1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 *
4 * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
5 *
6 * Most of this code is based on the SDL diagrams published in the 7th ARRL
7 * Computer Networking Conference papers. The diagrams have mistakes in them,
8 * but are mostly correct. Before you modify the code could you read the SDL
9 * diagrams as the code is not obvious and probably very easy to break.
10 */
11 #include <linux/errno.h>
12 #include <linux/filter.h>
13 #include <linux/types.h>
14 #include <linux/socket.h>
15 #include <linux/in.h>
16 #include <linux/kernel.h>
17 #include <linux/timer.h>
18 #include <linux/string.h>
19 #include <linux/sockios.h>
20 #include <linux/net.h>
21 #include <net/ax25.h>
22 #include <linux/inet.h>
23 #include <linux/netdevice.h>
24 #include <linux/skbuff.h>
25 #include <net/sock.h>
26 #include <net/tcp_states.h>
27 #include <linux/fcntl.h>
28 #include <linux/mm.h>
29 #include <linux/interrupt.h>
30 #include <net/rose.h>
31
32 /*
33 * State machine for state 1, Awaiting Call Accepted State.
34 * The handling of the timer(s) is in file rose_timer.c.
35 * Handling of state 0 and connection release is in af_rose.c.
36 */
rose_state1_machine(struct sock * sk,struct sk_buff * skb,int frametype)37 static int rose_state1_machine(struct sock *sk, struct sk_buff *skb, int frametype)
38 {
39 struct rose_sock *rose = rose_sk(sk);
40
41 switch (frametype) {
42 case ROSE_CALL_ACCEPTED:
43 rose_stop_timer(sk);
44 rose_start_idletimer(sk);
45 rose->condition = 0x00;
46 rose->vs = 0;
47 rose->va = 0;
48 rose->vr = 0;
49 rose->vl = 0;
50 rose->state = ROSE_STATE_3;
51 sk->sk_state = TCP_ESTABLISHED;
52 if (!sock_flag(sk, SOCK_DEAD))
53 sk->sk_state_change(sk);
54 break;
55
56 case ROSE_CLEAR_REQUEST:
57 rose_write_internal(sk, ROSE_CLEAR_CONFIRMATION);
58 rose_disconnect(sk, ECONNREFUSED, skb->data[3], skb->data[4]);
59 rose->neighbour->use--;
60 break;
61
62 default:
63 break;
64 }
65
66 return 0;
67 }
68
69 /*
70 * State machine for state 2, Awaiting Clear Confirmation State.
71 * The handling of the timer(s) is in file rose_timer.c
72 * Handling of state 0 and connection release is in af_rose.c.
73 */
rose_state2_machine(struct sock * sk,struct sk_buff * skb,int frametype)74 static int rose_state2_machine(struct sock *sk, struct sk_buff *skb, int frametype)
75 {
76 struct rose_sock *rose = rose_sk(sk);
77
78 switch (frametype) {
79 case ROSE_CLEAR_REQUEST:
80 rose_write_internal(sk, ROSE_CLEAR_CONFIRMATION);
81 rose_disconnect(sk, 0, skb->data[3], skb->data[4]);
82 rose->neighbour->use--;
83 break;
84
85 case ROSE_CLEAR_CONFIRMATION:
86 rose_disconnect(sk, 0, -1, -1);
87 rose->neighbour->use--;
88 break;
89
90 default:
91 break;
92 }
93
94 return 0;
95 }
96
97 /*
98 * State machine for state 3, Connected State.
99 * The handling of the timer(s) is in file rose_timer.c
100 * Handling of state 0 and connection release is in af_rose.c.
101 */
rose_state3_machine(struct sock * sk,struct sk_buff * skb,int frametype,int ns,int nr,int q,int d,int m)102 static int rose_state3_machine(struct sock *sk, struct sk_buff *skb, int frametype, int ns, int nr, int q, int d, int m)
103 {
104 enum skb_drop_reason dr; /* ignored */
105 struct rose_sock *rose = rose_sk(sk);
106 int queued = 0;
107
108 switch (frametype) {
109 case ROSE_RESET_REQUEST:
110 rose_stop_timer(sk);
111 rose_start_idletimer(sk);
112 rose_write_internal(sk, ROSE_RESET_CONFIRMATION);
113 rose->condition = 0x00;
114 rose->vs = 0;
115 rose->vr = 0;
116 rose->va = 0;
117 rose->vl = 0;
118 rose_requeue_frames(sk);
119 break;
120
121 case ROSE_CLEAR_REQUEST:
122 rose_write_internal(sk, ROSE_CLEAR_CONFIRMATION);
123 rose_disconnect(sk, 0, skb->data[3], skb->data[4]);
124 rose->neighbour->use--;
125 break;
126
127 case ROSE_RR:
128 case ROSE_RNR:
129 if (!rose_validate_nr(sk, nr)) {
130 rose_write_internal(sk, ROSE_RESET_REQUEST);
131 rose->condition = 0x00;
132 rose->vs = 0;
133 rose->vr = 0;
134 rose->va = 0;
135 rose->vl = 0;
136 rose->state = ROSE_STATE_4;
137 rose_start_t2timer(sk);
138 rose_stop_idletimer(sk);
139 } else {
140 rose_frames_acked(sk, nr);
141 if (frametype == ROSE_RNR) {
142 rose->condition |= ROSE_COND_PEER_RX_BUSY;
143 } else {
144 rose->condition &= ~ROSE_COND_PEER_RX_BUSY;
145 }
146 }
147 break;
148
149 case ROSE_DATA: /* XXX */
150 rose->condition &= ~ROSE_COND_PEER_RX_BUSY;
151 if (!rose_validate_nr(sk, nr)) {
152 rose_write_internal(sk, ROSE_RESET_REQUEST);
153 rose->condition = 0x00;
154 rose->vs = 0;
155 rose->vr = 0;
156 rose->va = 0;
157 rose->vl = 0;
158 rose->state = ROSE_STATE_4;
159 rose_start_t2timer(sk);
160 rose_stop_idletimer(sk);
161 break;
162 }
163 rose_frames_acked(sk, nr);
164 if (ns == rose->vr) {
165 rose_start_idletimer(sk);
166 if (!sk_filter_trim_cap(sk, skb, ROSE_MIN_LEN, &dr) &&
167 __sock_queue_rcv_skb(sk, skb) == 0) {
168 rose->vr = (rose->vr + 1) % ROSE_MODULUS;
169 queued = 1;
170 } else {
171 /* Should never happen ! */
172 rose_write_internal(sk, ROSE_RESET_REQUEST);
173 rose->condition = 0x00;
174 rose->vs = 0;
175 rose->vr = 0;
176 rose->va = 0;
177 rose->vl = 0;
178 rose->state = ROSE_STATE_4;
179 rose_start_t2timer(sk);
180 rose_stop_idletimer(sk);
181 break;
182 }
183 if (atomic_read(&sk->sk_rmem_alloc) >
184 (sk->sk_rcvbuf >> 1))
185 rose->condition |= ROSE_COND_OWN_RX_BUSY;
186 }
187 /*
188 * If the window is full, ack the frame, else start the
189 * acknowledge hold back timer.
