xref: /linux/net/ax25/ax25_out.c (revision 8fa5723aa7e053d498336b48448b292fc2e0458b) 
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 <net/ax25.h>
23 #include <linux/inet.h>
24 #include <linux/netdevice.h>
25 #include <linux/skbuff.h>
26 #include <linux/netfilter.h>
27 #include <net/sock.h>
28 #include <asm/uaccess.h>
29 #include <asm/system.h>
30 #include <linux/fcntl.h>
31 #include <linux/mm.h>
32 #include <linux/interrupt.h>
33 
34 static DEFINE_SPINLOCK(ax25_frag_lock);
35 
36 ax25_cb *ax25_send_frame(struct sk_buff *skb, int paclen, ax25_address *src, ax25_address *dest, ax25_digi *digi, struct net_device *dev)
37 {
38 	ax25_dev *ax25_dev;
39 	ax25_cb *ax25;
40 
41 	/*
42 	 * Take the default packet length for the device if zero is
43 	 * specified.
44 	 */
45 	if (paclen == 0) {
46 		if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
47 			return NULL;
48 
49 		paclen = ax25_dev->values[AX25_VALUES_PACLEN];
50 	}
51 
52 	/*
53 	 * Look for an existing connection.
54 	 */
55 	if ((ax25 = ax25_find_cb(src, dest, digi, dev)) != NULL) {
56 		ax25_output(ax25, paclen, skb);
57 		return ax25;		/* It already existed */
58 	}
59 
60 	if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
61 		return NULL;
62 
63 	if ((ax25 = ax25_create_cb()) == NULL)
64 		return NULL;
65 
66 	ax25_fillin_cb(ax25, ax25_dev);
67 
68 	ax25->source_addr = *src;
69 	ax25->dest_addr   = *dest;
70 
71 	if (digi != NULL) {
72 		ax25->digipeat = kmemdup(digi, sizeof(*digi), GFP_ATOMIC);
73 		if (ax25->digipeat == NULL) {
74 			ax25_cb_put(ax25);
75 			return NULL;
76 		}
77 	}
78 
79 	switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
80 	case AX25_PROTO_STD_SIMPLEX:
81 	case AX25_PROTO_STD_DUPLEX:
82 		ax25_std_establish_data_link(ax25);
83 		break;
84 
85 #ifdef CONFIG_AX25_DAMA_SLAVE
86 	case AX25_PROTO_DAMA_SLAVE:
87 		if (ax25_dev->dama.slave)
88 			ax25_ds_establish_data_link(ax25);
89 		else
90 			ax25_std_establish_data_link(ax25);
91 		break;
92 #endif
93 	}
94 
95 	ax25_cb_add(ax25);
96 
97 	ax25->state = AX25_STATE_1;
98 
99 	ax25_start_heartbeat(ax25);
100 
101 	ax25_output(ax25, paclen, skb);
102 
103 	return ax25;			/* We had to create it */
104 }
105 
106 EXPORT_SYMBOL(ax25_send_frame);
107 
108 /*
109  *	All outgoing AX.25 I frames pass via this routine. Therefore this is
110  *	where the fragmentation of frames takes place. If fragment is set to
111  *	zero then we are not allowed to do fragmentation, even if the frame
112  *	is too large.
