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
35 static void dn_slow_timer(unsigned long arg);
36
37 void 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
46 void dn_stop_slow_timer(struct sock *sk)
47 {
48 del_timer(&sk->sk_timer);
49 }
50
51 static 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);
106 out:
107 bh_unlock_sock(sk);
108 sock_put(sk);
109 }
110
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