xref: /openbmc/linux/net/ax25/ax25_subr.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
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  * Copyright (C) Frederic Rible F1OAT (frible@teaser.fr)
11  */
12 #include <linux/errno.h>
13 #include <linux/types.h>
14 #include <linux/socket.h>
15 #include <linux/in.h>
16 #include <linux/kernel.h>
17 #include <linux/sched.h>
18 #include <linux/timer.h>
19 #include <linux/string.h>
20 #include <linux/sockios.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 <net/sock.h>
27 #include <net/tcp_states.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 /*
35  *	This routine purges all the queues of frames.
36  */
37 void ax25_clear_queues(ax25_cb *ax25)
38 {
39 	skb_queue_purge(&ax25->write_queue);
40 	skb_queue_purge(&ax25->ack_queue);
41 	skb_queue_purge(&ax25->reseq_queue);
42 	skb_queue_purge(&ax25->frag_queue);
43 }
44 
45 /*
46  * This routine purges the input queue of those frames that have been
47  * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
48  * SDL diagram.
49  */
50 void ax25_frames_acked(ax25_cb *ax25, unsigned short nr)
51 {
52 	struct sk_buff *skb;
53 
54 	/*
55 	 * Remove all the ack-ed frames from the ack queue.
56 	 */
57 	if (ax25->va != nr) {
58 		while (skb_peek(&ax25->ack_queue) != NULL && ax25->va != nr) {
59 		        skb = skb_dequeue(&ax25->ack_queue);
60 			kfree_skb(skb);
61 			ax25->va = (ax25->va + 1) % ax25->modulus;
62 		}
63 	}
64 }
65 
66 void ax25_requeue_frames(ax25_cb *ax25)
67 {
68         struct sk_buff *skb, *skb_prev = NULL;
69 
70 	/*
71 	 * Requeue all the un-ack-ed frames on the output queue to be picked
72 	 * up by ax25_kick called from the timer. This arrangement handles the
73 	 * possibility of an empty output queue.
74 	 */
75 	while ((skb = skb_dequeue(&ax25->ack_queue)) != NULL) {
76 		if (skb_prev == NULL)
77 			skb_queue_head(&ax25->write_queue, skb);
78 		else
79 			skb_append(skb_prev, skb, &ax25->write_queue);
80 		skb_prev = skb;
81 	}
82 }
83 
84 /*
85  *	Validate that the value of nr is between va and vs. Return true or
86  *	false for testing.
87  */
88 int ax25_validate_nr(ax25_cb *ax25, unsigned short nr)
89 {
90 	unsigned short vc = ax25->va;
91 
92 	while (vc != ax25->vs) {
93 		if (nr == vc) return 1;
94 		vc = (vc + 1) % ax25->modulus;
95 	}
96 
97 	if (nr == ax25->vs) return 1;
98 
99 	return 0;
100 }
101 
102 /*
103  *	This routine is the centralised routine for parsing the control
104  *	information for the different frame formats.
105  */
106 int ax25_decode(ax25_cb *ax25, struct sk_buff *skb, int *ns, int *nr, int *pf)
107 {
108 	unsigned char *frame;
109 	int frametype = AX25_ILLEGAL;
110 
111 	frame = skb->data;
112 	*ns = *nr = *pf = 0;
113 
114 	if (ax25->modulus == AX25_MODULUS) {
115 		if ((frame[0] & AX25_S) == 0) {
116 			frametype = AX25_I;			/* I frame - carries NR/NS/PF */
117 			*ns = (frame[0] >> 1) & 0x07;
118 			*nr = (frame[0] >> 5) & 0x07;
119 			*pf = frame[0] & AX25_PF;
120 		} else if ((frame[0] & AX25_U) == 1) { 	/* S frame - take out PF/NR */
121 			frametype = frame[0] & 0x0F;
122 			*nr = (frame[0] >> 5) & 0x07;
123 			*pf = frame[0] & AX25_PF;
124 		} else if ((frame[0] & AX25_U) == 3) { 	/* U frame - take out PF */
125 			frametype = frame[0] & ~AX25_PF;
126 			*pf = frame[0] & AX25_PF;
127 		}
128 		skb_pull(skb, 1);
129 	} else {
130 		if ((frame[0] & AX25_S) == 0) {
131 			frametype = AX25_I;			/* I frame - carries NR/NS/PF */
132 			*ns = (frame[0] >> 1) & 0x7F;
133 			*nr = (frame[1] >> 1) & 0x7F;
134 			*pf = frame[1] & AX25_EPF;
135 			skb_pull(skb, 2);
136 		} else if ((frame[0] & AX25_U) == 1) { 	/* S frame - take out PF/NR */
137 			frametype = frame[0] & 0x0F;
138 			*nr = (frame[1] >> 1) & 0x7F;
139 			*pf = frame[1] & AX25_EPF;
140 			skb_pull(skb, 2);
141 		} else if ((frame[0] & AX25_U) == 3) { 	/* U frame - take out PF */
142 			frametype = frame[0] & ~AX25_PF;
143 			*pf = frame[0] & AX25_PF;
144 			skb_pull(skb, 1);
145 		}
146 	}
147 
148 	return frametype;
149 }
150 
151 /*
152  *	This routine is called when the HDLC layer internally  generates a
153  *	command or  response  for  the remote machine ( eg. RR, UA etc. ).
