xref: /linux/net/ax25/ax25_out.c (revision c537b994505099b7197e7d3125b942ecbcc51eb6) 
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 ((skb->len - 1) > paclen) {
121 		if (*skb->data == AX25_P_TEXT) {
122 			skb_pull(skb, 1); /* skip PID */
123 			ka9qfrag = 0;
124 		} else {
125 			paclen -= 2;	/* Allow for fragment control info */
126 			ka9qfrag = 1;
127 		}
128 
129 		fragno = skb->len / paclen;
130 		if (skb->len % paclen == 0) fragno--;
131 
132 		frontlen = skb_headroom(skb);	/* Address space + CTRL */
133 
134 		while (skb->len > 0) {
135 			spin_lock_bh(&ax25_frag_lock);
136 			if ((skbn = alloc_skb(paclen + 2 + frontlen, GFP_ATOMIC)) == NULL) {
137 				spin_unlock_bh(&ax25_frag_lock);
138 				printk(KERN_CRIT "AX.25: ax25_output - out of memory\n");
139 				return;
140 			}
141 
142 			if (skb->sk != NULL)
143 				skb_set_owner_w(skbn, skb->sk);
144 
145 			spin_unlock_bh(&ax25_frag_lock);
146 
147 			len = (paclen > skb->len) ? skb->len : paclen;
148 
149 			if (ka9qfrag == 1) {
150 				skb_reserve(skbn, frontlen + 2);
151 				skbn->nh.raw = skbn->data + (skb->nh.raw - skb->data);
152 				memcpy(skb_put(skbn, len), skb->data, len);
153 				p = skb_push(skbn, 2);
154 
155 				*p++ = AX25_P_SEGMENT;
156 
157 				*p = fragno--;
158 				if (first) {
159 					*p |= AX25_SEG_FIRST;
160 					first = 0;
161 				}
162 			} else {
163 				skb_reserve(skbn, frontlen + 1);
164 				skbn->nh.raw = skbn->data + (skb->nh.raw - skb->data);
165 				memcpy(skb_put(skbn, len), skb->data, len);
166 				p = skb_push(skbn, 1);
167 				*p = AX25_P_TEXT;
168 			}
169 
170 			skb_pull(skb, len);
171 			skb_queue_tail(&ax25->write_queue, skbn); /* Throw it on the queue */
172 		}
173 
174 		kfree_skb(skb);
175 	} else {
176 		skb_queue_tail(&ax25->write_queue, skb);	  /* Throw it on the queue */
177 	}
178 
179 	switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
180 	case AX25_PROTO_STD_SIMPLEX:
181 	case AX25_PROTO_STD_DUPLEX:
182 		ax25_kick(ax25);
183 		break;
184 
185 #ifdef CONFIG_AX25_DAMA_SLAVE
186 	/*
187 	 * A DAMA slave is _required_ to work as normal AX.25L2V2
188 	 * if no DAMA master is available.
189 	 */
190 	case AX25_PROTO_DAMA_SLAVE:
191 		if (!ax25->ax25_dev->dama.slave) ax25_kick(ax25);
192 		break;
193 #endif
194 	}
195 }
196 
197 /*
198  *  This procedure is passed a buffer descriptor for an iframe. It builds
199  *  the rest of the control part of the frame and then writes it out.
200  */
201 static void ax25_send_iframe(ax25_cb *ax25, struct sk_buff *skb, int poll_bit)
202 {
203 	unsigned char *frame;
204 
205 	if (skb == NULL)
206 		return;
207 
208 	skb->nh.raw = skb->data;
209 
210 	if (ax25->modulus == AX25_MODULUS) {
211 		frame = skb_push(skb, 1);
212 
213 		*frame = AX25_I;
214 		*frame |= (poll_bit) ? AX25_PF : 0;
215 		*frame |= (ax25->vr << 5);
216 		*frame |= (ax25->vs << 1);
217 	} else {
218 		frame = skb_push(skb, 2);
219 
220 		frame[0] = AX25_I;
221 		frame[0] |= (ax25->vs << 1);
222 		frame[1] = (poll_bit) ? AX25_EPF : 0;
223 		frame[1] |= (ax25->vr << 1);
224 	}
225 
226 	ax25_start_idletimer(ax25);
227 
228 	ax25_transmit_buffer(ax25, skb, AX25_COMMAND);
229 }
230 
231 void ax25_kick(ax25_cb *ax25)
232 {
233 	struct sk_buff *skb, *skbn;
234 	int last = 1;
235 	unsigned short start, end, next;
236 
237 	if (ax25->state != AX25_STATE_3 && ax25->state != AX25_STATE_4)
238 		return;
239 
240 	if (ax25->condition & AX25_COND_PEER_RX_BUSY)
241 		return;
242 
243 	if (skb_peek(&ax25->write_queue) == NULL)
244 		return;
245 
246 	start = (skb_peek(&ax25->ack_queue) == NULL) ? ax25->va : ax25->vs;
247 	end   = (ax25->va + ax25->window) % ax25->modulus;
248 
249 	if (start == end)
250 		return;
251 
252 	ax25->vs = start;
253 
254 	/*
255 	 * Transmit data until either we're out of data to send or
256 	 * the window is full. Send a poll on the final I frame if
257 	 * the window is filled.
