xref: /linux/net/ax25/ax25_out.c (revision 14b42963f64b98ab61fa9723c03d71aa5ef4f862) 
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/sched.h>
18 #include <linux/timer.h>
19 #include <linux/string.h>
20 #include <linux/sockios.h>
21 #include <linux/spinlock.h>
22 #include <linux/net.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 <asm/system.h>
31 #include <linux/fcntl.h>
32 #include <linux/mm.h>
33 #include <linux/interrupt.h>
34 
35 static DEFINE_SPINLOCK(ax25_frag_lock);
36 
37 ax25_cb *ax25_send_frame(struct sk_buff *skb, int paclen, ax25_address *src, ax25_address *dest, ax25_digi *digi, struct net_device *dev)
38 {
39 	ax25_dev *ax25_dev;
40 	ax25_cb *ax25;
41 
42 	/*
43 	 * Take the default packet length for the device if zero is
44 	 * specified.
45 	 */
46 	if (paclen == 0) {
47 		if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
48 			return NULL;
49 
50 		paclen = ax25_dev->values[AX25_VALUES_PACLEN];
51 	}
52 
53 	/*
54 	 * Look for an existing connection.
55 	 */
56 	if ((ax25 = ax25_find_cb(src, dest, digi, dev)) != NULL) {
57 		ax25_output(ax25, paclen, skb);
58 		return ax25;		/* It already existed */
59 	}
60 
61 	if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
62 		return NULL;
63 
64 	if ((ax25 = ax25_create_cb()) == NULL)
65 		return NULL;
66 
67 	ax25_fillin_cb(ax25, ax25_dev);
68 
69 	ax25->source_addr = *src;
70 	ax25->dest_addr   = *dest;
71 
72 	if (digi != NULL) {
73 		if ((ax25->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
74 			ax25_cb_put(ax25);
75 			return NULL;
76 		}
77 		memcpy(ax25->digipeat, digi, sizeof(ax25_digi));
78 	}
79 
80 	switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
81 	case AX25_PROTO_STD_SIMPLEX:
82 	case AX25_PROTO_STD_DUPLEX:
83 		ax25_std_establish_data_link(ax25);
84 		break;
85 
86 #ifdef CONFIG_AX25_DAMA_SLAVE
87 	case AX25_PROTO_DAMA_SLAVE:
88 		if (ax25_dev->dama.slave)
89 			ax25_ds_establish_data_link(ax25);
90 		else
91 			ax25_std_establish_data_link(ax25);
92 		break;
93 #endif
94 	}
95 
96 	ax25_cb_add(ax25);
97 
98 	ax25->state = AX25_STATE_1;
99 
100 	ax25_start_heartbeat(ax25);
101 
102 	ax25_output(ax25, paclen, skb);
103 
104 	return ax25;			/* We had to create it */
105 }
106 
107 EXPORT_SYMBOL(ax25_send_frame);
108 
109 /*
110  *	All outgoing AX.25 I frames pass via this routine. Therefore this is
111  *	where the fragmentation of frames takes place. If fragment is set to
112  *	zero then we are not allowed to do fragmentation, even if the frame
113  *	is too large.
