// SPDX-License-Identifier: GPL-2.0-only
/*
 * Generic HDLC support routines for Linux
 *
 * Copyright (C) 1999 - 2008 Krzysztof Halasa <khc@pm.waw.pl>
 *
 * 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;

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;

        /* First make sure "dev" is an HDLC device */
        if (!(dev->priv_flags & IFF_WAN_HDLC)) {
                kfree_skb(skb);
                return NET_RX_SUCCESS;
        }

        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 */
}
EXPORT_SYMBOL(hdlc_start_xmit);

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 = netdev_notifier_info_to_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)
                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;
}
EXPORT_SYMBOL(hdlc_open);

/* 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);
}
EXPORT_SYMBOL(hdlc_close);

int hdlc_ioctl(struct net_device *dev, struct if_settings *ifs)
{
        struct hdlc_proto *proto = first_proto;
        int result;

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

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

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

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->min_mtu             = 68;
        dev->max_mtu             = HDLC_MAX_MTU;
        dev->type                = ARPHRD_RAWHDLC;
        dev->hard_header_len     = 0;
        dev->needed_headroom     = 0;
        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",
                           NET_NAME_UNKNOWN, hdlc_setup);
        if (dev)
                dev_to_hdlc(dev)->priv = priv;
        return dev;
}
EXPORT_SYMBOL(alloc_hdlcdev);

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

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

        err = detach_hdlc_protocol(dev);
        if (err)
                return err;

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

        if (size) {
                dev_to_hdlc(dev)->state = kmalloc(size, GFP_KERNEL);
                if (!dev_to_hdlc(dev)->state) {
                        module_put(proto->module);
                        return -ENOBUFS;
                }
        }
        dev_to_hdlc(dev)->proto = proto;

        return 0;
}
EXPORT_SYMBOL(attach_hdlc_protocol);

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

        if (hdlc->proto) {
                err = call_netdevice_notifiers(NETDEV_PRE_TYPE_CHANGE, dev);
                err = notifier_to_errno(err);
                if (err) {
                        netdev_err(dev, "Refused to change device type\n");
                        return err;
                }

                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);

        return 0;
}
EXPORT_SYMBOL(detach_hdlc_protocol);

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

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();
}
EXPORT_SYMBOL(unregister_hdlc_protocol);

MODULE_AUTHOR("Krzysztof Halasa <khc@pm.waw.pl>");
MODULE_DESCRIPTION("HDLC support module");
MODULE_LICENSE("GPL v2");

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);
        result = register_netdevice_notifier(&hdlc_notifier);
        if (result)
                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);