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	setup_timer(&sk->sk_timer, dn_slow_timer, (unsigned long)sk);
40	sk_reset_timer(sk, &sk->sk_timer, jiffies + SLOW_INTERVAL);
41}
42
43void dn_stop_slow_timer(struct sock *sk)
44{
45	sk_stop_timer(sk, &sk->sk_timer);
46}
47
48static void dn_slow_timer(unsigned long arg)
49{
50	struct sock *sk = (struct sock *)arg;
51	struct dn_scp *scp = DN_SK(sk);
52
53	bh_lock_sock(sk);
54
55	if (sock_owned_by_user(sk)) {
56		sk_reset_timer(sk, &sk->sk_timer, jiffies + HZ / 10);
57		goto out;
58	}
59
60	/*
61	 * The persist timer is the standard slow timer used for retransmits
62	 * in both connection establishment and disconnection as well as
63	 * in the RUN state. The different states are catered for by changing
64	 * the function pointer in the socket. Setting the timer to a value
65	 * of zero turns it off. We allow the persist_fxn to turn the
66	 * timer off in a permant way by returning non-zero, so that
67	 * timer based routines may remove sockets. This is why we have a
68	 * sock_hold()/sock_put() around the timer to prevent the socket
69	 * going away in the middle.
70	 */
71	if (scp->persist && scp->persist_fxn) {
72		if (scp->persist <= SLOW_INTERVAL) {
73			scp->persist = 0;
74
75			if (scp->persist_fxn(sk))
76				goto out;
77		} else {
78			scp->persist -= SLOW_INTERVAL;
79		}
80	}
81
82	/*
83	 * Check for keepalive timeout. After the other timer 'cos if
84	 * the previous timer caused a retransmit, we don't need to
85	 * do this. scp->stamp is the last time that we sent a packet.
86	 * The keepalive function sends a link service packet to the
87	 * other end. If it remains unacknowledged, the standard
88	 * socket timers will eventually shut the socket down. Each
89	 * time we do this, scp->stamp will be updated, thus
90	 * we won't try and send another until scp->keepalive has passed
91	 * since the last successful transmission.
92	 */
93	if (scp->keepalive && scp->keepalive_fxn && (scp->state == DN_RUN)) {
94		if ((jiffies - scp->stamp) >= scp->keepalive)
95			scp->keepalive_fxn(sk);
96	}
97
98	sk_reset_timer(sk, &sk->sk_timer, jiffies + SLOW_INTERVAL);
99out:
100	bh_unlock_sock(sk);
101	sock_put(sk);
102}
103