1/*
2 * This program is free software; you can redistribute it and/or modify
3 * it under the terms of the GNU General Public License as published by
4 * the Free Software Foundation; either version 2 of the License, or
5 * (at your option) any later version.
6 *
7 * Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk)
8 * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
9 * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
10 */
11#include <linux/errno.h>
12#include <linux/types.h>
13#include <linux/socket.h>
14#include <linux/in.h>
15#include <linux/kernel.h>
16#include <linux/module.h>
17#include <linux/timer.h>
18#include <linux/string.h>
19#include <linux/sockios.h>
20#include <linux/spinlock.h>
21#include <linux/net.h>
22#include <linux/slab.h>
23#include <net/ax25.h>
24#include <linux/inet.h>
25#include <linux/netdevice.h>
26#include <linux/skbuff.h>
27#include <net/sock.h>
28#include <asm/uaccess.h>
29#include <linux/fcntl.h>
30#include <linux/mm.h>
31#include <linux/interrupt.h>
32
33static DEFINE_SPINLOCK(ax25_frag_lock);
34
35ax25_cb *ax25_send_frame(struct sk_buff *skb, int paclen, ax25_address *src, ax25_address *dest, ax25_digi *digi, struct net_device *dev)
36{
37	ax25_dev *ax25_dev;
38	ax25_cb *ax25;
39
40	/*
41	 * Take the default packet length for the device if zero is
42	 * specified.
43	 */
44	if (paclen == 0) {
45		if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
46			return NULL;
47
48		paclen = ax25_dev->values[AX25_VALUES_PACLEN];
49	}
50
51	/*
52	 * Look for an existing connection.
53	 */
54	if ((ax25 = ax25_find_cb(src, dest, digi, dev)) != NULL) {
55		ax25_output(ax25, paclen, skb);
56		return ax25;		/* It already existed */
57	}
58
59	if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
60		return NULL;
61
62	if ((ax25 = ax25_create_cb()) == NULL)
63		return NULL;
64
65	ax25_fillin_cb(ax25, ax25_dev);
66
67	ax25->source_addr = *src;
68	ax25->dest_addr   = *dest;
69
70	if (digi != NULL) {
71		ax25->digipeat = kmemdup(digi, sizeof(*digi), GFP_ATOMIC);
72		if (ax25->digipeat == NULL) {
73			ax25_cb_put(ax25);
74			return NULL;
75		}
76	}
77
78	switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
79	case AX25_PROTO_STD_SIMPLEX:
80	case AX25_PROTO_STD_DUPLEX:
81		ax25_std_establish_data_link(ax25);
82		break;
83
84#ifdef CONFIG_AX25_DAMA_SLAVE
85	case AX25_PROTO_DAMA_SLAVE:
86		if (ax25_dev->dama.slave)
87			ax25_ds_establish_data_link(ax25);
88		else
89			ax25_std_establish_data_link(ax25);
90		break;
91#endif
92	}
93
94	/*
95	 * There is one ref for the state machine; a caller needs
96	 * one more to put it back, just like with the existing one.
97	 */
98	ax25_cb_hold(ax25);
99
100	ax25_cb_add(ax25);
101
102	ax25->state = AX25_STATE_1;
103
104	ax25_start_heartbeat(ax25);
105
106	ax25_output(ax25, paclen, skb);
107
108	return ax25;			/* We had to create it */
109}
110
111EXPORT_SYMBOL(ax25_send_frame);
112
113/*
114 *	All outgoing AX.25 I frames pass via this routine. Therefore this is
115 *	where the fragmentation of frames takes place. If fragment is set to
116 *	zero then we are not allowed to do fragmentation, even if the frame
117 *	is too large.