114  */
115 void ax25_output(ax25_cb *ax25, int paclen, struct sk_buff *skb)
116 {
117 	struct sk_buff *skbn;
118 	unsigned char *p;
119 	int frontlen, len, fragno, ka9qfrag, first = 1;
120 
121 	if ((skb->len - 1) > paclen) {
122 		if (*skb->data == AX25_P_TEXT) {
123 			skb_pull(skb, 1); /* skip PID */
124 			ka9qfrag = 0;
125 		} else {
126 			paclen -= 2;	/* Allow for fragment control info */
127 			ka9qfrag = 1;
128 		}
129 
130 		fragno = skb->len / paclen;
131 		if (skb->len % paclen == 0) fragno--;
132 
133 		frontlen = skb_headroom(skb);	/* Address space + CTRL */
134 
135 		while (skb->len > 0) {
136 			spin_lock_bh(&ax25_frag_lock);
137 			if ((skbn = alloc_skb(paclen + 2 + frontlen, GFP_ATOMIC)) == NULL) {
138 				spin_unlock_bh(&ax25_frag_lock);
139 				printk(KERN_CRIT "AX.25: ax25_output - out of memory\n");
140 				return;
141 			}
142 
143 			if (skb->sk != NULL)
144 				skb_set_owner_w(skbn, skb->sk);
145 
146 			spin_unlock_bh(&ax25_frag_lock);
147 
148 			len = (paclen > skb->len) ? skb->len : paclen;
149 
150 			if (ka9qfrag == 1) {
151 				skb_reserve(skbn, frontlen + 2);
152 				skbn->nh.raw = skbn->data + (skb->nh.raw - skb->data);
153 				memcpy(skb_put(skbn, len), skb->data, len);
154 				p = skb_push(skbn, 2);
155 
156 				*p++ = AX25_P_SEGMENT;
157 
158 				*p = fragno--;
159 				if (first) {
160 					*p |= AX25_SEG_FIRST;
161 					first = 0;
162 				}
163 			} else {
164 				skb_reserve(skbn, frontlen + 1);
165 				skbn->nh.raw = skbn->data + (skb->nh.raw - skb->data);
166 				memcpy(skb_put(skbn, len), skb->data, len);
167 				p = skb_push(skbn, 1);
168 				*p = AX25_P_TEXT;
169 			}
170 
171 			skb_pull(skb, len);
172 			skb_queue_tail(&ax25->write_queue, skbn); /* Throw it on the queue */
173 		}
174 
175 		kfree_skb(skb);
176 	} else {
177 		skb_queue_tail(&ax25->write_queue, skb);	  /* Throw it on the queue */
178 	}
179 
180 	switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
181 	case AX25_PROTO_STD_SIMPLEX:
182 	case AX25_PROTO_STD_DUPLEX:
183 		ax25_kick(ax25);
184 		break;
185 
186 #ifdef CONFIG_AX25_DAMA_SLAVE
187 	/*
188 	 * A DAMA slave is _required_ to work as normal AX.25L2V2
189 	 * if no DAMA master is available.
190 	 */
191 	case AX25_PROTO_DAMA_SLAVE:
192 		if (!ax25->ax25_dev->dama.slave) ax25_kick(ax25);
193 		break;
194 #endif
195 	}
196 }
197 
198 /*
199  *  This procedure is passed a buffer descriptor for an iframe. It builds
200  *  the rest of the control part of the frame and then writes it out.
201  */
202 static void ax25_send_iframe(ax25_cb *ax25, struct sk_buff *skb, int poll_bit)
203 {
204 	unsigned char *frame;
205 
206 	if (skb == NULL)
207 		return;
208 
209 	skb->nh.raw = skb->data;
210 
211 	if (ax25->modulus == AX25_MODULUS) {
212 		frame = skb_push(skb, 1);
213 
214 		*frame = AX25_I;
215 		*frame |= (poll_bit) ? AX25_PF : 0;
216 		*frame |= (ax25->vr << 5);
217 		*frame |= (ax25->vs << 1);
218 	} else {
219 		frame = skb_push(skb, 2);
220 
221 		frame[0] = AX25_I;
222 		frame[0] |= (ax25->vs << 1);
223 		frame[1] = (poll_bit) ? AX25_EPF : 0;
224 		frame[1] |= (ax25->vr << 1);
225 	}
226 
227 	ax25_start_idletimer(ax25);
228 
229 	ax25_transmit_buffer(ax25, skb, AX25_COMMAND);
230 }
231 
232 void ax25_kick(ax25_cb *ax25)
233 {
234 	struct sk_buff *skb, *skbn;
235 	int last = 1;
236 	unsigned short start, end, next;
237 
238 	if (ax25->state != AX25_STATE_3 && ax25->state != AX25_STATE_4)
239 		return;
240 
241 	if (ax25->condition & AX25_COND_PEER_RX_BUSY)
242 		return;
243 
244 	if (skb_peek(&ax25->write_queue) == NULL)
245 		return;
246 
247 	start = (skb_peek(&ax25->ack_queue) == NULL) ? ax25->va : ax25->vs;
248 	end   = (ax25->va + ax25->window) % ax25->modulus;
249 
250 	if (start == end)
251 		return;
252 
253 	ax25->vs = start;
254 
255 	/*
256 	 * Transmit data until either we're out of data to send or
257 	 * the window is full. Send a poll on the final I frame if
258 	 * the window is filled.
