scp->stamp will be updated, thus
  	 * we won't try and send another until scp->keepalive has passed
  	 * since the last successful transmission.
  	 */
  	if (scp->keepalive && scp->keepalive_fxn && (scp->state == DN_RUN)) {

  		if (time_after_eq(jiffies, scp->stamp + scp->keepalive))

  			scp->keepalive_fxn(sk);
  	}

  	sk_reset_timer(sk, &sk->sk_timer, jiffies + SLOW_INTERVAL);

  out:
  	bh_unlock_sock(sk);
  	sock_put(sk);
  }