// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *
 * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
 * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
 */
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/spinlock.h>
#include <linux/net.h>
#include <linux/gfp.h>
#include <net/ax25.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <linux/uaccess.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>

void ax25_ds_nr_error_recovery(ax25_cb *ax25)
{
        ax25_ds_establish_data_link(ax25);
}

/*
 *      dl1bke 960114: transmit I frames on DAMA poll
 */
void ax25_ds_enquiry_response(ax25_cb *ax25)
{
        ax25_cb *ax25o;

        /* Please note that neither DK4EG's nor DG2FEF's
         * DAMA spec mention the following behaviour as seen
         * with TheFirmware:
         *
         *      DB0ACH->DL1BKE <RR C P R0> [DAMA]
         *      DL1BKE->DB0ACH <I NR=0 NS=0>
         *      DL1BKE-7->DB0PRA-6 DB0ACH <I C S3 R5>
         *      DL1BKE->DB0ACH <RR R F R0>
         *
         * The Flexnet DAMA Master implementation apparently
         * insists on the "proper" AX.25 behaviour:
         *
         *      DB0ACH->DL1BKE <RR C P R0> [DAMA]
         *      DL1BKE->DB0ACH <RR R F R0>
         *      DL1BKE->DB0ACH <I NR=0 NS=0>
         *      DL1BKE-7->DB0PRA-6 DB0ACH <I C S3 R5>
         *
         * Flexnet refuses to send us *any* I frame if we send
         * a REJ in case AX25_COND_REJECT is set. It is superfluous in
         * this mode anyway (a RR or RNR invokes the retransmission).
         * Is this a Flexnet bug?
         */

        ax25_std_enquiry_response(ax25);

        if (!(ax25->condition & AX25_COND_PEER_RX_BUSY)) {
                ax25_requeue_frames(ax25);
                ax25_kick(ax25);
        }

        if (ax25->state == AX25_STATE_1 || ax25->state == AX25_STATE_2 || skb_peek(&ax25->ack_queue) != NULL)
                ax25_ds_t1_timeout(ax25);
        else
                ax25->n2count = 0;

        ax25_start_t3timer(ax25);
        ax25_ds_set_timer(ax25->ax25_dev);

        spin_lock(&ax25_list_lock);
        ax25_for_each(ax25o, &ax25_list) {
                if (ax25o == ax25)
                        continue;

                if (ax25o->ax25_dev != ax25->ax25_dev)
                        continue;

                if (ax25o->state == AX25_STATE_1 || ax25o->state == AX25_STATE_2) {
                        ax25_ds_t1_timeout(ax25o);
                        continue;
                }

                if (!(ax25o->condition & AX25_COND_PEER_RX_BUSY) && ax25o->state == AX25_STATE_3) {
                        ax25_requeue_frames(ax25o);
                        ax25_kick(ax25o);
                }

                if (ax25o->state == AX25_STATE_1 || ax25o->state == AX25_STATE_2 || skb_peek(&ax25o->ack_queue) != NULL)
                        ax25_ds_t1_timeout(ax25o);

                /* do not start T3 for listening sockets (tnx DD8NE) */

                if (ax25o->state != AX25_STATE_0)
                        ax25_start_t3timer(ax25o);
        }
        spin_unlock(&ax25_list_lock);
}

void ax25_ds_establish_data_link(ax25_cb *ax25)
{
        ax25->condition &= AX25_COND_DAMA_MODE;
        ax25->n2count    = 0;
        ax25_calculate_t1(ax25);
        ax25_start_t1timer(ax25);
        ax25_stop_t2timer(ax25);
        ax25_start_t3timer(ax25);
}

/*
 *      :::FIXME:::
 *      This is a kludge. Not all drivers recognize kiss commands.
 *      We need a driver level  request to switch duplex mode, that does
 *      either SCC changing, PI config or KISS as required. Currently
 *      this request isn't reliable.
 */
static void ax25_kiss_cmd(ax25_dev *ax25_dev, unsigned char cmd, unsigned char param)
{
        struct sk_buff *skb;
        unsigned char *p;

        if (ax25_dev->dev == NULL)
                return;

        if ((skb = alloc_skb(2, GFP_ATOMIC)) == NULL)
                return;

        skb_reset_network_header(skb);
        p = skb_put(skb, 2);

        *p++ = cmd;
        *p++ = param;

        skb->protocol = ax25_type_trans(skb, ax25_dev->dev);

        dev_queue_xmit(skb);
}

/*
 *      A nasty problem arises if we count the number of DAMA connections
 *      wrong, especially when connections on the device already existed
 *      and our network node (or the sysop) decides to turn on DAMA Master
 *      mode. We thus flag the 'real' slave connections with
 *      ax25->dama_slave=1 and look on every disconnect if still slave
 *      connections exist.
 */
static int ax25_check_dama_slave(ax25_dev *ax25_dev)
{
        ax25_cb *ax25;
        int res = 0;

        spin_lock(&ax25_list_lock);
        ax25_for_each(ax25, &ax25_list)
                if (ax25->ax25_dev == ax25_dev && (ax25->condition & AX25_COND_DAMA_MODE) && ax25->state > AX25_STATE_1) {
                        res = 1;
                        break;
                }
        spin_unlock(&ax25_list_lock);

        return res;
}

static void ax25_dev_dama_on(ax25_dev *ax25_dev)
{
        if (ax25_dev == NULL)
                return;

        if (ax25_dev->dama.slave == 0)
                ax25_kiss_cmd(ax25_dev, 5, 1);

        ax25_dev->dama.slave = 1;
        ax25_ds_set_timer(ax25_dev);
}

void ax25_dev_dama_off(ax25_dev *ax25_dev)
{
        if (ax25_dev == NULL)
                return;

        if (ax25_dev->dama.slave && !ax25_check_dama_slave(ax25_dev)) {
                ax25_kiss_cmd(ax25_dev, 5, 0);
                ax25_dev->dama.slave = 0;
                ax25_ds_del_timer(ax25_dev);
        }
}

void ax25_dama_on(ax25_cb *ax25)
{
        ax25_dev_dama_on(ax25->ax25_dev);
        ax25->condition |= AX25_COND_DAMA_MODE;
}

void ax25_dama_off(ax25_cb *ax25)
{
        ax25->condition &= ~AX25_COND_DAMA_MODE;
        ax25_dev_dama_off(ax25->ax25_dev);
}