x25_dev.c

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/*
 *  X.25 Packet Layer release 002
 *
 *  This is ALPHA test software. This code may break your machine, randomly fail to work with new
 *  releases, misbehave and/or generally screw up. It might even work.
 *
 *  This code REQUIRES 2.1.15 or higher
 *
 *  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
 *  X.25 001    Jonathan Naylor Started coding.
 *      2000-09-04  Henner Eisen    Prevent freeing a dangling skb.
 */

#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <linux/if_arp.h>
#include <net/x25.h>
#include <net/x25device.h>

static int x25_receive_data(struct sk_buff *skb, struct x25_neigh *nb)
{
    struct sock *sk;
    unsigned short frametype;
    unsigned int lci;

    if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
        return 0;

    frametype = skb->data[2];
    lci = ((skb->data[0] << 8) & 0xF00) + ((skb->data[1] << 0) & 0x0FF);

    /*
     *  LCI of zero is always for us, and its always a link control
     *  frame.
     */
    if (lci == 0) {
        x25_link_control(skb, nb, frametype);
        return 0;
    }

    /*
     *  Find an existing socket.
     */
    if ((sk = x25_find_socket(lci, nb)) != NULL) {
        int queued = 1;

        skb_reset_transport_header(skb);
        bh_lock_sock(sk);
        if (!sock_owned_by_user(sk)) {
            queued = x25_process_rx_frame(sk, skb);
        } else {
            queued = !sk_add_backlog(sk, skb, sk->sk_rcvbuf);
        }
        bh_unlock_sock(sk);
        sock_put(sk);
        return queued;
    }

    /*
     *  Is is a Call Request ? if so process it.
     */
    if (frametype == X25_CALL_REQUEST)
        return x25_rx_call_request(skb, nb, lci);

    /*
     *  Its not a Call Request, nor is it a control frame.
     *  Can we forward it?
     */

    if (x25_forward_data(lci, nb, skb)) {
        if (frametype == X25_CLEAR_CONFIRMATION) {
            x25_clear_forward_by_lci(lci);
        }
        kfree_skb(skb);
        return 1;
    }

/*
    x25_transmit_clear_request(nb, lci, 0x0D);
*/

    if (frametype != X25_CLEAR_CONFIRMATION)
        printk(KERN_DEBUG "x25_receive_data(): unknown frame type %2x\n",frametype);

    return 0;
}

int x25_lapb_receive_frame(struct sk_buff *skb, struct net_device *dev,
               struct packet_type *ptype, struct net_device *orig_dev)
{
    struct sk_buff *nskb;
    struct x25_neigh *nb;

    if (!net_eq(dev_net(dev), &init_net))
        goto drop;

    nskb = skb_copy(skb, GFP_ATOMIC);
    if (!nskb)
        goto drop;
    kfree_skb(skb);
    skb = nskb;

    /*
     * Packet received from unrecognised device, throw it away.
     */
    nb = x25_get_neigh(dev);
    if (!nb) {
        printk(KERN_DEBUG "X.25: unknown neighbour - %s\n", dev->name);
        goto drop;
    }

    if (!pskb_may_pull(skb, 1))
        return 0;

    switch (skb->data[0]) {

    case X25_IFACE_DATA:
        skb_pull(skb, 1);
        if (x25_receive_data(skb, nb)) {
            x25_neigh_put(nb);
            goto out;
        }
        break;

    case X25_IFACE_CONNECT:
        x25_link_established(nb);
        break;

    case X25_IFACE_DISCONNECT:
        x25_link_terminated(nb);
        break;
    }
    x25_neigh_put(nb);
drop:
    kfree_skb(skb);
out:
    return 0;
}

void x25_establish_link(struct x25_neigh *nb)
{
    struct sk_buff *skb;
    unsigned char *ptr;

    switch (nb->dev->type) {
    case ARPHRD_X25:
        if ((skb = alloc_skb(1, GFP_ATOMIC)) == NULL) {
            printk(KERN_ERR "x25_dev: out of memory\n");
            return;
        }
        ptr  = skb_put(skb, 1);
        *ptr = X25_IFACE_CONNECT;
        break;

#if IS_ENABLED(CONFIG_LLC)
    case ARPHRD_ETHER:
        return;
#endif
    default:
        return;
    }

    skb->protocol = htons(ETH_P_X25);
    skb->dev      = nb->dev;

    dev_queue_xmit(skb);
}

void x25_terminate_link(struct x25_neigh *nb)
{
    struct sk_buff *skb;
    unsigned char *ptr;

#if IS_ENABLED(CONFIG_LLC)
    if (nb->dev->type == ARPHRD_ETHER)
        return;
#endif
    if (nb->dev->type != ARPHRD_X25)
        return;

    skb = alloc_skb(1, GFP_ATOMIC);
    if (!skb) {
        printk(KERN_ERR "x25_dev: out of memory\n");
        return;
    }

    ptr  = skb_put(skb, 1);
    *ptr = X25_IFACE_DISCONNECT;

    skb->protocol = htons(ETH_P_X25);
    skb->dev      = nb->dev;
    dev_queue_xmit(skb);
}

void x25_send_frame(struct sk_buff *skb, struct x25_neigh *nb)
{
    unsigned char *dptr;

    skb_reset_network_header(skb);

    switch (nb->dev->type) {
    case ARPHRD_X25:
        dptr  = skb_push(skb, 1);
        *dptr = X25_IFACE_DATA;
        break;

#if IS_ENABLED(CONFIG_LLC)
    case ARPHRD_ETHER:
        kfree_skb(skb);
        return;
#endif
    default:
        kfree_skb(skb);
        return;
    }

    skb->protocol = htons(ETH_P_X25);
    skb->dev      = nb->dev;

    dev_queue_xmit(skb);
}