lapb_out.c

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/*
 *  LAPB release 002
 *
 *  This code REQUIRES 2.1.15 or higher/ NET3.038
 *
 *  This module:
 *      This module 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.
 *
 *  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/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/inet.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <asm/uaccess.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <net/lapb.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 lapb_send_iframe(struct lapb_cb *lapb, struct sk_buff *skb, int poll_bit)
{
    unsigned char *frame;

    if (!skb)
        return;

    if (lapb->mode & LAPB_EXTENDED) {
        frame = skb_push(skb, 2);

        frame[0] = LAPB_I;
        frame[0] |= lapb->vs << 1;
        frame[1] = poll_bit ? LAPB_EPF : 0;
        frame[1] |= lapb->vr << 1;
    } else {
        frame = skb_push(skb, 1);

        *frame = LAPB_I;
        *frame |= poll_bit ? LAPB_SPF : 0;
        *frame |= lapb->vr << 5;
        *frame |= lapb->vs << 1;
    }

    lapb_dbg(1, "(%p) S%d TX I(%d) S%d R%d\n",
         lapb->dev, lapb->state, poll_bit, lapb->vs, lapb->vr);

    lapb_transmit_buffer(lapb, skb, LAPB_COMMAND);
}

void lapb_kick(struct lapb_cb *lapb)
{
    struct sk_buff *skb, *skbn;
    unsigned short modulus, start, end;

    modulus = (lapb->mode & LAPB_EXTENDED) ? LAPB_EMODULUS : LAPB_SMODULUS;
    start = !skb_peek(&lapb->ack_queue) ? lapb->va : lapb->vs;
    end   = (lapb->va + lapb->window) % modulus;

    if (!(lapb->condition & LAPB_PEER_RX_BUSY_CONDITION) &&
        start != end && skb_peek(&lapb->write_queue)) {
        lapb->vs = start;

        /*
         * Dequeue the frame and copy it.
         */
        skb = skb_dequeue(&lapb->write_queue);

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

            if (skb->sk)
                skb_set_owner_w(skbn, skb->sk);

            /*
             * Transmit the frame copy.
             */
            lapb_send_iframe(lapb, skbn, LAPB_POLLOFF);

            lapb->vs = (lapb->vs + 1) % modulus;

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

        } while (lapb->vs != end && (skb = skb_dequeue(&lapb->write_queue)) != NULL);

        lapb->condition &= ~LAPB_ACK_PENDING_CONDITION;

        if (!lapb_t1timer_running(lapb))
            lapb_start_t1timer(lapb);
    }
}

void lapb_transmit_buffer(struct lapb_cb *lapb, struct sk_buff *skb, int type)
{
    unsigned char *ptr;

    ptr = skb_push(skb, 1);

    if (lapb->mode & LAPB_MLP) {
        if (lapb->mode & LAPB_DCE) {
            if (type == LAPB_COMMAND)
                *ptr = LAPB_ADDR_C;
            if (type == LAPB_RESPONSE)
                *ptr = LAPB_ADDR_D;
        } else {
            if (type == LAPB_COMMAND)
                *ptr = LAPB_ADDR_D;
            if (type == LAPB_RESPONSE)
                *ptr = LAPB_ADDR_C;
        }
    } else {
        if (lapb->mode & LAPB_DCE) {
            if (type == LAPB_COMMAND)
                *ptr = LAPB_ADDR_A;
            if (type == LAPB_RESPONSE)
                *ptr = LAPB_ADDR_B;
        } else {
            if (type == LAPB_COMMAND)
                *ptr = LAPB_ADDR_B;
            if (type == LAPB_RESPONSE)
                *ptr = LAPB_ADDR_A;
        }
    }

    lapb_dbg(2, "(%p) S%d TX %02X %02X %02X\n",
         lapb->dev, lapb->state,
         skb->data[0], skb->data[1], skb->data[2]);

    if (!lapb_data_transmit(lapb, skb))
        kfree_skb(skb);
}

void lapb_establish_data_link(struct lapb_cb *lapb)
{
    lapb->condition = 0x00;
    lapb->n2count   = 0;

    if (lapb->mode & LAPB_EXTENDED) {
        lapb_dbg(1, "(%p) S%d TX SABME(1)\n", lapb->dev, lapb->state);
        lapb_send_control(lapb, LAPB_SABME, LAPB_POLLON, LAPB_COMMAND);
    } else {
        lapb_dbg(1, "(%p) S%d TX SABM(1)\n", lapb->dev, lapb->state);
        lapb_send_control(lapb, LAPB_SABM, LAPB_POLLON, LAPB_COMMAND);
    }

    lapb_start_t1timer(lapb);
    lapb_stop_t2timer(lapb);
}

void lapb_enquiry_response(struct lapb_cb *lapb)
{
    lapb_dbg(1, "(%p) S%d TX RR(1) R%d\n",
         lapb->dev, lapb->state, lapb->vr);

    lapb_send_control(lapb, LAPB_RR, LAPB_POLLON, LAPB_RESPONSE);

    lapb->condition &= ~LAPB_ACK_PENDING_CONDITION;
}

void lapb_timeout_response(struct lapb_cb *lapb)
{
    lapb_dbg(1, "(%p) S%d TX RR(0) R%d\n",
         lapb->dev, lapb->state, lapb->vr);
    lapb_send_control(lapb, LAPB_RR, LAPB_POLLOFF, LAPB_RESPONSE);

    lapb->condition &= ~LAPB_ACK_PENDING_CONDITION;
}

void lapb_check_iframes_acked(struct lapb_cb *lapb, unsigned short nr)
{
    if (lapb->vs == nr) {
        lapb_frames_acked(lapb, nr);
        lapb_stop_t1timer(lapb);
        lapb->n2count = 0;
    } else if (lapb->va != nr) {
        lapb_frames_acked(lapb, nr);
        lapb_start_t1timer(lapb);
    }
}

void lapb_check_need_response(struct lapb_cb *lapb, int type, int pf)
{
    if (type == LAPB_COMMAND && pf)
        lapb_enquiry_response(lapb);
}