xref: /linux/net/ax25/ax25_out.c (revision 44896afe214e780e172f1bbbea7a2e6d087c908d) 
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 
33 static DEFINE_SPINLOCK(ax25_frag_lock);
34 
35 ax25_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 
111 EXPORT_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  */
119 void 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  */
214 static 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 
244 void 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 
329 void 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  */
367 void 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 
379 int 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