xref: /openbmc/linux/net/ax25/ax25_out.c (revision 4f3db074) 
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 <linux/netfilter.h>
28 #include <net/sock.h>
29 #include <asm/uaccess.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 	/*
96 	 * There is one ref for the state machine; a caller needs
97 	 * one more to put it back, just like with the existing one.
98 	 */
99 	ax25_cb_hold(ax25);
100 
101 	ax25_cb_add(ax25);
102 
103 	ax25->state = AX25_STATE_1;
104 
105 	ax25_start_heartbeat(ax25);
106 
107 	ax25_output(ax25, paclen, skb);
108 
109 	return ax25;			/* We had to create it */
110 }
111 
112 EXPORT_SYMBOL(ax25_send_frame);
113 
114 /*
115  *	All outgoing AX.25 I frames pass via this routine. Therefore this is
116  *	where the fragmentation of frames takes place. If fragment is set to
117  *	zero then we are not allowed to do fragmentation, even if the frame
118  *	is too large.
119  */
120 void ax25_output(ax25_cb *ax25, int paclen, struct sk_buff *skb)
121 {
122 	struct sk_buff *skbn;
123 	unsigned char *p;
124 	int frontlen, len, fragno, ka9qfrag, first = 1;
125 
126 	if (paclen < 16) {
127 		WARN_ON_ONCE(1);
128 		kfree_skb(skb);
129 		return;
130 	}
131 
132 	if ((skb->len - 1) > paclen) {
133 		if (*skb->data == AX25_P_TEXT) {
134 			skb_pull(skb, 1); /* skip PID */
135 			ka9qfrag = 0;
136 		} else {
137 			paclen -= 2;	/* Allow for fragment control info */
138 			ka9qfrag = 1;
139 		}
140 
141 		fragno = skb->len / paclen;
142 		if (skb->len % paclen == 0) fragno--;
143 
144 		frontlen = skb_headroom(skb);	/* Address space + CTRL */
145 
146 		while (skb->len > 0) {
147 			spin_lock_bh(&ax25_frag_lock);
148 			if ((skbn = alloc_skb(paclen + 2 + frontlen, GFP_ATOMIC)) == NULL) {
149 				spin_unlock_bh(&ax25_frag_lock);
150 				printk(KERN_CRIT "AX.25: ax25_output - out of memory\n");
151 				return;
152 			}
153 
154 			if (skb->sk != NULL)
155 				skb_set_owner_w(skbn, skb->sk);
156 
157 			spin_unlock_bh(&ax25_frag_lock);
158 
159 			len = (paclen > skb->len) ? skb->len : paclen;
160 
161 			if (ka9qfrag == 1) {
162 				skb_reserve(skbn, frontlen + 2);
163 				skb_set_network_header(skbn,
164 						      skb_network_offset(skb));
165 				skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
166 				p = skb_push(skbn, 2);
167 
168 				*p++ = AX25_P_SEGMENT;
169 
170 				*p = fragno--;
171 				if (first) {
172 					*p |= AX25_SEG_FIRST;
173 					first = 0;
174 				}
175 			} else {
176 				skb_reserve(skbn, frontlen + 1);
177 				skb_set_network_header(skbn,
178 						      skb_network_offset(skb));
179 				skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
180 				p = skb_push(skbn, 1);
181 				*p = AX25_P_TEXT;
182 			}
183 
184 			skb_pull(skb, len);
185 			skb_queue_tail(&ax25->write_queue, skbn); /* Throw it on the queue */
186 		}
187 
188 		kfree_skb(skb);
189 	} else {
190 		skb_queue_tail(&ax25->write_queue, skb);	  /* Throw it on the queue */
191 	}
192 
193 	switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
194 	case AX25_PROTO_STD_SIMPLEX:
195 	case AX25_PROTO_STD_DUPLEX:
196 		ax25_kick(ax25);
197 		break;
198 
199 #ifdef CONFIG_AX25_DAMA_SLAVE
200 	/*
201 	 * A DAMA slave is _required_ to work as normal AX.25L2V2
202 	 * if no DAMA master is available.
203 	 */
204 	case AX25_PROTO_DAMA_SLAVE:
205 		if (!ax25->ax25_dev->dama.slave) ax25_kick(ax25);
206 		break;
207 #endif
208 	}
209 }
210 
211 /*
212  *  This procedure is passed a buffer descriptor for an iframe. It builds
213  *  the rest of the control part of the frame and then writes it out.
