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 * Copyright (C) Frederic Rible F1OAT (frible@teaser.fr)
8 */
9#include <linux/errno.h>
10#include <linux/types.h>
11#include <linux/socket.h>
12#include <linux/in.h>
13#include <linux/kernel.h>
14#include <linux/timer.h>
15#include <linux/string.h>
16#include <linux/sockios.h>
17#include <linux/net.h>
18#include <linux/slab.h>
19#include <net/ax25.h>
20#include <linux/inet.h>
21#include <linux/netdevice.h>
22#include <linux/skbuff.h>
23#include <net/sock.h>
24#include <net/tcp_states.h>
25#include <linux/uaccess.h>
26#include <linux/fcntl.h>
27#include <linux/mm.h>
28#include <linux/interrupt.h>
29
30/*
31 *	This routine purges all the queues of frames.
32 */
33void ax25_clear_queues(ax25_cb *ax25)
34{
35	skb_queue_purge(&ax25->write_queue);
36	skb_queue_purge(&ax25->ack_queue);
37	skb_queue_purge(&ax25->reseq_queue);
38	skb_queue_purge(&ax25->frag_queue);
39}
40
41/*
42 * This routine purges the input queue of those frames that have been
43 * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
44 * SDL diagram.
45 */
46void ax25_frames_acked(ax25_cb *ax25, unsigned short nr)
47{
48	struct sk_buff *skb;
49
50	/*
51	 * Remove all the ack-ed frames from the ack queue.
52	 */
53	if (ax25->va != nr) {
54		while (skb_peek(&ax25->ack_queue) != NULL && ax25->va != nr) {
55			skb = skb_dequeue(&ax25->ack_queue);
56			kfree_skb(skb);
57			ax25->va = (ax25->va + 1) % ax25->modulus;
58		}
59	}
60}
61
62void ax25_requeue_frames(ax25_cb *ax25)
63{
64	struct sk_buff *skb;
65
66	/*
67	 * Requeue all the un-ack-ed frames on the output queue to be picked
68	 * up by ax25_kick called from the timer. This arrangement handles the
69	 * possibility of an empty output queue.
70	 */
71	while ((skb = skb_dequeue_tail(&ax25->ack_queue)) != NULL)
72		skb_queue_head(&ax25->write_queue, skb);
73}
74
75/*
76 *	Validate that the value of nr is between va and vs. Return true or
77 *	false for testing.
78 */
79int ax25_validate_nr(ax25_cb *ax25, unsigned short nr)
80{
81	unsigned short vc = ax25->va;
82
83	while (vc != ax25->vs) {
84		if (nr == vc) return 1;
85		vc = (vc + 1) % ax25->modulus;
86	}
87
88	if (nr == ax25->vs) return 1;
89
90	return 0;
91}
92
93/*
94 *	This routine is the centralised routine for parsing the control
95 *	information for the different frame formats.
96 */
97int ax25_decode(ax25_cb *ax25, struct sk_buff *skb, int *ns, int *nr, int *pf)
98{
99	unsigned char *frame;
100	int frametype = AX25_ILLEGAL;
101
102	frame = skb->data;
103	*ns = *nr = *pf = 0;
104
105	if (ax25->modulus == AX25_MODULUS) {
106		if ((frame[0] & AX25_S) == 0) {
107			frametype = AX25_I;			/* I frame - carries NR/NS/PF */
108			*ns = (frame[0] >> 1) & 0x07;
109			*nr = (frame[0] >> 5) & 0x07;
110			*pf = frame[0] & AX25_PF;
111		} else if ((frame[0] & AX25_U) == 1) { 	/* S frame - take out PF/NR */
112			frametype = frame[0] & 0x0F;
113			*nr = (frame[0] >> 5) & 0x07;
114			*pf = frame[0] & AX25_PF;
115		} else if ((frame[0] & AX25_U) == 3) { 	/* U frame - take out PF */
116			frametype = frame[0] & ~AX25_PF;
117			*pf = frame[0] & AX25_PF;
118		}
119		skb_pull(skb, 1);
120	} else {
121		if ((frame[0] & AX25_S) == 0) {
122			frametype = AX25_I;			/* I frame - carries NR/NS/PF */
123			*ns = (frame[0] >> 1) & 0x7F;
124			*nr = (frame[1] >> 1) & 0x7F;
125			*pf = frame[1] & AX25_EPF;
126			skb_pull(skb, 2);
127		} else if ((frame[0] & AX25_U) == 1) { 	/* S frame - take out PF/NR */
128			frametype = frame[0] & 0x0F;
129			*nr = (frame[1] >> 1) & 0x7F;
130			*pf = frame[1] & AX25_EPF;
131			skb_pull(skb, 2);
132		} else if ((frame[0] & AX25_U) == 3) { 	/* U frame - take out PF */
133			frametype = frame[0] & ~AX25_PF;
134			*pf = frame[0] & AX25_PF;
135			skb_pull(skb, 1);
136		}
137	}
138
139	return frametype;
140}
141
142/*
143 *	This routine is called when the HDLC layer internally  generates a
144 *	command or  response  for  the remote machine ( eg. RR, UA etc. ).
145 *	Only supervisory or unnumbered frames are processed.
