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