118 */
119void ax25_output(ax25_cb *ax25, int paclen, struct sk_buff *skb)
120{
121	struct sk_buff *skbn;
122	unsigned char *p;
123	int frontlen, len, fragno, ka9qfrag, first = 1;
124
125	if (paclen < 16) {
126		WARN_ON_ONCE(1);
127		kfree_skb(skb);
128		return;
129	}
130
131	if ((skb->len - 1) > paclen) {
132		if (*skb->data == AX25_P_TEXT) {
133			skb_pull(skb, 1); /* skip PID */
134			ka9qfrag = 0;
135		} else {
136			paclen -= 2;	/* Allow for fragment control info */
137			ka9qfrag = 1;
138		}
139
140		fragno = skb->len / paclen;
141		if (skb->len % paclen == 0) fragno--;
142
143		frontlen = skb_headroom(skb);	/* Address space + CTRL */
144
145		while (skb->len > 0) {
146			spin_lock_bh(&ax25_frag_lock);
147			if ((skbn = alloc_skb(paclen + 2 + frontlen, GFP_ATOMIC)) == NULL) {
148				spin_unlock_bh(&ax25_frag_lock);
149				printk(KERN_CRIT "AX.25: ax25_output - out of memory\n");
150				return;
151			}
152
153			if (skb->sk != NULL)
154				skb_set_owner_w(skbn, skb->sk);
155
156			spin_unlock_bh(&ax25_frag_lock);
157
158			len = (paclen > skb->len) ? skb->len : paclen;
159
160			if (ka9qfrag == 1) {
161				skb_reserve(skbn, frontlen + 2);
162				skb_set_network_header(skbn,
163						      skb_network_offset(skb));
164				skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
165				p = skb_push(skbn, 2);
166
167				*p++ = AX25_P_SEGMENT;
168
169				*p = fragno--;
170				if (first) {
171					*p |= AX25_SEG_FIRST;
172					first = 0;
173				}
174			} else {
175				skb_reserve(skbn, frontlen + 1);
176				skb_set_network_header(skbn,
177						      skb_network_offset(skb));
178				skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
179				p = skb_push(skbn, 1);
180				*p = AX25_P_TEXT;
181			}
182
183			skb_pull(skb, len);
184			skb_queue_tail(&ax25->write_queue, skbn); /* Throw it on the queue */
185		}
186
187		kfree_skb(skb);
188	} else {
189		skb_queue_tail(&ax25->write_queue, skb);	  /* Throw it on the queue */
190	}
191
192	switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
193	case AX25_PROTO_STD_SIMPLEX:
194	case AX25_PROTO_STD_DUPLEX:
195		ax25_kick(ax25);
196		break;
197
198#ifdef CONFIG_AX25_DAMA_SLAVE
199	/*
200	 * A DAMA slave is _required_ to work as normal AX.25L2V2
201	 * if no DAMA master is available.
202	 */
203	case AX25_PROTO_DAMA_SLAVE:
204		if (!ax25->ax25_dev->dama.slave) ax25_kick(ax25);
205		break;
206#endif
207	}
208}
209
210/*
211 *  This procedure is passed a buffer descriptor for an iframe. It builds
212 *  the rest of the control part of the frame and then writes it out.
213 */
214static void ax25_send_iframe(ax25_cb *ax25, struct sk_buff *skb, int poll_bit)
215{
216	unsigned char *frame;
217
218	if (skb == NULL)
219		return;
220
221	skb_reset_network_header(skb);
222
223	if (ax25->modulus == AX25_MODULUS) {
224		frame = skb_push(skb, 1);
225
226		*frame = AX25_I;
227		*frame |= (poll_bit) ? AX25_PF : 0;
228		*frame |= (ax25->vr << 5);
229		*frame |= (ax25->vs << 1);
230	} else {
231		frame = skb_push(skb, 2);
232
233		frame[0] = AX25_I;
234		frame[0] |= (ax25->vs << 1);
235		frame[1] = (poll_bit) ? AX25_EPF : 0;
236		frame[1] |= (ax25->vr << 1);
237	}
238
239	ax25_start_idletimer(ax25);
240
241	ax25_transmit_buffer(ax25, skb, AX25_COMMAND);
242}
243
244void ax25_kick(ax25_cb *ax25)
245{
246	struct sk_buff *skb, *skbn;
247	int last = 1;
248	unsigned short start, end, next;
249
250	if (ax25->state != AX25_STATE_3 && ax25->state != AX25_STATE_4)
251		return;
252
253	if (ax25->condition & AX25_COND_PEER_RX_BUSY)
254		return;
255
256	if (skb_peek(&ax25->write_queue) == NULL)
257		return;
258
259	start = (skb_peek(&ax25->ack_queue) == NULL) ? ax25->va : ax25->vs;
260	end   = (ax25->va + ax25->window) % ax25->modulus;
261
262	if (start == end)
263		return;
264
265	/*
266	 * Transmit data until either we're out of data to send or
267	 * the window is full. Send a poll on the final I frame if
268	 * the window is filled.