146 */
147void ax25_send_control(ax25_cb *ax25, int frametype, int poll_bit, int type)
148{
149	struct sk_buff *skb;
150	unsigned char  *dptr;
151
152	if ((skb = alloc_skb(ax25->ax25_dev->dev->hard_header_len + 2, GFP_ATOMIC)) == NULL)
153		return;
154
155	skb_reserve(skb, ax25->ax25_dev->dev->hard_header_len);
156
157	skb_reset_network_header(skb);
158
159	/* Assume a response - address structure for DTE */
160	if (ax25->modulus == AX25_MODULUS) {
161		dptr = skb_put(skb, 1);
162		*dptr = frametype;
163		*dptr |= (poll_bit) ? AX25_PF : 0;
164		if ((frametype & AX25_U) == AX25_S)		/* S frames carry NR */
165			*dptr |= (ax25->vr << 5);
166	} else {
167		if ((frametype & AX25_U) == AX25_U) {
168			dptr = skb_put(skb, 1);
169			*dptr = frametype;
170			*dptr |= (poll_bit) ? AX25_PF : 0;
171		} else {
172			dptr = skb_put(skb, 2);
173			dptr[0] = frametype;
174			dptr[1] = (ax25->vr << 1);
175			dptr[1] |= (poll_bit) ? AX25_EPF : 0;
176		}
177	}
178
179	ax25_transmit_buffer(ax25, skb, type);
180}
181
182/*
183 *	Send a 'DM' to an unknown connection attempt, or an invalid caller.
184 *
185 *	Note: src here is the sender, thus it's the target of the DM
186 */
187void ax25_return_dm(struct net_device *dev, ax25_address *src, ax25_address *dest, ax25_digi *digi)
188{
189	struct sk_buff *skb;
190	char *dptr;
191	ax25_digi retdigi;
192
193	if (dev == NULL)
194		return;
195
196	if ((skb = alloc_skb(dev->hard_header_len + 1, GFP_ATOMIC)) == NULL)
197		return;	/* Next SABM will get DM'd */
198
199	skb_reserve(skb, dev->hard_header_len);
200	skb_reset_network_header(skb);
201
202	ax25_digi_invert(digi, &retdigi);
203
204	dptr = skb_put(skb, 1);
205
206	*dptr = AX25_DM | AX25_PF;
207
208	/*
209	 *	Do the address ourselves
210	 */
211	dptr  = skb_push(skb, ax25_addr_size(digi));
212	dptr += ax25_addr_build(dptr, dest, src, &retdigi, AX25_RESPONSE, AX25_MODULUS);
213
214	ax25_queue_xmit(skb, dev);
215}
216
217/*
218 *	Exponential backoff for AX.25
219 */
220void ax25_calculate_t1(ax25_cb *ax25)
221{
222	int n, t = 2;
223
224	switch (ax25->backoff) {
225	case 0:
226		break;
227
228	case 1:
229		t += 2 * ax25->n2count;
230		break;
231
232	case 2:
233		for (n = 0; n < ax25->n2count; n++)
234			t *= 2;
235		if (t > 8) t = 8;
236		break;
237	}
238
239	ax25->t1 = t * ax25->rtt;
240}
241
242/*
243 *	Calculate the Round Trip Time
244 */
245void ax25_calculate_rtt(ax25_cb *ax25)
246{
247	if (ax25->backoff == 0)
248		return;
249
250	if (ax25_t1timer_running(ax25) && ax25->n2count == 0)
251		ax25->rtt = (9 * ax25->rtt + ax25->t1 - ax25_display_timer(&ax25->t1timer)) / 10;
252
253	if (ax25->rtt < AX25_T1CLAMPLO)
254		ax25->rtt = AX25_T1CLAMPLO;
255
256	if (ax25->rtt > AX25_T1CLAMPHI)
257		ax25->rtt = AX25_T1CLAMPHI;
258}
259
260void ax25_disconnect(ax25_cb *ax25, int reason)
261{
262	ax25_clear_queues(ax25);
263
264	if (reason == ENETUNREACH) {
265		del_timer_sync(&ax25->timer);
266		del_timer_sync(&ax25->t1timer);
267		del_timer_sync(&ax25->t2timer);
268		del_timer_sync(&ax25->t3timer);
269		del_timer_sync(&ax25->idletimer);
270	} else {
271		if (ax25->sk && !sock_flag(ax25->sk, SOCK_DESTROY))
272			ax25_stop_heartbeat(ax25);
273		ax25_stop_t1timer(ax25);
274		ax25_stop_t2timer(ax25);
275		ax25_stop_t3timer(ax25);
276		ax25_stop_idletimer(ax25);
277	}
278
279	ax25->state = AX25_STATE_0;
280
281	ax25_link_failed(ax25, reason);
282
283	if (ax25->sk != NULL) {
284		local_bh_disable();
285		bh_lock_sock(ax25->sk);
286		ax25->sk->sk_state     = TCP_CLOSE;
287		ax25->sk->sk_err       = reason;
288		ax25->sk->sk_shutdown |= SEND_SHUTDOWN;
289		if (!sock_flag(ax25->sk, SOCK_DEAD)) {
290			ax25->sk->sk_state_change(ax25->sk);
291			sock_set_flag(ax25->sk, SOCK_DEAD);
292		}
293		bh_unlock_sock(ax25->sk);
294		local_bh_enable();
295	}
296}
297