190 */
191 if (((rose->vl + sysctl_rose_window_size) % ROSE_MODULUS) == rose->vr) {
192 rose->condition &= ~ROSE_COND_ACK_PENDING;
193 rose_stop_timer(sk);
194 rose_enquiry_response(sk);
195 } else {
196 rose->condition |= ROSE_COND_ACK_PENDING;
197 rose_start_hbtimer(sk);
198 }
199 break;
200
201 default:
202 printk(KERN_WARNING "ROSE: unknown %02X in state 3\n", frametype);
203 break;
204 }
205
206 return queued;
207 }
208
209 /*
210 * State machine for state 4, Awaiting Reset Confirmation State.
211 * The handling of the timer(s) is in file rose_timer.c
212 * Handling of state 0 and connection release is in af_rose.c.
213 */
rose_state4_machine(struct sock * sk,struct sk_buff * skb,int frametype)214 static int rose_state4_machine(struct sock *sk, struct sk_buff *skb, int frametype)
215 {
216 struct rose_sock *rose = rose_sk(sk);
217
218 switch (frametype) {
219 case ROSE_RESET_REQUEST:
220 rose_write_internal(sk, ROSE_RESET_CONFIRMATION);
221 fallthrough;
222 case ROSE_RESET_CONFIRMATION:
223 rose_stop_timer(sk);
224 rose_start_idletimer(sk);
225 rose->condition = 0x00;
226 rose->va = 0;
227 rose->vr = 0;
228 rose->vs = 0;
229 rose->vl = 0;
230 rose->state = ROSE_STATE_3;
231 rose_requeue_frames(sk);
232 break;
233
234 case ROSE_CLEAR_REQUEST:
235 rose_write_internal(sk, ROSE_CLEAR_CONFIRMATION);
236 rose_disconnect(sk, 0, skb->data[3], skb->data[4]);
237 rose->neighbour->use--;
238 break;
239
240 default:
241 break;
242 }
243
244 return 0;
245 }
246
247 /*
248 * State machine for state 5, Awaiting Call Acceptance State.
249 * The handling of the timer(s) is in file rose_timer.c
250 * Handling of state 0 and connection release is in af_rose.c.
251 */
rose_state5_machine(struct sock * sk,struct sk_buff * skb,int frametype)252 static int rose_state5_machine(struct sock *sk, struct sk_buff *skb, int frametype)
253 {
254 if (frametype == ROSE_CLEAR_REQUEST) {
255 rose_write_internal(sk, ROSE_CLEAR_CONFIRMATION);
256 rose_disconnect(sk, 0, skb->data[3], skb->data[4]);
257 rose_sk(sk)->neighbour->use--;
258 }
259
260 return 0;
261 }
262
263 /* Higher level upcall for a LAPB frame */
rose_process_rx_frame(struct sock * sk,struct sk_buff * skb)264 int rose_process_rx_frame(struct sock *sk, struct sk_buff *skb)
265 {
266 struct rose_sock *rose = rose_sk(sk);
267 int queued = 0, frametype, ns, nr, q, d, m;
268
269 if (rose->state == ROSE_STATE_0)
270 return 0;
271
272 frametype = rose_decode(skb, &ns, &nr, &q, &d, &m);
273
274 switch (rose->state) {
275 case ROSE_STATE_1:
276 queued = rose_state1_machine(sk, skb, frametype);
277 break;
278 case ROSE_STATE_2:
279 queued = rose_state2_machine(sk, skb, frametype);
280 break;
281 case ROSE_STATE_3:
282 queued = rose_state3_machine(sk, skb, frametype, ns, nr, q, d, m);
283 break;
284 case ROSE_STATE_4:
285 queued = rose_state4_machine(sk, skb, frametype);
286 break;
287 case ROSE_STATE_5:
288 queued = rose_state5_machine(sk, skb, frametype);
289 break;
290 }
291
292 rose_kick(sk);
293
294 return queued;
295 }
296