1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * X.25 Packet Layer release 002
4 *
5 * This is ALPHA test software. This code may break your machine,
6 * randomly fail to work with new releases, misbehave and/or generally
7 * screw up. It might even work.
8 *
9 * This code REQUIRES 2.1.15 or higher
10 *
11 * History
12 * X.25 001 Jonathan Naylor Started coding.
13 * X.25 002 Jonathan Naylor New timer architecture.
14 * Centralised disconnection processing.
15 */
16
17 #include <linux/errno.h>
18 #include <linux/jiffies.h>
19 #include <linux/timer.h>
20 #include <net/sock.h>
21 #include <net/tcp_states.h>
22 #include <net/x25.h>
23
24 static void x25_heartbeat_expiry(struct timer_list *t);
25 static void x25_timer_expiry(struct timer_list *t);
26
27 void x25_init_timers(struct sock *sk)
28 {
29 struct x25_sock *x25 = x25_sk(sk);
30
31 timer_setup(&x25->timer, x25_timer_expiry, 0);
32
33 /* initialized by sock_init_data */
34 sk->sk_timer.function = x25_heartbeat_expiry;
35 }
36
37 void x25_start_heartbeat(struct sock *sk)
38 {
39 mod_timer(&sk->sk_timer, jiffies + 5 * HZ);
40 }
41
42 void x25_stop_heartbeat(struct sock *sk)
43 {
44 del_timer(&sk->sk_timer);
45 }
46
47 void x25_start_t2timer(struct sock *sk)
48 {
49 struct x25_sock *x25 = x25_sk(sk);
50
51 mod_timer(&x25->timer, jiffies + x25->t2);
52 }
53
54 void x25_start_t21timer(struct sock *sk)
55 {
56 struct x25_sock *x25 = x25_sk(sk);
57
58 mod_timer(&x25->timer, jiffies + x25->t21);
59 }
60
61 void x25_start_t22timer(struct sock *sk)
62 {
63 struct x25_sock *x25 = x25_sk(sk);
64
65 mod_timer(&x25->timer, jiffies + x25->t22);
66 }
67
68 void x25_start_t23timer(struct sock *sk)
69 {
70 struct x25_sock *x25 = x25_sk(sk);
71
72 mod_timer(&x25->timer, jiffies + x25->t23);
73 }
74
75 void x25_stop_timer(struct sock *sk)
76 {
77 del_timer(&x25_sk(sk)->timer);
78 }
79
80 unsigned long x25_display_timer(struct sock *sk)
81 {
82 struct x25_sock *x25 = x25_sk(sk);
83
84 if (!timer_pending(&x25->timer))
85 return 0;
86
87 return x25->timer.expires - jiffies;
88 }
89
90 static void x25_heartbeat_expiry(struct timer_list *t)
91 {
92 struct sock *sk = from_timer(sk, t, sk_timer);
93
94 bh_lock_sock(sk);
95 if (sock_owned_by_user(sk)) /* can currently only occur in state 3 */
96 goto restart_heartbeat;
97
98 switch (x25_sk(sk)->state) {
99
100 case X25_STATE_0:
101 /*
102 * Magic here: If we listen() and a new link dies
103 * before it is accepted() it isn't 'dead' so doesn't
104 * get removed.
105 */
106 if (sock_flag(sk, SOCK_DESTROY) ||
107 (sk->sk_state == TCP_LISTEN &&
108 sock_flag(sk, SOCK_DEAD))) {
109 bh_unlock_sock(sk);
110 x25_destroy_socket_from_timer(sk);
111 return;
112 }
113 break;
114
115 case X25_STATE_3:
116 /*
117 * Check for the state of the receive buffer.
118 */
119 x25_check_rbuf(sk);
120 break;
121 }
122 restart_heartbeat:
123 x25_start_heartbeat(sk);
124 bh_unlock_sock(sk);
125 }
126
127 /*
128 * Timer has expired, it may have been T2, T21, T22, or T23. We can tell
129 * by the state machine state.
130 */
131 static inline void x25_do_timer_expiry(struct sock * sk)
132 {
133 struct x25_sock *x25 = x25_sk(sk);
134
135 switch (x25->state) {
136
137 case X25_STATE_3: /* T2 */
138 if (x25->condition & X25_COND_ACK_PENDING) {
139 x25->condition &= ~X25_COND_ACK_PENDING;
140 x25_enquiry_response(sk);
141 }
142 break;
143
144 case X25_STATE_1: /* T21 */
145 case X25_STATE_4: /* T22 */
146 x25_write_internal(sk, X25_CLEAR_REQUEST);
147 x25->state = X25_STATE_2;
148 x25_start_t23timer(sk);
149 break;
150
151 case X25_STATE_2: /* T23 */
152 x25_disconnect(sk, ETIMEDOUT, 0, 0);
153 break;
154 }
155 }
156
157 static void x25_timer_expiry(struct timer_list *t)
158 {
159 struct x25_sock *x25 = from_timer(x25, t, timer);
160 struct sock *sk = &x25->sk;
161
162 bh_lock_sock(sk);
163 if (sock_owned_by_user(sk)) { /* can currently only occur in state 3 */
164 if (x25_sk(sk)->state == X25_STATE_3)
165 x25_start_t2timer(sk);
166 } else
167 x25_do_timer_expiry(sk);
168 bh_unlock_sock(sk);
169 }
170
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