113  */
114 void ax25_output(ax25_cb *ax25, int paclen, struct sk_buff *skb)
115 {
116 	struct sk_buff *skbn;
117 	unsigned char *p;
118 	int frontlen, len, fragno, ka9qfrag, first = 1;
119 
120 	if (paclen < 16) {
121 		WARN_ON_ONCE(1);
122 		kfree_skb(skb);
123 		return;
124 	}
125 
126 	if ((skb->len - 1) > paclen) {
127 		if (*skb->data == AX25_P_TEXT) {
128 			skb_pull(skb, 1); /* skip PID */
129 			ka9qfrag = 0;
130 		} else {
131 			paclen -= 2;	/* Allow for fragment control info */
132 			ka9qfrag = 1;
133 		}
134 
135 		fragno = skb->len / paclen;
136 		if (skb->len % paclen == 0) fragno--;
137 
138 		frontlen = skb_headroom(skb);	/* Address space + CTRL */
139 
140 		while (skb->len > 0) {
141 			spin_lock_bh(&ax25_frag_lock);
142 			if ((skbn = alloc_skb(paclen + 2 + frontlen, GFP_ATOMIC)) == NULL) {
143 				spin_unlock_bh(&ax25_frag_lock);
144 				printk(KERN_CRIT "AX.25: ax25_output - out of memory\n");
145 				return;
146 			}
147 
148 			if (skb->sk != NULL)
149 				skb_set_owner_w(skbn, skb->sk);
150 
151 			spin_unlock_bh(&ax25_frag_lock);
152 
153 			len = (paclen > skb->len) ? skb->len : paclen;
154 
155 			if (ka9qfrag == 1) {
156 				skb_reserve(skbn, frontlen + 2);
157 				skb_set_network_header(skbn,
158 						      skb_network_offset(skb));
159 				skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
160 				p = skb_push(skbn, 2);
161 
162 				*p++ = AX25_P_SEGMENT;
163 
164 				*p = fragno--;
165 				if (first) {
166 					*p |= AX25_SEG_FIRST;
167 					first = 0;
168 				}
169 			} else {
170 				skb_reserve(skbn, frontlen + 1);
171 				skb_set_network_header(skbn,
172 						      skb_network_offset(skb));
173 				skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
174 				p = skb_push(skbn, 1);
175 				*p = AX25_P_TEXT;
176 			}
177 
178 			skb_pull(skb, len);
179 			skb_queue_tail(&ax25->write_queue, skbn); /* Throw it on the queue */
180 		}
181 
182 		kfree_skb(skb);
183 	} else {
184 		skb_queue_tail(&ax25->write_queue, skb);	  /* Throw it on the queue */
185 	}
186 
187 	switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
188 	case AX25_PROTO_STD_SIMPLEX:
189 	case AX25_PROTO_STD_DUPLEX:
190 		ax25_kick(ax25);
191 		break;
192 
193 #ifdef CONFIG_AX25_DAMA_SLAVE
194 	/*
195 	 * A DAMA slave is _required_ to work as normal AX.25L2V2
196 	 * if no DAMA master is available.
197 	 */
198 	case AX25_PROTO_DAMA_SLAVE:
199 		if (!ax25->ax25_dev->dama.slave) ax25_kick(ax25);
200 		break;
201 #endif
202 	}
203 }
204 
205 /*
206  *  This procedure is passed a buffer descriptor for an iframe. It builds
207  *  the rest of the control part of the frame and then writes it out.
208  */
209 static void ax25_send_iframe(ax25_cb *ax25, struct sk_buff *skb, int poll_bit)
210 {
211 	unsigned char *frame;
212 
213 	if (skb == NULL)
214 		return;
215 
216 	skb_reset_network_header(skb);
217 
218 	if (ax25->modulus == AX25_MODULUS) {
219 		frame = skb_push(skb, 1);
220 
221 		*frame = AX25_I;
222 		*frame |= (poll_bit) ? AX25_PF : 0;
223 		*frame |= (ax25->vr << 5);
224 		*frame |= (ax25->vs << 1);
225 	} else {
226 		frame = skb_push(skb, 2);
227 
228 		frame[0] = AX25_I;
229 		frame[0] |= (ax25->vs << 1);
230 		frame[1] = (poll_bit) ? AX25_EPF : 0;
231 		frame[1] |= (ax25->vr << 1);
232 	}
233 
234 	ax25_start_idletimer(ax25);
235 
236 	ax25_transmit_buffer(ax25, skb, AX25_COMMAND);
237 }
238 
239 void ax25_kick(ax25_cb *ax25)
240 {
241 	struct sk_buff *skb, *skbn;
242 	int last = 1;
243 	unsigned short start, end, next;
244 
245 	if (ax25->state != AX25_STATE_3 && ax25->state != AX25_STATE_4)
246 		return;
247 
248 	if (ax25->condition & AX25_COND_PEER_RX_BUSY)
249 		return;
250 
251 	if (skb_peek(&ax25->write_queue) == NULL)
252 		return;
253 
254 	start = (skb_peek(&ax25->ack_queue) == NULL) ? ax25->va : ax25->vs;
255 	end   = (ax25->va + ax25->window) % ax25->modulus;
256 
257 	if (start == end)
258 		return;
259 
260 	/*
261 	 * Transmit data until either we're out of data to send or
262 	 * the window is full. Send a poll on the final I frame if
263 	 * the window is filled.
264 	 */
265 
266 	/*
267 	 * Dequeue the frame and copy it.
