nr_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 Jonathan Naylor G4KLX ([email protected])
 * Copyright Darryl Miles G7LED ([email protected])
 */
#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/slab.h>
#include <net/ax25.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <asm/uaccess.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <net/netrom.h>

/*
 *  This is where all NET/ROM frames pass, except for IP-over-NET/ROM which
 *  cannot be fragmented in this manner.
 */
void nr_output(struct sock *sk, struct sk_buff *skb)
{
    struct sk_buff *skbn;
    unsigned char transport[NR_TRANSPORT_LEN];
    int err, frontlen, len;

    if (skb->len - NR_TRANSPORT_LEN > NR_MAX_PACKET_SIZE) {
        /* Save a copy of the Transport Header */
        skb_copy_from_linear_data(skb, transport, NR_TRANSPORT_LEN);
        skb_pull(skb, NR_TRANSPORT_LEN);

        frontlen = skb_headroom(skb);

        while (skb->len > 0) {
            if ((skbn = sock_alloc_send_skb(sk, frontlen + NR_MAX_PACKET_SIZE, 0, &err)) == NULL)
                return;

            skb_reserve(skbn, frontlen);

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

            /* Copy the user data */
            skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
            skb_pull(skb, len);

            /* Duplicate the Transport Header */
            skb_push(skbn, NR_TRANSPORT_LEN);
            skb_copy_to_linear_data(skbn, transport,
                        NR_TRANSPORT_LEN);
            if (skb->len > 0)
                skbn->data[4] |= NR_MORE_FLAG;

            skb_queue_tail(&sk->sk_write_queue, skbn); /* Throw it on the queue */
        }

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

    nr_kick(sk);
}

/*
 *  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 nr_send_iframe(struct sock *sk, struct sk_buff *skb)
{
    struct nr_sock *nr = nr_sk(sk);

    if (skb == NULL)
        return;

    skb->data[2] = nr->vs;
    skb->data[3] = nr->vr;

    if (nr->condition & NR_COND_OWN_RX_BUSY)
        skb->data[4] |= NR_CHOKE_FLAG;

    nr_start_idletimer(sk);

    nr_transmit_buffer(sk, skb);
}

void nr_send_nak_frame(struct sock *sk)
{
    struct sk_buff *skb, *skbn;
    struct nr_sock *nr = nr_sk(sk);

    if ((skb = skb_peek(&nr->ack_queue)) == NULL)
        return;

    if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL)
        return;

    skbn->data[2] = nr->va;
    skbn->data[3] = nr->vr;

    if (nr->condition & NR_COND_OWN_RX_BUSY)
        skbn->data[4] |= NR_CHOKE_FLAG;

    nr_transmit_buffer(sk, skbn);

    nr->condition &= ~NR_COND_ACK_PENDING;
    nr->vl         = nr->vr;

    nr_stop_t1timer(sk);
}

void nr_kick(struct sock *sk)
{
    struct nr_sock *nr = nr_sk(sk);
    struct sk_buff *skb, *skbn;
    unsigned short start, end;

    if (nr->state != NR_STATE_3)
        return;

    if (nr->condition & NR_COND_PEER_RX_BUSY)
        return;

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

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

    if (start == end)
        return;

    nr->vs = start;

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

    /*
     * Dequeue the frame and copy it.
     */
    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.
         */
        nr_send_iframe(sk, skbn);

        nr->vs = (nr->vs + 1) % NR_MODULUS;

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

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

    nr->vl         = nr->vr;
    nr->condition &= ~NR_COND_ACK_PENDING;

    if (!nr_t1timer_running(sk))
        nr_start_t1timer(sk);
}

void nr_transmit_buffer(struct sock *sk, struct sk_buff *skb)
{
    struct nr_sock *nr = nr_sk(sk);
    unsigned char *dptr;

    /*
     *  Add the protocol byte and network header.
     */
    dptr = skb_push(skb, NR_NETWORK_LEN);

    memcpy(dptr, &nr->source_addr, AX25_ADDR_LEN);
    dptr[6] &= ~AX25_CBIT;
    dptr[6] &= ~AX25_EBIT;
    dptr[6] |= AX25_SSSID_SPARE;
    dptr += AX25_ADDR_LEN;

    memcpy(dptr, &nr->dest_addr, AX25_ADDR_LEN);
    dptr[6] &= ~AX25_CBIT;
    dptr[6] |= AX25_EBIT;
    dptr[6] |= AX25_SSSID_SPARE;
    dptr += AX25_ADDR_LEN;

    *dptr++ = sysctl_netrom_network_ttl_initialiser;

    if (!nr_route_frame(skb, NULL)) {
        kfree_skb(skb);
        nr_disconnect(sk, ENETUNREACH);
    }
}

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

void nr_establish_data_link(struct sock *sk)
{
    struct nr_sock *nr = nr_sk(sk);

    nr->condition = 0x00;
    nr->n2count   = 0;

    nr_write_internal(sk, NR_CONNREQ);

    nr_stop_t2timer(sk);
    nr_stop_t4timer(sk);
    nr_stop_idletimer(sk);
    nr_start_t1timer(sk);
}

/*
 * Never send a NAK when we are CHOKEd.
 */
void nr_enquiry_response(struct sock *sk)
{
    struct nr_sock *nr = nr_sk(sk);
    int frametype = NR_INFOACK;

    if (nr->condition & NR_COND_OWN_RX_BUSY) {
        frametype |= NR_CHOKE_FLAG;
    } else {
        if (skb_peek(&nr->reseq_queue) != NULL)
            frametype |= NR_NAK_FLAG;
    }

    nr_write_internal(sk, frametype);

    nr->vl         = nr->vr;
    nr->condition &= ~NR_COND_ACK_PENDING;
}

void nr_check_iframes_acked(struct sock *sk, unsigned short nr)
{
    struct nr_sock *nrom = nr_sk(sk);

    if (nrom->vs == nr) {
        nr_frames_acked(sk, nr);
        nr_stop_t1timer(sk);
        nrom->n2count = 0;
    } else {
        if (nrom->va != nr) {
            nr_frames_acked(sk, nr);
            nr_start_t1timer(sk);
        }
    }
}