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Linux/net/ax25/ax25_ds_subr.c

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  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 

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