ax25_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) Alan Cox GW4PTS ([email protected])
 * Copyright (C) Jonathan Naylor G4KLX ([email protected])
 * Copyright (C) Joerg Reuter DL1BKE ([email protected])
 */
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/spinlock.h>
#include <linux/net.h>
#include <linux/slab.h>
#include <net/ax25.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/netfilter.h>
#include <net/sock.h>
#include <asm/uaccess.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>

static DEFINE_SPINLOCK(ax25_frag_lock);

ax25_cb *ax25_send_frame(struct sk_buff *skb, int paclen, ax25_address *src, ax25_address *dest, ax25_digi *digi, struct net_device *dev)
{
    ax25_dev *ax25_dev;
    ax25_cb *ax25;

    /*
     * Take the default packet length for the device if zero is
     * specified.
     */
    if (paclen == 0) {
        if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
            return NULL;

        paclen = ax25_dev->values[AX25_VALUES_PACLEN];
    }

    /*
     * Look for an existing connection.
     */
    if ((ax25 = ax25_find_cb(src, dest, digi, dev)) != NULL) {
        ax25_output(ax25, paclen, skb);
        return ax25;        /* It already existed */
    }

    if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
        return NULL;

    if ((ax25 = ax25_create_cb()) == NULL)
        return NULL;

    ax25_fillin_cb(ax25, ax25_dev);

    ax25->source_addr = *src;
    ax25->dest_addr   = *dest;

    if (digi != NULL) {
        ax25->digipeat = kmemdup(digi, sizeof(*digi), GFP_ATOMIC);
        if (ax25->digipeat == NULL) {
            ax25_cb_put(ax25);
            return NULL;
        }
    }

    switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
    case AX25_PROTO_STD_SIMPLEX:
    case AX25_PROTO_STD_DUPLEX:
        ax25_std_establish_data_link(ax25);
        break;

#ifdef CONFIG_AX25_DAMA_SLAVE
    case AX25_PROTO_DAMA_SLAVE:
        if (ax25_dev->dama.slave)
            ax25_ds_establish_data_link(ax25);
        else
            ax25_std_establish_data_link(ax25);
        break;
#endif
    }

    /*
     * There is one ref for the state machine; a caller needs
     * one more to put it back, just like with the existing one.
     */
    ax25_cb_hold(ax25);

    ax25_cb_add(ax25);

    ax25->state = AX25_STATE_1;

    ax25_start_heartbeat(ax25);

    ax25_output(ax25, paclen, skb);

    return ax25;            /* We had to create it */
}

EXPORT_SYMBOL(ax25_send_frame);

/*
 *  All outgoing AX.25 I frames pass via this routine. Therefore this is
 *  where the fragmentation of frames takes place. If fragment is set to
 *  zero then we are not allowed to do fragmentation, even if the frame
 *  is too large.
 */
void ax25_output(ax25_cb *ax25, int paclen, struct sk_buff *skb)
{
    struct sk_buff *skbn;
    unsigned char *p;
    int frontlen, len, fragno, ka9qfrag, first = 1;

    if (paclen < 16) {
        WARN_ON_ONCE(1);
        kfree_skb(skb);
        return;
    }

    if ((skb->len - 1) > paclen) {
        if (*skb->data == AX25_P_TEXT) {
            skb_pull(skb, 1); /* skip PID */
            ka9qfrag = 0;
        } else {
            paclen -= 2;    /* Allow for fragment control info */
            ka9qfrag = 1;
        }

        fragno = skb->len / paclen;
        if (skb->len % paclen == 0) fragno--;

        frontlen = skb_headroom(skb);   /* Address space + CTRL */

        while (skb->len > 0) {
            spin_lock_bh(&ax25_frag_lock);
            if ((skbn = alloc_skb(paclen + 2 + frontlen, GFP_ATOMIC)) == NULL) {
                spin_unlock_bh(&ax25_frag_lock);
                printk(KERN_CRIT "AX.25: ax25_output - out of memory\n");
                return;
            }

            if (skb->sk != NULL)
                skb_set_owner_w(skbn, skb->sk);

            spin_unlock_bh(&ax25_frag_lock);

            len = (paclen > skb->len) ? skb->len : paclen;

            if (ka9qfrag == 1) {
                skb_reserve(skbn, frontlen + 2);
                skb_set_network_header(skbn,
                              skb_network_offset(skb));
                skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
                p = skb_push(skbn, 2);

                *p++ = AX25_P_SEGMENT;

                *p = fragno--;
                if (first) {
                    *p |= AX25_SEG_FIRST;
                    first = 0;
                }
            } else {
                skb_reserve(skbn, frontlen + 1);
                skb_set_network_header(skbn,
                              skb_network_offset(skb));
                skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
                p = skb_push(skbn, 1);
                *p = AX25_P_TEXT;
            }

            skb_pull(skb, len);
            skb_queue_tail(&ax25->write_queue, skbn); /* Throw it on the queue */
        }

        kfree_skb(skb);
    } else {
        skb_queue_tail(&ax25->write_queue, skb);      /* Throw it on the queue */
    }

    switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
    case AX25_PROTO_STD_SIMPLEX:
    case AX25_PROTO_STD_DUPLEX:
        ax25_kick(ax25);
        break;

#ifdef CONFIG_AX25_DAMA_SLAVE
    /*
     * A DAMA slave is _required_ to work as normal AX.25L2V2
     * if no DAMA master is available.
     */
    case AX25_PROTO_DAMA_SLAVE:
        if (!ax25->ax25_dev->dama.slave) ax25_kick(ax25);
        break;
#endif
    }
}