268 	 * Check for race with ax25_clear_queues().
269 	 */
270 	skb  = skb_dequeue(&ax25->write_queue);
271 	if (!skb)
272 		return;
273 
274 	ax25->vs = start;
275 
276 	do {
277 		if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
278 			skb_queue_head(&ax25->write_queue, skb);
279 			break;
280 		}
281 
282 		if (skb->sk != NULL)
283 			skb_set_owner_w(skbn, skb->sk);
284 
285 		next = (ax25->vs + 1) % ax25->modulus;
286 		last = (next == end);
287 
288 		/*
289 		 * Transmit the frame copy.
290 		 * bke 960114: do not set the Poll bit on the last frame
291 		 * in DAMA mode.
292 		 */
293 		switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
294 		case AX25_PROTO_STD_SIMPLEX:
295 		case AX25_PROTO_STD_DUPLEX:
296 			ax25_send_iframe(ax25, skbn, (last) ? AX25_POLLON : AX25_POLLOFF);
297 			break;
298 
299 #ifdef CONFIG_AX25_DAMA_SLAVE
300 		case AX25_PROTO_DAMA_SLAVE:
301 			ax25_send_iframe(ax25, skbn, AX25_POLLOFF);
302 			break;
303 #endif
304 		}
305 
306 		ax25->vs = next;
307 
308 		/*
309 		 * Requeue the original data frame.
310 		 */
311 		skb_queue_tail(&ax25->ack_queue, skb);
312 
313 	} while (!last && (skb = skb_dequeue(&ax25->write_queue)) != NULL);
314 
315 	ax25->condition &= ~AX25_COND_ACK_PENDING;
316 
317 	if (!ax25_t1timer_running(ax25)) {
318 		ax25_stop_t3timer(ax25);
319 		ax25_calculate_t1(ax25);
320 		ax25_start_t1timer(ax25);
321 	}
322 }
323 
324 void ax25_transmit_buffer(ax25_cb *ax25, struct sk_buff *skb, int type)
325 {
326 	struct sk_buff *skbn;
327 	unsigned char *ptr;
328 	int headroom;
329 
330 	if (ax25->ax25_dev == NULL) {
331 		ax25_disconnect(ax25, ENETUNREACH);
332 		return;
333 	}
334 
335 	headroom = ax25_addr_size(ax25->digipeat);
336 
337 	if (skb_headroom(skb) < headroom) {
338 		if ((skbn = skb_realloc_headroom(skb, headroom)) == NULL) {
339 			printk(KERN_CRIT "AX.25: ax25_transmit_buffer - out of memory\n");
340 			kfree_skb(skb);
341 			return;
342 		}
343 
344 		if (skb->sk != NULL)
345 			skb_set_owner_w(skbn, skb->sk);
346 
347 		kfree_skb(skb);
348 		skb = skbn;
349 	}
350 
351 	ptr = skb_push(skb, headroom);
352 
353 	ax25_addr_build(ptr, &ax25->source_addr, &ax25->dest_addr, ax25->digipeat, type, ax25->modulus);
354 
355 	ax25_queue_xmit(skb, ax25->ax25_dev->dev);
356 }
357 
358 /*
359  *	A small shim to dev_queue_xmit to add the KISS control byte, and do
360  *	any packet forwarding in operation.
361  */
362 void ax25_queue_xmit(struct sk_buff *skb, struct net_device *dev)
363 {
364 	unsigned char *ptr;
365 
366 	skb->protocol = ax25_type_trans(skb, ax25_fwd_dev(dev));
367 
368 	ptr  = skb_push(skb, 1);
369 	*ptr = 0x00;			/* KISS */
370 
371 	dev_queue_xmit(skb);
372 }
373 
374 int ax25_check_iframes_acked(ax25_cb *ax25, unsigned short nr)
375 {
376 	if (ax25->vs == nr) {
377 		ax25_frames_acked(ax25, nr);
378 		ax25_calculate_rtt(ax25);
379 		ax25_stop_t1timer(ax25);
380 		ax25_start_t3timer(ax25);
381 		return 1;
382 	} else {
383 		if (ax25->va != nr) {
384 			ax25_frames_acked(ax25, nr);
385 			ax25_calculate_t1(ax25);
386 			ax25_start_t1timer(ax25);
387 			return 1;
388 		}
389 	}
390 	return 0;
391 }
392 
393