rose_out.c

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/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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);
}