1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 *
4 * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
5 * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
6 */
7#include <linux/errno.h>
8#include <linux/types.h>
9#include <linux/socket.h>
10#include <linux/in.h>
11#include <linux/kernel.h>
12#include <linux/timer.h>
13#include <linux/string.h>
14#include <linux/sockios.h>
15#include <linux/spinlock.h>
16#include <linux/net.h>
17#include <linux/gfp.h>
18#include <net/ax25.h>
19#include <linux/inet.h>
20#include <linux/netdevice.h>
21#include <linux/skbuff.h>
22#include <net/sock.h>
23#include <linux/uaccess.h>
24#include <linux/fcntl.h>
25#include <linux/mm.h>
26#include <linux/interrupt.h>
27
28void ax25_ds_nr_error_recovery(ax25_cb *ax25)
29{
30	ax25_ds_establish_data_link(ax25);
31}
32
33/*
34 *	dl1bke 960114: transmit I frames on DAMA poll
35 */
36void ax25_ds_enquiry_response(ax25_cb *ax25)
37{
38	ax25_cb *ax25o;
39
40	/* Please note that neither DK4EG's nor DG2FEF's
41	 * DAMA spec mention the following behaviour as seen
42	 * with TheFirmware:
43	 *
44	 * 	DB0ACH->DL1BKE <RR C P R0> [DAMA]
45	 *	DL1BKE->DB0ACH <I NR=0 NS=0>
46	 *	DL1BKE-7->DB0PRA-6 DB0ACH <I C S3 R5>
47	 *	DL1BKE->DB0ACH <RR R F R0>
48	 *
49	 * The Flexnet DAMA Master implementation apparently
50	 * insists on the "proper" AX.25 behaviour:
51	 *
52	 * 	DB0ACH->DL1BKE <RR C P R0> [DAMA]
53	 *	DL1BKE->DB0ACH <RR R F R0>
54	 *	DL1BKE->DB0ACH <I NR=0 NS=0>
55	 *	DL1BKE-7->DB0PRA-6 DB0ACH <I C S3 R5>
56	 *
57	 * Flexnet refuses to send us *any* I frame if we send
58	 * a REJ in case AX25_COND_REJECT is set. It is superfluous in
59	 * this mode anyway (a RR or RNR invokes the retransmission).
60	 * Is this a Flexnet bug?
61	 */
62
63	ax25_std_enquiry_response(ax25);
64
65	if (!(ax25->condition & AX25_COND_PEER_RX_BUSY)) {
66		ax25_requeue_frames(ax25);
67		ax25_kick(ax25);
68	}
69
70	if (ax25->state == AX25_STATE_1 || ax25->state == AX25_STATE_2 || skb_peek(&ax25->ack_queue) != NULL)
71		ax25_ds_t1_timeout(ax25);
72	else
73		ax25->n2count = 0;
74
75	ax25_start_t3timer(ax25);
76	ax25_ds_set_timer(ax25->ax25_dev);
77
78	spin_lock(&ax25_list_lock);
79	ax25_for_each(ax25o, &ax25_list) {
80		if (ax25o == ax25)
81			continue;
82
83		if (ax25o->ax25_dev != ax25->ax25_dev)
84			continue;
85
86		if (ax25o->state == AX25_STATE_1 || ax25o->state == AX25_STATE_2) {
87			ax25_ds_t1_timeout(ax25o);
88			continue;
89		}
90
91		if (!(ax25o->condition & AX25_COND_PEER_RX_BUSY) && ax25o->state == AX25_STATE_3) {
92			ax25_requeue_frames(ax25o);
93			ax25_kick(ax25o);
94		}
95
96		if (ax25o->state == AX25_STATE_1 || ax25o->state == AX25_STATE_2 || skb_peek(&ax25o->ack_queue) != NULL)
97			ax25_ds_t1_timeout(ax25o);
98
99		/* do not start T3 for listening sockets (tnx DD8NE) */
100
101		if (ax25o->state != AX25_STATE_0)
102			ax25_start_t3timer(ax25o);
103	}
104	spin_unlock(&ax25_list_lock);
105}
106
107void ax25_ds_establish_data_link(ax25_cb *ax25)
108{
109	ax25->condition &= AX25_COND_DAMA_MODE;
110	ax25->n2count    = 0;
111	ax25_calculate_t1(ax25);
112	ax25_start_t1timer(ax25);
113	ax25_stop_t2timer(ax25);
114	ax25_start_t3timer(ax25);
115}
116
117/*
118 *	:::FIXME:::
119 *	This is a kludge. Not all drivers recognize kiss commands.
120 *	We need a driver level  request to switch duplex mode, that does
121 *	either SCC changing, PI config or KISS as required. Currently
122 *	this request isn't reliable.
123 */
124static void ax25_kiss_cmd(ax25_dev *ax25_dev, unsigned char cmd, unsigned char param)
125{
126	struct sk_buff *skb;
127	unsigned char *p;
128
129	if (ax25_dev->dev == NULL)
130		return;
131
132	if ((skb = alloc_skb(2, GFP_ATOMIC)) == NULL)
133		return;
134
135	skb_reset_network_header(skb);
136	p = skb_put(skb, 2);
137
138	*p++ = cmd;
139	*p++ = param;
140
141	skb->protocol = ax25_type_trans(skb, ax25_dev->dev);
142
143	dev_queue_xmit(skb);
144}
145
146/*
147 *	A nasty problem arises if we count the number of DAMA connections
148 *	wrong, especially when connections on the device already existed
149 *	and our network node (or the sysop) decides to turn on DAMA Master
150 *	mode. We thus flag the 'real' slave connections with
151 *	ax25->dama_slave=1 and look on every disconnect if still slave
152 *	connections exist.
153 */
154static int ax25_check_dama_slave(ax25_dev *ax25_dev)
155{
156	ax25_cb *ax25;
157	int res = 0;
158
159	spin_lock(&ax25_list_lock);
160	ax25_for_each(ax25, &ax25_list)
161		if (ax25->ax25_dev == ax25_dev && (ax25->condition & AX25_COND_DAMA_MODE) && ax25->state > AX25_STATE_1) {
162			res = 1;
163			break;
164		}
165	spin_unlock(&ax25_list_lock);
166
167	return res;
168}
169
170static void ax25_dev_dama_on(ax25_dev *ax25_dev)
171{
172	if (ax25_dev == NULL)
173		return;
174
175	if (ax25_dev->dama.slave == 0)
176		ax25_kiss_cmd(ax25_dev, 5, 1);
177
178	ax25_dev->dama.slave = 1;
179	ax25_ds_set_timer(ax25_dev);
180}
181
182void ax25_dev_dama_off(ax25_dev *ax25_dev)
183{
184	if (ax25_dev == NULL)
185		return;
186
187	if (ax25_dev->dama.slave && !ax25_check_dama_slave(ax25_dev)) {
188		ax25_kiss_cmd(ax25_dev, 5, 0);
189		ax25_dev->dama.slave = 0;
190		ax25_ds_del_timer(ax25_dev);
191	}
192}
193
194void ax25_dama_on(ax25_cb *ax25)
195{
196	ax25_dev_dama_on(ax25->ax25_dev);
197	ax25->condition |= AX25_COND_DAMA_MODE;
198}
199
200void ax25_dama_off(ax25_cb *ax25)
201{
202	ax25->condition &= ~AX25_COND_DAMA_MODE;
203	ax25_dev_dama_off(ax25->ax25_dev);
204}
205