259 	 */
260 
261 	/*
262 	 * Dequeue the frame and copy it.
263 	 */
264 	skb  = skb_dequeue(&ax25->write_queue);
265 
266 	do {
267 		if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
268 			skb_queue_head(&ax25->write_queue, skb);
269 			break;
270 		}
271 
272 		if (skb->sk != NULL)
273 			skb_set_owner_w(skbn, skb->sk);
274 
275 		next = (ax25->vs + 1) % ax25->modulus;
276 		last = (next == end);
277 
278 		/*
279 		 * Transmit the frame copy.
280 		 * bke 960114: do not set the Poll bit on the last frame
281 		 * in DAMA mode.
282 		 */
283 		switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
284 		case AX25_PROTO_STD_SIMPLEX:
285 		case AX25_PROTO_STD_DUPLEX:
286 			ax25_send_iframe(ax25, skbn, (last) ? AX25_POLLON : AX25_POLLOFF);
287 			break;
288 
289 #ifdef CONFIG_AX25_DAMA_SLAVE
290 		case AX25_PROTO_DAMA_SLAVE:
291 			ax25_send_iframe(ax25, skbn, AX25_POLLOFF);
292 			break;
293 #endif
294 		}
295 
296 		ax25->vs = next;
297 
298 		/*
299 		 * Requeue the original data frame.
300 		 */
301 		skb_queue_tail(&ax25->ack_queue, skb);
302 
303 	} while (!last && (skb = skb_dequeue(&ax25->write_queue)) != NULL);
304 
305 	ax25->condition &= ~AX25_COND_ACK_PENDING;
306 
307 	if (!ax25_t1timer_running(ax25)) {
308 		ax25_stop_t3timer(ax25);
309 		ax25_calculate_t1(ax25);
310 		ax25_start_t1timer(ax25);
311 	}
312 }
313 
314 void ax25_transmit_buffer(ax25_cb *ax25, struct sk_buff *skb, int type)
315 {
316 	struct sk_buff *skbn;
317 	unsigned char *ptr;
318 	int headroom;
319 
320 	if (ax25->ax25_dev == NULL) {
321 		ax25_disconnect(ax25, ENETUNREACH);
322 		return;
323 	}
324 
325 	headroom = ax25_addr_size(ax25->digipeat);
326 
327 	if (skb_headroom(skb) < headroom) {
328 		if ((skbn = skb_realloc_headroom(skb, headroom)) == NULL) {
329 			printk(KERN_CRIT "AX.25: ax25_transmit_buffer - out of memory\n");
330 			kfree_skb(skb);
331 			return;
332 		}
333 
334 		if (skb->sk != NULL)
335 			skb_set_owner_w(skbn, skb->sk);
336 
337 		kfree_skb(skb);
338 		skb = skbn;
339 	}
340 
341 	ptr = skb_push(skb, headroom);
342 
343 	ax25_addr_build(ptr, &ax25->source_addr, &ax25->dest_addr, ax25->digipeat, type, ax25->modulus);
344 
345 	ax25_queue_xmit(skb, ax25->ax25_dev->dev);
346 }
347 
348 /*
349  *	A small shim to dev_queue_xmit to add the KISS control byte, and do
350  *	any packet forwarding in operation.
351  */
352 void ax25_queue_xmit(struct sk_buff *skb, struct net_device *dev)
353 {
354 	unsigned char *ptr;
355 
356 	skb->protocol = ax25_type_trans(skb, ax25_fwd_dev(dev));
357 
358 	ptr  = skb_push(skb, 1);
359 	*ptr = 0x00;			/* KISS */
360 
361 	dev_queue_xmit(skb);
362 }
363 
364 int ax25_check_iframes_acked(ax25_cb *ax25, unsigned short nr)
365 {
366 	if (ax25->vs == nr) {
367 		ax25_frames_acked(ax25, nr);
368 		ax25_calculate_rtt(ax25);
369 		ax25_stop_t1timer(ax25);
370 		ax25_start_t3timer(ax25);
371 		return 1;
372 	} else {
373 		if (ax25->va != nr) {
374 			ax25_frames_acked(ax25, nr);
375 			ax25_calculate_t1(ax25);
376 			ax25_start_t1timer(ax25);
377 			return 1;
378 		}
379 	}
380 	return 0;
381 }
382 
383