hdlc.c

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/*
 * Generic HDLC support routines for Linux
 *
 * Copyright (C) 1999 - 2008 Krzysztof Halasa <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of version 2 of the GNU General Public License
 * as published by the Free Software Foundation.
 *
 * Currently supported:
 *  * raw IP-in-HDLC
 *  * Cisco HDLC
 *  * Frame Relay with ANSI or CCITT LMI (both user and network side)
 *  * PPP
 *  * X.25
 *
 * Use sethdlc utility to set line parameters, protocol and PVCs
 *
 * How does it work:
 * - proto->open(), close(), start(), stop() calls are serialized.
 *   The order is: open, [ start, stop ... ] close ...
 * - proto->start() and stop() are called with spin_lock_irq held.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/errno.h>
#include <linux/hdlc.h>
#include <linux/if_arp.h>
#include <linux/inetdevice.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/notifier.h>
#include <linux/pkt_sched.h>
#include <linux/poll.h>
#include <linux/rtnetlink.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <net/net_namespace.h>


static const char* version = "HDLC support module revision 1.22";

#undef DEBUG_LINK

static struct hdlc_proto *first_proto;

int hdlc_change_mtu(struct net_device *dev, int new_mtu)
{
    if ((new_mtu < 68) || (new_mtu > HDLC_MAX_MTU))
        return -EINVAL;
    dev->mtu = new_mtu;
    return 0;
}

static int hdlc_rcv(struct sk_buff *skb, struct net_device *dev,
            struct packet_type *p, struct net_device *orig_dev)
{
    struct hdlc_device *hdlc = dev_to_hdlc(dev);

    if (!net_eq(dev_net(dev), &init_net)) {
        kfree_skb(skb);
        return 0;
    }

    BUG_ON(!hdlc->proto->netif_rx);
    return hdlc->proto->netif_rx(skb);
}

netdev_tx_t hdlc_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
    hdlc_device *hdlc = dev_to_hdlc(dev);

    if (hdlc->proto->xmit)
        return hdlc->proto->xmit(skb, dev);

    return hdlc->xmit(skb, dev); /* call hardware driver directly */
}

static inline void hdlc_proto_start(struct net_device *dev)
{
    hdlc_device *hdlc = dev_to_hdlc(dev);
    if (hdlc->proto->start)
        hdlc->proto->start(dev);
}



static inline void hdlc_proto_stop(struct net_device *dev)
{
    hdlc_device *hdlc = dev_to_hdlc(dev);
    if (hdlc->proto->stop)
        hdlc->proto->stop(dev);
}



static int hdlc_device_event(struct notifier_block *this, unsigned long event,
                 void *ptr)
{
    struct net_device *dev = ptr;
    hdlc_device *hdlc;
    unsigned long flags;
    int on;

    if (!net_eq(dev_net(dev), &init_net))
        return NOTIFY_DONE;

    if (!(dev->priv_flags & IFF_WAN_HDLC))
        return NOTIFY_DONE; /* not an HDLC device */

    if (event != NETDEV_CHANGE)
        return NOTIFY_DONE; /* Only interested in carrier changes */

    on = netif_carrier_ok(dev);

#ifdef DEBUG_LINK
    printk(KERN_DEBUG "%s: hdlc_device_event NETDEV_CHANGE, carrier %i\n",
           dev->name, on);
#endif

    hdlc = dev_to_hdlc(dev);
    spin_lock_irqsave(&hdlc->state_lock, flags);

    if (hdlc->carrier == on)
        goto carrier_exit; /* no change in DCD line level */

    hdlc->carrier = on;

    if (!hdlc->open)
        goto carrier_exit;

    if (hdlc->carrier) {
        netdev_info(dev, "Carrier detected\n");
        hdlc_proto_start(dev);
    } else {
        netdev_info(dev, "Carrier lost\n");
        hdlc_proto_stop(dev);
    }

carrier_exit:
    spin_unlock_irqrestore(&hdlc->state_lock, flags);
    return NOTIFY_DONE;
}



/* Must be called by hardware driver when HDLC device is being opened */
int hdlc_open(struct net_device *dev)
{
    hdlc_device *hdlc = dev_to_hdlc(dev);
#ifdef DEBUG_LINK
    printk(KERN_DEBUG "%s: hdlc_open() carrier %i open %i\n", dev->name,
           hdlc->carrier, hdlc->open);
#endif

    if (hdlc->proto == NULL)
        return -ENOSYS; /* no protocol attached */

    if (hdlc->proto->open) {
        int result = hdlc->proto->open(dev);
        if (result)
            return result;
    }

    spin_lock_irq(&hdlc->state_lock);

    if (hdlc->carrier) {
        netdev_info(dev, "Carrier detected\n");
        hdlc_proto_start(dev);
    } else
        netdev_info(dev, "No carrier\n");

    hdlc->open = 1;

    spin_unlock_irq(&hdlc->state_lock);
    return 0;
}



/* Must be called by hardware driver when HDLC device is being closed */
void hdlc_close(struct net_device *dev)
{
    hdlc_device *hdlc = dev_to_hdlc(dev);
#ifdef DEBUG_LINK
    printk(KERN_DEBUG "%s: hdlc_close() carrier %i open %i\n", dev->name,
           hdlc->carrier, hdlc->open);
#endif

    spin_lock_irq(&hdlc->state_lock);

    hdlc->open = 0;
    if (hdlc->carrier)
        hdlc_proto_stop(dev);

    spin_unlock_irq(&hdlc->state_lock);

    if (hdlc->proto->close)
        hdlc->proto->close(dev);
}



int hdlc_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
{
    struct hdlc_proto *proto = first_proto;
    int result;

    if (cmd != SIOCWANDEV)
        return -EINVAL;

    if (dev_to_hdlc(dev)->proto) {
        result = dev_to_hdlc(dev)->proto->ioctl(dev, ifr);
        if (result != -EINVAL)
            return result;
    }