154  *	Only supervisory or unnumbered frames are processed.
155  */
156 void ax25_send_control(ax25_cb *ax25, int frametype, int poll_bit, int type)
157 {
158 	struct sk_buff *skb;
159 	unsigned char  *dptr;
160 
161 	if ((skb = alloc_skb(ax25->ax25_dev->dev->hard_header_len + 2, GFP_ATOMIC)) == NULL)
162 		return;
163 
164 	skb_reserve(skb, ax25->ax25_dev->dev->hard_header_len);
165 
166 	skb->nh.raw = skb->data;
167 
168 	/* Assume a response - address structure for DTE */
169 	if (ax25->modulus == AX25_MODULUS) {
170 		dptr = skb_put(skb, 1);
171 		*dptr = frametype;
172 		*dptr |= (poll_bit) ? AX25_PF : 0;
173 		if ((frametype & AX25_U) == AX25_S)		/* S frames carry NR */
174 			*dptr |= (ax25->vr << 5);
175 	} else {
176 		if ((frametype & AX25_U) == AX25_U) {
177 			dptr = skb_put(skb, 1);
178 			*dptr = frametype;
179 			*dptr |= (poll_bit) ? AX25_PF : 0;
180 		} else {
181 			dptr = skb_put(skb, 2);
182 			dptr[0] = frametype;
183 			dptr[1] = (ax25->vr << 1);
184 			dptr[1] |= (poll_bit) ? AX25_EPF : 0;
185 		}
186 	}
187 
188 	ax25_transmit_buffer(ax25, skb, type);
189 }
190 
191 /*
192  *	Send a 'DM' to an unknown connection attempt, or an invalid caller.
193  *
194  *	Note: src here is the sender, thus it's the target of the DM
195  */
196 void ax25_return_dm(struct net_device *dev, ax25_address *src, ax25_address *dest, ax25_digi *digi)
197 {
198 	struct sk_buff *skb;
199 	char *dptr;
200 	ax25_digi retdigi;
201 
202 	if (dev == NULL)
203 		return;
204 
205 	if ((skb = alloc_skb(dev->hard_header_len + 1, GFP_ATOMIC)) == NULL)
206 		return;	/* Next SABM will get DM'd */
207 
208 	skb_reserve(skb, dev->hard_header_len);
209 	skb->nh.raw = skb->data;
210 
211 	ax25_digi_invert(digi, &retdigi);
212 
213 	dptr = skb_put(skb, 1);
214 
215 	*dptr = AX25_DM | AX25_PF;
216 
217 	/*
218 	 *	Do the address ourselves
219 	 */
220 	dptr  = skb_push(skb, ax25_addr_size(digi));
221 	dptr += ax25_addr_build(dptr, dest, src, &retdigi, AX25_RESPONSE, AX25_MODULUS);
222 
223 	ax25_queue_xmit(skb, dev);
224 }
225 
226 /*
227  *	Exponential backoff for AX.25
228  */
229 void ax25_calculate_t1(ax25_cb *ax25)
230 {
231 	int n, t = 2;
232 
233 	switch (ax25->backoff) {
234 	case 0:
235 		break;
236 
237 	case 1:
238 		t += 2 * ax25->n2count;
239 		break;
240 
241 	case 2:
242 		for (n = 0; n < ax25->n2count; n++)
243 			t *= 2;
244 		if (t > 8) t = 8;
245 		break;
246 	}
247 
248 	ax25->t1 = t * ax25->rtt;
249 }
250 
251 /*
252  *	Calculate the Round Trip Time
253  */
254 void ax25_calculate_rtt(ax25_cb *ax25)
255 {
256 	if (ax25->backoff == 0)
257 		return;
258 
259 	if (ax25_t1timer_running(ax25) && ax25->n2count == 0)
260 		ax25->rtt = (9 * ax25->rtt + ax25->t1 - ax25_display_timer(&ax25->t1timer)) / 10;
261 
262 	if (ax25->rtt < AX25_T1CLAMPLO)
263 		ax25->rtt = AX25_T1CLAMPLO;
264 
265 	if (ax25->rtt > AX25_T1CLAMPHI)
266 		ax25->rtt = AX25_T1CLAMPHI;
267 }
268 
269 void ax25_disconnect(ax25_cb *ax25, int reason)
270 {
271 	ax25_clear_queues(ax25);
272 
273 	ax25_stop_t1timer(ax25);
274 	ax25_stop_t2timer(ax25);
275 	ax25_stop_t3timer(ax25);
276 	ax25_stop_idletimer(ax25);
277 
278 	ax25->state = AX25_STATE_0;
279 
280 	ax25_link_failed(ax25, reason);
281 
282 	if (ax25->sk != NULL) {
283 		bh_lock_sock(ax25->sk);
284 		ax25->sk->sk_state     = TCP_CLOSE;
285 		ax25->sk->sk_err       = reason;
286 		ax25->sk->sk_shutdown |= SEND_SHUTDOWN;
287 		if (!sock_flag(ax25->sk, SOCK_DEAD)) {
288 			ax25->sk->sk_state_change(ax25->sk);
289 			sock_set_flag(ax25->sk, SOCK_DEAD);
290 		}
291 		bh_unlock_sock(ax25->sk);
292 	}
293 }
294