xref: /linux/net/ax25/ax25_out.c (revision 3f0a50f345f78183f6e9b39c2f45ca5dcaa511ca) 
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  *
4  * Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk)
5  * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
6  * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
7  */
8 #include <linux/errno.h>
9 #include <linux/types.h>
10 #include <linux/socket.h>
11 #include <linux/in.h>
12 #include <linux/kernel.h>
13 #include <linux/module.h>
14 #include <linux/timer.h>
15 #include <linux/string.h>
16 #include <linux/sockios.h>
17 #include <linux/spinlock.h>
18 #include <linux/net.h>
19 #include <linux/slab.h>
20 #include <net/ax25.h>
21 #include <linux/inet.h>
22 #include <linux/netdevice.h>
23 #include <linux/skbuff.h>
24 #include <net/sock.h>
25 #include <linux/uaccess.h>
26 #include <linux/fcntl.h>
27 #include <linux/mm.h>
28 #include <linux/interrupt.h>
29 
30 static DEFINE_SPINLOCK(ax25_frag_lock);
31 
32 ax25_cb *ax25_send_frame(struct sk_buff *skb, int paclen, const ax25_address *src, ax25_address *dest, ax25_digi *digi, struct net_device *dev)
33 {
34 	ax25_dev *ax25_dev;
35 	ax25_cb *ax25;
36 
37 	/*
38 	 * Take the default packet length for the device if zero is
39 	 * specified.
40 	 */
41 	if (paclen == 0) {
42 		if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
43 			return NULL;
44 
45 		paclen = ax25_dev->values[AX25_VALUES_PACLEN];
46 	}
47 
48 	/*
49 	 * Look for an existing connection.
50 	 */
51 	if ((ax25 = ax25_find_cb(src, dest, digi, dev)) != NULL) {
52 		ax25_output(ax25, paclen, skb);
53 		return ax25;		/* It already existed */
54 	}
55 
56 	if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
57 		return NULL;
58 
59 	if ((ax25 = ax25_create_cb()) == NULL)
60 		return NULL;
61 
62 	ax25_fillin_cb(ax25, ax25_dev);
63 
64 	ax25->source_addr = *src;
65 	ax25->dest_addr   = *dest;
66 
67 	if (digi != NULL) {
68 		ax25->digipeat = kmemdup(digi, sizeof(*digi), GFP_ATOMIC);
69 		if (ax25->digipeat == NULL) {
70 			ax25_cb_put(ax25);
71 			return NULL;
72 		}
73 	}
74 
75 	switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
76 	case AX25_PROTO_STD_SIMPLEX:
77 	case AX25_PROTO_STD_DUPLEX:
78 		ax25_std_establish_data_link(ax25);
79 		break;
80 
81 #ifdef CONFIG_AX25_DAMA_SLAVE
82 	case AX25_PROTO_DAMA_SLAVE:
83 		if (ax25_dev->dama.slave)
84 			ax25_ds_establish_data_link(ax25);
85 		else
86 			ax25_std_establish_data_link(ax25);
87 		break;
88 #endif
89 	}
90 
91 	/*
92 	 * There is one ref for the state machine; a caller needs
93 	 * one more to put it back, just like with the existing one.
94 	 */
95 	ax25_cb_hold(ax25);
96 
97 	ax25_cb_add(ax25);
98 
99 	ax25->state = AX25_STATE_1;
100 
101 	ax25_start_heartbeat(ax25);
102 
103 	ax25_output(ax25, paclen, skb);
104 
105 	return ax25;			/* We had to create it */
106 }
107 
108 EXPORT_SYMBOL(ax25_send_frame);
109 
110 /*
111  *	All outgoing AX.25 I frames pass via this routine. Therefore this is
112  *	where the fragmentation of frames takes place. If fragment is set to
113  *	zero then we are not allowed to do fragmentation, even if the frame
114  *	is too large.
