net/ax25/ax25_ds_subr.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /*
0003  *
0004  * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
0005  * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
0006  */
0007 #include <linux/errno.h>
0008 #include <linux/types.h>
0009 #include <linux/socket.h>
0010 #include <linux/in.h>
0011 #include <linux/kernel.h>
0012 #include <linux/timer.h>
0013 #include <linux/string.h>
0014 #include <linux/sockios.h>
0015 #include <linux/spinlock.h>
0016 #include <linux/net.h>
0017 #include <linux/gfp.h>
0018 #include <net/ax25.h>
0019 #include <linux/inet.h>
0020 #include <linux/netdevice.h>
0021 #include <linux/skbuff.h>
0022 #include <net/sock.h>
0023 #include <linux/uaccess.h>
0024 #include <linux/fcntl.h>
0025 #include <linux/mm.h>
0026 #include <linux/interrupt.h>
0027
0028 void ax25_ds_nr_error_recovery(ax25_cb *ax25)
0029 {
0030     ax25_ds_establish_data_link(ax25);
0031 }
0032
0033 /*
0034  *  dl1bke 960114: transmit I frames on DAMA poll
0035  */
0036 void ax25_ds_enquiry_response(ax25_cb *ax25)
0037 {
0038     ax25_cb *ax25o;
0039
0040     /* Please note that neither DK4EG's nor DG2FEF's
0041      * DAMA spec mention the following behaviour as seen
0042      * with TheFirmware:
0043      *
0044      *  DB0ACH->DL1BKE <RR C P R0> [DAMA]
0045      *  DL1BKE->DB0ACH <I NR=0 NS=0>
0046      *  DL1BKE-7->DB0PRA-6 DB0ACH <I C S3 R5>
0047      *  DL1BKE->DB0ACH <RR R F R0>
0048      *
0049      * The Flexnet DAMA Master implementation apparently
0050      * insists on the "proper" AX.25 behaviour:
0051      *
0052      *  DB0ACH->DL1BKE <RR C P R0> [DAMA]
0053      *  DL1BKE->DB0ACH <RR R F R0>
0054      *  DL1BKE->DB0ACH <I NR=0 NS=0>
0055      *  DL1BKE-7->DB0PRA-6 DB0ACH <I C S3 R5>
0056      *
0057      * Flexnet refuses to send us *any* I frame if we send
0058      * a REJ in case AX25_COND_REJECT is set. It is superfluous in
0059      * this mode anyway (a RR or RNR invokes the retransmission).
0060      * Is this a Flexnet bug?
0061      */
0062
0063     ax25_std_enquiry_response(ax25);
0064
0065     if (!(ax25->condition & AX25_COND_PEER_RX_BUSY)) {
0066         ax25_requeue_frames(ax25);
0067         ax25_kick(ax25);
0068     }
0069
0070     if (ax25->state == AX25_STATE_1 || ax25->state == AX25_STATE_2 || skb_peek(&ax25->ack_queue) != NULL)
0071         ax25_ds_t1_timeout(ax25);
0072     else
0073         ax25->n2count = 0;
0074
0075     ax25_start_t3timer(ax25);
0076     ax25_ds_set_timer(ax25->ax25_dev);
0077
0078     spin_lock(&ax25_list_lock);
0079     ax25_for_each(ax25o, &ax25_list) {
0080         if (ax25o == ax25)
0081             continue;
0082
0083         if (ax25o->ax25_dev != ax25->ax25_dev)
0084             continue;
0085
0086         if (ax25o->state == AX25_STATE_1 || ax25o->state == AX25_STATE_2) {
0087             ax25_ds_t1_timeout(ax25o);
0088             continue;
0089         }
0090
0091         if (!(ax25o->condition & AX25_COND_PEER_RX_BUSY) && ax25o->state == AX25_STATE_3) {
0092             ax25_requeue_frames(ax25o);
0093             ax25_kick(ax25o);
0094         }
0095
0096         if (ax25o->state == AX25_STATE_1 || ax25o->state == AX25_STATE_2 || skb_peek(&ax25o->ack_queue) != NULL)
0097             ax25_ds_t1_timeout(ax25o);
0098
0099         /* do not start T3 for listening sockets (tnx DD8NE) */
0100
0101         if (ax25o->state != AX25_STATE_0)
0102             ax25_start_t3timer(ax25o);
0103     }
0104     spin_unlock(&ax25_list_lock);
0105 }
0106
0107 void ax25_ds_establish_data_link(ax25_cb *ax25)
0108 {
0109     ax25->condition &= AX25_COND_DAMA_MODE;
0110     ax25->n2count    = 0;
0111     ax25_calculate_t1(ax25);
0112     ax25_start_t1timer(ax25);
0113     ax25_stop_t2timer(ax25);
0114     ax25_start_t3timer(ax25);
0115 }
0116
0117 /*
0118  *  :::FIXME:::
0119  *  This is a kludge. Not all drivers recognize kiss commands.
