1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 *
4 * Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk)
5 * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
6 * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
7 */
8#include <linux/errno.h>
9#include <linux/types.h>
10#include <linux/socket.h>
11#include <linux/in.h>
12#include <linux/kernel.h>
13#include <linux/module.h>
14#include <linux/timer.h>
15#include <linux/string.h>
16#include <linux/sockios.h>
17#include <linux/spinlock.h>
18#include <linux/net.h>
19#include <linux/slab.h>
20#include <net/ax25.h>
21#include <linux/inet.h>
22#include <linux/netdevice.h>
23#include <linux/skbuff.h>
24#include <net/sock.h>
25#include <linux/uaccess.h>
26#include <linux/fcntl.h>
27#include <linux/mm.h>
28#include <linux/interrupt.h>
29
30static DEFINE_SPINLOCK(ax25_frag_lock);
31
32ax25_cb *ax25_send_frame(struct sk_buff *skb, int paclen, const ax25_address *src, ax25_address *dest, ax25_digi *digi, struct net_device *dev)
33{
34	ax25_dev *ax25_dev;
35	ax25_cb *ax25;
36
37	/*
38	 * Take the default packet length for the device if zero is
39	 * specified.
40	 */
41	if (paclen == 0) {
42		if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
43			return NULL;
44
45		paclen = ax25_dev->values[AX25_VALUES_PACLEN];
46	}
47
48	/*
49	 * Look for an existing connection.
50	 */
51	if ((ax25 = ax25_find_cb(src, dest, digi, dev)) != NULL) {
52		ax25_output(ax25, paclen, skb);
53		return ax25;		/* It already existed */
54	}
55
56	if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
57		return NULL;
58
59	if ((ax25 = ax25_create_cb()) == NULL)
60		return NULL;
61
62	ax25_fillin_cb(ax25, ax25_dev);
63
64	ax25->source_addr = *src;
65	ax25->dest_addr   = *dest;
66
67	if (digi != NULL) {
68		ax25->digipeat = kmemdup(digi, sizeof(*digi), GFP_ATOMIC);
69		if (ax25->digipeat == NULL) {
70			ax25_cb_put(ax25);
71			return NULL;
72		}
73	}
74
75	switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
76	case AX25_PROTO_STD_SIMPLEX:
77	case AX25_PROTO_STD_DUPLEX:
78		ax25_std_establish_data_link(ax25);
79		break;
80
81#ifdef CONFIG_AX25_DAMA_SLAVE
82	case AX25_PROTO_DAMA_SLAVE:
83		if (ax25_dev->dama.slave)
84			ax25_ds_establish_data_link(ax25);
85		else
86			ax25_std_establish_data_link(ax25);
87		break;
88#endif
89	}
90
91	/*
92	 * There is one ref for the state machine; a caller needs
93	 * one more to put it back, just like with the existing one.
94	 */
95	ax25_cb_hold(ax25);
96
97	ax25_cb_add(ax25);
98
99	ax25->state = AX25_STATE_1;
100
101	ax25_start_heartbeat(ax25);
102
103	ax25_output(ax25, paclen, skb);
104
105	return ax25;			/* We had to create it */
106}
107
108EXPORT_SYMBOL(ax25_send_frame);
109
110/*
111 *	All outgoing AX.25 I frames pass via this routine. Therefore this is
112 *	where the fragmentation of frames takes place. If fragment is set to
113 *	zero then we are not allowed to do fragmentation, even if the frame
114 *	is too large.
