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  
x25_init_timers(struct sock * sk)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  
x25_start_heartbeat(struct sock * sk)37  void x25_start_heartbeat(struct sock *sk)
38  {
39  	mod_timer(&sk->sk_timer, jiffies + 5 * HZ);
40  }
41  
x25_stop_heartbeat(struct sock * sk)42  void x25_stop_heartbeat(struct sock *sk)
43  {
44  	del_timer(&sk->sk_timer);
45  }
46  
x25_start_t2timer(struct sock * sk)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  
x25_start_t21timer(struct sock * sk)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  
x25_start_t22timer(struct sock * sk)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  
x25_start_t23timer(struct sock * sk)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  
x25_stop_timer(struct sock * sk)75  void x25_stop_timer(struct sock *sk)
76  {
77  	del_timer(&x25_sk(sk)->timer);
78  }
79  
x25_display_timer(struct sock * sk)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  
x25_heartbeat_expiry(struct timer_list * t)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   */
x25_do_timer_expiry(struct sock * sk)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  
x25_timer_expiry(struct timer_list * t)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