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/timer.h>
20 #include <linux/string.h>
21 #include <linux/sockios.h>
22 #include <linux/net.h>
23 #include <linux/inet.h>
24 #include <linux/skbuff.h>
25 #include <linux/slab.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
33 /*
34 * This procedure is passed a buffer descriptor for an iframe. It builds
35 * the rest of the control part of the frame and then writes it out.
36 */
lapb_send_iframe(struct lapb_cb * lapb,struct sk_buff * skb,int poll_bit)37 static void lapb_send_iframe(struct lapb_cb *lapb, struct sk_buff *skb, int poll_bit)
38 {
39 unsigned char *frame;
40
41 if (!skb)
42 return;
43
44 if (lapb->mode & LAPB_EXTENDED) {
45 frame = skb_push(skb, 2);
46
47 frame[0] = LAPB_I;
48 frame[0] |= lapb->vs << 1;
49 frame[1] = poll_bit ? LAPB_EPF : 0;
50 frame[1] |= lapb->vr << 1;
51 } else {
52 frame = skb_push(skb, 1);
53
54 *frame = LAPB_I;
55 *frame |= poll_bit ? LAPB_SPF : 0;
56 *frame |= lapb->vr << 5;
57 *frame |= lapb->vs << 1;
58 }
59
60 lapb_dbg(1, "(%p) S%d TX I(%d) S%d R%d\n",
61 lapb->dev, lapb->state, poll_bit, lapb->vs, lapb->vr);
62
63 lapb_transmit_buffer(lapb, skb, LAPB_COMMAND);
64 }
65
lapb_kick(struct lapb_cb * lapb)66 void lapb_kick(struct lapb_cb *lapb)
67 {
68 struct sk_buff *skb, *skbn;
69 unsigned short modulus, start, end;
70
71 modulus = (lapb->mode & LAPB_EXTENDED) ? LAPB_EMODULUS : LAPB_SMODULUS;
72 start = !skb_peek(&lapb->ack_queue) ? lapb->va : lapb->vs;
73 end = (lapb->va + lapb->window) % modulus;
74
75 if (!(lapb->condition & LAPB_PEER_RX_BUSY_CONDITION) &&
76 start != end && skb_peek(&lapb->write_queue)) {
77 lapb->vs = start;
78
79 /*
80 * Dequeue the frame and copy it.
81 */
82 skb = skb_dequeue(&lapb->write_queue);
83
84 do {
85 skbn = skb_copy(skb, GFP_ATOMIC);
86 if (!skbn) {
87 skb_queue_head(&lapb->write_queue, skb);
88 break;
89 }
90
91 if (skb->sk)
92 skb_set_owner_w(skbn, skb->sk);
93
94 /*
95 * Transmit the frame copy.
96 */
97 lapb_send_iframe(lapb, skbn, LAPB_POLLOFF);
98
99 lapb->vs = (lapb->vs + 1) % modulus;
100
101 /*
102 * Requeue the original data frame.
103 */
104 skb_queue_tail(&lapb->ack_queue, skb);
105
106 } while (lapb->vs != end && (skb = skb_dequeue(&lapb->write_queue)) != NULL);
107
108 lapb->condition &= ~LAPB_ACK_PENDING_CONDITION;
109
110 if (!lapb_t1timer_running(lapb))
111 lapb_start_t1timer(lapb);
112 }
113 }
114
lapb_transmit_buffer(struct lapb_cb * lapb,struct sk_buff * skb,int type)115 void lapb_transmit_buffer(struct lapb_cb *lapb, struct sk_buff *skb, int type)
116 {
117 unsigned char *ptr;
118
119 ptr = skb_push(skb, 1);
120
121 if (lapb->mode & LAPB_MLP) {
122 if (lapb->mode & LAPB_DCE) {
123 if (type == LAPB_COMMAND)
124 *ptr = LAPB_ADDR_C;
125 if (type == LAPB_RESPONSE)
126 *ptr = LAPB_ADDR_D;
127 } else {
128 if (type == LAPB_COMMAND)
129 *ptr = LAPB_ADDR_D;
130 if (type == LAPB_RESPONSE)
131 *ptr = LAPB_ADDR_C;
132 }
133 } else {
134 if (lapb->mode & LAPB_DCE) {
135 if (type == LAPB_COMMAND)
136 *ptr = LAPB_ADDR_A;
137 if (type == LAPB_RESPONSE)
138 *ptr = LAPB_ADDR_B;
139 } else {
140 if (type == LAPB_COMMAND)
141 *ptr = LAPB_ADDR_B;
142 if (type == LAPB_RESPONSE)
143 *ptr = LAPB_ADDR_A;
144 }
145 }
146
147 lapb_dbg(2, "(%p) S%d TX %3ph\n", lapb->dev, lapb->state, skb->data);
148
149 if (!lapb_data_transmit(lapb, skb))
150 kfree_skb(skb);
151 }
152
lapb_establish_data_link(struct lapb_cb * lapb)153 void lapb_establish_data_link(struct lapb_cb *lapb)
154 {
155 lapb->condition = 0x00;
156 lapb->n2count = 0;
157
158 if (lapb->mode & LAPB_EXTENDED) {
159 lapb_dbg(1, "(%p) S%d TX SABME(1)\n", lapb->dev, lapb->state);
160 lapb_send_control(lapb, LAPB_SABME, LAPB_POLLON, LAPB_COMMAND);
161 } else {
162 lapb_dbg(1, "(%p) S%d TX SABM(1)\n", lapb->dev, lapb->state);
163 lapb_send_control(lapb, LAPB_SABM, LAPB_POLLON, LAPB_COMMAND);
164 }
165
166 lapb_start_t1timer(lapb);
167 lapb_stop_t2timer(lapb);
168 }
169
lapb_enquiry_response(struct lapb_cb * lapb)170 void lapb_enquiry_response(struct lapb_cb *lapb)
171 {
172 lapb_dbg(1, "(%p) S%d TX RR(1) R%d\n",
173 lapb->dev, lapb->state, lapb->vr);
174
175 lapb_send_control(lapb, LAPB_RR, LAPB_POLLON, LAPB_RESPONSE);
176
177 lapb->condition &= ~LAPB_ACK_PENDING_CONDITION;
178 }
179
lapb_timeout_response(struct lapb_cb * lapb)180 void lapb_timeout_response(struct lapb_cb *lapb)
181 {
182 lapb_dbg(1, "(%p) S%d TX RR(0) R%d\n",
183 lapb->dev, lapb->state, lapb->vr);
184 lapb_send_control(lapb, LAPB_RR, LAPB_POLLOFF, LAPB_RESPONSE);
185
186 lapb->condition &= ~LAPB_ACK_PENDING_CONDITION;
187 }
188
lapb_check_iframes_acked(struct lapb_cb * lapb,unsigned short nr)189 void lapb_check_iframes_acked(struct lapb_cb *lapb, unsigned short nr)
190 {
191 if (lapb->vs == nr) {
192 lapb_frames_acked(lapb, nr);
193 lapb_stop_t1timer(lapb);
194 lapb->n2count = 0;
195 } else if (lapb->va != nr) {
196 lapb_frames_acked(lapb, nr);
197 lapb_start_t1timer(lapb);
198 }
199 }
200
lapb_check_need_response(struct lapb_cb * lapb,int type,int pf)201 void lapb_check_need_response(struct lapb_cb *lapb, int type, int pf)
202 {
203 if (type == LAPB_COMMAND && pf)
204 lapb_enquiry_response(lapb);
205 }
206