115 */
116void ax25_output(ax25_cb *ax25, int paclen, struct sk_buff *skb)
117{
118	struct sk_buff *skbn;
119	unsigned char *p;
120	int frontlen, len, fragno, ka9qfrag, first = 1;
121
122	if (paclen < 16) {
123		WARN_ON_ONCE(1);
124		kfree_skb(skb);
125		return;
126	}
127
128	if ((skb->len - 1) > paclen) {
129		if (*skb->data == AX25_P_TEXT) {
130			skb_pull(skb, 1); /* skip PID */
131			ka9qfrag = 0;
132		} else {
133			paclen -= 2;	/* Allow for fragment control info */
134			ka9qfrag = 1;
135		}
136
137		fragno = skb->len / paclen;
138		if (skb->len % paclen == 0) fragno--;
139
140		frontlen = skb_headroom(skb);	/* Address space + CTRL */
141
142		while (skb->len > 0) {
143			spin_lock_bh(&ax25_frag_lock);
144			if ((skbn = alloc_skb(paclen + 2 + frontlen, GFP_ATOMIC)) == NULL) {
145				spin_unlock_bh(&ax25_frag_lock);
146				printk(KERN_CRIT "AX.25: ax25_output - out of memory\n");
147				return;
148			}
149
150			if (skb->sk != NULL)
151				skb_set_owner_w(skbn, skb->sk);
152
153			spin_unlock_bh(&ax25_frag_lock);
154
155			len = (paclen > skb->len) ? skb->len : paclen;
156
157			if (ka9qfrag == 1) {
158				skb_reserve(skbn, frontlen + 2);
159				skb_set_network_header(skbn,
160						      skb_network_offset(skb));
161				skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
162				p = skb_push(skbn, 2);
163
164				*p++ = AX25_P_SEGMENT;
165
166				*p = fragno--;
167				if (first) {
168					*p |= AX25_SEG_FIRST;
169					first = 0;
170				}
171			} else {
172				skb_reserve(skbn, frontlen + 1);
173				skb_set_network_header(skbn,
174						      skb_network_offset(skb));
175				skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
176				p = skb_push(skbn, 1);
177				*p = AX25_P_TEXT;
178			}
179
180			skb_pull(skb, len);
181			skb_queue_tail(&ax25->write_queue, skbn); /* Throw it on the queue */
182		}
183
184		kfree_skb(skb);
185	} else {
186		skb_queue_tail(&ax25->write_queue, skb);	  /* Throw it on the queue */
187	}
188
189	switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
190	case AX25_PROTO_STD_SIMPLEX:
191	case AX25_PROTO_STD_DUPLEX:
192		ax25_kick(ax25);
193		break;
194
195#ifdef CONFIG_AX25_DAMA_SLAVE
196	/*
197	 * A DAMA slave is _required_ to work as normal AX.25L2V2
198	 * if no DAMA master is available.
199	 */
200	case AX25_PROTO_DAMA_SLAVE:
201		if (!ax25->ax25_dev->dama.slave) ax25_kick(ax25);
202		break;
203#endif
204	}
205}
206
207/*
208 *  This procedure is passed a buffer descriptor for an iframe. It builds
209 *  the rest of the control part of the frame and then writes it out.
210 */
211static void ax25_send_iframe(ax25_cb *ax25, struct sk_buff *skb, int poll_bit)
212{
213	unsigned char *frame;
214
215	if (skb == NULL)
216		return;
217
218	skb_reset_network_header(skb);
219
220	if (ax25->modulus == AX25_MODULUS) {
221		frame = skb_push(skb, 1);
222
223		*frame = AX25_I;
224		*frame |= (poll_bit) ? AX25_PF : 0;
225		*frame |= (ax25->vr << 5);
226		*frame |= (ax25->vs << 1);
227	} else {
228		frame = skb_push(skb, 2);
229
230		frame[0] = AX25_I;
231		frame[0] |= (ax25->vs << 1);
232		frame[1] = (poll_bit) ? AX25_EPF : 0;
233		frame[1] |= (ax25->vr << 1);
234	}
235
236	ax25_start_idletimer(ax25);
237
238	ax25_transmit_buffer(ax25, skb, AX25_COMMAND);
239}
240
241void ax25_kick(ax25_cb *ax25)
242{
243	struct sk_buff *skb, *skbn;
244	int last = 1;
245	unsigned short start, end, next;
246
247	if (ax25->state != AX25_STATE_3 && ax25->state != AX25_STATE_4)
248		return;
249
250	if (ax25->condition & AX25_COND_PEER_RX_BUSY)
251		return;
252
253	if (skb_peek(&ax25->write_queue) == NULL)
254		return;
255
256	start = (skb_peek(&ax25->ack_queue) == NULL) ? ax25->va : ax25->vs;
257	end   = (ax25->va + ax25->window) % ax25->modulus;
258
259	if (start == end)
260		return;
261
262	/*
263	 * Transmit data until either we're out of data to send or
264	 * the window is full. Send a poll on the final I frame if
265	 * the window is filled.
