1/*
  2 * DECnet       An implementation of the DECnet protocol suite for the LINUX
  3 *              operating system.  DECnet is implemented using the  BSD Socket
  4 *              interface as the means of communication with the user level.
  5 *
  6 *              DECnet Socket Timer Functions
  7 *
  8 * Author:      Steve Whitehouse <SteveW@ACM.org>
  9 *
 10 *
 11 * Changes:
 12 *       Steve Whitehouse      : Made keepalive timer part of the same
 13 *                               timer idea.
 14 *       Steve Whitehouse      : Added checks for sk->sock_readers
 15 *       David S. Miller       : New socket locking
 16 *       Steve Whitehouse      : Timer grabs socket ref.
 17 */
 18#include <linux/net.h>
 19#include <linux/socket.h>
 20#include <linux/skbuff.h>
 21#include <linux/netdevice.h>
 22#include <linux/timer.h>
 23#include <linux/spinlock.h>
 24#include <net/sock.h>
 25#include <linux/atomic.h>
 26#include <net/flow.h>
 27#include <net/dn.h>
 28
 29/*
 30 * Slow timer is for everything else (n * 500mS)
 31 */
 32
 33#define SLOW_INTERVAL (HZ/2)
 34
 35static void dn_slow_timer(unsigned long arg);
 36
 37void dn_start_slow_timer(struct sock *sk)
 38{
 39	sk->sk_timer.expires	= jiffies + SLOW_INTERVAL;
 40	sk->sk_timer.function	= dn_slow_timer;
 41	sk->sk_timer.data	= (unsigned long)sk;
 42
 43	add_timer(&sk->sk_timer);
 44}
 45
 46void dn_stop_slow_timer(struct sock *sk)
 47{
 48	del_timer(&sk->sk_timer);
 49}
 50
 51static void dn_slow_timer(unsigned long arg)
 52{
 53	struct sock *sk = (struct sock *)arg;
 54	struct dn_scp *scp = DN_SK(sk);
 55
 56	sock_hold(sk);
 57	bh_lock_sock(sk);
 58
 59	if (sock_owned_by_user(sk)) {
 60		sk->sk_timer.expires = jiffies + HZ / 10;
 61		add_timer(&sk->sk_timer);
 62		goto out;
 63	}
 64
 65	/*
 66	 * The persist timer is the standard slow timer used for retransmits
 67	 * in both connection establishment and disconnection as well as
 68	 * in the RUN state. The different states are catered for by changing
 69	 * the function pointer in the socket. Setting the timer to a value
 70	 * of zero turns it off. We allow the persist_fxn to turn the
 71	 * timer off in a permant way by returning non-zero, so that
 72	 * timer based routines may remove sockets. This is why we have a
 73	 * sock_hold()/sock_put() around the timer to prevent the socket
 74	 * going away in the middle.
 75	 */
 76	if (scp->persist && scp->persist_fxn) {
 77		if (scp->persist <= SLOW_INTERVAL) {
 78			scp->persist = 0;
 79
 80			if (scp->persist_fxn(sk))
 81				goto out;
 82		} else {
 83			scp->persist -= SLOW_INTERVAL;
 84		}
 85	}
 86
 87	/*
 88	 * Check for keepalive timeout. After the other timer 'cos if
 89	 * the previous timer caused a retransmit, we don't need to
 90	 * do this. scp->stamp is the last time that we sent a packet.
 91	 * The keepalive function sends a link service packet to the
 92	 * other end. If it remains unacknowledged, the standard
 93	 * socket timers will eventually shut the socket down. Each
 94	 * time we do this, scp->stamp will be updated, thus
 95	 * we won't try and send another until scp->keepalive has passed
 96	 * since the last successful transmission.
 97	 */
 98	if (scp->keepalive && scp->keepalive_fxn && (scp->state == DN_RUN)) {
 99		if ((jiffies - scp->stamp) >= scp->keepalive)
100			scp->keepalive_fxn(sk);
101	}
102
103	sk->sk_timer.expires = jiffies + SLOW_INTERVAL;
104
105	add_timer(&sk->sk_timer);
106out:
107	bh_unlock_sock(sk);
108	sock_put(sk);
109}