115  */
116 void ax25_output(ax25_cb *ax25, int paclen, struct sk_buff *skb)
117 {
118 	struct sk_buff *skbn;
119 	unsigned char *p;
120 	int frontlen, len, fragno, ka9qfrag, first = 1;
121 
122 	if (paclen < 16) {
123 		WARN_ON_ONCE(1);
124 		kfree_skb(skb);
125 		return;
126 	}
127 
128 	if ((skb->len - 1) > paclen) {
129 		if (*skb->data == AX25_P_TEXT) {
130 			skb_pull(skb, 1); /* skip PID */
131 			ka9qfrag = 0;
132 		} else {
133 			paclen -= 2;	/* Allow for fragment control info */
134 			ka9qfrag = 1;
135 		}
136 
137 		fragno = skb->len / paclen;
138 		if (skb->len % paclen == 0) fragno--;
139 
140 		frontlen = skb_headroom(skb);	/* Address space + CTRL */
141 
142 		while (skb->len > 0) {
143 			spin_lock_bh(&ax25_frag_lock);
144 			if ((skbn = alloc_skb(paclen + 2 + frontlen, GFP_ATOMIC)) == NULL) {
145 				spin_unlock_bh(&ax25_frag_lock);
146 				printk(KERN_CRIT "AX.25: ax25_output - out of memory\n");
147 				return;
148 			}
149 
150 			if (skb->sk != NULL)
151 				skb_set_owner_w(skbn, skb->sk);
152 
153 			spin_unlock_bh(&ax25_frag_lock);
154 
155 			len = (paclen > skb->len) ? skb->len : paclen;
156 
157 			if (ka9qfrag == 1) {
158 				skb_reserve(skbn, frontlen + 2);
159 				skb_set_network_header(skbn,
160 						      skb_network_offset(skb));
161 				skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
162 				p = skb_push(skbn, 2);
163 
164 				*p++ = AX25_P_SEGMENT;
165 
166 				*p = fragno--;
167 				if (first) {
168 					*p |= AX25_SEG_FIRST;
169 					first = 0;
170 				}
171 			} else {
172 				skb_reserve(skbn, frontlen + 1);
173 				skb_set_network_header(skbn,
174 						      skb_network_offset(skb));
175 				skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
176 				p = skb_push(skbn, 1);
177 				*p = AX25_P_TEXT;
178 			}
179 
180 			skb_pull(skb, len);
181 			skb_queue_tail(&ax25->write_queue, skbn); /* Throw it on the queue */
182 		}
183 
184 		kfree_skb(skb);
185 	} else {
186 		skb_queue_tail(&ax25->write_queue, skb);	  /* Throw it on the queue */
187 	}
188 
189 	switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
190 	case AX25_PROTO_STD_SIMPLEX:
191 	case AX25_PROTO_STD_DUPLEX:
192 		ax25_kick(ax25);
193 		break;
194 
195 #ifdef CONFIG_AX25_DAMA_SLAVE
196 	/*
197 	 * A DAMA slave is _required_ to work as normal AX.25L2V2
198 	 * if no DAMA master is available.
199 	 */
200 	case AX25_PROTO_DAMA_SLAVE:
201 		if (!ax25->ax25_dev->dama.slave) ax25_kick(ax25);
202 		break;
203 #endif
204 	}
205 }
206 
207 /*
208  *  This procedure is passed a buffer descriptor for an iframe. It builds
209  *  the rest of the control part of the frame and then writes it out.
210  */
211 static void ax25_send_iframe(ax25_cb *ax25, struct sk_buff *skb, int poll_bit)
212 {
213 	unsigned char *frame;
214 
215 	if (skb == NULL)
216 		return;
217 
218 	skb_reset_network_header(skb);
219 
220 	if (ax25->modulus == AX25_MODULUS) {
221 		frame = skb_push(skb, 1);
222 
223 		*frame = AX25_I;
224 		*frame |= (poll_bit) ? AX25_PF : 0;
225 		*frame |= (ax25->vr << 5);
226 		*frame |= (ax25->vs << 1);
227 	} else {
228 		frame = skb_push(skb, 2);
229 
230 		frame[0] = AX25_I;
231 		frame[0] |= (ax25->vs << 1);
232 		frame[1] = (poll_bit) ? AX25_EPF : 0;
233 		frame[1] |= (ax25->vr << 1);
234 	}
235 
236 	ax25_start_idletimer(ax25);
237 
238 	ax25_transmit_buffer(ax25, skb, AX25_COMMAND);
239 }
240 
241 void ax25_kick(ax25_cb *ax25)
242 {
243 	struct sk_buff *skb, *skbn;
244 	int last = 1;
245 	unsigned short start, end, next;
246 
247 	if (ax25->state != AX25_STATE_3 && ax25->state != AX25_STATE_4)
248 		return;
249 
250 	if (ax25->condition & AX25_COND_PEER_RX_BUSY)
251 		return;
252 
253 	if (skb_peek(&ax25->write_queue) == NULL)
254 		return;
255 
256 	start = (skb_peek(&ax25->ack_queue) == NULL) ? ax25->va : ax25->vs;
257 	end   = (ax25->va + ax25->window) % ax25->modulus;
258 
259 	if (start == end)
260 		return;
261 
262 	/*
263 	 * Transmit data until either we're out of data to send or
264 	 * the window is full. Send a poll on the final I frame if
265 	 * the window is filled.