    /* Not handled by currently attached protocol (if any) */

    while (proto) {
        if ((result = proto->ioctl(dev, ifr)) != -EINVAL)
            return result;
        proto = proto->next;
    }
    return -EINVAL;
}

static const struct header_ops hdlc_null_ops;

static void hdlc_setup_dev(struct net_device *dev)
{
    /* Re-init all variables changed by HDLC protocol drivers,
     * including ether_setup() called from hdlc_raw_eth.c.
     */
    dev->flags       = IFF_POINTOPOINT | IFF_NOARP;
    dev->priv_flags      = IFF_WAN_HDLC;
    dev->mtu         = HDLC_MAX_MTU;
    dev->type        = ARPHRD_RAWHDLC;
    dev->hard_header_len     = 16;
    dev->addr_len        = 0;
    dev->header_ops      = &hdlc_null_ops;
}

static void hdlc_setup(struct net_device *dev)
{
    hdlc_device *hdlc = dev_to_hdlc(dev);

    hdlc_setup_dev(dev);
    hdlc->carrier = 1;
    hdlc->open = 0;
    spin_lock_init(&hdlc->state_lock);
}

struct net_device *alloc_hdlcdev(void *priv)
{
    struct net_device *dev;
    dev = alloc_netdev(sizeof(struct hdlc_device), "hdlc%d", hdlc_setup);
    if (dev)
        dev_to_hdlc(dev)->priv = priv;
    return dev;
}

void unregister_hdlc_device(struct net_device *dev)
{
    rtnl_lock();
    unregister_netdevice(dev);
    detach_hdlc_protocol(dev);
    rtnl_unlock();
}



int attach_hdlc_protocol(struct net_device *dev, struct hdlc_proto *proto,
             size_t size)
{
    detach_hdlc_protocol(dev);

    if (!try_module_get(proto->module))
        return -ENOSYS;

    if (size)
        if ((dev_to_hdlc(dev)->state = kmalloc(size,
                               GFP_KERNEL)) == NULL) {
            netdev_warn(dev,
                    "Memory squeeze on hdlc_proto_attach()\n");
            module_put(proto->module);
            return -ENOBUFS;
        }
    dev_to_hdlc(dev)->proto = proto;
    return 0;
}


void detach_hdlc_protocol(struct net_device *dev)
{
    hdlc_device *hdlc = dev_to_hdlc(dev);

    if (hdlc->proto) {
        if (hdlc->proto->detach)
            hdlc->proto->detach(dev);
        module_put(hdlc->proto->module);
        hdlc->proto = NULL;
    }
    kfree(hdlc->state);
    hdlc->state = NULL;
    hdlc_setup_dev(dev);
}


void register_hdlc_protocol(struct hdlc_proto *proto)
{
    rtnl_lock();
    proto->next = first_proto;
    first_proto = proto;
    rtnl_unlock();
}


void unregister_hdlc_protocol(struct hdlc_proto *proto)
{
    struct hdlc_proto **p;

    rtnl_lock();
    p = &first_proto;
    while (*p != proto) {
        BUG_ON(!*p);
        p = &((*p)->next);
    }
    *p = proto->next;
    rtnl_unlock();
}



MODULE_AUTHOR("Krzysztof Halasa <[email protected]>");
MODULE_DESCRIPTION("HDLC support module");
MODULE_LICENSE("GPL v2");

EXPORT_SYMBOL(hdlc_change_mtu);
EXPORT_SYMBOL(hdlc_start_xmit);
EXPORT_SYMBOL(hdlc_open);
EXPORT_SYMBOL(hdlc_close);
EXPORT_SYMBOL(hdlc_ioctl);
EXPORT_SYMBOL(alloc_hdlcdev);
EXPORT_SYMBOL(unregister_hdlc_device);
EXPORT_SYMBOL(register_hdlc_protocol);
EXPORT_SYMBOL(unregister_hdlc_protocol);
EXPORT_SYMBOL(attach_hdlc_protocol);
EXPORT_SYMBOL(detach_hdlc_protocol);

static struct packet_type hdlc_packet_type __read_mostly = {
    .type = cpu_to_be16(ETH_P_HDLC),
    .func = hdlc_rcv,
};


static struct notifier_block hdlc_notifier = {
    .notifier_call = hdlc_device_event,
};


static int __init hdlc_module_init(void)
{
    int result;

    pr_info("%s\n", version);
    if ((result = register_netdevice_notifier(&hdlc_notifier)) != 0)
        return result;
    dev_add_pack(&hdlc_packet_type);
    return 0;
}



static void __exit hdlc_module_exit(void)
{
    dev_remove_pack(&hdlc_packet_type);
    unregister_netdevice_notifier(&hdlc_notifier);
}


module_init(hdlc_module_init);
module_exit(hdlc_module_exit);