/*
 *  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 ax25_send_iframe(ax25_cb *ax25, struct sk_buff *skb, int poll_bit)
{
    unsigned char *frame;

    if (skb == NULL)
        return;

    skb_reset_network_header(skb);

    if (ax25->modulus == AX25_MODULUS) {
        frame = skb_push(skb, 1);

        *frame = AX25_I;
        *frame |= (poll_bit) ? AX25_PF : 0;
        *frame |= (ax25->vr << 5);
        *frame |= (ax25->vs << 1);
    } else {
        frame = skb_push(skb, 2);

        frame[0] = AX25_I;
        frame[0] |= (ax25->vs << 1);
        frame[1] = (poll_bit) ? AX25_EPF : 0;
        frame[1] |= (ax25->vr << 1);
    }

    ax25_start_idletimer(ax25);

    ax25_transmit_buffer(ax25, skb, AX25_COMMAND);
}

void ax25_kick(ax25_cb *ax25)
{
    struct sk_buff *skb, *skbn;
    int last = 1;
    unsigned short start, end, next;

    if (ax25->state != AX25_STATE_3 && ax25->state != AX25_STATE_4)
        return;

    if (ax25->condition & AX25_COND_PEER_RX_BUSY)
        return;

    if (skb_peek(&ax25->write_queue) == NULL)
        return;

    start = (skb_peek(&ax25->ack_queue) == NULL) ? ax25->va : ax25->vs;
    end   = (ax25->va + ax25->window) % ax25->modulus;

    if (start == end)
        return;

    /*
     * Transmit data until either we're out of data to send or
     * the window is full. Send a poll on the final I frame if
     * the window is filled.
     */

    /*
     * Dequeue the frame and copy it.
     * Check for race with ax25_clear_queues().
     */
    skb  = skb_dequeue(&ax25->write_queue);
    if (!skb)
        return;

    ax25->vs = start;

    do {
        if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
            skb_queue_head(&ax25->write_queue, skb);
            break;
        }

        if (skb->sk != NULL)
            skb_set_owner_w(skbn, skb->sk);

        next = (ax25->vs + 1) % ax25->modulus;
        last = (next == end);

        /*
         * Transmit the frame copy.
         * bke 960114: do not set the Poll bit on the last frame
         * in DAMA mode.
         */
        switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
        case AX25_PROTO_STD_SIMPLEX:
        case AX25_PROTO_STD_DUPLEX:
            ax25_send_iframe(ax25, skbn, (last) ? AX25_POLLON : AX25_POLLOFF);
            break;

#ifdef CONFIG_AX25_DAMA_SLAVE
        case AX25_PROTO_DAMA_SLAVE:
            ax25_send_iframe(ax25, skbn, AX25_POLLOFF);
            break;
#endif
        }

        ax25->vs = next;

        /*
         * Requeue the original data frame.
         */
        skb_queue_tail(&ax25->ack_queue, skb);

    } while (!last && (skb = skb_dequeue(&ax25->write_queue)) != NULL);

    ax25->condition &= ~AX25_COND_ACK_PENDING;

    if (!ax25_t1timer_running(ax25)) {
        ax25_stop_t3timer(ax25);
        ax25_calculate_t1(ax25);
        ax25_start_t1timer(ax25);
    }
}

void ax25_transmit_buffer(ax25_cb *ax25, struct sk_buff *skb, int type)
{
    struct sk_buff *skbn;
    unsigned char *ptr;
    int headroom;

    if (ax25->ax25_dev == NULL) {
        ax25_disconnect(ax25, ENETUNREACH);
        return;
    }

    headroom = ax25_addr_size(ax25->digipeat);

    if (skb_headroom(skb) < headroom) {
        if ((skbn = skb_realloc_headroom(skb, headroom)) == NULL) {
            printk(KERN_CRIT "AX.25: ax25_transmit_buffer - out of memory\n");
            kfree_skb(skb);
            return;
        }

        if (skb->sk != NULL)
            skb_set_owner_w(skbn, skb->sk);

        consume_skb(skb);
        skb = skbn;
    }

    ptr = skb_push(skb, headroom);

    ax25_addr_build(ptr, &ax25->source_addr, &ax25->dest_addr, ax25->digipeat, type, ax25->modulus);

    ax25_queue_xmit(skb, ax25->ax25_dev->dev);
}

/*
 *  A small shim to dev_queue_xmit to add the KISS control byte, and do
 *  any packet forwarding in operation.
 */
void ax25_queue_xmit(struct sk_buff *skb, struct net_device *dev)
{
    unsigned char *ptr;

    skb->protocol = ax25_type_trans(skb, ax25_fwd_dev(dev));

    ptr  = skb_push(skb, 1);
    *ptr = 0x00;            /* KISS */

    dev_queue_xmit(skb);
}

int ax25_check_iframes_acked(ax25_cb *ax25, unsigned short nr)
{
    if (ax25->vs == nr) {
        ax25_frames_acked(ax25, nr);
        ax25_calculate_rtt(ax25);
        ax25_stop_t1timer(ax25);
        ax25_start_t3timer(ax25);
        return 1;
    } else {
        if (ax25->va != nr) {
            ax25_frames_acked(ax25, nr);
            ax25_calculate_t1(ax25);
            ax25_start_t1timer(ax25);
            return 1;
        }
    }
    return 0;
}