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 	struct rose_sock *rose = rose_sk(sk);
105 	int queued = 0;
106 
107 	switch (frametype) {
108 	case ROSE_RESET_REQUEST:
109 		rose_stop_timer(sk);
110 		rose_start_idletimer(sk);
111 		rose_write_internal(sk, ROSE_RESET_CONFIRMATION);
112 		rose->condition = 0x00;
113 		rose->vs        = 0;
114 		rose->vr        = 0;
115 		rose->va        = 0;
116 		rose->vl        = 0;
117 		rose_requeue_frames(sk);
118 		break;
119 
120 	case ROSE_CLEAR_REQUEST:
121 		rose_write_internal(sk, ROSE_CLEAR_CONFIRMATION);
122 		rose_disconnect(sk, 0, skb->data[3], skb->data[4]);
123 		rose->neighbour->use--;
124 		break;
125 
126 	case ROSE_RR:
127 	case ROSE_RNR:
128 		if (!rose_validate_nr(sk, nr)) {
129 			rose_write_internal(sk, ROSE_RESET_REQUEST);
130 			rose->condition = 0x00;
131 			rose->vs        = 0;
132 			rose->vr        = 0;
133 			rose->va        = 0;
134 			rose->vl        = 0;
135 			rose->state     = ROSE_STATE_4;
136 			rose_start_t2timer(sk);
137 			rose_stop_idletimer(sk);
138 		} else {
139 			rose_frames_acked(sk, nr);
140 			if (frametype == ROSE_RNR) {
141 				rose->condition |= ROSE_COND_PEER_RX_BUSY;
142 			} else {
143 				rose->condition &= ~ROSE_COND_PEER_RX_BUSY;
144 			}
145 		}
146 		break;
147 
148 	case ROSE_DATA:	/* XXX */
149 		rose->condition &= ~ROSE_COND_PEER_RX_BUSY;
150 		if (!rose_validate_nr(sk, nr)) {
151 			rose_write_internal(sk, ROSE_RESET_REQUEST);
152 			rose->condition = 0x00;
153 			rose->vs        = 0;
154 			rose->vr        = 0;
155 			rose->va        = 0;
156 			rose->vl        = 0;
157 			rose->state     = ROSE_STATE_4;
158 			rose_start_t2timer(sk);
159 			rose_stop_idletimer(sk);
160 			break;
161 		}
162 		rose_frames_acked(sk, nr);
163 		if (ns == rose->vr) {
164 			rose_start_idletimer(sk);
165 			if (sk_filter_trim_cap(sk, skb, ROSE_MIN_LEN) == 0 &&
166 			    __sock_queue_rcv_skb(sk, skb) == 0) {
167 				rose->vr = (rose->vr + 1) % ROSE_MODULUS;
168 				queued = 1;
169 			} else {
170 				/* Should never happen ! */
171 				rose_write_internal(sk, ROSE_RESET_REQUEST);
172 				rose->condition = 0x00;
173 				rose->vs        = 0;
174 				rose->vr        = 0;
175 				rose->va        = 0;
176 				rose->vl        = 0;
177 				rose->state     = ROSE_STATE_4;
178 				rose_start_t2timer(sk);
179 				rose_stop_idletimer(sk);
180 				break;
181 			}
182 			if (atomic_read(&sk->sk_rmem_alloc) >
183 			    (sk->sk_rcvbuf >> 1))
184 				rose->condition |= ROSE_COND_OWN_RX_BUSY;
185 		}
186 		/*
187 		 * If the window is full, ack the frame, else start the
188 		 * acknowledge hold back timer.