266 	 */
267 
268 	/*
269 	 * Dequeue the frame and copy it.
270 	 * Check for race with ax25_clear_queues().
271 	 */
272 	skb  = skb_dequeue(&ax25->write_queue);
273 	if (!skb)
274 		return;
275 
276 	ax25->vs = start;
277 
278 	do {
279 		if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
280 			skb_queue_head(&ax25->write_queue, skb);
281 			break;
282 		}
283 
284 		if (skb->sk != NULL)
285 			skb_set_owner_w(skbn, skb->sk);
286 
287 		next = (ax25->vs + 1) % ax25->modulus;
288 		last = (next == end);
289 
290 		/*
291 		 * Transmit the frame copy.
292 		 * bke 960114: do not set the Poll bit on the last frame
293 		 * in DAMA mode.
294 		 */
295 		switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
296 		case AX25_PROTO_STD_SIMPLEX:
297 		case AX25_PROTO_STD_DUPLEX:
298 			ax25_send_iframe(ax25, skbn, (last) ? AX25_POLLON : AX25_POLLOFF);
299 			break;
300 
301 #ifdef CONFIG_AX25_DAMA_SLAVE
302 		case AX25_PROTO_DAMA_SLAVE:
303 			ax25_send_iframe(ax25, skbn, AX25_POLLOFF);
304 			break;
305 #endif
306 		}
307 
308 		ax25->vs = next;
309 
310 		/*
311 		 * Requeue the original data frame.
312 		 */
313 		skb_queue_tail(&ax25->ack_queue, skb);
314 
315 	} while (!last && (skb = skb_dequeue(&ax25->write_queue)) != NULL);
316 
317 	ax25->condition &= ~AX25_COND_ACK_PENDING;
318 
319 	if (!ax25_t1timer_running(ax25)) {
320 		ax25_stop_t3timer(ax25);
321 		ax25_calculate_t1(ax25);
322 		ax25_start_t1timer(ax25);
323 	}
324 }
325 
326 void ax25_transmit_buffer(ax25_cb *ax25, struct sk_buff *skb, int type)
327 {
328 	unsigned char *ptr;
329 	int headroom;
330 
331 	if (ax25->ax25_dev == NULL) {
332 		ax25_disconnect(ax25, ENETUNREACH);
333 		return;
334 	}
335 
336 	headroom = ax25_addr_size(ax25->digipeat);
337 
338 	if (unlikely(skb_headroom(skb) < headroom)) {
339 		skb = skb_expand_head(skb, headroom);
340 		if (!skb) {
341 			printk(KERN_CRIT "AX.25: ax25_transmit_buffer - out of memory\n");
342 			return;
343 		}
344 	}
345 
346 	ptr = skb_push(skb, headroom);
347 
348 	ax25_addr_build(ptr, &ax25->source_addr, &ax25->dest_addr, ax25->digipeat, type, ax25->modulus);
349 
350 	ax25_queue_xmit(skb, ax25->ax25_dev->dev);
351 }
352 
353 /*
354  *	A small shim to dev_queue_xmit to add the KISS control byte, and do
355  *	any packet forwarding in operation.
356  */
357 void ax25_queue_xmit(struct sk_buff *skb, struct net_device *dev)
358 {
359 	unsigned char *ptr;
360 
361 	skb->protocol = ax25_type_trans(skb, ax25_fwd_dev(dev));
362 
363 	ptr  = skb_push(skb, 1);
364 	*ptr = 0x00;			/* KISS */
365 
366 	dev_queue_xmit(skb);
367 }
368 
369 int ax25_check_iframes_acked(ax25_cb *ax25, unsigned short nr)
370 {
371 	if (ax25->vs == nr) {
372 		ax25_frames_acked(ax25, nr);
373 		ax25_calculate_rtt(ax25);
374 		ax25_stop_t1timer(ax25);
375 		ax25_start_t3timer(ax25);
376 		return 1;
377 	} else {
378 		if (ax25->va != nr) {
379 			ax25_frames_acked(ax25, nr);
380 			ax25_calculate_t1(ax25);
381 			ax25_start_t1timer(ax25);
382 			return 1;
383 		}
384 	}
385 	return 0;
386 }
387