1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 *	LAPB release 002
4 *
5 *	This code REQUIRES 2.1.15 or higher/ NET3.038
6 *
7 *	History
8 *	LAPB 001	Jonathan Naylor	Started Coding
9 *	LAPB 002	Jonathan Naylor	New timer architecture.
10 */
11
12#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13
14#include <linux/errno.h>
15#include <linux/types.h>
16#include <linux/socket.h>
17#include <linux/in.h>
18#include <linux/kernel.h>
19#include <linux/jiffies.h>
20#include <linux/timer.h>
21#include <linux/string.h>
22#include <linux/sockios.h>
23#include <linux/net.h>
24#include <linux/inet.h>
25#include <linux/skbuff.h>
26#include <net/sock.h>
27#include <linux/uaccess.h>
28#include <linux/fcntl.h>
29#include <linux/mm.h>
30#include <linux/interrupt.h>
31#include <net/lapb.h>
32
33static void lapb_t1timer_expiry(struct timer_list *);
34static void lapb_t2timer_expiry(struct timer_list *);
35
36void lapb_start_t1timer(struct lapb_cb *lapb)
37{
38	del_timer(&lapb->t1timer);
39
40	lapb->t1timer.function = lapb_t1timer_expiry;
41	lapb->t1timer.expires  = jiffies + lapb->t1;
42
43	lapb->t1timer_running = true;
44	add_timer(&lapb->t1timer);
45}
46
47void lapb_start_t2timer(struct lapb_cb *lapb)
48{
49	del_timer(&lapb->t2timer);
50
51	lapb->t2timer.function = lapb_t2timer_expiry;
52	lapb->t2timer.expires  = jiffies + lapb->t2;
53
54	lapb->t2timer_running = true;
55	add_timer(&lapb->t2timer);
56}
57
58void lapb_stop_t1timer(struct lapb_cb *lapb)
59{
60	lapb->t1timer_running = false;
61	del_timer(&lapb->t1timer);
62}
63
64void lapb_stop_t2timer(struct lapb_cb *lapb)
65{
66	lapb->t2timer_running = false;
67	del_timer(&lapb->t2timer);
68}
69
70int lapb_t1timer_running(struct lapb_cb *lapb)
71{
72	return lapb->t1timer_running;
73}
74
75static void lapb_t2timer_expiry(struct timer_list *t)
76{
77	struct lapb_cb *lapb = from_timer(lapb, t, t2timer);
78
79	spin_lock_bh(&lapb->lock);
80	if (timer_pending(&lapb->t2timer)) /* A new timer has been set up */
81		goto out;
82	if (!lapb->t2timer_running) /* The timer has been stopped */
83		goto out;
84
85	if (lapb->condition & LAPB_ACK_PENDING_CONDITION) {
86		lapb->condition &= ~LAPB_ACK_PENDING_CONDITION;
87		lapb_timeout_response(lapb);
88	}
89	lapb->t2timer_running = false;
90
91out:
92	spin_unlock_bh(&lapb->lock);
93}
94
95static void lapb_t1timer_expiry(struct timer_list *t)
96{
97	struct lapb_cb *lapb = from_timer(lapb, t, t1timer);
98
99	spin_lock_bh(&lapb->lock);
100	if (timer_pending(&lapb->t1timer)) /* A new timer has been set up */
101		goto out;
102	if (!lapb->t1timer_running) /* The timer has been stopped */
103		goto out;
104
105	switch (lapb->state) {
106
107		/*
108		 *	If we are a DCE, send DM up to N2 times, then switch to
109		 *	STATE_1 and send SABM(E).
110		 */
111		case LAPB_STATE_0:
112			if (lapb->mode & LAPB_DCE &&
113			    lapb->n2count != lapb->n2) {
114				lapb->n2count++;
115				lapb_send_control(lapb, LAPB_DM, LAPB_POLLOFF, LAPB_RESPONSE);
116			} else {
117				lapb->state = LAPB_STATE_1;
118				lapb_establish_data_link(lapb);
119			}
120			break;
121
122		/*
123		 *	Awaiting connection state, send SABM(E), up to N2 times.
124		 */
125		case LAPB_STATE_1:
126			if (lapb->n2count == lapb->n2) {
127				lapb_clear_queues(lapb);
128				lapb->state = LAPB_STATE_0;
129				lapb_disconnect_indication(lapb, LAPB_TIMEDOUT);
130				lapb_dbg(0, "(%p) S1 -> S0\n", lapb->dev);
131				lapb->t1timer_running = false;
132				goto out;
133			} else {
134				lapb->n2count++;
135				if (lapb->mode & LAPB_EXTENDED) {
136					lapb_dbg(1, "(%p) S1 TX SABME(1)\n",
137						 lapb->dev);
138					lapb_send_control(lapb, LAPB_SABME, LAPB_POLLON, LAPB_COMMAND);
139				} else {
140					lapb_dbg(1, "(%p) S1 TX SABM(1)\n",
141						 lapb->dev);
142					lapb_send_control(lapb, LAPB_SABM, LAPB_POLLON, LAPB_COMMAND);
143				}
144			}
145			break;
146
147		/*
148		 *	Awaiting disconnection state, send DISC, up to N2 times.
149		 */
150		case LAPB_STATE_2:
151			if (lapb->n2count == lapb->n2) {
152				lapb_clear_queues(lapb);
153				lapb->state = LAPB_STATE_0;
154				lapb_disconnect_confirmation(lapb, LAPB_TIMEDOUT);
155				lapb_dbg(0, "(%p) S2 -> S0\n", lapb->dev);
156				lapb->t1timer_running = false;
157				goto out;
158			} else {
159				lapb->n2count++;
160				lapb_dbg(1, "(%p) S2 TX DISC(1)\n", lapb->dev);
161				lapb_send_control(lapb, LAPB_DISC, LAPB_POLLON, LAPB_COMMAND);
162			}
163			break;
164
165		/*
166		 *	Data transfer state, restransmit I frames, up to N2 times.
167		 */
168		case LAPB_STATE_3:
169			if (lapb->n2count == lapb->n2) {
170				lapb_clear_queues(lapb);
171				lapb->state = LAPB_STATE_0;
172				lapb_stop_t2timer(lapb);
173				lapb_disconnect_indication(lapb, LAPB_TIMEDOUT);
174				lapb_dbg(0, "(%p) S3 -> S0\n", lapb->dev);
175				lapb->t1timer_running = false;
176				goto out;
177			} else {
178				lapb->n2count++;
179				lapb_requeue_frames(lapb);
180				lapb_kick(lapb);
181			}
182			break;
183
184		/*
185		 *	Frame reject state, restransmit FRMR frames, up to N2 times.
186		 */
187		case LAPB_STATE_4:
188			if (lapb->n2count == lapb->n2) {
189				lapb_clear_queues(lapb);
190				lapb->state = LAPB_STATE_0;
191				lapb_disconnect_indication(lapb, LAPB_TIMEDOUT);
192				lapb_dbg(0, "(%p) S4 -> S0\n", lapb->dev);
193				lapb->t1timer_running = false;
194				goto out;
195			} else {
196				lapb->n2count++;
197				lapb_transmit_frmr(lapb);
198			}
199			break;
200	}
201
202	lapb_start_t1timer(lapb);
203
204out:
205	spin_unlock_bh(&lapb->lock);
206}
207