214  */
215 static void ax25_send_iframe(ax25_cb *ax25, struct sk_buff *skb, int poll_bit)
216 {
217 	unsigned char *frame;
218 
219 	if (skb == NULL)
220 		return;
221 
222 	skb_reset_network_header(skb);
223 
224 	if (ax25->modulus == AX25_MODULUS) {
225 		frame = skb_push(skb, 1);
226 
227 		*frame = AX25_I;
228 		*frame |= (poll_bit) ? AX25_PF : 0;
229 		*frame |= (ax25->vr << 5);
230 		*frame |= (ax25->vs << 1);
231 	} else {
232 		frame = skb_push(skb, 2);
233 
234 		frame[0] = AX25_I;
235 		frame[0] |= (ax25->vs << 1);
236 		frame[1] = (poll_bit) ? AX25_EPF : 0;
237 		frame[1] |= (ax25->vr << 1);
238 	}
239 
240 	ax25_start_idletimer(ax25);
241 
242 	ax25_transmit_buffer(ax25, skb, AX25_COMMAND);
243 }
244 
245 void ax25_kick(ax25_cb *ax25)
246 {
247 	struct sk_buff *skb, *skbn;
248 	int last = 1;
249 	unsigned short start, end, next;
250 
251 	if (ax25->state != AX25_STATE_3 && ax25->state != AX25_STATE_4)
252 		return;
253 
254 	if (ax25->condition & AX25_COND_PEER_RX_BUSY)
255 		return;
256 
257 	if (skb_peek(&ax25->write_queue) == NULL)
258 		return;
259 
260 	start = (skb_peek(&ax25->ack_queue) == NULL) ? ax25->va : ax25->vs;
261 	end   = (ax25->va + ax25->window) % ax25->modulus;
262 
263 	if (start == end)
264 		return;
265 
266 	/*
267 	 * Transmit data until either we're out of data to send or
268 	 * the window is full. Send a poll on the final I frame if
269 	 * the window is filled.
270 	 */
271 
272 	/*
273 	 * Dequeue the frame and copy it.
274 	 * Check for race with ax25_clear_queues().
275 	 */
276 	skb  = skb_dequeue(&ax25->write_queue);
277 	if (!skb)
278 		return;
279 
280 	ax25->vs = start;
281 
282 	do {
283 		if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
284 			skb_queue_head(&ax25->write_queue, skb);
285 			break;
286 		}
287 
288 		if (skb->sk != NULL)
289 			skb_set_owner_w(skbn, skb->sk);
290 
291 		next = (ax25->vs + 1) % ax25->modulus;
292 		last = (next == end);
293 
294 		/*
295 		 * Transmit the frame copy.
296 		 * bke 960114: do not set the Poll bit on the last frame
297 		 * in DAMA mode.
298 		 */
299 		switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
300 		case AX25_PROTO_STD_SIMPLEX:
301 		case AX25_PROTO_STD_DUPLEX:
302 			ax25_send_iframe(ax25, skbn, (last) ? AX25_POLLON : AX25_POLLOFF);
303 			break;
304 
305 #ifdef CONFIG_AX25_DAMA_SLAVE
306 		case AX25_PROTO_DAMA_SLAVE:
307 			ax25_send_iframe(ax25, skbn, AX25_POLLOFF);
308 			break;
309 #endif
310 		}
311 
312 		ax25->vs = next;
313 
314 		/*
315 		 * Requeue the original data frame.
316 		 */
317 		skb_queue_tail(&ax25->ack_queue, skb);
318 
319 	} while (!last && (skb = skb_dequeue(&ax25->write_queue)) != NULL);
320 
321 	ax25->condition &= ~AX25_COND_ACK_PENDING;
322 
323 	if (!ax25_t1timer_running(ax25)) {
324 		ax25_stop_t3timer(ax25);
325 		ax25_calculate_t1(ax25);
326 		ax25_start_t1timer(ax25);
327 	}
328 }
329 
330 void ax25_transmit_buffer(ax25_cb *ax25, struct sk_buff *skb, int type)
331 {
332 	struct sk_buff *skbn;
333 	unsigned char *ptr;
334 	int headroom;
335 
336 	if (ax25->ax25_dev == NULL) {
337 		ax25_disconnect(ax25, ENETUNREACH);
338 		return;
339 	}
340 
341 	headroom = ax25_addr_size(ax25->digipeat);
342 
343 	if (skb_headroom(skb) < headroom) {
344 		if ((skbn = skb_realloc_headroom(skb, headroom)) == NULL) {
345 			printk(KERN_CRIT "AX.25: ax25_transmit_buffer - out of memory\n");
346 			kfree_skb(skb);
347 			return;
348 		}
349 
350 		if (skb->sk != NULL)
351 			skb_set_owner_w(skbn, skb->sk);
352 
353 		consume_skb(skb);
354 		skb = skbn;
355 	}
356 
357 	ptr = skb_push(skb, headroom);
358 
359 	ax25_addr_build(ptr, &ax25->source_addr, &ax25->dest_addr, ax25->digipeat, type, ax25->modulus);
360 
361 	ax25_queue_xmit(skb, ax25->ax25_dev->dev);
362 }
363 
364 /*
365  *	A small shim to dev_queue_xmit to add the KISS control byte, and do
366  *	any packet forwarding in operation.
367  */
368 void ax25_queue_xmit(struct sk_buff *skb, struct net_device *dev)
369 {
370 	unsigned char *ptr;
371 
372 	skb->protocol = ax25_type_trans(skb, ax25_fwd_dev(dev));
373 
374 	ptr  = skb_push(skb, 1);
375 	*ptr = 0x00;			/* KISS */
376 
377 	dev_queue_xmit(skb);
378 }
379 
380 int ax25_check_iframes_acked(ax25_cb *ax25, unsigned short nr)
381 {
382 	if (ax25->vs == nr) {
383 		ax25_frames_acked(ax25, nr);
384 		ax25_calculate_rtt(ax25);
385 		ax25_stop_t1timer(ax25);
386 		ax25_start_t3timer(ax25);
387 		return 1;
388 	} else {
389 		if (ax25->va != nr) {
390 			ax25_frames_acked(ax25, nr);
391 			ax25_calculate_t1(ax25);
392 			ax25_start_t1timer(ax25);
393 			return 1;
394 		}
395 	}
396 	return 0;
397 }
398 
399