189 		 */
190 		if (((rose->vl + sysctl_rose_window_size) % ROSE_MODULUS) == rose->vr) {
191 			rose->condition &= ~ROSE_COND_ACK_PENDING;
192 			rose_stop_timer(sk);
193 			rose_enquiry_response(sk);
194 		} else {
195 			rose->condition |= ROSE_COND_ACK_PENDING;
196 			rose_start_hbtimer(sk);
197 		}
198 		break;
199 
200 	default:
201 		printk(KERN_WARNING "ROSE: unknown %02X in state 3\n", frametype);
202 		break;
203 	}
204 
205 	return queued;
206 }
207 
208 /*
209  * State machine for state 4, Awaiting Reset Confirmation State.
210  * The handling of the timer(s) is in file rose_timer.c
211  * Handling of state 0 and connection release is in af_rose.c.
212  */
rose_state4_machine(struct sock * sk,struct sk_buff * skb,int frametype)213 static int rose_state4_machine(struct sock *sk, struct sk_buff *skb, int frametype)
214 {
215 	struct rose_sock *rose = rose_sk(sk);
216 
217 	switch (frametype) {
218 	case ROSE_RESET_REQUEST:
219 		rose_write_internal(sk, ROSE_RESET_CONFIRMATION);
220 		fallthrough;
221 	case ROSE_RESET_CONFIRMATION:
222 		rose_stop_timer(sk);
223 		rose_start_idletimer(sk);
224 		rose->condition = 0x00;
225 		rose->va        = 0;
226 		rose->vr        = 0;
227 		rose->vs        = 0;
228 		rose->vl        = 0;
229 		rose->state     = ROSE_STATE_3;
230 		rose_requeue_frames(sk);
231 		break;
232 
233 	case ROSE_CLEAR_REQUEST:
234 		rose_write_internal(sk, ROSE_CLEAR_CONFIRMATION);
235 		rose_disconnect(sk, 0, skb->data[3], skb->data[4]);
236 		rose->neighbour->use--;
237 		break;
238 
239 	default:
240 		break;
241 	}
242 
243 	return 0;
244 }
245 
246 /*
247  * State machine for state 5, Awaiting Call Acceptance State.
248  * The handling of the timer(s) is in file rose_timer.c
249  * Handling of state 0 and connection release is in af_rose.c.
250  */
rose_state5_machine(struct sock * sk,struct sk_buff * skb,int frametype)251 static int rose_state5_machine(struct sock *sk, struct sk_buff *skb, int frametype)
252 {
253 	if (frametype == ROSE_CLEAR_REQUEST) {
254 		rose_write_internal(sk, ROSE_CLEAR_CONFIRMATION);
255 		rose_disconnect(sk, 0, skb->data[3], skb->data[4]);
256 		rose_sk(sk)->neighbour->use--;
257 	}
258 
259 	return 0;
260 }
261 
262 /* Higher level upcall for a LAPB frame */
rose_process_rx_frame(struct sock * sk,struct sk_buff * skb)263 int rose_process_rx_frame(struct sock *sk, struct sk_buff *skb)
264 {
265 	struct rose_sock *rose = rose_sk(sk);
266 	int queued = 0, frametype, ns, nr, q, d, m;
267 
268 	if (rose->state == ROSE_STATE_0)
269 		return 0;
270 
271 	frametype = rose_decode(skb, &ns, &nr, &q, &d, &m);
272 
273 	switch (rose->state) {
274 	case ROSE_STATE_1:
275 		queued = rose_state1_machine(sk, skb, frametype);
276 		break;
277 	case ROSE_STATE_2:
278 		queued = rose_state2_machine(sk, skb, frametype);
279 		break;
280 	case ROSE_STATE_3:
281 		queued = rose_state3_machine(sk, skb, frametype, ns, nr, q, d, m);
282 		break;
283 	case ROSE_STATE_4:
284 		queued = rose_state4_machine(sk, skb, frametype);
285 		break;
286 	case ROSE_STATE_5:
287 		queued = rose_state5_machine(sk, skb, frametype);
288 		break;
289 	}
290 
291 	rose_kick(sk);
292 
293 	return queued;
294 }
295