1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * DECnet An implementation of the DECnet protocol suite for the LINUX
4 * operating system. DECnet is implemented using the BSD Socket
5 * interface as the means of communication with the user level.
6 *
7 * DECnet Socket Timer Functions
8 *
9 * Author: Steve Whitehouse <SteveW@ACM.org>
10 *
11 *
12 * Changes:
13 * Steve Whitehouse : Made keepalive timer part of the same
14 * timer idea.
15 * Steve Whitehouse : Added checks for sk->sock_readers
16 * David S. Miller : New socket locking
17 * Steve Whitehouse : Timer grabs socket ref.
18 */
19 #include <linux/net.h>
20 #include <linux/socket.h>
21 #include <linux/skbuff.h>
22 #include <linux/netdevice.h>
23 #include <linux/timer.h>
24 #include <linux/spinlock.h>
25 #include <net/sock.h>
26 #include <linux/atomic.h>
27 #include <linux/jiffies.h>
28 #include <net/flow.h>
29 #include <net/dn.h>
30
31 /*
32 * Slow timer is for everything else (n * 500mS)
33 */
34
35 #define SLOW_INTERVAL (HZ/2)
36
37 static void dn_slow_timer(struct timer_list *t);
38
39 void dn_start_slow_timer(struct sock *sk)
40 {
41 timer_setup(&sk->sk_timer, dn_slow_timer, 0);
42 sk_reset_timer(sk, &sk->sk_timer, jiffies + SLOW_INTERVAL);
43 }
44
45 void dn_stop_slow_timer(struct sock *sk)
46 {
47 sk_stop_timer(sk, &sk->sk_timer);
48 }
49
50 static void dn_slow_timer(struct timer_list *t)
51 {
52 struct sock *sk = from_timer(sk, t, sk_timer);
53 struct dn_scp *scp = DN_SK(sk);
54
55 bh_lock_sock(sk);
56
57 if (sock_owned_by_user(sk)) {
58 sk_reset_timer(sk, &sk->sk_timer, jiffies + HZ / 10);
59 goto out;
60 }
61
62 /*
63 * The persist timer is the standard slow timer used for retransmits
64 * in both connection establishment and disconnection as well as
65 * in the RUN state. The different states are catered for by changing
66 * the function pointer in the socket. Setting the timer to a value
67 * of zero turns it off. We allow the persist_fxn to turn the
68 * timer off in a permant way by returning non-zero, so that
69 * timer based routines may remove sockets. This is why we have a
70 * sock_hold()/sock_put() around the timer to prevent the socket
71 * going away in the middle.
72 */
73 if (scp->persist && scp->persist_fxn) {
74 if (scp->persist <= SLOW_INTERVAL) {
75 scp->persist = 0;
76
77 if (scp->persist_fxn(sk))
78 goto out;
79 } else {
80 scp->persist -= SLOW_INTERVAL;
81 }
82 }
83
84 /*
85 * Check for keepalive timeout. After the other timer 'cos if
86 * the previous timer caused a retransmit, we don't need to
87 * do this. scp->stamp is the last time that we sent a packet.
88 * The keepalive function sends a link service packet to the
89 * other end. If it remains unacknowledged, the standard
90 * socket timers will eventually shut the socket down. Each
91 * time we do this, scp->stamp will be updated, thus
92 * we won't try and send another until scp->keepalive has passed
93 * since the last successful transmission.
94 */
95 if (scp->keepalive && scp->keepalive_fxn && (scp->state == DN_RUN)) {
96 if (time_after_eq(jiffies, scp->stamp + scp->keepalive))
97 scp->keepalive_fxn(sk);
98 }
99
100 sk_reset_timer(sk, &sk->sk_timer, jiffies + SLOW_INTERVAL);
101 out:
102 bh_unlock_sock(sk);
103 sock_put(sk);
104 }