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 <linux/jiffies.h>
27#include <net/flow.h>
28#include <net/dn.h>
29
30/*
31 * Slow timer is for everything else (n * 500mS)
32 */
33
34#define SLOW_INTERVAL (HZ/2)
35
36static void dn_slow_timer(unsigned long arg);
37
38void dn_start_slow_timer(struct sock *sk)
39{
40	setup_timer(&sk->sk_timer, dn_slow_timer, (unsigned long)sk);
41	sk_reset_timer(sk, &sk->sk_timer, jiffies + SLOW_INTERVAL);
42}
43
44void dn_stop_slow_timer(struct sock *sk)
45{
46	sk_stop_timer(sk, &sk->sk_timer);
47}
48
49static void dn_slow_timer(unsigned long arg)
50{
51	struct sock *sk = (struct sock *)arg;
52	struct dn_scp *scp = DN_SK(sk);
53
54	bh_lock_sock(sk);
55
56	if (sock_owned_by_user(sk)) {
57		sk_reset_timer(sk, &sk->sk_timer, jiffies + HZ / 10);
58		goto out;
59	}
60
61	/*
62	 * The persist timer is the standard slow timer used for retransmits
63	 * in both connection establishment and disconnection as well as
64	 * in the RUN state. The different states are catered for by changing
65	 * the function pointer in the socket. Setting the timer to a value
66	 * of zero turns it off. We allow the persist_fxn to turn the
67	 * timer off in a permant way by returning non-zero, so that
68	 * timer based routines may remove sockets. This is why we have a
69	 * sock_hold()/sock_put() around the timer to prevent the socket
70	 * going away in the middle.
71	 */
72	if (scp->persist && scp->persist_fxn) {
73		if (scp->persist <= SLOW_INTERVAL) {
74			scp->persist = 0;
75
76			if (scp->persist_fxn(sk))
77				goto out;
78		} else {
79			scp->persist -= SLOW_INTERVAL;
80		}
81	}
82
83	/*
84	 * Check for keepalive timeout. After the other timer 'cos if
85	 * the previous timer caused a retransmit, we don't need to
86	 * do this. scp->stamp is the last time that we sent a packet.
87	 * The keepalive function sends a link service packet to the
88	 * other end. If it remains unacknowledged, the standard
89	 * socket timers will eventually shut the socket down. Each
90	 * time we do this, scp->stamp will be updated, thus
91	 * we won't try and send another until scp->keepalive has passed
92	 * since the last successful transmission.
93	 */
94	if (scp->keepalive && scp->keepalive_fxn && (scp->state == DN_RUN)) {
95		if (time_after_eq(jiffies, scp->stamp + scp->keepalive))
96			scp->keepalive_fxn(sk);
97	}
98
99	sk_reset_timer(sk, &sk->sk_timer, jiffies + SLOW_INTERVAL);
100out:
101	bh_unlock_sock(sk);
102	sock_put(sk);
103}
104