0120  *  We need a driver level  request to switch duplex mode, that does
0121  *  either SCC changing, PI config or KISS as required. Currently
0122  *  this request isn't reliable.
0123  */
0124 static void ax25_kiss_cmd(ax25_dev *ax25_dev, unsigned char cmd, unsigned char param)
0125 {
0126     struct sk_buff *skb;
0127     unsigned char *p;
0128
0129     if (ax25_dev->dev == NULL)
0130         return;
0131
0132     if ((skb = alloc_skb(2, GFP_ATOMIC)) == NULL)
0133         return;
0134
0135     skb_reset_network_header(skb);
0136     p = skb_put(skb, 2);
0137
0138     *p++ = cmd;
0139     *p++ = param;
0140
0141     skb->protocol = ax25_type_trans(skb, ax25_dev->dev);
0142
0143     dev_queue_xmit(skb);
0144 }
0145
0146 /*
0147  *  A nasty problem arises if we count the number of DAMA connections
0148  *  wrong, especially when connections on the device already existed
0149  *  and our network node (or the sysop) decides to turn on DAMA Master
0150  *  mode. We thus flag the 'real' slave connections with
0151  *  ax25->dama_slave=1 and look on every disconnect if still slave
0152  *  connections exist.
0153  */
0154 static int ax25_check_dama_slave(ax25_dev *ax25_dev)
0155 {
0156     ax25_cb *ax25;
0157     int res = 0;
0158
0159     spin_lock(&ax25_list_lock);
0160     ax25_for_each(ax25, &ax25_list)
0161         if (ax25->ax25_dev == ax25_dev && (ax25->condition & AX25_COND_DAMA_MODE) && ax25->state > AX25_STATE_1) {
0162             res = 1;
0163             break;
0164         }
0165     spin_unlock(&ax25_list_lock);
0166
0167     return res;
0168 }
0169
0170 static void ax25_dev_dama_on(ax25_dev *ax25_dev)
0171 {
0172     if (ax25_dev == NULL)
0173         return;
0174
0175     if (ax25_dev->dama.slave == 0)
0176         ax25_kiss_cmd(ax25_dev, 5, 1);
0177
0178     ax25_dev->dama.slave = 1;
0179     ax25_ds_set_timer(ax25_dev);
0180 }
0181
0182 void ax25_dev_dama_off(ax25_dev *ax25_dev)
0183 {
0184     if (ax25_dev == NULL)
0185         return;
0186
0187     if (ax25_dev->dama.slave && !ax25_check_dama_slave(ax25_dev)) {
0188         ax25_kiss_cmd(ax25_dev, 5, 0);
0189         ax25_dev->dama.slave = 0;
0190         ax25_ds_del_timer(ax25_dev);
0191     }
0192 }
0193
0194 void ax25_dama_on(ax25_cb *ax25)
0195 {
0196     ax25_dev_dama_on(ax25->ax25_dev);
0197     ax25->condition |= AX25_COND_DAMA_MODE;
0198 }
0199
0200 void ax25_dama_off(ax25_cb *ax25)
0201 {
0202     ax25->condition &= ~AX25_COND_DAMA_MODE;
0203     ax25_dev_dama_off(ax25->ax25_dev);
0204 }