xref: /linux/net/ax25/ax25_ds_subr.c (revision f3d9478b2ce468c3115b02ecae7e975990697f15)
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/sched.h>
16 #include <linux/timer.h>
17 #include <linux/string.h>
18 #include <linux/sockios.h>
19 #include <linux/spinlock.h>
20 #include <linux/net.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 
32 void 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  */
40 void 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_bh(&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_bh(&ax25_list_lock);
110 }
111 
112 void 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 
122 /*
123  *	:::FIXME:::
124  *	This is a kludge. Not all drivers recognize kiss commands.
125  *	We need a driver level  request to switch duplex mode, that does
126  *	either SCC changing, PI config or KISS as required. Currently
127  *	this request isn't reliable.
128  */
129 static void ax25_kiss_cmd(ax25_dev *ax25_dev, unsigned char cmd, unsigned char param)
130 {
131 	struct sk_buff *skb;
132 	unsigned char *p;
133 
134 	if (ax25_dev->dev == NULL)
135 		return;
136 
137 	if ((skb = alloc_skb(2, GFP_ATOMIC)) == NULL)
138 		return;
139 
140 	skb->nh.raw = skb->data;
141 	p = skb_put(skb, 2);
142 
143 	*p++ = cmd;
144 	*p++ = param;
145 
146 	skb->protocol = ax25_type_trans(skb, ax25_dev->dev);
147 
148 	dev_queue_xmit(skb);
149 }
150 
151 /*
152  *	A nasty problem arises if we count the number of DAMA connections
153  *	wrong, especially when connections on the device already existed
154  *	and our network node (or the sysop) decides to turn on DAMA Master
155  *	mode. We thus flag the 'real' slave connections with
156  *	ax25->dama_slave=1 and look on every disconnect if still slave
157  *	connections exist.
158  */
159 static int ax25_check_dama_slave(ax25_dev *ax25_dev)
160 {
161 	ax25_cb *ax25;
162 	int res = 0;
163 	struct hlist_node *node;
164 
165 	spin_lock_bh(&ax25_list_lock);
166 	ax25_for_each(ax25, node, &ax25_list)
167 		if (ax25->ax25_dev == ax25_dev && (ax25->condition & AX25_COND_DAMA_MODE) && ax25->state > AX25_STATE_1) {
168 			res = 1;
169 			break;
170 		}
171 	spin_unlock_bh(&ax25_list_lock);
172 
173 	return res;
174 }
175 
176 static void ax25_dev_dama_on(ax25_dev *ax25_dev)
177 {
178 	if (ax25_dev == NULL)
179 		return;
180 
181 	if (ax25_dev->dama.slave == 0)
182 		ax25_kiss_cmd(ax25_dev, 5, 1);
183 
184 	ax25_dev->dama.slave = 1;
185 	ax25_ds_set_timer(ax25_dev);
186 }
187 
188 void ax25_dev_dama_off(ax25_dev *ax25_dev)
189 {
190 	if (ax25_dev == NULL)
191 		return;
192 
193 	if (ax25_dev->dama.slave && !ax25_check_dama_slave(ax25_dev)) {
194 		ax25_kiss_cmd(ax25_dev, 5, 0);
195 		ax25_dev->dama.slave = 0;
196 		ax25_ds_del_timer(ax25_dev);
197 	}
198 }
199 
200 void ax25_dama_on(ax25_cb *ax25)
201 {
202 	ax25_dev_dama_on(ax25->ax25_dev);
203 	ax25->condition |= AX25_COND_DAMA_MODE;
204 }
205 
206 void ax25_dama_off(ax25_cb *ax25)
207 {
208 	ax25->condition &= ~AX25_COND_DAMA_MODE;
209 	ax25_dev_dama_off(ax25->ax25_dev);
210 }
211 
212