// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      LAPB release 002
 *
 *      This code REQUIRES 2.1.15 or higher/ NET3.038
 *
 *      History
 *      LAPB 001        Jonathan Naylor Started Coding
 *      LAPB 002        Jonathan Naylor New timer architecture.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/jiffies.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/inet.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>
#include <net/lapb.h>

static void lapb_t1timer_expiry(struct timer_list *);
static void lapb_t2timer_expiry(struct timer_list *);

void lapb_start_t1timer(struct lapb_cb *lapb)
{
        timer_delete(&lapb->t1timer);

        lapb->t1timer.function = lapb_t1timer_expiry;
        lapb->t1timer.expires  = jiffies + lapb->t1;

        lapb->t1timer_running = true;
        add_timer(&lapb->t1timer);
}

void lapb_start_t2timer(struct lapb_cb *lapb)
{
        timer_delete(&lapb->t2timer);

        lapb->t2timer.function = lapb_t2timer_expiry;
        lapb->t2timer.expires  = jiffies + lapb->t2;

        lapb->t2timer_running = true;
        add_timer(&lapb->t2timer);
}

void lapb_stop_t1timer(struct lapb_cb *lapb)
{
        lapb->t1timer_running = false;
        timer_delete(&lapb->t1timer);
}

void lapb_stop_t2timer(struct lapb_cb *lapb)
{
        lapb->t2timer_running = false;
        timer_delete(&lapb->t2timer);
}

int lapb_t1timer_running(struct lapb_cb *lapb)
{
        return lapb->t1timer_running;
}

static void lapb_t2timer_expiry(struct timer_list *t)
{
        struct lapb_cb *lapb = timer_container_of(lapb, t, t2timer);

        spin_lock_bh(&lapb->lock);
        if (timer_pending(&lapb->t2timer)) /* A new timer has been set up */
                goto out;
        if (!lapb->t2timer_running) /* The timer has been stopped */
                goto out;

        if (lapb->condition & LAPB_ACK_PENDING_CONDITION) {
                lapb->condition &= ~LAPB_ACK_PENDING_CONDITION;
                lapb_timeout_response(lapb);
        }
        lapb->t2timer_running = false;

out:
        spin_unlock_bh(&lapb->lock);
}

static void lapb_t1timer_expiry(struct timer_list *t)
{
        struct lapb_cb *lapb = timer_container_of(lapb, t, t1timer);

        spin_lock_bh(&lapb->lock);
        if (timer_pending(&lapb->t1timer)) /* A new timer has been set up */
                goto out;
        if (!lapb->t1timer_running) /* The timer has been stopped */
                goto out;

        switch (lapb->state) {

                /*
                 *      If we are a DCE, send DM up to N2 times, then switch to
                 *      STATE_1 and send SABM(E).
                 */
                case LAPB_STATE_0:
                        if (lapb->mode & LAPB_DCE &&
                            lapb->n2count != lapb->n2) {
                                lapb->n2count++;
                                lapb_send_control(lapb, LAPB_DM, LAPB_POLLOFF, LAPB_RESPONSE);
                        } else {
                                lapb->state = LAPB_STATE_1;
                                lapb_establish_data_link(lapb);
                        }
                        break;

                /*
                 *      Awaiting connection state, send SABM(E), up to N2 times.
                 */
                case LAPB_STATE_1:
                        if (lapb->n2count == lapb->n2) {
                                lapb_clear_queues(lapb);
                                lapb->state = LAPB_STATE_0;
                                lapb_disconnect_indication(lapb, LAPB_TIMEDOUT);
                                lapb_dbg(0, "(%p) S1 -> S0\n", lapb->dev);
                                lapb->t1timer_running = false;
                                goto out;
                        } else {
                                lapb->n2count++;
                                if (lapb->mode & LAPB_EXTENDED) {
                                        lapb_dbg(1, "(%p) S1 TX SABME(1)\n",
                                                 lapb->dev);
                                        lapb_send_control(lapb, LAPB_SABME, LAPB_POLLON, LAPB_COMMAND);
                                } else {
                                        lapb_dbg(1, "(%p) S1 TX SABM(1)\n",
                                                 lapb->dev);
                                        lapb_send_control(lapb, LAPB_SABM, LAPB_POLLON, LAPB_COMMAND);
                                }
                        }
                        break;

                /*
                 *      Awaiting disconnection state, send DISC, up to N2 times.
                 */
                case LAPB_STATE_2:
                        if (lapb->n2count == lapb->n2) {
                                lapb_clear_queues(lapb);
                                lapb->state = LAPB_STATE_0;
                                lapb_disconnect_confirmation(lapb, LAPB_TIMEDOUT);
                                lapb_dbg(0, "(%p) S2 -> S0\n", lapb->dev);
                                lapb->t1timer_running = false;
                                goto out;
                        } else {
                                lapb->n2count++;
                                lapb_dbg(1, "(%p) S2 TX DISC(1)\n", lapb->dev);
                                lapb_send_control(lapb, LAPB_DISC, LAPB_POLLON, LAPB_COMMAND);
                        }
                        break;

                /*
                 *      Data transfer state, restransmit I frames, up to N2 times.
                 */
                case LAPB_STATE_3:
                        if (lapb->n2count == lapb->n2) {
                                lapb_clear_queues(lapb);
                                lapb->state = LAPB_STATE_0;
                                lapb_stop_t2timer(lapb);
                                lapb_disconnect_indication(lapb, LAPB_TIMEDOUT);
                                lapb_dbg(0, "(%p) S3 -> S0\n", lapb->dev);
                                lapb->t1timer_running = false;
                                goto out;
                        } else {
                                lapb->n2count++;
                                lapb_requeue_frames(lapb);
                                lapb_kick(lapb);
                        }
                        break;

                /*
                 *      Frame reject state, restransmit FRMR frames, up to N2 times.
                 */
                case LAPB_STATE_4:
                        if (lapb->n2count == lapb->n2) {
                                lapb_clear_queues(lapb);
                                lapb->state = LAPB_STATE_0;
                                lapb_disconnect_indication(lapb, LAPB_TIMEDOUT);
                                lapb_dbg(0, "(%p) S4 -> S0\n", lapb->dev);
                                lapb->t1timer_running = false;
                                goto out;
                        } else {
                                lapb->n2count++;
                                lapb_transmit_frmr(lapb);
                        }
                        break;
        }

        lapb_start_t1timer(lapb);

out:
        spin_unlock_bh(&lapb->lock);
}