xref: /openbmc/linux/net/ax25/ax25_ds_subr.c (revision c4f7ac64)
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 
28 void 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  */
36 void 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 
107 void 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  */
124 static 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  */
154 static 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 
170 static 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 
182 void 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 
194 void ax25_dama_on(ax25_cb *ax25)
195 {
196 	ax25_dev_dama_on(ax25->ax25_dev);
197 	ax25->condition |= AX25_COND_DAMA_MODE;
198 }
199 
200 void ax25_dama_off(ax25_cb *ax25)
201 {
202 	ax25->condition &= ~AX25_COND_DAMA_MODE;
203 	ax25_dev_dama_off(ax25->ax25_dev);
204 }
205