266	 */
267
268	/*
269	 * Dequeue the frame and copy it.
270	 * Check for race with ax25_clear_queues().
271	 */
272	skb  = skb_dequeue(&ax25->write_queue);
273	if (!skb)
274		return;
275
276	ax25->vs = start;
277
278	do {
279		if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
280			skb_queue_head(&ax25->write_queue, skb);
281			break;
282		}
283
284		if (skb->sk != NULL)
285			skb_set_owner_w(skbn, skb->sk);
286
287		next = (ax25->vs + 1) % ax25->modulus;
288		last = (next == end);
289
290		/*
291		 * Transmit the frame copy.
292		 * bke 960114: do not set the Poll bit on the last frame
293		 * in DAMA mode.
294		 */
295		switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
296		case AX25_PROTO_STD_SIMPLEX:
297		case AX25_PROTO_STD_DUPLEX:
298			ax25_send_iframe(ax25, skbn, (last) ? AX25_POLLON : AX25_POLLOFF);
299			break;
300
301#ifdef CONFIG_AX25_DAMA_SLAVE
302		case AX25_PROTO_DAMA_SLAVE:
303			ax25_send_iframe(ax25, skbn, AX25_POLLOFF);
304			break;
305#endif
306		}
307
308		ax25->vs = next;
309
310		/*
311		 * Requeue the original data frame.
312		 */
313		skb_queue_tail(&ax25->ack_queue, skb);
314
315	} while (!last && (skb = skb_dequeue(&ax25->write_queue)) != NULL);
316
317	ax25->condition &= ~AX25_COND_ACK_PENDING;
318
319	if (!ax25_t1timer_running(ax25)) {
320		ax25_stop_t3timer(ax25);
321		ax25_calculate_t1(ax25);
322		ax25_start_t1timer(ax25);
323	}
324}
325
326void ax25_transmit_buffer(ax25_cb *ax25, struct sk_buff *skb, int type)
327{
328	unsigned char *ptr;
329	int headroom;
330
331	if (ax25->ax25_dev == NULL) {
332		ax25_disconnect(ax25, ENETUNREACH);
333		return;
334	}
335
336	headroom = ax25_addr_size(ax25->digipeat);
337
338	if (unlikely(skb_headroom(skb) < headroom)) {
339		skb = skb_expand_head(skb, headroom);
340		if (!skb) {
341			printk(KERN_CRIT "AX.25: ax25_transmit_buffer - out of memory\n");
342			return;
343		}
344	}
345
346	ptr = skb_push(skb, headroom);
347
348	ax25_addr_build(ptr, &ax25->source_addr, &ax25->dest_addr, ax25->digipeat, type, ax25->modulus);
349
350	ax25_queue_xmit(skb, ax25->ax25_dev->dev);
351}
352
353/*
354 *	A small shim to dev_queue_xmit to add the KISS control byte, and do
355 *	any packet forwarding in operation.
356 */
357void ax25_queue_xmit(struct sk_buff *skb, struct net_device *dev)
358{
359	unsigned char *ptr;
360
361	skb->protocol = ax25_type_trans(skb, ax25_fwd_dev(dev));
362
363	ptr  = skb_push(skb, 1);
364	*ptr = 0x00;			/* KISS */
365
366	dev_queue_xmit(skb);
367}
368
369int ax25_check_iframes_acked(ax25_cb *ax25, unsigned short nr)
370{
371	if (ax25->vs == nr) {
372		ax25_frames_acked(ax25, nr);
373		ax25_calculate_rtt(ax25);
374		ax25_stop_t1timer(ax25);
375		ax25_start_t3timer(ax25);
376		return 1;
377	} else {
378		if (ax25->va != nr) {
379			ax25_frames_acked(ax25, nr);
380			ax25_calculate_t1(ax25);
381			ax25_start_t1timer(ax25);
382			return 1;
383		}
384	}
385	return 0;
386}
387