269	 */
270
271	/*
272	 * Dequeue the frame and copy it.
273	 * Check for race with ax25_clear_queues().
274	 */
275	skb  = skb_dequeue(&ax25->write_queue);
276	if (!skb)
277		return;
278
279	ax25->vs = start;
280
281	do {
282		if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
283			skb_queue_head(&ax25->write_queue, skb);
284			break;
285		}
286
287		if (skb->sk != NULL)
288			skb_set_owner_w(skbn, skb->sk);
289
290		next = (ax25->vs + 1) % ax25->modulus;
291		last = (next == end);
292
293		/*
294		 * Transmit the frame copy.
295		 * bke 960114: do not set the Poll bit on the last frame
296		 * in DAMA mode.
297		 */
298		switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
299		case AX25_PROTO_STD_SIMPLEX:
300		case AX25_PROTO_STD_DUPLEX:
301			ax25_send_iframe(ax25, skbn, (last) ? AX25_POLLON : AX25_POLLOFF);
302			break;
303
304#ifdef CONFIG_AX25_DAMA_SLAVE
305		case AX25_PROTO_DAMA_SLAVE:
306			ax25_send_iframe(ax25, skbn, AX25_POLLOFF);
307			break;
308#endif
309		}
310
311		ax25->vs = next;
312
313		/*
314		 * Requeue the original data frame.
315		 */
316		skb_queue_tail(&ax25->ack_queue, skb);
317
318	} while (!last && (skb = skb_dequeue(&ax25->write_queue)) != NULL);
319
320	ax25->condition &= ~AX25_COND_ACK_PENDING;
321
322	if (!ax25_t1timer_running(ax25)) {
323		ax25_stop_t3timer(ax25);
324		ax25_calculate_t1(ax25);
325		ax25_start_t1timer(ax25);
326	}
327}
328
329void ax25_transmit_buffer(ax25_cb *ax25, struct sk_buff *skb, int type)
330{
331	struct sk_buff *skbn;
332	unsigned char *ptr;
333	int headroom;
334
335	if (ax25->ax25_dev == NULL) {
336		ax25_disconnect(ax25, ENETUNREACH);
337		return;
338	}
339
340	headroom = ax25_addr_size(ax25->digipeat);
341
342	if (skb_headroom(skb) < headroom) {
343		if ((skbn = skb_realloc_headroom(skb, headroom)) == NULL) {
344			printk(KERN_CRIT "AX.25: ax25_transmit_buffer - out of memory\n");
345			kfree_skb(skb);
346			return;
347		}
348
349		if (skb->sk != NULL)
350			skb_set_owner_w(skbn, skb->sk);
351
352		consume_skb(skb);
353		skb = skbn;
354	}
355
356	ptr = skb_push(skb, headroom);
357
358	ax25_addr_build(ptr, &ax25->source_addr, &ax25->dest_addr, ax25->digipeat, type, ax25->modulus);
359
360	ax25_queue_xmit(skb, ax25->ax25_dev->dev);
361}
362
363/*
364 *	A small shim to dev_queue_xmit to add the KISS control byte, and do
365 *	any packet forwarding in operation.
366 */
367void ax25_queue_xmit(struct sk_buff *skb, struct net_device *dev)
368{
369	unsigned char *ptr;
370
371	skb->protocol = ax25_type_trans(skb, ax25_fwd_dev(dev));
372
373	ptr  = skb_push(skb, 1);
374	*ptr = 0x00;			/* KISS */
375
376	dev_queue_xmit(skb);
377}
378
379int ax25_check_iframes_acked(ax25_cb *ax25, unsigned short nr)
380{
381	if (ax25->vs == nr) {
382		ax25_frames_acked(ax25, nr);
383		ax25_calculate_rtt(ax25);
384		ax25_stop_t1timer(ax25);
385		ax25_start_t3timer(ax25);
386		return 1;
387	} else {
388		if (ax25->va != nr) {
389			ax25_frames_acked(ax25, nr);
390			ax25_calculate_t1(ax25);
391			ax25_start_t1timer(ax25);
392			return 1;
393		}
394	}
395	return 0;
396}
397
398