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 <asm/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}
110