258 	 */
259 
260 	/*
261 	 * Dequeue the frame and copy it.
262 	 */
263 	skb  = skb_dequeue(&ax25->write_queue);
264 
265 	do {
266 		if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
267 			skb_queue_head(&ax25->write_queue, skb);
268 			break;
269 		}
270 
271 		if (skb->sk != NULL)
272 			skb_set_owner_w(skbn, skb->sk);
273 
274 		next = (ax25->vs + 1) % ax25->modulus;
275 		last = (next == end);
276 
277 		/*
278 		 * Transmit the frame copy.
279 		 * bke 960114: do not set the Poll bit on the last frame
280 		 * in DAMA mode.
281 		 */
282 		switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
283 		case AX25_PROTO_STD_SIMPLEX:
284 		case AX25_PROTO_STD_DUPLEX:
285 			ax25_send_iframe(ax25, skbn, (last) ? AX25_POLLON : AX25_POLLOFF);
286 			break;
287 
288 #ifdef CONFIG_AX25_DAMA_SLAVE
289 		case AX25_PROTO_DAMA_SLAVE:
290 			ax25_send_iframe(ax25, skbn, AX25_POLLOFF);
291 			break;
292 #endif
293 		}
294 
295 		ax25->vs = next;
296 
297 		/*
298 		 * Requeue the original data frame.
299 		 */
300 		skb_queue_tail(&ax25->ack_queue, skb);
301 
302 	} while (!last && (skb = skb_dequeue(&ax25->write_queue)) != NULL);
303 
304 	ax25->condition &= ~AX25_COND_ACK_PENDING;
305 
306 	if (!ax25_t1timer_running(ax25)) {
307 		ax25_stop_t3timer(ax25);
308 		ax25_calculate_t1(ax25);
309 		ax25_start_t1timer(ax25);
310 	}
311 }
312 
313 void ax25_transmit_buffer(ax25_cb *ax25, struct sk_buff *skb, int type)
314 {
315 	struct sk_buff *skbn;
316 	unsigned char *ptr;
317 	int headroom;
318 
319 	if (ax25->ax25_dev == NULL) {
320 		ax25_disconnect(ax25, ENETUNREACH);
321 		return;
322 	}
323 
324 	headroom = ax25_addr_size(ax25->digipeat);
325 
326 	if (skb_headroom(skb) < headroom) {
327 		if ((skbn = skb_realloc_headroom(skb, headroom)) == NULL) {
328 			printk(KERN_CRIT "AX.25: ax25_transmit_buffer - out of memory\n");
329 			kfree_skb(skb);
330 			return;
331 		}
332 
333 		if (skb->sk != NULL)
334 			skb_set_owner_w(skbn, skb->sk);
335 
336 		kfree_skb(skb);
337 		skb = skbn;
338 	}
339 
340 	ptr = skb_push(skb, headroom);
341 
342 	ax25_addr_build(ptr, &ax25->source_addr, &ax25->dest_addr, ax25->digipeat, type, ax25->modulus);
343 
344 	ax25_queue_xmit(skb, ax25->ax25_dev->dev);
345 }
346 
347 /*
348  *	A small shim to dev_queue_xmit to add the KISS control byte, and do
349  *	any packet forwarding in operation.
350  */
351 void ax25_queue_xmit(struct sk_buff *skb, struct net_device *dev)
352 {
353 	unsigned char *ptr;
354 
355 	skb->protocol = ax25_type_trans(skb, ax25_fwd_dev(dev));
356 
357 	ptr  = skb_push(skb, 1);
358 	*ptr = 0x00;			/* KISS */
359 
360 	dev_queue_xmit(skb);
361 }
362 
363 int ax25_check_iframes_acked(ax25_cb *ax25, unsigned short nr)
364 {
365 	if (ax25->vs == nr) {
366 		ax25_frames_acked(ax25, nr);
367 		ax25_calculate_rtt(ax25);
368 		ax25_stop_t1timer(ax25);
369 		ax25_start_t3timer(ax25);
370 		return 1;
371 	} else {
372 		if (ax25->va != nr) {
373 			ax25_frames_acked(ax25, nr);
374 			ax25_calculate_t1(ax25);
375 			ax25_start_t1timer(ax25);
376 			return 1;
377 		}
378 	}
379 	return 0;
380 }
381 
382