rose_in.c

  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 */
 37static 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_neigh_put(rose->neighbour);
 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 */
 74static 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_neigh_put(rose->neighbour);
 83		break;
 84
 85	case ROSE_CLEAR_CONFIRMATION:
 86		rose_disconnect(sk, 0, -1, -1);
 87		rose_neigh_put(rose->neighbour);
 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 */
102static 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_neigh_put(rose->neighbour);
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 */
214static 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_neigh_put(rose->neighbour);
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 */
252static 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_neigh_put(rose_sk(sk)->neighbour);
258	}
259
260	return 0;
261}
262
263/* Higher level upcall for a LAPB frame */
264int 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}