// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *
 * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
 */
#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/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/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <net/rose.h>

/*
 *      This procedure is passed a buffer descriptor for an iframe. It builds
 *      the rest of the control part of the frame and then writes it out.
 */
static void rose_send_iframe(struct sock *sk, struct sk_buff *skb)
{
        struct rose_sock *rose = rose_sk(sk);

        if (skb == NULL)
                return;

        skb->data[2] |= (rose->vr << 5) & 0xE0;
        skb->data[2] |= (rose->vs << 1) & 0x0E;

        rose_start_idletimer(sk);

        rose_transmit_link(skb, rose->neighbour);
}

void rose_kick(struct sock *sk)
{
        struct rose_sock *rose = rose_sk(sk);
        struct sk_buff *skb, *skbn;
        unsigned short start, end;

        if (rose->state != ROSE_STATE_3)
                return;

        if (rose->condition & ROSE_COND_PEER_RX_BUSY)
                return;

        if (!skb_peek(&sk->sk_write_queue))
                return;

        start = (skb_peek(&rose->ack_queue) == NULL) ? rose->va : rose->vs;
        end   = (rose->va + sysctl_rose_window_size) % ROSE_MODULUS;

        if (start == end)
                return;

        rose->vs = start;

        /*
         * Transmit data until either we're out of data to send or
         * the window is full.
         */

        skb  = skb_dequeue(&sk->sk_write_queue);

        do {
                if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
                        skb_queue_head(&sk->sk_write_queue, skb);
                        break;
                }

                skb_set_owner_w(skbn, sk);

                /*
                 * Transmit the frame copy.
                 */
                rose_send_iframe(sk, skbn);

                rose->vs = (rose->vs + 1) % ROSE_MODULUS;

                /*
                 * Requeue the original data frame.
                 */
                skb_queue_tail(&rose->ack_queue, skb);

        } while (rose->vs != end &&
                 (skb = skb_dequeue(&sk->sk_write_queue)) != NULL);

        rose->vl         = rose->vr;
        rose->condition &= ~ROSE_COND_ACK_PENDING;

        rose_stop_timer(sk);
}

/*
 * The following routines are taken from page 170 of the 7th ARRL Computer
 * Networking Conference paper, as is the whole state machine.
 */

void rose_enquiry_response(struct sock *sk)
{
        struct rose_sock *rose = rose_sk(sk);

        if (rose->condition & ROSE_COND_OWN_RX_BUSY)
                rose_write_internal(sk, ROSE_RNR);
        else
                rose_write_internal(sk, ROSE_RR);

        rose->vl         = rose->vr;
        rose->condition &= ~ROSE_COND_ACK_PENDING;

        rose_stop_timer(sk);
}